Hello, maybe someone can shed a little light on this subject. I've been
researching the different PAPR reduction techniques and I feel like I have a
pretty good handle on the subject although I've reached a road block.
I've successfully implemented the selected mapping technique in Matlab but
when I implemented the partial transmit sequence technique I got poor results,
only a very small PAPR reduction. Then I went through all of my programs and
rechecked the scaling and everything seemed to be working out good. Ok, so I
started analyzing the actual ofdm signal and how the partial transmit sequence
technique would actually change it and now it doesn't make any sense to me.
Supposedly in the technique you separate the data into blocks, do the IFFT first
and then multiply by a phase sequence. How would this reduce the PAPR??? All
this would do would be to shift the peak from say positive side to the negative
side or vice versa. In the selected mapping technique the data is rotated before
IFFT which makes complete sense to me.
Then I saw a simple example in a paper where they describe the phase rotations
as being after the ifft but when they do the example they do the phase rotations
before. What gives?