## 4 Results
### Criteria for Comparing the Relevant Characteristics
\begin{table}
\begin{tabular}{c c c c} \hline
**Criteria** & **[PERSON] et al. [74]** & **[PERSON] et al. [75]** & **[PERSON] et al. [76]** \\ \hline \multicolumn{4}{c}{**System-on-Chip (SoC)**} \\ \hline Microcontroller (Single-Board  Computer) & Arduino mlxr & Included in radon sensor & Unreferenced \\ \hline Based CPU & ARM Cortex-M0 + CPU (48 MHz) & - & - \\ \hline Wireless module & Arduino Mkr Wi-Fi 2020 & - & - \\ \hline Cryptographic coprocessor & ATECC508A & - & - \\ \multicolumn{4}{c}{**Communication technologies**} \\ \hline Gateway & - & Wirnet IoT Station-developed by & - \\  & & Kerlink & \\ \hline Wireless Protocols (available) & Sigfox and Wi-Fi (IEEE 802.11 b/g/n) & LoRaWAN & Wi-Fi (IEEE 802.11 b/g/n) and 4G \\ \hline Hardware communication protocol & UART/FC & UART & - \\ \hline
**Wireless Communications (used):** & **Sigfox (licence-free sub-1 GHz:** & **LoRaWAN (licence-free sub-1 GHz):** & **Wi-Fi (licence-free 2.4 GHz and 5 GHz):** \\ \hline Center frequency & 868,130 MHz & 868 MHz & 2.4 /5.0 GHz \\ \hline Bandwidth & 200 kHz (ultra-narrow) & 125/250/50 kHz (CSS Modulation) & 20/40 MHz \\ \hline Data rate (bits/s) & 100 & 250 ps -50 kbps & \textless{}300 Mbps \\ \hline Effective isotropic radiated power & 16 dBm & +14 dBm (receiver sensitivity: & - \\  & & \textless{}146 dBm) & - \\ \hline Constraints & 140 messages/day (ETSI regulations) & Limited message sizes (230 bytes & Max. payload 64 KB \\  & **Radon gas sensor** & & \\ \hline Radon sensor & Radon FILab RD200M & Algrade \(\mathcal{ER}\) Plus & RN53 (PIN diode)-Teviso Sensor \\ \hline Academic prototype/Commercial & Academic prototype (for indoor & Commercial sensor (for indoor & Academic prototype (for indoor \\ sensor & dosimetry) & dosimetry) & dosimetry) \\ \hline Radon detection technique & Pulsed Ion chamber & Photodiode detection for alpha & Photodiode detection for alpha \\  & & particles & particles \\ \hline First data out & \textless{}60 min & 24 h & - \\ \hline Data interval & 10 min update (60 min moving & 15 min-4h (60 min/1 month/LT \\  & average) & moving average) & - \\ \hline Sensitivity & 0.81 cph at 1 Bq/m\({}^{3}\) & 0.05 cph \#1 Bq/m\({}^{3}\) (15-20 Bq/m\({}^{3}\) per \\  & & hit per hour) & 150 cph/1000 Bq/m\({}^{3}\) \\ \hline Operating range & 10–40 \({}^{\circ}\)C, RH \(<\) 80\% & 0–40 \({}^{\circ}\)C, RH \(<\) 80\% & \textless{}20–60 \({}^{\circ}\)C, RH = 20\% \\ \hline Measurement range (Bq/m\({}^{3}\)) & 7–3700 & 0–99, y kBq/m\({}^{3}\) & - \\ \hline Typical accuracy (precision) & \textless{}\pm 10\% at 370 Bq/m\({}^{3}\) & \textless{}20\% at 300 Bq/m\({}^{3}\) (in 24 h) & \textless{}10\% typical @ 1000 Bq/m\({}^{3}\) \\ \hline Guaranteed accuracy & - & - & - \\ \hline Display & OLED Display & Contrast e-paper Display & None \\ \hline Other information & Built-in vibration sensor to prevent & Data storage and retrieval via USB & Must be isolated from visible light, for accuracy \\  & & **Environmental sensors included**: & \\ \hline Gas sensor (IAQ) & CCS811 (TVOC, eCO\({}_{2}\), MOX) & - & - \\ \hline Relative humidity/temperature: & BME280 & Included in radon sensor & Included in the prototype circuit board \\ \hline Barometric pressure & - & - & Included in the prototype circuit board \\ \hline \multicolumn{4}{c}{**Back-end web architecture**} \\ \hline Open-source virtualization platform & Proxomax VE (KVM hypervisor + LXC & ChirpStack-LoRaWAN Network & \\  & Containers + Storage + Networking & Server stack & Set of human-computer interfaces \\  & & func.) & Elastic Stack Suite & \\  & & (Beats-Logstash-Elasticsearch) & \\ \hline Programming tool for wiring devices & \multirow{2}{*}{Node-RED (browser-based editor)} & Gratana (dashboards, monitoring, & - \\  & & allam trigger) & \\ \hline Geographic Information System (GIS) & - & GeoNetwork & - \\ \hline Threshold for issuing alerts (action level) & \multirow{2}{*}{300 Bq/m\({}^{3}\)} & The emergence of volcanic eruptions & Unreferenced \\ \hline Messaging protocols & MQTT and SMITP (email) & MQTT & - \\ \hline Security protocols & HTTPS (SSL with ACME protocol) & None & None \\ \hline NFC device to secure credentials & \multirow{2}{*}{NXP NTAG PC plus} & None & None \\ \cline{3-3} configuration & & **Prototype dimensions, estimated power consumption, and price:** & \\ \hline Dimensions & \(15\times 15\times 30\) cm & \(40\times 30\times 21\) cm (after tropicalization) & n/a \\ \hline Overall power consumption (Wh) & n/a & n/a & n/a \\ \hline Overall price of the system & n/a & n/a & n/a \\ \hline \end{tabular}
\end{table}