DSP Contracts

DSP contracts in bijux-gnss-signal are runtime-neutral promises. They may be used by receiver stages, commands, validation helpers, and test fixtures, but they do not decide receiver scheduling, artifact policy, or navigation solver meaning.

Public DSP Map

module	contract	first proof
front_end	FIR front-end specification and response measurement	front-end source
quality	I/Q metrics, noise-floor estimation, DC-offset handling	quality source
local_code, sample_timing, signal	code phase, samples-per-code, wrapping, carrier wipeoff, sample-index timing	local-code, sample-timing, and signal source
nco	oscillator state and phase progression	NCO source
replica	acquisition signal models, code models, carrier trajectories, synthetic modulation	replica source
spectrum	PSD estimation, expected spectra, transfer application, null finding	spectrum source
tracking	correlators, DLL/FLL/PLL helpers, discriminators, lock thresholds, CN0, tracking uncertainty	tracking DSP source

Contract Flow

flowchart TD
    samples["samples and raw-IQ metadata"]
    timing["timing and code phase"]
    replica["local replica and carrier"]
    correlation["correlation and loop helpers"]
    quality["quality, CN0, uncertainty"]
    receiver["receiver stages consume results"]

    samples --> timing --> replica --> correlation --> quality --> receiver

What Callers May Rely On

• DSP types and helpers are reusable without a Receiver or command runtime.
• Long-duration timing, phase wrapping, and code-phase behavior must remain deterministic across chunk boundaries.
• Front-end and spectrum helpers report signal quality without deciding what a receiver should do with that quality.
• Tracking helpers expose reusable math; the receiver decides channel lifecycle, state names, reacquisition policy, and emitted artifacts.

What Callers Must Not Assume

• That internal helpers in dsp/math.rs are public promises just because receiver code happens to call nearby DSP modules.
• A DSP threshold is automatically a receiver lock policy.
• Replica generation owns synthetic scenario truth; receiver simulation owns scenario execution and truth artifacts.
• Signal-layer observation validation replaces core record meaning or receiver-side observation artifacts.

First Proof Check

Inspect the DSP guide, DSP source, and the focused signal integration tests for long-duration NCO phase, replica continuity, CBOC spectrum behavior, and local-code continuity.

If a downstream receiver test changes because a DSP primitive changed, update the signal proof first, then update receiver expectations only when the runtime handoff changed too.