Analysis And Realization Of Downlink Scheduling Algorithm Based On Quality Of Service In LTE System

With the rapid development of Internet applications, wireless communication systemshows the trends of broadband and IP. In this situation, the fourth-generation mobilecommunication technology has become the inevitable development direction. So theresearch of the“pre-4G” mobile communication system technology is the key of transitionfrom3G to4G.LTE system has a higher data services rate of the uplink and downlink,alower access delay, and a better user experience, which of these performancecharacteristics underline its strong market competitiveness and good developmentprospects.The paper is intend to study the LTE system downlink scheduling algorithm of MAClayer, and proposes improvement scheduling algorithm of which bases on QoS. Specificresearch work and results are as following:(1) The paper researched the network and functions architecture of LTE system, anddiscussed the downlink key technologies such as Orthogonal Frequency Division MultipleAccess, Adaptive Modulation and Coding, Hybrid Adaptive Repeated Request,and etc inLTE system. The paper also analysed three-layer protocol structure of LTE system deeply,and mainly focused on the research of scheduler in L2’s MAC layer.(2) Discussed and analysed the work mechanism and performance of traditional packetscheduling algorithms, we can get the result that the PF scheduling algorithms can supportsystem with optimization throughput and relative fairness among users from the FDD LTEsystem experimental platform.(3) We put forwarded an improved algorithm and implement proposal: on the basis ofthe PF traditional packet scheduling algorithm, the QoS weight factor which is dependedon users’ QoS factors such as delay, priority, the rate requirements and so on is added.Then we designed experiments to validate the performance of delay guarantee, priorityimpact and rate control in improved algorithm.(4) Through the analysis of the theoretical, research and experiments in the papers, we can draw a preliminary conclusion that the improved algorithm can satisfy the users’ QoSrequirements, while still retaining better system throughput and the relative fairnessamong users. So the improved algorithm takes much reference worth for studying onbetter performance guarantee in LTE system.