Weighted Fair Uplink/Downlink Access Provisioning in IEEE 802.11e WLANs

We present the unfairness problem between the uplink and the downlink flows in the IEEE 802.11e infrastructure basic service set (BSS) when the default settings of the enhanced distributed channel access (EDCA) parameters are used. First, we propose an analytical model to calculate the EDCA parameter set that ideally achieves a predetermined utilization ratio between uplink and downlink flows. Next, we design a simple and practical model-assisted measurement-based dynamic parameter adaptation algorithm. In the design of the proposed algorithm, we also consider the interactions of the bi-directional communication structure of transmission control protocol (TCP) with the medium access control (MAC) layer algorithm. Via simulations, we show that our solution provides short- and long-term fair access for uplink and downlink TCP and user datagram protocol (UDP) flows with different wired link propagation delays in a wired-wireless heterogeneous scenario. In the meantime, the quality-of-service (QoS) requirements of coexisting real-time flows can also be maintained.