Performance Investigation of IEEE802.11e EDCA under Non-saturation Condition based on the M/G/1/K Model

The IEEE 802.11e network provides different with QoS (quality of service) guarantee for different traffic streams. The enhanced distributed channel access (EDCA) in IEEE 802.11e MAC protocol is proposed to support prioritized QoS on the basis of the distributed coordination function (DCF) in IEEE 802.11. We first build a new Markov chain model for the EDCA. The model takes into account both the idle state that represents that there are no packets to be transmitted and differentiation based on different AIFS-value for different traffic. We can use the signal transfer function of the generalized state transition diagram to derive a probability distribution of the MAC layer service time and analyze the performance of EDCA from a non-saturated channel to a saturated medium by using M/G/1/K queuing model. The proposed model is calculated numerically and validated against simulation results, we observed a good match between the analytical model and simulation which conforms the veracity of proposed model. Simulation and theoretical results show that despite providing prioritized QoS, the EDCA still can not support strict QoS for real-time application like voice and video unless network works in the non-saturation case. On the other hand, it is inevitable that there is unfairness of channel access to prioritized traffic due to EDCA.