Local Accuracy Analysis of FSK-Based Joint Radar and Communications

This paper analyses the suitability of a frequency shift keying (FSK) based waveform for joint communications and radar applications. Since the communications performance of FSK signalling is well known, our analysis mainly focuses on radar estimation accuracy. More specifically, the Cramer-Rao lower bounds on delay and Doppler shift estimation error variances are derived based on the root mean square (RMS) time duration and the RMS bandwidth of the waveform. Importantly, we show that the RMS time duration of the proposed waveform is invariant to the frequency sequence used, which indicates a stable Doppler shift estimation performance. The delay estimation capability of the waveform is illustrated through the derivation of an approximation of the RMS bandwidth and its distribution. Numerical results are provided to compare the performance of the proposed waveform with state-of-the-art methods and illustrate the accuracy of the derived approximations.