Re: [Discuss-gnuradio] anyone successful in running tx_ofdm and rx_ofdm grc files?

[Achilleas Anastasopoulos]

Martin,

I think my question would have been clearer if i had said that when I
talk of symbol rate I do not define a symbol to be the OFDM symbol of
length
fft_length+CP_length, but its fft_length+CP_length components.

So for me symbol rate is

symbol_rate  =  (fft_length+CP_length) x OFDM_symbol_rate

The grc examples are defining this as the sample_rate, which
implies that they use one sample for each symbol (my definition).

In any case, from your answer I understand that the S&C operates on
ONE sample per symbol (my definition).

---

I still have trouble getting anything out of the S&C synchronizer:
The frequency offset output responds as expected when i introduce a
freq error but the "detect" output does not give anything out
even with noiseless input...


I have uploaded the follwoing grc files

http://web.eecs.umich.edu/~anastas/gnuradio/tx_ofdm2.grc
http://web.eecs.umich.edu/~anastas/gnuradio/rx_ofdm2.grc

which, illustrate my point. Any thoughts?

thanks for the help,
Achilleas


On Sun, May 19, 2013 at 11:45:42PM -0400, Achilleas Anastasopoulos wrote:
> I am having trouble setting some parameters and getting anything out of it...
>
> In particular
>
> in ofdm_rx
>
> 1) is the processing done on an 1 sample per symbol basis at the Scmidl&Cox ?

I don't understand the question. The correlator has no info about OFDM
symbol boundaries.

> In that case the input sample rate has to be set to the symbol rate?
> (what is called samp_rate in ofdm_tx)

This is the input sample rate. The bit rate depends on the number of
carriers used, the length of the CP and the modulation type on the
payload. The OFDM symbol rate is the sample rate / (fft_len + cp_len).