# An Energy-Efficient and Obstacle-Avoiding Routing Protocol for Underwater Acoustic Sensor Networks
## 5 Performance Evaluation
### Evaluation with Different Parameters
Moreover, under the interference of marine animals, the HHVBF protocol completes the routing that can avoid interference from marine animals is by forming a pipe for neighbor nodes of each hop and forwarding packets to all nodes in this pipe until the destination node receives the data. Therefore, the waiting time and transmission time of HHVBF are constantly increasing as the number of nodes participating in the forwarding increases. EOAR and VHGOR selects the nodes in the candidate forwarding relay set considering the interference area, which may reduce the number of nodes in the candidate forwarding relay set. EOAR and VHGOR can save the calculation time, waiting time and transmission time. Therefore, in the experiment, EOAR and VHGOR have less propagation delay than HHVBF. In addition, VHGOR does not use the method of priority-based forwarding, so when the best relay does not successfully receive the packet, retransmission occurs, causing the propagation delay to increase. This shows that the advantages of the EOAR are obvious: EOAR performs efficient routing performance when sensor nodes are densely deployed and there are marine animals in the network. Figure 7: Packet delivery ratio versus the numbers of nodes. Energy consumption is also a very important indicator of network performance evaluation. The energy consumption formula in EOAR is:  
\[E=\sum_{j=1}^{M}\Bigl{(}E_{t_{j}}+E_{r_{j}}+E_{t_{j}}\Bigr{)} \tag{12}\]  
where \(E_{t_{j}}\) is the energy consumption of node \(N_{j}\) to transmit packet, and \(E_{r_{j}}\) is the energy consumption of node \(N_{j}\) to receive packet, and \(E_{t_{j}}\) is the energy consumption of node \(N_{j}\) for idle overhear mode of sensor nodes. \(M\) is the total number of the sensor nodes. The energy consumption of underwater acoustic communication mainly includes the energy required to collect data, send data packets, receive data packets and the energy for calculation and idle state. In EOAR, only the nodes in candidate forwarding relay set are responsible for forwarding the packets to reduce the unnecessary node participation, thus EOAR can reduce the energy consumption. Besides, in order to prevent the same packet from being repeatedly forwarded by different nodes, EOAR sets a waiting time for each candidate forwarding relay. To further confirm that our proposed routing protocol has efficient performance, we compare its communication energy consumption with HHVBF and VHGOR. In this simulation, the number of sensor nodes is 300. The initial energy of each node is \(10^{9}\) J. The power consumption for transmitting state is 10W and the power consumption for the idle state is 30 mW. It can be seen from Figure 9 that the relationship between energy consumption and time in three different routing protocols. As time increases, node energy consumption increases gradually. In the beginning, the EOAR energy consumption is higher than the VHGOR and HHVBF protocols. For example, when the simulation time is 50 s, the energy consumption of EOAR is 3.5 \(\times\) 10\({}^{7}\) J, and it is higher than the other two protocols. This is because the current node needs to adopt the acoustic perceive method to calculate the interference area of animal-nodes in the EOAR protocol when it encounters the interference of the marine animals. However, after a period of communication, the total energy consumption of the EOAR protocol is lower than the other two protocols because EOAR is able to avoid packet collisions and reduce the number of nodes participating in forwarding. In the simulation time of 500 s, the total energy consumption of EOAR is lower than the total energy consumption of the other two protocols. Compared with HHVBF and VHGOR protocols, the energy consumption of EOAR is reduced by 53.4% and 32.7%, respectively. This proves that the EOAR protocol has obvious advantages in reducing communication energy consumption in long time operation. Figure 8: End-to-end delay versus number of nodes.