Floor Acquisition Multiple Access (FAMA) in Single-Channel Wireless Networks

The FAMA-NCS protocol is introduced for wireless LANs and ad-hoc networks that are based on a single channel and asynchronous transmissions (i.e., no time slotting). FAMA-NCS (for floor acquisition multiple access with non-persistent carrier sensing) guarantees that a single sender is able to send data packets free of collisions to a given receiver at any given time. FAMA-NCS is based on a three-way handshake between sender and receiver in which the sender uses non-persistent carrier sensing to transmit a request-to-send (RTS) and the receiver sends a clear-to-send (CTS) that lasts much longer than the RTS to serve as a “busy tone” that forces all hidden nodes to back off long enough to allow a collision-free data packet to arrive at the receiver. It is shown that carrier sensing is needed to support collision-free transmissions in the presence of hidden terminals when nodes transmit RTSs asynchronously. The throughput of FAMA-NCS is analyzed for single-channel networks with and without hidden terminals; the analysis shows that FAMA-NCS performs better than ALOHA, CSMA, and all prior proposals based on collision avoidance dialogues (e.g., MACA, MACAW, and IEEE 802.11 DFWMAC) in the presence of hidden terminals. Simulation experiments are used to confirm the analytical results.