JP2002077109A - Digital signal transmission system and its signal transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a digital signal transmission system to repeatedly transmit the same information a plurality of times at fixed time intervals while the system suppresses the increases of the hardware scale and throughput on the receiving side. SOLUTION: The transmitting-side signal transmitter of the digital signal transmission system transmits main audio, first spare, and second spare bit streams which are generated by adding error detecting codes to voice-coded signals in which the presence/absence of information varies depending upon control information in the bit streams by multiplexing the streams upon another by shifting the transmitting timing of the bit streams by prescribed periods of time. On the receiving-side signal transmitter side of the system, PES separating sections 221-223, variable length code decoding/separating sections 241-243, and error detecting sections 251-253 are provided by the number of repetitive transmitting times, namely, for three routes only. The signal transmitter performs error detection on the bit streams and decodes audio signals by selectively inputting received information transmitted without error to one audio decoding section 28.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital signal transmission system using, for example, a wireless transmission path, and more particularly, to a reception information transmitted without error by repeatedly transmitting the same digital signal a plurality of times with a certain time difference. The present invention relates to a digital signal transmission system for reproducing a digital signal based on a digital signal.

[0002]

2. Description of the Related Art In recent years, in the field of radio broadcasting and communication, various systems have been developed or developed which convert a transmission signal into a digital signal for each channel and wirelessly transmit the digital signal using a code decoding technique and a digital modulation / demodulation technique. Proposed.

When transmitting a transmission signal by digital radio,
It is necessary to protect a transmission signal from code errors due to fading or the like, and various error control techniques are used for that purpose. For example, in a mobile communication system such as a mobile phone system, a transmitting station voice-encodes a speech signal, then performs error correction coding using an error correction code, digitally modulates a carrier signal with the coded signal, and transmits the signal. Then, the receiving station digitally demodulates the received signal, performs error correction decoding processing on the demodulated signal to correct a code error, and then reproduces the speech signal by voice decoding.

Further, for example, when an error is detected in the reception information of the current frame, the current frame in which the error is detected is replaced with sound reception information of the previous frame, or
Alternatively, a method of estimating correct information based on past received information to compensate for errors has been used.

[0005]

However, a system using an error correction code is generally effective for a small number of code errors, but may not be effective for a burst error. Also, in the method of reproducing received information based on past received frames, it is effective if the correlation between the current frame to be reproduced and the past received frame is large, but the effectiveness is low if the correlation is small. .

For this reason, for example, in a radio broadcasting system,
A method has been considered in which the same audio signal is repeatedly transmitted a plurality of times with a certain time difference, and the signal is reproduced based on received information transmitted without error. However, in this method, when an error detection code is added to a signal of a voice coding system in which the presence or absence of information changes according to control information in a bit stream, a receiving side is used. It is necessary to have a number of voice decoders corresponding to the number of repetitive transmissions, resulting in an increase in hardware scale and processing amount.

The present invention has been made in view of the above circumstances, and its object is to reduce the increase in the hardware scale and the amount of processing on the receiving side so that the same information can be obtained at certain time intervals. It is an object of the present invention to provide a digital signal transmission system capable of repeatedly transmitting a plurality of times and a signal transmission device thereof.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for detecting an error in a signal of an encoding system in which the presence or absence of information changes according to control information in a bit stream. If a code is added, instead of preparing decoders by the number corresponding to the number of repeated transmissions, only a plurality of variable-length code decoding and bit stream separation processes necessary for error detection are performed. By preparing for each error, switching the received information transmitted without error and reproducing the digital signal with one decoder, the hardware scale and processing amount on the receiving side are greatly increased. It is realized without.

More specifically, a digital signal divided by a fixed frame length is variable-length coded and a packet stream to which an error detection code is added is generated for a plurality of systems, and multiplexed with a fixed time difference from each other. When the transmitted transmission stream is transmitted, on the receiving side, the transmission stream is received, the transmission is branched into the same number of systems as the number of systems generated on the transmission side, and each system is pre-allocated from the transmission stream. Separate packet streams different from each other, perform variable-length decoding, find an error detection code, determine whether there is a transmission error by comparing it with the added error detection code, and output the variable-length decoded output of a system without transmission errors. Is selected, and the original digital signal is obtained by compensating for the time difference set on the transmission side.

According to this configuration, even when a digital signal subjected to variable-length encoding is repeatedly transmitted, only a plurality of variable-length code decoding processes necessary for performing error detection are prepared, and each of them is prepared. Since error detection is performed, received information transmitted without error is switched, and a digital signal is reproduced by one decoder, the present invention can be realized without significantly increasing the hardware scale and processing amount on the receiving side.

After encoding a digital signal divided by a fixed frame length, a bit stream having a different length is generated for each frame, and a packet stream to which an error detection code is added is generated for a plurality of systems. When a transmission stream generated by multiplexing with a time difference of is transmitted, on the reception side, the transmission stream is received and branched into the same number of systems as the number of systems generated on the transmission side. In the system, a packet stream different from each other allocated in advance is separated from the transmission stream, and a bit stream is extracted to obtain an error detection code.
The presence or absence of a transmission error is determined by comparison with the added error detection code, a bit stream of a system having no transmission error is selected, and the original digital signal is decoded by compensating for the time difference set on the transmission side. .

According to this configuration, even in the case of repeatedly transmitting a digital signal of an encoding method in which the presence or absence of information changes according to control information in a bit stream, decoders are prepared by the number corresponding to the number of repeated transmissions. Instead, only a plurality of bit stream separation processes required for error detection are prepared, each error is detected, received information transmitted without error is switched, and digital Since the signal is reproduced, it can be realized without significantly increasing the hardware scale and processing amount on the receiving side.

Further, the digital signal divided by a fixed frame length is branched into a plurality of systems, each system is subjected to variable-length coding, and a coded bit stream having a different length for each frame is generated. Is added to generate a packet stream, and when a transmission stream generated by multiplexing with a certain time difference is transmitted, the reception side receives the transmission stream and receives the same number of transmission streams as the transmission side. The system branches into different systems, and in each system, a different packet stream assigned in advance is separated from a transmission stream, an error detection code is obtained by performing variable length decoding and bit stream extraction, and comparison with the added error detection code is performed. To determine the presence or absence of a transmission error,
The bit stream output of the system without transmission error is selected, and the original digital signal is decoded by compensating for the time difference set on the transmission side.

According to this configuration, even when a digital signal of a coding method that is variable-length coded and the presence or absence of information changes depending on control information in a bit stream is repeatedly transmitted, the decoder is repeatedly transmitted. Rather than preparing a number equivalent to the above, prepare only a plurality of variable-length code decoding and bit stream separation processes necessary for error detection, perform error detection for each, and transmit without errors. Since the received information is switched and the digital signal is reproduced by one decoder, it is possible to realize without increasing the scale of the hardware on the receiving side and the amount of processing.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a digital radio broadcasting system according to an embodiment of the present invention.
Reference numeral 0 denotes a transmitting-side signal transmission device, and reference numeral 20 denotes a receiving-side signal transmission device.

First, in the signal transmission device 10 on the transmitting side, an input audio signal ASin is branched and output to first to third paths. The first path includes an audio encoding processing unit 1
11, a variable length coding / multiplexing unit 121, an error detection code adding unit 131, a PES multiplexing unit 141, and a delay processing unit 151. The audio coding processing unit 11
2, a variable length coding / multiplexing unit 122, an error detection code adding unit 132, a PES multiplexing unit 142, and a delay processing unit 152 are provided.
3. Variable length coding / multiplexing unit 123 error detecting code adding unit 1
33, a PES multiplexing unit 143 is provided. The signal processed in each path is supplied to the TS multiplexing unit 16.

Here, the input audio signal ASin is divided into a fixed frame length by a frame dividing unit (not shown).

The first path is a path for creating a main audio PES packet.
1 encodes the input audio signal ASin for each frame. As an encoding method, for example, MPEG-
2 (Moving Pictures Experts Group 2) AAC
(Advanced Audio Coding) method is used.

More specifically, the audio encoding processing unit 111 performs a variable length encoding process to reduce the amount of code generation, and multiplexes control information to create an encoded bit stream. The multiplex processing of the control information is realized by a syntax as shown in FIG. In FIG. 2, (a)
An example of the syntax of a channel pair element is shown in (b)
Is the individual channel stream (common window) in (a)
Is shown. In this case, for the control information such as the common window and the ms mask present included in the channel pair element (CPE) in the bit stream, the presence or absence of the information is determined by 1/0. Therefore, the length of the bit stream generated for each frame changes, and the position where specific information exists also changes.

The encoded bit stream created by the audio encoding processing unit 111 is supplied to an error detection code adding unit 131. This error detection code adder 13
No. 1 adds an error detection code for detecting a transmission error for each frame to an important part of the bit stream. CRC (Cyclic Redundancy Check) or the like is used for the error detection code. Also, header information required by a frame configuration unit (not shown) is added, and the elementary stream (E
S) is generated.

Here, an important part of the bit stream is, for example, as shown in FIG.
2 bits or the second ICS (individ
ualchannel stream) is determined as 128 bits from the beginning.

However, as described above, since the length of the bit stream generated for each frame changes for each frame, the CPE is less than 192 bits as shown in FIG. May have a 128-bit second ICS. In such a case, 0 is added to the end and an error detection code is calculated.

The elementary stream generated by the error detection code adding section 131 is supplied to a PES multiplexing section 141. The PES multiplexing unit 141 adds PTS and DTS as time stamp information to the elementary stream.
And the like, and a PES header is created to create a PES packet.

Similarly, in the second route, each processing unit 11
2, 122, 132, and 142, a spare PES packet 1 is created using the same input audio signal. At this time, the bit rate of the audio encoding processing unit 112 is set to be equal to or smaller than that of the main audio encoding processing unit 111, depending on the available transmission speed of the line. When the same bit rate is used, the processing of each of the processing units 112, 122, 132, and 142 may be omitted, and the PES packet output from the PES multiplexing unit 141 on the first path may be used as it is. In the third route, the second
Processing units 113, 123, 133, 1
43, using the same input audio signal as the spare P
An ES packet 2 is created.

The PES packet of the main audio created by the PES multiplexing unit 141 on the first path and the PES packet on the second path
Spare PES packet 1 created by ES multiplexing section 142
Are the delay processing units 151 (delay time: T0 + T
1) The signal is supplied to a TS (transport stream) multiplexing unit 16 together with a spare PES packet 2 which is delayed by the delay processing unit 152 (delay time: T0) and is not subjected to the delay processing.

The TS multiplexing unit 16 receives the PEs from each path.
S packets are multiplexed, and each packet ID is added to a TS header to generate a transport stream.
This transport stream is wirelessly transmitted by a sending device (not shown).

Here, the delay times T0 and T1 are set to 90 seconds, for example. Therefore, on the wireless transmission path, as shown in FIG.
An S packet is transmitted first, followed by a TS packet including a spare PES packet 1 with a delay of T0 seconds, and a TS packet including a main audio PES packet with a delay of T1 seconds. . For this reason,
The PES packets of the main audio, the backup 1 and the backup 2 are shifted in time on the wireless transmission path, and even if there is a burst error, there is a high possibility that any of the PES packets is transmitted without error.

In the present embodiment, the sending order is set to preliminary 2,
Although the description has been made in the order of the spare 1 and the main audio, the order may be different.

On the other hand, the signal transmission device 20 on the receiving side
Separation unit 21 and PES arranged in first to third paths
Separation units 221 to 223, delay processing units (there is no first path) 231 to 232, variable-length code decoding / separation units 241 to 241
243, an error detection unit 251 to 253, an output selection control unit 26, a decoding output selection unit 27, and an audio decoding processing unit 28.

The received TS packet is transmitted to the TS separation unit 2
1 based on the packet ID included in the header, the primary audio PES packet, the backup PES packet 1, and the backup PES packet.
The packets are separated into ES packets 2 and output to the first to third paths, respectively.

The P of the main audio input to the first path
The ES packet is supplied to the PES separation unit 221. The PES separation unit 221 extracts the main audio elementary stream from the PES packet of the main audio. The extracted elementary stream is supplied to the variable length code decoding / separation unit 241.

The variable-length code decoding / separation unit 241 converts the encoded bit stream of the elementary stream
While decoding the variable length code, the coding parameter and control information are separated. As a result, the transmitting side can determine whether the protected part as an important part of the bit stream is as shown in FIG. 3A or 3B.

The output of the variable length code decoder / separator 241 is
The signal is supplied to the error detection section 251 and to the demodulation output selection section 26. The error detection unit 251 performs error detection by comparing an error detection code calculated using data of an important part in the received bit stream with the transmitted error detection code. The result is supplied to the output selection control unit 27.

The backup PES packet 1 input to the second path is supplied to the PES separation section 222, similarly to the first path, and after the elementary stream of the backup 1 is extracted, the delay processing section (Delay time T1) 231 is supplied to a variable-length code decoding / separation unit 242 via a variable-length code decoding / separation unit 242, where decoding of variable-length codes and separation of coding parameters and control information are performed. The output of the variable-length code decoding / separation unit 242 is supplied to an error detection unit 252 and a demodulation output selection unit 26, and the error detection unit 252 performs error detection of an important part in the received bit stream. The detection result is supplied to the output selection control unit 27.

The backup PES packet 2 input to the third path is supplied to the PES separation unit 223, similarly to the second path, and after the elementary stream of the backup 2 is extracted, the delay processing unit The signal is supplied to the variable-length code decoding / separation unit 243 via (delay time T0 + T1) 232, where the decoding of the variable-length code and the separation of the coding parameters and control information are performed. The output of the variable-length code decoding / separation unit 243 is supplied to an error detection unit 253 and a demodulation output selection unit 26, and the error detection unit 253 performs error detection on an important part in the received bit stream. The detection result is supplied to the output selection control unit 27.

The decoded outputs of backup 1 and backup 2 obtained through the second and third paths are delayed by delay processing sections 231 and 232 in accordance with the delay processing on the transmission side.
Is set at the same timing as the demodulated output of the main audio obtained by the path of FIG.

The output selection control unit 27 includes an error detection unit 25
Based on the error detection results of 1, 252, and 253, the decoding output selection unit 26 according to a predetermined priority from among the main audio, the spare 1, and the spare 2 in which no error was detected.
To select an audio encoding parameter to be decoded. The audio decoding processing unit 28 performs a decoding process based on the selected audio encoding parameter, returns the original frame-divided audio signal ASout, and outputs it to an audio signal reproducing device (not shown).

That is, in the system having the above configuration,
In the signal transmission device on the transmission side, a variable length code is used, and a main audio signal, a spare 1 bit, and a spare 2 bit in which an error detection code is added to a signal of a voice coding method in which the presence or absence of information changes according to control information in a bit stream. Although the streams are shifted by a predetermined time and transmitted in a multiplexed manner, the signal transmission device on the receiving side does not prepare the number of audio decoders corresponding to the number of repetitive transmissions.
Only the variable-length code decoding and bit stream separation processing parts necessary for error detection are repeatedly transmitted, that is, three paths are prepared, each error is detected, and the received information transmitted without error. Is selectively input to one audio decoding processor 28 to decode and reproduce the audio signal.

Therefore, according to the digital radio broadcasting system having the above configuration, it is necessary to perform error detection.
Since only the PES separation unit, the variable-length code decoding / separation unit, and the error detection unit, which have a relatively small hardware scale and processing amount, need only be repeated for the number of transmissions, compare the hardware scale and processing amount increase on the receiving side. It is possible to repeatedly transmit a plurality of times with a certain time difference with a small number of times.

In the above embodiment, the delay processing section on the receiving side is arranged after the PES separation section. However, the present invention is not limited to this. Then, the same result can be obtained by the same processing regardless of the arrangement.

In addition, for example, the audio signal is AAC
However, it is needless to say that other signal formats may be used. The signal is not limited to an audio signal, and may be an image signal or a video signal such as a holographic image. In addition, the present invention can be applied to not only broadcasting but also communication such as wireless telephone.

In addition, the configuration of each signal transmission device on the transmission side and the reception side, the multiplexing method of transmission signals, the type of transmission line, and the like can be variously modified without departing from the gist of the present invention.

[0044]

As described above, according to the present invention, a digital signal capable of repeatedly transmitting the same information a plurality of times at a fixed time difference with a small increase in the hardware scale and processing amount on the receiving side is reduced. A transmission system and a signal transmission device thereof can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a digital radio broadcasting system according to an embodiment of the present invention.

FIG. 2 is an exemplary view showing a description example of syntax of a code bit stream created in the embodiment.

FIG. 3 is a diagram showing an example of a bit stream protected by a CRC in the embodiment.

FIG. 4 shows a main audio on a wireless transmission path according to the embodiment;
6 is a time chart showing a timing relationship between the preliminary 1 and the preliminary 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Transmission side signal transmission apparatus 111-113 ... Audio coding processing part 121-123 ... Variable length coding / multiplexing part 131-133 ... Error detection code addition part 141-143 ... PES multiplexing part 151,152 ... Delay processing part Reference Signs List 16 TS multiplexing unit 20 Receiving-side signal transmission device 21 TS separation unit 221 to 223 PES separation unit 231, 232 Delay processing unit 241 to 243 Variable length code decoding / separation unit 251 to 253 Error detection unit 26 ... Output selection control unit 27 ... Decoding output selection unit 28 ... Audio decoding processing unit

Claims (6)

[Claims] 1. A transmission stream is generated by generating a plurality of streams of packet streams to which a digital signal divided by a fixed frame length is variable-length encoded and to which an error detection code is added, and multiplexing with a certain time difference from each other. A transmitting signal transmitting apparatus for transmitting and receiving, the transmitting stream from the transmitting signal transmitting apparatus is received, the transmitting side is branched into the same number of systems as the number of systems generated on the transmitting side, and each system is pre-allocated from the transmitting stream. Separate the different packet streams, perform variable-length decoding to determine the error detection code, compare with the added error detection code to determine the presence or absence of a transmission error, and perform variable-length decoding of the system without transmission errors. And a receiving-side signal transmission device for selecting an output and compensating for a time difference set on a transmitting side to obtain an original digital signal. Digital signal transmission system. 2. After encoding a digital signal divided by a fixed frame length, a bit stream having a different length is generated for each frame, and a plurality of packet streams to which an error detection code is added are generated for a plurality of streams. A transmission-side signal transmission device that generates and transmits a transmission stream by multiplexing with a time difference of, and the same number of systems as the number of systems generated on the transmission side by receiving a transmission stream from the transmission-side signal transmission device Branching, separating the different packet streams assigned in advance from the transmission stream in each system, extracting the bit stream, obtaining the error detection code, and comparing with the added error detection code to determine whether there is a transmission error. Determine,
Select the bit stream of the system without transmission error,
A digital signal transmission system comprising: a reception side signal transmission device that compensates for a time difference set on a transmission side and decodes an original digital signal. 3. A digital signal divided by a fixed frame length is branched into a plurality of systems, each system is subjected to variable-length coding, and a bit stream having a different length is generated for each frame to generate an error detection code. And a transmission-side signal transmission device that generates and transmits a transmission stream by multiplexing at a fixed time difference from each other, and receives and transmits a transmission stream from the transmission-side signal transmission device. It branches into the same number of systems as the side, separates mutually different packet streams assigned in advance from the transmission stream in each system, performs variable length decoding and bit stream extraction to obtain an error detection code, and detects the added error detection. Determine the presence or absence of a transmission error by comparing with the code, select the bit stream output of the system without transmission error,
A digital signal transmission system comprising: a reception side signal transmission device that compensates for a time difference set on a transmission side and decodes an original digital signal. 4. A transmission generated by generating a plurality of streams of packet streams to which a digital signal divided by a fixed frame length is variable-length-coded and to which an error detection code is added, and multiplexing with a certain time difference from each other. Used in a digital signal transmission system for transmitting a stream, receiving the transmission stream, branching into the same number of systems as the number of systems generated on the transmission side, and different packet streams previously allocated from the transmission stream in each system. Is separated, an error detection code is obtained by performing variable length decoding, a transmission error is determined by comparing the error detection code with the added error detection code, and a variable length decoding output of a system having no transmission error is selected. A signal of a digital signal transmission system characterized in that an original digital signal is obtained by compensating for a time difference set on a transmission side. Feeding apparatus. 5. After encoding a digital signal divided by a fixed frame length, a bit stream having a different length is generated for each frame, and a packet stream to which an error detection code is added is generated for a plurality of systems. Is used in a digital signal transmission system that transmits a transmission stream generated by multiplexing with a time difference of: receiving the transmission stream and branching into the same number of systems as the number of systems generated on the transmission side. The system separates different packet streams assigned in advance from the transmission stream, extracts the bit stream, finds an error detection code, determines whether there is a transmission error by comparing with the added error detection code, and determines whether there is a transmission error. Selects the bit stream of the system that did not have any, and compensates for the time difference set on the transmitting side to restore the original digital Signal transmission apparatus in a digital signal transmission system characterized by decoding the issue. 6. A digital signal divided by a fixed frame length is branched into a plurality of systems, each system is subjected to variable-length coding, and a bit stream having a different length is generated for each frame to generate an error detection code. Is used for a digital signal transmission system that transmits a transmission stream generated by multiplexing with a fixed time difference from each other and receiving the transmission stream, and the same number of systems as the transmission side. , And separates different packet streams assigned in advance from the transmission stream in each system, performs variable length decoding and bit stream extraction to obtain an error detection code, and compares it with the added error detection code. Determine the presence or absence of transmission errors, select the bit stream output of the system without transmission errors, and Signal transmission apparatus in a digital signal transmission system characterized by decoding the original digital signal to compensate for the boss was time difference.