KR20040104238A - Receiving apparatus for digital broadcasting system and method of using the same - Google Patents

Abstract

PURPOSE: A receiving device for a digital broadcasting system and a receiving method therefor are provided to receive a signal received after performing error correction coding by multi-stage and perform the error correction decoding of the received signal by the multi-stage. CONSTITUTION: A demodulating unit(500) receives a digitally modulated signal, and demodulates the received signal. An inner deinterleaver(605) deinterleaves data outputted from the demodulating unit. An inner decoder(610) decodes data outputted from the inner deinterleaver, and outputs the decoded data. An outer deinterleaver(620) deinterleaves the data outputted from the inner decoder. The first decoder decodes data outputted from the outer deinterleaver, and outputs the error-correction-decoded data. A block deinterleaver rearranges data outputted from the first decoder. The second decoder decodes data outputted from the block deinterleaver, and outputs the error-correction-decoded data.

Description

Receiving apparatus for digital broadcasting system and method of using the same}

The present invention relates to a receiving apparatus and a receiving method of a digital broadcasting system, and more particularly, to a receiving apparatus and a receiving method of a digital broadcasting system having a wide range of error correction by performing multiple stages of error correction decoding on a received signal. It is about.

Digital broadcasting, unlike analog broadcasting, has the advantage of system integration and interoperability through digital coding 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 digital terrestrial DTV (Digital Television) broadcasting system, there are standards such as American Advanced Television System Committee (ATSC) and European Digital Video Broadcasting-Terrestrial (DVB-T). ATSC employs 8-VSB (Vestigial Side Band) modulation and DVB-T uses OFDM (Orthogonal Frequency Division Multiplexing) modulation.

On the other hand, when transmitting digital broadcasting, it is necessary to compress and transmit a signal source in order to transmit a huge amount of data, so even a small error occurring in a channel has a great effect on the entire system. Accordingly, the error correction code is used in the digital broadcasting system to correct the error. In general, the error correction code used in digital broadcasting system is forward error correction (FEC), which is transmitted by adding additional symbols to the signal, and when an error occurs in the channel, the receiver detects a channel error by using algebraic properties. Or correct.

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. RS codes are most commonly used in digital broadcasting systems because of their excellent distance characteristics and efficient encoding and decoding algorithms. In addition, since the RS code detects and corrects errors on a block-by-block basis, the RS code has an excellent ability to correct burst errors. 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.

1 is a block diagram illustrating an example of a transmission apparatus of a general digital broadcasting system. Referring to the drawings, a transmission apparatus of a digital broadcasting system includes a scrambler 100, an FEC unit 200, and a modulator 30. The FEC unit 200 includes an RS encoder 210, an outer interleaver 220, a convolutional encoder 230, and an inner interleaver 240. The modulation unit 400 includes a mapping unit 410, an IFFT unit 420, a guard interval insertion unit 430, a synchronization information insertion unit 440, a shaping filter unit 450, and an RF unit 460. It includes.

The scrambler 100 randomizes each byte value of an input TS stream of an MPEG-2 format according to a predetermined pattern.

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 RS encoder (Reed-Solomon encoder) 210 receives the data passed through the scrambler 100 and performs RS coding in units of blocks for error correction. By RS coding, a parity for error correction is added, and the number of parities added varies depending on the transmission scheme.

The external interleaver 220 rearranges the data encoded in units of blocks in the RS encoder 210 to distribute a possible converging error. The convolutional encoder 230 convolutionally encodes the data rearranged in units of blocks from the external interleaver 220, and the convolutionally encoded bits are rearranged and output again by the internal interleaver 240.

The modulator 400 performs digital modulation suitable for the transmission method of the digital broadcasting system on the data encoded and output by the FEC unit 200. In the case of FIG. 1, the modulation unit 400 uses an OFDM modulation scheme. In this case, the mapping unit 410 maps the data output from the FEC unit 200 to symbols such as Quadrature Phase Shift Keying (QPSK), Quadrature Amplitude (QAM), 64-QAM, and the like. . An inverse fast fourier transform (IFFT) unit 420 performs an inverse fast Fourier transform of a signal in the frequency domain into a signal in the time domain. The guard interval inserter 430 inserts a guard interval to prevent inter symbol interference (ISI) in a multipath environment, and the sync information inserter 440 receives sync information for time synchronization acquisition and channel equalization at a receiver. Insert it. The shaping filter 450 performs shaping filtering on the symbol on which the synchronization information is applied, and the RF section 460 amplifies the shaping filtered symbol and transmits it through the antenna.

As described above, in a transmission apparatus of a conventional digital broadcasting system, a serial connection code using an RS encoder 210 as an outer encoder and a convolution encoder 230 as an inner encoder. I use a lot of concatenated code systems. However, even if the error correction encoding is performed using the serial connection code method, if an error occurs outside the correction range of the RS decoder used as an external decoder in the receiver, the error cannot be corrected. That is, the correction range of the RS decoder is related to the number of parities added during RS encoding, and there is a problem that the corresponding stream data is discarded because an error exceeding the correction range cannot be corrected.

Therefore, an error correcting and encoding function for correcting an error even when an error occurs outside the RS decoder's correction range is required for a transmission apparatus of a digital broadcasting system. In accordance with such a necessity, the present applicant has filed a patent for a 'transmission apparatus and transmission method of a digital broadcasting system' of Korean application No. 2002-61997.

Hereinafter, the present invention will be described in detail with reference to FIGS. 2 to 4 a transmission apparatus and a transmission method of a digital broadcasting system. In addition, the same parts as those shown in Fig. 1 will be referred to by the same reference numerals.

2 and 3 are block diagrams of a transmission apparatus of a digital broadcasting system filed by the present applicant. Referring to the drawings, a transmission apparatus of a previously-applied digital broadcasting system includes a scrambler 100, an FEC unit 300, and a modulator 400. The FEC unit 200 includes a multi-stage error correcting code generation unit 320, an external interleaver 320, a convolutional encoder 330, and an internal interleaver 340. The modulation unit 400 includes a mapping unit 410, an IFFT unit 420, a guard section insertion unit 430, a synchronization information insertion unit 440, a shaping filter unit 450, and an RF unit 460. do. As shown in FIG. 3, the multi-stage error correction encoder 310 includes a first RS encoder 311, a block interleaver 313, and a second RS encoder 315. That is, the transmission apparatus of the illustrated digital broadcasting system differs only in the configuration of the digital broadcasting system shown in FIG. 1 from the FEC unit 300, and the other configurations are the same.

In the transmission apparatus of the digital broadcasting system having such a configuration, the scrambler 100 randomizes each byte value of the input TS-2 (transport stream) signal of the MPEG-2 format according to a predetermined pattern.

The multi-stage error correcting code generation unit 210 of the FEC unit 300 performs coding for error correction that may occur during transmission on data input through the scrambler 100. That is, the first RS encoder 311 performs RS encoding on a block-by-block basis for error correction on the scrambled data passing through the scrambler 100. The block interleaver 313 performs block interleaving to rearrange the data encoded in the unit of blocks by the first RS encoder 311. Although the block interleaver 313 rearranges data, there are various methods. However, the most basic method is a method in which input bits are output in units of columns when the input bits are input in units of rows of a matrix. The second RS encoder 315 performs RS encoding to enable error correction on data interleaved and output from the block interleaver 313.

4 shows the data format after passing through the first RS encoder 311 and the second RS encoder 315. In FIG. 4, Po denotes parity added by the first RS encoder 311 and Pi denotes parity added by the second RS encoder 315. Pp represents parity for Po. In FIG. 4, 8 Po parities are added per 47 symbols and 20 Pi parities are added per 188 symbols.

The external interleaver 320 performs interleaving to rearrange the data output from the second RS encoder 315 in units of bytes, thereby distributing the coherence error that may occur in the channel. The convolutional encoder 330 convolutionally encodes data output from the external interleaver 320. The internal interleaver 340 interleaves the data encoded by the convolutional encoder 330 bit by bit to improve performance degradation due to multipath in the channel.

The modulator 400 performs appropriate digital modulation according to the transmission method of the digital broadcasting system on the data encoded and output by the FEC unit 300 by the process described with reference to FIG. 1. By this process, a multilevel error correction coded signal is transmitted to the receiving device.

By the way, the signal transmitted by multi-level error correction encoding in the transmission device of the digital broadcasting system can be accurately corrected only in the reception device having the corresponding structure. Accordingly, there is a need for a receiver of a digital broadcasting system capable of receiving a signal transmitted by multistage error correction encoding and performing multistage error correction decoding corresponding thereto.

The present invention has been made to solve the above problems, and an object of the present invention is to receive a signal transmitted by error correction coding in multiple stages, and to receive a digital broadcasting system capable of error correction decoding in multiple stages corresponding thereto. An apparatus and a method of receiving the same are provided.

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

2 is a block diagram of a transmission apparatus of a digital broadcasting system having a multi-stage error correcting code generation unit;

3 is a detailed block diagram of the multi-stage error correcting code generation unit of FIG. 2;

4 is a diagram for describing a data format generated by a multi-stage error correcting code generation unit;

5 is a block diagram of a receiving apparatus of a digital broadcasting system according to the present invention;

6 is a detailed block diagram of the multi-stage error correction decoder of FIG. 5;

7 is a flowchart provided to explain an operation method for a receiving apparatus of a digital broadcasting system according to the present invention;

8A and 8B are diagrams for describing a method of operating a multi-stage error correction decoder.

Explanation of symbols on the main parts of the drawings

500: demodulation section 510: tuner / IF section

520: A / D converter 530: demodulation / synchronization unit

540: lighting unit 550: FFT unit

600: FEC part 605: internal deinterleaver

610: internal decoder 620: external deinterleaver

630: multi-stage error correction decoder 631: first RS decoder

633: block deinterleaver 635: second RS decoder

650 descrambler

In order to achieve the above object, a receiver of a digital broadcasting system according to the present invention includes a demodulator for receiving and demodulating a digitally modulated signal, an internal deinterleaver for deinterleaving data output from the demodulator, and an internal deinterleaver. Outputs error-correction-decoded data to an internal decoder for outputting predetermined decoded data on output data, an external deinterleaver for reinterleaving data output from the internal decoder, and data output from the external deinterleaver. And a second decoder outputting error-correction-decoded data to data output from the block deinterleaver, and a block deinterleaver for rearranging data output from the first decoder.

Preferably, the apparatus further includes a descrambler for descrambling data output from the second decoder to output a TS stream in MPEG-2 format.

The internal deinterleaver is a symbol and bit deinterleaver, the internal decoder is a convolutional decoder, and the first and second decoders are Reed-Solomon decoders. In addition, the block deinterleaver may be a deinterleaver that rearranges and outputs the data when the input data is input in units of rows of a matrix.

The digitally modulated signal is a signal modulated by an OFDM modulation scheme, and the internal deinterleaver and the external deinterleaver preferably perform reverse operations of the internal interleaver and the external interleaver on the transmission side.

The demodulator may include a tuner / IF unit for removing a carrier from the digitally modulated signal, an A / D converter for analog-to-digital converting a signal output from the tuner / IF unit, and an output from the A / D converter. A demodulation / synchronization unit for performing timing synchronization with respect to the data, an equalization unit for compensating linear distortion with respect to the signal output from the demodulation / synchronization unit, and a fast Fourier transform of a signal output from the equalization unit into a signal in a frequency domain It can be configured to include an FFT unit for outputting.

On the other hand, the transmission method of the digital broadcasting system of the present invention, (a) receiving a digitally modulated signal and output demodulated data, (b) deinterleaving the demodulated data, (c) the Outputting predetermined decoded data with respect to the deinterleaved data, (d) deinterleaving the predetermined decoded data again, and (e) performing error correction decoded data with respect to the deinterleaved data again. Outputting, (f) rearranging the error correction decoded data, and (g) outputting the error correction decoded data with respect to the rearranged data. Preferably, the method further includes the step of outputting the TS stream in MPEG-2 format by descrambling the data output in the step (g).

In the step (b), it is preferable to deinterleave using a symbol and a bit deinterleaver. In the step (c), it is preferable to decode using a convolutional decoder. Also, in the above steps (e) and (g), it is preferable to decode using the Reed-Solomon decoder. In the step (f), if the input data is input in units of rows of the matrix, it is preferable to rearrange and output in units of columns.

In the step (a), the digitally modulated signal is a signal modulated by the OFDM modulation scheme, and the steps (b) and (d) respectively perform a reverse action of the internal interleaving and the external interleaving on the transmitting side. It is desirable to.

(A) step (a1) outputting a signal from which the carrier is removed from the digitally modulated signal, (a2) analog-to-digital converting the signal from which the carrier is removed, (a3) the analog Performing timing synchronization on the digitally converted data, (a4) compensating for the linear distortion of the timing synchronized data, and (a5) converting the linear distortion-compensated signal into a signal in the frequency domain by fast Fourier transforming It is preferable to include the step of outputting.

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

5 is a block diagram of a receiving apparatus of a digital broadcasting system having a multi-stage error correction decoding function according to the present invention. Referring to the drawings, the receiving apparatus of the digital broadcasting system includes a demodulator 500, an FEC unit 600, and a descrambler 650. The demodulator 500 includes a tuner / IF unit 510, an A / D converter 520, a demodulator / synchronizer 530, an equalizer 540, and an FFT unit 550. The FEC unit 600 includes an internal deinterleaver 605, an internal decoder 610, an external deinterleaver 620, and a multi-stage error correction decoder 630.

The tuner / IF unit 510 removes the RF signal from the signal received from the antenna and converts it into an intermediate frequency band or baseband. The A / D converter 520 converts the signal output from the tuner / IF unit 510 into a digital signal. The demodulator / synchronizer 530 performs timing synchronization with respect to the digital signal output from the A / D converter 520. The equalizer 540 compensates for linear distortion, such as ghost or frequency distortion, caused by incomplete elements in the transmission channel or receiver. The FFT unit 550 converts the signal output from the equalizer 540 into a signal in the frequency domain.

The FEC unit 600 corrects an error in the signal output from the FFT unit 550 and decodes the encoded data. The descrambler 650 descrambles data output from the FEC unit 600 and outputs a TS stream.

FIG. 6 is a detailed block diagram of the multi-stage error correction decoder 630 of FIG. 5. Referring to the drawings, the multi-level error correction decoding unit 630 includes a first RS decoder 631, a block deinterleaver 633, and a second RS decoder 635.

The first and second RS decoders 631 and 635 perform decoding corresponding to the encoding of the RS encoder in the multi-stage error correction encoder on the transmitting side. The block deinterleaver 633 performs deinterleaving corresponding to the block interleaving performed by the multistage error correction encoder on the transmitting side.

7 is a flowchart provided to explain an operation method for a receiving apparatus of a digital broadcasting system according to the present invention. Referring to Figures 5 to 6 will be described the operation method for the receiver of the digital broadcasting system according to the present invention.

First, in the demodulator 500, a demodulation process is performed on a signal received through an antenna (S700). In the demodulation unit 500, the signal after the demodulation process is transmitted to the FEC unit 600. The internal deinterleaver 605 of the FEC unit 600 performs internal deinterleaving corresponding to the interleaving performed by the internal interleaver on the transmitting side (S703). That is, the internal deinterleaver 605 performs the reverse action of the internal interleaver on the transmitting side.

The signal deinterleaved by the internal deinterleaver 605 is transferred to the internal decoder 610 to perform internal decoding, that is, decoding corresponding to the encoding performed by the internal encoder of the transmitter (S705). The signal decoded by the internal decoder 610 is transferred to the external deinterleaver 620, and external deinterleaving corresponding to interleaving performed by the external interleaver on the transmitting side is performed (S710).

The signal deinterleaved and output from the external deinterleaver 620 is transmitted to the multi-stage error correction decoder 630. The first RS decoder 631 of the multi-level error correction coder 630 corrects an error in the row direction with respect to the input data, and displays an erasure flag for the row when an error exceeding the error correction range occurs. Decryption is performed (S715). The first RS decoder 6310 may perform error correction on one segment of the segment, thereby strongly correcting a cluster error generated by an impulse noise, trellis decoding error, or the like.

Data output from the first RS decoder 631 is transferred to the block deinterleaver 633. The block deinterleaver 633 performs deinterleaving corresponding to the block interleaver in the multi-stage error correction encoder on the transmitting side, and basically stores the data in the row direction and outputs the data in the column direction. The second RS decoder 635 performs error correction on the data output from the block deinterleaver 633, and performs RS decoding (S725).

Unlike other coding schemes, the RS (Reed Solomon) code is a non-binary block code, and the element is not composed of only 0 or 1, but is composed of non-binary elements of 0, 1, ..., 2 ^m-1 . By RS coding, one block composed of k input symbols is encoded into n code symbols larger than k. Therefore, nk redundant symbols are added, which is called Reed Solomon Parity. The number of parity added by RS encoding may vary depending on the transmission scheme, such as 16 or 20 per 188 symbols. The first and second RS decoders 631 and 635 determine the accuracy of the received data using the added parity at the transmitting side. As a result of the accuracy determination, if an error is detected, the first and second RS decoders 631 and 635 locate the error, correct the distorted data, and restore the original signal. In general, error recovery is possible as many as half of the number of added parity symbols, and more errors cannot be recovered. Accordingly, the first RS decoder 631 does not correct the codeword for a row exceeding the error correction range, but instead displays an erasure flag in the corresponding column, and passes it to the second RS decoder 635.

The second RS decoder 635 uses the erasure flag and added parity to correct the error. In this case, since the erasure flag indicates the location of the error, using the erasure flag and the corresponding parity increases the error correction range twice as much as when using the parity alone to correct the error. Therefore, even when an error outside the error correction range of the first RS decoder 631 occurs, the error correction is performed by the second RS decoder 635 again after deinterleaving the data indicating the erasure flag. To improve the performance.

8A illustrates an example of a data format including whether data is corrected by the first RS decoder 631, and FIG. 8B illustrates an example of a data format in which error correction is performed by the second RS decoder 635. In FIG. 8A, the row marked in black represents a row beyond which the error correction cannot be performed, and in this case, an erasure flag is displayed. 8B shows a data format in which erasure flags are distributed by the block deinterleaver 633. Therefore, since the error correction is performed by including the erasure flag in the second RS decoder 635, the range of error correction is widened.

Data output from the second RS decoder 635 is descrambled by the descrambler 650 to output a TS stream. The TS stream is one of the multiplexing methods defined in MPEG-2, and is a multiplexing method defined for an environment in which transmission errors such as a noisy channel or loss of data may occur. In addition, the descrambling performed in the descrambler 650 should be performed in an appropriate manner according to the scrambled scheme at the transmitting side.

By the above process, the TS stream delivered from the transmission side can be received, and the range of error correction upon reception can be improved.

As described above, according to the present invention, an error correction coded signal is received in multiple stages, an error correction decoding process is performed using two RS decoders in multiple stages, and error correction is performed in comparison with a case of using one RS encoder. The range of becomes larger.

In addition, although the preferred embodiment of the present invention has been shown and described above, the present invention is not limited to the specific embodiments described above, but the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims. Of course, various modifications can be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or the prospect of the present invention.

Claims (16)

A demodulator for receiving and demodulating a digitally modulated signal; An internal deinterleaver for deinterleaving the data output from the demodulator; An internal decoder configured to output predetermined decoded data with respect to data output from the internal deinterleaver; An external deinterleaver for reinterleaving data output from the internal decoder; A first decoder configured to output error correction decoded data with respect to data output from the external deinterleaver; A block deinterleaver for rearranging data output from the first decoder; And A second decoder configured to output error correction-decoded data with respect to data output from the block deinterleaver; Receiving device of a digital broadcasting system, characterized in that it comprises a. The method of claim 1, And a descrambler configured to output a TS stream in an MPEG-2 format by descrambling the data output from the second decoder. The method of claim 1, The internal deinterleaver is a symbol and bit deinterleaver, and the internal decoder is a convolutional decoder. The method of claim 1, The first and second decoders are Reed-Solomon decoders. The method of claim 1, And the block deinterleaver is a deinterleaver for rearranging and outputting the input data in units of rows of a matrix. The method of claim 1, And the digitally modulated signal is a signal modulated by an OFDM modulation method. The method of claim 6, And the internal deinterleaver and the external deinterleaver respectively perform reverse functions of the internal interleaver and the external interleaver on the transmission side. The method of claim 6, wherein the demodulation unit, A tuner / IF unit which removes a carrier from the digitally modulated signal; An A / D converter configured to analog-digital convert the signal output from the tuner / IF unit; A demodulation / synchronization unit which performs timing synchronization with respect to data output from the A / D converter; An equalizer for compensating for linear distortion with respect to the signal output from the demodulator / synchronizer; And And an FFT unit for converting the signal output from the equalizer into a signal in a frequency domain by fast Fourier transforming. (a) receiving a digitally modulated signal and outputting demodulated data; (b) deinterleaving the demodulated data; (c) outputting predetermined decoded data for the deinterleaved data; (d) deinterleaving the predetermined decoded data again; (e) outputting error correction decoded data with respect to the deinterleaved data; (f) rearranging the error correction decoded data; And (g) outputting error correction decoded data with respect to the rearranged data; Receiving method of a digital broadcasting system comprising a. The method of claim 9, And descrambling the data output in the step (g) to output a TS stream in MPEG-2 format. The method of claim 9, In step (b), deinterleaving using a symbol and a bit deinterleaver, and in step (c), decoding using a convolutional decoder. The method of claim 9, In the steps (e) and (g), the receiving method of the digital broadcasting system, characterized in that the decoding using a Reed-Solomon decoder. The method of claim 9, In the step (f), if the input data is input in units of rows of a matrix, the receiving method of the digital broadcasting system is characterized in that the output is rearranged in units of columns. The method of claim 9, In the step (a), wherein the digitally modulated signal is a signal modulated by the OFDM modulation method. The method of claim 14, (B) and (d), respectively, the reception method of the digital broadcasting system, characterized in that to perform the reverse action of the internal interleaving and the external interleaving of the transmitting side. The method of claim 9, wherein step (a) comprises: (a1) outputting a signal from which a carrier is removed from the digitally modulated signal; (a2) analog-to-digital converting the signal from which the carrier is removed; (a3) performing timing synchronization on the analog-digital converted data; (a4) compensating for the linear distortion of the timing synchronized data; And and (a5) converting the linear distortion-compensated signal into a signal in a frequency domain by fast Fourier transforming and outputting the signal.