Trait ModulationParams 

pub trait ModulationParams:
    Copy
    + Default
    + 'static {
    const NTONES: u32;
    const BITS_PER_SYMBOL: u32;
    const NSPS: u32;
    const SYMBOL_DT: f32;
    const TONE_SPACING_HZ: f32;
    const GRAY_MAP: &'static [u8];
    const GFSK_BT: f32;
    const GFSK_HMOD: f32;
    const NFFT_PER_SYMBOL_FACTOR: u32;
    const NSTEP_PER_SYMBOL: u32;
    const NDOWN: u32;
    const LLR_SCALE: f32 = 2.83;
    const LLR_NSYM_MAX: u32 = 3;
    const LLR_NSYM_MID: Option<u32> = None;
    const INFO_SCRAMBLE_RVEC: Option<&'static [u8]> = None;
    const SPECTRUM_WINDOW: SpectrumWindow = SpectrumWindow::Rectangular;
}

Baseband modulation parameters (tones, symbol rate, Gray mapping, Gaussian shaping and the tunable DSP ratios the pipeline reads per protocol).

All constants are evaluated at compile time; the trait carries no data so implementors are typically zero-sized types.

Required Associated Constants

const NTONES: u32

Number of FSK tones (M in M-ary FSK).

const BITS_PER_SYMBOL: u32

Information bits carried per modulated symbol (= log2(NTONES)).

const NSPS: u32

Samples per symbol at the 12 kHz pipeline sample rate.

const SYMBOL_DT: f32

Symbol duration in seconds (= NSPS / 12000).

const TONE_SPACING_HZ: f32

Spacing between adjacent tones, in Hz.

const GRAY_MAP: &'static [u8]

Gray-code map: GRAY_MAP[tone_index] returns the NATURAL-bit pattern for that tone. The map covers at least the data alphabet (2^BITS_PER_SYMBOL entries) and at most the full tone set (NTONES entries). Protocols whose sync tones are part of the data alphabet (FT8 / FT4 / FST4 / WSPR) have len() == NTONES == 2^BITS_PER_SYMBOL; protocols that reserve additional sync-only tones (JT9, JT65, Q65) either trim the map to the data alphabet (JT9: 8 entries for 9 tones) or extend it with identity over the sync slots (JT65 / Q65). Pinned by tests/protocol_invariants.rs.

const GFSK_BT: f32

Gaussian bandwidth-time product. FT8 = 2.0, FT4 = 1.0, FST4 ≈ 1.0.

const GFSK_HMOD: f32

Modulation index h — the phase increment per symbol is 2π · h. FT8 and FT4 both use 1.0 (orthogonal tones at 1/T spacing).

const NFFT_PER_SYMBOL_FACTOR: u32

Per-symbol FFT size = NSPS * NFFT_PER_SYMBOL_FACTOR. FT8 = 2 (window is 2·NSPS), FT4 = 4 (window is 4·NSPS) — trade-off between frequency resolution and time localisation.

const NSTEP_PER_SYMBOL: u32

Coarse-sync time-step = NSPS / NSTEP_PER_SYMBOL. FT8 = 4 (quarter-symbol resolution), FT4 = 1 (symbol-granular).

const NDOWN: u32

Downsample decimation factor: baseband rate = 12 000 / NDOWN Hz. FT8 = 60 (→200 Hz), FT4 = 18 (→667 Hz). Proportional to tone spacing.

Provided Associated Constants

const LLR_SCALE: f32 = 2.83

LLR scale factor applied after standard-deviation normalisation. FT8 uses 2.83 (empirical, from WSJT-X ft8b.f90). Different bits-per-symbol counts may shift the optimum — FT4’s 2-bit LLR dynamics are not identical to FT8’s 3-bit case.

const LLR_NSYM_MAX: u32 = 3

Maximum coherent-integration depth for the 3rd LLR variant. compute_llr builds three variants llra/llrb/llrc from nsym ∈ {1, 2, LLR_NSYM_MAX} symbol blocks. WSJT-X uses nsym=1, 2, 4 for FT4 (get_ft4_bitmetrics.f90:69-71); we default to nsym=3 (FT8 path is calibrated to it). FT4 overrides to 4 for an extra ~3 dB SNR boost on stable signals — closes the recall gap on real-WAV recordings. FST4 overrides to 8, matching WSJT-X’s own 1/2/4/8-symbol correlation ladder in get_fst4_bitmetrics.f90 (issue #146 — FST4 had silently been using the uncalibrated FT8 default of 3, never wired to its own bit-metric depth). Any value ≥ 1 works — nt = NTONES^nsym combination hypotheses are computed generically, no per-nsym lookup table — but cost grows exponentially with nsym, so keep it at the WSJT-X-matched depth for the protocol rather than raising it further.

const LLR_NSYM_MID: Option<u32> = None

Optional extra coherent-integration depth strictly between the nsym=2 and nsym=LLR_NSYM_MAX variants, populating LlrSet’s llre slot. None for every protocol whose ladder has no gap (FT8: {1,2,3}; FT4: {1,2,4}) — llre stays empty and costs nothing. FST4 overrides to Some(4): WSJT-X’s get_fst4_bitmetrics.f90 tries all four of nsym ∈ {1,2,4,8} (fst4_decode.f90:429-433), but LLR_NSYM_MAX=8 alone only gives compute_llr_generic two depths + the deepest ({1,2,8}) — nsym=4 would otherwise never run. Diagnostic measurement (issue #146, fst4_diag_nsym4_ladder in tests/fst4_sweep.rs) found a real but modest effect: a standalone nsym=4 pass recovered 4/43 (~9%) of near-threshold FST4-30 AWGN failures and 2/38 (~5%) of FST4-300’s, over and above the existing {1,2,8,d} ladder.

const INFO_SCRAMBLE_RVEC: Option<&'static [u8]> = None

Optional 77-bit pre-LDPC scrambler. WSJT-X applies an FT4-specific scrambler in genft4.f90:64 (msgbits=mod(msgbits+rvec,2)) before computing CRC-14 and running LDPC encode; the receiver removes it after LDPC decode + CRC verify (ft4_decode.f90:430). Without this our decoder converges on a valid codeword whose unscrambled payload is the WSJT-X-transmitted message — but emerges as nonsense because we never undo the XOR.

Default None (FT8 / others don’t scramble); FT4 and FST4 both override to the same 77-element rvec (WSJT-X genfst4.f90:29-31 uses the identical array to genft4.f90’s). Length must be 77 when set.

const SPECTRUM_WINDOW: SpectrumWindow = SpectrumWindow::Rectangular

Window function applied per NSPS-sample chunk in crate::core::sync::compute_spectra before the NFFT1 FFT. Default = SpectrumWindow::Rectangular (preserves FT8’s existing synth-roundtrip behaviour); FT4 overrides to SpectrumWindow::Nuttall4 to match WSJT-X getcandidates4.f90:22 and suppress sidelobe leakage that otherwise inflates the per-bin baseline near strong signals.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors

impl ModulationParams for Fst4s15

const NTONES: u32 = 4

const BITS_PER_SYMBOL: u32 = 2

const NSPS: u32 = 720

const SYMBOL_DT: f32

const TONE_SPACING_HZ: f32

const GRAY_MAP: &'static [u8]

const GFSK_BT: f32 = 2.0

const GFSK_HMOD: f32 = 1.0

const NFFT_PER_SYMBOL_FACTOR: u32 = 2

const NSTEP_PER_SYMBOL: u32 = 2

const NDOWN: u32 = 18

const INFO_SCRAMBLE_RVEC: Option<&'static [u8]>

const LLR_NSYM_MAX: u32 = 8

const LLR_NSYM_MID: Option<u32>

impl ModulationParams for Fst4s30

const NTONES: u32 = 4

const BITS_PER_SYMBOL: u32 = 2

const NSPS: u32 = 1_680

const SYMBOL_DT: f32

const TONE_SPACING_HZ: f32

const GRAY_MAP: &'static [u8]

const GFSK_BT: f32 = 2.0

const GFSK_HMOD: f32 = 1.0

const NFFT_PER_SYMBOL_FACTOR: u32 = 2

const NSTEP_PER_SYMBOL: u32 = 2

const NDOWN: u32 = 42

const INFO_SCRAMBLE_RVEC: Option<&'static [u8]>

const LLR_NSYM_MAX: u32 = 8

const LLR_NSYM_MID: Option<u32>

impl ModulationParams for Fst4s60

const NTONES: u32 = 4

const BITS_PER_SYMBOL: u32 = 2

const NSPS: u32 = 3_888

const SYMBOL_DT: f32

const TONE_SPACING_HZ: f32

const GRAY_MAP: &'static [u8]

const GFSK_BT: f32 = 2.0

const GFSK_HMOD: f32 = 1.0

const NFFT_PER_SYMBOL_FACTOR: u32 = 2

const NSTEP_PER_SYMBOL: u32 = 2

const NDOWN: u32 = 108

const INFO_SCRAMBLE_RVEC: Option<&'static [u8]>

const LLR_NSYM_MAX: u32 = 8

const LLR_NSYM_MID: Option<u32>

impl ModulationParams for Fst4s120

const NTONES: u32 = 4

const BITS_PER_SYMBOL: u32 = 2

const NSPS: u32 = 8_200

const SYMBOL_DT: f32

const TONE_SPACING_HZ: f32

const GRAY_MAP: &'static [u8]

const GFSK_BT: f32 = 2.0

const GFSK_HMOD: f32 = 1.0

const NFFT_PER_SYMBOL_FACTOR: u32 = 2

const NSTEP_PER_SYMBOL: u32 = 2

const NDOWN: u32 = 205

const INFO_SCRAMBLE_RVEC: Option<&'static [u8]>

const LLR_NSYM_MAX: u32 = 8

const LLR_NSYM_MID: Option<u32>

impl ModulationParams for Fst4s300

const NTONES: u32 = 4

const BITS_PER_SYMBOL: u32 = 2

const NSPS: u32 = 21_504

const SYMBOL_DT: f32

const TONE_SPACING_HZ: f32

const GRAY_MAP: &'static [u8]

const GFSK_BT: f32 = 2.0

const GFSK_HMOD: f32 = 1.0

const NFFT_PER_SYMBOL_FACTOR: u32 = 2

const NSTEP_PER_SYMBOL: u32 = 2

const NDOWN: u32 = 512

const INFO_SCRAMBLE_RVEC: Option<&'static [u8]>

const LLR_NSYM_MAX: u32 = 8

const LLR_NSYM_MID: Option<u32>

impl ModulationParams for Ft4

const NTONES: u32 = 4

const BITS_PER_SYMBOL: u32 = 2

const NSPS: u32 = 576

const SYMBOL_DT: f32 = 0.048

const TONE_SPACING_HZ: f32 = 20.833

const GRAY_MAP: &'static [u8]

const GFSK_BT: f32 = 1.0

const GFSK_HMOD: f32 = 1.0

const NFFT_PER_SYMBOL_FACTOR: u32 = 4

const NSTEP_PER_SYMBOL: u32 = 2

const NDOWN: u32 = 18

const SPECTRUM_WINDOW: SpectrumWindow = crate::core::SpectrumWindow::Rectangular

const LLR_NSYM_MAX: u32 = 4

const INFO_SCRAMBLE_RVEC: Option<&'static [u8]>

impl ModulationParams for Ft8

const NTONES: u32

const BITS_PER_SYMBOL: u32 = 3

const NSPS: u32

const SYMBOL_DT: f32 = params::SYMBOL_DT

const TONE_SPACING_HZ: f32 = 6.25

const GRAY_MAP: &'static [u8]

const GFSK_BT: f32 = 2.0

const GFSK_HMOD: f32 = 1.0

const NFFT_PER_SYMBOL_FACTOR: u32 = 2

const NSTEP_PER_SYMBOL: u32 = 4

const NDOWN: u32 = 60

impl ModulationParams for Jt9

const NTONES: u32 = 9

const BITS_PER_SYMBOL: u32 = 3

const NSPS: u32 = 6912

const SYMBOL_DT: f32

const TONE_SPACING_HZ: f32

const GRAY_MAP: &'static [u8]

const GFSK_BT: f32 = 0.0

const GFSK_HMOD: f32 = 1.0

const NFFT_PER_SYMBOL_FACTOR: u32 = 2

const NSTEP_PER_SYMBOL: u32 = 2

const NDOWN: u32 = 8

impl ModulationParams for Jt65

const NTONES: u32 = 66

const BITS_PER_SYMBOL: u32 = 6

const NSPS: u32 = 4460

const SYMBOL_DT: f32

const TONE_SPACING_HZ: f32

const GRAY_MAP: &'static [u8]

const GFSK_BT: f32 = 0.0

const GFSK_HMOD: f32 = 1.0

const NFFT_PER_SYMBOL_FACTOR: u32 = 2

const NSTEP_PER_SYMBOL: u32 = 2

const NDOWN: u32 = 4

impl ModulationParams for Q65a30

const NTONES: u32 = 65

const BITS_PER_SYMBOL: u32 = 6

const NSPS: u32 = 3600

const SYMBOL_DT: f32

const TONE_SPACING_HZ: f32

const GRAY_MAP: &'static [u8]

const GFSK_BT: f32 = 0.0

const GFSK_HMOD: f32 = 1.0

const NFFT_PER_SYMBOL_FACTOR: u32 = 2

const NSTEP_PER_SYMBOL: u32 = 2

const NDOWN: u32 = 3

impl ModulationParams for Q65a60

const NTONES: u32 = 65

const BITS_PER_SYMBOL: u32 = 6

const NSPS: u32 = 7200

const SYMBOL_DT: f32

const TONE_SPACING_HZ: f32

const GRAY_MAP: &'static [u8]

const GFSK_BT: f32 = 0.0

const GFSK_HMOD: f32 = 1.0

const NFFT_PER_SYMBOL_FACTOR: u32 = 2

const NSTEP_PER_SYMBOL: u32 = 2

const NDOWN: u32 = 3

impl ModulationParams for Q65b60

const NTONES: u32 = 65

const BITS_PER_SYMBOL: u32 = 6

const NSPS: u32 = 7200

const SYMBOL_DT: f32

const TONE_SPACING_HZ: f32

const GRAY_MAP: &'static [u8]

const GFSK_BT: f32 = 0.0

const GFSK_HMOD: f32 = 1.0

const NFFT_PER_SYMBOL_FACTOR: u32 = 2

const NSTEP_PER_SYMBOL: u32 = 2

const NDOWN: u32 = 3

impl ModulationParams for Q65c60

const NTONES: u32 = 65

const BITS_PER_SYMBOL: u32 = 6

const NSPS: u32 = 7200

const SYMBOL_DT: f32

const TONE_SPACING_HZ: f32

const GRAY_MAP: &'static [u8]

const GFSK_BT: f32 = 0.0

const GFSK_HMOD: f32 = 1.0

const NFFT_PER_SYMBOL_FACTOR: u32 = 2

const NSTEP_PER_SYMBOL: u32 = 2

const NDOWN: u32 = 3

impl ModulationParams for Q65d60

const NTONES: u32 = 65

const BITS_PER_SYMBOL: u32 = 6

const NSPS: u32 = 7200

const SYMBOL_DT: f32

const TONE_SPACING_HZ: f32

const GRAY_MAP: &'static [u8]

const GFSK_BT: f32 = 0.0

const GFSK_HMOD: f32 = 1.0

const NFFT_PER_SYMBOL_FACTOR: u32 = 2

const NSTEP_PER_SYMBOL: u32 = 2

const NDOWN: u32 = 3

impl ModulationParams for Q65e60

const NTONES: u32 = 65

const BITS_PER_SYMBOL: u32 = 6

const NSPS: u32 = 7200

const SYMBOL_DT: f32

const TONE_SPACING_HZ: f32

const GRAY_MAP: &'static [u8]

const GFSK_BT: f32 = 0.0

const GFSK_HMOD: f32 = 1.0

const NFFT_PER_SYMBOL_FACTOR: u32 = 2

const NSTEP_PER_SYMBOL: u32 = 2

const NDOWN: u32 = 3

impl ModulationParams for UvExpress

const NTONES: u32 = 4

const BITS_PER_SYMBOL: u32 = 2

const NSPS: u32 = 10

const SYMBOL_DT: f32

const TONE_SPACING_HZ: f32 = 600.0

const GRAY_MAP: &'static [u8]

const GFSK_BT: f32 = 0.5

const GFSK_HMOD: f32 = 0.5

const NFFT_PER_SYMBOL_FACTOR: u32 = 4

const NSTEP_PER_SYMBOL: u32 = 2

const NDOWN: u32 = 4

impl ModulationParams for UvRobust

const NTONES: u32 = 4

const BITS_PER_SYMBOL: u32 = 2

const NSPS: u32 = 10

const SYMBOL_DT: f32

const TONE_SPACING_HZ: f32 = 600.0

const GRAY_MAP: &'static [u8]

const GFSK_BT: f32 = 0.5

const GFSK_HMOD: f32 = 0.5

const NFFT_PER_SYMBOL_FACTOR: u32 = 4

const NSTEP_PER_SYMBOL: u32 = 2

const NDOWN: u32 = 4

impl ModulationParams for UvStandard

const NTONES: u32 = 4

const BITS_PER_SYMBOL: u32 = 2

const NSPS: u32 = 10

const SYMBOL_DT: f32

const TONE_SPACING_HZ: f32 = 600.0

const GRAY_MAP: &'static [u8]

const GFSK_BT: f32 = 0.5

const GFSK_HMOD: f32 = 0.5

const NFFT_PER_SYMBOL_FACTOR: u32 = 4

const NSTEP_PER_SYMBOL: u32 = 2

const NDOWN: u32 = 4

impl ModulationParams for UvUltraRobust

const NTONES: u32 = 4

const BITS_PER_SYMBOL: u32 = 2

const NSPS: u32 = 10

const SYMBOL_DT: f32

const TONE_SPACING_HZ: f32 = 600.0

const GRAY_MAP: &'static [u8]

const GFSK_BT: f32 = 0.5

const GFSK_HMOD: f32 = 0.5

const NFFT_PER_SYMBOL_FACTOR: u32 = 4

const NSTEP_PER_SYMBOL: u32 = 2

const NDOWN: u32 = 4

impl ModulationParams for Wspr

const NTONES: u32 = 4

const BITS_PER_SYMBOL: u32 = 2

const NSPS: u32 = 8192

const SYMBOL_DT: f32

const TONE_SPACING_HZ: f32

const GRAY_MAP: &'static [u8]

const GFSK_BT: f32 = 1.0

const GFSK_HMOD: f32 = 1.0

const NFFT_PER_SYMBOL_FACTOR: u32 = 1

const NSTEP_PER_SYMBOL: u32 = 16

const NDOWN: u32 = 32