A simple distributed access control scheme for supporting QoS in IEEE 802.11 wireless LANs

Supporting quality of service (QoS) in wireless networks is a challenging problem. The point coordination function (PCK) in IEEE 802.11 LAN standard was developed to support the transmission of real-time data. However, PCF was not able to meet the requirements of real-time data. Therefore, several IEEE 802.11e drafts, whose main task is to support QoS, were released after IEEE 802.11. The polling scheme of PCF is extended in IEEE 802.11e into the more complex hybrid coordination function (HCK). We found that HCK has several performance issues that may affect its anticipated performance. In this paper, we address these issues and propose a QoS enhancement over PCK, called enhanced PCF (EPCF) that enables wireless LAN to send a combination of voice, data and isochronous data packets using the current IEEE 802.11 PCF. We compared the performance of the proposed model (EPCF) with the HCF function of the IEEE 802.11e through simulation and we extend the proposed model (EPCF) to work in a multi-hop wireless ad hoc mode. The simulation results demonstrated an enhanced performance of our scheme over the legacy PCK and a comparable performance to the IEEE 802.11e HCF in terms of average delay and system throughput. However, EPCF is much simpler than HCK, provides service differentiation on flow level, and can be incorporated easily into the current IEEE 802.11 standard.