## 5 Discussion
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**[PERSON]** & **[PERSON] et al. [77]** & **[PERSON] et al. [80]** & **[PERSON] [81]** \\ \hline \multicolumn{4}{c}{**System-on-Chip (SoC)**} \\ \hline Microcontroller (Single-Board & \multirow{2}{*}{Raspberry Pi 3 Model B v v12} & \multirow{2}{*}{Raspberry Pi 3 A +} & \multirow{2}{*}{Arduino UNO Rev3 (2 units)} \\ Computer) & & & \\ \hline \multirow{2}{*}{Based CPU} & \multirow{2}{*}{Quad Core 1.2 GHz Broadcom} & \multirow{2}{*}{Broadcom BCM2837B0, Cortex-A53} & \multirow{2}{*}{ATmega328P} \\  & & BCM2837 64 bit & (ARM8) 64-bit SoC \& 1.4 GHz & \\ \hline \multirow{2}{*}{Wireless module} & \multirow{2}{*}{ECM3438 wireless LAN and BLE} & 2.4/5 GHz IEEE 802.11b/g/n/ac & \multirow{2}{*}{SparkRun WiFi Shield-ESP8266} \\  & & onboard & transceiver & (2 units) \\ \hline \multirow{2}{*}{Cryptographic coprocessor} & - & - & - \\ \multicolumn{4}{c}{**Communication technologies**} \\ \hline Gateway & - & - & - \\ \hline Wireless Protocols (available) & Wi-Fi (EEE 802.11 b/g/n) & Wi-Fi (IEEE 802.11 b/g/n) & Wi-Fi (IEEE 802.11 b/g/n) \\ \hline Hardware communication protocol & \multirow{2}{*}{**Wi-Fi (licence-free 2.4 GHz and 5 GHz)**} & \multirow{2}{*}{**Wi-Fi (licence-free 2.4 GHz and 5 GHz)**} & \multirow{2}{*}{**Wi-Fi (licence-free 2.4 GHz and 5 GHz)**} \\ \hline Center frequency & 2.4/5.0 GHz & 2.4/5.0 GHz & 2.4/5.0 GHz & \\ Bandwidth & 20/40 MHz & 20/40 MHz & 20/40 MHz \\ \hline Data rate (bits/s) & \textless{}300 Mbps & \textless{}300 Mbps & \textless{}300 Mbps \\ \hline Effective isotropic radiated power & - & - & - \\ \hline Constraints & Max. payload 64 KB & Max. payload 64 KB & Max. payload 64 KB \\ \hline \multicolumn{4}{c}{**Radon gas sensor**} \\ \hline Radon sensor & SARAD Radon Scout sensor & Radon sensor from MidDec & Radon FTLab RD200M \\ \hline Academic prototype/Commercial & Commercial sensor (for indoor & Academic R \& D sensor & Academic prototype (for indoor \\ sensor & dosimetry) & dosimetry) \\ \hline \multirow{2}{*}{Radon detection technique} & Photodiode detection for alpha & - & Pulsed Ion chamber \\ \hline First data out & 120 min to 95\% of the final value & - & \textless{}60 min \\ \hline Data interval & 1–3 h or customized (1–255 min, & - & 10 min update (60 min moving average) \\ \hline Sensitivity & 1.8 cpm @ 1000 Bq/m\({}^{3}\) (immune to humidity)) & - & 0.81 cph at 1 Bq/m\({}^{3}\) \\ \hline Operating range & - & - & 10–40 \({}^{\circ}\)C, RH \textless{}80\% \\ \hline Measurement range (Bq/m\({}^{3}\)) & 0–100,000,00 Bq/m\({}^{3}\) & - & 7–300 \\ \hline Typical accuracy (precision) & \(\pm\)20\% at 200 Bq/m\({}^{3}\) or \textless{}10\% at 370 Bq/m\({}^{3}\) \\ \hline Guaranteed accuracy & - & - & - \\ \hline Display & None & - & OLED Display \\ \hline Other information & Setup/Data download via Radon & Built-in vibration sensor to prevent & errors \\ \hline \multicolumn{4}{c}{**Environmental sensors included**:} \\ \hline Gas sensor (IAQ) & - & - & - \\ \hline Relative humidity/temperature: & Included in the sensor (0–100\% and & -20-40 \({}^{\circ}\)C) & Included in the sensor & BME280 \\ \hline \multicolumn{4}{c}{**Barcmetric pressure**} \\ \hline \multicolumn{4}{c}{**Back-end web architecture**:} \\ \hline \multicolumn{4}{c}{Open-source virtualization platform} & - & Open-source project (MIT licensed) & - \\ \hline \multicolumn{4}{c}{**Downloading: www.smeiot.se**} \\ \hline Programming tool for wiring devices & Node-RED (browser-based editor) & - & GlassFish and SoupUI \\ \hline Geographic Information System (GIS) & Leaflet javascript library & - & - \\ \hline Threshold for is using alerts (action level) & 300 Bq/m\({}^{3}\) & - & 300 Bq/m\({}^{3}\) (adjustable) \\ \hline Messaging protocols & MQTT (Mosquito broker) & MQTT (Mosquito broker with & HTTP \\ OpenSQL) & & \\ \hline Security protocols & None & TLS with FSR encryption & None \\ \hline NFC device to secure credentials & None & None & None \\ \hline \multicolumn{4}{c}{**Prototype dimensions, estimated power consumption, and price**:} \\ \hline Dimensions & n/a & \(10\times 15\) cm & n/a \\ \hline Overall power consumption (Wh) & n/a & n/a & n/a \\ \hline Overall price of the system & n/a & n/a & \(\pm\)625.00 \& (\epsilon\) (material expenses) \\ \hline \hline \end{tabular}
\end{table}