Improvement of channel efficiency with fuzzy control approach for dynamic user variation under WLAN, IEEE 802.11

• Main Authors: Hsu Yu Hua, 徐裕華
• Other Authors: Horng Shi Jinn
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/27618315003632950932

碩士 === 國立臺灣科技大學 === 電機工程系 === 91 === In recent years, mobile ad hoc network (MANET) has become a widely used technology which is based on the IEEE 802.11 standards. The basic IEEE 802.11 Medium Access Control (MAC) protocol is implemented with Distributed Coordination Function (DCF). DCF channel efficiency is the target of this research work. In the DCF of IEEE 802.11, the MAC protocol is extended partially from wired network. Since there is no way to detect and listen to the wireless channel in wireless network, the MAC protocol has some modification for wireless environment from CSMA/CD (Carrier Sense Multiple Access with Collision Detection) to CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance). Due to the CA uses too much time on waiting to avoid the collisions, the channel efficiency on the implementation one become much lower than the analysis one. In contrarily, appropriate delay access can decrease the collisions in particularly when the environment is crowded with users. Current research works show that there is still lots space to improve on collision avoidance and delay access mechanism to enhance the channel efficiency. This thesis will be aimed at the collision avoidance mechanism with a new adaptive approach based on fuzzy control. Recently a lot of research also shows that in MANET environment channel efficiency can be affected by some parameters, such as amount of user variation, initialization of the contention window (CW), unit of the exponential backoff count down, average length of the packet and the priority of user transmission. In this work, we study the impact of dynamic user variation which makes the steady-state communication channel with low efficiency. We proposed a dynamic adaptive approach based on fuzzy logic control to relax the impact of variation and then to improve the channel efficiency.