Re: [Discuss-gnuradio] Re: Soft-DVB DVB-T transmitter

[Martin DvH]

On Tue, 2008-11-11 at 08:26 +0100, Vincenzo Pellegrini wrote:
> Martin ,
> sorry for the delay. My exams seem to have gone well even if it's not
> official yet.
Great
>  I also had to do a demo for a company I have a temporary
> contract with for developing some gnuradio based gsm-r security
> sentinels. Also the demo was smooth. (i already listed the project on
> the gnuradio wiki)
Good work.
> so i really hope i'll be able to prepare the 8Mhz stream for you
> within the next 2/3 days. Would this still be useful?
Yes it really would.

I am also really looking forward for the sources.
One of the things I am planning to do is use the structure of your code
as a basis for a DVB-T receiver.
It is always easier debugging a receiver when you can make a full loop.
(transmitter and receiver back-to-back)

Greetings,
Martin
> 2008/11/3, Martin DvH <address@hidden>:
> >
> > On Mon, 2008-11-03 at 14:13 +0100, Martin DvH wrote:
> >>
> >>
> >>
> >> ________________________________
> >>
> >> >  Van: address@hidden
> >> [mailto:address@hidden
> >> Namens Vincenzo Pellegrini
> >> >  Verzonden: maandag 3 november 2008 0:16
> >> >  Aan: Martin DvH
> >> >  CC: discuss-gnuradio
> >> >  Onderwerp: [Discuss-gnuradio] Re: Soft-DVB DVB-T transmitter
> >> >  
> >> >  
> >> >  This is Great... :)
> >> >  
> >> >  Yup, the playback cannot be smooth because of the wrong throughput,
> >> definitely.
> >> >  Did you use the USRP1 with interpolation factor = 16 ?
> >> Yes I did.
> >> >  
> >> >  I can prepare a modulated signal with the correct throughput for
> >> you.. this is not a problem... :)
> >> >  
> >> Please do, this would be great.
> >> >  what hard disc are you playing your signal back from?
> >>
> >> Internal 2.5" harddisk of my acer 6930 notebook (Aspire 6930G-734G32BN
> >> LX.AVB0X.135)
> >> 2.5" 320GB HDD 5400rpm, SATA
> > I checked now. It is a:
> > Western digital Scorpio 320 GB SATA (WDC WD3200BEVT-22ZCT0)
> > 2.5-inch SATA Hard Drive 320 GB, 3 Gb/s, 8 MB Cache, 5400 RPM
> >
> > Benchmark from tomshardware (h2benchw 3.6):
> > http://www.tomshardware.com/charts/2-5-hard-drive-charts/Minimum-Read-Transfer-Performance,687.html
> > minimum read transfer rate 33.5 MB/sec
> > average read transfer rate 52.2 MB/sec
> > maximum read transfer rate 68.2 MB/sec
> >
> >
> >
> >> I am not at home right now So I can't check the exact brand and model of
> >> the
> >> harddisk.
> >> It can do around 38 MB/sec so this is just enough (required 32 MB/sec)
> >>
> >> I also have 4GB of memory in this notebook, so I think it will buffer the
> >> complete file.
> >>
> >> I had to use my notebook because with my desktop PC (ASrock
> >> 939-DUAL-SATA2)
> >> The USB TX bandwidth is less then 32 MB/sec.
> >> (Which is strange because I CAN receive 32 MB/sec)
> >> I get UuUuUu on this machine when useing interpolation 16, so unusable.
> >>
> >> Regards,
> >> Martin
> >>
> >> >  
> >> >  regards
> >> >  
> >> >  vincenzo
> >> >  
> >> >  
> >> >  2008/11/3 Martin DvH <address@hidden>
> >>    
> >>
> >>
> >>            Hi,
> >>            
> >>            > > In fact: 8 complex Msps implement a 7 MHz channel while
> >> 9.142857143
> >>            > > complex Msps implement an 8 MHz channel.
> >>            > > Just try to go as close as possible to such sampling
> >> frequency by
> >>            > > using USRP2 and let me know what happens... it could
> >> turn out that we
> >>            > > need a resampler block.
> >>            > So if I use a fractional rate resampler with interpolation
> >> factor
> >>            > 10/8=1.25 I get a 7 Mhz channel with 10 Msps samplerate.
> >>            > If I use a fractional rate resampler with interpolation
> >> factor
> >>            > 10/9.142857143=1.09375 I get a 8 Mhz channel with 10 Msps
> >> samplerate
> >>            >
> >>            > If I use a fractional rate resampler with DECIMATION
> >> factor
> >>            > 9.142857143/8=8/7=1.142857143 I get a 8 Mhz channel with 8
> >> Msps
> >>            > samplerate with the out-of-band skirts folded back at the
> >> sides.
> >>            >
> >>            > Would be interesting to see if this last one works with a
> >> USRP1.
> >>            >
> >>            > I'll let you know how the experiments go.
> >>            
> >>            I resampled and scaled your ofdm_40.dump file so it now will
> >> use 8 Mhz bandwidth with a 8 Msps samplerate.
> >>            The reception never can be perfect this way but it seems
> >> good enough for
> >>            tests.
> >>            
> >>            My USB DVB-T receiver receives the transport stream without
> >> problems.
> >>            Mplayer playes the stream without problem for two loops and
> >> then crashes
> >>            with a broken frame.
> >>            My standalone settopbox DVB-T receiver now also receives the
> >> stream.
> >>            (8 MHz channel on UHF)
> >>            It has big problems displaying it. Sound is only a chop of
> >> sound now and
> >>            then and video stops, then runs for a second, then stops
> >> again.
> >>            
> >>            I think this is because the timestamps and framerate
> >> (playout speed)
> >>            don't match the data throughput of the MPEG stream anymore.
> >>            (It is getting the stream too fast)
> >>            
> >>            I put my resampled RF file at:
> >>    
> >> http://www.olifantasia.com/projects/gnuradio/mdvh/OTA/DVB-T/ofdm_40_bw8Mhz_s
> >> amplerate_8Msps_cshort.raw
> >>            
> >>            format is complex signed short integers (I 16 bit, Q 16 bit)
> >> at 8
> >>            Msamples/sec.
> >>            
> >>            
> >>            Greetings,
> >>            Martin
> >>            
> >>
> >>
> >>            > > more details will follow as soon as I find some time...
> >>            > Thanks and success with your second group of tests.
> >>            >
> >>            > Martin
> >>            > > best regards and greetings
> >>            > > to all fellow GNURadioers
> >>            > >
> >>            > > vincenzo
> >>            > >
> >>            > > PS
> >>            > > Rafael, just have a look back a this thread and you'll
> >> find all the
> >>            > > info you need to do your test broadcast. Thanks for your
> >> interest
> >>            > >
> >>            > >
> >>            > >
> >>            > >
> >>            > >
> >>            > >
> >>            > > 2008/10/31 Martin Dudok van Heel
> >> <address@hidden>
> >>            > >         Hi Vincenzo.
> >>            > >         How are things going with your exams.
> >>            > >
> >>            > >         I hope well.
> >>            > >
> >>            > >         Thanks for your help so far.
> >>            > >
> >>            > >         I finally got your DVB-T dump streams working.
> >>            > >         I first tried using an undersampled basicTX but
> >> never got it
> >>            > >         to work.
> >>            > >         (use a niquist mirror in the VHF range on
> >> channel 11 or 12
> >>            > >         (219.5 Mhz or 226.5 Mhz))
> >>            > >
> >>            > >         I now use a RFX900 and that works with a
> >> pinnacle PCTV-Solo
> >>            > >         72e usb DVB-T receiver card plugged into my PC.
> >>            > >         I use 858.0 Mhz (channel 69)
> >>            > >         I used a 10 dB attenuator on the antenna output
> >> to limit
> >>            > >         output power.
> >>            > >         I also modified the RFX900 to enable
> >> transmitting outside of
> >>            > >         the ISM band. (disable saw-filter. add 220 pF
> >> capacitor)
> >>            > >
> >>            > >         Apparantly the pinnacle 72e can receive 7 Mhz
> >> channels on the
> >>            > >         UHF channels.
> >>            > >         My standalone settopbox DVB-T receiver can't
> >> handle it.
> >>            > >
> >>            > >         I noticed you don't use the full possible range
> >> in your 16 bit
> >>            > >         streams.
> >>            > >         (only goes from -80 to +80 while you could use
> >> -8192 to 8192)
> >>            > >         Is this on purpose?
> >>            > >         I can multiply samples by 64 and get a cleaner
> >> signal. (But
> >>            > >         also more output power)
> >>            > >
> >>            > >
> >>            > >         I do have a request, I hope it is not too much
> >> work.
> >>            > >         Could you make a stream with 10 Msamples/sec
> >> samplerate and 8
> >>            > >         Mhz wide channel.
> >>            > >         This way I can use standard standalone DVB-T
> >> receivers and
> >>            > >         don't have the 7Mhz bandwith on UHF problem.
> >>            > >
> >>            > >         For the 10 Msps stream I would have to use my
> >> USRP2 to output
> >>            > >         it.
> >>            > >         It has a 100 Mhz DAC (in stead of 64 Msps in the
> >> USRP1)
> >>            > >         It has a gbit ethernet connection for the
> >> samples, so I can go
> >>            > >         up to 25 Msps.
> >>            > >         It can only do fixed interpolation rates so I
> >> have to choose
> >>            > >         from the table below.
> >>            > >         (8 Msamples/sec is not supported on the USRP2)
> >>            > >
> >>            > >
> >>            > >         USRP2
> >>            > >         dac_rate        interp  ethernet_sample_rate
> >>            > >         100             4       25
> >>            > >         100             5       20
> >>            > >         100             6       16.67
> >>            > >         100             7       14.29
> >>            > >         100             8       12.5
> >>            > >         100             9       11.11
> >>            > >         100             10      10      <----I think 10
> >> Msamples/sec
> >>            > >         should be optimal
> >>            > >         100             11      9.09
> >>            > >         100             12      8.33
> >>            > >         100             13      7.69
> >>            > >         100             14      7.14
> >>            > >
> >>            > >
> >>            > >         I think 10 Msamples/sec would be a good
> >> candidate.
> >>            > >
> >>            > >         Have you also tried using 8 Msamples/sec on the
> >> USRP1?
> >>            > >         I know there would be no room left for IF
> >> channel filtering,
> >>            > >         but it could in theory still work.
> >>            > >         If this works I would also very much appreciate
> >> a 8Mhz
> >>            > >         bandwidth stream with 8 MSPS samplerate so I can
> >> demonstrate
> >>            > >         with a standard USRP1.
> >>            > >
> >>            > >         Thanks for your help so far.
> >>            > >         I appreciate it very much.
> >>            > >
> >>            > >         And good luck with your exams.
> >>            > >
> >>            > >         Have a nice weekend.
> >>            > >
> >>            > >         Greetings,
> >>            > >         Martin
> >>            > >
> >>            > >
> >>            > >
> >>            > >
> >>            > > --
> >>            > > Vincenzo Pellegrini
> >>            
> >>            
> >>
> >>
> >>
> >>
> >>    --
> >>    Vincenzo Pellegrini
> >>    
> >>
> >>
> >>
> >>
> >>
> >>
> >> _______________________________________________
> >> Discuss-gnuradio mailing list
> >> address@hidden
> >> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
> >>
> >
> >
> 
>