Can FSK Be Optimised for Integrated Sensing and Communications?

TL;DR

This paper explores optimizing frequency shift keying (FSK) waveforms for joint radar and communication systems by designing initial phases to minimize sidelobe levels, enhancing radar sensing without compromising data rate or complexity.

Contribution

It introduces a min-max optimization approach for phase design in FSK waveforms, significantly reducing ambiguity function sidelobes while maintaining communication performance.

Findings

Optimized phase design reduces AF PSL to levels comparable with specialized radar waveforms.

The optimization has negligible impact on data rate and receiver complexity.

Error probability remains unaffected for large sub-pulse numbers and modulation orders.

Abstract

Motivated by the ideal peak-to-average-power ratio and radar sensing capability of traditional frequency-coded radar waveforms, this paper considers the frequency shift keying (FSK) based waveform for joint communications and radar (JCR). An analysis of the probability distributions of its ambiguity function (AF) sidelobe levels (SLs) and peak sidelobe level (PSL) is conducted to study the radar sensing capability of random FSK. Numerical results show that the independent frequency modulation introduces uncontrollable AF PSLs. In order to address this problem, the initial phases of waveform sub-pulses are designed by solving a min-max optimisation problem. Numerical results indicate that the optimisation-based phase design can effectively reduce the AF PSL to a level close to well-designed radar waveforms while having no impact on the data rate and the receiver complexity. For large numbers of waveform sub-pulses and modulation orders, the impact on the error probability is also insignificant.