Study Of Throughput And Fairness For Multicast Service In LTE System

With the progress of mobile communication technology and the rapid development of intelligent terminals such as mobile phones,mobile traffic is showing explosive growth.The demand for high-speed data transmission is extremely urgent.LTE system proposes multimedia broadcasting multicast technology(MBMS).MBMS can provide services for many users with fewer system resources.But there are some problems with MBMS,which is how to balance between user fairness and system throughput.We firstly introduce some related theories about MBMS of the LTE system and several multicast scheduling algorithms in the paper,then we point out several multicast scheduling algorithm's advantages and disadvantages in fairness,throughput and the utilization rate of each sub carrier.Although the traditional multicast scheduling algorithm can guarantee the fairness of the multicast group,but it reduces the system throughput.So in the paper we put forward an improved MCMPT scheme.In order to increase the system throughput,a new technique called CoMP is introduced to solve this problem.Multiple base stations work together to transmit the same data to a multicast group at the same time in the same RB(Resource block).It can greatly enhance the received signal strength of the cell users especially the cell edge users and improve the SINR.The traditional dynamic subcarrier allocation scheme(SPA)uses two subcarriers to transmit same data for group multicast.The data content transmitted by the two sub carriers is the same,although it can improve the throughput and the transmission reliability of the system by the use of frequency diversity gain,but the utilization of subcarriers are reduced.Therefore,an improved CTA scheme is proposed.Through the use of linear network coding,the base station will encode two data whose content are the same into three data and transmit them on three sub carriers.CTA scheme can not only improve the system throughput,but also improves the utilization of sub carriers.We evaluate the performance of the two algorithms in terms of fairness,throughput,and subcarrier utilization.The simulation results show that MCMPT scheme has been significantly improved the system throughput than the traditional multicast.Compared with the SPA scheme,the improved CTA scheme has been greatly improved in system throughput and subcarrier utilization rate.