M-WiMAX中马尔可夫预测的M-LWDF调度算法研究

Study on Markov Predictive M-LWDF Scheduling Algorithm in M-WiMAX

在M-WiMAX系统中为了获得多用户分集增益,更好地发挥自适应调制编码(AMC)的作用,在改进的最大加权时延优先算法(M-LWDF)基础上设计出一个预测的M-LWDF跨层分组调度算法(Pre-LWDF)来调度系统中的实时业务。M-LWDF调度算法在调度判决表达中以调度时刻瞬时速率作为参数,这会影响调度的稳定性和整体性能,尤其在移动无线通信中更加明显。提出用马尔可夫预测模型来计算下一调度时刻的瞬时速率,平滑当前瞬时速率,减小移动无线信道瞬时速率对调度性能的影响。平滑后的瞬时速率能更好地代表移动信道传输速率的变化趋势。仿真结果表明,该调度算法保证了实时业务流的服务质量,提高了系统的平均吞吐量和公平性。

In the M-WiMAX system,in order to obtain a multi-user diversity gain and better use Adaptive Modulation and Coding （AMC）,a predictive scheduling algorithm （Pre-LWDF） was designed with M-LWDF to schedule real-time traffic of WiMAX.M-LWDF algorithm uses instantaneous rate as a judgment parameter at time of the scheduling,therefore,the stability and overall performance of the scheduling algorithm are affected,especially in the mobile wireless communication.Markov prediction model was employed to calculate the instantaneous rate of the next scheduling time,and then smooth out the current instantaneous rate,thus the effect of instantaneous rate on scheduling performance was reduced.The smoothed instantaneous rate can better represent the transmission rate trends of the mobile wireless channel.Simulation results show that the scheduling algorithm insures QoS for rtPS and ertPS traffic and improves the system＇s average throughput and fairness.