A method for determining a transmission rate from the growth of a path metrics in a viterbi decoder and apparatus for this purpose,

摘要

A method in accordance with this invention includes the steps of (a) decoding a received signal and determining, for individual ones of n data rates, a value of a total cumulative metric associated with a most likely path through a decoder trellis; (b) comparing the value of the total cumulative metric to a plurality of total cumulative metric threshold values, individual ones of the plurality of total cumulative metric threshold values corresponding to an expected total cumulative metric for an individual one of the n data rates and being one of fixed or adaptively determined; and (c) identifying the received data rate based on the comparison. The step of determining a total cumulative metric includes the steps of (a) processing branch metrics to determine survivor metrics; (b) normalizing individual ones of the survivor metrics to form normalized survivor metrics; (c) accumulating the normalized survivor metrics to form cumulative metrics; (d) accumulating normalization values used to normalize each of the normalized survivor metrics; (e) at the end of decoding, outputting a cumulative metric that corresponds to a most likely path through the trellis; and (f) combining an accumulated normalization value with the outputted cumulative metric to form the total cumulative metric.