## 2 Radio Communication Technologies
### NB-IoT in One Glance: Why Choose NB-IoT? So far, some major characteristics of the main LPWAN technologies have been outlined, alongside the narrowband IoT (NB-IoT) technology. NB-IoT was introduced by using 3 GPP 5G technology as a new radio interface, whereby connected devices communicate through the cellular infrastructure. In addition, different data rates suitable for NB-IoT \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Sigfox** & **NB-IoT** & **LoRaWAN** \\ \hline \multirow{4}{*}{\begin{tabular}{c} **Modulation** \\ **techniques** \\ \end{tabular} } & \multicolumn{2}{c}{Downlink: QPSK +} & CSS(Chirp Spread \\  & DBPSK and GFSK & OFMDA & Spectrum \\  & & Uplink: BPSK/QPSK & modulation) radio \\  & & + SC FDMA & modulation \\ \hline \multirow{4}{*}{\begin{tabular}{c} **Handover** \\ **Costs (general)** \\ \end{tabular} } & Enabled\_end-devices & Disabled\_end-end-devices & Enabled\_end-devices \\  & & do not join a single & devices join a single & do not join a single \\  & base station & base station & base station \\ \hline \multirow{2}{*}{\begin{tabular}{c} **Module cost** \\ **Interference** \\ **immunity** \\ \end{tabular} } & \multirow{2}{*}{35} & \multirow{2}{*}{125} & \multirow{2}{*}{65} \\  & & & \\ \hline \multirow{2}{*}{\
\begin{tabular}{c} **Licence (standard specifications)** \\ \end{tabular} } & Sigfox based network & 3 GPP & LoRa-Alliance \\ \hline \multirow{2}{*}{
\begin{tabular}{c} **Topology** \\ \end{tabular} } & Star network & Network: Cellular & a star-of-stars \\  & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._  
Figure 3: A respective view of the characteristics of Sigfox, NB-IoT, and LoRaWAN across a scale of 0 to 100.  
were introduced in the range from tens of kbps in a 180 kHz bandwidth (which is the original LTE Cat-NB1 bandwidth) up to a few hundred kbps (which represents the LTE Cat-NB2 bandwidth). Being under LTE standards, NB-IoT operates in a licensed spectrum benefiting from the large LTE ecosystem of mobile operators. The estimations indicate that by 2025, over 5 billion devices will be connected through 5G NB-IoT [30; 31]. Generally, it is compatible with GSM (Global System for Mobile Communications), GPRS (General Packet Radio Service), and LTE, but not with 3G communication systems. With a software upgrade and enhancement, NB-IoT can be supported by the LTE systems. Additionally, due to having fewer bandwidth requirements, a high data rate, and reduced protocol schemes, NB-IoT provides important advances regarding its cost and use of energy [32]. NB-IoT has already been massively deployed in various smart applications, and its newest generation, 5G NB-IoT, is expected to advance the IoT domain revolution. A summarized review of the NB-IoT advancement goals gives the reasons why NB-IoT is a favorite choice for scalable, low-power, wide-area, and secure IoT connections:  
* Supporting a massive number (at least 52,547) of low-throughput connected devices within a cell site sector. This goal was initially based on connecting 40 devices per household to match the household density of a city such as London, which contains 1517 households per km\({}^{2}\), and with a cell site distance of 1732 m;
* Low power consumption enabling the connected devices and sensors to draw a low current (in the nanoamp range).