Research On Full-duplex Cooperative Communication Based On UAV Relay

In areas without infrastructure coverage,unmanned aerial vehicles(UAVs)have made great progress in wireless communication because of its low cost and flexible connectivity.This paper studies a novel mobile relay system,which can obtain the properties of high-mobility and high-performance by adopting an UAV as a relay node.The primary contents of this paper are as follows:First,two potential full-duplex relaying system,named Full-Duplex One-Way Relaying(FD-OWR)and Full-Duplex Two-Way Relaying(FD-TWR)are proposed,we aim to maximize the throughput of communications by adopting spectrum-efficient trajectory-based Amplify-and-Forward(AF)or Decode-and-Forward(DF)relay.We allocate different time slots to uplink and downlink to realize full-duplex communication between source node and destination node.A throughput detailed performance comparison between FD-TWR and FD-OWR are also proposed.Second,for a given power allocation,the optimal UAV trajectory is obtained by applying successive convex optimization algorithm.The results show that the optimized trajectory is a curved trajectory,where the UAV first moves to the source,then goes to the destination and finally arrives at its final location.While for fixed UAV trajectory,the optimal power allocation is achieved using water-filling algorithm.Then an alternative and iterative algorithm has been presented to achieve the jointly optimal solutions to the optimization problem.A joint optimization problem has been formulated to maximize the system throughput of communications by jointly optimizing the UAV trajectory and the source/relay transmission power,subject to the constraints on initial/final locations,maximum speed,maximum power of the UAV and information-causality of each node in practical situations.Numerical results show that by jointly optimizing the trajectory and power,the proposed two UAV-enabled full-duplex relay models are able to obtain significant throughput gains over the conventional static relay.Furthermore,UAV can achieve a significant throughput gain within shorter trajectory compared with the fixed relay trajectory.Finally,the throughput analysis of power allocation with fixed circular trajectory radius optimization is studied.The results show that the throughput of FD-TWR system is about twice as large as that of FD-OWR system for circular trajectory,and the throughput gain of both systems is much better than that of static relay.But slightly lower than the throughput gain of straight track.The throughput is basically consistent with static relay at the beginning,and when the growth begins is related to the speed of the UAV.The relationship between the radius of the UAV with optimal throughput and the distance between the source node and the destination node for circular trajectory is further discussed.The results show that the distance between the source node and the destination node is linearly related to the optimal UAV radius,and the optimal radius diameter is not greater than 1/2 of the distance between the source node and the destination node.