JPH03255727A - Automatic line switching system - Google Patents

Abstract

PURPOSE:To automatically make correspondence to the degradation cause of a transmission line at high speed by stopping transmission on a center side when the number of times for training exceeds the set number of times, and switching an active transmission line to an auxiliary transmission line when one of the S/N measured results of modulators/demodulators on the remote side and the center side is less than a set S/N. CONSTITUTION:When a transmission line 301 of a modulator/demodulator 100 on the center side is degraded and the number of measuring times in a training time number measuring part 118 exceeds the set value, the stop of transmission is commanded through a control part 119 to a modulation part 101 and the command is sent out to a sub channel modulation part 106. A modulator/ demodulator 200 on the remote side stops training signals and a control part 115 stores the result of received signal level measurement into a RAM 116. A control part 117 calculates the S/N and when the calculated S/N is less than the set bottom S/N, switchers 107 and 108 switch the transmission line to the auxiliary transmission line. Then, the modulation part 101 starts transmitting the training signals.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to line automation in a communication system in which two modems, one on the center side and one on the remote side, are installed facing each other via two transmission lines, one for use and one for backup. Regarding the switching method.

[Conventional technology]

In this type of communication system, the complex signal output from the automatic equalizer is displayed on the two-dimensional screen of an oscilloscope in each of the center-side and remote-side modem devices, and the displayed eye pattern is monitored. The quality of the received signal is evaluated. If eye deterioration is severe in at least one of the center-side and remote-side modulation/demodulators, the data signal speed is manually reduced. If the eye is severely degraded even at the lowest data signal rate that can be set, or if training is repeated, the external network controller (
The line was manually switched from active to standby using a line switch built into the NCU or modem. In addition, the data transmission speed was automatically switched, and only when data transmission could not be established at the set minimum data transmission speed was the line switched from the active line to the standby line.

[Problem to be solved by the invention]

The conventional line switching method described above is a manual method, requiring human labor for both the central and remote modem equipment, and the eye pattern must be constantly monitored.
The problem is that it requires a huge amount of time and money.

In addition, if the deterioration of line-of-sight quality becomes significant or the line is disconnected, you can manually switch the data signal speed of the center-side and remote-side modem while monitoring the eye pattern, even at the lowest data signal speed that can be set. If the eye is severely deteriorated or training is repeated,
There is a problem in that it takes a huge amount of time and money to switch lines.

On the other hand, with a method that automatically switches the data transmission speed and switches the line from the working line to the protection line for the first time when data transmission cannot be established at the set minimum data transmission rate, it takes an enormous amount of time to switch to the protection line. There is a problem in that there is a risk of prolonging data transmission failures.

[Means to solve the problem]

The automatic line switching method according to the present invention provides, in a communication system in which a center side modem and a remote side modem are installed facing each other via a working transmission line and a backup transmission line, the center side modem changes the number of training times. If the measured training number exceeds a preset number, the transmission of the training signal is stopped, the S/N of the working transmission line is measured, and the remote modem is In response to the instruction, the remote modem stops sending out the training signal, measures the S/N of the working transmission line, and sends an S/N signal to the center modem. /N measurement results, and the center-side modem is preliminarily set to select at least one of the S/N measurement result at the remote-side modem and the S/'N measurement result at the center-side modem. If the S/N is lower than the lowest S/N, the working transmission line is switched to the protection transmission line.

The center side modem changes the working transmission line to the protection transmission line, and then transmits a training signal to the remote modem via the protection transmission line, and the remote modem changes the training signal to the remote modem. When detected, the working transmission line may be switched to the protection transmission line.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

Referring to FIG. 1, in the automatic line switching system according to the present invention, a center side modem 100 and a remote side modem 200 are installed facing each other via working transmission lines 301 and 302 and protection transmission lines 303 and 304. Applies to communication systems. Each of the center modem 100 and the remote modem 200 has a subchannel.

The center-side modulation/demodulation device 100 has a modulation section 101 that modulates a carrier wave with transmission data. The modulator 10] is capable of switching the data transmission rate in N stages (N is a natural number). The coupling section 102 couples the signal modulated by the modulation section 101 and the output of the switch 03 which receives the sine wave generated from the sine wave generation section 1.4. Combining section 105 combines the output of combining section 102 and the output of sub-channel modulation section 106. A switch 107 that receives the output of the coupling section 105 switches between the working transmission line 301 and the backup transmission line 30 under control to be described later.
Switch between 3 and 3. Therefore, the center side modem 100
The transmitted signal is sent to the remote modem 2 via either the working transmission line 301 or the protection transmission line 303.
Sent to 00. Normally, the current transmission line 301 is used.

The remote modem 200 has a switch 201 that switches between the working transmission line 3.1 and the protection transmission line 303. The output of the switch 201 is the received signal of the remote modem 200 which is equal to the transmission signal of the center modem 100. This received signal is filtered by filters 202, 203 . and 2
04. Filter 202 extracts the audio band signal from the received signal. Filter 203 extracts the data channel signal from the received signal. Filter 204
extracts the subchannel signal from the received signal. The reception level measuring section 205 measures the level of the audio band signal supplied from the filter 202? #j Determine.

Demodulator 206 demodulates the data channel signal supplied from filter 203 and outputs received data. Demodulator 2
06 can switch the data transmission speed in N stages. The sub-channel demodulator 2.7 demodulates the sub-channel signal supplied from the filter 204. Control section 208 receives the output of sub-channel demodulation section 207 and controls reception level measurement section 205 and demodulation section 206 .

Control section 208 further controls modulation section 20.9.

Modulating section 209 modulates a carrier wave with transmission data.

The modulating section 209 stops sending out the training signal according to a command from the control section 208, and changes the data transmission speed in N stages. The coupling section 210 couples the signal modulated by the modulation section 2.9 with the output of the switch 211 that receives the sine wave generated from the sine wave generation section 212. The switch 211 is controlled by the control unit 208. The joint part 213 is the joint part 2
10 and the output of the sub-channel modulator 214 are combined.

The sub-channel modulation section 214 receives the measurement result of the reception level measurement section 2.5 and the output of the control section 208, and supplies the sub-channel signal to the coupling section 213. A switch 214 receiving the output of the coupling unit 213 connects the working transmission line 302 and the protection transmission line 304.
Switch between. Therefore, the transmission signal from the remote modem 200 is sent to the center modem 10 through either the working transmission line 302 or the backup transmission line 304.
Sent to 0.

The center side modem 100 has a switch 108 that switches between the working transmission line 3.2 and the protection transmission line 304. The output of the switch 108 is the received signal of the center side modem 100 which is equal to the transmission signal of the remote side modem 200. This received signal is filtered by filters 109, 110 . and 1
11. Filter 109 extracts the audio band signal from the received signal. Filter 110 extracts the data channel signal from the received signal. Filter 111
extracts the subchannel signal from the received signal. Reception level measuring section 112 measures the level of the audio band signal supplied from filter 109.

The demodulator 113 demodulates the data channel signal supplied from the filter 110 and outputs received data. Demodulator 1
13 is also capable of switching the data transmission speed in N stages. The sub-channel demodulation section 114 demodulates the sub-channel signal supplied from the filter 111. The control section 115 receives the output of the sub-channel demodulation section 114 and controls the received level measurement section 112, the switch 103, and the sub-channel modulation section 106. control.

The RAM 116 stores the output of the control section 115 and the measurement results of the reception level measurement section 112. The control unit 117 is a RAMI
16 and the output of the subchannel demodulator 114 are received. If the S/N stored in the RAM 116 is lower than the preset minimum S/N or if the sub-channel demodulator 114 cannot receive the sub-channel signal, the control unit 117 switches the transmission path to the switchers 107 and 108. Sends a control signal instructing switching from active to standby.

The training frequency measurement unit 118 measures the training frequency from the received data. If the measured number of training times exceeds a preset value, the number of training times measurement unit 118 notifies the control unit 119 to that effect. Control section 119 controls modulation section 101 , sub-channel modulation section 106 , and control section 117 .

In the remote modem 200, the training signal detection section 215 detects the training signal on the backup transmission path 303. The detection result of the training signal detection section 215 is supplied to the control section 216. When the training signal is detected by the training signal detection unit 215,
The control unit 216 connects the current transmission line 3 to the switching devices 201 and 214.
01 and 302 to backup transmission lines 303 and 304.

In the above configuration, both the center side modem 100 and the remote side modem 200 have data transmission speeds of 16.8 kbps, 14.4 kbps, and 12.0 kb.
It is assumed that three levels of ps can be selected. Now, both the center side modem 100 and the remote side modem 200 are one
Assume that it is set to 6.8 kbpS.

Assume that the state of the transmission path 301 deteriorates, data transmission is not established, and the number of training times measured by the training number measurement unit 118 exceeds a preset value.

In this case, the training frequency measurement unit 118 notifies the control unit 119 that the training frequency exceeds a preset value. Upon receiving this, the control unit 119 instructs the modulation unit 101 to stop transmitting the training signal, and also instructs the sub-channel modulation unit 106 to stop transmitting the training signal and measure the reception level. Sends a command to instruct the .

Sub-channel demodulator 207 of remote modem 200
demodulates the command from the center modem 100 and sends the demodulation result to the control unit 208. Control part 2
08 causes the modulation section 209 to stop transmitting the training signal. At the same time, the control unit 208 notifies the sub-channel modulation unit 214 that the transmission of the training signal has been stopped, and also causes the reception level measurement unit 205 to measure the level of the reception signal, and the measurement result L in the reception level measurement unit 205 is
1 is notified to the sub-channel modulation section 214.

Sub-channel demodulator 114 of center-side modem 100
demodulates the command from the remote modem 200 and sends the demodulation result to the control unit 115. Control part 1
15 stores the received signal level measurement result L1 in the RAM.
116, instructs the reception level measurement section 112 to perform measurement, sends a switching instruction signal to the switch 103, supplies the sine wave generated from the sine wave generation section 104 to the coupling section 102, and outputs the sine wave generated from the sine wave generation section 104 to the coupling section 102. A command requesting output of a sine wave and a command requesting reception level measurement are transmitted to 106. Measurement result L2 measured by reception level measuring section 112 is stored in RAM 116.

Sub-channel demodulator 207 of remote modem 200
demodulates the command from the center modem 100 and sends the demodulation result to the control unit 208. Control part 1
208 sends a switching instruction signal to the switch 211 to supply the sine wave generated from the sine wave generating section 212 to the coupling section 210, and at the same time starts outputting the sine wave to the sub-channel modulating section 214; and further instructs the reception level measurement section 205 to measure.
The measurement result L3 measured in is notified to the sub-channel modulation section 214.

Sub-channel demodulator 114 of center-side modem 100
demodulates the command from the remote modem 200 and sends the demodulation result to the control unit 115. Control part 1
15 sends a switching instruction signal to the switching device 103 to stop supplying the sine wave generated from the sine wave generating section 104 to the coupling section 102, and outputs the received received signal level measurement result L3.
is stored in the RAM 116 and instructs the reception level measuring section 112 to measure. Measurement result L4 measured by reception level measuring section 112 is stored in RAM 116. The control unit 117 takes out the measurement result of the received signal level stored in the RAMI 16 and calculates the S/N.

Letting SNI be the S/N of the transmission line 301, it is expressed by the following equation.

5NI-Ll-L2 (1) Letting the S/N of the transmission line 302 be SN2, it is expressed by the following equation.

5N2-L3-L4 (2) Here, L1=
If L3--50dBm and L2-L4=-34dBm, then 5NI-5N2-16dB.

Preset minimum S/N (SN3) or 20
dBm, since SN3>5NI-8N2, the control unit 117 transmits the switching control signal to the switch 1.
07 and 108 to cause the switchers 107 and 108 to switch to the backup transmission path, and cause the modulation section 101 to start sending out the training signal.

When the training signal detector 215 detects a training signal, it notifies the control unit 216 of the detection. The control section 216 sends a switching control signal to the switching devices 201 and 214 to cause the switching devices 201 and 214 to switch to the backup transmission path, and causes the modulation section 209 to cancel the suspension of transmission of the training signal.

Sub-channel demodulator 114 of center-side modem 100
If the control section 115 cannot receive the command from the remote modem 200 within T seconds, the control section 115 sends a command requesting the sub-channel modulation section 106 to measure the reception level. If the command from the remote modem 200 cannot be received within T seconds, the control unit 117
7 and switch 108 to switch the transmission line to the standby mode, and cause the modulation section 101 to start sending out the training signal.

Training detection unit 21 of remote modem 200
5 notifies the control unit 216 when the training signal is detected. The control section 216 controls the switching device 201 and the switching device 214 to switch the transmission path to the standby mode, and causes the modulation section 209 to cancel the transmission of the training signal.

〔Effect of the invention〕

As explained above, in the present invention, when data transmission is not established after a preset training number,
By measuring the S/N of the transmission line and detecting that the S/N falls below the preset minimum S/N or that the line is disconnected, the line can be instantly switched to a backup line to prevent deterioration of the transmission line. This has the effect of being able to automatically respond in an optimal and stable manner.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a communication system to which the automatic line switching system according to the present invention is applied. 100... Center side modulation/demodulation device, 101... Modulating section, 102... Coupling section, 103... Switching device, 104
... Sine wave generating section, 105... Coupling section, 106...
- Sub-channel modulation section, 107, 108...switcher, 1
09°110, -111...filter, 112...
Reception level measurement section, 113... Demodulation section, 114...
Sub-channel demodulator, 115...controller, 116...
RAM, 117...Control unit, 118...Training frequency measuring unit, 119...Control unit, 200...Remote side modulation/demodulation device, 201...Switching device, 202
, 203.204...Filter, 205...Reception level measurement section, 206...Demodulation section, 207...Sub channel demodulation section, 208...Control section, 209...Modulation section, 210.・・Connecting part, 211 ・・Switching device, 211・
... Sine wave generating section, 213... Coupling section, 214...
Sub-channel modulation section, 215... training detection section,
216... Control unit, 301, 302... Working transmission line, 303, 304... Protection transmission line.

Claims (1)

[Scope of Claims] 1. In an automatic line switching system in a communication system in which a center-side modem and a remote-side modem are installed facing each other via a working transmission line and a protection transmission line, measures the number of training sessions, and if the measured number of training sessions exceeds a preset number, stops sending the training signal, measures the S/N of the working transmission line, and transmits the training signal to the remote side. The modem on the remote side instructs the modem to stop transmitting the training signal, and in response to the instruction, the modem on the remote side stops transmitting the training signal and measures the S/N of the working transmission line. Notify the modem of the S/N measurement result to the modem, and the center modem may detect in advance at least one of the S/N measurement result at the remote modem and the S/N measurement result at the center modem. An automatic line switching system characterized in that when the S/N falls below a set minimum S/N, the working transmission line is switched to the protection transmission line. 2. The center side modem changes the working transmission line to the protection transmission line, and then transmits a training signal to the remote modem via the protection transmission line; An automatic line switching system characterized in that when a training signal is detected, the working transmission line is switched to the protection transmission line. 3. In an automatic line switching method in a communication system in which a center-side modem and a remote-side modem are installed facing each other via a working transmission line and a backup transmission line, the center-side modem measures the number of training sessions. and when the measured number of training times exceeds a preset number of times, stopping the transmission of the training signal, transmitting the specific signal a predetermined number of times, and measuring the S/N of the working transmission line; Instructing the remote modem to transmit the specific signal and stop sending the training signal, and the remote modem to stop sending the training signal and stop sending the specific signal a predetermined number of times according to the instruction. ,
measuring the S/N of the working transmission line and notifying the center side modem of the S/N measurement result, and the center side modem of the S/N measurement result of the remote side modem and the S/N measurement result of the remote side modem. If at least one of the S/N measurement results in the center-side modem is lower than a preset minimum S/N, or if the specific signal cannot be received even once, the working transmission line is changed to the protection transmission line. An automatic line switching method characterized by switching.