Downlink Scheduling Algorithm Analysis Based On QoS In LTE System

Packet scheduling algorithm is the key technology to ensure the quality of LTE network. With the rapid development of wireless networks, the quality-of-service(Qo S) requirements of real-time flows are becoming more and more diversified, so it has been one of the most important problem for packet scheduling to meet the Qo S requirements and maxmize the network throughput with limited radio resources.After discussing the existing international scheduling algorithms, this thesis proposes a new Delay-priority algorithm in terms of the characteristics of Video flow. The algorithm can not only ensure the delay requirements to reduce the packet-loss-ratio because of grouping timeout, but also improve the spectrum efficiency by making full use of the instantaneous downlink channel conditions when making scheduling decisions.After compairing the recently proposed hybrid scheduling strategies for both non-real-time and real-time flows, this thesis proposes an improving two-level packet scheduling algorithm based on the Qo S aware. The upper level computes the amount of data to be tansmitted within one frame of 10 TTIs to meet the delay requirments. Instead, at the lower level, two independent judgment for different flows has been properly tailored to our purposes. That is, we schedule non-real-time flows with the proportional fair scheduler and real-time flows with the Delay-priority scheduler, and then adjust the fairness of the mixed service adaptively through a closed-loop structure.Based on the Vienna system-level simulation platform, the superiority of Delay-priority algorithm is verified on the Qo S indicators compared with other traditional algorithms, and the computing complexity of Delay-priority is much lower. Also, by making a comparision between the improving two level scheduler and other hybrid schedulers, simulation results show that the proposed approach is able to decrease the delay and PLR of real-time flows and increase the throughput of non real-time flows, proving that this algorithm can greatly outperform the existing ones to satisfy the Qo S and fairness requirements in a mixed sevices downlink commucation.