Abstract: A method of estimating a digitized data signal transmitted as a sequence of data symbols. The received signal is generally distorted by transmission through a dispersive communications channel. The received symbols can exist in a plurality of different states depending on the number of symbols in the data alphabet and the extent of intersymbol interference. In the present method a near-instaneous soft decision is made (without the need for memory storage) for each estimated symbol using the following main steps. 1) Determine for each state at a given time increment k the respective partial path metric (M.sub.A) in respect of the state transition corresponding to the transmission of a first symbol type (A). 2) Determine for each state at the same time increment k the respective partial path metric (M.sub.B) in respect of the state transition corresponding to the transmission of a second symbol type (B). 3) Select the maximum value (M.sub.Amax and M.sub.

Abstract: A radio receiver includes apparatus for correcting phase and frequency offsets in a digitally modulated carrier signal. The receiver includes processing circuitry which outputs a baseband signal at point. The circuitry includes a local oscillator generating a signal intended to have a phase and frequency related (e.g. substantially equal) to the carrier signal. The baseband signal from the circuitry is input to a demodulator which generates a signal in the form of a sequence of digits corresponding to the original carrier signal. The baseband signal is sampled by a sampler and the demodulated signal is sampled by a sampler. Processing circuitry calculates the correlation function of the two sample signals and determines the value of the phase .PHI..sub.x at a time when the correlation function is a maximum. A control signal V.sub.c indicative of the phase .PHI..sub.