Performance Comparison of Dual Queue and EDCA for VoIP over IEEE 802.11 WLAN

Inhalt:
The popular IEEE 802.11 WLAN today does not provide any quality-of-service (QoS) because of its contention-based channel access nature of the medium access control (MAC). Therefore, we proposed a simple software upgradebased solution, called a dual queue scheme, to provide QoS to real-time services such as Voiceover- IP (VoIP) in our previous work. The dual queue scheme operates on top of the legacy MAC. We in this paper present a modified dual queue (MDQ) scheme by considering a practical implementation limitation. On the other hand, currently 802.11e MAC is being standardized in order to support QoS, and it includes a contention-based channel access mechanism, called enhanced distributed channel access (EDCA). Prioritized channel accesses are provided to different traffic classes under EDCA. In this paper, we comparatively analyze the performances of MDQ and EDCA via simulations in terms of delay, jitter, and throughput for various scenarios. We also consider an AP’s fast channel access scheme based on the channel access parameter adaptation of EDCA. The simulation results show that EDCA apparently provides a better performance in most situations. However, MDQ provides an acceptable performance close to that of EDCA so that it can be used when the EDCA is not available and/or the hardware upgrade to 802.11e is not desirable for the cost reason.