Re: [Discuss-gnuradio] OFDM TX/RX PAPR

[guillaume.tochou]

How do you reduce the PAPR with existing block in GRC ?

I've tried with Scrambler->Encoder CCSDS->Interleaver but it doesn't 
seems to work. I'm still not having any signal at the output of the OFDM 
receiver.

Guillaume


Le 27/03/2018 à 11:58, Ron Economos a écrit :
> Yes, I think the whitener does the trick. If you plot the PAPR of band 
> limited white noise, it's pretty much the same curve.
>
> Ron
>
> On 03/27/2018 02:36 AM, Müller, Marcus (CEL) wrote:
> > Oooh, that's a nice plot!
> > This is way better than I would have anticipated. Can I attribute that
> > to awesome whitening properties of the code itself and following
> > scramblers/interleavers?
> >
> > Marcus
> > On Tue, 2018-03-27 at 02:31 -0700, Ron Economos wrote:
> > > CCDF (Complementary Cumulative Distribution Function) is often used 
> > > to show PAPR probability. Here's what the GNU Radio DVB-T2 
> > > transmitter looks like at 32K (27841 active) carriers with an 
> > > without tone reservation PAPR reduction.
> > >
> > > Ron
> > > On 03/27/2018 02:09 AM, Müller, Marcus (CEL) wrote:
> > > > On Fri, 2018-03-23 at 14:21 -0700, Martin Braun wrote:
> > > > > If you've
> > > > > increased the number of carriers, PAPR also goes up (a bit).
> > > > Yep, by the same factor as you increase the number of carriers (proof
> > > > idea: time-symbol with worst PAPR is the discrete dirac over the 
> > > > vector
> > > > of FFT length N. That has a PAPR of N/1 = N if freq domain samples 
> > > > were
> > > > amplitude-limited to 1.)
> > > >
> > > > The probability to hit a PAPR that bad is, however, limited.
> > > > Considering an M-PSK modulation on the N subcarriers. Then there's a
> > > > total of M^N possible time-domain OFDM symbols, but only M·N of these
> > > > are worst-PAPR, so
> > > > P(worst PAPR for N carriers) = M·N/M^N = N / M^(N-1)
> > > > assuming equally likely symbols. Since M^N pretty certainly grows
> > > > faster than N, your likelihood of ending up in the "worst PAPR"
> > > > scenario actually drops with N.
> > > >
> > > > The story looks a bit different if you're not interested in the worst-
> > > > PAPR-symbol, but in all symbols that have a PAPR worse than some
> > > > threshold, e.g. 20dB. Especially for LTE, there's a lot of
> > > > simulative/monte carlo PAPR>threshold curves, as things like trading
> > > > clipping for amplifier efficiency plays a very commercially relevant
> > > > role there.
> > > >
> > > > Best regards,
> > > >
> > > > Marcus
>
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tx_ofdm.grc
Description: application/gnuradio-grc