Receiver-initiated collision avoidance in wireless networks

Many medium-access control (MAC) protocols for wireless networks proposed or implemented to date are based on collision-avoidance handshakes between sender and receiver. In the vast majority of these protocols, including the IEEE 802.11 standard, the handshake is sender initiated, in that the sender asks the receiver for permission to transmit using a short control packet, and transmits only after the receiver sends a short clear-to-send notification. We analyze the effect of making the collision-avoidance handshake, receiver initiated and compare the performance of a number of receiver-initiated protocols with the performance of sender-initiated collision avoidance protocols. Analytical and simulation results show that the best-performing collision avoidance MAC protocol based on receiver-initiated or sender-initiated collision avoidance is one in which a node with data to send transmits a dual-purpose small control packet inviting a given neighbor to transmit and asking the same neighbor for permission to transmit. The receiver-initiated protocols we present make use of carrier sensing, and are applicable to either baseband or slow frequency-hopping radios in which an entire packet can be sent within the same frequency hop (which is the case of frequency hopping spread spectrum (FHSS) commercial radios).