Research On Resource Management Of Unlicensed Band In LTE-A System

LTE-A(Long Term Evolution-Advanced),the forth generation mobile communication,is being rolled out by many operators worldwide.Striving to meet the market demands,operators are more and more interested in deploying some complementary access utilizing unlicensed spectrum to meet the traffic growth.Thus,the LTE-A in unlicensed band should considerd the fair coexistence with existing Wi-Fi networks.Besides,it should also consider the fair coexistence among LTE-A networks deployed by different operators so that the LTE-A networks can achieve comparable performance.Basing on the analysis,some enhancement techniques such as cross-layer resource allocation,transmission mode in unlicensed band and dynamic frequency selection are proposed.This thesis mainly studies on three areas:A resource allocation optimization algorithm with carrier aggregation in unlicensed band which aims at optimizing the system utility is proposed.To achieve an efficient solution,we break this problem into two sub-problems.Firstly,the sub-carriers on licensed band are allocated to users using KKT condition.Thus the users' data rate can be calculated in licensed band basing on the carrier allocation.Knowing the data rate in licensed band,the optimal rate that needs to be allocated to each user in unlicensed band can be obtained by an iterative approach which is deduced from the Lagrange dual method.Thus,the resource that should be allocated to users on unlicensed band can be determined.Simulation results show that the proposed algorithm has 20%gain compared with the contrast algorithm.Secondly,the user equipment assistant,and transmit power control method to let LTE-A access to unlicensed band is designed.Then the LTE-A transmitting mode on unlicensed band is proposed.The hidden nodes problem can also be solved by using the user feedback mechanism.The cross-layer resource scheduling in unlicensed band is studied.To be specifically,a controller is designed to semi-staticlly allocate the unlicensed spectrum to the macro cells that are from different operator.And then,the small cells that are in the coverage of the macro cell would access to the unlicensed band dynamically.Besides,the frequency reuse scheme for eNodeBs that from the same operator is also proposed.The last part of the thesis summarizes my contribution of the research field,and discusses futher research directions.