Research On Buffer-aided Relay Networks With Multi-source And Multi-destination

Combined mobile cellular networks with relay techniques becomes the current and future development trend of wireless communications and considered as an effective, can significantly improve system performance solution. Existing relay transmission techniques are based on a fixed strategy, for instance, relay receive data from the source at one time slot and forward it to the destination at the next time slot in half-duplex relay system. But this relay transmission strategy greatly affected by the instantaneous channel condition. For example, when source send data to relay but the channel condition between the source and the relay is not well or relay forward data to destination but the channel condition between the relay and the destination is bad, the traditional relay system usually difficult to achieve the desired performance.The combination of buffering and relay transmission technique can overcome the shortcomings of traditional relay transmission strategy. Setting the buffer in the relay and relay can store data received from the source, the degree freedom of link selection increases because relay need not to follow the traditional fixed transmission strategy. In buffer-aided relaying network, according to the current channel quality information and the data in buffer, system can adaptively choose link to send or receive data. Combination of relay transmission technique with buffering creates new areas of relay transmission technology.This paper studies the key technology in multi-user buffer aided relay networks which have a plurality of source and destination and a relay with buffering. At first, we introduce the traditional relay network and buffer-aided relay network, after that we describes the research status of buffer-aided relay networks.Secondly, we research the techniques on buffer-aided multi-relay networks which have many of relays and each relay has a buffer to storage the data send from the source and system can select which relay to receive the data. We propose three relay select scheme called max-max relay selection(MMRS), hybrid relay selection(HRS) and max-link relay selection(MLRS) and studies the outage probability and diversity gain of these schemes.Thirdly, aiming at the multi-user system, we propose a buffer-aided link selection technique can enhance the whole rate of system. At every time slot, according to the channel state information, system can select appropriate link adaptively. Specifically, we proposed an optimal link selection scheme to maximize the average throughput of the relay network. Using the Karush-Kuhn-Tucker(KKT) conditions, the decision function for the optimal link selection is also obtained under the Rayleigh fading channels. In this paper, we also present a suboptimal link selection policy which can significantly reduce the computational complexity.Finally, based on the buffer-aided link selection technique has been proposed in previous chapter, we analyzed the expense of delay which bring by buffer aided relay networks and given two scheme to control the delay. One scheme is to control the rate of source and another scheme is to control the buffer size. We derived the first scheme’s upper bound expression of average delay and compared the two strategies, simulation results show that for the system which not sensitive for the delay, the buffer-aided link selection technique in multi-user network can significantly improve overall system performance.