Skip to main content

Simulate LDPC codes, both encoding and decoding

Project description

License: MIT Build Status - GitHub codecov Sourcery


My implementation of LDPC codes. My notes regarding theory and implementation appears on GitHub Pages:
To install:

pip install sim-ldpc

To run tests simply clone, cd into the cloned repo, and run:

python -m pytest


python -m pytest --cov-report=html

to run also coverage tests, or

python -m pytest  -n auto --cov-report=html

to run tests in parallel (with number of CPU's dictated by machine) to speed up tests.

Verify static typing with

mypy --strict --config-file .mypy.ini .

Included modules

  • Utilities: implementing various utility operations to assist with encoding, decoding and simulations.
  • Encoder: implementing a generator based encoder, and encoders for IEEE802.11 (WiFi) LDPC codes.
  • Decoder: implementing several decoders
    • Log-SPA based BP decoder
    • MS decodcer
    • Gallager bit filpping decoder
    • Weighted bit flipping decoders, several variants
    • Parallel probabilistic bit flipping decoder (PPBF)

Basic Example

import numpy as np
from bitstring import BitArray, Bits
from ldpc.decoder import DecoderWiFi, bsc_llr
from ldpc.encoder import EncoderWiFi
from ldpc.wifi_spec_codes import WiFiSpecCode
from ldpc.utils import QCFile

# create information bearing bits
rng = np.random.default_rng()
info_bits = np.array(Bits(bytes=rng.bytes(41))[:648//2], dtype=np.int_)
# create encoder with frame of 648 bits, and rate 1/2. Possible rates and frame sizes are per the ieee802.11n spec.
enc = EncoderWiFi(WiFiSpecCode.N648_R12)
# encode bits
encoded = enc.encode(info_bits)

# verify validity of codeword
h = enc.h, np.array(encoded)) % 2  # creates an all zero vector as required.

# create a decoder which assumes a probability of p=0.05 for bit flips by the channel
# allow up to 20 iterations for the bp decoder.
p = 0.05
decoder = DecoderWiFi(spec=WiFiSpecCode.N648_R12, max_iter=20, channel_model=bsc_llr(p=p))

# create a corrupted version of encoded codeword with error rate p
corrupted = BitArray(encoded)
no_errors = int(len(corrupted)*p)
error_idx = rng.choice(len(corrupted), size=no_errors, replace=False)
for idx in error_idx:
    corrupted[idx] = not corrupted[idx]
decoded, llr, decode_success, num_of_iterations, syndrome, vnode_validity  = decoder.decode(corrupted)
# Verify correct decoding
print(Bits(decoded) == Bits(encoded))  # true
info = decoder.info_bits(decoded)

# a decoder can also be instantiated without a channel model, in which case llr is expected to be sent for decoding instead of
# hard channel outputs.
channel = bsc_llr(p=p)
channel_llr = channel(np.array(corrupted, dtype=np.int_))
decoder = DecoderWiFi(spec=WiFiSpecCode.N648_R12, max_iter=20)
decoded, llr2, decode_success, num_of_iterations, syndrome, vnode_validity  = decoder.decode(channel_llr)
print(Bits(decoded) == Bits(encoded))  # true
info = decoder.info_bits(decoded)

The example is also included as a jupyter notebook. Note however, that you need to launch the notebook from the correct path for it to be able to access installed packages. To run the notebook:

  1. create a new virtualenv
python3 -m venv ~/.virtualenv/LDPC_env
  1. activate it and install sim-ldpc, and notebook:
source ~/.virtualenv/LDPC_env/bin/activate
pip install sim-ldpc
pip install notebook
  1. run jupyter from within the virtual env for it to have access to all requirements:
  1. run the notebook


Project details

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Source Distribution

sim-ldpc-0.3.5.tar.gz (2.1 MB view hashes)

Uploaded source

Built Distribution

sim_ldpc-0.3.5-py3-none-any.whl (2.3 MB view hashes)

Uploaded py3

Supported by

AWS AWS Cloud computing and Security Sponsor Datadog Datadog Monitoring Fastly Fastly CDN Google Google Download Analytics Microsoft Microsoft PSF Sponsor Pingdom Pingdom Monitoring Sentry Sentry Error logging StatusPage StatusPage Status page