UWaterlooBroadband Communications Research (BBCR) Group Meeting    

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a Spring 2017 b

Date Speaker Email Category
2017-05-03 Nan Chen n37chen AT uwaterloo.ca Smart Grid
2017-05-10 Ahmed Abdalrahman AABDALRA AT uwaterloo.ca Smart Grid
2017-05-17 Mohamed Alhasani malhasan AT uwaterloo.ca Security
2017-05-24 Qi Yang yangqi AT xmu.edu.cn  
2017-05-31 Weisen Shi w46shi AT uwaterloo.ca SDN
2017-06-07 Junling Li j742li AT uwaterloo.ca SDN
2017-06-14 Farid Farmani ffarmani AT uwaterloo.ca Smart Grid
2017-06-21 Jinghuan Ma grandmajinghuan AT 163.com Smart Grid
2017-06-28 Chengcheng Zhao zccsq90 AT gmail.com Smart Grid
2017-07-05 Yuanyuan He lucia.yuanyuan.he AT gmail.com Security
2017-07-12 Yu Wang y2737wan AT uwaterloo.ca  
2017-07-19 Wen Wu w77wu AT uwaterloo.ca  
2017-07-26 Xiaohui Lin x223lin AT uwaterloo.ca  
2017-08-02 Ning Zhang n35zhang AT uwaterloo.ca SDN
2017-08-09 Qiang Ye q6ye AT uwaterloo.ca MAC
2017-08-16      
2017-08-23      

a Winter 2017 b

Date Speaker Email Category
2017-01-04 A-Long Jin along.jin AT uwaterloo.ca Data Center Network
2017-01-11 Cheng Huang Cheng.Huang AT uwaterloo.ca Security
2017-01-18 Feng Lyu f2lyu AT uwaterloo.ca VANET
2017-01-25 Peng Yang yangpeng AT hust.edu.cn SDN
2017-02-01 Xiao Ma x225ma AT uwaterloo.ca Cloud Computing
2017-02-08 Wenchao Xu w74xu AT uwaterloo.ca VANET
2017-02-15 Yujie Tang y59tang AT uwaterloo.ca Cognitive Radio Network
2017-02-22 Kaichuan Zhao k47zhao AT uwaterloo.ca D2D
2017-03-01 Xiaoming Yuan x47yuan AT uwaterloo.ca SDN
2017-03-08 Kaige Qu k2qu AT uwaterloo.ca Security
2017-03-15 Mingjun Dai m28dai AT uwaterloo.ca Resource Management
2017-03-22 Danyang Wang d293wang AT uwaterloo.ca Cognitive Radio Network
2017-03-29 Jianbing Ni j25ni AT uwaterloo.ca Security
2017-04-05 Qi Jiang q34jiang AT uwaterloo.ca Security
2017-04-12 Wenchao Xu w74xu AT uwaterloo.ca VANET
2017-04-19 Wenjuan Tang csutwinkle AT gmail.com Security
2017-04-26      


Date/Time: 2017-04-19, 10:30 am

Speaker: Wenjuan Tang

Title: Information Sharing for Health Big Data

Abstract: With the advancements of electronic medical equipment, e-healthcare system becomes a promising paradigm to continuously monitor health conditions and remotely diagnose phenomena. Meanwhile, it generates a large volume of health data and poses several security challenges, such as data sharing. In this presentation, we research some related works about health data sharing. And we propose a lightweight and privacy-preserving fog-assisted information sharing scheme (PFHD) for health big data. Specifically, we integrate fog computing into e-healthcare system to pre-process the raw health data and improve the efficiency of health data analysis. Furthermore, to prevent privacy leakage, we design a hierarchical attribute-based encryption method by encrypting the profile and health data with different access policies. In addition, we reduce the computation cost on devices by offloading health data encryption from devices to the fog server. Security discussions show that PFHD can achieve fine-grained health data sharing with privacy preservation. Performance evaluations demonstrate the efficiency of our scheme, especially in terms of encryption computation and storage costs.



Date/Time: 2017-04-12, 10:30 am

Speaker: Wenchao Xu

Title: Heterogeneous Resource Leveraging in Vehicular Networks

Abstract: Enabling connected vehicles has attracted a lot of attentions from industry to academic society to support the increasing in-vehicle Internet applications, such as video streaming, voice calling, traffic information sharing, etc. To fulfill the huge amount of wireless traffic generated by these applications, many radio access technologies have been considered to setup the vehicular Internet connections. For example, cellular networks can provide wide area network access for vehicle users, while some access technologies, e.g., Dedicated Short Range Communications (DSRC) and WiFi networks, are utilized for limited area vehicle to roadside (V2R) communication and Vehicle-to-Vehicle (V2V) communication. Due to the heavy traffic load from vehicular applications, especially in some dense areas, a single radio technology is not enough to support well for the future requirements in vehicular networks, e.g., high throughput, low end-to-end latency, highly adaptive to dynamic network condition, etc. Thus, the heterogeneous vehicular networks (HetVNET), which cooperatively utilize the above mentioned access technologies, i.e., wide area cellular network, limited area WiFi/DSRC for V2R and V2V communication networks, are considered to fulfill the vehicular data traffic tasks. In this talk, I will introduce the topic of resource leveraging in HetVNET, i.e., multiple data pipes, network data buffer, access resources, to enhance the network performance, such as data traffic throughput, access delay, etc. The preliminary work of V2V assisted queuing framework to enhance the traffic offloading in drive-thru Internet will be introduced. Then the future work including the resource leveraging for control plane and the software-defined heterogeneous vehicular network will be introduced. Finally the work plan will be given.



Date/Time: 2017-04-05, 10:30 am

Speaker: Qi Jiang

Title: Security analysis of password and smart card based two-factor authentication (2FA) Schemes

Abstract: Despite over two decades of continuous efforts, how to design a secure and efficient two-factor authentication scheme remains an open issue. Hundreds of new schemes have wave upon wave been proposed, yet most of them are shortly found unable to achieve some important security goals (e.g., truly two-factor security) and desirable properties (e.g., user anonymity), falling into the unsatisfactory "break-fix-break-fix" cycle. In this vicious cycle, protocol designers often advocate the superiorities of their improved scheme, but do not illustrate (or unconsciously overlooking) the aspects on which their scheme performs poorly. In this talk, a series of "improved schemes" over Xu et al.'s 2009 scheme are used as case studies to highlight that, if there are no improved measurements, more "improved schemes" generally would not mean more advancements. To figure out why the measurement of existing schemes is invariably insufficient, the state-of-the-art evaluation criteria set (i.e., Madhusudhan-Mittal's set) are investigated. Besides reporting its ambiguities and redundancies, viable fixes and refinements are given. It is showed that there are at least seven different attacking scenarios that may lead to the failure of a scheme in achieving truly two-factor security. Finally, a comparative evaluation of 26 representative two-factor schemes are presented, and the results outline the request for better measurement when assessing new schemes.



Date/Time: 2017-03-29, 10:30 am

Speaker: Jianbing Ni

Title: Security and Privacy Preservation for Mobile Crowdsensing

Abstract: Mobile Crowdsensing (MCS) is a compelling paradigm that enables a crowd of individuals to cooperatively collect and share data to measure and map phenomena of comment interest using their mobile devices (e.g., smartphones, cameras, smart glasses and wearable devices). Pairing with inherent mobility and intelligence, mobile users can collect, produce and upload various types of data to MCS service providers based on crowdsensing tasks released by customers, ranging from general information, such as temperature, air quality and traffic condition, to more specialized data, such as recommended places, health condition and voting intentions. Compared with traditional sensor networks, MCS supports large-scale sensing applications, improves sensing data trustworthiness and reduces the cost on deploying expensive hardware or software to acquire high-quality data.

Although the advantages of MCS are appealing, the architecture is confronted with various security and privacy threats. The service providers have their personal incentives and the servers are vulnerable to be compromised, as well as mobile devices. As a result, data security and user' privacy are being put at risk. The corruption of sensing reports may directly impact crowdsensing results, and further mislead customers to make irrational decisions. Moreover, the content of crowdsensing tasks may expose the intention of customers and the sensing reports might inadvertently reveal sensitive information about mobile users, including identity, location, preference, daily route and health status. Therefore, it is of importance to protect data security and user' privacy for MCS.

However, once data security and user' privacy are well protected, huge obstacles are triggered as follows: First of all, data protection techniques, e.g., data encryption, increase the data size and lead to reduplication detection impossible, and thereby possess large communication bandwidth. Secondly, if sensing reports are kept confidential, it is impossible for service providers to process and analyze them to generate crowdsensing results for customers. Thirdly, to recruit proper mobile users, service providers need the personal information about mobile users, which should be protected from the prospective of mobile users. Nonetheless, if these security and privacy issues are not addressed solidly, the enthusiasm of mobile users to participate in crowdsensing tasks would degrade. In short, the security and privacy preservation raises dilemmas in data communication, data processing, task allocation and user incentive for MCS.

The main objectives of this proposal are to resolve the above contradictions for MCS. In our preliminary work, we aim to address the conflict between data security and communication efficiency. Thus, we propose a fog-assisted secure data deduplication scheme (Fo-SDD) to improve communication efficiency with high confidentiality guarantee on sensing data. In Fo-SDD, fog nodes are able to detect and delete the repeated data in sensing reports learning nothing about the sensing reports, except that the identical reports leak the equality of the underlying sensing data. To further prevent this leakage, we extend the Fo-SDD using blind signatures to preserve the identities of mobile users. Besides, Chameleon hash function is leveraged to achieve contribution claiming and rewarding retrieving for anonymous mobile uses. Thus, all users can be fairly treated and encouraged. In summary, by leveraging encrypted data deduplication, Fo-SDD can significantly reduce the communication overhead between service providers and fog nodes, and prevent the curious service providers and fog nodes from obtaining sensitive information about mobile users from their sensing reports. Therefore, the contradictions between data security and communication efficiency can be balanced. For the further work, we intend to investigate the other three conflicts, namely, the conflict between data security and data processing, the conflict between privacy preservation and task allocation, and the conflict between privacy exposure and user incentive, and design secure and efficient mechanisms to resolve them. Our outcomes would improve the security and privacy protection in MCS and make a step further towards its comprehensive development.



Date/Time: 2017-03-22, 10:30 am

Speaker: Danyang Wang

Title: Spectrum Sensing and Power Recognition in Cognitive Radio Networks

Abstract: Hybrid interweave-underlay spectrum access in cognitive radio (CR) networks can explore spectrum opportunities when primary users (PUs) are either active or inactive, which significantly improves spectrum utilization. In this paper, we propose a high order cumulants based spectrum sensing and power recognition (CSR) detector for hybrid interweave-underlay spectrum access, where the primary system is with multiple transmit power levels. Specifically, to detect the idle spectrum when PU is absent, high order cumulants based spectrum sensing is performed in interweave model. When PU is detected, the working model is switched to underlay model, where detection of PU's transmit power level is performed to allow secondary user (SU) to adjust its power for fully exploring spectrum access opportunities without harmful interference to PU. Given a certain order and a certain lag, the test statistics of the proposed detector is derived by leveraging general likelihood ratio test. The proposed detector does not require any prior knowledge about the noise variance, thus it is robust to noise uncertainty. Closed-form results for threshold expression are derived, and numerical results are provided to evaluate the proposed detector.



Date/Time: 2017-03-15, 10:30 am

Speaker: Mingjun Dai

Title: Design of low complexity decoding in distributed storage system

Abstract: In distributed storage (DS) system, network coding (NC) is adopted to improve reliability of data storage. Normally, NC is operated within a large finite field and is non-zigzag decodable, which results in high decoding complexity. Dedicated to mobile terminal DS (MTDS) where the energy and computing capability is restricted, low decoding complexity design is becoming a must. In this work, we study the design of encoding and decoding for DS system within the framework of binary zigzag decoding (BZD), with the objective of reaping low decoding complexity. Firstly, based on BZD framework, we intend to design a series of storage code that can support arbitrary combination of storage packets lost, with the objective of low storage room overhead and accommodating to various back up degree of storaging. Next, within this storage code-based MTDS system, dedicated to data reconstruction or repair process, we design communication mechanisms to try to minimize the utilization of communication resources. For data reconstruction process, we design an optimal bandwidth consumption scheme. For data repair, by allowing multiple storage nodes to transmit simultaneously, we design schemes that are based on physical layer network coding to implement high communication efficiency repair. In addition, we also propose a novel correcting design to reap correcting ability (without additional checking bits). This work reduces finite field size from large to binary, and introduces zigzag decoding. It lays theoretical and technical foundations for reducing complexity. It reaps a relatively good performance among the following metrics: computing complexity, storage room, communication resources, and correcting ability.



Date/Time: 2017-03-08, 10:30 am

Speaker: Kaige Qu

Title: Side Channel Attacks on Cryptographic Devices and Countermeasures

Abstract: In modern life, all kinds of cryptographic devices are available for people, such as financial IC cards, and portable devices with cryptographic IP cores inside. Their security should be guaranteed to protect the property and privacy of users. Once the key that is stored in the cryptographic device is retrieved by attackers, the cryptosystem is totally broken. Compared to the conventional cryptanalysis, side channel attacks retrieve the key from the weakness in the physical implementation of a target cryptosystem rather than the weakness in the cryptographic algorithm itself. Power analysis attack is an important branch of side channel attack. It recovers the key from the instantaneous power consumption of the cryptographic devices. The experimental setup for power analysis and two typical types of it including SPA (Simple Power Attack) and CPA (Correlation Power Attack) are introduced in this talk. To prevent from power analysis attacks, countermeasures should be designed. In this talk, two main strategies of countermeasures are introduced.



Date/Time: 2017-03-01, 10:30 am

Speaker: Xiaoming Yuan

Title: Reservation-based dynamic scheduled MAC protocol for health monitoring

Abstract: Developments of wireless body area networks (WBANs) facilitate the pervasive health monitoring with mHealth applications. WBANs can support continuous health monitoring for the human body in convenience and high efficiency without any intervention. The monitoring data in health care have the characteristics of various data flows and heterogeneous data arrival rates, the transmission of which must be in timeliness and reliability, especially the burst data. Moreover, the energy-constraint nodes should be provident in energy consumption. Designing MAC protocols with high reliability and energy efficiency for WBANs is the prime consideration. In this paper, we propose a token-based two-round reservation MAC (TTR MAC) protocol based on IEEE 802.15.6 with considering the data features of health monitoring. With analyzing the characteristics of monitoring data, one-round reservation is conducted for periodic data and two-round reservation is generated adaptively for burst data to save energy. Besides, TTR MAC protocol assigns appropriate number of allocation slots to nodes in heterogeneous data arrival rates. Furthermore, a token is introduced on the basis of user priority and health severity index to indicate the transmission order of nodes with burst data, which highly decreases the average delay. In addition, a bit sequence scheduled algorithm is proposed for m-periodic (m > 1) monitoring data for network capacity expansion. The simulation results show that TTR MAC protocol achieves higher energy efficiency and longer lifetime compared with IEEE 802.15.6 and other one-round reservation MAC (OR MAC) protocols for both 1-periodic and m-periodic data.



Date/Time: 2017-02-22, 10:30 am

Speaker: Kaichuan Zhao

Title: User-Provided Networks: A Promising Aspect of Mobile Data Offloading

Abstract: Over the last few years, data traffic over cellular networks has seen an exponential rise, primarily due to the explosion of smartphones, tablets, and laptops. This increase brings an emergent challenge for the existing cellular network infrastructure. In order to mitigate this conflict, different innovative solutions, include Wi-Fi, and femtocells, have emerged to manage data traffic. User provided networks (UPN) is also a promising and effective solution, where the end user is at the same time a consumer and a provider of Internet access. In this talk, we first introduce some mobile data offloading technologies. Then, we introduce the definition of UPN and the challenges of this new model. Based on UPN, we will discuss the problem of sharing network resources among mobile users with the consideration of social ties between them. And in the end, we conclude our work and discuss future research.



Date/Time: 2017-02-15, 10:30 am

Speaker: Yujie Tang

Title: Cooperative Spectrum Sharing in Cognitive Radio Networking

Abstract:

Driven by the massive growth in communications data traffic as well as flourishing users' demands, we need to fully utilize the existing scarce spectrum resource. However, there have been several studies and reports over the years showing that a large portion of licensed spectrum is actually underutilized in both temporal and spatial domains. Moreover, aiming at facing the dilemma among the fixed spectrum allocation, the ever enormous increasing traffic demand and the limited spectrum resource, cognitive radio (CR) was proposed by Mitola to alleviate the under usage of spectrum. Thus, cognitive radio networking (CRN) has emerged as a promising paradigm to improve the spectrum efficiency and utilization by allowing secondary users (SUs) to utilize the spectrum hole of primary users (PUs). By using spectrum sensing, SUs can opportunistically access spectrum holes for secondary transmission without interfering the transmissions of the PUs and efficient spectrum utilization by multiple PUs and SUs requires reliable detection of PUs. Nevertheless, sensing errors such as false alarm and misdetection are inevitable in practical networks. Hence, the assumption that SUs always obtain the exact channel availability information is unreasonable. In addition, spectrum sensing must be carried out continuously and the SU must terminate its transmission as soon as it senses the re-occupancy by a PU. As a better alternative of spectrum sensing, cooperation has been leveraged in CRN, which is referred as cooperative cognitive radio networking (CCRN). In CCRN, in order to obtain the transmission opportunities, SUs negotiate with the PUs for accessing the spectrum by providing tangible service for PUs.

In this talk, we study cluster based spectrum sharing mechanism for CCRN, and investigate on exploiting the cooperative technique in heterogeneous network. First, we develop cooperation protocols for CRN. Simultaneous transmission can be realized through quadrature signalling method in our proposed cooperation protocol. The optimal power allocation has been analyzed and closed-form solution has been derived for amplify and forward mode. Second, we study a cluster based spectrum sharing mechanism. The spectrum sharing is formulated as a combinatorial non-linear optimization problem which is NP-hard. Afterwards, we solve this problem by decomposing it into cluster allocation and time assignment, and we show that the result is close to the optimal solution. Third, we propose a macrocell-femtocell network cooperation scheme for heterogeneous networks under closed access mode. The cooperation between the femtocell network and macrocell network is investigated. By implementing the cooperation, not only the macrocell users' (MUEs') and femtocell users' (FUEs') utility can be improved compared with the non-cooperation case, but also the energy consumption as well as the interference from the femtocell network to the macrocell network can be reduced.



Date/Time: 2017-02-08, 10:30 am

Speaker: Wenchao Xu

Title: Delay Analysis of In-Vehicle Internet Access Via On-Road WiFi Access Points

Abstract: Providing cost-effective and high throughput WiFi access for vehicle drivers and passengers is a promising solution to support the increasing demand for in-vehicle Internet applications. Prior to accessing Internet services via an on-road WiFi access point (AP), a vehicle user has to wait for a certain time duration, referred to as access delay, until the user is authenticated and assigned proper network layer parameters, such as an Internet Protocol (IP) address. Investigation of the access delay in a vehicular environment is critical, since a large access delay can significantly reduce the time duration that a vehicle actually benefits from Internet connectivity during its temporary existence within the coverage area of an on-road WiFi AP, especially with high vehicle moving speeds. In this paper, we propose an analytical model based on a Markov chain to study the dependency of the access delay on different factors, including the wireless channel conditions, the number of vehicles accessing the AP service, and the employed authentication mechanism, such as the WiFi protected access II (WPA2)-pre-shared key (PSK) and the WPA2-802.1X modes. The accuracy of the analytical model is studied via computer simulations, as well as experimental testing using commercial off-the-shelf (COTS) WiFi products, together with a channel emulator that emulates the wireless channel conditions in a vehicular environment. Simulation and experiment results highlight the accuracy of the proposed analytical model. Results in this study provide useful guidelines for future selection/development of suitable WiFi network access schemes in a vehicular environment.



Date/Time: 2017-02-01, 10:30 am

Speaker: Xiao Ma

Title: Online resource allocation for elastic service in mobile-edge cloud

Abstract: Mobile-edge cloud computing is a promising computing paradigm which helps relief the conflict between resource-consuming mobile applications and resource-constrained mobile devices. In mobile-edge cloud, pervasive mobile cloud services are provisioned by telecom operators to mobile users at the edge of wireless access network. Fully utilizing the potential of mobile-edge cloud remains challenging in four aspects: tradeoff between computing resource and communication overhead; heterogeneous mobile requests and computing capacity; dynamic requests and wireless network; tradeoff between service performance and system cost. To provision elastic services, we explore the resource allocation problem in Public cloud Assisted Mobile-Edge cloud (PAME)framework. Online access control and cloud outsourcing decision are coordinated to achieve the minimum outsourcing cost while ensuring desired service performance. We simplify the complexity by proposing the nested water-filling algorithm. Simulations are conducted to evaluate the outcome of our proposed algorithm. And in the end, we conclude our work and discuss future research.



Date/Time: 2017-01-25, 10:30 am

Speaker: Peng Yang

Title: Utility Maximized Worker Selection for Crowdsourcing Applications

Abstract: By exploiting the potential of human intelligence and advanced mobile devices, crowdsourcing provides an efficient way for data collection and distributed computing. An important yet challenging issue of crowdsourcing is worker selection. To achieve high platform utility, many existing works focus on designing game or auction based incentive mechanisms to motivate workers participate truthfully. However, even workers are truthful during the selection phase, there still exists a payment dilemma between workers and the platform. Hence, in this talk, we introduce learning based schemes for worker selection under different scenarios. To deal with the uncertainty of worker’s performance, we propose learning algorithms that carefully balance exploration and exploitation during worker selection. We theoretically proved that the proposed algorithms achieve asymptotically diminishing utility regret. Simulations based on real-world dataset show that the proposed algorithms have preferable performance with acceptable complexity. At the end, future research issues will be discussed.



Date/Time: 2017-01-18, 10:30 am

Speaker: Feng Lyu

Title: MoMAC: Mobility-Aware and Collision-Avoidance MAC for Safety Applications in VANETs

Abstract: With the increasing demand for emerging delay-sensitive vehicular safety applications, it is crucial to design an efficient media access control (MAC) protocol for reliable transmission in vehicular ad hoc networks (VANETs). To this end, the TDMA-based MAC has been proposed as a promising solution in VANETs, as a slotted channel can guarantee the stringent time requirement in vehicular communications. However, due to the varying vehicle mobility, existing TDMA-based MAC protocols result in collisions of slot assignment when multiple sets of vehicles move together. To avoid slot-assignment collisions, in this paper, we propose a mobility-aware TDMA-based MAC, referred to as MoMAC. The proposed MoMAC assigns every vehicle a time slot according to the underlying road topology and lane arrangement with taking into account varying vehicle mobility. In MoMAC, different lanes on the same road segment and different road segments at intersections are associated with disjoint slot sets. In this way, each vehicle can easily obtain the collision-avoidance slot assignment. By broadcasting the information of its own neighbors and collecting such information from neighbors, an individual vehicle can access a free time slot and detect slot collisions in a fully distributed way. We demonstrate the efficiency of MoMAC through theoretical analysis and extensive simulations. On average, 59:2% of transmission collisions can be avoided by adopting MoMAC in comparison with state-of-art TDMA MACs.



Date/Time: 2017-01-11, 10:30 am

Speaker: Cheng Huang

Title: Security and Privacy Issues in Vehicular Crowdsourcing Network

Abstract: Crowdsourcing, crowdsensing or participatory sensing have become the feasible ideas due to the rapidly development and flourish of smart vehicles. Being equipped with the powerful On-board Unit (OBU), various communication devices, and a wide range of embedded sensors, the smart vehicles can travel through almost everywhere, as the workers, to monitor the physical world in real time and provide intelligent services to the users. However, a barrier to widespread deployment of vehicular crowdsourcing/sensing service is the security and privacy concerns of both users and workers. Hence, in this talk, we will investigate security and privacy issues in vehicular crowdsourcing network(VCN). Specifically, we first introduce the general concept of vehicular crowdsourcing and its applications. Then, we discuss several security and privacy challenges in these applications and show some attack cases. In addition, two detailed scenarios will be considered in terms of security and privacy threats. Finally, we will point out some security and privacy issues for future research.



Date/Time: 2017-01-04, 10:30 am

Speaker: A-Long Jin

Title: Multi-Resource Fair Sharing in Datacenter Networks

Abstract: Large-scale datacenters have become the de facto standard computing platform for cloud applications. As implied by the essence of cloud computing, resources in underlying datacenters are shared among multiple tenants. It has been well understood that the performance of cloud applications heavily depend on the allocated share of computing resources (e.g., CPU and memory) and networking resources (e.g., bandwidth). Resource allocation under the notion of fairness and efficiency is a fundamental problem in the design of cloud computing systems. In this talk, I will discuss how multi-resource fair sharing can be achieved in datacenter networks.


a Fall 2016 b

 

a Spring 2016 b

 

a Wintebr 2016

 

 

a Fall 2015 b

 

a Spring 2015

 

 Winter 2015

 Fall 2014

 Spring 2014

 Winter 2014

 Fall 2013
Date Speaker Email Category
2013-09-06 Chengcheng Pei chengchengpei87 AT gmail.com Security
2013-09-13 Tom Hao Luan hluan@uwaterloo.ca VANET
2013-09-20 Nan Cheng n5cheng AT uwaterloo.ca VANET
2013-09-27 Kamal Rahimi krahimim AT uwaterloo.ca Energy-efficiency
2013-10-04 Ye Wang wangye.hitsz AT gmail.com CRN
2013-10-11 Chong Lou clou AT uwaterloo.ca Energy-efficiency
2013-10-18 Kuan Zhang k52zhang AT uwaterloo.ca Security
2013-10-25 Chengzhe Lai lcz.xidian AT gmail.com Security
2013-11-01 Yong Zhou y233zhou AT uwaterloo.ca Cooperative
2013-11-08 Amila P. K. Tharaperiya amila.gamage AT uwaterloo.ca Performance
2013-11-15 Xinsheng Zhou x29zhou AT uwaterloo.ca Coding Theory
2013-11-22 Yujie Tang y59tang AT uwaterloo.ca CRN
2013-11-29 Ahmed M. Hamza a55moham AT uwaterloo.ca Cooperative
2013-12-06 Ran Zhang r62zhang AT uwaterloo.ca Performance
2013-12-13 Rongxing Lu rxlu AT ntu.edu.sg Security
2013-12-17 Hao Liang & Prof. Shen h8liang AT uwaterloo.ca Smart Grid

 


Date/Time: 2013-12-17, 10:30 am

Speaker: Prof. Shen and Dr. Hao Liang

Title: Research Challenges in Smart Grid

Abstract: Most of the world's existing electricity grids are decades-old. Although they have significantly changed human life, their monitoring and control facilities gradually become out-of-date which may cause low energy efficiency/reliability in a world with ever-growing electricity demands. On the other hand, the information and communication technology has been significantly developed over the last few decades. By marrying the existing electricity grids with the state-of-art information and communication technology, the smart grid can achieve electricity delivery in a more efficient, reliable, economic, and secure way. The IEEE 2030 standard on smart grid was introduced in September 2011, which provides guidelines in understanding and defining the interoperability of information technology with the power system, end-user applications, and loads. However, acquiring necessary information through wireless networks and developing an information system to act on the acquired information are application-specific and need extensive research. This presentation will start with an introduction to the smart grid and a comparison between smart grid and existing electrical grid. Then, the research challenges in smart grid will be discussed. Specifically, we focus our discussions on wireless networking for decentralized microgrid and security and privacy preservation. Several open issues will be identified at the end of this presentation to inspire future research and collaborations.

 


Date/Time: 2013-12-13, 11:00 am

Speaker: Dr. Rongxing Lu

Title: Towards Efficient and Privacy-Preserving Computing in Big Data Era

Abstract: Big data, as it can mine new knowledge for economic growth and technical innovation, has recently received considerable attention, and many research efforts have been directed to big data processing due to its high volume, velocity and variety (referred to as "3V") challenges. However, in addition to "3V" challenges, the flourishing of big data also hinges on fully understanding and managing those newly rising security and privacy challenges. If data are not authentic, new mined knowledge will be unconvinced; while if privacy is not well addressed, people may be reluctant to share their data for big data analytics. As security has been investigated as new dimension "veracity" in big data, in this talk, we mainly aim to exploit new challenges of big data in term of privacy, and devote towards efficient and privacy-preserving computing in big data era. Specifically, we first formalize the general architecture of big data analytics, identify the corresponding privacy requirements, and introduce an efficient and privacy-preserving Cosine Similarity computing protocol as an example in response to the data mining's efficiency and privacy requirements in big data era.

 


Date/Time: 2013-12-06, 11:00 am

Speaker: Ran Zhang

Title: Radio Resource Management (RRM) in LTE-Advanced Systems with Carrier Aggregation

Abstract: In order to meet the ever-increasing demand for wireless broadband services from fast growing mobile users, the Long Term Evolution -Advanced (LTE-A) standard is proposed to effectively improve the system capacity and the spectral efficiency for the next-generation (4G) wireless mobile communications. Many advanced techniques are incorporated in LTE-A including Carrier Aggregation (CA), MIMO, Coordinated Multi-point Transmission (CoMP), relaying and enhanced Inter-cell Interference Coordination (eICIC) in Heterogeneous Networks (HetNets), to jointly ameliorate system performance. Among all the techniques, Carrier Aggregation is the most significant, albeit complex, improvement. Component carriers from various portions of the spectrum are logically concatenated resulting in a virtual block of a much larger band, enabling increased data throughput. However, the unique characteristics of CA have posed a set of emerging challenges as well as span-new opportunities on the Radio Resource Management (RRM) issues of the LTE-A systems. First, although the users with CA capabilities can transmit concurrently on multiple CCs to enjoy a higher throughput, the multi-CC transmission can incur more intensive interference for each component carrier and more power consumption for users. Thus the performance gain of CA under different cell load conditions and optimization objectives has to be fully evaluated in both uplink and downlink. Besides, as CA offers flexible CC selection and cross-CC load balancing and scheduling, enhanced RRM strategies should be designed to further optimize the overall utilization of the system resources. In addition, CA enables the frequency reuse on a CC resolution, offering another dimension for inter-cell interference management in the HetNets. Therefore, dynamic partial-spectrum-reuse interference mitigation mechanisms should be designed to take this advantage. In this proposal, we will emphasize and make full use of the new functionalities introduced by CA to optimize the RRM performance in LTE-A systems. The main objectives are: 1) to fully evaluate the benefits of CA from different perspectives under different scenarios via both theoretical analysis and simulations; 2) to explore the cross-layer design of the layer-3 CC selection, layer-2 packet scheduling and layer-1 power control; and 3) to provide analytical interference modeling for HetNets and propose dynamic interference mitigation strategies based on the partial spectrum reuse. In our preliminary work, we analyze the benefits of CA via investigating the user accommodation capabilities of CA-based LTE-A systems respectively for the legacy LTE users and LTE-A users. The adopted metric is equivalent capacity (EC), defined as the maximum number of users that can be admitted into the system given the user QoS requirements and traffic descriptors. Both LTE and LTE-A users are divided into heterogeneous user classes with different QoS requirements and traffic characteristics. Two bandwidth allocation strategies are studied, i.e., the fixed-weight strategy and the cognitive-weight strategy, where the bandwidth weights of different user classes are either prefixed or dynamically changing according to the cell load conditions. Specifically, considering the wireless fading statistics, we first exploit the concept of effective bandwidth to map the user throughput requirements into bandwidth requirements to provide the users with a probabilistic QoS guarantee. Leveraging the binomial-normal approximation, closed-form expressions of EC are then derived for both LTE and LTE-A users under two bandwidth allocation strategies. Furthermore, a net-profit-maximization problem is formulated to discuss the tradeoff among the bandwidth allocation weights, which combines the factors of operator service profits, user satisfaction and traffic load dynamics. We demonstrate via both theoretical analysis and simulations that when the user traffic is bursty, only a slightly higher spectrum utilization of LTE-A users than LTE users can result in a significant EC gain. For the remainder of the research, we will further study the RRM issues in the adaptive CC selection, cross-CC scheduling and interference management in the HetNets. We will propose a cross-layer CC selection and power control strategy for uplink CA, a semi-dynamic CC (de)activation scheme and a HetNet interference mitigation strategy based on the partial spectrum reuse. It is expected that this research can have impact on the future design of RRM functional blocks for optimizing the radio resource utilization.

 


Date/Time: 2013-11-29, 11:00 am

Speaker: Ahmed M. Hamza

Title: Closed Form Expressions for BER/SER of OFDM Systems with Integer Time Offset

Abstract: It is well known that both time and frequency offsets cause degradation to the performance of orthogonal frequency division multiplexing (OFDM) systems. The evaluation of this degradation can take two forms. The first one is to measure the loss in signal-to-noise ratio (SNR) due to these offsets, and the second one is to compute the probability of error due to these degradations. While it can be found in literature closed forms to calculate the probability of error for OFDM systems with frequency offset, to the best of my knowledge, there are no such formulas for OFDM systems with time offset. Most of literature dealing with the time offset in OFDM adopt the loss in SNR strategy to evaluate its effect. In this presentation, I will introduce the effects of time offset in OFDM system. Then, I will show a new derivation for an exact closed form for the BER/SER of OFDM systems with Integer Time Offset.

 


Date/Time: 2013-11-22, 11:00 am

Speaker: Yujie Tang

Title: Spectrum Sharing for Cognitive Radio Networks

Abstract: Spectrum bands are licensed to users. Unlicensed users can access idle licensed bands, referred to as spectrum holes, only through spectrum sensing. It is well known that the available spectrum is grossly underutilized by licensed users. Cognitive radio (CR) is a paradigm aiming at enhancing spectrum utilization. In cognitive radio networking (CRN), licensed users are referred to as primary users (PUs) and unlicensed users are secondary users (SUs). It is imperative that SU transmissions must not cause interference to PUs. However, in practice sensing errors are inevitable. Moreover, the spectrum obtained via sensing is not stable since PUs may reclaim their spectrum bands anytime. As an alternative, cooperative cognitive radio networking (CCRN) has been proposed. In CCRN, SUs negotiate with PUs for secondary transmission by relaying PUs' tra c through cooperative communication techniques, such as advanced coding or cooperative relaying, and then gain transmission opportunities as a reward. Whereas CCRN can avoid the interference problem to the PUs, and the PUs' utility can be improved through cooperation, only the SUs who cooperate with PUs can acquire the spectrum access opportunities which may not be fair from the perspective of the whole networks, and there may exist many starving SUs in the network. With the purpose of solving the aforementioned problem, we propose a cluster based two-phase cooperation scheme in which a group of SUs, with better link conditions, are selected by the PUs as cooperators. We refer to these SUs as intermediate users (IUs), who also act as cluster heads. After cooperating with the PUs, the IUs acquire access rights and share the spectrum with their respective cluster members.

 


Date/Time: 2013-11-15, 11:00 am

Speaker: Xinsheng Zhou

Title: Low-density Parity-check codes for wireless relay networks

Abstract: In wireless networks, it has always been a challenge to satisfy high traffic throughput demands. Besides limited power and spectrum resources, interference is also a factor that limits the throughput due to shared medium. In the past decades, various techniques, including cooperative communications, have been developed to achieve higher communication rates. In this thesis, we aim to address the challenges imposed by cooperative wireless networks. Especially, we focus on practical code constructions and designs for wireless relay networks. The thesis is divided into the following four topics: 1) constructing and designing low-density parity-check (LDPC) codes for half-duplex three-phase two-way relay channels, 2) extending LDPC code constructions to half-duplex three-way relay channels, 3) proposing maximum-rate relay selection algorithms and LDPC code constructions for the broadcast problem in wireless relay networks, and 4) proposing an iterative hard interference cancellation decoder for LDPC codes in 2-user multiple-access channels.

 


Date/Time: 2013-11-08, 11:00 am

Speaker: Amila Tharaperiya Gamage

Title: Resource management for relay and device-to-device communication assisted cellular/WLAN interworkings

Abstract: The demand for higher data rates with seamless coverage and diverse quality-of-service (QoS) requirements have been dramatically increased in recent years due to the growth of the number smart mobile devices and the applications that run on those devices. Interworking of wireless networks is a promising solution which can satisfy those data rate, coverage and QoS requirements. Further, it can enhance the energy efficiency of the users' equipment (UEs). However, there are areas where interworking cannot be used. At such areas, device-to-device (D2D) communication and cooperative relaying can be used for improving the performance of the networks to satisfy the rate, coverage and QoS requirements. Therefore, the objective of this research is to design a unified resource allocation scheme to allocate resources for relay and D2D communication assisted interworking cellular network and wireless local area network (WLAN). To achieve this goal, three research problems are studied. In the first research problem, we study uplink resource allocation for cellular/WLAN interworking system to support multi-homing capable users with voice and data traffic requirements. Cellular network is based on orthogonal frequency division multiple access and WLAN operates on both contention-based and contention-free polling-based channel access mechanisms. Resources to be allocated are the transmit power levels at the UEs, subcarriers of cellular network, and transmission opportunities in both channel access mechanisms of WLAN. The problem is formulated based on the physical layer and the medium access control layer technologies of the two networks to ensure the feasibility of resource allocation decisions. To enhance the energy efficiency of the UEs, power distribution among multiple network interfaces of the UEs is included in the problem formulation. The optimal resource allocation problem is a multiple time-scale Markov decision process (MMDP) as cellular network and WLAN operate at different time scales, and due to QoS constraints. We propose optimal decision policies for the upper and the lower levels of the MMDP by using the theory for Markov decision processes and convex optimization. As this MMDP based resource allocation method has a high time complexity, we propose a heuristic resource allocation algorithm which significantly reduces the time complexity. In the second and the third research problems, we study resource allocation for relay assisted cellular/WLAN interworking, and resource allocation for relay and D2D communication assisted cellular/WLAN interworking, respectively. In the second problem, we will consider each hop of the relay links to be established using both cellular network and WLAN. In the third problem, we will simultaneously solve uplink and downlink resource allocations to accurately consider the hop gain. Use of these two concepts further improves the novelty of this research.

 


Date/Time: 2013-11-01, 11:00 am

Speaker: Yong Zhou

Title: Link-Layer Cooperative Communication in Multi-Hop Mobile Ad Hoc Networks

Abstract: Channel fading and transmission interference are two main causes of performance degradation in wireless communications. Due to the scarcity of the radio spectrum, it is almost impossible to allocate an exclusive channel for each source-destination pair, especially in a mobile ad hoc network (MANET). Hence, enabling concurrent transmissions in the same channel is necessary to achieve high spatial reuse and enhance spectrum utilization. On the other hand, cooperative communication is a promising and practical technique for realizing spatial diversity through a virtual antenna array formed by multiple antennas of different nodes. There has been a growing interest in developing efficient cooperation schemes to combat channel fading. However, the existing works mainly focus on exploiting the benefits and demonstrating the effectiveness of cooperative communication in fully-connected networks, where spatial reuse is not considered. In this research, we will consider both spatial reuse and cooperative communication in a multi-hop MANET, where interference among concurrent transmissions is the main issue. The time-varying channel fading and spatial distributions of both source and relay locations, that can affect the interference distribution, are taken into consideration. We aim to provide a tractable performance analysis framework for such a network scenario under both the protocol and physical interference models. Under the protocol interference model, we intend to identify a criterion of beneficial cooperation by analyzing the trade-off between enhanced single-link cooperation gain and reduced spatial reuse. Under the physical interference model, we aim at developing an opportunistic cooperation mechanism to activate cooperation when necessary, and developing a joint cooperation and signal-to-interference-plus-noise ratio (SINR) based power allocation mechanism to eliminate unnecessary interference. The characterization of interference and the analysis of transmission capacity will be carried out. The analytical results are expected to provide insights into the link-layer issues of cooperative communication in a multi-hop MANET, i.e., when to cooperate, whom to cooperate with, and how to cooperate.

 


Date/Time: 2013-10-25, 11:00 am

Speaker: Chengzhe Lai

Title: Secure and Privacy-preserving Authentication Schemes for Roaming Service in 3GPP Networks

Abstract: Seamless roaming over wireless networks is highly desirable to mobile users; however, ensuring the secure and efficient roaming is a challenging issue. In this talk, we first introduce the definition of roaming, 3GPP LTE roaming scenario, and EPS-AKA, which is an authentication protocol used to protect the security of the LTE system. Then, we analyze the security weaknesses in EPS-AKA, and present our two recent works: (1) A lightweight group authentication protocol for machine-type communication in LTE networks is proposed, named LGTH, which can not only authenticate all MTC devices simultaneously, but also minimize the authentication overhead. Through security analysis, we conclude that the proposed LGTH can provide robust security, and avoid the authentication signaling congestion in the LTE networks; (2) To simultaneously provide universal secure roaming service and better privacy preservation, a conditional privacy-preserving authentication with access linkability for roaming service is developed, named APP. In specific, APP can provide strong anonymous authentication, session key agreement, user tracking, and anonymous user linking. Meanwhile, APP has the efficient revoking mechanism for dynamic membership, which can revoke a group of users at the same time. Finally, I will draw the conclusion and give some future research directions.

 


Date/Time: 2013-10-18, 11:00 am

Speaker: Kuan Zhang

Title: Sybil Defense in Social Network: Challenges and Countermeasures

Abstract: Social networks are vulnerable to Sybil attack, where a Sybil forges a considerable number of fake identities to disseminate spams and infuse false or biased information via these pseudonymous identities. For example, in a distributed voting system, an adversary can easily change the overall popularity of an option by providing plenty of false praise, or bad-mouthing the option through these fake identities. We summarize the existing Sybil defense techniques, and further provide some new research areas. Unlike traditional analysis about Sybil defense, we first categorize the Sybil defense methods, mainly according to their designed time, and then classify the methods by their approaches.The research on the Sybil defense technique has experienced four phases: (1) traditional security key-based approaches, (2) specific peer-to-peer system feature-based solutions, (3) social network-based methods, and (4) social community-based techniques. Finally, we present some open research directions on Sybil defense in social networks.

 


Date/Time: 2013-10-11, 11:00 am

Speaker: Chong Lou

Title: Duty Cycling in Wireless Ad Hoc Networks: Capacity and Energy Consumption Analysis

Abstract: Periodic sleeping, i.e., duty cycling is commonly adopted in energy-constrained wireless networks to save the energy waste caused by idle listening in the case of low traffic load. It allows nodes to enter the low power mode by turning the transceiver off according to the sleep-wake scheduling. Most related works are carried out towards wireless sensor networks with a collision-free assumption where a single flow with one or few packets are delivered. Little attention has been paid on the contention-based channel access schemes that are essential for wireless ad hoc networks. Capacity and energy analysis as the first step for QoS provision have not been analyzed in on-going studies. In this talk, I will mainly concern about two problems: (1). Given that collisions decrease the network performances of delay and consume additional energy, how to consider the sleep scheduling protocol design. (2). Given the stochastic delay requirement, how to achieve energy-efficiency regarding random packet arrival and dynamic load. To address above problems, I will first present a coordinated sleep scheduling protocol where each node is assigned with a wake-up probability. By adjusting the wake-up probability, the amount of energy consumption can be effectively reduced while satisfying the stochastic delay requirement. Then a discrete-time Markov Chain based approach to analyze the capacity and energy consumption is proposed as well as preliminary simulation results. The performance analysis results can be used to develop call admission and routing procedures. Finally, I will talk about a soft-threshold call admission control scheme in the underlying network.

 


Date/Time: 2013-10-04, 11:00 am

Speaker: Ye Wang

Title: Multi-Strategy Dynamic Spectrum Access in Sensing Agent Aided Cognitive Radio Networks

Abstract: Dynamic spectrum access (DSA) is envisaged to be an effective approach to mitigate the problem of crowded electromagnetic radio spectrum. Compared with the static spectrum allocation, DSA technology can greatly enhance the utilization efficiency of limited spectrum resources. Recently, cognitive radios (CR) have been proposed as a powerful technical supporting the implementation of the DSA technique. Strategy to determine how to dynamically use the spectrum resource between primary and secondary system is crucial for the performance of DSA technology. A well-designed DSA strategy enables the secondary system not only to work efficiently but also to benefit the primary side. Although existing DSA strategies have successfully improved spectrum efficiency, it is still a challenging work to design a comprehensive strategy. Most of the existing DSA strategies are usually suffering from obvious drawbacks in certain aspect of performance metrics. In this talk, I will introduce a multi-strategy DSA framework, in which secondary system is capable of using single or multiple DSA strategies simultaneously to flexibly match its requirements and further improve the system performance. Moreover, I would like to discuss with you on some open issues in cognitive radios networks.

 


Date/Time: 2013-09-27, 11:00 am

Speaker: Kamal Rahimi

Title: An Energy Efficient MAC Protocol for Fully Connected Wireless Ad Hoc Networks

Abstract: Energy efficiency is an important performance measure of wireless network protocols, especially for battery-powered mobile devices such as smartphones. This talk presents a new energy-efficient medium access control (MAC) scheme for fully connected wireless ad hoc networks. The proposed scheme reduces energy consumption by putting radio interfaces in the sleep state periodically and by reducing transmission collisions, which results in high throughput and low packet transmission delay. The proposed MAC scheme can also address the energy saving in realtime traffics which require very low packet transmission delay. An analytical model is established to evaluate the performance of the proposed MAC scheme. Analytical and simulation results demonstrate that the proposed scheme has a significantly lower power consumption, achieves substantially higher throughput, and has lower packet transmission delay in comparison with existing power saving MAC protocols.

 


Date/Time: 2013-09-20, 11:00 am

Speaker: Nan Cheng

Title: Vehicular WiFi Offloading: Challenges and Solutions

Abstract: WiFi offloading is envisioned as a promising solution to the mobile data explosion problem in cellular networks. WiFi offloading for moving vehicles, however, poses unique characteristics and challenges, due to high mobility, fluctuating mobile channels, etc. In this paper, we focus on the problem of WiFi offloading in vehicular communication environments. Specifically, we discuss the challenges and identify the research issues related to drive-thru Internet access and effectiveness of vehicular WiFi offloading. Moreover, we review the state-of-the-art offloading solutions, in which advanced vehicular communications can be employed. We also shed some lights on the path for future research on this topic.

 


Date/Time: 2013-09-13, 11:00 am

Speaker: Tom Hao Luan

Title: Integrity-Oriented Content Transmission in Highway Vehicular Ad Hoc Networks

Abstract: The effective inter-vehicle transmission of content files, e.g., images, music and video clips, is the basis of media communications in vehicular networks, such as social communications and video sharing. However, due to the presence of diverse node velocities, severe channel fadings and intensive mutual interferences among vehicles, the inter-vehicle or vehicle-to-vehicle (V2V) communications tend to be transient and highly dynamic. Content transmissions among vehicles over the volatile and spotty V2V channels are thus susceptible to frequent interruptions and failures, resulting in many fragment content transmissions which are unable to finish during the connection time and unusable by on-top media applications. The interruptions of content transmissions not only lead to the failure of media presentations to users, but the transmission of the invalid fragment contents would also result in the significant waste of precious vehicular bandwidth. On addressing this issue, in this work we target on provisioning the integrity-oriented inter-vehicle content transmissions. Given the initial distance and mobility statistics of vehicles, we develop an analytical framework to evaluate the data volume that can be transmitted upon the short-lived and spotty V2V connection from the source to the destination vehicle. Provided the content file size, we are able to evaluate the likelihood of successful content transmissions through the model. Based upon this analysis, we propose an admission control scheme at the transmitters, that filters the suspicious content transmission requests which are unlikely to be accomplished over the transient inter-vehicle links. Using extensive simulations, we demonstrate the accuracy of the developed analytical model, and the effectiveness of the proposed admission control scheme. In the simulated scenario, with the proposed admission control scheme applied, it is observed that about 30% of the network bandwidth can be saved for effective content transmissions.

 


Date/Time: 2013-09-06, 11:00 am

Speaker: Chengcheng Pei

Title: Physical layer security

Abstract: Wireless networks play an extremely important role nowadays. However, security in wireless networks remains a challenging issue. Traditionally, security in wireless networks is addressed above physical layer through cryptography techniques. Currently, more and more researchers start to research the potential of wireless physical layer to provide security. They focus on different research topics, such as channel-based key generation, secrecy capacity, location distinction, physical layer authentication. In this talk, I will introduce the main idea of physical layer security firstly. Then, I will talk about main research topics in physical layer security. After that, I propose a cyclic-frequency-based physical layer authentication. The performance of our proposed scheme can be demonstrated by the measurements of practical channels in wireless networks. I will give our future research directions at the end of this talk.

 


 Spring 2013

 Winter 2013

 Fall 2012

 Spring 2012
Date Speaker Email Category
2012-05-04 Jian Qiao qiaojian1 AT gmail.com Performance
2012-05-11 Ning Lu luning.ee AT gmail.com Performance
2012-05-25 Khaled AlMotairi kalmotairi AT gmail.com Performance
2012-06-01 Muhammad Ismail m6ismail AT uwaterloo.ca Performance
2012-06-08 Miao Wang miaowang.buaa AT gmail.com Performance
2012-06-15 Khadige Abboud khabboud AT engmail.uwaterloo.ca Performance
2012-06-22 Jing Liu j.liu.sh AT gmail.com Performance
2012-06-29 Neda Mohammadizadeh n7mohammadizadeh AT uwaterloo.ca Performance
2012-07-06 Xinsheng Zhou x29zhou AT uwaterloo.ca Performance
2012-07-13 Yujie Tang y59tang AT uwaterloo.ca Performance
2012-07-27 Sandra L. Cespedes Umana slcesped AT bbcr.uwaterloo.ca Performance
2012-08-10 Xiaohui Liang x27liang AT bbcr.uwaterloo.ca Security
2012-08-17 Rongxing Lu rxlu AT bbcr.uwaterloo.ca Security
2012-08-24 Yejun He yjhe AT szu.edu.cn Performance
2012-08-31 Shimin Gong GONG0012 AT e.ntu.edu.sg Performance

 


Date/Time: 2012-08-31, 11:00 am

Speaker: Shimin Gong

Title: Spectrum Sensing under Distribution Uncertainty in Cognitive Radio Networks

Abstract:The harmonic coexistence of secondary users (SUs) and primary users (PUs) in cognitive radio networks requires SUs to identify the idle spectrum bands. One common approach to achieve spectrum awareness is through spectrum sensing, which usually assumes known distributions of the received signals. However, due to the nature of wireless channels, such an assumption is often too strong to be realistic, and leads to unreliable detection performance in practical networks. In this talk, we study the sensing performance under distribution uncertainty, i.e., the actual distribution functions of the received signals are not fully known. Firstly, we define a series of uncertainty models based on signals' moment statistics. Then we present corresponding mathematical formulations to study the detection performance with different uncertainty models. Moreover, in order to make use of the distribution information embedded in historical data, we extract a reference distribution from channel observations, and define a new uncertainty model in terms of such reference distribution. With this uncertainty model, we propose two iterative procedures to study the false alarm probability and detection probability, respectively. Numerical results show that the detection performance with a reference model is less conservative compared with that of the uncertainty models merely based on signal statistics.

 


Date/Time: 2012-08-24, 11:00 am

Speaker: Yejun He

Title: Peak-to-Average Power Ratio Reduction in FMBC-OQAM System

Abstract:The filter bank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) has attracted increasing attention recently. In this paper, we address the problem of PAPR reduction for FBMC-OQAM systems using Tone Reservation (TR) technique. Due to the overlapping structure of FBMC-OQAM signals, directly applying TR schemes of OFDM systems to FBMC-OQAM systems is not effective. We improve the tone reservation (TR) technique by employing sliding window for the PAPR reduction of FBMC-OQAM signals, called sliding window tone reservation (SW-TR) technique. The proposed SW-TR technique uses the peak reduction tones (PRTs) of several consecutive data blocks to cancel the peaks of the FBMC-OQAM signal inside a window. Furthermore, we propose a method to overlap the sliding windows to control the out-of-window peak regrowth caused by the peak-canceling signal. The simulation results show that the proposed SW-TR technique is effective in reducing the PAPR of the FBMC-OQAM signal.

 


Date/Time: 2012-08-17, 11:00 am

Speaker: Rongxing Lu

Title: Key Challenges in Cloud Computing

Abstract:Cloud computing will play a vital role in the future Internet of Services. In this talk, we will identify some key challenges in cloud computing, not only including the challenges for infrastructure providers, but also additional cross-cutting challenges, i.e., security, privacy and trust, availability and energy efficiency. In addition, some mechanism for data security in cloud computing are also discussed.

 


Date/Time: 2012-08-10, 11:00 am

Speaker: Xiaohui Liang

Title: SEER: A Secure and Efficient Service Review System for Service-oriented Mobile Social Networks

Abstract:In this talk, we introduce service-oriented mobile social networks (S-MSNs) and propose a Secure and Efficient sErvice Review (SEER) system to enable user feedback. Each service provider independently maintains a SEER system for itself, which collects and stores user reviews about its services without requiring any central trusted authority. The service reviews can then be made available to interested users in making wise service selection decisions. We identify three unique service review attacks and then develop sophisticated security mechanisms for SEER to deal with these attacks. Specifically, SEER enables users to distributedly and cooperatively submit their reviews in an integrated chain form by using hierarchical and aggregate signature techniques. It discourages service providers to reject, modify or delete their reviews. The integrity of reviews is therefore improved. Through security analysis and performance evaluation, we show that SEER effectively resists the service review attacks and achieves significantly better performance in terms of submission rate and delay than a service review system that does not adopt user cooperation or the chain review structure.

 


Date/Time: 2012-07-27, 11:00 am

Speaker: Sandra L. Cespedes Umana

Title: IP Mobility Support in Multi-hop Vehicular Communications Networks

Abstract:Vehicular communications networks are envisioned to be supported by a set of dissimilar wireless access networks and different administrative domains. The heterogeneous infrastructure will serve as the platform for the deployment of safety and infotainment applications, which will help on achieving a safer, efficient, and enjoyable transportation system. Lately, the support of infotainment services –and consequently, of IP-based applications– has drawn substantial attention. From traditional Internet-based applications and driver assistance services, to innovative peer-to-peer applications that enable the instant sharing of information between neighboring vehicles, are some of the services that will make traveling a more convenient and pleasant experience. In addition, it is expected that innovative services will incentive a faster adoption of the equipment and the supporting infrastructure required for vehicular communications. On the other hand, the combination of infrastructure-to-vehicle and vehicle-to-vehicle communications, namely the multi-hop Vehicular Communications Network (VCN), appears as a promising solution for the ubiquitous access to IP services in vehicular environments. For example, by employing multi-hop communications, the network coverage of the slowly growing infrastructure can be extended. In addition, longer bidirectional connections between road side access routers and vehicles can be established through multi-hop paths. The bidirectionality of links is a strong requirement of most IP applications, and it is difficult to be achieved when asymmetric links appear in the vehicular wireless network. Although multi-hop communications have been often proposed for disseminating safety and delay-sensitive information, the deployment of seamless infotainment traffic faces unique challenges due to the characteristics of the highly-mobile and multi-hop VCN. Not only the standards for communications in vehicular environments suffer from limitations for the deployment of IP traffic, but also the IP mobility support in VCN has traditionally focused on vehicles using one-hop connections to the infrastructure. Additional complexity is added when urban vehicular scenarios are considered, in which commuters and pedestrians actively access infotainment applications that should be freely transferrable along the heterogeneous VCN. In this thesis, we address the challenges of multi-hop VCN, and investigate the seamless provision of IP services over such network. Three different schemes are proposed and analyzed. First, we study the limitations of current standards for the provision of IP services, such as 802.11p/WAVE, and propose a framework that enables multi-hop communications and a robust IP mobility mechanism over WAVE. An accurate analytical model is developed to evaluate the throughput performance, and to determine the feasibility of the deployment of IP-based services in 802.11p/WAVE networks. Then, the IP mobility support is extended to asymmetric multi-hop VCN. The proposed IP mobility and routing mechanisms react to the asymmetric links, and also employ geographic location and road traffic information to enable predictive handovers. Moreover, since multi-hop communications suffer from security threats, it ensures that all mobility signalling is authenticated among the participant vehicles. Last, we extend our study to a heterogeneous multi-hop VCN, and propose a hybrid scheme that allows for the on-going IP sessions to be transferred along the heterogeneous communications system. The proposed global IP mobility scheme focuses on urban vehicular scenarios, and enables seamless communications for in-vehicle networks, commuters, and pedestrians. The overall performance of IP applications over multi-hop VCN are improved substantially by the proposed schemes. This is demonstrated by means of analytical evaluations, as well as extensive simulations that are carried out in realistic highway and urban vehicular scenarios. More importantly, we believe that our dissertation provides useful analytical tools, for evaluating the throughput and delay performance of IP applications in multi-hop vehicular environments. In addition, we provide a set of practical and efficient solutions for the seamless support of IP traffic along the heterogeneous and multi-hop vehicular network, which will help on achieving ubiquitous drive-thru Internet, and infotainment traffic access in both urban and highway scenarios.

 


Date/Time: 2012-07-13, 11:00 am

Speaker: Yujie Tang

Title: Decentralized Cognitive Radio Control Based on Feedback from Primary Link Control Information

Abstract:The “listen-before-talk” paradigm underlies many cognitive radio access proposals. However, in this talk, we exploit the bidirectional interaction of most primary communication links. By intelligently controlling their access parameters based on the inference from observed link control signals of primary user (PU) communications, cognitive secondary users (SUs) can achieve higher spectrum efficiency while limiting their interference to the PU network. We propose a discounted distributed power control algorithm to achieve non-intrusive secondary spectrum access without either a centralized controller or active PU cooperation. We present an analytical study of its convergence property. We show that the link control feedback information inherent in many two-way primary systems can be used as important reference signal among multiple SU pairs to distributively achieve a joint performance assurance for primary receiver’s quality of service.

 


Date/Time: 2012-07-06, 11:00 am

Speaker: Xinsheng Zhou

Title: Low-density parity-check codes for two-way relay channels

Abstract:In next generation wireless networks, we are trying to make the high bit rates available in a larger portion of the cell, especially to users in an exposed position in between several base stations. Relay gives a solution that can achieve the cooperative diversity. In this talk, we focus on the practical code design for two-way relay channels, which includes code construction, encoding and decoding algorithm, an analytic tool called density evolution and code optimization.

 


Date/Time: 2012-06-29, 11:00 am

Speaker: Neda Mohammadizadeh

Title: End-to-end Cooperative Congestion Control in Heterogeneous Wireless Networks

Abstract:As different wireless networks and services continue their growth, it is expected that multiple networks become available to the end users. With the co-existence of heterogeneous networks, communication between any two end users can be achieved through multi-path transmission. In such a scenario, ensuring a reliable end-to-end connection is necessary, while delay, congestion, and flow need to be controlled. In this presentation, we will discuss a cooperative end-to-end congestion control proposal that provides reliable packet delivery through heterogeneous wireless networks to satisfy the requested QoS. As a result, the cooperation between available networks can minimize the overall congestion over the whole association.

 


Date/Time: 2012-06-22, 11:00 am

Speaker: Jing Liu

Title: A Validation platform with CR for Wireless Body Area Network

Abstract:Wireless Body Area Networks (WBAN) has great potential to revolutionize the future health technology. The task group IEEE 802.15.6 works for the standardization of WBAN to serve a variety of medical and non-medical applications with low-power nodes. The 2.4GHz proposal is the most mature and ready for mass production. However, there are high chances of interference since many wireless devices including IEEE 802.11 and IEEE 802.15.4 operate at ISM band. This study evaluates WBAN works on 2.4 GHz under WiFi interference and introduces cognitive radio access technology to improve the performance of the network. Currently, most existing works on CR focus on theoretical analysis and software simulation without verifying feasibility and performance in practical network scenario. In this study, we develop a hybrid cognitive validation platform for WBAN to realize the practical situations by integration computer software and hardware devices. The experiment shows that close approximation to real situation is achieved by scenario validation on the validation platform and the introduction of CR algorithm significant alleviate the negative impact of collision caused by interference and improve system performance.

 


Date/Time: 2012-06-15, 11:00 am

Speaker: Khadige Abboud

Title: Node Cluster Stability in Vehicular Ad hoc Networks

Abstract: Vehicles are envisioned to be equipped with on-board communication capabilities in the near future. This will enable communication among vehicles and road-side units in a vehicular ad hoc network (VANET). The envisioned VANET will enhance the intelligent transportation systems (ITS) and support not only public-safety applications, but also a wide range of infotainment applications. However, the deployment of VANETs requires designing the necessary networking protocols, such as for routing and medium access control, that guarantee efficient and reliable communications among vehicles and road side units. Urban roads and highways are highly susceptible to a large number of vehicles and traffic jams. Therefore, the networking protocols for VANETs should be scalable to support such large sized networks. Node clustering (i.e., organizing the network into smaller groups of nodes), just as in traditional ad hoc networks, is a potential approach to improve the scalability of networking protocols such as for routing and medium access control in VANETs. Unlike traditional networks, the high node mobility in VANETs causes frequent network topology changes and fragmentations. Consequently, forming and maintaining stable clusters in VANETs are challenging tasks. Although many recent clustering approaches have been proposed in the VANET literature, the theoretical basis for cluster stability has not been firmly founded. In this proposal, we present three steps of studying cluster stability for VANETs: i) determining the steady-state cluster characteristics (cluster size and cluster overlap) that maximize the performance of generic routing and medium access control; ii) modelling the time variation of cluster characteristics due to vehicle mobility; and iii) analysing the impact of stable clustering on the performance of network protocols. For the first step, we have analysed the impact of some cluster characteristics on the generic routing overhead using steady-state mobility models. Preliminary results present some cluster characteristics that minimize the routing overhead.

 


Date/Time: 2012-06-08, 11:00 am

Speaker: Miao Wang

Title: Capacity and Delay Analysis Exploiting Mobility Diversity in VANETs

Abstract: Improving road safety and traffic efficiency has been a long-term endeavor for not only government but also automobile industry and academia. After the U.S. Federal Communication Commission (FCC) allocated a 75 MHz spectrum at 5.9 GHz for vehicular communications , a vehicular ad hoc network (VANET), as an instantiate of the mobile ad hoc network (MANET), opens a new door to combat the road fatalities. In VANETs, a variety of applications ranging from safety related (e.g. emergency report, collision warning) to non-safety related (e.g. information sharing) can be enabled by vehicle-to-vehicle (V-2-V) and vehicle-to-roadside (V-2-I) communications. However, the flourish of VANET still hinges up fully understanding and managing the challenges that the public concerns, for example, capacity and connectivity issues. Over the past years, several works have considered VANET's unique characteristics and addressed some capacity and message delivery issues in VANETs. However, as we know, none of them take the mobile characteristic differentiation among vehicles into consideration. We demonstrate that with the involvement of the mobility differentiation-based protocols in VANETs, both the infected time of safety message-transmission, and the network capacity, will present enhanced. In this proposal, we will emphasize VANET's characteristics and present the concept of hybrid VANETs. The main objectives are Q1) using mobility characteristics of vehicle to study the mobility differentiation; Q2) addressing the achievable asymptotic throughput capacity in hybrid VANETs; Q3) developing an efficient mobility differentiation-based nonsafety-related routing protocol to achieve that capacity scaling law; Q4) proposing a mobility differentiation-based safety-related broadcasting protocol and analyze the infected time. Further, the future research is also addressed in the proposal, which includes four main parts: 1) based on the aforesaid model, we will show the infected time delay analysis and the resource allocation problems; 2) the path planning for vehicles will be proposed to attain the optimal traffic flow with the mobility diversity based-broadcasting protocol; 3) we will propose a novel secure and privacy-preserving broadcasting/routing scheme for VANETs; 4) with revealing the unique characteristics in other networks, to develop the mobility diversity in other different networks is regarded as another future work.

 


Date/Time: 2012-06-01, 11:00 am

Speaker: Muhammad Ismail

Title: Cooperation in wireless communication networks

Abstract: The concept of cooperation in wireless communication networks has drawn significant attention recently from both academia and industry as it can be effective in addressing the performance limitations of wireless networks due to user mobility and the scarcity of network resources. In this presentation, we aim to shed some light on potential benefits of such an approach and discuss its challenging issues. We focus on three cooperation scenarios, namely, cooperation to improve channel reliability through spatial diversity, cooperation to improve throughput through resource aggregation, and cooperation to achieve seamless service provision. Challenging issues which arise at different layers of the network protocol stack are discussed, with an emphasis on the medium access control, network, and transport layers. We also present some future research directions in this area.

 


Date/Time: 2012-05-25, 11:00 am

Speaker: Khaled Almotairi

Title: Design and Performance Evaluation of Multi-channel Ad Hoc Wireless Networks

Abstract: In the past decade, the development of wireless communication technologies has made the use of the Internet ubiquitous. With the increasing number of new inventions and applications using wireless communication, more interference is introduced among wireless devices that results in limiting the capacity of wireless networks. Many approaches have been proposed to improve the capacity. One approach is to exploit multiple channels by allowing concurrent transmissions, and therefore it can provide high capacity. Many available, license-exempt, and non-overlapping channels are the main advantages of using this approach. Another approach that increases the network capacity is to adjust the transmission power; hence, it reduces interference among devices and increases the spatial reuse. Integrating both approaches provides further capacity. However, without careful transmission power control (TPC) design, the network performance is limited. The first part of this thesis tackles the integration to efficiently use multiple channels with an effective TPC design in a distributed manner. We examine the deficiency of uncontrolled asymmetrical transmission power in multi-channel ad hoc wireless networks. To overcome this deficiency, we propose a novel distributed transmission power control protocol called the distributed power level (DPL) protocol for multi-channel ad hoc wireless networks. DPL allocates different maximum allowable power values to different channels so that the nodes that require higher transmission power are separated from interfering with the nodes that require lower transmission power. As a result, nodes select their channels based on their minimum required transmission power to reduce interference over the channels. We also introduce two TPC modes for the DPL protocol: symmetrical and asymmetrical. For the symmetrical mode, nodes transmit at the power that has been assigned to the selected channel, thereby creating symmetrical links over any channel. The asymmetrical mode, on the other hand, allows nodes to transmit at a power that can be lower than or equal to the power assigned to the selected channel. In the second part of this thesis, we propose the multi-channel MAC protocol with hopping reservation (MMAC-HR) for multi-hop ad hoc networks to overcome the multi-channel exposed terminal problem, which leads to poor channel utilization over multiple channels. The proposed protocol is distributed, does not require clock synchronization, and fully supports broadcasting information. In addition, MMAC-HR does not require nodes to monitor the control channel in order to determine whether or not data channels are idle; instead, MMAC-HR employs carrier sensing and independent slow channel hopping without exchanging information to reduce the overhead. In the last part of this thesis, a novel multi-channel MAC protocol is developed without requiring any change to the IEEE 802.11 standard known as the dynamic switching protocol (DSP) based on the parallel rendezvous approach. DSP utilizes the available channels by allowing multiple transmissions at the same time and avoids congestion because it does not need a dedicated control channel and enables nodes dynamically switch among channels. Specifically, DSP employs two half-duplex interfaces: One interface follows fast hopping and the other one follows slow hopping. The fast hopping interface is used primarily for transmission and the slow hopping interface is used generally for reception. Moreover, the slow hopping interface never deviates from its default hopping sequence to avoid the busy receiver problem. Under single-hop ad hoc environments, an analytical model is developed and validated. The maximum saturation throughput and theoretical throughput upper limit of the proposed protocol are also obtained.

 


Date/Time: 2012-05-11, 11:00 am

Speaker: Ning Lu

Title: The Quest for Asymptotic Performance Limits of Vehicular Ad Hoc Networks

Abstract: This research proposal investigates asymptotic performance limits, i.e., network capacity and delay, of VehiculAr NETworks (VANETs) . The problem is of great importance since fundamental guidance on design and deployment of VANETs is very limited. Moreover, unique characteristics of VANETs impose distinguished challenges on such investigation. In the proposal, we first study the unicast capacity and average packet delay considering social-proximity feature of VANETs. Specifically, the network involves N vehicles moving and communicating on a scalable grid-like street layout following the social-proximity model: each vehicle has a restricted mobility region around a specific social spot, and transmits via a unicast flow to a destination vehicle which associates with the same social spot. Moreover, the spatial distribution of the vehicle decays following a power-law distribution from the central social spot towards the border of the mobility region. With vehicles communicating using a variant of the two-hop relay scheme, the asymptotic bounds of throughput capacity and average packet delay are derived in terms of the number of social spots, the size of the mobility region and the decay factor of the power-law distribution. By identifying these key impact factors of performance mathematically, our results can be applied to predict the network performance of real-world scenarios of VANETs. Secondly, we propose to investigate downlink capacity and delay of VANETs in the presence of cellular base stations, roadside access points, and wireless mesh backbone, respectively. After that, tradeoffs between cost and performance need to be considered for these three types of infrastructure. Lastly, considering the primary goal of vehicular networks to support safety message disseminations, we propose to study the real-time capacity of a safety signaling system, in which only safety applications run on top of VANETs. The results of this research can provide insight on the design and deployment of future VANETs.

 


Date/Time: 2012-05-04, 11:00 am

Speaker: Jian Qiao

Title: Medium Access Control for Millimeter Wave Networks with Directional Antenna

Abstract: Millimeter-wave (mmWave) communications is a promising enabling technology for high rate (multi-Gigabit) multimedia applications due to the large available bandwidth. It provides great potential for a variety of broadband multimedia applications. In order to effectively and efficiently utilize the wireless medium among multiple users with various quality of service (QoS) requirements, a simple but robust, efficient and fair sharing medium access control (MAC) protocol for the future mmWave network will be in high demand. Current MAC protocols have been designed for narrowband systems supporting applications with lower transmission data rate. They can not be applied to mmWave networks supporting multimedia applications with stringent QoS requirements. The unique features of mmWave communication (e.g., large bandwidth, high propagation loss, and utilization of directional antenna) also make mmWave networks different from other wireless networks. There is an increasing interest in the MAC protocol design for mmWave networks to support multimedia applications with high data rate requirements and performance guarantee. The proposed research is to design an efficient MAC taking into consideration the salient features provided by mmWave networks and various QoS requirements of multiple services. In this proposal, we first present the system model of the mmWave networks, as the research platform. The unique features of mmWave system (e.g., vulnerable channel, high propagation loss, and various types of applications) bring challenges on realizing reliable multi-Gbps transmissions, such as short coverage, link blockage, throughput limitation and QoS variance. To deal with these challenges, some important research issues related to MAC are investigated, concurrent transmission scheduling, beamforming, multi-hop transmission, integration of multiple radio bands, and multi-packet transmission/reception (MPTR). The motivations of these research issues are to increase the network capacity, extend transmission range, keep network connectivity, and provide various QoS requirements for applications. The problems and performance constraints when applying these issues in mmWave networks are pointed out. In addition, the possible solutions are proposed taking into consideration the characteristics of mmWave networks. Researches on concurrent transmission scheduling in mmWave networks are conducted by formulating it as an optimization model to maximize the number of flows scheduled in the network such that the quality of service (QoS) requirement of each flow is satisfied. The optimization model is decomposed and solved by a flip-based heuristic scheduling algorithm with low computational complexity. Extensive simulations demonstrate that the proposed algorithm can significantly improve the network performance in terms of network throughput and the number of supported flows. In the future, to complete the thesis, the MAC layer researches on multi-hop transmission, beamforming, multiple radio band integration, and MPTR, would be conducted to utilize the resource efficiently and achieve reliable multi-Gbps transmission for mmWave networks.

 


 Winter 2012

 Fall 2011
Date Speaker Email Category
2011-09-02 Xiaohui Liang x27liang AT bbcr.uwaterloo.ca Security
2011-09-09 Mrinmoy Barua mbarua AT ecemail.uwaterloo.ca Security
2011-09-16 Mohammad Towhidul Islam towhid.uwaterloo AT gmail.com Performance
2011-09-23 Yong Zhou zhouyongccmip AT gmail.com Performance
2011-09-23 Kuan Zhang garnekuan AT gmail.com Performance
2011-09-30 Tom Luan hluan AT bbcr.uwaterloo.ca Performance
2011-10-05 Prof. shigang Chen (Invited) sgchen AT cise.ufl.edu RFID
2011-10-07 Bin Cao caobinhit AT gmail.com CRN
2011-10-14 Younghyun Kim m.s.yhkim AT gmail.com Mobility
2011-10-21 Sandra Cespedes slcesped AT uwaterloo.ca Smartgrid
2011-10-28 Renyong Wu wurenyong AT gmail.com Mobility
2011-11-04 Ran Zhang zhangran2006 AT gmail.com Performance
2011-11-11 Zhongming Zheng forezero AT gmail.com Performance
2011-11-18 Sanaa Taha staha AT uwaterloo.ca Security
2011-11-25 Khadige Abboud khabboud AT engmail.uwaterloo.ca Performance
2011-12-02 Ning Zhang zhangningbupt AT gmail.com CRN
2011-12-09 Miao Wang miaowang.buaa AT gmail.com VANET
2011-12-16 Ning Lu n7lu AT uwaterloo.ca Performance
2011-12-23 Sailesh Bharati sbharati AT bbcr.uwaterloo.ca VANET

 


Date/Time: 2011-12-23, 10:30 am

Speaker: Sailesh Bharati

Title: Cooperative ADHOC MAC (CAH-MAC) for Vehicular Ad Hoc Networks

Abstract: Due to the rapid advancement in wireless communication and automotive industry, the paradigm of vehicular ad-hoc networks (VANETs) emerges as a promising approach to provide road safety, vehicle traffic management and other infotainment applications. Cooperative communication on the other hand can enhance reliability of a communication link between nodes in VANETs, to mitigate wireless channel impairments. In this paper, we present a cooperative scheme for ADHOC MAC protocols in VANETs, referred as Cooperative ADHOC MAC (CAH-MAC). In CAH-MAC, neighboring nodes cooperate in utilizing a unreserved time slot for retransmitting of a packet which failed to reach the receiver due to a poor channel condition. Through mathematical analysis and simulation, we show that our scheme increases throughput of the network by using unreserved time slots for the cooperation.

 


Date/Time: 2011-12-16, 11:00 am

Speaker: Ning Lu

Title: A Primer on Spatial Modeling and Analysis in Wireless Networks

Abstract: The performance of wireless networks depends critically on their spatial configuration, because received signal power and interference depend critically on the distances between numerous transmitters and receivers. This is particularly true in emerging network paradigms that may include femtocells, hotspots, relays, white space harvesters, and meshing approaches, which are often overlaid with traditional cellular networks. These heterogeneous approaches to providing high-capacity network access are characterized by randomly located nodes, irregularly deployed infrastructure, and uncertain spatial configurations due to factors like mobility and unplanned user-installed access points. This major shift is just beginning, and it requires new design approaches that are robust to spatial randomness, just as wireless links have long been designed to be robust to fading. The objective of this talk is to illustrate the power of spatial models and analytical techniques in the design of wireless networks, and to provide an entry-level tutorial.

 


Date/Time: 2011-12-09, 11:00 am

Speaker: Miao Wang

Title: Capacity analysis in VANET

Abstract: In vehicular ad hoc network (VANET), improving uploading efficiency is crucial to enabling the copious applications such as reporting sensed data for traffic management or environment monitoring. Depending on the applications the contents to be uploaded can be of large volume, therefore there exist the fundamental demands of the delivery with high throughput. We derive the achievable capacity scaling law for such applications in VANET as $\Theta (\frac{1}{{\log n}})$, with the number of road-side units scaling as $\Theta (\frac{n}{{\log n}})$. Furthermore, by exploring the mobility diversity among vehicles, we propose a novel two-hop forwarding scheme to make the network throughput approach to the throughput scaling law. In specific, the source node distributes the contents to multiple relay nodes with the largest mobility diversity so that the number of concurrent transmissions can be increased. The simulation results demonstrate the effectiveness of the proposed transmission scheme in terms of increasing network throughput.

 


Date/Time: 2011-12-02, 11:00 am

Speaker: Ning Zhang

Title: Energy-Efficient and Trust-aware Cooperation in Cognitive Radio Networks

Abstract: A cooperative framework in cognitive radio networks, which addresses energy efficiency of the primary users (PUs) and trustworthiness of secondary users (SUs), is proposed. Specifically, the cooperation involves a PU selecting the most suitable SU as the cooperative relay and allocating the spectrum access intervals for relaying its message and rewarding the SU for its help in relaying the PU’s message. Based on the PU’s strategy, the selected SU determines its optimal transmission power. The above sequential decision procedure, with the PU as the leader and the SU as the follower, is formulated as a Stackelberg game. The outcomes of the proposed cooperative strategy, including partner selection, cooperation in an untrustworthy environment, and energy efficiency consideration, are analyzed. Numerical results show that, with the proposed relay selection scheme, the PU can achieve high energy saving through cooperation with the trustworthy SU.

 


Date/Time: 2011-11-25, 11:00 am

Speaker: Khadige Abboud

Title: Vehicular traffic flow models: an overview

Abstract: Unlike traditional ad hoc networks, the high mobility of nodes in vehicular ad hoc networks (VANETs) imposes new challenges on the design of efficient network protocols for VANETs. This calls for a careful study for the VANET structure, i.e., the movement scenario of vehicles. Traffic flow characteristics such as congestion times and locations are very important metrics for decision making in traffic management, road designs, and transit scheduling. Thus, modelling vehicular traffic flow has taken great attention from researchers in civil engineering for many years.The evolution of the proposed vehicular traffic flow models has been towards a more realistic representation of the traffic flow. In general, the vehicular traffic flow models can be categorized into three types (microscopic, mesoscopic, and macroscopic) according to the level of details the model reveals about the vehicles behaviour on road. In this talk we will go over some of the proposed traffic flow models in literature. Adopting the right vehicular traffic flow model will enhance the analysis/evaluation of network protocols in VANETs.

 


Date/Time: 2011-11-18, 11:00 am

Speaker: Sanaa Taha

Title: EM3A: Efficient Mutual Multi-hop Mobile Authentication Scheme for PMIP Networks

Abstract: Mobile wireless networks are envisioned to support multi-hop communications to boost the network coverage and improve services availability. A multi-hop-enabled Proxy Mobile IP (PMIP) scheme helps in providing seamless communications, so that a roaming mobile node may use relay nodes without breaking its active IP sessions. Although existing authentication schemes use relay nodes to forward authentication credentials between mobile node (MN) and the point of attachment, a mutual authentication between MN and relay node (RN) is still required to early prevent authentication attacks. The difficulty of generating a security association between two arbitrary nodes, MN and RN, makes proposing a preserving authentication scheme a challenge. In this research, we propose EM3A, a novel mutual authentication scheme that guarantees the authenticity of both MN and RN. EM3A thwarts authentication attacks, including DoS, colluding, impersonating, replay, and man-in-themiddle attacks. EM3A works in conjunction with a proposed scheme for key establishment, based on symmetric polynomials, to generate a shared secret key between MN and RN. This scheme achieves lower revocation overhead than that achieved by existing symmetric polynomial-based schemes. For a PMIP domain with n points of attachment, our scheme achieves t x 2^n secrecy, whereas the existing symmetric polynomial-based authentication schemes achieve only t-secrecy. Computation and communication overhead analysis, as well as simulation results, show that EM3A achieves low authentication delay and is suitable for seamless multi-hop IP communications.

 


Date/Time: 2011-11-11, 11:00 am

Speaker: ZhongMing ZHENG

Title: RNP-SA: Joint Relay Placement and Sub-carrier Allocation in Green Radio Communication Networks with Sustainable Energy

Abstract: Green energy has been emerging as a promising alternative energy source to power wireless communication networks, including base stations (BSs) and relay nodes (RNs). Unlike the traditional energy sources, green energy is renewable and sustainable in nature while its capacity and availability are variable and dependent on the location and weather. In this paper, network deployment and resource allocation issues are re-visited in a two-tiered wireless communication network (BSs, RNs, and wireless users) with an energy sustainability constraint. Specifically, the deployment of green RNs, i.e., nodes powered by green energy, and sub-carrier allocation are jointly studied to provide full network coverage and fulfill mobile users’ quality of service (QoS) requirements. To this end, the RN placement and sub-carrier allocation (RNP-SA) issues are jointly formulated into a mixed integer non-linear programming problem. The objective is to use a minimal number of green RNs, along with the existing green BSs, to fulfill the QoS requirements of all users, by allocating an appropriate set of sub-carriers to each RN and BS and ensuring the harvested energy can sustain the users’ traffic demands. Two low-complexity heuristic algorithms, namely, RNP-SA with top-down/bottom-up approaches (RNP-SA-t/b) are presented and analyzed in different network scenarios. Extensive simulations show that the proposed algorithms provide simple yet efficient solutions and offer important guidelines on network deployment and management in a green radio network with sustainable energy sources.

 


Date/Time: 2011-11-04, 11:00 am

Speaker: Ran Zhang

Title: Interworking in heterogeneous wireless networks: Introduction and Future Trends

Abstract: As the deployment of various wireless technologies (2G, 3G, WLAN, WiMAX, etc.) in combination with the evolution of Mobile Terminals(MTs) with multiple network interfaces and the development of IP-based applications (non-real-time and real-time), the future fourth generation(4G) of wireless networks are well accepted to be heterogeneous, integrating different networks to provide seamless Internet access for mobile users with multimode access capability. Specifically, handover management is one of most important and impending issues to be considered. In this presentation, we will first show the overall procedure of vertical handover between different wireless access technologies, followed by the introduction of forthcoming link layer standard 802.21 and IP layer protocol Mobile IP that support seamless mobility. At last, resource management and decision strategies in handover prepration phase will be elaborated in a high level.

 


Date/Time: 2011-10-28, 11:00 am

Speaker: Renyong Wu

Title: Overlapping communities in dynamic networks: detection & applications

Abstract: Many practical problems on mobile networks, such as routing strategies in MANETs and sensor reprogramming in WSNs in online social networks (OSNs) share a ubiquitous, yet interesting feature in their organizations: community structure. Knowledge of this structure provides us not only crucial information about the networks principles, but also key insights into designing more effective algorithms for practical problems. This presentation tries to answer two questions: 1) how to detect the overlapping community structure in dynamic network? 2) how to apply the overlapping community structure in designing algorithms.

 


Date/Time: 2011-10-21, 11:00 am

Speaker: Sandra Cespedes

Title: Enabling smart electric networks: A walk through the Smart Grid communication technologies and standards

Abstract: Smart electric networks, also known as Smart Grids, are a set of technologies that enable a more reliable and efficient electricity supply system, a better operation and connection of different power generators, a better participation of consumers in the optimization of the energy system, and a better distribution of the available electricity power. During this talk, we will discuss about the different communication technologies and standards that allow for the development of Smart Grid technologies, with a particular emphasis on those related to Advance metering infrastructure (AMI) networks, such as IEEE 802.15.4g and 6LoWPAN. We will also introduce our work about the evaluation of different forwarding mechanisms for routing in unreliable AMI networks, and our proposal of a framework to enable IP communications in mobile Vehicle to Grid communications.

 


Date/Time: 2011-10-14, 11:00 am

Speaker: Younghyun Kim

Title: Dynamic Bandwidth Allocation in Mobile Hotspots

Abstract: In this work, we will develop a dynamic bandwidth allocation (DBA) scheme considering the mobility in mobile hotspots. Specifically, mobility in mobile hotspots can be categorized into two types: 1) host mobility, and 2) vehicle mobility. Host mobility is a getting on (off) event when a vehicle stops at a station. In the case of vehicle mobility, a vehicle moving from a BS to another BS is defined as a handoff vehicle. On the other hand, a vehicle newly entering into a BS’s region, e.g., a vehicle from a bus terminal, is called by a new vehicle. First, to provide each vehicle fair bandwidth allocation, we have conducted DBA based on host mobility which is able to affect the number of passengers in each vehicle. Also, we will consider vehicle mobility where handoff vehicles should have a higher priority than new vehicles. Finally, the overall DBA scheme with both host mobility and vehicle mobility will be completed during my visit period in Waterloo.

 


Date/Time: 2011-10-07, 11:00 am

Speaker: Bin Cao

Title: Towards Efficient Radio Spectral Utilization: User Cooperation in Cognitive Radio Networking

Abstract: To improve radio spectral efficiency in the wireless network, cognitive radio networking (CRN) is a promising approach. In CRN, there can be dynamic spectrum-sensing access (DSA) and cooperative networking access (CNA) frameworks for secondary users (SUs) to occupy spectrum bands which are licensed to primary users (PUs). For DSA framework, the randomness of transmission opportunity, accurate sensing, interference, and high energy consumption are considerably challenging. To tackle these issues, CNA is an effective framework for CRN, since the SU's transmission opportunity can be offered by the PU for service done for the PU, e.g., by relaying the PU's traffic, or by leasing a spectral band from an inactive PU. In this presentation, the proposed cooperation scheme in CNA is introduced. Specifically, a quadrature signaling based two-phase cooperation between active PUs and SUs is firstly discussed, wherein, the optimization problem is formulated as a weighted sum throughput maximization, and a cross-layer multi-user coordination is presented. Cooperative leasing scheme between inactive PUs and SUs is also addressed. In the cooperative leasing scheme, the secondary base station (SBS) leases spectrum bands from inactive PUs, and then SUs lease spectrum from the SBS and perform cooperative communications with other SUs. Finally, throughput performance under cooperation is evaluated and demonstrated.

 


Date/Time/Location: 2011-10-05, 3:00 pm - 4:00 pm, EIT 3142

Speaker: Prof. Shigang Chen invited by Prof. Zhuang

Title: Recent Advance in Application-level Protocol Design for RFID Systems

Abstract: RFID (radio frequency identification) technologies are expected to revolutionize warehouse management and exert a profound impact on our daily lives. Comparing with barcodes that have to be read from a very close range by a laser scanner, RFID tags have great advantages: they can be read wirelessly over a distance, and can perform simple computations. RFID technologies have many important applications in automatic toll payment, access control to parking garages, object tracking, and theft prevention. In this talk, we will discuss recent advance in application-level protocols design for RFID systems. We will cover an array of interesting problems, including missing-tag detection, dynamic information collection, tag number estimation, and reading throughput improvement. In particular, we will focus on sensor-augmented RFID systems. After RFID tags are deployed to make the attached objects wirelessly identifiable, a natural next step is to invent new ways to benefit from this "infrastructure". For example, sensors may be added to these tags to gather real-time information about the state of the objects or about the environment where these objects reside. This leads to the problem of designing efficient protocols to collect such information from tags. It is a new problem that existing work cannot solve well. A series of newly developed protocols are able to collect information from sensor-augmented tags with nearly optimal performance in terms of protocol execution time and energy expenditure. The latter is particularly important for battery-powered active tags.

 


Date/Time: 2011-09-30, 11:00 AM

Speaker: Tom Luan

Title:MAC in Motion, Video in Motion and Multimedia in Motion: Delivering Differential Services in Drive-Thru Internet

Abstract: The pervasive adoption of IEEE 802.11 radios in the past decade has made possible for the easy Internet access from a vehicle, notably drive-thru Internet. However, originally designed for the static indoor applications, the performance of IEEE 802.11 in the outdoor vehicular environment is still unclear especially when a large number of fast-moving users transmitting simultaneously. In this talk, we first discuss on the throughput performance of fundamental IEEE 802.11 DCF in the in-motion drive-thru Internet scenario. Due to the high mobility and transient connectivity of vehicles, we show that the DCF MAC should be adaptively adjusted according to the node velocities. We then extend to investigate on performance the EDCA MAC in delivering the multimedia services to drive-thru Internet. Lastly, based on the Interrupted and variable download throughput of vehicles, we describe the adaptive mechanisms to achieve smooth video delivery to in-motion vehicular users.

 


Date/Time: 2011-09-23, 11:30 AM

Speaker: Kuan Zhang

Title:Wireless computing

Abstract: Wireless computing is the fusion of wireless communication, computing and sensing. With the challenges emerging, energy consumption, unknown and unreliability, and sensing requirements should be considered in both theoretical issues and practical applications. The related work focuses on these challenges. Routing, localization in wireless sensor network, and sensing in wireless body area network are conducted in both theoretical research and practical implementation. Finally, the outlook of wireless computing is proposed.

 


Date/Time: 2011-09-23, 11:00 AM

Speaker: Yong Zhou

Title:Cooperative Cross-layer MAC Protocol for Wireless Multi-Hop Ad-Hoc Networks

Abstract: In this presentation, I will talk about a novel link-utility-based cooperative MAC (LC-MAC) protocol for wireless multi-hop networks. By fully utilizing the broadcast nature of wireless multi-hop networks, the node that has overheard data packets in the previous hop may become a partner of the transmitter in the current hop. As diversity gain can be achieved by virtual antenna array formed by transmitter and partner, one-phase cooperative transmission is introduced to improve the throughput. In LCMAC, based on the instantaneous channel measurements, each node tries to maximize its own link-utility (indicator of a node’s ability to cooperate) by jointly adjusting transmission rate and power. Subsequently, distributed backoff procedure is activated to select the best node that has the maximum link-utility. The optimal transmission type, rate and power are uniquely determined by the best node. Since only local information is required, LC-MAC is a completely distributed protocol. Finally, extensive simulations are performed to investigate the impact of scenario and protocol parameters on the performance of LCMAC.

 


Date/Time: 2011-09-16, 11:00 AM

Speaker: Mohammad Towhidul Islam

Title:Collaborative Data Access and Sharing in Mobile Distributed Systems

Abstract: Data/content dissemination among the mobile devices is the fundamental building block for all the applications in wireless mobile collaborative computing, known as mobile peer-to-peer (MP2P). Different parameters such as node density, scheduling among neighboring nodes, mobility pattern, and node speed have a tremendous impact on data diffusion in an MP2P environment. We have developed analytical models for object diffusion time/delay in a wireless mobile network to apprehend the complex interrelationship among these different parameters. In the analysis, we calculate the probabilities of transmitting a single object from one node to multiple nodes using the epidemic model of spread of disease. We also incorporate the impact of node mobility, radio range, and node density in the networks into the analysis. Utilizing these transition probabilities, we construct an analytical model based on the Markov process to estimate the expected delay for diffusing an object to the entire network both for single object and multiple object scenarios. We then calculate the transmission probabilities of multiple objects among the nodes in wireless mobile networks considering network dynamics. Through extensive simulations, we demonstrate that the proposed scheme is efficient for data diffusion in mobile networks.

 


Date/Time: 2011-09-09, 11:00 AM

Speaker: Mrinmoy Barua

Title:Security and Privacy Preservation in eHealth Care System

Abstract: Recently electronic health (eHealth) care system has drawn a lot of attention from the research community and the industry to face the challenges of rapidly growing elderly population and rapidly rising health care spending. Recent advances in wireless body area networks (WBANs) have made it possible to deploy wearable sensors on the bodies of patients in a residential setting or a mobile setting, allowing continuous monitoring of physiological signals (such as electrocardiogram (ECG), blood oxygen levels) and other health related information (such as physical activity levels). Integrating this technology with existing 3G or future 4G wireless technologies permits real-time mobile and permanent monitoring of patients, even during their daily normal activities. In such a heterogeneous wireless environment, secure communication of the patient PHI with data integrity and confidentiality guarantees is an essential part of a reliable eHealth care system. In addition, instead of storing the PHI locally, the recent advancement of cloud computing allows us to store all PHI at cloud storage and ensures availability with reduces the capital and operational expenditures. However, electronic PHI stored at the third party cloud storage are open to potential abuse and security threats. Stored data confidentiality with patient-centric access control is considered as one the biggest challenges raised by cloud storage used in eHealth care system. In this presentation, I will describe the overall eHealth care system and its possible application scenarios. This presentation contains interrelated secure communication in WBAN, trust-based secure data forwarding, and patient-centric data access control policy. A proposed on-demand routing protocol in an Ad-hoc Network for eHealth application will be presented, where cooperative mobile users forward PHI towards health-service-provider. Finally, extensive security and performance analyses of the proposed work will be shown.

 


Date/Time: 2011-09-02, 11:00 AM

Speaker:Xiaohui Liang

Title: Enabling Pervasive Healthcare with Privacy Preservation in Smart Community

Abstract: Smart community is an emerging Internet of Things application. It supports a variety of high-value automated services such as pervasive healthcare through a multi-hop community network of smart homes in a local residential region. In this paper, we study privacy preserving data communication between patients and an online healthcare provider (referred to as vender) for efficient remote healthcare monitoring (RHM) in a smart community environment. We propose to adopt patients attribute structure instead of their identities for authentication and preserve identity privacy during patient-to-vender communication, and we suggest to build a receiver chain among smart homes to enable vender-to-patient communication and achieve location privacy. The privacy preserving properties of the proposed data communication scheme are analyzed, and its effectiveness and efficiency are demonstrated through extensive simulation.

 


 Spring 2011

 Winter 2011
Date Speaker Email Category
2011-01-07 Mohamed Elsalih Mahmoud moh.elsalih AT gmail.com Security
2011-01-14 Xiaohui Liang x27liang AT bbcr.uwaterloo.ca Security
2011-01-21 Bin Cao caobinhit AT hotmail.com Performance
2011-01-28 Jian Qiao qiaojian1 AT gmail.com Performance
2011-02-04 Xu Li easylix AT gmail.com Algorithm
2011-02-11 Qinghua Shen q2shen AT uwaterloo.ca Performance
2011-02-18 Sanaa Taha staha AT engmail.uwaterloo.ca Security
2011-02-25 Rongxing Lu rxlu AT bbcr.uwaterloo.ca Security
2011-03-04 Shan Chang cschangshan AT gmail.com Security
2011-03-11 Mohamed Elsalih Mahmoud moh.elsalih AT gmail.com Security
2011-03-15 Prof. Nasir Ghani nghani AT ece.unm.edu Performance
2011-03-18 David (Bong Jun) Choi bjchoi AT engmail.uwaterloo.ca Performance
2011-03-18 Mahdi Asefi
masefi AT engmail.uwaterloo.ca Performance
2011-03-25 Ning Lu n7lu AT uwaterloo.ca Performance
2011-04-01 Hao Liang h8liang AT ecemail.uwaterloo.ca Performance
2011-04-08 Prof. Yanchao Zhang yczhang AT asu.edu Security
2011-04-29 Muhammad Ismail m6ismail AT uwaterloo.ca Performance

 


Date/Time: 2010-04-29, 11:00 AM

Speaker:Muhammad Ismail

Title: Cooperative radio resource management in heterogeneous wireless access medium

Abstract: Currently, there exist different wireless networks that offer a variety of access options. Such wireless access networks include the cellular systems, the IEEE 802.11 wireless local area networks (WLANs), and the wireless metropolitan area networks (WMANs). With overlapped coverage areas from these networks, cooperative radio resource management will lead to better service quality to mobile users and enhanced performance for the networks. In this talk, I will present a cooperative radio resource management framework which addresses: bandwidth allocation to support applications with high required data rate, call admission control and power control to achieve energy saving in green radio communications. Also, I will present some preliminary research work related to cooperative bandwidth allocation to support mobile terminals with multi-homing capabilities in heterogeneous wireless access medium.

 


Date/Time: 2010-04-08, 14:00 PM

Speaker:Prof. Yanchao Zhang invited by Prof. Zhuang

Title: Secure Data Access in Remote Sensor Networks

Abstract: Sensor networks are large-scale multi-hop wireless networks consisting of densely deployed, spatially distributed, and autonomous devices using sensors to cooperatively monitor biological, physical, or environmental phenomena. Many sensor networks are envisioned to be deployed in remote and extreme areas such as oceans, mountains, and deserts, where there is no stable high-speed communication link connecting a sensor network to the outside data center. The sheer amount of data continuously generated thus must be stored inside the network and queried on demand. Security and privacy issues are the key factors that determine the proper functioning and dependability of remote sensor networks and thus have recently drawn significant attention from the research community. This talk will focus on two critical security and privacy issues in remote sensor networks. Specifically, I will first discuss how to realize distributed privacy-preserving access control such that only authorized users can access the sensed data, while no one, including the network owner, can tell the identity of any user. This issue is important for data users who are sensitive to the disclosure of their data access patterns which may be used against their interest. Then I will illustrate how a data user can verify the correctness of any data-query result by taking multidimensional range queries as an example. This issue is also critical especially when the data- query results are the basis for making critical military or business decisions. Our results can push wireless sensor networks towards a more dependable solution to data sensing in remote and extreme environments.

 


Date/Time: 2010-04-01, 11:00 AM

Speaker:Hao Liang

Title: DRMAC: Double-Loop Receiver-Initiated MAC for Cooperative Data Dissemination via Roadside WLANs

Abstract: In this talk, we discuss data dissemination in delay tolerant networks (DTNs) via roadside wireless local area networks (RS-WLANs). The data dissemination service is destined to a group of nomadic nodes roaming in a large network region with low node density. The local nodes within the coverage area of an RS-WLAN can provide packet caching and relaying capabilities. We present a cooperative data dissemination approach where information packets are first pre-downloaded to the local nodes within the RS-WLAN before the visit of a nomadic node, and then opportunistically scheduled to transmit to the nomadic node upon its arrival. In order to resolve the channel contention among multiple direct/relay links and exploit the predictable traffic characteristics as a result of packet pre-downloading, a double-loop receiver-initiated medium access control (DRMAC) scheme is proposed. The MAC scheme can achieve spatial and temporal diversity based on the outer-loop and inner-loop MAC, respectively. A receiver initiated mechanism is used to reduce the MAC overhead, where the ACK message is used as an invitation of channel contention. An analytical model is established to evaluate the performance of the proposed MAC scheme. Numerical results indicate that the proposed MAC scheme can significantly improve the average number of delivered packets from an RS-WLAN to a nomadic node as compared with the existing MAC schemes.

 


Date/Time: 2010-03-25, 11:00 AM

Speaker:Ning Lu

Title: Delay and Capacity Trade-Offs in Mobile Ad Hoc Networks

Abstract: At the cost of increase in delay, the original work of Grossglauser and Tse showed that mobile ad hoc networks are able to achieve a constant per-node throughput. However, a useful network metric in capacity should be constrained by delay, which is one of the most important concerns from an application point of view. Recently, substantial research has been done to understand the delay-capacity relationship in mobile ad hoc networks. In this survey, we walk along the line of investigation of tradeoffs between delay and capacity under different mobility models. And we try to understand some fundamental questions: (i) how representative are these mobility models studied in the literature? (ii) can the delay-capacity relationship be significantly different under some other reasonable mobility model? (iii) what sort of delay-capacity trade-off are we likely to see in a real world scenario? In doing this, we provide a better understanding on how mobility model affect delay-capacity tradeoff.

 


Date/Time: 2010-03-18, 11:30 AM

Speaker:David (Bong Jun) Choi

Title: Energy Efficient Protocols for Delay Tolerant Networks

Abstract: The delay tolerant networks (DTNs) is characterized by frequent disconnections and long delays of links among devices due to mobility, sparse deployment of devices, attacks, and noise, etc. Considerable research efforts have been devoted recently to DTNs to enable communications between network entities with intermittent connectivity. Unfortunately, many mobility scenarios in DTNs depend on mobile devices that have limited energy capacity, and the fundamental problem is that traditional power-saving mechanisms are designed assuming well connected networks. Due to much larger inter-contact durations than contact durations, devices spend most of their life time in the neighbor discovery, and centralized power-saving strategies are difficult. Consequently, devices consume a significant amount of energy in the neighbor discovery, rather than in infrequent data transfers. Therefore, distributed energy efficient neighbor discovery protocols for DTNs are essential to minimize the degradation of network connectivity and maximize the benefits from mobility. In this thesis, we develop sleep scheduling protocols in the medium access control (MAC) layer that are adaptive and distributed under different clock synchronization conditions: synchronous, asynchronous, and semi-asynchronous. In addition, we propose a distributed clock synchronization protocol to mitigate the clock synchronization problem in DTNs. Our research accomplishments are briefly outlined as follows: Firstly, we design an adaptive exponential beacon (AEB) protocol. By exploiting the trend of contact availability, beacon periods are independently adjusted by each device and optimized using the distribution of contact durations. The AEB protocol significantly reduces energy consumption while maintaining comparable packet delivery delay and delivery ratio. Secondly, we design two asynchronous clock based sleep scheduling (ACDS) protocols. Based on the fact that global clock synchronization is difficult to achieve in general, predetermined patterns of sleep schedules are constructed using hierarchical arrangements of cyclic difference sets such that devices independently selecting different duty cycle lengths are still guaranteed to have overlapping awake intervals with other devices within the communication range. Thirdly, we design a distributed semi-asynchronous sleep scheduling (DSA) protocol. Although the synchronization error is unavoidable, some level of clock accuracy may be possible for many practical scenarios. The sleep schedules are constructed to guarantee contacts among devices having loosely synchronized clocks, and parameters are optimized using the distribution of synchronization error. We also define conditions for which the proposed semi-asynchronous protocol outperforms existing asynchronous sleep scheduling protocols. Lastly, we design a distributed clock synchronization (DCS) protocol. The proposed protocol considers asynchronous and long delayed connections when exchanging relative clock information among nodes. We demonstrate the convergence and the performance of the protocol using numerical analysis and simulations. As a result, smaller synchronization error achieved by the proposed protocol allows more accurate timing information and renders neighbor discovery more energy efficient.

 


Date/Time: 2010-03-18, 11:00 AM

Speaker:Mahdi Asefi

Title:A Mobility-Aware and Quality-Driven Retransmission Limit Adaptation Scheme for Video Streaming over VANETs

Abstract: An adaptive MAC retransmission limit selection scheme is proposed to improve the performance of IEEE 802.11p standard MAC protocol for video streaming applications over vehicular area networks (VANETs). A multi-objective optimization framework is applied at road side unit (RSU) which jointly minimizes the probability of playback freezes and start-up delay of the streamed video at the destination vehicle by tuning the MAC retransmission limit with respect to channel statistics as well as packet transmission rate. Periodic channel statues estimation is performed at RSU which is video transmitter by information acquired from received signal strength (RSS) considering Doppler shift effect. Also, estimation of access probability between RSU and destination vehicle is done via information about the most recent location of the vehicle and considered in design of adaptive MAC scheme. These information are enclosed inside the UDP packet header. Compared to non-adaptive IEEE 802.11p standard MAC, our method results in significantly less playback freezes while introducing slight increase in start-up delay.

 


Date/Time: 2010-03-15, 11:00 AM

Speaker:Prof. Nasir Ghani invited by Prof. Mark

Title:Network Services Scheduling for Emerging Applications

Abstract: The last decade has seen many advances in next-generation networking technologies. For example, ubiquitous IP and Ethernet networks (Layers 2, 3) have evolved to multi-gigabit speeds with full quality of service (QoS) provisions, as enabled by gains in high-speed electronics technologies. Concurrently, developments in optical wavelength division multiplexing (WDM) sub-systems have revolutionized the fiber-optic layer (Layer 1), delivering flexible "wavelength" circuit connectivity with terabits/fiber yields. As these technologies have matured, many scientific research organizations have actively deployed wireline networking infrastructures to support expanded distributed computing needs. For example, many "e-science" applications already need massive dataset transfers, i.e., petabytes-exabytes range, placing huge burdens on network resource provisioning. Given these trends, it is very plausible that even the most scalable backbones may not be able to handle all user requests in an "on-demand" manner. As a result, the concept of advance reservation (AR) of connections is becoming an increasingly critical concern. Namely, the ability to reserve connections at future time instants, i.e., network scheduling, allows operators to stagger demands and improve resource assignments and utilization. Moreover, AR services also have broad relevance to data-center management and other commercial applications. In light of the above, various studies have looked at this area, both at the IP/Ethernet and optical DWDM network layers. Along these lines, this talk will survey this exciting new field and outline several new research directions. In particular, refined AR scheduling strategies will be presented to help lower request blocking rates and improve resource efficiencies. Furthermore, novel network control plane extensions will also be detailed to help translate theoretical AR algorithms into practical real-world settings, i.e., distributed operation, multiple domains.

 


Date/Time: 2010-03-11, 11:00 AM

Speaker:Mohamed Elsalih Mahmoud

Title: Efficient Packet-Drop Thwarting Protocol for Multi-hop Wireless Networks

Abstract: In multi-hop wireless network (MWN), the mobile nodes relay others’ packets for enabling new applications and enhancing the network deployment and performance. However, the selfish nodes drop the packets because packet relay consumes their resources without benefits, and the malicious nodes drop the packets to launch Black-Hole and Sink-Hole attacks. Packet drop attacks adversely degrade the network fairness and performance in terms of throughput, delay, and packet delivery ratio. Moreover, due to the nature of wireless transmission and multi-hop packet relay, the attackers can analyze the network traffic in undetectable way to learn the users’ locations in number of hops and their communication activities causing a serious threat to the users’ privacy. In this thesis, we propose efficient security protocols for thwarting packet drop attacks and preserving users’ privacy in multi-hop wireless networks. First, we design a fair and efficient cooperation incentive protocol to stimulate the selfish nodes to relay others’ packets. The source and the destination nodes pay credits (or micropayment) to the intermediate nodes for relaying their packets. In addition to cooperation stimulation, the incentive protocol enforces fairness by rewarding credits to compensate the nodes for the consumed resources in relaying others’ packets. The protocol also discourages launching Resource-Exhaustion attacks by sending bogus packets to exhaust the intermediate nodes’ resources because the nodes pay for relaying their packets. For fair charging policy, both the source and the destination nodes are charged when the two nodes benefit from the communication. Since micropayment protocols have been originally proposed for web-based applications, we propose a practical payment model specifically designed for MWNs to consider the significant differences between web-based applications and cooperation stimulation. Although the non-repudiation property of the public-key cryptography is essential for securing the incentive protocol, the public-key cryptography requires too complicated computations and has a long signature tag. For efficient implementation, we use the public-key cryptography only for the first packet in a series and use the efficient hashing operations for the next packets, so that the overhead of the packet series converges to that of the hashing operations. Since a trusted party is not involved in the communication sessions, the nodes usually submit undeniable digital receipts (proofs of packet relay) to a centralized trusted party for updating their credit accounts. Instead of submitting large-size payment receipts, the nodes submit brief reports containing the alleged charges and rewards and store undeniable security evidences. The payment of the fair reports can be cleared with almost no processing overhead. For the cheating reports, the evidences are requested to identify and evict the cheating nodes. Since the cheating actions are exceptional, the proposed protocol can significantly reduce the required bandwidth and energy for submitting the payment data and clear the payment with almost no processing overhead while achieving the same security strength as the receipt-based protocols. Second, the payment reports are processed to extract financial information to reward the cooperative nodes, and contextual information such as the broken links to build up a trust system to measure the nodes’ packet-relay success ratios in terms of trust values. A node’s trust value is degraded whenever it does not relay a packet and improved whenever it does. A node is identified as malicious and excluded from the network once its trust value reaches to a threshold. Using trust system is necessary to keep track of the nodes’ long-term behaviors because the network packets may be dropped normally, e.g., due to mobility, or temporarily, e.g., due to network congestion, but the high frequency of packet drop is an obvious misbehavior. Then, we propose a trust-based and energy-aware routing protocol to route traffics through the highly trusted nodes having sufficient residual energy in order to establish stable routes and thus minimize the probability of route breakage. A node’s trust value is a real and live measurement to the node’s failure probability and mobility level, i.e., the low-mobility nodes having large hardware resources can perform packet relay more efficiently. In this way, the proposed protocol stimulates the nodes not only to cooperate but also to improve their packet-relay success ratio and tell the truth about their residual energy to improve their trust values and thus raise their chances to participate in future routes. Finally, we propose a privacy-preserving routing and incentive protocol for hybrid ad hoc wireless network. Micropayment is used to stimulate the nodes’ cooperation without submitting payment receipts. We only use the lightweight hashing and symmetric-key-cryptography operations to preserve the users’ privacy. The nodes’ pseudonyms are efficiently computed using hashing operations. Only trusted parties can link these pseudonyms to the real identities for charging and rewarding operations. Moreover, our protocol protects the location privacy of the anonymous source and destination nodes. Extensive analysis and simulations demonstrate that our protocols can secure the payment and trust calculation, preserve the users’ privacy with acceptable overhead, and precisely identify the malicious and the cheating nodes. Moreover, the simulation and measurement results demonstrate that our routing protocols can significantly improve route stability and thus the packet delivery ratio due to stimulating the selfish nodes’ cooperation, evicting the malicious nodes, and making informed decisions regarding route selection. In addition, the processing and submitting overheads of the payment-reports are incomparable with those of the receipts in the receipt-based incentive protocols. Our protocol also requires incomparable overhead to the signature-based protocols because the lightweight hashing operations dominate the nodes’ operations.

 


Date/Time: 2010-03-04, 11:00 AM

Speaker: Shan Chang

Title: SHIELD: Detecting Sybil Attacks in Private Vehicular Networks via Location-hidden Trajectories

Abstract: In private vehicular networks, where privacy, especially the location privacy of anonymous vehicles is highly concerned, anonymous verification of vehicles is indispensable. . Consequently, an attacker who succeeds in forging multiple hostile identifies can easily launch a Sybil attack, gaining a disproportionately large influence. In this paper, we propose a novel Sybil attack detection mechanism SHIELD using the trajectories of vehicles for identification while still preserving their location privacy. More specifically, when a vehicle approaches a road-side unit (RSU), it actively demands an authorized message from the RSU as the proof of appearance at this RSU and time. We design a location-hidden authorized message generation scheme for two objectives: first, RSU signatures on messages are signer-ambiguous so that the RSU location information is concealed from the resulted authorized message; second, two authorized messages signed by the same RSU within the same given period of time (temporarily linkable) are recognizable so that they can be used for identification. With the temporal limitation on the linkability of two authorized messages, authorized messages used for long-term identification is prohibited. With this scheme, vehicles can generate a location-hidden trajectory for location-privacy-preserved identification by collecting a consecutive series of authorized messages. Utilizing social relationship among trajectories according to the similarity definition of two trajectories, SHIELD can recognize and therefore dismiss “communities” of Sybil trajectories. Rigorous security analysis and extensive trace-driven simulations demonstrate the efficacy of SHIELD.

 


Date/Time: 2010-02-25, 11:00 AM

Speaker: Rongxing Lu

Title: Social Theory in Secure Vehicular Communications

Abstract: In this talk, we mainly discuss how to use social theory to explore the challenging issues in vehicular ad hoc network (VANET). Specfically, we will carefully study human factors in real word, and utilize them to not only provide the security and privacy preservation but also improve performance in VANET.

 


Date/Time: 2010-02-18, 11:00 AM

Speaker: Sanaa Taha

Title: Anonymity and Location Privacy Considerations in Mobile IPv6

Abstract: Mobile IP v6 protocol, the successor of Mobile IPv4, has been proposed to solve the problem of the Triangle Routing by introducing the Route Optimization. However, during increasing the network performance by the Route Optimization technique, the anonymity and the location of the mobile node are revealed to network users as well as eavesdroppers. In this work, based on the CL-PKC and the Anonymizer, a new practical solution for the anonymity and location privacy in Mobile IPv6 networks is proposed. The new technique achieves high level of anonymity and location privacy while keeping the network performance as good as using the Route Optimization. Moreover, the proposed technique does not require changing the existing standard security mechanisms which are implemented in Mobile IPv6 protocol (IPSec, the Return Routability Procedure)

 


Date/Time: 2010-02-11, 11:00 AM

Speaker: Qinghua Shen

Title: A survey of WBAN: application, physical layer and MAC

Abstract: The idea of using wireless body area network(WBAN) to support continuous and unobtrusive monitoring of physiological signals for medical and entertainment applications is attractive. However, the WBAN technology is in the early stage of development, and several research challenges have to be overcome. This talk will start with sets of applications to illustrate the technical requirements of WBAN, then the test results of channel character for body area network, including implant channel and on body channel, and will end by introducing an energy-saving MAC for WBAN.

 


Date/Time: 2010-02-04, 11:00 AM

Speaker: Xu Li

Title: Location service for wireless ad hoc networks

Abstract: Hello protocol is the basic technique for neighborhood discovery in wireless ad hoc networks. It requires nodes to claim their existence/aliveness by periodic ‘hello’ messages. Central to any hello protocol is the determination of ‘hello’message transmission rate. No fixed optimal rate exists in the presence of node mobility. The rate should in fact adapt to it,high for high mobility and low for low mobility. In this talk, we propose a novel mobility prediction based hello protocol, named ARH (Autoregressive Hello protocol). In this protocol, each node predicts its own position by an ever-updated autoregression-based mobility model, and neighboring nodes predict its position by the same mobility model. The node transmits ‘hello’ message (for location update) only when the predicted location is too different from the true location (causing topology distortion), triggering mobility model correction on both itself and each of its neighbors. ARH evolves along with network dynamics, and seamlessly tunes itself to the optimal configuration on the fly using local knowledge only. Through extensive simulation, we demonstrate the effectiveness and efficiency of ARH, in comparison with the best known competitive protocol TAP (Turnover based Adaptive hello Protocol) . It comes out that ARH achieves the same high neighborhood discovery performance as TAP with dramatically less message overhead (about 50% lower ‘hello’ rate).

 


Date/Time: 2010-01-28, 11:00 AM

Speaker: Jian Qiao

Title: Challenges to Realize Multi-Gigabit Millimeter Wave Networks

Abstract: Multiple GHz of internationally available, unlicensed spectrum around the 60 GHz carrier frequency has the ability to support high-throughput wireless communications. While the large free spectrum (7~GHz) make it very attractive for bandwidth-intensive multimedia applications, 60 GHz implementations must overcome many challenges. For example, the high attenuation and directional nature of the 60 GHz wireless channel as well as limited gain amplifiers and excessive phase noise in 60 GHz transceivers are explicit implementation difficulties. The challenges associated with the unique features of millimeter wave (mmWave) communications motivate commercial deployment of short-range outdoor mesh networks, wireless local area networks (WLANs), wireless personal area networks (WPANs), and vehicular networks. In this report, we detail review the research challenges in different layers of mmWave networks, including RF design, modulation, channel estimation, MAC protocols, and resource scheduling, taking account of different usage models. Several research issues are proposed and the corresponding methodologies are presented.

 


Date/Time: 2010-01-21, 11:00 AM

Speaker: Bin Cao

Title: Projection and Its Applications in Wireless Communications

Abstract: In this talk, I will give an introduction to a mathematical while full of physical meaning tool in signal processing and wireless communications. The presentation will focus on the fundamentals of a geometrical concept which is called Projection. As a powerful tool in signal processing, projection is widely used in filtering, estimation and detection problems. After introducing the definition of projection, we will talk about its special case Orthogonal Projection. Then the oblique projection is highlighted and we will go through its operator, properties, calculations,and the impact to Gaussian white noise. Finally, some application examples are given to show the utilization of projection in wireless communications, such as optimal filtering, mixed signals separation, joint channel and transmitted symbol estimation,decoding block codes,interpolation of missing data samples, intersymbol interference (ISI) cancelation. The application scenarios in this talk are based on physical layer in wireless communications, while the applications are expected to extend to higher levels. I hope this talk may give you a new point of view when you conduct your research beyond physical layer.

 


Date/Time: 2010-01-14, 1:30 PM

Speaker: Xiaohui Liang

Title: Security and Privacy Preservation in Mobile Heatlthcare Social Networks (MHSN)

Abstract: In our work on a privacy-preserving emergency call (PEC) scheme for patients in an MHSN, we study the privacy preservation problem in an emergency application. The PEC will disseminate emergency data in a fast, effective and privacy-preserving emergency call to the nearby healthcare workers relying on the cooperation of mobile users. When a patient is in an emergency, the patient's PDA launches the PEC to collect the personal information (PI). The PI contains not only the personal health records but also the physiological conditions which are continuously monitored by the body sensors. The PEC then generates an emergency call with the PI and provides it to every user within a patient's one-hop neighborhood. If a physician is near the patient, the PEC ensures that the time used to notify the physician of the emergency is the shortest. We demonstrate via theoretical analysis that the PEC is able to provide a fine-grained access control on a patient's PI, where the access policy is pre-defined by the patient. Moreover, the PEC can withstand multiple types of attacks, including the identity theft attack, the forgery attack, and the collusion attack. We also propose an effective revocation mechanism to make the scheme resistant to the insider attack.

 


Date/Time: 2010-01-07, 1:30 PM

Speaker: Mohamed Elsalih Mahmoud

Title: Lightweight Privacy-Preserving Routing and Incentive Protocol for Hybrid Ad Hoc Wireless Network

Abstract: We propose a privacy-preserving routing and incentive protocol, called PRIPO, for hybrid ad hoc wireless network. PRIPO uses micropayment to stimulate node cooperation without submitting payment receipts. The lightweight hashing and symmetric-key-cryptography operations are implemented to preserve the users' privacy. The nodes' pseudonyms are efficiently computed using hashing operations. Only a trusted party can link these pseudonyms to the real identities for charging and rewarding operations. Moreover, PRIPO protects the location privacy of the anonymous source and destination nodes. Extensive analysis and simulations demonstrate that PRIPO can secure the payment and preserve the users' privacy with acceptable overhead.

 


 Fall 2010
Date Speaker Email Category
2010-09-02 Prof. Kui Ren (Invited) kren AT ece.iit.edu Security
2010-09-16 Rongxing Lu rxlu AT bbcr.uwaterloo.ca Security
2010-09-23 Yongkang Liu y257liu AT bbcr.uwaterloo.ca Performance
2010-09-30 Le Chen knnnn.evacl AT gmail.com Security
2010-10-07 Sandra Cespedes U. slcesped AT uwaterloo.ca Performance
2010-10-07 Nizar H. Alsharif nezar421 AT hotmail.com Performance
2010-10-14 Mohamed Elsalih Mahmoud moh.elsalih AT gmail.com Security
2010-10-21 Xin Sheng Zhou x29zhou AT uwaterloo.ca Performance
2010-10-28 Ho Ting Cheng htcheng AT bbcr.uwaterloo.ca Resource Management
2010-11-04 Sanaa Taha staha AT uwaterloo.ca Security
2010-11-11 Mohamed Elsalih Mahmoud moh.elsalih AT gmail.com Security
2010-11-18 Hongtao Zhang h15zhang AT uwaterloo.ca Chaos
2010-09-02 Prof. Peng-Jun Wan (Invited) wan AT cs.iit.edu Wireless Networks
2010-11-25 Rongxing Lu rxlu AT bbcr.uwaterloo.ca Security
2010-12-02 Sandra Cespedes U. slcesped AT uwaterloo.ca Tutorial
2010-12-02 Xigang Huang xigang_h AT hotmail.com Performance
2010-12-16 Mahdi Asefi masefi AT uwaterloo.ca Performance

 


Date/Time: 2010-12-16, 3:00 PM

Speaker: Mahdi Asefi

Title: A Quality-Driven Multi-hop Data Delivery Scheme for Video Streaming in Urban VANET Scenarios

Abstract: The inherent characteristics of vehicular networks, such as dynamic topology and high mobility, pose challenging conditions for the deployment of delay-sensitive applications, e.g., video streaming. We propose an integrated network-layer scheme for seamless delivery of video packets in urban Vehicular Ad-hoc Network (VANET) scenarios. A new quality-driven routing scheme for delivering video streams from a fixed network to a destination vehicle via multi-hop communications is proposed. The routing scheme aims to optimize the visual quality of the transmitted video frames by minimizing the distortion, the start-up delay, and the frequency of the streaming freezes. Numerical results show the stability of our integrated scheme, at the same time that achieves a better performance for the video quality metrics.

 


Date/Time: 2010-12-02, 3:30 PM

Speaker: Xigang Huang

Title: Energy Efficient Cooperative Communications for Wireless Body Area Networks

Abstract: It is expected that Wireless Body Area Network (WBAN) will greatly improve the quality of our life because of its myriad applications for our human beings. However, one of the challenges is to design energy efficient communication protocols to support the reliable communication as well as to prolong the network lifetime. Cooperative communications have the advantage of spatial diversity to combat multipath fading, thus improving the link reliability and boosting energy efficiency. In this talk, we investigate the energy efficient cooperative communications for WBAN. We first analyze the outage performance of three transmission schemes, namely direct transmission, single relay cooperation, and multi-relay cooperation. To minimize the energy consumption, we then study the problem of optimal power allocation with the constraint of targeted outage probability. Two strategies of power allocation are considered: \emph{power allocation with and without posture state information}. Simulation results verify the accuracy of the analysis and demonstrate that: 1) power allocation making use of the posture information can reduce the energy consumption; 2) within a possible range of the channel quality in WBAN, cooperative communication is more energy efficient than direct transmission only when the path loss between the transmission pair is higher than a threshold; and 3) for most of the typical channel quality due to the fixed transceiver locations on human body, cooperative communication is effective in reducing energy consumption.

 


Date/Time: 2010-12-02, 3:00 PM

Speaker: Sandra Cespedes U.

Title: On the standardization process of Internet protocols: What is going on at the IETF?

Abstract: Have you ever wondered how the Internet protocols such as IP, TCP, HTTP, and others, became standards for vendors and Internet operators? Do you think your idea could improve the performance of an existent technology but you do not know about the process to make it part of that technology? During this tutorial, we will tackle those questions by introducing the general process for standardization of Internet protocols and technologies at the Internet Engineering Task Force (IETF). The different areas covered by active IETF working groups (WG) and the forms of participating and contributing will be described. We will also briefly present the current discussions taking place in three different WGs: Mobility Extensions for MIPv6, Network-based mobility extensions, and Multipath TCP.

 


Date/Time: 2010-11-25, 3:00 PM

Speaker: Rongxing Lu

Title: GRS: The Green, Reliability, and Security of Emerging Machine to Machine Communication

Abstract: Machine to Machine (M2M) communication is characterized by involving a large number of intelligent machines sharing information and making collaborative decisions without the direct human interventions. Due to its potentially supporting a large amount of ubiquitous characteristics and achieving better cost-efficiencies, M2M communication has been quickly becoming a market-changing force for a wide variety of real-time monitoring applications, such as remote eHealthcare system, smart home, environmental monitoring, and industrial automation. However, the flourish of M2M communication still hinges up the fully understanding and managing the existing challenges: energy efficiency (green), reliability and security (GRS). Without the GRS guarantees, M2M communication cannot be widely accepted as a promising communication paradigm. In this talk, we explore the emerging M2M communication in terms of the potential green, reliability, and security issues, and aim to promote an energy-efficient, reliable and secure M2M communication environment. Specifically, we first formalize M2M communication architecture to incorporate three domains, i.e., M2M domain, network domain and application domain, and accordingly define GRS requirements in a systemic manner. We then introduce a number of GRS enabling techniques by exploring activity scheduling, redundancy utilization and cooperative security mechanisms. These techniques hold promise in propelling development of M2M communication applications.

 


Date/Time: 2010-11-19, 3:00 PM

Speaker: Prof. Peng-Jun Wan, Illinois Institute of Technology, USA, Invited By Prof. Weihua Zhuang

Title: Wonders of Wireless Interference in Multihop Wireless Networks

Abstract: Wireless interference is a major obstacle for achieving low communication latency and high network capacity in multihop wireless networks. The first part of this talk explores the very rich nature of the world of wireless interference. This part has a strong plane geometric flavor. The second part of this talk exploits those intrinsic properties discovered in the first part to develop efficient constant-approximation algorithms for minimizing communication latency in multihop wireless networks. This part has a strong graph-theoretic and algorithmic flavor. The third part of this talk further utilizes those properties to characterize the stability region of the simple longestqueue- first scheduling policy. This part has a strong queueing-theoretic and stochastic flavor. The talk is concluded with with some open research problems.

 


Date/Time: 2010-11-18, 3:00 PM

Speaker: Hongtao Zhang

Title: Chaos Synchronization and Its Application to Secure Communication

Abstract: Chaos theory is well known as one of three revolutions in physical sciences in 20th-century, as one physicist called it: "Relativity eliminated the Newtonian illusion of absolute space and time; quantum theory eliminated the Newtonian dream of a controllable measurable process; and chaos eliminates the Laplacian fantasy of deterministic predictability". Chaos has been widely applied to many scientific disciplines. One of most important engineering applications is secure communication because of the properties of random behaviours and sensitivity to initial conditions of chaos systems. In this presentation, we try to solve two main challenges in chaos-based secure communication schemes: chaos generation and chaos synchronization. In the end, we design a novel synchronization scheme, intermittent impulsive synchronization scheme (IISS). IISS can not only be flexibly applied to the scenario where the control window is restricted but also improve the security of chaos-based secure communication via reducing the control window width and decreasing the redundancy of synchronization signals.

 


Date/Time: 2010-11-11, 3:00 PM

Speaker: Mohamed Elsalih Mahmoud

Title: Trust-Based Energy-Aware Routing and Incentive Protocol for Multi-hop Wireless Networks

Abstract: Node cooperation in relaying others' packets and route stability are essential for high-performance multi-hop wireless networks and reliable data transmission. In this paper, we propose routing protocol called TETO for stimulating node cooperation and establishing stable routes. TETO uses credits (or micropayment) to stimulate the nodes' cooperation and processes the payment receipts to evaluate the nodes' quality of packet relay in terms of trust values. Stable routes are established through the highly trusted nodes having sufficient residual energy. Extensive analysis and simulations demonstrate that TETO can secure the payment and trust calculation and significantly improve route stability and thus the packet delivery ratio.

 


Date/Time: 2010-11-04, 3:00 PM

Speaker: Sanaa Taha

Title: Anonymity and Location Privacy Considerations in Mobile IPv6

Abstract: Mobile IP v6 protocol, the successor of Mobile IPv4, has been proposed to solve the problem of the Triangle Routing by introducing the Route Optimization. However, during increasing the network performance by the Route Optimization technique, the anonymity and the location of the mobile node are revealed to network users as well as eavesdroppers. In this work, based on the CL-PKC and the Anonymizer, a new practical solution for the anonymity and location privacy in Mobile IPv6 networks is proposed. The new technique achieves high level of anonymity and location privacy while keeping the network performance as good as using the Route Optimization. Moreover, the proposed technique does not require changing the existing standard security mechanisms which are implemented in Mobile IPv6 protocol (IPSec, the Return Routability Procedure)

 


Date/Time: 2010-10-28, 3:00 PM

Speaker: Ho Ting (Anderson) Cheng

Title: Sensing-Access Tradeoff in Cognitive Radio Networks

Abstract: There is a natural tradeoff between channel sensing and channel access in cognitive radio networks (CRNs). In this talk, I would like to discuss the issue of sensing-access balancing in multichannel CRNs. In this ongoing research, Hangguan and I propose a stopping rule-driven channel access scheme for a secondary user pair in multichannel CRNs. In the proposed approach, we first formulate the sensing-access tradeoff problem as a 1-stage look-ahead stopping problem. We derive two stopping conditions, namely power-limited stopping and bandwidth-limited stopping, whereby a desired tradeoff between sensing overhead and throughput increase can be achieved. Once a stopping condition is reached, a secondary user pair stops sensing and starts accessing previously sensed free channels for packet transmission. Simulation results show that, in the case of perfect sensing, the proposed approach outperforms a greedy approach by at least 80% in terms of throughput.

 


Date/Time: 2010-10-21, 3:00 PM

Speaker: Xinsheng Zhou

Title: Low-density parity-check codes for wireless relay networks

Abstract: Due to the broadcast characteristic of wireless communications, nodes other than the destination could receive the signals for free. Relaying these information could help the destination node to decode the messages when they cannot be decoded from the source node signals directly. Relaying can also increase the rate given the same total transmitting power or reduce the total transmitting power given the same rate, lightening that we should utilize relaying when possible rather than sending messages directly. In addition, interference is considered as a negative effect in today's wireless communication networks. However recent research showed that if the network is well designed, interference messages could be fully decoded and hence removed. In this research proposal, we focus on designing practical codes and their encoders and decoders for wireless relay networks. Low-density parity-check codes have been known as capacity approaching codes for single user channels. We extended these codes to two-way relay channels, three-way broadcast channels and wireless relay networks. Joint encoding and joint decoding on multiple blocks are explored. For a multiple access channel, we proposed a simpler interference cancellation joint decoder which is only 0.2 dB away from the higher complexity sub-optimal belief propagation joint decoder. For two-way relay channels, we showed that the required Eb/No to decode the source message is 1.5 dB less when the relay node helps assuming the received power and the noise power are the same in two blocks. For three-way broadcast channels, we showed that the path loss coefficient of the joint encoding and joint decoding scheme is only 3 dB away from the theoretic achievable value. We also explored a preliminary heuristic relay scheme for wireless relay networks.

 


Date/Time: 2010-10-14, 3:00 PM

Speaker: Mohamed Elsalih Mahmoud

Title: RISE: Receipt-Free Cooperation Incentive Scheme for Multihop Wireless Networks

Abstract: In this work, we propose a receipt-free cooperation incentive scheme for multihop wireless networks. The nodes submit lightweight payment reports containing their alleged charges and rewards, and store undeniable security evidences. The fair reports can be cleared with almost no processing overhead. For the cheating reports, the evidences are requested to identify and evict the cheating nodes. Since cheating actions are exceptional, our scheme can significantly reduce the overhead of submitting and processing the payment data. Extensive analysis and simulations demonstrate that the proposed scheme can clear the payment with almost no processing overhead while achieving the same security strength as the receipt-based schemes.

 


Date/Time: 2010-10-07, 3:00 PM

Speaker: Sandra Cespedes U. (Nizar H. Alsharif)

Title: Routing Protocols in Vehicular Ad hoc Networks: A tutorial

Abstract: Vehicular Ad hoc networks (VANET) have emerged as a platform for the deployment of a new generation of safety and comfort applications. In VANET, new technologies are integrated with the capabilities of wireless networks in order to provide ubiquitous connectivity while on the road to mobile users, and to enable vehicle-to-vehicle communications that improve safety for drivers and passengers. Although VANET is considered a special case of general Mobile Ad hoc Networks (MANET), it has unique characteristics, such as high node mobility and unreliable channel conditions, that pose many challenging research issues for the dissemination of information and the efficient delivery of data packets. In this tutorial, we discuss the problem of routing in VANET. We identify the special characteristics and review the different strategies that address them in order to provide a routing mechanism in VANET. The existing approaches are also discussed and evaluated according to the results provided in the literature.

 


Date/Time: 2010-09-30, 3:00 PM

Speaker: Le Chen

Title: Secure Localization Based on Bounded Retrieval Model

Abstract: As we know, the location of a device is an important attribute in many scenarios, such as Delay Tolerant Network, Location-based Routing, Vehicular Ad Hoc Networks, etc. If some dishonest device in the network cheats its position or several malicious devices collude together to pretend a legal device at an empty position, then it may cause serious confusions or even potential dangers. Therefore, how to securely verify the location of a certain device, either fixed or mobile, will be an essential task for the system to guarantee. Although a device using a GPS receiver can easily determine its own location by computing the information broadcasted by various satellites, it still cannot convince others that its location is exactly the same as it claimed. In this talk we will briefly introduce a proposed secure positioning (secure localization) scheme, in which a prover (person or device) can prove its geographic location to several verifiers around it under the Bounded Retrieval Model. We will also suggest some possible applications of this scheme.

 


Date/Time: 2010-09-23, 3:00 PM

Speaker: Yongkang Liu

Title: Multi-hop Transmission using Heterogeneous Channels in Dynamic Spectrum Access Networks

Abstract: The dynamic spectrum access networks (DySPAN) represent a category of communication networks where the free portion of the licensed spectrum bands can be opportunistically utilized for secondary transmissions. The existing solutions in the DySPAN perform well only in the homogeneous channel condition with slowly varying spectrum opportunities. Since the power level of secondary transmission is constrained based on the interference introduced into the primary system, there exists the need to enable multi-hop transmission in the DySPAN for the end-to-end communication. Furthermore, spectrum opportunities exhibit short available time windows with spatial variations over the frequency bands. Therefore, the highly dynamic network resource and the inherent multi-channel structure make the protocol design for a multi-hop DySPAN very challenging. In this study, we consider a general multi-hop architecture in the DySPAN characterized by the integration of heterogeneous spectrum opportunities and multiple services. The heterogeneity of the spectrum opportunities is investigated in terms of channel usage pattern and the statistics of wireless channels along with several research problems which have not been well addressed in existing works. Preliminary research results are presented, including a quality of service (QoS) aware medium access control (MAC) scheme for the DySPAN nodes to distributively determine the set of channels in the spectrum sensing and decision to satisfy their QoS requirements, and an opportunistic routing scheme in a highly dynamic environment by jointly considering physical characteristics of spectrum bands and diverse activities of primary systems in the route selection and the channel access decision. Analytical models are established to characterize the performance of our proposed schemes, and the effectiveness and efficiency are verified by simulations. Based on the insights obtained in the preliminary research, further research issues are discussed.

 


Date/Time: 2010-09-16, 3:00 PM

Speaker: Rongxing Lu

Title: Secure Handshake with Symptoms-matching: The Essential to the Success of mHealthcare Social Network

Abstract: In our aging society, mHealthcare social network (MHSN) built upon wireless body sensor network (WBSN) and mobile communications provides a promising platform for the seniors who have the same symptom to exchange their experiences, give mutual support and inspiration to each other, and help forwarding their health information wirelessly to a related eHealth center. However, there exist many challenging security issues in MHSN such as how to securely identify a senior who has the same symptom, how to prevent others who don‘t have the symptom from knowing someone‘s symptom? In this talk, to tackle these challenging security issues, we propose a secure same-symptom-based handshake (SSH) scheme, and apply the provable security technique to demonstrate its security in the random oracle model. In addition, we discuss a promising application -- social-based patient health information (PHI) collaborative reporting in MHSN, and conduct extensive simulations to evaluate its efficiency in terms of PHI reporting delay.

 


Date/Time: 2010-09-02, 10:00 AM (EIT 3142)

Speaker: Prof. Kui Ren, Illinois Institute of Technology, USA, Invited By Prof. Xuemin (Sherman) Shen

Title:Storage Security in Cloud Computing

Abstract: Cloud storage has great potential of providing data owners with on-demand scalable storage services at reduced cost. By outsourcing massive storage in cloud, data owners can be relieved from the burden of local hardware and software management. However, the fact that owners no longer have physical possession of the outsourced data obsoletes traditional cryptographic primitives for storage correctness protection. Hence, enabling efficient storage correctness auditing in the cloud environment with new approaches becomes imperative and challenging. Furthermore, the outsourced data may not be static in nature and may be accessed and dynamically updated as needed later on. Thus, incorporating data dynamics is also inherently demanded by any practical storage auditing solution, which makes the solution design even more challenging. As storage-auditing schemes normally require data owners to check the cloud data periodically to maintain correctness guarantee, it still imposes cumbersome computation and online burdens from data owners' perspective. One effective solution to this would be introducing a third-party auditor (TPA) to perform regular auditing tasks on behalf data owners. Enabling public auditability can save not only owners' computation and on-line overheads but also provide a means for fair assessment of cloud storage service risks. The further involved design challenge is that introducing a TPA should not bring in any privacy breach against owner's data when allowing the TPA to perform auditing tasks. In this talk, I will present a few recent research efforts on storage security in cloud computing that tackle the above-mentioned issues. I will also discuss some other security research issues in the context of cloud computing.

 


 Spring 2010
Date Speaker Email Category
2010-05-06 Hao Liang h8liang AT ecemail.uwaterloo.ca Performance
2010-05-13 Mohamed Elsalih Mahmoud moh.elsalih AT gmail.com Security
2010-05-20 Sandra Cespedes U. slcesped AT uwaterloo.ca Performance
2010-05-27 Ho Ting Cheng htcheng AT bbcr.uwaterloo.ca Resource Management
2010-06-03 Subodha Gunawardena shgunawa AT ecemail.uwaterloo.ca Performance
2010-06-04 Prof. Xue Liu (Invited) xueliu AT cse.unl.edu Performance
2010-06-10 Juncheng Jia j6jia AT bbcr.uwaterloo.ca Performance
2010-06-16 Prof. Zhisheng Niu (Invited) niuzhs AT tsinghua.edu.cn Performance
2010-06-17 Yongkang Liu yongkang.liu.phd AT gmail.com Performance
2010-06-24 Nizar H. Alsharif nezar421 AT hotmail.com Performance
2010-06-24 Xiaoxia Zhang x79zhang AT bbcr.uwaterloo.ca Performance
2010-07-07 David Choi bjchoi AT engmail.uwaterloo.ca Performance
2010-07-07 Khaled Ali k23ali AT engmail.uwaterloo.ca Performance
2010-07-08 Prof. Liuqing Yang (Invited) lqyang AT ece.ufl.edu Performance
2010-07-15 Xu Li easylix AT gmail.com Performance
2010-07-22 Hongtao Zhang h15zhang AT uwaterloo.ca Performance
2010-07-29 Mohamed Elsalih Mahmoud moh.elsalih AT gmail.com Security
2010-08-05 Sanying Li s68li AT bbcr.uwaterloo.ca Performance
2010-08-12 Rongfei Fan rongfei AT ualberta.ca Performance
2010-08-12 Jian Qiao qiaojian1 AT gmail.com Performance
2010-08-19 Hongzhi Zhu hongzi AT cs.sjtu.edu.cn Performance
2010-08-26 Kaoru OTA kota AT bbcr.uwaterloo.ca Performance

 


Date/Time: 2010-08-26, 2:30 PM

Speaker: Kaoru OTA

Title: Dynamic Itinerary Planning for Mobile Agents with a Content-Specific Approach in Wireless Sensor Networks

Abstract: We study data fusion in sensor networks using mobile agents (MAs),which are capable of saving energy of sensor nodes and performing advanced computation functions based on the requests of various applications. Research on MAs still remains unfledged in development of application-oriented data fusion, which is highly desired in wireless sensor networks (WSNs) deployed in recent days for environmental and disaster monitoring. In this paper, we propose a dynamic itinerary planning for MAs (DIPMA) to collect data from sensor networks with an application-oriented approach. In particular, the DIPMA algorithm is applied to the data collection for frost prediction which is a real-world application in agriculture using next-generation sensor networks. The performance of the DIPMA is evaluated by simulations and the experimental results show that the total execution time of MA can be reduced significantly with our approach while frost prediction accuracy is maintained.

 


Date/Time: 2010-08-19, 2:30 PM

Speaker: Hongzhi Zhu

Title: Exploiting Temporal Dependency for Opportunistic Forwarding in Urban Vehicular Networks

Abstract: Inter-contact times (ICTs) between moving objects are one of the key metrics in vehicular networks, and they are also central to forwarding algorithms and the end-to-end delay. Recent study on the tail distribution of ICTs based on theoretical mobility models and empirical trace data shows that the delay between two consecutive contact opportunities drops exponentially. While theoretical results facilitate problem analysis, how to design practical opportunistic forwarding protocols in vehicular networks, where messages are delivered in carry-and-forward fashion, is still unclear. In this paper, we study three large sets of Global Positioning System (GPS) traces of more than ten thousand public vehicles, collected from Shanghai and Shenzhen, two metropolises in China. By mining the temporal correlation and the evolution of ICTs between each pair of vehicles, we develop higher order Markov chains to characterize urban vehicular mobility patterns, which adapt as ICTs between vehicles continuously get updated. Then, the next hop for message forwarding is determined based on the previous ICTs. With our message forwarding strategy, it can dramatically increase delivery ratio (up to 80%) and reduce end-to-end delay (up to 50%) while generating similar network traffic comparing to current strategies based on the delivery probability or the expected delay.

 


Date/Time: 2010-08-12, 3:00 PM

Speaker: Jian Qiao

Title: Multi-hop Transmission in Millimeter Wave WPANs with Directional Antenna

Abstract: Millimeter-wave (mmWave) communications is a promising enabling technology for high rate (Giga-bit) multimedia applications. However, because oxygen absorption peaks at 60 GHz, mmWave signal power degrades significantly over distance. Therefore, a traffic flow transmitting over multiple short hops is preferred to improve the flow throughput. We design a hop selection metric for the piconet controller (PNC) to select appropriate relay hops for a traffic flow, aiming to improve the flow throughput and balance the traffic loads across the network. We then propose a multi-hop concurrent transmission (MHCT) scheme to exploit the spatial capacity of the mmWave WPAN by allowing multiple communication links to transmit simultaneously. By deriving the probability that two links can transmit simultaneously as the function of the link length, the MHCT scheme is capable of improving spatial multiplexing gain in comparison with the single hop concurrent transmission (SHCT) schemes. For time division multiplexing, we theoretically demonstrate that by properly breaking single long hop into multiple short hops, the resource can be utilized more efficiently, thus supporting more traffic flows in the network within the same time interval. In addition, the per-flow throughput is obtained analytically. Extensive simulations are conducted to validate the analysis and demonstrate that the proposed MHCT scheme can significantly improve the average traffic flow throughput.

 


Date/Time: 2010-08-12, 3:00 PM

Speaker: Rongfei Fan

Title: Spectrum Sensing in Cognitive Radio Networks: Optimal Sensing Time Configuration

Abstract: In this talk, optimal multi-channel cooperative sensing strategies in cognitive radio networks are investigated. A cognitive radio network with multiple potential channels is considered. Secondary users cooperatively sense the channels and send the sensing results to a coordinator, in which energy detection with a soft decision rule is employed to estimate whether there are primary activities in the channels. An optimization problem is formulated, which maximizes the throughput of secondary users while keeping detection probability for each channel above a pre-defined threshold. In particular, two sensing modes are investigated: slotted-time sensing mode and continuous-time sensing mode. With a slotted-time sensing mode, the sensing time of each secondary user consists of a number of mini-slots, each of which can be used to sense one channel. The initial optimization problem is shown to be a nonconvex mixed-integer problem. A polynomial-complexity algorithm is proposed to solve the problem optimally. With a continuous-time sensing mode, the sensing time of each secondary user for a channel can be any arbitrary continuous value. The initial nonconvex problem is converted into a convex bilevel problem, which can be successfully solved by existing methods.

 


Date/Time: 2010-08-05, 3:00 PM

Speaker: Sanying Li

Title: Channel Allocation for Smooth Video Delivery over Cognitive Radio Networks

Abstract: To address the impact of the network dynamics on video streaming, the playout buffer is typically deployed at the receiver. With different buffer storage, users thus have different tolerance to the network dynamics. In this paper, we exploit this feature for channel allocation in cognitive radio (CR) networks. We first model the channel availability as an on-off process which is stochastically known. Based on the bandwidth capacity and the specific buffer storage of users, we then intelligently allocate the channels to maximize the overall network throughput while providing users with the smooth video playback, which is formulated as an optimization framework. Given the channel conditions and the video packet storage in the playout buffer, we propose a centralized scheme for provisioning the superior video service to users. Simulation results confirm that by exploiting the playout buffer of users, the proposed channel allocation scheme is robust against intense network dynamics and provides users with the elongated smooth video playback.

 


Date/Time: 2010-07-29, 3:00 PM

Speaker: Mohamed Elsalih Mahmoud

Title: Trust-based, Energy-aware, and Incentive-compatible Routing Protocol for Multi-hop Wireless Network

Abstract: Route stability is essential for high-performance networks. One intermediate node can break a route in multi-hop wireless networks and thus node selection is important for establishing stable routes. Cooperation stimulation can improve route stability due to motivating the nodes to relay the network packets. However, stimulation alone is not sufficient to guarantee route stability because the network nodes are autonomous and thus their behaviors are not predictable. For example, some nodes may provide very poor packet relay quality due to low hardware-resources, faulty software or hardware, or malicious behavior. Moreover, some nodes may break the routes because they lack the required energy for packet relay. In this paper, we propose a trust-based, energy-aware, and incentive-compatible routing protocol for multi-hop wireless networks. In addition to cooperation stimulation, the nodes’ quality of packet relay are evaluated and represented in trust values. A node’s trust values are calculated from its past behavior, and reflect the expected future behavior. Then, we propose a routing mechanism to integrate a node’s trust values and energy capability in routing decision-making. This way, the proposed protocol not only stimulates the nodes’ cooperation but also stimulates them to provide high packet relay quality and tell the truth about their energy capabilities to increase their chances to be selected by the routing protocol. Extensive analysis and simulations demonstrate that the proposed protocol is secure, and can improve the network performance significantly due to improving the routes’ stability by selecting trusted nodes.

 


Date/Time: 2010-07-22, 3:00 PM

Speaker: Hongtao Zhang

Title: Advances in chaos-based secure communication

Abstract: Chaos theory studies the behavior of dynamical systems with extreme sensitivity to initial conditions and is applied to many scientific disciplines such as mathematics, physics, biology, economics, engineering, etc. In particular, chaotic signal is a natural carrier to mask the message in secure communication due to its sensitivity to initial conditions and noise-like dynamics. For instance, at the transmitter end, Alice encrypts the message by a chaotic signal and sends it to the receiver end by a public channel. And then, at the receiver end, to recover the original message, Bob needs to achieve the same chaotic signal, called chaos synchronization, and utilizes it to decrypt the cipher. Therefore, generating chaos and chaos synchronization are two most important issues in this process. In this talk, aiming at these two issues, we present a set of new solutions to improve the security and feasibility of chaos-based secure communication.

 


Date/Time: 2010-07-15, 1:30 PM

Speaker: Xu Li

Title: Coordinated computing in wireless sensor and robot networks

Abstract: Wireless sensor and robot network (WSRN) are the confluence point where the two traditional fields WSN and robot networks meet, and node collaborate to accomplish distributed sensing and actuation tasks. Leveraged by the control and mobility of robots, the networking process and applications embrace a whole new set of possibilities. For instance, robots and sensors may coordinate to deploy, repair and relocate sensors to improve coverage, build routes and fix network partition to ensure data communication, change network topology to shape routing patterns and balance energy consumption, and respond to reported events in a timely and effective manner. The benefits are limited only by imagination. In this talk, we will examine some of these unique mobility-involved coordination issues.

 


Date/Time: 2010-07-08, 2:30 PM

Speaker: Prof. Liuqing Yang, University of Florida, USA, Invited By Prof. Weihua Zhuang

Title: Cooperative Sensing: The Detection Perspective

Abstract: In cooperative communication systems, multiple transmit and/or receive antennas can increase the degrees of freedom to enhance the transmission reliability and improve the data rate. Partly inspired by these benefits, cooperative sensing has been drawing increasing interests recently. In this talk, we will consider the detection perspective of the spectrum sensing problem in cognitive radio networks. It is well known that, to improve the sensing performance, cooperation among the secondary users can be utilized to achieve space diversity. However, the exact amount of diversity has never been quantified in the literature. This talk will illustrate the quantification of the diversity order for various cooperative spectrum sensing strategies. We will also point out some interesting tradeoffs between the system efficiency and reliability, which can be used to guide practical system design with different preferences.

 


Date/Time: 2010-07-07, 3:00 PM

Speaker: Khaled Ali

Title: QoS Support for Voice Packet Transmission over Cognitive Radio Networks

Abstract: Cognitive Radio Networks (CRNs) provide a solution for the spectrum scarcity problem facing the wireless communications community. However, due to the infancy of CRNs, further research is needed before we can truly benefit from CRNs. The basic concept of CRNs relies on utilizing the unused spectrum of a primary network, without interfering with the activity of primary users (PUs). In order to successfully achieve that, users in a CRN has to perform spectrum sensing, spectrum management, spectrum mobility, and spectrum sharing. The latter, which is the focus of our research, deals with how secondary users (SUs) share the unused spectrum. Furthermore, to be able to utilize CRNs in practical applications, a certain level of quality-ofservice (QoS) should be guaranteed to SUs in such networks. QoS requirements vary according to the application. Interested in voice communications, we propose a packet scheduling scheme that orders the SUs' transmissions according to the packet drop rate and the number of packets queued waiting for transmission. Two medium access control (MAC) layer protocols, based on the mentioned scheduling scheme, are proposed for a centralized CRN. In addition, the scheduling scheme is adapted for a distributed CRN, by introducing a feature that allows SUs to organize access to the available spectrum without the need for a central unit. Finally, extensive simulation based experiments are carried out to evaluate the proposed protocols and compare their performance with that of other MAC protocols designed for CRNs. These results reflect the effectiveness of our proposed protocols to guarantee the required QoS for voice packet transmission, while maintaining fairness among SUs in the CRN.

 


Date/Time: 2010-07-07, 3:00 PM

Speaker: David Choi

Title: DSA: Distributed Semi-Asynchronous Sleep Scheduling Protocol in Mobile Wireless Networks

Abstract: Synchronization error is unavoidable in mobile wireless multihop networks, especially in sparse networks, due to underlying synchronization errors and lack of effective synchronization algorithms. However, some level of clock synchronization is possible among nodes. In this paper, we propose a distributed semi-asynchronous sleep scheduling protocol (DSA) considering loosely synchronized clocks in sparse wireless mobile networks. The sleep schedules are constructed to guarantee contacts among distributed nodes having synchronization errors. The protocol can be optimized using the distribution of the synchronization error to maximize the energy efficiency. Using simulation results, we show that DSA achieves higher energy efficiency than existing asynchronous sleep scheduling protocols.

 


Date/Time: 2010-06-24, 2:30 PM

Speaker: Xiaoxia Zhang

Title: An Energy-Efficient Bit Allocation Scheme in Wireless Sensor Networks

Abstract: Sensors that are capable of sensing, data processing and communicating have enabled the realization of wireless sensor networks (WSN). In WSN, a large number of nodes are densely deployed in an area to measure some physical phenomenon. Generally, wireless sensor nodes carry very limited irreplaceable power sources. Thus, two primary concerns in WSN are to save the overall energy consumption and to prolong the network lifetime, namely the time when all the nodes are functional. Motivated by these two concerns, this thesis mainly focuses on the energy efficient transmission and bit allocation schemes in multi-source single-sink wireless sensor networks from an information theoretic point of view. Specifically, this thesis investigates the interactions between source coding and channel coding to gain cooperation between them in terms of energy efficiency. For transmission through AWGN channels with path loss, this work shows that the overall energy consumption can be minimized if each source transmits with minimum power and cooperates with other sensors in TDMA mode. Moreover, for correlated source coding, the Slepian-Wolf coding theorem is applied for resource efficiency. Combining the transmission with correlated source coding, we derive an optimal closed form bit allocation scheme to minimize the overall energy consumption. The spirit is to allocate more bits to the nodes with better channel conditions and less bits to the nodes with worse channel conditions. Based on this solution, we further maximize the network lifetime and develop a heuristic algorithm to average the distribution of energy consumption among all sensors. Both proofs and simulation results are presented to show the superiority of our schemes.

 


Date/Time: 2010-06-24, 2:30 PM

Speaker: Nizar H. Alsharif

Title: ESPR: Efficient Security Scheme for Position-Based Routing in Vehicular Ad Hoc Networks

Abstract: Vehicular Ad hoc Network (VANET) is a promising emerging technology that enables road safety, traffic management, and passengers and drivers comfort applications. Many applications require multi-hop routing; position-based routing (PBR) is a well-recognized routing paradigm that performs well in the vehicular context to enable these applications. However, there are many security challenges and various routing attacks which may prevent the deployment of PBR protocols. In this study, we propose a novel security scheme called ESPR to secure PBR protocols in VANETs. ESPR considers both digital signature and keyed Hash Message Authentication Code (HMAC) to meet the unique requirements of PBR. In ESPR, all legitimate members share a secret key. ESPR scheme applies a novel probabilistic key distribution to allow unrevoked members to update the shared secret key. Furthermore, it defines a set of plausibility checks that enables network members to detect and avoid PBR at- tacks autonomously. By conducting security analysis and performance evaluation, ESPR scheme demonstrated to outperform its counterparts in terms of communication overhead and delay while achieving robust and secure operation.

 


Date/Time: 2010-06-17, 3:00 PM

Speaker: Yongkang Liu

Title: Opportunistic Routing in Dynamic Spectrum Access Networks

Abstract: In this talk, we exploit the heterogeneity of wireless channels and propose an efficient opportunistic cognitive routing (OCR) scheme for dynamic spectrum access (DSA) networks. We first introduce a novel routing metric by jointly considering physical characteristics of spectrum bands and diverse activities of primary users (PU) in each band. To effectively explore the spectrum opportunities, a proper channel sensing sequence for fast and reliable message delivery is determined by secondary users (SU) in a distributed way. We then propose a greedy forwarding scheme that SUs can select the next hop relay based on the geometry information and channel access opportunity of their one hop neighbors. For the proposed OCR, as routing control messages are locally exchanged, SUs can efficiently make the routing decision and opportunistically access the available channels. We further evaluate the performance of OCR via extensive simulations. It is shown that our proposed scheme outperforms existing opportunistic routing schemes in dynamic spectrum access (DSA) networks by exploiting the heterogeneity of spectrum bands for opportunistic channel access.

 


Date/Time: 2010-06-16, 11:00 AM

Speaker: Prof. Zhisheng Niu, Tsinghua University, Beijing, China, Invited By Prof. Weihua Zhuang

Title: Paradigm Shift toward Globally Resource-optimized and Energy-Efficient Networks (GREEN)

Abstract: The explosive development of ICT (information and communication technology) industry has emerged as one of the major sources of world energy consumption. In particular, China has already become the No.1 country with the largest market of telephone users as well as Internet users, while it is still in a fast growing phase. As a result, having the information and communication networks in China more green is one of the most critical issues for a sustainable future of both China itself and the whole world. In this talk, I will address the paradigm shift of the information networks, in particular the wireless communication networks, from the viewpoint of energy-efficiency, and propose a new concept of GREEN: Globally Resource-optimized and Energy-Efficient Networks. Specifically, power saving mechanisms of both wireless local area network (WLAN) and the base station cooperation schemes in cellular networks will be discussed. Theoretical modeling and simulation studies have shown that the data retrieval schemes and the base station coordination schemes can greatly improve the energy-efficiency of the wireless networks, while the resource utilization can be kept at a satisfactory level.

 


Date/Time: 2010-06-10, 3:00 PM

Speaker: Juncheng Jia

Title: Software Defined Radio for Cognitive Radio Network Research

Abstract: Cognitive radio communication and networking are proposed to achieve high-performance data communication and improve the spectrum efficiency. Testbed evaluation of protocols and algorithms is quite important for the research and development of cognitive radio networks. In this talk, I will briefly introduce the usage of software defined radio as the experimental testbed for cognitive radio. I will focus on the testbed platform based on the widely used USRP hardware and GNU Radio software. Such a platform not only includes necessary components for cognitive radio operations, but also has good programmability, which ease the development effort and shorten the development time greatly. I will present our recent work on cooperative relay for cognitive radio network which uses this platform for experiment. Furthermore, I will demonstrate the performance improvement of the software implementation with particular focus on OFDM transmission, which is quite important for cognitive radio. With various enhancement methods for both flow graph design and inside-block optimization, we are able to fully exploit the hardware capability of USRP hardware and achieve high data transmission speed on air with general purpose computers.

 


Date/Time: 2010-06-4, 11:00 AM

Speaker: Prof. Xue Liu, University of Nebraska Lincoln, USA, Invited By Prof. Weihua Zhuang

Title: Two Vignettes of Cyber-Physical Systems Research

Abstract: Cyber-Physical Systems is a new frontier of research for computer science and engineering. It has been highlighted by the August 2007 US President's Council of Advisors on Science and Technology (PCAST) report and recommended by the Federal Networking and Information Technology R&D (NITRD) as a top priority for federal research investments. In this talk, I will present two pieces of our recent work focusing on power management and temporal performance guarantees for cyber-physical systems, exemplified by large scale Internet Data Centers and real-time embedded systems. First, I will show how we can jointly consider the cyber and physical aspects of Internet Data Centers to minimize the total electricity cost in a multi-electricity market environment. Then I will present Universal Feasible Region Analysis, which is a schedulability analysis framework for ensuring response time guarantee for networked embedded systems under general workload.

 


Date/Time: 2010-06-03, 3:00 PM

Speaker: Subodha Gunawardena

Title: Capacity Analysis and Call Admission Control for QoS Support in Cognitive Radio Networks

Abstract: The growing demands towards wireless communication services over the recent years have increased the demand for radio spectrum. However, inefficient spectrum management together with the scarcity of the radio spectrum has become a limiting factor for the development of modern wireless networks. The idea of cognitive radio networks (CRNs) is introduced to use licensed spectrum for the benefit of the unlicensed secondary users. However, the randomness of primary user activities leads to random nature of resource availability for the secondary networks, making it a challenging task to support applications which require specific quality-of-service (QoS) guarantees. With the ever increasing demands for multimedia wireless services, CRNs will need to support real time traffic with service satisfaction. This research investigates the voice and interactive data traffic support over CRNs, considering their service requirements. In particular, constant-rate and on-off voice traffic capacities are analyzed over CRNs with centralized and distributed coordination. Some generic channel access schemes are considered as the coordination mechanism, and queuing delay of a voice packet is considered as the service requirement. Furthermore, the issues in the capacity analysis of interactive data traffic flows over voice/data integrated networks with distributed coordination are discussed. Finally, the design challenges of a call admission control (CAC) algorithm for non fully connected CRNs are discussed.

 

Date/Time: 2010-05-27, 3:00 PM

Speaker: Ho Ting (Anderson) Cheng

Title: Call-Level Resource Management for Wireless Mesh Networks

Abstract: Effective and efficient resource management is imperative to support multimedia services with diverse quality-of-service (QoS) requirements in future wireless networks. In this talk, I am going to address the issues of distributed call admission control (CAC) and QoS-aware resource allocation in multi-hop wireless mesh networks (WMNs) with decentralized control. We first formulate two optimization problems for QoS-aware end-to-end resource allocation in multi-hop WMNs, namely user capacity optimization for QoS-sensitive multimedia traffic and system throughput optimization for background data traffic. By introducing additional interference tolerability to each multimedia flow, we propose a new approach for distributed CAC and end-to-end resource allocation based on the Karush-Kuhn-Tucker (KKT) interpretations. The proposed approach is demonstrated effective in fosterin