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University: Carleton University 1125 Colonel By Drive,
Spectral Efficiency of IP Traffic in IEEE 802.11b Wireless LAN This project is part of the study designed to determine the spectral efficiency of the IP traffic in a typical indoor wireless LAN setting. Under this project, two limited sets of data were collected from existing operational IEEE 802.11b network, application specific data, and channel capacity by map data. The application specific data was categorized into three categories; (1) email, (2) Intranet download and (3) Internet browsing. The traffic generation parameters, of both, the mobile station, and the access point were observed for all three categories. The observed parameters were; physical source, logical source, physical destination, logical destination, MAC addresses of the source and the destination, packet arrival time, and packet size of each packet. The channel capacity by map data was obtained in the following way. At one position within the observed floor one file was downloaded 20 times. The downloaded file size was observed once every second (average data rate for one second). This experiment was then repeated for various other physical positions of the mobile station, and the access point. Furthermore, received signal to interference ratio was measured at each location. This project uses the two limited sets of data, discussed above, to build an empirical IEEE802.11b wireless LAN model, which is capable of reproducing the measured traffic and physical channel statistics, and which can be scaled, changed, or updated in any way so as to provide the modeler with the ability to model, and measure the network capacity for any possible scenario. OPNET software was selected for the design of the simulation model because OPNET already has an IEEE802.11 mobile station and access point model complete with the entire OSI protocol stack. As well as because OPNET software has the required functionality of being transparent, easily changed, updated, and scaled. An operational IEEE802.11b model therefore requires: o IEEE802.11 MAC layer model o Access Point o Mobile Station o Mobile station source model o Access Point Source model o Physical channel model IEEE 802.11 OPNET’s MAC layer model was used, although it was altered in order to enable the modeling of a scenario in which more than one access points use the same physical channel in the same general area. This provides the modeler with the ability to model the operation of multiple BSS utilizing the same physical channel in very close proximity. The project also involves the construction of mobile station, and access point source model, as well as the physical channel model, based on the collected data. |
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