AIS Receiver

Decodes AIS position reports from ships in the hosted 250 kS/s SDRangel recording centered on 162 MHz. Two Frequency Xlating FIR Filters select channel A (161.975 MHz) and channel B (162.025 MHz) at 50 kS/s, gr-ais's AIS Demod recovers the GMSK bits of each, HDLC Deframer checks the CRC of every burst, AIS PDU to NMEA prints the !AIVDM sentences to the console, and the AIS Map plots every vessel on the Thames estuary as its reports arrive. The receive chain is upstream's ais_rx tool, block by block.

Author GNU Radio World
Category gr-ais
Blocks 20
Connections 12
File gr-ais/ais_receiver.grc

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Blocks used

Block	Module	Used
Variable	`GNU Radio`	7
AIS Demod	`gr-ais`	2
AIS PDU to NMEA	`gr-ais`	2
Frequency Xlating FIR Filter	`GNU Radio`	2
HDLC Deframer	`GNU Radio`	2
AIS Map	`GNU Radio`	1
GR World Recording	`GNU Radio`	1
GUI Layout	`GNU Radio`	1
QT GUI Waterfall Sink	`GNU Radio`	1
Throttle	`GNU Radio`	1

Flowgraph source

gr-ais/ais_receiver.grc

options:
    parameters:
        author: GNU Radio World
        comment: ''
        copyright: ''
        description: Decodes AIS position reports from ships in the hosted 250 kS/s SDRangel recording centered on 162 MHz. Two Frequency Xlating FIR Filters select channel A (161.975 MHz) and channel B (162.025 MHz) at 50 kS/s, gr-ais's AIS Demod recovers the GMSK bits of each, HDLC Deframer checks the CRC of every burst, AIS PDU to NMEA prints the !AIVDM sentences to the console, and the AIS Map plots every vessel on the Thames estuary as its reports arrive. The receive chain is upstream's ais_rx tool, block by block.
        generate_options: qt_gui
        id: AIS_Receiver
        title: AIS Receiver
    states:
        coordinate: [10, 10]
        rotation: 0
        state: enabled
blocks:
-   name: bits_per_sec
    id: variable
    parameters:
        comment: AIS symbol rate
        value: '9600'
    states:
        coordinate: [510, 10]
        rotation: 0
        state: enabled
-   name: center_freq
    id: variable
    parameters:
        comment: Recording center frequency
        value: '162000000'
    states:
        coordinate: [290, 130]
        rotation: 0
        state: enabled
-   name: channel_a_freq
    id: variable
    parameters:
        comment: AIS channel A
        value: '161975000'
    states:
        coordinate: [510, 130]
        rotation: 0
        state: enabled
-   name: channel_b_freq
    id: variable
    parameters:
        comment: AIS channel B
        value: '162025000'
    states:
        coordinate: [730, 10]
        rotation: 0
        state: enabled
-   name: channel_rate
    id: variable
    parameters:
        comment: "Per-channel rate after decimation\n(5.2 samples per symbol)"
        value: samp_rate/decim
    states:
        coordinate: [730, 130]
        rotation: 0
        state: enabled
-   name: decim
    id: variable
    parameters:
        comment: "Channel filter decimation,\nas ais_rx computes it for 5\nsamples per symbol"
        value: '5'
    states:
        coordinate: [950, 10]
        rotation: 0
        state: enabled
-   name: samp_rate
    id: variable
    parameters:
        comment: Recording sample rate
        value: '250000'
    states:
        coordinate: [290, 10]
        rotation: 0
        state: enabled
-   name: channel_a
    id: freq_xlating_fir_filter_xxx
    parameters:
        affinity: ''
        alias: ''
        center_freq: channel_a_freq - center_freq
        comment: Selects channel A and decimates to 50 kS/s
        decim: decim
        maxoutbuf: '0'
        minoutbuf: '0'
        samp_rate: samp_rate
        taps: firdes.low_pass(1, samp_rate, 11000, 1000)
        type: ccf
    states:
        coordinate: [680, 300]
        rotation: 0
        state: enabled
-   name: channel_b
    id: freq_xlating_fir_filter_xxx
    parameters:
        affinity: ''
        alias: ''
        center_freq: channel_b_freq - center_freq
        comment: Selects channel B and decimates to 50 kS/s
        decim: decim
        maxoutbuf: '0'
        minoutbuf: '0'
        samp_rate: samp_rate
        taps: firdes.low_pass(1, samp_rate, 11000, 1000)
        type: ccf
    states:
        coordinate: [680, 540]
        rotation: 0
        state: enabled
-   name: deframer_a
    id: digital_hdlc_deframer_bp
    parameters:
        affinity: ''
        alias: ''
        comment: Unstuffs, checks the CRC, and emits each AIS packet as a PDU
        max: '64'
        maxoutbuf: '0'
        min: '11'
        minoutbuf: '0'
    states:
        coordinate: [1470, 320]
        rotation: 0
        state: enabled
-   name: deframer_b
    id: digital_hdlc_deframer_bp
    parameters:
        affinity: ''
        alias: ''
        comment: ''
        max: '64'
        maxoutbuf: '0'
        min: '11'
        minoutbuf: '0'
    states:
        coordinate: [1490, 560]
        rotation: 0
        state: enabled
-   name: demod_a
    id: ais_demod
    parameters:
        affinity: ''
        alias: ''
        bits_per_sec: bits_per_sec
        clockrec_gain: '0.01'
        coherent: 'True'
        comment: Frequency sync, AGC, clock recovery and Viterbi GMSK demodulation to NRZI-decoded bits
        fftlen: '1024'
        maxoutbuf: '0'
        minoutbuf: '0'
        omega_relative_limit: '0.01'
        samples_per_symbol: channel_rate/bits_per_sec
    states:
        coordinate: [1090, 270]
        rotation: 0
        state: enabled
-   name: demod_b
    id: ais_demod
    parameters:
        affinity: ''
        alias: ''
        bits_per_sec: bits_per_sec
        clockrec_gain: '0.01'
        coherent: 'True'
        comment: ''
        fftlen: '1024'
        maxoutbuf: '0'
        minoutbuf: '0'
        omega_relative_limit: '0.01'
        samples_per_symbol: channel_rate/bits_per_sec
    states:
        coordinate: [1100, 510]
        rotation: 0
        state: enabled
-   name: nmea_a
    id: ais_pdu_to_nmea
    parameters:
        affinity: ''
        alias: ''
        comment: Prints each packet as a !AIVDM sentence
        designator: A
        maxoutbuf: '0'
        minoutbuf: '0'
    states:
        coordinate: [1830, 310]
        rotation: 0
        state: enabled
-   name: nmea_b
    id: ais_pdu_to_nmea
    parameters:
        affinity: ''
        alias: ''
        comment: ''
        designator: B
        maxoutbuf: '0'
        minoutbuf: '0'
    states:
        coordinate: [1820, 550]
        rotation: 0
        state: enabled
-   name: recording
    id: wasm_gr_world_recording
    parameters:
        affinity: ''
        alias: ''
        comment: "157 s of both AIS channels at\n250 kS/s, centered on 162 MHz"
        length: '0'
        maxoutbuf: '0'
        minoutbuf: '0'
        offset: '0'
        progress: 'True'
        recording: sdrangel/ais
        repeat: 'True'
        type: complex
    states:
        coordinate: [20, 300]
        rotation: 0
        state: enabled
-   name: throttle
    id: blocks_throttle2
    parameters:
        affinity: ''
        alias: ''
        comment: ''
        ignoretag: 'True'
        limit: auto
        maximum: '0.1'
        maxoutbuf: '0'
        minoutbuf: '0'
        samples_per_second: samp_rate
        type: complex
        vlen: '1'
    states:
        coordinate: [340, 290]
        rotation: 0
        state: enabled
-   name: vessel_map
    id: wasm_ais_map_sink
    parameters:
        affinity: ''
        alias: ''
        basemap: light
        comment: "Both channels' packets,\ndecoded and plotted by MMSI;\nselect a row or marker for details"
        expire_seconds: '1200'
        name: '"Ships on the Thames estuary"'
        receiver_latitude: '0'
        receiver_longitude: '0'
        show_labels: 'True'
        show_receiver: 'False'
        stale_seconds: '180'
        trail_seconds: '1800'
        units: nautical
        update_time: '0.25'
    states:
        coordinate: [1870, 700]
        rotation: 0
        state: enabled
-   name: wasm_gui_layout_0
    id: wasm_gui_layout
    parameters:
        affinity: ''
        alias: ''
        columns: '12'
        comment: ''
        layout: '{"recording":[0,0,12,1],"waterfall":[0,1,12,3],"vessel_map":[0,4,12,9]}'
        row_height: '60'
    states:
        coordinate: [1180, 10]
        rotation: 0
        state: enabled
-   name: waterfall
    id: qtgui_waterfall_sink_x
    parameters:
        affinity: ''
        alias: ''
        alpha1: '1'
        alpha10: '1'
        alpha2: '1'
        alpha3: '1'
        alpha4: '1'
        alpha5: '1'
        alpha6: '1'
        alpha7: '1'
        alpha8: '1'
        alpha9: '1'
        average: '1.0'
        axislabels: 'True'
        bw: samp_rate
        color1: '0'
        color10: '0'
        color2: '0'
        color3: '0'
        color4: '0'
        color5: '0'
        color6: '0'
        color7: '0'
        color8: '0'
        color9: '0'
        comment: ''
        fc: center_freq
        fftsize: '1024'
        freqhalf: 'True'
        grid: 'False'
        int_max: '10'
        int_min: '-140'
        label1: ''
        label10: ''
        label2: ''
        label3: ''
        label4: ''
        label5: ''
        label6: ''
        label7: ''
        label8: ''
        label9: ''
        legend: 'True'
        maxoutbuf: '0'
        minoutbuf: '0'
        name: AIS channels A and B
        nconnections: '1'
        type: complex
        update_time: '0.1'
        wintype: window.WIN_RECTANGULAR
    states:
        coordinate: [680, 710]
        rotation: 0
        state: enabled
connections:
- [channel_a, '0', demod_a, '0']
- [channel_b, '0', demod_b, '0']
-   src_blk_id: deframer_a
    src_port_id: out
    snk_blk_id: nmea_a
    snk_port_id: print
-   src_blk_id: deframer_a
    src_port_id: out
    snk_blk_id: vessel_map
    snk_port_id: in
-   src_blk_id: deframer_b
    src_port_id: out
    snk_blk_id: nmea_b
    snk_port_id: print
-   src_blk_id: deframer_b
    src_port_id: out
    snk_blk_id: vessel_map
    snk_port_id: in
- [demod_a, '0', deframer_a, '0']
- [demod_b, '0', deframer_b, '0']
- [recording, '0', throttle, '0']
- [throttle, '0', channel_a, '0']
- [throttle, '0', channel_b, '0']
- [throttle, '0', waterfall, '0']
metadata:
    file_format: 2
    grc_version: 3.11.0.0