Research On The Access Performance Of Wireless Ad Hoc Network Based On IEEE802.11

A wireless ad hoc network is a network temporarily and autonomously established by wireless nodes through distributed protocols, without relying on pre-existing fixed network infrastructure and with the characteristics of multihop, distributed and mobility. This kind of network will play an increasingly important role in many environments, e.g. military communication, disaster recovery and distributed computing. As an important part of the wireless ad hoc network protocol suite, the media access control (MAC) protocol largely determines the network performance which can be measured in terms of throughput, transmission delay, etc. Currently, the IEEE 802.11 MAC protocol is widely used in testbeds and simulations for researching on wireless multi-hop ad hoc networks.Focus on how to improve the wireless ad hoc MAC protocol, the thesis deeply analyses the key factors which determine the access performance of the channel. Against the drawbacks of binary exponential backoff (BEB) algorithm, the thesis proposes a channel access method based on game model to improve the performance of IEEE802.11 MAC protocol.The main research content of the thesis involves:1. The thesis studies the performance of IEEE802.11 DCF protocol through theoretical analysis and experimental simulation. At first, a two-dimensional Markov Chain model is established to describe the backoff procedure of DCF; then we use this model to quantitatively analyze the saturation throughput of 802.11 DCF. At last, analyze by simulation the number of contending nodes and the initial contention window to the effect of access performance, and derive the formula of the optimal initial contention window in case of the given number of contending nodes.2. Game theory is introduced to analyze the channel access of wireless ad hoc network. We emphatically analyzes how to choose the payoff function of contention access game (CAG), and prove the game with chosen payoff function has a unique nontrivial nash equilibrium.3. According to the drawbacks of IEEE802.11 DCF, we propose an improved channel access method, and compare with the existing IEEE802.11 DCF by performance simulation. The experimental results indicate that, compared with the basic access mode of DCF, the mechanism based on game model has lower conditional collision probability and better throughput performance.