QoS (quality-of-service) improvement in IEEE 802.11 e enhanced distributed channel access (EDCA)

Abstract

The IEEE 802.11e medium access control (MAC) is an emerging supplement to the IEEE 802.11 wireless local area network (WLAN) standard to support quality-of-service (QoS). IEEE 802.11e MAC is based on both controlled and contention-based channel access mechanisms. The controlled channel access is based on the poll-and-response protocol. On the other hand, the contention-based channel access, called EDCA, is based on the carrier-sense multiple access with collision avoidance (CSMA/CA). This paper proposes an algorithm that enhances the QoS of the enhanced distributed channel access (EDCA) in 802.11e. The proposed algorithm, named enhanced distributed contention control (EDCC), estimates the congestion level of the channel without overheads and adapts it for deciding transmission of data. Simulation experiments show that the proposed algorithm increases the channel utilization ratio more than 30%, reduces collision rate more than 50%, and reduces voice drop rate about 8% and video drop rate about 75% in comparison with EDCA. Moreover, the complexity of the proposed algorithm remains similar to the EDCA, enabling the design of low-cost implementations.