## 2 Related Studies  
In this section, we analyze the state-of-the-art research studies on IoT and WSN. With the fourth industrial revolution, it is observed that communication, computation, and storage costs have remarkably decreased, which make integration of IoT and WSN possible and cost-effective globally. We studied many review articles and original research. Existing review articles lack, in many aspects, research challenges, issues, limitations, and future directions of IoT and WSN, but the systematic literature review (SLR) given in this work is precise enough to deal with the aspects of IoT and WSN area. Related work of review papers is provided next. Moreover, Table 2 is presented which shows the comparison between the proposed research work and the existing state-of-the-art analysis. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Abbreviation** & **Description** \\ \hline SG & smart grid \\ \hline SIRP & self-optimized smart routing protocol \\ \hline SLR & systematic literature review \\ \hline UASN & underwater acoustic sensor networks \\ \hline WSN & wireless sensor network \\ \hline WSAN & wireless sensor area network \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._ \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Reference** & **Year** & \
\begin{tabular}{c} **Review** \\ **Type** \\ \end{tabular} & **DC** & **Application Types** &
\begin{tabular}{c} **IoT and WSN** \\ **Architecture Used** \\ \end{tabular} & **Challenges and Issues** & **R. Q.** \\ \hline
[1] & 2015 & LR & Industry &
\begin{tabular}{c} 802.11 (WiFi) technology in smart cities \\ \end{tabular} & WSN & \(\times\) & & \(\times\) \\ \hline
[4] & 2020 & LR & Science & \
\begin{tabular}{c} IoT sensing applications discussed using sensing technology \\ \end{tabular} & WSN using RFID &
\begin{tabular}{c} Energy harvesting, communication interference, fault tolerance, higher capacities to handling data processing, cost feasibility. \\ \end{tabular} & \(\times\) \\ \hline
[5] & 2016 & SO & Industry & IoT application in smart grids & IoT & Challenges discussed along with solutions to cope with & \(\times\) \\ \hline
[6] & 2017 & SO & Industry & \
\begin{tabular}{c} Deployment techniques discussed using sensor network \\ \end{tabular} & WSN &
\begin{tabular}{c} Communication cost, coverage time, accuracy, etc. \\ \end{tabular} & \(\times\) \\ \hline
[10] & 2016 & LR & \
\begin{tabular}{c} WSN applications in urban areas \\ \end{tabular} & Urban areas & WSN &
\begin{tabular}{c} Problems and solution of each WSN application \\ \end{tabular} & \(\times\) \\ \hline
[17] & 2014 & SO & Industry & \
\begin{tabular}{c} Network security protocols discussed in industrial applications \\ \end{tabular} & WSN &
\begin{tabular}{c} Challenges of stack protocol and their solutions \\ \end{tabular} & \(\times\) \\ \hline
[19] & 2020 & SLR & Smart factories &
\begin{tabular}{c} Scope and conceptualization of IoT in Industry 4.0 \\ \end{tabular} & IoT & \(\times\) & & ✓ \\ \hline
[27] & 2020 & LR & Smart IoT devices &
\begin{tabular}{c} Detailed survey on security threat models applicable for IoT and WSN. They also discussed communication attacks and taxonomy of IoT and WSN \\ \end{tabular} & Both & ✓ & \(\times\) \\ \hline
[28] & 2019 & LR & – &
\begin{tabular}{c} Discussed technical and social perspective of IoT for future technology enhancement \\ \end{tabular} & IoT & ✓ & \(\times\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparative analysis of the existing review papers. Key: deployment category—DC, literature review—LR, security overview—SO, bibliometric literature review—BLR, systematic literature review—SLR. The authors in [1] discussed the very novel technology \"WiFi\". They discussed how this technology helps IoT devices-used in various applications, such as smart cities, healthcare systems, and smart houses--communicate effectively. [PERSON] et al. [4] discussed RFID and WSN technology in detail.