# Void Avoidance Opportunistic Routing Protocol for Underwater Wireless Sensor Networks
## 4 Simulation Results
### Impact of the Number of Sinks and Deployment on EEDOR-VA  
We examine the effect of various network architecture designs with (1) single and multiple sinks and (2) different sink deployment techniques on EEDOR-VA performance. **Number of Sinks:** to examine the impact of the number of randomly deployed sinks on the network performance, scenario 2 with 16 sinks for the multi-sinks' architecture and the transmission power level = 8.5 watt is used. Figure 14 shows the total energy consumption for single and multiple sinks. We see that the total energy consumption of single sink structure networks is higher than the total energy consumption of multi-sink structure networks. The reason is that in EEDOR-VA, the number of sinks impacts the hop count discovery and forwarding procedure. Using multiple sinks increases a node's chance of reaching one of the sinks through fewer hops, which means decreasing the number of HCREQs required to reach one of the sinks. Moreover, data packets are transmitted via the nodes with discovered hop count to reach the closest sink. In contrast, in the one sink architecture, the HCREQ will be rebroadcasted until that single sink is reached or until rebroadcasted from all the nodes in the network. Consequently, more energy is consumed in single sink networks than multi-sink networks. Figure 15 shows that the packet delivery ratio for both single- and multi-sink architectures is quite variable in the network topologies with the lowest number of deployed nodes. According to the figure, when using EEDOR-VA with the lowest number of nodes topology (i.e., 100 nodes), increasing the number of deployed sinks on the sea surface will increase the number of nodes that can communicate with one of these sinks. Consequently, the chance of one of the sinks receiving the data packet will be increased, resulting in a higher packet delivery ratio in a multi-sink topology. In contrast, with the same number of nodes (i.e., 100 node topology) and one-sink network architecture, all data packets must reach that single sink to be successfully delivered. The number of nodes that cannot reach that single sink is high. This effect explains the very low packet delivery ratio shown in Figure 15 for a 100 node network. On the other hand, the number of sinks has an insignificant effect on the PDR in the topologies with a greater number of deployed nodes, and this is due to the increased probability of reaching the sink(s). Figure 14: Impact of the number of sinks on the total energy consumption. **Sinks deployment:** Two sink deployment methods, pre-planned and random, are used to examine the EEDOR-VA performance. Random deployment is widely used in the literature, while the pre-planned deployment is used in [19]. The pre-planned method used in our simulation is illustrated in Figure 16. In this method, all the sinks are deployed in specific locations with the same distance from each other to cover the area of interest on the sea surface, while in the random deployment, the sinks are distributed randomly on the sea surface. In this method, the distance between any two sinks is variable. Figure 17, which presents the simulation results related to the PDR for both sink deployment methods, shows that the deployment method has no noticeable impact on our proposed protocol EEDOR-VA. The reason behind this is that as long as there is a path between the forwarder node and any of the deployed sinks, the data packet will be transmitted. In other words, the sink deployment methods have nothing to do with the data packet forwarding process we implemented in the EEDOR-VA protocol. The comparison of energy consumption between both deployment methods is illustrated in Figure 18. As shown in the figure, the 95% confidence interval error bars show that there is no significant difference in the energy consumption between the two deployment methods.