Research Of Relaying Strategies For Cooperative Communications

In the wireless communication systems, the receiver can achieve diversity gains and better performance of bit error rate with the help of the relay. Now, it has become clear that different relaying strategies have different effect on the performance of the receiver. So this thesis studies in depth the relaying protocols in single-relay and multi-relay wireless networks.We briefly introduced the background and history of cooperative communication system's development at the beginning, and then we analyzed three typical relaying protocols: amplify and forward, decode and forward and coded cooperation.In single-relay wireless networks, we focus on DAF and DAF-DF protocols proposed in 2005. Analytical and simulation results show that both of them can get considerable gains over AF and DF under different channel conditions.In wireless networks with multiple relays, we designed two new relaying strategies: MR-HDAF and MR-DAF-DF. Analytical results show that MR-HDAF can achieve lower symbol error probability and simulation results indicate that MR-DAF-DF and MR-HDAF protocols outperform the two conventional ones: AF and ADF in any kind of channel condition, particularly when the relays are closed to the destination or halfway between the source and the destination. Interestingly, we further show that the performance gain of MR-DAF-DF and MR-HDAF over AF or ADF is correlated to the number of relays and becomes saturated as the number of relays is large.