A Delay-Awareness Routing Protocol in Intermittently Connected Underwater Acoustic Sensor Networks

The rapid development of underwater technology has opened up new possibilities and introduced new challenges for MAC and protocol designs. The packet delay reduction becomes critical issues in underwater sensor networks (USNs) since the propagation speed of water is rather slow compared with radio waves. In addition, due to the property of intermittent link connectivity in underwater, the existing message-based and synchronization-based approaches can not meet packet delivery requirements. In this paper, a tailored multihop routing protocol is designed for transmission delay reduction without packet exchanges and retransmissions. The observation of delivery analysis with different link qualities gives insights on relay nodes selection for lower delivery loss rate. To prevent excessive redundant packets, this work includes a strategy of adjusting the number of packet cloning dynamically between each hop.