Study On Scheduling Algorithm Of LTE Downlink Based On QoS

With the rapid development of wireless multimedia business,the LTE system is required to have features that high throughput,low latency,and the quality of service.It makes the contradiction that between the limited band resources and the growing demand for data services more serious.OFDM is the most important technologies of LTE downlink,it can greatly improve the band utilization and data transfer rate and bring greater flexibility to the scheduling of LTE systems.Therefore,it is necessary to research the problem that how to allocate resources efficiently and take into account the user's QoS based on the OFDM technology.First,this paper introduces the principle of LTE system,network architecture and QoS mechanism,as well as the key technology of LTE downlink OFDM technology,including principle,system implementation and characteristics of wireless fading channels,which provides theoretical support for the subsequent modeling and simulation.Then introduced two resource allocation optimization criteria,rate adaptive criterion RA and margin adaptive criterion MA.Base on the two kinds of criteria,analyzed and simulated some resource allocation algorithms,including the water filling algorithm,greedy algorithm under single user condition,the MaxSNR+WPA algorithm,RR+EPA algorithm,Shen algorithm under multiuser conditions.On the basis of analyzing the principle,advantages and disadvantages of each algorithm,it is concluded that there are still many problems to be solved in LTE downlink resource allocation,such as poor fairness among users,no guarantee of QoS and low efficiency.This article mainly studies the resource adaptive scheduling algorithm based on QoS under the LTE downlink multiuser environment.For this research direction,firstly the resource allocation is divided into subcarrier allocation and power allocation based on RA criterion.In the subcarrier allocation process,first,allocating a subcarrier for each user according to the RR algorithm,second,allocating the remaining subcarriers with the user's current channel status information,service type,rate constraint factor,the rate constraint factor can be dynamically adjusted according to the user service type,which determines the upper limit of the user rate;In the power distribution process,since the allocation of subcarriers has been completed,the optimization problem of objective function under RA criterion can be relaxed as a convex optimization problem,Removing the subcarriers with a low gain-to-noise ratio when solved linear equations,it can be a constraint to simplify the optimization problem.Using the binary iterative search algorithm to solve the optimal solution if the equation has only one unknown variable,then use the optimal solution to find the user's dynamic water injection line,he power distribution is completed by this water injection line.Finally through the MATLAB simulation tool,modeling from the base station,users,noise,path loss and other aspects,combined with the Uma scene parameter configuration and 3GPP 36.942 protocol specification to set the corresponding simulation parameters,building the static LTE system-level simulation environment.Simulation analysis of the proposed algorithm in terms of cell throughput,user SINR,the user's capacity under a single business scenario,the user's capacity under the mixed business scenario.The results show that the proposed algorithm can balance the fairness of the user with the throughout,resource allocation is more flexible and can control the user's transfer rate by setting a different fairness factor,achieved the differentiated resource allocation,and guaranteed the user's quality of service QoS requirements from the fairness,quality of communication link of client,the business transmission rate,while have a faster convergence rate.