Ieee 802.11a Mac Layer Protocol Performance Analysis

WLAN (Wireless Local Area Network) combines Internet technology and mobile communications technology, and inherits their strongpoint. Through WLAN, data can be transferred with high speed and by lost cost. With the rising popularity of IEEE 802.11 family wireless networks, and the explosive increase of multimedia traffic (such as audio, video) in the internet, the research on performance of wireless networks becomes more and more important.IEEE 802.11a protocol can provide high data rates as much as 54Mbps, which is also the highest speed in the IEEE 802.11 family. Besides, it works at the 5GHz spectrum area, which prevents it from frequency interference and signal contention.When the MAC (Medium Access Control) protocol is taken into consideration, it is one of the most important factors in performance problem of wireless networks. So it is significant to study the performance of IEEE 802. 11a MAC protocol.In this paper, we used a more practical system performance algorithm, which could be simulated precisely. Depending on the exponential backoff mechanism of DCF, we brought in a two-dimensional Markov chain model including the case with a non-saturated sending probability, as well as the influence of the retry limit. On the basis of this, the paper improved the RTS/CTS threshold, with which the system throughput and the average packet delay could be improved. The NS-2 simulation has proved the analytical model to be practical.Aiming at the potential problems in the already existing Markov models, this thesis is trying to make some improvements and innovations in the following aspects: (1) Introducing the Wireless Local Area Network and its Medium Access Controlsublayer, as well as the Carrier Sense Multiple Access/ Collision Avoidance underthe Distributed Coordination Function, in which the Inter Frame Space,bi-exponential backoff mechanism, Basic access mechanism and RTS/CTS accessmechanism is emphasized.