Delay Analysis of an Enhancing IEEE 802.11 Point Coordination Function MAC Protocol
The widespread use of multimedia networking applications has brought more requirements to the network, creating a need for end-to-end Quality of Service (QoS). The contention-free Point Coordination Function (PCF) with Round Robin scheme, where the Access Point controls all transmissions based on a polling mechanism, is defined in IEEE 802.11 standard to provide QoS service. This network suffers from inefficiency in the delay sensitive traffic and makes. It is difficult to provide priority-differentiated service. In this paper, a useful enhance mechanism is derived from a two-level-polling model with a parallel scheme between the polling and switch over processes. We consider two different polling schemes according to station classify: key station and normal station. This mechanism allows for a delay guarantee as well as priority service. An analytical is developed for evaluating the queuing length for the station and waiting time for the packets at nodes. Based on this model, we achieve several closed-form expressions for mean cycle time, mean queue length and mean waiting time. To verify the correctness of our analytical model, we also develop a simulator for the 802.11 PCF MAC. The simulation results well match the analytical results.