Project Name: Viterbi Decoder

Introduction

Viterbi Algorithm has been a legendary decoding algorithm for Convolutional Codes. It was found by Andrew J. Viterbi which was published on his paper "Error Bounds for Convolutional Codes and an Asymptotically Optimum Decoding Algorithm," in IEEE Transactions on Information Theory, Volume IT-13, April 1967. Research and development then increasing to find more better and more eficient code generator for the Convolutional Codes and the architectural implementation of the Viterbi Algorithm.

Viterbi Algorithm is well used to find a maximally-likelihood decoded bits from a convolutional coded transmitted bits which transmission channel is interferenced by heavy noise such as Additive White Noise Gaussian (AWGN). Enough redundancies are added to combat the impairment of the transmission channel. As a result, Viterbi Algorithm could get an amazing low decoded Bit Error Rate (BER) compared to uncoded transmitted bits, showed by its BER to Eb/No graphical property. This performance could be parameterized by the Constraint Length (K) and Code Rate (R) of the Convolutional Encoder. And yes, we have trade offs around speed, area, and power while trying to implement the Viterbi Algorithm in a real hardware (full/semi custom VLSI).

Current Status

• VDK3R1/2 is available on CVS repository. [Very simple, easy to debug, and could be used for initial study of Viterbi Decoder, I hope :-)] (May 2000).

• Finished working on functional & design specifications of VDK7R1/2. Behavioural simulation using is OK. No source is available, as we decide to skip this and moved to decoder with K=9.

• First release for VDK9R1/2, still much work, fix and "flames" needed (February 2001). The source is synthesizable, except for the register (memory) part.

• Branch Metric Generator and Add Compare Select Unit of VDK9R1/2 has been implemented on Xilinx Virtex FPGA XCV 300.

Specifications

VDK3R1/2

• Encoding Rate (R) : 1/2
• Constraint Length (K) : 3
• Generator Polynomials : 7₈ and 5₈
• Big Endian Encoded Input
• Hard Decision

VDK7R1/2

Stopped, moved on to the next specs.

VDK9R1/2

• Encoding Rate (R) : 1/2
• Constraint Length (K) : 9
• Generator Polynomials : 753₈ and 561₈
• Big Endian Encoded Input
• 3 bit quantized Soft Decision

Next Steps

• See each specs page for detailed TODO List.
• Create Link Sections [where was my bookmarks ? :-)]
• Punctured Code (?)
• Documentation.

Documentation

Software & Tools

Author & Maintainer:

• Sarwono Sutikno

• Dian Tresna Nugraha
• M. Zalfany Urfianto
• Chris Curtis
• Xerandy

Mailing list:

• ecc@opencores.org_NOSPAM