Efficient collision detection for auto rate fallback algorithm

The physical rate adaptation in 802.11 is a deeply investigated, though still open issue. Since 802.11 uses the random access distributed coordination function (DCF) mechanism to access the medium, collisions can occur when two or more stations want to transmit data simultaneously. The challenge of rate adaptation schemes is to adapt the physical transmission rate based on channel-related losses, i.e. collisions should not influence the choice of the rate. In this paper we propose a new rate adaptation algorithm that behaves like auto rate fallback (ARF), but makes use of the RTS/CTS handshake, when necessary, to decide whether the physical transmission rate should be changed. Main advantages of this algorithm are its simple implementation and the good performance it attains in presence of collisions. We evaluate the performance of this new rate adaptation algorithm, comparing it with other well known algorithms, by using the new NS-3 simulator.