JPH03243037A - Reception signal control system for modem system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] A modem system in which a slave station modem equipped with a terminal device is connected to a master station modem on the host side via downlink and uplink lines to transmit data between the host and the terminal device. In order to reliably prevent malfunctions of terminal equipment due to abnormalities in received data, the slave station modem is equipped with a divergence state detection section that detects the divergence state of the modem reception section and/or a test state that monitors the test state from the master station. A monitoring unit is provided, and the data received by the terminal device is fixed to a predetermined logical value during divergence or testing, for example, Z-clamping is performed.

[Industrial Application Field] The present invention relates to a multi-point connected modem system for transmitting data between a host and a plurality of terminals.

In a modem system in which multiple slave station modems are multi-point connected to a master station modem via downlinks and uplinks, the terminal device (DT) responds to polling from the host.
E) When data is being transmitted from the slave station modem receiving section, a divergence condition occurs in which the tap coefficient overflows and reception becomes impossible, or when a loop test is performed from the master station to a specific slave station. In some cases, abnormal received data may be output to the terminal device, causing the terminal device to malfunction.
It is desirable to prevent modem divergence and terminal malfunctions during testing.

[Prior Art] In a conventional multi-point connected modem system, as shown in FIG. 12-1 to 12n are multi-point connected (AC connected).

The host side transmits transmission data for terminal boring to the downlink 100 through the master station modem 10, and the transmission data is received and demodulated by the slave station modems 12-1 to 12-n, and sent to a terminal equipment (DTE (not shown)). It is output as received data RD. The terminal device that has determined that it is being called outputs transmission data SD to the slave station modem, sends it to the master station modem 10 via the uplink 200, demodulates it, and notifies the host.

[Problems to be Solved by the Invention] However, in such a conventional multi-point connected modem system, for example, as shown in FIG. When a divergence state in which the tap coefficient overflows occurs in the automatic equalizer and reception becomes impossible, meaningless garbage data is output as reception data RD to the terminal device.

Further, as shown in FIG. 10, in response to a remote loop formation command from the host, the downlink 100 is connected via the master station modem 10 in order to perform a loop test of the slave station modem 12-1, for example.
If the test data is sent to the terminal device, the slave station modems 12-2 to 12-n other than the slave station modem 12-1 to be tested also receive the test data from the downlink 100, and send the test data to the terminal device as received data RD. will be sent.

In this case, from the perspective of the terminal device, the garbage data at the time of divergence or the test data of the test pseudonym becomes meaningless data, and there is a possibility that the terminal device malfunctions due to the garbage data or test data.

The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a received signal control method for a modem system that reliably prevents malfunction of a terminal device due to anomalies in received data.

[Failure to solve the problem] FIG. 1 is a diagram explaining the principle of the present invention.

First, the present invention connects a plurality of slave station modems 12-1 to 12-n to a master station modem 10 connected to a host via a downlink 100 and an uplink 200, and each slave station modem 1
Terminal devices 14-1 to 14- connected to 2-1 to 12-n
The target is a modem system with a multipoint connection that performs data transmission between a master station and a host on the master station side.

In the present invention for such a modem system, each of the slave station modems 12-1 to 12-n is provided with a divergence detection section 16 for detecting the divergence state of the modem reception section, and the detection output of the divergence detection section 16 is When the terminal device ff116-1 is obtained,
The received data RD for 16-n is fixed to a predetermined logical value.

Furthermore, in addition to the divergence detection section 16, each of the slave station modems 12-1 to 12-n is provided with a test state monitoring section 18 for monitoring the test state by the master station modem 10.
Even when a monitoring output indicating a test state is obtained from 8, the received data RD for the terminal devices ff114-1 to 14n is fixed to a predetermined logical value.

Of course, each of the slave station modems 12-1 to 12-n is provided with only the test state monitoring section 18, and the terminal device 1 is provided in the test state.
The received data RD for 4-1 to 14-n may be fixed to a predetermined logical value.

[Operation] According to the reception signal control method of the modem system according to the present invention having such a configuration, when the slave station modem becomes unable to communicate due to the divergence state, it becomes an abnormal state in which garbage data is output to the terminal device. Also, since the received data RD for the terminal device is fixed to a predetermined logical value (0, 1, or Z clamp) in the divergent state, malfunctions due to the received data RD of the terminal device can be reliably prevented.

Also, even if a loop test is performed on a specific slave modem by forming a remote loop from the master station, if a test state is detected using test data from the master station in a slave modem other than the one being tested, Received data RD for terminal device
is fixed at a predetermined logical value to prohibit the output of test data to the terminal device, thereby reliably preventing the terminal devices of other slave station modems from performing slave operation during the test.

[Example] FIG. 2 is a configuration diagram of a modem system according to the present invention.

In FIG. 2, 10 is a master station modem, and a host 20
The transmission data SD from the host 20 is modulated into an analog signal and sent to the downlink 100, and the analog signal from the uplink 200 is received and demodulated to receive data R.
D is output to the host 20.

Downlink 100 and uplink 20 from master station modem 10
0, a plurality of slave station modems 12-1, 12-2.
...12-n are multi-point connected. Each of the slave station modems 12-1 to 12-n has a terminal device (DT
E) 14-1 to 14-n are connected.

The slave station modem 12-12-n receives the polling transmission data constantly sent from the master station modem 10 via the downlink 100 and sends it as received data RD to the terminal device 14-.
1 to 14-n. Terminal devices 14-1 to 14
-n determines its own call from the received data RD,
Transmission data SD is output to the corresponding slave station modems 12-1 to 12-n, modulated into analog signals by the slave station modems 12-1 to 12-n, and transmitted to the uplink 200, and transmitted to the master station modem 10. Data is sent to the host 20 by reception demodulation.

In the present invention, for such a modem system with multi-point connection, a divergence detection section for detecting the divergence state of the modem reception section is provided in each of the slave station modems 12-1 to 12-n, and a divergence detection section is provided for each of the slave station modems 12-1 to 12-n. A test state monitoring unit is provided to monitor the test state of the test state, and when a divergence detection output and/or a test state monitoring output is obtained, a corresponding terminal device 14-1 is provided.
14-n is configured to be fixed at a predetermined logical value.

FIG. 3 is an embodiment configuration diagram showing an embodiment of the slave station modem of FIG. 2.

In FIG. 3, a downlink line 100 serving as a receiving line is connected to a receiving analog section 22, and the line received signal is separated by a separation transformer received by the receiving analog section 22, and then sent to a demodulating section 2.
Output to 4. The demodulation unit 24 A/D converts the received analog signal from the reception analog unit 22 and inputs it to a digital signal processor (hereinafter referred to as rDSPJ), and performs processing to cancel line deterioration factors of the downlink 100. That is, the DSP controls the AGC circuit, automatic equalizer (AEQ), carrier automatic phase control circuit (CAPC) under program control.
), it is equipped with a phase jitter removal circuit using a prediction filter (PRDF), the AGC circuit keeps the received signal level constant and compensates for the signal level, the AEQ removes the code amount interference component, and the CAP
A frequency offset and a phase error are removed by C, and a phase jitter component is further removed by a prediction filter.

The received signal that has been subjected to cancellation processing of line deterioration factors by the demodulation section 24 is given to the control section 26, and it is determined whether the signal point coordinates are correct through determination processing using table data. The signal point coordinates determined in this way are converted into a data bit string per modulation by mapping processing, and finally the bit strings for each modulation are connected and outputted to the terminal device as received data RD.

A divergence detection section 16 for detecting a divergence state in the modem reception section of such a slave station modem is provided for the demodulation section 24,
Further, the test state monitoring section 18 that monitors the test state is controlled by the control section 2.
It is provided as one function of 6.

Next, to explain the transmitting side of the slave station modem in Fig. 3,
Transmission data SD from the terminal device is first given to the control unit 26, divided into bit data per modulation corresponding to the modulation speed of the modem system, and converted into signal point coordinates on a complex plane by mapping processing. The signal is output to the modulation section 28. In the modulation section 28, the real component Re of the signal point coordinates is amplitude-modulated by cosωt, and the imaginary component 1m is amplitude-modulated by sinωt, and by mixing both, a quadrature amplitude modulation signal (QAM) is sent to the transmitting analog section. After the signal is outputted to 30 and converted into an analog signal, the power is amplified and sent to the uplink 200 as a transmission line.

The configuration of the receiving side and the transmitting side of the slave station modem shown in FIG. 3 is the same as that of the master station modem 10 of FIG. 2, except for the divergence detecting section 16 and the test state monitoring section 18 on the receiving side.

FIG. 4 shows a block diagram of an embodiment of the reception side in the slave station modem of FIG. 3.

In FIG. 4, a modem receiving section 300 is comprised of the reception side control functions of the reception analog section 22, demodulation section 24, and control section 26 shown in FIG. A divergence detection section 16 is provided for the modem reception section 300, and the divergence detection section 16 receives a signal indicating a divergence state from the modem reception section 300, specifically, the demodulation section 24, and monitors the presence or absence of a divergence state. When a divergence condition is detected, a divergence detection output that becomes logic level 1 is generated. Further, the test state monitoring unit 18 takes in the received data RD received and demodulated by the modem receiving unit 300 and monitors the presence or absence of a test state, and when a test state is detected, the logic level becomes 1 indicating that the test state is present. Produces test status monitoring output.

The received data RD from the modem receiving section 300, the detection output of the divergence detection section 16, and the monitoring output of the test state monitoring section 18 are given to the received data control section 32.

In the normal state where both the divergence detection output and the test state monitoring output are at logic level 0, the reception data control unit 32 outputs the reception data RD from the modem reception unit 300 as is to the terminal device, but the divergence detection output and the test state monitoring output are Alternatively, when either one of the test state monitoring outputs is obtained and the logic level becomes 1, the output of the received data RD to the terminal device is prohibited, and a 2-clamp (zero-cross clamp) is set, for example.

FIG. 5 is a block diagram showing an embodiment of the divergence detection section 16 of FIG. 4 together with the modem receiving side.

In FIG. 5, first, on the modem receiving side, there is an automatic equalizer (A E Q) 32 that removes the code amount interference of the received signal, and a carrier automatic that removes the frequency offset and phase error contained in the output of the automatic equalizer 32. Phase control circuit (CAP
C) 36 and a determination circuit 38 that determines correct signal point coordinates from the output of the carrier automatic phase control circuit 36. Here, the determination circuit 38 may be either a hard decision circuit that determines the correct signal point based on table data or a soft decision circuit that uses a Piterbi decoding circuit that determines the correct signal point based on trellis encoding on the transmitting side. One or both may be used.

A signal obtained by detecting the difference between the input signal and the output signal of the determination circuit 38 by the subtractor 4o, that is, a determination error signal, is supplied to the divergence state detection unit 16. The determination error signal from the subtracter 40 is integrated by an integrating circuit 42 provided in the divergence state detection section 16, and the integral output of the integrating circuit 42 is given to a determining circuit 44, which determines whether or not there is divergence by comparing it with a predetermined threshold. is determined. The output of the integrating circuit 16 takes a value of 0 to 1.0, for example, and the closer it is to 1, the better the reception quality is.

The judgment circuit 44
As the threshold Th for detecting the divergent state,
For example, Th=Q,5 is set, and when the integrated judgment error signal becomes less than the threshold value Th=Q,5, a divergence detection output that becomes logic level 1 is generated.

FIG. 6 is a block diagram showing an embodiment of the test state monitoring section of the present invention, which is configured by a test command diffraction section 46 and a test command recognition section 48 under program control of the control section 26 shown in FIG. , the recognition result of the test command recognition section 48 is given to the received signal control section 32.

The test command diffraction section 46 diffracts the test command from the received data RD, and notifies the test command recognition section 48 of the diffraction result. For example, when the test command recognition unit 48 recognizes that the diffracted test command is a loop test of a slave station modem, it provides the received signal control unit 32 with a test state monitoring output that has a logic level of 1 indicating that it is in a test state. This allows Z-clamping to be performed on the terminal device.

FIG. 7 is an explanatory diagram when the slave station modem diverges according to the reception control method of the present invention; for example, a divergence state in which reception quality is significantly degraded due to overflow of the tap coefficient of the automatic equalizer provided in the slave station modem 121, etc. If this occurs, Z-clamping of the received data RD to the terminal device is performed based on the detection output of the divergence detector 16 provided in the slave station modem 12-n, and the slave station modem 12-n enters the divergent state. It is also possible to reliably prevent garbage data from being sent to the terminal device and causing malfunctions.

FIG. 8 is an explanatory diagram illustrating received signal control according to the present invention during a slave station loop test. In response to a remote loop formation command from the host, a test loop is formed in the slave station modem 12-1 as shown in the figure, for example. , test data SD from host
is transmitted from the master station modem 10 to the downlink lOO, looped back by the slave station modem 12-1 in a loop state, and returned to the host via the master station modem 10 via the uplink 200 as a receiving pig RD. Suppose that During such a loop test, test data is received by all of the slave station modems 12-2 to 12-n other than the slave station modem 12-1 that is the subject of the test, and is sent to the terminal device as received data RD. It will now be sent. However, in the present invention, each of the slave station modems 12-2 to 12-n detects that the received data RD is in the receiving state and Z-clamps the received data RD for the terminal device, so that the test data is Since the received data RD is not given to the terminal device, malfunction of the terminal device due to test data can be reliably prevented.

Although the above embodiment takes as an example the case where each of the slave station modems 12-1 to 12-n is provided with both the divergence detection section 16 and the test state monitoring section 18, other embodiments may be used. As a result, only the divergence detection section 16 may be provided in the slave station modems 12-1 to 12-n, or only the test state monitoring section 18 may be provided.

[Effects of the Invention] As explained above, according to the present invention, it is possible to solve a situation where the modem goes into oscillation state due to deterioration of the line condition and outputs garbage data to the terminal data due to the inability to communicate, or when testing the modem. As a result, even when normal data communication is not possible, malfunction of the terminal device due to garbage data or test data can be reliably prevented, and a highly reliable modem system can be realized.

[Brief explanation of drawings]

Figure 1 is a diagram explaining the principle of the present invention; Figure 2 is a configuration diagram of a modem system of the invention; Figure 3 is a diagram of the configuration of a slave station modem of the invention; Figure 4 is a diagram of the reception side configuration of a slave station modem of the invention. FIG. 5 is a block diagram of an embodiment of the divergence state detection section of the present invention. FIG. 6 is a block diagram of an embodiment of the test state monitoring section of the present invention. Figure 7 is an explanatory diagram when the slave station modem of the present invention diverges; Figure 8 is an explanatory diagram during the slave station loop test of the present invention; Figure 9 is an explanatory diagram when the conventional slave station modem diverges; Figure 10 is an explanatory diagram at the time of a conventional slave station loop test. In the figure, 10 master station modem 12, 12-1 to 12-n slave station modem 14, 14-
1 = 14-n Terminal equipment (DTE) 16 Divergence state detection section 18 Test state monitoring section 20: Host 22: Reception analog section 24: Demodulation section 26 Two control section 28: Modulation section 30, Transmission analog section 32: Reception signal control (RD control unit) 34 Automatic equalizer (AEQ) 36 Automatic carrier phase control circuit (CAPC) 38: Judgment circuit 40: Subtractor 42, integration circuit 44: Judgment circuit 46: Test command diffraction unit 48: Test command recognition unit 100: Down line 200: Up line 300/modem receiving unit

Claims (3)

[Claims] (1) Connect multiple slave station modems (12-1 to 12-n) to the master station modem (10) connected to the host via the downlink (100) and uplink (200), and Terminal devices (14) connected to modems (12-1 to 12-n)
-1 to 14-n) and a master station host, each of the slave station modems (12-1 to 12-n) has a divergence state of the modem receiving section. A divergence detection section (16) is provided to detect the received data (R
D) is fixed to a predetermined logical value. (2) Each of the slave station modems (12-1 to 12-n) is provided with the master station modem (12-n) in addition to the divergence detection section (16).
Test status monitoring unit (18) that monitors the test status according to 0)
The terminal device (14-1 to 14-1
4-n) is fixed to a predetermined logical value. (3) A plurality of slave station modems (12-1 to 12-n) are connected to the master station modem (10) equipped with a host via the downlink (100) and uplink (200), and each slave station Terminal device (14-1) connected to modem (12-1 to 12-1)
1 to 14-n) and a host on the master station side, each of the slave station modems (12-1 to 12-n) is provided with the master station modem (10). A test state monitoring section (18) is provided to monitor the test state of the terminal device (14-1 to 14-n) when a monitoring output indicating the test state is obtained from the test state monitoring section (18). Received data (RD) for
A receiving signal control method for a modem system, characterized in that the signal is fixed to a predetermined logical value.