We propose to develop new non-data aided (NDA) digital feedforward symbol timing estimators for linear and nonlinear modulations, with a view to reducing the sampling rate of the estimators. The proposed estimators relyon the fact that sufficient statistics exist for a signal sampled at the Nyquistrate. We propose an ad hoc extension to the timing estimator based on the log nonlinearity which performs better than existing estimators at thisrate when the operating signal-to-noise ratio (SNR) and the excess bandwidthare low. We propose another alternative estimator for operating at the Nyquist rate that has reduced self-noise at high SNR for large rolloff factors. Thiscan be viewed as an extension of the timing estimator based on the square law nonlinearity. For continuous phase modulations (CPM), we propose two novel estimators that can operate at the symbol rate for MSK type signals. Among the class of NDA feedforward timing estimators we are not aware of any other estimator that can function at symbol rate for this type of signals. We also propose several new estimatorsfor the MSK modulation scheme which operate with reduced sampling rate and are robust to carrier frequency offset and phase offset.
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