## 4 Evaluation of the Routing Protocols  
Different types of design philosophies and application requirements have to be considered in most of the routing schemes proposed for UWSN. None of these protocols work efficiently for every parameter such as localization, reliability, node mobility, network life-time, latency and energy-efficiency. Every protocol has its own edge and also few drawbacks. An overview of the key features and drawbacks of the considered routing protocols are depicted in Table 3.  
Figure 13: Data transmission in Vertical Sink Mobility (VSM) [64]. \begin{table}
\begin{tabular}{p{42.7 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Sl. ** & **Name of Protocols** & **the** & **Key Features** & **Main Drawbacks** \\ \hline \hline \multirow{6}{*}{1} & & 1. End-to-End forwarding. & 1. In sparse network packet delivery rate \\  & & 4. Doesn’t require any state information. & 4. If the network delay is not available, the network delay is not available. \\  & & 5. Scalable to the network demand. & 2. Difficult to find proper routing radius threshold. \\ \hline \multirow{6}{*}{2} & & 1. The data transmission is done by ho-by-hop technique. & 1. Gives more signal overhead \\  & (HH-VBF) [51] & 2. In Sparse region, it gives better packet delivery ratio than VBF. & 1. It works only in greedy mode. 2. Packet delivery ratio degrades in sparse network. \\ \hline \multirow{6}{*}{3} & & 1. Packet forwarding decision by a node is taken depending on its depth and the prior sender. & 1. It works only in greedy mode. 2. Packet delivery ratio \\  & (DBR) [52] & 2. Only the depth information of the node is necessary. & 2. Packet delivery ratio degrades in sparse network. \\ \hline \multirow{6}{*}{4} & & 1. It is a cluster based scheme. & 1.It might not be an energy destination. \\  & & 2. It forms a virtual tunnel for a strong connection from source to the destination. & 1. It is a cluster based scheme. & 1. It might not be an energy destination. \\  & & 2. Localization free protocol. & 1. Energy consumption is higher than \\  & & 3. Next hop is selected based on the nodes having minimum depth. & 1. Energy consumption is higher than \\  & (CoDBR) [54] & 4. Unlike DBR simultaneously same data is transmitted twice. & 1. In the node \\  & (CoDBR) [54] & 5. Data packet is dropped if it crosses the maximum allowable bit error rate. & 2. Network life is shorter than DBR. \\  & & 6. It has higher reliability than DBR but it’s energy consumption is also higher than DBR. & 1. Energy consumption is higher than DBR. \\  & & 7. It offers 83\% more throughput and and 90\% less packet drop. & \\ \hline \multirow{6}{*}{6} & & 1. Depth based and localization free protocol. & 1. As the node increases, energy \\  & & 2. It measures link quality precisely with triangle metric. & 1. As the node increases, energy \\  & & 3. Next forwarding node is selected basing on residual energy and triangle metric based link quality. & 1. As the node increases, energy \\  & & 4. Its network lifetime is longer than DBR and EEDBR. & 1. As the node increases, energy \\  & (RE-PBR) [56] & 5. Comparing it to the DBR and EEDBR it gives better delivery ratio. & 1. As the node increases, energy \\  & & 6. It consumes less energy than DBR and EEDBR but provides higher reliability than these two protocol. & 1. Network is disrupted when a hole is created due to absence of any node near to the sink. \\ \hline \multirow{6}{*}{7} & & 1. Per hop forwarding is followed. & 1. Network is disrupted when a hole is created whether to forward the data. \\  & & 3. It gives better delivery ratio than VBF. & 1. Network is disrupted when a hole is created whether to forward the data. \\  & (DFR) [57] & 3. It gives better delivery ratio than VBF. & 1. It gives better delivery ratio than VBF. \\  & & 4. Shorter end-to-end delay and less communication overhead than VBF. & 1. It works only in greedy mode. 2. Packet delivery ratio degrades in sparse network. \\ \hline \multirow{6}{*}{4} & & 1. It is a cluster based scheme. & 1. It might not be an energy destination. \\  & & 2.