KR100695068B1 - Transmission device of simple digital broadcasting system and its transmission method - Google Patents

Abstract

A transmission apparatus of a digital broadcasting system according to the present invention includes an RS encoder for RS-Reed-Solomon encoding on an input TS stream, an external interleaver for rearranging data encoded by the RS encoder, and an external interleaver. A convolutional encoder for convolutionally encoding the rearranged data, a bit interleaver for rearranging the data encoded by the convolutional encoder in bit units, and an interleaver for rearranging the data rearranged by the bit interleaver in symbol units And an internal interleaver, and a modulator for digitally modulating the data rearranged from the internal interleaver, wherein the symbol interleaver is configured to convert the data rearranged by the bit interleaver when the FFT mode of the modulator is smaller than the N mode (N is a natural number). After loading so as to be rearranged by symbol unit. Here, the FFT mode is any one of the 2K mode, the 4K mode, and the 8K mode, and the N mode is the 8K mode. As a result, the digital broadcasting system does not need to change the configuration of the system according to the FFT mode, thereby simplifying the design of the system.

Digital Broadcasting System, FFT Mode, OFDM, Interleaver

Description

Apparatus and method for transmission of digital broadcasting system having simple design}

1 is a block diagram schematically showing a transmission apparatus of a general digital broadcasting system;

FIG. 2 is a view illustrating an operation of a symbol interleaver according to the FFT mode of FIG. 1;

3 is a block diagram schematically showing a transmission apparatus of a digital broadcasting system according to the present invention;

4 is a flowchart illustrating a transmission method according to FIG. 3, and

FIG. 5 is a diagram illustrating an operation of a symbol interleaver according to the FFT mode of FIG. 3.

Explanation of symbols on the main parts of the drawings

10, 100: scrambler 20, 200: FEC

21, 210: external encoder 23, 230: external interleaver

25, 250: internal encoder 27, 270: internal interleaver

27a, 271: bit interleaver 27b, 273: symbol interleaver

275 memory 277 controller                 

30, 300: modulator 33, 330: mapping / OFDM modulator

35, 350: Protection section insertion section 37, 370: D / A conversion section

39, 390: RF section

The present invention relates to a transmission apparatus and a transmission method of a digital broadcasting system, and more particularly, to a transmission apparatus and a transmission method of a digital broadcasting system that can not only simplify the design but also improve the performance of interleaving.

Digital broadcasting, unlike analog broadcasting, has the advantage of system integration and interoperability through digital code system. Accordingly, digital broadcasting has a condition that can be the core of so-called media convergence using a computer and a network, and it is an opportunity to change the analog broadcasting area that has been unilateral and downward with an interactive function.

In order to ensure the integration and interoperability of digital broadcasting, standardization must precede. In the case of a transmission method for digital terrestrial digital television (DTV) broadcasting, a US method using 8-VSB (Vestigial Side Band) and a European method based on Coded Orthogonal Frequency Multiplexing (COFDM) have been proposed. In addition, Terrestrial Digital Multimedia Television Broadcasting (DMB-T) based on Time-Domain Synchronous Orthogonal Frequency Devision Multiplexing (TDS-OFDM), ADTB-T (Advanced Digital Television Broadcast-Terrestrial) with improved VSB, and SMCC (COFDM) Various transmission methods such as synchronized multi-carrier CDMA (CDMA), other CDTB-T (Chinese Digital Television Broadcasting-Terrestrial), and BDB-T have been proposed.

When transmitting digital broadcasting, it is necessary to compress and transmit a signal source to transmit a huge amount of data, so even a small error occurring in a channel has a great effect on the whole system. Therefore, it is necessary to reduce the error in the channel. To reduce the error, increase the power to increase the signal-to-noise ratio (SNR) .However, if the power is increased, problems such as loss of power, cost increase due to high output of the transmission device, and interference between channels are caused. Will occur. To overcome this problem, digital broadcasting systems use error correction codes to correct errors occurring in channels without increasing power. The error correcting code can correct an error occurring in a channel without increasing power, thereby reducing the probability of an error occurring in a receiver.

The error correction code can be largely divided into ARQ (Automatic Repeat Request) and FEC (Forward Error Correction). ARQ is a method in which the transmitting side retransmits data when an error is detected at the receiving side, when the transmitting side sends a signal to transmit the data again. This method is not suitable for digital broadcasting systems because the receiver needs a return channel that can send a signal to the transmitter to retransmit. On the other hand, FEC attaches an additional symbol to a signal and transmits it, and when an error occurs in a channel, the receiver uses algebraic properties to detect or correct a channel error.

FEC can be roughly divided into a block code and a convolution code. The block code is encoded and decoded by dividing the information into blocks, and includes a Hamming code, a BCH code, and a Reed Solomon (RS) code. Among them, RS codes are most commonly used in digital broadcasting systems because of their excellent distance characteristics and efficient encoding and decoding algorithms. Since RS codes detect and correct errors on a block basis, the ability to correct burst errors is excellent.

In contrast, a convolution code is a code whose output bit is affected not only by the current input bit but also by the past input bit, and is effective for correcting a random error. Since most decoders use a Viterbi decoder, a convolutional code is also called a Viterbi code.

1 is a block diagram schematically illustrating a transmission apparatus of a general digital broadcasting system. Referring to the drawings, a transmission apparatus of a digital broadcasting system includes a scrambler 10, a forward error correction (FEC) unit 20, and a modulator 30. Here, the FEC unit 20 includes an outer encoder 21, an outer interleaver 23, an inner encoder 25, and an inner interleaver 27. do. The internal interleaver 27 also includes a bit interleaver 27a and a symbol interleaver 27b. The modulator 30 includes a mapping / OFDM modulator 33, a guard interval insertion unit 35, a D / A converter 37, and an RF unit 39.                         

The scrambler 10 randomizes each data value of an input TS (Transport Stream) according to a predetermined pattern. This process is reversed in the receiver to restore the original value.

The FEC unit 20 encodes data input through the scrambler 10 to correct an error that may occur during transmission. That is, the external encoder 21 receives data passed through the scrambler 10 and performs encoding in block units to enable error correction. In general, the external encoder 21 performs RS encoding by using a Reed-Solomon encoder. By RS coding, a parity (check symbol) for error correction is added, and the size of the added parity varies depending on the transmission scheme. For example, in the case of the DVB-T system, 16 parities are added per TS stream of 188 bytes, and the error correction coded total bytes are 204 bytes.

The external interleaver 23 performs a function of distributing the coherence error that may occur by rearranging the data encoded in units of blocks in the external encoder 21. The internal encoder 25 generally uses a convolutional encoder, and convolutionally encodes data that is rearranged and output from the external interleaver 23. In the DVB-T scheme, it is common to use a convolutional code having a constraint length of 7 and a code rate of 1/2. Data convolutionally encoded by the internal encoder 25 is rearranged and output again by the internal interleaver 27. At this time, the bit interleaver 27a rearranges the convolutional coded data in bit units, and the symbol interleaver 27b in the symbol unit carried on the OFDM subcarrier the data rearranged in bit units by the bit interleaver 27a. Rearrange                         

The modulator 30 performs appropriate digital modulation on the data encoded and output by the FEC unit 20 according to the transmission method of the digital broadcasting system. The mapping / OFDM modulator 33 maps and IFFTs the data output from the internal interleaver 27 into symbols such as Quadrature Phase Shift Keying (QPSK), Quadrature Amplitude Modulation (16-QAM), 64-QAM, and the like. OFDM modulation such as (Inverse Fast Fourier Transform) is performed. The guard interval inserting part 35 inserts a guard interval to prevent inter symbol interference (ISI) in a multipath environment. In addition, the D / A converter 37 performs a D / A (Digital to Analog) conversion on the signal into which the protection interval is inserted, and the RF unit 39 amplifies the antenna by performing high frequency amplification on the D / A converted signal. Send it through.

However, the symbol interleaver 27b provided in the internal interleaver 27 of the general digital broadcasting system transmitter uses different interleaving methods depending on the system using the data received from the internal encoder 25. That is, the symbol interleaver 27b generates different interleaving addresses according to the FFT mode of the system used, and rearranges the data in units of bits based on the generated interleaving addresses.

FIG. 2 is a diagram illustrating an operation of a symbol interleaver according to the FFT mode of FIG. 1. Referring to the drawings, the symbol interleaver 27b in the 2K FFT mode system should generate an interleaving address with a value between 0 and N (where N is the number of valid symbols) corresponding to the 2K mode. The symbol interleaver 27b must generate an interleaving address with a value between 0 and 2N in response to the 4K mode. In addition, the symbol interleaver 27b in the 8K FFT mode system must generate an interleaving address with a value between 0 and 4N corresponding to the 8K mode. For example, the DVB-T digital broadcasting system uses only the 2K FFT mode and the 8K FFT mode. In each case, a different interleaving address generator (not shown) is used. That is, the interleaving address generators are different for the two modes. Therefore, the digital broadcasting system requires a different design according to the FFT mode. This becomes a factor that complicates the design of the receiver as well as the transmitter of the digital broadcasting system. In particular, when the symbol interleaver generates an interleaving address using the lookup table, the symbol interleaver must have a different lookup table for each FFT mode, which makes the design of the digital broadcasting system more complicated.

In addition, when the FFT mode is a small number of FFT modes such as 2K and 4K, the number of symbols of valid data is small, so the interleaving effect is also smaller than that of 8K. Therefore, when the FFT modes are 2K and 4K, the interleaving performance may be lower than when the FFT mode is 8K.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a transmission apparatus and a transmission method of a digital broadcasting system that can not only simplify the design but also improve the performance of interleaving.

A transmission apparatus of a digital broadcasting system according to the present invention for achieving the above object, an RS encoder for RS (Reed-Solomon) coding for the input TS stream (transport stream), the data encoded by the RS encoder is grown An external interleaver to concatenate, a convolutional encoder convolutionally encoding the data rearranged by the external interleaver, a bit interleaver for rearranging the data encoded by the convolutional encoder in units of bits, and the data rearranged by the bit interleaver And an internal interleaver having an interleaver to rearrange the symbols in units of symbols, and a modulator for digitally modulating the data rearranged from the internal interleaver. Here, the symbol interleaver loads the data rearranged by the bit interleaver to be the N mode when the FFT mode of the modulator is smaller than the N mode (N is a natural number), and then rearranges the data in units of symbols. . The FFT mode is any one of 2K mode, 4K mode, and 8K mode, and the N mode is 8K mode.

Preferably, the transmission apparatus of the digital broadcasting system includes a memory for loading the data encoded by the bit interleaver when the FFT mode of the modulator is smaller than an N mode (N is a natural number), and And a controller for retrieving the data and controlling the symbol interleaver to rearrange the loaded data in units of symbols when the loaded data is equal to the N mode.

On the other hand, in the transmission apparatus of the digital broadcasting system according to the present invention, a step of RS (Reed-Solomon) encoding for the input TS stream (transport stream), the step of convolutional coding the data rearranged by the RS encoding step Rearranging the data encoded by the convolution encoding step by bit, rearranging the data rearranged by the bit unit rearrangement by symbol unit, and rearranging the data by symbol unit Wherein the symbol unit rearrangement step comprises: reordering the data rearranged by the bit unit rearrangement step when the FFT mode of the modulation step is smaller than the N mode (N is a natural number). Provided is a transmission method of a digital broadcasting system, comprising the step of loading a mode.

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

3 is a block diagram schematically showing a transmission apparatus of a digital broadcasting system according to the present invention. Referring to the drawings, a transmission apparatus of a digital broadcasting system includes a scrambler 100, an FEC unit 200, and a modulator 300. Here, the FEC unit 200 includes an external encoder 210, an external interleaver 230, an internal encoder 250, and an internal interleaver 270. The internal interleaver 270 includes a bit interleaver 271, a symbol interleaver 273, a memory 275, and a controller 277. The modulator 300 includes a mapping / OFDM modulator 330, a guard interval insertion unit 350, a D / A converter 370, and an RF unit 390.

4 is a flowchart illustrating a transmission method according to FIG. 3. With reference to the drawings will be described in more detail the operation of the transmission device of the digital broadcasting system according to the present invention.

The scrambler 100 randomizes the data values of the input TSs according to a predetermined pattern (S100). This process is reversed in the receiver to restore the original value.

The FEC unit 200 performs encoding for correcting an error that may occur during transmission on data input through the scrambler 100. That is, the external encoder 210 receives data passing through the scrambler 100 and performs encoding in block units to enable error correction. In general, the external encoder 210 performs RS encoding using an RS encoder (Reed-Solomon encoder) (S200). By RS coding, a parity (check symbol) for error correction is added, and the size of the added parity varies depending on the transmission scheme. For example, in the case of the DVB-T system, 16 parities are added per TS stream of 188 bytes, and the error correction coded total bytes are 204 bytes.

The external interleaver 230 performs a function of distributing the coherence error that may occur by rearranging the data encoded in the block unit in the external encoder 210 (S300). The internal encoder 250 generally uses a convolutional encoder, and convolutionally encodes the data rearranged from the external interleaver 230 (S400). In the DVB-T scheme, it is common to use a convolutional code having a constraint length of 7 and a code rate of 1/2. Data convolutionally encoded by the internal encoder 250 is rearranged and output again by the internal interleaver 270. At this time, the bit interleaver 271 rearranges the convolutional coded data in units of bits (S500), and the symbol interleaver 273 uses the bit interleaver 271 when the FFT mode of the digital broadcasting system is smaller than the N mode. The rearranged data is loaded into the memory 275 until it becomes the N mode. Here, the FFT mode is any one of the 2K mode, the 4K mode, and the 8K mode, and the N mode is the 8K mode. Therefore, when the FFT mode of the digital broadcasting system is smaller than the 8K mode (S600), the data rearranged by the bit interleaver 271 is loaded into the memory 275 until it has the same size as the 8K mode (S700).

The controller 277 retrieves the data loaded in the memory 277 and controls the symbol interleaver 273 to rearrange the loaded data in symbol units when the loaded data becomes the same size as the 8K mode. When the data loaded in the memory 275 becomes the same size as that of the 8K mode, the symbol interleaver 273 rearranges the data loaded in the memory 275 in symbol units carried on the OFDM subcarrier under the control of the controller 277. (S900).

FIG. 5 is a diagram illustrating an operation of a symbol interleaver according to the FFT mode of FIG. 3. As described above, when the FFT mode of the digital broadcasting system is smaller than the 8K mode, for example, when the FFT mode is the 2K mode, the data rearranged by the bit interleaver 271 may be stored in memory until the same size as that of the 8K mode. 275). That is, in this case, the data loaded in the memory 275 is rearranged by the symbol interleaver 273 by subcarrier symbol units after four OFDM symbols in the 2K mode are loaded. In the same manner, when the FFT mode is the 4K mode, the data loaded in the memory 275 is rearranged by the symbol interleaver 273 by subcarrier symbol units after two OFDM symbols in the 4K mode are loaded. In addition, when the FFT mode is 8K mode, the symbol interleaver 273 is rearranged in the subcarrier symbol unit immediately without loading the memory 275. As a result, since the symbol interleaver 273 does not need to be configured differently according to the FFT mode of the digital broadcasting system, only an 8K interleaving address generator is provided, thereby simplifying the design of the digital broadcasting system.

The modulator 300 performs digital modulation suitable for the transmission method of the digital broadcasting system on the data encoded and output by the FEC unit 200. The mapping / OFDM modulator 330 maps and IFFTs the data output from the internal interleaver 270 to symbols such as Quadrature Phase Shift Keying (QPSK), Quadrature Amplitude Modulation (Q-QAM), 64-QAM, and the like. OFDM modulation such as (Inverse Fast Fourier Transform) is performed. The guard interval inserting unit 350 inserts a guard interval to prevent inter symbol interference (ISI) in a multipath environment. In addition, the D / A converter 370 performs a D / A (Digital to Analog) conversion on the signal into which the protection interval is inserted, and the RF unit 390 amplifies the antenna by applying high frequency amplification to the D / A converted signal. Send it through.

The transmission apparatus of the digital broadcasting system according to the present invention does not need to change the configuration of the system according to the FFT mode, and only the 8K mode interleaving address generator is provided, thereby simplifying the system design.

In addition, since the transmission apparatus of the digital broadcasting system according to the present invention may have a time interleaving effect when interframe interleaving is performed by collecting several FFT frames, subcarriers such as 2K and 4K. It is possible to improve the performance of interleaving for a small number of FFT modes.

According to the present invention, since the digital broadcasting system does not need to change the configuration of the system according to the FFT mode, the design of the system is simplified.

Although the preferred embodiments of the present invention have been illustrated and described above, the present invention is not limited to the specific embodiments described above, and the present invention is not limited to the specific embodiments of the present invention without departing from the spirit of the present invention as claimed in the claims. Anyone of ordinary skill in the art can make various modifications, and such changes are within the scope of the claims.

Claims (7)

An RS encoder for re-solomon (RS) encoding the input transmission signal; An external interleaver for rearranging data encoded by the RS encoder; A convolution encoder for convolutionally encoding data rearranged by the external interleaver; An internal interleaver having a bit interleaver for rearranging the data encoded by the convolutional encoder in units of bits and a symbol interleaver for rearranging the data rearranged by the bit interleaver in units of symbols; And And a modulator for digitally modulating the rearranged data from the internal interleaver. The symbol interleaver rearranges the data rearranged by the bit interleaver in units of symbols when the inverse Fourier transform mode of the modulator is N mode (N is a natural number), and the inverse Fourier transform mode is smaller than the N mode. And if it is small, reload the data rearranged by the bit interleaver to be in the N mode and rearrange the data by the symbol unit. The method of claim 1, The inverse Fourier transform mode is any one of a 2K mode, a 4K mode, and an 8K mode, and the N mode is an 8K mode. The method of claim 2, And a memory for loading the data encoded by the bit interleaver if the inverse Fourier transform mode of the modulator is smaller than the N mode (N is a natural number). The method of claim 3, And a controller for retrieving the data loaded in the memory, and controlling the symbol interleaver to rearrange the loaded data in units of symbols when the loaded data becomes equal to the N mode. Transmission apparatus of digital broadcasting system. RS (Reed-Solomon) encoding for the input transmission signal; Rearranging the data encoded by the RS encoding step; Convolutionally encoding the data rearranged by the rearrangement step; Rearranging the data encoded by the convolutional encoding step by bit; Rearranging the data rearranged by the bit unit rearrangement by symbol unit; And And digitally modulating the rearranged data in symbol units. The symbol unit rearrangement step rearranges the data rearranged by the bit unit rearrangement step in symbol units when the inverse Fourier transform mode of the modulation step is N mode (N is a natural number), and the inverse Fourier transform. And if the mode is smaller than the N mode, loading the data rearranged by the bit unit rearrangement so as to be the N mode, and rearranging the loaded data in symbol units. Transmission method of broadcasting system. The method of claim 5, The inverse Fourier transform mode is any one of a 2K mode, a 4K mode, and an 8K mode, and the N mode is an 8K mode. The method of claim 6, Retrieving the loaded data; And And rearranging the loaded data by the symbol unit when the loaded data is equal to the N mode.

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