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i am doing project on PAPR reduction in OFDM signals using PTS scheme..but i am not getting what actually Partial transmit sequence means..i would be greatful to you if you can explain me....thanks in advance
partial transmit sequence is a methode for reducing PAPR by divide bit stream into few subblocks then multiply the subblocks with few combination of phase rotation, and choose the lowest PAPR each subblock.
for example:
we have signal X
X=[a1,b1,c1,d1,a2,b2,c2,d2,a3,b3,c3,d3,a4,b4,c4,d4]
if you chose to make 4 subblock,then X become;
X1=[a1,b1,c1,d1,0,0,0,0,0,0,0,0,0,0,0,0];
X2=[0,0,0,0,a2,b2,c2,d2,0,0,0,0,0,0,0,0];
X3=[0,0,0,0,0,0,0,0,a3,b3,c3,d3,0,0,0,0];
X4=[0,0,0,0,0,0,0,0,0,0,0,0,a4,b4,c4,d4];
then each subblock X1,X2,X3,X4 multiply with few phase rotation combination. then IFFT. chose the lowest PAPR. and you can add X1+X2+X3+X4
phase rotation use to rotate the phase of OFDM signal
as i know, there are two kind phase rotation i.e phase rotation with weighting factor W=2 and phase rotation with weighting factor W=4
weighting factor W=2 using +1 and -1
weighting factor W=4 using complex number for example 1+j
for signal,
X=[a1,b1,c1,d1,a2,b2,c2,d2,a3,b3,c3,d3,a4,b4,c4,d4]
if you chose to make 4 subblock,then X become;
X1=[a1,b1,c1,d1,0,0,0,0,0,0,0,0,0,0,0,0];
X2=[0,0,0,0,a2,b2,c2,d2,0,0,0,0,0,0,0,0];
X3=[0,0,0,0,0,0,0,0,a3,b3,c3,d3,0,0,0,0];
X4=[0,0,0,0,0,0,0,0,0,0,0,0,a4,b4,c4,d4];
if we use W2, so we generate phase rotation combination, for example:
mb1=[1 , 1,-1,-1];
mb2=[1 ,-1, 1,-1];
mb3=[-1,-1, 1, 1];
mb4=[-1, 1,-1, 1];
mb5=[ 1, 1, 1, 1];
mb6=[-1,-1, 1, 1];
mb7=[-1,-1,-1, 1];
mb8=[-1, 1,-1,-1];
and we multiply each subblock with this phase rotation combination, and we choose the lowest PAPR from the result
Thanks a lot again .....do we multiply X1 with mb1,mb2......mb8 , X2 with mb1,mb2....mb8...and so on and calculate PAPR for X1mb1,X1mb2 and so on, add those with low PAPR, like if X1mb1,X2mb1,X3mb1 and X4mb1 each have lowest PAPR then we add X1mb1+X2mb1+X3mb1+X4mb1 and transmit the sum signal as OFDM signal?? please help, I am really confused...
computational complexity depends on number of process that pass through system. may be multiplication and addition process. in PTS, length of phase rotation equal than length of subblock, so multiplication occur in all subblock with different value of phase. in slm, we use only one value of phase rotation each subblock. so that pts more complex than slm
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