KR101424069B1 - OFDM transmitting/receiving apparatus and method - Google Patents

OFDM transmitting/receiving apparatus and method Download PDF

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KR101424069B1
KR101424069B1 KR1020070054080A KR20070054080A KR101424069B1 KR 101424069 B1 KR101424069 B1 KR 101424069B1 KR 1020070054080 A KR1020070054080 A KR 1020070054080A KR 20070054080 A KR20070054080 A KR 20070054080A KR 101424069 B1 KR101424069 B1 KR 101424069B1
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symbol
ofdm
transport streams
unit
allocated
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KR1020070054080A
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Korean (ko)
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KR20080105907A (en
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박의준
김기보
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삼성전자주식회사
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Abstract

An OFDM transceiver and method are disclosed. The transmission processor generates an Orthogonal Frequency Division Multiplexing (OFDM) symbol in which two or more transport streams are respectively allocated, and the signal converter converts the generated OFDM symbol into an OFDM signal and transmits the OFDM symbol to at least one receiver.
OFDM symbol, hierarchical transmission

Description

[0001] The present invention relates to an OFDM transmitting / receiving apparatus and method,

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

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

FIGS. 3A and 3B are schematic diagrams for explaining an example in which a MUX generates an OFDM symbol by distributing high-priority data and low-priority data on a symbol-by-symbol basis,

FIGS. 4A and 4B are schematic diagrams for explaining an example of generating an OFDM symbol by distributing high-priority data and low-priority data by symbol units or subcarrier units,

5 is a schematic diagram for explaining an example of generating an OFDM symbol by distributing high priority data and low priority data on a subcarrier basis,

6A to 6C are schematic diagrams for explaining an embodiment in which high-priority data and low-priority data are allocated on a subcarrier-by-subcarrier basis in FIGS. 4A, 4B, and 5,

FIGS. 7A and 7B are schematic diagrams for explaining an embodiment in which a ratio at which high-priority data and low-priority data are allocated is changed;

8 is a schematic diagram for explaining a case where a super frame is used as a unit of a transmission operation,

9 is a block diagram illustrating an OFDM receiving apparatus according to an exemplary embodiment of the present invention.

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

11 is a block diagram illustrating an OFDM receiving apparatus according to another embodiment of the present invention.

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

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

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

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

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an OFDM transceiver apparatus and method, and more particularly, to an OFDM transceiver apparatus and method capable of transmitting and receiving a plurality of OFDM signals in which at least two transport streams are allocated at various transmission ratios.

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

In designing the OFDM transmission / reception system, the designer designs the system considering the channel environment of the receiving apparatus. That is, in the case of a mobile reception environment in which the channel environment is poor, the designer can improve the data reception rate by using a robust modulation scheme and an encoding algorithm with high error correction capability, and transmit more information To increase the data rate. Hereinafter, data considering a poor channel environment is referred to as HP (High Priority) data, and data considering a superior channel environment is referred to as LP (low priority) data.

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

For example, when the 64QAM modulation scheme is used, the OFDM transmission apparatus maps HP data to the first 2 bits of one 6-bit symbol and LP data to the next 4 bits. Therefore, when the 64QAM scheme is used, the existing OFDM transmission apparatus transmits HP data more stably by transmitting twice as many LP data as HP data, and LP data transmits a relatively large amount of data. When the 16QAM modulation scheme is used, the OFDM transmission apparatus transmits HP data to the first 2 bits of one 4-bit symbol and LP data to the next 2 bits.

However, the conventional OFDM transceiver supports 16QAM or 64QAM only when HP data and LP data are transmitted together, but it does not support other coding schemes such as QPSK, thereby lowering the degree of freedom in system operation. In addition, the conventional OFDM transceiver only supports 16QAM or 64QAM, so that the transmission ratio of HP data and LP data is 1: 1 and 1: 2, and as a result, the data adjustment ratio is not free. In addition, the conventional OFDM transceiver has a limit to support only HP data and LP data as a transport stream.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and it is an object of the present invention to provide a method and apparatus for mapping OFDM signals using various modulation schemes during hierarchical transmission, The present invention provides an OFDM transceiver and method capable of freely controlling the rate of transmission of low-priority data suitable for a fixed reception channel and transmitting and receiving two or more hierarchical data.

According to an aspect of the present invention, there is provided an OFDM transmission apparatus including: a transmission processing unit for generating an OFDM symbol in which two or more transport streams are allocated; And a signal converter for converting the generated OFDM symbol into an OFDM signal and transmitting the OFDM symbol to at least one receiver.

Wherein the transmission processing unit comprises: a plurality of coding units for coding the two or more transport streams to perform error correction coding; A plurality of modulators for modulating the coded two or more transport streams; And a multiplexer for allocating each of the modulated transmission streams to at least one of a symbol unit and a subcarrier unit to generate the OFDM symbol.

Wherein the transmission processing unit allocates one of the two or more transport streams for each of a plurality of subcarriers constituting the at least one OFDM symbol so that the at least one OFDM symbol includes the at least two transport streams.

The transmission processing unit 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.

The ratio information in which the two or more transport streams are allocated is defined by the at least one receiver and the mutual protocol, and is transmitted to the at least one receiving device.

The area information to which the two or more transport streams are allocated is defined by the at least one receiver and the mutual protocol, and is transmitted to the at least one receiver.

The transmission processing unit adjusts the transmission rate of the two transport streams by adjusting a ratio of the at least two transport streams allocated and a region allocated to each of the transport operation units each having a predetermined number of OFDM symbols.

The coding information, the modulation scheme information, the allocated ratio information, and the allocated area information used in the transmission processing unit are transmitted for each transmission operation unit.

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

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

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

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

Wherein the generating comprises: coding the two or more transport streams to perform error correction coding; Modulating the coded two or more transport streams; And generating the OFDM symbol by allocating each of the modulated transmission streams to at least one of a symbol unit and a subcarrier unit.

The generating step allocates one of the two or more transport streams for each of a plurality of subcarriers constituting the at least one OFDM symbol so that the at least one OFDM symbol includes the at least two transport streams.

Wherein the generating step allocates 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.

The generating step adjusts a rate at which the at least two transport streams are allocated and an allocated area for each transmission operation unit including a predetermined number of OFDM symbols.

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

The performing of the coding may include coding the two or more transport streams using different coding rates according to a reception channel environment.

The performing step codes data for a mobile receiver of 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.

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

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

Meanwhile, an OFDM receiving apparatus according to an exemplary embodiment of the present invention demodulates an OFDM signal received from a transmitter and generates a plurality of OFDM symbols in which two or more transport streams are allocated to at least one of symbol units and subcarrier units, grandfather; A demultiplexer for demultiplexing the plurality of generated OFDM symbols and outputting a symbol assigned a processable transmission stream among the two or more transport streams; And a reception processor for performing error correction on a symbol input from the demultiplexer.

The signal demodulation unit applies the symbol deinterleaving method and the subcarrier deinterleaving method to the demodulated OFDM signal to generate the plurality of OFDM symbols.

A demodulator for demodulating a symbol input from the demultiplexer and generating a transport stream; And a decoding unit decoding the generated transport stream to perform error correction.

The demultiplexer outputs the symbols using the ratio information and the intra-symbol area information allocated to the two or more transport streams provided from the transmitter on a symbol unit and a sub-carrier unit basis.

The two or more transport streams are coded at respective coding rates according to a receiving channel environment in the transmitter.

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

Meanwhile, an OFDM reception method according to an embodiment of the present invention includes demodulating an OFDM signal received from a transmitter, generating a plurality of OFDM symbols in which two or more transport streams are allocated 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 processable transport stream among the two or more transport streams is allocated; And performing error correction on a symbol input from the demultiplexer.

The generating step generates the plurality of OFDM symbols by applying one of a symbol deinterleaving method and a subcarrier deinterleaving method to the demodulated OFDM signal.

Wherein the performing comprises: demodulating the output symbol to generate a transport stream; And decoding the generated transport stream to perform error correction.

The outputting step outputs the symbol using the ratio information and the in-symbol area information allocated to the two or more transport streams provided from the transmitter on a symbol unit and a sub-carrier unit basis.

Wherein the outputting step selects and outputs at least one of a symbol assigned a transport stream coded with a low code rate and a code assigned a transport stream coded with a high code rate among the two or more transport streams.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

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

1, the OFDM transmission apparatus 100 includes first and second transmission processing units 120 and 130, a multiplexer (MUX) 140, and a signal conversion unit 150. [ The OFDM transmission apparatus 100 is applied to the DVB-T standard, and transmits different contents or the same contents in a hierarchical manner.

The hierarchical scheme is a scheme of modulating at least two input transport streams into a plurality of OFDM signals using different coding rates or different modulation schemes in consideration of a channel environment for receiving the transport streams. For example, the two transport streams are High Priority (HP) data and Low Priority (LP) data. In three cases, MP (Middle Low Priority) is added to transmit and at least two transport streams are transmitted.

The first and second transmission processing units 120 and 130 and the MUX 140 generate a plurality of Orthogonal Frequency Division Multiplexing (OFDM) symbols to be transmitted to at least one receiving apparatus 10 and 20. At this time, the MUX 140 allocates two or more transport streams TS1 and TS2 on a symbol-by-symbol basis or allocates different transport streams for a plurality of sub-carriers forming one symbol to generate an OFDM symbol.

When receiving at least two transport streams TS1 and TS2 to be transmitted to the receiving apparatuses 10 and 20 from the source circle (not shown), the first and second transmission processing units 120 and 130 and the mux 140 are received And generates a plurality of OFDM symbols by modulating the transport streams TS1 and TS2 into signals that can be loaded on a plurality of subcarriers.

At least two transport streams TS1 and TS2 are encoded or modulated at different coding rates in the first and second transmission processing units 120 and 130 for hierarchical transmission and then generated as OFDM symbols in the mux 140 . For example, when the receiver is a mobile receiver (for example, 10), the first transmission processing unit 120 encodes the transport stream TS1 at a low coding rate in order to increase the data reception rate.

When the receiver is a fixed receiver (for example, 20), the second transmission processing unit 130 encodes the transport stream TS2 at a higher code rate than the transport stream TS1 so that it can view the broadcast at a high resolution . In this case, since a coding algorithm and a robust modulation scheme having a high error correction capability are used at a low code rate, a mobile receiving apparatus 10 such as a DMB phone can provide a broadcast in which a break of a moving picture is minimized.

The signal converting unit 150 converts an OFDM symbol generated by the MUX 140 into an OFDM signal and transmits the OFDM symbol to the at least one receiving apparatus 10 or 20. That is, the data transmitted to at least one receiving device 10, 20 includes at least two transport streams TS1, TS2, and each receiving device 10, 20 selects and processes the corresponding transport stream.

The at least one receiving device (10, 20) includes a mobile receiving device (10) and a fixed receiving device (20).

The mobile receiving apparatus 10 is a device for receiving an OFDM symbol while moving, for example, a DMB phone. The mobile receiving apparatus 10 selects only a transport stream TS1 encoded at a low coding rate among OFDM symbols transmitted from the transmitting apparatus 100, Treat it as a possible signal. The fixed receiving apparatus 20 is a device for receiving an OFDM symbol in a fixed state, and may be a digital TV used in a general household. For example, Only the stream TS2 is selected and processed as a viewable signal.

It goes without saying that the receiving apparatuses 10 and 20 can process both the transport stream encoded at a low encoding rate and the transport stream encoded at a high encoding rate into a viewable signal.

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

2, the OFDM transmitting apparatus 100 includes a signal processing unit 110 and a signal converting unit 150 including a first signal processing unit 120, a second signal processing unit 130, and a mux 140 . The transmission processing unit 110 generates a plurality of OFDM symbols by allocating different transport streams to each other on a symbol basis. The signal conversion unit 150 converts the generated OFDM symbols into at least one reception device 10, 20).

Hereinafter, the case where 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, but the number of input transport streams may be added. Accordingly, it is preferable that the number of the n-th signal processing units (n is a positive number, not shown) increases.

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

The first scrambler 121 scrambles the input first transport stream TS1. Scrambling is a randomization of a stream in order to eliminate the problem that the same number of bits are repeated in the synchronous signal transmission system to lose the synchronization signal.

The first coding unit 122 encodes the first transport stream TS1 input from the first scrambler 121 so as to detect and correct an error of the transport stream in the receiving apparatuses 10 and 20 and performs error correction coding ). In particular, the first coding unit 122 codes the first transport stream TS1 in consideration of the mobile reception environment, i.e., the mobile reception apparatus 10. The first coding unit 122 includes a first outer coder 122a, a first outer interleaver 122b, a first inner coder 122c, and a second inner interleaver 122b. (Inner Interleaver) 122d.

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

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, LDPC (Low Density Parity Check) coding, or the like.

The first inner interleaver 122d 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 converts the first transport stream TS1 coded by the first coding unit 122 into PSK, BPSK (Binary Phase Shift Key), QPSK (Quadrature Phase Shift Keying), 16QAM Quadrature Amplitude Modulation), 64QAM, 128QAM, and 256QAM, to high-priority data (HP). The first symbol mapping unit 123 may output the high priority data HP in symbol form.

The second signal processing unit 130 includes a second scrambler 131, a second coding unit 132 and a second symbol mapping unit 133 and receives low priority data LP from the second transport stream TS2 . The low priority data LP is data generated from the second transport stream TS2 in consideration of the fixed reception apparatus 20. [ Hereinafter, the first transmission stream output from the first signal processing unit 120 is referred to as high priority data HP and the second transmission stream output from the second signal processing unit 130 is referred to as low priority data LP.

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

The second coding unit 132 encodes the second transport stream TS2 input from the second scrambler 131 to detect and correct an error in the transport stream in the receiving apparatuses 10 and 20 and performs error correction coding ). In particular, the second coding unit 132 codes the second transport stream TS2 in consideration of the fixed reception environment, i.e., the fixed reception apparatus 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, an RS coding scheme, or the like to externalize the second transport stream TS2. The second outer interleaver 132b outer-interleaves the second transport stream TS2 received 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, or the like in order to internally encode the second transport stream TS2 input from the second interleaver 151. [ The second inner interleaver 132d 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 to the modulation unit performs one of various modulation schemes such as a BPSK scheme, a QPSK scheme, a 16QAM scheme, a 64QAM scheme, a 128QAM scheme, and a 256QAM scheme on the second transport stream TS2 coded by the second coding unit 132 To low-priority data (LP). The second symbol mapping unit 133 may output the low-order data LP in symbol form. The first and second symbol mapping units 123 and 133 may use the same or different modulation schemes.

The first coding unit 122 and the second coding unit 132 can code the first transport stream TS1 and the second transport stream TS2 at different coding rates or the same coding rate. For example, when the first coding unit 122 codes the first transport stream into a stream suitable for the mobile reception apparatus 10, the first coding unit 122 encodes the code used in the second coding unit 132 The first transport stream TS1 can be encoded with a lower code rate than that of the first transport stream TS1, or can be encoded with the same code rate.

When the first and second transport streams TS1 and TS2 are coded at the same coding rate, the first and second symbol mapping units 123 and 133 convert the first and second transport streams TS1 and TS2 into a hierarchical And modulates the first and second transport streams TS1 and TS2 using different schemes for transmission. That is, the first symbol mapping unit 123 generates a symbol suitable for the mobile reception apparatus 10 from the coded first transport stream TS1, and the second symbol mapping unit 133 generates the coded second transport stream TS1 TS2 from the fixed receiving apparatus 20 by using different modulation schemes.

For example, when the first and second transport streams TS1 and TS2 are coded at the same coding rate, the first symbol mapping unit 123 uses the QPSK modulation scheme, and the second symbol mapping unit 133 uses the QPSK modulation scheme. 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 use one of 64QAM, 128QAM, and 256QAM.

On the other hand, when a stream (symbol) suitable for the mobile reception apparatus 10 and the fixed reception apparatus 20 is created when the first and second transport streams TS1 and TS2 are coded with different code rates, The two symbol mapping units 123 and 133 multiplex the first and second transport streams TS1 and TS2 using a different modulation scheme or the same modulation scheme to hierarchically transmit the first and second transport streams TS1 and TS2, To output high-priority (HP) data and low-priority (LP) data.

A method of generating high-priority (HP) data and low-priority (LP) data according to the coding and modulation schemes described above will be described in detail as follows.

First, high priority data (HP) is data that is sent so that it can be received even in a harsh environment, and low priority data (LP) is data that is received in an excellent environment. For example, when high-priority data (HP) is used for mobile data reception, it is required to be able to view even a small screen. Therefore, the reception performance should be excellent since data transmission is small and must be received in an environment like a car. In addition, when low-priority data (LP) is used for terrestrial data reception, transmission of a relatively large amount of data is required in order to enable viewing on a large screen.

[Table 1] is a table showing coding parameters used in DVB-S2. For example, the size of an LDPC block coded by the LDPC coding scheme can be described by 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 the number of data bits before BCH external encoding is 16008, LDPC coding outputs 6464 bits of LDPC blocks. On the other hand, when mapping is performed using the 16QAM scheme, 6 bits are represented per symbol, so a total of 10800 symbols are required to represent one LDPC block. Since high priority data (HP) generally requires higher reception performance than low priority data (LP), when applying the same modulation scheme such as QPSK to HP and LP, high priority data (HP) do. For example, 4/5 coding may be used for the high-priority data (HP), and 4/5 coding for the QPSK modulation method for the low-priority data (LP).

[Table 2] is a table showing an example of the data transmission rate (Spectral Efficiency) and the reception performance when the coding scheme as shown in [Table 1] is applied and then modulated.

Mode Data transfer rate (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 16APSK 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 32APSK 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 preceding English refers to the modulation scheme and the following numbers refer to the coding rate. For example, 'QPSK 1/4' implies applying QPSK modulation after applying a 1/4-rate LDPC code. In addition, when the QPSK uses 2 bits, the data rate is a data amount of one symbol. If 1/4 coding is used, 0.5 data transmission rate can be calculated. [Table 2] Since the post-enhancement LDPC coding was applied, a value of '0.490243' was measured instead of '0.5'. Further, the smaller the numerical value, the better the reception performance.

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

In this manner, the high-priority data HP and low-priority data LP having the desired reception performance can be created by adding independent coding and independent modulation, and the data transmission allocation can be made in coding and modulation, ) And the low priority data (LP). Therefore, the transmission rate can be adjusted by subcarrier allocation or symbol allocation of high priority data HP and low priority data LP.

The multiplexer 140 multiplexes the 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 low- (LP), and allocates the first and second transport streams TS1 and TS2 on a symbol-by-symbol basis or on a subcarrier-by-subcarrier basis to generate an OFDM symbol. The multiplexer 140 multiplexes the first and second transport streams TS1 and TS2 on a symbol basis or on a subcarrier basis on the basis of the predefined allocation ratio and the intra-symbol allocation region between the transmission apparatus 100 and the reception apparatuses 10 and 20, And the rate at 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 can change the ratio of the first and second transport streams TS1 and TS2 allocated to the transport operation unit and the allocated area. The transmission operation unit is a unit composed of a plurality of symbols and includes coding scheme information, modulation scheme information, first and second transport streams TS1 and TS2 used in the first signal processing unit 120 and the second signal processing unit 130, And informs the receiving apparatuses 10 and 20 of the ratio information and the allocated area information allocated by the mux 140. Therefore, the coding scheme, the modulation scheme, the allocated ratio information, and the information on the allocated area can be transmitted to the receiving apparatuses 10 and 20 by each transmission operation unit. 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.

FIGS. 3A and 3B are schematic diagrams for explaining an example in which a MUX generates OFDM symbols by distributing high-priority data and low-priority data on a symbol-by-symbol basis.

Referring to FIGS. 3A and 3B, the MUX 140 generates an OFDM symbol by allocating one of the first and second transport streams to a plurality of symbols forming one frame, The allocation ratio of the data (LP) and the allocated area, i.e., the allocated location are considered. 3A, the MUX 140 repeatedly allocates high priority data HP and low priority data LP to symbols to generate OFDM symbols. Thus, when the number of symbols allocated to the high-priority data HP and the low-priority data LP is the same in one frame, the transmission ratio of the high-priority data HP to the low-priority data LP is 1: 1 Transmission ratio.

In the case of FIG. 3B, the MUX 140 continuously allocates the high priority data HP to a plurality of symbols and successively allocates low priority data LP to other symbols to generate OFDM symbols. At this time, the transmission ratio of the high-priority data HP and the low-priority data LP is M: N (N) according to the number of symbols allocated to the high-priority data HP and low- . Here, M and N are the same or different as positive numbers.

4A and 4B are schematic diagrams for explaining an example of generating an OFDM symbol by distributing high-priority data and low-priority data on a symbol unit or a subcarrier unit basis.

Referring to FIGS. 4A and 4B, the multiplexer 140 multiplexes high-priority data HP and low-priority data HP so that high-priority data HP and low-priority data LP are mixed in at least one symbol among a plurality of symbols forming a frame. And distributes low priority data (LP) to generate OFDM symbols. As described above, each symbol has a plurality of subcarriers. Accordingly, the mux 140 allocates one of the high priority data HP and the low priority data LP for each of a plurality of subcarriers forming a symbol, The allocation ratio of the data (LP) and the position, i.e., the area, of the allocated subcarriers are considered.

4A, the MUX 140 repeatedly allocates the high-priority data HP and the low-priority data LP to the symbols, while the high-priority data HP and the low-priority data LP) are all allocated to generate an OFDM symbol. At this time, the mux 140 allocates one of the high priority data HP and the low priority data LP for each of a plurality of subcarriers constituting a part of the symbols (1, 2).

4B, the MUX 140 continuously allocates the high-priority data HP to a plurality of symbols, allocates the high-priority data HP and the low-priority data LP to some symbols (3) And low-priority data (LP) is consecutively allocated to other symbols to generate an OFDM symbol. At this time, the transmission ratio of the high-priority data HP and the low-priority data LP is M (n) according to the number of symbols and sub-carriers to which the high-priority data HP and low- : N can be. Here, M and N are the same or different as positive numbers.

5 is a schematic diagram for explaining an example of generating an OFDM symbol by allocating high-priority data and low-order data on a subcarrier-by-subcarrier basis;

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

FIGS. 6A to 6C are schematic diagrams for explaining an embodiment in which high-priority data and low-priority data are allocated on a subcarrier-by-subcarrier basis in FIG. 4A, FIG. 4B, and FIG. 6A to 6C, the MUX 140 allocates high priority data HP and low priority data LP to a plurality of subcarriers constituting one symbol. At this time, the MUX 140 considers the allocation ratio of the high priority data HP and the low priority data LP and the allocated subcarrier area. 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 a plurality of subcarriers by an allocated ratio, and then consecutively allocates the low priority data LP to a plurality of subcarriers.

6B and 6C, the multiplexer 140 multiplexes the high priority data HP and the low priority data LP so that the high priority data HP and the low priority data LP are scattered on a plurality of subcarriers. To a plurality of subcarriers. 6B and 6C, the ratio of the high-priority data HP and the low-priority data LP allocated to a plurality of sub-carriers is the same, but the positions of the allocated sub-carriers are different.

FIGS. 7A and 7B are schematic diagrams for explaining an embodiment in which a ratio at which high-priority data and low-priority data are allocated is changed.

Referring to FIG. 7A, f denotes a frequency, and the MUX 140 has allocated high priority data HP and low priority data LP to a plurality of subcarriers at a ratio of 1: 1 in one symbol. Referring to FIG. 7B, the MUX 140 allocates the high priority data HP and the low priority data LP to a plurality of subcarriers at a ratio of M: N in one symbol.

Referring to FIGS. 3A to 7B, the MUX 140 includes a ratio of allocating high priority data HP and low priority data LP to a plurality of subcarriers or a plurality of symbols, The position of the subcarrier is performed in a predetermined manner. The number of subcarriers or the number of OFDM symbols occupied by the high priority data HP and the low priority data LP is changed according to the allocation ratio.

8 is a schematic diagram for explaining 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 areas to a plurality of frames forming a super frame. The information on the allocation ratio and the allocation area, the coding scheme, the modulation scheme, and the like can be generated by the MUX 140 over a separate channel, and can be provided to the reception apparatuses 10 and 20.

Referring again to FIG. 2, the signal converting unit 150 converts a plurality of OFDM symbols output from the MUX 140 into OFDM signals and transmits the OFDM symbols to the receiving apparatuses 10 and 20. The signal converter 150 includes an interleaver 151, an inverse discrete Fourier transform (IDFT) unit 152, a guard interval (GI) inserter 153, and a signal converter 154.

The interleaver 151 interleaves a plurality of OFDM symbols input from the MUX 140. More specifically, when high priority data HP and low priority data LP are allocated in units of symbols as shown in FIG. 3A and FIG. 3B in the MUX 140, the interleaver 151 performs symbol interleaving for a plurality of OFDM symbols To be applied.

When the high priority data HP and the low priority 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 sub-carrier interleaving for some symbols (1, 2, 3) and symbol interleaving for some symbols (4).

In the case where high priority data HP and low priority data LP are allocated in the MUX 140 as shown in FIG. 5, the interleaver 151 applies subcarrier interleaving.

The IDFT unit 152 performs an inverse discrete Fourier transform on the interleaved OFDM symbol to convert the OFDM symbol in the frequency domain into the OFDM symbol in the time domain. The inverse fast Fourier transform may be performed using IFFT (Inverse Fast Fourier Transform) instead of the IDFT unit 152. [

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

The signal converter 154 converts the OFDM symbol input from the GI inserter 153 into an analog OFDM signal and up-converts the analog OFDM signal to generate an RF signal. The generated RF signal includes high priority data HP and low priority data LP and is transmitted to the reception apparatuses 10 and 20 through the antenna.

According to the above-described transmission apparatus 100, the transmission apparatus 100 codes at least two transport streams TS1 and TS2 at different coding rates in order to hierarchically transmit at least two transport streams TS1 and TS2. Thereby generating high-priority data HP and low-priority data LP.

In order to adjust the transmission rate of the high priority data HP and the low priority data LP, the transmitting apparatus 100 transmits the high priority data HP and the low priority data LP to the symbol or subcarrier Adjust the percentage to be assigned. In particular, the transmitting apparatus 100 generates high-priority data HP and low-priority data LP by generating OFDM symbols by allocating them to one of high-priority data HP and low-priority data LP on a symbol basis or on a sub- The transmission rate can be variously implemented.

As the low priority data LP is more allocated to symbols or subcarriers, the fixed receiving apparatus 20 can reproduce a high quality moving picture, and the mobile receiving apparatus 10 can reproduce the additional data included in the high priority data HP It is possible to play back seamless video.

In addition, when the coding rate applied to at least two transport streams TS1 and TS2 is the same, the transmitting apparatus 100 can generate the high-priority data HP and the low-priority data LP by applying the modulation scheme differently .

The transmitting apparatus 100 may include a plurality of n-th signal processing units (not shown) as well as high priority data HP and low priority data LP to generate a plurality of intermediate priority data MP Of course.

9 is a block diagram illustrating an OFDM receiving apparatus according to an embodiment of the present invention.

9, an OFDM receiving apparatus includes a signal demodulator 910, a demultiplexer (hereinafter referred to as 'demux') 920, and a reception processor 930. The OFDM receiving apparatus may be the mobile receiving apparatus 10, the fixed receiving apparatus 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 demodulation unit 910 and outputs a symbol to which a processable transport stream among the two or more transport streams is allocated.

The reception processing unit 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 receiving apparatus according to an embodiment of the present invention.

10, the signal demodulation unit 910 of the OFDM receiving apparatus includes a signal converter 911, a GI removing unit 912, a DFT unit (Discrete Fourier Transform) 913, and a deinterleaver 914, The processing unit 930 includes a symbol demapping unit 931, a decoding unit 932, and a descrambler 933.

The signal demodulation unit 910 down-converts the signal received through the antenna, and converts the down-converted signal into a digital signal. The received signal includes high priority data HP and low priority data LP. In addition, the antenna calculates the ratio of the high-priority data HP and the low-order data LP allocated to the plurality of OFDM symbols in the transmitting apparatus 100 and the allocated position information, the coding scheme applied in the transmitting apparatus 100, , A modulation method, and the like.

The GI removal unit 912 removes the GI inserted in the OFDM symbol, which is a digital signal.

The DFT unit 913 performs discrete Fourier transform on the GI-removed OFDM symbol to convert the OFDM symbol in the time domain into the OFDM symbol in the frequency domain. An FFT (Fast Fourier Transform) method may be used instead of the DFT unit 913.

The deinterleaver 914 deinterleaves a plurality of OFDM symbols input from the DFT unit 913 and separates the OFDM symbols allocated with the high priority data HP and the low priority data LP in units of symbols or subcarriers Output.

When the transmitting apparatus 100 generates the OFDM symbol by allocating the high priority data HP and the low priority data LP on a symbol basis as shown in FIGS. 3A and 3B, the deinterleaver 914 outputs the OFDM symbol to the DFT unit 913 To the OFDM symbol.

3A and 3B, when the OFDM symbol is generated by allocating the high-priority data HP and the low-priority data LP on a subcarrier-by-subcarrier basis, the deinterleaver 914 outputs the high- Subcarrier deinterleaving is applied to a plurality of OFDM symbols input from the OFDM symbol input unit 913.

5, when the transmitting apparatus 100 mixes and allocates the high-order data HP and the low-order data LP on a symbol unit or a subcarrier unit basis, the deinterleaver 914 receives the high- Symbol deinterleaving and subcarrier deinterleaving are mixedly applied to a plurality of input OFDM symbols.

The demultiplexer 920 demultiplexes a plurality of OFDM symbols input from the deinterleaver 914 so as to allocate data that can be processed out of the high priority data HP and the low priority data LP included in the plurality of OFDM symbols Print the symbol. For example, when the receiving apparatus shown in FIG. 9 is the mobile receiving apparatus 10, the demux 920 may be a symbol assigned a high priority data HP among a plurality of OFDM symbols, First, a symbol having subcarriers allocated with data HP is output. When the receiving apparatus is the fixed receiving apparatus 20, the demux 920 may be configured to receive a symbol assigned low priority data LP among a plurality of OFDM symbols, or a symbol having a subcarrier allocated low priority data among a plurality of OFDM symbols .

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

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, Decoder 932d.

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

The outer deinterleaver 932c outer deinterleaves the transport stream input from the inner decoder 932b. The outer decoder 932d outer-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.

9 and 10 receives the OFDM signal including the high-priority data HP and the low-priority data LP and then performs the processing among the high-priority data HP and the low-priority data LP And selects the possible data from the demultiplexer 920 and provides it to the reception processor 930. However, when the transmitting apparatus 100 transmits the OFDM signal by the Burst Transmission Mode scheme, the transmitting apparatus 100 transmits information in which the high priority data HP and the low priority data LP are located, or the high priority data HP) and the low priority data (LP) are transmitted to the receiving apparatus in advance, the receiving apparatus can receive the processable data from the corresponding position in the OFDM signal based on the position information or the time information.

11 is a block diagram illustrating an OFDM receiving apparatus according to another preferred embodiment of the present invention.

11, the OFDM receiver includes a signal demodulator 1110, a demux 1120, and first to nth reception processors 1130-1 to 1130-n. The receiving apparatus shown in FIG. 11 is an example of a device that can receive and decode both high-priority data HP and low-priority data LP included in an OFDM signal.

The signal demodulation unit 1110 is similar to the signal demodulation unit 910 described with reference to FIG. 10, and thus a detailed description thereof will be omitted. The demux 1120 separates a plurality of OFDM symbols into a symbol corresponding to the high priority data HP and a symbol corresponding to the low priority data LP and transmits the symbols to the first reception processing unit 1130 and the second reception processing unit Time. The nth reception processing section 1130-n is a block for processing the medium priority data MP. Operations of the first to n < th > reception processing units 1130-1 to 1130-n are similar to those of the reception processing unit 930 described with reference to Fig. 10, and therefore 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, in which two streams TS1 and TS2 are received and high priority data and low priority data are generated hierarchically Will be described. However, the number of input transport streams may be two or more and may be the same or different contents.

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

The first and second scrambled 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 step 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 to transmit the first and second transport streams TS1 and TS2, Lt; / RTI >

The coded first and second transport streams TS1 and TS2 are symbol-mapped by the first and second symbol mapping units 123 and 133 to generate high priority data HP and low priority data LP S1230). In step S1230, the high-priority data HP and the low-priority data LP may be output in symbol form.

The high-priority data HP and the low-priority data LP generated in step S1230 are allocated on a symbol-by-symbol basis in the MUX 140 and are generated as a plurality of OFDM symbols as shown 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 the number of the OFDM symbols to which the low priority data is allocated in one transmission operation unit in consideration of the 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 low-order data is allocated in one transmission operation unit, considering the predefined area information.

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

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

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

The signal converter 154 converts the OFDM symbol input from the GI inserter 153 into an analog OFDM signal, and upconverts the analog OFDM signal to generate an RF signal (S1280). The generated RF signal includes high priority data HP and low priority data LP and is transmitted to the reception apparatuses 10 and 20 through the 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 FIG. 1, FIG. 2, FIG. 4A, FIG. 4B and FIG. 13, and two transmission streams TS1 and TS2 are received to hierarchically generate high- Will be described. However, the number of input transport streams may be two or more and may be the same or different contents. Since steps S1310 to S1380 are substantially the same as steps S1210 to S1280 described with reference to Fig. 12, 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 by the first and second symbol mapping units 123 and 133 to generate high priority data HP and low priority data LP S1330).

The generated high-priority data HP and low-order data LP are allocated in units of symbols or subcarriers in the mux 140 and are generated as a plurality of OFDM symbols as shown in FIG. 4A or 4B (S1340).

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

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

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

The signal converter 154 converts the OFDM symbol input from the GI inserter 153 into an analog OFDM signal, and upconverts the analog OFDM signal to generate an RF signal (S1380). The generated RF signal is transmitted to the receiving apparatuses 10 and 20 via 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 FIG. 1, FIG. 2, FIG. 5, and FIG. 14. In a case where high-priority data and low-priority data are hierarchically generated by receiving two transport streams TS1 and TS2 . Since steps S1410 to S1480 are substantially the same as steps S1210 to S1280 described with reference to Fig. 12, a detailed description 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 by the first and second symbol mapping units 123 and 133 to generate high priority data HP and low priority data LP S1430).

The generated high-priority data HP and low-priority data LP are allocated in units of muxes or subcarriers in the mux 140 and are generated as a plurality of OFDM symbols as shown in FIG. 5 (S1440).

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

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

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

The signal converter 154 converts the OFDM symbol input from the GI inserting unit 153 into an analog OFDM signal, and upconverts the analog OFDM signal to generate an RF signal (S1480). The generated RF signal is transmitted to the receiving apparatuses 10 and 20 via the antenna.

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

Hereinafter, an OFDM reception method will be described with reference to FIG. 1 to FIG. 10 and FIG. 15, and a case of generating a transport stream by receiving an OFDM signal including high-priority data and low-priority data will be described. The OFDM signal may further include a plurality of intermediate priority data MP, and the high priority data HP, the low priority data LP and the intermediate 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 converted into a digital signal (S1510).

The GI inserted in the OFDM symbol, which is a digital signal, is removed in the GI removal unit 912 (S1520).

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

The deinterleaver 914 deinterleaves the plurality of OFDM symbols input from the step S1530 (S1540) and outputs the OFDM symbols allocated with the high priority data HP and the low priority data LP separately on a symbol unit or a subcarrier basis (S1550). In step S1540, the deinterleaver 914 selectively uses symbol deinterleaving or subcarrier deinterleaving.

The demultiplexer 920 demultiplexes a plurality of OFDM symbols input from the deinterleaver 914 so as to allocate data that can be processed out of the high priority data HP and the low priority data LP included in the plurality of OFDM symbols And outputs a symbol (S1560).

The symbol demapping unit 931 demaps the symbol input from the demux 920 to generate a transport stream (S1570).

The decoding unit 930 decodes the transport stream input from step S1570 and performs 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 transmitting apparatus 100 generates OFDM symbols after allocating high-priority data HP and low-order data LP to different symbols or different sub-carriers, , The allocated rate can be changed in various ways depending on the operation mode. In other words, the transmission apparatus 100 can transmit data at a variable ratio instead of transmitting the transmission ratio between the high-priority data HP and the low-priority data LP at a limited ratio such as 1: 1 or 1: 2, Thereby improving the degree of freedom in the operation.

As described above, according to the OFDM transmitting and receiving apparatus and method of the present invention, symbol mapping between high-priority data and low-order data can be performed using various modulation schemes such as QPSK as well as QAM scheme in hierarchical transmission. Thus, the transmitting apparatus can improve the degree of freedom in system operation by generating OFDM symbols to which various modulation schemes are applied.

According to the present invention, an OFDM symbol is generated by allocating high-priority data and low-priority data on a symbol unit or a subcarrier unit, respectively. In this case, the ratio of allocating high-priority data and low- It is possible to adjust.

Further, according to the present invention, it is possible to generate and transmit high priority data, low priority data and medium priority data from three or more input transport streams. Accordingly, it is possible to generate and transmit data having a code rate according to the degree of poorness of the reception channel environment.

In addition, according to the present invention, a receiving apparatus extracts data suitable for a receiving channel environment from a hierarchical OFDM signal, thereby providing a more stable moving picture. In particular, in the case of a fixed reception environment having a good channel environment, the receiving apparatus can provide a high-resolution moving image by extracting low-priority data including more data from the OFDM signal. In case of a mobile receiving environment with poor channel environment, It is possible to provide a seamless service by extracting high-priority data having a low code rate from the OFDM signal.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be construed as limiting the scope of the invention as defined by the appended claims. It will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the present invention.

Claims (36)

  1. Considering at least one of a symbol rate and a different modulation scheme in consideration of a channel environment, allocates at least one of a symbol unit and a subcarrier unit based on ratio information on two or more transport streams processed and allocated area information A transmission processor for generating OFDM (Orthogonal Frequency Division Multiplexing) symbols; And
    And a signal converter for converting the generated OFDM symbol into an OFDM signal and transmitting the OFDM symbol to at least one receiver.
  2. The method according to claim 1,
    The transmission processing unit,
    A plurality of coding units for coding the two or more transport streams to perform error correction coding;
    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 modulated transmission streams to at least one of the symbol unit and the subcarrier unit.
  3. 3. The method according to claim 1 or 2,
    Wherein the transmission processing unit allocates one of the two or more transport streams for each of a plurality of subcarriers constituting the at least one OFDM symbol so that the at least one OFDM symbol includes the two or more transport streams. .
  4. 3. The method according to claim 1 or 2,
    Wherein the transmission processing unit 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 To the digital broadcast transmission apparatus.
  5. 3. The method according to claim 1 or 2,
    Wherein the ratio information in which the two or more transport streams are allocated is defined by the at least one receiver and the at least one receiver, and is transmitted to the at least one receiver.
  6. 3. The method according to claim 1 or 2,
    Wherein the area information to which the at least two transport streams are allocated is defined by the at least one receiver and the at least one receiver.
  7. 3. The method according to claim 1 or 2,
    Wherein the transmission processing unit adjusts a transmission ratio of the two transport streams by adjusting a ratio in which the at least two transport streams are allocated and a region to be allocated for each transmission operation unit including a predetermined number of OFDM symbols, Device.
  8. 8. The method of claim 7,
    Wherein the coding information, the modulation scheme information, the allocated ratio information, and the allocated region information used in the transmission processing unit are transmitted for each transmission operation unit.
  9. 3. The method of claim 2,
    The coding unit includes:
    And coding the two or more transport streams using respective independent coding rates according to a reception channel environment.
  10. 10. The method of claim 9,
    Wherein the coding unit codes data for a mobile receiver among the two or more transport streams at a low coding rate and codes data for a fixed receiver at a higher coding rate than the low coding rate.
  11. 3. The method of claim 2,
    Wherein the modulating unit performs modulation using one of PSK, Quadrature Phase Shift Keying (QPSK), 16QAM (Quadrature Amplitude Modulation), 64QAM, 128QAM and 256QAM.
  12. The method according to claim 1,
    Wherein the signal converter interleaves the generated OFDM symbol using one of a symbol interleaving scheme and a subcarrier interleaving scheme.
  13. Considering at least one of a symbol rate and a different modulation scheme in consideration of a channel environment, allocates at least one of a symbol unit and a subcarrier unit based on ratio information on two or more transport streams processed and allocated area information Generating an Orthogonal Frequency Division Multiplexing (OFDM) symbol; And
    And converting the generated OFDM symbol into an OFDM signal and transmitting the OFDM symbol to at least one receiver.
  14. 14. The method of claim 13,
    Wherein the generating comprises:
    Performing error correcting coding by coding the two or more transport streams;
    Modulating the coded two or more transport streams; And
    And generating the OFDM symbol by allocating each of the modulated transmission streams to at least one of the symbol unit and the subcarrier unit.
  15. The method according to claim 13 or 14,
    Wherein the generating step allocates one of the two or more transport streams for each of a plurality of subcarriers constituting the at least one OFDM symbol so that the at least one OFDM symbol includes the at least two transport streams. Way.
  16. The method according to claim 13 or 14,
    Wherein the generating step allocates one of the two or more transport streams for 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,
    Wherein the ratio information in which the two or more transport streams are allocated is defined by the at least one receiver and the mutual protocol, and is transmitted to the at least one receiver.
  18. The method according to claim 13 or 14,
    Wherein the area information of the OFDM symbol to which the two or more transport streams are allocated is multiplexed together with the two or more transport streams and transmitted.
  19. The method according to claim 13 or 14,
    Wherein the generating step adjusts a ratio of the at least two transport streams to be allocated and an allocated area for each transmission operation unit including a predetermined number of OFDM symbols.
  20. 20. The method of claim 19,
    Wherein the coding information, the modulation scheme information, the allocated ratio information, and the allocated area information used in the generating step are transmitted for each transmission operation unit.
  21. 15. The method of claim 14,
    Wherein the performing comprises:
    Wherein the at least two transport streams are coded using respective coding rates according to a reception channel environment.
  22. 22. The method of claim 21,
    Wherein the step of coding comprises coding the data for the mobile receiver of the two or more transport streams at a low coding rate and coding the data for the fixed receiver at a higher coding rate than the low coding rate. Way.
  23. 15. The method of claim 14,
    Wherein the step of performing the modulation is performed using one of PSK, Quadrature Phase Shift Keying (QPSK), 16QAM (Quadrature Amplitude Modulation), 64QAM, 128QAM and 256QAM.
  24. 14. The method of claim 13,
    Wherein the generating comprises interleaving the generated OFDM symbols using one of a symbol interleaving scheme and a sub-carrier interleaving scheme.
  25. A signal demodulator for demodulating an OFDM signal received from a transmitter and generating a plurality of OFDM symbols allocated to at least one of a symbol unit and a subcarrier unit on the basis of ratio information in which two or more transport streams are allocated and allocated area information;
    A demultiplexer for demultiplexing the generated OFDM symbols and outputting a symbol to which a processable transport stream among the two or more transport streams is allocated; And
    And a reception processor for performing error correction on a symbol input from the demultiplexer,
    Wherein the at least two transport streams are processed using at least one of different coding rates and different modulation schemes in consideration of a channel environment.
  26. 26. The method of claim 25,
    Wherein the signal demodulating unit comprises:
    Wherein the plurality of OFDM symbols are generated by applying one of a symbol deinterleaving method and a subcarrier deinterleaving method to the OFDM signal to be demodulated.
  27. 26. 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 decoding the generated transport stream to perform error correction.
  28. 26. The method of claim 25,
    Wherein the demultiplexer outputs the symbols using the allocated ratio information and the in-symbol region information on a symbol unit and a sub-carrier unit basis by the two or more transport streams provided from the transmitter.
  29. 26. The method of claim 25,
    Wherein the at least two transport streams are coded at the different coding rates according to a reception channel environment in the transmitter.
  30. 30. The method of claim 29,
    Wherein the demultiplexer selects and outputs at least one of the two or more transport streams.
  31. Demodulating an OFDM signal received from a transmitter and generating a plurality of OFDM symbols allocated to at least one of a symbol unit and a subcarrier unit on the basis of ratio information and allocated area information in which two or more transport streams are allocated;
    Demultiplexing the generated plurality of OFDM symbols and outputting a symbol to which a processable transport stream among the two or more transport streams is allocated; And
    And performing error correction on a symbol input from the demultiplexer,
    Wherein the at least two transport streams are processed using at least one of different coding rates and different modulation schemes in consideration of a channel environment.
  32. 32. The method of claim 31,
    Wherein the generating comprises:
    Wherein the plurality of OFDM symbols are generated by applying one of a symbol deinterleaving method and a subcarrier deinterleaving method to the OFDM signal to be demodulated.
  33. 32. The method of claim 31,
    Wherein the performing comprises:
    Demodulating the output symbol to generate a transport stream; And
    And decoding the generated transport stream to perform error correction.
  34. 32. The method of claim 31,
    Wherein the outputting step comprises:
    Wherein the at least two transport streams provided from the transmitter output the symbol using the allocated ratio information and the in-symbol region information on a symbol unit and a sub-carrier unit basis.
  35. 32. The method of claim 31,
    Wherein the at least two transport streams are coded at the different coding rates according to a reception channel environment in the transmitter.
  36. 36. The method of claim 35,
    Wherein the outputting step comprises:
    Wherein at least one of a symbol assigned a transport stream coded with a low coding rate and a symbol assigned a transport stream coded with a high coding rate among the two or more transport streams is selected and output.
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20030021258A (en) * 2000-07-12 2003-03-12 퀄컴 인코포레이티드 Multiplexing of real time services and non-real time services for ofdm systems
JP2005136471A (en) * 2003-10-28 2005-05-26 Casio Comput Co Ltd Ofdm receiver using diversity, ofdm reception circuit using diversity, and ofdm reception method using diversity
KR20060097114A (en) * 2003-10-01 2006-09-13 코닌클리즈케 필립스 일렉트로닉스 엔.브이. Multi-carrier ofdm uwb communications systems

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20030021258A (en) * 2000-07-12 2003-03-12 퀄컴 인코포레이티드 Multiplexing of real time services and non-real time services for ofdm systems
KR20060097114A (en) * 2003-10-01 2006-09-13 코닌클리즈케 필립스 일렉트로닉스 엔.브이. Multi-carrier ofdm uwb communications systems
JP2005136471A (en) * 2003-10-28 2005-05-26 Casio Comput Co Ltd Ofdm receiver using diversity, ofdm reception circuit using diversity, and ofdm reception method using diversity

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