Optimal Relay Placement For Wireless Relay Communication System

Relay technology can effectively overcome the channel fading and broaden the coverage of the network.Now,it has become the key technology of wireless communication system.In the wireless relay communication system,the reasonable placement of relay nodes can minimize the outage probability and improve the transmission performance.In this paper,the optimal relay placement algorithm is studied under different conditions.The contributions are as follows:(1)The optimal relay placement algorithm is proposed in the dual-hop UAV relay communication system.First,the dual-hop UAV relay communication system model is described.Then,taking the minimum outage probability of the destination node as the objective function,the actual relay placement problem is transformed into the optimal mathematical optimization model.Under the decoding and forwarding(DF)condition,the closed-form solution of optimal relay placement in non-cooperative and cooperative modes is proposed by using Karush-Kuhn-Tucker(KKT)optimization algorithm.Under the amplification and forwarding(AF)condition,the particle swarm optimization(PSO)approach is used for optimization model solution.Finally,simulation tests are carried out for the above two methods.Some useful conclusions for relay placement are obtained which can provide useful theoretical support for practical application.(2)The optimal relay placement algorithm for multi-hop high-altitude relay communication is proposed.First,a multi-hop high-altitude relay communication system model is described and the outage probability in non-cooperative and cooperative modes is studied.Then,the practical problem of optimal relay placement is transformed into the optimization problem by minimum outage probability of the destination node.Next,the optimization model is established which has been proved to be a convex optimization model.According to different situations,the numerical and analytical solutions of the optimal relay placement are obtained respectively.Finally,the simulation results show that the system performance of the proposed optimal location placement algorithm is close to that of the conventional PSO,but the computational complexity of the proposed algorithm is lower.(3)The optimal relay placement algorithm for multi-hop relay communication system under AF condition is proposed.Based on the asymptotic expression of outage probability of destination node,the outage probability,the position of relays and actual layout conditions are chosen as the objective function,the optimization parameter,and the constraint condition.The optimization model for relay placement is proposed and the above optimal model is proved to be convex model.Then,the classical KKT algorithm is used to find the closed-form of the optimal position.Simulation results show that the proposed algorithm has a great engineer prospect.