JPH0371739A - Adaptive error controller - Google Patents

Abstract

PURPOSE:To attain efficient transmission by applying proper error correction correction in response to a line bit error ratio. CONSTITUTION:A retransmission request signal 33 sent to a line quality measuring section 14 is inputted to a retransmission request number counter 52 via a retransmission request signal input section 56 and counted up. The count 41 is inputted to a computing element 61 together with a transmission bit count 39. Then a value of the former divided by the latter is regarded as a bit error ratio 34 at that point of time. A discriminator 61 selects a changeover switch 64 to the position of a terminal B when the bit error rate 34 is a threshold level set in a threshold value storage section 65 of a nonvolatile memory 62 or over and selects the switch 64 to the position of a terminal A when lower. Thus, the transmission efficiency is kept high.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an error control device in data transmission, and more particularly to an adaptive error control device that performs appropriate error correction control in response to changes in error rate.

``Prior Art'' Normally, data errors occur due to various causes during data transmission, and it is necessary for the receiving side to detect and correct these errors. Therefore, several error control devices have been proposed to detect and correct this data error.

One of them is an error control device using retransmission, which corrects the error by retransmitting the data when a data error is detected. An example of such a device is a modem device (hereinafter referred to as an MNP modem) that uses the Microcom Nesotoworking protocol. This M
In addition to correcting errors through retransmission control, NP modems provide functions such as compressing user data, changing packet size according to line speed and line error rate, and switching transmission speeds.

Further, as another error correction control device, there is one that uses a correction code that performs correction only on the receiving side by using an error correction code derived from code theory. With this device,
On the transmitting side, an extra symbol sequence is added to the symbol sequence necessary to represent the original information, and on the receiving side, errors are corrected based on the added redundant code to reproduce correct information.

In conventional error control devices, the above-described error correction control is performed independently, and there is no device that uses these in combination.

"Problems to be Solved by the Invention" As described above, conventional error control devices perform either error correction control using retransmission or error correction control using correction codes independently. However, for example the normal M
NP modems allow the line speed to be changed at any time, so if error control is performed only by retransmission, for example, increasing the line speed will increase the line error rate and increase the number of retransmissions. Transmission efficiency decreases. Therefore, there is a problem in that even though the line speed is increased, the effective data transmission speed is reduced.

On the other hand, in a device that performs only error control using correction codes, redundant codes other than the original information are added. in this case,
For example, even if the line speed is slow and the line error rate is very low, extra redundant codes are always added, so the amount of information that is originally transmitted within a unit time is reduced. In other words, there is a problem in that the transmission speed is increasingly reduced.

In this way, in devices such as conventional MNP modems, the error control method is limited to one, as described above, so if the error rate changes due to, for example, changing the line speed, the transmission The drawback was that efficiency could not be maintained at a high level.

SUMMARY OF THE INVENTION An object of the present invention is to provide an adaptive error control device that maintains high transmission efficiency by performing error correction control according to line error rate.

"Means for Solving the Problem" The present invention includes (i) a retransmission means for retransmitting corresponding data when a retransmission request is made, and (11) a redundant code addition means for adding a redundant code for error correction to the data. and (iii)
a measuring means for measuring the error rate of data due to E transmission;
v) The adaptive error control device is provided with mode switching means for switching to a mode for adding a redundant code to transmission data when the measurement result by the measuring means exceeds a threshold value.

In the present invention, when the bit error rate of the line is low, error correction control is performed by retransmission, and when the bit error rate of the line is high, in addition to the error correction control by retransmission, error correction control is performed using correction codes. shall be.

"Example" Hereinafter, the present invention will be described in detail with reference to Examples.

FIG. 1 shows a transmission/reception system using an adaptive error control device according to an embodiment of the present invention.

In this system, user data 31 input to the data retransmission section 12 of the transmitting device 11 includes header information and a frame check sequence (hereinafter referred to as Fe2). >, etc. are added, and then input as raw data 32 to the control 11B 13 and the line quality measuring section 14.

The data retransmission section 12 is equipped with a memory (not shown), and is configured to store the transmitted data for a while.

The line quality measuring unit 14 is configured to take in the raw data 32 and the retransmission request signal 33 sent back from the receiving device 21 on the other side. Based on these, the estimated bit error rate 34 is sent to the control unit 13.

The control unit 13 determines and switches whether to send the raw data 32 from the data retransmission unit I2 directly to the data transmission unit 15 or to send it to the data transmission unit 15 via the encoding unit 16.

The data transmitter 15 is configured to transmit either the raw data 35 from the controller 13 or the redundant data 37 from the encoder 16 to the receiver 21 via the line 17.

In the receiving device 21, the data received by the data receiving B 22 is branched into two parts, one of which is input to the decoding unit 23 and the other directly to the control unit 24. Then, the control unit 24 selects one of these two pieces of data that has a matching data format, and outputs it.

The retransmission control section 25 inspects the data from the control section 24, and if there is no error, it is taken into the device as is, and if there is an error, it outputs a retransmission request signal 33 to the transmitting side. .

Next, the operation of the transmitting/receiving system configured as above will be explained.

First, the operation in the initial transmission mode will be explained.

When user data 31 in packet format is manually input to the data retransmission unit 12 of the transmitting device 11, necessary header information and FC
.

Figure 2 shows the control unit 13 and line quality measurement unit 14 in Figure 1.
This is a detailed representation of the inside of the .

In this figure, a computing unit 51 is disposed in the line quality measuring unit 14, and at its input end there is a retransmission request number counter 52 for counting the retransmission request signal 33 and a transmission bit number counter 53 for counting the number of bits of transmitted data. is connected, and the output side is connected to the control section 13 via the output section 54.

The control unit 13 is also equipped with a determiner 61, whose input end is connected to a nonvolatile memory 62, an output unit 54 in the line quality measurement unit 14, and a transmission bit number counter 53, and whose output side is connected to a switch 64. It is connected to the. This non-volatile memory 62 stores a reference number of bits for setting the interval for measuring the error rate and an error rate threshold value that serves as a reference for deciding to add a redundant code to the raw data 32. is configured via.

The raw data 32 manually input to the line quality measurement unit 14 configured as described above is once stored in the transmission data buffer 55 and then read out, and the number of bits thereof is cumulatively counted by the transmission bit number counter 53. . That is, the bits of subsequent transmitted data packets are also continuously counted. Then, this transmission bit count value 39 is calculated by the arithmetic unit 5.
1 and also the discriminator 61 of the control section 13 (FIG. 2).

In the initial state, the switch 64 of the control unit 13 is set to the A terminal side (Fig. 2), and the raw data 32 is set to the A terminal side (Fig. 2).
5, which is directly transmitted to the line 17 via the data transmitter 15 (FIG. 1).

In the receiving device 21, the data receiving section 22 receives the data from the line 17, and directly transmits it to the control section 2 as raw data 42.
4 and the decoding unit 23. Decoding unit 23
Then, this raw data 42 is regarded as encoded data and decoded, but since it is not originally decoded data, it is converted into data in an abnormal header information format.

The control unit 24 receives this abnormal data 43 and the data receiving unit 22.
It compares the raw data 42 directly inputted from the raw data packet, determines that the header information format is correct, that is, the raw data 42 is the original raw data packet, and transfers it to the retransmission control unit 25.

The retransmission control section 25 detects errors in the header information section and the data section by checking the CRC value of the frame check sequence section, for example, and if there is no error, this data is treated as correct packet data 46 and sent to 5) Data (not shown). Pass it to the processing section. And when an error is detected,
A retransmission request signal 33 containing identification information such as the packet, data number, etc. is transmitted to the data retransmission unit 12 and line quality measurement unit 14 of the transmitting device 11.

As a result, the data retransmission unit 12 retransmits the corresponding packet data in its memory (as shown in FIG. 1).

Thereafter, data transmission is performed in the same manner while error correction is performed by retransmission.

On the other hand, the retransmission request signal 33 sent to the line quality measurement 214
is input to the retransmission request number counter 52 via the retransmission request signal input section 56, and is counted up (FIG. 2). This count value 41 is the transmission bit count value 39 described above.
This is also manually input to the computing unit 51. Then, the value obtained by dividing the former by the latter is regarded as the bit error rate 34 at that point.

The reason we say "regarded" here is that it is not possible to determine whether the retransmission request signal 33 corresponds to a 1-bit error in a certain data packet or to a larger number of bit errors. It is. Therefore, for example, if there is a burst error of f number of consecutive bits, the actual bit error rate will be even higher.

The bit error rate 34 determined in this way is sequentially input to the determiner 61 of the control unit 13. The determiner 61 successively compares this bit error rate 34 with a threshold value set in a threshold storage section 65 of the nonvolatile memory 62.

Then, the determiner 61 determines that the bit error rate 34 exceeds the threshold value and the transmission bit count value 39 from the transmission bit number counter 53 becomes the value set in the reference bit number storage section 66 of the nonvolatile memory 62. At this time, the switching signal 47 is output to the switch 64, and the switch 64 is switched to the B terminal side. At the same time, the reset signal 38 from the determiner 61
As a result, the retransmission request count counter 5 of the line quality measurement unit 14
2 and the transmission bit number counter 53 are reset.

On the other hand, if it is below the threshold, a switching signal with the opposite level to the switching signal described above is output in order to switch to the A terminal side, but since it is on the A terminal side in the initial state, the current state is maintained. (See Figure 2 above).

Here, when the bit error rate 34 from the line quality measurement unit 14 exceeds a predetermined threshold, the decision is made not to immediately make a decision and switch, but to make a decision at a predetermined interval. This is to prevent chattering related to switching by obtaining a bit error rate that has been averaged and whose fluctuations have converged.

In this way, the control unit 13 decides to perform error correction using redundant codes, and switches the raw data 32 to be sent to the encoding unit 16 as raw data 36.

The encoding unit 16 adds a redundant code for error correction to the raw data packet 32 and sends it as redundant data 37 to the data transmitting unit 15 . The data is then transmitted via the data transmitter 15 to the line 11).

The redundant data 45 input to the data receiving section 22 of the receiving device 21 is manually input to both the control section 24 and the decoding section 23. The redundant data 37 supplied to the decoding section 23 is decoded and becomes the original raw data 44 with errors corrected, which is manually input to the control section 24 .

FIG. 3 is for illustrating the operation of error correction using a Hamming code, as an example.

Here, to simplify the explanation, a case will be described in which redundancy check bit 3 is added to information bit 4.

As an example, if the information to be transmitted is "0100",
Input data P(x) input to the encoding unit 16 is expressed by the following equation (1).

P(x) = (0100) =X'-=・(1) Also, if the generating polynomial is G(x), the human data P
(x) is expressed as the following equation (2).

x3-P(x,) =G(x) Q(x) +R(
x)...(2) However, Q(x) is the quotient and R(x) is the remainder.

Q(x) and R(x) that satisfy this equation (2) are as shown in the following equations (3> and (4)).

Q(X) =X' + 1 −・−・・・(3)R(
X) =X' +X=1 (4) Therefore, the encoded redundant data 37 output from the encoding unit 16 is as shown in the following (5).

F(x) = x3-P(x) +R(x)=x3
・x2 + x2 + It is converted into a word transmission sequence 72 and transmitted. If, for example, a noise sequence 73 is added during the transmission/reception process or on the line, bit errors as shown in the reception sequence 74 will occur in the received signal. However, this reception series 7
4 is converted into a signal shown in a received information sequence 75 by decoding. That is, even if a bit error occurs in the code word transmission sequence 72, the original transmission information sequence 71 can be restored by decoding. Here, we took up the case of a Hamming code as a redundant code, but for example, B CH (
Base-Chaudhuri-Hocquen-1<
hem) code etc. can also be used.

The control unit 24 that has taken in the raw data 44 restored in this way also receives the encoded redundant data 45, but among these, the one with the correct header information format, that is, the raw data 44, is It is determined that it is the original raw data packet and is sent to the retransmission control unit 25.

Although most of the errors in the raw data 44 supplied to the retransmission control unit 25 have already been corrected, there may be cases where the errors cannot be completely corrected, such as when burst errors occur continuously. Therefore, this retransmission control unit 25 performs error detection in the same manner as in the process described above, and if there is no error, passes this data as it is to a data processing unit (not shown) as correct kerat data 46. In addition, when an error is detected, a retransmission request signal 3 containing information such as a number specifying the packet is sent.
3 is transmitted to the data retransmission unit 12 and line quality measurement unit 14 of the transmitting device 11.

Same below! Thus, the given data is transmitted while performing both error correction by adding redundant codes and error correction by retransmission.

In this way, in this embodiment, when the bit error rate is low, error correction is performed by retransmission, and when the bit error rate exceeds a predetermined threshold, error correction is also performed by adding redundant codes. I can do it.

Note that in this embodiment, the threshold value of the data error rate is set to a predetermined value, but it is thought that one guideline for this is, for example, about 10-'. However, it goes without saying that this will vary depending on the state of the line, the redundant code used, and other conditions.

In addition, in this embodiment, the bit error rate is measured at predetermined intervals in order to prevent chattering from occurring in the switching operation of whether or not to add a redundant code, but there is a method in which the threshold value itself has a width. Stable operation can also be obtained by

"Effect of the invention.

As described above, according to the adaptive error control device of the present invention, efficient transmission can be performed by performing appropriate error correction control according to the line bit error rate. That is, since the actual data (transmission rate) can be maintained at a high rate, it is possible to shorten the line usage time.Therefore, there is an effect that communication costs can be reduced.

[Brief explanation of drawings]

The drawings are for explaining one embodiment of the present invention, of which FIG. 1 is a block diagram showing a transmitting/receiving system using an adaptive error control device, and FIG. 2 is a block diagram showing the control unit 1 in FIG. 1.
3 and a block diagram showing the inside of the line quality measuring section 14. FIG. 3 is an explanatory diagram showing the operation of error correction using the )\lamming code. 11... Transmission device, 12... Data retransmission section, 13... Control section, 14... Line quality measuring section, 15...... Data transmitter, 16...
. . . Encoding unit, 21 . . . Receiving device, 22.
...Data receiving section, 23...Decoding section,
24... Control unit, 25... Retransmission control unit, 51... Arithmetic unit, 52... Retransmission request number counter, 53... Transmission bit number counter, 61...determiner, 62...nonvolatile memory, 64...switcher.

Claims (1)

[Claims] Retransmission means for retransmitting the corresponding data when a retransmission request is made; redundant code addition means for adding a redundant code for error correction to the data; and measurement means for measuring the error rate of data due to transmission. and when the measurement result by this measurement means exceeds the threshold,
An adaptive error control device comprising: mode switching means for switching to a mode in which the redundant code is added to transmission data.