Channel Fairness Algorithm Based On Queue Management In Multirate 802.11 WLAN

With the continuous development of wireless technology,wireless LAN began to be widely used in people's lives and work,it has become an important part of the Internet.However,with the increasing number of users in the wireless network,the limited wireless channel has seriously affected the system throughput and fairness among users.The network bandwidth can not meet the demand of network resources for network applications.Therefore,the limited network resources being fair and efficient distribution becomes particularly important.The main research results of this paper are as follows:In multirate wireless local area networks,high-rate sites and low-rate sites have the same opportunity to allocate wireless channels,that is,low-rate sites have a long-term use of wireless channels,making high-rate sites and low-rate sites achieve the same throughput,which to some extent hinders the entire network to obtain higher throughput,resulting in the low efficiency of the overall network.In this paper,an optimized active queue management algorithm is proposed.With the wireless station not being modified,the downlink data of the AP is set to several data queues,and the queue length is set according to the radio channel transmission rate of each data stream.The data flow of the high-rate station sets a lower packet loss rate,while setting a higher packet loss rate for the data flow of the lowrate site,maintaining the virtual queue length of the different data flows in their respective ideal ranges to ensure that different wireless stations Occupy the same channel time.The simulation results show that the algorithm realizes the fairness of the channel occupied by each sites and effectively improves the total throughput of the network.Through the analysis of the IEEE 802.11 protocol,the wireless stations,including the AP,have the same channel access probability,so that the uplink and downlink data flow occupies unfair time of wireless channel,because of the TCP transmission control the asymmetry of the rejection of the DATA segment and the ACK segment is also a problem.In some way,the downlink flow will decrease the transmission rate due to the discretization of the DATA segment.For the cumulative acknowledgment,the transmit rate does not decrease if there are packet loss for ACK segment,which causes the uplink flow to suppress the downlink flow.Therefore,this paper increases the packet loss rate of the ACK segment and reduces the packet loss rate of the DATA segment to limit the transmission of the TCP uplink flow,thus ensuring the fairness of the uplink and downlink data flows.Simulation results show that the algorithm can improve the unfairness of data flow between uplink and downlink and improve the overall performance of the network.