# DOW-PR DOlphin and Whale Pods Routing Protocol for Underwater Wireless Sensor Networks (UWSNs)
## 2 Previous Work
This scheme also provides a model in order to decrement noise, path losses and other attenuation factors for the sensors that are present at the region in UWSNs where the depth is less. H2-DAB protocol, which is also abbreviated as hop by hop dynamic addressing based protocol, is free of location information, as it belongs to a beacon based routing protocol class, as localization information of the node is costly, so, in this way, it reduces the cost of hardware. This scheme counts the hop number from the sink nodes present on the surface, and assigns a distinct address to all sensors that are part of the network by using the beacon mechanism from the nodes present on the surface (sink nodes). The node that has larger dynamical and distinct address will forward the packet towards the node that has a dynamically smaller address, up until it reaches the destination node or sink node. In [31], this scheme is used by using the concept of unique IDs of the sensing nodes. If it is assumed that packets are forwarded towards the sinks, then multi sink architecture must be taken into consideration in case any sink node detected the data packet successfully. In [32], mutilpath routing protocol is introduced in which it is considered that a source node sends a multipath route request towards the destination node before it sends the data packet to the destination. In response to the request, multiple paths/routs are created between source and destination. On the basis of two parameters, the source node sorts out the optimal route. Those two parameters are path length (number of hops) and energy distribution factor along this paths. Source node selects power for the transmission and will send the data packet through that path in which energy is evenly and fairly distributed. The node that is present at the destination will receive redundant data packets as repetition of packets due to multiple paths. It is totally dependent upon the destination node to choose one fault free packet and discard the others. In a multipath based routing scheme, more energy will be consumed because of redundancy of packets as the data packets received through different paths. The authors in [2] proposed DBR in which the information about the full dimension and location of a node is not required. DBR is based on the depth information, which can be easily found by a depth sensor integrated within every sensor node to forward a packet from the source node to the sink. DBR uses a greedy mechanism to find one hop forwarding path. However, the selected forwarding node may not be able to forward the packet due to occurrence of void hole, which reduces the PDR. In [33], the authors propose an Energy-Efficient Depth-Based Routing scheme (EEDBR) to enhance the life of the network and stability period of the network by considering the depth and the energy remaining in the nodes. EEDBR achieved the significant improvement E2 ED along with the better utilization of the energy bank, especially for nodes that are shallower. EEDBR protocol implements the phenomenal through formulating the holding time and that depends upon current energy storage level. There is a lack of energy fairness because energy is unevenly distributed among sensors. Further, a detailed qualitative comparison of different characteristics of underwater sensor networks is provided in Table 1.  
First and foremost, the problem of void holes (absence of forwarder in the transmission range of the source node) occurrence is exploited by the authors in our baseline paper i.e., WDFAD-DBR [3]. The design of the algorithm ensures the significant reduction of the packet-drop due to successful void holes mitigation, especially when the network is sparse. WDFAD-DBR considers the depth of the forwarders at the immediate and next hop. The weighting value is assigned to potential forwarders at each hop in such a way that maximum advanced distance can be achieved. The priority of the two-hop path selection effectively overcomes the frequent upward hemispherical void regions.