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A method of estimating DC offset based solely on the received signal, without using any training information, is presented. This method takes into account the non-Gaussian statistical distribution of the modulated desired signal in order to produce a DC estimate that is more accurate than the conventional sample average of the received signal. Specifically, two iterative algorithms are derived based on the generalized expectation-maximization algorithms for jointly estimating the DC offset, the noise variance, and the parameters that characterize the signal distribution. As an application, we consider the special case where the modulated signal has a constant-envelope characteristic. Using the GSM/EDGE air interface, we demonstrate that the proposed method yields significant reduction in the DC-offset estimation error, which translates into performance gains in receiver sensitivity when used in direct-conversion receivers.