Impact Of Performance On Full-duplex Relay Communication System

With the higher demand for communication services, the future mobile communication is bound to the faster speed, better performance,more extensive coverage, higher network load balance and so on. Relay communication technology has the advantage of increasing the coverage rate and improving the communication rate of cell edge users, and has become an important technology now. Relay contains one-way relay and two-way relay and two-way relay can improve the spectrum efficiency compared with one-way relay, but they are always investigated in half-duplex. Due to the nature of half-duplex relay, compared with traditional direct transmission, relay transmission requires double consumption of resources. In order to improve the spectrum efficiency of relay transmission system, full duplex relay transmission is been studied by numerous scholars. Ideally, full-duplex relay could achieve twice spectrum utilization than half duplex, but in practice, due to the full duplex working relay nodes, the residual self-interference (RSI) since the introduction of a relay, so it is sure to affect the spectrum efficiency of the system. And relative to the direct link will be a certain delay, relay forwarding is bound to have a certain processing time and the limitations in actual communication would seriously affect the quality of the relay.Besides, the signals through direct link is neglected or treated as interference and the measure is not reasonable when the direct link is stronger. So how to exploit the direct link effectively has become a hot spot of relay research.The first topic of the paper investigates the performance of rate and power allocation in a full-duplex two-way relay (FD TWR) that adopts an amplify-and-forward (AF) protocol under residual self-interference (RSI).Different from the previous works on FD TWR, the proposed scheme exploits the direct link instead of neglecting it or treating it as interference.Based on this scheme, we present an expression of the system rate. Then,we investigate the power allocation and the optimization problem under joint power constraint is presented and proved to be quasi-concave. Then we convert it to a quasi-convex problem with its convenient derivation and obtain the optimal power strategies combined with bisection. Finally,theoretical results are validated through simulations. The results reflect the comprehensive influence of the direct link and RSI on the performance. And these also proved the advantages of exploiting the direct link and power allocation on the proposed scheme.The second topic of the paper investigates the outage performance and relay location optimization of full-duplex decode-and-forward (DF)relaying. Exploiting the direct link and more practical RSI model, we derive the closed-form outage probability of the system when the processing delay at relay is larger than 1. Then based on the outage probability, the optimization problem of relay location is formulated and solved. According to the theoretical analysis results, we can see that the comprehensive influence of the direct link and RSI on the system clearly.It is shown that the optimal relay location will move towards the source S as RSI increases or the direct link becomes stronger. Furthermore, the theoretical results indicate that our analysis outperform the system which treats the direct link as interference even when the processing delay is larger than 1. Finally, simulations prove our theoretical derivation and reflect the system performance intuitively.Finally, we considered the power allocation based on the second part of the research on the same system model. Then we minimizes the outage probability and solve the optimization problem. The simulations show that the optimal scheme has the advantages of the existence and system,and the power allocation improves the performance of the system.