Reducing the Variations in Delay in IEEE 802.11 DCF

IEEE 802.11 is a widely used standard for MAC and PHY layers of WLANs. Unfortunately the access methods offered in this standard cannot support QoS (Quality of Service) for real-time traffics. One parameter which is important in providing QoS is jitter (variance in packet delays). Majority of the proposed mechanisms for enabling DCF (Distributed Coordination Function) with QoS capabilities does not consider jitter and focus only on delay and throughput. In this paper, we propose a new scheme that provides QoS in DCF and reduce the jitter. We do this by differentiating traffics by using different IFS (Inter-Frame Space) and the minimum and maximum size of CW (Contention Window) to provide QoS and multiplicative decrease of the CW size after a successful transmission, instead of resetting it to its minimum size. Results of our simulations show that this scheme can provide lower jitter for audio traffic while not degrading the delay and throughput.