## 2 Related Work
### Localization-Aware Routing Protocols
To minimize the interference, neighbor node with fewer neighbors is selected. We have updated neighbor tables using piggy back mechanism to reduce communication overhead. The detailed discussion of the proposed work is presented in the upcoming sections. Detailed comparison of the routing protocols for UWSNs discussed above is given in Table 1. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Protocol** & **Features** & **Flaws/Deficiency** & **Advantages Achieved** \\ \hline DBR [9] & Localization-free DBR protocol for underwater monitoring that handles dynamic networks. & Duplicate packets transmission, excessive energy consumptions and high end-to-end delay because of holding time. Due to greedy approach, void hole occurs. Inefficient for sparse and highly dense networks. & Improved network lifetime and data delivery ratio. \\ \hline EEDBR [10] & Localization-free routing protocol for underwater monitoring and surveillance applications with controlled flooding. & High end-to-end delay due to holding time, no mechanism to avoid void hole and high energy consumption in dense networks. & Improved network lifetime, data delivery ratio and minimized energy consumption. \\ \hline AMCTD [11] & Localization-free routing protocol with adaptive mobility of carrier nodes. & High transmission loss due to distant transmissions of medium-depth nodes. Inefficient for data-sensitive applications due to mobility of carrier nodes especially during instability period. & Prolonged network lifetime and reduced energy expenditure of low-depth sensor nodes specifically in stability period. Upholds the network throughput in the sparse condition with adaptive mobility of carrier nodes. & Prolonged network lifetime and reduced transmission loss. Minimized end-to-end delay and critical data loss in delay-sensitive applications. \\ \hline \multirow{2}{*}{
\begin{tabular}{} \end{tabular} } & Localization-free routing for time critical applications along with adaptive mobility of carrier nodes. & Overhead in terms of control packets exchange and the problem of encounters void hole exist. & No need for full dimension location information. Achieved high data delivery ratio in both sparse and dense network. \\ \hline Delay-sensitive schemes & Delay-sensitive routing protocols as an improvement to localization-free routing schemes; DBR, EEDBR, and AMTCD. & Duplicate packets transmission in DSDDR, high energy consumption in dense networks in DSEDR and high transmission loss due to distant transmissions of medium-depth nodes in DSEMRCID. & \\ \hline H2-DAB [16] & Localization-free beacon based routing scheme for critical underwater monitoring missions, route selection is based on hop-id. & Request and replay inquiry act as overhead and increased end-to-end delay as well as energy consumption of the network. & No need for full dimension location information. Achieved high data delivery ratio in both sparse and dense network. \\ \hline R-ERP\({}^{2}\)R [18] & Localization-free beacon based routing protocol, route selection is based on multiple metrics (physical distance, link quality and residual energy). & Consider multiple metrics for next forward selection with create computational overhead. Moreover, physical distance calculation creates hello packet overhead. & Prolonged network lifetime, improved packet delivery ratio, reduced end-to-end delay and energy expenditure for both grid and random topologies. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of different existing schemes.