An Uninterrupted Collision-Free Channel Access Scheme over IEEE 802.11 WLANs

Abstract

IEEE 802.11 distributed coordination function, (DCF), provides contention-based distributed channel access for stations to share the wireless medium. However, Performance of IEEE 802.11 DCF protocol, in terms of delay and throughput, degrades dramatically as the number of active stations increases, especially when each station transmits in its saturated state. Therefore, development of an efficient Medium Access Control (MAC) protocol providing both high throughput for data traffic and quality of service (QoS) for real-time applications has become a major focus in WLAN research. In this paper, we propose an adaptive collision-free MAC adaptation. Proposed scheme prevents collisions and allows stations to enter an uninterrupted collision-free state, regardless of the traffic types (saturated or unsaturated) and the number of stations on the medium. Simulation results indicate that proposed scheme dramatically enhances the overall throughput and supports QoS maintaining real-time services at high level over 802.11-based WLANs.