KR101288762B1 - Error correcting apparatus and method in digital audio broadcasting receiver - Google Patents

Abstract

The present invention relates to a digital broadcast receiver, and more particularly, to an apparatus and a method for correcting an error in a receiver of a digital broadcast system.

An apparatus for correcting an error in a receiver of a digital broadcasting system according to the present invention includes a receiver for buffering packets received from a transmitter in a frame error correction (FEC) frame, and a packet buffered in the frame error correction frame. A decoder for detecting an error by decoding them, a packet size detector for detecting a size of packets buffered in the frame error correction frame, and a size of the packets detected by the packet size detector if there is an error. A cyclic redundancy check checker for performing a cyclic redundancy check (CRC) check on the packets buffered in the error correction frame; and if the cyclic redundancy check check result is 'bad' The packet size information of the performed packets to a predetermined size. It includes portions defining header modification.

DAB, Forward Error Correction (FEC), FEC-FRAME, Cyclic Redundancy Check (CRC)

Description

ERROR CORRECTING APPARATUS AND METHOD IN DIGITAL AUDIO BROADCASTING RECEIVER}

1 is a diagram illustrating a structure of a packet used in a general DAB broadcasting system;

2 is a diagram illustrating a method of buffering packets to be transmitted in an FEC frame by a transmitter of a general DAB broadcasting system.

3 is a configuration diagram of an FEC frame according to a general DAB broadcasting system;

4 is a view illustrating R-S data packets in a general DAB broadcasting system;

FIG. 5 is a diagram illustrating a case in which decoding is not performed because an error occurs in header information when a receiving end receives a packet transmitted by a transmitting end in a general DAB broadcasting system.

6 is a block diagram of an FEC demodulation block in a DAB receiver according to an embodiment of the present invention;

7 is a detailed configuration diagram of an R-S decoder according to an embodiment of the present invention;

8 is a flowchart illustrating a method for performing FEC decoding in a receiver of a DAB broadcasting system according to an embodiment of the present invention;

9 is a diagram illustrating a process of successfully performing FEC decoding even if an error occurs in a packet header in a receiver of a DAB broadcasting system according to an embodiment of the present invention.

The present invention relates to a digital broadcast receiver, and more particularly, to an apparatus and method for error correction in a digital audio broadcast receiver.

 Conventional analog broadcasting such as FM (Amplitude Modulation) and AM (Amplitude Modulation) has sound quality due to effects such as multipath fading due to increasing density of skyscrapers and houses, and the Doppler effect of carrier frequency generated when receiving mobile objects. Deterioration is intensifying. In addition, as the number of radio stations in the FM band increases, the frequency congestion is very serious, and the interference between channels makes it difficult to allocate new channels.

In order to solve such problems of analog broadcasting, switching to digital broadcasting is essential. Accordingly, TV and radio broadcasters are currently optimizing broadcast contents and broadcasting equipment for digital broadcasting. Such digital broadcasting includes European Digital Video Broadcasting (DVB), Digital Audio Broadcasting (DAB), and Korean Digital Multimedia Broadcasting (DMB).

All of these digital broadcast systems are based on EUREKA-147, developed as a project of the European Advanced Technology Development Plan (EUREKA). The dual DAB modulates and broadcasts an audio signal by high efficiency encoding (data compression) using an orthogonal frequency division multiplex (OFDM) scheme. As a high efficiency coding method, MUSICAM (Masking pattern adapted Universal Sub-band Integrated Coding And Multiplexing) is used.

Unlike AM and FM, the DAB has the advantage of being able to broadcast high quality audio at the CD level and broadcasting data such as text, graphics, and traffic information.

As described above, the digitization of the broadcasting system is essential, and therefore, the development of the digital audio broadcasting receiver is required. In particular, it is necessary to develop a technology for demodulating broadcast data in a digital audio broadcast receiver.

The present invention relates to an apparatus and method for demodulating broadcast data in a digital audio broadcast receiver.

The present invention relates to an apparatus and method for correcting errors in broadcast data received at a digital audio broadcast receiver.

An apparatus for correcting an error in a receiver of a digital broadcasting system according to the present invention includes a receiver for buffering packets received from a transmitter in a frame error correction (FEC) frame, and a packet buffered in the frame error correction frame. A decoder for detecting an error by decoding them, a packet size detector for detecting a size of packets buffered in the frame error correction frame, and a size of the packets detected by the packet size detector if there is an error. A cyclic redundancy check checker for performing a cyclic redundancy check (CRC) check on the packets buffered in the error correction frame, and the cyclic redundancy check check if the cyclic redundancy check check result is 'bad' The packet size information of the performed packets to a predetermined size. It includes portions defining header modification.

A method for correcting an error in a receiver of a digital broadcasting system according to the present invention may include receiving and buffering packets transmitted by a transmitter in a frame error correction (FEC) frame, and buffering the frame error correction frame. Decoding the decoded packets and checking for an error; if there is an error as a result of the decoding, detecting the size of the packets buffered in the frame error correcting frame; Performing a cyclic redundancy check (CRC) check on the buffered packets; and if the cyclic redundancy check check result is 'bad', the packet size of the packets on which the cyclic redundancy check is performed Modifying the information to a predetermined size.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a detailed description of preferred embodiments of the present invention will be given with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

In current European DAB systems, Frame Error Correction (FEC) adds new outer interleaving and outer coding to DAB packet mode to increase the data throughput while increasing DAB mobility. ) The structure is specified in the standard.

The transmitting side FEC frame structure proposed in the European Telecommunications Standards Institute (ETSI) EN 300 401 v1.4.1 standard is as follows.

First, the DAB transmitter generates a broadcast stream for transmission with a packet size of 12 x 188 bytes (2256 bytes). The generated 2256 bytes are called application data, and the buffer of the FEC frame buffering these application data is called an application data table.

1 illustrates a structure of a packet 110 used in a general DAB broadcasting system.

As shown in FIG. 1, the packet 110 is composed of 24, 48, 72, and 96 byte units, which are integer multiples of 24 bytes, and each packet 110 includes a 3-byte packet header 100 and a 2-byte cyclic redundancy check (Cyclic). Redundancy Check (CRC) information 102 is included. The upper two bits of the packet header 100 include information on the length of the packet 110. If the upper two bits are '00', the packet 110 indicates that the packet 110 is 24 bytes. .

2 is a diagram illustrating a method of buffering packets to be transmitted in an FEC frame by a transmitter of a general DAB broadcasting system.

In the transmitter of the general DAB broadcasting system, as shown in FIG. 2, packets to be transmitted are filled into the application data table 200 from the numbers 204 and 206 as shown. When all the application data are collected in the application data table 200 capable of buffering 2256 bytes, as shown by reference numeral 208, all 12 times of Reed-Solomon (RS) encoding are performed for 188 bytes in the horizontal direction, and RS encoding is performed. RS data, which is later parity data, is stored in the RS data table 202. The data corresponding to one column 210 after one R-S encoding is a total of 204 (188 + 16) bytes. Hereinafter, in the present specification, data generated by performing R-S encoding on the application data in the horizontal direction will be referred to as R-S data.

The size of this R-S data is 192 bytes, which is 12 x 16. That is, the R-S data table 202 is filled with a total of 192 bytes of R-S data.

Application data and R-S data generated through the above-described processes are composed of the FEC frame as shown in FIG. 3 and transmitted.

3 is a block diagram of an FEC frame 300 according to a general DAB broadcasting system. As shown in FIG. 3, an application data table 304 having a size of 2256 bytes (12 × 188) in which the DAB packets 110 shown in FIG. 1 are buffered and the RS data 202 in FIG. 2 are buffered. The RS data table 302 having a size of byte (16 × 12) constitutes one FEC frame.

4 is a diagram illustrating R-S data packets in a general DAB broadcasting system.

In a typical DAB broadcasting system, the R-S data table is transmitted using nine consecutive packets as shown in FIG. 4.

The R-S data packet has a total of 24 bytes and has 2 bytes of header information 400 and 22 bytes of R-S data information 402. Finally, when viewed from the FEC output terminal of the transmitter, a total of 2472 bytes of information including 24 × 9 bytes of the R-S data packet shown in FIG. 4 is added to 12 × 188 bytes of application data, and the amount of information required to transmit one FEC frame.

At this time, the receiving end receiving the configured 2472 bytes stores the data in the buffer as shown in FIG. 2 described above, and in the vertical direction as in the case of filling the application data table 200 and the RS data table 202 of the FEC-frame. By subtracting, the effect of block interleaving can be achieved.

However, a receiver according to a general DAB broadcasting system may not correctly decode corresponding broadcast data when an error occurs in the packet header 100 when sending a packet to a higher layer after data demodulation. These problems will be described with reference to FIG. 5 below.

FIG. 5 is a diagram illustrating a case in which decoding is not performed because an error occurs in header information when a receiving end receives a packet transmitted by a transmitting end in a general DAB broadcasting system.

In FIG. 5, reference numeral 500 denotes an FEC frame for transmitting a DAB broadcast data packet of a transmitter, and reference numeral 550 denotes an FEC frame of a receiver, which buffers a data packet transmitted by the transmitter, respectively. Reference numerals 502a, 504a, 552a, 554a, 554b, etc., all indicate two-bit packet size information indicating the length of a packet among three-byte packet header information in the DAB broadcasting system.

When transmitting the broadcast data packets, the transmitter first transmits application data in the same form as the packet shown in FIG. 1, and then transmits the R-S data to the FEC packet set as shown in FIG. 3. In this case, it is assumed that the size of the packet 0 502 is 48 bytes and the size of the packet 1 502 is 72 bytes when the packets filled in the FEC frame 500 are transmitted.

In the present invention, the R-S decoding and CRC checking are performed at the receiving end, respectively. If the R-S decoding results in no error in the received packets, the CRC checking may not be performed. On the other hand, if the R-S decoding is performed but the received packets are not correctly decoded due to the error of the received packets, error correction is performed once again by performing the CRC check. The present invention considers the worst case among the two cases described above, and considers a case where CRC check is performed because the error of the packet cannot be corrected even though the receiver performs R-S decoding. That is, FIG. 5 illustrates an example in which a CRC check is performed because an error is not corrected even after performing R-S decoding.

First, a packet 0 (502) having a packet size information (502a) of '01' indicating a size of 48 bytes is transmitted from a transmitter, and an error occurs in a header part due to distortion of a radio channel environment. When the packet 0 is filled in, the packet length information 552a may be incorrectly determined as '00', that is, 24 bytes. In this case, the receiver performs a CRC check on the packet 0 552 having a size of 24 bytes.

However, since the transmitting end transmits the packet 0 502 having a size of 48 bytes, the receiving end of the CRC check result for the packet 0 552 may not be 'good'. Therefore, the receiver inserts the last 2 bytes of the packet 0 552 as CRD check result 'bad' and transmits the packet to the upper layer, and discards the packet at the upper layer. In addition, the receiving end determines that the packet received later and stored in the FEC frame 550 is a new packet, that is, packet 1 (554). After the packet 0 552, the first two bits are determined as the packet size information 554a. In FIG. 5, since '01' is located at the point where the packet size information 554a indicating the packet length of the packet 1 554 is located, the actual packet 1 504 transmitted by the transmitting end is 72 bytes long. It shows that the size of packet 1 554 is mistaken for 48 bytes. Therefore, since the first and second rows in packets 1 (554) were packets corresponding to packet 0 (502) at the transmitting end, the CRC check resulted in 'bad' like the previous packet 0 (552) at the receiving end. do. In addition, at the receiving end, packet 1 554 also cannot be decoded, and if such an error continues to occur, there is a problem that the packet buffered in the entire FEC frame 550 cannot be decoded.

That is, even if the packet 1 504 transmitted from the transmitting end has no error, the receiving end cannot decode the data of the packet 1 504 transmitted from the transmitting end. Although the reference number 554b of the FEC frame 550 of the receiving end is actually the packet length of Packet 1 504 transmitted by the transmitting end, the receiving end does not detect this. Therefore, although the packet 0 502 at the receiving end fails to decrypt the packet 1 504, the packet 1 504 is incorrectly determined by correctly receiving the packet 1 504 so that the cyclic redundancy check (CRC) check may cause a 'good'. Even the CRC check result of the data of the error occurs (fail), and the data of the packet 1 (504) is forced to discard.

As described above, in the receiver of a general DAB broadcasting system, if the packet size information of the packet header is continuously missed, there is a problem that, in severe cases, it is determined that all packet data in the FEC frame has failed to be decoded.

Therefore, there is a need for an apparatus and method for error correction in a DAB receiver for preventing packet reception failure due to a packet header information error in a receiver of such a general DAB system. An error correction apparatus and method are proposed.

6 is a block diagram of an FEC demodulation block in a DAB receiver according to an embodiment of the present invention.

First, the convolution decoder 600 receives a demodulated packet received through an RF receiver and not demodulated, performs convolutional decoding, and then outputs the convolutional decoder to a frame detection unit 602. In this case, the convolution decoder 600 only performs decoding on the received packets and does not know whether an error has occurred in the received packets. The error of the received packets is checked by the R-S decoder 606 to be described later.

The frame detector 602 detects a start position of a packet to be buffered in an FEC frame by using the convolutional decoding outputted data. The FEC frame buffering unit 604 buffers the data to have a row of 12 bytes as large as the FEC frame size. The RF unit and the demodulator, the convolution decoder 600, the frame detector 602, and the FEC frame buffering unit 604 will be referred to as a receiver 620.

The R-S decoder 606 performs R-S decoding on data buffered in an FEC frame through the FEC frame buffering unit 604 to correct an error. If there are no errors in the received packets as a result of the decoding of the R-S decoder 606, the operations of the packet size detector 608, the CRC checker 610, and the header correction unit 612 to be described later may not be performed.

If an error occurs after the R-S decoding is performed, the packet size detection unit 608 examines the packet size of the packets buffered in the FEC frame. In this case, it is determined that the header is present at the first position in the packet data buffered in the FEC frame, and the packet size is detected by detecting packet size information of 2 bits at the position. The reason for detecting the location of the header information in order to detect the packet size is that the transmitting end transmits the data in units of a predetermined size (24 bytes). When packet 0 is received, the 2 bits of the first position in the FEC frame are determined by the packet size. This is because, as the information, the packet size information of the packets buffered afterwards can be determined as the packet size information by two bits positioned immediately after the previous packet.

 The packet size detector 608 transfers the detected packet size to the CRC checker 610, and the CRC checker 610 performs a CRC check on data equal to the packet size delivered by the packet size detector. If there is no error as a result of the CRC check, it is determined that the packet size is correct and indicates that the CRC result is 'good' in the last 2 bytes of the packet which has performed the CRC check, and then transmits packet data to the upper application processor 614.

However, if the CRC check result is 'bad', the CRC check unit 610 determines that the packet size detection unit 608 has detected an incorrect packet size, and causes the header correction unit 612 to indicate the packet size information of the packet in error. To set the size to 24 bytes. The reason why the packet size information of the packet in error is set to 24 bytes is that the transmission unit of packet data in the DAB broadcasting system is one of 24, 48, and 72 bytes, which is an integer multiple of 24 bytes. In other words, in the present invention, the packet size is corrected in units of 24 bytes, but any unit may be used as long as it is a predetermined transmission unit at the transmitting end.

In the header corrector 612, if the result of the CRC checker 610 is 'bad', the packet size information of the packet on which the CRC check is performed is set to '00'.

In the above description, the CRC check unit 610 transmits the packet determined as 'good' or 'bad' to the application processor 614 in the unit of the inspected packet, but the CRC for the packets buffered in the FEC frame After all the checks are performed, the FEC may be transmitted to the application processor 614 in FEC frame units.

The application processor 614 discards the CRC 'bad' packets among the received packets and decodes the 'good' packets using a predetermined audio / video codec and provides them to the user.

7 is a detailed block diagram of an R-S decoder 606 according to an embodiment of the present invention.

The R-S decoder 606 according to the embodiment of the present invention includes a decoding unit 606a and an error detector 606b. First, the decoding unit 606a is a block that performs RS decoding on the packets buffered in the FEC frame, and the error detector 606b transmits the packets buffered in the FEC frame to the application processor 614 according to the RS decoding result. The packet size detection unit 608 determines whether to transmit. That is, the error detector 606b notifies the packet size detector 608 that an error has occurred if there is an error as a result of the R-S check.

8 is a flowchart illustrating a method of performing FEC decoding in a receiver of a DAB broadcasting system according to an embodiment of the present invention.

In step 800, the receiving unit 620 receives and demodulates the packet data transmitted from the transmitter, and in step 802, the convolutional decoder 600 convolutionally decodes the demodulated data, and in step 804, the frame detection unit 602 performs the convolutional decoding. The start point of the FEC frame, which is the start address of the data to be buffered in the FEC frame, is detected.

In step 806, the FEC frame buffering unit 604 buffers the packet data received from the frame start position received from the frame detector 602 in the FEC frame. In step 808, the RS decoder 606 buffers the packet that is buffered in the FEC frame. RS decodes the data. In step 810, if the decoding succeeds because an error does not occur in the R-S decoding in step 808, the R-S decoder 606 proceeds to step 820 and transmits the decoded packet data to the application processor 614.

On the other hand, if it is not possible to decode the packet as a result of the check in step 810, in step 812, the packet size detector 608 detects the packet length 100a information in the header information from the RS decoded packets and checks the detected packet size by the CRC checker. To 610. In step 814, the CRC checker 610 performs a CRC check on the packets buffered in the FEC frame by the packet size, and determines whether an error occurs as a result of the CRC check in step 816.

If there is a CRC error as a result of the check in step 816, the flow proceeds to step 818 to control the header correction unit 612 to correct the size of the packet in which the CRC result error was present to 24 bytes. In step 818, the header corrector 612 sets the packet size of the header information of the packet to '00', which is 24 bytes, and transmits the packet whose packet size information is corrected to the application processor 614 in step 820. do.

On the other hand, if there is no CRC error as a result of the check in step 816, the CRC check unit 610 transmits the CRC checked packets to the application processor 614.

9 is a diagram illustrating a process of successfully performing FEC decoding even if an error occurs in a packet header in a receiver of a DAB broadcasting system according to an embodiment of the present invention.

Referring to FIG. 9, it can be seen that packet 1 504 (packet number 904 in FIG. 9), which was lost due to the decoding, can be decoded.

The transmitting end transmits packet 0 902 and packet 1 904 buffered in the FEC frame 900 to the receiving end. In this case, since the packet 0 902 is 48 bytes in size, the packet size information 900a of the header information is set to '01', and then the CRC result 902b is attached and transmitted. Since packet 2 904 is 72 bytes in size, it is assumed that the packet size information 902a of the header information is set to '10' and then the CRC result 904b is attached and transmitted.

The receiving end receives the packets transmitted from the transmitting end and buffers them in the FEC frame 940. In this case, it is assumed that an error occurs due to a worsening channel environment, and the packet length is detected as '00' as shown by reference numeral 902a of packet 0 (902) of the transmitting end. That is, it is assumed that an error occurs as a result of the R-S decoding to perform the CRC check.

In this case, the packet size detection unit 608 of the receiving end determines that the length of the packet 0 950 is 24 bytes in the FEC frame 940 as shown by reference numeral 950a, and the CRC check unit 610 is the size of the packet 0 950. CRC check is performed on 24 bytes. However, since the length of the packet sent from the transmitter is different, the CRC result is naturally 'bad'. When the packet 0 950 is transmitted to a higher layer, the CRC 'bad' is also transmitted to the last 2 bytes. Then, the packet size detection unit 608 of the receiving end judges the received packet as a new packet, and determines the packet length with '00', which is the 2 bits 960a located at the beginning of the packet 1 960, and the CRC check unit ( 610 performs a CRC check on the packet length of 24 bytes. However, since the packet determined by the receiver at packet 1 960 is some packets of packet 0 902 transmitted by the transmitter, 'bad' is inevitably generated when the CRC check is performed.

Accordingly, as shown by reference numeral 960a, the header correction unit 612 sets the packet length to '00' to indicate that the packet length is 24 bytes, and then transmits the packet length to the application processor 614. That is, packet 0 902 transmitted from the transmitting end cannot be recovered.

The packet size detection unit 608 then detects the header information of the packet 970 located next to the packet 960. In this case, the packet size detector 608 may accurately detect the packet length '10' of the header information of the packet 970, and thus, the packet size 970 may know that the length of the packet 970 is 72 bytes. Therefore, the CRC check is performed on 72 bytes, and the CRC check result of the packet 970 is 'good', so that the receiver can perform decoding without losing the packet 970. That is, if some packet header information is incorrectly detected in a receiver of a general DAB system, the packets buffered in the FEC frame cannot be decoded, but the DAB receiver according to an embodiment of the present invention generates an error in the header of some packets. Even if the packet is received later, the error can be corrected successfully.

Therefore, unlike FIG. 5 described above, in the receiver according to the exemplary embodiment of the present invention, even if an error occurs in the previously received packets as shown in FIG. 9, only the minimum packets are lost by decoding only a packet unit of a predetermined size to lower the packet error rate. Can be.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but is capable of various modifications within the scope of the invention. Therefore, the scope of the present invention should not be limited by the illustrated embodiments, but should be determined by the scope of the appended claims and equivalents thereof.

As described above, by applying the present invention, the receiver of the DAB broadcasting system can lower the packet error rate.

Claims (7)

An apparatus for correcting an error in a receiver of a digital broadcasting system, A receiver which buffers the packets received from the transmitter in a frame error correction (FEC) frame, A decoder which decodes the packets buffered in the FEC frame and checks for an error; A packet size detector for detecting a packet size with respect to the packets buffered in the FEC frame, if there is an error in the decoding result; A CRC checker configured to perform a cyclic redundancy check (CRC) check on the packets buffered in the FEC frame as many as the detected packet size; And a header correction unit for modifying packet size information of the packets on which the CRC check has been performed to a predetermined packet size, if there is an error in the CRC check. The method according to claim 1, The receiver may further comprise: A radio frequency (RF) unit for receiving the packets transmitted by the transmitter; A demodulator for frequency downconverting and outputting the packets received by the RF unit; A convolution decoder for convolutionally decoding the packets output by the demodulator; A frame detector for detecting a start point of a packet to be buffered in the FEC frame among the convolutionally decoded packets; And an FEC frame buffering unit configured to buffer the convolutionally decoded packets by the FEC frame size based on the detected starting point. The method according to claim 1, The header correction unit, And correcting the packet size information to 24 bytes if there is an error in the CRC check result. The method according to claim 1, The CRC inspection unit, If there is no error as a result of the CRC check, it is determined that there is no error in the packet size detected by the packet size detection unit, and the error correction apparatus in the receiver of the digital broadcasting system, characterized in that for transmitting the packets to which the CRC check has been performed . The method according to claim 1, The decoder is an error correction apparatus in a receiver of a digital broadcasting system, characterized in that the Reed-Solomon decoder. A method for correcting an error in a receiver of a digital broadcasting system, Buffering the packets received from the transmitter in a frame error correction (FEC) frame; Decoding packets buffered in the FEC frame to check for errors; If there is an error in the decoding result, detecting a packet size of the packets buffered in the FEC frame; Performing a cyclic redundancy check (CRC) check on the packets buffered in the FEC frame as many as the detected packet size; If there is an error in the CRC check, correcting the packet size information of the packets on which the CRC check has been performed to a predetermined packet size. The method according to claim 6, The process of modifying the packet size information to a predetermined packet size, And correcting the packet size information to 24 bytes if there is an error as a result of the CRC check.

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