## 5 Simulation Results  
The simulation was performed using MATLAB. The proposed network is a cube of dimensions 1000 m \(\times\) 1000 m \(\times\) 1000 m in which 200 nodes are randomly deployed. Underwater communications usually deploy few source nodes at the bottom of the network, as in DBR and EEDBR [29]. Therefore, the proposed scheme considers two source nodes at the bottom of the network. These nodes sense the desired attribute and convert it into packets. Packets are generated at the rate of one packet per second. The size of a single packet is 50 bytes. Among the available modems [30], every node uses the LinkQuestUWM2000 modem to communicate with other nodes [31] and has an initial energy of 70 J [29]. This modem has a data rate of 10 kbps and consumes 8 W, 0.8 W and 8 mW power in transmit, receive and idle mode, respectively. Additionally, it can work up to a maximum depth of 2000 m (or 4000 m). The beam width in the omni-directional mode of the transducer is 210\({}^{\circ}\). This eases the selection of a forwarder node close to the surface of the water for a sender node. On the basis of the specifications of the modem, the transmission range of a node is 300 m in all directions and can be increased to 450 m to avoid the condition in which no neighbor node is found. These features of the modem make it the best choice for the proposed protocol. For each measurement, 20 simulations were performed. The NEFP and EHRDBR protocols were chosen for comparison with the proposed protocol because of their similarity to the proposed protocol. The NEFP protocol uses the forwarding probability of a packet and the packet holding time to route data packets in a restricted forwarding zone. This zone is defined by the angle formed among the source, relay and destination. The proposed  
Figure 3: Flow chart of the proposed scheme. protocol also uses the packet holding time to minimize interference. However, the proposed protocol defines the holding time in a unique manner. The EHRDBR first detects a dead node (energy hole) and then moves an active node to replace the dead node. The proposed protocol, in contrast, increases the transmission range to include one or more active nodes in the transmission range of a sender node. Following the DBR protocol, the random walk mobility model is considered to take into account the movements of sensor nodes with water currents. According to this model, nodes move in random directions with a speed that ranges from 1 to 5 m/s. For the MAC (medium access control)layer, the 802.11-DYNAV protocol is considered [32]. The performance metrics are described below. * **Round:** The time that lapses from the transmission of a single or more packets by one or more source nodes to its successful reception at the sink or drop. * **Total Energy Consumption:** This is the amount of energy consumed by all live nodes in one round. It includes energy consumption during hello packets' exchange, transmission and reception of a packet and while remaining in the idle state. * **Dead Nodes:** Sensor nodes that consume all the initially assigned energy. * **Live Nodes:** Sensor nodes that have not yet consumed all the initially assigned energy. * **End-To-End Delay:** This is the time taken by a data packet from transmission by a source node to reception at destination. * **Packet Delivery Ratio:** Ratio of the total packets received successfully at the sink to the total packets transmitted. Figure 4 shows the plot of the total number of dead nodes in the network. For almost the first 58 rounds, nodes died with the slowest rate in the LF-IEHM. This is due to the availability of more live forwarder nodes. This allows a sender node to select forwarder nodes within its normal transmission range, consuming less energy. In addition, the use of the response time (in addition to the pressure levels of the forwarder nodes when multiple forwarder nodes have the same pressure levels) ensures that a single forwarder node is not constantly selected by a sender node in the proposed protocol.