JPH0480571B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a multiplex concentrator. In particular, when the quality of the trunk line is normal, transmission is performed with the minimum delay time, and even when the quality of the trunk line deteriorates or there is a failure, data transmission for all terminal devices is ensured, and optimal throughput is achieved. This invention relates to improvements in multiplexing systems and devices.

[Description of prior art]

A general multiplexing/concentrating/demultiplexing device is installed oppositely between a terminal device and a communication control device provided at a center station via a relay line and a modulation/demodulation device.

It is desirable that the communication speed of data transmission performed between the communication control device and the terminal device be high in order to improve line usage efficiency. However, as the communication speed increases, the data signal becomes more susceptible to line noise and the like, increasing the error rate and causing problems in data transmission.

Furthermore, when a microwave relay transmission line is used as a relay line, if the electric field strength becomes unstable due to fading or the like, erroneous data transmission is performed in bursts, causing problems in data transmission.

If these problems occur, data transmission can be continued by lowering the communication speed and reducing the error rate of the relay line. However, in this state, the line usage efficiency is poor, so it is necessary to restore the communication speed as soon as the line quality improves.

However, in systems using conventional multiplexing/concentrating/separating equipment, if the line quality of the trunk line deteriorates, this is avoided by reducing the transmission speed of the trunk line. Manual intervention was required to communicate the information and to change the speed of the multiplexing/demultiplexing device and modem. For this reason, maintenance personnel must be assigned to the center station and the opposite station, and a state of low data transmission efficiency continues for a long time, resulting in a reduction in system throughput. In addition, when the relay line is a microwave relay transmission line, unstable electric field strength may cause line deterioration immediately even if the line quality is restored, and there is a drawback that speed changes must be repeated. Ta.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a multiplexing and concentrating system in which quality recovery of a trunk line is determined without human intervention and communication speeds of a modem and a multiplexing and concentrating and demultiplexing device are automatically changed.

[Key points of the invention]

The present invention includes a multiplexing/concentrating/demultiplexing device that multiplexes and demultiplexes a large number of low-speed digital signals into one high-speed digital signal, and a modulation/demodulation device that transmits/receives the high-speed digital signal to/from an opposing station. , in a multiplexing and concentrating system comprising a monitoring means for monitoring the transmission quality with the opposite station, and a means for changing the clock speed of the high-speed digital signal based on the output of the monitoring means, the multiplexing and concentrating and separating the The device includes a means for changing the clock speed that transmits a high-speed clock signal when the monitoring means detects that the transmission quality has been restored for a first time while the clock speed is set low. means for automatically controlling to transmit a high-speed clock signal; means for measuring a predetermined time after being controlled by the means to transmit a high-speed clock signal; When deterioration is detected, said means for automatically controlling said means for changing said clock speed at a high speed only when said means for automatically controlling said clock speed is detected to have recovered over a second time period which is longer than said first time period. It is characterized in that it is controlled to transmit a clock signal.

[Explanation based on examples]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is a block diagram showing details of the multiplexing/concentrating/separating devices 3 and 7 shown in FIG.

First, the configuration and connections of this embodiment will be explained based on FIGS. 1 and 2.

This embodiment system includes a communication control device 1, low-speed lines 2-1 to 2-n and 8-1 to 8-n, multiplexing and demultiplexing devices 3 and 7, modem devices 4 and 6, and trunk lines. 5 and terminal devices 9-1 to 9-n
The multiplexing/concentrating/separating devices 3 and 7 are comprised of low-speed line level conversion circuits 10-1 to 10-1.
10-n and low-speed line transmitting/receiving circuits 11-1 to 1
1-n, concentrator multiplexing circuit 12, and switching circuit 13
, a transmitting/receiving circuit 14, a data frame level conversion circuit (hereinafter referred to as a data level conversion circuit) 15, a speed switching signal level conversion circuit (hereinafter referred to as a signal level conversion circuit) 16,
It is composed of a control circuit 17 and a frame monitoring circuit 18.

As shown in FIG. 1, each of the n inputs and outputs of the communication control device 1 is connected to each of the n first inputs and outputs of the multiplexing concentrator and demultiplexer 3 via low-speed lines 2-1 to 2-n. The second input/output of the multiplexing/concentrating/separating device 3 is connected to the first input/output of the modem 4, and the second input/output of the modem 4 is connected to the modem 6 via the trunk line 5. The second input/output of the modem 6 is connected to the first input/output of the multiplexing concentrator 7, and the n second input/outputs of the multiplexing concentrator 7 are connected to the first input/output. are connected to terminal devices 9-1 through 8-n via low-speed lines 8-1 through 8-n, respectively.
It is connected to each input/output of 9-n.

FIG. 2 is a block diagram of each of the multiplexing concentrators 3 and 7. As shown in FIG. As shown in this Figure 2,
The second input/output of the low-speed line level conversion circuits 10-1 to 10-n are respectively connected to the transmitting/receiving circuits 11-1 to 11-n.
connected to each of the first input and output of 11-n,
Each of the second input/outputs of the transmitting/receiving circuits 11-1 to 11-n is connected to each of the n first input/outputs of the line concentrating multiplexing circuit 12, and the line concentrating multiplexing circuit 12
The second output of the switching circuit 13 is connected to the first input of the switching circuit 13, the output of the switching circuit 13 is connected to the first input of the transmitting/receiving circuit 14, and the first output of the transmitting/receiving circuit 14 is connected to the first input of the switching circuit 13. connected to the first input. A second output of the data level converter circuit 15 is connected to a second input of the transmitter/receiver circuit 14 , and a second output of the transmitter/receiver circuit 14 is connected to a second input of the line concentrator/multiplexer circuit 12 . The second output of the transmitter/receiver circuit 14 is also connected to the input of the frame monitoring circuit 18 , the output of the frame monitoring circuit 18 is connected to the input of the control circuit 17 , and the first output of the control circuit 17 is connected to the input of the switching circuit 13 . , a second output of the control circuit 17 is connected to a third input of the switching circuit 13 , a third output of the control circuit 17 is connected to a third input of the concentrator multiplexing circuit 12 , It is connected to the third input of the transmitting/receiving circuit 14 and the input of the signal level conversion circuit 16, respectively.

Furthermore, if a station consisting of a multiplexing concentrator 3 and a modem 4 is called station A, and a station consisting of a multiplexing concentrator 7 and a modem 6 is called a station B, the low speed of station A is Line level conversion circuit 10-1
Each of the first input/outputs of ~10-n is connected to each of the n input/outputs of the communication control device 1, and the second input/output of the data level conversion circuit 15 of station A is connected to the first input/output of the modem device 4. connected to the input/output of station A
The output of the signal level conversion circuit 16 is connected to the second input of the modem 4, and the first input/output of the low-speed line level conversion circuits 10-1 to 10-n of station B are connected to the terminal device 9. -1 to 9-n are respectively connected, and the second input/output of the data level conversion circuit 15 of station B is connected to the first input/output of the modulation/demodulation device 6, and the level conversion circuit for the station B signal is connected. circuit 1
The output of 6 is connected to a second input of modem 6.

Next, the operation of this embodiment will be explained based on FIGS. 3 to 5.

Here, FIG. 3 shows the structure of a data frame used for data transmission between the multiplexing concentrators 3 and 7, and FIG. 3A shows the data character section 20 corresponding to the transmission data. and the same B
is the control character part 2 corresponding to the control frame
It has 2.

FIG. 4 is a time chart showing the operation of the system of this embodiment, where 1 and 1' represent the operation of the transmitter of station A, 2 and 2' represent the operation of the receiver of station A, and 3 and 1' represent the operation of the receiver of station A. 3' represents the operation of the transmitting section of station B, and 4 and 4' represent the operation of the receiving section of station B. In Fig. 4, the time axis T is such that the right end of 1 and the left end of 1' are 2
The right end of 2' and the left end of , the right end of 3 and the left end of 3', and the right end of 4 and the left end of 4' are joined, and are shown separated in the figure. . Furthermore, in the time periods divided by the codes α and β, the transmission speeds of this embodiment method are “α” and “β”, respectively, and the codes t ₁ to t
Each t ₅ indicates the time length of the time interval to which this symbol is attached. Also, the symbol I and C ₁ to C ₆ are the third
3 shows transmission data of frame configurations A and B in the figure.

Further, FIG. 5 is a diagram showing the transition of the data transmission state performed between the multiplexing/concentrating/separating devices 3 and 7. As shown in FIG.

First, based on FIGS. 1, 2, 3, and 4, the operation of each part constituting the system of this embodiment in connection with switching the transmission rate will be explained.

As shown in FIG. 1, data from a communication control device 1 is input to a multiplexing/concentrating/separating device 3 via low-speed lines 2-1 to 2-n, concentrating/multiplexing the data in this device 3, and transmitting data to a modem/modulator. 4 and 6 and the relay line 5 to the multiplexing/concentrating/separating device 7 of the opposite station, and are separated into low-speed lines 8-1 to 8-n and transmitted to the terminal devices 9-1 to 9-n. . On the other hand, data from the terminal devices 9-1 to 9-n is transmitted through the low-speed line 8-
1 to 8-n to the multiplexing/concentrating/separating device 7, concentrating and multiplexing the signals in this device, and inputting the signals to the multiplexing/concentrating/separating device 7 of the opposing station via the modulation/demodulation devices 4, 6 and the relay line 5. The signals are separated into low-speed lines 2-1 to 2-n and transmitted to the communication control device 1. In this way, data transmission between the terminal devices 9-1 to 9-n and the communication control device 1 is performed mutually.

Next, as shown in FIG. 2, the low-speed data from the communication control device 1 or the terminal devices 9-1 to 9-n is transferred to the low-speed circuit level conversion circuits 10-1 to 10-n.
The level is converted by n, and the transmitting/receiving circuits 11-1 to 11
- After being serial-parallel converted by n, the line concentrator multiplexing circuit 1
2 and is multiplexed by this circuit. After passing through the switching circuit 13, the multiplexed data frame is subjected to parallel-to-serial conversion in the transmitting/receiving circuit 14, and further level-converted in the data level conversion circuit 15, and then provided to the modulation/demodulation device 4 or 6.

On the other hand, the data frame input to the modulation/demodulation device 6 or 4 is level-converted by a level conversion circuit 15 and input to the transmitting/receiving circuit 14, where it is serial-to-parallel converted and then separated by a line concentrator/demodulator 12 to support low-speed lines. be done. The separated low-speed data is parallel-to-serial converted by the transmitting/receiving circuits 11-1 to 11-n of each low-speed line, and then sent to the low-speed line level conversion circuit 10.
-1 to 10-n, the level is converted and sent to a low-speed line.

Now, in station A, the output of the transmitter/receiver circuit 14 is given to the line concentrator/multiplexer circuit 12 and also to the frame monitoring circuit 18. The frame monitoring circuit 18 performs a cyclic code check calculation on the characters of the data character section 20 included in the received data frame to detect the presence or absence of data errors. This calculation requires, for example, CRC−
In the case of the CCITT method, the generator polynomial X ¹⁶ +X ¹² +
X ⁵ +1 is used.

When the frame monitoring circuit 18 of the station A detects that the received data frame I has a frame error that continues for a certain period of time "t ₁ " or more, as shown in FIG. As shown in FIG. 2A, a deterioration signal is output from the frame monitoring circuit 18 to the control circuit 17. When this deterioration signal is received by the control circuit 17, the control circuit 17 outputs a switching signal to the switching circuit 13 and also sends out the control frame _C1 . Continuing, Figure 4 1
As shown in FIG.
A control frame C ₁ is transmitted in place of the data signal from the line concentrator multiplexer 12 .

When this control frame C ₁ is received by the frame monitoring circuit 18 of the opposite station B, the frame monitoring circuit 18 sends it to the control circuit 17 as shown in FIG.
A frame response signal is sent. When this frame response signal is received by the control circuit 17, a switching signal is output from the control circuit 17 to the switching circuit 13, and a control frame _C2 is sent from the control circuit 17 to the transmitting/receiving circuit 14. It is further transmitted to station A as shown in FIG.

On the other hand, when a certain period of time "t ₂ " has elapsed since the start of transmission of the control frame C ₁ at station A, the control circuit 17 of station A controls the transmitting/receiving circuit 14, line concentrator multiplexing circuit 12, and signal level converting circuit 16. A speed switching signal is sent to each of them, and further, a speed switching signal is sent from the signal level conversion circuit 16 to the modulation/demodulation device 4, and the transmission speed is switched from "α" to "β". Also, at the opposite station B, the control frame
When C ₁ is normally received for a certain period of time "t ₂ ", a speed switching signal is sent from the control circuit 17 of the opposite station B to each of the transmitting/receiving circuit 14, line concentrator multiplexing circuit 12, and signal level converting circuit 16. Further, a speed switching signal is sent from the signal level conversion circuit 16 to the modulation/demodulation device 6, and the transmission speed is switched from "α" to "β".

Thereafter, as shown in FIG. 4, a control frame C3 is sent from the control circuit 17 of the station A to the control circuit ₁₇ of the opposing station B at the transmission rate "β". When this control frame _C3 is received by the frame monitoring circuit 18 of the opposite station B, as shown in FIG.
A frame response signal is sent from the frame monitoring circuit 18 to the control circuit 17. When this frame response signal is received by the control circuit 17, a control frame _C4 is sent from the control circuit 17 to the transmitting/receiving circuit 14,
As shown in FIG. 4, it is further transmitted to station A.

When this control frame _C4 is received by the control circuit ₁₇ of station A, as shown in FIG. ₄ is received for a certain period of time "t ₃ ", a switching signal is sent from the control circuit 17 to the switching circuit 13 as shown in FIG. Data frame I from concentrator 12 instead of control frame C ₄ from
is sent.

When the control frame C ₄ is received for a certain period "t ₃ " at the opposite station B, a switching signal is sent from the control circuit 17 to the switching circuit 13 as shown in FIG. From transmitter/receiver circuit 1
4, the data frame I from the line concentrator and multiplexer 12 is sent out in place of the control frame C ₄ from the control circuit 17.

Next, while data transmission is being carried out at speed "β", the frame monitoring circuit 18 of station A detects errors in the received data for a certain period of time "t ₄ ", as shown in FIG. 4 2 and 2'. If not detected, a deterioration cancellation signal is sent from the frame monitoring circuit 18 to the control circuit 17, as shown in FIG. 4 1'. From this control circuit 17, a switching signal is output to the switching circuit 13, and as shown in FIG.
As shown in , the control frame _C5 is sent to the transmitter/receiver circuit 1.
4, and further transmitted to the opposing station B.

When this control frame _C5 is received by the frame monitoring circuit 18 of the opposite station B, a control frame response signal is sent from the frame monitoring circuit 18 to the control circuit 17, as shown in FIG. 4'. In response to this frame response signal, a control frame _C6 is sent from the control circuit 17 to the transmitting/receiving circuit 14, and further transmitted to station A.

When this control frame _C6 is received by the frame monitoring circuit 18 of station A, the frame monitoring circuit 18 sends it to the control circuit 1 as shown in FIG.
A frame response signal is sent at 7. In response to this control frame response signal, a control frame _C6 is sent from the control circuit 17 to the transmitting/receiving circuit 14, and further transmitted to station B.

When this control frame C ₆ is received by the frame monitoring circuit 18 of the opposing station B, a deterioration release signal is sent from the frame monitoring circuit 18 to the control circuit 17. In response to this deterioration cancellation signal, a speed switching signal is sent from the control circuit 17 to the line concentrator multiplexing circuit 12, the transmitting/receiving circuit 14, and the level converting circuit 16, and the transmission speed is switched from "β" to "α".

Furthermore, when a certain period of time " _t5 " has elapsed after the control frame _C6 was sent to the opposite station B, the transmission rate at the station A is also switched from "β" to "α" by the same operation as the opposite station B. It will be done. Continuing on from this, the fourth
As shown in FIG. 1', a control frame _C7 is sent from the control circuit 17 of station A to the transmitter/receiver circuit 14, and further transmitted to the opposing station B.

When this control frame _C7 is received by the frame monitoring circuit 18 of the opposite station B, a frame response signal is sent from the frame monitoring circuit 18 to the control circuit 17 as shown in FIG. 4'. In response to this frame response signal, a control frame _C8 is sent from the control circuit 17 to the transmitting/receiving circuit 14, and is transmitted to station A as shown in FIG. 4, 3'.

When this control frame _C8 is received by the frame monitoring circuit 18 of station A, the frame monitoring circuit 18 sends it to the control circuit 17 as shown in FIG.
A control frame response signal is sent. In response to this control frame response signal, a control frame _C8 is sent from the control circuit 17 to the transmitting/receiving circuit 14, and the fourth
The signal is transmitted to the opposing station B as shown in FIG. 1'.

On the other hand, when the control frame C ₈ is received at station A for a certain period of time "t ₃ ", as shown in FIG.
A switching signal is sent out, and instead of the control frame from the control circuit 17, the data frame I is sent out from the concentrator multiplexing circuit 12 to the transmitting/receiving circuit 14.

Further, when the control frame C ₈ is received at the B station for a certain period of time "t ₃ ", as shown in FIG.
A switching signal is sent out, and instead of the control frame from the control circuit 17, the data frame I is sent out from the concentrator multiplexing circuit 12 to the transmitting/receiving circuit 14.

Next, the data transmission operation performed between the multiplexing concentrators 3 and 7 will be explained based on the state transition diagram shown in FIG.

Reference numeral 24 in FIG. 5 indicates that the trunk line 5 is in a normal data transmission state, and in this state data transmission is performed at the transmission rate "α". Here, if quality deterioration of the trunk line 5 occurs,
Immediately, a transition is made to the first motion training state 25 via path 32. In this state 25, the transmission rate "α" has been changed to the transmission rate "β".
When the data transmission operation is confirmed at the speed "β" for a certain period "t ₃ " in this state 25,
A transition is made to the first abnormal data transmission state 26 via the route 33. In this state 26, “t ₄ ” for a certain period of time
If no error occurs in the data transmission over the above steps, a transition is made to the second motion training state 27 via path 34. In this state 27, the transmission rate 'β' has been returned to the transmission rate 'α'. On the other hand, if an error frame occurs during a data transmission operation at the transmission rate "α" for a certain period "t ₃ " in the state 27, a transition is made to the third operation training state 29 via the path 36. In this state 29,
The transmission rate "α" has been changed to the transmission rate "β". On the other hand, when it is confirmed in state 27 that the data transmission operation at the transmission rate "α" is normal for a certain period "t ₃ ", the state shifts to state 28 via route 35.
In this state 28, data transmission is being performed at the transmission rate "α". Here, the normality of the data transmission operation is confirmed again at the transmission rate "α" for a certain period "T". This state 28 is hereinafter referred to as a data transmission normality confirmation state. In this state 28, if the quality deterioration of the trunk line 5 occurs again, it will move to the third operation training state 29, and if the quality deterioration of the trunk line 5 does not occur, the normal A transition is made to data transmission state 24.

On the other hand, when the data transmission operation is confirmed at the transmission rate "β" for a certain period of time " _t3 " or more in the third operation training state 29, the data transmission state at the time of the second abnormality is changed via the route 38. Move to 30. In this state 30, if no error occurs in data transmission for a certain period of time "t ₄ '", route 3
9 to move to a fourth movement training state 31. Here, this fixed period " _t4 '" is set to be longer than the fixed period " _t4 " for confirmation performed in the data transmission state 26 during the first abnormality, and the conditions for checking line quality are set to be stricter. be done. In the fourth motion training state 31, the transmission rate "β" has been restored to the transmission rate "α". This state 31
When it is confirmed that the data transmission operation is normal at the transmission speed "α" for a certain period "t ₃ ", the route 40
The state then moves to the data transmission normality confirmation state 28 via . Subsequently, the above-described state transition is repeated.

[Effects of the Invention] As described above, the present invention automatically lowers the transmission speed when the error rate of the relay line increases temporarily, thereby realizing transmission with a low error rate. When the line condition is restored, the transmission speed can be automatically restored to its normal value, so (1) it is possible to contact the opposite station, change the speed of the demultiplexer and modem, and restore data transmission. (2) Communication with low error rate can be achieved even when relay line quality deteriorates; (3) Even when relay line quality is temporarily unstable,
This has the effect of providing optimal throughput.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention. FIG. 2 is a block diagram showing a multiplexing concentrator/separator according to the present invention. FIG. 3 is a configuration diagram of a data frame used in data transmission according to the present invention. FIG. 4 is a time chart explaining the operation of the system according to the embodiment of the present invention. FIG. 5 is a state transition diagram showing the data transmission state of the present invention. 1... Communication control device, 2-1 to 2-n, 8-1
~8-n...low-speed line, 3,7...multiplexing concentrator/demultiplexer, 4,6...modem/demodulator, 5...relay line, 9-1~9-n...terminal device, 10-1~ 1
0-n...Level conversion circuit for low-speed line, 11-1
~11-n...Low-speed line transmitting/receiving circuit, 12...
Concentrator multiplexing circuit, 13...Switching circuit, 14...Transmitting/receiving circuit, 15...Data level conversion circuit, 1
6... Signal level conversion circuit, 17... Control circuit, 18... Frame monitoring circuit, 19... Flag character, 20... Data character, 21,
23...Frame check character, 22...
control character.

Claims (1)

[Scope of Claims] 1. A multiplexing/concentrating/demultiplexing device that multiplexes and demultiplexes a large number of low-speed digital signals into one high-speed digital signal, and a modulation/demodulation device that transmits/receives the high-speed digital signal to/from an opposite station, the multiplexing/concentrating/demultiplexing device In the multiplexing and concentrating system, the device includes monitoring means for monitoring the transmission quality with the opposite station, and means for changing the clock speed of the high-speed digital signal based on the output of the monitoring means. The switching concentrator and separator is configured such that when the monitoring means detects that the transmission quality has been restored for a first time while the clock speed is set low, the means for changing the clock speed is set to a high speed clock. means for automatically controlling the transmission of the signal; means for timing a predetermined time after being controlled by the means to transmit the high-speed clock signal; and within the predetermined time, the monitoring means again controls the When a deterioration in transmission quality is detected, the automatic control means changes the clock speed only when it is detected that the transmission quality has recovered over a second period of time that is longer than the first period of time. A multiplexing and concentrating method characterized in that the clock signal is controlled to transmit a high-speed clock signal.