KR102597664B1 - Method for determining reserved tones and transmitter for performing PAPR reduction using tone reservation - Google Patents

Abstract

A reservation tone design method is disclosed. This reservation tone design method includes randomly selecting indexes of the reservation tone, generating a kernel signal based on the randomly selected indexes, calculating an average comparison standard for the generated kernel signal, and calculating the average comparison standard value. Preliminarily determining the indexes of the reserved tones by comparing them with the pre-stored average value of the comparison standard, randomly rearranging the order of the indexes of the determined reserve tones, and comparing while changing each of the randomly changed indexes of the reserved tones. It includes the step of calculating a reference average value and finally determining the indexes with the minimum calculated comparison reference average value as the indexes of the reserved tone.

Description

Transmitter for performing PAPR reduction using reserved tone design method and tone reservation method { Method for determining reserved tones and transmitter for performing PAPR reduction using tone reservation }

The present invention relates to a transmitter that performs PAPR reduction using a reservation tone design method and a tone reservation method. More specifically, it relates to a transmitter that determines carrier indices reserved for PAPR and performs PAPR reduction using a tone reservation method. It's about the transmitter.

Recently, broadcasting communication services have become multi-functional, broadband, and high-quality. In particular, with the development of electronic technology, the spread of portable broadcasting devices such as high-definition digital TVs and high-end smartphones is increasing, and accordingly, the demand for various reception methods and support for various services for broadcasting services is increasing.

Meanwhile, many transmission and reception systems provide broadcasting services through OFDM (Orthogonal Frequency Division Multiplexing). In the case of the OFDM method, data transmission is performed using multiple carriers (or sub-carriers) within a certain frequency band, so data can be transmitted at high speed and multipath fading (multipath fading) is possible. It has strong characteristics against fading.

However, the OFDM method has a problem in that the ratio of the average power to the maximum power (Peak-to-Average Power Ratio, PAPR) of the transmission signal is very large. That is, data is transmitted through multi-carriers by performing an Inverse Fast Fourier Transform (IFFT) on a signal in the frequency domain, and the amplitude of the OFDM signal can be expressed as the sum of the sizes of the multi-carriers. Therefore, when the phases of multi-carriers match each other, an OFDM signal with a high maximum is generated, and this signal exhibits a very high PAPR.

A signal with a very high PAPR not only reduces the efficiency of the high power linear amplifier, but also operates in a nonlinear region outside the linear operating range of the high power linear amplifier, distorting the signal and thus deteriorating system performance. There is a problem. Accordingly, it is requested to explore ways to reduce PAPR.

The present invention was conceived to solve the above-mentioned problems. The purpose of the present invention is to provide a method of determining carrier indices reserved for PAPR reduction and to provide a transmitter that performs PAPR reduction using the reserved carrier indices. .

A reservation tone design method according to an embodiment to achieve the above object includes randomly selecting indexes of a reservation tone and generating a kernel signal based on the randomly selected indexes, and responding to the generated kernel signal. calculating a comparison standard average value for the comparison standard and comparing the calculated comparison standard average value with a pre-stored comparison standard average value to preliminary determine indices of the reserved tone; randomly rearranging the order of the determined indexes of the reserve tone; A step of calculating the comparison standard average value while changing each of the randomly changed indexes of the reservation tone, and finally determining the indexes at which the calculated comparison standard average value is minimum as the indexes of the reservation tone. Includes.

Here, the generating step randomly selects carrier indexes for the reservation tone from among the remaining indexes excluding the carrier indexes into which the pilot is inserted, inserts 1 into the carriers of the randomly selected indexes, and performs IFFT (inverse fast The kernel signal can be generated by performing fourier transform.

In addition, the comparison standard average value is the size of peak signals that satisfy a preset condition among the remaining peak signals excluding the peak signal of the largest size among the plurality of peak signals of the kernel signal generated based on the indexes of the reservation tone. It may be the average value of .

Here, the preset condition is within a preset range based on the size of the remaining peak signals excluding the peak signal with the largest size among the plurality of peak signals, and the size of the peak signal with the second largest size. It may be a condition that falls within a range preset at the top.

Meanwhile, the preliminary determination step compares a smaller comparison standard average value among the calculated comparison standard average value and the pre-stored comparison standard average value with a preset value, and compares the kernel signal with a comparison standard average value smaller than the preset value. The indices for can be preliminarily determined as the indices of the reservation tone.

In addition, the final determining step sequentially sequentially changes each of the indexes included in the randomly changed reservation tone indices into indices in which a pilot is not located and the preliminarily determined reservation tone is not located among the indexes of the carriers. While changing, the comparison standard average value is calculated, and the indexes for the comparison standard average value having the minimum value among the calculated comparison standard average values can be finally determined as the indexes of the reserved tone.

Meanwhile, a transmitter according to an embodiment of the present invention includes a frame generator that generates a frame including a plurality of OFDM symbols with a 16K FFT size, and a pilot insertion unit that inserts a pilot into first carriers of each of the plurality of OFDM symbols. and a PAPR reduction unit that inserts a signal for reducing PAPR (Peak to Average Power Ratio) into second carriers reserved in at least one of the plurality of OFDM symbols into which the pilot is inserted, The second carriers have carrier indices defined as in Table 4.

Here, the frame may include preamble symbols, subframe boundary symbols, and data symbols.

In addition, the reserved second carriers have a pilot insertion pattern Dx=6,8,12,16,24 where the preamble pilot is inserted in the preamble symbol and the subframe boundary pilot is inserted in the subframe boundary symbols. ,32 and Dy=1, and when an edge pilot is inserted into the first and last carriers in each of the subframe boundary symbols, it has carrier indices as shown in Table 4, and the Dx is the adjacent pilot where the pilot is inserted. It is the difference in carrier indices between carriers, and Dy represents the difference in symbol indices between consecutive pilots on a specific carrier.

In addition, the reserved second carriers have locations where distributed pilots are inserted in the data symbols based on pilot insertion patterns Dx=3,4,6,8,12,16,24,32 and Dy=2,4. is defined, and when an edge pilot is inserted into the first carrier and the last carrier in each of the data symbols, it has carrier indices as shown in Table 4, where Dx is the difference in carrier indices between adjacent carriers into which the pilot is inserted, and Dy represents the difference in symbol indices between consecutive pilots on a specific carrier.

Meanwhile, a transmitter according to an embodiment of the present invention includes a frame generator that generates a frame including a plurality of OFDM symbols with a 16K FFT size, and a pilot insertion unit that inserts a pilot into first carriers of each of the plurality of OFDM symbols. and a PAPR reduction unit for inserting a signal for reducing the PAPR (Peak to Average Power Ratio) into reserved second carriers in at least one of the plurality of OFDM symbols into which the pilot is inserted. 2 Carriers have carrier indices defined as Table 5.

Here, the frame may include preamble symbols, subframe boundary symbols, and data symbols.

In addition, the reserved second carriers are defined based on Dx = 3, 4 and Dy = 1 at the position where the preamble pilot is inserted in the preamble symbol and the position where the subframe boundary pilot is inserted in the subframe boundary symbols. When an edge pilot is inserted into the first carrier and the last carrier in each of the subframe boundary symbols, it has carrier indices as shown in Table 5, where Dx is the difference in carrier indices between adjacent carriers into which the pilot is inserted, and Dy represents the difference in symbol indices between consecutive pilots on a specific carrier.

According to the various embodiments of the present invention as described above, when performing PAPR reduction, new peaks can be prevented from occurring, and PAPR can be reduced more effectively.

1 is a diagram for explaining a PAPR reduction method according to an embodiment of the present invention;
Figure 2 is a diagram to explain problems that may occur when reducing PAPR;
3 is a diagram for explaining a frame structure according to an embodiment of the present invention;
4 to 9 are diagrams for explaining a method of determining a reservation tone according to an embodiment of the present invention;
10 is a flowchart illustrating a method for determining a reservation tone according to an embodiment of the present invention;
11 is a block diagram showing the configuration of a transmitter according to an embodiment of the present invention;
12 is a block diagram showing the configuration of a receiver according to an embodiment of the present invention, and
Figure 13 is a flowchart illustrating a method for a transmitter to reduce PAPR using a reservation tone according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail with reference to the attached drawings.

The present invention relates to a method of reducing PAPR using a tone reservation (TR) method in a system that transmits signals using the OFDM method. In particular, in the present invention, in order to effectively reduce PAPR while avoiding collision with the pilot by considering the positions of carriers where pilots exist in the OFDM symbol, carriers at specific positions are used as reserved tones.

First, the method of reducing PAPR according to the reservation tone method is as follows. Specifically, in the reserved tone method, tones are reserved for some of the carriers, and the reserved tones are used to reduce PAPR without transmitting data. At this time, the receiver ignores reserved tones that do not transmit information signals and restores information signals only at the tone location of the data, so the receiver has the advantage of a simple structure.

Meanwhile, the reserved tone method uses a gradient algorithm to reduce peaks. Hereinafter, a method of reducing peaks using a gradient algorithm will be described in more detail with reference to FIG. 1.

Figure 1 shows the configuration of a transmitter that reduces PAPR using a reserved tone method.

Referring to FIG. 1, input data (i.e., broadcast data, L1 signaling including signaling information for broadcast data, pilot, etc.) 10 and a reservation tone 20 are input to the tone reservation unit 30, The reserved tone signal is allocated by the tone reservation unit 30 to a carrier position pre-arranged between the transmitter and the receiver.

Meanwhile, when the sum of the input data 10 and the reserved tone 20 is input to the IFFT unit 40, IFFT is performed, and then the time domain is output by the P/S (parallel/serial) converter 50. A signal x is generated. At this time, the peak reduction unit 60 reduces the PAPR for the output signal x.

The peak reduction unit 60 generates a kernel signal with impulse characteristics using the reserved tone. Here, the kernel signal is used to clip the output signal x.

Specifically, the peak reduction unit 60 detects the peak for the output signal x. That is, the peak reduction unit 60 detects the position, size, and phase of the peak for the output signal x. In order to reduce the peak of the output signal x, the peak reduction unit 60 circularly shifts, scales, and rotates the kernel signal based on the position, size, and phase of the peak for the output signal x. Then, this is added to the output signal x.

Afterwards, the peak reduction unit 60 calculates the PAPR for the output signal x whose peak has been reduced. In addition, when the calculated PAPR does not satisfy the target (or desired) PAPR level, the peak reduction unit 60 performs the above-described operation until the PAPR for the output signal x satisfies the target PAPR level. The process may be repeated, or the above-described process may be repeated a number of times (e.g., N) predetermined by the system.

As such, in the reserved tone method, the peak of the data signal is reduced by adding a kernel signal to the data signal. However, as the kernel signal is added to the data signal, a new peak may occur in the data signal.

For example, as shown in Figure 2(a), if IFFT is performed after inserting 1 into the carriers to which reserved tones are assigned in the frequency domain, a peak at a specific point in the time domain is obtained, as shown in Figure 2(b). A kernel signal may be generated.

In this case, when the kernel signal is added to the data signal, the peak of the data signal may be reduced by the first peak of the kernel signal. However, since parts other than the first peak are also added to the data signal, if the sizes of peaks other than the first peak are large, new peaks may be generated in the data signal.

Therefore, in the present invention, the location of the reservation tone (i.e., carrier indices used for the reservation tone) that can minimize the size of peaks other than the first peak is determined, and the corresponding carrier indices are used to reduce the PAPR. Please use it.

Hereinafter, a method for determining carrier indices where a tone is reserved in the present invention will be described.

First, since the present invention transmits signals in frames defined in the ATSC (Advanced Television System Committee) 3.0 standard, the frame structure defined in the ATSC 3.0 standard will be described with reference to FIG. 3.

According to the ATSC 3.0 standard, as shown in FIG. 3, the frame includes a bootstrap 310, a preamble 320, and at least one subframe 330-1,...,330-n. ) is composed of.

Specifically, the bootstrap 310 is located at the beginning of each frame, the preamble 320 is located after the bootstrap 310, and at least one subframe 330-1,..., 330-n is the preamble. (320) It is located next.

They are composed of at least one OFDM symbol, and the number of carriers of each OFDM symbol can be determined according to the FFT mode (i.e., the FFT size, and the FFT size can be 16K).

Meanwhile, each subframe may be composed of a subframe boundary symbol located at the boundary between other subframes and a data symbol located between the subframe boundary symbols. That is, among the OFDM symbols constituting each subframe, the first and last OFDM symbols are subframe boundary symbols, and the remaining OFDM symbols excluding these are data symbols.

Meanwhile, according to the ATSC 3.0 standard, pilots are inserted into the preamble and subframe for channel estimation and synchronization.

The types of pilots inserted into the preamble and subframe are shown in Table 1 below.

Referring to Table 1, the preamble pilot is inserted into the preamble, the scattered pilot (SP) is inserted into the data symbol, and the subframe boundary pilot is inserted into the subframe boundary symbol. . Additionally, a continuous pilot (CP) is inserted into the preamble, data symbol, and subframe boundary symbol, and an edge pilot (edge pilot) is inserted into the data symbol and subframe boundary symbol.

Meanwhile, the position where the pilot is inserted may be defined by the indexes of the carriers into which the pilot is inserted, or may be determined based on a specific pilot pattern (eg, Dx, Dy). Here, Dx is the difference in carrier indices between adjacent carriers into which pilots are inserted in the frequency direction (for this, ATSC 3.0 defines it as Separation of pilot bearing carriers (that is, in the frequency direction), and DVB -T2 (Digital Video Broadcasting-Terrestrial version 2) defines it as Difference in carrier index between adjacent scattered-pilot-bearing carriers), Dy is the difference in number of symbols between consecutive pilots on a specific carrier in the time direction. (In relation to this, in ATSC 3.0 it is defined as Number of symbols forming one scattered pilot sequence (time direction), and in DVB-T2 it is defined as Difference in symbol number between successive scattered pilots on a given carrier).

First, the position where the preamble pilot is inserted can be determined based on Dx and Dy. In the case of the preamble pilot, Dy = 1, so the preamble pilot is inserted at the same position for each preamble symbol. Specifically, the preamble pilot may be inserted into cells (i.e., carriers) having a carrier index k that satisfies k mod Dx=0 in the preamble symbol. Here, Dx can be 3, 4, 6, 8, 12, 16, 24, 32, and the system can select one of these values depending on the channel environment.

The location where the distributed pilot is inserted can be determined based on Dx and Dy. Specifically, the distributed pilot may be inserted into a carrier with index k in the lth OFDM symbol that satisfies Equation 1 below.

Here, Dx and Dy can be defined as in Table 2 below, and SPa_b means a pilot pattern with a=Dx and b=Dy.

Meanwhile, the system can select one of SPa_b defined as in Table 2 according to the channel environment.

The location where the subframe boundary pilot is inserted can be determined based on Dx and Dy. In the case of the subframe boundary pilot, Dy = 1, so the subframe boundary pilot is inserted at the same position for each subframe boundary symbol. Specifically, the subframe boundary pilot may be inserted into cells having a carrier index k that satisfies k mod Dx=0 in the subframe boundary symbol. Here, Dx can be 3, 4, 6, 8, 12, 16, 24, 32, and the system can select one of these values depending on the channel environment.

The position where continuous pilots are inserted is defined by the indexes of the carriers into which the pilots are inserted.

Specifically, continuous pilots can be inserted at different positions depending on the FFT size, and the indices of carriers into which continuous pilots are inserted in 16K can be defined as shown in Table 3 below.

Accordingly, when the system has a 16K FFT size, continuous pilots can be inserted based on Table 3.

The edge pilot may be inserted into the remaining symbols excluding the preamble symbol, that is, the first and last carriers of OFDM symbols constituting the data symbol and subframe boundary symbol.

Meanwhile, as described above, when a pilot is inserted, in the present invention, a method of determining the location of a reservation tone will be described with reference to FIGS. 4 to 9.

First, the indices of the reserved tone are randomly selected. Here, the indices of the reserved tone represent carrier indices allocated for the reserved tone. Meanwhile, the number N _TR of carriers allocated for reservation tones may have different values depending on the FFT size. For example, if the FFT size is 16K, N _TR =144.

Specifically, carrier indices for the reservation tone are randomly selected from the remaining indices excluding the indices of the carriers into which the pilot is inserted.

That is, randomly select indexes for the reservation tone (S410), determine whether the selected indexes overlap with the indexes of the pilot (S420), and select the reservation tone from among the remaining indexes excluding the indexes of the carriers into which the pilot is inserted. Carrier indices can be randomly selected.

Here, the pilot may include a preamble pilot, distributed pilot, subframe boundary pilot, continuous pilot, and edge pilot, and the position where each pilot is inserted has been described above.

Afterwards, a kernel signal is generated based on randomly selected indices. Specifically, if the randomly selected indices do not overlap with the pilot indices (S420-N), 1 may be inserted into the carriers of the randomly selected indices and IFFT may be performed to generate a kernel signal (S430). .

Then, a comparison standard average value for the kernel signal is calculated, and the calculated comparison standard average value is compared with a pre-stored comparison standard average value to preliminary determine indexes of the reserved tones.

Specifically, if the calculated comparison standard average value is smaller than the previously stored comparison standard average value (S440-Y), the previously stored comparison standard average value is replaced with the calculated comparison standard average value (S450). Here, the predetermined comparison standard average value may be a comparison standard average value calculated and stored based on indices for randomly selected reservation tones before performing the above-described process. At this time, indexes for randomly selected reservation tones may also be stored, and in step S450, previously stored indexes may also be updated.

In addition, when the comparison standard average value is smaller than the preset value (S460-Y), the indices based on the calculation of the comparison standard average value can be preliminary determined as indexes for the reservation tone (S470).

That is, the smaller comparison standard average value among the calculated comparison standard average value and the pre-stored comparison standard average value is compared with a preset value, and as a result of the comparison, if the comparison standard average value is smaller than the preset value, a kernel signal with the comparison standard average value is generated. The base indices can be preliminarily determined as indices for the reserved tone.

However, if the pre-stored comparison standard average value is smaller than the calculated comparison standard average value, the above-described process is repeated until the calculated comparison standard average value becomes smaller than the pre-stored comparison standard average value, and the calculated comparison standard average value is lower than the preset value. Indexes for the reservation tone can be preliminary determined by determining whether the tone is small.

In addition, after the pre-stored comparison standard average value is replaced with the calculated comparison standard average value, if the comparison standard average value is higher than the preset value, the above-described process is repeated until the comparison standard average value becomes smaller than the preset value to set the reservation tone. Indexes can be preliminarily determined.

Meanwhile, the comparison standard average value is the average value of the sizes of peak signals that satisfy preset conditions among the remaining peak signals excluding the peak signal of the largest size among the plurality of peak signals of the kernel signal generated based on the indexes of the reserved tone. am.

Here, the preset condition is within a preset range from the top based on the size of the remaining peak signals excluding the peak signal of the largest size among the plurality of peak signals (e.g., within the top 10%), and the second size is This may be a condition within a preset range (for example, within the top 20%) based on the size of the large peak signal. However, these numbers are just an example.

Hereinafter, with reference to FIGS. 5 to 8, the method of calculating the comparison standard average value will be described in more detail.

First, assume that the kernel signal generated based on the indices of randomly selected reservation tones is as shown in FIG. 5. Referring to FIG. 5, the kernel signal consists of peak signals having various sizes in the time domain. In this case, a plurality of peak signals of the kernel signal can be divided according to size, and a histogram showing the number of peak signals for each size can be displayed as shown in FIG. 6.

Thereafter, based on the histogram as shown in FIG. 6, a comparison standard average value may be calculated.

Specifically, as shown in FIG. 7, using a histogram, the first group belonging to the top 10% in order of relative size among the remaining peak signals excluding the largest peak signal (i.e., the first peak signal) Determine peak signals. And, as shown in FIG. 8, the second group of peak signals having a size of 80% or more of the second largest peak signal (i.e., the second peak signal) are determined using the histogram.

Then, peak signals belonging to each of the first and second groups are compared to determine peak signals commonly belonging to the first and second groups, and an average value of the magnitude of the common peak signals is calculated. The value calculated in this way is an average value based on comparison of the indices of randomly selected reservation tones.

In this way, in the present application, the comparison standard average value is calculated using peak signals that fall within a certain rank in order of size and have a magnitude greater than a certain percentage based on the magnitude of the second peak signal, and the comparison standard average value is If it is smaller than the set value, the indices based on the calculation of the comparison standard average value are preliminarily determined as indices for the reserved tone.

Here, the preset value is a value obtained through simulation. When adding the kernel signal to the data signal to reduce PAPR, the remaining portion excluding the first peak signal among the plurality of peak signals constituting the kernel signal, especially the two It can be set to a value that can prevent new peaks from being generated by peak signals of a certain size or greater, including the th peak signal.

Meanwhile, if the indexes for the reservation tone are preliminary determined, the indexes for the reservation tone can be finally determined using the preliminary determined indexes. Please refer to FIG. 9 for a more detailed explanation.

First, the order of the indexes of the preliminarily determined reservation tones is randomly rearranged (S910). In this case, K=0, N_nochange=0 can be set.

For example, if the preliminarily determined indices of the reserved tone are '1, 4, 8, 9', the order of these indices can be randomly rearranged, such as '8, 1, 9, 4'.

Then, the comparison standard average value is calculated while changing each of the randomly changed indexes of the reservation tone, and the indexes at which the calculated comparison standard average value is the minimum are finally determined as the reservation tone indexes.

Specifically, each index included in the randomly changed reservation tone indices is sequentially changed to indexes in which the pilot is not located and the preliminarily determined reservation tone is not located among the carrier indexes, and an average value is calculated as a comparison standard, The indices for the comparison standard average value having the minimum value among the calculated comparison standard average values can be finally determined as the indexes of the reserved tone.

To this end, first, optimization is performed on the Kth index among the indices of randomly changed reservation tones (S920).

Here, optimization refers to the process of determining the indexes that have the minimum comparison standard average value when calculating the comparison standard average value while sequentially changing the Kth index to other indexes.

Specifically, the Kth index among the indexes of the randomly changed reservation tones is sequentially changed to an index among the carrier indexes where the pilot is not located and where the preliminarily determined reservation tone is not located, and each time the index is changed, it is a comparison standard. By calculating the average value, it is possible to determine indices that have the minimum average value based on comparison.

As in the above-mentioned example, it is assumed that the indexes of the preliminarily determined reservation tones are '1, 4, 8, 9', and the randomly rearranged state is '8, 1, 9, 4'. Here, it is assumed that the number of carriers for one OFDM symbol is 10, and the indices of carriers into which pilots are inserted are '3, 7'. However, this is just an example for convenience of explanation.

Specifically, given that K = 0, randomly rearranged indices, that is, index 8, which is the 0th index in '8, 1, 9, 4', '3, 7', which are indices where the pilot is located, and other reservations By sequentially changing the indexes where the tones are located, excluding '1, 9, 4', the remaining indices can be used to calculate the average value based on comparison.

That is, if the indices are '0, 1, 9, 4', 1 is inserted into the carriers with indices of 0, 1, 9, and 4 (i.e., the 0th, 1st, 9th, and 4th carriers) By performing IFFT, a kernel signal can be generated and the average value compared to the generated kernel signal can be calculated. Likewise, compare cases where the indices are '2, 1, 9, 4', '5, 1, 9, 4', '6, 1, 9, 4', and '8, 1, 9, 4', respectively. The standard average value can be calculated.

Then, the comparison standard average value having the minimum value among the calculated comparison standard average values is determined, and it is determined whether the Kth index among the indices when the comparison standard average value is minimum has changed (S930). In other words, it is determined whether the Kth index when the comparison standard average value is minimum is a different value from the existing Kth index.

In the above example, if the indices when the comparison standard average value is the minimum are '5, 1, 9, 4', the 0th index is considered to have changed from 8 to 5 based on '8, 1, 9, 4'. You can.

In this way, when the K-th index is changed (S930-Y), set N_nochange=0 (S940) and K=(K+1) mod N _TR (S950), and set the K-th index to the changed indexes (i.e., as described above). In one example (K+1) mod N _TR for '5, 1, 9, 4') Repeat the above-described process for the th index. Here, N _TR is the number of carriers used for reservation tones.

However, in the above example, if the indices when the comparison standard average value is minimum are '8, 1, 9, 4', the 0th index is considered unchanged based on '8, 1, 9, 4'. You can.

In this way, if the Kth index is not changed (S930-N), set N_nochange=N_nochange+1 (S960) and determine whether N_nochange=N _TR is satisfied (S970).

Accordingly, when N_nochange=N _TR is satisfied (S970-Y), K=0 is set, the order of the indices is randomly rearranged (S980), and the above-described process is repeated.

However, if N_nochange=N _TR is not satisfied (S970-N), it is determined whether N_nochange=2*N _TR is satisfied (S990).

Accordingly, if N_nochange=2*N _TR is not satisfied (S990-N), set K=(K+1) mod N _TR (S995) and repeat the above-described process. However, if N_nochange=2*N _TR is satisfied (S990-Y), the indices output in step S990 are finally determined as indices for the reserved tone (S997).

According to this method, when indexes for reservation tones are determined and PAPR reduction is performed based on them, the magnitude of the second peak signal and the next sequentially higher magnitude peak signals in the kernel signal is overall reduced. It can be. Accordingly, the difference between the second peak signal in the kernel signal and the peak signals with the next sequentially higher magnitudes is reduced, so that when the kernel signal is added to the data signal to reduce PAPR, a new peak is not generated. .

Meanwhile, the indices for the reservation tone determined according to the above-described method are shown in Tables 4 and 5 below. That is, Table 4 and Table 5 show the set of carriers reserved for PAPR when the FFT size is 16K.

Specifically, Table 4 shows the set of carriers reserved for all symbols except the preamble symbol and subframe boundary symbols when Dx=3 and Dx=4. That is, Table 4 shows the set of carriers reserved for data symbols, preamble symbols, and subframe boundary symbols except for cases where Dx=3 and Dx=4.

Specifically, the position where the distributed pilot is inserted in the data symbols is defined based on the pilot insertion pattern Dx = 3, 4, 6, 8, 12, 16, 24, 32 and Dy = 2, 4, and the edge pilot is inserted into the data symbols. When inserted into the first carrier and the last carrier in each symbol, the position where the preamble pilot is inserted in the preamble symbol, and the position where the subframe boundary pilot is inserted in the subframe boundary symbols, the pilot insertion pattern Dx=6,8,12 ,16,24,32 and Dy=1, and if the edge pilot is inserted into the first and last carriers in each of the subframe boundary symbols, it is reserved for the preamble symbol, subframe boundary symbols, and data symbols. The three carriers are listed in Table 4.

And, Table 5 shows the set of carriers reserved for the preamble symbol and subframe boundary symbols when Dx=3 and Dx=4.

Specifically, the position where the preamble pilot is inserted in the preamble symbol and the position where the subframe boundary pilot is inserted in the subframe boundary symbols are defined. The pilot insertion pattern is defined based on Dx=3,4 and Dy=1, and the edge pilot is defined as the subframe boundary symbol. When inserted into the first and last carriers of each frame boundary symbol, the sets of carriers reserved for the preamble symbol and sub-frame boundary symbols are shown in Table 5.

That is, in Tables 4 and 5, Dy = 1 for preamble pilots and subframe boundary pilots inserted into preamble symbols and subframe boundary symbols, respectively, and Dy = 2 for distributed pilots inserted into data symbols. ,4.

In addition, in the case of distributed pilots inserted into data symbols in Table 4, Dx = 3, 4, 6, 8, 12, 16, 24, 32, and in Table 4, the preamble inserted into the preamble symbol and subframe boundary symbols For pilots and subframe boundary pilots, Dx=6,8,12,16,24,32. And, in Table 5, for preamble pilots and subframe boundary pilots inserted into preamble symbols and subframe boundary symbols, Dx = 3, 4. And in Tables 4 and 5, for edge pilots, subframe Boundary symbols and data symbols are inserted into the first and last carriers, respectively.

Meanwhile, in the data symbol, carriers with carrier indices defined in Table 4 are reserved, and these index values can be circularly shifted to define other carrier indices reserved for PAPR reduction. Here, the amount of circular shift can be determined by Dx and Dy.

Specifically, in the data symbol corresponding to index l, the reserved carrier set S _i can be calculated based on Equation 2 below.

Here, S ₀ represents the set of reserved carriers corresponding to the carrier indices defined in Table 4, N _TR is the number of cells reserved per OFDM symbol, and d ₀ is the index of the first OFDM symbol of the subframe. , and d _end represents the index of the last data symbol.

Figure 10 is a flowchart for explaining a reservation tone design method according to an embodiment of the present invention.

First, the indices of the reserved tone are randomly selected, and a kernel signal is generated based on the randomly selected indices (S1010).

Thereafter, the comparison standard average value for the generated kernel signal is calculated, and the calculated comparison standard average value is compared with the pre-stored comparison standard average value to preliminary determine the indexes of the reserved tone (S1020).

Then, the order of the indexes of the determined reserve tones is randomly rearranged (S1030), the average value of the comparison standard is calculated while changing each of the indexes of the randomly changed reserve tones, and the indexes for which the calculated average value of the comparison standard is the minimum are reserved. It is finally decided using the tone indices (S1040).

Here, step S1010 randomly selects carrier indices for the reservation tone from among the remaining indices excluding the carrier indices into which the pilot is inserted, inserts 1 into the carriers of the randomly selected indices, and performs IFFT to generate a kernel signal. can do.

Meanwhile, the comparison standard average value is the average value of the sizes of peak signals that satisfy preset conditions among the remaining peak signals excluding the peak signal of the largest size among the plurality of peak signals of the kernel signal generated based on the indexes of the reserved tone. am. Here, the preset condition is within a preset range from the top based on the size of the remaining peak signals excluding the peak signal with the largest size among the plurality of peak signals, and is based on the size of the peak signal with the second largest size. This may be a condition that falls within a range preset at the top.

Meanwhile, in step S1020, the smaller comparison standard average value among the calculated comparison standard average value and the pre-stored comparison standard average value is compared with a preset value, and the indexes for the kernel signal with the comparison standard average value smaller than the preset value are used as indexes of the reserved tone. can be determined preliminaryly.

In addition, step S1040 calculates an average value as a comparison standard by sequentially changing each of the indices included in the randomly changed reservation tone indices to indices in which the pilot is not located and the preliminarily determined reservation tone is not located among the indexes of the carriers. And, the indexes for the comparison standard average value having the minimum value among the calculated comparison standard average values can be finally determined as the indexes of the reserved tone.

Meanwhile, the method of determining carrier indices for reserved tones has been described above.

Meanwhile, in the present invention, carrier indices defined as in Table 4 and Table 5 are reserved for reservation tones, and the PAPR for the data signal can be reduced by using this and transmitted to the receiver.

Figure 11 is a block diagram for explaining the configuration of a transmitter according to an embodiment of the present invention.

Referring to FIG. 11, the transmitter 1100 includes a frame generation unit 1110, a pilot insertion unit 1120, and a PAPR reduction unit 1130.

The frame generator 1110 generates a frame. Specifically, a frame containing a plurality of OFDM symbols with a 16K FFT size can be generated.

Here, the frame includes a preamble symbol, sub-frame boundary symbols, and data symbols, and the specific structure is as shown in FIG. 3.

In this case, the frame generator 1110 may insert L1 signaling and broadcast data into symbols by considering the location where the pilot is inserted and the location of the reservation tone.

Specifically, a frame consists of carriers in the frequency domain and an integer number of OFDM symbols in the time domain. In this case, the frame generator 1110 inserts L1 signaling into carriers on which the pilot and reservation tones are not located among the plurality of carriers of the preamble symbol, and the pilot and reservation tones are located among the plurality of carriers of the subframe symbols. Broadcast data can be inserted into carriers that do not support broadcasting. Meanwhile, carriers into which pilots are inserted and carriers reserved for PAPR reduction have been described above.

The pilot insertion unit 1120 inserts a pilot into the frame. Specifically, the pilot insertion unit 1120 may insert a pilot into the first carriers of each of a plurality of OFDM symbols.

In this case, the pilot may include a preamble pilot, continuous pilot, subframe boundary pilot, distributed pilot, and edge pilot.

Accordingly, the pilot insertion unit 1120 inserts the preamble pilot and continuous pilot into the preamble, inserts the subframe boundary pilot, continuous pilot, and edge pilot into the subframe boundary symbol, and inserts the distributed pilot, continuous pilot, and edge pilot into the data symbol. A pilot can be inserted.

Here, the pilot insertion unit 1120 determines the position where the pilot is inserted based on a specific pilot pattern (e.g., Dx, Dy) predefined in the system, or determines the position where the pilot predefined in the system is inserted. The position where the pilot is inserted can be determined based on the carrier indices. Meanwhile, the position where the pilot is inserted depending on the pilot type has been described above.

The PAPR reduction unit 1130 performs PAPR reduction using a reserved tone. Specifically, the PAPR reduction unit 1130 may insert a signal for PAPR reduction into reserved second carriers in at least one of a plurality of OFDM symbols into which a pilot is inserted. That is, the PAPR reduction unit 1130 may insert a reservation tone signal (e.g., cells that do not contain data and L1 signaling) into carriers reserved for PAPR in order to reduce the PAPR of the output waveform. .

To this end, the transmitter 1100 may further include an IFFT unit (not shown) for generating a signal in the time domain by performing IFFT on a frame in which data and pilot are inserted in the frequency domain.

In this case, the PAPR reduction unit 1130 can use a gradient algorithm, which has been described above with reference to FIG. 1. However, this is only an example, and of course, the PAPR reduction unit 1130 can use various algorithms according to the tone reservation method.

Meanwhile, reserved second carriers can be defined as Table 4 and Table 5.

For example, the reserved second carriers have a pilot insertion pattern Dx=6,8,12,16,24, 32 and Dy=1, and when the edge pilot is inserted into the first and last carriers in each of the subframe boundary symbols, it has carrier indices defined as shown in Table 4.

In addition, in the reserved second carriers, the position where the distributed pilot is inserted in the data symbols is defined based on the pilot insertion pattern Dx = 3, 4, 6, 8, 12, 16, 24, 32 and Dy = 2, 4. , when the edge pilot is inserted into the first and last carrier in each of the data symbols, it has carrier indices defined as shown in Table 4.

Meanwhile, in the reserved second carriers, the position where the preamble pilot is inserted in the preamble symbol and the position where the subframe boundary pilot is inserted in the subframe boundary symbols are defined based on the pilot insertion pattern Dx = 3, 4 and Dy = 1, When an edge pilot is inserted into the first carrier and the last carrier in each of the subframe boundary symbols, it has carrier indices defined as shown in Table 5.

Here, Dx is the difference in carrier indices between adjacent carriers into which pilots are inserted, and Dy represents the difference in symbol indices between consecutive pilots on a specific carrier.

In this way, the transmitter 1000 may perform PAPR reduction using a reservation tone and transmit a signal with reduced PAPR to a receiver (not shown).

Meanwhile, the transmitter 1100 may further include other components in addition to the components shown in FIG. 11.

For example, the transmitter 1100 may further include components for encoding and modulating data and L1 signaling.

Specifically, the transmitter 1100 includes an encoder (not shown) for encoding broadcast data and L1 signaling, a bit interleaver (not shown) for interleaving the encoded broadcast data and L1 signaling, and a constellation of the interleaved broadcast data and L1 signaling. A constellation mapper (not shown) for mapping to a constellation to generate a modulation symbol, and a time interleaver (not shown) and a frequency interleaver (not shown) for interleaving broadcast data and L1 signaling in the time domain and frequency domain, respectively. ) and the like may further be included.

In addition, the transmitter 1100 further includes an IFFT unit (not shown) that performs IFFT on frames into which broadcast data, L1 signaling, and pilots are inserted, and a guard interval for inserting a guard interval into the PAPR reduction processed signal. After the insertion part (not shown) and the guard interval are inserted, the bootstrap part (not shown) inserts information about L1 signaling into the bootstrap symbols, and the signal into which the bootstrap symbols are inserted is up-converted into a signal in the RF band. It may further include a transmission unit (not shown) for transmitting to the receiving side.

Figure 12 is a block diagram for explaining the configuration of a receiver according to an embodiment of the present invention.

Referring to FIG. 12, the receiver 1200 includes a reception unit 1210, a reservation tone removal unit 1220, and a signal processing unit 1230.

The receiving unit 1210 receives the frame transmitted from the transmitter 1100. Specifically, the receiver 1210 may synchronize the frame, receive a signal through an allocated frequency band, and down-convert the received RF band signal to a baseband signal. Additionally, the receiver 1210 may perform Fast Fourier Transform (FFT) to restore symbols mapped to the frequency domain. That is, the receiver 1210 can restore a plurality of OFDM symbols mapped to the frame.

The reservation tone remover 1220 removes the reservation tone from a plurality of OFDM symbols constituting the frame.

Specifically, the reserved tone removal unit 1220 determines the location of the reserved tone in the symbols and removes the reserved tone from the corresponding location. Accordingly, the reserved tone removal unit 1220 can remove the reserved tone and extract only data.

Here, information on carrier indices allocated for reservation tones may be pre-stored in the receiver 1200 or may be provided from the transmitter 1100. Meanwhile, the carrier indices allocated for reserved tones are shown in Tables 4 and 5.

The signal processing unit 1230 processes a plurality of OFDM symbols from which reservation tones have been removed. That is, the signal processing unit 1230 can process the received data as the reservation tone is removed.

Specifically, the signal processing unit 1230 deinterleaves broadcast data and L1 signaling in the frequency domain and time domain through a frequency deinterleaver (not shown) and a time deinterleaver (not shown), and a constellation demapper (not shown). The signal mapped to the constellation can be extracted, and the broadcast data and L1 signaling can be restored by deinterleaving and decoding the broadcast data and L1 signaling through a bit deinterleaver (not shown) and a decoder (not shown). In this case, since L1 signaling includes signaling information about broadcast data, L1 signaling can be used when restoring broadcast data.

Figure 13 is a flowchart for explaining a method of inserting a reservation tone signal according to an embodiment of the present invention.

First, a frame containing a plurality of OFDM symbols with a 16K FFT size is generated (S1310).

Afterwards, a pilot is inserted into the first carriers of each of the plurality of OFDM symbols (S1320).

Then, a signal for PAPR reduction is inserted into the second carriers reserved in at least one of the plurality of OFDM symbols into which the pilot is inserted (S1330).

Here, the frame includes preamble symbols, subframe boundary symbols, and data symbols.

In this case, the reserved second carriers may have carrier indices defined as Tables 4 and 5.

Specifically, the reserved second carriers have a pilot insertion pattern Dx=6,8,12,16,24,32 where the preamble pilot is inserted in the preamble symbol and the subframe boundary pilot is inserted in the subframe boundary symbols. and Dy = 1, and when the edge pilot is inserted into the first carrier and the last carrier in each of the subframe boundary symbols, it has carrier indices defined as shown in Table 4.

In addition, in the reserved second carriers, the position where the distributed pilot is inserted in the data symbols is defined based on the pilot insertion pattern Dx = 3, 4, 6, 8, 12, 16, 24, 32 and Dy = 2, 4. When an edge pilot is inserted into the first carrier and the last carrier in each of the data symbols, it has carrier indices defined as shown in Table 4.

In addition, in the reserved second carriers, the position where the preamble pilot is inserted in the preamble symbol and the position where the subframe boundary pilot is inserted in the subframe boundary symbols are defined based on Dx = 3, 4 and Dy = 1, and the edge pilot is defined. When inserted into the first carrier and the last carrier in each of the subframe boundary symbols, they have carrier indices defined as shown in Table 5.

Here, Dx is the difference in carrier indices between adjacent carriers into which pilots are inserted, and Dy represents the difference in symbol indices between consecutive pilots on a specific carrier.

Meanwhile, a non-transitory computer readable medium storing a program that sequentially performs the reservation tone design method according to the present invention may be provided.

A non-transitory readable medium refers to a medium that stores data semi-permanently and can be read by a device, rather than a medium that stores data for a short period of time, such as registers, caches, and memories. Specifically, the various applications or programs described above may be stored and provided on non-transitory readable media such as CD, DVD, hard disk, Blu-ray disk, USB, memory card, ROM, etc.

In addition, although the bus is not shown in the above block diagram showing the transmitter and receiver, communication between each component in the transmitter and receiver may be performed through the bus. Additionally, each device may further include a processor such as a CPU or microprocessor that performs the various operations described above, and each device may further include memory to perform the various operations described above.

In addition, in embodiments of the present invention, terms such as “module,” “unit,” and “part” are terms for referring to components that perform at least one function or operation, and these components are hardware or It may be implemented in software or a combination of hardware and software. In addition, a plurality of "modules", "units", "parts", etc. are integrated into at least one module or chip, except in cases where each needs to be implemented with individual specific hardware, and is integrated into at least one processor. It can be implemented as (not shown).

In addition, although preferred embodiments of the present invention have been shown and described above, the present invention is not limited to the specific embodiments described above, and the technical field to which the invention pertains without departing from the gist of the present invention as claimed in the claims. Of course, various modifications can be made by those of ordinary skill in the art, and these modifications should not be understood individually from the technical idea or perspective of the present invention.

100: Transmitter 110: Frame generator
120: Pilot insertion part 130: PAPR reduction part

Claims (16)

delete delete delete delete delete delete In the transmitter,
It includes a PAPR reduction unit that generates a signal for reducing the PAPR (Peak to Average Power Ratio) of the OFDM symbol,
The size of the OFDM symbol is 16K,
The PAPR reduction unit generates a signal to reduce the PAPR of the OFDM symbol using a carrier set having the following carrier indices:
In clause 7,
The OFDM symbol is,
A transmitter, which is one of a preamble symbol, a subframe boundary symbol, and a data symbol. According to clause 8,
The PAPR reduction unit,
The position where the preamble pilot is inserted in the preamble symbol and the position where the subframe boundary pilot is inserted in the subframe boundary symbol are defined based on the pilot insertion pattern Dx=6,8,12,16,24,32 and Dy=1. When an edge pilot is inserted into the first and last carriers in the subframe boundary symbol, a signal for reducing the PAPR of the OFDM symbol is generated using the carrier set,
wherein Dx is the difference in carrier indices between adjacent carriers into which pilots are inserted, and Dy is the difference in symbol indices between consecutive pilots on a specific carrier. According to clause 8,
The PAPR reduction unit,
The position where the distributed pilot is inserted in the data symbol is defined based on the pilot insertion pattern Dx = 3, 4, 6, 8, 12, 16, 24, 32 and Dy = 2, 4, and the edge pilot is inserted in the data symbol. When inserted into the first and last carriers, a signal for reducing the PAPR of the OFDM symbol is generated using the carrier set,
wherein Dx is the difference in carrier indices between adjacent carriers into which pilots are inserted, and Dy is the difference in symbol indices between consecutive pilots on a specific carrier. delete delete delete In the receiver,
a receiving unit that receives a frame including OFDM symbols from a transmitter; and
It includes a processor that processes the received frame based on the location of the reserve tone for PAPR (Peak to Average Power Ratio) reduction,
The size of the OFDM symbol is 16K,
The location of the reserve tone is represented by a carrier set with carrier indices as follows:
According to clause 14,
The OFDM symbol is,
A receiver, which is one of a preamble symbol, a subframe boundary symbol, and a data symbol. According to clause 15,
The processor,
The position where the preamble pilot is inserted in the preamble symbol and the position where the subframe boundary pilot is inserted in the subframe boundary symbol are defined based on the pilot insertion pattern Dx=6,8,12,16,24,32 and Dy=1. And when an edge pilot is inserted into the first carrier and the last carrier in each of the subframe boundary symbols, the received frame is processed using the carrier set,
wherein Dx is the difference in carrier indices between adjacent carriers into which pilots are inserted, and Dy is the difference in symbol indices between consecutive pilots on a specific carrier.

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