Patent ID: 7617440
Filing Date: 2009-11-10
Classification: H03M

Abstract:
1. A Viterbi decoder comprising: a cascade block including serially connected add-compare-select unit and transpose units that outputs two state metrics at a time, a cascade block T counter generating a plurality of counter signals that count sets of cascade outputs from 0 to 2 a best state register storing and outputting a best state value; a first comparator comparing a first state metric with the best state value generating a first comparison signal if the first state metric is greater than the best state value; a second comparator comparing a second state metric with the best state register value generating a second comparison signal if the second state metric is greater than the best state value; a first multiplexer having a first input receiving the first state metric, a second input receiving the second state metric, a third input receiving the best state value signals, a first control input receiving the first comparison signal, a second control input receiving the second comparison signal and an output supplying a selected one of the first state metric, the second state metric of the best state value dependent upon the state of the first comparison signal and the state of the second comparison signal; a second multiplexer having a number of inputs equal to twice a number of add-compare-select units in said cascade unit each receiving k−1 combinations of T counter signals, having a first input receiving said indication of a last active add-compare-select unit, a second control input receiving the first comparison signal, a third control input receiving the second comparison signal and an output supplying a selected one of said k−1 combinations of T counter signals dependent upon said indication of a last active add-compare-select unit, the state of the first comparison signal and the state of the second comparison signal; and a best state index register having an input connected to said output of said second multiplexer for storing one of said k−1 combinations of T counter signals.