Software Defined Radio - how does it work? Part 10
Hello, Habr.
In the “anniversary” part of the series about SDR, I want to talk about one of the protocols, thanks to which many hams “involuntarily” joined the world of digital broadband signals. This standard was also the first (and as far as is known, the only) attempt to transmit digital sound at short wavelengths.
')
As many have probably already guessed, we will talk about the DRM standard - Digital Radio Mondiale (not to be confused with other DRM, Digital Rights Management).
Well, because If we are going to talk about SDR, then we will see not only how to receive DRM, but also how to transmit it. Continued under the cut.
The history of the DRM standard is not easy. It was first introduced in 2003, and test transmissions have been made since 2007, and with varying success continue periodically and still.
DRM was based on two main ideas.
The DRM standard is essentially somewhat surreal - for years radio stations have been operating, broadcasts are broadcasting ... But there are no receivers of this standard on sale. At all. None. It is clear that since the standard is digital, then the usual receiver can only hear hissing, and no one has yet learned how to decode QAM by ear. So the reception of DRM was entertainment only for ham radio. It seems that 1-2 receivers did exist, about which there are even a couple of videos on youtube ( 1 and 2 ), but there is nothing on sale now on Ebay or Amazon.
The second problem of receiving DRM is that in the cities of HF broadcasting is de facto dead - there is so much interference from household equipment and power supplies that even if you turn on the HF radio, you will hear one pop and noise - decoding in such conditions does not work will, in the best case, the receiver will be able to show the screensaver of the station, but without sound. You can of course put the antenna on the balcony or on the roof, carefully configure it, and in principle, it’s quite possible to receive and decode DRM from a city apartment for radio amateurs. Ordinary people will not bother with this 100%, no one will climb onto the roof to hang an antenna to receive an audio signal with a bitrate of 12Kbit / s.
In general, there are no receivers, no audience. But there is a broadcast. The gopher from the movie is resting ...
By the way, right now, at the time of writing (July 2019), DRM + test broadcasting is being carried out in St. Petersburg, so those who wishto be a gopher can try to receive a signal (there is nothing to listen to, there are no receivers, or even software SDR decoders for DRM +). For reception, you can use RTL-SDR, and if you're lucky, then in the FM band you can see a digital signal with a width of about 100KHz. Decoders, however, as already mentioned, could not be found for him.
The first reports of DRM hams on radioscanner date back to 2008. Reception of a digital signal with a width of 10KHz is not possible on a regular household (and even amateur) receiver, so those who wanted to had to solder the converter to output the IF receiver to the sound card. After the appearance of SDR, the problem resolved by itself, there you can choose any bandwidth within the capabilities of the receiver (for the first SDRs based on a sound card it was usually 48KHz, which is more than enough). The decoding itself was carried out using a very convenient and high-quality Dream program.
As mentioned above, DRM stations work quite regularly, and finding them on the air is not so difficult. For example, on websdr such a signal is very easily distinguishable on the spectrum - if a 10KHz digital signal is visible in the broadcast range, then this is it. Example screenshot of a station operating at 15 MHz taken at the time of writing:
Just decoding it using websdr will not work, the bandwidth of the online receiver is too small. However, anyone can listen to DRM, a file recorded from real air can be downloaded here . For decoding, you can use the already mentioned Dream program, a working version with all the necessary DLLs can be found on the radioscanner website .
If we talk about “iron” receivers, then, for example, the Gospell GR-216 receiver was announced, but it is not “live” on either eBay or Amazon.
Edit: as prompted in the comments, now this receiver is sold on the Australian market under the brand name Tecsun Q-3061. The issue price is 500AUD, or about $ 350.
Those who want to host DRM stations themselves can see the schedule at https://www.drm.org/what-can-i-hear/broadcast-schedule-2/ .
Now we turn to no less interesting - the possibility of transmitting DRM signals (and if I am not mistaken, this is described in RuNet for the first time). This can be done using GNU Radio and the gr-drm module .
Technically, DRM uses QAM modulation, and has quite a few bitrate and bandwidth settings. Also, not only sound (both mono and stereo) can be transmitted, but also text, channel logo and other service information. For HF (AD modes), the occupied band can vary from 4.5 to 20 KHz, however, in practice, only 10 KHz signals were encountered. For VHF (mode E), as already mentioned, a 100KHz band is used.
Table from www.drm.org/DRM_Handbook_2018.pdf :
A more detailed description of the standard is in PDF , you can read briefly on Signalwiki .
Let's get back to our connection graph. As you can see, the DRM encoder generates a signal from several components.
Well, the most interesting thing is that all this can be run without problems on a regular PC. Gr-drm is included in the PothosSDR package for Windows, but alas, it doesn’t work there - there is a signal, but decoding occurs with errors. Under Ubuntu, everything starts normally.
You can use a WAV file or a full SDR transceiver such as HackRF as an output device in GNU Radio. For those who want to experiment on their own, the GRC file is under the spoiler.
Alas, USRP does not transmit to HF, but I do not have HackRF. So it was not possible to make a real broadcast test, however I can confirm that sound decoding through Dream occurs without errors.
Oddly enough, despite the seemingly 99% hopelessness, the DRM standard is still alive. However, it is unlikely that he will be successful and go beyond any local experiments - the sound quality in DRM no longer meets modern standards, and there are no receivers on the market. From a technical point of view, what seemed like a “breakthrough” in 2003 is now of little relevance.
But on the other hand, the DRM standard contains many interesting ideas, its reception was (and is) an interesting experience for radio amateurs, which anyone can join in while the drm stations are on the air.
This completes the series of articles about SDR, I hope someone was interested and useful.
All successful experiments.
In the “anniversary” part of the series about SDR, I want to talk about one of the protocols, thanks to which many hams “involuntarily” joined the world of digital broadband signals. This standard was also the first (and as far as is known, the only) attempt to transmit digital sound at short wavelengths.
')
As many have probably already guessed, we will talk about the DRM standard - Digital Radio Mondiale (not to be confused with other DRM, Digital Rights Management).
Well, because If we are going to talk about SDR, then we will see not only how to receive DRM, but also how to transmit it. Continued under the cut.
Story
The history of the DRM standard is not easy. It was first introduced in 2003, and test transmissions have been made since 2007, and with varying success continue periodically and still.
DRM was based on two main ideas.
- Sound transmission at short wavelengths with “digital quality”, without noise and fading, with a bit rate from 6 to 34Kbit / s. However, “digital quality” here can be written only in quotation marks, because at 12Kbit bitrate, the sound comes
fromquite...relatively low quality. In addition, the HF signal is really subject to both noise and fading, and in order for the “digit” to be decoded, a very high signal-to-noise ratio is needed - such that the regular analog signal will sound even better. In general, it’s enough to try to accept DRM at least once in real life in order to understand that the idea will not take off. But broadcasting was nevertheless periodically carried out, including from Russia (see KDPV), and some radio stations sometimes still broadcast in DRM. - Sound transmission in the FM band. This standard has been called DRM +. Here the idea was to save the frequency resource - thanks to digital compression, up to 4 audio transmissions can be transmitted immediately in the 100KHz band, which promised good advantages in large cities such as London, where there are no free frequencies anymore. On the other hand, DAB already worked in Europe, and another standard was simply not needed here. According to Wikipedia, the test broadcast of DRM + was carried out in Scotland in the 2010th year, while some real cases of broadcasting DRM + have not yet been heard.
The DRM standard is essentially somewhat surreal - for years radio stations have been operating, broadcasts are broadcasting ... But there are no receivers of this standard on sale. At all. None. It is clear that since the standard is digital, then the usual receiver can only hear hissing, and no one has yet learned how to decode QAM by ear. So the reception of DRM was entertainment only for ham radio. It seems that 1-2 receivers did exist, about which there are even a couple of videos on youtube ( 1 and 2 ), but there is nothing on sale now on Ebay or Amazon.
The second problem of receiving DRM is that in the cities of HF broadcasting is de facto dead - there is so much interference from household equipment and power supplies that even if you turn on the HF radio, you will hear one pop and noise - decoding in such conditions does not work will, in the best case, the receiver will be able to show the screensaver of the station, but without sound. You can of course put the antenna on the balcony or on the roof, carefully configure it, and in principle, it’s quite possible to receive and decode DRM from a city apartment for radio amateurs. Ordinary people will not bother with this 100%, no one will climb onto the roof to hang an antenna to receive an audio signal with a bitrate of 12Kbit / s.
In general, there are no receivers, no audience. But there is a broadcast. The gopher from the movie is resting ...
By the way, right now, at the time of writing (July 2019), DRM + test broadcasting is being carried out in St. Petersburg, so those who wish
DRM Reception
The first reports of DRM hams on radioscanner date back to 2008. Reception of a digital signal with a width of 10KHz is not possible on a regular household (and even amateur) receiver, so those who wanted to had to solder the converter to output the IF receiver to the sound card. After the appearance of SDR, the problem resolved by itself, there you can choose any bandwidth within the capabilities of the receiver (for the first SDRs based on a sound card it was usually 48KHz, which is more than enough). The decoding itself was carried out using a very convenient and high-quality Dream program.
As mentioned above, DRM stations work quite regularly, and finding them on the air is not so difficult. For example, on websdr such a signal is very easily distinguishable on the spectrum - if a 10KHz digital signal is visible in the broadcast range, then this is it. Example screenshot of a station operating at 15 MHz taken at the time of writing:
Just decoding it using websdr will not work, the bandwidth of the online receiver is too small. However, anyone can listen to DRM, a file recorded from real air can be downloaded here . For decoding, you can use the already mentioned Dream program, a working version with all the necessary DLLs can be found on the radioscanner website .
If we talk about “iron” receivers, then, for example, the Gospell GR-216 receiver was announced, but it is not “live” on either eBay or Amazon.
Edit: as prompted in the comments, now this receiver is sold on the Australian market under the brand name Tecsun Q-3061. The issue price is 500AUD, or about $ 350.
Those who want to host DRM stations themselves can see the schedule at https://www.drm.org/what-can-i-hear/broadcast-schedule-2/ .
DRM Transmission
Now we turn to no less interesting - the possibility of transmitting DRM signals (and if I am not mistaken, this is described in RuNet for the first time). This can be done using GNU Radio and the gr-drm module .
Technically, DRM uses QAM modulation, and has quite a few bitrate and bandwidth settings. Also, not only sound (both mono and stereo) can be transmitted, but also text, channel logo and other service information. For HF (AD modes), the occupied band can vary from 4.5 to 20 KHz, however, in practice, only 10 KHz signals were encountered. For VHF (mode E), as already mentioned, a 100KHz band is used.
Table from www.drm.org/DRM_Handbook_2018.pdf :
A more detailed description of the standard is in PDF , you can read briefly on Signalwiki .
Let's get back to our connection graph. As you can see, the DRM encoder generates a signal from several components.
- Fast Access Channel (FAC). Contains information about ODFM signal properties and SDC / MSC configuration. Channel information is transmitted every 0.4s, which allows the receiver to quickly begin receiving a station signal. Signal parameters can be configured in the DRM Configuration block.
- Service Description Channel (SDC). Describes the MSC transmission channel.
- Main Service Channel (MSC). Contains data frames; QAM16 or QAM64 can be used for transmission.
Well, the most interesting thing is that all this can be run without problems on a regular PC. Gr-drm is included in the PothosSDR package for Windows, but alas, it doesn’t work there - there is a signal, but decoding occurs with errors. Under Ubuntu, everything starts normally.
You can use a WAV file or a full SDR transceiver such as HackRF as an output device in GNU Radio. For those who want to experiment on their own, the GRC file is under the spoiler.
rdm_transmit.grc
<?xml version='1.0' encoding='utf-8'?> <?grc format='1' created='3.7.11'?> <flow_graph> <timestamp>Tue Apr 29 11:37:08 2014</timestamp> <block> <key>options</key> <param> <key>author</key> <value>Felix Wunsch</value> </param> <param> <key>window_size</key> <value>3000, 2000</value> </param> <param> <key>category</key> <value>Custom</value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>description</key> <value>Generic DRM Transmitter. For the MSC, only SM and EEP is implemented.</value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(1016, 16)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>generate_options</key> <value>no_gui</value> </param> <param> <key>hier_block_src_path</key> <value>.:</value> </param> <param> <key>id</key> <value>drm_transmitter</value> </param> <param> <key>max_nouts</key> <value>0</value> </param> <param> <key>qt_qss_theme</key> <value></value> </param> <param> <key>realtime_scheduling</key> <value></value> </param> <param> <key>run_command</key> <value>{python} -u {filename}</value> </param> <param> <key>run_options</key> <value>run</value> </param> <param> <key>run</key> <value>True</value> </param> <param> <key>thread_safe_setters</key> <value></value> </param> <param> <key>title</key> <value>DRM Transmitter</value> </param> </block> <block> <key>variable</key> <param> <key>comment</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(240, 60)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>file_dest</value> </param> <param> <key>value</key> <value>"D:\\MyProjects\\GNURadio\\gr-drm-master\\apps\\sound_drm_out.wav"</value> </param> </block> <block> <key>variable</key> <param> <key>comment</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(56, 60)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>file_source</value> </param> <param> <key>value</key> <value>"D:\\MyProjects\\GNURadio\\gr-drm-master\\apps\\sound.wav"</value> </param> </block> <block> <key>variable_drm_config</key> <param> <key>audio_sample_rate</key> <value>12000</value> </param> <param> <key>comment</key> <value>Before generating the flow graph, define the path to a 24 kHz wav-file and change the parameters of the UHD sink. Do not forget to set the correct audio_sample_rate.</value> </param> <param> <key>_enabled</key> <value>1</value> </param> <param> <key>_coordinate</key> <value>(1208, 12)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>tp</value> </param> <param> <key>long_interl</key> <value>True</value> </param> <param> <key>msc_mapping</key> <value>2</value> </param> <param> <key>msc_prot_level_2_16</key> <value>1</value> </param> <param> <key>msc_prot_level_2_64</key> <value>0</value> </param> <param> <key>RM</key> <value>1</value> </param> <param> <key>sdc_mapping</key> <value>0</value> </param> <param> <key>SO</key> <value>3</value> </param> <param> <key>station_label</key> <value>"Radioscanner Test"</value> </param> <param> <key>text_message</key> <value>"DRM transmission with GNU Radio"</value> </param> </block> <block> <key>analog_sig_source_x</key> <param> <key>amp</key> <value>1</value> </param> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>1</value> </param> <param> <key>freq</key> <value>7000</value> </param> <param> <key>_coordinate</key> <value>(576, 624)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>analog_sig_source_x_0</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>offset</key> <value>0</value> </param> <param> <key>type</key> <value>complex</value> </param> <param> <key>samp_rate</key> <value>drm.FS_SOUNDCARD</value> </param> <param> <key>waveform</key> <value>analog.GR_COS_WAVE</value> </param> </block> <block> <key>audio_sink</key> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>device_name</key> <value></value> </param> <param> <key>_enabled</key> <value>0</value> </param> <param> <key>_coordinate</key> <value>(1184, 556)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>audio_sink_0</value> </param> <param> <key>num_inputs</key> <value>1</value> </param> <param> <key>ok_to_block</key> <value>True</value> </param> <param> <key>samp_rate</key> <value>48000</value> </param> </block> <block> <key>audio_source</key> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>device_name</key> <value></value> </param> <param> <key>_enabled</key> <value>0</value> </param> <param> <key>_coordinate</key> <value>(56, 156)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>audio_source_0</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>num_outputs</key> <value>1</value> </param> <param> <key>ok_to_block</key> <value>True</value> </param> <param> <key>samp_rate</key> <value>44100</value> </param> </block> <block> <key>blocks_complex_to_real</key> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>1</value> </param> <param> <key>_coordinate</key> <value>(1008, 640)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>blocks_complex_to_real_0</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>vlen</key> <value>1</value> </param> </block> <block> <key>blocks_multiply_const_vxx</key> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>const</key> <value>32768</value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>1</value> </param> <param> <key>_coordinate</key> <value>(272, 236)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>blocks_multiply_const_vxx_0</value> </param> <param> <key>type</key> <value>float</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>vlen</key> <value>1</value> </param> </block> <block> <key>blocks_multiply_const_vxx</key> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value>Prevent clipping</value> </param> <param> <key>const</key> <value>7e-3</value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(688, 468)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>blocks_multiply_const_vxx_1</value> </param> <param> <key>type</key> <value>complex</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>vlen</key> <value>1</value> </param> </block> <block> <key>blocks_multiply_xx</key> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>1</value> </param> <param> <key>_coordinate</key> <value>(864, 624)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>blocks_multiply_xx_0</value> </param> <param> <key>type</key> <value>complex</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>num_inputs</key> <value>2</value> </param> <param> <key>vlen</key> <value>1</value> </param> </block> <block> <key>blocks_wavfile_sink</key> <param> <key>bits_per_sample</key> <value>16</value> </param> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>1</value> </param> <param> <key>file</key> <value>file_dest</value> </param> <param> <key>_coordinate</key> <value>(1200, 620)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>blocks_wavfile_sink_0</value> </param> <param> <key>nchan</key> <value>1</value> </param> <param> <key>samp_rate</key> <value>drm.FS_SOUNDCARD</value> </param> </block> <block> <key>blocks_wavfile_source</key> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>1</value> </param> <param> <key>file</key> <value>file_source</value> </param> <param> <key>_coordinate</key> <value>(56, 228)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>blocks_wavfile_source_0</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>nchan</key> <value>1</value> </param> <param> <key>repeat</key> <value>False</value> </param> </block> <block> <key>cell_mapping_cc</key> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value>Multiplex the three logical channels and the pilot cells and create transmission frames.</value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(1184, 264)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>cell_mapping_cc_0</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>tp</key> <value>tp</value> </param> </block> <block> <key>digital_ofdm_cyclic_prefixer</key> <param> <key>alias</key> <value></value> </param> <param> <key>cp_len</key> <value>tp.ofdm().nfft()*tp.ofdm().cp_ratio_enum()/tp.ofdm().cp_ratio_denom()</value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>input_size</key> <value>tp.ofdm().nfft()</value> </param> <param> <key>_coordinate</key> <value>(456, 448)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>digital_ofdm_cyclic_prefixer_1</value> </param> <param> <key>tagname</key> <value></value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>rolloff</key> <value>0</value> </param> </block> <block> <key>drm_audio_encoder_sb</key> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(456, 240)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>drm_audio_encoder_sb_0</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>len_out</key> <value>tp.msc().L_MUX()</value> </param> <param> <key>tp</key> <value>tp</value> </param> </block> <block> <key>drm_generate_fac_b</key> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(56, 344)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>drm_generate_fac_b_0</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>tp</key> <value>tp</value> </param> </block> <block> <key>drm_generate_sdc_b</key> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(56, 296)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>drm_generate_sdc_b_0</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>tp</key> <value>tp</value> </param> </block> <block> <key>drm_interleaver_cc</key> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value>Additional interleaving</value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(952, 240)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>drm_interleaver_cc_0</value> </param> <param> <key>depth</key> <value>drm.INTL_DEPTH_DRM</value> </param> <param> <key>interl_seq</key> <value>tp.msc().cell_interl_seq()</value> </param> <param> <key>long_interl</key> <value>tp.cfg().long_interl()</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> </block> <block> <key>drm_scrambler_bb</key> <param> <key>alias</key> <value></value> </param> <param> <key>block_len</key> <value>tp.msc().L_MUX()</value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(608, 240)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>drm_scrambler_bb_0</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> </block> <block> <key>drm_scrambler_bb</key> <param> <key>alias</key> <value></value> </param> <param> <key>block_len</key> <value>tp.fac().L()</value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(608, 344)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>drm_scrambler_bb_0_0</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> </block> <block> <key>drm_scrambler_bb</key> <param> <key>alias</key> <value></value> </param> <param> <key>block_len</key> <value>tp.sdc().L()</value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(608, 296)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>drm_scrambler_bb_0_1</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> </block> <block> <key>fft_vxx</key> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>fft_size</key> <value>tp.ofdm().nfft()</value> </param> <param> <key>forward</key> <value>False</value> </param> <param> <key>_coordinate</key> <value>(232, 440)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>fft_vxx_0</value> </param> <param> <key>type</key> <value>complex</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>nthreads</key> <value>1</value> </param> <param> <key>shift</key> <value>True</value> </param> <param> <key>window</key> <value></value> </param> </block> <block> <key>mlc_bc</key> <param> <key>alias</key> <value></value> </param> <param> <key>channel_type</key> <value>"FAC"</value> </param> <param> <key>comment</key> <value>Apply channel coding and interleaving</value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(744, 340)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>mlc_bc_0</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>tp</key> <value>tp</value> </param> </block> <block> <key>mlc_bc</key> <param> <key>alias</key> <value></value> </param> <param> <key>channel_type</key> <value>"MSC"</value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(744, 236)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>mlc_bc_0_0</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>tp</key> <value>tp</value> </param> </block> <block> <key>mlc_bc</key> <param> <key>alias</key> <value></value> </param> <param> <key>channel_type</key> <value>"SDC"</value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(744, 292)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>mlc_bc_0_1</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>tp</key> <value>tp</value> </param> </block> <block> <key>rational_resampler_xxx</key> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value>Ingoing sample rate is assumed to be 48 kHz. 250 kHz is one of the lowest achievable rates of the USRP.</value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>decim</key> <value>drm.FS_SOUNDCARD / 1000</value> </param> <param> <key>_enabled</key> <value>0</value> </param> <param> <key>fbw</key> <value>0</value> </param> <param> <key>_coordinate</key> <value>(864, 448)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>rational_resampler_xxx_0</value> </param> <param> <key>interp</key> <value>250</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>taps</key> <value></value> </param> <param> <key>type</key> <value>ccc</value> </param> </block> <block> <key>rational_resampler_xxx</key> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>decim</key> <value>441</value> </param> <param> <key>_enabled</key> <value>0</value> </param> <param> <key>fbw</key> <value>0</value> </param> <param> <key>_coordinate</key> <value>(248, 136)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>rational_resampler_xxx_0_0</value> </param> <param> <key>interp</key> <value>240</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>taps</key> <value></value> </param> <param> <key>type</key> <value>fff</value> </param> </block> <block> <key>virtual_source</key> <param> <key>comment</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(56, 468)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>sym_in</value> </param> <param> <key>stream_id</key> <value>symbols</value> </param> </block> <block> <key>virtual_sink</key> <param> <key>comment</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(1408, 292)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>sym_out</value> </param> <param> <key>stream_id</key> <value>symbols</value> </param> </block> <block> <key>uhd_usrp_sink</key> <param> <key>alias</key> <value></value> </param> <param> <key>ant0</key> <value>TXA</value> </param> <param> <key>bw0</key> <value>0</value> </param> <param> <key>center_freq0</key> <value>5e6</value> </param> <param> <key>norm_gain0</key> <value>False</value> </param> <param> <key>gain0</key> <value>0</value> </param> <param> <key>ant10</key> <value></value> </param> <param> <key>bw10</key> <value>0</value> </param> <param> <key>center_freq10</key> <value>0</value> </param> <param> <key>norm_gain10</key> <value>False</value> </param> <param> <key>gain10</key> <value>0</value> </param> <param> <key>ant11</key> <value></value> </param> <param> <key>bw11</key> <value>0</value> </param> <param> <key>center_freq11</key> <value>0</value> </param> <param> <key>norm_gain11</key> <value>False</value> </param> <param> <key>gain11</key> <value>0</value> </param> <param> <key>ant12</key> <value></value> </param> <param> <key>bw12</key> <value>0</value> </param> <param> <key>center_freq12</key> <value>0</value> </param> <param> <key>norm_gain12</key> <value>False</value> </param> <param> <key>gain12</key> <value>0</value> </param> <param> <key>ant13</key> <value></value> </param> <param> <key>bw13</key> <value>0</value> </param> <param> <key>center_freq13</key> <value>0</value> </param> <param> <key>norm_gain13</key> <value>False</value> </param> <param> <key>gain13</key> <value>0</value> </param> <param> <key>ant14</key> <value></value> </param> <param> <key>bw14</key> <value>0</value> </param> <param> <key>center_freq14</key> <value>0</value> </param> <param> <key>norm_gain14</key> <value>False</value> </param> <param> <key>gain14</key> <value>0</value> </param> <param> <key>ant15</key> <value></value> </param> <param> <key>bw15</key> <value>0</value> </param> <param> <key>center_freq15</key> <value>0</value> </param> <param> <key>norm_gain15</key> <value>False</value> </param> <param> <key>gain15</key> <value>0</value> </param> <param> <key>ant16</key> <value></value> </param> <param> <key>bw16</key> <value>0</value> </param> <param> <key>center_freq16</key> <value>0</value> </param> <param> <key>norm_gain16</key> <value>False</value> </param> <param> <key>gain16</key> <value>0</value> </param> <param> <key>ant17</key> <value></value> </param> <param> <key>bw17</key> <value>0</value> </param> <param> <key>center_freq17</key> <value>0</value> </param> <param> <key>norm_gain17</key> <value>False</value> </param> <param> <key>gain17</key> <value>0</value> </param> <param> <key>ant18</key> <value></value> </param> <param> <key>bw18</key> <value>0</value> </param> <param> <key>center_freq18</key> <value>0</value> </param> <param> <key>norm_gain18</key> <value>False</value> </param> <param> <key>gain18</key> <value>0</value> </param> <param> <key>ant19</key> <value></value> </param> <param> <key>bw19</key> <value>0</value> </param> <param> <key>center_freq19</key> <value>0</value> </param> <param> <key>norm_gain19</key> <value>False</value> </param> <param> <key>gain19</key> <value>0</value> </param> <param> <key>ant1</key> <value></value> </param> <param> <key>bw1</key> <value>0</value> </param> <param> <key>center_freq1</key> <value>0</value> </param> <param> <key>norm_gain1</key> <value>False</value> </param> <param> <key>gain1</key> <value>0</value> </param> <param> <key>ant20</key> <value></value> </param> <param> <key>bw20</key> <value>0</value> </param> <param> <key>center_freq20</key> <value>0</value> </param> <param> <key>norm_gain20</key> <value>False</value> </param> <param> <key>gain20</key> <value>0</value> </param> <param> <key>ant21</key> <value></value> </param> <param> <key>bw21</key> <value>0</value> </param> <param> <key>center_freq21</key> <value>0</value> </param> <param> <key>norm_gain21</key> <value>False</value> </param> <param> <key>gain21</key> <value>0</value> </param> <param> <key>ant22</key> <value></value> </param> <param> <key>bw22</key> <value>0</value> </param> <param> <key>center_freq22</key> <value>0</value> </param> <param> <key>norm_gain22</key> <value>False</value> </param> <param> <key>gain22</key> <value>0</value> </param> <param> <key>ant23</key> <value></value> </param> <param> <key>bw23</key> <value>0</value> </param> <param> <key>center_freq23</key> <value>0</value> </param> <param> <key>norm_gain23</key> <value>False</value> </param> <param> <key>gain23</key> <value>0</value> </param> <param> <key>ant24</key> <value></value> </param> <param> <key>bw24</key> <value>0</value> </param> <param> <key>center_freq24</key> <value>0</value> </param> <param> <key>norm_gain24</key> <value>False</value> </param> <param> <key>gain24</key> <value>0</value> </param> <param> <key>ant25</key> <value></value> </param> <param> <key>bw25</key> <value>0</value> </param> <param> <key>center_freq25</key> <value>0</value> </param> <param> <key>norm_gain25</key> <value>False</value> </param> <param> <key>gain25</key> <value>0</value> </param> <param> <key>ant26</key> <value></value> </param> <param> <key>bw26</key> <value>0</value> </param> <param> <key>center_freq26</key> <value>0</value> </param> <param> <key>norm_gain26</key> <value>False</value> </param> <param> <key>gain26</key> <value>0</value> </param> <param> <key>ant27</key> <value></value> </param> <param> <key>bw27</key> <value>0</value> </param> <param> <key>center_freq27</key> <value>0</value> </param> <param> <key>norm_gain27</key> <value>False</value> </param> <param> <key>gain27</key> <value>0</value> </param> <param> <key>ant28</key> <value></value> </param> <param> <key>bw28</key> <value>0</value> </param> <param> <key>center_freq28</key> <value>0</value> </param> <param> <key>norm_gain28</key> <value>False</value> </param> <param> <key>gain28</key> <value>0</value> </param> <param> <key>ant29</key> <value></value> </param> <param> <key>bw29</key> <value>0</value> </param> <param> <key>center_freq29</key> <value>0</value> </param> <param> <key>norm_gain29</key> <value>False</value> </param> <param> <key>gain29</key> <value>0</value> </param> <param> <key>ant2</key> <value></value> </param> <param> <key>bw2</key> <value>0</value> </param> <param> <key>center_freq2</key> <value>0</value> </param> <param> <key>norm_gain2</key> <value>False</value> </param> <param> <key>gain2</key> <value>0</value> </param> <param> <key>ant30</key> <value></value> </param> <param> <key>bw30</key> <value>0</value> </param> <param> <key>center_freq30</key> <value>0</value> </param> <param> <key>norm_gain30</key> <value>False</value> </param> <param> <key>gain30</key> <value>0</value> </param> <param> <key>ant31</key> <value></value> </param> <param> <key>bw31</key> <value>0</value> </param> <param> <key>center_freq31</key> <value>0</value> </param> <param> <key>norm_gain31</key> <value>False</value> </param> <param> <key>gain31</key> <value>0</value> </param> <param> <key>ant3</key> <value></value> </param> <param> <key>bw3</key> <value>0</value> </param> <param> <key>center_freq3</key> <value>0</value> </param> <param> <key>norm_gain3</key> <value>False</value> </param> <param> <key>gain3</key> <value>0</value> </param> <param> <key>ant4</key> <value></value> </param> <param> <key>bw4</key> <value>0</value> </param> <param> <key>center_freq4</key> <value>0</value> </param> <param> <key>norm_gain4</key> <value>False</value> </param> <param> <key>gain4</key> <value>0</value> </param> <param> <key>ant5</key> <value></value> </param> <param> <key>bw5</key> <value>0</value> </param> <param> <key>center_freq5</key> <value>0</value> </param> <param> <key>norm_gain5</key> <value>False</value> </param> <param> <key>gain5</key> <value>0</value> </param> <param> <key>ant6</key> <value></value> </param> <param> <key>bw6</key> <value>0</value> </param> <param> <key>center_freq6</key> <value>0</value> </param> <param> <key>norm_gain6</key> <value>False</value> </param> <param> <key>gain6</key> <value>0</value> </param> <param> <key>ant7</key> <value></value> </param> <param> <key>bw7</key> <value>0</value> </param> <param> <key>center_freq7</key> <value>0</value> </param> <param> <key>norm_gain7</key> <value>False</value> </param> <param> <key>gain7</key> <value>0</value> </param> <param> <key>ant8</key> <value></value> </param> <param> <key>bw8</key> <value>0</value> </param> <param> <key>center_freq8</key> <value>0</value> </param> <param> <key>norm_gain8</key> <value>False</value> </param> <param> <key>gain8</key> <value>0</value> </param> <param> <key>ant9</key> <value></value> </param> <param> <key>bw9</key> <value>0</value> </param> <param> <key>center_freq9</key> <value>0</value> </param> <param> <key>norm_gain9</key> <value>False</value> </param> <param> <key>gain9</key> <value>0</value> </param> <param> <key>clock_rate</key> <value>0.0</value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>dev_addr</key> <value></value> </param> <param> <key>dev_args</key> <value>""</value> </param> <param> <key>_enabled</key> <value>0</value> </param> <param> <key>_coordinate</key> <value>(1168, 424)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>uhd_usrp_sink_0</value> </param> <param> <key>type</key> <value>fc32</value> </param> <param> <key>clock_source0</key> <value></value> </param> <param> <key>sd_spec0</key> <value></value> </param> <param> <key>time_source0</key> <value></value> </param> <param> <key>clock_source1</key> <value></value> </param> <param> <key>sd_spec1</key> <value></value> </param> <param> <key>time_source1</key> <value></value> </param> <param> <key>clock_source2</key> <value></value> </param> <param> <key>sd_spec2</key> <value></value> </param> <param> <key>time_source2</key> <value></value> </param> <param> <key>clock_source3</key> <value></value> </param> <param> <key>sd_spec3</key> <value></value> </param> <param> <key>time_source3</key> <value></value> </param> <param> <key>clock_source4</key> <value></value> </param> <param> <key>sd_spec4</key> <value></value> </param> <param> <key>time_source4</key> <value></value> </param> <param> <key>clock_source5</key> <value></value> </param> <param> <key>sd_spec5</key> <value></value> </param> <param> <key>time_source5</key> <value></value> </param> <param> <key>clock_source6</key> <value></value> </param> <param> <key>sd_spec6</key> <value></value> </param> <param> <key>time_source6</key> <value></value> </param> <param> <key>clock_source7</key> <value></value> </param> <param> <key>sd_spec7</key> <value></value> </param> <param> <key>time_source7</key> <value></value> </param> <param> <key>nchan</key> <value>1</value> </param> <param> <key>num_mboards</key> <value>1</value> </param> <param> <key>samp_rate</key> <value>48000 * 250 / 48</value> </param> <param> <key>hide_cmd_port</key> <value>False</value> </param> <param> <key>hide_lo_controls</key> <value>True</value> </param> <param> <key>stream_args</key> <value></value> </param> <param> <key>stream_chans</key> <value>[]</value> </param> <param> <key>sync</key> <value></value> </param> <param> <key>len_tag_name</key> <value></value> </param> <param> <key>otw</key> <value></value> </param> </block> <connection> <source_block_id>analog_sig_source_x_0</source_block_id> <sink_block_id>blocks_multiply_xx_0</sink_block_id> <source_key>0</source_key> <sink_key>1</sink_key> </connection> <connection> <source_block_id>audio_source_0</source_block_id> <sink_block_id>rational_resampler_xxx_0_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>blocks_complex_to_real_0</source_block_id> <sink_block_id>audio_sink_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>blocks_complex_to_real_0</source_block_id> <sink_block_id>blocks_wavfile_sink_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>blocks_multiply_const_vxx_0</source_block_id> <sink_block_id>drm_audio_encoder_sb_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>blocks_multiply_const_vxx_1</source_block_id> <sink_block_id>blocks_multiply_xx_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>blocks_multiply_const_vxx_1</source_block_id> <sink_block_id>rational_resampler_xxx_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>blocks_multiply_xx_0</source_block_id> <sink_block_id>blocks_complex_to_real_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>blocks_wavfile_source_0</source_block_id> <sink_block_id>blocks_multiply_const_vxx_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>cell_mapping_cc_0</source_block_id> <sink_block_id>sym_out</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>digital_ofdm_cyclic_prefixer_1</source_block_id> <sink_block_id>blocks_multiply_const_vxx_1</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>drm_audio_encoder_sb_0</source_block_id> <sink_block_id>drm_scrambler_bb_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>drm_generate_fac_b_0</source_block_id> <sink_block_id>drm_scrambler_bb_0_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>drm_generate_sdc_b_0</source_block_id> <sink_block_id>drm_scrambler_bb_0_1</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>drm_interleaver_cc_0</source_block_id> <sink_block_id>cell_mapping_cc_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>drm_scrambler_bb_0</source_block_id> <sink_block_id>mlc_bc_0_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>drm_scrambler_bb_0_0</source_block_id> <sink_block_id>mlc_bc_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>drm_scrambler_bb_0_1</source_block_id> <sink_block_id>mlc_bc_0_1</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>fft_vxx_0</source_block_id> <sink_block_id>digital_ofdm_cyclic_prefixer_1</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>mlc_bc_0</source_block_id> <sink_block_id>cell_mapping_cc_0</sink_block_id> <source_key>0</source_key> <sink_key>2</sink_key> </connection> <connection> <source_block_id>mlc_bc_0_0</source_block_id> <sink_block_id>drm_interleaver_cc_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>mlc_bc_0_1</source_block_id> <sink_block_id>cell_mapping_cc_0</sink_block_id> <source_key>0</source_key> <sink_key>1</sink_key> </connection> <connection> <source_block_id>rational_resampler_xxx_0</source_block_id> <sink_block_id>uhd_usrp_sink_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>rational_resampler_xxx_0_0</source_block_id> <sink_block_id>drm_audio_encoder_sb_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>sym_in</source_block_id> <sink_block_id>fft_vxx_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> </flow_graph> Alas, USRP does not transmit to HF, but I do not have HackRF. So it was not possible to make a real broadcast test, however I can confirm that sound decoding through Dream occurs without errors.
Conclusion
Oddly enough, despite the seemingly 99% hopelessness, the DRM standard is still alive. However, it is unlikely that he will be successful and go beyond any local experiments - the sound quality in DRM no longer meets modern standards, and there are no receivers on the market. From a technical point of view, what seemed like a “breakthrough” in 2003 is now of little relevance.
But on the other hand, the DRM standard contains many interesting ideas, its reception was (and is) an interesting experience for radio amateurs, which anyone can join in while the drm stations are on the air.
This completes the series of articles about SDR, I hope someone was interested and useful.
All successful experiments.
Source: https://habr.com/ru/post/461653/
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