A Novel IEEE 802.11e-Based QoS Protocol for Voice Communications over WLANs

摘要

Voice over WLAN (VoWLAN) is widely acknowledged as one of the key, emerging applications for wireless LANs. As with any multi-service network, there is the need to provision the WLANs with the QoS mechanisms capable of guaranteeing the requirements of various services. The upcoming IEEE 802.11e (EDCA) standard is on the way to define the required QoS mechanisms into the protocol architecture of IEEE 802.11 WLANs. However, recent studies have shown that EDCA performs poorly when the medium is highly loaded. This situation has led many researchers to design techniques aiming to improve the performance of EDCA. Unfortunately, the main deficiency of many of the proposed mechanisms to date comes from their inability to properly interoperate with legacy IEEE 802.11 (DCF) systems. Moreover, the implementation of many of the proposed QoS mechanisms requires important and incompatible changes to the IEEE 802.11e specifications. In this paper we introduce a novel IEEE 802.11e-based QoS protocol capable of providing QoS support to voice communications, and able to properly interoperate with legacy DCF based stations. Our design has been based on an in-depth analysis of the several operation modes of both standards. This should ensure full compatibility of operation: an important feature since the transition from the IEEE 802.11 to the IEEE 802.11e will take some time making more likely the existence of hybrid scenarios where both standards will have to coexist. Our results show that the proposed mechanism outperforms the IEEE 802.11e standard by offering better QoS guarantees to the voice service over a wider range of load conditions and traffic mix scenario.