JPH09172395A - Branching wiring communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set output levels to become equal reception levels on a center device-side for respective terminal equipments in the branching wiring communication system of CATV and an intra-hotel line. SOLUTION: The reception level of the center device 1 on a prescribed terminal equipment 5 is set to be a reference level. The reception level of the other terminal equipment 5 is compared with the reference level in a control part 13 on the center-side, and a result is re-transmitted to the pertinent terminal equipment 5 as a level control signal. The terminal equipment 5 receiving it adjusts a variable attenuator 54 based on the level control signal based on the level control signal and the reception level on the center device 1-side is made equal to the reference level. The reception levels on the center device 1-side become equal by similarly controlling all the terminal equipments. Communication is stabilized and up noise is reduced. Even if a level defect occurs with a communication loop, it is fed back and the communication level becomes normal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a branch wiring communication system, and in particular, a plurality of terminal devices are branched and connected to a communication line connected to a center device to perform bidirectional communication between the center device and each of the terminal devices. The present invention relates to a branch wiring communication system such as a CATV or a hotel premises communication system.

[0002]

2. Description of the Related Art A system configuration example of a branch wiring communication system is shown in FIG. In this communication system, a communication line 2 connected to a center device 1 is branched into a large number of branch lines by a plurality of branching devices 3 and a relay amplifying device 4, and a plurality of terminal devices 5 are connected to arbitrary positions, respectively. Bidirectional communication of RF signals is performed between the device 1 and each terminal device 5, and is used as a CATV, a hotel premises communication system, or the like. Uplink signals transmitted from each terminal device 5 reach the center device 1 under different line conditions (differences in the numbers of the branching devices 3 and the relay amplifying devices 4, etc.), so even if the output level is the same, the center device 1 side Stable reception processing cannot be performed, such as variations in the reception level at the station and increased ingress noise.

Therefore, it is necessary to adjust the signal output level on the side of each terminal device 5 in order to suppress variations in the reception level on the side of the center device 1. Therefore, conventionally, as shown in FIG. 4A, an output adjuster 64 for adjusting the output level is provided at the output end of the transmission unit of the terminal device having the modulation circuit 62 and the amplifier 63, and only the transmission side of the upstream signal is provided. Independently adjust the output level manually, or Fig. 4
As shown in (b), the level detector 72 detects the reception level of each downlink signal received from the center device which is the reception target of the demodulation circuit 71, and the control unit 73 generates a control voltage accordingly. A method of controlling the output level of the upstream signal from the transmission circuit 76 by the output adjuster 75 via the control circuit 74 has been used.

[0004]

In the above-described conventional branch wiring communication system, in the case of adjusting the output of only the upstream signal, it is troublesome because it is manually adjusted, and it is readjusted every time the line condition is changed. I have to do it again.
In the case of automatically adjusting the upstream signal output level according to the downlink signal reception level, it is possible to respond to some extent even if the line condition is changed, but the reception level at the center device side because the condition is slightly different between the downlink line and the uplink line. It is not possible to perfectly match the variations in.

An object of the present invention is to reduce the upstream and downstream noise by making the reception level of the upstream signal from each terminal device on the side of the center device constant and automatically reducing it to the output level required for communication. Another object of the present invention is to provide a branch wiring communication system that enables stable communication.

[0006]

In a branch wiring communication system of the present invention, a plurality of terminal devices are branched and connected to a communication line connected to a center device, and bidirectional communication is performed between the center device and each of the terminal devices. In the branch wiring communication system for performing the above, the center device generates an output control signal indicating a value according to the reception level of the signal received from each of the terminal devices, transmits the output control signal to the terminal device, and the terminal device receives the output signal. The configuration is such that the output level of the signal transmitted to the center device is adjusted according to the value of the output control signal.

Further, in the above structure, the center device identifies the terminal device that is the output source of the received signal and detects the reception level of the signal, and the difference between the detected reception level and the predetermined reference level. And means for generating an output control signal indicating the corresponding level adjustment value, and means for transmitting this output control signal to the terminal device of the output source, wherein each terminal device is the device addressed to itself. Means for receiving the output control signal and detecting the level adjustment value; variable attenuating means for variably attenuating the output level of the transmission signal from the transmitting means to the center device according to the value of the attenuation amount control signal; It may be configured to include a unit that generates the attenuation amount control signal having a value corresponding to the detected level adjustment value and supplies the attenuation amount control signal to the variable attenuation unit to adjust the attenuation amount.

Further, the center device has means for transmitting a monitor signal requesting a return of a response signal addressed to itself to any of the terminal devices, and each terminal device receives the monitor signal addressed to itself. Then, there is a means for transmitting the response signal from the transmitting means to the center device through the variable attenuating means, and the center device transmits the monitoring signal to an arbitrary terminal device and determines the reception level of the returned response signal. With the reference level, the monitor signal may be sequentially transmitted to other terminal devices, and the returned response signal may be subjected to level comparison.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a system configuration diagram showing an embodiment of the present invention, and FIG. 2 is a detailed configuration diagram of a center device and a terminal device thereof. In FIG. 1, a communication line 2 connected to a center device 1 is branched into a large number of branch lines by a plurality of branching devices 3 for branching a line and a relay amplifying device 4 for signal level compensation, and a plurality of branch lines are provided at arbitrary positions. Terminal device 5
Is connected. Each terminal device 5 has a unique terminal number (I
D), and using this ID, the center device 1 and R
Bidirectional communication of F signal is performed. In FIG. 2, the center device 1 receives the upstream signal from each terminal device 5 through the communication line 2 and identifies the ID of the transmission source thereof.
And a level detector 12 for detecting the reception level of the signal
And a control unit 13 that compares the detected reception level with a preset reference level and adds a level control signal indicating a level adjustment value corresponding to the difference to the monitoring signal to the terminal device 5 of the ID, A terminal device 5 that supports downlink signals such as monitoring signals and communication data signals through the communication line 2.
And a transmission circuit 14 for transmitting to the. The control unit 13
Can set the signal level of the received signal from a certain terminal device as the reference level. The terminal device 5 is
Of the downlink signals from the center device 1 through the communication line 2, a receiving circuit 51 that receives and detects a signal addressed to itself (addition of its own ID), and a level control signal is confirmed when the supervisory signal is received, and the level adjustment value is set. A control unit 52 that generates a corresponding control voltage, and a variable attenuator 54 by the control voltage from the control unit 52.
Control circuit 53 for controlling the amount of attenuation, a transmission circuit 55 for outputting an upstream signal such as a response signal or communication data signal to the center device 1 with its own ID added, and a control circuit for the upstream signal from the transmitting circuit 55. A variable attenuator 54 which gives a level attenuation according to the control voltage from 54 and sends it to the communication line 2.

Next, the operation will be described with reference to the flow chart of FIG. 3 together with FIGS. When communication starts,
First, in the center device 1, the control unit 13 controls the transmission circuit 14 so that any one terminal device 5 (for example, ID = ID
The monitor signal is transmitted to 1) and the response signal (ACK) is monitored. I that matches the ID (ID1) added to the monitoring signal
In the first terminal device 5 to which D is assigned, the reception circuit 51 receives this signal, the control unit 52 controls the transmission circuit 55, and returns ACK to the center device 1. In the center device 1, this signal is received by the receiving circuit 11, and the level detector 1
In step 2, this level is detected and set in the control unit 13 as a communication level reference. The reference level value can be set in advance by the system administrator.

Next, another ID (ID
The monitoring signal with 2) is sent to the other terminal device 5 and AC
K is monitored. Another (second) matching this ID2
The terminal device 5 returns ACK to the center device 1. In the center device 1, the signal is received by the receiving circuit 11, the level is detected by the level detector 12, and the control unit 13 compares the received level with the reference level. Calculate whether there is. It should be noted that the difference can be represented by several step values for each predetermined range. The reception level for this ID2 is
Due to the difference in the number of branches (the number of branching devices 3) on the communication line 2 and the number of relay amplifying devices 4 inserted, a difference occurs with the reference level corresponding to ID1. As a result of the comparison, the control unit 13 generates a level control signal indicating that the output level on the terminal device 5 side should be increased by that amount if it is lower than the reference level, and that the output level should be reduced by that amount if it is higher than the reference level. Then, it is added to the monitoring signal and the ID is sent again from the transmission circuit 14.
Send at 2. The second terminal device 5 matching ID2 receives and detects the signal again in the receiving circuit 21. The control unit 52 recognizes the level control signal in the detected data, generates a corresponding control voltage, and supplies the control voltage to the control circuit 53.
ACK is transmitted from the transmission circuit 55. Variable attenuator 54
Is controlled by the control circuit 53, and when the level control signal has a value at which the output level should be increased, the transmission circuit 55 is correspondingly increased.
The attenuation amount of the signal (ACK) output from is reduced, and when the output level is a value to be reduced, the attenuation amount is increased accordingly. The control voltage generated by the control unit 52 and the attenuation amount of the variable attenuator 54 are configured to change corresponding to the step value for displaying the difference from the reference level in the level control signal. As described above, the ACK transmitted from the second terminal device 5 with ID2 becomes the level equivalent to the reference level on the side of the center device 1.

In the above procedure, the IDs are sequentially changed (ID3, I
D4, ...) while iteratively executing it for all the remaining terminal devices 5, all the reception signals at the center device 1 are equal in the upstream signals from all the terminal devices 5 connected on the line. Becomes

The center device 1 and each terminal device 5 have a communication loop as shown in FIG. Since the center device 1 recognizes the reception level of the upstream signal from each terminal device 5 for each communication, not only when the branching device 3, the relay amplification device 4, and the terminal device 5 are newly installed or when the accommodation position is changed,
When a communication level failure occurs due to a change in the line condition such as a change in the amplification factor of the relay amplification device 4, feedback is applied to the terminal device 5 (variable attenuator 54) in a variable adjustable range in this communication loop, and the center device 1 The reception level at is returned to the reference level. This protects the communication function of the communication system.

[0015]

According to the branch wiring communication system of the present invention, each center terminal device generates an output control signal indicating a value corresponding to the reception level of the signal received from the plurality of terminal devices, and transmits the output control signal to the terminal device. Since the output level of the signal to be transmitted to the center device is adjusted according to the value of the output control signal received by the center device, the signal levels from the plurality of terminal devices are all equal on the side of the center device, and the ingress noise of the uplink is generated. Is also reduced, and stable communication becomes possible.

[Brief description of the drawings]

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

FIG. 2 is a detailed configuration diagram of a center device and a terminal device shown in FIG.

FIG. 3 is a flowchart showing an example of a system operation procedure of the present invention.

FIG. 4 is a block diagram showing a conventional example, where FIG. 4 (a) is a transmission unit of a terminal device that adjusts the output of only an upstream signal, and FIG. 4 (b) is an upstream signal according to the reception level of the downstream signal. 4 shows a transmitter of a terminal device for automatically adjusting an output level.

[Explanation of symbols]

 1 center device 2 communication line 3 branching device 4 relay amplifying device 5 terminal device 11 receiving circuit 12 level detector 13 control unit 14 transmitting circuit 51 receiving circuit 52 control unit 53 control circuit 54 variable attenuator 55 transmitting circuit

Claims (3)

[Claims] 1. A branch wiring communication system for branching and connecting a plurality of terminal devices to a communication line connected to a center device for bidirectional communication between the center device and each of the terminal devices, wherein the center device is the An output control signal indicating a value corresponding to the reception level of the signal received from each terminal device is generated and transmitted to the terminal device, and transmitted to the center device according to the value of the output control signal received by each terminal device. A branch wiring communication system, characterized in that the output level of a signal to be adjusted is adjusted. 2. The center device identifies a terminal device that is an output source of a received signal and detects a reception level of the signal, and calculates a difference between the detected reception level and a predetermined reference level to handle the difference. And a means for generating an output control signal indicating a level adjustment value, and a means for transmitting this output control signal to the output source terminal device, wherein each terminal device outputs the output control signal addressed to itself. Means for receiving and detecting the level adjustment value; variable attenuation means for variably attenuating the output level of the transmission signal from the transmission means to the center device according to the value of the attenuation amount control signal; and the detected level adjustment 2. The branch wiring communication system according to claim 1, further comprising means for generating the attenuation amount control signal having a value corresponding to the value and supplying it to the variable attenuation means to adjust the attenuation amount. 3. The center device has means for transmitting a monitor signal requesting a return of a response signal addressed to itself to any of the terminal devices, and each terminal device receives the monitor signal addressed to itself. Then, there is a means for transmitting the response signal from the transmission means to the center device through the variable attenuation means, the center device transmitting the monitoring signal to any terminal device, and the reception level of the response signal returned. 3. The branch wiring communication system according to claim 2, wherein the reference level is used, and the response signal returned by sequentially transmitting the supervisory signal to other terminal devices is subjected to level comparison. Stem.