Re: [Discuss-gnuradio] OFDM example from gr-digital with UHD

[Marcus Müller]

Hi Gabriele,

have you tried adding more gain on the TX side?
Also, you will need to increase sampling rate. Right now, you're using
100kHz, which is 1/1000 of the master clock rate of the N200. If I'm not
mistaken, the maximum decimation for the N200 is 512, and hence the
minimum rate would be 100MHz/512 = 195.3125kHz. You probably just want
to use 200kHz or something similarly practical.

I hope that helps!

Best regards,
Marcus

On 06/25/2015 02:23 PM, Gabriele Galiero wrote:
> Hello, I was interested to test tx_ofdm.grc and rx_ofdm.grc from
> gr-digital, at the same time using USRP N200 devices.
>
> TX OFDM:
>
> The changes that I did were, removing throttle block and adding an UHD
> Sink instead, with center frequency 430 MHz, which is the frequency band
> for which my department has license to transmit.
>
> RX OFDM:
>
> In this case I removed all blocks before throttle (included), and placed
> there an UHD Source at the same center frequency.
>
> Flow graphs attached in the files.
>
> I monitored the output signal and the received signal. I also used a
> spectrum analyzer to check the actual signal that is being transmitted.
> Pics are attached.
>
> In the tx signal measured by a spectrum analyzer, we can see that the
> spectrum is not that we desire. I would like to ask if I am doing
> something wrong with the configuration. Before transmission there was no
> signal at that frequency and tx and rx antennas are suitable for the
> carrier frequency.
>
> In addition I tried to transmit a file instead of just random bits. In
> reception I was not receiving the file. The config was just adding a
> file sink at the end of the rx block and a file source at the beginning
> of the tx block. Could you please help me with some tip?
>
> Attachments:
> http://www.ruby-forum.com/attachment/10886/tx_ofdm.jpg
> http://www.ruby-forum.com/attachment/10887/rx_ofdm.png
> http://www.ruby-forum.com/attachment/10888/tx_signal.jpg
> http://www.ruby-forum.com/attachment/10889/rx_signal.jpg
> http://www.ruby-forum.com/attachment/10890/tx_sig_spectrum.jpg
>
>