JPS59107660A - Data communication system - Google Patents

Abstract

PURPOSE:To reduce a communication time and to improve the quality of communication by utilizing a backward channel of a full duplex line for reflexing a data to measure an error rate on a transmission line, and changing a data communication speed based on the measured result. CONSTITUTION:A repeater 104 is connected to a modulation and demodulation device 102 at a transmission and a receiving side of a data communication system via an output line 103 and the repeaters 104 are connected by a full duplex relay line 105. A reflexing route is provided between the devices 2 by using the backward channel of the full duplex relay line 105, a reflexing loop 110 is formed to the device 102 at the receiving side and the device 102 at the transmission side is provided with a collation check circuit 111. Further, a digital data transmitted from the device 102 at the transmission side is reflexed to the transmission side via a loop 110 and the backward channel and collated with the transmitted data at the circuit 111. The result of collation is informed to a data terminal device 100, the error rate of the relay line 105 is measured and the data communication speed is changed based on the result of measurement.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a data communication system for transmitting and receiving data over trunk lines that are configured in a wired or wireless manner.

Conventionally, when the data communication speed transmitted by a data terminal device is switched, the speed is often determined by the operator's judgment based on an assumption of the data error rate on the trunk line. However, in the case of facsimile communication, for example, the hold time on the line is long, and depending on the size of the A4 size screen, the data communication speed of 1200 bps can take up to nearly 10 minutes. In this case, if the VA communication rate on the trunk line is good and the data communication speed is increased, the holding time of the line will be shortened. could not be changed.

The present invention has been made in view of the above-mentioned problems, and it is possible to measure the data error rate by using a backward channel during data communication, and to make it possible to make the 1-data communication speed variable. It provides a communication method.

That is, in the present invention, when a data communication line is configured in full-duplex mode and, for example, in the case of facsimile communication, data transmission and reception is not checked while the screen is being transmitted, and when the backward channel is free, the back The data is looped back to the word channel, the data is checked on the sending side, and the speed can be changed based on the incorrect measurement results, thereby reducing data communication time and ensuring data communication quality. be.

Hereinafter, the present invention will be explained based on embodiments shown in the drawings.

First, the data communication system shown in FIG. 1 and to which the present invention is applied will be explained with reference to FIGS. 2 and 3.

The communication system shown in the figure is a data terminal device 100.

Subscriber line 101. Modem f1.102. Output line 103
A relay device (or exchange) 104 is provided on the transmitting side and a receiving side, respectively, and these are connected by a trunk line 105.

The operation of this system is as follows. First, data is input from the data terminal device 100 to the modulation/demodulation device 102 through the subscriber line 101. The data waveform at this time is shown in FIG. 2(a) l/C. Modem 10
At step 2, one data bit is modulated by a plurality of digital bits, and the output line 103 has a waveform shown in the figure. The relay device 104 transmits the signal on the trunk line 105 in a further time-division multiplexed waveform as shown in FIG.

On the other hand, on the receiving side, the reverse conversion to the above is performed.

Next, the data communication operation will be explained in more detail with reference to the waveforms shown in FIG.

FIG. 3(a) shows the original data communication waveform, for example, 12
00 bps speed. Figure 0)) is the output waveform of the modulator, and in this case shows a state in which one data bit is transmitted by five digital bits using a simple multi-point sampling method. Part (e) of the same figure shows that some kind of error has occurred on the transmission path. In this case, the result is the same figure (
d) The digital bit waveform indicated by K is transmitted, but since the data bits are regenerated by majority decision on the receiving side, there is no effect of the error in Figure (C), and the original waveform is The figure (el) shows what can be obtained.

FIG. 4 shows yet another example. In this case, the same figure (a
) is assumed to have a data rate of 2400 bpa. As in FIG. 3, if an error occurs on the transmission path due to noise superimposition or the like, the reproduced waveform in FIG. 3(e) shows that the original information is not reproduced. Therefore, it can be seen that in this case the maximum data rate must be 1200 bps.

Next, FIG. 5 is a block diagram showing an embodiment of the data communication system of the present invention.

In Figure VC, the present invention includes data terminal equipment 100, subscriber line 1011 modem 102 . An output line 103 and a relay device (or exchange) 104 are provided on the transmitting side and the receiving side, respectively, and these are connected by a full-duplex trunk line 105 to transmit the signal.

Further, in the present invention, a loopback route is provided between the modem devices 102 and 102 using the backward channel of the full-duplex trunk line, and when the backward channel is vacant, the modem device on the receiving side 102K to form a folding loop 110, the digital data sent from the transmitting side is looped back to the transmitting side via the tt folding loop 110 and the backward channel, and the transmitting side
Verification check circuit 111 provided in the modem 102
The configuration is such that the data is checked against the sent data.

In this case, a delay circuit is required to synchronize and check the frame synchronization signal, but this can be easily constructed using conventional techniques.

The result of the verification check of the returned data is notified to the sending data terminal device 100. This data terminal device 1
00, the error rate measurement result of the trunk line 105 from the above check is compared with a preset data error rate, and the data is automatically set to achieve the highest data communication speed within the predetermined error rate range. A circuit (not shown) is provided to change the communication speed. Therefore, the data terminal device 100 increases or decreases the data communication speed to the extent possible based on the above results.

If you change the data communication speed, you need to notify the receiving side of this as well. This is notified by transmitting an interoffice signal such as a common channel signal, and the reception speed is changed so that data transmission and reception are synchronized.

The operation of the data communication system of the present invention configured in this way will be explained with reference to FIGS. 6A and 6B.

First, in Figure 6A, the data rate is 2400 on the transmitting side.
bps data is modulated with 32 Kbps digital bits and sent to the receiving side via the forward (FW) channel of trunk line 105. In response to this, the receiving side modulates the modulation data to 'O1' and returns the modulated data 1 via the folding loop 110 to the backward ( BW) channel to the sender.

On the transmitting side, a verification check circuit 111 verifies the digital bit error rate of the returned data with a predetermined data error rate. On the other hand, in the case of Figure 6B, the data rate is set to 1.
In this example, the speed is 200 bps, and the other operations are the same as in the case of FIG. 6A above. Based on these results, the data terminal device 100 sets the highest data communication speed within the allowable error rate. The data is then checked by the communication center.

As explained above, the present invention utilizes a backward channel in a full-duplex line to loop back data.
This has the effect of making it possible to measure the error rate on the transmission path and change the data communication speed based on the result. Accordingly, the data communication time can be shortened and the data communication quality can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a configuration example of a communication system to which the present invention is applied, FIGS. 2, 3, and 4 are waveform diagrams showing waveforms of each part of the system, and FIG. 5 is a block diagram showing a configuration example of a communication system to which the present invention is applied. A block diagram showing an embodiment of the data communication system, and FIGS. 6A and 6B are waveform diagrams showing waveforms of each part in the above embodiment, respectively. 100... Data terminal device 101... Subscriber line 102... Modulation/demodulation device 103... Output line 10
4... Relay device 105... Relay line 110.
...Return loop 111... Verification check circuit Applicant NEC Corporation District 3 ↓ JLrL-Plate 1----Sokusame ■ 320- (0) Rejection supplementary report (e) Regenerated liquid form Fig. 4 (e) Cell d, i cell reciprocating liquid form

Claims (1)

[Claims] Having a plurality of data communication speeds, upon data communication,
In addition to being able to communicate by switching data communication speeds, a data modulation/demodulation device is provided between the data terminal equipment and the trunk line, and one data bit is modulated into multiple digital bits for transmission and reception. In a full-duplex data communication system that transmits and receives data at a constant speed, the digital signal M on the trunk line is transmitted from the transmitting side through the trunk line, packed word channel, and receiver modem during data communication. A return route is provided to return the transmitted data to the transmitting side, and the error rate on the trunk line is measured from the data returned to the data modulator/demodulator via the above route every month. 1. A data communication system comprising: a verification check circuit, and further comprising: a circuit for automatically changing the data communication speed based on the error rate measurement result in the data terminal device.