# Energy-Efficient Clustering Multi-Hop Routing Protocol in a UWSN
## 4 Performance Evaluation
### Simulation Results
#### 4.2.2 Residual Energy at the Nodes  
In Figure 5, the residual energy of the nodes is shown in different network scenarios. At each round, the nodes generated packets and then forwarded them to the sink node. In Figure 5a, the residual energy of the node decreased according to the timeline, while the number of rounds increased. It is clear that our EECMR performed better in terms of conserving energy; the residual energy in EECMR was higher than that of DBR, LEACH, and EEBLC. DBR was developed for routing protocols in underwater wireless sensor networks, so DBR performed better than LEACH. EEBLC allows nodes to become the cluster head in turns according to their location and residual energy, and the nodes can save energy when varying the number of nodes and transmission range.  
In Figure 5b, we varied the number of nodes in the network, while three protocols decreased the residual energy. Despite this, the residual energy in EECMR was higher than in EEBLC, LEACH, or DBR. However, the residual energy of the nodes in LEACH declined quickly compared to EECMR. This can be explained as follows. In a dense network  
Figure 4: Number of dead nodes: (**a**) Transmission range 200 m, 450 nodes in 1000 rounds; (**b**) Transmission range 200 m, nodes 50 to 450; (**c**) Transmission range 150 m, 450 nodes in 1000 rounds; (**d**) Transmission range 150 m, nodes 50 to 450.  
deployment, the nodes consume higher energy to perform more communication tasks, such as transmitting and receiving packets to the larger number of nodes. The nodes in EECMR can act as a cluster head or cluster relay; therefore, the cluster head has the information of its cluster member, which reduces the number of transmissions between nodes. As noted in the previous section, the number of dead nodes in EECMR is less because the nodes conserve energy while sending packets. EEBLC performs better than the others in the case of a low transmission range which ensures a long network lifetime. In LEACH, the node that elects to become a cluster head broadcasts information to the three-dimensional area network; as a consequence, the node consumes more energy. In DBR, the node selects the upper-level depth to become its forwarder. If the number of nodes increases, the forwarder may receive more packets, and then it sends these to the upper-level depth before reaching the sink. More transmission at the nodes and forwarders leads to high energy consumption, as shown in Figure 5.  
In Figure 5c,d, the decrease in the transmission range led to higher energy consumption in EECMR, EEBLC, LEACH, and DBR. These protocols gradually diminished the residual energy with respect to the number of rounds. When increasing the number of rounds with a low transmission range, EERBLC performs better than EECMR. When the number of nodes increases, LEACH and EEBLC perform better than EECMR in the case of a low transmission range, and the node consumes more energy.  
Figure 5: Average residual energy of a node: (**a**) Transmission range 200 m, 450 nodes in 1000 rounds; (**b**) Transmission range 200 m, nodes 50 to 450; (**c**) Transmission range 150 m, 450 nodes in 1000 rounds; (**d**) Transmission range 150 m, nodes 50 to 450.  
of a low number of nodes; EECMR performs better than LEACH in the case of dense deployment.  
In a comparison of the residual energy performance with different transmission ranges in EECMR, the residual energy for a 200 m transmission distance was higher than a 150 m transmission range. This can be explained as follows. The cluster heads in EECMR aggregate the data of all cluster members and then forward these to the cluster relay which belongs to another cluster. Since the number of data packets is re-transmitted via multi-hop, the amount of energy consumption increases. In addition, the change in the network topology causes the re-established cluster to consume energy-transmitting and -receiving control packets. However, the total received packets at the sink should be considered. This is presented in the next section.