JP2000224136A - Data transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide more stable data transmission by generating a transmission signal with less jitters through the adoption of rate conversion at a simple rate in the case of transmitting data streams of a plurality of systems as one system. SOLUTION: A transmitter side is provided with a means that applies rate conversion and multiplexing to main data, auxiliary data related to the main data at least in a prescribed number of word, and a synchronization extract code so as to obtain the same packet period of that off the main data at a prescribed rate and transmits transmission data streams generated through a multiplexing processing, when transmitting the main data with a data stream configuration in units of prescribed packets, and a receiver side is provided with a means that demultiplexes and decodes the original main data and the original auxiliary data from the received transmission data stream.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a data transmission system in which data of a plurality of systems is integrated into one system, transmitted using a transmission line which may have an error, and returned to the data of a plurality of systems.

[0002]

2. Description of the Related Art The configuration of a conventional data transmission device used for digital terrestrial broadcasting is shown in FIG. 8 and will be described below.
When transmitting program material data in a terrestrial digital broadcasting system, a multiplexing device of a program creation studio
(MUX: Multiplex) 20 creates a main data Di in which a plurality of compressed moving image data, compressed audio data (D1, D2), etc. are unified (multiplexed), and this is combined with control data Dss to be described later on a terrestrial digital signal. Send to the broadcasting station. At the transmitting station, the received main data Di is stored in, for example, 56 carriers.
OFDM (Orthogona) which performs 00 multi-carrier modulation
l Frequency Division Multiplexer) The signal is processed by the modulator 22 to generate a terrestrial broadcast transmission signal, which is transmitted to each home, another transmitting station, or the like. Here, the control data Dss will be described. In terrestrial digital broadcasting, since the program of the HDTV system and the program of the current (NTSC) TV system are mixed, a situation occurs in which the form and system of the signal to be processed at the transmitting station are switched over time. At this time, in the OFDM modulator 22, since it is technically difficult to instantaneously switch to the corresponding transmission mode, control data Dss indicating the switching timing is received in parallel with the main data Di, and based on the control data Dss. Then, the internal processing that operates in a pipeline manner is gradually switched. Compressed data (D
1, D2) is usually in units of 188 words (W), and is broken down into a world standard MPEG (Moving Pictogram) composed of 1W synchronization code 47h and 187W compression information.
ure Experts Group).

[0003] The MUX 20 multiplexes a plurality of compressed data into one system as described above.
Main data Di having a unit of 204 W which has been subjected to scramble processing for preventing DC bias of data words and interleave processing for improving burst error resistance, etc., by adding an error correction code 16 W to the unit of compressed data so as to be suitable for transmission. Create and output In addition, OFDM which is the receiving side
Error correction, descrambling,
In the deinterleaving process, the existence of a synchronization code for calculating and detecting a 204 W data unit is important. Here, the error correction processing may be omitted. As described above, this transmission system does not transmit only the main data of a single program, but controls the data related to the change of the program in order to efficiently handle the main data of a plurality of programs of different systems. The data Dss also needs to be created and output. As shown in FIG. 10, since the control data Dss is synchronized with the switching of the main data Di, 204 W
The unit changes. The main data Di and the control data Dss are transmitted to the OFDM modulator 22, where they are modulated for terrestrial digital broadcasting and transmitted from an antenna.

Next, the data transfer rate in this transmission system will be described. OFDM modulator 2
Fast Fourier transform unit (F
The clock frequency of FT (Fast Fourier Transform) is
It is specified as 8.127 MHz. In addition, the transmission rate is four-phase differential phase shift keying (DQPSK: Differ
ential Quadrature Phase Shift Keying), 16-level quadrature amplitude modulation (16QAM: 16 Quadrature Amplitude Modul)
ation), 64QAM, etc., depending on the primary modulation scheme used. The transmittable rate differs greatly depending on the primary modulation scheme. Therefore, a value related to 8.127 MHz is used as the transfer frequency of the main data Di created in the MUX 20. Usually, the main data Di is 8.
Data is transferred in byte units at a frequency of 4.063 MHz, which is half the frequency of 127 MHz. Also in this case, the main data D
Since i is transmitted at 4.063 MHz and in units of 204 W, control signal Dss also mixes enable signal information indicating a portion not requiring transmission. However, in a modern urban location environment, a program creation studio that creates compressed data for program material and a transmitting station that emits radio waves rarely exist at the same point. Usually, they have to be installed in remote locations,
The MUX 20 is installed in a program creation studio, while the OFDM modulator 22 is installed in a transmitting station located on a small mountain or the like that is advantageous for radio wave transmission. Under such conditions, as shown in FIG. 9, the transmission unit 21T-Tx for transmission on the MUX 20 side.
1, 21T-2 and the transmission units 21R-1, 21R-2 for reception on the OFDM modulator 22 side. In this case, the aforementioned main data Di and control data Dss
Is transmitted using different transmission paths 8A and 8B.

[0005]

Since different frequency bands or channel bands are used for the transmission lines 8A and 8B, it is actually difficult to secure a large number of transmission lines since finite radio resources are used. Not easy. In addition, there is a possibility that an error may be mixed in data during transmission due to an air discharge due to lightning in a transmission path or an influence of a truck equipped with an illegal CB radio. Further, there may be a time lag between the main data Di and the control data Dss sent using different routes. In addition, about 1.5 Mbps as a dedicated communication voice line between two points (studio-transmitting station)
When transmitting the audio data and the auxiliary data Ds including the control data Dss, the above point becomes a further problem. In order to solve these problems, it is necessary to convert a plurality of streams of data into one stream and perform a conversion to take measures against errors in the transmission line, and to create a time gap for inserting auxiliary data and the like. Rate conversion is essential. Here, the rate of the rate conversion varies depending on the amount of auxiliary data inserted into the main data and the number of parity data added for error correction. If the speed ratio is complicated, the system construction will be hindered. The present invention eliminates these drawbacks, and when a plurality of data streams are transmitted as one stream, a transmission signal with less jitter can be created by adopting a simple ratio rate conversion, thereby achieving more stable data transmission. It is intended to be realized.

[0006]

According to the present invention, in order to achieve the above object, when transmitting main data having a data stream configuration in a predetermined packet unit, a transmitting side is provided with the main data and at least a predetermined word number of the main data. Means for transmitting the auxiliary data related to the main data and the synchronization extraction code at a predetermined rate so as to have the same packet cycle as the packet cycle of the main data, multiplexing the data, and transmitting the transmission data stream generated by the multiplexing; The receiving side has means for separating and decoding the original main data and the auxiliary data from the received transmission data stream. The multiplexing is to multiplex the auxiliary data of 12 to 48 words, the synchronization extraction code, and the error correction code with respect to 204 words constituting the packet unit of the main data, and perform the predetermined rate conversion. ,
(The number of words constituting the packet unit of the transmission data stream) / (2 which constitutes the packet unit of the main data)
04 words) times, and the ratio of the number of words is represented by integers of 21 or less, and the difference between the integers is 3
It is a value that is represented by a numerical value that is within. In addition, the multiplexing is to multiplex the auxiliary data of 24 to 36 words, the synchronization extraction code, and the error correction code with respect to 204 words constituting a packet unit of the main data, and perform the predetermined rate conversion. , (The number of words forming the packet unit of the transmission data stream) / (204 words forming the packet unit of the main data), and the ratio of the number of words is 20.
It is represented by the following integers, and the difference between the integers is a value represented by a numerical value within 2 or less.
In addition, the multiplexing includes multiplexing the auxiliary data of 12 words, the synchronization extraction code of 2 words, and the error correction code of 20 words with respect to 204 words constituting a packet unit of the main data. The predetermined rate conversion is performed at 7/6 times, and the actual data rate of the transmission data stream is 40 Mbps or less, and the actual data rate of the auxiliary data is 1.536 Mbps or more. Further, a data stream configuration is used in which two words of the auxiliary data are assigned to accompanying information that changes in 204 word units. Further, the multiplexing includes multiplexing the auxiliary data of 11 to 34 words, the synchronization extraction code, and the error correction code for 187 words constituting a packet unit of the main data,
The predetermined rate conversion is performed by multiplying (the number of words constituting the packet unit of the transmission data stream) / (187 words constituting the packet unit of the main data), and the ratio of the number of words is 18 or less. The values are represented by integers, and are represented by numerical values in which the difference between the integers is within two. Also, the multiplexing
For each of the 187 words constituting the packet unit of the main data, the auxiliary data of any one of the words 11, 17, and 34, the synchronization extraction code, and the error correction code are multiplexed. , 18/17
This is performed at any one of the magnifications of 12 times, 12/11 times, and 13/11 times. In addition, the multiplexing is performed for 16 to 188 words constituting a packet unit of the main data.
The 47-word auxiliary data, the synchronization extraction code, and the error correction code are multiplexed, and the predetermined rate conversion is performed at any one of 51/47 times and 5/4 times. . In the data rate conversion,
After converting the rate of at least one system of main data, auxiliary data related to the main data is multiplexed, and an error correction code or the like is added to perform transmission line coding to create one system data stream. Also, by setting the amount of auxiliary data to be added to a value in which the ratio of the rate conversion is represented by integers equal to or less than 21 and the difference between the integers representing the ratio is within 3 or less, The transmission system has a low clock jitter after conversion. Further, error correction and interleave processing are required as a countermeasure against errors in the transmission path. Becomes indispensable.

[0007]

FIG. 1 shows the configuration of an embodiment of a data transmission system according to the present invention. This transmission system includes a transmission processing unit 1T, a transmission path 8, and a reception processing unit 1R. The transmission processing section 1T includes the auxiliary data Ds and the main data D
A clock CKi matching the rate of i and the main data Di and a start signal PSYN indicating a packet unit of the data stream of the main data Di are input. Transmission processing unit 1T
Is the transmission line encoded input data (main data), as described later.
12W auxiliary data Ds per 204 words of Di,
A transmission data stream Dot consisting of a total of 238 W with an error correction code of 20 W and a synchronization extraction code of 2 W added and having a data rate 7/6 times that of the main data Di is created and output. The transmission data stream Dot becomes a Dor containing an error or the like rarely via the transmission path 8, and is input to the reception processing unit 1R. The reception processing unit outputs the 204 W main data D from the received transmission data stream Dor.
i and auxiliary data Ds are separated and extracted, and the rate is increased by 6/7 to return to the original continuous state and output. Also, the clock CKo that matches the rate of the main data Di and the main data Di
Output a start signal PSYN indicating the stream unit of.

Here, the creation of the transmission data stream Dot in the transmission processing section 1T will be described in detail with reference to FIG. In the transmission processing unit 1T, the main data Di having a packet configuration of 204 words (W) is the auxiliary data Ds of 12W,
It is converted into a transmission data stream composed of a total of 238 W to which a 20 W error correction code and a 2 W synchronization extraction code have been added. That is, in order to add a total of 34 W of auxiliary data Ds, an error correction code, and a synchronization extraction code, the input main data Di having a bit rate of 32.5 Mbps has a bit rate of 238/204 times every 204 W. 9M
The rate is converted to bps, and the data is changed to 204 W data Dst having a pause period of 34 W in between. Subsequently, auxiliary data Ds (12 W) having a bit rate of 37.9 Mbps
Is performed to create data Dmt. Furthermore, data Dot composed of a total of 238 W is generated by adding a synchronization extraction code (2 W) at the start of the stream (packet) and an error correction code (20 W) at the end of the stream as transmission path coding.

Here, the auxiliary data Ds (1
2W), error correction code (20W), synchronization extraction code (2
W) and the like are collectively referred to as additional data. The rate ratio of the main data Di (204 W) and the data Dot composed of a total of 238 W to which the additional data (34 W) is added is as follows. 204: (204 + 34) = 204: 238 = 6: 7 32.5 Mbps: 37.9 Mbps In this example, the clock CKi of the main data Di is set to 7 /
The clock CKt of the transmission line coded stream can be created by performing the PLL by a simple ratio by six times. An example of rate conversion other than the above example is shown below. 204: (204 + 17) = 204: 221 = 12: 13 ≒ 32.5 Mbps: 35.2 Mbps In this example, the clock CKi of the main data Di is 13 /
The clock CKt of the transmission line coded stream can be created by performing the PLL by a simple ratio of 12 times.

Further, another example will be described. 204: (204 + 51) = 204: 255 = 12: 15 ≒ 32.5 Mbps: 40.6 Mbps 204: (204 + 12) = 204: 216 = 17: 18 ≒ 32.5 Mbps: 34.4 Mbps 204: (204 + 24) = 204: 228 = 17: 19 ≒ 32.5 Mbps: 36.3 Mbps 204: (204 + 36) = 204: 240 = 17: 20 ≒ 32.5 Mbps: 38.2 Mbps 204: (204 + 48) = 204: 252 = 17: 21 ≒ 32. 5 Mbps: 40.1 Mbps In each of the above examples, the rate conversion ratio is represented by integers of 21 or less, and the difference between the integers is represented by a simple ratio of 3 or less. The clock CKt can be easily created from the clock CKi to be executed. The receiving side can create a clock CKt of the main data Di from the transmission clock CKr created from the received information. Although data cannot be concluded due to the progress of devices, the data rate is 4
If it exceeds 0 Mbps, the operation of various digital elements used in the above processing becomes severe in terms of speed. Therefore, the rate after the rate conversion is 40 Mbps or less, a lot of additional data is allocated, and the ratio becomes simple: 204: 238 =
The 67.9 Mbps mode at 37.9 Mbps is optimal.

An example of rate conversion other than the above is shown below. In this example, 11 to 34 words of auxiliary data D per 187 words forming a packet unit of the main data Di.
s, a synchronization extraction code, and an error correction code are added and multiplexed, and the rate conversion is performed by a factor of (the number of words forming the packet unit of the transmission data stream) / (187 words forming the packet unit of the main data). And the ratio of the number of words is represented by integers of 18 or less, and the difference between the integers is a value represented by a numerical value within 2 or less. In addition, for 187 words constituting a packet unit of the main data Di, auxiliary data Ds of any one of words 11, 17, and 34, a synchronization extraction code and an error correction code are added and multiplexed, and the data is 18/17 times. 12/11 times,
Any rate conversion of 13/11 times is performed. Also, for 188 words constituting a packet unit of the main data Di, 16-47 words of auxiliary data Ds, a synchronization extraction code and an error correction code are added and multiplexed.
One of the rate conversions of 2 × and 5/4 × is performed.

Next, the detailed configuration and operation of the transmission processing section 1T will be described. The detailed configuration of the rate converter 2 is shown in FIG. 3 and the operation timing is shown in FIG. The rate conversion unit 2 includes main data Di, a pulse PSYN indicating a break between packets of the main data Di, and a rate CKi of the main data Di.
Is entered. The rate converter 2 has a FIFO memory 2-
1 to output data Dst whose time has been shortened. Further, the rate conversion unit 2 outputs a pulse STt indicating the output timing of the data Dst and a clock CKt having a relationship of 7/6 with the clock CKi. The detailed configuration of the multiplexing unit 3 is shown in FIG. 5, and the operation timing is shown in FIG. The multiplexing unit 3 receives data Dst and auxiliary data Ds whose time has been reduced. The multiplexing unit 3 sets the data Ds using the pulse STt from the rate conversion unit 2 as timing.
The multiplexed data Dmt is created by switching between t and the auxiliary data Ds. The detailed configuration of the transmission path encoding unit 4 will be described with reference to FIG. The multiplexed data Dmt is input to the transmission path coding unit 4. The transmission path encoding unit 4 creates transmission path encoded transmission data Dot using the pulse STt from the rate conversion unit 2 as timing. Further, the transmission path encoding unit 4
Then, after performing a scrambling process for dispersing DC bias, auxiliary data and a code for synchronization extraction are added.
8 W is added with 20 W calculated by parity, which is a code for error correction. Further, in order to cope with continuous errors, an interleaving process for changing the data transmission order is performed. Then, the data in the byte state is converted into a 1-bit serial signal and output.

Next, the detailed configuration and operation of the reception processing section 1R will be described. The transmission path decoding unit 5 receives the signal Dor mixed with an error or the like via the transmission path and outputs the transmission path decoded data Dmr, the timing signal STr indicating the start point thereof, and the clock CKr of the data Dmr. Is done. In this transmission path decoding processing, a data rate is extracted from serial input data and a clock CKr is reproduced.
Subsequently, the synchronization code included in the 1-bit serial signal is periodically searched for and converted to byte-state data. Further, in order to cope with a continuous error, the reverse order of the interleaving process for changing the data transmission order is performed, and the data order is restored. Further, the error is corrected with reference to the added parity signal. Thereafter, a process reverse to the scramble process for dispersing the DC bias is performed to restore the original data. The demultiplexing unit 6 receives the data Dmr subjected to transmission line decoding, the pulse STr and the clock CKr from the transmission line decoding unit 5. The demultiplexing unit 6 separates the auxiliary data Der and the data Dsr and outputs them. The data Dsr is added to the rate inverse converter 7.
, The pulse STr from the transmission path decoding unit 5 and the clock CK
r is input. The rate reverse conversion unit 7 uses the FIFO memory to reduce the time-interrupted data Dsr
To the original main data Di at a continuous rate. Also, the clock CKr which has a 6/7 relationship with the clock CKr
Output r. Further, it outputs a pulse PSYN indicating a break in the main data Di. Here, the configuration of the transmission channel decoding unit 5 is opposite to that of the transmission channel encoding unit 4, the configuration of the demultiplexing unit 6 is opposite to that of the multiplexing unit 3, and the configuration of the rate inverse conversion unit 7 is Since the configuration is opposite to that of the unit 2, the detailed configuration
The description of the operation is omitted.

[0014]

According to the present invention, when a plurality of systems of data are integrated into one system for transmission coding, a transmission signal with less jitter can be created by adopting a simple rate conversion so that a more stable transmission signal can be obtained. Data transmission can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the overall configuration of a data transmission system according to the present invention.

FIG. 2 is a time chart showing the operation of the present invention.

FIG. 3 is a block diagram showing a configuration of a rate conversion unit 2 of the present invention.

FIG. 4 is a time chart showing the operation of the rate conversion unit 2 of the present invention.

FIG. 5 is a block diagram showing a configuration of a multiplexing unit 3 of the present invention.

FIG. 6 is a time chart showing the operation of the multiplexing unit 3 of the present invention.

FIG. 7 is a block diagram illustrating a configuration of a transmission line encoding unit 4 according to the present invention.

FIG. 8 is a block diagram showing a configuration example of a conventional terrestrial broadcasting device.

FIG. 9 is a block diagram showing a configuration example of a conventional terrestrial broadcasting device.

FIG. 10 is a time chart showing an example of data transfer between conventional terrestrial broadcasting devices.

[Explanation of symbols]

1T: transmission processing unit, 1R: reception processing unit, 2: rate conversion unit, 3: multiplexing unit, 4: transmission line encoding unit, 5: transmission line decoding unit, 6: demultiplexing unit, 7: rate reverse Conversion unit 8: Transmission path.

Claims (8)

[Claims] When transmitting main data having a data stream configuration in a predetermined packet unit, the transmitting side transmits, to the transmitting side, the main data, at least a predetermined number of words, auxiliary data related to the main data, and a synchronization extraction code, Means for transmitting a transmission data stream generated by the multiplexing by performing a predetermined rate conversion so as to have the same packet cycle as the packet cycle of the main data, and having a receiving side transmit the transmission data stream from the received transmission data stream. A data transmission system comprising means for separating and decoding the original main data and the auxiliary data. 2. The multiplexing method according to claim 1, wherein the auxiliary data of 12 to 48 words, the synchronization extraction code, and the error correction code are multiplexed with respect to 204 words constituting a packet unit of the main data. The predetermined rate conversion is performed by (times the number of words constituting the packet unit of the transmission data stream) / (204 words constituting the packet unit of the main data) times.
And the ratio of the number of words is represented by integers of 21 or less,
A data transmission system characterized in that the difference between the integers is a value represented by a numerical value that is within three. 3. The multiplexing method according to claim 1, wherein the auxiliary data of 24 to 36 words, the synchronization extraction code, and the error correction code are multiplexed with respect to 204 words constituting a packet unit of the main data. The predetermined rate conversion is performed by (times the number of words constituting the packet unit of the transmission data stream) / (204 words constituting the packet unit of the main data) times.
And the ratio of the number of words is represented by integers of 20 or less,
A data transmission system characterized in that the difference between the integers is a value represented by a numerical value that is within two. 4. The multiplexing method according to claim 1, wherein the multiplexing is performed by adding 12 words of the auxiliary data, 2 words of the synchronization extraction code, and 20 words of an error correction code to 204 words constituting a packet unit of the main data. Are multiplexed, the predetermined rate conversion is performed at 7/6 times, and the actual data rate of the transmission data stream is 40 Mbps or less, and the actual data rate of the auxiliary data is 1.536 Mbps or more. A data transmission system, characterized in that: 5. The data transmission system according to claim 1, wherein two words of said auxiliary data are assigned to ancillary information that changes in units of 204 words. 6. The multiplexing method according to claim 1, wherein the multiplexing is performed by multiplexing 11 to 34 words of the auxiliary data, the synchronization extraction code, and the error correction code for 187 words constituting a packet unit of the main data. The predetermined rate conversion is performed by (times the number of words constituting the packet unit of the transmission data stream) / (187 words constituting the packet unit of the main data).
And the ratio of the number of words is represented by integers of 18 or less,
A data transmission system characterized in that the difference between the integers is a value represented by a numerical value that is within two. 7. The multiplexing method according to claim 1, wherein the multiplexing is performed by using any one of 11, 17, and 34 of the auxiliary data and the synchronization extracting code for 187 words constituting a packet unit of the main data. The error correction code is multiplexed, and the predetermined rate conversion is performed on 18/17.
A data transmission system characterized in that the data transmission is performed at any one of multiplication, 12/11, and 13/11. 8. The method according to claim 1, wherein the multiplexing is performed by multiplexing the auxiliary data of 16 to 47 words, the synchronization extraction code, and the error correction code for 188 words constituting a packet unit of the main data. Wherein the predetermined rate conversion is performed at one of 51/47 times and 5/4 times.