A Novel MAC scheme for solving the QoS parameter adjustment problem in IEEE 802.11e EDCA

We present a novel MAC scheme for solving the QoS parameter adjustment problem in IEEE 802.11e EDCA. The default values of the QoS parameters in EDCA, contention window (CW), arbitration Interframe Space (IFS) etc only yield good performance for few scenarios. We first propose a simple adaptation scheme, called a-EDCA, where the access point adapts the CWs based on the network conditions. The main contribution of this work is the second approach, called i-EDCA, where we make modifications to the backoff phase of EDCA and introduce a random IFS scheme. Simulation results show that both approaches result in stable capacity ratios between priority classes and very high channel utilization, compared to EDCA, when the number of stations is increased. Moreover, i-EDCA yields close to optimal channel utilization for a large number of scenarios without any need of adapting the parameters. In i-EDCA, the capacity for each class is directly proportional to its CW. Results also show that i-EDCA has improved fairness and prevents low priority classes to be starved under higher loads, a problem found in EDCA.