A multi-language DSP modem implementation and validation suite covering QPSK modulation, RRC filtering, channel modeling, synchronization, and forward error correction.

cd python
pip install -r requirements.txt
pytest tests/

cd cpp
cmake -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build
ctest --test-dir build

python tools/generate_vectors.py --modulation qpsk --snr 10 --out test_vectors/

This project is the foundation of an upcoming book that walks through building this entire DSP modem system from scratch — no black boxes, no hand-waving.

The book covers every layer of the stack:

• Signal theory — complex baseband, Nyquist criteria, spectral shaping
• Modulation — Gray-coded QPSK, 8-PSK, and 16-QAM symbol mapping
• Pulse shaping — root-raised cosine filter design and matched filtering
• Channel modeling — AWGN, phase noise, and frequency offset impairments
• Synchronization — timing recovery (Mueller-Müller, Gardner) and carrier phase lock (Costas loop)
• Error correction — forward error correction fundamentals and BER validation
• Multi-language implementation — the same algorithms built in Python, MATLAB/Octave, C++, and C for embedded targets
• Verification methodology — test vectors, golden references, and cross-language comparison

The goal is that a reader can follow along and reproduce every result in this repository, understanding not just how each block works but why it is designed that way.

Stay tuned — updates will be tracked in docs/.

• QPSK (primary target)
• 8-PSK, 16-QAM (planned)

• Gray-coded symbol mapping
• Root-raised cosine (RRC) matched filtering
• AWGN / phase noise / frequency offset channel models
• Mueller-Müller and Gardner timing error detectors
• Costas loop carrier phase recovery
• BER vs Eb/N0 validation against theory