Data transmission system

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a data transmission system, and more particularly to a data transmission system that performs error correction coding / decoding of transmission data.

【0002】

[Conventional technology]

An example of a conventional data transmission device is shown in FIG. This example is disclosed in Japanese Patent Application Laid-Open No. 4-129351. In the figure, the input video signal supplied to the input terminal is first input to the compression coding circuit 15 and encoded. For example, entropy coding is used for coding the compression coding circuit 15, and the compression coding rate is a coding method that fluctuates with time. Note that 101 is an input terminal and 201 is an output terminal.

【0003】

The variable rate compression coding data output from the compression coding circuit 15 is input to the cellization circuit 16. In this cell formation circuit 16, cell formation is performed in units of pixel blocks composed of a certain number of pixels. That is, as shown in FIG. 12, one compression-encoded data obtained by compress-coding an input video signal of T for a certain period of time, that is, a signal obtained by compress-coding a pixel block consisting of a certain number of pixels. Alternatively, a plurality of cells are configured.

【0004】

When such cell formation is performed, the amount of data in the coded output of a certain pixel block does not always match an integral multiple of the cell, so that a surplus portion may occur. Therefore, so-called dummy data D such as all "0" is inserted in this remaining portion. As described above, one or a plurality of (integer) cells are generated for each pixel block and input to the next variable length cell blocking circuit 17.

【0005】

In this variable-length cell blocking circuit 17, variable-length cell blocking is performed. In the example of FIG. 11, the cell generated from the video signal of T for a certain period of time T of FIG. 12 described in the cell-forming circuit 16 above is regarded as a cell block. That is, one or a plurality of cells obtained by forming cells in pixel block units form a cell block.

【0006】

The variable-length cell-blocking output obtained by the variable-length cell-blocking circuit 17 is input to the error correction coding circuit 18 and encoded. However, since the input to the error correction coding circuit 18 is a variable length cell block, its output is shown in FIG. In FIG. 13, P1 -1 and P1 -2 of the pixel block, P2 -1 and P2 -2 of the pixel block, P3 -1 and P3-2 of the pixel block are inspection cells, and 2 cells are used for each cell block. Each inspection cell K is added.

【0007】

In this way, in order to perform error correction coding of the variable length cell block, it is assumed that the fixed length cell block is sufficiently long, and the part corresponding to the difference from the actual variable length cell block is from all "0" data. Error correction coding is performed assuming that there is a cell (dummy cell). In this way, error correction is performed while reducing the transmission delay as much as possible to enable data transmission.

【0008】

[Problems to be Solved by the Invention]

In the above-mentioned conventional technique, error correction coding is performed by adding a constant length error correction redundant bit regardless of the actual length of the variable length data. Therefore, even when the actual data length is short, an error correction redundant bit having a certain length is added. Therefore, when the frequency of appearance of input data having a short data length is high, there is a drawback that the error correction coding processing time increases and the transmission efficiency deteriorates. In the case of a random error, if the input data length is half, the redundant bit is also half and the same error correction capability can be obtained.

【0009】

The present invention has been made to solve the above-mentioned drawbacks of the prior art, and an object of the present invention is to suppress an increase in error correction coding processing time for variable length data and to transmit data without lowering transmission efficiency. It is to provide a data transmission system that can be performed.

【0010】

[Means for solving problems]

The data transmission system according to the present invention provides selection means for selecting one of a plurality of error correction coding methods according to the data length of the data to be transmitted, and error correction coding for the data by this selected method. It is characterized by including a coding means for performing and outputting.

【0011】

Further, the data transmission system according to the present invention includes a selection means for selecting one of a plurality of error correction / decoding coding methods according to the data length of the received data, and error correction / decoding for the data by this selected method. It is characterized by including a decoding means for performing and outputting the data.

【0012】

Then, the data length of the data is measured by a counter or added to the data. The selection means is characterized in that, among the plurality of error correction coding methods, an error correction coding method that maintains a predetermined error correction capability and minimizes the number of added error correction redundant bits is selected. And.

【0013】

In short, in this data transmission system, error correction coding is performed on variable length data for each data length by adding a redundant bit for error correction that is the minimum necessary for a predetermined error correction capability. Therefore, if the error correction redundant bit required when the data length is L is T, then when the data length is L / 2, the same error correction capability (in the case of random error) can be obtained. , Error correction coding in which the redundant bit for error correction is T / 2 should be performed. Therefore, the error correction coding processing time can be shortened and the transmission efficiency can be improved accordingly.

【0014】

BEST MODE FOR CARRYING OUT THE INVENTION

Next, an embodiment of the present invention will be described with reference to the drawings.

【0015】

FIG. 1 is a block diagram showing an embodiment of a data transmission system according to the present invention. In the figure, the data transmission system according to the present embodiment has a data length detection unit 1 that detects the data length of variable length data having a predetermined frame configuration, and data of variable length data corresponding to the variable length data. Includes an error correction coding control unit 2 and an error correction coding unit 3 that perform error correction coding that minimizes the number of redundant bits added while the error correction capability does not drop below a certain level based on the length. It is composed of.

【0016】

In addition, this system has a data length detection unit 5 that detects the data length of the input error correction coded data of arbitrary length, and error correction / decoding corresponding to the detected data length based on a predetermined rule. It is configured to include an error correction / decoding control unit 6 and an error correction / decoding unit 7 that perform the above on the input data. Note that 4 is a network.

【0017】

In such a configuration, variable-length data having a predetermined frame configuration is input from the input terminal 100 to the data length detection unit 1 and the error correction coding unit 3, respectively. The data length detection unit 1 detects the data length L of the variable length data constituting the frame based on the above-mentioned frame configuration rule. Next, based on the data length L of the variable length data detected by the data length detection unit 1, the error correction coding control unit 2 maintains the predetermined error correction capability and adds an error correction redundant bit. The error correction coding method that minimizes the number of is selected, and the selection signal S is output to the error correction coding unit 3.

【0018】

The error correction coding unit 3 performs error correction coding on the input variable length data according to the selection signal S of the error correction coding method output from the error correction coding control unit 2, and then performs error correction coding. Send coded data to network 4.

【0019】

Further, the error correction coded data received through the network 4 is input to the data length detection unit 5 and the error correction decoding unit 7.

【0020】

Similar to the data length detection unit 1, the data length detection unit 5 detects the data length L ́ of the error correction coded data received based on the rules of the frame configuration and outputs the data length L ́ to the error correction / decoding control unit 6. The error correction / decoding control unit 6 determines the error correction coding method selected by the error correction coding control unit 2 based on the data length L ́ detected by the data length detection unit 5. Then, the control unit 6 selects an error correction decoding method corresponding to the error correction coding method, and outputs the selection signal S ́ to the error correction decoding unit 7.

【0021】

Finally, the error correction / decoding unit 7 performs error correction / decoding on the received error correction coded data according to the selection signal S ́ of the error correction / decoding method from the error correction / decoding control unit 6. , Output to output terminal 200.

【0022】

Further, the above operation will be described in detail with reference to FIGS. 2 to 4. First, variable length data having a frame configuration in which a frame start code and a frame end code (both are unique codes) are added before and after the variable length data as shown in Fig. 2 is sent from the input terminal. It is assumed that the data is input to the data length detection unit 1 and the error correction coding unit 3.

【0023】

The data length detection unit 1 first detects the frame start code, and then starts counting the variable length data based on the frame start code. Then, when the frame end code is detected, the count is stopped, and the data length L (see FIG. 2) of the variable length data constituting the frame is obtained.

【0024】

Next, the error correction coding control unit 2 based on the data length L of the variable length data detected by the data length detection unit 1 maintains the predetermined error correction capability and adds redundancy for error correction. Select the error correction coding method that minimizes the bits. Then, the selection signal S is output to the error correction coding unit 3.

【0025】

Here, there are the following methods for selecting the error correction coding method. That is, a correspondence table between the data length Ln shown in FIG. 4A and the error correction coding method FECCn is prepared, and the error correction coding control unit 2 selects the error correction coding method by referring to the table. .. In addition to this, various methods can be considered. Further, the relationship between the data length Ln in the correspondence table shown in (a) of the figure and the number of redundant bits Tn required for the error correction coding method FECCn is basically a proportional relationship. Here, assuming a random error, if the relationship between the data L1 and the data length Ln is L1 = Ln / 2, the relationship between the corresponding redundant bit T1 and the data length Tn is also T1 = Tn / 2.

【0026】

The error correction coding unit 3 performs error correction coding on the input variable length data according to the selection signal S of the error correction coding method output from the error correction coding control unit 2, and shows FIG. After adding redundant bits to the variable length data as shown, the coded data is sent to network 4.

【0027】

The error correction coded data (see FIG. 3) received through the network 4 is input to the data length detection unit 5 and the error correction decoding unit 7.

【0028】

Similar to the data length detection unit 1, the data length detection unit 5 uses the frame start code and frame end code of the frame signal (see FIG. 3) as the basis for the data length L ́ of the received error correction coded data (Fig. 3). 3) is obtained and output to the error correction / decoding control unit 6.

【0029】

The error correction / decoding control unit 6 uses the data length L ́ detected by the data length detection unit 5 to perform an error correction / decoding method corresponding to the error correction coding method selected by the error correction coding control unit 2. , Select by referring to the correspondence table shown in (b) of FIG. 4, and output the selection signal S ́ to the error correction decoding unit 7. Here, in the tables of FIGS. 4 (a) and 4 (b), L1, L2, L3 ..., Ln and L1 ́, L2 ́, L3 ́ ..., Ln ́ and FECC1, FECC2, FECC3 ... , FECCn and FECD1, FECD2, FECD3 ..., FECDn are assumed to have a one-to-one correspondence with each other.

【0030】

Finally, the error correction / decoding unit 7 performs error correction / decoding on the received error correction coded data according to the error correction / decoding method selection signal S ́ from the error correction / decoding control unit 6. Output to the output terminal.

【0031】

[Example]

Next, examples of the present invention will be described in detail with reference to the drawings. FIG. 5 shows the configuration of an embodiment of the present invention.

【0032】

Input data having a constant data length N is input to the variable length coding unit 8 from the input terminal. The variable-length coding unit 8 performs variable-length coding on the input data and outputs the variable-length coded data to the frame configuration unit 9. The frame configuration unit 9 adds a start code and an end code to the input variable-length coded data based on a predetermined rule to configure the frame. The variable-length coded data framed by the frame component 9 is input to the data length detection unit 1 and the error correction coding unit 3, respectively.

【0033】

The data length detection unit 1 detects the data length L of the variable length data framed based on the above-mentioned frame configuration rule. Next, the error correction coding control unit 2 based on the data length L of the variable length data detected by the data length detection unit 1 has a preset error correction capability P (network quality, quality required by the applied service). The error correction coding method that minimizes the added error correction redundant bits is selected, and the selection signal S is output to the error correction coding unit 3.

【0034】

The error correction coding unit 3 performs error correction coding on the input variable length data after framing according to the selection signal S of the error correction coding method output from the error correction coding control unit 2. After that, it is output to the frame component 10. The frame configuration unit 10 frames the input error correction coded data based on the same rules as the frame configuration unit 9, and sends the framed error correction coded data to the network 4.

【0035】

Further, the error correction encoded data received through the network 4 is input to the data length detection unit 5 and the error correction decoding unit 7.

【0036】

Similar to the data length detection unit 1, the data length detection unit 5 detects the data length L ́ of the error correction coded data received based on the rules of the frame configuration and outputs the data length L ́ to the error correction / decoding control unit 6. The error correction / decoding control unit 6 determines the error correction coding method selected by the error correction coding control unit 2 based on the data length L ́ detected by the data length detection unit 5. An error correction decoding method corresponding to the error correction coding method is selected, and the selection signal S ́ is output to the error correction decoding unit 7.

【0037】

The error correction / decoding unit 7 performs error correction / decoding on the received error correction coded data according to the selection signal S ́ of the error correction / decoding method from the error correction / decoding control unit 6, and the result is The framed variable-length coded data obtained as is output to the frame separation unit 11.

【0038】

The frame separation unit 11 deletes the start code and end code added by the frame configuration unit 10 with respect to the input framed variable length coded data, and the variable length is changed from the framed variable length coded data. Only the coded data is separated and output to the variable length decoding unit 12. Finally, the variable-length decoding unit 12 performs variable-length decoding on the input variable-length coded data, restores the input data input from the input terminal, and outputs the input data to the output terminal 200.

【0039】

Next, the operation of the embodiment of the present invention will be described in detail with reference to FIGS. 5 to 7.

【0040】

As shown in FIG. 6A, input data a having a constant data length N is input to the variable length coding unit 8 from the input terminal. The variable-length coding unit 8 performs variable-length coding on the input data a, and outputs the variable-length coded data b as shown in FIG. 6B to the frame configuration unit 9. The frame configuration unit 9 adds a frame start code S and a frame end code E (both are unique word codes) before and after the input variable length coded data b to configure the frame. To make it. Then, it is output to the data length detection unit 1 and the error correction coding unit 3 as framed variable length coded data c (see FIG. 6C).

【0041】

The data length detection unit 1 first detects the frame start code S, then starts counting the variable length data based on the frame start code S, stops the count when the frame end code E is detected, and configures the frame. Find the data length L (see Fig. 6 (c)) of the variable length data.

【0042】

Next, the error correction coding control unit 2 based on the data length L of the variable length data detected by the data length detection unit 1 maintains the preset error correction capability P and is for error correction to be added. The error correction coding method that minimizes the redundant bits is selected, and the selection signal S is output to the error correction coding unit 3.

【0043】

Here, a method of selecting an error correction coding method will be described with reference to FIG. 7. Figure 7 shows an example in which Read-Solomon coding is used as the error correction coding method and the data length L can take seven types of values of 20, 30, 40, ..., 80. There is. The error correction capability P set in the example in the figure is Reed-Solomon coding (RS (24,20)) with 4 bytes of redundant bit T added when the minimum data length L = 2 bytes is targeted. (Represented) is to be executed, and it is possible to correct errors up to 2 bytes.

【0044】

Error correction coding using data length L (20,30,40, ..., 80 bytes) and Reed-Solomon coding as shown in (a) of Fig. 7 created in consideration of the above conditions. Prepare a correspondence table with the method (RS (24,20), RS (36,30), RS (48,80) ... RS (96,80)), and use the error correction coding control unit 2 Refer to the table and select the error correction coding method. Further, the relationship between the data length L in the correspondence table shown in FIG. 6A and the number of redundant bits T required for error correction coding is proportional, and in this example, L / 5 = T.

【0045】

Returning to FIG. 6, the error correction coding unit 3 performs Reed-Solomon coding on the input variable length data according to the selection signal S of the error correction coding method output from the error correction coding control unit 2. Then, it is output to the frame component 10 as error correction coded data d (see FIG. 6 (d)). In the frame configuration unit 10, the input error correction coded data is framed by the same method as in the frame configuration unit 9, and the framed error correction coded data e (see FIG. 6 (e)) is displayed. Send to network 4.

【0046】

The framed error correction coded data e received through the network 4 is input to the data length detection unit 5 and the error correction decoding unit 7, respectively. Similar to the data length detection unit 1, the data length detection unit 5 detects the frame start code S and the end code E based on the rules of the frame configuration (see FIG. 6 (e)), and forms the received frame. The data length L ́ (see FIG. 6 (e)) of the error correction coded data e is obtained and output to the error correction / decoding control unit 6.

【0047】

In the error correction decoding control unit 6, the error correction coding method (Reed-Solomon coding RS (24)) selected by the error correction coding control unit 2 is based on the data length L ́ detected by the data length detection unit 5. , 20), etc.) are selected with reference to the correspondence table shown in Fig. 7 (b), and the selection signal S ́ is output to the error correction decoding unit 7. Here, the data length L (20,30,40, ..., 80 bytes) in Fig. 7 (a) and the data length L ́ (24,36, ..., 96) in Fig. 7 (b) are There is a one-to-one correspondence with each other due to the relationship of (data length L ́) = (data length L) + (redundant bit T).

【0048】

The error correction / decoding unit 7 performs error correction / decoding on the received framed error correction coded data e according to the error correction / decoding method selection signal S ́ from the error correction control unit 6. The resulting framed variable-length coded data f (see FIG. 6 (f)) is output to the frame separator 11.

【0049】

The frame separation unit 11 deletes the start code and the end code added by the frame configuration unit 10 with respect to the input framed variable-length coded data f, and deletes the framed variable-length coded data f from the framed variable-length coded data f. Only the variable-length coded data g (see FIG. 6 (g)) is separated and output to the variable-length decoding unit 12. Finally, the variable-length decoding unit 12 performs variable-length decoding on the input variable-length coded data g, restores the input data a input from the input terminal 100, and outputs the input data a to the output terminal.

【0050】

The data h in FIG. 6 (h) is also coded and decoded in the same manner. That is, the data h becomes the variable-length coded data i in the figure (i), and the frame start code S and the frame end code E are added to become the data j in the figure (j). After that, it is coded according to the selection signal S to obtain the data k in the figure (k).

【0051】

This data k is framed into the data l in the figure (l) and sent to the network 4. Then, the data l is decoded to become the data m in the figure (m). The start code S and the end code E are deleted from this data m, and the data n in the figure (n) is obtained.

【0052】

Next, other embodiments of this system will be described with reference to FIG. Variable-length data having a predetermined frame configuration is input from the input terminal 100 to the data length detection unit 1 and the data length multiplexing unit 13, respectively.

【0053】

The data length detection unit 1 detects the data length L of the variable length data constituting the frame based on the above-mentioned frame configuration rule. Next, the data length multiplexing unit 13 multiplexes the data length L detected by the data length detecting unit 1 into the variable length data having the above frame configuration, and outputs the data to the error correction coding unit 3. An example in which this data length L is multiplexed is shown in FIG.

【0054】

On the other hand, the error correction coding control unit 2 selects an error correction coding method based on the data length L, which maintains a predetermined error correction capability and minimizes the added redundant bits for error correction. Then, the selection signal S is output to the error correction coding unit 3. In the error correction coding unit 3, the selection signal S of the error correction coding method output from the error correction coding control unit 2 for the variable length data having a frame configuration output from the data length multiplexing unit 13. After performing error correction coding according to the above, the coded data is sent to the network 4. The transmitted coded data is shown in FIG.

【0055】

The error correction coded data received through the network 4 is input to the data length separation unit 14 and the error correction decoding unit 7. The data length separation unit 14 separates the data length L of the variable length data multiplexed by the data length multiplexing unit 13 based on the rules of the frame configuration, and outputs the data length to the error correction / decoding control unit 6. The error correction / decoding control unit 6 determines the error correction coding method selected by the error correction coding control unit 2 based on the data length L output from the data length separation unit 14. Then, an error correction decoding method corresponding to the error correction coding method is selected, and the selection signal S ́ is output to the error correction decoding unit 7. Finally, the error correction compounding unit 7 performs error correction decoding on the received error correction coded data according to the selection signal S ́ of the error correction decoding method from the error correction decoding control unit 6. , Output to output terminal 200.

【0056】

As described above, in this system, the transmitting side selects one of a plurality of error correction coding methods according to the data length of the data to be transmitted, and error correction coding is performed on the data by this selected method. Is output, and on the receiving side, one of a plurality of error correction / decoding coding methods is selected according to the data length of the received data, and error correction / decoding is performed on the received data using this selected method. Is being output. As a result, when the variable length data is transmitted by performing error correction coding, it is possible to suppress the increase in the error correction coding processing time and perform the data transmission without lowering the transmission efficiency. The data length of the data to be transmitted is measured by using a counter or the like, or is multiplexed and added to the data in advance.

【0057】

In the above description, the well-known Reed-Solomon coding method is used as the coding / decoding method, but it is clear that other methods may be used. For example, a BCH (Bose-Chaudhuri-Hocquenghem) coding method, a Hamming code method, a Viterbi code method, or the like may be used. However, the Reed-Solomon coding method is the most popular, and it is best to use it.

【0058】

In connection with the description of the claims, the present invention may further take the following aspects.

【0059】

(10) The data transmission system according to any one of claims 1 to 4, wherein one of the plurality of error correction coding methods is a Reed-Solomon coding method.

【0060】

(11) The data transmission system according to any one of claims 5 to 8, wherein one of the plurality of error correction decoding methods is a Reed-Solomon coding method decoding method.

【0061】

(12) The data transmission system according to claim 9, further comprising a measuring means for measuring the data length of the data.

【0062】

(13) The data transmission system according to claim 9, wherein the information indicating the data length of the data is added to the data.

【0063】

(14) The selection means selects, among the plurality of error correction coding methods, an error correction coding method that maintains a predetermined error correction capability and minimizes the number of added error correction redundant bits. The data transmission system according to any one of claims 9, (12) and (13).

【0064】

[Effect of the invention]

As described above, the present invention detects the data length of variable-length data, maintains the error correction capability at a constant level for each data length, and minimizes the number of redundant bits to be added. When error correction coding is performed and variable length data is transmitted by selecting and executing an error correction coding method, data transmission can be performed without reducing the increase in error correction coding processing time and transmission efficiency. It has the effect of being able to do it.

[Simple explanation of drawings]

[Figure 1]

It is a block diagram which shows the structure of the data transmission system by one Embodiment of this invention.

[Figure 2]

It is a frame block diagram of variable length data in the data transmission system of FIG.

[Fig. 3]

It is a frame block diagram of the error correction coded data in the data transmission system of FIG.

[Fig. 4]

(a) shows the correspondence between the data length and the error correction coding method in the data transmission system of FIG. 1, and (b) shows the correspondence between the data length and the error correction decoding method in the data transmission system of FIG. It is a figure.

[Fig. 5]

It is a block diagram which shows a more specific embodiment of the data transmission system of FIG.

[Fig. 6]

(a) to (n) are diagrams showing data processed by each part of the data transmission system of FIG.

[Fig. 7]

(a) shows the correspondence between the data length and the error correction coding method in the data transmission system of FIG. 5, and (b) shows the correspondence between the data length and the error correction decoding method in the data transmission system of FIG. It is a figure. It is a figure which shows the correspondence between a data length and an error correction coding method.

[Fig. 8]

It is a block diagram which shows the structure of the data transmission system by another embodiment of this invention.

[Fig. 9]

It is a frame block diagram of the variable length data in the data transmission system of FIG.

[Fig. 10]

It is a frame block diagram of the error correction coded data in the data transmission system of FIG.

[Fig. 11]

It is a block diagram which shows the structure of the conventional data transmission system.

[Fig. 12]

It is a time chart which shows the operation of the system of FIG.

[Fig. 13]

It is a figure which shows the example of the error correction coded data in the system of FIG.

[Explanation of symbols]

1,5 Data length detector 2 Error correction coding control unit 3 Error correction coding unit 4 network 6 Error correction decoding control unit 7 Error correction decoding unit 8 Variable length coder 9,10 Frame components 11 Frame separator 12 Variable length decoding unit 13 Data length multiplex 14 Data length separator