# DOW-PR DOlphin and Whale Pods Routing Protocol for Underwater Wireless Sensor Networks (UWSNs)
## 6 Performance Comparison and Analysis
### Simulation Results in the Whale Pods Routing Scenario  
The simulations have been repeated for the whale pod routing version of the proposed DOW-PR protocol. It has been shown in the results that there is a great deal of improvement compared to its predecessor dolphin pod routing in all the prescribed performance metrics. Referring to Figure 14b, it can be observed that the energy tax of the whale pod DOW-PR protocol is reduced throughout the density of the network (i.e., from 200 to 500 nodes). The reasons behind this is that the packet(s) generated/forwarded from the nodes in the vicinity of the embedded sink does not have to travel a long distance. Instead, it is collected locally. This means that the few forwarders involved have a lesser amount of energy consumed. It can also be easily judged through Figure 14d in which there is huge reduction in average APD and therefore reduces the number of hops propagated. However, the percentage improvement in energy tax reduces as nodes number increases. This is due to the fact that the collision probability increases at the receiver and number of retransmissions will consume quite a lot more energy. Moreover, it is further analyzed that there are more number of copies generated or forwarded as the messages pass through more hops. Next, the deployment of an additional sink in the whale pod scenario causes a significant improvement in the PDR (refer to Figure 14a). It can be seen that our updated scheme i.e., whale pod routing protocol beats the dolphin pod routing regardless of any number of nodes in the network. Behind this improvement, there are multiple reasons that include the high probability of finding the sink in the range of nodes, less number of hops count, less propagation distance and so on. The closest proximity nodes to the embedded sink either directly communicate with the sink or through a fewer number of hops and therefore the probability of packets drop reduces. \begin{table}
\begin{tabular}{c c c c c} \hline
**Node Number** & **200** & **300** & **400** & **500** \\ \hline Improvement with Tr = 1000 m & 38.46\% & 30.12\% & 28.32\% & 28.49\% \\ \hline Tr = 2000 m & 35.68\% & 31.50\% & 29.90\% & 29.51\% \\ \hline Average Improvement & 37.07\% & 30.81\% & 29.11\% & 29.00\% \\ \hline \end{tabular}
\end{table} 
Table 6: Overall Energy saved in dolphin pods routing compared to WDFAD-DBR. \begin{table}
\begin{tabular}{c c c c c} \hline
**Node Number** & **200** & **300** & **400** & **500** \\ \hline Improvement with Tr = 1000 m & 24.76\% & 24.11\% & 22.50\% & 20.12\% \\ \hline Tr = 2000 m & 31.17\% & 26.89\% & 24.62\% & 23.17\% \\ \hline Average Improvement & 27.96\% & 25.5\% & 23.56\% & 21.64\% \\ \hline \end{tabular}
\end{table} 
Table 7: Overall End-to-End delay improvement of dolphin pods with WDFAD-DBR. \begin{table}
\begin{tabular}{c c c c c} \hline
**Node Number** & **200** & **300** & **400** & **500** \\ \hline Improvement with Tr = 1000 m & 14.61\% & 7.12\% & 4.23\% & 3.56\% \\ \hline Tr = 2000 m & 9.17\% & 5.05\% & 2.5\% & 1.5\% \\ \hline Average Improvement & 11.89\% & 6.085\% & 3.365\% & 2.53\% \\ \hline \end{tabular}
\end{table} 
Table 5: Overall PDR improvement in dolphin pods routing compared to WDFAD-DBR. Last but not least is the important metric end-to-end delay that needs to be optimized especially when there is run-time data needed in the network. The end-to-end delay has been investigated for both DOW-PR scenarios. The simulation results show the obvious improvement in end-to-end delay and this is because of the same argument described repeatedly in the above text i.e., the locally available embedded sink reduces the propagation distance. For instance, if the node at the seabed generated a packet, then it has to propagate at least the full \(z\)-coordinate (i.e., 10 km) to be collected by the sink at the sea surface. On the other hand, in the whale pod scenario, the same packet will be received at the embedded sink and propagated through the distance of 2.5 km at the most.