US 5,970,104 A · Method and apparatus for generating branch metrics and branch indices for convolutional code Viterbi decoders

Abstract

A Viterbi decoder generates a branch metric table from first and second data signals taken at two sample times and provides selected branch metrics to an add/compare/select circuit in response to branch indices from a branch index generator. The branch metrics in the branch metric table are the sixteen combinations of the sum of the first and second parallel data signals at first and second sample times and the inverse of such signals. The branch index generator generates the branch indices in response to a received state from the add/compare/select circuit, convolutional code polynomials and the possible states of a radix-4 trellis. The add/compare/select generates a survivor path decision based on the selected branch metrics.

Claims7

Dependent claims

A method for generating branch metric indices for Viterbi decoding, the method comprising:

generating states of an encoder at selected first and second times;
generating branch indices and generator polynomials in response to the states of the encoder at each of the first and second times;
generating first and second parallel data signals in response to data received at the selected first and second times, respectively;
generating a branch metric in response to the branch indices by:
generating a branch metric table, including table elements representing a sum of the first and second parallel data signals and the inverses of the first and second data signals;
and
retrieving from the branch table a branch metric corresponding to at least one generated branch metric.

4 more elements

A Viterbi decoder comprising:

a branch index generator for generating a plurality of branch indices, each branch index corresponding to a branch transitions between a first plurality of states and a second plurality of states indicative of received data and to convolutional code polynomials;
a branch metric table for receiving and storing branch metrics indicative of received data at selected first and second times, the branch metric table including sixteen elements, with each element corresponding to combinations of a sum of (i) the first and second parallel data signals at the first and second times and (ii) inverses of the first and second parallel data signals at the first and second times;
and
a selection circuit coupled to the branch metric table for selecting, for each one of the first plurality of states, a corresponding one of the second plurality of states in response to the branch indices corresponding to the each one of the first plurality of states.

1 more element

Dependencies are inferred from the claim text.

Method and apparatus for generating branch metrics and branch indices for convolutional code Viterbi decoders

Life of this patent

Method and apparatus for generating branch metrics and branch indices for convolutional code Viterbi decoders

Life of this patent

Abstract

Claims7