# DOW-PR DOlphin and Whale Pods Routing Protocol for Underwater Wireless Sensor Networks (UWSNs)
## 6 Performance Comparison and Analysis
### Simulation Results in the Dolphin Pods Routing Scenario
Moreover, the proposed scheme in this paper selects the next expecting hop by considering the weighting sum of the depth difference of the two hops, the PFN number, suppressed nodes number and the hop number of the expected next forwarding node, which reduces the total energy to a very low level. Energy tax is directly proportional to the total energy consumption, and inversely related to nodes number and number of packets generated (refer to Equation (21). WDFAD-DBR selects the next forwarding node by taking the accumulative advancement between the two hops, but it does not consider the receiving energy consumption due to available PFNs number and suppressed nodes number. Dolphin pod considers the energy efficient forwarder/path based upon the receiving energy consumption in potential forwarding nodes number and suppressed nodes number associated with the source node. Dolphin pod gives weight to both parameters by setting the division factors \(DIV_{PFN}\) and \(DIV_{SUP}\). If the number of PFNs and SUP nodes number are less, then the division factors (\(DIV_{PFN}\) and \(DIV_{SUP}\)) are set to very low values and, therefore, the receiving energy consumption in this case is negligible. Consequently, the forwarder selection criteria will then only be based on the weighting sum of depth difference of the hops (H) value as from Equation (10). For the case, if number of PFNs and number of suppressed nodes of a PFN are greater, dolphin pod set the division factors to a high value and will then be based on number of PFNs and suppressed nodes number means the receiving energy is consumed in larger amounts, so the forwarder/path, which has a low value of fitness function, will be selected. It can also be easily judged through Figure 12b in which there is huge reduction in energy tax. 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 the number of retransmissions will consume quite a lot more energy. The analysis shows that there are 37.07%, 30.81%, 29.11% and 25% more energy conserved for 200, 300, 400 and 500 nodes, respectively (refer to Table 6). Primarily, end-to-end delay increases for both dolphin pod routing and WDFAD-DBR protocol by increasing the nodes density i.e., from 100 to 250 nodes. For any further increase in node density, the end-to-end delay appears to be reduced, and this is due to number of reasons that included reducing hops count, increasing collision probability and better successful packets delivery at the destination. In a dense network scenario, there are enough nodes readily available at the edge of the transmission range for selecting the next hop forwarding node. Dolphin pod considers the hop number of each node in fitness function, which reduces the APD as well as end-to-end delay. The analysis shows that there are 37.07%, 30.81%, 29.11% and 29.00% average improvement in end-to-end delay for 200, 300, 400 and 500 nodes, respectively (refer to Table 7). Along with the above-mentioned improvements in the performance metrics, we also investigate the other important metric, the average number of packets dropped in the network. Referring to Figure 13, it can be easily noticed that there is a significant reduction of packet drop in the proposed DOW-PR scheme as compared to WDFAD-DBR. The reasoning behind this improvement is that our mechanism ensures better life span of the individual local nodes and the network as well. The logical arguments are somehow similar to energy tax improvement described earlier. WDFAD-DBR does not take into account the void hole occurrence probability; instead, it only considered the packet upward distance advancement at the two hops. On the other hand, the proposed DOW-PR scheme considered the potential forwarder nodes number at both one and two hops.