JPH10145309A - Data transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct data transmission in the system setting which is proper to the state of a line. SOLUTION: A test means 101 of a transmitter side equipment 1 sends test data from a transmitter side modem 15 via a line 3. A transmission error rate detection means 201 of a receiver side equipment 2 detects a transmission error rate, based on the test data received by a receiver side modem 21, and when the detected transmission error rate is in excess of a preset specified value, a reception speed revision means 202 reduces the data reception speed. A transmission speed revision request transmission means 203 sends a transmission speed revision request to the transmitter side equipment 1. Moreover, a transmission speed revision means 102 of the transmitter side equipment 1 reduces the data transmission speed, based on a transmission speed revision request corresponding to the receiver side equipment 2 and sends the test data again. Furthermore, a reception sensitivity revision means 205 of the receiver side equipment 2 revises the reception sensitivity, corresponding to a transmission loss rate detected by a transmission loss rate detection means 204.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for transmitting data via a line, and more particularly, to a data transmission system capable of performing a line test to perform data transmission with a system setting suitable for the state of the line. About the system.

[0002]

2. Description of the Related Art In a data transmission system such as mobile communication, for example, a plurality of MCUs (minimum code) are used.
d Unit) is transmitted for each packetized still image data. In such a system, since a low-quality line is used as a transmission path, there is a high possibility that an error will occur during transmission. For example, when the above-described still image data is transmitted at a high bit rate, it is reproduced. There is a high possibility that the quality of the image will be reduced. For this reason, in such a system as described above, in accordance with the state of the quality of the line used as the transmission path, the data transmission speed optimization processing, the transmission packet length optimization processing, and the error data generation processing are performed. Responses such as retransmission processing and bit error correction processing using an error correction code have been made.

[0003]

However, in the above system, for example, in the data transmission speed optimizing process, the modem between the transmitting side device and the receiving side device is changed every time the transmission speed is changed. There was a problem that it took time to synchronize between the devices. In addition, in the transmission packet length optimization processing, when the packet length is subdivided in accordance with the deterioration of the line state, control data such as headers, error detection, and correction codes added to each packet relatively increases. As a result, there is a problem that the transmission throughput is reduced.

Further, in the data retransmission processing, when it takes time to restore the line state, the packet retransmission processing is frequently performed between the modems, so that there is a problem that the time required for the data transmission is greatly increased. Was. Also, in the error correction processing using the error correction code, since the error correction code is added to all of the transmission packets, the entire data transmission amount increases, and thus the transmission time becomes longer. there were. In this case, there is also a problem that an error that cannot be corrected even with an error correction code occurs, particularly when a transmission line having a high transmission error rate is used. As described above, especially in a system for transmitting data via a low-quality transmission path, a system that can efficiently perform data transmission regardless of the state of a line used as the transmission path has been desired.

The present invention has been made to solve such a conventional problem. By testing a line used for data transmission, it is possible to perform data transmission with a system setting suitable for the state of the line. It is an object of the present invention to provide a data transmission system that can perform the data transmission. More specifically, the present invention provides a data transmission system capable of detecting a transmission error rate of a line by a test and performing data transmission at a transmission rate at which the detected transmission error rate is equal to or less than a predetermined value. The purpose is to: It is another object of the present invention to provide a data transmission system capable of detecting a transmission loss rate of a line by a test and performing data transmission with reception sensitivity corresponding to the detected transmission loss rate.

[0006]

In order to achieve the above object, in the data transmission system according to the present invention, a test of a transmission error rate of a line is performed as follows. That is, for example, when transmitting still image data packetized for each of a plurality of MCUs, in the transmitting apparatus, the test unit transmits test data for detecting the transmission error rate of the line from the transmitting side transmitting unit to the line. The test data transmission processing is performed a plurality of times by transmitting the test data at the maximum data transmission rate allowed by the system. Here, the test data is, for example, a plurality of MCs to be transmitted.
It is constituted by the average data length of U.

In the receiving device, the transmission error rate detecting means detects the transmission error rate based on a plurality of test data received by the receiving side receiving means via the line. As a result of this detection, if the detected transmission error rate exceeds a preset specified value, the reception speed changing unit reduces the data reception speed by the reception side reception unit to, for example, one step lower than that adopted by the system. At the same time, the transmission rate change request transmission means causes the reception side transmission means to transmit a transmission rate change request to the transmission side device. Further, in the transmission-side device, the transmission-side reception means receives the transmission rate change request from the reception-side apparatus, and based on the transmission rate change request received by the transmission rate change means, changes the data transmission rate by the transmission-side transmission means on the reception side. After lowering the transmission error rate corresponding to the device, test data is transmitted again to test the transmission error rate of the line.

In this way, the transmission error rate of the line is tested while gradually decreasing the transmission rate of the system, and the transmission rate at which the detected transmission error rate becomes equal to or less than a predetermined value is set to the data transmission rate. Transmission speed used in such a case. Therefore, similarly to the test data, the data to be transmitted is expected to be transmitted via the line at a transmission error rate equal to or less than a preset specified value, so that data transmission can be performed reliably and efficiently. It can be carried out.

Here, the test data length may be arbitrarily determined. However, when the test data is configured with a data length close to the data length of the transmission target as described above, the transmission of the data to be transmitted is performed. A line test can be performed according to a transmission situation very similar to the above. The predetermined value of the transmission error rate may be arbitrarily set in accordance with the usage status of the system, and the lower the specified value, the lower the transmission speed is set, and the higher the quality of data transmission. It can be performed.

In the data transmission system according to the present invention, a test of the transmission loss rate of the line is performed as follows. That is, for example, when transmitting still image data packetized for each of a plurality of MCUs, in the transmitting apparatus, the test unit transmits test data for detecting the transmission loss rate of the line from the transmission unit to, for example, the transmission target of the transmission target. The transmission is performed via the line with the same transmission intensity as when transmitting the MCU. And
In the receiving device, the transmission loss rate detecting means detects the transmission loss rate based on the test data received by the receiving means, and the reception sensitivity changing means corresponds to the detected transmission loss rate,
Change the receiving sensitivity set for the receiving means.

In this manner, the receiving device receives the data to be transmitted with the reception sensitivity changed as described above. Therefore, it is possible to receive data to be transmitted, which is expected to suffer the same transmission loss as the test data by the line, so as to be within the receiving sensitivity range, and to perform data transmission reliably and efficiently. Can be.

Here, the test data need not always be transmitted at the same transmission intensity as the data to be transmitted, and even if the transmission intensity of the test data is different from the transmission intensity of the data to be transmitted. Based on the transmission loss rate for test data, it is possible to predict the reception sensitivity to be set when performing data transmission.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment according to the present invention will be described with reference to the drawings. FIG. 1 shows an example of a data transmission system according to the present invention. The data transmission system includes a transmitting device 1 for transmitting data, a receiving device 2 for receiving data, and transmitting data. A line 3 is provided. In this example, when transmitting still image data divided into a plurality of MCUs from the transmitting device 1 via the line 3 to the receiving device 2 for each MCU, the transmission data of the line 3 is transmitted by transmitting test data in advance. The transmission rate and the transmission loss rate are detected, and data to be transmitted is transmitted at a transmission speed and reception sensitivity based on the detection results.

The transmitting device 1 includes an image input device 11 for inputting image data, an information source coder 12 for dividing the image data into a plurality of MCUs and compressing the data, and a transmission of data transmitted for each MCU. A pixel block disperser 13 for dispersing the order, an error detection encoder 14 for performing error detection encoding on data, and a transmission-side modulator / demodulator 15 for modulating or demodulating data.
And a display 16 for displaying the test status and data transmission status of the line 3, and a transmission-side main control unit 17 for controlling a line test process in the transmission-side device 1.

The image input device 11 comprises image input means such as a still camera, inputs still image data, digitizes the input still image data, and outputs it to the information source encoder 12. The information source encoder 12 converts the still image data input from the image input device 11 into a plurality of MCs.
The data is divided into U, and the data for each divided MCU is subjected to a compression encoding process, and the compressed data for each MCU is output to the pixel block disperser 13.

FIG. 2 shows an example in which the pixel block disperser 13 divides, for example, still image data into MCUs of 6 × 8 blocks for each MCU input from the information source encoder 12. In the same image frame, each MCU is dispersed by block interleaving so that MCUs located in the same image are transmitted at a time apart from each other, and the MCUs are distributed in the distributed order by the error detection encoder 14.
Output to That is, in the example shown in FIG. 2, transmission is performed for the MCU composed of a total of 48 blocks, for example, in the numerical order (1 to 48) shown in FIG. In addition, an identification number is added to each MCU, so that the receiving-side apparatus 2 can reconstruct original still image data from a plurality of MCUs distributed and received.

According to the above-mentioned distributed processing, even if an error occurs continuously in a certain range of data such as a burst error during data transmission, the original image data has
It is possible to leave the normally received MCU on the upper, lower, left, and right neighbors of the MCU in which the error has occurred. Therefore, for the MCU in which an error has occurred, an image close to the original image can be reproduced by performing an interpolation process based on the normal MCUs adjacent to the upper, lower, left, and right sides in the receiving device 2. Note that this interpolation processing is performed by an image data interpolator 25 provided in the reception-side device 2 described later.

Also, for example, when the MCUs are dispersed as shown in FIG. 2, FIG. 3 (a) shows a case where a burst error occurs in the fifth to sixteenth transmitted MCUs.
FIG. 3B shows a case where a burst error has occurred in the 20th to 31st transmitted MCUs, and FIG.
As shown in the case where a burst error has occurred in the second transmitted MCU, １ ／ of the total number of MCUs or less, that is, FIG.
In the example of, even if a burst error occurs in 12 or less MCUs, the normally received MCU is adjacent to the upper, lower, left, and right sides of the erroneous MCU. For this reason, the transmission error rate of line 3 in data transmission is 1 /
In this example, the predetermined value of the transmission error rate of the line 3 is set to 1/4, and the transmission rate of the system is set so that the transmission error rate of the line 3 becomes 1/4 or less. Change the settings. More preferably, by setting the prescribed value of the transmission error rate of the line 3 to be smaller than 1/4, data transmission can be performed more reliably.

The error detection encoder 14 performs error detection encoding on data for each MCU input from the pixel block disperser 13 and outputs the data to the transmission-side modulator / demodulator 15. By this error detection encoding process, the receiving side device 2 can detect a code error occurring during transmission. The transmission-side modulator / demodulator 15 modulates the data for each MCU input from the error detection encoder 14 by a method suitable for the line 3 and transmits the modulated data for each MCU to the reception-side device 2 via the line 3. Send sequentially. The display 16 is composed of image output means such as a display screen, and displays and outputs the test status of the line 3 and the data transmission status.

The transmission-side main control unit 17 includes a test unit 101 for transmitting test data, and a transmission speed changing unit 102 for reducing the data transmission speed. The test means 101 transmits the test data for detecting the transmission error rate and the transmission loss rate of the line 3 to the reception-side apparatus 2 a plurality of times via the line 3 by the transmission-side modem 15. Here, the test data includes an average data length of a plurality of MCUs of the still image data to be transmitted, and the receiving apparatus 2 via the line 3 with the same transmission intensity as when the MCU to be transmitted is transmitted. Sent to Thus, in this example, the line 3
, Test data can be transmitted in a state very similar to that of transmitting data to be transmitted via the network, and the transmission error rate and transmission loss rate of the line 3 for the data to be transmitted can be more accurately predicted. .

The test data includes, for example, information specified in advance with the reception-side device 2 and a code such as an error detection code. Can be detected. The number of times test data is transmitted may be, for example, several percent of the total number of MCUs to be transmitted.
It is optional and may be determined according to the usage status of the system, required test accuracy, and the like. Transmission speed changing means 102
When the transmission rate change request is received from the reception-side device 2, the data transmission speed of the transmission-side modem 15 is reduced corresponding to the reception-side device 2.

The transmission-side main control unit 17 sends an AC signal to the reception-side device 2 as a response for confirming reception in the transmission processing.
K (positive response) or NAK (negative response) is transmitted. With the above configuration, the transmission-side apparatus 1 tests the transmission error rate of the line 3 by transmitting the test data via the line 3, and transmits the data to be transmitted at a data transmission rate based on the test result. Do.

The receiving-side apparatus 2 includes a receiving-side modulator / demodulator 21 for modulating or demodulating data, an error-detecting decoder 22 for detecting and decoding data, and an MCU distributed in the transmitting-side apparatus 1. A pixel block rearranger 23 for relocating to a position, an information source decoder 24 for expanding data for each MCU to reconstruct still image data, and an image data interpolator 25 for performing interpolation processing on the still image data. And a display 26 for displaying image data and the like, and a receiving-side main control unit 27 for controlling a line test process in the receiving-side device 2.

The receiving modem 21 sequentially receives the data for each MCU transmitted from the transmitting device 1 via the line 3, demodulates the received data for each MCU, and outputs the demodulated data to the error detection decoder 22. I do. The error detection decoder 22 detects a code error occurring during transmission by performing error detection decoding on the data for each MCU input from the reception-side modulator / demodulator 21 in accordance with the transmission-side device 1, and detects the error in each MCU. The data is output to the pixel block rearranger 23. The pixel block rearranger 23 rearranges the data for each MCU input from the error detection decoder 22 in the original arrangement order by performing the reverse processing to the distributed processing performed in the transmission side apparatus 1 and rearranges the data. The obtained data for each MCU is output to the information source decoder 24.

The information source decoder 24 converts the data for each MCU input from the pixel block rearranger 23 into the transmission side device 1.
The still image data is reconstructed from the decompressed data for each MCU and output to the image data interpolator 25. The image data interpolator 25 is an information source decoder 24
For MCUs in which errors occur during transmission among the MCUs of the still image data input from, interpolation processing is performed by using the MCUs normally received in the upper, lower, left, and right neighbors, and a still image close to the original image is processed. The data is reproduced, and the reproduced still image data is output to the display 26. As described above, since the MCUs are distributed by the transmitting device 1 and transmitted to the receiving device 2, even when a burst error occurs during transmission, it is necessary to effectively perform the above-described interpolation processing. Can be.

The display 26 comprises image output means such as a display screen, and displays and outputs the still image data input from the image data interpolator 25, the test status of the line 3, and the like. In addition, the display unit 26 displays the data transmission status by blanking out the MCU part where the transmission error has occurred during the data transmission and sequentially displaying and outputting the normally received MCU data.

The receiving side main control section 27 includes a transmission error rate detecting means 201 for detecting a transmission error rate of the line 3, a receiving rate changing means 202 for lowering the data receiving rate, and a transmission rate changing means for the transmitting side apparatus 1. A transmission rate change request transmission means 203 for transmitting a request, a transmission loss rate detection means 204 for detecting a transmission loss rate of the line 3, and a reception sensitivity change means 205 for changing the reception sensitivity in the receiving device 2 are provided. I have.

The transmission error rate detection means 201 is
The transmission error rate on the line 3 is detected based on a plurality of test data transmitted from the communication line 3 via the line 3. That is,
The transmission error rate is calculated from the ratio of the number of test data in which a transmission error has occurred to the total number of test data. Here, in the present example, 1 is added to the bit string of the test data received by the receiving device 2.
If an error is detected even in a bit, the test data is counted as test data in which a transmission error has occurred.

The reception rate changing means 202 sets the detected transmission error rate to a predetermined value, that is, 1 / in this example.
If it exceeds 4, the data reception speed by the reception-side modulator / demodulator 21 is reduced to the next lower speed adopted by the system. When the detected transmission error rate exceeds a preset specified value, that is, １ ／ in this example, the transmission rate change request transmitting unit 203 transmits a transmission rate change request to the transmission side apparatus 1. The receiving speed changing unit 202 and the transmission speed changing request transmitting unit 203 transmit the line 3 again.
When the test is performed, there is no need to perform the tuning process between the reception-side modem 21 and the transmission-side modulator / demodulator 15, and the time required for the tuning process can be saved.

The transmission loss rate detection means 204 is
The transmission loss rate in the line 3 is detected based on a plurality of test data transmitted from the network. That is, for example, the average reception intensity is calculated by periodically detecting the reception intensity of the test data, and the transmission loss is calculated by a value such as the logarithm (for example, in dB) of the ratio of the average reception intensity of the test data to the average transmission intensity of the test data. Detect rate. Receiving sensitivity changing means 205
Is the reception-side modem 2 corresponding to the detected transmission loss rate.
Change the reception sensitivity set to 1.

Here, an example of the above-described reception sensitivity change processing will be described with reference to FIG. FIG. 3 shows an example in which dB (decibel) is used as a unit of the receiving sensitivity, and a receivable range of 0 to −50 dB is set to the level area 1.
(0-10 dB) and level area 2 (-10-4
0 dB) and a level area 3 (-40 to -50 dB). The receiving sensitivity of the system is 30d
B, and the system default is -10 to
A reception sensitivity range of −40 dB (setting B) is set. In this case, as a result of the above-described transmission loss rate detection, when it is predicted that the reception intensity of the data to be transmitted is an intensity within the level area 1 (for example, the reception sensitivity setting switching point 1 or more) such as -5 dB, For example, the reception sensitivity range of the system is changed to 0 to -30 dB (setting A). Also, if the result of the transmission loss rate detection indicates that the reception strength of the data to be transmitted is within the level area 3 (for example, the reception sensitivity setting switching point 2 or less) such as -45 dB, for example, the reception of the system is performed. Change the sensitivity range to -20 to -50 dB (setting C).

The receiving-side main control unit 27 sends an AC signal to the transmitting-side apparatus 1 as a response for confirming reception in the transmission processing.
K (positive response) or NAK (negative response) is transmitted. With the above configuration, the receiving device 2 detects the transmission error rate and the transmission loss rate of the line 3 based on the test data transmitted from the transmitting device 1 via the line 3, and based on the detection result, The data to be transmitted is received at the reception speed and the reception sensitivity.

Next, the test processing of the transmission error rate and the transmission loss rate of the line 3 by the present system will be described with reference to the drawings. FIG. 5 shows a conceptual diagram of the line test processing in the present system.

First, the transmitting apparatus 1 sends the test data to the transmitting apparatus 2 via the line 3 a plurality of times (test data # 1) at the highest data transmission rate (transmission rate 1) adopted by the system.
~ # N) Transmit. The receiving device 2 receives a plurality of test data transmitted from the transmitting device 1 via the line 3 and detects a transmission error rate and a transmission loss rate based on the received plurality of test data. Here, if the detected transmission error rate is equal to or less than the specified value, transmission of data to be transmitted is performed at the tested data transmission rate (transmission rate 1). For example, as shown in FIG. If the detected transmission error rate exceeds the specified value, the receiving device 2 reduces the data receiving speed to a lower speed (transmission speed 2) permitted by the system and transmits the data. NAK to
And a transmission rate change request.

In the transmitting device 1, the receiving device 2 sends the NA
When the K and the transmission rate change request are received, the data transmission rate is reduced corresponding to the receiving apparatus 2, and the test data is transmitted a plurality of times again at the reduced data transmission rate (transmission rate 2) (test data # 1 to #n). The receiving device 2 again detects the transmission error rate and the transmission loss rate based on the plurality of received test data. Here, when the transmission error rate exceeds the specified value, the test is performed again by lowering the transmission speed. For example, as shown in FIG. 5, when the transmission error rate is less than the specified value, Is the receiving device 2
An ACK is transmitted to the transmitting device 1, the receiving sensitivity is changed in accordance with the transmission loss rate, and the process stands by to receive data to be transmitted transmitted from the transmitting device 1.

In the transmitting device 1, the AC from the receiving device 2
When K is received, for example, the transmission target data (MCU # 1, MCU # 2, M
CU # 3,...) Are transmitted to the reception-side apparatus 2 via the line 3 at a data transmission rate (transmission rate 2) at which the transmission error rate is equal to or less than a specified value. The receiving device 2 receives the data transmitted from the transmitting device 1 at the data receiving speed (transmission speed 2) at which the transmission error rate is equal to or less than the specified value and the receiving sensitivity changed based on the test.

As described above, in the data transmission system according to the present invention, the test of the transmission error rate and the transmission loss rate of the line is performed by transmitting the test data via the line. The data to be transmitted can be transmitted by the system setting, so that the data transmission is performed reliably and efficiently without retransmitting the data, optimizing the packet size, or changing the transmission speed after the data transmission is started. be able to.

Here, the line used for data transmission is arbitrary, and may be a wired line or a wireless line. In the above embodiment, still image data divided into a plurality of MCUs is used as data to be transmitted. However, data to be transmitted is arbitrary and may not necessarily be divided into a plurality of blocks. . Further, in the above embodiment, the test was performed in a situation close to the data length and the transmission intensity when transmitting the data to be transmitted, but the data length and the transmission intensity of the test data are arbitrary.
The point is that the transmission error rate and the transmission loss rate of the line can be detected.

In the above embodiment, the transmission order is determined for each MCU of still image data as shown in FIG. 2. In this case, a burst error occurs in less than 1/4 of the total number of MCUs. Even if the error occurs, the normally received MCU will be adjacent to the upper, lower, left, and right neighbors of the MCU in which the error has occurred.
It was set. Here, the present invention is not limited to the case shown in FIG.
Even if a burst error occurs in less than / 4 MCUs, the transmission order should be determined for each MCU so that the normally received MCU is adjacent to the upper, lower, left, and right neighbors of the erroneous MCU. This will be described in detail with reference to the drawings.

First, as in the above embodiment, the still image data is divided into M blocks of even block rows (vertical) × even block columns (horizontal).
The case of dividing into CUs will be described. For example, in the case shown in FIG. 2 described above, the still image data is
As a method of distributing the transmission order of these MCUs, first, MCUs in odd-numbered columns and odd-numbered rows are assigned numbers from 1 to 12 in the order from left column to right column. Go. Next, the MCU of the even column and the even row
Are similarly assigned numbers from 13 to 24. Next, numbers from 25 to 36 are similarly assigned to the MCUs in the odd columns and the even rows. Finally, numbers from 37 to 48 are similarly assigned to the MCUs of the even-numbered columns and the odd-numbered rows.

When the transmission order is assigned to all the MCUs as described above, the numbers assigned to the most adjacent MCUs at the top, bottom, left, and right are the numbers 13 to 24 and the left of these numbers. Are assigned numbers from 25 to 36. Here, in the case of FIG. 2, for example, the number 25 is adjacent to the left side of the number 13, and the number 33 is adjacent to the left side of the number 21. Therefore, for example, even when a burst error occurs in MCUs for 12 blocks from number 13 to number 24, that is, 1/4 of the total number of MCUs 48, for example, even if a burst error occurs,
All of the upper, lower, left and right MCUs adjacent to 3 are MCs of normal reception
The same applies to MCUs corresponding to numbers 14 to 24 where a burst error has occurred.

The above is because the MCUs adjacent to each other at the top, bottom, left and right
Holds for the case where the assigned number is the closest among the above, the same holds for all other MCUs. The above is generally described as an even N (vertical) × even M (horizontal) block (total NM)
The case will be described. In this case, for example, (NM / 4
+1) to NM / 2, (NM / 4 +
1) The difference between the number of the MCU (ie, the MCU located on the second row in the second column) and the MCU adjacent to the left is represented by N
This should be compared with M / 4. Here, the number of the MCU adjacent to the left side is (NM / 2 + 1), and the difference between the numbers of these two MCUs, that is, NM / 4 is NM
In the case of / 4 or more, the same holds true. Here, since these NM / 4 coincide, as described above, even if a burst error occurs in an MCU of 1/4 or less of the total number of MCUs, the M
The normally received MCU is adjacent to the CU vertically and horizontally.

Next, a case where the still image data is divided into MCUs of odd block rows (vertical) × odd block columns (horizontal) will be described. In this case, for example, FIG.
As shown in FIG. 5, first, the MCUs in the odd-numbered columns and odd-numbered rows and the MCUs in the even-numbered columns and even-numbered rows are stored in the order from the left column to the right column.
Numbers from 13 to 13 are assigned. Next, the MCU of the odd-numbered column and the even-numbered row, and the M of the even-numbered column and the odd-numbered row
Similarly, numbers from 14 to 25 are assigned to the CU.

When the transmission order is assigned as described above, the numbers adjacent to the numbers 1 to 13 above, below, right and left are always numbers from 14 to 25. Therefore, here, a case will be described in which a burst error occurs after any of the MCUs of numbers 1 to 13. Among the MCUs with these numbers, the MCUs whose numbers are closest to the vertically and horizontally adjacent MCUs are the MCUs of numbers 4 to 13
And number 2 from number 14 adjacent to the left side of these MCUs.
Up to 3 MCUs. Here, for example, the MCU of number 7
Is adjacent to the MCU of number 17 on the left side of this MCU. Therefore, for example, 1 from number 7 to number 16
Even if a burst error occurs in the MCU for 0 block, the MCs adjacent to the top, bottom, left and right of the MCU in which the error occurred
U are all MCUs for normal reception. Therefore, all MC
U number of 1/4 of 25, that is, 6 (plus decimal number)
Even when a burst error occurs in the following MCU, the same holds true.

The above is generally described as an odd number N (vertical) ×
The case of an odd number M (horizontal) block (total number NM) will be described. In this case, for example, of the MCU from 1 to (NM + 1) / 2, the {(N + 1) / 2 + 1} th MCU (that is, the MCU located in the second row of the second column) and the MCU adjacent to the left side thereof The difference between the numbers should be compared with NM / 4. Here, the number of the MCU adjacent to the left side is {(NM + 1) / 2 + 1}, and these two M
The difference between CU numbers, that is, (NM-N) / 2 is NM / 4
In the case described above, the same holds as above. That is, when (NM−2N) / 4 is equal to or greater than 0, that is, when M is equal to or greater than 2, a burst error occurs in less than 1/4 of the total number of MCUs. Also, the normally received MCU is adjacent to the upper, lower, left, and right neighbors of the MCU in which the error has occurred.

Here, the result that the above does not hold when M = 1 is a result that comes out because there is no block located on the left side of the MCU in this case. = 1, for example, FIG.
As shown in (b), the difference between the numbers of vertically adjacent MCUs is always at least 1/4 of the total number of MCUs.

Next, a case where the still image data is divided into MCUs of odd block rows (vertical) × even block columns (horizontal) will be described. Note that the same applies to a case where the MCU is divided into MCUs of even block rows × odd block columns. In this case, for example, FIG.
As shown in the case of a block, first, numbers from 1 to 10 are allocated to the MCUs in the odd-numbered columns and the odd-numbered rows and the MCUs in the even-numbered columns and the even-numbered rows in the order from the left column to the right column. To go. Next, the MC of the odd-numbered column and the even-numbered row
Similarly, numbers from 11 to 20 are assigned to U and the MCUs in the even columns and odd rows.

When the transmission order is assigned as described above, the numbers adjacent to the numbers 1 to 10 above, below, right and left are always numbers 11 to 20. Therefore, here, a case will be described in which a burst error occurs after any of the MCUs of numbers 1 to 10. Among the MCUs of these numbers, the MCUs adjacent to the MCUs vertically and horizontally are closest to the MCUs numbered 4 to 10.
And number 11 to number 1 adjacent to the left side of these MCUs.
Up to 7 MCUs. Here, for example, the MCU of number 7
For, the MCU of number 14 is adjacent to the left side of this MCU. Therefore, even if a burst error occurs in the MCUs of 7 blocks from number 7 to number 13,
All the MCUs adjacent to the top, bottom, left, and right of the MCU in which the error occurred are MCUs for normal reception. For this reason, even when a burst error occurs in an MCU of 1/4 of the total number of MCUs, that is, 5 or less, the same holds true as described above.

The above is generally described as an odd number N (vertical) ×
A case of an even M (horizontal) block (total number NM) will be described. In this case, for example, among the MCUs from 1 to NM / 2, the {(N + 1) / 2 + 1} th MCU (ie, 2
The difference between the number of the MCU located on the second row in the column and the MCU adjacent to the left side may be compared with NM / 4. Here, the number of the MCU adjacent to the left side is (N
M / 2 + 1), the difference between the numbers of these two MCUs,
That is, when (NM-N-1) / 2 is equal to or greater than NM / 4, the same holds true. That is, when (NM−2N−2) / 4 is 0 or more, that is, when M is 4 or more, a burst error occurs in の or less of the total number of MCUs. Even
The normally received MCU is adjacent to the upper, lower, left and right neighbors of the MCU in which the error has occurred.

Here, when M = 2, a result is obtained that the above does not hold.
(D) shows an example of the case of 5 vertical blocks × 2 horizontal blocks. In this case, 1/4 of 10 which is the total number of MCUs is used.
Are 2.25, for example, MCUs of number 4 and number 5
When a burst error occurs in two or less MCUs, the normally received MCs are placed above, below, left and right of these MCUs.
U is adjacent, but because there is a fractional part of 0.25,
This is because (NM-N-1) / 2 does not become NM / 4 or more. However, when M = 2, the above can be realized by assigning the transmission order by a method as shown in FIG. 6 (e), for example.

As described above, the still image data is divided into MCUs of an arbitrary number of vertical blocks (rows) × an arbitrary number of horizontal blocks (columns).
, The number of M of の or less of the total number of MCUs
Even if a burst error occurs in the CU, the normally received MC is located in the upper, lower, left, and right neighbors of the MCU in which the error occurred.
The transmission order can be determined for each MCU so that U is adjacent.

In the above embodiment, 1/4 is used as the predetermined value of the transmission error rate. However, the specified value may be set arbitrarily in accordance with the usage of the system. As the value is set lower, the transmission speed is set lower, and data can be transmitted with high quality.
Further, in the above embodiment, the test was performed by decreasing the speed one step at a time from the highest data transmission speed adopted by the system. However, depending on the data to be transmitted and the use condition of the system, the initial data transmission speed may be reduced. As a setting, a lower speed than the maximum data transmission rate allowed by the system may be used, and the test is performed by reducing the data transmission rate not two steps but two steps or three steps. Is also good.

Further, in the above embodiment, by providing the receiving device with the receiving speed changing means, it is possible to perform data transmission without performing the tuning process with the transmitting device. By transmitting a synchronization signal, transmission speed designation information, and the like to the receiving side device, it is also possible to perform tuning processing and the like between the transmitting side device and the receiving side device. Further, in the above-described embodiment, the reception sensitivity is changed using three setting ranges such as setting A, B, and C as the setting of the reception sensitivity.
The method of changing the receiving sensitivity is arbitrary. In short, the receiving sensitivity may be set so that the data to be transmitted falls within the range of the receiving sensitivity.

In the above embodiment, an example has been described in which data is transmitted only in one direction from the transmitting device to the receiving device. However, the functions of the transmitting device and the receiving device shown in the above embodiment are not described. By providing a plurality of communication devices provided together in a system and connecting the plurality of communication devices to each other via a line, a line test and data transmission can be performed bidirectionally between arbitrary communication devices.

When each means relating to the main control unit provided in the transmitting device and the receiving device is constituted by software, the system may be provided with a single-function communication modem, and the system can be manufactured at low cost. Can be configured.

[0056]

As described above, according to the data transmission system of the present invention, the transmission error rate of a line is detected by testing the line, and an appropriate transmission rate for data transmission is determined based on the detected transmission error rate. Since the transmission speed is changed, the transmission of the data to be transmitted can be performed reliably and efficiently. Further, according to the data transmission system according to the present invention, the transmission loss of the line is detected by testing the line, and the data transmission is performed at the receiving sensitivity corresponding to the detected transmission loss ratio. Data transmission can be reliably performed within the receiving sensitivity.

[Brief description of the drawings]

FIG. 1 is a configuration example of a data transmission system according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining distributed processing of an MCU.

FIG. 3 is a diagram for explaining a burst error occurring in an MCU.

FIG. 4 is a diagram for explaining a process of changing reception sensitivity.

FIG. 5 is a conceptual diagram of a line test process by the data transmission system according to the present invention.

FIG. 6 is a diagram for explaining MCU distributed processing.

[Explanation of symbols]

1... Transmitting device, 2... Receiving device, 3... Line, 11... Image input device, 12... Information source coder, 13... Pixel block disperser, 14. , 15 ... Transmitter / demodulator, 16 ... Display, 17 ... Transmitter main controller, 21 ... Receiver modulator / demodulator, 22 ... Error detection decoder, 23 ... Pixel block rearranger .. 24 information source decoder, 25 image data interpolator, 26 display, 27 receiving main control unit, 101 testing means, 102 transmission rate changing means, 201 Transmission error rate detection means, 202
Receiving speed changing means, 203 transmission speed change request transmitting means, 204 transmission loss rate detecting means, 205 sensitivity changing means,

Claims (2)

[Claims] 1. A data transmission system for receiving data transmitted from a transmission side device via a line at a reception side device, the transmission side device comprising: transmission side transmission means for transmitting data via a line; Test means for transmitting test data for detecting the transmission error rate of the transmission side from the transmission side transmission means, transmission side reception means for receiving a transmission rate change request from a reception side device, Transmission speed changing means for reducing the data transmission speed of the transmission side transmission means in accordance with the reception side apparatus, the reception side apparatus comprising: a reception side reception means for receiving data via a line; Receiving side transmitting means for transmitting data via the transmission side, transmission error rate detecting means for detecting a transmission error rate based on test data received by the receiving side receiving means, and a detected transmission error rate A receiving speed changing means for lowering the data receiving speed by the receiving side receiving means if the predetermined value exceeds a predetermined value; and a transmitting side if the detected transmission error rate exceeds a predetermined value. A data transmission system, comprising: a transmission rate change request transmitting means for transmitting a transmission rate change request to a device from a receiving side transmitting means. 2. A data transmission system in which data transmitted from a transmitting device via a line is received by a receiving device, wherein the transmitting device includes: a transmitting unit for transmitting data via the line; Test means for transmitting test data for detecting a loss rate from the transmitting means, wherein the receiving device receives data via a line, and receives the test data based on the test data received by the receiving means. Transmission loss rate detection means for detecting the transmission loss rate by using the transmission loss rate detection means, and reception sensitivity change means for changing the reception sensitivity set in the reception means in accordance with the transmission loss rate detected by the transmission loss rate detection means. A data transmission system, comprising: