JP2000308029A - Catv system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a CATV system which can realize the smooth shifting from an analog CATV system to a digital CATV system with less investment when an already existing analog CATV operating station shifts to the digital CATV system. SOLUTION: A CATV system is provided with a plurality of analog head ends 1 which respectively distribute analog video signals to each terminal 2 through cables 3 in areas A and B and a digital head end 10 which collectively transmits digital video signals to the analog head ends 1. A common video frequency channel is set to each analog head end 1 for distributing the digital video signals transmitted from the digital head end 10 and the end 10 transmits the digital video signals to each analog head end 1 at the frequency corresponding to the common video frequency channel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CATV system for distributing an analog video signal and a digital video signal.

[0002]

In recent years, with the development of multimedia, cable television broadcasting (CATV)
Is becoming popular.

In this conventional CATV system, as shown in FIG. 5, an analog head end (control center) 1 is installed in each area, and the analog head end 1 is installed in a subscriber's home or the like. Terminal 2
Are connected by cables 3, and an analog video signal is distributed from the analog head end 1 to each terminal 2 on a predetermined video frequency channel.

[0004] In such analog CATV systems, digital CATV is expected to spread from now on due to demands for multi-channel broadcasting, video-on-demand (VOD) and bi-directional realization. Will be.

With the transition from analog CATV to digital CATV, existing analog CATV
It is necessary to start the distribution of the digital video signal without interrupting the distribution service to the subscriber who is receiving the current analog broadcast when the operation station starts broadcasting the digital CATV.

In this case, the existing analog CATV operation station constructs a completely new digital CATV system in the area, or as shown in FIG.
A method is considered in which a digital head end 4 is provided alongside an existing analog head end 1 and a digital video signal is distributed to a wired line of an existing analog CATV system.

[0007] However, in each method, each CATV
The investment amount for introducing the digital CATV system becomes very large for the operation bureau of the present invention, and there is a problem that it becomes a big obstacle when trying to smoothly transition from the analog CATV system to the digital CATV system.

[0008] Further, when a digital CATV system is installed in each CATV operation station, there is a problem that the installation space must be secured in each of them.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems when migrating from an existing analog CATV system to a digital CATV system.
That is, the present invention reduces the amount of investment when an existing analog CATV system operation station shifts to a digital CATV system, and solves the problems such as installation space and the like that occur when a new digital CATV system is installed. It is an object of the present invention to provide a CATV system that can realize a smooth transition from a CATV system to a digital CATV system, and that can make use of current facilities to increase the number of channels.

[0010]

A CAT according to the first invention is provided.
In order to achieve the above objectives, the V system has a plurality of analog headends for distributing analog video signals to each terminal via a cable in each area, and digitally collectively for the plurality of analog headends. A digital head end for transmitting a video signal; and a common video frequency channel for distributing a digital video signal transmitted from the digital head end to a terminal is set in the plurality of analog head ends. The digital head end transmits a digital video signal to the plurality of analog head ends at a frequency corresponding to the video frequency channel.

[0011] In the CATV system according to the first aspect of the present invention, in each area, a plurality of analog headends that distribute analog video signals on a predetermined video frequency channel to each terminal via a cable are provided in common with each area. Digital video signals are collectively distributed from one digital head end.

The analog head end of each area receiving the supply of the digital video signal from the digital head end sets a common video frequency channel for distributing the digital video signal to the terminal.

The digital head end collects digital programs to be supplied to a common video frequency channel set in the analog head end, and transmits the digital video signal to the analog head end in each area. Then, the analog head end in each area directly distributes the digital video signal transmitted from the digital head end to each terminal.

As described above, according to the first aspect,
A digital video signal can be newly distributed to an analog CATV system that distributes an analog video signal in each area, thereby increasing the number of channels.

The distribution of the digital video signal is
This can be realized only by installing one common digital headend for a plurality of areas, and there is no need to make a major change to the existing analog CATV system. Since it is possible to reduce the amount of investment required for the transition to the system and to solve problems such as the installation space when a new digital CATV system is installed, the analog CATV system can be replaced with a digital CATV system.
A smooth transition to a TV system can be realized.

According to a second aspect of the present invention, there is provided a CATV system in addition to the configuration of the first aspect, wherein
The common video frequency channel is a vacant channel in each analog head end.

In the CATV system according to the second aspect of the present invention, a common video frequency channel for distributing a digital video signal set in each analog head end to a terminal generally includes various types such as an amateur radio, a cordless phone, and a pager. The channel is set to an empty channel provided in a video frequency channel for delivering an analog video signal to a terminal in order to avoid interference by a wireless device. Therefore, according to the second aspect, distribution of a digital video signal can be performed without restricting distribution of an existing analog video signal.

According to a third aspect of the present invention, a CATV system includes, in addition to the configuration of the first aspect,
The digital head end transmits a plurality of digitally modulated video signals using one common video frequency channel.

According to the CATV system according to the third aspect of the present invention, a plurality of digital video signals are distributed in one video frequency channel, so that the number of display channels in the terminal can be increased.

According to the fourth aspect, digital modulation of the video signal transmitted from the digital head end to the analog head end is performed by QAM modulation.

According to a fifth aspect of the present invention, in order to achieve the above object, in addition to the configuration of the first aspect,
A display channel for displaying an image based on a digital video signal distributed to a terminal is uniquely set in the plurality of analog head ends.

In the CATV system according to the fifth aspect, a display channel for displaying an image based on a digital video signal is uniquely set for each analog head end in each area. This eliminates the need to change the existing display channel configuration for each area.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a system configuration diagram showing an example of an embodiment of a CATV system according to the present invention. In FIG. 1, A and B represent existing analog CAs, respectively.
The area where a TV system is constructed is shown. In each of the areas A and B, each terminal 2 installed in a subscriber's home or the like is connected to an analog head end 1 installed respectively by a cable 3, and an analog head end 1 is connected. An analog video signal is distributed from the head end 1 to each terminal 2 on a predetermined video frequency channel.

In the CATV system of each of the areas A and B, one common digital head end 10 is installed. The analog head end 1 of each of the areas A and B is connected to the digital head end 10 via a coupler (MIX) 11, and a digital video signal is transmitted from the digital head end 10 to each analog head end 1. It is to be sent.

The digital head end 10 transmits a plurality of (for example, four) digital video signals digitally modulated by, for example, a method such as QAM to one analog head end 1 through one transmission channel.
The analog head end 1 of each of the areas A and B receiving the supply of the digital video signal from the digital head end 10
Prepares a video frequency channel for distributing this digital video signal to the terminal.

Here, in general, a video frequency channel for distributing an analog video signal to a terminal is vacant in a specific frequency band in order to avoid interference by various wireless devices such as an amateur radio, a cordless phone, and a pager. Since channels are provided, the empty channels are unified in the analog head end 1 of each of the areas A and B.

The digital head end 10 creates a transmission channel in which digital programs to be supplied to a frequency band corresponding to a vacant channel of the analog head end 1 are created, and the digital video signal is converted to an analog head of each of the areas A and B. Send to End1.

The analog head end 1 of each of the areas A and B distributes the digital video signal transmitted from the digital head end 10 to each terminal 2 as it is. In this manner, the digital video signal supplied from the digital head end 10 is transmitted to the terminal 2 in each of the areas A and B.
Of available channels.

Note that the frequency band of an empty channel, which was difficult to use in the analog system due to the intrusion of radio waves generated from various wireless devices, is less deteriorated in the digital system. Can be used.

FIG. 2 shows a display method of a digital program supplied from the digital head end 10 as described above. In FIG. 2, the digital head end 1
0 is assigned to transmission channels C19, C28, C32 and C49 corresponding to the unoccupied channels unified in the analog head end 1 of each of the areas A and B, respectively.
Three or four digital programs are collected and transmitted to the analog head end 1 in each of the areas A and B.

In each of the areas A and B, the digital program of each transmission channel is displayed on each terminal 2 which has received the distribution from the analog head end 1 by the display channel assigned to the corresponding free channel. You.

For example, in an empty channel between the display channels 20 and 25 (transmission channels C35 and C31),
The digital program of the transmission channel C19 is displayed. As described above, the digital video signal transmitted from the digital head end 10 is directly delivered to each terminal 2 without being subjected to any processing such as frequency conversion in the analog head end 1 and displayed on the corresponding available channel. Is done.

FIG. 3 shows the configuration of the analog head end 1 and the digital head end 10. This figure 3
In, the digital head end 10 multiplexes digital video signals from a plurality of receiving devices (IRDs) 10a with a multiplexer 10b, and QAM-modulates the multiplexed signals with a QAM modulator 10C. This IRD 10a
A predetermined number of digital video signal distribution systems including the multiplexer 10b and the QAM modulator 10c are appropriately constructed.

Next, the configuration of a data signal including EPG information will be described.

The EPG information supplied periodically or irregularly from the EPG supply company 11 is stored in the EPG receiving device 10d.
Received by On the other hand, the data generator 10e generates other data such as viewing control information. Then, the multiplexer 10f multiplexes the EPG information from the EPG receiver 10d and various data from the data generator 10e, and QAM-modulates the multiplexed signal by the QAM modulator 10g.

The digital video signals and data from the QAM modulators 10c and 10g are mixed by the mixer 10h and transmitted to the analog headends 1A and 1B through separate channels. As described above, digital video signals and data are multiplexed based on the MPEG2 standard.

The analog head end 1A in the area A is
For example, a local broadcast signal is output from the analog video signal generator 1a, and is modulated by the modulator 1b, and data such as billing information generated by the data generator 1c is analog-modulated by the modulator 1d.

The analog video signal and the data from the modulator 1d and the digital video signal and data from the digital head end 4 are mixed in a mixer 1e corresponding to the coupler 11 in FIG. Is done. The analog head end 1B in the area B has the same configuration.

A plurality of analog headends 1 existing for each area with respect to one digital headend 10
A and 1B are connected, and the digital head end 10
The digital video signal and the data from the transmission are transmitted to the analog headends 1A and 1B arranged in the respective areas A and B, respectively, and are passed through the analog headends 1A and 1B, respectively. It is distributed to each terminal 2 connected to the end 1A, 1B.

Further, the EP supplied from the EPG supply company
For G, all program information including analog channels and digital channels is supplied from an affiliated program information supply company. Then, the digital head end 10 automatically receives the EPG from the EPG supplier every day or irregularly, and continuously transmits the analog head end 1.

FIG. 4 shows a digital terminal 2 connected to the analog headends 1A and 1B in each analog area.
FIG. 3 is a block diagram showing the configuration of FIG. In FIG. 4, digital and analog video signals and data from the digital head end 10 are distributed and input to a program tuner 20 and a data tuner 21.

The analog video signal video / audio signal input to the program tuner 20 is subjected to signal processing by an analog video signal processing circuit 22A. The signal is output to the audio output circuit 24.

The analog video signal processing circuit 22 A demodulates the NTSC analog video IF signal output from the program tuner 20 by an NTSC demodulator (NTSC Demodulator), and converts the analog video IF signal into an analog video signal transmitted from the analog head end 11. If scrambled, the signal is descrambled by an analog descramble circuit, and then input to the CPU / Decoder 25 at the subsequent stage. The video / audio signals of the digital video signal system are signal-processed by the digital video signal processing circuit 22B and then input to the CPU / Decoder 25.

The digital video signal processing circuit 22B
The M-modulated digital video IF signal is down-compartmented by an IF down converter and demodulated by a QAM demodulation unit.

When the digital video signal transmitted from the digital head end 10 is scrambled, the digital video signal is descrambled by a digital descrambling circuit, and then a TS-Demuliple is output.
x), MPEG2 transport stream (TS)
Is demodulated and input to the CPU / Decoder 25 at the subsequent stage.

The digital video signal and the digital audio signal are output from the CPU / Decoder 25 to the video output circuit 23 and the audio output circuit 24 via the video conversion circuit 26 and the audio conversion circuit 27, respectively.

On the other hand, the digital data signal input to the data tuner 21 is transmitted to the digital data signal processing circuit 2.
CPU / Decoder 25 after signal processing by 2C
And output from the CPU / Decoder 25 to the video output circuit 23 and the audio output circuit 24 via the video conversion circuit 26 and the audio conversion circuit 27, respectively.

The data signal processing circuit 22C, like the digital video signal processing circuit 22B, converts the QAM-modulated digital data IF signal into an IF downconverter (IF Downconverter).
convertor) and demodulated by the QAM demodulation unit.

Then, a TS demodulation unit (TS-Demuliplex)
And demodulates various data such as EPG data multiplexed on a transport stream (TS) according to the MPEG2 standard, and inputs the demodulated data to a CPU / Decoder 25 at a subsequent stage.
4, reference numeral 28 denotes a viewing control management unit, 29 denotes an IC card I / F, 30 denotes a display unit such as a channel, 31 denotes an operation key input unit, and 32 denotes a remote control receiving unit.

In the above configuration, as described above, the analog head end 1 of each of the areas A and B has unified vacant channels, and the digital head end 10 switches to the transmission channel of the frequency band corresponding to the vacant channel. A transmission channel in which digital broadcasting programs are assembled is constructed, and the digital video signal is transmitted to the analog head end 1 in each of the areas A and B.

The analog head end 1 of each of the areas A and B distributes the digital video signal to the terminal 2 through the mixer 1e (combiner 11) without performing any processing such as frequency conversion. The terminal 2 operates the remote controller or the operation key input unit 31 to select a desired channel, and when an analog program channel is selected, tunes to a corresponding frequency and displays an analog video signal.

When a digital program channel (for example, transmission channels C19 and C28 in FIG. 2) is selected, the digital head end 1 is synchronized with the selected channel.
The digital video signal transmitted from 0 is displayed. In addition,
In the above example, each analog head end 1 may set a display channel for the terminal 2 to specify a digital program independently for each of the areas A and B.

For example, in area A, transmission channel C
The digital program transmitted on the transmission channel C19 is set to be displayed on the display channels 21, 22, 23 and 24, respectively. In the area B, the digital program transmitted on the transmission channel C19 is displayed on the display channels 26, 27 and 2 respectively.
You may set so that it may be displayed on 8,29.

In the above description, the areas where the digital program is supplied from the digital head end 10 are described as two areas A and B. However, when there are three or more analog areas, the same applies. A digital program can be supplied from one digital head end 10.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram showing a display method of a digital program supplied from a digital head end in the same example.

FIG. 3 is a configuration diagram illustrating a CATV system according to an embodiment of the present invention.

FIG. 4 is a configuration diagram showing a terminal according to the embodiment of the present invention.

FIG. 5 is a system configuration diagram showing a conventional example.

FIG. 6 shows a digital C in an existing analog CATV system.
FIG. 2 is a system configuration diagram illustrating an example of a method of providing an ATV system in parallel.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Analog head end 2 ... Terminal 3 ... Cable 10 ... Digital head end 11 ... Coupling A, B ... Area

Claims (5)

[Claims] 1. A plurality of analog head ends for distributing analog video signals to respective terminals via cables in respective areas, and a digital head for transmitting digital video signals collectively to the plurality of analog head ends. And a common video frequency channel for distributing a digital video signal transmitted from the digital head end to a terminal is set in the plurality of analog head ends, and corresponds to the common video frequency channel. A CATV system, wherein the digital headend transmits a digital video signal to the plurality of analog headends according to a frequency. 2. The CATV system according to claim 1, wherein the common video frequency channel is a vacant channel in each analog head end. 3. The CA according to claim 1, wherein the digital head end transmits a plurality of digitally modulated video signals through one common video frequency channel.
TV system. 4. The CATV system according to claim 3, wherein said digital modulation is QAM modulation. 5. The CATV system according to claim 1, wherein a display channel for displaying an image based on a digital video signal distributed to a terminal is independently set in the plurality of analog head ends.