Research On Hybrid Precoding And D2D Communication Technology For 5G

In recent years,in response to the call of green communication,a large number of precoding algorithms and D2D(Device to Device)communication schemes have been proposed.Precoding the channel can improve the performance of the communication system and save energy consumption at the same time.Using D2 D communication technology can improve the utilization of system frequency resources.Therefore,it is of great significance to study the beamforming scheme of large-scale MIMO system and D2 D communication technology.The main research contents of this paper are as follows:(1)In the large-scale MIMO communication scenario,the use of all-digital precoding scheme can improve the performance of the communication system,but it is accompanied by huge energy cost consumption.To improve the energy efficiency of the system,the full digital channel precoding matrix is decomposed into a low-dimensional digital moment and an analog moment by the antenna gain.Since the client in D2 D communication can improve the system energy efficiency by reuse the frequency resources of the cellular network,in order to maximize the use of frequency resources,D2 D communication technology can be used in the multifrequency band.(2)To balance the energy consumption and performance of large-scale MIMO systems,a power iteration hybrid coding scheme based on target transformation is proposed in this paper.The hybrid precoding matrix of channel is designed by the combination of power iteration algorithm and Aitken acceleration algorithm,and the computational complexity is greatly reduced.The results show that,compared with other existing precoding schemes,the proposed algorithm can achieve higher total system accessibility,lower computational complexity,and smaller bit error rate,and its performance is close to the optimal all-digital precoding scheme.It can be seen that the coding algorithm proposed in this paper has good validity and reliability.(3)To solve the problem of reasonable energy distribution of D2 D communication system,a derivative based multi-band D2 D communication energy efficiency optimization scheme is presented in this paper.The expressions of the probability of successful transmission and the energy efficiency of the system are derived from the stochastic geometric model.The nonconvex optimization problem is transformed into the sum of several convex optimization problems by decomposition operation.Finally,the optimal solution is obtained by derivation formula.The simulation results show that the proposed resource allocation scheme can obtain the approximate optimal solution and the complexity is much lower than the branch-and-bound algorithm.To sum up,this paper realizes the improvement of communication energy efficiency from two aspects: the design of channel precoding matrix and the allocation of frequency resources,which well realizes the concept of "green communication".