# EE-UWSNs: A Joint Energy-Efficient MAC and Routing Protocol for Underwater Sensor Networks
## 3 The Proposed EE-UWSNs Protocol
### Simulation Results  
The proposed EE-UWSNs protocol is tested in a volume of 1 km\({}^{3}\). A Poisson distribution for each transmitter was assumed. The sensors are deployed randomly in the 3D region at different depths following a uniform distribution. Figure 8 illustrates the system model and the simulation parameters are given in Table 1. The proposed EE-UWSNs protocol is compared with four other protocols, which are the DACAP/FBR and CSMA/CA/FBR, DACAP/DUCS, and DACAP/CBAR protocols.  
Figure 7: The programming structure of the sensor node.  
Figure 9 shows the average energy consumption per sensor node during different simulation durations. The longer the simulation, the higher the average energy consumption, due to the increase in the period of operation of the sensors. The proposed protocol outperforms other protocols in terms of the average energy consumption of the sensors. It outperforms CSMA/CA/FBR and DACAP/FBR by 68.49% and 60.34%, respectively. In addition, it has superiority over DACAP/DUCS by 10.51% and over DACAP/CBAR by 20.69%, despite their reliance on the principle of clustering to save energy. The reason behind the improvement is the introduction of the principle of inactivation. During the inactivation period, nodes will be powered-off and thus energy will be saved. Furthermore, the time at which the first sensor's battery becomes empty is analyzed. It is assumed that the starting energy per node is 500 joules. Simulation results show that the first sensor exhausts its battery after 1999.14 time slots, 2259.01 time slots, 17,899.40 time slots, 17,899.40 time slots, 2259.01 time slots, 2269.01 time slots, 2279.01 time slots, 2289.01 time slots, 229.01 time slots, 229.01 time slots, 230.01 time slots, 240.01 time slots, 250.01 time slots, 260.01 time slots, 270.01 time  
15,863.25 time slots, and 20,001.57 time slots in the case of CSMA/CA/FBR, DACAP/FBR, DACAP/DUCS, DACAP/CBAR, and the EE-UWSNs proposed protocol, respectively. This result indicates that the proposed protocol prolongs the network lifetime as the energy-balancing scheme is adopted.  
Figure 10 studies the average number of collisions during different simulation times. Increasing the simulation time leads to an increase in the average number of collisions due to the increase in the data transmission/reception period. The proposed EE-UWSNs protocol achieves the lowest number of collisions compared to the other protocols. It has superiority over CSMA/CA/FBR by 83.45% and over DACAP/FBR by 81.87%. Our proposed EE-UWSNs outperforms DACAP/DUCS and DACAP/CBAR by 86.87% and 90.24%, respectively. The reasons for this lie in applying the principle of inactivation, as well as narrowing the scope of transmission to a specific area. These measures reduce the number of nodes responsible for transmitting and forwarding packets and thus decrease the proportion of collisions.  
Figure 11 illustrates the values of the average end-to-end delay of the proposed EE-UWSNs and the other protocols under various simulation times. As shown in the figure, the proposed protocol achieves the lowest delay compared to the other protocols. The percentages of improvement over CSMA/CA/FBR and DACAP/FBR are 45.62% and 45.75%, respectively. Moreover, EE-UWSNs achieve superiority over DACAP/DUCS by 14.39% and over DACAP/CBAR by 50.64%. The reason behind the improvement is the method of selecting the inactive nodes and relay nodes, which depends on the score value, which takes into account the distance to the desired destination, as well as the consumed energy. Thus, the active relay nodes are the nodes that are closest to the destination. Therefore, the propagation delays will be reduced. In addition, nodes enter the inactive mode only under a certain condition, i.e., when they do not have any packet to transmit. This reduces the queuing delay caused during the inactivation period. Since the possibility  
Figure 9: Average energy consumption per node.  
of collisions is reduced, the number of retransmissions decreases, and, thus, the delay is reduced.