Research On Multiple Access Protocols For Wireless Local Area Network

As one of the most effective wireless access methods, Wireless Local Area Network (WLAN) can expand Internet service to mobile environment successfully, and it has been interpreted as an integral part of future's personal communication systems.The research work in this dissertation carries a deep study on new techniques of WLAN and put emphasis on the multiple access protocol to improve the throughput and reduce the collision of frames based on the IEEE 802.11 protocols. The major achievements and results are listed as follows:1. A novel algorithm, called Enhanced Distributed Contention Control algorithm, for improving the performance of DCF (Distributed Coordination Function) operations of IEEE 802.11 Wireless LAN (WLAN). EDCC algorithm is proposed, which is an extension of the existing IEEE 802.11 DCF Medium Access Protocol (MAC) by estimating the values of slot utilization and contention degree. EDCC algorithm has the following characteristics: simplicity, integrability, complete distribution, adaptiveness and no transmission overhead. Results show that the EDCC algorithm can provide higher channel utilization and a lower network load compared with IEEE 802.11 DCF protocotols.2. To improve the channel throughput of IEEE 802.11 protocol with the Binary Exponential Backoff algorithm (BEB), we propose a novel Enhanced Distributed Contention Control backoff algorithm based on the Slow contention window Decrease mechanism (SD_EDCC). By integrating the slow CW decrease scheme with Distributed Contention Control mechanism to effectively capture the channel state information of the actual contention level after a successful transmission, SD_EDCC algorithm can record the current backoff stage of the latest successful transmission under the overload network precisely. As a result, it decreases the collision times and improves the channel utilization. Our performance analysis and numerical results show that its performance is much better than the other three existing backoff algorithms.3. A novel Collision Reduced Multiple Access protocol (CRMA) is proposed based on the slow contention window decrease mechanism and runtime optimization method. The CRMA protocol can record the current backoff stage of the latest successful transmission under the overload network precisely. As a result, it decreases the collision times and improve the channel utilization. The CRMA protocol could be...