Research On Resource Allocation Scheme Based On Energy Efficiency Optimization In Massive MIMO System

In recent years,with the increasing requirements of wireless communication equipment and multimedia services,the traffic in wireless communication networks increases dramatically.The large scale multiple input multiple output(MIMO)technology has attracted wide attention due to its spatial diversity characteristics,which can greatly improve system throughput and transmission reliability.However,with the increase of the number of antennas,the energy consumption of the large-scale MIMO system also increases.Therefore,how to improve the energy efficiency(EE)of the large-scale MIMO system has become one of research hotspots.At present,for the problem of EE optimization in large-scale MIMO systems,most of the existing researches assume that the perfect channel state information(CSI)is known at the base station,and the consideration of the EE impact factor is relatively simple.The power consumption model and the establishment of constraints are also far from the actual environment.Regarding the issue above,in this paper,we will start with a single cell and study the resource allocation scheme with the goal of maximizing EE,then extend the system model to multiple cells.The main contents of this paper are as follows:Chapter 1 introduces the background of the research,the opportunities and challenges faced by large-scale MIMO,and the research status of resource allocation in wireless communication system.Chapter 2 describes the fading characteristics of wireless channel and the model of large-scale MIMO system,then gives the capacity expressions of large-scale MIMO under the theoretical condition,perfect CSI and imperfect CSI and three common linear detection algorithms respectively.Chapter 3 focues on the single-cell large-scale MIMO systems,a resource allocation algorithm jointly optimizes the user transmit power and the number of antennas with the aim to maximize the EE is proposed.The proposed algorithm uses the maximum ratio combing(MRC)receiver,with satisfying the lowest data rate,the transmit power of per-user is limited as the same time.In the iterative process,instead of the constant interference adopted in the previous work,we update interference dynamically based on the Dinkelbach algorithm.Simulation results show that the proposed algorithm can improves the EE performance greatly and reduces the transmit power consumption with a few iterations.Chapter 4 expands the single-cell system to the multi-cell large-scale MIMO system with imperfect CSI,and a resource allocation algorithm which jointly optimizes the pilot sequence length,pilot symbol power and data symbol power is proposed.With considering the actual power consumption model,the influence of pilot contamination and the constraint of maximum transmission power,a non-convex function modeled with the goal of maximizing EE is established.Then,the properties of fractional programming and logarithmic function are ueed to transform the non-convex problem into a series of difference of convex(D.C)subproblems,finally,based on the D.C programming,the three variable joint optimization with the target of EE is realized by the alternating optimization algorithm.Simulation results show that with the increasing of the maximum symbol transmission power,the proposed scheme can still have the great EE performance.Chapter 5 finishes the dissertation with summary and prospect.