Incomplete cooperation-based service differentiation in WLANs

In the IEEE 802.11 wireless LAN (WLAN), the fundamental medium access control (MAC) mechanism-distributed coordination function (DCF), only supports best-effort service, and is unaware of the quality-of-service (QoS). IEEE 802.11e enhanced distributed channel access (EDCA) supports service differentiation by differentiating contention parameters. This may introduce the problem of non-cooperative service differentiation. Hence, an incompletely cooperative EDCA (IC-EDCA) is proposed in this paper to solve the problem. In IC-EDCA, each node that is cooperative a priori adjusts its contention parameters (e.g., the contention window (CW)) adaptively to the estimated system state (e.g., the number of competing nodes of each service priority). To implement IC-EDCA in current WLAN nodes, a frame-analytic estimation algorithm is presented. Moreover, an analytical model is proposed to analyze the performance of IC-EDCA under saturation cases. Extensive simulations are also carried out to compare the performances of DCF, EDCA, incompletely cooperative game, and IC-EDCA, and to evaluate the accuracy of the proposed performance model. The simulation results show that IC-EDCA performs better than DCF, EDCA, and incompletely cooperative game in terms of system throughput or QoS, and that the proposed analytical model is valid.