matlab-generate-gnss-waveform

What it does

Generate multi-satellite GNSS baseband waveforms with properly encoded navigation data. Channel impairments (Doppler, delay, noise) can come from a realistic satellite scenario OR from user-specified custom values. Supports GPS, Galileo, and NavIC constellations. The waveform carries real ephemeris so a receiver can decode it for position estimation.

How it works

Follows a 6-step workflow:

• Step 0: Determine signal type, channel mode, and data source. Choose scenario-driven or custom values for Doppler/delay/SNR and select data source (RINEX or almanac) accordingly. Print a standalone configuration summary before code execution.
• Step 1: Configure waveform generator per constellation (gpsWaveformGenerator, galileoWaveformGenerator) with specified sample rate, center frequency, and bit duration. Validate stepTime against known values per constellation.
• Step 2: Set up satelliteScenario if in SCENARIO MODE. Create ground station, define wave duration, and add satellites using GPS Galile o/NavIC-specific methods. Use almanac by default unless RINEX is provided.
• Step 3: Compute channel parameters from physics (scenario mode) or skip to Step 3c in custom mode. Calculate dopShifts, ltncy, and snrs based on a link budget; verify visible satellites are present.
• Step 3c: In CUSTOM MODE, accept user-provided Doppler, delay, and/or SNR. Expand static values to a time-varying matrix if needed.
• Step 4: Encode navigation data. For real ephemeris, use the same data source as the scenario; for dummy data, generate random bits. When RINEX was used for orbit propagation, use matching RINEX-based nav encoding helpers. Constellation-specific nav data encoding patterns are invoked (GPS Almanac or RINEX, Galileo mappings, NavIC RINEX, etc.).
• Step 5: Generate waveform with channel. Both SCENARIO and CUSTOM modes converge here: configure HelperGNSSChannel with per-satellite Doppler, delay, and SNR; iterate over time steps to produce the waveform, updating channel parameters per step. NavIC uses a separate path with its own helpers. Verify waveform length and non-zero content.

When to use it

• For generating GNSS baseband signals (GPS, Galileo, NavIC) for receiver testing
• For simulating multi-satellite channels with Doppler and delay from orbital dynamics
• For testing with specific Doppler/delay/SNR values (custom channel mode)
• For end-to-end GNSS receiver simulations needing decodable navigation data

What it can touch

• gpsWaveformGenerator
• galileoWaveformGenerator
• satelliteScenario
• HelperAddGalileoSatellitesToScenario
• rinexread (when using RINEX paths)
• HelperGPSAlmanac2Config, HelperGPSNAVDataEncode, HelperGalileoNavigationData, HelperGPSRINEX2Config, HelperGNSSChannel, and related constellation-specific helpers
• NavIC-specific helpers (HelperNavICBBWaveform, HelperNavICRINEX2Config, HelperNavICRINEX2Config)

Caveats

• Compatibility requires >=R2026a. License information is listed as NOASSERTION.
• Not suited for signal acquisition, tracking loops, navigation decoding, or position estimation in some configurations (per the When NOT to Use guidance).
• NavIC handling differs between L5/S/L1 and may require RINEX toolbox availability. RINEX-based workflows rely on corresponding Navigation Toolbox presence.
• Before code generation, a standalone configuration summary must be printed and confirmed in interactive mode.