Re: [Discuss-gnuradio] rx_ofdm Does Not Work Past Synchronizer

[Martin Braun]

On 03/19/2014 12:25 AM, Jonathan Fox wrote:
> So I have the stock python scripts (tx_ofdm and rx_ofdm) located in the
> gr-digital examples and put USRP sources and sinks in the appropriate
> spots. I left sampling alone (100K for TX, 3.2M for RX) and had the
> TX/RX frequency at 500 MHz. The USRPs used are N210s with WBX
> daughterboards. I tested the USRP used for TX out by outputting a signal
> to another and looking at it on the GNU Radio spectrum analyzer. Also,
> this is through SMA cables and a 30 dB attenuator, no over the air
> transmission. I placed file sinks after each block in the process; each
> file is a binary file. After multiple runs I felt like something wasn't
> working after looking at the binary files.

Maybe you're probably screwing up your tx signal by clipping, although I
can't say for sure from your flow graphs (where exactly do you put the
UHD sink?) See
http://video.fosdem.org/2014/AW1125/Sunday/Tutorial_OFDM_Packet_Transceivers.webm,
starting around ~27 mins for an explanation, or search the mailing list
archive.

Martin

> 
> When I execute, only the file sinks placed after the Schmidl & Cox OFDM
> Synchronizer freq_offset and detect have data in them, at least their
> files have some size to them, implying something has been written. The
> file sinks after FFT (or the header/payload demux) have no data, 0 KB.
> 
> When I discovered that the receive didn't work, I took the grc file
> another user made back in October with both TX mod and RX demod in the
> same flowgraph to see if that would work (files attached). Again same
> issue, all the binary files after the FFT have no data so something is
> getting screwed up in my demod.
> 
> Has any user on this list run into this issue before or can offer some
> insight to why the receiver is failing?
> 
> Thank you,
> 
> Jon
> 
> Attached is the python script, grc file, and screen shot of the TXRX
> combo in GRC.
> 
> 
> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>