Note: Descriptions are shown in the official language in which they were submitted.
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Description
Title of Invention: METHOD FOR DETERMINING RESERVED
TONES AND TRANSMITTER FOR PERFORMING PAPR
REDUCTION USING TONE RESERVATION
Technical Field
[11 Apparatuses and methods consistent with the exemplary embodiments of
the
inventive concept relate to a method of determining reserved tones and a
transmitter
performing peak to average power ratio (PAPR) reduction using tone
reservation, and
more particularly, to a transmitter determining carrier indices reserved for
PAPR
reduction and performing PAPR reduction using tone reservation.
Background Art
[2] Recently, broadcast and communication services become multi-functional
and
wideband high quality. Also, in accordance with the development of electronic
tech-
nologies, various broadcast receiving devices such as a high-definition
digital
television, a high specification smartphone, and the like have been introduced
and in-
creasingly used. As a result, the demand on various receiving methods and
various
service supports for broadcast services has been increased.
[31 Meanwhile, many transmitting and receiving systems provide broadcast
services
through an Orthogonal Frequency Division Multiplexing (OFDM) scheme. Since the
OFDM scheme performs data transmission using a plurality of carriers (or sub-
carriers) in a predetermined frequency band, it may transmit data at high
speed and has
characteristics that it is strong against multipath fading.
[4] However, in the OFDM scheme, a transmission signal occasionally has a
large peak-
to-average power ratio (PAPR). Data is transmitted through multi-carriers by
performing Inverse Fast Fourier Transform (IFFT) on a signal of a frequency
domain.
Here, a size of an amplitude of an OFDM signal may be represented by a sum of
am-
plitudes of the multi-carriers. Therefore, in the case where phases of the
multi-carriers
are the same, an OFDM signal having a high maximum value is generated, which
represents a very high PAPR.
[51 An OFDM signal having a very high PAPR deteriorates efficiency of a
high power
amplifier and the high power amplifier is operated in a non-linear region out
of a linear
operation range thereof, and thus, the OFDM signal is distorted. Accordingly,
there is a
problem that performance of a transmission and/or reception system is
degraded. As a
result, research into a method for reducing the PAPR is requested.
Disclosure of Invention
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Technical Problem
[6] Exemplary embodiments of the inventive concept may overcome the above
problem
and other disadvantages not described above. However, the exemplary
embodiments
are not required to overcome the disadvantages described above, and may not
overcome the above problem described above.
171 The exemplary embodiments provide a method of determining carrier
indices
reserved for PAPR reduction, and also provide a transmitter of performing the
PAPR
reduction using the reserved carrier indices.
Solution to Problem
[81 According to an exemplary embodiment, there is provided a method of
determining
reserved tones to be used for reduction of a peak to average power ratio
(PAPR) of a
signal. The method may include: selecting carrier indices for the reserved
tones and
generating a kernel signal based on the selected carrier indices for the
reserved tones;
calculating a comparison reference average value of the kernel signal,
selecting one of
the calculated comparison reference average value and a prestored comparison
reference average value, and preliminarily determining carrier indices of the
reserved
tones based on the selection; re-arranging an order of the preliminarily
determined
carrier indices of the reserved tones; calculating a comparison reference
average value
of a kernel signal generated, whenever each of the re-arranged carrier indices
of the
reserved tones is changed, to another carrier index to generate a plurality of
comparison reference average values, and finally determining carrier indices
of the
reserved tones which generates a kernel signal having the smallest comparison
reference average value among the plurality of comparison reference average
values as
the indices of the reserved tones.
191 In the generating the kernel signal based on the randomly selected
carrier indices for
the reserved tones, the kernel signal may be generated by randomly selecting
carrier
indices for the reserved tones among carrier indices other than carrier
indices into
which a pilot is inserted, inserting one (1) into carriers of the randomly
selected carrier
indices, and performing IFFT on the carriers into which one (1) is inserted.
[10] The comparison reference average value of the kernel signal may be an
average value
of amplitudes of peak signals satisfying a predetermined condition, except a
peak
signal having the greatest amplitude, among the plurality of peak signals of
the kernel
signal.
[11] The predetermined condition may be a condition that the peak signals
belong to a
predetermined top range of amplitude except the peak signal having the
greatest
amplitude and another predetermined top range of amplitude based on an
amplitude of
a peak signal having the second-largest amplitude, among the plurality of peak
signals
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of the kernel signal.
[12] In the preliminarily determining the carrier indices of the reserved
tones, a smaller
comparison reference average value among the calculated comparison reference
average value and the prestored comparison reference average value may be
compared
with a preset value, and carrier indices for a kernel signal having the
smaller
comparison reference average value which is smaller than the preset value is
pre-
liminarily determined as the indices of the reserved tones.
[13] The comparison reference average values may be calculated by
sequentially
changing respective carrier indices included in the re-arranged carrier
indices of the
reserved tones to other carrier indices where a pilot is not positioned and
the pre-
liminarily determined reserved tones are not positioned.
[14] According to an exemplary embodiment, there is provided a transmitter
which may
include: a frame generator configured to generate a frame including a
plurality of
OFDM symbols having a Fast Fourier Transform (FFT) size of 16K; a pilot
inserter
configured to insert a pilot into first carriers of the plurality of OFDM
symbols, re-
spectively; and a PAPR reducer configured to insert a signal for reducing a
PAPR into
second carriers reserved in at least one of the plurality of OFDM symbols into
which
the pilot is inserted, wherein the second carriers have carrier indices
defined as in
Table 4.
[15] The frame may include a preamble symbol, subframe boundary symbols,
and data
symbols.
[16] The second carriers may have the carrier indices, when a position in
the preamble
symbol into which a preamble pilot is to be inserted and a position in the
subframe
boundary symbols into which a subframe boundary pilot is to be inserted are
defined
based on a pilot insertion pattern (Dx=6, 8, 12, 16, 24, 32), and an edge
pilot is to be
inserted into a first carrier and a last carrier in each of the subframe
boundary symbols,
and Dx is a difference of carrier indices between adjacent carriers into which
the pilot
is to be inserted.
[17] The second carriers may have the carrier indices defined as in Table
4, when a
position in the data symbols into which a scattered pilot is to be inserted is
defined
based on a pilot insertion pattern (Dx=3, 4, 6, 8, 12, 16, 24, 32 and Dy=2, 4)
and an
edge pilot is to be inserted into a first carrier and a last carrier in each
of the data
symbols, and Dx is a difference of carrier indices between adjacent carriers
into which
the pilot is to be inserted, and Dy is a difference of symbol indices between
successive
pilots on a specific carrier.
[18] According to an exemplary embodiment, there is provided a transmitter
which may
include: a frame generator configured to generate a frame including a
plurality of
OFDM symbols having a Fast Fourier Transform (FFT) size of 16K; a pilot
inserter
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configured to insert a pilot into first carriers of the plurality of OFDM
symbols, re-
spectively; and a PAPR reducer configured to insert a signal for reducing a
PAPR into
second carriers reserved in at least one of the plurality of OFDM symbols into
which
the pilot is inserted, wherein the second carriers have carrier indices
defined as in
Table 5.
[19] The frame may include a preamble symbol, subframe boundary symbols,
and data
symbols.
[20] The second carriers may have the carrier indices defined as in Table
5, when a
position in the preamble symbol into which a preamble pilot is to be inserted
and a
position in the subframe boundary symbols into which a subframe boundary pilot
is to
be inserted are defined based on Dx=3, 4, and an edge pilot is to be inserted
into a first
carrier and a last carrier in each of the subframe boundary symbols, and Dx is
a
difference of carrier indices between adjacent carriers into which the pilot
is to be
inserted.
Advantageous Effects of Invention
[21] According to various exemplary embodiments of the present disclosure,
when PAPR
reduction is performed, it is possible to prevent a new peak from occurring,
thereby
more efficiently reducing a PAPR.
Brief Description of Drawings
[22] The above and/or other aspects of the exemplary embodiments will be
more apparent
by describing certain exemplary embodiments of the inventive concept with
reference
to the accompanying drawings, in which:
[23] FIG. 1 is a diagram illustrating a method for reducing PAPR according
to an
exemplary embodiment;
[24] FIG. 2 is a diagram illustrating a problem that is able to occur when
PAPR is
reduced, according to an exemplary embodiment;
[25] FIG. 3 is a diagram illustrating a frame structure according to an
exemplary em-
bodiment;
[26] FIGs. 4 to 9 are diagrams illustrating a method for determining
reserved tones
according to an exemplary embodiment;
[27] FIG. 10 is a flowchart illustrating the method for determining
reserved tones
according to an exemplary embodiment;
[28] FIG. 11 is a block diagram illustrating a configuration of a
transmitter according to
an exemplary embodiment;
[29] FIG. 12 is a block diagram illustrating a configuration of a receiver
according to an
exemplary embodiment; and
[30] FIG. 13 is a flowchart illustrating a method in which the transmitter
reduces PAPR
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using reserved tones according to an exemplary embodiment.
Best Mode for Carrying out the Invention
[31] -
Mode for the Invention
[32] Hereinafter, the exemplary embodiments of the inventive concept will
be described
in more detail with reference to the accompanying drawings.
[33] The exemplary embodiments relate to a method for reducing a PAPR using
a tone
reservation (TR) scheme, in a system in which a signal is transmitted by an
OFDM
scheme. Particularly, according to the exemplary embodiments, in order to
efficiently
reduce a PAPR while avoiding collision with pilots by considering positions of
carriers
in which the pilots exist in an OFDM symbol, carriers of specific positions
are used as
reserved tones.
[34] First, a method for reducing a PAPR according to a tone reservation
method is as
follows. In the tone reservation method, tones are reserved for some of
carriers. Here,
the reserved tones do not transmit data and are used to reduce a PAPR. In this
case,
since a receiver neglects the reserved tones which do not transmit data and
restores the
data only from a signal at a tone position of data, there is an advantage that
a structure
of the receiver is simple.
[35] Meanwhile, in the tone reservation method, a gradient algorithm is
used to reduce a
peak. Hereinafter, a method for reducing a peak using the gradient algorithm
will be
described in more detail with reference to FIG. 1.
[36] FIG. 1 illustrates a configuration diagram of a transmitter which
reduces a PAPR
using the tone reservation method.
[37] Referring to FIG. 1, reserved tones 10 and data (i.e., broadcast data,
an Li signaling
including signaling information about the broadcast data, pilots, etc.) 20 are
input to a
tone reserver 30, and a tone reservation signal is allocated by the tone
reserver 30 to a
predetermined carrier position known between a transmitter and a receiver by
the tone
reserver 30.
[38] Meanwhile, if a sum of the reserved tones 10 and the input data 20 is
input to an
Inverse Fast Fourier Transform (IFFT) unit 40, IFFT is performed, and
thereafter, an
output signal x of a time domain is generated by a parallel/serial (P/S)
converter 50. In
this case, a peak reducer 60 reduces a PAPR of the output signal x.
[39] The peak reducer 60 generates a kernel signal having impulse
characteristics using
the reserved tones. Here, the kernel signal is used to clip the output signal
x.
[40] Specifically, the peak reducer 60 detects a peak of the output signal
x. That is, the
peak reducer 60 detects a position, an amplitude, and a phase of the peak of
the output
signal x. In addition, in order to reduce the peak of the output signal x, the
peak
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reducer 60 performs at least one of circular shifting, scaling, and phase
rotation on the
kernel signal based on the position, the amplitude, and the phase of the peak
of the
output signal x, and then adds the results to the output signal x.
[41] Thereafter, the peak reducer 60 calculates the PAPR of the output
signal x having a
reduced peak. In addition, if the calculated PAPR does not meet a target (or a
desired)
PAPR level, the peak reducer 60 may repeat the above-mentioned process until
the
PAPR for the output signal x meets the target PAPR level, or may repeat the
above-
mentioned process as many as the number of times (e.g., N) predefined by a
system.
[42] As such, according to a tone reservation method, the peak of a data
signal is reduced
by adding the kernel signal to the data signal. However, as the kernel signal
is added to
the data signal, a new peak may also occur in the data signal. Here, the data
signal may
be an OFDM signal
[43] For example, as illustrated in FIG. 2, when IFFT is performed in a
frequency domain
after 1 (one) is inserted into carriers to which reserved tones are allocated,
a kernel
signal having a peak at a particular time point in a time domain may be
generated.
[44] In this case, if the kernel signal is added to the data signal, a peak
of the data signal
may be reduced by a first peak, i.e., the greatest peak of amplitude, of the
kernel signal.
However, since other portions except the first peak are added to the data
signal, when
amplitudes of the other peaks except the first peak are large, a new peak may
occur in
the data signal by the other peaks.
[45] Therefore, according to an exemplary embodiment, the positions of
reserved tones
(i.e., carrier indices used for the reserved tones) which may minimize the
amplitudes of
the other peaks of the kernel signal except the first peak of the kernel
signal are de-
termined, and these carrier indices are used as the reserved tones in order to
reduce a
PAPR of the data signal.
[46] Hereinafter, a method of determining carrier indices in which tones
are reserved
according to an exemplary embodiment will be described.
[47] First, according to an exemplary embodiment, since a signal is
transmitted through a
frame defined in an Advanced Television System Committee (ATSC) 3.0 standard,
a
frame structure defined in the ATSC 3.0 standard will be described with
reference to
FIG. 3.
[48] According to the ATSC 3.0 standard, as illustrated in FIG. 3, the
frame includes a
bootstrap 310, a preamble 320, and one or more subframes 330-1, ..., 330-n.
[49] Specifically, the bootstrap 310 is positioned at a start of each
frame, the preamble
320 is positioned following the bootstrap 310, and the one or more subframes
330-1,
..., 330-n are positioned following the preamble 320.
[50] The bootstrap 310, the preamble 320, and the one or more subframes 330-
1, ..., 330-n
comprise one or more OFDM symbols, and the number of carriers for each OFDM
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symbol may be determined depending on an FFT mode (i.e., in an FFT size, the
FFT
size may be 16K).
[511 Meanwhile, each subframe may include subframe boundary symbols and
data
symbols. The subframe boundary symbols are positioned at boundaries with other
subframes, and the data symbols are positioned between the subframe boundary
symbols. That is, a first OFDM symbol and the last OFDM symbol among the OFDM
symbols configuring each subframe are the subframe boundary symbols, and the
remaining OFDM symbols other than the subframe boundary symbols are the data
symbols.
[521 Meanwhile, according to the ATSC 3.0 standard, pilots are inserted
into the preamble
and the subframes for channel estimation and synchronization.
[531 Types of pilots inserted into the preamble and the subframes are as
illustrated in the
following Table 1.
[541 [Table 11
Symbol T e Preamble Scattered Subframe Continual Edge
yp
Pilot Pilot Boundary Pilot Pilot Pilot
Preamble V V
Data V V V
Subframe
V V V
Boundary
[551 Referring to Table 1, a preamble pilot is inserted into the preamble,
a scattered pilot
(SP) is inserted into the data symbol, and a subframe boundary pilot is
inserted into the
subframe boundary symbol. In addition, a continual pilot (CP) is inserted into
the
preamble symbol, the data symbol, and the subframe boundary symbol, and an
edge
pilot is inserted into the data symbol and the subframe boundary symbol.
[56] Meanwhile, a position into which a pilot is to be inserted may be
defined by an index
of a carrier into which the pilot is to be inserted, or may be determined
based on
specific pilot patterns (e.g., Dx and Dy). Here, Dx means a difference in
carrier index
between adjacent carriers into which a pilot is to be inserted, in a frequency
direction
(in regard to this, in ATSC 3.0, defined as separation of pilot bearing
carriers (that is,
in the frequency direction), and in Digital Video Broadcasting-Terrestrial
Version 2
(DVB-T2), defined as difference in carrier index between adjacent scattered-
pilot-bearing carriers), and Dy means a difference of the number of symbols
between
successive pilots on a specific carrier, in a time direction (in regard to
this, in ATSC
3.0, defined as number of symbols forming one scattered pilot sequence (time
direction), and in DVB-T2, defined as a difference in symbol number between
successive scattered pilots on a given carrier).
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[57] First, the position into which the preamble pilot is to be inserted
may be determined
based on Dx. In the case of preamble pilot, since Dy is 1 (Dy=1), the preamble
pilot is
inserted to the same position of every preamble symbol. Specifically, the
preamble
pilot may be inserted into cells (i.e., carriers) having a carrier index k
satisfying k mod
Dx=0 in the preamble symbol. Here, Dx may be 3, 4, 6, 8, 12, 16, 24, and 32,
and the
system may select one of these values depending on a channel environment.
[58] The position into which the scattered pilot is to be inserted may be
determined based
on Dx and Dy. Specifically, the scattered pilot may be inserted into a carrier
having an
index k in a first OFDM symbol satisfying following mathematical expression 1.
[59] k mod (Dx Dy )= Dx (I mod Dy) ... (1)
[60] Here, Dx and Dy may be defined as illustrated in following Table 2,
and SPa b
means a pilot pattern, which a is Dx (a=Dx) and b is Dy (b=Dy).
[61] [Table 2]
Pilot Pattern DX DY Pilot Pattern DX DY
SP3 2 3 2 SP12 2 12 2
SP3 4 3 4 SP12 4 12 4
SP4 2 4 2 SP16 2 16 2
SP4 4 4 4 SP16 4 16 4
SP6 2 6 2 SP24 2 24 2
SP6 4 6 4 SP24 4 24 4
SP8 2 8 2 SP32 2 32 2
SP8 4 8 4 SP32 4 32 4
[62] Meanwhile, the system may select one of SPa b defined in Table 2
depending on the
channel environment.
[63] A position into which a subframe boundary pilot is to be inserted may
be determined
based on Dx. Specifically, the subframe boundary pilot may be inserted into
cells
having a carrier index k satisfying k mod Dx=0 in the subframe boundary
symbol(except when k = 0 and k = NoC - 1. Cells in the subframe boundary
symbol
for which k = 0 or k = NoC - 1 shall be edge pilots). Here, Dx may be 3, 4, 6,
8, 12, 16,
24, and 32, and the system may select one of these values depending on a
channel en-
vironment. However, an edge pilot is inserted into a first carrier and a last
carrier of
subframe boundary symbols, respectively.
[64] A position into which a continual pilot is to be inserted is defined
by an index itself
of carriers into which the continual pilot is inserted.
[65] Specifically, the continual pilot may be inserted into different
positions depending on
an FFT size, and in an FFT size of 16K, an index of carriers into which the
continual
pilot is to be inserted may be defined as illustrated in following Table 3.
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[66] [Table 31
118 178 334 434 614 670 938 1070 1274 1358 1502 1618 1730 1918 2062 2078 2318
2566 2666
2750 2894 3010 3214 3250 3622 3686 3886 3962 4082 4166 4394 4558 4646 4718
5038 5170
5210 5342 5534 5614 5926 5942 6058 6134 6350 6410 6650 6782 6934 7154 7330
7438 7666
7742 7802 7894 8146 8258 8470 8494 8650 8722 9022 9118 9254 9422 9650 9670
9814 9902
10102 10166 10454 10598 10778 10822 11062 11138 11254 11318 11666 11758 11810
11974
12106 12242 12394 12502 12706 12866 13126 13190 13274 13466 13618 13666
[67] Accordingly, in a case where the FFT size is 16K, the system may
insert the
continual pilot based on Table 3.
[68] An edge pilot may be inserted into a first carrier and a last carrier
of the symbols
other than the preamble symbol, that is, a first carrier and a last carrier of
OFDM
symbols configuring a data symbols and subframe boundary symbols.
[69] Meanwhile, carrier indices can be considered to be either absolute
carrier indices or
relative carrier indices. Absolute carrier indices are indexed on the maximum
possible
number of carriers regardless of whether carrier reduction has been configured
and
hence range from 0(i.e. an index of a first carrier) to NoC,,,,, - 1(i.e. an
index of a last
carrier)(Here, N0C,,,,,=13825). Relative carrier indices are indexed on the
configured
number of carriers and hence range from 0(i.e. an index of a first carrier) to
NoC-1(i.e.
an index of a last carrier)(Here, NoC = 13825, 13633, 13441, 13249 or 13057).
Preamble, scattered, subframe boundary, and edge pilot locations depend on the
relative carrier indices. Continual pilot locations depend on the absolute
carrier indices.
[70] Meanwhile, in the case where at least one pilot is inserted as
described above, a
method for determining reserved tones according to an exemplary embodiment
will be
described with reference to FIGs. 4 to 9.
[71] First, indices for reserved tones are randomly selected. Here, the
indices for the
reserved tones represent carrier indices to be allocated to the reserved
tones.
Meanwhile, the number of carriers NTR allocated to the reserved tones may have
different values depending on an FFT size. For example, in the case where an
FFT size
is 16K, NTR is 144 (NTR=144).
[72] Specifically, carrier indices for reserved tones are randomly selected
from among
indices other than indices of carriers into which a pilot is inserted.
[73] That is, the indices for the reserved tones are randomly selected
(S410), and it is de-
termined whether o the selected indices overlap indices of the pilot (S420),
thereby
making it possible to randomly select the carrier indices for the reserved
tones among
the indices other than the indices of the carriers into which the pilot is
inserted.
[74] Here, the pilot may include a preamble pilot, a scattered pilot, a
subframe boundary
pilot, a continual pilot, and an edge pilot, and the positions into which the
respective
pilots are inserted are as described above.
1751
Thereafter, a kernel signal is generated based on the randomly selected
indices for
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the reserved tones. Specifically, in a case where the randomly selected
indices do not
overlap the indices of the pilot (No in S420), the kernel signal may be
generated by
inserting one (1) into the carriers for the randomly selected indices and
performing
IFFT, as shown in FIG. 2 (S430).
[76] In addition, a comparison reference average value of amplitudes of the
kernel signal
is calculated, the calculated comparison reference average value is compared
with a
prestored comparison reference average value, and the indices of the reserved
tones are
preliminarily determined based on the comparison.
[77] Specifically, if the calculated comparison reference average value of
the kernel signal
is smaller than the prestored comparison reference average value (Yes in
S440), the
prestored comparison reference average value is replaced with the calculated
comparison reference average value (S450). Here, the prestored comparison
reference
average value may be a comparison reference average value which is calculated
and
stored based on randomly selected indices for the reserved tones, before
performing
the above-mentioned processes. In this case, the randomly selected indices for
the
reserved tones may also be stored, and in S450, prestored indices may also be
updated.
[78] In addition, if the comparison reference average value of the kernel
signal is smaller
than a preset value (Yes in S460), the indices which form the basis of the
calculation of
the comparison reference average value may be preliminarily determined as
indices of
the reserved tones to be used for PAPR reduction (S470).
[79] That is, a smaller comparison reference average value among the
calculated
comparison reference average value and the prestored comparison reference
average
value is compared with the preset value, and as a result of the comparison, if
the
comparison reference average value is smaller than the preset value, indices
which
form the basis of the generation of the kernel signal having the comparison
reference
average value are preliminarily determined as the indices of the reserved
tones.
[80] However, if the calculated comparison reference average value of the
kernel signal is
not smaller than the prestored comparison reference average value, the indices
of the
reserved tones may be preliminarily determined by repeating the above-
mentioned
process until the calculated comparison reference average value becomes
smaller than
the prestored comparison reference average value, and determining whether the
calculated comparison reference average value is smaller than the preset
value.
[81] In addition, after the prestored comparison reference average value is
replaced with
the calculated comparison reference average value, if the comparison reference
average
value is greater than or equal to the preset value, the indices for the
reserved tones may
be preliminarily determined by repeating the above-mentioned process until the
comparison reference average value becomes smaller than the preset value.
[82] According to an exemplary embodiment, the comparison reference average
value of
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the kernel signal is an average value of amplitudes of peak signals which
satisfy a pre-
determined condition, except a peak signal having the greatest amplitude,
among a
plurality of peak signals of the kernel signal generated based on the randomly
selected
indices for the reserved tones.
[83] According to an exemplary embodiment, the predetermined condition may
be a
condition that the peak signals, except the peak signal having the greatest
amplitude of
the kernel signal generated based on the randomly selected indices for the
reserved
tones, belong to a predetermined amplitude range (for example, within top
10%), and
belong to another predetermined amplitude range (for example, within top 20%)
based
on amplitude of a peak signal having the second-largest amplitude. However,
the
above-mentioned numerical values are merely examples.
[84] Hereinafter, a method of calculating a comparison reference average
value will be
described in more detail with reference to FIGs. 5 to 8.
[85] First, it is assumed that a kernel signal generated based on randomly
selected indices
for reserved tones is as illustrated in FIG. 5. Referring to FIG. 5, the
kernel signal
comprises a plurality of peak signals having various amplitudes in a time
domain. In
this case, the plurality of peak signals of the kernel signal are classified
depending on
amplitudes, and a histogram illustrating the number of peak signals according
to the
amplitudes may be illustrated as in FIG. 6.
[86] Thereafter, a comparison reference average value of a kernel signal
may be
calculated based on the histogram as illustrated in FIG. 6.
[87] Specifically, as illustrated in FIG. 7, a first group of peak signals
which belong to
within top 10% in order of amplitude among peak signals other than a peak
signal
having the greatest amplitude (i.e., a first peak signal) is determined using
the
histogram. In addition, as illustrated in FIG. 8, a second group of peak
signals having
an amplitude of 80% or more of the amplitude of a peak signal which is the
second-
largest amplitude (i.e., a second peak signal) is determined using the
histogram.
[88] In addition, peak signals which commonly belong to the first and
second groups are
determined by comparing the peak signals that belong to the first group and
the second
group, respectively, and an average value of amplitudes of the peak signals
which
commonly belong to the first and second groups is calculated. The calculated
value as
described above is a comparison reference average value for the randomly
selected
indices for the reserved tones.
[89] As such, according to the present exemplary embodiment, the comparison
reference
average value is calculated using the peak signals having the amplitude of a
specific
percentage or more based on the amplitude of the second peak signal while
belonging
to within a specific range in order of amplitude, among the peak signals, and
if the
comparison reference average value is smaller than the preset value, the
indices which
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form the basis of the calculation of the comparison reference average value is
pre-
liminarily determined as the indices of the reserved tones.
[90] Here, the preset value, which is a value obtained by simulation, may
be set to a value
which may prevent an occurrence of a new peak by the peak signals other than
the first
peak signal among the plurality of peak signals configuring the kernel signal,
par-
ticularly, the peak signals having a specific amplitude or more including the
second
peak signal, when the kernel signal is added to a data signal in order to
reduce a PAPR.
[91] Meanwhile, if the carrier indices of the reserved tones are
preliminarily determined,
carrier indices for the reserved tones may be finally determined using the
preliminarily
determined carrier indices. A detailed description thereof will be provided
with
reference to FIG. 9.
[92] First, an order of the preliminarily determined indices of the
reserved tones is
randomly re-arranged (S910). In this case, K may be set to zero (K=0) and
N nochange may be set to zero (N nochange=0).
[93] For example, in a case where the preliminarily determined indices of
the reserved
tones are '1, 4, 8, and 9', an order of these indices may be randomly re-
arranged such as
'8, 1, 9, and 4'.
[94] In addition, the randomly re-arranged indices are changed to other
indices, and kernel
signals are generated based on the changed indices. Further, comparison
reference
average values of the kernel signals are calculated and compared to one
another, and as
a result of the comparison, indices based on which a kernel signal having the
smallest
comparison reference average value is generated are finally determined as
indices of
the reserved tones to be used for reduction of the PAPR of the data signal.
[95] Specifically, a comparison reference average value may be calculated
while se-
quentially changing the respective indices included in the randomly re-
arranged indices
of the reserved tones to indices, among carrier indices, where a pilot is not
positioned
and the preliminarily determined reserved tones are not positioned, and
indices for the
smallest comparison reference average value among the calculated comparison
reference average values may be finally determined as the indices of the
reserved tones
to be used for reduction of the PAPR of the data signal.
[96] To this end, first, an optimization for a K-th index among the
randomly re-arranged
indices of the reserved tones is performed (S920).
[97] Here, the optimization means a process of determining indices which
generate the
smallest comparison reference average value, when the comparison reference
average
value is calculated while sequentially changing the K-th index to other
indices.
[98] Specifically, the indices which generate the smallest comparison
reference average
value may be determined by sequentially changing the K-th index among the
randomly
re-arranged indices of the reserved tones to an index among the carrier
indices in
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which the pilot is not positioned and the preliminarily determined reserved
tone is not
positioned, and calculating a comparison reference average value whenever the
index
is changed.
[99] As in the example described above, it is assumed that the indices of
the preliminarily
determined reserved tones are '1, 4, 8, and 9', and a state in which the
indices of the
preliminarily determined reserved tones are randomly re-arranged is '8, 1, 9,
and 4'.
Here, it is assumed that the number of carriers for one OFDM symbol is 10, and
indices of carriers into which the pilot is inserted are '3 and 7'. However,
this is merely
an example for convenience of explanation.
[100] Specifically, in the way that K=0, a comparison reference average
value may be
calculated by sequentially changing an index 8, which is a zero-th index (i.e.
a first
value among the randomly re-arranged indices '8, 1, 9, and 4') among the
randomly re-
arranged indices, that is, '8, 1, 9, and 4' to an index other than '3 and 7',
which are the
indices in which the pilot is positioned, and '1, 9, and 4', which are indices
in which
other reserved tones are positioned.
[101] That is, in a case where the indices are '0, 1, 9, and 4', a kernel
signal may be
generated by inserting 1 into carriers of which indices are 0, 1, 9, and 4,
and
performing IFFT, and a comparison reference average value of the generated
kernel
signal may be calculated. Similarly, a comparison reference average value may
also be
calculated for a case where indices are '2, 1, 9, and 4', '5, 1, 9, and 4',
'6, 1, 9, and 4',
and '8, 1, 9, and 4', respectively.
[102] In addition, the comparison reference average value having the
minimum value
among the calculated comparison reference average values is determined, and it
is de-
termined whether the K-th index among indices when the comparison reference
average value has the minimum value is changed (S930). That is, it is
determined
whether the K-th index when the comparison reference average value has the
minimum
value is a value different from the existing K-th index.
[103] In the above-mentioned example, in a case where indices when the
comparison
reference average value has the minimum value are '5, 1, 9, and 4', it may be
estimated
that the zero-th index based on '8, 1, 9, and 4' is changed from 8 to 5.
[104] As such, if the K-th index is changed (Yes in S930), N nochange is
set to 0
(N nochange=0) (S940) and K is set to (K+1) mod NTR (K=(K+1) mod NTR) (S950),
and the above-mentioned process is repeated for a (K+1) mod NTR-th index for
the
indices (i.e., in the above-mentioned example, '5, 1, 9, and 4') in which the
K-th index
is changed. Here, NTR is the number of carriers used for the reserved tones.
[105] However, in the above-mentioned example, in a case where the indices
when the
smallest comparison reference average value is generated are '8, 1, 9, and 4',
it may be
estimated that the zero-th index based on '8, 1, 9, and 4' is not changed.
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[106] As such, if the K-th index is not changed (No in S930), N nochange is
set to
N nochange+1 (N nochange=N nochange+1) (S960) and it is determined whether
N nochange=NTR is satisfied (S970).
[107] Accordingly, if N nochange=NTR is satisfied (Yes in S970), it is
determined that
K=0, an order of indices is randomly re-arranged (S980), and the above-
mentioned
process is repeated.
[108] However, if N nochange=NTR is not satisfied (No in S970), it is
determined whether
N nochange=2*NTR is satisfied (S990).
[109] Accordingly, if N nochange=2*NTR is not satisfied (No in S990), K is
set to (K+1)
mod NTR (K=(K+1) mod NTR) (S995), and the above-mentioned process is repeated.
However, if N nochange=2*NTR is satisfied (Yes in S990), indices output from
S990
are finally determined as the indices for the reserved tones (S997).
[110] In the case where the indices of the reserved tones are determined
according to the
method as described above, and a PAPR reduction is performed based on the de-
termined indices of the reserved tones, amplitudes of a second peak signal and
peak
signals having the next sequentially high amplitude in the kernel signal may
be
generally reduced. Accordingly, since a difference between the second peak
signal and
the peak signals having the next sequentially high amplitude in the kernel
signal is
reduced, when the kernel signal is added to the data signal in order to reduce
a PAPR,
a new peak may not occur.
[111] Meanwhile, the indices of the reserved tones determined according to
the above-
mentioned method are as illustrated in following Table 4 and Table 5. That is,
Table 4
and Table 5 illustrate a set of carriers reserved for PAPR reduction in a case
where an
FFT size is 16K.
[112] Specifically, Table 4 illustrates a set of carriers reserved for all
symbols except a
preamble symbol and subframe boundary symbols in a case where Dx is 3 and Dx
is 4.
That is, Table 4 illustrates a set of carriers reserved for data symbols, and
a preamble
symbol and subframe boundary symbols except the case where Dx is 3 and Dx is
4.
[113] Specifically, in a case where positions in data symbols into which a
scattered pilot is
to be inserted are defined based on a pilot insertion pattern Dx=3, 4, 6, 8,
12, 16, 24,
and 32, and Dy=2 and 4, and an edge pilot is to be inserted into a first
carrier and a last
carrier in each of the data symbols, and in a case where a position in a
preamble
symbol into which a preamble pilot is to be inserted and a position in
subframe
boundary symbols into which a subframe boundary pilot is to be inserted are
defined
based on a pilot insertion pattern Dx=6, 8, 12, 16, 24, and 32, and an edge
pilot is to be
inserted into a first carrier and a last carrier in each of the subframe
boundary symbols,
a set of carrier to be reserved for the preamble symbol, the subframe boundary
symbols, and the data symbols is as illustrated in Table 4.
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[114] Table 5 illustrates a set of carriers reserved for a preamble symbol
and subframe
boundary symbols in a case in which Dx is 3 and Dx is 4.
[115] Specifically, in a case in which a position in a preamble symbol into
which a
preamble pilot is to be inserted and a position in subframe boundary symbols
into
which a subframe boundary pilot is to be inserted are defined based on a pilot
insertion
pattern (Dx=3 and 4), and an edge pilot is to be inserted into a first carrier
and a last
carrier in each of the subframe boundary symbols, a set for carriers reserved
for the
preamble symbol and the subframe boundary symbols is as illustrated in Table
5.
[116] That is, in Table 4 and Table 5, in the case of scattered pilots to
be inserted into the
data symbols, Dy is 2 and 4.
[117] In addition, in Table 4, in the case of scattered pilots to be
inserted into the data
symbols, Dx is 3, 4, 6, 8, 12, 16, 24, and 32, and in Table 4, in the case of
preamble
pilots and subframe boundary pilots to be inserted into the preamble symbol
and the
subframe boundary symbols, Dx is 6, 8, 12, 16, 24, and 32. In addition, in
Table 5, in
the case of preamble pilots and subframe boundary pilots to be inserted into
the
preamble symbol and the subframe boundary symbols, Dx is 3 and 4.
[118] In addition, in Tables 4 and 5, an edge pilot is to be inserted into
a first carrier and a
last carrier in each of the subframe boundary symbols and the data symbols.
[119] [Table 4]
FFT Size
(Number of
Reserved Tone Reservation Carrier Indices
Tones)
421, 548, 589, 621, 644, 727, 770, 813, 857, 862, 1113, 1187, 1201, 1220,
1393,
1517, 1821, 1899, 1924, 2003, 2023, 2143, 2146, 2290, 2474, 2482, 2597, 2644,
2749, 2818, 2951, 3014, 3212, 3237, 3363, 3430, 3515, 3517, 3745, 3758, 4049,
4165, 4354, 4399, 4575, 4763, 4789, 4802, 4834, 4970, 5260, 5386, 5395, 5402,
5579, 5716, 5734, 5884, 5895, 6073, 6123, 6158, 6212, 6243, 6521, 6593, 6604,
1 6K 6607, 6772, 6842,
6908, 6986, 7220, 7331, 7396, 7407, 7588, 7635, 7665, 7893,
(144) 7925, 7949, 8019,
8038, 8167, 8289, 8295, 8338, 8549, 8555, 8660, 8857, 8925,
9007, 9057, 9121, 9364, 9375, 9423, 9446, 9479, 9502, 9527, 9860, 9919, 9938,
10138, 10189, 10191, 10275, 10333, 10377, 10988, 11109, 11261, 11266, 11362,
11390, 11534, 11623, 11893, 11989, 12037, 12101, 12119, 12185, 12254, 12369,
12371, 12380, 12401, 12586, 12597, 12638, 12913, 12974, 13001, 13045, 13052,
13111, 13143, 13150, 13151, 13300
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[120] [Table 5]
FFT Size
(Number of
Reserved Tone Reservation Carrier
Indices
Tones)
509, 739, 770, 890, 970, 989, 1031, 1033, 1121, 1223, 1231, 1285, 1526, 1559,
1603, 1615, 1690, 1771, 1903, 1910, 1958, 2033, 2146, 2225, 2302, 2306, 2345,
2447, 2477, 2561, 2578, 2597, 2635, 2654, 2687, 2891, 2938, 3029, 3271, 3479,
3667, 3713, 3791, 3977, 4067, 4150, 4217, 4387, 4501, 4541, 4657, 4733, 4742,
4963, 5011, 5149, 5311, 5362, 5491, 5531, 5609, 5722, 5747, 5798, 5842, 5881,
16K 5959, 5983, 6059,
6166, 6178, 6214, 6230, 6382, 6557, 6625, 6811, 6881, 6994,
(144) 7261, 7535, 7546,
7711, 7897, 7898, 7918, 7997, 8125, 8398, 8483, 8530, 8686,
8731, 8855, 9001, 9026, 9110, 9206, 9223, 9325, 9466, 9493, 9890, 9893, 10537,
10570, 10691, 10835, 10837, 11098, 11126, 11146, 11198, 11270, 11393, 11629,
11657, 11795, 11867, 11909, 11983, 12046, 12107, 12119, 12353, 12482, 12569,
12575, 12662, 12691, 12739, 12787, 12902, 12917, 12985, 13010, 13022, 13073,
13102, 13141, 13159, 13225, 13255, 13303
[121] Meanwhile, for data symbols, carriers having carrier indices defined
in Table 4 are
reserved, and these index values are circular-shifted, thereby making it
possible to
define other carrier indices reserved for PAPR reduction. Here, an amount of
circular-
shifted index values may be determined by Dx and Dy.
[122] Specifically, in a data symbol corresponding to an index 1, a set SI
of reserved carriers
may be calculated based on following mathematical expression 2.
[123]... (2)
S1 = ik+ Dx* (I mod Dy), -, - 05n<NTR -0 - d 1<d
o - - -end
[124] Here, So represents a set of reserved carriers corresponding to
carrier indices defined
in Table 4, NTR represents the number of cells reserved per an OFDM symbol, do
represents indices of a first OFDM symbol of a subframe, and den,' represents
an index
of the last data symbol.
[125] In the meantime, when a position where a preamble pilot is inserted
in the preamble
symbol and a position where a sub frame boundary pilot is inserted in the sub
frame
boundary symbols are defined based on pilot insertion pattern
Dx=6,8,12,16,24,32, the
set of carriers to be reserved for the preamble symbols and the sub frame
boundary
symbols are as shown in Table 4.
[126] In the meantime, other than the above, even in the case where a
position where a
preamble pilot is inserted in the preamble symbol and a position where a sub
frame
boundary pilot is inserted in the sub frame boundary symbols are defined based
on
pilot insertion pattern Dx=6,12,16,24,32, the set of carriers to be reserved
for the
preamble symbols and the sub frame boundary symbols are as described in Table
4.
[127] In this case, when a position where a preamble pilot is inserted in
the preamble
symbol and a position where a sub frame boundary pilot is inserted in the sub
frame
boundary symbols are defined based Dx=3,4,8, the set of carriers to be
reserved for the
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preamble symbols and the sub frame boundary symbols are as described in Table
5.
[128] FIG. 10 is a flowchart illustrating a method of determining reserved
tones according
to an exemplary embodiment.
[129] First, indices of reserved tones are randomly selected, and a kernel
signal is
generated based on the randomly selected indices (S1010).
[130] Thereafter, a comparison reference average value of the generated
kernel signal is
calculated, the calculated comparison reference average value is compared with
a
prestored comparison reference average value, and indices of the reserved
tones are
preliminarily determined (S1020).
[131] In addition, the order of the preliminarily determined indices of the
reserved tones is
randomly re-arranged (S1030), a comparison reference average value is
calculated
while changing each of the randomly re-arranged indices of the reserved tones,
and
indices which forms a basis of the smallest comparison reference average value
are
finally determined as indices of the reserved tones (S1040).
[132] Here, in S1010, a kernel signal may be generated by randomly
selecting carrier
indices for the reserved tones among indices other than carrier indices into
which a
pilot is inserted, inserting 1 into carriers of the randomly selected indices,
and
performing IFFT.
[133] The comparison reference average value of the kernel signal is an
average value of
amplitudes of peak signals which satisfy a predetermined condition, except a
peak
signal having the greatest amplitude, among a plurality of peak signals of the
kernel
signal generated based on the randomly selected indices for the reserved
tones. The
predetermined condition may be a condition that the peak signals belong to a
prede-
termined top range based on amplitude, except the peak signal having the
greatest
amplitude, among the plurality of peak signals of the kernel signal, and
belong to
another predetermined top range based on amplitude of a peak signal having the
second-largest amplitude.
[134] In S1020, a smaller comparison reference average value among the
calculated
comparison reference average value and the prestored comparison reference
average
value may be compared with a preset value, and indices for the kernel signal
having a
comparison reference average value smaller than the preset value may be
preliminarily
determined as indices of the reserved tones.
[135] In addition, in S1040, the comparison reference average value may be
calculated
while sequentially changing the respective indices included in the randomly re-
arranged indices of the reserved tones to indices, among indices of carries,
where a
pilot is not positioned and the preliminarily determined reserved tones are
not po-
sitioned, and indices which generate the smallest comparison reference average
value
among the calculated comparison reference average values may be finally
determined
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as indices of the reserved tones to be used for reduction of the PAPR of the
data signal.
[136] Meanwhile, the method for determining the carrier indices for the
reserved tones is as
described above.
[137] Meanwhile, according to the present exemplary embodiments, the
carrier indices
defined as illustrated in Table 4 and Table 5 may be reserved for the reserved
tones and
a PAPR of a data signal may be reduced using the reserved carrier indices, so
as to be
transmitted to a receiver.
[138] FIG. 11 is a block diagram illustrating a configuration of a
transmitter according to
an exemplary embodiment.
[139] Referring to FIG. 11, a transmitter 1100 includes a frame generator
1110, a pilot
inserter 1120, and a PAPR reducer 1130.
[140] The frame generator 1110 generates a frame. Specifically, the frame
generator may
generate a frame including a plurality of OFDM symbols having an FFT size of
16K.
[141] Here, the frame includes a preamble symbol, subframe boundary
symbols, and data
symbols, and a detailed structure thereof is as illustrated in FIG. 3.
[142] In this case, the frame generator 1110 may insert an Li signaling and
broadcast data
into the symbols by considering a position into which a pilot is to be
inserted and
positions of reserved tones.
[143] Specifically, the frame is constituted by carriers in a frequency
domain and an integer
number of OFDM symbols in a time domain. In this case, the frame generator
1110
may insert the Li signaling into carriers among a plurality of carriers of the
preamble
symbol in which the pilot and the reserved tones are not to be positioned, and
may
insert the broadcast data into carriers among a plurality of carriers of the
subframe
symbols in which the pilot and the reserved tones are not to be positioned.
Meanwhile,
the carriers into which the pilot is to be inserted and the carriers reserved
for PAPR
reduction are as described above.
[144] The pilot inserter 1120 inserts the pilot into the frame.
Specifically, the pilot inserter
1120 may insert the pilot into first carriers of the plurality of OFDM
symbols, re-
spectively.
[145] In this case, the pilot may include a preamble pilot, a continual
pilot, a subframe
boundary pilot, a scattered pilot, and an edge pilot.
[146] Accordingly, the pilot inserter 1120 may insert the preamble pilot
and the continual
pilot into the preamble symbol, may insert the subframe boundary pilot, the
continual
pilot, and the edge pilot into the subframe boundary symbols, and may insert
the
scattered pilot, the continual pilot, and the edge pilot into the data
symbols.
[147] Here, the pilot inserter 1120 may determine a position into which the
pilot is to be
inserted based on a specific pilot pattern (e.g., Dx and Dy) predefined in a
system, or
based on carrier indices predefined in the system. Meanwhile, the position
into which
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the pilot is to be inserted depending on a pilot type is as described above.
[148] The PAPR reducer 1130 performs PAPR reduction using reserved tones.
Specifically, the PAPR reducer 1130 may insert a signal for reducing PAPR into
second carriers reserved in at least one of the plurality of OFDM symbols into
which
the pilot is inserted. That is, the PAPR reducer 1130 may insert a tone
reservation
signal (e.g., cells which do not include data and Li signaling) into carriers
reserved for
PAPR reduction, in order to reduce a PAPR of an output waveform.
[149] To this end, the transmitter 1100 may further include an IFFT unit
(not illustrated)
for performing IFFT on the data and the frame into which the pilot is inserted
in a
frequency domain to generate a signal of a time domain.
[150] In this case, the PAPR reducer 1130 may use a gradient algorithm, as
described
above with reference to FIG. 1. However, this is merely one example, and the
PAPR
reducer 1130 may use various algorithms according to a tone reservation
method.
[151] Meanwhile, the second reserved carriers may be defined as illustrated
in Table 4 and
Table 5.
[152] For example, the second reserved carriers have carrier indices
defined as in Table 4,
when a position in a preamble symbol into which a preamble pilot is to be
inserted and
a position in subframe boundary symbols into which a subframe boundary pilot
is to be
inserted are defined based on a pilot insertion pattern (Dx=6, 8, 12, 16, 24,
32), and an
edge pilot is to be inserted into a first carrier and a last carrier in each
of the subframe
boundary symbols.
[153] In addition, the second reserved carriers have carrier indices
defined as illustrated in
Table 4 in data symbols, in a case in which a position into which a scattered
pilot is to
be inserted is defined based on a pilot insertion pattern (Dx=3, 4, 6, 8, 12,
16, 24, 32
and Dy=2, 4), and an edge pilot is to be inserted into a first carrier and a
last carrier in
each of the data symbols.
[154] Meanwhile, the second reserved carriers have carrier indices defined
as in Table 5,
when a position in a preamble symbol into which a preamble pilot is to be
inserted and
a position in subframe boundary symbols into which a subframe boundary pilot
is to be
inserted are defined based on a pilot insertion pattern (Dx=3 and 4), and an
edge pilot
is to be inserted into a first carrier and a last carrier in each of the
subframe boundary
symbols.
[155] Here, Dx is a difference of carrier indices between adjacent carriers
into which a pilot
is to be inserted, and Dy is a difference of symbol indices between successive
pilots on
a specific carrier.
[156] As such, the transmitter 1100 may perform PAPR reduction using the
reserved tones
and may transmit a signal of which a PAPR is reduced to a receiver (not
illustrated).
[157] Meanwhile, the transmitter 1100 may further include components other
than the
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components illustrated in FIG. 11.
[158] For example, the transmitter 1100 may further include components for
encoding and
modulating the data and the Li signaling.
[159] Specifically, the transmitter 110 may further include an encoder (not
illustrated) for
encoding the broadcast data and the Li signaling, a bit interleaver (not
illustrated) for
interleaving the encoded broadcast data and Li signaling, a constellation
mapper (not
illustrated) for mapping the interleaved broadcast data and Li signaling to
con-
stellation to generate a modulated symbol, and a time interleaver (not
illustrated) and a
frequency interleaver (not illustrated) for interleaving the broadcast data
and the Li
signaling in a time domain and a frequency domain, respectively.
[160] In addition, the transmitter 1100 may further include an IFFT unit
(not illustrated)
which performs IFFT for the broadcast data, the Li signaling, and the frame
into which
the pilot is inserted, and may further include a guard interval inserter (not
illustrated)
for inserting a guard interval into a signal that the PAPR reduction is
performed, a
bootstrap unit (not illustrated) for inserting information on the Li signaling
into
bootstrap symbols after the guard interval is inserted, and a transmitting
unit (not il-
lustrated) for up-converting a signal into which the bootstrap symbols are
inserted into
a signal of a radio frequency (RF) band and transmitting the up-converted
signal to a
receiving side.
[161] FIG. 12 is a block diagram illustrating a configuration of a receiver
according to an
exemplary embodiment.
[162] Referring to FIG. 12, a receiver 1200 includes a receiving unit 1210,
a reserved tone
remover 1220, and a signal processor 1230.
[163] The receiving unit 1210 receives a frame transmitted from the
transmitter 1100.
Specifically, the receiving unit 1210 may synchronize the frame, may receive
the
signal through an allocated frequency band, and may down-convert a received RF
band
signal into a baseband signal. In addition, the receiving unit 1210 may
perform a Fast
Fourier Transform (FFT) to restore symbols mapped to the frequency domain.
That is,
the receiving unit 1210 may restore a plurality of OFDM symbols mapped to the
frame.
[164] The reserved tone remover 1220 removes reserved tones from a
plurality of OFDM
symbols constituting the frame.
[165] Specifically, the reserved tone remover 1220 determines positions of
the reserved
tones in the symbols and removes the reserved tones from the corresponding
positions.
Accordingly, the reserved tone remover 1220 may remove the reserved tones and
may
extract only data.
[166] Here, information on the carrier indices allocated for the reserved
tones may be
prestored in the receiver 1200, or may be provided from the transmitter 1100.
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Meanwhile, the carrier indices allocated for the reserved tones are as
illustrated in the
Table 4 and Table 5 described above.
[167] The signal processor 1230 processes a plurality of OFDM symbols from
which the
reserved tones are removed. That is, the signal processor 1230 may process
data
received as the reserved tones are removed.
[168] Specifically, the signal processor 1230 may deinterleave the
broadcast data and the
Li signaling in the frequency domain and the time domain using a frequency
dein-
terleaver (not illustrated) and a time deinterleaver (not illustrated), may
extract the
signal mapped to the constellation using a constellation demapper (not
illustrated), may
deinterleave and decode the broadcast data and the Li signaling using a bit
dein-
terleaver (not illustrated) and a decoder (not illustrated), and may restore
the broadcast
data and the Li signaling. In this case, because the Li signaling includes
signaling in-
formation on the broadcast data, the Li signaling may be used upon restoring
the
broadcast data.
[169] FIG. 13 is a flowchart illustrating a method for inserting a reserved
tone signal
according to an exemplary embodiment of the present disclosure.
[170] First, a frame including a plurality of OFDM symbols having an FFT
size of 16K is
generated (S1310).
[171] Thereafter, a pilot is inserted into first carriers of the plurality
of OFDM symbols, re-
spectively (S1320).
[172] In addition, a signal for reducing a PAPR is inserted into second
carriers reserved in
at least one of the plurality of OFDM symbols into which the pilot is inserted
(S1330).
[173] Here, the frame includes the preamble symbol, the subframe boundary
symbols, and
the data symbols.
[174] In this case, the second reserved carriers may have the carrier
indices defined as in
Table 4 and Table 5.
[175] The second reserved carriers have the carrier indices defined as in
Table 4, when a
position in the preamble symbol into which a preamble pilot is to be inserted
and a
position in the subframe boundary symbols into which a subframe boundary pilot
is to
be inserted are defined based on a pilot insertion pattern (Dx=6, 8, 12, 16,
24, 32), and
an edge pilot is to be inserted into a first carrier and a last carrier in
each of the
subframe boundary symbols. In addition, the second carriers reserved have the
carrier
indices defined as illustrated in Table 4 in the data symbols, in the case
where a
position into which a scattered pilot is to be inserted is determined based on
a pilot
insertion pattern (Dx=3, 4, 6, 8, 12, 16, 24, 32 and Dy=2, 4), and an edge
pilot is to be
inserted into a first carrier and a last carrier in each of the data symbols.
[176] In addition, the second reserved carriers have the carrier indices
defined as in Table
5, when a position in the preamble symbol into which a preamble pilot is to be
inserted
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and a position in subframe boundary symbols into which a subframe boundary
pilot is
to be inserted are defined based on Dx=3 and 4, and an edge pilot is to be
inserted into
a first carrier and a last carrier in each of the subframe boundary symbols.
[177] Here, Dx is a difference of carrier indices between adjacent carriers
into which the
pilot is to be inserted, and Dy is a difference of symbol indices between
successive
pilots on a specific carrier.
[178] Meanwhile, a non-transitory computer readable medium having a program
stored
therein may be provided, wherein the program sequentially performs the method
for
determining reserved tones according to the exemplary embodiments.
[179] The non-transitory computer readable medium does not mean a medium
storing data
for a short period such as a register, a cache, a memory, or the like, but
means a
machine-readable medium semi-permanently storing the data. Specifically,
various ap-
plications or programs described above may be stored and provided in the non-
transitory computer readable medium such as a compact disc (CD), a digital
versatile
disk (DVD), a hard disk, a Blu-ray disk, a universal serial bus (USB), a
memory card,
a read-only memory (ROM), or the like.
[180] In addition, although a bus is not illustrated in the block diagram
illustrating the
transmitter and the receiver, communications between the respective components
in
the transmitter and the receiver may also be performed via the bus. In
addition, the re-
spective apparatuses may further include a processor such as a central
processing unit
(CPU), a microprocessor, or the like which performs various operations
described
above, and may further include a memory for performing various operation
described
above.
[181] A term "module", "unit" "part", or the like as represented by a block
in FIGs. 1, 11
and 12, in the exemplary embodiments, is a term for referring to the component
performing at least one function or operation, and such component may be im-
plemented in hardware or software or a combination of hardware and software.
In
addition, a plurality of "modules", "units", "parts", or the like may be
integrated into at
least one module or chip and may be implemented in or by at least one
processor (not
illustrated) such as a microprocessor, except for a case in which they need to
be each
implemented in individual specific hardware.
[182] Hereinabove, although the exemplary embodiments have been shown and
described,
it should be understood that the inventive concept is not limited to the
disclosed em-
bodiments and may be variously changed without departing from the spirit and
the
scope of the inventive concept. Therefore, the exemplary embodiments should be
construed as including all the changes, equivalents, and substitutions
included in the
spirit and scope of the present disclosure.
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Industrial Applicability
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