## 2 Outdoor Positioning in the IoT Ecosystem
### Application-Specific IoT Requirements  
A localization system is composed of hardware and software components on both sides of the end node and network control. In the end-node side, LS can have size limitations. Therefore, it leads to choosing shorter antenna dimensions as radio frequency interfaces. By decreasing the antenna dimensions, path loss increases. As a result, the number of gateways on the receiver side in an invariant environment has increased to earn the same accuracy. On the network control side, by increasing the number of end nodes, the volume of generated data increases. Therefore, a more powerful network control server is needed to handle data and earn required accuracy. According to the mentioned contents, different IoT applications based on their purpose have different localization system requirements [14]. In this section, important requirements for IoT localization system are identified and discussed. * Security and Privacy: Long-range communication protocols provide connectivity for IoT systems and IoT systems provide information about the system, environment, and people. The information which is collected by IoT and IoT communication signals in LPWAN should be sent securely, otherwise, it can lead to security (disclose sensitive information about environment) and privacy problems (potentially disclose end-node location). Poor authentication and encryption methods can lead to end-node privacy violence [15]. To provide a secure localization system, it is important to consider privacy and security requirements in each step of architecture. With the release of General Data Protection Regulation (GDPR), authors in [16] present an appropriate privacy-by-design to guarantee the GDPR compliance through the integration of a specialized GDPR-based access control system. * Coverage Range: Different IoT systems work in different environment situations (for example, the smart industry has a harsh environment). LPWANs (LoRaWAN, Sigfox, and NB-IoT) has different coverage range and function in different situations. As a result, the efficiency and coverage range of the different LPWAN technologies can be varied in different systems. Therefore, a network technology should be compatible with the environmental situation and required range. Energy Consumption: Energy Consumption is one of the most important issues in IoT systems. IoT systems are embedded in different environments for an important purpose. Therefore, long battery life and the low energy consumption is a fundamental point for these systems. One of the important aspects to decrease energy consumption is multiple cheap network interfaces adoption such as Bluetooth, Wi-Fi, and LPWAN for short- and long-range positioning. In this case, end nodes look for nearby localization systems with the short-range network interfaces and, eventually, switch to a long-range search [17]. The authors in [18] try to standardize Application Programming Interfaces (APIs) designed to discover, access, and localize end nodes. Latency: low latency in some IoT categories is an essential priority because of the hard real-time limitations. In these cases, adopted LPWAN technology should provide services with specific maximum latency. Deployment: NB-IoT is a new emerging technology while LoRaWAN and Sigfox ecosystems are mature communication technology. Additionally, we need to choose the best LPWAN technology based on our system (local or public network). Accuracy: IoT systems can be divided into two categories based on required location accuracy: high accuracy and low accuracy. smart healthcare and smart factory need high accuracy based on their direct interaction with human safety. Smart cities and smart transportation need accuracies in the meter level. Therefore, the localization error rate of the adopted LPWAN method should be acceptable in the system. Scalability: LPWAN technologies are supposed to cover a wide-area environment.