Convolutional Encoder and Viterbi Decoder

This project is a fork of https://github.com/xukmin/viterbi that introduces Python support, enabling effortless utilization of the Viterbi module within the Python environment.

Install

pip install viterbi

Usage

The following is a convolutional encoder with a constraint length of 7. The diagram indicates the binary values and polynomial form, indicating the left-most bit is the most-significant-bit (MSB). The generating polynomials are 1011011 and 1111001 can be alternatively expressed in octal as 133 and 171, respectively.

Expressed in code as:

from viterbi import Viterbi
dot11a_codec = Viterbi(7, [0o133, 0o171])

You can use the viterbi decoder like this:

from viterbi import Viterbi

dot11a_codec = Viterbi(7, [0o133, 0o171])
bits = [0, 1, 0, 1, 0, 0, 0, 0, 1, 1, 1, 0]
output = dot11a_codec.encode(bits)
# [0, 0, 1, 1, 0, 1, 0, 0, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1]
dot11a_codec.decode(output)
# [0, 1, 0, 1, 0, 0, 0, 0, 1, 1, 1, 0]

Puncturing

This library also allows you to puncture the original encoded data by specifying a puncture pattern or decode data that has already been punctured.

from viterbi import Viterbi

# Puncture Pattern: [1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 1]
dot11a_codec = Viterbi(7, [0o133, 0o171], [1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 1])

Using in C++

You can find the way to use the Viterbi decoder in C++ in the README of the original project.