## 3 Experimental Setup  
Performance analyses were carried out in two different scenarios, indoors and outdoors. For each of the scenarios, tests were conducted with both unencrypted and AES encrypted communication for analyzing different QoS metrics--packet delivery ratio (PDR), current and energy consumption, network lifetime, link quality in terms of RSSI, latency, and throughput. Tests were performed with the commercially available XBee S2C module, which works with the Zigbee protocol at a 2.4 GHz band with 16 channels [43]. However, there are few other commercially available Zigbee modules, which are also popular among the research community for experimental analyses [44; 45; 46]. The specifications of these modules along with their corresponding transceiver chipset models are summarized in Table 3 below [47]:  
As it is evident that even though there are a wide range of choices of Zigbee modules for different use cases, there core specifications and performances are very close to each other. XBee 3 and XBee 3 pro have higher programmable memories and can be tuned to higher Tx power, which improves the transmission range and affects the current and power consumption. However, when tuned to the same transmission power, they perform analogously with other modules, including XBee S2C [47]. For the ease of programmability, ease of integrability with sensors and microprocessors, XBee S2C is the module that this \begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Zigbee** & **Transceiver** & **Programmable** & **Programmable** & **No. of** & **Receiver** & **Tx Power** & **Tx and Rx** \\
**Module** & **Transceiver** & **Memory** & **CPU Clock** & **Channels** & **Sensitivity** & & **Current** \\ \hline \hline \multirow{4}{*}{XBee S2C} & Silicon Labs & 32 KB Flash/ & Up to & & & & Tx: 33 mA \# \\  & EM357 SoC & 32 KB RAM & Up to & & & 3.1 mW & 3.3 VDC/ (+5 dBm/ & 45 mA \#\\) & & & & & & (-100 dBm/ & 6.3 mV \#\\) & & & & & (boost mode) & (+8 dBm) boost & Rx: 28 mA \# \\  & & & & & & mode & 3.3 VDC/ \# \\  & & & & & & mode & 31 mA boost \\ \hline \multirow{4}{*}{XBee-Pro S2C} & Silicon Labs & 32 KB Flash/ & Up to & & & & Tx: 120 mA \# \\  & EM357 SoC & 2 KB RAM & Up to & & & 63 mV \# \\) & & & & & & (+18 dBm) & Rx: 31 mA \# \\  & & & & & & & 3.3 VDC \# \\ \hline \multirow{4}{*}{XBee S2D} & Silicon Labs & 32 KB Flash/ & Up to & & & & Tx: 33 mA \# \\  & EM357 SoC & 2 KB RAM & 50.33 MHz & & & & 3.1 mW & 3.3 VDC/ \# \\ \cline{1-1}  & & & & & & (+5 dBm/ & 45 mA boost \# \\) & & & & & & (-100 dBm/ & 6.3 mW \# \\) & & & & & (boost mode) & (+8 dBm) boost & Rx: 28 mA \# \\  & & & & & & mode & 3.3 VDC/ \# \\  & & & & & & mode & 31 mA boost \\  & & & & & & & mode \\ \hline \multirow{4}{*}{XBee 3} & Silicon Labs & 1 MB/128 KB & & & & & Tx: 40 mA \# \\  & ER32 MG SoC & & RAM & & & normal mode & +8 dBm & Rx: 17 mA \\ \cline{1-1}  & & & & & & & Tx: 135 mA \# \\) & & & & & & normal mode & & Rx: 19 dBm \# \\ \cline{1-1}  & & & & & & & Rx: 17 mA \# \\ \hline \end{tabular}
\end{table} 
Table 3: Technical specifications of the popular commercial Zigbee modules. study focuses on. However, the analysis and study from this work can be generalized for the above-mentioned modules as most of those share the same specifications including the same/similar transceiver chipset. XBee S2C has an indoor range of up to 60 m, and all the tests were performed at 0-40 m distances. It can be tuned to three different transmit powers: 1 dBm, 3 dBm, and 5 dBm. Moreover, the user has the option to enable the boost mode, which would allow the modules to automatically switch to transmit power of 8 dBm when the link quality degrades. However, the boost mode is not considered in this study as it is not a stable state and longtime transmitting at this power level may damage the device. Outdoor link quality (RSSI) analysis is conducted in an open space by placing the coordinator node at one end and the end nodes at a distance ranging from 0 to 40 m from the coordinator.