iLPS: Local Positioning System with Simultaneous Localization and Wireless Communication

Abstract

This paper presents a novel RF local positioning system, iLPS, specifically designed for challenging indoor non-lineof-sight (NLOS) scenarios and/or urban canyons where global positioning systems (GPS) fail to reliably operate. iLPS enables decimeter-level localization of numerous tags concurrently with wireless communication using frequency-shifting active reflector anchors and orthogonal frequency division multiple access (OFDMA) waveforms. OFDMA signals are devised with carefully assigned subcarriers so that each tag can estimate the time-difference-of-arrival (TDoA) by analyzing the channel impulse response (CIR) from the main and reflector anchors without interfering each other. The proposed active reflection scheme efficiently eliminates the stringent time synchronization requirement while providing the diversity gain for enhanced information decoding reliability at the tag. Significant challenges from NLOS multipaths and the usage of relatively narrow bandwidth of 80MHz in the ISM-band are successfully mitigated by machine learning assisted algorithms. Field trials with the prototype system on Universal Software Radio Peripheral (USRP) confirm that iLPS can achieve decimeter-level accuracy localization and concurrent wireless communication over up to 100m distances.