An Intelligent Modulation Controller with Fuzzy Function for IEEE 802.11 Multi-Rate/Range Transmission

• Main Authors: Yung-Da Wang, 王永達
• Other Authors: Shiann-Tsong Sheu
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/03730993192297764360

碩士 === 淡江大學 === 電機工程學系 === 90 === Mobile devices in the IEEE 802.11 wireless local area network (WLAN) have the ability to transmit data frames at one of four transmission rates 1/2/5.5/11 Mb/s. This is because the commercial WLAN transceivers have equipped with several different modulation schemes. Based on the characteristic of modulation scheme, a higher transmission rate will result in a shorter transmission distance and a longer time consumption on data frame transmission. If the channel environment is relatively clear and the transmission distance is short, one should choose a higher transmission rate to transmit data frame to maximize channel utilization. On the contrary, a lower transmission rate should be selected to minimize the frame loss and frame error probabilities. Therefore, the problem of choosing a proper transmission rate to accommodate varying environment is a new and valuable problem in the pervasive LANs. To our knowledge, it is very difficult and impractical to formalize an indoor environment since the channel status is quite unstable and unpredictable. Instead of, we propose an Intelligent Modulation Controller ( IMC ), which employs the powerful fuzzy set function, for intelligently selecting the transmission rate for frame transmissions. This fuzzy control function refers the average received signal strength indicator ( RSSI ), the average frame error rate ( FER ) and the average medium access control ( MAC ) delay to make a right decision. Simulation results demonstrate that the proposed fuzzy controller indeed enhances the network throughput and the access delay.