JPH0716194B2 - Monitor method - Google Patents

Description

The present invention relates to a monitor system in a multipoint communication system.

In recent years, in data communication systems, not only data communication but also network management have been performed in order to improve reliability of data communication.

In order to realize this network management, it is necessary to monitor the states such as line quality, reception level, frequency offset, and signals entering the data terminal equipment (DTE).

On the other hand, since the master station modem connected in multipoint needs to receive signals from many slave station modems, there is a time during which the received signal is cut off for several tens of ms, for example.

Therefore, if the state when the carrier is not received is monitored as it is, there is a possibility that the data communication may be erroneously determined to be impossible. Therefore, it is necessary for network management to reliably determine the state of carrier disconnection and the inability to communicate data.

[Prior Art] Conventionally, in a multipoint communication system in which a plurality of slave station modems are multipoint connected to a master station modem connected to a center via a dedicated line, the master station and slave station modems are provided. A monitor (AGC (Automatic Gain Control) circuit, SQD (Signal Quality Detect) circuit, offset detection circuit, etc. are installed in the monitor to monitor the reception level, line quality, frequency offset, etc., and thereby manage the network. I am trying to realize.

[Problems to be Solved by the Invention] However, in such a conventional monitoring method, there is a time when the reception signal is disconnected because the reception signal from many slave station modems is required in the master station modem. Therefore, if the state when the carrier is not being received is monitored as it is, the state of the carrier disconnection may be mistakenly determined to be data communication impossible. As a result, there is a problem in that network management cannot be performed reliably.

The present invention has been made in view of the above-mentioned conventional problems, and a monitoring method capable of reliably performing network management by maintaining a state at the time of carrier reception during a normal carrier disconnection. Is intended to provide.

[Means for Solving the Problems] FIG. 1 is a diagram illustrating the principle of the present invention.

In FIG. 1, 2 is a master station modem connected to the center 1, 6 is a plurality of slave station modems connected to the master station modem 2, 13 is a monitor provided in the master station modem 2, and 20 is a line state. Is a holding means for holding the monitor value detected by the detecting means 20, and 19 is a converging means for gradually converging the monitor value.

[Operation] In the present invention, the monitor value indicating the state at the time of carrier reception is held for a certain time during the normal carrier disconnection, and the monitor value is gradually changed to the carrier disconnection state when the carrier disconnection exceeds the certain time. Since they are brought close to each other, it is possible to prevent the carrier disconnection at the normal time from being erroneously determined as the data communication failure.

As a result, normal network management can be performed.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a diagram showing a communication system for implementing the present invention.

In FIG. 2, 1 is a center, 2 is a master station modem,
The center 1 and the master station modem 2 are data terminal devices (hereinafter, DT
E) Connected via 3,4. A plurality of slave station modems 6 are respectively connected to the master station modem 2 via a dedicated line 5, and a terminal 7 such as a keyboard is connected to each slave station modem 6.

As shown in FIG. 3, the slave station modem 6 has a modem section 8 for performing demodulation and a monitor 10 for monitoring the modem section 8 and the DTE 9.

Reference numeral 11 denotes an alarm detector, and the output state of the monitor 10 is detected by the alarm detector 11.

On the other hand, the master station modem 2 has, as shown in FIG. 4, a modem unit 12 for performing demodulation and a monitor 13 for monitoring the line state. The monitor 13 includes an AGC circuit 14 that keeps the reception level at a constant level, an SQD circuit 15 that detects the line quality, an offset detection circuit 16 that detects a frequency offset, and an AGC circuit.
Hold circuit (hold means) 17 for holding each output of circuit 14, SQD circuit 15 and offset detection circuit 16 for a certain period of time, timer 18 for setting a certain period of time in hold means 17, AGC circuit 14, SQD circuit 15 and offset And a converging circuit (converging means) 19 that gradually brings each output of the detection circuit 16 closer to the state when the carrier is disconnected.

The AGC circuit 14, SQD circuit 15 and offset detection circuit
16 as a whole constitutes a detecting means 20 for detecting the line state.

Next, the monitor system of the present invention will be described.

First, immediately after the reception carrier is cut off, the AGC circuit 14, SQD
Each output of the circuit 15 and the offset detection circuit 16 is held by the hold circuit 17 in the state of receiving the carrier. here,
If the carrier detection signal (CD) is off, the monitor value is held as it is, and if the CD is on, the monitor value is released.

Next, if the reception carrier disconnection is normal, the hold circuit
At 17, the monitor value is held as it is, and when the CD is on, the monitor value is released.

That is, as shown in FIG. 5, when the received carrier is as shown in FIG. 5 (a), the monitor value is shown in FIG. 5 (b).
As indicated by the dotted line C, the state at the time of carrier reception is maintained.

Next, when the reception carrier disconnection is abnormal and exceeds a certain time, the convergence value is gradually brought close to the monitor value by the convergence circuit 19. Then, a certain time t after the CD is turned off
The carrier is disconnected during this period (see FIGS. 6 (a) and 6 (b)).

Therefore, in the master station modem 2, even if the time period during which the received signal is interrupted exists for several tens of ms, the state at the time of carrier reception is held during this time. There is nothing to do. Further, since the monitor value after the timeout for a certain period of time is gradually brought closer to the state of carrier disconnection, it is not necessary to severely set the time of carrier disconnection.

As a result, network management can be performed in the multipoint communication system.

[Effects of the Invention] As described above, according to the present invention, the state at the time of carrier reception is held during the normal carrier interruption, and the monitor value is gradually changed to the carrier interruption state when the carrier interruption is abnormal. Since they are brought close to each other, it is possible to reliably perform network management without erroneously determining a carrier disconnection as being incapable of data communication.

[Brief description of drawings]

1 is a diagram for explaining the principle of the present invention, FIG. 2 is a diagram showing a communication system for carrying out the present invention, FIG. 3 is a block diagram of a slave station modem, FIG. 4 is a block diagram of a master station modem, FIG. 5 is an explanatory diagram when the carrier disconnection is normal, and FIG. 6 is an explanatory diagram when the carrier disconnection is abnormal. In the figure, 1 ... Center 2 ... Master station, 3,4,9 ... DET, 5 ... Dedicated line, 6 ... Slave station modem, 7 ... Terminal, 8 ... Modem section, 10 ... Monitor, 11 ... Alarm detection circuit, 12 ... Modem section, 13 ... Monitor, 14 ... AGC circuit, 15 ... SQD circuit, 16 ... Offset detection circuit, 17 ... Hold circuit (hold means), 18 ...... Timer, 19 …… Converging circuit (converging means), 20 …… Detecting means.

Claims (1)

[Claims] 1. A multipoint communication system comprising a master station modem (2) connected to a center (1) and a plurality of slave station modems (6) connected to the master station modem (2). In the monitor (1) provided in the master station modem (2)
3) A detecting means (20) for detecting a line state, a holding means (17) for holding a monitor value detected by the detecting means (20), and a converging means (19) for gradually converging the monitor value. Is provided, and the monitor value is held for a certain time when the carrier is cut off, and when the fixed time is exceeded, the monitor value is gradually brought closer to the carrier cut-off state.