Research Of Receiver-Centric Centralized-Request Transmission Method In Wireless Local Area Network

On the conditions of Wireless Local Area Network (WLAN) accessed to the Internet, the inherent characteristics of wireless link (such as, high error rate, rapid change of RTT, handoff, etc.) leads to the limitation of the traditional TCP based on fixed hosts and wired networks under the environment of the wireless networks. One mainly reason is that , TCP can not distinguish the reasons for packets loss, and congestion-unrelated packets loss caused by wireless links can also trigger TCP congestion control algorithm, resulting in the unnecessary contraction of congestion window ,which depress the performance of protocol badly. The other reason is that the simultaneous-send problem of TCP under IEEE802.11 WLAN also brings a poor performance of the protocol.Based on RCP, we proposed an improved method, that is, RC2RP, which allows for better solutions of simultaneous-send problem, loss recovery, congestion control, etc. Consequently the network performances are improved. We have done the work as following.Firstly, we validated that simultaneous-send problem under WLAN seriously affects the performance of RCP, and we conduct a deep analysis of the problem. Next, we proposed the RC2RP which designed to cut down the REQs, to lessen the competition of wireless link, to enhance the use of channel, and finally to improve the network performance. And then, we considered both RC2RP and wireless link so that a kind of end-to-end available bandwidth measurement is put forward to enhance RC2RP. A new model is adopted to monitor the network, so we can classify various packets loss, and deal with the packets loss more reasonably. Lastly, we referred to a cross-layer method in order to decline the REQs loss and more improved RC2RP.With the help of the RCP and QualNet software, we simulated and implemented the basic functional modules of RC2RP, the end-to-end available bandwidth measurement improvement, the cross-layer improvement module as well. Moreover, we make a contrast among all the experimental results. We come to a conclusion that RC2RP has a better end to end throughput compared with RCP and TCP.