A Novel EDCC Algorithm for IEEE 802.11 Protocol
Hong He · Chinese Journal of Computers · 2005
This paper presents a novel algorithm, called Enhanced Distributed Contention Control algorithm, for improving the performance of DCF (Distributed Coordination Function) Operations of IEEE 802.11 Wireless LAN (WLAN). EDCC algorithm is an extension of the existing IEEE 802.11 DCF Medium Access Protocol (MAC) by estimating the values of slot utilization and contention degree. Recent research shows that the IEEE 802.11 backoff mechanism has one main drawback: in a high load network the increase of the CW_SIZE is obtained at the cost of a continuous collision after a successful transmission because no state information indicating the actual contention level is maintained. The DCC (Distributed Contention Control) mechanism can solve the problem by estimating the value of network’s slot utilization and using it to schedule itself transmitting action. But the DCC mechanism doesn’t think of the correlation of slot_utilization when a node transmits two successive frames in a high load network. As a result, the distortion of the slot utilization’s estimation is big. The Enhanced DCC algorithm reduces the distortion of estimating slot utilization by using an ARMA( α ) Filter method to utilize the successively estimated value of slot utilization. At the same time, EDCC algorithm keeps the main characteristics: simplicity, integrability, complete distribution, adaptiveness and no transmission overhead. Results show that the EDCC algorithm can provide higher channel utilization and a lower network load compared with DCC algorithm.