Precise Phase-Based Ranging and Motion Detection for IoT By Reusing OFDM Data Subcarriers

This paper investigates a precise ranging technique for IoT able to employ an extensive number of phases extracted from OFDM subcarriers including both pilot and data subcarri-ers. The authors focus on laying out an analytical framework backed up by experiment. The work is based on a bi-static or multi-static setup in the fashion of integrated sensing and communication (ISAC). The optimal range estimation rule and capability of micro motion monitoring are addressed. An optimal subcarrier selection method along with quantitative assessment of range ambiguity is provided. In particular, a decision-feedback phase extraction technique is introduced in order to make use of data subcarriers in addition to the pilot subcarriers. Phase noise characteristics measured on software defined radios (SDRs) are reported, confirming that the phase noise can be roughly viewed as an iid wide-sense stationary (WSS) Gaussian random process. Sensitivity of motion detection and estimation as well as range ambiguity assessment results measured in both norm of phase difference and pairwise error probability are provided.