Merit of PHY-MAC Cross-Layer Carrier Sensing: A MAC-Address-based Physical Carrier Sensing Scheme for Solving Hidden-Node and Exposed-Node Problems in Large-Scale Wi-Fi Networks

This paper examines how various carrier-sensing schemes affect the exposed-node (EN) and hidden-node (HN) phenomena. In the process, we identify a new carrier-sensing mechanism for alleviating EN and HN that is more effective than previously proposed schemes. This scheme, referred to as the MP scheme, uses MAC-address-based Physical carrier sensing to determine if the medium is busy. In MP, the addresses of transmitter and receiver of a packet are incorporated into the PHY header. Making use of this address information for its carrier-sensing operation, a node can drastically reduce the detrimental effects of EN and HN. In ns2 simulations, MP yields superior throughput and fairness performance that exceed our original expectation. Specifically, we find that the total network throughput achieved by MP is more than twice that of the 802.11b basic-access mode, and more than four times that of the 802.11b RTS/CTS mode, under various node-density and packet-size assumptions. At the same time, the Jains fairness index of MP is almost twice that of the 802.11b basic-access and RTS/CTS modes. We believe this is a first paper to propose and investigate the merit of cross-layer carrier sensing that jointly makes use of the attributes of the physical and MAC layers in its operation