OFDM-Based Joint Communication and Ranging with Improved Accuracy Under Signal Bandwidth Constraints by Ideal Sinc Interpolation: Cramer-Rao Lower Bound and 60 GHz Over-the-Air Validation

Joint communication and sensing (JCAS) integrates communication and sensing into the same system. As orthogonal frequency division multiplexing (OFDM) remains the standard in 5G and beyond, communication-centric JCAS is a critical technology. We propose OFDM-based joint communication and ranging that improves delay estimation accuracy under signal bandwidth constraints for channels with a dominant path, using ideal sinc interpolation achieved by frequency-domain zeropadding. The Cramer-Rao Lower Bound (CRLB) is derived for the variance of delay estimation in zero-mean additive white Gaussian noise (AWGN) channels. An over-the-air (OTA) 60 GHz testbed was built with carrier frequency offset (CFO) calibration. We demonstrate sub-ns delay estimation, leading to decimeterlevel ranging accuracy, and the measured standard deviation of repeated delay estimations are shown to approach the CRLB benchmark. The proposed method leverages fast Fourier transform (FFT) for efficient computations and proves effective for well-controlled industrial settings like liquid level detection and structural displacement measurements.