KR20080105907A - Ofdm transmitting/receiving apparatus and method - Google Patents

Ofdm transmitting/receiving apparatus and method Download PDF

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Publication number
KR20080105907A
KR20080105907A KR1020070054080A KR20070054080A KR20080105907A KR 20080105907 A KR20080105907 A KR 20080105907A KR 1020070054080 A KR1020070054080 A KR 1020070054080A KR 20070054080 A KR20070054080 A KR 20070054080A KR 20080105907 A KR20080105907 A KR 20080105907A
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South Korea
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symbol
ofdm
transport streams
method
allocated
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KR1020070054080A
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Korean (ko)
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KR101424069B1 (en
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김기보
박의준
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삼성전자주식회사
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00Arrangements for detecting or preventing errors in the information received
    • H04L1/0001Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0002Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00Baseband systems
    • H04L25/02Details ; Arrangements for supplying electrical power along data transmission lines
    • H04L25/03Shaping networks in transmitter or receiver, e.g. adaptive shaping networks ; Receiver end arrangements for processing baseband signals
    • H04L25/03828Arrangements for spectral shaping; Arrangements for providing signals with specified spectral properties
    • H04L25/03866Arrangements for spectral shaping; Arrangements for providing signals with specified spectral properties using scrambling
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00Modulated-carrier systems
    • H04L27/26Systems using multi-frequency codes
    • H04L27/2601Multicarrier modulation systems
    • H04L27/2626Arrangements specific to the transmitter
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00Modulated-carrier systems
    • H04L27/26Systems using multi-frequency codes
    • H04L27/2601Multicarrier modulation systems
    • H04L27/2647Arrangements specific to the receiver
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00Modulated-carrier systems
    • H04L27/32Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
    • H04L27/34Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
    • H04L27/36Modulator circuits; Transmitter circuits

Abstract

An apparatus and a method for transmitting and receiving OFDM are provided to symbol-map data with high and low priority by using various modulation methods like QAM(Quadrature Amplitude Modulation) or QPSK(Quadrature Phase Shift Keying). An OFDM transmitting device(100) includes transmission processors(120,130), and a signal transducer(150). The transmission processor generates OFDM(Orthogonal Frequency Division Multiplexing) symbol to which two or more transmission streams are allocated respectively. The signal transducer transduces the generated OFDM symbol into the OFDM signal and transmits the OFDM signal to at least one receiver.

Description

OPDM transmitting / receiving apparatus and method

1 is a block diagram showing an OFDM transmitter according to an embodiment of the present invention;

2 is a block diagram showing an example of a detailed configuration of an OFDM transmitter according to an embodiment of the present invention;

3A and 3B are schematic diagrams for explaining an example in which MUX generates OFDM symbols by distributing high priority data and Zhou line data in symbol units;

4A and 4B are schematic diagrams for explaining an example in which MUX generates OFDM symbols by distributing high priority data and Zhou line data in symbol units or subcarrier units;

FIG. 5 is a schematic diagram illustrating an example in which a mux generates an OFDM symbol by distributing the high priority data and the main line data in subcarrier units; FIG.

6A through 6C are schematic diagrams for describing an exemplary embodiment in which the high priority data and the main line data are allocated in subcarrier units in FIGS. 4A, 4B, and 5;

7A and 7B are schematic diagrams for describing an exemplary embodiment in which a ratio at which high priority data and Zhou line data are allocated is changed;

8 is a schematic diagram illustrating a case where a super frame is used as a transmission operation unit;

9 is a block diagram showing an OFDM receiver according to an embodiment of the present invention;

10 is a block diagram showing an example of a detailed configuration of an OFDM receiver according to an embodiment of the present invention;

11 is a block diagram showing an OFDM receiver according to another embodiment of the present invention;

12 is a flowchart illustrating an OFDM transmission method according to an embodiment of the present invention;

13 is a flowchart for explaining an OFDM transmission method according to another embodiment of the present invention;

14 is a flowchart for explaining an OFDM transmission method according to another embodiment of the present invention;

15 is a flowchart illustrating an OFDM reception method according to an embodiment of the present invention.

The present invention relates to an OFDM transceiver and method, and more particularly, to an OFDM transceiver and method capable of transmitting and receiving a plurality of OFDM signals in which at least two transport streams are allocated at various transmission rates.

The DVB-T (Digital Video Broadcasting Terrestrial) system is one of the terrestrial digital broadcasting systems for Europe. The DVB-T system transmits and receives desired data using an Orthogonal Frequency Division Multiplexing (OFDM) scheme, which is a multicarrier modulation scheme. Multi-carrier modulation is to transmit data using a plurality of subcarriers.

When designing an OFDM transceiver system, the designer designs the system in consideration of the channel environment of the receiver. That is, the designer can improve the data reception rate by using a robust modulation method and a coding algorithm with high error correction capability in the case of a mobile reception environment having a poor channel environment, and transmit more information in a mobile reception environment having a good channel environment. The focus should be on improving the data rate. Hereinafter, data considering poor channel environment is called HP (High Priority) data, and data considering excellent channel environment is called LP (Low Priority) data.

In a digital broadcasting environment, these two channel environments can coexist. To this end, the conventional OFDM transmission and reception apparatus codes data using a modulation scheme such as 16QAM, 64QAM, and then transmits HP data and LP data mixed in one subcarrier.

For example, in the case of using the 64QAM modulation scheme, the OFDM transmitter maps HP data in the first 2 bits and LP data in the next 4 bits of one 6-bit symbol. Therefore, the conventional OFDM transmitter transmits the LP data more stably than the HP data when the 64QAM method is used, and the LP data transmits a relatively large amount of data. In addition, when using the 16QAM modulation scheme, the OFDM transmitter transmits HP data in the first two bits of one 4-bit symbol and LP data in the next two bits.

However, the conventional OFDM transceiver transmits HP data and LP data mixedly, and only supports 16QAM or 64QAM, but does not support other coding schemes such as QPSK. In addition, the conventional OFDM transceiver supports only 16QAM or 64QAM to support the transmission ratio of HP data and LP data 1: 1 and 1: 2, and as a result, the data adjustment ratio is not free. In addition, the conventional OFDM transceiver has a limitation that supports only the HP data and LP data as a transport stream.

Accordingly, an object of the present invention is to solve the above problems, and an object of the present invention is to map OFDM signals using various modulation schemes for hierarchical transmission, and to provide high priority data suitable for a mobile receiving channel. The present invention provides an OFDM transceiver and method and method capable of freely adjusting the rate of transmission of the main line data suitable for a fixed reception channel and transmitting and receiving two or more hierarchical data.

An OFDM transmission apparatus according to an embodiment of the present invention for achieving the above object comprises: a transmission processor for generating an Orthogonal Frequency Division Multiplexing (OFDM) symbol to which two or more transport streams are respectively allocated; And a signal converter converting the generated OFDM symbol into an OFDM signal and transmitting the same to at least one receiver.

The transmission processor may include: a plurality of coding units configured to perform error correction encoding by coding the two or more transport streams; A plurality of modulators for modulating the coded two or more transport streams; And a multiplexer for generating the OFDM symbol by allocating each of the two or more modulated transport streams to at least one of a symbol unit and a subcarrier unit.

The transmission processor allocates one of the two or more transport streams to a plurality of subcarriers of the at least one OFDM symbol such that the two or more transport streams are mixed in at least one OFDM symbol.

The transmission processor generates the OFDM symbol by allocating one of the two or more transport streams for each of a plurality of subcarriers constituting the plurality of OFDM symbols such that the two or more transport streams are mixed in all of the plurality of OFDM symbols.

Rate information to which the two or more transport streams are allocated is defined by mutual agreement with the at least one receiver and is transmitted to the at least one receiver.

Area information to which the two or more transport streams are allocated is defined by mutual agreement with the at least one receiver and is transmitted to the at least one receiver.

The transmission processor adjusts a transmission rate of the two transport streams by adjusting a ratio in which the at least two transport streams are allocated and an area allocated to each transmission operation unit including a set number of OFDM symbols.

The coding information used in the transmission processor, the modulation scheme information, the information of the allocated ratio, and the information of the allocated region are included and transmitted for each transmission operation unit.

The coding unit codes the two or more transport streams using independent code rates according to a reception channel environment.

The modulator modulates one of PSK, Quadrature Phase Shift Keying (QPSK), Quadrature Amplitude Modulation (16QAM), 64QAM, 128QAM, and 256QAM.

The signal converter interleaves the generated OFDM symbol using one of a symbol interleaving method and a subcarrier interleaving method.

On the other hand, the OFDM transmission method according to an embodiment of the present invention, generating an Orthogonal Frequency Division Multiplexing (OFDM) symbol to which two or more transport streams are allocated; And converting the generated OFDM symbol into an OFDM signal and transmitting the same to at least one receiver.

The generating may include: performing error correction encoding by coding the two or more transport streams; Modulating the at least two coded transport streams; And assigning each of the at least two modulated transport streams to at least one of a symbol unit and a subcarrier unit to generate the OFDM symbol.

The generating step allocates one of the two or more transport streams to a plurality of subcarriers of the at least one OFDM symbol such that the two or more transport streams are mixed in at least one OFDM symbol.

The generating may allocate one of the two or more transport streams to a plurality of subcarriers of the plurality of OFDM symbols such that the two or more transport streams are mixed in all of the plurality of OFDM symbols.

The generating step adjusts a ratio and a region to which the at least two transport streams are allocated for each transmission operation unit including a set number of OFDM symbols.

The coding information used in the generating step, the modulation scheme information, the information of the allocated ratio, and the information of the allocated region are included and transmitted for each transmission operation unit.

In the performing, the two or more transport streams are coded using different code rates according to a reception channel environment.

The performing of the step of coding the data for the mobile receiver of the two or more transport streams at a low code rate, and the data for the fixed receiver is coded at a higher code rate than the low code rate.

The performing of the modulation is performed using one of PSK, Quadrature Phase Shift Keying (QPSK), Quadrature Amplitude Modulation (16QAM), 64QAM, 128QAM, and 256QAM.

The generating step interleaves the generated OFDM symbol using one of a symbol interleaving method and a subcarrier interleaving method.

Meanwhile, an OFDM receiver according to an embodiment of the present invention demodulates an OFDM signal received from a transmitter to generate a plurality of OFDM symbols in which two or more transport streams are assigned to at least one of a symbol unit and a subcarrier unit. grandfather; A demultiplexer for demultiplexing the generated plurality of OFDM symbols and outputting a symbol to which a processable transport stream of the two or more transport streams is allocated; And a reception processor that performs error correction on a symbol input from the demultiplexer.

The signal demodulator generates the plurality of OFDM symbols by applying one of a symbol deinterleaving scheme and a subcarrier deinterleaving scheme to the demodulated OFDM signal.

The reception processor may include a demodulator configured to demodulate a symbol input from the demultiplexer to generate a transport stream; And a decoding unit for decoding the generated transport stream and performing error correction.

The demultiplexer outputs the symbol by using ratio information and area information within a symbol in which the two or more transport streams provided from the transmitter are allocated in symbol units and subcarrier units.

The two or more transport streams are coded through respective code rates according to a reception channel environment at the transmitter.

The demultiplexer selects and outputs at least one of the two or more transport streams.

On the other hand, the OFDM reception method according to an embodiment of the present invention, demodulating the OFDM signal received from the transmitter, generating a plurality of OFDM symbols in which at least two transport streams are assigned to at least one of a symbol unit and a subcarrier unit; Demultiplexing the generated plurality of OFDM symbols and outputting a symbol to which a transportable transport stream among the two or more transport streams is allocated; And performing error correction on a symbol input from the demultiplexer.

The generating may generate the plurality of OFDM symbols by applying one of a symbol deinterleaving scheme and a subcarrier deinterleaving scheme to the demodulated OFDM signal.

The performing may include: demodulating the output symbol to generate a transport stream; And performing error correction by decoding the generated transport stream.

The outputting may include outputting the symbol using ratio information and area information within a symbol in which the two or more transport streams provided from the transmitter are allocated in symbol units and subcarrier units.

The outputting may include selecting and outputting at least one of a symbol assigned with a low code rate transport stream and a symbol assigned with a high code rate transport stream among the two or more transport streams.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. However, in describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted.

1 is a block diagram illustrating an OFDM transmitter according to an embodiment of the present invention.

Referring to FIG. 1, the OFDM transmitter 100 includes first and second transmitters 120 and 130, a multiplexer (MUX) 140, and a signal converter 150. The OFDM transmitter 100 applies to the DVB-T standard and transmits different contents or the same contents in a hierarchical manner.

In the hierarchical method, at least two transport streams are modulated into OFDM signals of a plurality of layers by using different coding rates or different modulation schemes in consideration of a channel environment for receiving a transport stream, and then transmitted. For example, two transport streams are HP (High Priority) data and LP (Low Priority) data, and in three cases, an additional MP (Middle Low Priority) is added and at least two transport streams are transmitted.

The first and second transmitters 120 and 130 and the MUX 140 generate a plurality of Orthogonal Frequency Division Multiplexing (OFDM) symbols to be transmitted to at least one receiver 10 or 20. In this case, the MUX 140 generates OFDM symbols by allocating two or more transport streams TS1 and TS2 in symbol units or by assigning different transport streams to a plurality of subcarriers constituting one symbol.

When receiving at least two transport streams TS1 and TS2 to be transmitted to the receivers 10 and 20 from a source source (not shown), the first and second transmission processors 120 and 130 and the mux 140 are received. A plurality of OFDM symbols are generated by modulating the transport streams TS1 and TS2 into signals capable of being loaded on a plurality of subcarriers.

At least two transport streams TS1 and TS2 are generated as OFDM symbols in the MUX 140 after being encoded or modulated at different code rates by the first and second transmission processors 120 and 130 for hierarchical transmission. . For example, when the receiver is a mobile receiving apparatus (eg, 10), the first transmission processor 120 encodes the transport stream TS1 at a low code rate to increase the data reception rate.

In addition, when the receiver is a fixed reception device (for example, 20), the second transmission processor 130 encodes the transport stream TS2 at a code rate higher than that of the transport stream TS1 so that the broadcast can be viewed in high resolution. . Here, since a lower code rate uses a coding algorithm having a higher error correction capability and a stronger modulation scheme, the mobile receiving apparatus 10 such as a DMB phone may provide a broadcast with minimal interruption of a video.

The signal converter 150 converts an OFDM symbol generated by the MUX 140 into an OFDM signal and transmits the OFDM symbol to at least one receiver 10 or 20. That is, data transmitted to at least one receiver 10 or 20 includes at least two transport streams TS1 and TS2, and each receiver 10 and 20 selects a corresponding transport stream and performs signal processing.

At least one receiving apparatus 10 and 20 includes a mobile receiving apparatus 10 and a fixed receiving apparatus 20.

The mobile receiving apparatus 10 may be a DMB phone as a device for receiving OFDM symbols while moving, and selects and views only a transport stream TS1 encoded with a low code rate among OFDM symbols transmitted from the transmitting apparatus 100. Treat it as a possible signal. The fixed reception device 20 is a device for receiving OFDM symbols in a fixed state, and may be, for example, a digital TV used in a general home, and is encoded with a high code rate among OFDM symbols transmitted from the transmission device 100. Only stream TS2 is selected and processed into a viewable signal.

In addition, the receivers 10 and 20 may receive and process both a transport stream encoded with a low code rate and a transport stream encoded with a high code rate as a viewable signal.

2 is a block diagram illustrating an example of a detailed configuration of an OFDM transmitter according to an embodiment of the present invention.

Referring to FIG. 2, the OFDM transmitter 100 includes a signal processor 110 and a signal converter 150 including a first signal processor 120, a second signal processor 130, and a mux 140. . The transmission processor 110 generates a plurality of OFDM symbols by allocating different transport streams on a symbol basis, and the signal converter 150 generates at least one receiver 10 through an antenna. 20).

Hereinafter, an example in which two transport streams TS1 and TS2 are input to the first signal processor 120 and the second signal processor 130 will be described as an example. However, the number of input transport streams may be added. Accordingly, it is preferable that the number of the n th signal processing unit (n is a positive number, not shown) also increases.

First, the first signal processing unit 120 includes a first scrambler 121, a first coding unit 122, and a first symbol mapping unit 123, and the high priority data HP from the first transport stream TS1. ) The high priority data HP is data generated from the first transport stream TS1 in consideration of the mobile receiving apparatus 10.

The first scrambler 121 scrambles the input first transport stream TS1. Scrambling is to randomize the stream in order to solve the problem that the same number of bits is repeated and the synchronization signal is lost in the synchronous signal transmission scheme.

The first coding unit 122 codes the first transport stream TS1 input from the first scrambler 121 to detect and correct an error of the transport stream in the receivers 10 and 20. ). In particular, the first coding unit 122 codes the first transport stream TS1 in consideration of the mobile receiving environment, that is, the mobile receiving device 10. To this end, the first coding unit 122 may include a first outer coder 122a, a first outer interleaver 122b, a first inner coder 122c, and a first inner interleaver. (Inner Interleaver) 122d.

The first outer coder 122a externally encodes the scrambled first transport stream TS1. The first outer coder 122a may use a Bose-Chaudhuri-Hochquenghem (BCH), a Reed Solomon (RS) coding scheme, or the like.

The first outer interleaver 122b outer-interleaves the first transport stream TS1 input from the first outer coder 122a to distribute the encoded first transport stream.

The first inner coder 122c internally encodes the first transport stream TS1 input from the first outer interleaver 122b. The first inner coder 122c may use convolution coding, turbo coding, low density parity check (LDPC) coding, or the like.

The first inner interleaver 122d inner interleaves the first transport stream TS1 input from the first inner coder 122c. At least one of the first outer coder 122a, the first outer interleaver 122b, and the first inner interleaver 122d may be selectively provided.

The first symbol mapping unit 123 applied to the modulation unit may use the PSK coded by the first coding unit 122 to perform PSK, Binary Phase Shift Key (BPSK), Quadrature Phase Shift Keying (QPSK), and 16QAM ( Quadrature Amplitude Modulation) is used to convert high-priority data (HP) using one of a variety of modulation schemes, including 64QAM, 128QAM, and 256QAM. The first symbol mapping unit 123 may output the high priority data HP in a symbol form.

The second signal processor 130 includes a second scrambler 131, a second coding unit 132, and a second symbol mapping unit 133, and extracts the main line data LP from the second transport stream TS2. Create The main line data LP is data generated from the second transport stream TS2 in consideration of the fixed receiving device 20. Hereinafter, the first transport stream output from the first signal processor 120 is called high priority data HP, and the second transport stream output from the second signal processor 130 is called main line data LP.

The second scrambler 131 scrambles the input second transport stream TS2.

The second coding unit 132 codes the second transport stream TS2 input from the second scrambler 131 to detect and correct an error of the transport stream in the receivers 10 and 20, thereby correcting the error correction encoding (FEC). ). In particular, the second coding unit 132 codes the second transport stream TS2 in consideration of the fixed reception environment, that is, the fixed reception device 20. To this end, the second coding unit 132 includes a second outer coder 132a, a second outer interleaver 132b, a second inner coder 132c, and a second inner interleaver 132d.

The second outer coder 132a may use a BCH, RS coding scheme, etc. to externally encode the second transport stream TS2. The second outer interleaver 132b outer-interleaves the second transport stream TS2 input from the second outer coder 132a to distribute the encoded second transport stream.

The second inner coder 132c may use convolution coding, turbo coding, LDPC coding, etc. to internally encode the second transport stream TS2 input from the second interleaver 151. The second inner interleaver 132d inner interleaves the second transport stream TS2 input from the second inner coder 132c. At least one of the second outer coder 132a, the second outer interleaver 132b, and the second inner interleaver 132d may be selectively provided.

The second symbol mapping unit 133 applied as a modulator may use one of various modulation schemes such as a BPSK scheme, a QPSK scheme, a 16QAM, a 64QAM, a 128QAM, and a 256QAM, using the second transport stream TS2 coded by the second coder 132. To the main line data LP. The second symbol mapping unit 133 may output the main line data LP in the form of a symbol. The first and second symbol mapping units 123 and 133 may use the same or different modulation schemes.

The first coder 122 and the second coder 132 may encode the first transport stream TS1 and the second transport stream TS2 using different code rates or the same code rate. For example, when the first coding unit 122 codes the first transport stream into a stream suitable for the mobile receiving apparatus 10, the first coding unit 122 is a code used in the second coding unit 132. The first transport stream TS1 may be coded at a lower code rate than the rate, or coded at the same code rate.

When the first and second transport streams TS1 and TS2 are coded at the same code rate, the first and second symbol mapping units 123 and 133 hierarchically classify the first and second transport streams TS1 and TS2. In order to transmit, the first and second transport streams TS1 and TS2 are modulated using different methods. That is, the first symbol mapping unit 123 makes a symbol suitable for the mobile receiving apparatus 10 from the coded first transport stream TS1, and the second symbol mapping unit 133 makes the coded second transport stream ( Different modulation schemes may be used to make a symbol suitable for the fixed receiving device 20 from TS2).

For example, when the first and second transport streams TS1 and TS2 are coded at the same code rate, the first symbol mapping unit 123 uses a QPSK modulation scheme, and the second symbol mapping unit 133 Modulation can be made using one of 16QAM, 64QAM, 128QAM and 256QAM. As another example, the first symbol mapping unit 123 may use a 16QAM modulation scheme, and the second symbol mapping unit 133 may modulate using one of 64QAM, 128QAM, and 256QAM.

On the other hand, when the first and second transport streams TS1 and TS2 are coded at different code rates, streams (symbols) suitable for the mobile receiving apparatus 10 and the fixed receiving apparatus 20 are made. The two symbol mapping units 123 and 133 transmit the first and second transport streams TS1 and TS2 by using different modulation schemes or the same modulation scheme to hierarchically transmit the first and second transport streams TS1 and TS2. Modulate and output high-priority (HP) data and Zhou-Shen (LP) data.

A method of generating high priority (HP) data and Zhou line (LP) data by the above-described coding scheme and modulation scheme will now be described in detail.

First, high-priority data HP is generally data to be received even in a harsh environment, and Zhou-Sun data LP is data to be received in an excellent environment. For example, when high-priority data HP is used for mobile data reception, the user should be able to view a small screen. Therefore, the reception performance should be excellent since the data transmission should be received in a small vehicle-like environment. In addition, when the main line data LP is used for terrestrial data reception, a relatively large amount of data needs to be transmitted in order to enable viewing on a large screen.

[Table 1] is a table showing coding parameters used in DVB-S2. As an example, the size of an LDPC block coded using the LDPC coding scheme may be described through the following table.

LDPC code BCH uncoded block BCH coded block BCH t-error correction LDPC Coded Block 1/4 16008 16200 12 64800 1/3 21408 21600 12 64800 2/5 25728 25920 12 64800 1/2 32208 32400 12 64800 3/5 38688 38880 12 64800 2/3 43040 43200 10 64800 3/4 48408 48600 12 64800 4/5 51648 51840 12 64800 5/6 53840 54000 10 64800 8/9 57472 57600 8 64800 9/10 58192 58320 8 64800

According to [Table 1], when LDPC coding has 16008 data bits before BCH external encoding, an LDPC block including 64800 bits is output. On the other hand, when mapping in the 16QAM scheme, 6 bits are represented per symbol, and a total of 10800 symbols are required to represent one LDPC block. High-priority data (HP) generally requires higher reception performance than Z-serial data (LP), so when applying the same modulation scheme to HP and LP as QPSK, etc., high-priority data (HP) uses a lower coding rate. do. For example, 1/4 coding may be used for the QPSK modulation scheme for the high priority data HP and 4/5 coding may be used for the QPSK modulation scheme for the main line data LP.

[Table 2] is a table showing an example of data efficiency (Spectral Efficiency) and reception performance when modulating after applying the coding scheme as shown in [Table 1].

Mode Spectral Efficiency Receive Performance QPSK 1/4 0.490243 -2.35 QPSK 1/3 0.656448 -1.24 QPSK 2/5 0.789412 -0.30 QPSK 1/2 0.988858 1.00 QPSK 3/5 1.188304 2.23 QPSK 2/3 1.322253 3.10 QPSK 3/4 1.487473 4.03 QPSK 4/5 1.587196 4.68 QPSK 5/6 1.654663 5.18 QPSK 8/9 1.766451 6.20 QPSK 9/10 1.788612 6.42 8PSK 3/5 1.779991 5.50 8PSK 2/3 1.980636 6.62 8PSK 3/4 2.228124 7.91 8PSK 5/6 2.478562 9.35 8PSK 8/9 2.646012 10.69 8PSK 9/10 2.679207 10.98 16 APSK 2/3 2.637201 8.97 16APSK 3/4 2.966728 10.21 16APSK 4/5 3.165623 11.03 16APSK 5/6 3.300184 11.61 16APSK 8/9 3.523143 12.89 16APSK 9/10 3.567342 13.13 32 APSK 3/4 3.703295 12.73 32APSK 4/5 3.951571 13.64 32APSK 5/6 4.119540 14.28 32APSK 8/9 4.397854 15.69 32APSK 9/10 4.453027 16.05

Referring to [Table 2], in the mode, the first English letter indicates a modulation scheme and the second number indicates a coding rate. For example, 'QPSK 1/4' means applying a QPSK modulation after applying a 1/4 rate LDPC code. In addition, the data rate is the amount of data in one symbol. When QPSK uses 2 bits, if the data is 1/4 encoded, 0.5 data rate can be calculated. However, [Table 2] is outside the BCH in [Table 1]. Since the LDPC coding was applied after the luxury, the value of '0.490243' was measured instead of '0.5'. Also, the lower the numerical value, the better the reception performance.

Referring to Tables 1 and 2, the reception performance is influenced not only by the coding scheme but also by the modulation scheme. As an example, when the high priority data (HP) uses a 3/5 rate LDPC code for 8PSK and the main line data (LP) uses a 9/10 rate LDPC code for QPSK, reception of the high priority data (HP) is performed. The performance is 5.50, and the reception performance of the main line data is 6.42, so that high priority data (HP) can obtain better reception performance.

As such, high-priority data (HP) and raw data (LP) with desired reception performance can be created by adding independent coding and independent modulation, and data transmission assignment is based on data rate and high-priority data (HP) in coding and modulation. ) And the distribution of use of the main line data LP. Therefore, it is possible to adjust the transmission rate by subcarrier allocation or symbol allocation of the high priority data HP and the main line data LP.

The mux 140 includes first and second transport streams TS1 and TS2 modulated by the first symbol mapping unit 123 and the second symbol mapping unit 133, that is, the high priority data HP and the main line data. (LP) is multiplexed, and the first and second transport streams TS1 and TS2 are allocated in symbol units or in subcarrier units to generate OFDM symbols. The MUX 140 transmits the first and second transport streams TS1 and TS2 in symbol units or subcarriers, respectively, based on a predetermined allocation ratio between the transmitter 100 and the receivers 10 and 20 and an allocation area within a symbol. It is assigned in units, and the ratio to which the first and second transport streams TS1 and TS2 are allocated can be adjusted according to the transmission mode.

At this time, the MUX 140 may change the ratio and the area to which the first and second transport streams TS1 and TS2 are allocated for each transmission operation unit. The transmission operation unit is a unit composed of a plurality of symbols, and includes coding scheme information, modulation scheme information, and first and second transmission streams TS1 and TS2 used by the first signal processor 120 and the second signal processor 130. It is a unit for notifying the reception apparatuses 10 and 20 of the ratio information and the area information allocated by the MUX 140. Accordingly, the coding scheme, modulation scheme, the allocated ratio information, and the information about the allocated region may be included in each transmission operation unit and transmitted to the reception apparatuses 10 and 20. For example, the transmission operation unit may be a frame composed of 68 OFDM symbols or a super frame composed of a plurality of frames.

3A and 3B are diagrams for describing an example in which MUX generates OFDM symbols by distributing high priority data and Zhou line data in symbol units.

Referring to FIGS. 3A and 3B, the MUX 140 generates an OFDM symbol by allocating one of the first and second transport streams for each of a plurality of symbols constituting one frame, and generates high priority data (HP) and a main line. Consider the allocation ratio of the data LP and the allocation area, that is, the location to be allocated. In the case of FIG. 3A, the mux 140 repeatedly allocates the high priority data HP and the main line data LP to a symbol to generate an OFDM symbol. Thus, when the number of symbols allocated to the high priority data HP and the main line data LP is the same within one frame, the transmission ratio of the high priority data HP and the main line data LP is 1: 1. Will have a transmission rate.

In the case of FIG. 3B, the mux 140 continuously allocates the high priority data HP to a plurality of symbols and consecutively allocates the main line data LP to other symbols to generate an OFDM symbol. At this time, according to the number of symbols to which the high priority data HP and the Zhou line data LP are allocated in the MUX 140, the transmission ratio of the high priority data HP and the Zhou line data LP is M: N. This can be Here, M and N are the same or different as positive numbers.

4A and 4B are schematic diagrams for describing an example in which MUX generates OFDM symbols by distributing high-priority data and main-line data in symbol units or subcarrier units.

4A and 4B, the mux 140 includes the high priority data HP so that the high priority data HP and the main line data LP are mixed in at least one symbol of a plurality of symbols constituting the frame. The OFDM data is generated by distributing the main line data LP. As described above, each symbol has a plurality of subcarriers. Accordingly, the mux 140 allocates one of the high priority data HP and the Zhou line data LP to each of the plurality of subcarriers constituting the symbol, and the mux 140 assigns the high priority data HP and the Zhou line Consider the allocation ratio of the data LP and the position of the subcarrier to be allocated, that is, the area.

In the case of FIG. 4A, the mux 140 repeatedly allocates the high priority data HP and the main line data LP to a symbol, but some symbols ① and ② have the high priority data HP and the main line data ( All of the LP) is allocated to generate an OFDM symbol. In this case, the MUX 140 allocates one of the high priority data HP and the main line data LP to each of a plurality of subcarriers constituting some symbols ① and ②.

In the case of FIG. 4B, the mux 140 continuously allocates the high priority data HP to a plurality of symbols, and assigns both the high priority data HP and the main line data LP to some symbols ③. An OFDM symbol is generated by sequentially assigning ZnO data LP to other symbols. At this time, according to the number of symbols and subcarriers to which the high priority data HP and the main line data LP are allocated in the MUX 140, the transmission ratio of the high priority data HP and the main line data LP is M. Can be: N Here, M and N are the same or different as positive numbers.

FIG. 5 is a schematic diagram illustrating an example in which a mux generates an OFDM symbol by dividing the high priority data and the main line data in subcarrier units.

Referring to FIG. 5, the MUX 140 generates an OFDM symbol by distributing one of the high priority data HP and the main line data LP for each of a plurality of subcarriers constituting each symbol. As a result, the high priority data HP and the main line data LP are mixed in all the symbols constituting the frame. In this case, the MUX 140 considers an allocation ratio of the high priority data HP and the main line data LP and the subcarrier area to be allocated.

6A through 6C are schematic diagrams for describing an exemplary embodiment in which the high priority data and the main line data are allocated in subcarrier units in FIGS. 4A, 4B, and 5. 6A to 6C, the MUX 140 allocates high priority data HP and Zhou line data LP to a plurality of subcarriers forming one symbol. In this case, the MUX 140 considers an allocation ratio of the high priority data HP and the main line data LP and the subcarrier area to be allocated. The allocation ratio may vary depending on the transmission rate.

In the case of FIG. 6A, the mux 140 continuously allocates the high priority data HP to the plurality of subcarriers by the allocated ratio, and subsequently allocates the main line data LP to the plurality of subcarriers.

6B and 6C, the mux 140 collects the high priority data HP and the main line data LP such that the high priority data HP and the main line data LP are scattered on a plurality of subcarriers. Assign to multiple subcarriers. 6B and 6C, the ratios of the high priority data HP and the main data LP are allocated to the plurality of subcarriers are the same, but the positions of the allocated subcarriers are different.

7A and 7B are schematic diagrams for describing an exemplary embodiment in which a ratio in which high priority data and Zhou line data are allocated is changed.

Referring to FIG. 7A, f denotes a frequency, and the MUX 140 allocates high priority data HP and Zhou line data LP to a plurality of subcarriers in a ratio of 1: 1 in one symbol. In addition, referring to FIG. 7B, the MUX 140 allocates the high priority data HP and the main line data LP to a plurality of subcarriers in a ratio of M: N in one symbol.

Referring to FIGS. 3A to 7B, the MUX 140 has a ratio of allocating the high priority data HP and the main line data LP to a plurality of subcarriers or a plurality of symbols, and an area to be allocated, that is, allocated. The location of the subcarriers is performed according to the predefined method. According to the allocation ratio, the number of subcarriers or the number of OFDM symbols occupied by the high priority data HP and the main line data LP is changed.

8 is a schematic diagram illustrating a case where a super frame is used as a transmission operation unit. The MUX 140 may generate an OFDM symbol by applying different allocation ratios and allocation regions for each of the plurality of frames forming the super frame. Information such as an allocation ratio, information on an allocation region, a coding scheme, a modulation scheme, and the like, may be generated by the MUX 140 through a separate channel, which may be provided to the receiving apparatuses 10 and 20.

Referring back to FIG. 2, the signal converter 150 converts the plurality of OFDM symbols output from the MUX 140 into OFDM signals and transmits the OFDM symbols to the receivers 10 and 20. To this end, the signal converter 150 includes an interleaver 151, an inverse discrete fourier transform (IDFT) 152, a guard interval (GI) insertion unit 153, and a signal converter 154.

The interleaver 151 interleaves a plurality of OFDM symbols input from the mux 140. In detail, when the high priority data HP and the main line data LP are allocated in symbol units in the MUX 140 as shown in FIGS. 3A and 3B, the interleaver 151 performs symbol interleaving for a plurality of OFDM symbols. Apply.

In addition, when the high priority data HP and the main line data LP are allocated in the mux 140 as shown in FIGS. 4A and 4B, the interleaver 151 adaptively applies symbol interleaving and subcarrier interleaving. For example, the interleaver 151 applies subcarrier interleaving to some symbols ①, ②, and ③, and applies symbol interleaving to some symbols ④.

In addition, when the high priority data HP and the main line data LP are allocated in the mux 140 as shown in FIG. 5, the interleaver 151 applies subcarrier interleaving.

The IDFT unit 152 performs inverse discrete Fourier transform on the interleaved OFDM symbol to convert the OFDM symbol in the frequency domain into an OFDM symbol in the time domain. In place of the IDFT unit 152, an Inverse Fast Fourier Transform (IFFT) may be used.

The GI insertion unit 153 inserts a guard interval (GI) into an OFDM symbol input from the IDFT unit 152 to prevent interference between OFDM symbols. The guard interval is a signal used to reduce the influence of the interference phenomenon of the multipath channel due to the characteristics of OFDM.

The signal converter 154 converts an OFDM symbol input from the GI insertion unit 153 into an analog OFDM signal, and up-converts the analog OFDM signal to generate an RF signal. The generated RF signal includes the high priority data HP and the main line data LP and is transmitted to the receivers 10 and 20 through an antenna.

According to the transmitter 100 described above, the transmitter 100 codes at least two transport streams TS1 and TS2 at different code rates so as to transmit at least two transport streams TS1 and TS2 hierarchically. Thus, the high priority data HP and the main line data LP are generated.

In addition, the transmitter 100 transmits the high priority data HP and the main line data LP to the symbol or subcarrier in the mux 140 to adjust the transmission rates of the high priority data HP and the main line data LP. Adjust the percentage allocated. In particular, the transmitting apparatus 100 generates an OFDM symbol by allocating one of the high priority data (HP) and the main line data (LP) on a symbol basis or a subcarrier basis, thereby generating the high priority data (HP) and the main line data (LP). Can be variously implemented, that is, the transmission rate.

The more the line data LP is allocated to a symbol or a subcarrier, the fixed reception device 20 can reproduce a high quality video, and the mobile reception device 10 is applied to additional data included in the high priority data HP. You can play a smooth video.

In addition, when the code rates applied to at least two transport streams TS1 and TS2 are the same, the transmitter 100 may generate the high priority data HP and the main line data LP by differently applying a modulation scheme. .

In addition, the transmitter 100 may include a plurality of n-th signal processing units (not shown) as well as high-priority data HP and Zhou-line data LP to generate a plurality of intermediate-priority data MPs. Of course.

9 is a block diagram showing an OFDM receiver according to an embodiment of the present invention.

Referring to FIG. 9, the OFDM receiver includes a signal demodulator 910, a demultiplexer (hereinafter referred to as a 'demux') 920, and a reception processor 930. The OFDM receiver may be a mobile receiver 10, a fixed receiver 20, or the like shown in FIG.

The signal demodulator 910 demodulates the OFDM signal received from the transmitter as shown in FIG. 1 to generate a plurality of OFDM symbols. Here, each OFDM symbol is a symbol in which two or more transport streams are allocated to at least one of a symbol unit and a subcarrier unit.

The demux 920 demultiplexes a plurality of OFDM symbols generated by the signal demodulator 910 and outputs a symbol to which a processable transport stream is allocated among two or more transport streams.

The reception processor 930 performs error correction on the symbols input from the demux 920 to generate a transport stream.

10 is a block diagram illustrating an example of a detailed configuration of an OFDM receiver according to an embodiment of the present invention.

According to FIG. 10, the signal demodulator 910 of the OFDM receiver includes a signal converter 911, a GI remover 912, a discrete fourier transform 913, and a deinterleaver 914. The processor 930 includes a symbol demapping unit 931, a decoding unit 932, and a descrambler 933.

The signal demodulator 910 down-converts the signal received through the antenna and converts the signal into a digital signal. The received signal includes high priority data HP and main line data LP. In addition, the antenna is a ratio of the high priority data (HP) and the main line data (LP) allocated to the plurality of OFDM symbols in the transmitter 100, the allocated position information, the coding scheme applied in the transmitter 100, the code rate , A control signal including a modulation scheme may be received.

The GI remover 912 removes a GI inserted into an OFDM symbol which is a digital signal.

The DFT unit 913 performs Discrete Fourier Transform on the OFDM symbols from which the GI is removed, thereby converting the OFDM symbols in the time domain into the OFDM symbols in the frequency domain. A Fast Fourier Transform (FFT) method may be used in place of the DFT unit 913.

The deinterleaver 914 deinterleaves a plurality of OFDM symbols input from the DFT unit 913 to separate OFDM symbols to which high priority data HP and main line data LP are allocated, respectively, in symbol units or subcarrier units. Output

When the transmitter 100 generates the OFDM symbols by allocating the high priority data HP and the main line data LP in symbol units as shown in FIGS. 3A and 3B, the deinterleaver 914 includes a DFT unit 913. The symbol deinterleaving is applied to a plurality of OFDM symbols input from

In addition, when the transmitter 100 generates OFDM symbols by allocating the high priority data HP and the main line data LP in subcarrier units as shown in FIGS. 3A and 3B, the deinterleaver 914 includes a DFT unit. Subcarrier deinterleaving is applied to the plurality of OFDM symbols input from 913.

In addition, when the transmitter 100 mixes and assigns the high priority data HP and the main line data LP in symbol units or subcarrier units as shown in FIG. 5, the deinterleaver 914 is provided from the DFT unit 913. The symbol deinterleaving and the subcarrier deinterleaving are mixedly applied to a plurality of input OFDM symbols.

The demux 920 demultiplexes a plurality of OFDM symbols input from the deinterleaver 914 and allocates processable data among the high priority data HP and the main line data LP included in the plurality of OFDM symbols. Print a symbol. For example, when the receiver shown in FIG. 9 is the mobile receiver 10, the demux 920 is a symbol to which high priority data HP is allocated among a plurality of OFDM symbols or a plurality of OFDM symbols. First, a symbol having a subcarrier to which data HP is allocated is output. When the receiver is the fixed receiver 20, the demux 920 is a symbol to which Zhou line data LP is allocated among the plurality of OFDM symbols, or a symbol having subcarriers to which Zhou line data is allocated among the plurality of OFDM symbols. Outputs

The symbol demapping unit 931 applied to the demodulator demaps a symbol input from the demux 920 to generate a transport stream. The symbol demapping unit 931 demaps a symbol by using a demodulation method corresponding to a modulation method used in the transmitter 100. That is, the symbol demapping unit 931 demaps using one of various demodulation schemes such as a BPSK demodulation scheme, a QPSK demodulation scheme, 16QAM, 64QAM, 128QAM, and 256QAM.

The decoding unit 930 decodes the transport stream input from the symbol demapping unit 931 and performs error correction. For this purpose, the inner deinterleaver 932a, the inner decoder 932b, the outer deinterleaver 932c, and the outer are performed. Decoder 932d.

The inner deinterleaver 932a inner deinterleaves the transport stream input from the symbol demapping unit 931. The inner decoder 932b internally decodes the deinterleaved transport stream. The inner decoder 932b may use a convolution decoding, turbo decoding, LDPC decoding scheme, or the like.

The outer deinterleaver 932c outer deinterleaves the transport stream input from the inner decoder 932b. The outer decoder 932d decodes the transport stream input from the outer deinterleaver 932c. The outer decoder 932d may use BCH decoding, RS decoding, or the like.

The descrambler 933 descrambles the transport stream input from the outer decoder 932d.

The receiver described with reference to FIGS. 9 and 10 receives an OFDM signal including high priority data HP and Zhou line data LP, and then processes among high priority data HP and Zhou line data LP. Possible data are selected by the demux 920 and provided to the receiving processor 930. However, when the transmitter 100 transmits an OFDM signal by the burst transmission mode, the transmitter 100 may include information in which the high priority data HP and the main data LP are located, or the high priority data ( Since the HP and the time line data LP are transmitted to the receiver in advance, the receiver may receive data that can be processed from the corresponding position among the OFDM signals based on the position information or the time information.

11 is a block diagram showing an OFDM receiver according to another embodiment of the present invention.

Referring to FIG. 11, an OFDM receiver includes a signal demodulator 1110, a demux 1120, and first through n th receivers 1130-1,..., 1130-n. The receiver shown in FIG. 11 is an example of an apparatus capable of receiving and decoding both high priority data HP and main line data LP included in an OFDM signal.

Since the signal demodulator 1110 is similar to the signal demodulator 910 described with reference to FIG. 10, a detailed description thereof will be omitted. The demux 1120 divides a plurality of OFDM symbols into symbols corresponding to high-priority data HP and symbols corresponding to Zhou-line data LP, and respectively, the first receiving processor 1130 and the second receiving processor (not shown). Output to The nth reception processing unit 1130-n is a block for processing the intermediate priority data MP. Since the operations of the first to nth reception processing units 1130-1,..., 1130-n are similar to the reception processing unit 930 described with reference to FIG. 10, a detailed description thereof will be omitted.

12 is a flowchart illustrating an OFDM transmission method according to an embodiment of the present invention.

Hereinafter, an OFDM transmission method will be described with reference to FIGS. 1, 2, 3A, 3B, and 12, and hierarchically generating high-priority data and main-line data by receiving two transport streams TS1 and TS2. The case will be described. However, the number of input transport streams may be two or more and may be the same or different content.

The first and second transport streams TS1 and TS2 are scrambled by the first and second scramblers 121 and 131, respectively (S1210).

The scrambled first and second transport streams TS1 and TS2 are subjected to error correction coding (FEC) by the first coding unit 122 and the second coding unit 132, respectively (S1220). In operation S1220, the first coding unit 122 and the second coding unit 132 may use the same or different coding schemes, or may use the same or different coding rates for the first and second transport streams TS1 and TS2. Can be coded.

The coded first and second transport streams TS1 and TS2 are symbol-mapped in the first and second symbol mapping units 123 and 133, respectively, to generate high priority data HP and main line data LP ( S1230). In operation S1230, the high priority data HP and the main line data LP may be output in a symbol form.

The high priority data HP and the main data LP generated in operation S1230 are allocated in symbol units in the MUX 140, respectively, and are generated as a plurality of OFDM symbols as illustrated in FIG. 3A or 3B (S1240). In this case, the MUX 140 adjusts the number of OFDM symbols to which the high priority data HP is allocated and OFDM symbols to which the main line data is allocated in one transmission operation unit in consideration of a predetermined allocation ratio. In addition, the mux 140 adjusts the position of the OFDM symbol to which the high priority data is allocated and the position of the OFDM symbol to which the main line data is allocated in one transmission operation unit in consideration of the predefined region information.

The generated plurality of OFDM symbols are symbol interleaved in the interleaver 151 (S1250).

The IDFT unit 152 performs inverse fast Fourier transform on the interleaved OFDM symbol to generate an OFDM symbol in the time domain (S1260).

In order to prevent interference between OFDM symbols, the GI insertion unit 153 inserts a guard period (GI) into the OFDM symbol input from step S1260 (S1270).

The signal converter 154 converts an OFDM symbol input from the GI insertion unit 153 into an analog OFDM signal, and generates an RF signal by up-converting the analog OFDM signal (S1280). The generated RF signal includes the high priority data HP and the main line data LP and is transmitted to the receivers 10 and 20 through an antenna.

13 is a flowchart illustrating an OFDM transmission method according to another embodiment of the present invention.

Hereinafter, an OFDM transmission method will be described with reference to FIGS. 1, 2, 4A, 4B, and 13, and hierarchically generating high-priority data and main-line data by receiving two transport streams TS1 and TS2. The case will be described. However, the number of input transport streams may be two or more, and may be the same or different content. In addition, since steps S1310 to S1380 are substantially the same as steps S1210 to S1280 described with reference to FIG. 12, a detailed description thereof will be omitted.

The first and second transport streams TS1 and TS2 are scrambled by the first and second scramblers 121 and 131, respectively (S1310).

The scrambled first and second transport streams TS1 and TS2 are subjected to error correction coding (FEC) by the first coding unit 122 and the second coding unit 132, respectively (S1320).

The coded first and second transport streams TS1 and TS2 are symbol-mapped in the first and second symbol mapping units 123 and 133, respectively, to generate high priority data HP and main line data LP ( S1330).

The generated high priority data HP and the main line data LP are allocated in symbol units or subcarrier units in the mux 140, respectively, and are generated as a plurality of OFDM symbols as shown in FIG. 4A or 4B (S1340).

The generated plurality of OFDM symbols are symbol interleaved or subcarrier interleaved in the interleaver 151 (S1350).

The IDFT unit 152 performs inverse discrete Fourier transform on the interleaved OFDM symbol to generate an OFDM symbol in the time domain (S1360).

In order to prevent interference between OFDM symbols, the GI insertion unit 153 inserts a guard interval (GI) into the OFDM symbol input from step S1360 (S1370).

The signal converter 154 converts an OFDM symbol input from the GI insertion unit 153 into an analog OFDM signal, and up-converts the analog OFDM signal to generate an RF signal (S1380). The generated RF signal is transmitted to the receivers 10 and 20 through the antenna.

14 is a flowchart illustrating an OFDM transmission method according to another embodiment of the present invention.

Hereinafter, an OFDM transmission method will be described with reference to FIGS. 1, 2, 5, and 14. In the case where two transport streams TS1 and TS2 are received and hierarchically generated data and main line data are generated hierarchically, Explain. Since steps S1410 to S1480 are substantially the same as steps S1210 to S1280 described with reference to FIG. 12, detailed descriptions thereof will be omitted.

The first and second transport streams TS1 and TS2 are scrambled by the first and second scramblers 121 and 131, respectively (S1410).

The scrambled first and second transport streams TS1 and TS2 are subjected to error correction coding (FEC) by the first coding unit 122 and the second coding unit 132, respectively (S1420).

The coded first and second transport streams TS1 and TS2 are symbol-mapped in the first and second symbol mapping units 123 and 133, respectively, to generate high priority data HP and main line data LP ( S1430).

The generated high priority data HP and the main line data LP are allocated in symbol units or subcarrier units in the mux 140, respectively, and are generated as a plurality of OFDM symbols as shown in FIG. 5 (S1440).

The generated plurality of OFDM symbols are subcarrier interleaved in the interleaver 151 (S1450).

The IDFT unit 152 performs inverse discrete Fourier transform on the interleaved OFDM symbol to generate an OFDM symbol in the time domain (S1460).

In order to prevent interference between OFDM symbols, the GI insertion unit 153 inserts a guard period (GI) into the OFDM symbol input from step S1460 (S1470).

The signal converter 154 converts an OFDM symbol input from the GI insertion unit 153 into an analog OFDM signal, and up-converts the analog OFDM signal to generate an RF signal (S1480). The generated RF signal is transmitted to the receivers 10 and 20 through the antenna.

15 is a flowchart illustrating an OFDM reception method according to an embodiment of the present invention.

Hereinafter, an OFDM reception method will be described with reference to FIGS. 1 to 10 and 15, and a case of generating a transport stream by receiving an OFDM signal including high priority data and Zhou line data will be described. The OFDM signal may further include a plurality of middle-priority data MPs, and the high-priority data HP, the main-order data LP, and the middle-priority data MP may be the same or different contents.

The OFDM signal received through the antenna is down converted by the signal demodulator 910 and then converted into a digital signal (S1510).

The GI inserted into the OFDM symbol which is a digital signal is removed by the GI remover 912 (S1520).

The OFDM symbol from which the GI is removed is converted into an OFDM symbol in the frequency domain by a fast Fourier transform in the DFT unit 913 (S1530).

The deinterleaver 914 deinterleaves a plurality of OFDM symbols input from step S1530 (S1540), and separates and outputs OFDM symbols to which high priority data (HP) and main line data (LP) are allocated in symbol units or subcarrier units, respectively. (S1550). In operation S1540, the deinterleaver 914 selectively uses symbol deinterleaving or subcarrier deinterleaving.

The demux 920 demultiplexes a plurality of OFDM symbols input from the deinterleaver 914, and assigns processable data among the high priority data HP and the main line data LP included in the plurality of OFDM symbols. The symbol is output (S1560).

The symbol demapping unit 931 generates a transport stream by demapping a symbol input from the demux 920 (S1570).

The decoding unit 930 decodes the transport stream input from step S1570 to perform error correction (S1580).

The descrambler 933 descrambles the transport stream input from step S1580 (S1590).

As described with reference to FIGS. 1 to 15, the transmitter 100 allocates the high priority data HP and the main line data LP to different symbols or different subcarriers, and then generates an OFDM symbol. At this time, the allocated ratio can be changed in various ways according to the operation mode. That is, the transmitter 100 may transmit the transmission ratio between the high-priority data HP and the main-line data LP at various ratios rather than at a limited ratio such as 1: 1 or 1: 2, thereby operating the system. Freedom of image can be improved.

As described above, according to the OFDM transmission and reception apparatus and method according to the present invention, hierarchical data may be symbol-mapped using various modulation schemes such as QPSK as well as QAM scheme. As a result, the transmitter can improve the degree of freedom in system operation by generating OFDM symbols to which various modulation schemes are applied.

In addition, according to the present invention, OFDM symbols are generated by allocating the high priority data and the main line data in symbol units or subcarrier units, and in this case, various ratios of the high priority data and the main line data to the symbols or subcarriers are varied. It is possible to adjust.

In addition, according to the present invention, it is possible to generate and transmit high priority data, Zhou line data and middle priority data from three or more input transport streams. Thus, data having an appropriate code rate can be generated and transmitted according to the degree of poorness of the reception channel environment.

In addition, according to the present invention, the reception apparatus can provide a more stable video by extracting the appropriate data according to the reception channel environment from the hierarchical OFDM signal. In particular, in the case of a fixed reception environment having excellent channel environment, the receiver can provide a high resolution video by extracting the Zhou line data containing more data from the OFDM signal, and in the case of a mobile reception environment in which the channel environment is poor, Can provide a seamless service by extracting high priority data having a low code rate from an OFDM signal.

While the above has been shown and described with respect to preferred embodiments of the present invention, the present invention is not limited to the specific embodiments described above, it is usually in the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims. Various modifications may be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or the prospect of the present invention.

Claims (36)

  1. A transmission processor for generating an Orthogonal Frequency Division Multiplexing (OFDM) symbol to which at least two transport streams are allocated; And
    And a signal converter converting the generated OFDM symbol into an OFDM signal and transmitting the same to at least one receiver.
  2. The method of claim 1,
    The transmission processing unit,
    A plurality of coding units configured to perform error correction encoding by coding the two or more transport streams;
    A plurality of modulators for modulating the coded two or more transport streams; And
    And a multiplexer for generating the OFDM symbol by allocating each of the two or more modulated transport streams to at least one of a symbol unit and a subcarrier unit.
  3. The method according to claim 1 or 2,
    The transmission processor allocates one of the two or more transport streams to a plurality of subcarriers of the at least one OFDM symbol such that the two or more transport streams are mixed in at least one OFDM symbol. .
  4. The method according to claim 1 or 2,
    The transmission processor generates the OFDM symbol by allocating one of the two or more transport streams for each of a plurality of subcarriers constituting the plurality of OFDM symbols such that the two or more transport streams are mixed in all of the plurality of OFDM symbols. Digital broadcast transmitter.
  5. The method according to claim 1 or 2,
    The ratio information to which the two or more transport streams are allocated is defined by mutual agreement with the at least one receiver, and is transmitted to the at least one receiver.
  6. The method according to claim 1 or 2,
    The region information to which the two or more transport streams are allocated is defined by mutual agreement with the at least one receiver, and is transmitted to the at least one receiver.
  7. The method according to claim 1 or 2,
    The transmission processor adjusts a transmission rate of the two transport streams by adjusting a ratio in which the at least two transport streams are allocated and an area allocated to each transmission operation unit including a set number of OFDM symbols. Device.
  8. The method of claim 7, wherein
    And the coding information used in the transmission processor, the modulation scheme information, the information of the allocated ratio, and the information of the allocated region are included and transmitted for each transmission operation unit.
  9. The method of claim 2,
    The coding unit,
    And transmitting the two or more transport streams using independent code rates according to a reception channel environment.
  10. The method of claim 9,
    And the coding unit codes data for a mobile receiver among the two or more transport streams at a low code rate, and codes data for a fixed receiver at a high code rate higher than the low code rate.
  11. The method of claim 2,
    The modulation unit modulates using one of PSK, Quadrature Phase Shift Keying (QPSK), Quadrature Amplitude Modulation (16QAM), 64QAM, 128QAM, and 256QAM.
  12. The method of claim 1,
    And the signal conversion unit interleaves the generated OFDM symbol using one of a symbol interleaving method and a subcarrier interleaving method.
  13. Generating an Orthogonal Frequency Division Multiplexing (OFDM) symbol to which at least two transport streams are allocated; And
    Converting the generated OFDM symbol into an OFDM signal and transmitting the same to at least one receiver.
  14. The method of claim 13,
    The generating step,
    Performing error correction encoding by coding the two or more transport streams;
    Modulating the at least two coded transport streams; And
    And assigning each of the at least two modulated transport streams to at least one of a symbol unit and a subcarrier unit to generate the OFDM symbol.
  15. The method according to claim 13 or 14,
    The generating may include assigning one of the two or more transport streams to each of the plurality of subcarriers of the at least one OFDM symbol such that the two or more transport streams are mixed in at least one OFDM symbol. Way.
  16. The method according to claim 13 or 14,
    The generating may include allocating one of the two or more transport streams to each of a plurality of subcarriers constituting the plurality of OFDM symbols so that the two or more transport streams are mixed in all of the plurality of OFDM symbols. Way.
  17. The method according to claim 13 or 14,
    The ratio information to which the two or more transport streams are allocated is defined by mutual agreement with the at least one receiver, and is transmitted to the at least one receiver.
  18. The method according to claim 13 or 14,
    The area information of the OFDM symbol to which the at least two transport streams are allocated is transmitted by being multiplexed with the at least two transport streams.
  19. The method according to claim 13 or 14,
    The generating may include adjusting a rate at which the at least two transport streams are allocated and a region in which the at least two transport streams are allocated for each transmission operation unit including a set number of OFDM symbols.
  20. The method of claim 19,
    The coding information used in the generating step, the modulation scheme information, the information of the allocated ratio and the information of the allocated area is included in each transmission operation unit and transmitted.
  21. The method of claim 14,
    The step of performing,
    OFDM coding method characterized in that for coding the two or more transport streams using the respective code rate according to the receiving channel environment.
  22. The method of claim 21,
    The performing of the step of OFDM coding data for the mobile receiver of the two or more transport streams at a low code rate, coding the data for a fixed receiver at a higher code rate than the low code rate Way.
  23. The method of claim 14,
    The performing of the OFDM modulation method using one of PSK, Quadrature Phase Shift Keying (QPSK), Quadrature Amplitude Modulation (16QAM), 64QAM, 128QAM, and 256QAM.
  24. The method of claim 13,
    The generating may include: interleaving the generated OFDM symbol using one of a symbol interleaving method and a subcarrier interleaving method.
  25. A signal demodulator for demodulating an OFDM signal received from a transmitter to generate a plurality of OFDM symbols in which at least two transport streams are assigned to at least one of a symbol unit and a subcarrier unit;
    A demultiplexer for demultiplexing the generated plurality of OFDM symbols and outputting a symbol to which a transportable transport stream of the two or more transport streams is allocated; And
    And a reception processor for performing error correction on a symbol input from the demultiplexer.
  26. The method of claim 25,
    The signal demodulation unit,
    And a plurality of OFDM symbols generated by applying one of a symbol deinterleaving scheme and a subcarrier deinterleaving scheme to the demodulated OFDM signal.
  27. The method of claim 25,
    The reception processing unit,
    A demodulator for demodulating a symbol input from the demultiplexer to generate a transport stream; And
    And a decoding unit to decode the generated transport stream and perform error correction.
  28. The method of claim 25,
    And the demultiplexer outputs the symbols using ratio information and area information within a symbol in which the two or more transport streams provided from the transmitter are allocated in symbol units and subcarrier units.
  29. The method of claim 25,
    And the at least two transport streams are coded by different code rates according to a reception channel environment in the transmitter.
  30. The method of claim 29,
    And the demultiplexer selects and outputs at least one of the two or more transport streams.
  31. Demodulating an OFDM signal received from a transmitter to generate a plurality of OFDM symbols in which two or more transport streams are assigned to at least one of a symbol unit and a subcarrier unit;
    Demultiplexing the generated plurality of OFDM symbols and outputting a symbol to which a transportable transport stream among the two or more transport streams is allocated; And
    Performing error correction on a symbol input from the demultiplexer.
  32. The method of claim 31, wherein
    The generating step,
    And generating one of the plurality of OFDM symbols by applying one of a symbol deinterleaving scheme and a subcarrier deinterleaving scheme to the demodulated OFDM signal.
  33. The method of claim 31, wherein
    The step of performing,
    Demodulating the output symbol to generate a transport stream; And
    And performing error correction by decoding the generated transport stream.
  34. The method of claim 31, wherein
    The outputting step,
    And at least two transport streams provided from the transmitter output the symbol by using ratio information allocated in symbol units and subcarrier units and region information within a symbol.
  35. The method of claim 31, wherein
    And said at least two transport streams are coded by different code rates according to a reception channel environment at said transmitter.
  36. The method of claim 35, wherein
    The outputting step,
    And selecting at least one of a symbol to which a transport stream coded with a low code rate and a symbol to which a transport stream coded with a high code rate are allocated are selected and output from the two or more transport streams.
KR1020070054080A 2007-06-01 2007-06-01 OFDM transmitting/receiving apparatus and method KR101424069B1 (en)

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