JPH0342533B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speed switching system for data transmission speed of a trunk line.

In general, a multiplexing/demultiplexing device or a multiplexing/concentrating/demultiplexing device is installed opposite to each other via a trunk line and a modulation/demodulation device between a terminal device and a communication control device provided in a center station.

In data transmission between a communication control device and a terminal device, the communication speed of a relay line is often set to a higher speed in order to increase line utilization efficiency. At this time, as the communication speed increases, the signal becomes more susceptible to line noise, etc., and the data error rate of the relay line increases, causing problems in data transmission at that communication speed. If the communication speed is reduced to avoid this, the data error rate of the relay line will decrease and data transmission can continue, but
Since the line usage efficiency deteriorates, it is necessary to quickly restore the communication speed when the line quality becomes good. However, in the past, one station notified the opposite station of the restoration of the data transmission speed using means such as a telephone, and each station individually manually connected the demultiplexer or multiplex concentrator to the modulation/demodulation. Performing a speed change with the device.

In this way, conventional systems require human intervention to make decisions after the quality of the trunk line has been restored, to contact the opposing station, and to change the speed of the demultiplexer, demultiplexer, demultiplexer, and modem. However, there are disadvantages in that a state of low data transmission efficiency is maintained, the throughput of the system is reduced, and maintenance personnel must be assigned to both the center station and the opposite station.

An object of the present invention is to determine failure recovery without human intervention when recovering from a fault in a trunk line in a data transmission system using a demultiplexer/multiplexer/demultiplexer or multiplexer/demultiplexer. An object of the present invention is to provide a transmission speed switching method that can automatically change the communication speed of a concentrator and separate equipment, quickly improve the throughput of a data communication system, and shorten the time for efficiency decline.

The method of the present invention is a transmission speed switching method for returning the changed transmission speed to the original speed when deterioration in the transmission quality of a relay line between multiple stations is detected. means and
monitoring means for detecting recovery of transmission quality; generating a first control signal in response to detection of recovery of transmission quality by the monitoring means; and receiving the first control signal from the partner station by the monitoring means. generating a second control signal in response, generating a third control signal in response to the reception of the second control signal from the partner station by the monitoring means, and after generating the third control signal; Alternatively, a fourth control signal is generated at a predetermined time after receiving the third control signal from the partner station, and when the monitoring means does not detect an error in the fourth control signal from the partner station, a fifth control signal is generated. control signal generating means for generating a control signal; sending means for sending the first to fifth control signals to the partner station; and the second or third control signal from the partner station by the monitoring means. and clock control means for returning the clock frequencies of the multiplexing/demultiplexing means and the modulation/demodulation means of the own station to the original frequencies before the change in response to the detection of the transmission quality or the recovery of transmission quality.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a system configuration diagram showing the principle of the present invention.

Low-speed lines 2-1 to 2-n from the communication control device 1 provided on the center side are connected to a multiplexing/demultiplexing device or a multiplexing/concentrating/separating device 3. This demultiplexing device 3 and the multiplexing demultiplexing device or multiplexing concentrator demultiplexing device 10 provided on the terminal side are mutually connected via high speed modem devices 4, 5, 6 and 7 and trunk lines (high speed lines) 8 and 9. Connected. Terminal devices 12-1 to 12-n are connected to low-speed lines 11-1 to 11-1.
1-n to a demultiplexer or demultiplexer 10.

FIG. 2 is a block diagram showing the demultiplexing device or demultiplexing device 3 and 10 used in FIG. In the figure, the demultiplexing device includes level conversion circuits 13, 14, 15, and 16 provided for low-speed lines, transmitting/receiving circuits 17, 18, 19, and 20, a multiplexing/demultiplexing circuit 21, and a transmitting/receiving circuit provided for high-speed lines. A frame monitoring circuit 26, a control frame generation circuit 27, a speed control circuit 28, and a level conversion circuit 29 and 30 are added to the conventional separation device including circuits 22 and 23 and level conversion circuits 24 and 25. has been done. The low-speed data input to the low-speed line is sent to the level conversion circuit 13,
After level conversion by 14, 15 and 16, serial-to-parallel conversion is performed by transmitting/receiving circuits 17, 18, 19 and 20, etc., and sent to a multiplexing/demultiplexing circuit 21.
In the multiplexing/demultiplexing circuit 21, parallel data from the low-speed line is time-division multiplexed and sent to the level conversion circuit 2 via the high-speed line transmitting/receiving circuits 22 and 23.
4 and 25, level-converted and sent to a high-speed line modem. On the other hand, the multiplexed data sent from the opposing station via the relay lines 8 and 9 is serial-parallel converted by the transmitting/receiving circuits 22 and 23 via the level converting circuits 24 and 25, and is converted into serial/parallel data by the transmitting/receiving circuits 22 and 23, and then sent to the multiplexing/demultiplexing circuit 21 for each low-speed Transmission/reception circuits 17, 18, 19 and 2 for each low-speed line are separated according to the line.
0, where it is parallel-to-serial converted and then sent to a low-speed line via level conversion circuits 13, 14, 15 and 16.

Next, the transmission speed switching operation will be explained.

Normally, in data transmission between the multiplexing and demultiplexing devices 3 and 10 via the trunk line 8 or 9, a signal having a frame structure as shown in FIG. 3 is used. This includes a flag character 31 for frame synchronization, an address character 32, a control character 33 indicating data,
It consists of an information field 34 for multiplexed data and a frame check character 35.

After the data frame received from the opposite station via the relay line 8 is input to the receiving section of the transmitting/receiving circuit 22, the flag character 31 is detected, and the following data string is serial-parallel converted and sent to the multiplexing/demultiplexing circuit 21 and Added to frame monitoring circuit 26. The frame monitoring circuit 26 performs a cyclic code check on the received data, and compares it with the frame check character 35 in the received frame to detect frame errors. At this time, when no frame errors are detected for a certain period of time at a speed lowered from the normal data transmission speed, the frame monitoring circuit 26 indicates to the control frame generation circuit 27 and the speed control circuit 28 that the trunk line has recovered. A recovery signal is output as shown in FIG. Here, FIG. 5 shows the operation of this embodiment, and S ₁
shows the operation of the transmitting section _R1 of the level conversion circuit 24 of the multiplexing and demultiplexing device 3, _S2 is the transmitting section of the level conversion circuit 24' of the multiplexing and demultiplexing device 10, and _R2 is the operation of the receiving section. ing.

When the control frame generation circuit 27 receives the recovery signal, it sends a control frame A for changing the communication speed to the transmission/reception circuit 22 of the demultiplexing device (Fig. 4a).
(see). When the transmitting/receiving circuit 22 receives this control frame A, it transmits this control frame A instead of the multiplexed data from the multiplexing/demultiplexing circuit 21, as shown in C1 of _S1 in FIG. The frame monitoring circuit 26 of the multiplexing and demultiplexing device 10 of the opposite station is
When this control frame A is received via the relay line 8, a control frame response signal is sent to the control frame generation circuit 27. The control frame generation circuit 27 sends the control frame B (see FIG. 4b) to the transmitting/receiving circuit 22, and transmits it to the opposite station via the relay line 8 as shown in C2 of _S2 in FIG. In the frame monitoring circuit 26 of the multiplexing and demultiplexing device 3 of the opposite station,
When this control frame B is received, a control frame response signal is sent to the control frame generation circuit 27 as shown in FIG. The control frame generating circuit 27 sends the control frame B to the transmitting/receiving circuit 22 according to this response signal, and further, the control frame B is sent to the transmitting/receiving circuit 22 in accordance with the response signal, and further, the control frame B is sent to the transmitting/receiving circuit ₂₂ in response to the response signal.
Control frame B is transmitted to trunk line 8 as shown in C2. Thereafter, a speed restoration signal is sent from the speed control circuit 28 to the transmitting/receiving circuit 22, the multiplexing/demultiplexing circuit 21, and the level converting circuit 29, thereby restoring the communication speed of the multiplexing/demultiplexing device 3 and the modulation/demodulation device 4 to the original communication speed.

Frame monitoring circuit 26 of demultiplexing device 10
is the control frame B, such as C2 of R ₂ in Figure 5.
When received, a reception signal is sent to the speed control circuit 28. As a result, the speed control circuit 28 sends a speed recovery signal to the transmitting/receiving circuit 22 and the multiplexing/demultiplexing circuit 21.
and is sent to the level conversion circuit 29 to restore the transmission speed between the multiplexer/demultiplexer 10 and the modulator/demodulator 6 to the original state. On the multiplexing/demultiplexing device 3 side, the transmission speed is changed to the original transmission speed by the speed restoration signal, and the control frame C is sent from the control frame generation circuit 27.
is sent to the transmitting/receiving circuit 22, and further transmitted to the opposing multiplexing/demultiplexing device 10 as indicated by C3 of _S1 in FIG. 5 via the level conversion circuit 24, modem device 4, and relay line 8. On the other hand, although there is a time delay in the multiplexing and demultiplexing device 10, the transmission speed is restored to the original value, so the control frame C from the multiplexing and demultiplexing device 3 is
is received correctly. When this control frame C is recognized by the frame monitoring circuit 26 of the multiplexing/demultiplexing device 10 and no error is detected for a certain period of time, a control frame recognition signal is sent from the frame monitoring circuit 26 to the control frame generation circuit 27 as shown in FIG. Sent out. In response to this, the control frame generation circuit 27 generates a response control frame B, and transmits it to the opposite station as shown in _S2 in FIG. Prior to this, in the demultiplexer 10, after switching the transmission rate, the control frame C was sent to the control frame generation circuit 27.
is generated and sent to the opposite station. When the multiplexing and demultiplexing device 3 receives the control frame C as shown in _R1 in FIG. 5, the control frame monitoring circuit 26 detects the presence or absence of an error for a certain period of time, and if there is no error, the control frame recognition signal is transmitted to the control frame generation circuit 27. Control frame B is sent to the transmitting/receiving circuit 22 instead of sending control frame C.

As described above, each of the multiplexing and demultiplexing devices 3 and 10 receives the response control frame B to the control frame C sent by its own station, and confirms that the communication path is normal after the transmission speed is restored. Therefore, the multiplexed data from the multiplexing/demultiplexing circuit 21 of each station's equipment is taken into the transmitting/receiving circuit 22 instead of the control frame, and the level converting circuit 2
4 to the trunk line 8.

FIG. 6 is a block diagram showing one embodiment of the present invention.

First, multiplexing processing will be explained. Each low-speed signal from each of the low-speed lines CH1 to CH4 is applied to each interface circuit 101 to 104, subjected to processing such as level conversion, and then sent to transmitting/receiving circuits 105 and 106. As a transmitter/receiver circuit, 1981
You can use the HDLC/SDLC protocol controller 8273 described on page 8-163 of the Intel Component Data Catalog published in 2016. In the transmitting/receiving circuits 105 and 106, the low-speed signal is converted from a serial signal to a parallel signal. CPU
Under the control of a (central processing unit) 118, the parallel signals of each channel are sequentially sent to a data bus 107, and a RAM (random access memory) 119
Parallel signals of each channel are stored at each address. Next, multiplexing processing is performed by reading out the contents of this RAM 119 in an appropriate order as parallel signals, and this multiplexed parallel signal is sent to the transmitter/receiver circuit 11.
Give to 5. The transmitter/receiver circuit 115 converts the applied multiplexed parallel signal into a multiplexed serial signal and sends it to the high-speed line. Since the separation process can be performed in the completely opposite manner, a description thereof will be omitted.

Next, the speed switching operation will be explained. The frame of the high-speed signal from the high-speed line is sent to the transmitter/receiver circuit 115.
is monitored by a frame monitoring circuit within the frame.
Now, if the deterioration in transmission quality is recovered, that is, the frame monitoring circuit does not detect a frame error for a certain period of time, the frame monitoring circuit sends an interrupt signal to 118, interrupts the demultiplexing process, and ROM (read only Various control signals are processed based on the interrupt processing program in
It is configured in RAM 119 and sent out to a high-speed line. Furthermore, the system timing controller 1
20 to change the transmission speed. Furthermore, after checking the transmission quality using the control signal sent after the speed change, the suspended multiplexing/demultiplexing process is continued.

As described above, according to the communication speed switching method according to the present invention, when the error rate of the relay line between multiplexing and demultiplexing devices increases, the receiving side automatically determines a failure in the line, thereby first After automatically lowering the communication speed of the opposite station, it is possible to automatically lower the communication speed of the opposite station, which is useful for contacting the opposite station, changing the speed of the demultiplexer and modem, and restoring data transmission. This eliminates the need for human intervention, shortens the time from failure occurrence to failure recovery, and eliminates the need to station maintenance personnel at both opposing stations.

[Brief explanation of drawings]

Fig. 1 is a system configuration diagram for explaining the principle of the present invention, Fig. 2 is a block diagram of the multiplexing/demultiplexing device or multiplexing/concentrating/demultiplexing device shown in Fig. 1, and Fig. 3 is the system configuration of Fig. 1. Figures 4a and 4b are block diagrams of control frames for the fallback system, and Figure 5 is a time chart showing the fallback operation of the multiplexing/demultiplexing device in the system configuration of Figure 1. and FIG. 6 is a block diagram showing one embodiment of the present invention. In the figure, 1... communication control device, 2-1 to 2
-n, 11-1 to 11-n low speed line, 3, 10...
...multiplexing/separating device (or multiplexing/concentrating/separating device),
4 to 7...High speed modulation/demodulation device, 8, 9...Relay line, 12-1 to 12-n...Terminal device, 24, 2
5, 29, 30...Level conversion circuit, 13-16
... Level conversion circuit, 26 ... Frame monitoring circuit, 17-20 ... Transmission and reception circuit, 27 ... Control frame generation circuit, 21 ... Multiplexing and demultiplexing circuit, 28
...Speed control circuit, 22, 23, 105, 10
6,115,116...transmission/reception circuit, 104-1
04...Interface circuit, 117...Read-only memory, 118...Central processing unit, 119...
... Random access memory, 120 ... System timing controller.

Claims (1)

[Scope of Claims] 1. In a transmission rate switching method for restoring a transmission rate changed upon detection of deterioration in transmission quality of multiplexed data on a relay line between stations A and B to the original rate, in the station A: When no data frame errors are detected for a certain period of time, it is determined that the line quality at the reduced speed has been restored, and the first control frame A is sent to the B station instead of the multiplexed data, and the B station transmits the data. The frames are constantly monitored, and when the first control frame A from the A station is detected, a response frame B is sent back to the A station, and when the A station receives the response frame B from the B station, the B station transmits the response frame B to the station A, returns the speed of the A station to the original speed, and sends a second control frame C to the B station at the original speed, and the B station receives the response from the A station. Upon receiving frame B, the speed of the B station is returned to the original speed, and the second control frame C is sent to the A station at the original speed, and the B station receives the second control frame from the A station. C, and when the second control frame is normally received for a certain period of time, the response frame B is
When the second control frame C from the B station is correctly received for a certain period of time, the A station returns the response frame B to the B station, and the A station and the B station Upon receiving the response frame B sent from the partner station in response to the detection of the second control frame C sent at the original speed, the multiplexed data is switched in place of the control frame. A transmission speed switching method characterized by transmission.