Research On Downlink User Scheduling Algorithm In LTE-A CoMP System

Inter-cell interference severely restricts the performance of cell edge users. Tosolve the problem, scholars propose CoMP technology, which is regarded as an effectivesolution to the problem and has received extensive attention in LTE-Advanced system.As user scheduling policy directly affects system performance, so studying the userscheduling algorithm is essential for CoMP. In order to meet the different goals andneeds, scholars have proposed a variety of CoMP user scheduling algorithms. But thereare some flaws. The main work is summarized as follows:Firstly, it proposes a user scheduling algorithm based on SLNR in order to reducecomputational complexity and overcome the drawback of adaptive user pairing. Tradi-tional CoMP user scheduling algorithms mostly use SINR as an important part inscheduling weight factor, but SINR with high computational complexity. Besides, adap-tive user pairing uses marginal utility stop criteria that will lead the algorithm to stopprematurely. It gives two small algorithms based on SLNR, and the purposes of the twoalgorithms are achieving maximum capacity and guaranting a certain degree of fairnessbetween users respectively. The algorithms mainly change the selecting main user crite-ria and stopping mechanisms. Using SLNR instead of SINR can greatly reduce thecomplexity, selecting paired user with the least leakage to reduce interference betweenusers, by introducing a temporary node to decide whether to stop to avoide the algo-rithm stopped prematurely. Simulation shows that the proposed algorithm based onmaximum capacity can improve the average cell throughput about27%comparing tothe traditional algorithm based on SINR, and the proposed algorithm based on fairnesscan efficiently improve cell-edge user throughput, and further to ensure fairness.Secondly, it also proposes a scheduling algorithm based on QoE to solve the prob-lem that traditional scheduling algorithms just focus on throughput and ignore the userexperience. User experience determines the degree of user acceptance for communica-tion services. The higher quality of the user experience, the higher the degree of recog-nition of communication system. Cell edge users suffer bad experience as they are faraway from base station, in order to improe the performance of edge user, the algorithmfirstly takes "strengthens with weakness" policy to divide all users into groups. Thenconsidering two indicators that are maximum allowable delay and the average transfer rate, and also taking fairness among users into consideration to get QoE scheduling pri-ority. Finally, it can schedule users combined with user groups and user scheduling pri-ority. Simulation results show that the scheduling algorithm can increase the user capac-ity of the system greatly at the cost of a small reduction of system throughput. Besides,it can guarantee the fairness between users to a certain degree.