A Game Theory Based Dynamic Transmission Opportunity Adjustment in WLANs

IEEE 802.11e is standardized to enhance real time multimedia applications’ quality of service (QoS). This standard introduces two access mechanisms called Enhanced distributed channel access (EDCA) and HCF Controlled Channel Access (HCCA) as well as four Access Categories (ACs) for different types of applications. Each AC has four adjustable parameters : Arbitrary Inter-Frame Space Number(AIFSN), minimum Size of Contention Window(CWmin), maximum size of Contention Window (CWmax), and TXOP_limit. A TXOP_limit (TXOP) is time interval, in which a wireless station can transmit a number of frames consecutively, without releasing the channel and any further contention with other wireless stations. TXOP improves network throughput as well as service differentiation. Proper TXOP adjustment can lead to better bandwidth utilization and QoS provisioning. This paper studies the determination of TXOP in EDCA mode of IEEE 802.11e using a game theory based approach called GDTXOP. Based on GDTXOP, each wireless node chooses its appropriate TXOP according to its queue length and media access delay. OPNET simulator simulated the proposed method and its accuracy is evaluated and verified. The results of the simulation indicate that tuning TXOP appropriately improves both channel utilization for all levels of traffic priority and fairness. This improvement does not impair the quality of high-priority traffics. The proposed approach improves channel utilization, while preserving fairness and efficiency in WLANs and minimizing selfishness behaviours of stations in a distributed environment. Simulation results show the proposed method improves fairness while not disrupting the quality of service.