The Analysis And Improvement Of DCF Protocol In IEEE802.11 Wireless Local Network

It is of great significant to estimate the competing terminals in IEEE802.11 network actually and in real-time. If the best back-off window as well as the threshold switches of the basic mechanism and the RTS/CTS mechanism in DCF protocol is set automatically according to the n value, the throughput performance of the network can be greatly optimized, at the meantime, the estimation of n in different cells is conductive to allocate resource rationally. This paper discussed the estimation of competing terminals in IEEE802.11 network. We modified the markov model of DCF protocol, obtained the relation between collision probability p and number of competing terminals n, and tracked it by the Extended Kalman Filter. The previous markov model is saturated, and in this passage the markov was improved to non saturation. The simulation result showed that the model for the network actually estimate the number of competing terminals.On the other hand, both the quality of service and access capacity are greatly damaged in the traditional IEEE 802.11 wireless local network where the voice over IP service is based, so they become the bottleneck of the development of VoIP over WLAN. In this paper, we chose the G.729 coded frames which is the long PPDU mode of IEEE 802.11b as an example and calculated the VoIP frame forming efficiency, IEEE 802.11 b frame forming efficiency and the DCF protocol efficiency to analyze the saturation normalized system throughput.Meanwhile, we calculated the theoretical voice transport capacity of IEEE 802.11 a/b, so as to provide the basement of improving the current capacity of VoWLAN.