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 Winter 2014
Date Speaker Email Category


 Fall 2013

 Spring 2013

 Winter 2013
Date Speaker Email Category
2013-01-04 Rongxing Lu rxlu AT bbcr.uwaterloo.ca Security
2013-01-11 Zhu Han (Invited) zhan2 AT uh.edu Smart Grid
2013-01-18 Ahmed M. Hamza a55moham AT uwaterloo.ca Performance
2013-01-25 Ning Zhang zhangningbupt AT gmail.com CRN
2013-02-01 Tom Luan hluan AT uwaterloo.ca VANET
2013-02-08 Nan Cheng wmchengnan AT gmail.com Smart Grid
2013-02-14 Qiang Ye yqnjupt AT 163.com Green Comm.
2013-02-22 Yongkang Liu yongkang.liu.phd AT gmail.com Cognitive Networks
2013-03-01 Ning Lu luning.ee AT gmail.com VANET
2013-03-08 Sanna Taha staha AT uwaterloo.ca VANET
2013-03-15 Sailesh Bharati sbharati AT uwaterloo.ca VANET
2013-03-22 Ruilong Deng dengruilong AT gmail.com Sensor Networks
2013-03-29 Good Friday    
2013-04-05 Chong Lou CLOU AT uwaterloo.ca Ad hoc Networks
2013-04-12 Neda Mohammadizadeh n7mohamm AT uwaterloo.ca Performance
2013-04-19 Sailesh Bharati sbharati AT uwaterloo.ca VANET
2013-04-19 Subodha Gunawardena shgunawa AT uwaterloo.ca CRN
2013-04-26 Kuan Zhang garnekuan AT gmail.com Security


Date/Time: 2013-04-26, 11:00 am

Speaker: Kuan Zhang

Title:POMP: An Efficient Packet Forwarding Protocol with Private Profile Matching in Mobile Social Networks

Abstract: Mobile Social Networks (MSNs), which facilitate social interactions among mobile users in proximity, have received considerable attention in recent years. In this paper, we propose an efficient packet forwarding protocol (POMP) with private profile matching for MSNs, which not only improves the packet forwarding efficiency, but also preserves user privacy. Specifically, we exploit the feature of the common communities to evaluate the forwarding capabilities of neighbors to the source, and select the optimal relays having more common communities with the destination to store-carry-and-forward the packets. Secondly, we utilize Merkle hash tree and a homomorphic encryption technique to attain mobile users’ profile matching without disclosing their privacy to each other. Detailed privacy analyses show that the POMP can protect the mobile user’s private information from disclosure to others with low profile similarity and resist the profile forgery attack. In addition, the extensive real-trace based simulations are also carried out to demonstrate the effectiveness and efficiency of the POMP in terms of delivery ratio, average delay, and communication overhead.


Date/Time: 2013-04-19, 11:15 am

Speaker: Subodha Gunawardena

Title:Capacity Analysis for QoS Support in Cognitive Radio Networks

Abstract: The growing interest towards wireless communication services over the recent years has increased the demand for radio spectrum. Inefficient spectrum management together with the scarcity of the radio spectrum is a limiting factor for the development of modern wireless networks. As a solution, the idea of cognitive radio networks (CRNs) is introduced to use licensed spectrum for the benefit of the unlicensed secondary users. However, the preemptive priority of the licensed users results in random resource availabilities at the secondary networks, which makes the quality-of-service (QoS) support challenging. With the increasing demand for elastic/interactive data services (internet based services) and wireless multimedia services, QoS support becomes essential for CRNs. This research investigates the voice and elastic/interactive data service support over CRNs, in terms of their delay requirements. The packet level delay requirements of the voice service and session level delay requirements of the elastic/interactive data services are studied. In particular, constant-rate and on-off voice traffic capacities are analyzed over CRNs with centralized and distributed network coordination. Some generic channel access schemes are considered as the coordination mechanism, and call admission control algorithms are developed for non-fully-connected CRNs. Advantage of supporting voice traffic flows with different delay requirements in the same network is also discussed. The mean response time of the elastic data traffic over a centralized CRN is studied, considering the shortest processor time with and without preemption and shortest remaining processor time service disciplines, in comparison with the processor sharing service discipline. Effects of the traffic load at the base station and file length (service time requirement) distribution on the mean response time are discussed. Finally, the relationship between the mean response times of interactive and elastic data traffic is studied.


Date/Time: 2013-04-19, 10:30 am

Speaker: Sailesh Bharati

Title:Link-Layer Cooperative Communication in Vehicular Networks

Abstract: Vehicular ad hoc networks (VANETs) are a special kind of communication networks, where vehicles communicate with each other or with stationary road side units. VANETs are expected to support a large spectrum of mobile distributed applications that range from vehicle-collision warning and vehicle-traffic alert dissemination (safety applications), to file-sharing and location-aware advertisements (infotainment). As communication nodes are organized in an ad hoc manner to form a communication network, VANETs possess some special characteristics, such as the highly dynamic network topology (with high node mobility and frequent link breakage) and stringent quality of service requirement (for high priority for delay sensitive safety messages), as compared with the general mobile ad hoc networks (MANETs). Hence, directly applying the existing communication protocols designed for MANETs may not be reliable and efficient in VANETs. Investigation and development of VANET communication protocols are required to support the wide range of applications. The objective of this research is to develop a link-layer cooperative framework to improve communication reliability and throughput in VANETs. In this proposal, we present three fundamental issues related to link-layer cooperation: (a) how to utilize the available radio resources efficiently for more reliable transmission in the existing distributed TDMA MAC protocols, (b) how to support broadcast services for safety related applications, and (c) how to address channel conflict problems for multi-channel MAC protocols. In a preliminary study, we propose a cooperative MAC scheme called Cooperative ADHOC MAC (CAH-MAC), in which neighbor nodes cooperate to increase the throughput by utilizing unreserved time slots for retransmission of failed packets. Numerical results demonstrate the performance of the CAH-MAC and the effects of node mobility in CAH-MAC. In further research, we will consider realistic mobility and channel models in evaluating the performance of CAH-MAC and develop a link-layer cooperation framework for broadcast services and multi-channel MAC.


Date/Time: 2013-04-12, 11:00 am

Speaker: Neda Mohammadizadeh

Title:Cooperation of Heterogeneous Wireless Networks in End-to-End Congestion Control for QoS Provisioning

Abstract: Sharing radio resources of multiple wireless networks with overlapped coverage areas has a potential of improving the transmission throughput. However, the improvement cannot be achieved in congestion scenarios using independent congestion control procedures among the end-to-end paths. Although various network characteristics make the congestion control complex, this variety can be useful for congestion avoidance if the networks cooperate with each other. In this way, the traffic can be shifted from a congested network to non-congested ones, and the overall transmission throughput does not degrade in a congestion scenario. In this talk, first, a proposed cooperative congestion control algorithm will be described, in which the state of an end-to-end path is provided at the destination terminal by measuring the queuing delay and estimating the congestion level. Second, the decision on when to start/stop cooperation will be explained based on the network characteristics, instantaneous traffic condition, and requested quality of service. Simulation results demonstrate the throughput improvement of the proposed scheme over non-cooperative congestion control.


Date/Time: 2013-04-05, 11:00 am

Speaker: Chong Lou

Title:A Survey on Energy-efficient Routing Solutions in Wireless Ad hoc Networks

Abstract: The constituent mobile devices in wireless ad hoc network have batteries with limited energy. Therefore, a critical design issue is the development of energy conservation schemes to increase the device and network operation time. Energy-efficient routing is an effective mechanism to respond to such challenge in wireless ad hoc networks. The main factors which influence the power awareness of a routing solution are routing protocol and route selection of the most energy efficient path. This survey offers state-of-art contributions to the pool of energy-efficient routing solutions for wireless ad hoc networks, not limited to wireless sensor networks (WSN). We include a thorough overview of design factors and challenges, related metrics and energy consumption models evaluating the performance of energy efficiency, and then outline the routing protocols proposed in underlying networks. Moreover, we focus on route selection problems. Firstly we analyze the fundamental and QoS-enabled route selection problems, followed by link and route costs associated with route selection. And then, existing algorithms that are coupled or decoupled from routing protocols are further classified according to their main objectives. Finally, a discussion of highlight trends in protocol and algorithm design for further research is discussed.


Date/Time: 2013-03-22, 11:00 am

Speaker: Ruilong Deng

Title:Globally Optimizing Network Utility with Spatiotemporally-Coupled Constraint in Rechargeable Sensor Networks

Abstract: Energy harvesting, emerging as a promising technology to extend the lifetime of wireless sensor networks, opens up a new research area referred to as rechargeable sensor networks (RSNs). This talk is concerned with the network utility maximization problem in static-routing RSNs with limited battery capacity. In such a problem, due to the constrained energy consumption rate, one node's sampling rate is coupled with some other nodes. Moreover, the energy consumption rate of each node is constrained by its energy harvesting rate and current battery level to avoid depletion or overcharge of the battery, so it is also coupled across the time horizon. Therefore the problem has the spatiotemporally-coupled constraint, which, to the best of our knowledge, has not been thoroughly investigated. To this end, we will globally optimize the problem. By dual decomposition, we decouple it into separable subproblems, which can be distributively solved without the need to coordinate with other nodes or time horizon. We then propose a distributed algorithm in the context of joint rate and battery control, which converges to the globally optimal solution. Numerical results, based on the real solar data, demonstrate that the proposed algorithm always achieves the higher network utility than existing approaches. The impact of battery capacity on the network utility is also investigated.


Date/Time: 2013-03-15, 11:00 am

Speaker: Sailesh Bharati

Title:Effects of Time Slot Reservation in Cooperative ADHOC MAC for Vehicular Networks

Abstract: Cooperative medium access control (MAC) protocols have been proposed for improving communication reliability and throughput in wireless networks. In a recent study, a cooperative MAC scheme called Cooperative ADHOC MAC (CAH-MAC) has been proposed to increase the network throughput by reducing the wastage of time slots under a static network scenario. Particularly, neighbor nodes cooperate to increase the transmission reliability by utilizing unreserved time slots for retransmission of failed packets. In this work, we focus on a mobile networking scenario and study the effects of time slot reservation on the performance of CAH-MAC under highly dynamic vehicular environments. We find out that the introduction of time slot reservation results in cooperation collisions, degrading the system performance. To tackle this challenge, we present an enhanced CAH-MAC (eCAH-MAC) that is able to avoid cooperation collisions and thus efficiently utilize a time slot. In eCAH-MAC, the cooperative relay transmission phase is delayed, so that cooperation collisions can be avoided and time slots can be efficiently reserved. Through extensive simulations, we demonstrate that eCAH-MAC uses time slot more efficiently than CAH-MAC in direct and/or cooperative transmissions and in reserving time slots in the presence of relative mobility among nearby nodes.


Date/Time: 2013-03-08, 11:00 am

Speaker:Sanna Taha

Title:Securing IP mobility for Vehicular Ad Hoc Networks

Abstract: The proliferation of Intelligent Transportation Systems (ITSs) applications, such as Internet access and Infotainment, highlights the requirements for improving the underlying mobility management protocols for Vehicular Ad Hoc Networks (VANETs). Mobility management protocols in VANETs are envisioned to support mobile nodes (MNs), i.e., vehicles, with seamless communications, in which service continuity is guaranteed while vehicles are roaming through different RoadSide Units (RSUs) with heterogeneous wireless technologies. Due to its standardization and widely deployment, IP mobility (also called Mobile IP (MIP)) is the most popular mobility management protocol used for mobile networks including VANETs. In addition, because of the diversity of possible applications, the Internet Engineering Task Force (IETF) issues many MIP's standardizations, such as MIPv6 and NEMO for global mobility, and Proxy MIP (PMIPv6) for localized mobility. However, many challenges have been posed for integrating IP mobility with VANETs, including the vehicle's high speeds, multi-hop communications, scalability, and efficiency. From a security perspective, we observe three main challenges: 1) each vehicle's anonymity and location privacy , 2) authenticating vehicles in multi-hop communications, and 3) physical-layer location privacy. In this presentation, we address those security challenges by proposing three security schemes to be employed for different mobility management scenarios in VANETs, namely, the MIPv6, PMIPv6, and Network Mobility (NEMO) protocols.


Date/Time: 2013-03-01, 11:00 am

Speaker: Ning Lu

Title:VeMail: A Message Handling System Towards Efficient Transportation Management

Abstract: In this talk, we discuss an electronic mail system, namely VeMail, for handling messages between vehicles and Intelligent Transportation Systems (ITS), to improve the efficiency of transportation management. After elaborating the reasons of using Internet email as a basis of messaging for ITS, we describe the key components of the VeMail system, including mail server, mail client, and mail proxy. Considering the intermittent connectivity of vehicles to the mail server, we propose an optimal probabilistic message retrieval (OPMR) scheme for VeMail, in which each vehicle optimally selects an online period for email retrieval. Simulation results demonstrate that the proposed scheme outperforms the regular mail retrieval method in terms of the connection time with the mail server.


Date/Time: 2013-02-22, 11:00 am

Speaker: Yongkang Liu

Title:Small Cell Deployment in Cognitive Cellular Networks

Abstract: The smartphone fever along with the roaring mobile traffic pose great challenges for cellular networks to provide seamless wireless access to end users. Operators and vendors realize that new techniques are required to improve the spectrum efficiency to meet the ever-increasing user demand. In this talk, we are going to exploit the great opportunities provided by the cognitive radio technology in the conventional cellular networks. Specifically, we first present challenging issues including interference management, network coordination, and interworking between access networks in a tiered cognitive cellular network with both macrocells and small cells. Taking into consideration the different network characteristics of macrocells and small cells, we then propose cognitive routing and adaptive resource management framework to improve the spectrum utilization efficiency and to mitigate the co-channel interference between macrocell and small cell users. A game theory based approach for efficient power control has also been provided.


Date/Time: 2013-02-14, 11:00 am

Speaker: Qiang Ye

Title:A Brief Literature Survey: Techniques for Energy Saving in Green Wireless Communication Networks

Abstract: Due to the huge booming of the subscribers and their increasing demands for better services in future wireless communication networks, providers and operators start to think how to build more advanced communication technologies to satisfy users’ service requirements and how to extend the network coverage to maintain a large number of users in their networks in order to make more profit from them. However, this kind of behaviors can certainly incur both transmission power and operational power increment of the network. The rising energy costs and carbon footprint of operating cellular network make the energy saving issue more critical and serious. Therefore, current research activities intend to find some optimal tradeoff between energy efficiency and quality of service provided by the network. In this work, we try to make a brief summary of the advantages and drawbacks of some current promising techniques and ideas as well as future research directions in achieving energy efficiency in wireless communication networks.


Date/Time: 2013-02-08, 11:00 am

Speaker: Nan Cheng

Title:Vehicle-Assisted Data Delivery for Smart Grid:An Optimal Stopping Approach

Abstract: The booming smart grid produces a large amount of data that should be transmitted to the utility control center (UCC), typically by means of the cellular network. This may pose a prohibitive transmission cost and choke the cellular network. As an effort to address this issue, we propose a vehicle assisted data delivery method to offload the cellular network, in which vehicles are utilized to carry and deliver the data from distributed locations to the UCC through the deployed roadside units. Two data forwarding schemes are developed based on the theory of optimal stopping rules to increase the data delivery probability. Simulation results are given to demonstrate that the proposed method can achieve high data delivery ratio through the roadside network so that it can efficiently offload the cellular network and reduce the communication cost.


Date/Time: 2013-02-01, 11:00 am

Speaker: Tom Luan

Title:Dimensioning the End-to-End Performance of Vehicular Ad Hoc Networks

Abstract:The end-to-end communication performance of multi-hop transmissions lies the basis of the upper-layer media applications in vehicular communications. There, however, lacks an accurate and practical analytical framework to effectively evaluate the end-to-end throughput and delay performance in VANET with the specific features of VANET, e.g., channel fading, node mobility and MAC contentions, taken into considerations. In this work, we adopt the queuing theory to analyse the multi-hop performance of vehicular communications. We start by investigating on the single-hop performance and then extends the results on the analysis of multi-hop communications.


Date/Time: 2013-01-25, 11:00 am

Speaker:Ning Zhang

Title: Security-aware Cooperation in Cognitive Radio Networks

Abstract:Cognitive radio network (CRN) is envisaged to increase spectrum efficiency by allowing unlicensed users to opportunistically exploit the unused spectrum bands which are owned by licensed users. In order to access the spectrum bands without creating interference to the licensed users, unlicensed users need to conduct spectrum sensing. While spectrum sensing might be inaccurate due to multipath fading and shadowing. To address this problem, two types of cooperation have been proposed in the literature: cooperative spectrum sensing and cooperative networking based spectrum access. Whereas cooperation can also incur security issues, e.g.,malicious users might participate into cooperation, corrupting or disrupting the communication of legitimate users, selfish users might refuse to contribute to cooperation for self-interests, etc.Those security issues are of great importance and need to be addressed before the widespread deployment of cooperation in CRNs. However, in the literature, the work on the security aspects of cooperation in CRNs is very limited. In this talk, we study the cooperation in different forms in CRNs, taking security into consideration. Preliminary research results are presented, including a risk-aware cooperative framework for CRNs to improve the energy efficiency of licensed users and offer transmission opportunities to unlicensed users, considering the trustworthiness of unlicensed users, and cooperative spectrum access schemes, which enhance the physical layer security of licensed users through cooperation with unlicensed users. Finally, further works are discussed.


Date/Time: 2013-01-18, 11:00 am

Speaker: Ahmed M. Hamza

Title: Performance Modeling, Design, and Analysis of Cooperative Communications in Cellular Networks

Abstract:Although base station cooperation or what is called coordinated multi-point proves that it can achieve high gains in theory, there are some challenges that need to be solved in order for it to be practically deployed. In this proposal, we investigate two challenges, the base station grouping (clustering) and timing synchronization problems, and develop solutions for both problems. For the clustering problem, a scheme based on choosing the base stations that can satisfy the timing synchronization requirements of the users inside the cluster is proposed. With the aid of simulations, we compare this scheme to the existing clustering schemes that do not take this requirement into consideration and show that the performance of our proposed scheme outperforms the performance of other schemes. For the timing synchronization problem, we propose a scheme that solves this problem by linearly combining two consecutive received symbols in the frequency domain. Simulation results are provided to demonstrate that our proposed scheme can solve this problem and enable the usage of base station cooperation in any scenario.


Date/Time: 2013-01-11, 10:00 am

Speaker: Zhu Han

Title: Bad Data Injection in Smart Grid: Attack and Defense Mechanism

Abstract:In smart grid, the strong coupling between cyber and physical operations makes power systems vulnerable to cyber attacks. If the attackers are able to penetrate into the power grid network and inject the malicious data, the energy management system may produce the false state estimation, which potentially results wrong decisions on billing, power dispatch and erroneous analysis, and even causes a generator self-destruct. In this talk, we discuss two examples from the attacker and defender points of view. Without prior knowledge of the power grid topology, the attacker’s goal is to make inferences through phasor observations. We show that when the system dynamics are small and can be approximated linearly, linear independent component analysis (ICA) can be applied to estimate the Jacobian matrix multiplied by the eigenvectors of the covariance matrix of the state variables. The inferred structural information can then be used to launch unobservable attacks. For defense strategy, we propose the proposed “adaptive CUSUM algorithm”, and each recursion comprises two interleaved stages: Stage 1 introduces the linear unknown parameter test, and Stage 2 applies the multi-thread CUSUM algorithm for quickest change detection. The proposed scheme is able to determine the possible existence of adversary at the control center as quickly as possible without violating the given constraints such as a certain level of detection accuracy and false alarm.


Date/Time: 2013-01-04, 11:00 am

Speaker: Rongxing Lu

Title: Anonymization Technology of Social Networks

Abstract:Social network can be utilized to discover useful knowledge and valuable findings. However, in order to prevent potential re-identification attacks, social network data should be anonymized before being released for research purposes. In this talk, we will introduce several anonymization technologies for social networks.


 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 fostering frequency reuse and increasing the number of multimedia flows supported in the system, outperforming its conventional resource allocation counterpart. Our approach is also of low complexity, leading to a preferred candidate for practical implementation.


Date/Time: 2010-05-20, 3:00 PM

Speaker: Sandra Cespedes U.

Title: Mobility Management in Urban Vehicular Networks: A Multilayer Approach

Abstract: The extensive deployment of wireless access networks, and the introduction of innovative wireless devices have triggered an increasing demand for Internet access from anywhere, and at any time. When the Internet is accessed in an urban vehicular network, it involves the access from computers and entertainment systems installed in vehicles, buses, or trains, as well as the access from mobile devices being used by passengers and people commuting between terminal stations. A major challenge of such scenario is how to provide seamless communications, regardless of the changes in the point of attachment, the access network, or the administrative domain. In this talk, we introduce a multilayer approach to address that challenge. We first propose an interworking scheme to manage the mobility from the network-layer and a shim layer (i.e., an extra layer between network and transport). The scheme supports legacy nodes, mobility-enabled nodes and mobile networks. Moreover, the scheme does not require any synchronization among the different network operators providing the access. Preliminary results are presented for the aforementioned scheme. Then, we propose to incorporate to the scheme the dynamics of the vehicular network, and the mobility patterns of its users, so that it adapts to maximize what is best for the users depending on their current behaviours. Finally, we propose to study the use of multipath sessions at the transport layer, as a supportive mechanism for transparent handovers and smooth communications. With a mobility management architecture that involves different layers in the stack of communication protocols, we intend to provide a customized solution that fits in an urban vehicular environment. It integrates the different possible users and the different possible configurations at the network side. More important, it incorporates the special characteristics of a vehicular network to boost the mobility performance perceived by the mobile users. With such a solution, a ubiquitous Internet could be provided to all the players in the vehicular network, whether they have or not mobility support, at a level where all the dissimilar access networks and the different network operators appear to the users as one single and universal network.


Date/Time: 2010-05-13, 3:00 PM

Speaker: Mohamed Elsalih Mahmoud

Title: Credit-based Mechanism Protecting Multi-hop Wireless Networks from Rational and Irrational Packet Drop

Abstract: The existing credit-based mechanisms stimulate the rational packet droppers to relay other nodes' packets for improving the performance of multi-hop wireless networks. However, they cannot identify the irrational packet droppers such as compromised or broken nodes, which has negative impact on the network performance. In this paper, we propose a credit-based mechanism that uses credits to stimulate the rational packet droppers to behave cooperatively, and uses reputation system to identify the irrational ones. Payment receipts are processed to reward the cooperative nodes, and to detect the broken links so that a reputation system can be built to identify the irrational packet droppers. Our evaluations demonstrate that our mechanism can secure the payment, and precisely identify and evict the irrational packet droppers.


Date/Time: 2010-05-06, 3:00 PM

Speaker: Hao Liang

Title: DTCoop: Delay Tolerant Cooperative Communications in DTN/WLAN Integrated Networks

Abstract: In this work, we consider a DTN/WLAN integrated network where nomadic nodes with high mobility comprise a delay tolerant network (DTN) while local nodes with low mobility reside in the coverage area of wireless local area networks (WLANs). A message dissemination service is considered, where data traffic is generated by a server in the Internet and destined to a group of nomadic nodes. In order to facilitate message dissemination, a delay tolerant cooperative communication (DTCoop) scheme is proposed. The messages for dissemination are first pre-downloaded to a group of storage local nodes within a WLAN before the visit of a nomadic node, and then scheduled for transmission when a nomadic node comes into the transmission range. Analysis and simulation results are presented to evaluate the performance of the proposed DTCoop scheme. It is shown that our proposed scheme can significantly improve the message delivery performance from a WLAN to a nomadic node as compared with existing schemes without message pre-downloading or message scheduling.


  Winter 2010

  Fall 2009

  Spring 2009
Date Speaker Email Category
2009-05-07 Feng Wang f22wang AT uwaterloo.ca Performance
2009-05-14 Mohammed Towhidul Islam mtislam AT uwaterloo.ca Performance
2009-05-28 Mohamad Awad Mohamad AT ieee.org Performance
2009-06-04 Yanfei Fan yfan AT bbcr.uwaterloo.ca Security
2009-06-11 Mohamed Elsalih Mahmoud moh.elsalih AT gmail.com Security
2009-06-18 Albert Wasef awasef AT bbcr.uwaterloo.ca Security
2009-07-09 Mohamed Elsalih Mahmoud moh.elsalih AT gmail.com Security
2009-08-06 Prof. Hai Jiang (Invited) hai.jiang AT ece.ualberta.ca Performance


Date/Time: 2009-08-06, 3:00 PM

Speaker: Prof. Hai Jiang, University of Alberta, Invited By Prof. Weihua Zhuang

Title: Cognitive Medium Access: Exploration, Exploitation, and Competition

Abstract: The design of medium access protocols in cognitive radio networks is considered using a reinforcement machine learning approach. In the network model under consideration, the cognitive users wish to opportunistically exploit the availability of empty frequency bands in the spectrum with multiple bands. The availability probability of each band is assumed to be unknown to the cognitive user in advance. Hence efficient medium access strategies must strike a balance between exploring, that is to spend time on learning the channel statistics, and exploiting, that is to access the channel with the largest availability probability based on the information learned thus far. By adopting a Bayesian approach for the classical bandit problem in reinforcement machine learning, the optimal medium access strategy is derived. To avoid the prohibitive computational complexity of the optimal strategy, a low-complexity asymptotically optimal strategy is developed. The proposed strategy does not require any prior statistical knowledge about the availability probability of each channel. Multi-user cases are also investigated when the channel availability information is known or unknown, respectively.


Date/Time: 2009-07-09, 3:00 PM

Speaker: Mohamed Elsalih Mahmoud

Title: A New Research Direction for Stimulating Cooperation in Multi-hops Wireless Networks

Abstract: In recent years the interest in multi-hop wireless networks has been growing significantly. In these networks, the mobile nodes work as routers to relay packets generated from other nodes. The nodes? cooperation is essential for proper network operation. Selfish nodes do not cooperate to save their resources and thus to improve the efficiency of their devices. However, they use the other devices to relay their packets. This selfish behavior causes fairness, performance and security problems in the network. In the literature, reputation and credit based mechanisms have been proposed to enforce and stimulate the nodes? cooperation respectively. In reputation based mechanisms, the network nodes monitor each other to identify and punish selfish nodes. A reputation system is used to differentiate between a node?s unwillingness and inability (due to mobility or full buffer) to cooperate and also to suppress the impact of false accusations. These mechanisms do not achieve fairness because they do not differentiate among nodes with different contributions to the network. In addition, they are not efficient because the nodes work in promiscuous modes which are provably inefficient. In credit based mechanisms, credits are used to stimulate the nodes? cooperation and to achieve fairness by rewarding cooperative nodes. These mechanisms impose huge overhead due to extensively using cryptographic mechanisms to secure the payment process. Although, lots of papers have been published to alleviate the aforementioned problems, we believe that they are essential. Therefore, this paper proposes a novel direction which combines the features of the two existing solutions. Fairness is achieved by using credits to reward cooperative nodes. The overhead is much reduced with using a cheating detection system (CDS) to secure the payment system instead of using cryptographic primitives. Our simulations show that the overhead of implementing the proposed solution is incomparable with the existing mechanisms, and the cheating detection system can detect the cheaters efficiently at different attacking strategies and under high ratio of attackers.


Date/Time: 2009-06-18, 3:00 PM

Speaker: Albert Wasef

Title: A tutorial on security in vehicular ad hoc networks (VANETs)

Abstract: Recently vehicular ad-hoc networks (VANETs) have attracted extensive attentions for their promises in revolutionizing the transportation systems. VANETs have a wide variety of safety-related applications such as forward collision warning, side blind zone warning, lane change assist warning, lane departure warning, etc. VANETs consist of network entities, mainly including vehicles and Road-Side Units (RSUs). Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) communications are two basic vehicular communication modes, which respectively allow vehicles to communicate with each other or with the roadside infrastructure. Any malicious behavior of a user, such as injecting false information, modifying and replaying the disseminated messages, could be fatal to other legal users. Furthermore, the privacy of users must be guaranteed in the sense that the privacy-related information of a vehicle should be protected to prevent an observer from revealing the real identities of the users, tracking their locations, and inferring sensitive data. In this presentation, I will give a tutorial on the different security mechanisms used in VANETs. In addition, some open research topics will be pointed out.


Date/Time: 2010-06-11, 3:00 PM

Speaker:Mohamed Elsalih Mahmoud

Title: DSC: Cooperation Incentive Mechanism for Multi-hop Cellular Networks

Abstract: Muli-hop cellular network is a promising network architecture which incorporates the ad hoc characteristic into the cellular system aiming to improve current cellular network performance. Unlike single hop cellular network, due to involving autonomous devices in packet forwarding, routing process suffers from new security challenges which endanger the practical implementation of the network. One security challenge is that selfish devices do not relay other nodes? packets because cooperation consumes their resources and does not provide any immediate advantages. Selfish nodes degrade the network throughput, connectivity and power consumption. In order to stimulate the nodes? cooperation, we propose a micro-payment mechanism to reward the forwarding nodes and charge the communicating ones. The security analysis shows that the proposed mechanism is robust against rational attacks, and it can thwart some irrational ones. To evaluate the cost of applying our mechanism, an implementation model is proposed. The performance analysis based on the implementation model demonstrates that the overhead is acceptable.


Date/Time: 2010-06-04, 3:00 PM

Speaker:Yanfei Fan

Title: An Efficient Privacy-Preserving Scheme against Traffic Analysis Attacks in Network Coding

Abstract: Privacy threat is one of the critical issues in network coding, where attacks such as traffic analysis can be easily launched by a malicious adversary once enough encoded packets are collected. Furthermore, the encoding/mixing nature of network coding precludes the feasibility of employing the existing pri-vacy-preserving techniques, such as Onion Routing, in network coding enabled networks. In this paper, we propose a novel pri-vacy-preserving scheme against traffic analysis in network coding. With homomorphic encryption operation on Global Encoding Vectors (GEVs), the proposed scheme offers two significant pri-vacy-preserving features, packet flow untraceability and message content confidentiality, for efficiently thwarting the traffic analysis attacks. Moreover, the proposed scheme keeps the random coding feature, and each sink can recover the source packets by inverting the GEVs with a very high probability. Theoretical analysis and simulative evaluation demonstrate the validity and efficiency of the proposed scheme.


Date/Time: 2010-05-28, 3:00 PM

Speaker:Mohamad Awad

Title: Resource Allocation for OFDMA Networks with Imperfect CSI

Abstract: I will present a scheme for the allocation of subcarriers, rate and power in orthogonal frequency division multiple access (OFDMA) networks. The scheme addresses practical implementation issues of resource allocation in OFDMA networks: inaccuracy of channel state information (CSI) available to the resource allocation unit (RAU) and diversity of subscribers' quality of service (QoS) requirements. In addition to embedding the effect of CSI imperfection in the evaluation of subscribers' expected rate, the resource allocation problem is posed as a network utility maximization (NUM) one which is solved via decomposing it into a hierarchy of subproblems. These subproblems coordinate their allocations to achieve a final allocation that satisfies aggregate rate constraints imposed by the call admission control (CAC) unit and OFDMA-related constraints. Complexity analysis shows that the proposed scheme is computationally efficient. In addition, performance evaluation findings support our theoretical claims: a substantial data rate gain can be achieved by considering the CSI imperfection and multiservice classes can be supported with QoS guarantees.


Date/Time: 2010-05-14, 3:00 PM

Speaker:Mohammed Towhidul Islam

Title: SPID: A Novel P2P-based Information Diffusion Scheme for Mobile Networks

Abstract: Information sharing among mobile devices is increasingly prevalent because of widespread usage of those devices for day-to-day computational purposes. We propose a novel peer-to-peer based information diffusion scheme for mobile ad hoc networks. Due to mobility and bandwidth constraints, it is not always possible to share a complete content within a single transmission from one mobile device to another. To address this problem, we introduce segmentation of contents into smaller pieces for efficient information exchange. In the mobile ad hoc network, since it is impossible for a node to know the content of every other node in the network, we propose a Spatial-Popularity based Information Diffusion (SPID) scheme that determines urgency of dissemination of content according to the necessity in a neighbourhood. Substantially, the segmentation policy and popularity based information dissemination reduce content acquiring time for each peer. In addition, we devise a method to skip dissemination of same content by peers with overlapping neighbours. Extensive simulation studies demonstrate that the proposed scheme is efficient in data distribution in the mobile ad hoc networks, and prove superiority to other existing methods.


Date/Time: 2010-05-07, 3:00 PM

Speaker:Feng Wang

Title: Adaptive Weighted Scheduling in Cognitive Radio Networks

Abstract: A problem in modern wireless communications is the scarcity of electromagnetic radio spectrum. The traditional fixed spectrum assignment strategy results in spectrum crowding on most frequency bands. Due to limited availability of radio spectrum and high inefficiency in its usage, cognitive radio networks have been seen as a promising solution to reducing current spectrum under-utilization while accommodating for the increasing amount of services demands and applications in wireless networks. Compared with the traditional networks, cognitive radio networks exhibit some distinct features, which result in necessity of further research in the resource allocation and scheduling that have been solved for the traditional networks. In this thesis, we focus on the packet scheduling in a single cell cognitive radio system with a single channel. An adaptive weight factor is introduced to adjust the priority of different cognitive radio users to be selected for service. The purpose of this research is to solve the unfairness problem of the traditional proportional scheduling schemes when used directly in a cognitive radio network, which lead to a user starved for a long time if it experiences a poor channel condition when the channel is available and experiences a good channel condition when the channel is not available. An adaptive weighted scheduling scheme is proposed to improve the performance in terms of throughput and fairness by jointly considering the instantaneous propagation conditions, adaptive weighted factor and the channel availability. The saturated traffic and non saturated traffic cases are considered. Some important performance metrics are investigated in the simulation, such as the system throughput, fairness, and service probability, and are quantified by the impact of weights and channel conditions. Extensive simulations have been conducted to demonstrate the effectiveness and efficiency of the proposed scheduling scheme.

Last update: Copyright ©2009-2012, Rongxing Lu