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Coding for Cooperative Networks

Current wireless networks could not support the throughput requirements for rich Internet applications due to shared medium and interference. One of the promising approaches to break the bottleneck is cooperative networks. In this context, our research focus on the following issues.

In relay channels, relay nodes are used to facilitate the communications between the source nodes and destination nodes. When two nodes are communicating each other with the help of one relay node, the communication channels can be modeled as two-way relay channels. From coding perspective, current research focuses on two-way relay channels involves understanding the fundamental limit, designing the practical codes and interacting with the modulation and detection. In our research, we aim to develop efficient coding schemes for the two-way relay channels.

Fig 1: Three phases of half-duplex two-way relay channels. In phase 1, node 1 broadcasts messages to node 2 and 3. In phase 2, node 2 broadcasts messages to node 1 and 3. In phase 3, the relay node 3 encodes both source messages and broadcasts them to node 1 and node 3.

Fig 2: Code design for two-way relay channels. The codeword, represented as middle layer circles, can be divided into three parts. The leftmost part and the middle part can be used as the codes for node 1 and node 2 respectively by using lower layer parity check relations. The relay node uses the upper layer parity check relations to generate additional bits and forward them to node 1 and node 2.

As of today, interference is still considered as noise and hence limiting the usage of the wireless networks. However, if the interference signal can be decoded, it can be cancelled when we decode the desired information. The question is HOW, especially in a large wireless network when everyone is sending and receiving.

Current Researchers:

Xin Sheng Zhou.