+\begin{table}[h]
+\caption{WSN research topics vs testbed requirements}
+\label{Tablex:ch3}
+\resizebox{\textwidth}{!}{%
+\begin{tabular}{|c|c|}
+\hline
+\textbf{WSN research topic} & \textbf{Testbed requirement} \\ \hline
+Energy efficiency & Energy consumption estimation and measurement \\ \hline
+Mobile sensor nodes & Mobile nodes and localization infrastructure \\ \hline
+Realistic WSN context & Deployment in target environments \\ \hline
+Scalability and performance in WSNs & simulations and hybrid testbeds, large network size \\ \hline
+Sensor node design & Development of sensor nodes, monitoring, measurement, debugging \\ \hline
+Interoperability and platform support & Support for different platforms, heterogeneity \\ \hline
+Application and protocol design & Tool support for development,debugging and deployment \\ \hline
+\end{tabular}
+}
+\end{table}
+
+
+Several sensor nodes testbeds are available to support the research efforts in WSNs, but only a few of them provide common evaluation goals for a large number of users~\cite{ref187,ref181}. However, all the WSN testbeds have usually many common properties, such as a typical number of sensors of the order of hundreds and sometimes only tens of nodes; the deployment of the sensor nodes in a static grid topology; metrics and debug information are obtained via wired connections. Therefore, the WSN testbeds impose strong limitations on the WSNs in terms of size and topology. Moreover, the cost of performing an experiment on a testbed is much higher than through a simulation because setting up the experiments, instrumenting the nodes, gathering the metrics on the performance, and so on is so expensive. For evaluating the systems and protocols on a large sensor networks, the simulation tools are the better choice due to the costs for hardware and maintenance~\cite{ref186}. Hence, the simulation tools stay the most practical tools to obtain a feedback on the performance of a new solution~\cite{ref180}.