# Void Hole Avoidance for Reliable Data Delivery in IoT Enabled Underwater Wireless Sensor Networks
## 2 Related Work and Problem Statement
\begin{table}
\begin{tabular}{p{85.4 pt} p{85.4 pt} p{85.4 pt} p{85.4 pt}} \hline \hline
**Technique** & **Features** & **Achievements** & **Limitations** \\ \hline \hline \multirow{2}{*}{AHH-VBF [1]} & Location-aware routing protocol, concept of adaptive virtual pipeline & Reduced duplicate packets and unnecessary energy consumption is avoided & Void hole problem exists \\ \hline \multirow{2}{*}{GEDAR [15]} & GEographic and opportunistic routing with Depth Adjustment-based topology control for communication & Void hole avoidance results in increased performance of the network & High energy consumption and high end-to-end delay \\ \hline \multirow{2}{*}{HydroCast [16]} & Pressure-based routing protocol and efficient anycast routing algorithm & Improved packet delivery ratio & Low performance and increased energy consumption \\ \hline \multirow{2}{*}{H2-DARP-PM [17]} & Hop-by-Hop Dynamic Addressing-based routing protocol for Pipeline Monitoring & Improved packet delivery ratio & High energy consumption \\ \hline \multirow{2}{*}{Delay-sensitive schemes [18]} & Improved delay-sensitive versions, adaptable to time-critical applications & Minimize end-to-end delay and improve performance and network lifetime & Duplication of packets occurs, high energy consumption and void hole problem exists \\ \hline \multirow{2}{*}{ACH\({}^{2}\)[28]} & Free association mechanism where nodes associate with CHs & Minimizing energy consumption and enhances network lifetime & Transmission delay \\ \hline \multirow{2}{*}{ISO and EM wave-based communication schemes [19]} & Free Space Optical and electromagnetic wave-based communication schemes & Reduced energy consumption & High end-to-end delay \\ \hline \multirow{2}{*}{CBSST [20]} & Cluster-Based Sleep/wakeup Scheduling Technique for WSN & Reduced energy consumption, enhanced network lifetime and packet delivery ratio & Keeping the same CH throughout the network lifetime causes problems for network lifetime \\ \hline \multirow{2}{*}{UCBNL [21]} & A high efficiency Uneven Cluster deployment algorithm Based on Network Layered for ever coverage in UWSNs & Enhanced packet delivery ratio, less energy consumption and improved network lifetime & Irregular clustering causes alteration in the network \\ \hline \multirow{2}{*}{PSO-ECHS [22]} & Energy-efficient CH Selection that is based on particle swarm optimization & Energy efficiency achieved & Only for homogeneous networks \\ \hline \multirow{2}{*}{EDDEEC [29]} & Enhanced Developed Distributed Energy-Efficient Clustering & Shows improved performance in terms of stability period, network lifetime and packet delivery ratio. & Imbalanced clustering and reelection increases overhead \\ \hline \multirow{2}{*}{Energy-efficient routing protocol [23]} & SEEC, CSEEC and CDSEEC for UWSNs & Reduced energy consumption & Low packet delivery ratio \\ \hline \multirow{2}{*}{DBR [24]} & Handles dynamic networks efficiently, requires only local depth information and greedy forwarding & Improved network lifetime and packet delivery ratio & Void holes, increased energy consumption and high end-to-end delay \\ \hline \multirow{2}{*}{iAMCTD [25]} & Location-free routing protocol specially designed for time-critical applications & Improved network lifetime, minimized end-to-end delay & Void holes still exist \& overhead due to control packets’ exchange \\ \hline \multirow{2}{*}{E-CARP [26]} & Distributed cross-layer reactive protocol, important for sensory data collection and transmission & Improved network lifetime and reduced energy consumption & Reduced throughput and high path loss due to mobility \\ \hline \multirow{2}{*}{ARCR [27]} & Network is divided into clusters and mobile nodes used to collect data from other sensor nodes and forward them to the sink & Achieves energy efficiency, maximum network lifetime and load balancing & Network disconnects when the relay nodes are disorganized \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of UWSN routing schemes discussed in related work.