Research On Adaptive Multi-relay Selection Strategy For Device To Device Communication System

In recent years, with the rapid development of mobile communication, people get more need fora local shared data service which is similar to cellular communication. This demand promotes theemergence and development of D2D technology. D2D communication technology can increase thesystem frequency utilization and improve the quality of the service of edge users. Due to thepresence of channel fading in radio channel, D2D users cannot communicate directly when they arefar from each other. This thesis studies the relay selection strategy in D2D communication system.A single relay selection strategy in D2D system is studied in this thesis. As the traditional relayselection algorithm cannot coordinate the channel state information and the nodes’ distances factors.A single relay selection strategy which can switch between two strategies (i.e. distance-basedstrategy and SNR-based strategy) is studied. It can reduce the complexity of the system with theguarantee of system performance. Simulation results show that the channel utilization improvesgreatly with this strategy. The error rate and outage probability of D2D system in DF and AF modelis studied in this thesis, whose performances are verified by simulations.Three multi-relay selection strategies in D2D system are researched from the point ofcomplexity of the system, quality of service, and network lifetime. These algorithms coordinate theinterference of relays to BS and determine the number of the relays dynamically according to BSinterference threshold. This thesis compares their performances and gives their applicationscenarios; seen from the simulation results, the strategy which takes both residual energy andchannel quality into consideration is more suitable for D2D communication system for its highnetwork lifetime.The performances optimizations in D2D system are researched at the last part of this thesis.Including the allocation of power between source node and relay node, the error rate can reduceeffectively by controlling the transmission power of both nodes. For multi-relay communicationsystem, this thesis optimizes the selection of cellular frequency resource which is reused by D2Dsystem, which can improve the receive SNR of destination node. In order to reduce the probabilityof collision system, this paper studies the setting problem of relay timer; simulation shows thecollision probability can greatly reduce with the optimization to the initial setting time.