# A Mobility-Assisted Localization Algorithm for Three-Dimensional Large-Scale UWSNs
## 5 Simulation  
In this section, we present the simulation results to evaluate the performance of the localization scheme in this paper. The simulation tool is MATLAB (R2016a). The simulation monitoring area is \(600\) m \(\times\)\(600\) m \(\times\)\(500\) m. To sense the data of the whole simulation environment, we used 800 sensor nodes (the transmission range of sensor nodes is tens of meters) in UWSNs. The random distribution of sensor nodes in 3D underwater space is shown in Figure 9. Moreover, anchor nodes are deployed according to the communication range of anchor nodes and the length of the monitoring area. Therefore, the plane position coordinates of anchor nodes were obtained as known conditions. In Figure 10, we show the distribution diagram of anchor nodes on the horizontal plane of the projection (\(R=300\) m, \(k=0.5\), \(l=600\) m). Other related parameter settings of the localization scheme are given in Table 4. \begin{table}
\begin{tabular}{l l} \hline \hline
**Sign** & \multicolumn{1}{c}{**Meaning**} \\ \hline \(a_{i}\) & The number of the sensor node; \\ \(z_{a_{i}}\) & The depth of the corresponding sensor node; it can be regarded as a known condition; \\ \(Loc_{a_{i}}\) & If the node \(a_{i}\) is localized, the \(Loc_{a_{i}}=1\), or else \(Loc_{a_{i}}=0\); \\ \(M_{b_{j}}\) & The number of the localization message received from the \(b_{j}\) mobile anchor node; \\ \(D_{a_{i}}\) & Number of anchor nodes to which the distance measurement from the sensor node \(a_{i}\) is available; \\ \(d_{a_{i}b_{j}}\) & The projection distance between the ordinary sensor node \(a_{i}\) and anchor node \(b_{j}\); \\ \(\eta_{a_{i}}\) & The confidence value of the node \(a_{i}\); \\ \(C_{a_{i}}\) & The \(a_{i}\) sensor node located in Phase I and \(\eta_{a_{i}}\geq\lambda\); it can be used as a new reference node \(C_{a_{i}}\); \\ \(\lambda\) & The confidence threshold, 0.9; \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Definition of related symbols. Sensor nodes drift as a whole due to the influence of water flow and other factors, and the relative positions between the nodes remain unchanged during the drift. The drift model is shown in Equation (1). As shown in Figure 11, the position of sensor nodes in the projection plane changes due to drift. In the simulation process, we divided the localization scheme of MALS-TSF in this paper into two types, namely, anchor nodes are deployed according to Figure 8, and anchor nodes are evenly distributed. The remaining conditions remain unchanged. Then, compare them with the TP-TSFLA proposed in Reference [21], as shown in Figure 12. The image shows that, under different transmission ranges, the proposed localization scheme, MALS-TSF, has a higher localization ratio. In the initial stage of transmission range change, the effect is obvious. It is worth noting that, as the transmission range increases, the effect of the proposed deployment is no longer obvious compared to other deployment \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Monitoring area & 600 m x 600 m x 500 m \\ Number of sensor nodes & 800 \\ Anchor node interval & 30 s\(\sim\)100 s \\ Transmission range of anchor & 150 m\(\sim\)250 m \\ Mobile anchor nodes & Depends on monitoring area and transmission range of mobile anchor nodes \\ \(v_{anchor}\) & 1 m/s \\ \(v_{acoustic}\) & 1500 m/s \\ \(v_{max}\) & 25 cm/s \\ \(l_{cy}\) & 5 m \\ \(\lambda\) & 0.9 \\ Simulation times & 100 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Related parameter setting. Figure 10: Deployment distribution of anchor nodes on the horizontal plane of the projection. Figure 9: Random distribution of sensor nodes in 3D UWSNs. plans. The number of anchor nodes used in the localization scheme in this paper is less than the number of anchor nodes in TP-TSFLA, which saves some costs. According to the above figure, although the transmission range of the anchor node is large, the localization rate of the sensor node is high.