Radio Resource Optimization In Device-to-Device Communication Networks Based On Time-Reversal

With the advent of the 5G era,various wireless mobile communication systems develop and evolve,the demand for higher speed,high quality and low delay communication is increasing day by day,and the limited spectral resources can't meet the explosive growth of the users' need.Therefore,it is urgent to solve the problem of how to improve spectrum utilization.Device-to-Device(D2D)communication is widely regarded as the key technique of 5G systems for improving system performance.D2 D technology can dramatically improve spectrum utilization and communication quality.However,it may generate interference to the existing cellular networks and degrade the overall performance.Because time-reversal technology produces a adaptive temporal and spatial effects which efficiently suppress the system interference,so this thesis makes use of the focusing effects of time-reversal to achieve the goal of optimizing the spectrum utilization in D2 D communication system and proposes two resource optimization schemes to avoid interference while improving the system performance.Specific research contents include as follows:First,Since D2 D users reuse the link resources of the cellular users to bring interference to the entire system,an anti-interference resource optimization scheme based on time-reversal is proposed.The scheme includes two procedures:(1)The time-reversal mirror as a channel filter is incorporated into uplink transmission system to perform channel signature for each user,by treating each multipath as a virtual antenna to produce the synchronization focusing,interference cancellation is achieved and useful signals are extracted,at the same time,signal-to-interference-plus-noise-ratio of the system users is obtained.(2)According to the signal-to-interference-plus-noise-ratio,a power control algorithm is adopted to adjust user transmission power in combination with the convex optimization theory to maximize the throughput of system.Simulation results show that the proposed scheme effectively suppresses mutual interference between cellular users and D2 D users in the heterogeneous network,satisfies the requirement of reliability of communication,and improves quality-of-service of users.Second,D2 D users and cellular users which evenly distribute share resources in the current resource optimization schemes,but the problem of unfairness of resource allocation is caused by the random distribution of users.So this thesis proposes a joint channel signature and resource scheduling scheme.Firstly,this scheme constructs a D2 D channel model based on time-reversal technology to suppress interference;Then,based on the game model,a power allocation is adopted to D2 D users;Finally,within the capacity-oriented restricted region,D2 D users are assigned cellular resources according the priority and when the resource sharing parameter threshold is met,D2 D users with the least interference to the idle cellular users are selected to share channel resources of the idle cellular users.Simulation results show that the proposed scheme can reduce interference,improve system throughput and the fairness among users.