Dear Brian, Marcus, and Derek, Your help and advice is greatly appreciated, thank you very much. I will look into how the PAPR might be reduced and if I do come up with something which can be contributed to GNU radio, I will certainly look into that.
Take care, Manav On Tue, Jun 23, 2020 at 4:36 PM Derek Kozel <de...@bitstovolts.com> wrote: > To add on to what Marcus and Brian have said, one of the ways of slightly > reducing this problem is Crest Factor Reduction. It would be very useful to > have some of the standard CFR algorithms added to GNU Radio. Peak > Cancellation is one that has looked promising to me. Peak Windowing and > Noise Shaping are two others. > > If you do implement any of these methods please consider contributing them > back to GNU Radio so that we can all benefit. > > Regards, > Derek > > On 6/23/2020 3:49 PM, Brian Padalino wrote: > > On Tue, Jun 23, 2020 at 10:38 AM Manav Kohli <mpk2...@columbia.edu> wrote: > >> Hello, >> >> This problem is visualized here: >> https://www.dropbox.com/s/w7kdmf9dewwdomx/20M_2974_20_15_nocal_packet_time_tx.png?dl=0 >> >> This is an OFDM packet consisting of 6 symbols: the default sync word >> 1&2, SIG field and three data symbols. The data symbols are QPSK modulated >> and the sync words are BPSK. >> >> Is there any way that I could reduce or eliminate these large spikes that >> even with a moderate baseband scaling still go considerably above a >> magnitude of 1? I have tried to use different data, and a different number >> of packet data symbols, but to no avail. I am definitely able to reduce the >> overall baseband scaling and get those spikes within range, but this is not >> desirable as I am trying to maximize transmit power. >> >> The usage of the USRP-2974 and sampling rate is immaterial; this happens >> using a variety of different radios (should not matter as this is a GNU >> radio "issue") and sampling rates. >> >> If anyone has seen this before or may have any advice, please let me know. >> > > It's the nature of OFDM to have a high Peak-to-Average-Power Radio > (PAPR). You can look at PAPR reduction techniques, but otherwise you're in > for around 10dB PAPR. > > Good luck. > > Brian > >> >
