Re: DVB-T example loopback

[Herman Tibor]

Hi Ron,

Thank you for the advice, it's working now! I'll start to construct the loopback version.

Cheers,

Tibor

Herman Tibor

Ron Economos <w6rz@comcast.net> ezt írta (időpont: 2022. febr. 10., Cs, 12:27):

You just have to match the parameters between the transmit and receive flow graphs. The only difference is that the transmitter is using 64QAM and the receiver is using 16QAM.

So you can either change the transmitter to 16QAM or change the receiver to 64QAM.

You should add a throttle block to the transmitter (right before the file sink will work).

Since you're not transmitting over the air, the sample rate doesn't matter if you're just creating a baseband file and playing it later.

However, if you want to play the output stream in real-time, the sample rate and bitrate of the Transport Stream do matter. Also, the performance of the computer running the receiver flow graph has to be sufficient for real-time. That's why the receive flow graph is configured for 16QAM as most 4 core CPUs can support that bitrate.

Ron

On 2/10/22 02:59, Herman Tibor wrote:

Hi everyone,

I'd like to teach students about OFDM modulation and I'd like to use Gnuradio for the purpose. I'm trying to create a baseband signal with the dvbt_tx_8k.grc project and decode it with the dvbt_rx_8k.grc project. The problem is that the rx project cannot decode the baseband signal created with the tx project. Has anyone tried this before? What am I missing? Do I need to set something differently in the RX project compared to the default? 

Is it possible to do it without actually transmitting the baseband signal? I would think so. But then what is the sample rate? The variable is only used in the UHD: USRP sink block, which I'd like to skip.

I know I can download a sample baseband file, which works and I can see it is generated, because the SNR is basically infinite. But I'd like to go further and demonstrate with a longer video and possibly loop back the tx to rx to modify the signal on the fly and finally play the stream in vlc.

Thanks,

Tibor

Herman Tibor