[USRP-users] DVB-x (was: Again performance issues B210, while BladeRF performs fine)

Ralph A. Schmid, dk5ras ralph at schmid.xxx
Thu Apr 2 02:00:08 EDT 2015


Hi,

I adjusted the subject...

The issue with DVB-T were the 10 threads in FFT settings; reducing this to
one thread gives a stable and spectrum-wise OK looking signal, around 40dB
above noise when transmitted over a distance of one or two meters. So I took
my old laptop, went through the hassle installing a completely new Windows 7
and the DVB-T receiver stuff (DVBViewer and a RTL2832 based RX), and I was
able to find "something" on the chosen channel, with 55% signal strength, a
garbled channel name showed up, but no picture. At least somehow it looks
like a DVB-T signal, when I find some time I will try tweaking the settings
if I can get real reception. Oh, the receiver is OK, I can watch normal TV
with it, using just 15cm of wire as antenna. Next week I should have access
to a DVB-x antenna tester, maybe this beast can tell me more about the
signal. 

What example with the supplied test.ts is recommended for being received
with a normal receiver?

Ralph.

> -----Original Message-----
> From: USRP-users [mailto:usrp-users-bounces at lists.ettus.com] On Behalf Of
> Ralph A. Schmid, dk5ras via USRP-users
> Sent: Wednesday, April 1, 2015 1:58 PM
> To: 'Ron Economos'
> Cc: 'usrp-users'
> Subject: Re: [USRP-users] Again performance issues B210, while BladeRF
> performs fine
> 
> I will give it a try later this evening, however from the first test in
the lunch
> break I found that DVB-T still produces lots of U, while DVB-T2 is stable.
I did
> not yet test DVB-S2, but this will be one of the next projects...
> 
> Thanks a lot for all the assistance! It is amazing what you created with
all
> those TV mode projects!!
> 
> Ralph.
> 
> > -----Original Message-----
> > From: Ron Economos [mailto:w6rz at comcast.net]
> > Sent: Tuesday, March 31, 2015 12:50 PM
> > To: Ralph A. Schmid, dk5ras
> > Cc: 'usrp-users'
> > Subject: Re: [USRP-users] Again performance issues B210, while BladeRF
> > performs fine
> >
> > For the DVB-T transmit flow, delete the Rational Resampler block and
> > set
> the
> > sample rate to (8000000.0 * 8) / 7 for an
> > 8 MHz wide channel. For other channel widths, the sample rate formula
is:
> >
> > (8000000.0 * channel width in MHz) / 7
> >
> > On my setup, I'm getting better performance with the B210.
> > I was just doing some testing with the DVB-S2 flow, and I was able to
> > do
> 36
> > Msps. With bladeRF, I can't go over 24 Msps.
> >
> > It all seems to be related to the USB3.0 controller. On the B210, I'm
> using a
> > VL80X based controller, which seems pretty fast.
> >
> > On bladeRF, the VL80X controller doesn't work well at all and causes
> > hard crashes (where you have to power down to recover). I have to use
> > the
> built-
> > in NEC uPD720200 controller instead. It's slower, but solid as a rock.
> >
> > Ron
> >
> > On 03/31/2015 03:09 AM, Ralph A. Schmid, dk5ras wrote:
> > > OK, with your tips the signal is less broken, but still not stable;
> > > I already was using the vv009-4kfft.grc anyway. CPU is running at
> > > around 80%, not critical, but who knows?! I will try tweaking a bit
> > > if I can get it more stable. This is a very interesting case for
> > > fine tuning, as it is right at the edge small changes get visible at
once.
> > >
> > > Edit before sending: Now I have a solid signal, after assigning 4
> > > cores to the VM. Just the question remains, why does the B210 use
> > > the given resources so bad, compared to the BladeRF? And still I am
> > > not sure if I'd better use four virtual cores, or two virtual cores
> > > with two "virtual-virtual" ones each :) At first sight both variants
> > > behave
> > identical.
> > >
> > > Reception of the signal needs to wait until the DVB-T2 receiver is
> > > here, I expect it by next week. The DVB-T package I did not get to
> > > run, it transmits, but only some garble. The gnuradio fft view looks
> > > perfect, but the real spectrum is completely different, both with
> > > BladeRF and B210 it is the same crap coming out of the antenna.
> > > Maybe I
> > missed something...
> > >
> > > Ralph.
> > >
> > >> -----Original Message-----
> > >> From: Ron Economos [mailto:w6rz at comcast.net]
> > >> Sent: Tuesday, March 31, 2015 8:55 AM
> > >> To: Ralph A. Schmid, dk5ras
> > >> Cc: 'usrp-users'
> > >> Subject: Re: [USRP-users] Again performance issues B210, while
> > >> BladeRF performs fine
> > >>
> > >> I'm using the UHD sink.
> > >>
> > >> BTW, the AD9361 has built-in sin(x)/x correction, so you should set
> > >> that option to "Off" in the Pilot Generator and IFFT block.
> > >> It will still work fine either way, but the correct setting is "Off"
> > >> for B210 and "On" for bladeRF.
> > >>
> > >> Also, if you still end up with performance issues, the
> > >> vv009-4kfft.grc
> > > test flow
> > >> graph requires quite a bit less CPU performance than the
> > >> vv003-cr23.grc
> > > test
> > >> flow graph.
> > >>
> > >> Ron
> > >>
> > >> On 03/30/2015 11:13 PM, Ralph A. Schmid, dk5ras wrote:
> > >>> Hey, thanks a lot, I will give this a try later this day! What do
> > >>> you recommend, the osmocom sink, or the UHD sink?
> > >>>
> > >>> Ralph.
> > >>>
> > >>>
> > >>>> -----Original Message-----
> > >>>> From: USRP-users [mailto:usrp-users-bounces at lists.ettus.com] On
> > >>>> Behalf Of Ron Economos via USRP-users
> > >>>> Sent: Tuesday, March 31, 2015 12:52 AM
> > >>>> To: usrp-users at lists.ettus.com
> > >>>> Subject: [USRP-users] Again performance issues B210, while
> > >>>> BladeRF performs fine
> > >>>>
> > >>>> Just joined the mailing list to respond to this question. I'm the
> > >>> developer of
> > >>>> gr-dvbt2 and coincidently, I've just bought a B210.
> > >>>>
> > >>>> The fix for the underruns is to add some buffering. In the USRP
> > >>>> Sink block Device Address field, add the following:
> > >>>>
> > >>>> "send_frame_size=65536,num_send_frames=128"
> > >>>>
> > >>>> This works well here with a VL80X based USB3.0 controller.
> > >>>>
> > >>>> Ron
> > >>>>
> > >
> 
> 
> 
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