aff3ct-ldpc-decoder

This repository contains a simple CLI LDPC decoder using AFF3CT as a library.

Currently it only supports the CCSDS AR4JA r=1/2 k=1024 code, but it is relatively simple to include support for other codes by obtaining the alist describing the code (for instance with ldpc-toolbox) and ajusting some of the decoder parameters.

This repository is based on the examples in my_project_with_aff3ct.

Building

The first step is to compile AFF3CT into a library.

Get the AFF3CT library:

$ git submodule update --init --recursive

Compile the library on Linux/MacOS/MinGW:

$ cd lib/aff3ct
$ mkdir build
$ cd build
$ cmake .. -G"Unix Makefiles" -DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_FLAGS="-funroll-loops -march=native" -DAFF3CT_COMPILE_EXE="OFF" -DAFF3CT_COMPILE_STATIC_LIB="ON" -DAFF3CT_COMPILE_SHARED_LIB="ON"
$ make -j4

Compile the library on Windows (Visual Studio project)

$ cd lib/aff3ct
$ mkdir build
$ cd build
$ cmake .. -G"Visual Studio 15 2017 Win64" -DCMAKE_CXX_FLAGS="-D_CRT_SECURE_NO_DEPRECATE /EHsc /MP4" -DAFF3CT_COMPILE_EXE="OFF" -DAFF3CT_COMPILE_STATIC_LIB="ON" -DAFF3CT_COMPILE_SHARED_LIB="ON"
$ devenv /build Release aff3ct.sln

Now the AFF3CT library has been built in the lib/aff3ct/build folder.

Copy the cmake configuration files from the AFF3CT build

$ mkdir -p cmake/Modules
$ cp lib/aff3ct/build/lib/cmake/aff3ct-*/* cmake/Modules

Compile the code on Linux/MacOS/MinGW:

$ mkdir build
$ cd build
$ cmake .. -G"Unix Makefiles" -DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_FLAGS="-funroll-loops -march=native"
$ make

Compile the code on Windows (Visual Studio project)

$ mkdir build
$ cd build
$ cmake .. -G"Visual Studio 15 2017 Win64" -DCMAKE_CXX_FLAGS="-D_SCL_SECURE_NO_WARNINGS /EHsc"
$ devenv /build Release my_project.sln

The compiled binary is in build/bin/aff3ct-ldpc-decoder.

Usage

The input file should be a binary file formed by a concatenation of 2048-symbol frames using soft-symbols encoded as float's. Positive symbols represent the bit 1 and negative symbols represent the bit 0. The output file is a binary file formed by a concatenation of 1024-bit frames using hard-symbols. The output is packed as 8 bits per byte, so each output frame is stored as 128 bytes.

The executable needs the path to the alist file describing the LDPC code to run. This can be found in the alists/ directory.

Run as:

./build/bin/aff3ct-ldpc-decoder alists/ccsds_ar4ja_r1_2_k1024.alist input_frames output_frames