galileo/README.md

Galileo receiver baseband model

This repository is a modular Python reference model for a Galileo receiver baseband and a starting point for bit-true/RTL verification. It currently implements E1B data and E1C pilot processing with a BOC(1,1) local replica, streaming real-IF or complex-IQ front ends, FFT PCPS acquisition, independent tracking channels, fixed-point boundary models, and hardware sizing models. The floating reference uses numpy.float64/numpy.complex128 throughout; single-precision formats are accepted only when explicitly reading legacy files.

The repository intentionally contains no fabricated Galileo PRN sequences. SyntheticCodeProvider creates deterministic non-ICD codes for closed-loop verification. These codes cannot receive a live Galileo signal. Validated official tables can be installed under data/ and loaded through FileCodeProvider without changing acquisition or tracking APIs.

An external globsky/SignalSim checkout is now validated as a second code and sample source. SignalSimCodeProvider parses that checkout at run time without copying its tables. The installed commit generates combined E1B/E1C BOC(1,1) complex IQ; both acquisition and tracking pass on its IQ8 output. See the measured SignalSim integration report.

Status and limitations

• E1 profile: 1.023 Mcps, 4092 chips, 4 ms, 1575.42 MHz.
• BOC(1,1) is implemented; CBOC and unambiguous BOC are API extension points.
• E1B bit-transition hypotheses and E1C secondary wipeoff/search are available for acquisition. E1C tracking supports known-phase wipeoff.
• The code-table provider, not the DSP engine, determines whether codes are synthetic or official.
• The floating-point model is executable. The fixed PCPS model is bit-true at I/O, FFT output, product, power, and accumulator boundaries; an FFT vendor/butterfly schedule must be selected before claiming bit identity with a particular RTL FFT core.
• Channel impairments include Doppler rate, sampling-clock offset, carrier offset, AWGN, clipping, and quantization. Multipath, jerk, oscillator phase noise, and interference are future channel-model plug-ins.
• Combined E1B/E1C tracking is represented by separate manager channels; a weighted combining policy is intentionally not assumed.

Install and test

Python 3.11 or newer is required.

python -m pip install -e '.[test]'
python -m pytest

All automated tests use deterministic seeds and run headlessly. Plots import Matplotlib only when explicitly requested.

Configuration and CLI

YAML keys map to strict dataclasses in galileo_rx.config; unknown keys and unsafe long integrations raise descriptive errors. Physical quantities carry unit suffixes. See configuration details.

python -m galileo_rx.cli generate --config configs/acquisition_example.yaml --output samples.bin
python -m galileo_rx.cli acquire --config configs/acquisition_example.yaml --input samples.bin --output acquisition.json
python -m galileo_rx.cli track --config configs/tracking_example.yaml --input samples.bin --acquisition-result acquisition.json --output tracking.csv
python -m galileo_rx.cli run --config configs/acquisition_example.yaml --input samples.bin
python -m galileo_rx.cli compare-fixed --config configs/acquisition_example.yaml --input samples.bin
python -m galileo_rx.cli validate-signalsim --signalsim-path signalsim/SignalSim --config configs/signalsim_validation.yaml --output-dir reports/signalsim_validation

The CLI uses synthetic codes by design. Replace the provider with FileCodeProvider after installing independently validated tables for live signal work.

validate-signalsim is the exception: it explicitly uses the detected external SignalSim table and IQ conventions and writes quantitative JSON/Markdown/plot artifacts. Its quick regression is:

MPLBACKEND=Agg pytest -m signalsim -v

Runnable source examples are in examples/:

python examples/generate_e1_signal.py
python examples/run_acquisition.py
python examples/run_tracking.py
python examples/run_complete_receiver.py

Architecture

The generic acquisition and tracking engines depend on SignalProfile and CodeProvider, not E1 constants. Adding E5a/E5b therefore means defining a profile, modulation replica, and validated code provider; engine interfaces do not change.

sample source -> streaming front end -> sample buffer -> PCPS acquisition
                                            |                 |
                                            +---- tracking manager
                                                  +-- E1B channel
                                                  +-- E1C channel

float blocks <-> fixed block boundaries <-> cycle transactions <-> RTL

The floating algorithms and equations are in algorithms.md, fixed-point assumptions and starting widths in fixed_point_plan.md, and the two acquisition plus two tracking hardware options in rtl_mapping.md. The module-level contract is duplicated close to the code in src/galileo_rx/rtl_model/architecture.md.

Exact phase-gate test and example commands are recorded in development_phases.md.

Phase completion record

1. Profiles, typed configuration, code providers, BOC, generator, and I/O.
2. Streaming front end, FFT PCPS, detector metrics, long integration, plots.
3. Stateful EPL/VEVL tracking, FLL/PLL/DLL, locks, C/N0.
4. Multi-channel manager and separate E1B/E1C handling.
5. Fixed formats, NCO, mixer/correlator, PCPS boundary model, comparison/sweep.
6. Cycle transaction types, scheduler/resource equations, RTL documentation.

Assumptions and unresolved implementation choices are called out in the linked documents rather than hidden in constants.