Research On Cooperative System Using Relay Diversity Over Nakagami-m Fading Channels

With the development of wireless communication technology, people are paying more attention to the decline in communication quality which is caused by multipath fading and they have obtained a lot of research achievements. Research shows that diversity is one of the effective means to overcome multipath fading. MIMO technology can be widely applied in the real environment because of it spatial diversity characteristic. To obtain spatial diversity, Sendonaris and Laneman proposed to constitute a distributed virtual multi-antenna system through using multiple source node. The way to get diversity through ocooperation of neighboring nodes is called cooperative diversity.The present research on cooperative diversity exists several following questions:(1) Most of the current relay selection systems only focus on the best relay selection, and few paper discuss the situation when the optimal relay is occupied.(2) Most of the relay system models assume that each link has a Rayleigh channel whose coefficients satisfy iid which makes it a simplified.According to the above two issues, this paper completed the two following tasks:1.We study the performance of DF relay system with Maximum Ratio Combining(MRC), Selective Combining(SC), Equal Gain Combining(EGC) over Nakagami-m channels. We derived the PDF, CDF, and MGF expression of end-to-end. In addition, we obtained the average SEP and the mathematical expression of the probability of interruption for each combing algorithm. The simulation shows that system performance improves with the increase of repeaters, and different decoding methods have different effects on system performance.2.We study the performance of AF relay system over Nakagami-m channels. When the best relay have been occupied, we select the Nth-best relay to replace it and discuss the performance of the system. Also, we analyse the GSC combing method. The simulation shows that GSC system is a good trade-off between complexity and performance, and the system can also achieve a good performance when choosing the2th-best relay. In addition, we simulated to compare the performance of GSC and Nth best system with MRC,SC,EGC ways.