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 > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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