LDPC Code Simulation

Requirements

• CMake Version 3.10
• C++17

Getting Started

Building the binary:

$ cmake .
$ cmake --build . --target TARGET

where the target can be the following:

• --target ldpcsim produces an executeable containing the simulator, which is used by e.g. the commandline. See Running the Simulator.

• --target ldpc produces a shared library containing the simulator for external usage. See Python Wrapper.

Running the Simulator

After successful build the simulator can be executed. Note the usage:

$ ./ldpcsim --help
Usage: ldpc [options] codefile output-file snr-range 

Positional arguments:
codefile                LDPC parity-check matrix file containing all non-zero entries.
output-file             Results output file.
snr-range               {MIN} {MAX} {STEP}

Optional arguments:
-h --help               shows help message and exits
-v --version            prints version information and exits
-G --gen-matrix         Generator matrix file.
-i --num-iterations     Number of iterations for decoding. (Default: 50)
-s --seed               RNG seed. (Default: 0)
-t --num-threads        Number of frames to be decoded in parallel. (Default: 1)
--channel               Specifies channel: "AWGN", "BSC", "BEC" (Default: AWGN)
--decoding              Specifies decoding algorithm: "BP", "BP_MS" (Default: BP)
--max-frames            Limit number of decoded frames.
--frame-error-count     Maximum frame errors for given simulation point.
--no-early-term         Disable early termination for decoding.

Code File Format

The code file lists the the non-zero entries of the matrix line-by-line, where the left number refers to the row index and the right to the column index. For example, the matrix

0 0 1 0
0 1 0 0
0 0 0 1
1 1 1 0

is represented as

0 2
1 1
2 3
3 0
3 1
3 2

Optionally, a puncturing (or shortening) patter may be specified a the top of the file:

Puncture 2 bits associated with column index 1 and 3

puncture [2]: 1 3 

A sample k=128, n=1024 LDPC code with parity-check matrix h.txt and generator matrix g.txt can be found in tests/code/.

Python Wrapper

The simulator may be used as Python Module in a threaded application.

from pyLDPC import ldpc

# initialize with codefile & simfile
code = ldpc.LDPC("doc/exmp_code.txt")

# simulate AWGN with 100 iters and MinSum decoding
code.simulate(snr=[0, 6, 0.2], iterations=100, decoding="BP_MS")

# stop the simulation
code.stop_simulation()

# retrieve the results
print(code.get_results())

Contributing

If you found a bug or have any suggestions or improvements, feel free to start a discussion or submit a PR!