## 4 Proposed 3D-UWSN Design
### Network Model  
The proposed DEDG 3D-UWSN is constructed to monitor the underwater marine environment. A 3D-UWSN absorbs its surroundings by collecting data and transmitting the information. This 3D-UWSN is constructed as \(x_{i}\times y_{i}\times z_{i}\), i.e., the coordinates \((x_{i},y_{i},z_{i})\) of the network area in 3D. This 3D structure is divided into two levels, \(L_{1}\) and \(L_{2}\), based on the depths of the ocean. \(L_{1}\) and \(L_{2}\) are assumed to cover shallow ocean and deep ocean, respectively. In this network, \(N\) and \(M\) numbers of sensor nodes are employed in \(L_{1}\) and \(L_{2}\), respectively. \(L_{1}\) is composed of \(l\) number of sensors as \(L_{1}=\{s_{1},s_{2},s_{3},\ldots,s_{l}\}\), and \(L_{2}\) is composed of \(m\) number of sensors as \(L_{2}=\{s_{1},s_{2},s_{3},\ldots,s_{m}\}\). The deployed sensors are capable of performing underwater environment sensing tasks and transmitting the collected information to their neighboring sensors or the sink node through the deployed AUVs. The sensors are equipped with acoustic transceivers, namely, a vertical and horizontal transceiver to allow communication between them and the AUV. The sensing model of the sensor nodes is a spherical ball with radius \(R_{s}\). The sensing is performed within this radius. We assume that these sensors are sea-bottom anchored and are considered quasi-stationary due to the ocean current and energy constrained; each sensor node has its unique identifier, and the sensors are homogeneous in terms of initial energy and communication range. The location of the sensors is known. The AUV moves above level 1 and level 2 and collects data. We assume that the AUVs start from their source places, dive to the CHs (each elected cluster head that gathers the data from its cluster members) and collect data from all the CHs successively, then arrive at the sink node. The AUVs act as temporary sinks. The AUVs are equipped with both an acoustic modem and a radio transmitter to communicate with the sensor nodes and the sink node, respectively. The AUVs' initial velocity is known, and the velocity is not constant during the AUVs' movement path; the energy of the AUVs is unlimited. A single sink node is equipped with both acoustic transceivers to handle multiple, parallel communications with the sensor nodes and also a long-range RF and satellite transmitters to communicate with the AUVs in order to receive the collected data and also to transmit data to the on-shore station. The data are gathering by the AUVs from the CHs; here, the two AUVs are appointed as \(AV_{1}\) and \(AV_{2}\), respectively. \(AV_{1}\) collects data from \(L_{1}\) CHs and \(AV_{2}\) from \(L_{2}\) CHs. A super node acts as gateway \(GW\) in between the \(L_{1}\) and \(L_{2}\), which is responsible for selecting the inter-cluster route when the waiting time in the CHs is exceeded. The designed DEDG 3D-UWSN architecture is depicted in Figure 1.  
This DEDG 3D-UWSN supports the processes of clustering, scheduling, movement prediction of AUVs, inter-cluster routing and event message delivery. The energy consumption in the underwater sensor depends on the performance of the following processes: sensing, transmitting, receiving and idle. The sensor nodes are capable of sending and receiving 1-bit data within the network. In the DEDG 3D-UWSN, the sensor nodes are clustered, and an optimal CH is selected. The CH is responsible for gathering sensed data from the active members in the cluster. The moving AUV collects data from four CHs at a  
Figure 1: DEDG 3D-UWSN architecture. time. This ensures the minimization of data gathering delay from the CHs at each level. The CHs are selected with the MO-SHO algorithm, which takes into account the node parameters. Every CH waits for a certain time period until the waiting time for the arrival of the AUV. The AUV moves above level 1 and level 2 and collects data. If the waiting time is exceeded, then the gateway helps in selecting an inter-cluster routing path towards the sink.