DFT-BASED FREQUENCY OFFSET ESTIMATORS FOR 16-APSK

Abstract

In this paper, we analyze several DFT-based frequency offset estimators for use with the 16-APSK digital modulation scheme. Even a small frequency offset between radio transmitters and receivers can cause phase information to be lost, so a system to align the phases is required to reliably demodulate PSK signals. These estimators have been adapted for 16-APSK from methods originally intended for use with QPSK and CPM. These methods consist of a coarse search and a fine search with an optional dichotomous search to improve accuracy. We analyze the estimator error variance and bit error rate associated with several methods of frequency estimation. These estimators exhibit small estimate error and variance and can provide bit error rates close to the ideal AWGN BER.