Simulation Design And Research Of WLAN's MAC Layer's Protocol Based On OPNET

Wireless Local Area Network is composed of a group of mobile node which connect through wireless medium in local area.With the development of wireless technique and Internet,the application of WLAN grows step by step.Wireless channel use medium share access technique,so we need to solve the problem that how to distribute limited channel in multiuser,and the protocol of MAC layer is set to distribute shared channel resource fairly and effectively.It is an important task to choose proper MAC layer's standard,configue channel resource based on network's service and improve system's throughput and quality of service in recent wireless network's research.WLAN's broad criterion is IEEE 802.11,and DCF(Distributed Coordination Function) is the most important MAC's layer's access mechanism in IEEE 802.11.In this paper , we design the simulation of basic access mode and optional access mode(RTS/CTS),accomplish the function of supporting quality of service in MAC's layer with EDCF mode and propose one arithmetic which based on binary exponential backoff arithmetic in original protocol to imporve system's performance index of throughput and delay using user-defined parameter.OPNET simulation platform is the advanced network technique's envioronment in current research.This paper use OPNET Modeler 10.0 to simulate 802.11 MAC's layer's protocol.We analyse the theory of basic mode DCF and optional mode RTS/CTS,finish the simulation of these two mode in OPNET platform,discuss the EDCF principle based on quality of service,acheive the differeniciation of service's priority,propose user-defined parameter arithmetic based on binary exponential backoff arithmetic and try to simulate it in OPNET platform.Through the analysis of user-defined parameter arithmetic,we get the conclusion that WLAN should adopts the method how to avoid collision and improve throughput,and we also indicate the direction of improving backoff arithmetic for the future.