## 2 Background
### Comparison of LPWAN Communication Methods  
Table 2 shows a comparison of the technical specifications of Sigfox, LoRa, and NB-IoT, which are widely used LPWAN technologies. Founded in France in 2010, Sigfox is a global leader in providing IoT services. It has built a global network that can connect billions of devices at low power and low cost as a complementary technology and is currently being used in 70 countries around the world. As it was the first to provide IoT network services, it currently has the widest coverage and largest number of partners. The features of Sigfox include low power, low cost, and simplicity (convenience of use) as shown in Figure 3. It can be applied to elderly tracking and protection services, child tracking and protection service, and self-service lockers. In elderly tracking and protection services, an alert or notification is sent to family members as well as service managers. In child tracking and protection services, children carry a small device with a built-in GPS in a bag, which allows parents to track their location during and after school with a smartphone or PC. Self-service lockers integrate Sigfox with the cloud and a smartphone to realize a low-cost, simple transfer-based locker system [4]. Reprinted/adapted with permission from Ref. [4]. 2020, Sigfox.LoRa is a wireless technology that requires low power and exhibits excellent battery performance. It uses an unlicensed band of 1 GHz or less; thus, anyone can use it for free after registration. LoRa has been used for services such as the tracking of missing elderly people with dementia, IoT-based CCTV (CCTV for crime prevention, heatwave warning notification system), and smart water management for waterworks [5]. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Communication Method** & \multicolumn{2}{c}{**Advantage**} & \multicolumn{2}{c}{**Disadvantage**} \\ \hline Sigfox & - & Long-range communication & - & Only small data transmission is \\ Asset location, flood monitoring, & - & Low cost & possible \\ water/gas monitoring, preventive & - & Low power & - & Limited downlinks \\ maintenance & - & Open backend & - & Unsuitable for real-time monitoring \\ \hline LoRa & - & Simple operating procedure with & - & Narrow chipset ecosystem \\ Equipment monitoring, valve actuators, & & ID-based authentication & - & Need to build a new network \\ water quality monitoring, plug & - & Long battery life with low power & - & Concerns about interference with \\ monitoring & - & Cheap and simple chips, modules & - & Unicensed band frequencies \\  & & & - & Concerns about support service due \\  & & & to non-standard technology \\ \hline NB-IoT & - & Transmits large amounts of data & - & Concerns over the mobile operator’s \\ Vending machine, electricity & - & Communication technology & - & monopoly in the market \\ management, parking payments, fleet of & & suitable for cities & - & Narrow ecosystem \\ cars/trucks & & & - & High cost \\  & & & - & Concerns about roaming service \\  & & & disputes between network operators \\ \hline LTE-M & - & Secure service quality with licensed & & \\ Traffic lights, delivery trucks, blockchain & - & - & Secure service continuity based on & - & Expensive and complex chips, \\ payments & - & Standard technology & - & Relatively high-power consumption \\  & - & Provides LTE-level security & & \\  & - & Real-time, high mobility & & \\ \hline  & - & Expansion of existing national & & \\
3G, 4G & - & network & - & Limited coverage (excluding roads) \\ Video camera, private car & - & Fast data transfer speed & - & Low coverage scalability \\  & - & Creates a large-scale ecosystem & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Advantages and Disadvantages of Communication Methods [4; 5; 6; 7]. NB-IoT is a narrowband-IoT standard that supports a LPWAN through an established mobile communication network. A wide service area of more than 10 km is possible.