A MACA-based Collision Avoidance MAC Protocol for Underwater Acoustic Sensor Networks

Although the exchange of RTS and CTS is implemented before data transmission in MACA, collision may still occur, because a sensor node cannot receive control packets in a timely manner due to the existence of propagation delay in underwater acoustic sensor networks (UW-ASN). In this paper, a MACA-based collision avoidance MAC protocol named fixed interval MACA (FI-MACA) is proposed for general UW-ASN. The time interval between the RTS and the data packet is fixed, and the CTS packet arrives at the sender just before the sender should transmit the data packet. Before sending an RTS to contend to access the channel, a sensor node listens to the channel for a fixed period of time. To solve the hidden station problem, the receiver also listens to the channel for a while before responding a CTS to the sender. The advantage of FI-MACA is that the sensor nodes can detect collisions effectively with low complexity. Simulation results show that FI-MACA performs well in terms of throughput and energy efficiency.