Performance Analysis Of IEEE 802.11b MAC Protocal

With the rapid development of information technology, requirements for network communications also have been improved. People hope to achieve communication with others anywhere and anytime without the limitation of area or other objective conditions. Wireless Local Area Network (WLAN), as an important part in personal communication, has launched a new wave of mobile computing. It has been used widely in real life recently and will be more widely used in the future. Compared with the traditional cable LAN, WLAN has many advantages, such as easy installation, easy use, cost saving and easy expanded, which makes WLAN to be the best choice in lots of real network deployment.WLAN is a combined technology of Internet and Mobile communication and it inherits their respective strongpoint. WLAN is widely deployed, and its IEEE 802.11b standard is used mostly. Nowadays, the existing theory analysis models of backoff mechanism used for terminals accessing shared medium channel are mostly based on the assumption of saturated network. But the real network is not always saturated, so this paper proposes a improved theory analysis model including backoff process for the idle state, which makes it applicable even in the unsaturated network. This model also considers maximal times for retransmission and that the backoff timer decrements only when the channel is not busy. Based on this improved analysis model, throughput and access delay, two key performance of IEEE 802.11b MAC protocol, are analyzed and a method for calculating access delay is introduced. Then, NS2's simulation results verify the model's reasonability. The analysis based on this improved model can express the actual network performance more accurately, plan the network more efficiently, and guide the real network deployment better.