多优先等级公平性MAC接入机制

Fairness access scheme in MAC with multi-priority levels

针对WLANs中多优先等级公平性接入问题,提出了一种自适应MAC接入机制,包含信道状态信息监测算法和增大较低优先等级节点竞争窗口线性调整算法。定义感知窗口并提出调整算法用于监测信道状态信息,不同优先等级节点采用相同的感知窗口尺寸,从而能分析计算获得一致的信道状态信息参数,并基于信道状态信息估计网络信息(活动节点个数)数据。提出增大较低优先等级节点竞争窗口线性调整算法,设置最高优先等级节点,采用最优竞争窗口尺寸,按优先等级关系线性增大较低优先等级节点的竞争窗口尺寸,控制节点接入信道的概率,从而保持吞吐量权重优先等级比例关系。针对三种优先等级网络进行验证,仿真结果证明,提出的自适应接入机制能保持吞吐量权重比率关系,具有较好的有效性和可扩展性。

To solve the problem of weighted throughput fairness with multiple priority levels in WLAN,an adaptive MAC access mechanism is proposed,which includes monitoring algorithm of channel state information and linear adjustment algorithm to increase sizes of contention window(CW)of lower priority nodes.The detection window(DW)is defined and the adjustment algorithm is proposed to monitor the channel status information.Nodes with different priority levels use the same DW sizes,so that they can analyze and get the unanimous channel state information,and then estimate the network information(active node number)data based on the channel state information.A backoff algorithm is proposed to increase the CW sizes reversely according to the priority levels.The optimal CW sizes are used for nodes with the highest priority level,and CW sizes of other nodes with lower priority levels are increased according to the priority levels,so as to control the access probability of nodes for the purpose of weighted throughput.The simulation results of three priority levels show that the proposed access mechanism can maintain the throughput ratios between multiple priority levels and has better effectiveness and scalability.