## 2 Related Word
### Localization Free Routing Protocols  
In DBR [28], the sensor node's depth parameters are considered to establish a routing path from the source node to the sink node. The packets are routed through randomly deployed sensor nodes by using a greedy routing approach. The forwarder node is chosen based on the depth information of the sensor node. In HydroCast [29], a greedy approach and a hydraulic pressure indicator for reliable communication is used. The next forwarder node is chosen based on link quality. Whenever a data packet undergoes a void region, it shifts to the shallower node. Thus, the HydroCast protocol fixed the void issue and increased the packet delivery ratio. In LLSR [30], the succeeding node is selected based on the neighboring node with the least total hop counts to the sink node. If multiple neighboring nodes have similar hop count numbers, the best-quality link is preferred as the successor node. The void node beacon has unlimited hop count as an indicator to avoid being selected as a successor node. This routing approach can reduce delays in route selection. IVAR [31] is a beacon-based localization-free forwarding scheme that forwards the data greedily. This protocol is structured into two stages. Initially, the sink node broadcasts the beacon messages holding the hop count and depth information. Afterwards randomly positioned nodes reset their hop count value to the lowest and relay the beacon across other nodes. In the second stage, routing, only senders with fewer hops forward messages. In MLCEE [32], an energy-balanced approach is used for effective energy utilization. The nodes are distributed across various horizontal layers using a random distribution. The cluster heads are chosen based on their remaining battery level and Bayesian probability. Subsequently, data is transferred to the sink nodes via these cluster heads by using a multi-hop approach. This routing technique effectively ensures fair energy distribution inside the network. In VH-ANCRP [33], the network is partitioned into grids, and a cluster head is affixed at the center of each grid for gathering data from the node of the same grid. Nodes are free to relocate, and in case they leave the network boundaries, it broadcasts a void declaration message. If the void node has neighboring nodes linked to the cluster head, it transmits a response to the void node containing specific instructions on how to establish communication with it. Then, the void node sends its neighbor a route request. In VAPR [34], the sonobuoys generate beacon signals to the randomly scattered sensor nodes. The beacon signals provide information, i.e., depth measure, hop number, and serial number, to calculate the next hop direction and create a trail to the nearest sonobuoy. When each node receives beacons from previous nodes, it modifies its variables, which include the least hop count, sequence number, data transmission path, and next-hop routing path. To avoid void areas, data are sent over a path with a greater hop count, resulting in extensive end-to-end delay and increased energy use. In CARP [35], the data forwarding is focused on the hop count value and communication link quality amongst the transmitter and the nearby nodes. The next forwarder node is selected based on its recent track record of effective data transmissions. It uses hop count to avoid loops to effectively route across void regions. In EECOR [36], the packet is forwarded to the destination node under unfavorable channel conditions using the opportunistic routing method. The source node collects depth information and energy information from its immediate nodes. The forwarding set is formed first, followed by the best relay set, which is selected, and packets are transmitted to these nodes operating fuzzy logic-based relay selection. By coordinating among the certain best relay nodes, the high-priority node sends packets, while other nodes stop packet transmission, making this protocol energy efficient.