## 5 Networking Parameter Adjustment Method for Optimized Systematic Performance
### Systematic Performance Calculation of UWSN's  
The control node collects the corresponding state information periodically in the network. Quantified values of the coverage, connectivity, durability and rapid-reactivity performance can be computed through Equations (2) to (12). These quantified values are compared with the current mission requirements. If each performance item of this network satisfies the mission demands, the control node is not changed and adjusts the network topology and works continuously. If one or more performance item cannot meet the demands, the network should be optimized and adjusted. In order to provide an intuitive evaluation for the quantified values of each systematic performance item, this paper assumes an ideal UWSN as shown in Figure 7. Suppose there are nine sensor nodes distributed within 2 \(\times\) 2 \(\times\) 2 km\({}^{3}\), and \(N_{1}\)-\(N_{5}\) can only communicate with each other underwater, and \(N_{6}\)-\(N_{9}\) can do it both underwater and overwater. Other performance features of the sensor nodes are \(r_{b}\) = 2 km, \(b_{b}\) = 5 kbps, \(b^{\prime}b_{b}\) = 5 Mbps, \(d_{b}\) = 1 km, \(h_{b}\) = 100%, \(k_{b}\) = 4, \(c_{b}\) = 1, and \(c_{b}\) = 10\({}^{6}\) J, for \(e_{b}\), the lifetime of sensor nodes is 10\({}^{7}\) s (about four months) in normal working state. In addition to the sensor nodes, the network contains a master node and a UUV, and their performance features are \(v_{s}\) = 5 m/s, \(v_{u}\) = 2 m/s, \(b_{u}\) = 20 kbps, \(d_{u}\) = 1 km, \(h_{u}\) = 100% and the lifetime of the UUV is 7 \(\times\) 10\({}^{4}\) s (about 20 h). Assume that the velocity of acoustic channel is 1500 m/s, and the bit error rate of transmission is \(\eta\) = 0.1. Suppose the value of each systematic performance item in the  
Figure 6: Process of UWSN optimization. network is 1. According to the abovementioned assumption, the values of the constraint parameters can be determined. When we substitute the above parameter values into Equation (4), then Equation (13) will be obtained:  
\[9\times 10^{9}\cdot\pi\cdot\alpha+10^{9}\cdot\beta=1 \tag{13}\]  
Since the sensor nodes play a dominant role in the coverage, their significance is supposed to be 0.9 and that of the UUV is supposed to be 0.1. Then \(\alpha\) and \(\beta\) can be described by Equation (14):  
\[\alpha=\frac{1}{10^{9}\cdot\pi^{\prime}},\ \beta=10^{-9} \tag{14}\]  
Then Equation (4) can be rewritten as Equation (15). \[\Theta=\frac{n_{b}\cdot d_{b}^{3}}{10^{9}\cdot c_{b}}\cdot\left[1-(1-h_{b})^{c_ {b}}\right]+10^{-9}\cdot n_{u}\cdot d_{u}^{3}\cdot h_{u} \tag{15}\]  
In a similar way, we set \(B\) = 40 kbps, then \(I\) = 0.25. In order to decrease the radio communication, the data transmitted over water that is rare but important is just for some urgent control message. Assume the proportion of data transmitted under water is \(\omega\) = 0.9999. Putting these values in Equation (8), we have \(6.5\cdot\alpha+10\cdot\beta=1\). The two terms in this equation denote the sensor nodes' and UUV's contribution to connectivity. Setting \(\alpha\) = 0.14, \(\beta\) = 0.009, their contribution ratios are 0.91 and 0.09. Generally, Equation (8) can be rewritten as Equation (16):  
\[\Phi=1.4\times 10^{-5}\cdot k_{b}\cdot\left[8999.1\cdot l\cdot b_{b}+b_{b}^{ \prime}\right]+0.009\cdot l\cdot v_{u}\cdot n_{u}\cdot b_{u} \tag{16}\]  
For durability, suppose the energy consumption speed of each node is the same. The coefficients \(\alpha\) and \(\beta\) are constant and we have \(8\times 10^{9}\cdot\alpha+10^{9}\cdot\beta=0.1\). Also suppose the ratio of communication energy consumption to the total energy consumption is 80%, take \(\alpha\) = \(10^{-11}\), \(\beta\) = \(2\times 10^{-11}\), then \(p_{b}\) can be described by Equation (17):  
\[p_{b}=10^{-11}\cdot r_{b}^{3}+2\times 10^{-11}\cdot d_{b}^{3} \tag{17}\]  
Putting these parameters in Equation (9), we have \(\alpha\cdot\left(10^{7}+7\times 10^{4}\cdot\beta\right)=1\), where \(\beta\) is the contribution coefficient of the UUV to the durability of the network.