Time-Synchronized Joint Communication and Precise Wireless Localization of Multiple on-Body Sensor Nodes for Human Gait and Movement Measurement

For the analysis of human motion, multisensory approaches combining inertial sensors, electromyography, and optical or wireless positioning systems capable of determining absolute positions can provide significant advantages. Radio location systems offer the inherent advantage of simultaneously using their measurement signals for data transmission. However, conventional time-based radio location systems, such as ultra-wideband, face challenges in collecting data from many on-body sensor nodes with precise time synchronization due to protocol complexity and time-division requirements. This paper introduces a novel wireless positioning approach that overcomes these limitations. The method relies exclusively on the phase information of radio fields emitted by body-mounted wireless sensor beacons, which are already used for data transmission. These phase holograms transmitted by the beacons are recorded and analyzed using the Holographic Extended Kalman Filter. The localization algorithm directly evaluates phase differences between spatially distributed base station antennas, making narrowband radio signals sufficient for precise localization. Frequency division multiplexing enables multiple narrowband beacons to transmit data concurrently with perfect time synchronization while their positions are determined with high precision. An experimental system validated the approach, demonstrating time-synchronized localization and simultaneous on-body sensor data collection and transmission. This advancement supports real-time sensory applications, particularly in medical human motion assessment.