Chapter 5
SC-FDMA
Prof. Kim Young Ju
Chungbuk National University
Wireless Communication Engineering
Peak to Average Power Ratio
1
Peak to Average Power Ratio
- The PAPR of the transmit signal is defined as
Example:
Example:
Matlab code:
a = [-1 -1 -1];
y = ifft(a,64);
papr = 10*log10(max(abs(y).^2) / mean(abs(y).^2));
PAPR=4.7712 dB
2
72
CCDF
P
b bilit
D
i t ib ti
F
ti
•
P
ro
b
a
bilit
y
D
i
s
t
r
ib
u
ti
on
F
unc
ti
on
C
lti
D
i t ib ti
F
ti
•
C
umu
l
a
ti
ve
D
i
s
t
r
ib
u
ti
on
F
unc
ti
on
•
C
omplementary
•
C
omplementary
Cumulative Distribution Function
3
CCDF
* N = Number of total subcarriers
4
73
PAPR Reduction Techniques
• Coding
[2]
3
-
bits data word
Data block PAPR(dB) Data block PAPR(dB)
-1 -1 -1 4.7712 1 -1 -1 2.2185
3
bits
data
word
-1 -1 1 2.2185 1 -1 1 4.7712
-1 1 -1 4.7712 1 1 -1 2.2185
111
2 2185
111
4 7712
-
1
1
1
2
.
2185
1
1
1
4
.
7712
: High PAPR
5
PAPR Reduction Techniques
• Coding
4
bits data word
Data block PAPR(dB) Data block PAPR(dB)
-1 -1 -1 -1 6.0206 1 -1 -1 -1 2.4792
4
-
bits
data
word
-1 -1 -1 1 2.4792 1 -1 -1 1 3.7482
-1 -1 1 -1 2.4792 1 -1 1 -1 6.0206
-1 -1 1 1 3.7482 1 -1 1 1 2.4792
-1 1 -1 -1 2.4792 1 1 -1 -1 3.7482
-
11
-
11
6 0206
11
-
11
2 4792
-
1
1
-
1
1
6
.
0206
1
1
-
1
1
2
.
4792
-1 1 1 -1 3.7482 1 1 1 -1 2.4792
-1 1 1 1 2.4792 1 1 1 1 6.0206
: used codeword
6
74
PAPR Reduction Techniques
• Coding
The 3
-
bit data word is mapped onto a 4
-
bit codeword such that the set of permissible sequence
4
bit D t
bl k
3
bit D t
bl k
The
3
bit
data
word
is
mapped
onto
a
4
bit
codeword
such
that
the
set
of
permissible
sequence
does not contain those that result in high PAPR.
4
-
bit
D
a
t
a
bl
oc
k
-1 -1 -1 1
-
1
-
11
-
1
3
-
bit
D
a
t
a
bl
oc
k
-1 -1 -1
-
1
-
11
1
1
1
1
-1 1 -1 -1
-1 1 1 1
1
1
1
-1 1 -1
-1 1 1
Mapping
1 -1 -1 -1
1 -1 1 1
11
11
1 -1 -1
1 -1 1
11
1
1
1
-
1
1
1 1 1 -1
1
1
-
1
1 1 1
HIGH PAPR=4.7712 dB HIGH PAPR=2.4792 dB
7
PAPR Reduction Techniques
• Partial Transmit Sequence
[3][4]
a
Input data block of N symbols is partitioned into disjoint
subblocks
a
.
Input
data
block
of
N
symbols
is
partitioned
into
disjoint
subblocks
.
b.The subcarriers in each subblock are weighted by a phase factor for that subblock.
8
75
