JPH07288799A - Communication control method for catv system - Google Patents

Abstract

PURPOSE:To transmit control signals different in communication specifications without increasing the number of transmission channels for control signal transmission. CONSTITUTION:A CATV system is provided with a signal transmission line 2 including plural channels formed by dividing. the frequency band, plural TV receivers 32a and 32b connected to the signal transmission tune 2 through terminal equipments 31a and 31b, and a CTAV center 1 which is connected to one end of the signal transmission line 2 and is provided with an information processor 11 which sends control signals for terminal equipments 31a and 31b to the transmission line 2 through FSK modulators 12a and 12b. This communication control method is applied to the CATV system like this one where terminal equipments 31a and 31b different in communication specifications are connected to the transmission line 2 in common. Selected one of plural control signals different in communication specifications is sent to one channel of the transmission line 2 only for a required period, and the control signal is cut off including the carrier signal when it is unnecessary.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CATV system communication control method. More specifically, the present invention relates to a novel communication control method in a CATV system that is a video and audio cable broadcasting system and includes terminal devices of two or more different control specifications.

[0002]

2. Description of the Related Art FIG. 2 is a diagram schematically showing a basic configuration of a CATV system currently being implemented.

As shown in the figure, the CATV system is
A transmission line 2 including a transmission medium 21 such as an optical fiber or a coaxial cable and a relay amplifier 22 inserted in the middle thereof.
And a plurality of TV receivers 32 each connected to the transmission path 2 via the terminal device 31, and a video signal and an audio signal to be reproduced by each TV receiver 32, and each terminal device 31
It is mainly composed of a CATV center 1 which controls communication with respect to.

The CATV center 1 has an information processing device 11 for generating a control signal for communication control, and an FSK modulator 12 for converting the control signal generated by the information processing device 11 into a signal suitable for the transmission line 2. And are provided. Also, a TV that modulates video and audio signals into signals suitable for the transmission path.
A modulator 13 is also provided, and these FSK modulator 12 and T
Each output of the V modulator 13 is transmitted via the head end 14 to the transmission line 2
Sent to.

A plurality of channels are formed on the transmission line 2 by dividing a predetermined signal transmission band. Each terminal device 31
Sets the receivable channel by the command data obtained by demodulating the control signal received from the CATV center 1, and then demodulates the TV signal of the channel selected by the viewer from among the channels to receive the TV signal. Video and audio are supplied to the image receiver 32.

That is, in a general CATV system, a basic channel that can be viewed without consideration as long as a subscription procedure is provided, and a pay channel that can be viewed only by subscribers who have a fee contract are provided. Therefore, the CATV center 1 sends command data to the terminal device of each subscriber so that the pay channel subscribed by the subscriber can be received. With such a control method, only the terminal device that is legally contracted can watch the pay channel, and further, the CATV center side can deal with the contract change and the like.

On the other hand, the CATV system is a broadcasting system which has begun to operate relatively recently, and rapid technological development is still in progress. Therefore, in a single service area managed by a specific CATV center, a terminal device of a new control system is additionally connected, and signal transmission at a higher communication speed is made due to progress of equipment and diversification of functions. Are becoming required.

FIG. 3 is a diagram schematically showing a conventional method in the case where a CATV center requires a plurality of types of control signals because terminal devices having different communication specifications are connected to one signal transmission path. is there.

As shown in the figure, in this CATV system, among a plurality of terminal devices connected to one transmission path 2, terminal devices 31a and 31b having different communication specifications are included. In addition, these plural types of terminal devices 31a,
Corresponding to 31b, the CATV center 1 is provided with a plurality of types of FSK modulators 12a and 12b corresponding to each communication specification. Configured to transmit the control signal. That is, the FSK modulator 12a is configured to send a control signal to the terminal device 31a via the channel A, and the FSK modulator 12b is configured to send a control signal to the terminal device 31b via the channel B, respectively. The channels in the transmission line 2 are formed by dividing the signal transmission band.

[0010]

On the other hand, the number of channels of the signal transmission line of the CATV system is limited. That is,
In a typical CATV system, for example, a band of 70 to 80 MHz is allocated for a control signal, and this band is further divided into a plurality of bands of about 0.5 to 1 MHz to form a plurality of data channels.

On the other hand, the information equipment and its application fields have been developed more and more in recent years, and the number of channels allocated for control signals is already insufficient in the CATV system. Therefore, even if an attempt is made to implement a new excellent communication control method in the CATV system, it may not be possible to receive the channel allocation for the control signal. Further, it is not preferable in a practical system to increase the number of channels for transmission of control signals, which is not profitable in itself.

[0012] Therefore, the present invention solves the above-mentioned problems of the prior art and, even in a system including terminals having different communication specifications, a novel communication that does not increase the number of channels dedicated for command data transmission. It is to provide a control method.

[0013]

According to the present invention, a signal transmission line including a plurality of channels formed by dividing a frequency band, and a plurality of signal transmission lines connected to the signal transmission line via terminal devices, respectively. A CATV system including a TV receiver and a CATV center including an information processing device for transmitting a control signal for each of the terminal devices to the transmission line via an FSK modulator, and a CATV center connected to one end of the signal transmission line. In a CATV system in which terminal devices having different communication specifications are commonly connected to the transmission path, one control signal selected from a plurality of types of control signals according to a plurality of different communication specifications is transmitted to the transmission path. One of the channels is sent for a necessary period, and the control signal including the carrier signal is cut off during the period when the control signal is unnecessary. The communication control method CATV system is provided that.

[0014]

The control method according to the present invention is characterized mainly in that control signals relating to different communication specifications are transmitted in one channel by so-called time division multiplexing.

The reason why control signals of different systems cannot be transmitted in one channel in the conventional communication control system is as follows. That is, each terminal device is a CATV
When the control signal sent from the center is received, FSK
Command data is demodulated based on the carrier signal output from the modulator. Therefore, the FSK modulator is configured to constantly transmit the carrier signal even when there is no control signal to be transmitted. On the other hand, in various communication control systems of CATV, not only the data format of command data transmitted as a control signal is different, but also the communication speed and the modulation system itself are different. Therefore, when signals with different communication control methods are superimposed and transmitted in one channel, a plurality of carrier signals are superimposed on the transmission path, and the terminal device cannot demodulate the command data.

On the other hand, in the communication control method according to the present invention, the CATV center side controls so that a plurality of control signals are not simultaneously transmitted to one channel on the transmission path. That is, when transmitting the control signal, only the FSK data modulator that generates the control signal raises the carrier signal for transmission, and after transmission, controls not only the control signal but also the carrier signal. In this way, control signals of other communication specifications are alternately transmitted to the completely vacant channels. Therefore, only one carrier signal can be transmitted to one channel at a time,
The command data can be reliably demodulated on the terminal device side.

As described above, according to the present invention, since it is possible to transmit control signals of a plurality of types of communication specifications by using one transmission channel, it is possible to increase the number of channels for transmitting control signals. Various control signals can be transmitted.

Hereinafter, the present invention will be described more specifically with reference to the drawings, but the following disclosure is merely an example of the present invention and does not limit the technical scope of the present invention.

[0019]

FIG. 1 is a diagram showing a configuration example of a CATV system for implementing a control system according to the present invention.

As shown in the figure, the basic structure of this CATV system is the same as that of the conventional CATV system, and the main feature is the structure of the control signal generating means in the CATV center 1.

That is, in this CATV system, C
The ATV center 1 includes a plurality of FSK modulators 12a and 12b. The inputs of the FSK modulators 12a and 12b are connected to different ports of the information processing device 11, respectively. The outputs of the FSK modulators 12a and 12b are connected to the head end 14 via switching circuits 15a and 15b, respectively. Furthermore, each of the switching circuits 15a and 15b is configured to be turned on or off individually according to the RS signal output from the information processing device 11. That is, when the switching circuit is turned on by the RS signal, the control signal superimposed on the carrier signal is sent to the transmission line. On the other hand, when the switching circuit is OFF, no signal including the carrier signal is transmitted. Therefore, if only a specific switching circuit is turned on and the other switching circuits are shut off, only one control signal is transmitted to the signal transmission line, and a plurality of carrier signals are not superimposed on the transmission line.

In the CATV system configured as described above, the communication control method according to the present invention is realized as follows.

In this CATV system, two types of terminal devices 31a and 31b controlled by mutually different control specifications A and B are connected to one transmission line 2. Now, the terminal device 31 controlled by the communication control specification A
It is assumed that a control signal needs to be transmitted to a. CA
In the TV center 1, first, the information processing device 11 to the R
S signal is sent and only each switching circuit 15a is turned on. Therefore, the FSK converter 12a is provided in the head end 14 and the transmission line.
Only the control signal of the communication specification A output from is output.

That is, in the CATV center, for example, a 16-bit personal computer is used as the information processing device 11 for control, and its plural RS-232C ports (serial ports) are connected to the respective FSK modulators. There is. Here, when the RS signal is "H", the carrier signal output from the switching circuits 15a and 15b is ON, and when the RS signal is "L", the carrier signal output from the switching circuits 15a and 15b is O.
The specific operation will be described below assuming that the CATV center is configured in each FF.

First, all RS signals from the RS-232C ports of the information processing device 11 are set to "L", and the FSK modulator 12
Turn off both carrier signals a and 12b. Next, when transmitting data to the terminal device 31a controlled by the communication specification A, only the RS signal to the switching circuit 15a is set to "H" to turn on the carrier signal of the FSK modulator 12a, and then the FSK converter. Send the command data to 12a. Therefore, the carrier signal from the FSK converter 12a is first sent to the transmission line 2, and then the control signal modulated based on the command data is sent. At this time, signals other than the control signal from the FSK converter 12a are cut off to the transmission line 2, and no other carrier signal or transmission signal is sent to the same channel.

When transmitting data to the terminal device 31b controlled by the communication specification B, only the RS signal to the FSK modulator 12b is set to "H" and the other RS signals are set to "L". Therefore, only the carrier signal of the FSK modulator 12b is transmitted to the transmission line 2. Then, the command data is sent to the FSK modulator 12b and sent to the transmission line 2 as a control signal.

By the series of operations as described above, it is possible to prevent the state in which a plurality of control signals are simultaneously transmitted to one channel of the transmission path. In other words, this control method makes it possible to transmit a plurality of control signals having different communication specifications on one channel.

[0028]

As described above, according to the communication control method of the present invention, it is possible to transmit a plurality of control signals of different systems by using one channel. More types of communication control methods can be incorporated into one service area without increasing the number of channels dedicated to the above. Therefore, for example, when a facility of an existing CATV system is used to realize a new excellent CATV system or to start a new service that requires more complicated control in the existing CATV system. It can be applied to advantage.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a configuration of a command system in a communication control method according to the present invention.

FIG. 2 is a diagram schematically showing a basic configuration of a general CATV system.

FIG. 3 is a diagram schematically showing a configuration of a system when a plurality of types of communication control methods are implemented in one service area by a conventional communication control method.

[Explanation of symbols]

 1 ... CATV center, 11 ... Information processing device, 12, 12a, 12b ... FSK modulator, 13 ... TV modulator, 14 ... Head end, 15a, 15b ... Switching circuit , 2 ... transmission line, 21 ... transmission medium, 22 ... relay amplifier, 31, 31a, 31b ... terminal device, 32, 32a, 32b ... receiver

Claims (5)

[Claims] 1. A signal transmission path including a plurality of channels formed by dividing a frequency band, a plurality of TV receivers connected to the signal transmission path through terminal devices, respectively, and a terminal device of the terminal device. A CATV system comprising an information processing device for sending a control signal for each to the transmission line via an FSK modulator, and a CATV center connected to one end of the signal transmission line, the terminals having different communication specifications. In a CATV system in which devices are commonly connected to the transmission line, one control signal selected from a plurality of types of control signals according to different communication specifications is required for one channel of the transmission line. Communication control method of CATV system characterized by transmitting only for a period and cutting off the control signal including the carrier signal during the period when the control signal is unnecessary Law. 2. The CATV system control method according to claim 1, wherein the information processing device selectively inputs command data having different specifications to the FSK modulator. Communication control method. 3. The control method according to claim 1 or 2, wherein the plurality of terminal devices include those corresponding to different signal transmission rates. 4. The control method according to claim 1 or 2, wherein the plurality of terminal devices include those controlled by command data of different data formats. 5. The control method according to claim 1 or 2, wherein the plurality of terminal devices include those controlled by control signals according to different coding schemes.