The enhanced distributed coordination function (EDCF) is one of the main features of 802.11e quality of service (QoS) enhancement over legacy 802.11 distributed coordination function (DCF). In order to control network performance, a network designer needs to understand how the EDCF parameters affects the QoS performance explicitly. However, we are unaware of any publications regarding EDCF analysis that includes all of the protocol details. Most evaluations only use numerical results. We propose a simple but extremely accurate analytical model to compute the saturation throughput performance of 802.11e EDCF, with the assumption of ideal channel conditions and same different inter frame space (DIFS). The analysis consists of two cases. The first case demonstrates how different nodes can achieve differentiate access in uplink. In the second scenario, there are multiple flows in one node, and they compete for the channel in downlink. With the help of the analysis, we show how to design a distributed MAC weighted round robin (WRR) packet scheduler to emulate an ideal network layer scheduler. Simulation comparison indicates that the MAC layer scheduler can achieve higher utilization, smaller delay than the network layer WRR and bandwidth ratio as wanted.
['Jie Hui', 'Michael Devetsikiotis']
Designing improved MAC packet schedulers for 802.11e WLAN