🎷 🆒 🤘🏼 制作调制解调器：使用OFDM和GNU无线电无线传输数字数据 ⏪ 🕖 🐒

哈Ha

本文可以看作是文章“我们分析拨号调制解调器的声音 ”的续篇，该文章讨论了调制解调器之间建立通信的方法。今天，我们将更进一步，并在实践中了解如何传输数据，为此，我们将使用OFDM和GNU Radio创建一个简单的调制解调器实现。

从字面意义上讲，我们将通过空中传输数据-扬声器和麦克风足以接收和传输。

对于那些对它如何工作感兴趣的人，继续进行下去。

因此，我们的任务是使最简单的调制解调器能够从A点到B点传输数据。有多种调制数字信号的方法，我们将使用OFDM-一种在现代通信系统中广泛使用的方法。在OFDM中，傅立叶变换数字信号被转换为几个并行子载波，从而确保了传输通道的高速和高效。从数字电视和无线电到LTE，OFDM的使用很多。我们的音频通道在参数方面更窄，更适中，因此速度会降低，但基本上本质上不会改变。严格来说，OFDM 不是用于空中数据传输，尽管对于短距离而言，常规的麦克风和扬声器就足够了。

GNU Radio的OFDM

测试接收和传输的最小图形如下所示：

GNU Radio 3.8的源代码：

ofdm1.grc

options:
  parameters:
    author: ''
    category: '[GRC Hier Blocks]'
    cmake_opt: ''
    comment: ''
    copyright: ''
    description: ''
    gen_cmake: 'On'
    gen_linking: dynamic
    generate_options: qt_gui
    hier_block_src_path: '.:'
    id: ofdm_test_1
    max_nouts: '0'
    output_language: python
    placement: (0,0)
    qt_qss_theme: ''
    realtime_scheduling: ''
    run: 'True'
    run_command: '{python} -u {filename}'
    run_options: prompt
    sizing_mode: fixed
    thread_safe_setters: ''
    title: OFDM Test 1
    window_size: ''
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [8, 8]
    rotation: 0
    state: enabled

blocks:
- name: fft_len
  id: variable
  parameters:
    comment: ''
    value: '64'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [448, 12.0]
    rotation: 0
    state: enabled
- name: packet_len
  id: variable
  parameters:
    comment: ''
    value: '12'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [336, 12.0]
    rotation: 0
    state: enabled
- name: samp_rate
  id: variable
  parameters:
    comment: ''
    value: '2400'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [216, 12.0]
    rotation: 0
    state: enabled
- name: blocks_file_source_0
  id: blocks_file_source
  parameters:
    affinity: ''
    alias: ''
    begin_tag: pmt.PMT_NIL
    comment: ''
    file: D:\Temp\1\data2.txt
    length: '0'
    maxoutbuf: '0'
    minoutbuf: '0'
    offset: '0'
    repeat: 'True'
    type: byte
    vlen: '1'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [32, 128.0]
    rotation: 0
    state: enabled
- name: blocks_stream_to_tagged_stream_0
  id: blocks_stream_to_tagged_stream
  parameters:
    affinity: ''
    alias: ''
    comment: ''
    len_tag_key: '"key"'
    maxoutbuf: '0'
    minoutbuf: '0'
    packet_len: packet_len
    type: byte
    vlen: '1'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [488, 156.0]
    rotation: 0
    state: enabled
- name: blocks_throttle_0
  id: blocks_throttle
  parameters:
    affinity: ''
    alias: ''
    comment: ''
    ignoretag: 'True'
    maxoutbuf: '0'
    minoutbuf: '0'
    samples_per_second: samp_rate
    type: byte
    vlen: '1'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [272, 168.0]
    rotation: 0
    state: enabled
- name: blocks_udp_sink_0
  id: blocks_udp_sink
  parameters:
    affinity: ''
    alias: ''
    comment: ''
    eof: 'True'
    ipaddr: 127.0.0.1
    port: '40868'
    psize: '128'
    type: byte
    vlen: '1'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [424, 476.0]
    rotation: 180
    state: enabled
- name: channels_channel_model_0
  id: channels_channel_model
  parameters:
    affinity: ''
    alias: ''
    block_tags: 'True'
    comment: ''
    epsilon: '1.0'
    freq_offset: 0 * 1.0/fft_len
    maxoutbuf: '0'
    minoutbuf: '0'
    noise_voltage: '0.1'
    seed: '0'
    taps: 1.0 + 1.0j
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [1112.0, 280]
    rotation: 270
    state: enabled
- name: digital_ofdm_rx_0
  id: digital_ofdm_rx
  parameters:
    affinity: ''
    alias: ''
    comment: ''
    cp_len: fft_len//4
    fft_len: fft_len
    header_mod: '"BPSK"'
    log: 'False'
    maxoutbuf: '0'
    minoutbuf: '0'
    occupied_carriers: ((-4,-3,-2,-1,1,2,3,4),)
    packet_len_key: '"key"'
    payload_mod: '"QPSK"'
    pilot_carriers: ((-6,-5,5,6),)
    pilot_symbols: ((-1,1,-1,1),)
    scramble_bits: 'False'
    sync_word1: None
    sync_word2: None
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [776, 428.0]
    rotation: 180
    state: enabled
- name: digital_ofdm_tx_0
  id: digital_ofdm_tx
  parameters:
    affinity: ''
    alias: ''
    comment: ''
    cp_len: fft_len//4
    fft_len: fft_len
    header_mod: '"BPSK"'
    log: 'False'
    maxoutbuf: '0'
    minoutbuf: '0'
    occupied_carriers: ((-4,-3,-2,-1,1,2,3,4),)
    packet_len_key: '"key"'
    payload_mod: '"QPSK"'
    pilot_carriers: ((-6,-5,5,6),)
    pilot_symbols: ((-1,1,-1,1),)
    rolloff: '0'
    scramble_bits: 'False'
    sync_word1: None
    sync_word2: None
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [776, 80.0]
    rotation: 0
    state: enabled
- name: qtgui_freq_sink_x_0
  id: qtgui_freq_sink_x
  parameters:
    affinity: ''
    alias: ''
    alpha1: '1.0'
    alpha10: '1.0'
    alpha2: '1.0'
    alpha3: '1.0'
    alpha4: '1.0'
    alpha5: '1.0'
    alpha6: '1.0'
    alpha7: '1.0'
    alpha8: '1.0'
    alpha9: '1.0'
    autoscale: 'False'
    average: '1.0'
    axislabels: 'True'
    bw: samp_rate
    color1: '"blue"'
    color10: '"dark blue"'
    color2: '"red"'
    color3: '"green"'
    color4: '"black"'
    color5: '"cyan"'
    color6: '"magenta"'
    color7: '"yellow"'
    color8: '"dark red"'
    color9: '"dark green"'
    comment: ''
    ctrlpanel: 'False'
    fc: '0'
    fftsize: '1024'
    freqhalf: 'True'
    grid: 'False'
    gui_hint: ''
    label: Relative Gain
    label1: Rx Spectrum
    label10: ''
    label2: ''
    label3: ''
    label4: ''
    label5: ''
    label6: ''
    label7: ''
    label8: ''
    label9: ''
    legend: 'True'
    maxoutbuf: '0'
    minoutbuf: '0'
    name: Rx Spectrum
    nconnections: '1'
    showports: 'True'
    tr_chan: '0'
    tr_level: '0.0'
    tr_mode: qtgui.TRIG_MODE_FREE
    tr_tag: '""'
    type: complex
    units: dB
    update_time: '0.10'
    width1: '1'
    width10: '1'
    width2: '1'
    width3: '1'
    width4: '1'
    width5: '1'
    width6: '1'
    width7: '1'
    width8: '1'
    width9: '1'
    wintype: firdes.WIN_BLACKMAN_hARRIS
    ymax: '10'
    ymin: '-140'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [1232, 92.0]
    rotation: 0
    state: enabled

connections:
- [blocks_file_source_0, '0', blocks_throttle_0, '0']
- [blocks_stream_to_tagged_stream_0, '0', digital_ofdm_tx_0, '0']
- [blocks_throttle_0, '0', blocks_stream_to_tagged_stream_0, '0']
- [channels_channel_model_0, '0', digital_ofdm_rx_0, '0']
- [digital_ofdm_rx_0, '0', blocks_udp_sink_0, '0']
- [digital_ofdm_tx_0, '0', channels_channel_model_0, '0']
- [digital_ofdm_tx_0, '0', qtgui_freq_sink_x_0, '0']

metadata:
  file_format: 1

将纯文本文件用作数据源（在我的情况下，它包含字符串“ Hello Habr !!”），然后将数据分为多个块，这些块被馈送到OFDM发送器。OFDM是一种相当复杂的调制类型，在OFDM编码器的设置中，您需要指定很多不太明显的参数。

可在此处找到有关值的更详细分析。当然，OFDM接收器块的参数必须与传输参数匹配。Channel Model

模块用于模拟通信通道，QT GUI Frequency Sink模块用于可视化频谱。值得一提的是低采样频率（采样率= 2400），这样做是为了使信号占据适合在音频通道上传输的频谱中的一小段。

不幸的是，我没有找到用于在GNU Radio中显示接收到的数据的内置单元，因此我必须使用UDP。UDP Sink块用于输出数据； Python程序用于接收数据：

import socket

UDP_IP = "127.0.0.1"
UDP_PORT = 40868

sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) # UDP
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sock.bind((UDP_IP, UDP_PORT))
sock.settimeout(0.5)

while True:
    try:
        data, addr = sock.recvfrom(128) 
        print("Msg:", data, 'Hex:', ' '.join('{:02x}'.format(x) for x in data))
    except socket.timeout:
        pass

这使您可以在控制台中显示接收到的数据，这非常方便。如果有人知道的话，也许有一种更简单的方法输出到GNU Radio，并在注释中写上。

如果一切都正确完成，我们可以运行GNU Radio和我们的脚本进行接收，结果应如下所示：

您似乎可以关闭该主题？不，有趣的一切才刚刚开始。

直播

在上面的示例中，一切都很简单。但是有一个“但是”-GNU Radio使用所谓的“复杂信号”，实际上是一对相位相差90度的数字。这对于计算机处理很方便，但是我们不能只获取并广播一个复数。

有两种选择。 SDR发送器（HackRF，LimeSDR，USRP等）的所有者可能没有进一步阅读，而只是为GNU Radio准备了现成的模块，其中的所有操作都是“自动”完成的。但是由于我们将使用声卡传输信号，我们必须自己进行转换，为此我们使用DSP上任何文章中的流程图：

在这里OFDM是我们的发射器，Fc载波频率，我们将其设置为4KHz，以便信号达到扬声器和麦克风的最大灵敏度。传输图的流程图也相应复杂：

为了方便测试，我使用WAV File Sink，以便可以单独记录和播放保存的文件。我们还可以打开文件并查看其频谱，我们可以确保中心频率确实为4KHz：

接待处

最后，最后一步：创建用于接收信号的框图。实际上，这里的一切都是相同的，只是顺序相反。

我们将原始信号乘以相移的参考信号，然后借助LPF切断高频分量。输出是可以用于进一步处理的复杂信号。

GNU Radio中的接收图如下：

值得注意的是，音频源模块用于从声卡接收数据，QT GUI频率接收器模块用于可视化接收到的信号。

为了进行测试，我在智能手机上录制了WAV文件；将其带到计算机的麦克风时，解码的文本出现在屏幕上：

结论

如您所见，使用GNU Radio接收和发送信号非常有趣和清晰。OFDM具有相当多的参数；希望的人可以自己尝试FFT块大小，载波数，传输频率等。

感谢大家的关注和成功的实验。

对于那些希望的人，消息来源是破坏者。

ofdm2.grc

options:
  parameters:
    author: ''
    category: Custom
    cmake_opt: ''
    comment: ''
    copyright: ''
    description: Transmit a pre-defined signal (a complex sine) as OFDM packets.
    gen_cmake: 'On'
    gen_linking: dynamic
    generate_options: qt_gui
    hier_block_src_path: '.:'
    id: ofdm_test_2
    max_nouts: '0'
    output_language: python
    placement: (0,0)
    qt_qss_theme: ''
    realtime_scheduling: ''
    run: 'True'
    run_command: '{python} -u {filename}'
    run_options: prompt
    sizing_mode: fixed
    thread_safe_setters: ''
    title: OFDM Test 2
    window_size: 1280, 1024
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [8, 12.0]
    rotation: 0
    state: enabled

blocks:
- name: audio_samp_rate
  id: variable
  parameters:
    comment: ''
    value: '24000'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [648, 20.0]
    rotation: 0
    state: true
- name: carrier_freq
  id: variable
  parameters:
    comment: ''
    value: '4000'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [792, 20.0]
    rotation: 0
    state: true
- name: fft_len
  id: variable
  parameters:
    comment: ''
    value: '64'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [448, 20.0]
    rotation: 0
    state: enabled
- name: len_tag_key
  id: variable
  parameters:
    comment: ''
    value: '"packet_len"'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [320, 20.0]
    rotation: 0
    state: enabled
- name: packet_len
  id: variable
  parameters:
    comment: ''
    value: '12'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [216, 20.0]
    rotation: 0
    state: enabled
- name: samp_rate
  id: variable
  parameters:
    comment: ''
    value: '2400'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [536, 20.0]
    rotation: 0
    state: enabled
- name: analog_sig_source_x_0
  id: analog_sig_source_x
  parameters:
    affinity: ''
    alias: ''
    amp: '1'
    comment: ''
    freq: carrier_freq
    maxoutbuf: '0'
    minoutbuf: '0'
    offset: '0'
    phase: '0'
    samp_rate: audio_samp_rate
    type: float
    waveform: analog.GR_COS_WAVE
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [1080, 88.0]
    rotation: 0
    state: true
- name: analog_sig_source_x_0_0
  id: analog_sig_source_x
  parameters:
    affinity: ''
    alias: ''
    amp: '1'
    comment: ''
    freq: carrier_freq
    maxoutbuf: '0'
    minoutbuf: '0'
    offset: '0'
    phase: '0'
    samp_rate: audio_samp_rate
    type: float
    waveform: analog.GR_SIN_WAVE
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [1080, 344.0]
    rotation: 0
    state: true
- name: analog_sig_source_x_0_0_0
  id: analog_sig_source_x
  parameters:
    affinity: ''
    alias: ''
    amp: '1'
    comment: ''
    freq: carrier_freq
    maxoutbuf: '0'
    minoutbuf: '0'
    offset: '0'
    phase: '0'
    samp_rate: audio_samp_rate
    type: float
    waveform: analog.GR_SIN_WAVE
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [1376, 824.0]
    rotation: 180
    state: true
- name: analog_sig_source_x_0_1
  id: analog_sig_source_x
  parameters:
    affinity: ''
    alias: ''
    amp: '1'
    comment: ''
    freq: carrier_freq
    maxoutbuf: '0'
    minoutbuf: '0'
    offset: '0'
    phase: '0'
    samp_rate: audio_samp_rate
    type: float
    waveform: analog.GR_COS_WAVE
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [1376, 672.0]
    rotation: 180
    state: true
- name: audio_sink_0
  id: audio_sink
  parameters:
    affinity: ''
    alias: ''
    comment: ''
    device_name: ''
    num_inputs: '1'
    ok_to_block: 'True'
    samp_rate: audio_samp_rate
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [1608, 224.0]
    rotation: 0
    state: disabled
- name: audio_source_0
  id: audio_source
  parameters:
    affinity: ''
    alias: ''
    comment: ''
    device_name: ''
    maxoutbuf: '0'
    minoutbuf: '0'
    num_outputs: '1'
    ok_to_block: 'True'
    samp_rate: audio_samp_rate
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [1376, 584.0]
    rotation: 180
    state: enabled
- name: blocks_add_xx_0
  id: blocks_add_xx
  parameters:
    affinity: ''
    alias: ''
    comment: ''
    maxoutbuf: '0'
    minoutbuf: '0'
    num_inputs: '2'
    type: float
    vlen: '1'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [1480, 264.0]
    rotation: 0
    state: true
- name: blocks_complex_to_float_0
  id: blocks_complex_to_float
  parameters:
    affinity: ''
    alias: ''
    comment: ''
    maxoutbuf: '0'
    minoutbuf: '0'
    vlen: '1'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [1128, 256.0]
    rotation: 0
    state: true
- name: blocks_file_source_0
  id: blocks_file_source
  parameters:
    affinity: ''
    alias: ''
    begin_tag: pmt.PMT_NIL
    comment: ''
    file: D:\Temp\1\data2.txt
    length: '0'
    maxoutbuf: '0'
    minoutbuf: '0'
    offset: '0'
    repeat: 'True'
    type: byte
    vlen: '1'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [32, 224.0]
    rotation: 0
    state: enabled
- name: blocks_float_to_complex_0
  id: blocks_float_to_complex
  parameters:
    affinity: ''
    alias: ''
    comment: ''
    maxoutbuf: '0'
    minoutbuf: '0'
    vlen: '1'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [744, 768.0]
    rotation: 180
    state: true
- name: blocks_multiply_xx_0
  id: blocks_multiply_xx
  parameters:
    affinity: ''
    alias: ''
    comment: ''
    maxoutbuf: '0'
    minoutbuf: '0'
    num_inputs: '2'
    type: float
    vlen: '1'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [1336, 176.0]
    rotation: 0
    state: true
- name: blocks_multiply_xx_0_0
  id: blocks_multiply_xx
  parameters:
    affinity: ''
    alias: ''
    comment: ''
    maxoutbuf: '0'
    minoutbuf: '0'
    num_inputs: '2'
    type: float
    vlen: '1'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [1336, 344.0]
    rotation: 0
    state: enabled
- name: blocks_multiply_xx_0_1
  id: blocks_multiply_xx
  parameters:
    affinity: ''
    alias: ''
    comment: ''
    maxoutbuf: '0'
    minoutbuf: '0'
    num_inputs: '2'
    type: float
    vlen: '1'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [1168, 696.0]
    rotation: 180
    state: true
- name: blocks_multiply_xx_0_1_0
  id: blocks_multiply_xx
  parameters:
    affinity: ''
    alias: ''
    comment: ''
    maxoutbuf: '0'
    minoutbuf: '0'
    num_inputs: '2'
    type: float
    vlen: '1'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [1176, 864.0]
    rotation: 180
    state: true
- name: blocks_null_sink_0
  id: blocks_null_sink
  parameters:
    affinity: ''
    alias: ''
    bus_structure_sink: '[[0,],]'
    comment: ''
    num_inputs: '1'
    type: float
    vlen: '1'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [1608, 168.0]
    rotation: 0
    state: true
- name: blocks_stream_to_tagged_stream_0
  id: blocks_stream_to_tagged_stream
  parameters:
    affinity: ''
    alias: ''
    comment: ''
    len_tag_key: '"key"'
    maxoutbuf: '0'
    minoutbuf: '0'
    packet_len: packet_len
    type: byte
    vlen: '1'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [424, 252.0]
    rotation: 0
    state: enabled
- name: blocks_throttle_0
  id: blocks_throttle
  parameters:
    affinity: ''
    alias: ''
    comment: ''
    ignoretag: 'True'
    maxoutbuf: '0'
    minoutbuf: '0'
    samples_per_second: samp_rate
    type: byte
    vlen: '1'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [248, 264.0]
    rotation: 0
    state: enabled
- name: blocks_udp_sink_0
  id: blocks_udp_sink
  parameters:
    affinity: ''
    alias: ''
    comment: ''
    eof: 'True'
    ipaddr: 127.0.0.1
    port: '40868'
    psize: '128'
    type: byte
    vlen: '1'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [104, 748.0]
    rotation: 180
    state: enabled
- name: blocks_wavfile_sink_0
  id: blocks_wavfile_sink
  parameters:
    affinity: ''
    alias: ''
    bits_per_sample: '16'
    comment: ''
    file: D:\Temp\1\ofdm.wav
    nchan: '1'
    samp_rate: audio_samp_rate
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [1608, 308.0]
    rotation: 0
    state: disabled
- name: digital_ofdm_rx_0
  id: digital_ofdm_rx
  parameters:
    affinity: ''
    alias: ''
    comment: ''
    cp_len: fft_len//4
    fft_len: fft_len
    header_mod: '"BPSK"'
    log: 'False'
    maxoutbuf: '0'
    minoutbuf: '0'
    occupied_carriers: ((-4,-3,-2,-1,1,2,3,4),)
    packet_len_key: '"key"'
    payload_mod: '"QPSK"'
    pilot_carriers: ((-6,-5,5,6),)
    pilot_symbols: ((-1,1,-1,1),)
    scramble_bits: 'False'
    sync_word1: None
    sync_word2: None
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [440, 700.0]
    rotation: 180
    state: enabled
- name: digital_ofdm_tx_0
  id: digital_ofdm_tx
  parameters:
    affinity: ''
    alias: ''
    comment: ''
    cp_len: fft_len//4
    fft_len: fft_len
    header_mod: '"BPSK"'
    log: 'False'
    maxoutbuf: '0'
    minoutbuf: '0'
    occupied_carriers: ((-4,-3,-2,-1,1,2,3,4),)
    packet_len_key: '"key"'
    payload_mod: '"QPSK"'
    pilot_carriers: ((-6,-5,5,6),)
    pilot_symbols: ((-1,1,-1,1),)
    rolloff: '0'
    scramble_bits: 'False'
    sync_word1: None
    sync_word2: None
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [664, 176.0]
    rotation: 0
    state: enabled
- name: low_pass_filter_0
  id: low_pass_filter
  parameters:
    affinity: ''
    alias: ''
    beta: '6.76'
    comment: ''
    cutoff_freq: carrier_freq
    decim: audio_samp_rate//samp_rate
    gain: '1'
    interp: '1'
    maxoutbuf: '0'
    minoutbuf: '0'
    samp_rate: audio_samp_rate
    type: fir_filter_fff
    width: '1000'
    win: firdes.WIN_HAMMING
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [960, 648.0]
    rotation: 180
    state: true
- name: low_pass_filter_0_0
  id: low_pass_filter
  parameters:
    affinity: ''
    alias: ''
    beta: '6.76'
    comment: ''
    cutoff_freq: carrier_freq
    decim: audio_samp_rate//samp_rate
    gain: '1'
    interp: '1'
    maxoutbuf: '0'
    minoutbuf: '0'
    samp_rate: audio_samp_rate
    type: fir_filter_fff
    width: '1000'
    win: firdes.WIN_HAMMING
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [960, 816.0]
    rotation: 180
    state: true
- name: qtgui_freq_sink_x_0
  id: qtgui_freq_sink_x
  parameters:
    affinity: ''
    alias: ''
    alpha1: '1.0'
    alpha10: '1.0'
    alpha2: '1.0'
    alpha3: '1.0'
    alpha4: '1.0'
    alpha5: '1.0'
    alpha6: '1.0'
    alpha7: '1.0'
    alpha8: '1.0'
    alpha9: '1.0'
    autoscale: 'False'
    average: '1.0'
    axislabels: 'True'
    bw: samp_rate
    color1: '"blue"'
    color10: '"dark blue"'
    color2: '"red"'
    color3: '"green"'
    color4: '"black"'
    color5: '"cyan"'
    color6: '"magenta"'
    color7: '"yellow"'
    color8: '"dark red"'
    color9: '"dark green"'
    comment: ''
    ctrlpanel: 'False'
    fc: '0'
    fftsize: '1024'
    freqhalf: 'True'
    grid: 'False'
    gui_hint: ''
    label: Relative Gain
    label1: Rx Spectrum
    label10: ''
    label2: ''
    label3: ''
    label4: ''
    label5: ''
    label6: ''
    label7: ''
    label8: ''
    label9: ''
    legend: 'True'
    maxoutbuf: '0'
    minoutbuf: '0'
    name: Rx Spectrum
    nconnections: '1'
    showports: 'True'
    tr_chan: '0'
    tr_level: '0.0'
    tr_mode: qtgui.TRIG_MODE_FREE
    tr_tag: '""'
    type: complex
    units: dB
    update_time: '0.10'
    width1: '1'
    width10: '1'
    width2: '1'
    width3: '1'
    width4: '1'
    width5: '1'
    width6: '1'
    width7: '1'
    width8: '1'
    width9: '1'
    wintype: firdes.WIN_BLACKMAN_hARRIS
    ymax: '10'
    ymin: '-140'
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [728, 612.0]
    rotation: 0
    state: enabled
- name: rational_resampler_xxx_0
  id: rational_resampler_xxx
  parameters:
    affinity: ''
    alias: ''
    comment: ''
    decim: '1'
    fbw: '0'
    interp: audio_samp_rate//samp_rate
    maxoutbuf: '0'
    minoutbuf: '0'
    taps: ''
    type: ccf
  states:
    bus_sink: false
    bus_source: false
    bus_structure: null
    coordinate: [912, 236.0]
    rotation: 0
    state: true

connections:
- [analog_sig_source_x_0, '0', blocks_multiply_xx_0, '0']
- [analog_sig_source_x_0_0, '0', blocks_multiply_xx_0_0, '1']
- [analog_sig_source_x_0_0_0, '0', blocks_multiply_xx_0_1_0, '1']
- [analog_sig_source_x_0_1, '0', blocks_multiply_xx_0_1, '1']
- [audio_source_0, '0', blocks_multiply_xx_0_1, '0']
- [audio_source_0, '0', blocks_multiply_xx_0_1_0, '0']
- [blocks_add_xx_0, '0', audio_sink_0, '0']
- [blocks_add_xx_0, '0', blocks_null_sink_0, '0']
- [blocks_add_xx_0, '0', blocks_wavfile_sink_0, '0']
- [blocks_complex_to_float_0, '0', blocks_multiply_xx_0, '1']
- [blocks_complex_to_float_0, '1', blocks_multiply_xx_0_0, '0']
- [blocks_file_source_0, '0', blocks_throttle_0, '0']
- [blocks_float_to_complex_0, '0', digital_ofdm_rx_0, '0']
- [blocks_float_to_complex_0, '0', qtgui_freq_sink_x_0, '0']
- [blocks_multiply_xx_0, '0', blocks_add_xx_0, '0']
- [blocks_multiply_xx_0_0, '0', blocks_add_xx_0, '1']
- [blocks_multiply_xx_0_1, '0', low_pass_filter_0, '0']
- [blocks_multiply_xx_0_1_0, '0', low_pass_filter_0_0, '0']
- [blocks_stream_to_tagged_stream_0, '0', digital_ofdm_tx_0, '0']
- [blocks_throttle_0, '0', blocks_stream_to_tagged_stream_0, '0']
- [digital_ofdm_rx_0, '0', blocks_udp_sink_0, '0']
- [digital_ofdm_tx_0, '0', rational_resampler_xxx_0, '0']
- [low_pass_filter_0, '0', blocks_float_to_complex_0, '0']
- [low_pass_filter_0_0, '0', blocks_float_to_complex_0, '1']
- [rational_resampler_xxx_0, '0', blocks_complex_to_float_0, '0']

metadata:
  file_format: 1

制作调制解调器：使用OFDM和GNU无线电无线传输数字数据

GNU Radio的OFDM

直播

接待处

结论

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