UC Santa Cruz

Prior work on persistent and non-persistent transmission strategies of CSMA and CSMA/CD indicated that no persistence provides better performance; however, this result applies only to a specific approach to persistence. We introduce time-based persistence in which a node with a packet to send that finds the channel busy persists for a limited amount of time, and provide a simple unifying analysis of the impact of time-based persistence in channel-access protocols that use carrier sensing and operate in ad-hoc wireless networks. We focus on CSMA with priority acknowledgments (ACK) and CSMA with collision detection (CSMA/CD) and ACKs. Our analysis takes into account the effect that receive-to-transmit turnaround times have on performance, and shows that CSMA and CSMA/CD with time-based persistence can attain the same throughput values relative to a non-persistent strategy.