JPH11205766A - Digital network system using catv system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To send information that is requested by a customer at a desired timing and to unnecessitate an expensive terminal equipment by separately transmitting digital information requested by each terminal to respective terminals by a device on a center. SOLUTION: A hub type network is constituted on a center by connecting servers 10 which distribute various digital information (content) and a router 11 through a switching hub 12 and this network is connected to an HFC relay transmission network 18 of a CATV system through a digital multiplexer 15. The multiplexer 15 preliminarily allocates an individual frequency to a signal (n) from the switching hub which is connected to as many numbers (n) of cable modems 16 as are allowed by a channel map. Thus, a cable modem that is installed at a subscriber's home gets a state in which information such as video can always be provided to the subscriber like a dedicated line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital network system using a CATV system, and a conventional analog transmission broadcast type system mainly for retransmission broadcasting in a CATV system. It is possible to individually distribute to each terminal device in response to a request from the terminal device.

[0002]

2. Description of the Related Art A conventional CATV system uses the entire transmission band for transmitting analog signals (terrestrial retransmission broadcasting and independent broadcasting), and assigns a frequency of 6 MHz to one channel, for example, 90 to 550 MHz. In the case of a system having a transmission band of 73 channels, analog signals of 73 channels can be transmitted. Recently, there is also a system in which a transmission band is widened so that a part thereof can be used for transmitting a digital signal. For example, 90 to 550 MHz is used for transmitting an analog signal, and an expanded portion of 550 to 770 MHz is used for transmitting a digital signal. Some are used for In this case, in the digital transmission band, by using the MPEG2 compression technique, four channels can be transmitted at 6 MHz, and 144 channels can be transmitted at 550 to 770 MHz.

[0003]

In recent years, since digital satellite broadcasting has started and the number of Internet users has increased rapidly, it is expected that CATV systems will be used for such digital broadcasting transmission and Internet networks. In the CATV system capable of digital transmission, transmission of digital satellite broadcasting and use for the Internet have already begun. However, since the conventional CATV system is a one-to-n type communication mode in which the same information is transmitted simultaneously from one center-side device to an unspecified number of terminal-side devices, a limited number of channels (for example, 1
(44 channels), the customer selects a desired channel from the provided channels to watch the broadcast or derives the information, or the customer can watch the desired broadcast at the timing requested by the customer. It was difficult to extract information. This is the same when the MPEG2 compression technique is used, and in this case, the MPEG2 compression technique is used.
An expensive terminal-side device called a set-top box (STB) for viewing compressed digital broadcasts is required, and there is a problem that it is difficult for customers to introduce them.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a CATV which can transmit information desired by a customer at a timing desired by the customer and does not require an expensive terminal device.
An object of the present invention is to provide a digital network system using a transmission path.

[0005] A digital network system using a CATV transmission line according to the first aspect of the present invention is a CA system.
A digital signal transmission band for transmitting a digital signal from a center device to a terminal device is provided separately from an analog signal transmission band for transmitting a broadcast signal or the like in a signal transmission band in a TV system, and the digital signal transmission band is a frequency. A plurality of digital channels are secured by division or the like, and each digital channel can be assigned one or more channels per one terminal device according to a request from the terminal device, and the center device is allocated to each terminal device. The digital information requested by each terminal device can be individually transmitted to each terminal device via a digital channel.

According to a second aspect of the present invention, a digital network system using a CATV transmission line includes a request to allocate a digital channel from a terminal device to a center device, a request to transmit digital information through a digital channel, and the like. , Or via a telephone line of a CATV system.

A digital network system using a CATV transmission path according to a third aspect of the present invention uses an MPEG2 information compression technique for transmitting a large amount of information such as a moving image among digital signal transmissions using a digital channel. It is characterized by using.

[0008]

FIG. 1 shows an outline of a digital network system using a CATV system of the present invention. FIG. 2 shows an example of a channel map in this network system, and FIG. 3 shows an example of a device configuration of a terminal device. In this network system, as shown in the channel map of FIG. 2, 70 to 250 MHz is used as an analog signal transmission band for transmitting an NTSC signal (analog television signal).
The data is transmitted to the HFC (hybrid fiber coaxial) relay transmission network 18 in the same manner as the system. FIG.
Channel map of 10-55MHz and 250-77
0 MHz is a digital signal transmission band in which digital signals are transmitted. 10 to 55 MHz is used for an upstream signal from the terminal side to the center side, and 250 to 770 MHz is used for a downstream signal from the center side to the terminal side. The NTSC signal can be received by an existing home terminal (not shown) on the terminal side (user side) and can be viewed on a television at the user's home.

This digital network system is shown in FIG.
As shown in FIG. 3, a server 10 for distributing various types of digital information (contents) and a router 11 are connected via a switching hub 12 to a center side to form a hub-type network. Are connected to the HFC relay transmission network 18 of the CATV system via the digital multiplexer 15 (center-side device). The server 10 includes a multimedia server for distributing a movie or the like, a billing server for storing billing information of a user, and a search server for searching for information. There is a server that supplies a database, and a database server that stores a (paid) database. The router 11 is connected to the Internet or the like. The multimedia server 10
Is the MP of the movie etc. stored in the video head end 13.
Various movies desired by the user are output after being compressed by the EG2 encoder 14 (functioning as a video-on-demand device). The MPEG2 encoder 14 compresses the information amount equivalent to that of the current TV video to 1/25 and
The purpose of this system is to enable transmission to a bps transmission line. A movie of the same quality as that of a current television can be transmitted to one channel of the present system and provided to a user. Various network devices other than the illustrated server and router can be connected to the hub-type network, and it is possible to provide various digital contents according to a user's desire. As shown in Fig. 1, an ultra-high-speed backbone for cables is built,
It is also possible to construct a large-scale digital network by connecting the CATV centers in the region with this backbone.

The digital multiplexing device 15 multiplexes digital information output from the various servers 10 and the router 11 and transmits the multiplexed digital information to the HFC relay transmission network 18, and various digital information transmitted from each user through the relay transmission network 18. This is for transmitting a signal (for example, a signal for requesting a channel or a signal for requesting content) to each server 10 or the router 11. In this case, the digital multiplexing device 15 and the terminal device of each user (the cable modem 16,
All users can freely access the digital multiplexing device 15 from the terminal device to the PC 17) having the MPEG2 decoder, but the user can extract digital information from the digital multiplexing device 15 by digital multiplexing. Access device 15 to request a digital channel,
It is only possible if it is approved. In other words, the digital multiplexing device 15 transmits one (1) to as many (n) cable modems 16 as the channel map allows.
An individual frequency is assigned in advance to the signal n from the switching hub so as to be connected by the body 1. That is, video signals and the like output from the switching hub 12 apparently form a transmission path directly connected to the cable modem 16.
This transmission line has a maximum of 7.911 for one cable modem.
Signals can be transmitted at a transmission speed of Mbps. As a result, the cable modem installed in the subscriber company home can always provide a state in which information such as video can be provided to the subscriber in the same manner as a dedicated line.

The digital multiplexing device 15 modulates the downstream digital signal to the terminal side by 64QAM to a 6 MHz band.
It is possible to transmit at a transmission rate of 31.644 Mbps. In this case, 4 channels at 6 MHz are secured and 250 to 7
342 digital channels are secured in a 70 MHz digital signal transmission band. And up to 7.91 on each channel
A transmission speed of 1 Mbps can be obtained.

A digital signal transmitted from the digital multiplexing device 15 can be received by a cable modem (C / M) 16 at a user's home via an HFC relay transmission network, and data demodulated by the modem is subjected to an MPEG2 decoding function. And a multimedia terminal (PC) 17 provided with The PC 17 can decode and view the MPEG2 compressed movie transmitted from the multimedia server. Digital contents other than movies are compressed by a compression technique other than MPEG2, and this restoration can be performed by the cable modem 16. Note that M
The PEG2 decoding function may be built in the cable modem 16.

In the present invention, the digital network device on the center side is not limited to those shown in FIGS. 1 and 3, and various LAN-type networks can be adopted. External communication network can be connected. FIG.
As shown in (1), a large-scale digital network system can be configured by connecting CATV systems in a region with an ultra-high speed backbone.

In addition, the terminal side can access the center side by using a telephone line instead of the upstream line of the CATV system.

[0015]

According to the digital network system using the CATV system of the present invention, the following effects can be obtained. 1. Various information requested by the user can be transmitted at a timing requested by the user with a limited number of channels. In particular, the present invention is suitable for an Internet line having a small amount of information in the up direction and a large amount of information in the down direction, or for on-demand distribution of digital broadcasting. 2. Since many digital channels can be secured even in a limited transmission band by MPEG2 compression technology,
The cost per channel can be reduced. 3. An expensive set-top box (ST
B) is not required, and a personal computer having an MPEG2 decoding function, for example, can be used as a terminal.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an outline of a digital network system using a CATV transmission line according to the present invention.

FIG. 2 is a channel map in a digital network system using the CATV transmission line of the present invention.

FIG. 3 is a device configuration diagram showing an embodiment of a digital network system using a CATV transmission line according to the present invention.

[Explanation of symbols]

 10 Server 11 Router 12 Switching Hub 13 Video Headend 14 MPEG2 Encoder 15 Digital Multiplexer

Continuation of the front page (72) Inventor Toshikazu Nakai 4-7-1 Hatchobori, Chuo-ku, Tokyo Inside Japan Telecom Co., Ltd.

Claims (3)

[Claims] A digital signal transmission band for transmitting a digital signal from a center device to a terminal device is provided separately from an analog signal transmission band for transmitting a terrestrial broadcast signal or the like in a signal transmission band in a CATV system. In the digital signal transmission band, a plurality of digital channels are secured by frequency division or the like, and each digital channel can be assigned one or more channels to one terminal device according to a request from the terminal device. CAT characterized in that digital information requested by each terminal device can be individually transmitted to each terminal device through a digital channel assigned to the terminal device.
Digital network system using V system. 2. A request for allocating a digital channel from a terminal device to a center device, a request for transmitting digital information through a digital channel, or the like is made through an up line of a CATV system or through a telephone line. A digital network system using the CATV system according to claim 1, wherein: 3. An MPE for transmitting large-capacity information such as a moving image, among digital signal transmission using a digital channel.
2. The method according to claim 1, wherein a G2 information compression technique is used.
A digital network system using the CATV system according to claim 2.