DFR: Directional flooding-based routing protocol for underwater sensor networks

Unlike terrestrial sensor networks, underwater sensor networks (UWSNs) have different characteristics such as a long propagation delay, a narrow bandwidth and high packet loss. Hence, existing path setup-based routing protocols proposed for terrestrial sensor networks are not applicable in the underwater environment. For example, they take much time when establishing a path between source and destination nodes due to the long propagation delay. In addition, the path establishment requires much overhead of control messages. Moreover, the dynamic and high packet loss degrades reliability, which invokes more retransmissions. Even though exiting routing protocols such as VBF were proposed to improve the reliability, they did not take into account the link quality. That is, there is no guarantee that packets reach the sink safely especially when a link is errorprone. In this paper, we therefore propose a directional floodingbased routing protocol, called DFR. Basically, DFR relies on a packet flooding technique to increase the reliability. However, the number of nodes which flood a packet is controlled in order to prevent a packet from flooding over the whole network and the nodes to forward the packet are decided according to the link quality. In addition, DFR also addresses a well-known void problem by allowing at least one node to participate in forwarding a packet. Our simulation study using ns-2 proves that DFR is more suitable for UWSNs especially when links are prone to packet loss.