# Self-Organizing and Scalable Routing Protocol (SOSRP) for Underwater Acoustic Sensor Networks
## 5 Simulation Results
### Faulty Tolerance  
Because of random deployment of nodes, if a node has \(N\) number of neighbors. It will have at least \(N\) number of possible paths leading to the sink. Among the available paths, the one with smallest hop count and shortest distance to sink is considered an optimal path while others are alternate. Alternate path is the best possible route available after optimal path, selected based on the path selection criterion when fault is detected. To further evaluate the fidelity of SOSRP, a fault probability of 0.2 is realized, e.g., in case of 5000 optimal paths found, only 1000 pragmatic paths will be detected.  
In multi-hop communication, it is desirable to keep the hop count minimum in the path to limit the end-to-end delay and the energy consumption. The results obtained compare the total number of paths generated by SOSRP with number of hops in each path for optimal and pragmatic behavior of protocol. The results are shown in Figures 14 and 15. In Figure 14 the number of hops in the route is shown for a network size of 50 nodes, and 100 nodes in the case of Figure 15.  
Figure 14: Number of hops for 50 nodes and different transmission ranges: (**a**) 70 m, (**b**) 100 m.  
Figure 13: Energy consumption for the longest path (\(2000\times 2000\times 500\) m).  
It is noticeable from the results that SOSRP successfully responds to fault detected in the optimal path by selecting a new route to the sink. However, this increases the number of paths with higher hop count, thus affecting the end-to-end delay and energy consumption of the network.  
This effect can be observed in Figure 13(a), where 50 nodes are deployed with transmission range of 70 meters. The figure shows the influence of transmission range in pragmatic behavior of network, increasing the hops up to 12 in the alternate path. Similar results can be witnessed in Figure 14(a).  
However, increasing the transmission range to 100 meters removes this problem, as shown in Figures 13(b) and 14(b), where the highest number of hops in both optimal and alternate path is four and five respectively, and where pragmatic behavior causes more routes with higher hop count.  
The results shown in Figure 16 depict the end-to-end delay of optimal and alternate path, for different network sizes and keeping transmission range 70 and 100 meters. The results show similar behavior of end-to-end delay in alternate path with respect to the optimal path. This effect is evident in Figure 15(a). However, it can be also observed that alternate path offers more delay in data transmission as compared to optimal path with a maximum of approximately 1.7 s. Furthermore, increasing the transmission range can mitigate the end-to-end delay because of a reduced number of hops in the newly formed routes. This effect can be observed in Figure 15(b) for a transmission range of 100 meters, where the obtained delay for alternate and optimal path is approximately 1.3 and 0.7 s respectively, which is much less than the delay observed in Figure 15(a).  
Figure 16: End-to-end delay for optimal and alternate paths for different transmission ranges: (**a**) 70 m, (**b**) 100 m.  
Figure 15: Number of hops for 100 nodes and different transmission ranges: (**a**) 70 m, (**b**) 100 m.  
In order to examine the performance of SOSRP, the percentage of increase for end-to-end delay and energy consumption is calculated. It is performed by measuring the two parameters for optimal and alternate path. The results obtained are shown in Figure 17.  
Figure 17 shows the percentage of increase in maximum end-to-end delay and total energy consumption, obtained in pragmatic behavior of protocol. The influence of increasing the transmission range and network size is obvious in both cases (a) and (b), reducing the percentage of end-to-end delay and energy consumption. This low increment indicates a proper operation of SOSRP.