# A Comprehensive Review of Indoor Localization Techniques and Applications in Various Sectors
## 1 Introduction  
As the need for consistent indoor localization keeps increasing, researchers are looking at creative and flexible solutions for a variety of uses. Indoor localization is the capacity to precisely locate assets, people, or objects in enclosed environments where signal attenuation and blockage make it difficult to use standard Global Navigation Satellite System (GNSS) technology [1]. Many industries, including emergency response, logistics, healthcare, and industrial operations, view this capacity as critical. Each of these industries has its own set of problems that necessitate the development of specific localization solutions to enhance effectiveness, security, and decision-making [2]. In healthcare, the real-time tracking of patients, medical staff, and critical equipment is enhanced by accurate indoor localization, leading to optimized workflows and improved patient safety [3, 4]. In industrial environments, where efficiency and safety are paramount, assets are tracked, workflows are monitored, and worker safety is ensured by localizationsystems, even in the presence of heavy machinery, metallic obstructions, and dynamic conditions. In the retail and logistics sectors, inventory management is improved, supply chain processes are streamlined, and the customer experience is enhanced through personalized navigation and product tracking, all facilitated by indoor localization [5]. In military and emergency response operations, mission success and personnel safety are critically dependent on indoor localization [6; 7]. Systems that function in GNSS-denied settings, such as urban warfare zones or collapsed buildings, are often required in these environments, where accurate real-time tracking can determine the difference between success and failure. Soldiers, first responders, and assets are tracked in such high stakes situations, improving coordination, decision-making, and overall mission outcomes [8]. Emerging technologies like lightweight, low-power MEMS-based sensors are being developed to provide scalable and affordable indoor localization solutions to fulfill these various demands. The combination of real-time data fusion with AI-driven analytics improves accuracy and flexibility, especially in dynamic and uncertain contexts [9]. However, for these systems to reach their full potential, issues including signal interference, multipath propagation, infrastructure reliance, and data security still need to be resolved. Indoor spaces introduce complexities not found in outdoor environments dominated by GNSS [10]. Factors such as signal attenuation, multipath interference, and non-line-of-sight (NLOS) conditions necessitate the development of robust, hybrid localization systems tailored to specific use cases. As research continues to advance, solutions that combine multiple technologies, such as Bluetooth Low Energy (BLE), Wi-Fi, RFID, ultra-wideband (UWB), and inertial navigation systems (INS), are being explored to overcome these challenges. These innovations promise to provide accurate, secure, and efficient localization solutions across various sectors, transforming operations and paving the way for smarter, safer, and more efficient environments [11]. Indoor localization technologies are revolutionizing healthcare by enabling the precise real-time tracking of patients, medical staff, and critical assets. This capability significantly enhances operational efficiency and patient safety within healthcare facilities. By leveraging technologies such as BLE, Wi-Fi, and advanced localization algorithms, these systems can deliver highly accurate location data even in complex, crowded environments. Machine learning (ML) technology using Wi-Fi data is transforming indoor localization by enabling precise and efficient position estimation [12; 13]. For example, BLE-based solutions that utilize iBeacons can achieve an impressive localization accuracy within 12 cm, which helps optimize workflows and reduce delays in busy hospital settings.