Module gmsk 

Gaussian Minimum Shift Keying (CCSDS 211.0). Gaussian Minimum Shift Keying (GMSK) Modulation

GMSK is a continuous-phase modulation with Gaussian pulse shaping and modulation index h = 0.5. The Gaussian filter smooths the frequency transitions, yielding excellent spectral containment and a nearly constant envelope.

Used in Proximity-1 links (CCSDS 211.0, BT = 0.25) and other near-Earth LEO communication systems.

Modulation

The instantaneous frequency deviation is the NRZ data convolved with a Gaussian pulse truncated to 4 symbol periods. The phase is the running integral of the frequency deviation.

Demodulation

Soft-decision differential detection: computes the cross-product of consecutive symbol-spaced samples to approximate the phase difference, then scales by 1/σ² for LLR output.

Structs

Gmsk

GMSK modulator/demodulator with configurable parameters.

Functions

demodulate_gmsk

Demodulates GMSK using soft-decision differential detection.

modulate_gmsk

Modulates packed bits using GMSK.

output_len

Returns the number of output samples for a GMSK frame.