Architecture of Achieving QoS for Multiple Flows per Node in WLANs

This paper proposes an effective architecture to achieve QoS in distributed WLANs when multiple traffic streams are present and flowing through every single station. The 802.11e standard specifies a multiple-state-machine (MSM) structure in the medium access control (MAC) to address this QoS concern. However, our research indicates that the MSM structure was suboptimal. It increases the collision rate and weakens the stability of the network. Instead, we propose a QoS scheduler over the MAC state machine (called local scheduler multi flow, LSMF): the proposed LSMF architecture prevents every flow in a node from initiating its own contention simultaneously, consequently, improves the overall network throughput and stability. We evaluate the performance of our LSMF model through mathematical analysis and simulations in comparison with the 802.11e MSM model, and prove the LSMF architecture is superior in both QoS effectiveness and flexibility for multiple flows per node case.