Partially-parrallel trellis decoder apparatus and method

A method for decoding an encoded signal received over a communication channel comprising the steps of:

• constructing a maximum likelihood sequence estimation trellis from the encoded signal;
• determining from the encoded signal at least a first state information set corresponding to a first state metric, a second state information set corresponding to a second state metric, and a third state information set corresponding to a third state metric;
• updating a primary communication channel estimate using the first state information set and the encoded signal;
• processing the first state information set using the primary communication channel estimate and modifying the trellis;
• updating a secondary communication channel estimate using the second state information set and the encoded signal;
• processing the second state information set using the second communication channel estimate and modifying the trellis;
• processing the third state information set using the primary communication channel estimate and modifying the trellis;
• and
• back-tracing the trellis to construct a maximum likelihood estimated sequence.

A radiotelephone, having a receiver with a digital decoder for decoding a received signal, comprising:

• an s-state trellis decoder, where s is an integer greater than or equal to 3, for computing state information sets and state metrics for state transitions from a time t=(n−1)T to a time t=nT from the received signal;
• a primary adaptive channel estimator, coupled to the s-state trellis decoder, for updating a primary channel estimate using a first state information set and the received signal and for processing the first state information set according to an updated primary channel estimate and for processing a third state information set according to the updated primary channel estimate;
• and
• a secondary adaptive channel estimator, coupled to the s-state trellis decoder, for updating a secondary channel estimate using a second state information set and the received signal and for processing the second state information set according to an updated secondary channel estimate.