Two-way ranging with carrier frequency and phase offset compensation based on software defined radio

Abstract

In the context of Two-Way Ranging (TWR)measurements, distinct transmitter and receiver devices lead to discrepancies in clock timing, resulting in a Carrier Frequency Offset (CFO) and Carrier Phase Offset (CPO) that diminish the accuracy of distance measurements. Furthermore, moving objects also exacerbate these issues, increasing measurement errors. The effect of the CFO leads to variations and bit value inversion in the code in one frame when measuring two-way ranging distances with N random number sequence. In order to resolve this issue, the Fast Fourier Transform (FFT) is used in this work to determine the CFO and peak cross-correlation for the searching CPO. In outdoor experiments using Software Defined Radio (SDR) conducted over a maximum distance of 80 m, it was found that the precision of measurements was accurate within 1.25 m, and the overall accuracy was within 0.82 m when the Signal-to-Noise Ratio (SNR) was greater than 5 dB.