# An Internet of Things (IoT) Application on Volcano Monitoring
## 2 IoT for Volcano Monitoring  
In the last few years, a lot of new network protocols and devices have been developed. Many of them are well known such as WiFi, Bluetooth, ZigBee, and 2G/3G/4G cellular, but there are also several new emerging networking options such as NB-IoT [57; 58], LoRa (long range) [59; 60], and Sigfox [61; 62]. Depending on the application, factors such as range, data requirements, security, and battery life will determine the most suitable option for communications. Table 1 summarizes the main communication protocols employed for the IoT [63; 64; 65]. Since volcanic areas are remote and lack easy access to power supply facilities, the chosen communication option must offer both low-power consumption and long-range operation capabilities, that is, low-power wide-area networks (LPWAN) [63; 64; 66]. A LPWAN is a type of wireless telecommunication wide area network, designed to allow long-range communications at a low bit rate among things operated on a battery. There are a number of competing standards and vendors in the LPWAN space, the most prominent of which include NB-IoT, Sigfox, and LoRa [67]. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Frequency Bands (MHz) 1** & **Nominal Range** & **Data Rates 1** \\ \hline NFC & 13.56 & 10 cm & 100–424 kbps \\ \hline Bluetooth & 2400 & 0.5–100 m & 1 Mbps \\ \hline ZigBee & 2400 & 10–100 m & 250 kbps \\ \hline WiFi & 2400/5000 & 50–100 m & 150–250 Mbps (typical) \\ \hline Cellular & 900/1800/ & 35 km max for GSM, 1900/2100 & 35 km max for HSPA 200 km max for HSPA 200 km max for HSPA 200 km max for HSPA 200 km 200 km 200 km 200 km 200 km  
NB-IoT is a cellular radio access technology set up by the 3 rd Generation Partnership Project. It employs quadrature phase shift keying (QPSK) modulation and provides low-power wide-area IoT connectivity in a licensed spectrum and occupies a frequency band width of 200 KHz. Based on the LTE protocol [68], NB-IoT reduces LTE protocol functionalities to the minimum and enhances them as required for IoT applications. Since this technology operates in licensed bands, NB-IoT has not been considered for the application described in this article, leaving LoRa and Sigfox as the two possible options for the communications. Sigfox [61; 62] is a proprietary ultra-narrowband technology that operates on the 868-MHz frequency band, with a maximum uplink data rate of 100 bps and a maximum packet payload of 12 bytes, allowing to send up to 140 messages per day. It employs the binary phase-shift keying (BPSK), which is a standard radio transmission encoding, taking very narrow chunks of spectrum and changing the carrier phase to encode the data. This allows the receiver to only listen in a tiny slice of spectrum, which mitigates the effect of noise. It requires an inexpensive endpoint radio and a more sophisticated base station to manage the network. Sigfox is a bidirectional communication protocol that shows an asymmetrical connection between the endpoints and the base station. LoRa [59] is a physical layer technology that modulates the signals in a sub-GHz Industrial, Scientific, and Medical (ISM) band using a proprietary spread spectrum technique developed and commercialised by the Semtech Corporation [69]. A bidirectional communication is provided by a special chirp spread spectrum (CSS) technique, which spreads a narrowband input signal over a wider channel bandwidth. The resulting signal has noise-like properties, making it harder to detect or jam. The processing gain enables resilience to interference and noise, and provides adaptive data rate capabilities with a maximum payload length of 256 bytes. The communication frequencies that LoRa uses are mainly those that operate with a license-free Industrial, Scientific, and Medical (ISM) radio band, although the technology can operate at any frequency below 1 GHz. This is a key enabler for inexpensive, world-wide deployments and interoperability.