# Void Avoidance Opportunistic Routing Protocol for Underwater Wireless Sensor Networks
## 4 Simulation Results
### Scenario 1:
#### 4.1.2 Results and Analysis  
**Total Energy consumption:** Figure 6 illustrates the total energy consumption for the three protocols. It can be observed that DBR has the largest total energy consumption since it depends on the greedy flooding technique to forward the data packets from the source nodes to reach the surface sink(s). This greedy technique used by DBR results in a number of transmissions occurring at the same time, which makes collisions between the transmitted packets more likely. Moreover, the depth threshold mechanism used by DBR for selecting next-hop forwarding nodes affects the overall energy consumption by reducing the number of relay nodes. Reducing the number of relay nodes increases the probability of packet loss and therefore increases retransmissions, which increases the energy consumption. In contrast, the total energy consumed by EEDOR is almost constant because the network density has an insignificant effect on our next-hop forwarding method. On the other hand, EEDOR-VA's total energy consumption also increases with increasing the density of the network. The difference between the total energy consumption in the three protocols, especially between DBR and the other two, EEDOR and EEDOR-VA, increases rapidly with the increase in the density of the nodes. The large variation in energy consumption shown in Figure 6 among the three protocols as the network density increases is caused mainly by an increase in the size of the forwarding set and redundant transmissions in DBR as the network density increases. EEDOR and EEDOR-VA constrain the number of redundant transmissions due to the coordination method based on the proposed holding time. However, the hop count discovery procedure in EEDOR-VA gives the protocol an extra energy cost. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Value** \\ \hline Network size & 500 m \(\times\) 500 m \(\times\) 500 m \\ Number of sinks & 5 \\ Number of nodes & 200–800 \\ Maximum transmission range & 100 m \\ Initial energy & 70 J \\ Data packet size & 50 bytes \\ Data rate & 104 bps \\ Frequency & 25 kHz \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Summary of Scenario One Simulation Parameters. Figure 6: Total Energy Consumption vs. Number of Nodes. The 95% confidence interval error bars in Figure 7 also show that our EEDOR-VA protocol has a smaller error range in mean energy consumption per node than the other two protocols. Additionally, the EEDOR-VA error range decreases as the topology density increases. The small error range indicates that the energy consumption is more balanced between all nodes. The DBR large variation in mean energy consumption per node as shown by the error bars in Figure 7 happens because some of the nodes, especially near the surface, retransmit more often than others because DBR does not incorporate any energy balancing strategies. EEDOR and EEDOR-VA waiting time techniques in the forwarding set selection phase help in choosing the next-hop forwarder and balancing the energy consumption by suppressing the retransmissions. **Packet Delivery Ratio (PDR):** In this network topology, a high value of packet delivery ratio of routing protocols means that the network is unlikely to have void areas. The PDR is high because increasing the number of nodes increases the number of forwarding nodes in the routing path and, as a result, increases the PDR. We can observe from Figure 8 that the packet delivery ratio of EEDOR-VA is always higher than that of other routing protocols, mainly because it omits all the routes that lead to a void area. Our technique can deal with the void problem without implementing any recovery mode, which eliminates the recovery mode high overhead. Furthermore, the packet delivery ratio of DBR and EEDOR is not as high as EEDOR-VA because both the DBR and EEDOR protocols do not consider if there is at least one route between the source and the sink(s) or not.