Research On Full-duplex Relay Transmission Scheme Based On Multi-carrier Modulation

The full-duplex(FD)relay system can receive and transmit signals in the same frequency band at the same time slot.Compared with the traditional half-duplex relay system,it can theoretically double the spectrum efficiency.However,the loop interference problem at the relay node cannot be completely solved by the current loop interference cancellation technology,and the residual loop interference seriously restricts the system performance.To solve the problem of repeated iterations of residual loop interference at the relay node in full-duplex one-way single-relay systems,we study a relay transmission scheme,which can further suppress residual loop interference for full-duplex relay systems.In this paper,we first briefly introduce the basic principle of full-duplex relay system,summarize typical full-duplex relay systems,describe the commonly used relay forwarding strategy and loop interference cancellation scheme.Then we analyze the signal-to-interferenceand-noise-ratio of the destination node and system outage probability of the full-duplex one-way single relay system.For the scenario where the nodes in full-duplex relay system are all Rayleigh single-path channels,through the in-depth analysis the signal transceiving process of loop interference signal at the relay node,we propose a full-duplex relay equivalent channel transmission scheme.That is the residual loop interference signal within several iterations is equivalent to a multipath signal,and the remaining loop interference signal is treated as symbol trailing.Based on this,we establish a full-duplex relay equivalent channel model.Aiming at this model,we use orthogonal frequency division multiplexing(OFDM)to combat multipath interference of the equivalent channel,deduce the optimal amplifying factor by minimizing the system outage probability to weaken the interference caused by trailing portion of the residual loop interference,and perform full-duplex relay signal transmission.Simulation results are presented to verify correctness of the optimal amplifying factor and evaluate the performance of the proposed scheme.For the scenario where the channels both between the source node and the relay node and between the relay node and the destination node are Rayleigh multipath channels,considering the OFDM transmission scheme requires too long cyclic prefix(CP)to combat multipath interference,we propose a full-duplex relay transmission scheme,which can use OFDM without cyclic prefix to transmit information and use interference reconstruction cancellation algorithm to eliminate inter-symbol interference and inter-carrier interference caused by the multi-path signals channel to ensure the system has high spectrum efficiency.The optimal amplifying factor is obtained by maximizing the signal-to-interference-and-noise-ratio of the destination node,and the simulation results are presented to verify that the proposed scheme can transmit data with high spectrum efficiency under multipath channels.