Experimental Demonstration of Joint Sensing and Communications Using Spectrally Efficient High-Accuracy Range Estimation

We propose a novel approach to joint sensing and communications based on the use of spectrally sparse sensing waveforms combined with standard communications signals. Efficient spectrum utilization in wireless networks is becoming more important as the number of wireless systems increases dramatically, leading to challenges in sensing the environment without impacting communication throughput. Our approach is based on the use of a spectrally efficient sensing waveform that provides near-optimal ranging accuracy while occupying a very small spectral footprint. The sensing waveform consists of two discrete tones, the separation of which, along with the signal-to-noise ratio, determines the ranging accuracy. The spectral space between the two tones is not utilized for sensing and can thus be occupied with communications data, with negligible impact on data throughput or sensing accuracy. We implement a 40-MHz binary phase shift keyed (BPSK) waveform with ranging tones placed at
$\pm$
80 MHz, in the second nulls of the data spectrum, at a carrier frequency of 4 GHz using an arbitrary waveform generator. We demonstrate the ability to track the motion of a walking person in an indoor environment and the locations of two people in an outdoor environment. Measured range standard deviations were 1.3 mm for a corner reflector in a semi-anechoic chamber and were 12 and 15 mm for the two-person outdoor case.