IEEE 802.11 DCF Improvement: Waiting DIFS while Waiting Back-off

Abstract

With the emergence of time-sensitive applications such as games and telephony, the introduction of the Quality of Service (QoS) in general and the improvement of transmission delays in particular have become a must in wireless networks. The distributed coordination function (DCF) being the fundamental access method and the basis of the wireless LANs IEEE 802.11 MAC protocol, a great number of works have been done to improve it. In DCF, after sensing an idle channel, stations have to wait before the transmission of each frame a length of time called DIFS (DCF Inter Frame Space) followed by another called back-off. If the medium becomes busy during the back-off process, the back-off timer is paused and resumed when the medium is sensed free for a DIFS again. This time loss becomes considerable when the number of interruptions of back-off process grows. This paper proposes a contribution to improve DCF by combining IFS and back-off time. The simulation results show that the approach benefits are proportional to the contention level of the network and to the number of hops in multi-hop network topologies.