Performance analysis of IEEE 802 11 wireless local area networks WLANs in error prone channels

Abstract

Wireless communication always attracts extensive research interest, as it is a core part of modern communication technology. The research focus is on IEEE 802.11 network performance analysis. The first part of this thesis focuses on throughput analysis of IEEE 802.11 Wireless Local Area Networks (WLANs) in error-prone channels. This work includes the development of analytical model based on two-dimensional Markov chain approach, for various aspects of IEEE 802.11 network performance analysis. Analytical models are developed and analyzed for the performance enhancement of IEEE802.11 network, both in saturation as well as in non-saturation regime under homogeneous link conditions. Second part of this thesis focuses on throughput analysis of IEEE 802.11 multirate WLANs in error-prone channels. Rate adaptation has become one of the basic functionalities in today s 802.11 multirate WLANs. The Automatic Rate Fallback (ARF) is a simple rate adaptation algorithm, which was originally developed for Lucent Technologies WaveLAN-II wireless LAN (WLAN) devices. The design of ARF algorithm has not considered the possible packet losses due to collisions. A new mathematical model is developed to analyze the saturation throughput of the IEEE802.11 Distributed Coordination Function (DCF) with Loss Differentiating Auto Rate Fallback (LD-ARF) rate adaptation algorithm. This new model differentiates the two types of losses and improves the accuracy of the rate adaptation process. The new algorithm accounts Media Access Control (MAC) layer changes in order to have loss differentiation ability. Initially, LD-ARF is modeled using discrete time Markov chain through which the station distribution is obtained according to their physical rate. Then, this model is combined with the throughput model of DCF to obtain the system throughput. This algorithm is extensively evaluated through simulations and shown to perform well especially in an environment where both collision losses and link error losses can coexist. newline newline newline