Performance of IEEE 802.11 MAC protocol over a wireless LAN with distributed radio bridges

In this thesis, the performance, in terms of throughput and access delay, of the proposed distributed Wireless Local Area Network employing the IEEE 802.11 Medium Access Control protocol is analyzed extensively by computer simulations. The proposed network is based on using the same frequency for the entire coverage area with multiple receivers or radio bridges (RBs), with or without capture effect at each receiver. Different channel environments, including the Additive White Gaussian Noise (AWGN) channel, log-normal shadowing channel, Rayleigh fading channel, and log-normal shadowing plus Rayleigh fading channel, are considered in the simulations. The effects of various parameters are also studied. The results show that the performance can be improved significantly by using more RBs except for A W G N channel. The performance improvement of multiple RBs over one R B depends on the system parameters. In the log-normal shadowing plus Rayleigh fading channel, the throughput with 4 RBs and no capture can be improved by at least 120% over one RB. It is found that multiple RBs are more effective in a system with large number of stations and for channels severely degraded by shadowing or fading. With the use of capture, the performance can be improved by multiple RBs. But the performance improvement of multiple RBs is about the same as no capture cases. The effect of capture ratio is studied. It is found that the performance increases with decreasing the capture ratio. The performance of one and two dimensional models are found to be slightly different. The throughput does not change with packet size; however, the access delay degrades with packet size. Finally, it is found that the performance is not significantly affected by the length of the acknowledgment time-out.Applied Science, Faculty ofElectrical and Computer Engineering, Department ofGraduat