## 6 Simulation Evaluation of the Dynamic VWSN
### Evaluation Environments  
We evaluate the adaptivity of a VWSN topology constructed from the network, which is composed of two sensor networks and one wired link. Each of the sensor networks consists of 150 sensor nodes deployed in a domain of size \(1000\times 1000\) m\({}^{2}\). For one of the sensor networks, we deploy 150 sensor nodes at randomly-selected positions in the rectangular area with corners, denoted in meters along the coordinate axes of the domain, at \((0,0)\) and \((400,1000)\); we deploy the other 150 sensor nodes at randomly-selected positions in the rectangular area given by \((600,0)\) and \((1000,1000)\). Additionally, one wired link connects the two sensor networks, and its endpoint nodes are static once they are chosen. We assume the wireless communication range is 100 m.  
In this simulation, we construct a three-tiered VWSN topology. We use OMNeT++ [30] to perform the simulation experiments, and the parameter settings are shown in Table 1. When the physical topology described above is used, the value of \(E^{M_{x}^{1}}+E^{M_{y}^{1}}\) is comparatively high, which means that many virtual links are added between first-tier modules; this results in low modularity. To correct for this, we set \(C_{\text{inter}}^{1}\) to a value lower than \(C_{\text{inter}}^{N}\) in the higher tier. The flow of simulation is described below. 1. The VWSN provider receives, from a user, a request to construct a new VWSN topology and data on traffic patterns. 2. The VWSN provider constructs a VWSN topology and calculates the routing tables, connection tables and long-link tables for each node. 3. The VWSN provider informs the gateway about the tables of each node and the traffic pattern. 4. The gateway sends the information to each node. 5. Each node sends a data packet periodically according to the received traffic pattern. The traffic pattern consists of some traffic flow information: a source node, a destination node and a flow rate. In this paper, flow rates are randomly selected from among \(\frac{1}{10}\), \(\frac{1}{20}\), \(\frac{1}{30}\), \(\frac{1}{40}\), \(\frac{1}{50}\), \(\frac{1}{60}\), \(\frac{1}{70}\), \(\frac{1}{80}\), \(\frac{1}{90}\) and \(\frac{1}{100}\). The number of flows is 0.2% of the number of all of the possible combinations of two nodes included in the VWSN topology. The pairs of source node and destination node are also selected randomly. The TTL of each data packet is set to 50. From the simulations, we identified the reasons for failure to recover the data delivery ratio. These are listed in Table 2. Physical topology and the result of modular division have a strong influence on adaptivity within our proposed method and can lead to different reasons for failure to recover the data delivery ratio. Therefore, we use five physical topologies and perform 100 trials with each topology. In this paper, we show the results of only two physical topologies; the results for the omitted topologies show the same characteristics. We call these physical topologies \(T1\) and \(T2\). Each physical topology with the result of modular division by the Newman algorithm is shown in Figure 4. Each color shows the group of each module. \begin{table}
\begin{tabular}{c c c} \hline
**Method** & **Parameter** & **Value** \\ \hline \multirow{3}{*}{BICM} & \(C_{\text{intra}}^{N}(N\
eq 1)\) & 0.1 \\  & \(C_{\text{inter}}^{1}(N\
eq 1)\) & 0.1 \\  & \(C_{\text{inter}}^{1}\) & 0.01 \\ \hline Bio-inspired & \(\eta\) & 4 \\  & \(\Phi\) & 6 \\ \hline \end{tabular}
\end{table} 
Table 1: Parameter settings. BICM, brain-inspired configuring method. \begin{table}
\begin{tabular}{p{113.8 pt} p{284.5 pt}} \hline \hline
**Abbreviation** & **Description of Reasons for the Recovery Failure** \\ \hline \multirow{3}{*}{_phyFrag_} & The physical topology fragments into some subnetworks. This leads to unreachable nodes from a source node because no physical path exists between them. \\ \hline \multirow{3}{*}{_LOFrag_} & A zeroth-tier virtual topology in the first-tier module fragments into some zeroth-tier virtual subnetworks.