Research On Key Technologies Of Large-Scale Distributed Antenna System

The number of mobile terminal devices is growing exponentially,which leads to an ever-increasing demand for the system capacity.In response to the increasing demand for the system rate,large-scale antenna systems were proposed as one of the key technologies for the next-generation mobile communication networks.Firstly,massive MIMO technology was proposed based on the traditional MIMO system,as concentrated large number of antennas at the base station.And then,the large-scale distributed antenna system as the combination of large-scale antenna system and distributed antenna system become another research hotpot.The antenna selection technology is one of the key technologies of large-scale DAS.In this paper,the antenna selection technology has been studied in detail,and the main is as follows:1.This paper firstly introduces the structure of DAS and large-scale DAS as well as existing research results and summarizes,then makes the performance comparison between large-scale DAS and large-scale CAS based on the compound fading channel model.In the large-scale DAS,as the RAUs are randomly and uniformly distributed in different geographical locations of the cell,the average access distance of the users is greatly reduced compare to the large-scale CAS.Which can improve the cell coverage,increase cell-edge user rates,and solve the far-near effect problem in large-scale CAS.So,the large-scale DAS has better system capacity and energy efficient performance than large-scale CAS.2.On the basis of a large number of literature research,the existing variety of classic global antenna selection algorithms have been studied,including: greedy optimal algorithm,greedy sub-optimal algorithm,channel norm-based algorithm,decreasing algorithm and random selection algorithm.And then we have done some simulations to compare and analysis the system capacity and complexity performance of each algorithm.An improved global antenna selection algorithm has been proposed based on the greedy sub-optimal algorithm,which can make the number of selected RAUs change dynamically.In addition,this article also studied the virtual-cell technology in large-scale DAS,including non-overlapping divided virtual-cell and virtual-cell merge.3.In the actual system,users may join or leave the system dynamically.And this article has also proposed the local RAU set update algorithm by observing the law of RAU setchange with the improved global antenna selection algorithm.The simulation result shows that the local algorithms can greatly reduce the complexity and its system capacity performance is close to the global algorithm.At the end of the thesis,we have summarized the work done and prospect of the future research.