Transmission and reception method and apparatus for reducing peak to average power ratio in orthogonal frequency division multiplexing system
A transmission and reception method and apparatus for reducing a PAPR in an orthogonal frequency division multiplexing (OFDM) system are provided. A transmission method includes performing constellation rotation with respect to L input data symbols, performing L-point DFT spreading and circular extension on the constellation-rotated L data symbols to be K symbols, performing frequency domain (FD) windowing processing by multiplying the K circular-extended data symbols by a circular filter coefficient, and transmitting the processed data symbols.
1. A transmission method for reducing a peak-to-average power ratio (PAPR) in an orthogonal frequency division multiplexing (OFDM) system, the method comprising:
performing a constellation rotation with respect to L input data symbols;
performing an L-point discrete Fourier transform (DFT) spreading and circular extension on the L constellation-rotated data symbols to be K symbols;
performing a frequency domain (FD) windowing processing by multiplying the K circular-extended data symbols by a circular filter coefficient; and
transmitting the processed data symbols,
wherein L denotes a number of data symbols to be transmitted through a single OFDM symbol, and K denotes a circular filter spreading (CFS)-OFDM spreading factor.
2. The method of claim 1 , wherein, when binary phase shift keying (BPSK) is used as a constellation, an optimal phase value θ opt for the constellation rotation is determined to be an equation provided below:
θ
opt
=
π
(
K
-
1
L
±
1
2
)
.
3. The method of claim 2 , wherein the constellation rotation is performed by applying a shift index (shiftindex) optimized in the BPSK with respect to an element (S) i,j in a K-by-L circular filter matrix, as shown in an equation provided below:
(
S
^
)
i
,
j
=
p
i
ⅇ
-
j
2
π
(
i
-
1
-
shiftindex
)
(
j
-
1
)
L
where
shiftindex
=
K
-
1
2
±
L
4
,
wherein i denotes a frequency index and j denotes a symbol index.
4. The method of claim 1 , wherein, when QPSK is used as a constellation, an optimal phase value θ opt for the constellation rotation is determined to be an equation provided below:
θ
opt
=
π
(
K
-
1
L
±
1
or
3
4
)
,
wherein L denotes the number of data symbols to be transmitted through a single OFDM symbol, and K denotes a CFS-OFDM spreading factor.
5. The method of claim 4 , wherein the constellation rotation is performed by applying a shift index (shiftindex) optimized in the QPSK with respect to an element (S) i,j in a K-by-L circular filter matrix, as shown in an equation provided below:
(
S
^
)
i
,
j
=
p
i
ⅇ
-
j
2
π
(
i
-
1
-
shiftindex
)
(
j
-
1
)
L
where
shiftindex
=
K
-
1
2
±
L
or
3
L
8
,
wherein i denotes a frequency index and j denotes a symbol index.
6. A transmitting apparatus in an orthogonal frequency division multiplexing (OFDM) system, the apparatus comprising:
a transmission module configured to:
perform a constellation rotation with respect to L input data symbols,
execute an L-point discrete DFT spreading and a circular extension on the L constellation-rotated data symbols to be K symbols, and
perform a frequency domain (FD) windowing processing by multiplying the K circular-extended data symbols by a circular filter coefficient,
wherein L denotes a number of data symbols to be transmitted through a single OFDM symbol, and K denotes a circular filter spreading (CFS)-OFDM spreading factor.
7. The apparatus of claim 6 , wherein, when binary phase shift keying (BPSK) is used as a constellation, an optimal phase value θ opt for the constellation rotation is determined to be an equation provided below:
θ
opt
=
π
(
K
-
1
L
±
1
2
)
.
8. The apparatus of claim 7 , wherein the constellation rotation is performed by applying a shift index (shiftindex) optimized in the BPSK with respect to an element (S) i,j in a K-by-L circular filter matrix, as shown in an equation provided below:
(
S
^
)
i
,
j
=
p
i
ⅇ
-
j
2
π
(
i
-
1
-
shiftindex
)
(
j
-
1
)
L
where
shiftindex
=
K
-
1
2
±
L
4
,
wherein i denotes a frequency index and j denotes a symbol index.
9. The apparatus of claim 6 , wherein, when QPSK is used as a constellation, an optimal phase value θ opt for the constellation rotation is determined to be an equation provided below:
θ
opt
=
π
(
K
-
1
L
±
1
or
3
4
)
,
wherein L denotes the number of data symbols to be transmitted through a single OFDM symbol, and K denotes a CFS-OFDM spreading factor.
10. The apparatus of claim 9 , wherein the constellation rotation is performed by applying a shift index (shiftindex) optimized in the QPSK with respect to an element (S) i,j in a K-by-L circular filter matrix, as shown in an equation provided below:
(
S
^
)
i
,
j
=
p
i
ⅇ
-
j
2
π
(
i
-
1
-
shiftindex
)
(
j
-
1
)
L
where
shiftindex
=
K
-
1
2
±
L
or
3
L
8
,
wherein i denotes a frequency index and j denotes a symbol index.
11. A method for operating a base station in an orthogonal frequency division multiplexing (OFDM) system, the method comprising:
performing a constellation rotation with respect to L input data symbols;
performing an L-point discrete Fourier transform (DFT) spreading and circular extension on the L constellation-rotated data symbols to be K symbols;
performing a frequency domain (FD) windowing processing by multiplying the K circular-extended data symbols by a circular filter coefficient; and
transmitting the FD window processing performed data symbols,
wherein L denotes a number of data symbols to be transmitted through a single OFDM symbol, and K denotes a circular filter spreading (CFS)-OFDM spreading factor.
12. The method of claim 11 , wherein, when binary phase shift keying (BPSK) is used as a constellation, an optimal phase value for the constellation rotation is determined to be an equation provided below:
θ
opt
=
π
(
K
-
1
L
±
1
2
)
.
13. The method of claim 12 , wherein the constellation rotation is performed by applying a shift index (shiftindex) optimized in the BPSK with respect to an element (S) i,j in a K-by-L circular filter matrix, as shown in an equation provided below:
(
S
^
)
i
,
j
=
p
i
ⅇ
-
j
2
π
(
i
-
1
-
shiftindex
)
(
j
-
1
)
L
where
shiftindex
=
K
-
1
2
±
L
4
,
wherein i denotes a frequency index and j denotes a symbol index.
14. The method of claim 11 , wherein, when QPSK is used as a constellation, an optimal phase value θ opt for the constellation rotation is determined to be an equation provided below:
θ
opt
=
π
(
K
-
1
L
±
1
or
3
4
)
,
wherein L denotes the number of data symbols to be transmitted through a single OFDM symbol, and K denotes a CFS-OFDM spreading factor.
15. The method of claim 14 , wherein the constellation rotation is performed by applying a shift index (shiftindex) optimized in the QPSK with respect to an element (S) i,j in a K-by-L circular filter matrix, as shown in an equation provided below:
(
S
^
)
i
,
j
=
p
i
ⅇ
-
j
2
π
(
i
-
1
-
shiftindex
)
(
j
-
1
)
L
where
shiftindex
=
K
-
1
2
±
L
or
3
L
8
,
wherein i denotes a frequency index and j denotes a symbol index.
16. A base station for an orthogonal frequency division multiplexing (OFDM) system, the base station comprising:
a controller configured to:
perform a constellation rotation with respect to L input data symbols,
execute an L-point discrete DFT spreading and a circular extension on the L constellation-rotated data symbols to be K symbols, and
perform a frequency domain (FD) windowing processing by multiplying the K circular-extended data symbols by a circular filter coefficient; and
a transceiver configured to transmit the FD window processing performed data symbols,
wherein L denotes a number of data symbols to be transmitted through a single OFDM symbol, and K denotes a circular filter spreading (CFS)-OFDM spreading factor.
17. The base station of claim 16 , wherein, when binary phase shift keying (BPSK) is used as a constellation, an optimal phase value for the constellation rotation is determined to be an equation provided below:
θ
opt
=
π
(
K
-
1
L
±
1
2
)
.
18. The base station of claim 17 , wherein the constellation rotation is performed by applying a shift index (shiftindex) optimized in the BPSK with respect to an element (S) i,j in a K-by-L circular filter matrix, as shown in an equation provided below:
(
S
^
)
i
,
j
=
p
i
ⅇ
-
j
2
π
(
i
-
1
-
shiftindex
)
(
j
-
1
)
L
where
shiftindex
=
K
-
1
2
±
L
4
,
wherein i denotes a frequency index and j denotes a symbol index.
19. The base station of claim 16 , wherein, when QPSK is used as a constellation, an optimal phase value θ opt for the constellation rotation is determined to be an equation provided below:
θ
opt
=
π
(
K
-
1
L
±
1
or
3
4
)
,
wherein L denotes the number of data symbols to be transmitted through a single OFDM symbol, and K denotes a CFS-OFDM spreading factor.
20. The base station of claim 19 , wherein the constellation rotation is performed by applying a shift index (shiftindex) optimized in the QPSK with respect to an element (S) i,j in a K-by-L circular filter matrix, as shown in an equation provided below:
(
S
^
)
i
,
j
=
p
i
ⅇ
-
j
2
π
(
i
-
1
-
shiftindex
)
(
j
-
1
)
L
where
shiftindex
=
K
-
1
2
±
L
or
3
L
8
,
wherein i denotes a frequency index and j denotes a symbol index.