JPH03293844A - Line automatic switching system - Google Patents

Abstract

PURPOSE:To reduce expenses of personnel arrangement and to shorten the interruption time of data communication by measuring the reception signal quality of a current transmission line and measuring S/N at the time of degradation of this quality to a prescribed value or lower and automatically switching the current transmission line to a stand-by transmission line in the case of the S/N measurement result which is not adapted to any transmission speed. CONSTITUTION:A MODEM 01 on the main station side and a MODEM 02 on the counter station side are connected by current transmission lines 03 and 04, and the reception signal quality of current transmission lines 03 and 04 are measured in MODEMs 01 and 02, and when the reception signal quality is degraded 10 the prescribed value or lower, S/N of current transmission lines 03 and 04 is measured, and the transmission speed is automatically switched to a transmission speed adapted to this measured S/N in accordance with the measurement result. If the measurement result is not adapted to any transmission speed, current transmission lines 03 and 04 are automatically switched to stand-by transmission line 06 to 09. Thus, required expenses of personnel arrangement are reduced and interruption time of data communication is shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a system in which a modem automatically switches a transmission line used for communication by a modem.

[Conventional technology]

When a modem (hereinafter referred to as MODEM) switches the transmission line used for data communication from the active to the backup, the complex signal sent from the automatic equalizer of each opposing MODEM is displayed on an oscilloscope as a two-dimensional screen. and evaluate the quality of the received signal based on the resulting eye pattern,
If the quality deterioration in either of the two MODEMs becomes severe, the transmission speed can be manually switched to a lower one. The system allows switching from the working transmission line to the protection transmission line by manual operation.

If each MODEM has a function to automatically switch the transmission speed, the same switching should be performed manually after the quality of the received signal becomes insufficient even at the lowest transmission speed. It has become.

[Problem to be solved by the invention]

However, in order to manually switch between the active and backup transmission lines, it is necessary for staff to monitor the eye pattern.
In addition, it requires prior meetings between opposing MODEMs, which increases the cost of staffing.
The 0 time is large in the case where the switching to the preliminary transmission cycle is performed, and during this period, data communication is interrupted, causing other drawbacks.

[Means for resolving issues]

In order to solve the above-mentioned problems, the present invention takes the following measures.

In other words, in an MOI (MOI) EM that has multiple transmission speeds and has a transmission speed switching function, the received signal quality of the working transmission line is measured, and when the quality of the received signal falls below a predetermined value, the working transmission line is Measures the SIN of the transmission line, and automatically switches to the appropriate transmission speed among the transmission speeds according to the result. If the measurement result does not match any of the transmission speeds, the system switches from the working transmission line to the backup transmission line. The switching is done automatically.

[Effect]

Therefore, the transmission speed is automatically and optimally switched, and the switching to the protection transmission line is also automatically carried out.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to block diagrams showing embodiments.

In the figure, the main station side tDMODΣMO1 and the opposite station side OMODEMO2 are the working transmission line *C below, the working line)
Connected by O3, 04 and one exchange network OS
Public channel MO@~09 via pw! MODEMO1 includes a modulator (hereinafter referred to as MOD) 1 that modulates a carrier wave using transmission data 8D1, and a sine wave generator (hereinafter referred to as SW) via a switch (hereinafter referred to as 8W) 2.
c) A combiner (hereinafter referred to as CPU) 4 that mixes the output of 3 with the output of MODI, and an output of a subchannel modulator (hereinafter referred to as 80M) 5 that modulates the subcarrier according to various command signals as the CPU 4C) output. Furthermore, a switching device (hereinafter referred to as 5) selects and sends the output of the CPU 1i to be mixed to the working line
EL) 7, and correspondingly MODEMO
2 includes 8EL8, a filter (hereinafter referred to as FIL) 1 that passes the audio frequency band, FILlo that passes the main channel signal from MODI, FILll that passes the sub-channel signal from 8CM5, and a reception level control based on the output of FIL8. The reception level measuring section (hereinafter referred to as
RLM) 12° A demodulator (hereinafter referred to as DEM) that demodulates the output of FILlo into received data RDI 13. A sub-channel demodulator (
8CD) 14, and a control section (hereinafter referred to as CNT) 15 that responds to the output thereof.

In addition, in order to transmit the transmission data 8D of MODEMO2, etc., MODEMO2 also has the MOD of MODE:MOl.
Like I to 5EL7, MODI6. CPU17.5
WIII.

8WG19. The CPU20, 8CM21, 8EL22 are equipped, and the MODEMO1 is connected through the current port 804.
Then, like 5EL8 to CNT15 of MODEMO2, 5EL23, FIL24 to 25, PLM27.0
1M2B, 5CD29°CNT30 has legs, CN
The output of T30 and the output of RLM27 are given to a memory (hereinafter referred to as MEM) 31 such as a RAM, and CNT32 controls BELT 23 according to the contents thereof.

On the other hand, the output of the DEM 28 is sent out as received data RD, and the received signal quality measuring unit (
Hereinafter, RQM) 33, CNTj4 that responds to the output of this
This is the network control unit (hereinafter referred to as NC1J) 3!
, 3IO control, and make O calls to public lines 0@ and 07, which are used as backup transmission lines.

MODEMO2 is also provided with 19M37 to which received data RD1 is given, and is also a public channel @OS.

0! NCU38.38 that performs detection of incoming calls via I
A carrier detection unit (hereinafter referred to as CHD) 4G is connected to the output of the NCU 38 on the receiving side, and the pcNT 41 responds to the output of this to control 5ILII and 22.

Here, during normal operation, the transmission data is 8D.

Transmission via SDzOMODl, 16, these D
EMI3.

The received data RD, , RD are received via the working lines 03 and 04, and the data communication using the working lines 03 and 04 is performed with a predetermined quality, but the quality of the received signal deteriorates due to deterioration of the SIN, etc. Then, MODI,H becomes in a state where it transmits a training signal.

The quality of this received signal is determined by III according to 19M33.37.
If the quality is lowered by p than the predetermined value and, for example, an error in the received data RD weight becomes unacceptable, this will be detected by RQMj3 and the CNT34 will
commands MODI to stop transmitting the training signal, and also sends a command signal to 8CM5 instructing it to stop transmitting the training signal and measure the reception level.

This command signal is received via MODEMO2080D14, and in response, CNT15 instructs MOD16 to stop transmitting the training signal, and P
The LM 12 is instructed to measure the reception level.

Therefore, the noise level in the no-signal state is RL)/112
The measured value L1 is transmitted via the 80M21 and received by the 5CD211, and the measured value L1 is stored in the MKM31 via the CNT 30.

After receiving the measurement value L1, the CNT 30 turns on 8W2 to transmit the output of 8WG3, and also sends a command signal to 80M5 instructing to measure the reception level.

This ;mantle signal is received in the same manner as described above, and PLM1
2 measures the sine wave signal 0 reception level and sends the measured value Lm to 80MH again, so the measured value L1
is stored in the MEM 31 through the same route as described above.

Furthermore, after transmitting a command signal instructing the BCM 5 to stop transmitting the training signal, the CNT 30 transmits a command signal to the BCM 5, and then
In order to instruct the LM 27 to control the reception level, the noise level in a no-signal state is measured by the RLM 27, and this measured value L2 is stored in the MEM 31.

Furthermore, CNT 3 Q becomes 8 when SW2 is turned on.
In order to send a command signal instructing the transmission of a sine wave signal to 0M5, CNT15 turns on 5W18 in response to this, and turns on 5WG1! The CNT 15 transmits the IQ output, and the CNT 15 sends a command signal to the 8CM 21 indicating the start of transmission of a sine wave signal, and upon reception of this, the CNT 30 requests the RLM 2T to measure the reception level again. In order to issue the command, the reception level of the sine wave signal is now measured, and the measured value L4 is stored in MΣMs1.

Therefore, the working line @03C) The noise level measurement value L1 and the signal level measurement value, Moreover, these are individually stored in the MIM 31.

Then, CN'l'32 reads 8/ according to the contents of MIM31.
NO operation tube operation -, transmission speed switching or working line 03
．． 04 to public lines 06 to 08.

In other words, the S/N of the working time @03 is set to SN H, and the S/N of the working time [
If "S" of 104 is BN2, each can be obtained by the following equations.

8N1= Lt Ls −−−−−−−−
--------(118N2 = Lz L4 -----
−−−1−−−−−−−−−−(21 Here,
Ls=Lz=50dBmsLs=L4--34
When dBm, 8N1=SN! = 16 dB.

In addition, the transmission speed of MODl, 16 is set to 16.8 Kbpi.
+14.4Kbpm + 12.0Kbp@3R floor switching, and if the minimum transmission speed OIZ, OKhpm, the required 5/N is BNg = 20dB, then 8N, ) IN, ! 8N! 0 relationship is established, even if the transmission speed is the lowest, the working line 03
．． Since 0408/N is non-conforming, CNT32 is 8E.
Control L7, 23 and NCU! 5. Switching to public lines a@, ay via 38 is performed.

In addition, NCU35.3@ is CNT32 C)11 when CNTJI4 responds to the quality deterioration detection of RQM33.
11N), make a call to MODEMO2, and
NT31.

39C) The line is held according to the response to the incoming call, and the carrier wave sent from MODI in response to the switching of 5EL7.23 is transmitted to the public circuit @oe, as and NCU3@
CNT41 controls SEL@, 22 according to this O output, and NCU38.
In order to switch to II, the switching to the backup transmission line via the switching network 05 is completed, and data communication is resumed.

However, if the working time [03,040 column specified and 90/N matches one of O among each transmission speed, CNT32 is MO
A command is given to DI to perform O switching to an appropriate transmission speed, and a restoration command is given to NCU $5.31 to release public lines 06-090.

In addition, if the command signal indicating the start of communication from NODIM O2 cannot be received by 8CD21 even after a certain period of time has passed after switching to the public line gos~09, the CNT30 will determine this. , 80M5 sends a command signal O instructing to measure the reception level,
Resume the above O5/N#J determination.

Note that since 8/N also deteriorates when either of the working lines 03 and 04 is disconnected, switching to the protection transmission line is similarly performed.

c #4o effect] As is clear from the above explanation, according to the present invention, the received signal quality of the working transmission line is measured, and when this quality has decreased by a predetermined value, the SIN of the working transmission line is determined. The system automatically switches from the working transmission line to the protection transmission line when the measurement results do not match any of the transmission speeds, thereby eliminating the need to artificially monitor the quality of the received signal and perform switching operations. Since switching to the backup transmission line is performed optimally and at high speed, staffing costs can be reduced, and data communication interruption time is shortened, which is particularly important when switching over data transmission lines for various purposes. You can get the following effect.

[Brief explanation of the drawing]

The figure is a block diagram showing an embodiment of the present invention. 01.02...Modulation/demodulation equipment, 03,04...-Working transmission line, os-os-...Public line, 1.16...
...Modulation section, 2.18・3〇〇switch, 3.1s・
...Sine wave generator, 7,8°22.23--Switcher, 12.27--Reception level measurement section, 15,30
, 32, 34, 49... control unit, 31... mesori, 33.37-... received signal quality measurement unit, 35, 5
L38.39--Network control unit. Tokken Applicant: NEC Corporation

Claims (1)

[Claims] In a modulation/demodulation device that has a plurality of transmission speeds and is equipped with a transmission speed switching function, the received signal quality of a working transmission line is measured, and when the quality of the received signal falls below a predetermined value, the S/D of the working transmission line is changed. N, and automatically switches to a suitable transmission speed among the transmission speeds according to the measurement result, and when the measurement result does not match any of the transmission speeds, the transmission line is switched from the current transmission line. An automatic line switching method characterized by automatically switching to a backup transmission line.