# Energy-Efficient Wireless Hopping Sensor Relocation Based on Prediction of Terrain Conditions
## 4 Simulation Results and Analysis  
Unlike hopping sensor relocation studies so far, one of the most significant contributions this paper is the use of OMNeT++ [26], which can realistically reflect wireless communications situations in real-world environments. Table 1 describes the environment parameters used in the simulation for performance evaluation. As shown in Figure 7, 285 hopping sensors are randomly scattered to the whole area of 250 m \(\times\) 150 m to collect data. As mentioned in the previous Sections, since the aim of our research is not clustering techniques, we assume that the 15 cluster zones and headers are properly pre-set up in \begin{table}
\begin{tabular}{c c} \hline \hline network area & 250 m \(\times\) 150 m \\ \hline number of all member hopping sensor nodes & 285 \\ \hline number of cluster headers & 15 \\ \hline minimum number of members for each cluster to properly gather data & \\ (i.e., a sensing hole occurs if number of current members lower than the value) & 10 \\ \hline the probability that an obstacle exists & 0\%, 1\%, 2\%, 3\% \\ \hline maximum communication radius for each sensor node & 20 m \\ \hline maximum communication radius when highly jumping & 29 m \\ \hline maximum distance that a sensor node moves forward with one jump & 2 m \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Simulation environments. well-known ways. If there are fewer than 10 member sensor nodes in each cluster zone, excluding the cluster headers, the cluster header determines that its zone is a sensing hole. As shown in Figure 7, obstacles are randomly generated with values of 1%, 2%, and 3% over the entire area. Although the size of the obstacle is very large in Figure 7d, the obstacle is actually 1 m \(\times\) 1 m. Only for visual effects, we make the obstacle appear to be large. A communication model between sensors is used, IEEE 802.11, and the regular transmission radius is assumed to be 20 m. More specifically, _antennaType_, _transmitterType_, and _receiverType_ parameters are set as IdealRadioMedium module environment in OMNeT++ [27]. While jumping as high as possible, each hopping sensor has a maximum radius of 29 m of transmission. It also can move forward 2 m with one jump. In order to reflect the effect of the realistic environment (wind, etc. ), the movement model of each hopping sensor node is assumed with two-dimensional standard normal distribution, where standard deviations are 0.3 and the correlation is zero, as shown in Figure 1. The movement of the hopping sensor is indicated by a solid line as shown in Figure 7. For the performance analysis of the proposed relocation protocol, the sensing hole occurred in the middle of area, as shown in Figure 7.  
We assume the scenario that the sensor nodes continuously gather data in the middle cluster zone, and they consume energy rapidly. Each sensor in the middle cluster generates a data collection event with an exponential distribution (average of 5 min). For convenience, the initial energy value for sensing is set to 100, and the energy consumption is 1 for each event occurred. Any energy model can be adopted, but a specific energy model is not considered here for simplicity. The main flow of the paper is about the creation and restoration of the sensing hole. An occurrence of a sensing hole (less than 10 member sensor nodes) is determined by a cluster header after HELLO message for every 15-minute interval. In particular, to perform the simulation on relocation of member sensor nodes to recover the sensing hole occurred, sensor nodes in other zones are assumed to perform no data collection. It also indicates in yellow that a sensor has become faulted due to energy depletion after continuous data collection in Figure 7.  
In the majority of the hopping sensor relocation protocols so far, each sensor node knows all network information; like a central-based relocation protocol, it only considers the shortest path  
Figure 7: Simulation snapshots for each environment. between cluster zones.