# Energy-Efficient Clustering Multi-Hop Routing Protocol in a UWSN
###### Abstract  
Underwater wireless sensor networks are currently seeing broad research in various applications for human benefits. Large numbers of sensor nodes are being deployed in rivers and oceans to monitor the underwater environment. In the paper, we propose an energy-efficient clustering multi-hop routing protocol (EECMR) which can balance the energy consumption of these nodes and increase their network lifetime. The network area is divided into layers with regard to the depth level. The data sensed by the nodes are transmitted to a sink via a multi-hop routing path. The cluster head is selected according to the depth of the node and its residual energy. To transmit data from the node to the sink, the cluster head aggregates the data packet of all cluster members and then forwards them to the upper layer of the sink node. The simulation results show that EECMR is effective in terms of network lifetime and the nodes' energy consumption. underwater wireless sensor network; energy-efficient; clustering; depth-based routing 202121627.12. The underwater sensor nodes transmit their data to the sink at the surface. The sink then forwards the aggregated data to the nearest base station on the mainland. The sink node is equipped with two types of transceivers: (1) a radio transceiver, which can communicate with the base station by radio frequency; and (2) an acoustic transceiver for communication with the sensor nodes. The underwater node is embedded with an acoustic transceiver for transmission between nodes. The transmission medium of the underwater environment is different to that of a terrestrial wireless sensor network (TWSN) with respect to channel modeling, path loss, and topology [2; 3]. The underwater wireless sensor nodes are moved by currents with velocities of around 1-3 m/s. The acoustic channel is modeled differently from the radio propagation channel. In both TWSNs and UWSNs, data packets are sent from a sensor node to the base station via either a one-hop path or a multi-hop path. It is necessary to route the data packet from one node to another node without loss. Since each sensor node is equipped with a battery, which may be difficult to replace or charge, the re-transmission of data packets may consume high energy, which results in a short network lifetime or many dead nodes. In TWSNs, many clustering protocols have been developed to minimize the energy consumption of sensors while successfully transmitting data packets to the destination. In TWSNs, all nodes are homogeneous and energy-constrained, and a low-energy adaptive clustering hierarchy (LEACH) successfully reduces the energy consumption of nodes while maintaining their network lifetime [6]. In [7], a clustering protocol for UWSNs was reviewed, demonstrating that the clustering protocol is suitable for underwater transmission. As with clustering in TWSNs, the clustering protocol is designed to reduce the control information, resulting in a reduction in the overall energy consumption, extended node lifetime, and greater network reliability. However, as a result of the effect of the current on the underwater sensor node, the cluster protocol should maintain connectivity to the network to ensure full coverage. In [8], a depth-based routing protocol (DBR) was developed to route a packet from any sensor to the sink node according to the node's depth level. The DBR allows nodes to forward data to the node at a higher layer near the sink. Figure 1: Underwater wireless sensor network (UWSN) model. In the present paper, we develop a clustering protocol with regard to the location of nodes and residual energy of nodes. We propose an energy-efficient clustering multi-hop routing protocol (EECMR) for UWSNs so that each node can maintain its transmission link to the sink node at the surface and its neighbor sensor nodes. Our contribution through this work is as follows:  
* The underwater sensor nodes update the routing path and cluster to connect to the sink without disruption. The sink collects data, which are then transmitted to an onshore gateway.