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

[Aditya Dhananjay]

And if you are running over the air, try setting the TX and RX sampling rate to have the same value.

In any case, I would first run in loopback mode (as shown in your png file) and save the over-the-air transmissions for later.

On Tue, Mar 18, 2014 at 7:51 PM, Aditya Dhananjay <address@hidden> wrote:

Hi Jon,

Disclaimer: I haven't run your code, but based on eyeballing the png file:

It looks like your "delay" block is not configured properly. The delay should be fft_len + cp_len which is 80 (instead of 72).

Best,

Aditya

On Tue, Mar 18, 2014 at 7:25 PM, Jonathan Fox <address@hidden> 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.

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.

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