JP2011512727A - Preamble transmitter / receiver and method for digital video broadcast system - Google Patents

Abstract

An apparatus and method for transmitting a preamble in a digital video broadcast (DVB) system are provided. The apparatus generates a modulated signaling sequence (MSS) using a plurality of received sequences, and outputs a modulated sequence by differentially modulating the modulated signaling sequence; and the modulated A scrambler that scrambles the sequence by multiplying it by a scrambling sequence, and receives the scrambled sequence through each assigned subcarrier, converts the received sequence into a time domain signal, and then generates the preamble. And a second processing unit for transmission.
[Selection] Figure 8

Description

  The present invention relates to a digital video broadcasting (hereinafter referred to as “DVB”) system, and more particularly, to a preamble transmitting / receiving apparatus and method in a component of a frame in a digital video broadcasting system.

  In general, a “digital broadcast system” refers to a broadcast system that uses digital transmission techniques such as digital audio broadcast (DAB), digital video broadcast (DVB), and digital multimedia broadcast.

  Among them, the DVB system, which is a European digital broadcast technology, is a transmission standard for supporting not only existing digital broadcasts but also mobile / portable digital multimedia services.

  The DVB system can multiplex broadcast data based on MPEG2 TS (Moving Picture Experts Group 2 Transport Stream) and simultaneously transmit an IP-based data stream. Also, in the DVB system, various services can be transmitted after being multiplexed into one IP stream. After receiving this transmitted IP stream data, the terminal can demultiplex it into individual services, demodulate this service, and output it via the user terminal screen. At this time, the user terminal needs information indicating the types of the various services provided by the DVB system and the contents included in each service.

FIG. 1 is a diagram illustrating a frame structure of a physical layer in a conventional DVB system.
Referring to FIG. 1, the frame structure can be simply divided into preamble parts P1 and P2 and a body part BODY. The preamble parts P1 and P2 transmit frame signaling information, and the body part is composed of parts used to transmit data and payload.

The purpose of the preamble P1 in FIG. 1 is as follows.
First, the preamble P1 is used to scan the initial signal of the frame at the receiver. Second, the preamble P1 is used to detect the frequency offset and tune the center frequency at the receiver. Third, the preamble P1 is used not only to transmit Fast Fourier Transform (FFT) size and other transmission (TX) information, but also to transmit frame identification information. Finally, the preamble P1 is used to detect and correct frequency and time synchronization at the receiver.

  With respect to the structure of the preamble P1 in FIG. 1, the part A in which information is transmitted is fixed to a 1K orthogonal frequency division multiplexing (OFDM) symbol regardless of the FFT size of the payload in which data is transmitted, and has a length of 112 μs. . When the remaining parts B and C are each configured with a 1/2 protection interval, they are added to both sides of the 1K symbol and have a length of 56 μs. As shown in FIG. 1, the total length of the preamble P1 is 224 μs.

FIG. 2 is a diagram illustrating a position of a carrier in which a preamble sequence in the related art is transmitted.
FIG. 2 is a diagram for explaining an internal structure of the 1K OFDM symbol shown in FIG.
As shown in FIG. 2, the 1K OFDM symbol includes 853 carriers. Of the 853 carriers that make up 1K OFDM, only 384 carriers are used for transmission of the preamble sequence.

FIG. 3 is a block diagram illustrating a configuration of a transmitter that transmits a preamble in a conventional DVB system.
Among the 853 carriers, the position of the carrier used for transmitting the preamble sequence can be determined in advance. In FIG. 3, the carrier position is determined in advance and stored in a carrier distribution sequence (CDS) table 300.

The operation of the modulation signaling sequence (MSS) processing unit 310 is as follows.
First, the MSS processing unit 310 receives the first sequence (hereinafter, “S1”) and the second sequence (hereinafter, “S2”), and generates a complementary set of sequences (CSS). To do. S1 and S2 include 3-bit information and 4-bit information, respectively. The CSS generated by S1 and S2 has 8 and 16 combinations, respectively, and the CSS _S1 and CSS _S2 generated by S1 and S2 have lengths of 64 and 256, respectively. Such CSS is characterized by a low peak-to-average power ratio (PAPR) and orthogonality between the CSSs.

The signals S1 and S2 can be expressed as shown in Table 1 below. In Table 1 below, the signals S1 and S2 are expressed in hexadecimal numbers.

A series of steps in which the sequences S1 and S2 are output as a sequence modulated by the MSS processing unit 310 through the phase offset processing unit 325 is as follows.
Equation (1) indicates a sequence generated by the combination of S1 and S2 in the MSS processing unit 310, and this sequence is indicated by MSS_SEQ.
(Equation 1)
MSS_SEQ = {CSS _S1 , CSS _S2 , CSS _S1 } (1)

MSS_SEQ in Equation (1) is modulated by DBPSK in a differential two-phase phase shift (DBPSK) (hereinafter referred to as “DBPSK”) modulation unit (or DBPSK mapper) 320. The following formula (2) represents a DBPSK modulated sequence and is represented by MSS_DIFF.
(Equation 2)
MSS_DIFF = DBPSK (MSS_SEQ) (2)

The phase offset processing unit 325 outputs a finally modulated sequence by applying a 180 ° phase offset to 64 bits (or cells) of the most significant bit (MSB) in this modulated sequence.
The phase offset processing unit 325 does not apply the phase offset to the remaining bits except for the 64 most significant bits. Since all the 64 most significant bits have the same offset value, the phase offset value does not affect the demodulation process of the DBPSK demodulator at the receiver. Therefore, the receiver does not require the reverse process of the phase offset process.

Finally, the output of the phase offset processing unit 325 is defined as the following formula (3).
(Equation 3)
MSS = {− MSS_DIFF _{383, 382,. . . , 320} , MSS_DIFF _{319, 318,. . . , 0} } (3)

A sequence output through the MSS processing unit 310, the DBPSK modulation unit 320, and the phase offset processing unit 325, that is, a modulated sequence is allocated to 384 active carriers for P1 by the carrier allocation unit 330.
The operation of the inverse fast Fourier transform (IFFT) processing unit 340 and the preamble generation unit 350 is substantially the same as that of FIG. 1 in a configuration in which two guard intervals are added to improve symbol robustness with respect to P1. The operation is the same.

FIG. 4 is a block diagram illustrating a configuration of a receiver that receives a preamble in a conventional DVB system.
Referring to FIG. 4, the preamble detector 400 of the receiver detects the preamble and inputs it to the FFT processor 410. The FFT processing unit 410 performs FFT on the detected preamble, and then outputs the result to the demultiplexing unit (DEMUX) 420.

  Next, the DEMUX 420 demultiplexes the data of the active carrier to which the preamble is transmitted, and outputs the demultiplexed data to the DBPSK demodulator 430. The DBPSK demodulator 430 outputs the signal to the signal detection unit 440 after performing the reverse process of the phase offset processing unit 325, that is, after performing DBPSK demodulation in which the MSB signal of the preamble is phase-shifted by the length 64 at the receiver. To do. The signal detection unit 440 outputs desired information by detecting S1 and S2 from the demodulated sequence.

FIG. 5 is a flowchart illustrating a reception method for receiving a preamble in a conventional DVB system.
Referring to FIG. 5, the receiver performs initialization at step 500 and performs tuning for the preamble at step 505. The receiver performs guard interval correlation (GIC) on the signal received in step 510, and determines in step 515 whether or not the preamble P1 has been detected.

  If, at step 515, the receiver fails to detect preamble P1, the receiver returns to step 510. On the other hand, if the receiver detects the preamble P1, the receiver adjusts the coarse time and the fine frequency offset in step 520.

  The receiver then performs a power correlation to estimate the power of the active carrier at step 525, and then further determines whether the preamble P1 is detected at step 530.

  If the detection of the preamble P1 fails, the receiver returns to step 510, and if the receiver has successfully detected the preamble P1, the receiver performs a coarse frequency offset adjustment at step 535. Thereafter, the receiver performs DBPSK demodulation, which is the reverse process of the differential modulation scheme at the transmitter, in step 540, calculates a correlation value between preambles in step 545, and in steps 550, S1 and S2 The signal of is detected.

  Since the above-described conventional preamble configuration uses differential modulation (ie, DBPSK), non-coherent reception is possible. However, there is a problem that PAPR becomes large because the characteristics of complementary sequences change due to the execution of differential modulation. Accordingly, there is a need for an improved apparatus and method for transmitting and receiving a preamble among the components of a frame in a DVB system.

  Accordingly, the present invention has been proposed to solve the above-described problems of the prior art, and an object of the present invention is to provide an apparatus and method that can reduce the PAPR of a preamble by scrambling. .

  To achieve the above object, according to an aspect of the present invention, there is provided a preamble transmission apparatus in a digital video broadcast (DVB) system. The transmitter generates a modulated signaling sequence (MSS) using a plurality of received sequences, and outputs a modulated sequence by differentially modulating the modulated signaling sequence; and the modulation A scrambler that scrambles the generated sequence by a scrambling sequence, and receives the scrambled sequence through a plurality of assigned subcarriers, converts the received sequence into a time domain signal, and then the preamble. And a second processing unit for generating and transmitting.

  According to another aspect of the present invention, a preamble transmission method in a digital video broadcast (DVB) system is provided. The transmission method includes a step of generating a modulated signaling sequence (MSS) using a plurality of received sequences, a step of outputting the modulated sequence, and a scrambling sequence by multiplying the modulated sequence by a scrambling sequence. Receiving the scrambled sequence through a plurality of assigned subcarriers, converting the received sequence into a time domain signal, and generating and transmitting the preamble. It is characterized by that.

  According to yet another aspect of the present invention, a preamble receiver in a digital video broadcast (DVB) system is provided. The receiving apparatus detects a preamble from a received signal, converts the detected preamble into a frequency domain signal, and then demultiplexes the frequency domain signal; and the demultiplexed A descrambler that descrambles the demultiplexed sequence by multiplying the sequence by a descrambling sequence; a second that differentially demodulates the descrambled sequence and detects a plurality of sequences from the demodulated sequence; And a processing unit.

  According to yet another aspect of the present invention, a preamble reception method in a digital video broadcast (DVB) system is provided. The receiving method includes a step of detecting a preamble from a received signal, a step of converting the detected preamble into a frequency domain signal, a step of demultiplexing the frequency domain signal, and the demultiplexed sequence. And a step of descrambling by multiplying by a descrambling sequence, a step of differentially demodulating the descrambled sequence, and a step of detecting a plurality of sequences from the demodulated sequence. .

  The present invention uses a differential modulation scheme when transmitting a preamble, which is one of physical channels, in a DVB system, thereby solving the PAPR increase problem using scrambling, thereby reducing the PAPR of the preamble P1. There is an effect that can be reduced.

It is a figure which shows the frame structure of the physical channel in the conventional DVB system. It is a figure which shows the position of the carrier in which the preamble sequence in a prior art is transmitted. It is a block diagram which shows the structure of the transmitter which transmits the preamble in the conventional DVB system. It is a block diagram which shows the structure of the receiver which receives the preamble in the conventional DVB system. It is a flowchart which shows the receiving method which receives the preamble in the conventional DVB system. It is a block diagram which shows the structure of the transmitter which transmits the preamble in the DVB system by embodiment of this invention. It is a figure which shows embodiment of the PRBS encoder of Numerical formula (5). 3 is a flowchart illustrating a transmission method for transmitting a preamble in a DVB system according to an embodiment of the present invention. It is a block diagram which shows the structure of the receiver which receives the preamble in the DVB system by embodiment of this invention. 3 is a flowchart illustrating a reception method for receiving a preamble in a DVB system according to an embodiment of the present invention.

  Other objects, advantages and salient features of the present invention will become apparent to those skilled in the art from the accompanying drawings and the following detailed description made from the embodiments of the present invention.

  The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of the embodiments of the present invention as defined in the appended claims and their equivalents. While including various specific details to assist in this understanding, it is merely one embodiment. Accordingly, it will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the scope or spirit of the invention. . In addition, from the viewpoints of clarity and conciseness, detailed descriptions of functions and configurations well known to those skilled in the art are omitted.

  The terms and words used in the following description and claims are not limited to the dictionary meaning, but are used by the inventor to make the understanding of the invention clear and consistent. Accordingly, it is to be defined based on the claims and their equivalents, and the description of the embodiments of the present invention is merely provided for illustrative purposes and does not limit the purpose of the present invention. It will be apparent to those skilled in the art of the present invention.

Those skilled in the art will appreciate that “a”, “an”, and “the”, ie, the singular forms in the English specification, include the plural unless specifically stated otherwise in the context. Thus, for example, reference to “a component surface” includes one or more surfaces.
The term “substantially” does not require that the presented feature, parameter, or value be set precisely, but is known to the tolerance, measurement error, measurement accuracy limit and those skilled in the art, Alternatively, it means that deviations or changes including elements obtained by those skilled in the art without experimentation occur within a range that does not exclude the effect that these characteristics are intended to provide.

  The present invention relates to a preamble to which signaling information is transmitted, and more particularly to a preamble P1 to which initial information is transmitted. Embodiments of the present invention propose a method for solving the above-mentioned problem that the use of differential modulation increases the peak-to-average power ratio (PAPR) of the complementary sequence to the preamble.

Hereinafter, embodiments of the present invention will be described.
Table 2 shows the PAPR of the preamble when the differential modulation scheme is not applied to the preamble P1. When 128 preamble signals are generated by the combination of the first and second sequences S1 and S2, the maximum PAPR is 10.29 dB, the minimum PAPR is 6.72 dB, and the average PAPR is 8 .21 dB.

However, Table 3 shows the PAPR of the preamble when applying the differential modulation scheme. In this case, the maximum PAPR of the preamble is 10.50 dB, the minimum PAPR is 7.14 dB, and the average PAPR is 7.14 dB. As described above, it can be seen from the comparison between Table 2 and Table 3 that the PAPR increases because the characteristics of the complementary sequences contradict each other due to the use of the differential modulation method. From the results of Table 2 and Table 3, it can be seen that the average PAPR increases by 0.42 dB due to the influence of differential modulation.

As a method for solving the above problem, that is, for reducing the PAPR, the DVB system can solve the problem that the PAPR due to differential modulation becomes large by applying scrambling.
FIG. 6 is a block diagram illustrating a configuration of a transmitter that transmits a preamble in the DVB system according to an embodiment of the present invention.

  Referring to FIG. 6, the transmitter includes a CDS table 600, an MSS processing unit 610, a DBPSK modulation unit 620, a phase offset processing unit 630, a scrambler 635, a carrier allocation unit 640, an IFFT processing unit 650, and a preamble generation unit 660. Including. Here, the CDS table 600, the MSS processing unit 610, the DBPSK modulation unit 620, the phase offset processing unit 630, the carrier allocation unit 640, the IFFT processing unit 650, and the preamble generation unit 660 are the CDS in the conventional transmitter of FIG. The table 300, the MSS processing unit 310, the DBPSK modulation unit 320, the phase offset processing unit 325, the carrier allocation unit 330, the IFFT processing unit 340, and the preamble generation unit 350 perform the same operations. Omitted.

  The scrambler 635 according to the embodiment of the present invention can prevent a complementary set (CSS) of the sequence generated by the MSS processing unit 610 from increasing the PAPR by the DBPSK modulation unit 620 and the phase offset processing unit 630. That is, in the embodiment, the scrambler 635 generates a new sequence by multiplying the modulated sequence output from the phase offset processing unit 630 by the scrambling sequence. Further, the scrambler 635 can operate in an arbitrary sequence when executing an operation of changing the signal from the MSS processing unit 610 into an arbitrary form.

The output MSS_SCR of the scrambler 635 is expressed as Equation (4).
(Equation 4)
MSS_SCR = SCR (MSS) (4)

In Equation (4) described above, the term “SCR” indicates the scrambling operation of the scrambler 635. A new sequence is generated by multiplying the modulated sequence input to the scrambler 635 by the scrambling sequence.
For example, when a BSPK sequence of length K is input as a modulated sequence, ie, {1 ₀ , −1 ₁ , −1 ₂ , 1 ₃ ,. . . , 1 _K−1 } is input as a modulated sequence, the scrambling sequence can also be generated with an arbitrary BPSK sequence of length K.

The scrambling sequence is {-1 ₀ , 1 ₁ , -1 ₂ , -1 ₃ ,. . . , −1 _K−1 }, the scrambler 635 uses this modulated sequence {1 ₀ , −1 ₁ , −1 ₂ , 1 ₃ ,. . . , 1 _K−1 } to the scrambling sequence {−1 ₀ , 1 ₁ , −1 ₂ , −1 ₃ ,. . . , −1 _K−1 } to obtain a new BPSK sequence of length K as {−1 ₀ , −1 ₁ , 1 ₂ , −1 ₃ ,. . . , −1 _K−1 }. That is, the scrambler 635 generates a new sequence MSS_SCR by multiplying the sequence modulated using Equation (4) by the scrambling sequence.

  The scrambler 635 has a length 384 used by the scrambler 635 for a sequence modulated by the DBPSK modulation unit 620 and the phase offset processing unit 630, that is, a modulated sequence having a length 384 expressed by 1 or −1. Scrambling is performed by multiplying a scrambling sequence having This scrambling sequence will be described in detail in the following embodiment.

The scrambler 635 generates a scrambling sequence for reducing the PAPR of the preamble P1. In a DVB system, a scrambler 635 can generate a scrambling sequence using an existing PRBS using a pseudo-random binary sequence (PRBS) defined as Equation (5) below.
(Equation 5)
1 + X ₁₄ + X ₁₅ (5)

FIG. 7 is a diagram illustrating an example of the PRBS encoder of Equation (5).
7, the PRBS register 710 receives an initial value sequence (100010111100101) and generates a PRBS sequence (1110100011100100011100100 ...).

The PAPR scrambling sequence with initial value and length 384 is shown in Table 4 below.

  The scrambling sequence shown in Table 4 is used as a scrambling sequence for the scrambler used to reduce the PAPR of the preamble P1. In the PRBS encoder of FIG. 7, the sequence of length 384 generated with the initial values in Table 4 is converted from 0 or 1 to 1 or −1 and output from the phase offset processing unit by the scrambler 635. Reduce the PAPR by multiplying with the modulated sequence.

Table 5 below shows PAPRs of 128 preambles P1 when PAPR reduction scrambling is used in the embodiment of the present invention. Here, it can be seen that the maximum PAPR is 9.10 dB, the minimum PAPR is 6.71 dB, and the average PAPR is 8.01 dB. Compared to Table 3, a gain of 1.4 dB can be obtained with maximum PAPR.

  In an embodiment, a new sequence is generated by the scrambler 635 described above. Furthermore, each scrambling sequence can be stored in a look-up table for future use or can be determined when needed. As an example, in FIG. 6, the output of the DBPSK modulator 620 can be stored in a lookup table, the output of the scrambler 635 can be stored in a lookup table, or all of the blocks 600-635 can be stored. The output can be stored in a look-up table for operation of the scrambler 635.

FIG. 8 is a flowchart illustrating a transmission method for transmitting a preamble in a DVB system according to an embodiment of the present invention.
Referring to FIG. 8, the transmitter receives S1 and S2 in step 801, and generates an MSS by selecting a sequence corresponding to S1 and S2 in step 803.

  The transmitter differentially modulates the MSS at step 805 and applies a 180 ° phase offset to the 64 bits of the most significant bit (MSB) at step 807. In step 809, the transmitter performs scrambling by multiplying the scrambling sequence generated by Equation (5) by the sequence modulated in step 807.

  In step 811, the transmitter receives the scrambled sequence through each assigned subcarrier. Next, in step 813, a time domain signal is generated by performing IFFT on the scrambled sequence received through each of the assigned subcarriers. Finally, in step 815, the transmitter generates a preamble having the configuration shown in FIG.

  Because the scrambling operation performed by the scrambler 635 is performed after DBPSK modulation, the embodiment of the present invention can detect the detection performance of S1 and S2 when the scrambling operation is performed before DBPSK modulation. More stable than that. That is, the embodiment of the present invention is strong in the detection performance of S1 and S2.

FIG. 9 is a block diagram illustrating a configuration of a receiver that receives a preamble in a DVB system according to an embodiment of the present invention.
Referring to FIG. 9, the receiver includes a preamble detector 900, an FFT processor 910, a DEMUX 920, a descrambler 930, a DBPSK demodulator 940, and a signal detector 950. Here, the preamble detector 900, the FFT processor 910, the DEMUX 920, the DBPSK demodulator 940, and the signal detector 950 are the preamble detector 400, FFT processor 410, DEMUX 420, DBPSK demodulator 430, and Since the same operation as that of the signal detection unit 440 is performed, a detailed description thereof will be omitted.

  The descrambler 930 according to the embodiment of the present invention performs the reverse process of the scrambler 635 on the sequence obtained by demultiplexing the data of the active carrier on which the preamble is transmitted. That is, the descrambler 930 performs descrambling by multiplying the demultiplexed sequence by the descrambling sequence.

  Here, the descrambling sequence has the same length as the demultiplexed sequence. This descrambled sequence can be predetermined and stored in a look-up table or generated using PRBS in the same manner as the scrambling sequence described above.

FIG. 10 is a flowchart illustrating a reception method for receiving a preamble in a DVB system according to an embodiment of the present invention.
Referring to FIG. 10, the receiver performs initialization in step 1000 and performs tuning for the preamble in step 1005. The receiver performs a protection interval-correlation (GIC) on the signal received in step 1010, and determines in step 1015 whether the preamble P1 has been detected.

  If, in step 1015, the preamble P1 cannot be detected, the receiver returns to step 1010. However, if the receiver detects the preamble P1, the receiver performs coarse time adjustment and fine frequency offset adjustment in step 1020. The receiver then performs power correlation to estimate the power of the active carrier at step 1025, and further determines whether the preamble P1 has been detected at step 1030.

  If, at step 1030, the receiver fails to detect preamble P1, the receiver returns to step 1010, and if the receiver has successfully received preamble P1, the receiver adjusts the coarse frequency offset at step 1035. Execute. The receiver then performs descrambling using a descrambling sequence in accordance with an embodiment of the present invention in step 1040 and then performs differential demodulation in step 1045, which is the reverse of the transmitter differential modulation scheme. To do. Thereafter, the receiver measures the correlation value between the preambles at step 1050 and detects the signals S1 and S2 at step 1055.

  Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the scope and spirit of the invention. The scope of the present invention should not be limited to the above-described embodiments, but should be defined within the scope of the appended claims and their equivalents.

600 carrier distribution sequence (CDS) table 610 MSS processing unit 620 DBPSK modulation unit 630 phase offset processing unit 635 scrambler 640 carrier allocation unit 650 IFFT processing unit 660 preamble generation unit 710 PRBS register 900 preamble detection unit 910 FFT processing unit 920 DEMUX
930 Descrambler 940 DBPSK demodulator 950 Signal detector

Claims (27)

An apparatus for transmitting a preamble in a digital video broadcasting (DVB) system, comprising:
A first processing unit that generates a modulation signaling sequence (MSS) using a plurality of received sequences, and outputs a modulated sequence by differentially modulating the modulation signaling sequence;
A scrambler that scrambles the modulated sequence by multiplying it by a scrambling sequence;
A second processing unit that receives each of the scrambled sequences through a plurality of assigned subcarriers, converts the received sequence into a time domain signal, and then generates and transmits the preamble. A preamble transmitter. The first processing unit generates a modulation signaling sequence using the received plurality of sequences, and a modulation signaling sequence processing unit,
The preamble transmission apparatus according to claim 1, further comprising a differential modulation unit that differentially modulates the modulation signaling sequence. The second processing unit receives the scrambled sequence through the respective assigned subcarriers; and
An inverse fast Fourier transform (IFFT) processing unit that converts the scrambled sequence received through the respective assigned subcarriers into a time domain signal;
The preamble transmission apparatus according to claim 1, further comprising: a preamble generation unit that generates and transmits the preamble.   The preamble transmitter according to claim 1, wherein the modulated sequence and the scrambling sequence have the same length.   The preamble transmission apparatus according to claim 1, wherein the scrambling sequence is generated using a pseudo-random binary sequence (PRBS).   The preamble transmission apparatus according to claim 1, wherein the scrambling sequence is stored in a lookup table.   The preamble transmission apparatus according to claim 1, wherein the differential modulation of the modulation signaling sequence (MSS) is performed by differential binary phase shift keying (DBPSK) modulation. A method for transmitting a preamble in a digital video broadcast (DVB) system, comprising:
Generating a modulated signaling sequence (MSS) using the received plurality of sequences;
Outputting the modulated sequence;
Scrambled by multiplying the modulated sequence by a scrambling sequence;
Receiving each of the scrambled sequences over a plurality of assigned subcarriers;
Converting the received sequence into a time domain signal;
A preamble transmission method comprising: generating and transmitting the preamble.   9. The preamble transmission method according to claim 8, wherein outputting the modulated sequence includes differentially modulating the modulation signaling sequence. Transmitting the preamble comprises receiving the scrambled sequence through the respective assigned subcarriers;
Converting the scrambled sequence received through the respective assigned subcarriers into a time domain signal;
The preamble transmission method according to claim 8, further comprising: generating and transmitting the preamble.   The preamble transmission method according to claim 8, wherein the modulated sequence and the scrambling sequence have the same length.   The preamble transmission method according to claim 8, further comprising a step of generating the scrambling sequence using a pseudo random binary sequence (PRBS).   The preamble transmission method according to claim 8, further comprising a step of storing the scrambling sequence in a lookup table.   The preamble transmission method according to claim 9, wherein the differential modulation of the modulation signaling sequence (MSS) is performed by differential binary phase shift (DBPSK) modulation. An apparatus for receiving a preamble in a digital video broadcast (DVB) system, comprising:
A first processing unit that detects a preamble from a received signal, converts the detected preamble into a frequency domain signal, and then demultiplexes the frequency domain signal;
A descrambler that descrambles the demultiplexed sequence by multiplying the demultiplexed sequence by a descrambling sequence;
A preamble receiving apparatus comprising: a second processing unit that differentially demodulates the descrambled sequence and detects a plurality of sequences from the demodulated sequence. The first processing unit includes a preamble detection unit that detects the preamble from a received signal;
A fast Fourier transform (FFT) processing unit for converting the preamble into the frequency domain signal;
The preamble reception apparatus according to claim 15, further comprising a demultiplexer (DEMUX) that demultiplexes data of an active carrier to which the preamble is transmitted. The second processing unit includes a differential demodulation unit that differentially demodulates the descrambled sequence;
The preamble reception apparatus according to claim 15, further comprising: a signal detection unit that detects the plurality of sequences from the demodulated sequence.   The preamble receiver according to claim 15, wherein the demultiplexing sequence and the descrambling sequence have the same length.   The preamble receiver according to claim 15, wherein the descrambling sequence is generated using a pseudo-random binary sequence (PRBS).   The preamble receiving apparatus according to claim 15, wherein the descrambling sequence is stored in a lookup table.   The preamble receiver according to claim 15, wherein the differential demodulation is performed by differential two-phase phase shift (DBPSK) demodulation. A method of receiving a preamble in a digital video broadcast (DVB) system, comprising:
Detecting a preamble from the received signal;
Converting the detected preamble into a frequency domain signal;
Demultiplexing the frequency domain signal;
Descrambling by multiplying the demultiplexed sequence by a descrambling sequence;
Differentially demodulating the descrambled sequence;
And a method of detecting a plurality of sequences from the demodulated sequence.   23. The preamble reception method according to claim 22, wherein the step of demultiplexing the frequency domain signal includes a step of demultiplexing data of an active carrier on which the preamble is transmitted.   The preamble reception method of claim 22, wherein the demultiplexing sequence and the descrambling sequence have the same length.   The method of claim 22, further comprising generating the descrambling sequence using a pseudo-random binary sequence (PRBS).   The method of claim 22, further comprising the step of storing the descrambling sequence in a lookup table. The preamble reception method according to claim 22, wherein the differential demodulation of the descrambling sequence is performed by differential two-phase phase shift (DBPSK) demodulation.

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