Experimental Study Of Long-distance IEEE802.11n Wireless Link Performance

LDmesh(Long distance wireless mesh) networks based on IEEE802.11featurelow cost, flexible structure and are easy to build. They are suitable for providing ruralarea with Internet access, long-distance education, telemedicine, environment monitorand so on. However, with the increasing of data service requirement, LDmeshnetworks based on IEEE802.11a/b/g cannot meet the need of high-speed datacommunication. IEEE802.11N, the new WiFi protocol, provide with data rate high to600Mbps. Therefore, it is very essential to apply the technique of IEEE802.11n toLDmesh networks, so as to improve the performance of networks.In this dissertation we analyze the main features of IEEE802.11n protocol anddesign a lot of experiment to study its performance in long distance wireless link. Inthe experiment, we realize the functions of customizing wireless-card parameters bymodifying wireless-card driver program called ATH9K. We accomplish manyfunctions, such as enabling/disabling CSMA and ACK, setting ACK timeout,AMPDU length limit and MCS, providing technique support for802.11nlong-distance experiment. Besides, in order to improve the precision of thisexperiment, we develop PktRecord, a tool of statistics, which can get the rightstatistics data.In the outdoor environment of long-distance link, we have carried out theexperiment of frame aggregation comparison and rate adaptation algorithm evaluation,etc, and finish data processing. The results demonstrate that the high throughput ofIEEE80211n in long distance links mainly depend on bandwidth, mcs and frameaggregaton. we can improve the performance of long distance wireless links by rateadaptation, which can set IEEE802.11n paratmeters based on link qulity.