gr-iridium

Out-of-tree GNU Radio module available in GNU Radio World

Channel layout of the Iridium satellite downlink band — Repository artwork

gr-iridium detects and demodulates bursts from the Iridium satellite network. Its FFT burst tagger and channelizer locate activity across a wideband capture, while tagged-burst conversion and downmixing isolate each transmission at a demodulation-friendly sample rate. A QPSK demodulator, frame sorter, and frame printer turn those bursts into timestamped raw bit frames for downstream parsing with iridium-toolkit.

Main authors: Tobias Schneider, Stefan Zehl
Last modified: 2025-03-29
Project: Upstream repository

Example flowgraphs

These GNU Radio World examples contain one or more blocks from gr-iridium.

Iridium PRBS15 Decoder TestDeterministic gr-iridium decoder sanity check using the upstream synthetic PRBS15 golden fixture. A successful run prints one 179-bit RAW frame at 100% confidence; the expected prefix is shown on the canvas and the full reference frame is pinned by gr-iridium's CI.
Iridium Recording ReceiverDetects and demodulates Iridium downlink bursts from the hosted 12 MS/s iridium_cf32 SigMF recording. The FFT burst tagger finds transmissions across the capture, Burst Downmix isolates them at 250 kS/s, and the QPSK demodulator prints recovered RAW frames to the console for use with iridium-toolkit.