1. A method of decoding a current symbol of a digital information sequence for a first time, comprising: processing, for a first time, a current symbol of the digital information sequence simultaneously at each of a decoder and an estimator, wherein: the decoder is coupled to the estimator; and the processing comprises: obtaining, at the decoder, an estimate of a previously processed symbol of the digital information sequence from the estimator; selecting, at the decoder, a subset of branches in a first state-based diagram based on the estimate of the previously processed symbol; calculating branch metrics corresponding to the subset of branches in the first state-based diagram; and decoding, at the decoder, the current symbol of the digital information sequence based on the calculated branch metrics, wherein the decoding occurs while the estimator processes the current symbol for the first time.