# Adaptive Power-Controlled Depth-Based Routing Protocol for Underwater Wireless Sensor Networks
## 2 Related Works
presented a distance vector opportunistic routing (DVOR) protocol that utilizes distance vector mechanisms to route data packets to the destination via the shortest path. [PERSON] et al., in [13], drew inspiration from the distance vector mechanism of DVOR and introduced a concurrent working mechanism to reduce forwarding delay. In [14], [PERSON] et al. proposed an energy-aware and hole-avoidance routing protocol for underwater sensor networks. This protocol avoids network holes and provides efficient routing by considering the residual energy of nodes and the communication capability between parent and sibling nodes when selecting the next hop. Compared to multi-route routing protocols, single-route routing schemes allow only one node to receive the data packet at each hop, which can significantly reduce data packet collisions and energy consumption. Clearly, the latter is suitable for applications that do not require frequent data transmission but may not be suitable for applications that involve a large amount of data [3; 15]. In terms of power control, due to the fact that the distance between each pair of connected nodes in an underwater acoustic network is not always the maximum transmission distance for acoustic signals, there is a certain redundancy in the transmission power of the nodes. Therefore, appropriate power control for sensor nodes can improve the energy efficiency of the network. In fact, power control has been emphasized as an effective method for topology control in underwater sensor networks, aiming to improve data transmission and reduce energy costs [16]. The authors in [17] proposed five principles for saving sensor energy and prolonging the network lifetime, which include using finite levels of power, applying the multi-hop transmission, narrowing the scope of transmission, applying the inactivation mode, and balancing energy consumption. In [18], [PERSON] et al. compared the energy consumption between single-hop direct transmission and multi-hop transmission via relay nodes. When transmitting through relay nodes, the source node adjusts the transmission power to cover the relay node's location. Through theoretical analysis, the authors demonstrated that multi-hop transmission is more energy-efficient when the relay node is located on the line between the source and destination nodes or is not far from the line. [PERSON] et al. proposed an adaptive power control and depth-aware routing scheme [19]. In their study, each node set its transmission power to the target node based on the received signal strength indicator (RSSI). This technique allows for better adaptation to the communication environment and reduces environmental interference. Therefore, our routing protocol also incorporates this technology in terms of power control. Segmenting long-distance transmissions into shorter-distance transmissions through power control mechanisms can effectively reduce energy consumption. However, this introduces a certain path delay and node data processing delay. Therefore, when introducing such a mechanism, it is necessary to balance energy consumption and end-to-end delay according to the system's performance requirements. In addition to the aforementioned protocols, researchers have proposed numerous other routing protocols for underwater sensor networks. A more comprehensive description of these protocols can be found in [20; 21].