DFR: An efficient directional flooding-based routing protocol in underwater sensor networks

Unlike terrestrial sensor networks, underwater sensor networks (UWSNs) have salient features such as a long propagation delay, narrow bandwidth, and high packet loss over links. Hence, path setup-based routing protocols proposed for terrestrial sensor networks are not applicable because a large latency of the path establishment is observed, and packet delivery is not reliable in UWSNs. Even though routing protocols such as VBF (vector based forwarding) and HHVBF (hop-by-hop VBF) were introduced for UWSNs, their performance in terms of reliability deteriorates at high packet loss. In this paper, we therefore propose a directional flooding-based routing protocol, called DFR, in order to achieve reliable packet delivery. DFR performs a so-called controlled flooding, where DFR changes the number of nodes which participate in forwarding a packet according to their link quality. When a forwarding node has poor link quality to its neighbor nodes geographically advancing toward the sink, DFR allows more nodes to participate in forwarding the packet. Otherwise, a few nodes are enough to forward the packet reliably. In addition, we identify two types of void problems which can occur during the controlled flooding and introduce their corresponding solutions. Our simulation study using ns-2 simulator proves that DFR is more suitable for UWSNs, especially when links are prone to packet loss.