UC Santa Cruz

We present and analyze CSMA/CDS, a simple extension of carrier-sense multiple access (CSMA) that attains collision detection (CD) through the collaboration among nodes endowed with half-duplex radios in wireless local area networks (WLAN). CSMA/CDS uses two mechanisms to provide feedback to nodes attempting to transmit data packets concurrently. Using carrier sensing to access the channel, a node transmits a common pilot before sending its data packet, and a designated passive listener sends a collision pilot if it does not hear the common pilot after detecting carrier. This ensures that no collisions of data packets can occur. The throughput of CSMA/CDS is analyzed and compared with the performance of CSMA with priority ACKs and CSMA with collision detection (CSMA/CD), which assumes full-duplex transceivers. The results show that the throughput of CSMA/CDS is much better than the throughput of CSMA and is comparable to that of CSMA/CD.