Cramér-Rao lower bounds for QAM phase and frequency estimation

Abstract

In this paper, we present the true Cramér-Rao lower bounds (CRLBs) for the estimation of phase offset for common quadrature amplitude modulation (QAM), PSK, and PAM signals in AWGN channels. It is shown that the same analysis also applies to the QAM, PSK, and PAM CRLBs for frequency offset estimation. The ratio of the modulated to the unmodulated CRLBs is derived for all QAM, PSK, and PAM signals and calculated for specific cases of interest. This is useful to determine the limiting performance of synchronization circuits for coherent receivers without the need to simulate particular algorithms. The bounds are compared to the existing true CRLBs for an unmodulated carrier wave (CW), BPSK, an..