Research On Energy Efficiency Based Resource Allocation Schemes In Distributed Antenna Systems

With the rapid development of wireless communication systems and the explosive popularization of smart phone terminals,the rise of data rate requirement leads high demand of high-capacity and high speed communication systems with multiple services.Increasing requirement of data rate results in increasing power consumption,thus nowdays the communication systems with low power consumption,high data rate and broad coverage area attract considerable attention.Distributed antenna systems have been widely concerned by industry due to its advantages of broad coverage area,low power consumption,high system capacity.Meanwhile,resource optimization is also an important method to meet the demand of user's transmission rate and reduce communication system's energy consumption.Resource optimization mainly includes optimal allocation of spectrum resource and transmission power.Efficient spectrum resource allocation can improve spectral efficiency and enhance system capacity;Optimizing transmission power resource can reduce power consumption of system and increase system's energy efficiency.In this thesis,we study resource allocation problem in distributed antenna systems,which aims to maximize the system's energy efficiency.To address the resource allocation problem in distributed antenna systems,in the third chapter,we discuss the Orthogonal Frequency Division Multiple based distributed antenna systems,and optimize distributed antenna selection,subcarriers assignment and power allocation to maximize system's energy efficiency.Since the optimization problem is a combinatorial problem,which could be decomposed into two sub-problems.Firstly,we propose a joint antenna selection and subcarriers assignment algorithm,which can optimize antenna selection and subcarriers assignment base on channel state information;Secondly,the lagrangian dual method is used to obtain the optimal transmission power,and the maximum energy efficiency of system can be obtained through Dinkelbach method.Finally,the simulation results demonstrate the effectiveness of the proposed algorithm.Additionally,when there is a large number of distributed antenna units,based on channel condition,the user only need to select the best antenna units to form virtual cell for serving oneself.In the fourth chapter,we study the power allocation problem in distributed antenna systems with a large number of distributed antenna units.Firstly,we establish an energy efficiency optimization problem;Secondly,we propose an antenna units selection algorithm to assign the antennas with the associated users based on channel large scale fading information;In addition,the optimization problem can be transformed into a subtractive form,and solved interior point method to get the optimal transmission power,and the optimal system energy efficiency can be obtained by bisection method.Finally,simulation results demonstrate the effectiveness of proposed algorithm,illustrate the effect of the antenna set size of user on system energy efficiency,and show the better system performance compared with other algorithms.