# An Enhanced Mechanism for Fault Tolerance in Agricultural Wireless Sensor Networks
## 5 Fault-Tolerant Scheme for WSN in Precision Agriculture
### Fault-Tolerant Clusters
#### 5.1.2 Fault-Tolerant CH
Hence, the WSN continued to provide the final user with the indispensable data without any interruptions. This last feature is very important in such systems. Based on all of the above, we can conclude that the proposed scheme for fault tolerance in WSNs provides a safe and available service. ### Comparative Analysis

Table 3 presents a comparative analysis between some recent works and our proposed scheme. Obviously, the main objective of the vast majority of research works was to reduce the energy consumption and to extend the WSN's lifetime. However, it is evident that fault detection has not been extensively addressed by the majority of the proposed solutions. Furthermore, the most effective methods result in a lot of complexities. This inevitably leads to significant delays and congested connections. In our proposal, we address energy depletion and hardware errors for fault tolerance through the sensor nodes, Cluster Heads, and Base Station without adding much complexity and without affecting the response delays or network load. In fact, the fault detection strategy has received its due attention as an integral part of the fault tolerance technique. \begin{table}
\begin{tabular}{p{42.7 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Reference** & \begin{tabular}{c} **Fault detection** \\ **Mechanism** \\ \end{tabular} & **Fault Tolerance Mechanism** & **Fault type** & **Advantage** & **Limitations** \\ \hline \multirow{4}{*}{[35]} & \multirow{4}{*}{\begin{tabular}{c} Particle swarm \\ optimization for \\ faulty node detection \\ \end{tabular} } & Selection of the CH on the basis of residual energy, coverage, etc. & & & \begin{tabular}{c} Lower energy \\ consumption and \\ lower packet loss \\ \end{tabular} & & \begin{tabular}{c} Congestion, extended \\ delays, and protocol \\ complexity \\ \end{tabular} \\  & & & & \\ \cline{1-1}  & & & & \\ \cline{1-1}  & & & & \\ \cline{1-1}  & & & & \\ \cline{1-1}  & & & & \\ \hline \multirow{3}{*}{[39]} & \multirow{3}{*}{None} & Backup CH selection using fuzzy logic technique. & \begin{tabular}{c} Cluster member \\ energy depletion and \\ hardware errors \\ \end{tabular} & \begin{tabular}{c} Fast fault detection \\ and recovery \\ \end{tabular} & \begin{tabular}{c} Network energy \\ depletion and \\ congestion \\ \end{tabular} \\ \hline \multirow{3}{*}{[40]} & \multirow{3}{*}{None} & Topology construction method based on potential game and cut vertex detection. & \begin{tabular}{c} Network energy \\ depletion \\ \end{tabular} & \begin{tabular}{c} Reduction in energy \\ consumption and \\ increased energy \\ efficiency \\ \end{tabular} & \begin{tabular}{c} Extended delays, \\ cluster construction \\ protocol complexity, \\ and congestion \\ \end{tabular} \\ \hline \multirow{3}{*}{[48]} & \multirow{3}{*}{None} & System reliability prediction and Fault Tree Analysis. & \begin{tabular}{c} Hardware failures \\ and communication \\ errors \\ \end{tabular} & \
\begin{tabular}{c} Design and \\ implementation of a \\ reliable WSN by \\ considering \\ environmental \\ conditions \\ \end{tabular} &
\begin{tabular}{c} Used only for \\ small-scale WSN; \\ difficult to predict \\ possible failures \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Feature comparison. ### Discussion on the Other Cost Issues

One of the issues that define the practicality of a WSN application is its deployment cost [50]. In our setting, we consider precision agriculture where the user can physically reach various locations on the crop field. Hence, unlike other regular WSN settings, this is not an inaccessible terrain and the user is able to deploy, fix, and even replace devices at specific locations. Hence, the cost associated with deployment via other means (aircraft, drones, etc.) is not applicable in our case. In fact, when planting the crops or seeds, the farmer needs to walk around and go to different parts of the field where the necessary tasks for the deployment of the WSN can also be performed.