UC Santa Cruz

This paper introduces Carrier-Sense Multiple Access with Transmission Acquisition (CSMA/TA) for wireless local area networks (WLANs) with stations endowed with half-duplex radios using single antennas. In contrast to traditional contention-based channel-access methods, CSMA/TA seeks to increase the likelihood of having the last transmission from a group of colliding transmissions succeed. To accomplish this, a station senses the channel before sending a pilot packet. After finishing the transmission of the pilot, the station is required to wait for a certain amount of time before sensing the channel again. If the channel is sensed to be idle again, the station understands that ``it has acquired its right to transmit a data frame'' and proceeds with that. The throughput of CSMA/TA is compared with the throughputs of CSMA and CSMA/CD. An important feature of the analysis presented in this paper is the consideration of the impact of the receive-to-transmit and transmit-to-receive turnaround times. It is shown that CSMA/TA performs better than ideal CSMA and CSMA/CD if the propagation delays in  the network are larger than the turnaround times, and its performance can still surpass CSMA/CD and CSMA if turnaround times are larger than propagation delays but not too much larger.