O-ACK: An adaptive wireless MAC protocol exploiting opportunistic token-passing and ack piggybacking

Bandwidth is a shared and limited resource of the wireless LAN. The MAC protocols are mainly responsible for efficiently sharing it among all the stations. The IEEE 802.11 standard uses Distributed Coordination Function (DCF) as its default MAC protocol which employs Carrier Sense Multiple Access using Collision Avoidance (CSMA/CA) scheme with binary exponential backoff algorithm. Despite its ubiquitous acceptance, it has two major drawbacks: i) channel idle time and ii) collision overhead. Besides, this protocol uses explicit ack which comes with significant overheads, for example preamble, frame header etc. In this paper, we propose a scheme called O-ACK which reduces the overhead of explicit ack and backoff interval by leveraging piggybacking, packet overhearing and token based scheduling. Our NS2 based simulation results confirm that this protocol significantly outperforms the DCF protocol.