Abstract
Quality of service (QoS) in multimedia applications has become an important issue. Due to the lack of radio link stability, QoS in wireless networks is more challenging than that in wired networks. This thesis provides an enhancement for the most widely deployed wireless LAN technology, IEEE 802.11. Because of the suffering from severe variation in channel condition, some forms of diversity have been proposed to combat the effects of fading. Spatial diversity is one of the well-known forms of diversity. In this thesis, a solution to improve the performance of the polling-based Point Coordination Function (PCF) in 802.11 via user spatial cooperation diversity is proposed. Wireless stations are assigned partners so that they can overcome the fluctuant channel conditions. The proposed method not only increases users’ throughput, but also balance the load of help among all wireless stations. The use of spatial diversity has critical influence on the performance of PCF. The simulation results show that the proposed method outperforms the original polling-based system no matter in throughput, delay, or packet loss ratio. The solutions proposed in this thesis are fully complied with IEEE 802.11. By extensive simulation, it has been shown that the proposed solutions are both efficient and practical.