EPCF: a lightweight multi-priority PCF for QoS support in IEEE 802.11 wireless LANs

Quality of service (QoS) support in wireless LANs is a challenging problem. In this paper, we propose a QoS enhancement over the legacy point coordination function (PCF) of IEEE 802.11, called enhanced PCF (EPCF). EPCF enables wireless LANs to send a combination of voice, data and isochronous data packets using the current IEEE 802.11 PCF. Due to the limitations of PCF, it was extended in the new IEEE 802.11e into the more complex hybrid coordination function (HCF). We found that HCF has several performance issues that may affect its anticipated performance. We also compare the performance of the proposed scheme (EPCF) with the HCF function through simulation. Simulation results demonstrate an enhanced performance of our scheme over the legacy PCF and a comparable performance to the IEEE 802.11e HCF in terms of the average delay and system throughput. However, EPCF is much simpler than HCF, provides service differentiation on flow level, and is easy to embed in the current IEEE 802.11 standard. Moreover, we extend the proposed scheme (EPCF) to work in a multi-hop wireless ad hoc mode.