# Investigating Master-Slave Architecture for Underwater Wireless Sensor Network
## 4 System Model
### Restricting Extra Reception of Packets:
This is achieved by adapting distance-based transmission methods for packet transmission and selecting the best master for forwarding, whose responsibility is to keep the network free of energy holes. The collision of packets occurs whenever packet traffic is high since the ERPMSA-UWSN suppresses the redundant transmissions which leads the network to have low packet traffic and thus minimizes the collision of packets. For these reasons, the network throughput for our proposed protocol, in sparse as well as dense networks, is higher than the existing ones i.e., WDFAD-DBR whether sparse or dense networks. The slow growth noted in the dense network is justified because ERPMSA-UWSN has limited sources of data packet after suppressing the majority of the PFNs. In contrast to WDFAD, there are multiple packet resources in the network, which may cause a collision and cause packet loss in the network. In the case of a dense network, we produce more chance of finding the best master for the transmission, leading the network out of energy holes and void holes situations and preventing packet drop. This behavior of the PDR is well justified by the packet drop profile as shown in Figure 13. It can be seen that the amount of packet drop decreases with the increase in the number of nodes, and ERPMSA-UWSN shows less packet drop compared to WDFAD in both sparse as well as dense networks. Next, we breakdown the energy tax of the proposed scheme (ERPMSA-UWSN) and the competing protocol (WDFAD). Transmission energy has a higher proportion in energy consumption than the other energies i.e., idle state, receiving, processing, and sensing energies. In Underwater acoustic networks, packet transmission is the costliest process, especially since the transmission of the data packet is the most energy-consuming due to its large size compared to other packets. This evaluation of energy is already validated through experimental findings in [45]. The energy cost of transmitting one single bit is approximately equal to thousands of processing [46]. The algorithm's computational complexity is also an energy-consuming factor i.e., the cost that a network must bear for the complex computation. A decreasing trend has been noted in the energy usage with the increase in node numbers. It is because of the increased probability of a master's abounded existence, which leads to the successful transmission of packets. Furthermore, an increase in node number also suppresses the energy wastage, caused by the re-transmission of the packet. An increase in nodes also leads to the enriched energy resources that might contribute to this decreasing trend. The method adopted for selecting the next forwarder (master) is superficially more contributive in the campaign of energy optimization. It targets the extra transmissions of

Figure 12: (**a**) PDR against the number of nodes; (**b**) energy tax versus the node count; (**c**) end-to-end delay against number of nodes; (**d**) APD compared to the node count. Comparison of ERPMA-UWSN with WDFAD. Figure 13: Packet drop profile. the data packet by introducing a new packet (CTRL PACK), which is smaller in size and suppresses the additional data packet transmissions. Data packet has a size of 72 bytes, while CTRL PACK has a size of 5 bytes, which makes a mighty difference in the energy equation. Master nodes have only the privilege to receive the data packet, while slaves remain unprivileged in the sense of data packet reception. In contrast, WDFAD used to send the data packet to each node that lies in its range, and at last one of them must transmit, while the remaining one must drop that packet. Saving transmission energy put a great influence on the total energy cost which results in low energy consumption. Our scheme adopted the adaptive transmission power leveling mechanism which consequently leads to the economization of energy. As transmission energy is applied based on the displacement of the node in the transmission range i.e., farther node means more transmission power is exerted and vice versa.