Distance aware collision avoidance protocol for ad-hoc underwater acoustic sensor networks

This paper proposes a channel access protocol for ad-hoc underwater acoustic networks which are characterized by long propagation delays and unequal transmit/receive power requirements. The protocol saves transmission energy by avoiding collisions while maximizing throughput. It is based on minimizing the duration of a hand-shake by taking advantage of the receiver´s tolerance to interference when the two nodes are closer than the maximal transmission range. Nodes do not need to be synchronized, can move, are half-duplex, and use the same transmission power. This protocol achieves a throughput several times higher than that of the slotted FAMA, while offering similar savings in energy. Although carrier sensing ALOHA offers a higher throughput, it wastes much more power on collisions.