A Virtual Collision Mechanism to Decrease Collisions in IEEE 802.11 MAC Layer

This paper proposes a mechanism to decrease collisions in IEEE 802.11 DCF (distributed coordination function) for high load BSSs (basic service sets). Two slots are assembled together to form a super slot, and the station´s backoff counter decreases in terms of super slot time as long as the channel is sensed idle. When a station sends a packet in a super slot, it sends the packet at the first slot with probability q and at the second slot with probability (1-q). Thereby, if more than one station transmits packets in a super slot all together, a part of collisions is changed into successful transmissions or virtual collisions. When a BSS is under high load, applying this mechanism in DCF greatly improves the throughput and lowers the energy consumed by collisions. In a word, this method is easy way to implement and improves DCF´s performance considerably.