Telecommunications – Interference signal transmission
Reexamination Certificate
1996-12-18
2001-02-13
Kostak, Victor R. (Department: 2711)
Telecommunications
Interference signal transmission
C455S001000, C348S014160
Reexamination Certificate
active
06188871
ABSTRACT:
BACKGROUND OF THE INVENTION
Multi-channel television services via fiber optics and coaxial cables using digital compressing technique such as MPEG and digital modulation techniques such as QAM (Quadrature Amplitude Modulation) and QPSK (Quadrature Phase Shift Keying) have nowadays been developing. However, to receive signals emitted from a CATV center and to view a CATV program, it is normally necessary to use a set-top-converter (STC) composed of a MPEG decoder and a QAM demodulator.
A conventional CATV system provides subscribers with multi-channel services by the above-mentioned method. Therefore, when a subscriber wants to view CATV programs on a plurality of TV sets, he or she must provide the TV sets with separate STCs respectively. The considerable expense falls on the subscriber. Japanese Laid-open Patent Publication No. 7-59072 discloses such a unit that is attached to one CATV terminal, allowing a plurality of TV sets to receive the CATV programs. This attempt may be an improvement but still requires a large-scale CATV terminal.
As described above, any conventional CATV system requires each subscriber to provide each TV set with a CATV terminal unit or a large-scale CATV terminal to enjoy a plurality of CATV programs on a plurality of TV sets. This increases the subscriber's charge. A CATV center to which all functions of the system are concentrated may not be so flexible to manage each of areas to be covered.
SUMMARY OF THE INVENTION
The present invention relates to a bi-directional CATV system capable of providing a plurality of services and, more particularly, to regional common-use blocks composing a system capable of separating multiplexed signals transmitted from a CATV center and reorganizing signals to provide individual subscribers with different services and a CATV system that uses the regional common-use blocks. The present invention is therefore intended to provide a regional common-use block composing a system that can effectively manage by regional groups of subscriber terminals and reduce charges of subscribers by eliminating the necessity of using a large-scale terminal unit and to provide a CATV system using the regional common-use blocks.
The system according to the present invention is to bring out functional blocks corresponding to STCs installed in subscribers' houses in the conventional system and to commonly use the STCs by a unit regional group of subscribers and control them by switching so that an output of each STC can be transmitted to a plurality of subscribers, thus minimizing the number of STCs used in a regional common-use block as compared with the conventional system.
A subscriber who desires to view CATV programs on a plurality of TV sets in his or her home may seldom enjoy CATV at a time on two TV sets installed in different places, e.g., in a living room and a dining room. Therefore, the system according to the present invention makes it possible to effectively use vacant STCs in common and reduce the number of necessary STCs, as compared with the conventional system.
According to the present invention, video-audio signals and data requested by each subscriber can be transmitted as mixed or combined signal data in a vacant channel of TV signals. This enables each subscriber to receive a desired CATV program on each TV set through a simple receiver attached thereto, bearing a cost of a receiver plus a part of expenses for a STC used in common. Consequently, total expenses charged on a subscriber who receives CATV services with a plurality of TV sets are lower in comparison with the conventional case.
The above-mentioned features of the system according to the present invention may promote use of CATV services. Each provider of CATV services can also expect an increase in audience fee by increasing the number of subscribers. Furthermore, the use of regional common-use blocks enables the provider to provide the suitable services to respective areas and to easily maintain the system, since all essential parts are contained in a CATV center and regional common-use blocks.
Thus, the present invention is intended to reduce costs of a CATV installation and subscriber terminals, to provide a CATV rich in content of services, and to improve maintainability, extendability and safety of the system.
(1) Accordingly, an object of the present invention is to provide a regional common-use block which comprises: separating means for separating video, audio and data in a multiplexed signal transmitted from a CATV center; a plurality of converting means consisting of elementary means (e.g., an analog demodulator, a digital demodulator or digital demodulator and compressed digital demodulator) for taking-out video, audio and data by converting signals separated by the separating means; an upward signal decoding portion; switching means for switching connections between the converters and subscribers' lines according to the successive subscriber's requests received from the upward signal decoding portion and RF-modultors for modulating TV signals to be transmitted to subscribers lines switched and connected by the switching means with a predetermined frequency of one of plural vacant channels; and which is characterized in that the converting means digitally demodulates signals (e.g., QPSK modulated signals, QAM modulated signals) contained in signals from the CATV center, decode the compressed digital signal and take out original video and audio signals and, then, the switching means converts the taken-out video and audio signals with RF (radio-frequency) of a predetermined vacant channel, makes connection to lines of the requesting subscribers and transmits the modulated video and audio signals to the subscribers.
(2) Another object of the present invention is to provide a regional common-use block of a CATV system, which is mentioned in item (1) and characterized in that a telephone interface (I/F) portion is further provided as an additional element for dealing with a telephone signal in such a manner that a signal from the telephone I/F portion is mixed with a TV signal modulated by the RF modulator and then transmitted together via a cable to a subscriber, thus enabling each subscriber to exchange necessary information by using a simple receiver (e.g., TV set, telephone set) without recognizing a network.
(3) Another object of the present invention is to provide a regional common-use block of a CATV system, which is mentioned in item (1) or (2) and characterized in that, in case when a broadcast program requested by a subscriber has been already converted by the converting means and connected to another subscriber, the switching means can connect the output of the same converting means to the requesting subscriber, thus increasing the working efficiency of the converting means.
(4) Another object of the present invention is to provide a regional common-use block of a CATV system, which is mentioned in any one of items (1) to (3) and characterized in that a data base relating to subscribers is further provided as an additional element and the switching means are controlled according to a connecting method determined with reference to the data base.
(5) Another object of the present invention is to provide a regional common-use block of a CATV system, which is mentioned in item (4) and characterized in that the data base relating to subscribers contains information on what program each subscriber is entitled to view and a requested program is supplied to a line of a requesting subscriber who is found entitled according to the information stored in the data base but the program will not supplied to the subscriber who is not entitled.
(6) Another object of the present invention is to provide a regional common-use block of a CATV system, which is mentioned in any one of items (1) to (5) and characterized in that a TV signal and/or a telephone signal taken-out by the converting means and modulated by the RF modulator according to the subscriber's request is mixed in free-charge broadcast analog and digital signals separated b
Ishiyama Katsuyuki
Kanai Kuniyuki
Kitamura Hideo
Yamaguchi Shinpei
Kostak Victor R.
Sharp Kabushiki Kaisha
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