The Research On Relay Selection In Cooperative Communication Systems

With the rapid development of wireless communication technology, people’sdemand about wireless communication system is higher to obtain wirelesscommunication services with high speed and high quality. This would be a greatchallenge to the anti-fading performance of communication system. The wirelesscooperative communication system takes the advantage of virtual MIMO to form avirtual antenna array. This would overcomes the channel fading impaction effectivelyand can be put into practice with a slight change in the upper communication protocol,and without changing the network structure. The cooperative communication canovercome the difficulty of installing multiple antennas on mobile terminals, andimprove the system performance at the same time. The basic idea of cooperativesystem is sharing antennas among users to obtain diversity gain. During the process,the fatal problem is how to choose one or more relays in the alternative relay set toassist data transmission. Therefore, this paper focuses on the relay selection ofcooperative communication system and does some explorations and researches. Thenwe propose several algorithms based on the optimal factor. Finally, these algorithmsare analyzed theoretically and verified through simulations.First, we propose a relay selection algorithm applying the optimal amplify factorin full-duplex relay. This algorithm applies the threshold to switch between theoptimal factor and the marginal factor to obtain better system performance and savesthe relay amplify power at the same time. We verify the advantages of this algorithmin terms of outage probability, relay weighting factor and received signal tointerference and noise through mathematical analyses and simulations.Second, three relay selection algorithms based on the optimal amplify factor areprovided in this paper, i.e., the improved single relay selection algorithm applyingoptimal amplify factor, the fair single relay selection algorithm applying optimalamplify factor and the power efficient distributed multiple relays selection algorithmrespectively. These relay selection algorithms all have their advantages anddisadvantages and can be applied in different communication situations.The four relay selection algorithms proposed in this paper can solve theself-interference at full-duplex relay and improve the system performance to someextent. Meanwhile, the power consumption of the relay can be reduced and thus thelife of the relay can be extended.