# Performance Evaluation of Routing Protocols for Underwater Wireless Sensor Networks
## 2 Literature Review
### Improved Cooperative Routing Scheme for UWSNs Using Energy Harvesting (EH-UWSN)  
The authors proposed the Improved Cooperative Routing Scheme EH-UWSN in [17]. EH-UWSN is a routing protocol that saves energy and has high throughput. The authors show how energy can be gained by coordinating the transfer of data packets using next-hop. Using Energy Harvesting, the nodes can charge their batteries from the outside. The goal is to extend the network's life and move data by working together while limiting energy. At the sink node, the combination method is determined by the ratio of signal to noise (SNRC).  
Multilayer Sinks and Cooperation-Based Data Routing Techniques (MuLSi-Co) for Underwater Acoustic Wireless Sensor Networks (UIA-WSNs)  
The authors in [18] introduced two routing schemes: the multilayer sink and Multilayer Sinks and Cooperation-Based Data Routing strategies. The first routing protocol suggests a network structure with multiple layers instead of a single solid structure. It also suggests putting sinks in the best place, which reduces the number of communication hops. Additionally, it is a good idea to pick the best forwarder from the nodes based on how close they are to the sink. Because of this, the network performs well. Unlike traditional algorithms, the one proposed does not need to know where the nodes are. However, because there is only one link, the MuLSi algorithm does not meet the requirement that it works reliably.  
Thus, the MuLSi-Co algorithm uses how the nodes work together to obtain reliable communication. In cooperation, the destination node receives more than one copy of the same information. Then, it puts these packets together to ensure that the data is received correctly. The synchronization problem is solved by the fact that the relay sends data without delay. Additionally, the fact that the data is overheard eliminates any redundant communications.  
After the sink and other sensor nodes are installed, information about the sinks and nodes is shared. Information is gathered in parts to reduce the amount of data that needs to be handled, the amount of traffic, and the amount of energy needed. The goal of gathering information or knowledge is to find out how far away nodes are from the sink and their neighbors so that the best ones can be selected to forward data. Using the fact that nodes can broadcast, the proposed algorithms try to stop packets from being sent more than once. When both nodes hear the same data packet, they remove it from their memory. They think that the data has been sent to another place. In the proposed algorithm, acknowledgement is not considered. This is done to reduce traffic, data overhead, and energy costs.  
The selection of the relay is the most important part of cooperation. The best relay choice from nearby ones tends to improve performance. The cooperation method works well, but it takes more time and energy. Therefore, the suggested MuLSi-Co chooses the relay closest to the destination to reduce the amount of time it takes and the effects of the channel. The data are moved forward in the proposed cooperative algorithm in three steps. The sender sends its data to the relay and forwarder in the first step. In the second step, the forwarder keeps the data for a while. It waits for the relay data. The relay sends data to the forwarder as it receives it. In the third stage, two copies of the same data are combined to make one reliable data packet.