Iridium Recording Receiver

Detects 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.

Author GNU Radio World
Category gr-iridium
Blocks 14
Connections 7
File gr-iridium/iridium_recording.grc

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Blocks used

Block	Module	Used
Variable	`GNU Radio`	6
burst_downmix	`gr-iridium`	1
fft_burst_tagger	`gr-iridium`	1
frame_sorter	`gr-iridium`	1
GR World Recording	`GNU Radio`	1
GUI Layout	`GNU Radio`	1
iridium_frame_printer	`gr-iridium`	1
iridium_qpsk_demod	`gr-iridium`	1
tagged_burst_to_pdu	`gr-iridium`	1

Flowgraph source

gr-iridium/iridium_recording.grc

options:
    parameters:
        author: GNU Radio World
        comment: ''
        copyright: ''
        description: Detects 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.
        generate_options: qt_gui
        id: Iridium_Recording_Receiver
        title: Iridium Recording Receiver
    states:
        coordinate: [10, 10]
        rotation: 0
        state: enabled
blocks:
-   name: burst_sample_rate
    id: variable
    parameters:
        comment: Iridium demodulator input rate (10 samples per symbol)
        value: '250000'
    states:
        coordinate: [590, 10]
        rotation: 0
        state: enabled
-   name: burst_width
    id: variable
    parameters:
        comment: Occupied width used by the detector and input filter
        value: '40000'
    states:
        coordinate: [820, 10]
        rotation: 0
        state: enabled
-   name: center_freq
    id: variable
    parameters:
        comment: Recording center frequency
        value: '1621500000'
    states:
        coordinate: [1000, 10]
        rotation: 0
        state: enabled
-   name: fft_size
    id: variable
    parameters:
        comment: Approximately one millisecond at the recording rate
        value: '16384'
    states:
        coordinate: [1180, 10]
        rotation: 0
        state: enabled
-   name: max_burst_len
    id: variable
    parameters:
        comment: 90 ms at the recording rate
        value: '1080000'
    states:
        coordinate: [1360, 10]
        rotation: 0
        state: enabled
-   name: sample_rate
    id: variable
    parameters:
        comment: Recording sample rate
        value: '12000000'
    states:
        coordinate: [1560, 10]
        rotation: 0
        state: enabled
-   name: burst_downmix
    id: iridium_burst_downmix
    parameters:
        affinity: ''
        alias: ''
        comment: Filters, centers, and decimates each detected burst
        handle_multiple_frames_per_burst: 'False'
        hard_max_queue_len: '0'
        input_taps: firdes.low_pass_2(1, sample_rate, burst_width/2, burst_width, 40)
        maxoutbuf: '0'
        minoutbuf: '0'
        output_sample_rate: burst_sample_rate
        search_depth: '1750'
        start_finder_taps: firdes.low_pass_2(1, burst_sample_rate, 2500, 5000, 60)
    states:
        coordinate: [110, 470]
        rotation: 0
        state: enabled
-   name: burst_tagger
    id: iridium_fft_burst_tagger
    parameters:
        affinity: ''
        alias: ''
        burst_post_len: '192000'
        burst_pre_len: '32768'
        burst_width: burst_width
        center_frequency: center_freq
        comment: Detects energy bursts across the Iridium downlink band
        debug: 'False'
        fft_size: fft_size
        history_size: '512'
        max_burst_len: max_burst_len
        max_bursts: '0'
        maxoutbuf: '0'
        minoutbuf: '0'
        sample_rate: sample_rate
        threshold: '10'
    states:
        coordinate: [330, 150]
        rotation: 0
        state: enabled
-   name: bursts_to_pdus
    id: iridium_tagged_burst_to_pdu
    parameters:
        affinity: ''
        alias: ''
        comment: Copies tagged stream bursts into message PDUs
        drop_overflow: 'False'
        max_burst_size: max_burst_len
        max_outstanding: '500'
        maxoutbuf: '0'
        minoutbuf: '0'
        relative_center_frequency: '0'
        relative_sample_rate: '1'
        relative_span: '1'
        sample_offset: '0'
    states:
        coordinate: [780, 200]
        rotation: 0
        state: enabled
-   name: frame_printer
    id: iridium_iridium_frame_printer
    parameters:
        affinity: ''
        alias: ''
        comment: Prints RAW frames to the console
    states:
        coordinate: [1350, 510]
        rotation: 0
        state: enabled
-   name: frame_sorter
    id: iridium_frame_sorter
    parameters:
        affinity: ''
        alias: ''
        comment: Orders recovered frames by timestamp
        maxoutbuf: '0'
        minoutbuf: '0'
    states:
        coordinate: [1070, 510]
        rotation: 0
        state: enabled
-   name: qpsk_demod
    id: iridium_iridium_qpsk_demod
    parameters:
        affinity: ''
        alias: ''
        channels: '1'
        comment: Demodulates Iridium QPSK bursts into raw frames
        maxoutbuf: '0'
        minoutbuf: '0'
    states:
        coordinate: [710, 510]
        rotation: 0
        state: enabled
-   name: recording
    id: wasm_gr_world_recording
    parameters:
        affinity: ''
        alias: ''
        comment: 1.25-second B210 recording centered at 1621.5 MHz
        length: '0'
        maxoutbuf: '0'
        minoutbuf: '0'
        offset: '0'
        progress: 'True'
        recording: iridium_cf32
        repeat: 'False'
        type: complex
    states:
        coordinate: [10, 240]
        rotation: 0
        state: enabled
-   name: wasm_gui_layout_0
    id: wasm_gui_layout
    parameters:
        affinity: ''
        alias: ''
        columns: '12'
        comment: ''
        layout: '{}'
        row_height: '60'
    states:
        coordinate: [300, 10]
        rotation: 0
        state: enabled
connections:
-   src_blk_id: burst_downmix
    src_port_id: burst_handled
    snk_blk_id: bursts_to_pdus
    snk_port_id: burst_handled
-   src_blk_id: burst_downmix
    src_port_id: cpdus
    snk_blk_id: qpsk_demod
    snk_port_id: cpdus
- [burst_tagger, '0', bursts_to_pdus, '0']
-   src_blk_id: bursts_to_pdus
    src_port_id: cpdus
    snk_blk_id: burst_downmix
    snk_port_id: cpdus
-   src_blk_id: frame_sorter
    src_port_id: pdus
    snk_blk_id: frame_printer
    snk_port_id: pdus
-   src_blk_id: qpsk_demod
    src_port_id: pdus
    snk_blk_id: frame_sorter
    snk_port_id: pdus
- [recording, '0', burst_tagger, '0']
metadata:
    file_format: 2
    grc_version: 3.11.0.0