Research On Cooperative Diversity Based On Network Coding

Transmission reliability and spectrum efficiency are two key performance evaluation criteria for wireless communication systems. On the one hand, cooperative diversity is a powerful technology combating signal fading due to multi-path propagation in wireless medium, which can enhance the reliability of transmission. On the other hand, network coding can increase the spectral efficiency. Then, there is reason to believe that effective incorporation of network coding into cooperative diversity can greatly improve their overall performance.Two kinds of cooperative diversity technologies based on network coding are studied: cooperative diversity based on signal superposition and cooperative diversity based on code superposition. First, a cooperative diversity scheme based on signal superposition is presented by using the idea of analog network coding in the physial layer for reference. The two modulated signals of local information and relay information are superimposed in the relay node through proper power allocation before transmission for exploiting degrees of freedom in wireless channels. Second, a cooperative diversity scheme based on code superposition is proposed by integrating the idea of packet level network coding in the physial layer. In the relay node, the two codewords for local information and relay information are XORed in physical layer before transmission for more efficient use of system resources. Simulation results show that cooperative diversity scheme based on signal superposition can significantly reduce the bit error rate at high SNR, while cooperative diversity scheme based on code superposition can improve system performance well at low SNR. Finally, the whole work is summarized and also research outlook for future work is carried out.