Evaluating a QoS-supportive MAC layer protocol for WLANs

Abstract

In spite of the tremendous boom in the wireless LAN arena, applications such as streaming video and audio still bring unique and challenging quality of service (QoS) requirements to such networks. To this effect, IEEE 802.11e medium access control (MAC) standard specifies a set of QoS enhancement features which allows traffic classification (high priority or HP and low priority or LP), prioritization and support for various classes of service (preferential and non-preferential service) for various traffic types over a wireless LAN. Thus HP traffic enjoys privileged service hence encounters lesser delay than an application which declares its traffic to be of type LP. However, it is possible for an application to falsely classify its LP traffic as HP traffic in pursuit of preferential service. Such selfish behavior by applications may destroy the QoS capabilities of the network. Currently, the standard does not address this issue. To provide relevant incentives to applications to behave truthfully, a new MAC protocol has been designed which promises fair sharing of resources amongst both HP and LP traffic such that the ldquoutilityrdquo of both traffic classes is maximized. This paper presents an evaluation of this new MAC protocol through simulations and analysis results. Specifically, this paper analyses the incentive mechanism proposed in this MAC and studies its effect on system performance. It also compares this MAC scheme to a scheme similar to that suggested in IEEE 802.11e. Finally, a QualNet simulation is provided which demonstrates the feasibility of incorporating our scheme in the current IEEE 802.11e standard and the efficiency of our scheme over the same in the presence of selfish users.