Service Differentiation without Prioritization in IEEE 802.11 WLANs

Wireless LANs carry a mixture of traffic, with different delay and throughput requirements. The usual way to provide low-delay services is to give priority to such traffic. However, this creates an incentive for throughput sensitive traffic also to use this service, which degrades overall network performance. We show, analytically and by simulation, that the performance of both delay and throughput sensitive traffic can be improved by scaling IEEE 802.11's $(CW_{{\rm min}})$ and TXOP limit parameters in equal proportion. This reduces, but does not eliminate, the incentive for bulk data users to use the low-delay service. We further show that this incentive can be removed, while still giving improved performance to both classes, by reducing the $(CW_{{\rm min}})$ of the high throughput class by a constant that is independent of the traffic load.