Review of Positioning Technologies and Antenna Designs for Indoor, Outdoor, and Wearable Applications

This paper presents a systematic review of positioning technologies and antenna designs for indoor and outdoor applications. The indoor positioning analysis focuses on RF-based systems including Bluetooth Low Energy (BLE), ultra-wideband (UWB), Wi-Fi, and ZigBee, examining their operational principles, measurement techniques (e.g., RSSI, ToA, AoA), and implementation challenges. For outdoor environments, the review covers Global Navigation Satellite Systems (GNSS) including GPS, GLONASS, Galileo, and BeiDou, alongside regional navigation satellite systems (RNSS) including NavIC, QZSS, detailing their constellation architectures, frequency bands, signal bandwidths, and positioning methods (e.g., SPP, DGNSS, RTK, PPP). A comprehensive evaluation of antenna technologies addresses conventional designs (e.g., survey grade choke ring, cavity-backed annular slots, microstrip patches) and wearable implementations (e.g., textile-based, flexible substrates), emphasizing multipath mitigation, miniaturization, and body interaction effects. The work highlights the critical relationship between positioning system performance and antenna characteristics, including radiation patterns, gain, polarization and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SAR</i>. By integrating these technical aspects, this review serves as a unified reference for state-of-the-art localization systems and their associated antennas, highlighting practical implementation constraints across different operational environments. A general guideline is provided for future works in the field of flexible wearable antennas to maintain higher efficiency of operation with reliable characteristics to suit positioning applications.