Viterbi decoder

A Viterbi decoder requires two functions at declaration time.

There are hard decision and soft decision Viterbi decoders.

Viterbi decoders tend to produce errors in short bursts.

There are both hardware (in modems) and software implementations of a Viterbi decoder.

The Hamming distance is used as a metric for hard decision Viterbi decoders.

They are particularly suitable for implementation in hardware, and the Viterbi decoder allows optimal decoding.

A soft decision Viterbi decoder receives a bitstream containing information about the reliability of each received symbol.

A hardware Viterbi decoder for basic (not punctured) code usually consists of the following major blocks:

The Viterbi decoder at the receiving end accepts input from the Spread Time convolver.

Typically, the frame is decoded at each possible rate, and using the quality metrics of the Viterbi decoder, the correct result is chosen.

GPL Viterbi decoder software for four standard codes.

A hard decision Viterbi decoder receives a simple bitstream on its input, and a Hamming distance is used as a metric.

Soft-decision decoders are often used in Viterbi decoders and turbo code decoders.

The Viterbi decoder implements a soft-decision algorithm to demodulate digital data from an analog signal corrupted by noise.

The CTF is also used to weigh the reliability of the demapped data when they are provided to the Viterbi decoder.

Online Generator of optimized software Viterbi decoders (GPL).

Generic Viterbi decoder hardware (GPL).

Extrinsic information output with optional scaling and limiting Free simulation software Viterbi Decoder (Optional)

A Viterbi decoder uses the Viterbi algorithm for decoding a bitstream that has been encoded using forward error correction based on a convolutional code.

An optional BPSK variable rate demodulator and Viterbi decoder module is also available for this rack to allow reception of SPOT4 vegetation data.

Since this separates the symbols in a codeword, it becomes less likely that a burst from the Viterbi decoder disturbs more than one Reed-Solomon symbol in any one codeword.

These include critical demodulation and Forward Error Correction modules such as Fast Fourier Transform, Viterbi Decoder and Reed Solomon Decoder.

For many codes of practical interest, under reasonable noise conditions, the lazy decoder (using Lazy Viterbi algorithm) is much faster than the original Viterbi decoder (using Viterbi algorithm).

For an example of its use once loaded see `src/modules/base/pos.cc' or `src/modules/base/phrasify.cc'. 25.4 Viterbi decoder Another common tool is a Viterbi decoder.

Sometimes it is enough (e.g. if BPSK is used or if other ambiguities are detected by other circuits, such as a Viterbi decoder or a frame synchronizer) and sometimes it isn't.