Service differentiation mechanisms for WLANs

Designing a medium access control (MAC) protocol that simultaneously provides service differentiation and high throughput, and allows individual users to share limited spectrum resources fairly is a challenging problem for wireless LANs when applications have diverse performance requirements, such as high throughput, low delay, and delay jitter. In this paper, we propose efficient flow-based and class-based weighted fair queueing (WFQ) mechanisms with very simple-state information that considers only collisions, like the standard IEEE 802.11e MAC protocol. We utilize an analytical throughput model to obtain the optimal parameter settings for both mechanisms. Simulation results show that both mechanisms provide weighted throughput within 1% of the given throughput ratio. Additionally, we propose a novel and efficient priority mechanism. Our key technique involves each node changing its backoff counter based on both its own packet’s priority level and the priority level of the transmitted packet. Specifically, a node will increase its backoff counter linearly with a higher-priority packet transmission and decrease it exponentially with a lower-priority packet transmission. Simulation results show that our mechanism always protects high-priority traffic while still providing high throughput.