Research On Integrated Optimization Of Spectral Effciencyand Energy Efficiency In Distributed Antenna System

As a key technology,the Distributed Antenna System(DAS)is being used in the new generation of heterogeneous network in the fourth generation mobile communication,which is also called the Long Term Evolution Advance(LTE-A)system.The Distributed Antenna System will be widely used in the fifth generation mobile communication system in the future for the reasons that it can effectively shorten the access distance of the users,and the reliability of the link,and the Spectral Efficiency(SE)as well as the Energy Efficiency(EE)can be improved.However,with the increasing quantity of mobile users and the Wireless message volume,the energy consumption problem is becoming more and more severe.Therefore,how to meet the requirements of more users with less energy turns out to be the focus of the research nowadays.In this thesis,we will consider both Spectral Efficiency and Energy Efficiency in the optimal scheduling problem of radio resourcein DAS.1.Compared with the traditional Centralized Antenna System(CAS),as the antenna unit of the DASsystem is closer to the user,the DAS system can greatly improve the Spectral Efficiency,thereby increase the system capacity.In this thesis,we based on the Composite Fading Channel,which is universally applicable,to mathematically model the communication system,and then analyze and compare the effect on Spectral Efficiency between different single antenna selection method in DAS system.The results of simulation show that,compared with the traditional CAS system,the DAS system has greatly improved in Spectral Efficiency.Finally,we discuss the applicable scene of different antenna selection method based on simulation results.2.The Energy Efficiency of the uplink in DAS system is studied.First of all,the upper and lower bound expressions of the Energy Efficiency of the DAS system based on the user’s positions are analyzed and deduced.Furthermore,the relationship between the Energy Efficiency and the Spectrum Efficiency is analyzed.The simulation results show that the Energy Efficiency of DAS in the uplink is superior to the traditional CAS system.The DAScan effectively improve the Energy Efficiency of the user at the edge of the cell.Otherwise,as the Spectral Efficiency gradually increase,the Energy Efficiency first increase and then decrease.Therefore,the optimal scheduling of radio resources should consider both the Spectral Efficiency and the Energy Efficiency.3.Due to the fact that the resource allocation method with maximum Spectral Efficiency or Capacity may lead to great energy consumption and the decreasion of Energy Efficiency,which is inconsistent with the theme of "Green Communication",this thesis also studies the resource allocation problem in the downlink of the DAS system based on OFDM(DAS-OFDM).In this thesis,the algorithm to solve the problem of resource allocation takes full account of the different user requirements in different situations.The problem of non-convex combination resource allocation optimization is decomposed into two sub-problems--carrier allocation and power allocation.The Lagrangian multiplier method and the sub-gradient algorithm are used to obtain the power values of each carrier by finite iteration.The simulation results show that the proposed resource allocation algorithm can effectively improve the Energy Efficiency of the system under the premise of satisfying the user fairness.