JPS59107661A - Data communication system - Google Patents

Abstract

PURPOSE:To reduce a communication time by measuring a bit error rate on a relay line in a short time by a bit rate on the relay line before data communication, and deciding the maximum speed of the data communication speed of transmission and receiving. CONSTITUTION:A repeater device 104 is connected respectively to a modulation and demodulation device 102 at a transmission and a receiving side, the devices 104 are connected by a relay line 105, the device 102 at the receiving side is formed with a reflexing loop 110 and the device 102 at the transmission side is provided with a collation check circuit 111. Prior to the communication of a digital data by the data communication system, the test pattern of a digital signal bit is transmitted from the device 104 at the transmission side, it is reflexed at the loop 110 of the receiving side, and the error rate on the relay line 105 is detected on the circuit 111 at the transmission side. Further, the highest data communication speed permitted for a data terminal device 100 is decided based on the detected error rate, and the communication time is reduced and the quality of communication is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a data communication system for transmitting and receiving data over a wired or wireless trunk line.

Conventionally, when the data communication speed transmitted from a data terminal device is changed, the decision is often made based on the judgment of the operator, taking into consideration the data error rate on the trunk line. However, in the case of facsimile communication, for example, the hold time is long, and depending on the screen, it can take up to 10 minutes or more if the data communication speed is 1200 bps on an A4 sheet of paper. In this case, the error rate of the trunk line is very good (and the data communication speed is 4800 t]ps).
If the time is increased to 1/4, the time will be reduced to 1/4. In particular, if the wired or wireless equipment used as a relay is constructed of portable equipment and the network configuration used is constantly changing, it is assumed that the error rate on the relay line will change from moment to moment. be done. Conventionally, there has been a problem in that in such cases, the error rate cannot often be determined until the data communication is actually performed.

The present invention has been made in view of the above points. Before omitting data communication, the bit rate on the trunk line is measured in a short time at the bit rate on the trunk line, and data that can be transmitted and received is measured. The purpose of this invention is to provide a data communication method that makes it possible to determine the maximum communication speed.

III. The present invention utilizes the fact that the data communication speed can be changed but the bit rate on the trunk line is constant, and sets the mode to a test mode before data communication is performed between the transmitting and receiving modem devices. It is configured to measure the Kg j) rate on the trunk line by transmitting and receiving a certain test pattern in loopback mode between the modulation and demodulation equipment, and to determine the maximum data communication speed by calculating backward from this value. This is what I did.

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 also to FIGS. 2 and 3.

The communication system shown in the figure includes data terminal equipment 100° subscriber line 101. Modem/demodulator 102. 03 and a relay device (or exchange) 104 are provided on the transmitting side and the 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
This is shown in Figure (a). The modulator/demodulator 102 modulates the date pit with an arbitrary number of digital bits, and the output line 103 has the waveform shown in FIG. 2 (bl).

The relay device 104 transmits the signal on the trunk line 105 in the θU format which is further time-division multiplexed as shown in FIG.

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

FIG. 3(a) shows the original data communication waveform, for example, 12
00 bps speed. FIG. 6(b) shows the output waveform of the modulator, and in this case shows a state in which one data bit is transmitted through five digital pits using the simple multi-point sampling method. (C) in the same figure shows that some kind of error has occurred on the transmission path. In this case, as a result, the same figure (
The digital pit waveform shown in d) is transmitted, but since the receiving side reproduces the data bits based on majority decision, there is no effect of the error in the same figure (CI), and the original waveform is FIG.

FIG. 4 shows yet another example. In this case, the same figure (a
) is assumed to have a data rate of 2400 bps K. As in Figure 3, if a υ error occurs on the transmission path due to noise superimposition, etc., the reproduced waveform of el in the figure shows that the original information is not reproduced. Therefore, in this case, the maximum data rate is 1200bps. I know what I have to do.

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

In the figure, the present invention includes a data terminal device 100, a subscriber line 101 . Modem/demodulator 102. An output line 103 and a relay device (or switching device) 104 are provided on the transmitting side and the receiving side, respectively, and these are connected by a trunk line 105.

Further, in the present invention, a loopback route is provided between the modulation and demodulation devices 102 and 102, and the digital data generated by the test pattern is looped back through the loopback loop 110, and the verification check circuit 111 provided in the modulation and demodulation device 102 outputs the transmitted data. The configuration is such that the verification is performed. In this case, using the frame synchronization signal 7 and inserting the necessary delay circuit can be easily constructed using conventional technology. If the data error rate required for the system is determined in advance and the relationship between that value and the digital bit increase rate is determined, the l'43 high speed of the data transmission speed δ can be immediately determined.

171+ of the data communication system of the present invention configured as described above
The operation will be explained with reference to FIGS. 6A and 6B.

First, in Figure 6A, the data rate is 24001 on the transmitting side.
)ps test data is modulated by 32Kl)ps digital bits and sent to the receiving side via the FW channel of the trunk line 105. On the receiving side, in response to this, the change tν
The modulated data is demodulated into data at 2400 bps by the first transmitter 102, and the modulated data is returned via the return loop 110 and sent to the transmitting side via the BW channel of the trunk line 105. On the transmitting side, a verification check circuit 111 verifies the digital pit error rate of the returned data with a predetermined data error rate. On the other hand, in the case of FIG. 6B, the data rate was tested at 1200 bps, and other operations are the same as in the case of FIG. 6A.

In this way, by transmitting and receiving a fixed test pattern, the power factor on the trunk line is measured, and the maximum data communication speed is determined by calculating backward from this value.

As explained above, the present invention utilizes the fact that the speed of digital pits on the relay line is constant and measures the power factor on the transmission line in advance using a test pattern before data communication. This has the effect of being able to determine the maximum speed at which data communication is possible.

[Brief explanation of drawings]

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 applies. The block diagrams of FIGS. 6A and 6B showing one embodiment of the data jm transmission system are based on the test conditions of the above embodiment, respectively.
FIG. 100...Data terminal device 101...Subscriber line 102...Post-modulation equipment W 103...Output line 1
04...Relay device 105...Relay line 11
0...Return loop 111...Verification check circuit Applicant NEC Corporation 32 Whistle 2 ■Thursday J12＼↓ ”TUL for “Tabori-------] -↓ □ (0) しt) A nodo';1'' (r bow [pe) Machizumi Yagata 4th sword (e) A Nodo**E〆] Re-settlement waveform

Claims (1)

[Claims] With multiple data communication speeds, when communicating data,
It is possible to communicate by switching the data communication speed, and has a data modulation/demodulation device between the data terminal device and the trunk line, and transmits and receives one data bit by modulating it into a plurality of digital pits. In addition, the digital signal speed on the trunk line is a data communication system in which transmission and reception are carried out at a constant speed.In addition, the data modem device r is provided with a verification check circuit, and during data communication, a return loop is provided via the trunk line and the receiving side modem device, and transmission is performed at a constant speed. The digital signal pit test pattern sent from the side is returned via the loop, the error rate on the relay line is detected by the above verification check circuit on the sending side, and the maximum speed allowed is determined based on the error rate. A data communication method characterized by being configured to determine a data communication speed.