# WLQRP: A Weighting Link-Quality-Based Routing Protocol for Underwater Sensor Networks
## 2 Related Works
Instead, it uses depth as a factor for selecting the next hop node and only requires depth information. This protocol avoids the need for complex location techniques. The transmission of data is limited to a one-way flow, from the lower level to the higher level. This routing protocol selects the next node based on whether it is closer to the surface of the sea than the node at this point, and if the packet is closer to the sea, it will be transmitted to that specific node. On this basis, [PERSON], [PERSON] et al. [20] proposed an improved protocol, FDBR (fuzzy depth-based routing), which not only utilizes depth information but also takes hop count and energy information into account more comprehensively. This leads to enhanced network energy usage and improved delay performance. In order to reduce the probability of encountering void holes in the sparse networks, [PERSON] et al. [21] presented a weighting depth and forwarding area division DBR routing protocol called WDFAD-DBR. [PERSON] et al. [22] proposed VAPR (void-aware pressure routing), a void-aware pressure routing protocol, which utilizes the sequence number, hop number, and depth information to enable the selection of the next hop node closest to the surface receiver, thereby selecting the shortest data transmission path and maintaining a high packet transmission rate even in the presence of voids. In order to extend the life cycle of the network and balance the energy consumption, EEDBR [23] considers two indexes, depth and remaining energy, when forwarding packets. When a node receives a packet, it calculates the retention time based on its remaining energy and position in the forwarding list. In ref. [24], [PERSON] et al. proposed pressure routing (hydro cast) for underwater sensor networks. The next hop node is selected in a similar way to DBR, but it adopts an anti-gap mechanism and limits co-channel interference to improve network performance. [PERSON], [PERSON] et al. [25] proposed a confined energy depletion (CED) opportunistic routing (OR) mechanism in which the depth factor of the compute node is used to further narrow the selection range of the next-hop trunks. In ref. [26], a geographic and cooperative opportunistic routing protocol (GCORP) is proposed. In the GCORP protocol, initially, a multiple sink-based network architecture is established. Then, a relay forwarding set is determined by the source node on the basis of the depth fitness factor. [PERSON] et al. [27] proposed the energy and depth variance-based opportunistic void avoidance (EDOVE) scheme to gain energy balancing and void avoidance in the network. EDOVE considers not only the depth parameter, but also the normalized residual energy of the one-hop nodes and the normalized depth variance of the second hop neighbors. The H2-DAB (hop-by-hop hop dynamic addressing based) protocol proposed by [PERSON] et al. [28] does not even need to use any location information. In this protocol, the surface receiver first broadcasts a hello packet to the submarine nodes, and all the nodes receive it and obtain hop count information from that node to the receiver. In the subsequent packet transmission, the forwarding of the next node is determined solely by the hop count information. [PERSON] et al. [29] designed a Nonuniform clustering (NC) algorithm in which clusters are generated according to different node densities. The simulation results show that compared with the classical routing algorithm, the proposed algorithm has a higher transmission efficiency, requires less energy consumption, and can more effectively extend the network's lifetime. In ref. [30], the whole network model is regarded as a 3D cube from the grid point of view, and this 3D cube is divided into many small cubes, where a cube is seen as a cluster. The proposed protocol shapes an energy consumption model considering the residual energy and location of sensor nodes to select the optimal cluster-heads. [PERSON] et al. [31] proposed the ACUN protocol.