JPH08163179A - Data compression transmitter - Google Patents

Abstract

PURPOSE: To measure a state in which the quality of a communication channel is deteriorated, to set a dictionary reset period, to reduce the delivery period of erroneous information when a bit error occurs in the communication channel and to efficiently use the communication channel in a data compression transmitter by an LZ code. CONSTITUTION: Transmission side equipment performs data compression by selecting plural kinds of frame length corresponding to a quality deteriorated state informed from reception side equipment, and initializes compressed data, and attaches an error detection code on the compressed data, and assembles it in a transmission frame. then, sends it out to the communication channel. The reception side equipment disassembles a received transmission frame, and performs error detection, and expands the compressed data, then, restores original information. Expansion dictionary memery 33 is initalized at every transmission frame, and a comparator 40 compares a threshold value held in quality threshold value memory 37 with the coefficient value of a quality measuring counter 39 which holds the number of times of bit errors generated in fixed time, and judges the case that the coefficient value exceeds the threshold value as the quality deteriorated state, and informs it to the transmission side equipment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication control device connected to each other through a communication line, compressing the information on the transmitting side and then transmitting the information to the communication line, and expanding the compressed information received on the receiving side. The present invention relates to a data compression transmission device that restores original information by doing the above.

[0002]

2. Description of the Related Art In recent years, information transmission plays an extremely important role in the information society, and means for efficiently transmitting a large amount of information has become important. In order to use the communication line efficiently when transmitting information, in a communication control device mutually connected via the communication line, the sending side device compresses the information before sending it to the communication line and receiving it. By decompressing the compressed information and restoring the original information in the side device,
It has been proposed to reduce the amount of effective transmission information and use communication lines efficiently. As an information compression / decompression method in information communication, L is a kind of universal code that is known to have a short processing delay time and excellent compression efficiency.
empel-Ziv code (or Ziv-Lempel
A code, hereinafter referred to as an LZ code. ) And LZW
Improved schemes such as codes and LZSS codes are widely used.

The basic algorithm of the LZ code is to decompose the data sequence to be compressed into subsequences, search the past subsequence of the data sequence for the longest match, and obtain the position and length information. The amount of information is compressed by substituting and expressing the subsequence. Encoding (compression processing) and decoding (decompression processing) algorithms in the LZ code will be described with reference to FIG.

First, the procedure of compression processing will be described.
In the initial state, the compression dictionary is empty. When the compression process is started, the input original data is decomposed into the subsequence D1. Since the compression dictionary is empty at that time point and there is no past data sequence to refer to, the replacement expression for the subsequence D1 is not performed, and the dictionary information such as the bit pattern, position information and length of the subsequence D1 is compressed. Register with. Since the subsequence D2 does not match the dictionary information registered in the compression dictionary, the replacement expression for the subsequence D2 is not performed,
The dictionary information of the subsequence D2 is registered in the compression dictionary. Subsequence D
3 has the same bit pattern as the subsequence D1 registered in the compression dictionary, the subsequence D registered in the compression dictionary
The partial sequence D3 is replaced and expressed by the dictionary information D1 'of 1.
The subsequence D4 is replaced and expressed by the dictionary information D2 ′ registered in the compression dictionary, and the subsequence D5 is not registered in the compression dictionary and therefore is not registered as replacement and additionally registered in the compression dictionary.
Is replaced with the dictionary information D5 'registered in the compression dictionary, and the above operation is repeated to obtain compressed data.

Next, the procedure of decompression processing will be described.
In the initial state, the decompression dictionary is empty. When the decompression process is started, the subsequence D1 is extracted by verifying the compressed data, and when it is detected that the subsequence D1 is not dictionary information, the subsequence D1 is set as the decompressed data as it is and the subsequence D1 is set in the decompression dictionary. Register dictionary information about. Similarly, it is detected that the partial sequence D2 is not the dictionary information, the partial sequence 2 is set as the restored data as it is, and the dictionary information about the partial sequence D2 is registered in the decompression dictionary. Then, the subsequence D1 'is extracted, and when it is detected that the subsequence D1' is dictionary information indicating the subsequence D1, the subsequence D1 'is replaced by the bit pattern of the subsequence D1 registered in the decompression dictionary, Set it in the restored data. Hereinafter, the subsequence D2 'restores the bit pattern by the subsequence D2 registered in the decompression dictionary, and the subsequence D5 is not the dictionary information, so it is set as the restored data as it is, and the dictionary information is registered in the decompression dictionary. D5 'restores the bit pattern by the subsequence D5 registered in the decompression dictionary and sets it as the restored data.

By repeatedly performing the above processing continuously, data compression processing and decompression processing are realized in the LZ code.

The LZ code according to the above algorithm has the following features. That is, if some of the compressed data is destroyed for some reason, the original data cannot be correctly restored by the decompression process. In particular, the subsequence in which the destroyed portion in the compressed data is registered in the decompression dictionary instead of the dictionary information (for example, the subsequence D of the compressed data in FIG. 6).
1, D2, D5), the decompression dictionary is not created correctly and contains an error. Therefore, a decompression error continuously occurs in the decompression process after referring to the registration information of the decompression dictionary. I will end up.

Due to the above characteristics, in the LZ code, if the compressed data is destroyed for some reason, the compression dictionary and the decompression dictionary are initialized in synchronism with each other, so that the LZ code is continuously restored due to a dictionary error. It is necessary to prevent mistakes.

A conventional technique for realizing a data compression transmission device using the LZ code having the above characteristics will be described below. FIG. 7 is a block diagram showing the configuration of a communication system including a conventional data compression transmission device. In addition, FIG.
It is a timing diagram explaining operation | movement of the conventional data compression transmission apparatus.

In FIG. 7, reference numeral 70 is a data compression transmission device, 71 is a data expansion transmission device, 72 is a communication line, and 73 is a communication line.
Is a data input line, and 74 is a data output line.

The data compression transmission device 70 divides the original data received from the data input line 73 into a bit string of fixed length L, and performs compression processing on the fixed length bit string while constructing a compression dictionary by LZ code. The compressed data is sent to the communication line 72, and the compression dictionary is initialized when the compression process is completed for the fixed length bit string. Upon receiving the compressed data from the communication line 72, the data decompression transmission device 71 restores the original data while constructing the decompression dictionary by decompressing the compressed data by the LZ code, and when the restoration of the original data is completed, the decompression dictionary is initialized. Turn into.

By repeating the above operation,
The compression dictionary in the data compression transmission device 70 on the transmission side and the decompression dictionary in the data decompression transmission device 71 on the reception side are initialized in synchronization with each other periodically, and due to a bit error or the like occurring during transmission of the compressed data on the communication line 72. When the compressed data is destroyed, it is possible to suppress the continuous spread of the restoration error of the original data only within a certain range.

[0013]

However, in the above-described conventional data compression transmission apparatus, since the compression dictionary is always initialized at a constant period in the compression process on the transmission side, the dictionary information accumulated in the past is periodically stored. Therefore, there is a problem that the compression efficiency by the LZ code cannot be improved to a certain level or more, and the communication line cannot be effectively used.

When a bit error occurs in the communication line, the decompression dictionary contains an error, so that the restored data for the period until the dictionary is initialized contains an error.
During that time, there was a problem that erroneous information was transmitted to the receiving side terminal.

The present invention solves the above-mentioned conventional problems, and detects whether or not a bit error has occurred in the compression information received in the decompression processing on the receiving side, thereby detecting the communication quality of the communication line in the dictionary. It is possible to reduce the invalid period of the decompression dictionary when a bit error occurs and to obtain a higher compression efficiency by monitoring the above and increasing / decreasing the dictionary initialization period of the LZ code according to the deterioration state of the communication quality. It is an object of the present invention to provide a data compression transmission device that does.

Further, according to the present invention, an idle indicating no communication is given to the terminal connected to the data compression transmission device on the receiving side during the dictionary invalid period until the error of the expansion dictionary information due to the bit error occurrence or the initialization of the dictionary. An object of the present invention is to provide a data compression transmission device capable of continuously transmitting a pattern and preventing erroneous information transmission to a receiving terminal.

[0017]

In order to achieve the above-mentioned object, the present invention provides a unit clock, which is bit-synchronized with data received from a data input line connected to a data compression transmission apparatus of the transmission side in a transmission side apparatus. A first clock generating means for generating, a plurality of frame length storing means for holding information on a unit frame length for data compression, and a memory for holding a quality deterioration state of a communication line notified from a receiving side data compression transmission apparatus. Means, and a first selecting means for selecting one of a plurality of frame length storing means according to the quality deterioration state notified from the storing means at each frame synchronization timing and outputting the held contents, and a first clock generating means. The unit counts by 1 for each unit clock generated by the means, and when the count value becomes equal to the unit frame length of data compression displayed by the first selection means, Frame length counting means for generating the frame synchronization timing, compression dictionary storage means for retaining the compression dictionary information used for the data compression processing and initializing the retained contents at each frame synchronization timing, and compression for each frame synchronization timing A data compression unit that compresses the information received from the data input line while referring to and updating the compression dictionary information held in the dictionary storage unit, and outputs the compressed data;
An error detection code is added to the compressed data, the first error control means for outputting the error detection code, and a transmission frame assembling means for assembling the compressed data with the error detection code added into a transmission frame are provided. Second side clock generation means for generating a unit clock bit-synchronized with the data received from the communication line connected to the receiving side data compression transmission device, and the transmission frame received via the communication line is decomposed and compressed with error detection code Transmission frame decomposing means for extracting data and outputting the data, second error control means for verifying the compressed data with error detection code, detecting presence or absence of a bit error in the compressed data, and transmitting the compressed data, and data. Decompression dictionary storage that retains decompression dictionary information used for decompression processing and initializes the retained contents at each frame synchronization timing Stage, a data decompression unit that decompresses the compressed data while receiving and decompressing the decompressed dictionary information and updating the decompressed dictionary information, restores the original information, and generates the frame synchronization timing, and maintains the communication quality observation time in the initial state. , A holding value is decremented by 1 each time the unit clock is generated by the second unit clock generating means, and a quality measuring timing is generated when the holding value becomes equal to 0, and the holding value is initialized to 0 in the initial state. The quality measurement / counting means counts one by one for each error detection notification and initializes the holding value to 0 at each quality measurement timing, and holds one or a plurality of thresholds regarding the number of bit error occurrences in the communication line. The quality threshold value storage means, the value held by the quality measurement / counting means each time a quality measurement timing is received, and the bit error occurrence held in the quality threshold value storage means. Generates a quality notification signal that indicates a communication quality deterioration state when the value held by the quality measurement / counting means exceeds the threshold value, and a communication quality non-deterioration state when the held value is less than the threshold value. And a comparison means for doing so.

Further, according to the present invention, in the above-mentioned receiving side data compression transmission apparatus, an idle pattern generating means for continuously generating an idle pattern indicating a non-communication state, and an error in the compressed data received from the second error control means. By the detection notification, the input data from the idle pattern generating means is selected, this is output to the data output line, and the frame synchronization timing is received from the data decompressing means, whereby the restored original information input from the data decompressing means. And a second selection means for selecting this and outputting it to the data output line.

[0019]

The present invention relates to a unit frame length in which the first selecting means compresses data according to the information about the quality deterioration state of the communication line notified from the receiving side device in the transmitting side data compression transmitting device. Input from a plurality of frame length storage means for holding information is selected, and in the state where quality is deteriorated, a shorter unit frame length is selected,
Display this. The counting means counts one by one for each unit clock bit-synchronized with the information received from the data input line, and generates a framing completion signal when the counted value becomes equal to the unit frame length selected and displayed by the selecting means. The data compression means compresses the information received from the data input line while referring to and updating the compression dictionary information held in the compression dictionary storage means which is initialized every time the framing completion signal generated by the counting means is received. Then, the first error control means adds an error detection signal to the compressed data, and the transmission frame assembling means assembles the compressed data with error detection code into a transmission frame and sends it to the communication line.

Further, in the receiving side data compression transmitting apparatus, the transmission frame disassembling means decomposes the transmission frame received from the communication line and extracts the compressed data with error detection code, and the second error control means the error detecting means. The compressed data is extracted from the signed compressed data, a bit error in the compressed data is detected, and the data decompression means generates a transmission frame synchronization signal when receiving the compression data and retains the contents held by receiving the transmission frame synchronization signal. The expanded dictionary information held in the initialized expanded dictionary storage means is referenced / updated to expand the compressed data and restore the original information. The clock means generates a quality measurement signal each time a unit clock synchronized with the information bit received from the communication line is received. The quality measurement counting means initializes the count value to 0 every time the quality measurement signal is received, counts the number of times of receiving the bit error detection notification, and the comparing means counts the quality measurement count each time the quality measurement signal is received. The count value of the means and the threshold value for judging the quality deterioration state of the communication line held in the quality threshold value storage means are compared, and if the count value exceeds the threshold value, the quality deterioration state is determined, and if the count value is less than or equal to the threshold value. Generates a quality notification signal indicating a non-degraded state.

According to the present invention, in the data compression transmission apparatus on the receiving side, the idle pattern generating means continuously generates an idle pattern indicating a non-communication state, and the second selecting means outputs the idle pattern from the second error control means. When the error detection signal is received, the idle pattern input from the idle pattern generating means is selected, and when the transmission frame synchronization signal generated by the data decompressing means is received, the original data input from the data decompressing means is selected, and this is selected as the data. Send to the output line.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the data compression transmission device of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a communication system including a data compression transmission device of the present invention. In FIG. 1, 1A is a data compression transmission apparatus on the transmission side, 1B is a data compression transmission apparatus on the reception side, 2A and 2B are communication lines, 3 is a data input line, 4 is a data output line, 5A, 5B, 5C, and 5D is a data terminal, 6 is a host computer, 7 is a multiplexer, and 8 is a demultiplexer.

In FIG. 1, a multiplexing device 7 multiplexes the data output from the data terminals 5A, 5B and the host computer 6, compresses the data by the data LZ code multiplexed in the transmitting side data compression transmission device 1A, and compresses it. The data is sent to the communication line 2A. The compressed data received from the communication line 2A is transmitted to the receiving side data compression transmission apparatus 1B as L
The data decompressed by the Z code and multiplexed by the demultiplexer 8 is demultiplexed, and each demultiplexed data is delivered to the data terminal 5C or 5d. The data compression transmission devices 1A and 1B have the same configuration, and the LZ
It has both a code compression function and a data decompression function.

FIG. 2 is a block diagram showing the configuration of the data compression section of the transmission side data compression transmission apparatus 1A in the above embodiment. In FIG. 2, reference numeral 21 denotes a clock generator A (first
And a unit clock that is bit-synchronized with the data input from the data input line 3. Reference numeral 22 denotes a register (a storage unit that holds the quality deterioration state of the communication line). When a quality notification signal notified from the receiving side data compression transmission apparatus 1B via the communication line 2B is received, the value is held and a read pulse is given. By receiving the framing completion signal from the frame length counter 25, the held content is output as a frame length switching signal.
Reference numerals 23A and 23B denote frame length memories (frame length storage means), respectively, and a unit length L of compression indicating how many bits of input data are collectively compressed by the LZ encoder 27.
A and LB (where LA> LB) are held respectively.
A selector A (first selection means) 24 is connected to the frame length memories 23A and 23B, selects the value of the frame length memory 23A in the initial state, and outputs it.
When the frame length switching signal output from the register 22 is 0, the held content LA of the frame length memory 23A is output, and when the frame length switching signal is 1, the held content LB of the frame length memory 23B is output. Reference numeral 25 denotes a frame length counter (frame length counting means), which holds 0 in the initial state, counts by 1 each time a unit clock is received from the clock generator 21, and the count value is equal to the value output by the selector 24. When it becomes, the framing completion signal is generated and
It is initialized to 0. Reference numeral 26 is a compression dictionary memory (compression dictionary storage means), in which the compression dictionary to be compressed which is held in the initial state is initialized to the unregistered state, and the LZ encoder 27 is used.
Holds the compression dictionary information generated by, and upon receiving a framing completion signal from the frame length counter 25, initializes the contents held in the compression dictionary memory 26 and puts the compression dictionary in an unregistered state. Reference numeral 27 is an LZ encoder (data compression means), which reads a bit string of original data from the data input line 3, and every time a framing completion signal is received from the frame length counter 25, with respect to all bit strings of the original data read so far. The compression processing is performed by the LZ code, and the compressed data is output. In the above compression processing, the LZ encoder 27 refers to the compression dictionary information held in the compression dictionary memory 26, and additionally updates the compression dictionary by registering the information that is not registered in the compression dictionary. 28
Is an error controller A (first error control means), which calculates an error detection code for the compressed data received from the LZ encoder 27, adds it to the end of the compressed data, and holds it. Reference numeral 29 denotes a transmission frame assembling unit (transmission frame assembling means), which adds a header indicating the beginning of the transmission frame to the beginning of the compressed data with error detection code received from the error controller A28, and a trailer indicating the end of the frame at the end. To assemble a transmission frame and send it to the communication line 2A.

FIG. 3 is a block diagram showing the configuration of the data decompression unit of the receiving side data compression transmission apparatus 1B in the above embodiment. In the figure, reference numeral 30 denotes a clock generator B (second clock generator), which generates a unit clock bit-synchronized with the data received from the communication line 2A. 31
Is a transmission frame disassembly unit (transmission frame disassembly unit), which receives data from the communication line 2A every time it receives a unit clock from the clock generator B30,
When one transmission frame is received, the header and trailer are removed from the transmission frame, the compressed data and the error detection code are extracted, and this is sent to the error controller B32. An error controller B (second error control means) 32 receives the compressed data with an error detection code from the transmission frame decomposer 31 and sends only the compressed data excluding the error detection code to the LZ composite device 34. At the same time, the occurrence of a bit error in the compressed data section is verified, and if a bit error is detected, an error detection signal is generated. Reference numeral 33 denotes a decompression dictionary memory (first stage of decompression dictionary storage), in which the decompression dictionary held in the initial state is initialized to an unregistered state, holds decompression dictionary information generated by the LZ compound device 34, and stores in the LZ compound device 34.
By receiving the transmission frame synchronization signal received from, the decompression dictionary memory is initialized and the registered contents of the decompression dictionary are set to the unregistered state. 34 is an LZ compound device (data expansion means)
When the bit string of the compressed data received from the error controller B32 is read, a transmission frame synchronization signal is generated, and the bit string is subjected to data decompression processing by the LZ code to restore the original data and restore it to the selector B3.
Send to 6. In the decompression process, the LZ composite device 34 refers to the decompression dictionary information held in the decompression dictionary memory 33, and additionally registers information not registered in the decompression dictionary in the decompression dictionary and updates the decompression dictionary. To do. Three
Reference numeral 5 denotes an idle pattern generator (idle turn generating means), which continuously sends out an idle pattern indicating a non-communication state in a data terminal or the like accommodated in the data compression transmission device 1B. A selector B (second selection means) 36 is connected to the output line of the LZ composite device 34 and the idle pattern generator 35, reads the original data output from the LZ composite device 34 in the initial state, and performs error control. When the error detection signal generated by the device B32 is received,
When the idle pattern output from the idle pattern generator 35 is read and sent to the data output line 4 and the transmission frame synchronization signal generated by the LZ composite device 34 is received, the data output from the LZ composite device 34 is read and the data is output. It is sent to the output line 4. A quality threshold memory (quality threshold storage means) 37 holds a threshold N relating to the number of bit error occurrences. Reference numeral 38 denotes a timer (time measuring means), which holds a preset quality measurement time T in the initial state, subtracts the timer value by 1 each time a unit clock is received from the clock generator B30, and sets the timer value to 0. When they become equal, a quality measurement signal is generated and the timer value is initialized to T. Reference numeral 39 denotes a quality measuring counter (quality measuring / counting means), the count value of which is initialized to 0 in the initial state, counts by one each time an error detection signal is received from the error controller B32, and the quality measuring signal from the timer 38. Is received, the count value is initialized to 0. Reference numeral 40 denotes a comparator (comparison means), which receives the quality measurement signal from the timer 38, compares the threshold value N regarding the number of bit error occurrences held in the quality threshold value memory 37 with the measurement value of the quality measurement counter 39, and calculates the total value. If the numerical value exceeds the threshold value N, the communication line 2A
If the integer value is less than or equal to the threshold value N, it is determined that the communication quality of the communication line 2A has not deteriorated and the quality notification signal is determined as a quality notification signal. 0 is generated and sent to the communication line 2B.

Next, the operation of the data compression transmission apparatus having the above configuration will be described with reference to the drawings. FIG. 4 is a timing chart for explaining the operation of the data compression transmission device of this embodiment. FIG. 5 is a schematic diagram for explaining the structure of a transmission frame handled by the data compression transmission device.

In the initial state, the frame length counter 2
The count value of 5, the content stored in the compression dictionary memory 26, the content stored in the expansion dictionary memory 33, and the count value of the quality measurement counter 39 are initialized to 0, respectively, and the value stored in the timer 38 is initialized to the quality measurement time T. , The selector A24 outputs the content LA held in the frame length memory 23A, and the selector B36
Outputs the data received from the LZ combiner 34.

In the transmission side data compression transmission apparatus 1A,
The selector A24 receives the frame length switching signal generated based on the quality notification signal notified from the receiving side data compression transmission apparatus 1B via the communication line 2A. If the frame length switching signal is 0, the frame is switched. When the frame length switching signal is 1, the LA, which is stored in the long memory 23A and indicates the unit length of the longer compression, is read and output. When the frame length switching signal is 1, the unit length L of the shorter compression stored in the frame length memory 23B is read.
B is read and this is output. Frame length counter 2
5 counts by 1 each time the unit clock generated by the clock generator A21 is received, and the counted value is the selector A24.
When it becomes equal to the output value of, a framing completion signal is generated. As a result, if the communication quality of the communication line 24 is deteriorated at that time, the frame length counter 25 generates a framing completion signal for each shorter cycle LB, and the communication quality is not deteriorated. In this case, the framing completion signal is generated every longer period LA.

The compression dictionary memory 26 initializes the contents held therein each time it receives a framing completion signal. When the LZ encoder 27 receives the bit string of the original data from the data input line 3 and receives the framing completion signal, the LZ encoder 27 performs compression processing by the LZ code on the original data read from the data input line 3 and makes an error in the compressed data. It is sent to the controller A28. As a result, the LZ encoder 27 causes the frame length memory 23A selected by the selector A24 at that time,
The number of bits held in any of 23B (LA or L
The data compression processing by the LZ code is performed in units of B). Therefore, when the communication quality of the communication line 2A is not deteriorated, a longer LA bit is selected as a unit of compression, and when the communication quality is deteriorated, a shorter LB bit is selected as a unit of compression. Therefore, the compression process and the dictionary reset process are performed based on the selected unit length of compression.

Upon receiving the compressed data from the LZ encoder 27, the error controller A28 calculates an error detection code for the compressed data and adds the result to the end of the compressed data. Upon receiving the compressed data to which the error detection code is added from the error controller A28, the transmission frame assembler 29 adds a header indicating the beginning of the transmission frame to the beginning and a trailer indicating the end of the transmission frame to the end. Thus, the transmission frame is assembled and sent to the communication line 2A.

In the receiving side data compression apparatus, when the transmission frame decomposer 31 receives the transmission frame transmitted from the transmission side data compression transmission apparatus 1A via the communication line 2A, the transmission frame header and trailer are transferred from the transmission frame. Then, the compressed data to which the error detection code has been added is extracted. Upon receiving the compressed data to which the error detection code is added, the error controller B32 sends the compressed data and compares the content of the error detection code and the compressed data,
When it is detected that a bit error has occurred in the compressed data, an error detection signal is generated.

When the timer 38 receives the unit clock from the clock generator 30, the timer 38 subtracts the timer value from the preset fixed value T by one, and when the timer value becomes equal to 0, the timer 38 generates the quality measurement signal and the timer. The value is initialized to T. The quality measurement counter 39 uses the error controller 32.
1 is counted each time an error detection signal that occurs is received, and when the quality measurement signal is received from the timer 38, the count value is initialized to 0. As a result, the quality measurement counter 3
9 is a communication line 2 for every fixed period T for observing communication quality.
The number of times of reception of a frame including a bit error occurring in A is held.

Upon receiving the quality measurement signal from the timer 38, the comparator 40 compares the threshold value N regarding the number of bit error occurrences held in advance in the quality threshold memory 37 with the count value of the quality measurement counter 39, and the count value is When the threshold value N is exceeded, it is determined that the communication quality of the communication line 2A has deteriorated, and 1 is generated as a quality notification signal. When the count value is equal to or less than the threshold value N, the communication quality of the communication line 2A deteriorates. It is determined that the quality notification signal is not present and 0 is generated as the quality notification signal. This quality notification signal is notified to the transmission side data compression transmission apparatus 1B via the communication line 2B, and is used when selecting the unit length of compression processing as described above.

Upon receiving the compressed data from the error controller B32, the LZ combiner 34 restores the original data by generating a transmission frame sync signal and performing data decompression processing by the LZ code. Expansion dictionary memory 33
When receiving the transmission frame synchronization signal from the LZ combiner 34, initializes the held expansion dictionary. Therefore, the LZ combiner 34 restores the original data while referring to and updating the decompression dictionary initialized each time the compressed data is received from the error controller B32.

When the error detection signal is not received, the selector B36 selects the output of the LZ composite device 34 and sends the correctly restored original data to the data output line 4. When the selector B 36 receives the error detection signal, that is, when the original data erroneously restored is output from the composite device 34, the idle pattern generator 35 generates an idle pattern indicating a non-communication state as data. When the selector B36 receives the frame synchronization signal next time, it determines that the original data has been correctly restored, selects the output of the LZ composite device 34, and sends it to the data output line 4. As a result, even if a bit error occurs in the communication line 2A and the decompression dictionary contains an error, the idle pattern can be continuously output to the data output line 4 from that point until the decompression dictionary is initialized. It will be possible.

By repeating the above operation in the transmitting side and the receiving side data compression transmitting apparatus,
In the communication line 2A, the number of occurrences of bit errors in a certain observation period is compared with the threshold value N to determine the deterioration state of the communication quality, and when it is determined that the communication quality of the communication line 2A has deteriorated, the LZ code is used. By setting the unit number of bits for compression / expansion of LB to a shorter LB bit, it is possible to further reduce the invalid section of the expansion dictionary when a bit error occurs. When it is determined that the communication quality has not deteriorated, the number of unit bits for code compression / expansion is set to a longer LA bit, which enables data transmission with higher compression efficiency.

When it is detected that a bit error has occurred in the communication line 2A and the transmission frame has been destroyed, original data including an error restored from the compressed data is output from the LZ composite device 34. Only during the period, it is possible to output an idle pattern indicating a non-communication state in the data compression transmission device 1B on the receiving side to the data output line 4 to prevent the transmission of error information to a data terminal accommodated in the data compression transmission device. Becomes

In the present embodiment, the receiving side data compression / transmission apparatus determines the communication quality deterioration of the communication line 2A with only one threshold value and sets the compression unit length to two types. However, a plurality of threshold values are provided. It is also possible to perform more detailed quality monitoring, and in that case, by selecting the number of thresholds + 1 compression unit length according to the deterioration state of communication quality, finer control of the initialization period of the dictionary is possible. Is possible.

[0039]

As is apparent from the above embodiments, according to the present invention, in compressing and transmitting data between the data compression transmission devices connected via the communication line,
In the receiving side data compression transmission apparatus, the deterioration state of the communication quality is determined by actually measuring the bit error rate of the receiving communication line, and the communication quality is improved by increasing or decreasing the LZ code dictionary initialization period according to the deterioration state. If it is not deteriorated, the dictionary initialization cycle is set to a larger value to improve compression efficiency, and if the communication quality is deteriorated, the dictionary initialization section is set to a smaller value and the compression efficiency is slightly deteriorated. This has the effect of shortening the section for restoring the original data based on the dictionary, and further shortening the transmission duration of erroneous information to a data terminal or the like.

Further, according to the present invention, when the receiving side data compression transmission apparatus detects that the compressed data is destroyed due to a bit error or the like occurring during transmission through the communication line, the data is erroneously restored to the restored data. Instead, by transmitting an idle pattern indicating a non-communication state, it is possible to prevent the transmission of erroneous information to a connected data terminal or the like.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a communication system including a data compression transmission device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a data compression unit of the device.

FIG. 3 is a block diagram showing a configuration of a data decompression unit of the same device.

FIG. 4 is a timing diagram illustrating the operation of the device.

FIG. 5 is a schematic diagram illustrating a structure of a transmission frame handled by the device.

FIG. 6 is a schematic diagram illustrating the concept of a data compression / decompression method using LZ code.

FIG. 7 is a block diagram showing a configuration of a communication system including a conventional data compression transmission device.

FIG. 8 is a timing diagram illustrating the operation of a conventional data compression transmission device.

[Explanation of symbols]

1A Data compression transmission device on transmission side 1B Data compression transmission device on reception side 2 Communication line 3 Data input line 4 Data output line 21 Clock generator A (first clock generation means) 22 Register (holds deterioration state of communication line) Storage means 23 Frame length memory (frame length storage means) 24 Selector A (first selection means) 25 Frame length counter (frame length counting means) 26 Compression dictionary memory (compression dictionary storage means) 27 LZ encoder (data compression) Means) 28 Error controller A (first error control means) 29 Transmission frame assembler (transmission frame assembling means) 30 Clock generator (second clock generation means) 31 Transmission frame decomposing device (transmission frame decomposing means) 32 Error controller (second error control means) 33 Expansion dictionary memory (expansion dictionary storage means) 34 L Z compound device (data decompression means) 35 idle pattern generator (idle pattern generation means) 36 selector B (second selection means) 37 quality threshold memory (quality threshold storage means) 38 timer (timekeeping means) 39 quality measurement counter ( Quality measuring / counting means) 40 Comparator (comparing means)

Claims (4)

[Claims] 1. Connected to each other through a communication line, compressing input information at a transmitting side and then sending out to the communication line,
Generates a unit clock bit-synchronized with the data received from the data input line connected to the data compression transmission device at the transmission side of the data compression transmission device that decompresses the information compressed at the reception side and restores the original information First clock generating means, a plurality of frame length storing means for holding information on a unit frame length for data compression, and a storing means for holding a quality deterioration state of the communication line notified from the receiving side data compression transmission apparatus. A first selecting means for selecting one of the plurality of frame length storing means according to a quality deterioration state notified from the storing means at each frame synchronization timing and outputting the held content; and the first selecting means. 1 for each unit clock generated by the clock generation means
Holds the frame length counting means for generating a frame synchronization timing when the counted value becomes equal to the unit frame length of the data compression displayed by the first selecting means, and the compression dictionary information used for the data compression processing. The compression dictionary storage means for initializing the held contents at each frame synchronization timing, and the information received from the data input line while referring to and updating the compression dictionary information held in the compression dictionary storage means for each frame synchronization timing. Data compression means for compressing and outputting compressed data, first error control means for adding an error detection code to the compressed data and outputting the same, and assembling the compressed data with the error detection code added to a transmission frame And a communication line connected to the data compression transmission device on the receiving side in the receiving side device. Second clock generating means for generating a unit clock bit-synchronized with the data to be received, and transmission frame decomposing means for decomposing the transmission frame received via the communication line to extract the error detection coded compressed data and outputting it. Second error control means for verifying the compressed data with error detection code to detect the presence or absence of a bit error in the compressed data and transmitting the compressed data, and holding the expansion dictionary information used for the data expansion processing, Decompression dictionary storage means for initializing the held contents at each synchronization timing, and decompressing the compressed data while receiving the compressed data and referring / updating the decompression event information to restore the original information and generate the frame synchronization timing. The data decompression means and the communication quality observation time in the initial state are held, and the second unit clock generation means is held. The holding value is decremented by 1 each time the unit clock is generated, and when the holding value becomes equal to 0, a timing means for generating a quality measurement timing, and the holding value is initialized to 0 in the initial state, A quality measurement / counting unit that counts one by one and initializes a holding value to 0 at each quality measurement timing; a quality threshold value storage unit that holds one or a plurality of threshold values related to the number of bit error occurrences in a communication line; When the value held by the quality measurement / counting means exceeds the threshold value by comparing the value held by the quality measurement / counting means with the threshold value relating to the number of bit error occurrences held by the quality threshold value storage means each time the quality measurement timing is received. Is the communication quality deterioration state,
Further, a data compression transmission apparatus comprising a comparison means for generating a quality notification signal indicating a communication quality non-deterioration state when the held value is equal to or less than a threshold value. 2. The transmission side apparatus selects a unit frame length for data compression that is shorter as the quality deterioration is larger, according to the communication quality deterioration state of the communication line notified from the reception side apparatus, and the selected unit frame length is selected. The compression of the input information is performed while initializing the compression dictionary for each, and this is sent to the communication line.The receiving side device initializes the decompression dictionary each time the compressed data is received from the communication line and then compresses the compressed data. Decompress the original information by decompressing it, output it to the data output line, measure the frequency of bit errors in the received compressed data, and determine and notify the communication quality deterioration state of the communication line. The data compression transmission device according to claim 1. 3. The idle pattern generation means, in the receiving side device, by idle pattern generation means for continuously generating an idle pattern indicating a non-communication state, and error detection notification in the compressed data received from the second error control means. Selecting the input data from the means, outputting the data to the data output line, and receiving the frame synchronization timing from the data decompressing means to select the restored original information input from the data decompressing means. 2. The compressed data transmission device according to claim 1, further comprising a second selection means for outputting to an output line. 4. When a bit error is detected in the compressed data received from the communication line, the original information including the error restored based on the compressed data is not sent to the data output line and the non-communication state is set. The data compression transmission apparatus according to claim 3, wherein the idle pattern shown is transmitted.