[srslte-users] Issue running examples

[Ismael Gomez]

On Tue, 31 Mar 2015 at 05:06 Tom Tsou <tom at tsou.cc> wrote:

> On Sun, Mar 29, 2015 at 8:54 PM, Eric Sollenberger <ericps1 at vt.edu> wrote:
> > I think I read somewhere that you guys have been using USRP B210's for
> your
> > development, have you run these examples on USRP N210's by any chance? If
> > not do you have any expectation for whether or not it should run?
>
> The N210 doesn't support reconfigurable clocking, so you can't set the
> clock to a 'nice' LTE rate that is some multiple or fraction of 30.72
> MHz. You can get around that by performing sample rate conversion on
> the host, but that does add a fair amount of overhead and complexity
> to the application. In summary, running LTE on the N210 is far less
> convenient than the B200.
>
> > I ran uhd_fft on one of the USRPs to verify that a signal was being
> > transmitted by the USRP running pdsch_enodeb, and I saw periodic bursts
> > towards the center of the FFT. I'm assuming this is the PSS/SSS and PBCH,
> > but since there isn't a UE connected, no actual data is being sent and so
> > the spectrum does not look like a typical OFDM waveform.
>
> On an idle downlink, you should still see reference signals and
> periodic SIB data on the shared channel in addition to the MIB and
> synchronization symbols in the center. The spectrum should still look
> very much like an OFDM signal.
>

The pdsch_enodeb example sends data continuously even if no UE is attached.
It only reproduces the PHY Downlink functionality, so there is no
attachment procedure at all. If you don't see the spectrum correctly, it is
most certainly an amplitude issue. Try running it with -l 1.0 argument,
which sets the signal amplitude. By default this example sets very low
amplitude to avoid saturation due to PAPR. We'll solve it very soon (today
or tomorrow).


>
>  -TT
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