Performance Analysis Of MAC In IEEE802.11Wireless Networks

With the development of wireless communication technology, IEEE802.11wireless network is developing dramatically. Wireless Local Area Network (WLAN) technology has been widely used in our daily life and work due to its convenience, flexibility, low cost and extendibility. Wireless network helps people get rid of the shackle of cable and enables mobile terminals accessing the Internet at anytime and anywhere. However, compared with wired network, there is still wide performance gab between the wired and wireless network. This is due to the inherent characteristics of wireless network, as well as protocols in the MAC layer. Thus, many scholars mainly foucs on researching the performance analysis and improvement of IEEE802.11MAC layer protocol.At present, the performance analysis of IEEE802.11WLAN is mainly based on the two-dimensional Markov chain model proposed by Bianchi. Most of these modles are based on the assumption that the physical channel is ideal, that is, a station located within the transmission range of the transmitter can correctly receive the message without collision. However, the performance analysis for IEEE802.11DCF under non ideal channel model has attracted more attention in recent years. This paper is based on the above idea. Considering the maximum number of retransmission times and the freezing state, we proposes an improved bi-dimensional Markov chain model for estimating the performance of DCF under a non ideal channel. Then through the improved model, we analyze the performance of IEEE802.11DCF Wireless LAN, derive the expressions of the saturation throughput and the average packet delay. As the system in real network environment is not always saturated, we also propose a model for DCF protocol in non-saturation condition, which we obtain a method on calculating the throughput and packet delay. Finally, simulation results under NS2are given to validate the accuracy of the model.