## 6 Simulation Experiment
### Simulation Experiment on Networking and Systematic Performance Calculation of UWSNs  
Firstly, the different parameters that influence the systematic performance items are tested. The complete coverage of the network is crucial in every underwater monitoring mission. The nodes are deployed on CBCL and NBCL, and the CDNM is used to generate the network. It can work out the minimum number of sensor nodes, number of sensor nodes out of the Voronoi cells and the number of sensor nodes in the Voronoi cells where the detection radii of the nodes are 0.67 km, 1 km, 2 km, as shown in Figure 8.  
Form Figure 8, for the coverage of network, it can be seen that the detection radii of the nodes are 0.67 km, 1 km, 2 km, so the number of nodes in our approach, compared with NBCL for the same monitored space, is separately decreased by 16.3%, 25.3% and 30.5%. At the same time, it is observedthat the number of the required nodes decreases when the detection radius of the node increases. This is because that the number of required nodes is inversely proportional to the cube of the detection radius due to the 3D deployment of nodes underwater. In addition, both the detection and communication radius of the nodes determine the energy state of nodes. In light of the different detection radii, when the communication radii of the detection radii are changed at different times, different average energy consumption of nodes can be obtained. Moreover, the network connectivity is associated with the number, detection radii and communication radii of sensors, as shown in Figure 9.  
From Figure 9, for the detection and communication radii of sensor nodes, the average energy consumption and the connectivity in our approach is better than that in the NBCL. For the connectivity,  
Figure 9: The energy consumption and connectivity: (**a**) \(d_{b}=0.67\); (**b**) \(d_{b}=1\); (**c**) \(d_{b}=2\). it is observed that the bigger the communication radius of a sensor node is, the greater the corresponding connectivity will become. In CBCL, from the right part of Figure 9a, when the detection radius is \(d_{b}\) = 0.67, the communication radii are \(r_{b}\) = 1.15, \(r_{b}\) = 1.33, \(r_{b}\) = 1.89 and \(r_{b}\) = 2.13, respectively, and the corresponding average connectivities of the network are 6, 11, 19 and 38. On the contrary, the bigger the detection radius of a sensor node is, the less the corresponding connectivity will become, and from the right part of Figure 9b,c, the detection radii \(d_{b}\) = 1 and \(d_{b}\) = 2, that the corresponding average connectivities are 31 and 3 when the communication radius was \(r_{b}\) = 3.46. Durability is determined by the first \(m\) nodes whose energy is exhausted. The lifetime of a sensor is impacted by the total energy and energy consumption rate. For the average energy consumption of sensors, it is observed that the bigger the communication radius of a sensor node is, the greater the corresponding energy consumption will become. In CBCL, from the left part of Figure 9a, when \(d_{b}\) = 0.67, \(r_{b}\) = 1.15, \(r_{b}\) = 1.33, \(r_{b}\) = 1.89 and \(r_{b}\) = 2.13, that the corresponding average energy consumption of the sensor node is 0.183, 0.405, 0.722 and 1.225. The same relationship occurs between the detected radius and node energy consumption. Without considering wake-up of nodes joining the network, we assume that the lifetime of an UWSN is the interval from when the network starts working to when 20% of the active sensor nodes shut down due to energy exhaustion. For Figure 9c, the UWSN lifetime is shown in Table 3.  
From Table 3 we can see that the more active sensor nodes in the network, the longer lifetime the UWSN enjoys. According to Equations (6) to (10), for the detection radius and communication radius in Figure 9b, a relationship between the value of the systematic performance items and communication radius and detection radius can be observed, as shown in Figure 10.  
As shown in Figure 10a, the network coverage increases as the detection radius of the node increases.