# A Comprehensive Review of Indoor Localization Techniques and Applications in Various Sectors
## 3 Methodology and Application of Indoor Localization in Various Fields
### Strategic Insights: Indoor Localization in Military Applications  
#### 3.3.1 UWB-Based Methodology for Military and Emergency Operation  
[PERSON] et al. [36] introduced the Pouect system, a robust indoor positioning solution designed for military and firefighter operations, particularly in environments where GNSS signals are unavailable. This system combines multiple technologies, including GPS, long-range radio (LoRa) operating in the 868 MHz and 2.4 GHz bands, UWB, and altimeters, to ensure accurate and continuous localization. Figure 21 illustrates the communication framework for LoRa-2.4 GHz nodes, demonstrating the exchange of signals between the Host and Responder nodes via signal preambles, packet headers, and range indicators. By integrating these technologies, the Pouect system can adapt to complex and dynamic operational scenarios. The hardware architecture consists of four primary types of nodes. Trackers are worn by soldiers or firefighters and are equipped with transceivers for GPS, LoRa, UWB, and altimeter modules. These trackers are lightweight and portable, allowing agents to carry them easily during missions. Beacons are deployed strategically around the operational area to serve as reference points, providing an absolute positioning system by leveraging GPS and LoRa communications. Additionally, pebbles are small nodes carried by agents and deployed at key locations within buildings to enhance the indoor positioning network through LoRa and UWB ranging. Lastly, dust nodes (DNs) are portable UWB-enabled devices that can be deployed in large numbers to create a dense localization network within the operation area. The software architecture of the Pouect system uses a publish-subscribe MQTT bus for communication between the nodes. It comprises several key services, including input/output services that handle communication with transceivers and sensors, publishing raw data to the MQTT bus. Computation services process these data to generate location estimates, such as altitude measurements, LoRa-based distance calculations, and sensor fusion outputs. Additionally, logging services store data for later analysis and debugging, ensuring all messages are tagged with metadata like timestamps and quality of service. Figure 21: Communication framework for LoRa-2.4 GHz nodes. The Poucet system employs a combination of localization techniques to provide reliable positioning. For long-range localization, the system uses LoRa 868 MHz communication, which can penetrate walls and floors. Beacons deployed outside the buildings serve as reference points, and distances are estimated based on signal attenuation using a weighted attenuation algorithm. For medium-range localization, LoRa 2.4 GHz is used, offering coverage of up to 50 m indoors with distance estimation based on TOF ranging. For short-range, high-precision localization, the system leverages UWB technology. UWB measures the time of flight between trackers and dust nodes or pebbles using a Two-Way Ranging (TWR) protocol, achieving centimeter-level accuracy. Additionally, altimeters are used to measure atmospheric pressure for altitude sensing. The system broadcasts corrections from stationary beacons to ensure consistent and accurate altitude measurements throughout the mission. To integrate data from multiple technologies, the system employs a multi-input sensor fusion algorithm based on the Uncertainty Weighted Localization (UWL) method. This algorithm optimizes position estimates by treating discrepancies between nodes as attractive or repulsive forces. Local optimizations occur within each node, while global optimizations are achieved through data exchanges between nodes, ensuring high reliability and accuracy in the overall positioning system. This hybrid approach allows the Poucet system to deliver reliable and accurate localization in GNSS-denied environments.