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UBC Theses and Dissertations

Performance analysis of destination multiplexing for wireless LANs Zhuang, Youli


This thesis describes the performance of the IEEE 802.11 Medium Access Control (MAC) protocol with and without destination multiplexing. The IEEE 802.11 MAC protocol, the most widely used standard for Wireless Local Area Networks (WLANs), allows the wireless channel to be effectively shared by portable computers or wireless stations. In this thesis we consider the most common WLAN structure, one where wireless stations connect to a "backbone" wired LAN through a fixed base station or access point (AP). We consider the traffic from APs to wireless stations since typically most of the data flows in this direction. We also take into account fading since it is unavoidable in real wireless channels. An AP using First In First Out (FIFO) packet scheduling transmits or retransmits a data frame until it is successfully received. Fading that lasts for several retransmissions will degrade the performance of the system. Destination multiplexing selects a different destination after a failed transmission. Because of the statistical independence of the fading between the AP and different wireless stations, a transmission to another destination is more likely to be successful. We performed a computer simulation study of throughput and average delay for the overall system. The following factors were studied in our simulations: different data rates, different number of nodes, collision effect, different data frame length, effect of RTS/CTS control frames, different algorithms in selection of next frame, and the effect of fading channel parameters. Our results show that under some conditions destination multiplexing can improve the throughput more than 20 to 30 percent and decrease the average delay significantly.

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