Boosting VoIP Capacity via Service Differentiation in IEEE 802.11e EDCA Networks

Pingping Dong,Yi Pan,Haodong Wang,Jianxin Wang

doi:10.1155/2015/235648

Abstract

This paper considers the performance problem of VoIP over 802.11e WLANs caused by the unfairness between uplink and downlink as well as the inefficient EDCA. A novel medium access control scheme named BEDCA (Balanced EDCA) is presented, which provides service differentiation between the access point (AP) and the mobile stations (STAs) to enhance VoIP capacity. In BEDCA, the expression of AP's contention window is obtained which is a relative constant value independent of the participating STAs. The minimum contention window of the STAs is traffic-aware based on the proposed algorithm. The performance improvement of BEDCA is verified through intensive simulations and the results show the capacity improvement of 82.1% compared to EDCA.

Highlights

In recent years, the wireless LAN (WLAN) has become the dominant Internet access method because of its attractive features, including low cost, high bandwidth, ease of deployment, and mobility support
We propose a novel access scheme for 802.11e WLANs with the goal to improve the QoS of VoIP over WLAN by differentiating the service between the access point (AP) and STAs
We derive the expression of the optimal access probability that maximizes the throughput where we find that the optimal access probability of AP is a relative constant value independent of the number of the STAs

Summary

Introduction

The wireless LAN (WLAN) has become the dominant Internet access method because of its attractive features, including low cost, high bandwidth, ease of deployment, and mobility support. Distributed coordination function (DCF) is the fundamental 802.11 media access control (MAC) technique. As the VoIP applications are characterized by their real-time nature, they impose upper limits on delay and jitter in addition to usual requirements on packet loss and throughput, which are properly supported only in overprovisioned scenarios with DCF. To overcome this limitation, IEEE 802.11e [2], known as the enhanced distributed channel access (EDCA), has been introduced to differentiate the channel access priorities of the different QoS requirements [3]. A high-priority data packet has a large chance to win the media contention for being transmitted than a low-priority one

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