WO1998001998A1 - Control system for cable television - Google Patents

Control system for cable television Download PDF

Info

Publication number
WO1998001998A1
WO1998001998A1 PCT/SE1997/001131 SE9701131W WO9801998A1 WO 1998001998 A1 WO1998001998 A1 WO 1998001998A1 SE 9701131 W SE9701131 W SE 9701131W WO 9801998 A1 WO9801998 A1 WO 9801998A1
Authority
WO
WIPO (PCT)
Prior art keywords
subscriber
cable television
headend
television system
signals
Prior art date
Application number
PCT/SE1997/001131
Other languages
French (fr)
Inventor
Ann-Louise Ulfsparre
Original Assignee
Telefonaktiebolaget Lm Ericsson
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Telefonaktiebolaget Lm Ericsson filed Critical Telefonaktiebolaget Lm Ericsson
Priority to AU34704/97A priority Critical patent/AU3470497A/en
Publication of WO1998001998A1 publication Critical patent/WO1998001998A1/en

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
    • H04K3/00—Jamming of communication; Counter-measures
    • H04K3/20—Countermeasures against jamming
    • H04K3/28—Countermeasures against jamming with jamming and anti-jamming mechanisms both included in a same device or system, e.g. wherein anti-jamming includes prevention of undesired self-jamming resulting from jamming
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
    • H04K3/00—Jamming of communication; Counter-measures
    • H04K3/20—Countermeasures against jamming
    • H04K3/22—Countermeasures against jamming including jamming detection and monitoring
    • H04K3/224—Countermeasures against jamming including jamming detection and monitoring with countermeasures at transmission and/or reception of the jammed signal, e.g. stopping operation of transmitter or receiver, nulling or enhancing transmitted power in direction of or at frequency of jammer
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/16—Analogue secrecy systems; Analogue subscription systems
    • H04N7/162—Authorising the user terminal, e.g. by paying; Registering the use of a subscription channel, e.g. billing
    • H04N7/165—Centralised control of user terminal ; Registering at central
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/16—Analogue secrecy systems; Analogue subscription systems
    • H04N7/166—Passage/non-passage of the television signal, e.g. jamming, band suppression
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/16—Analogue secrecy systems; Analogue subscription systems
    • H04N7/173—Analogue secrecy systems; Analogue subscription systems with two-way working, e.g. subscriber sending a programme selection signal
    • H04N7/17309—Transmission or handling of upstream communications
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
    • H04K2203/00—Jamming of communication; Countermeasures
    • H04K2203/10—Jamming or countermeasure used for a particular application
    • H04K2203/14—Jamming or countermeasure used for a particular application for the transfer of light or images, e.g. for video-surveillance, for television or from a computer screen
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
    • H04K2203/00—Jamming of communication; Countermeasures
    • H04K2203/30—Jamming or countermeasure characterized by the infrastructure components
    • H04K2203/36—Jamming or countermeasure characterized by the infrastructure components including means for exchanging jamming data between transmitter and receiver, e.g. in forward or backward direction

Definitions

  • the present invention relates to a method and a device for signal control in a cable television system.
  • the television signal is usually transmitted on a broadband line from headends of the cable television system to different splitting points.
  • the television signal is divided into different frequency bands or channels on which different television programs are transmitted by means of an amplitude modulated signal.
  • Different subscribers are then connected to these splitting points, which deliver the television channels for which the subscriber subscribes, and jam the other channels, in particular premium television channels.
  • Such other traffic can consist of two way data communication traffic for control of the splitting points and also of data traffic generated by different interactive subscriber services.
  • a unit for controlling the system and managing all data traffic between the headend and the splitting points which for example can comprise interdiction apparatuses, and giving instructions to the splitting points.
  • the US patent No 4 912 760 describes a cable television interdiction apparatus having means for controlling a plurality of voltage controlled oscillators for selectively jamming only unauthorized premium programming transmitted in clear from a headend to a particular subscriber.
  • the US patent No 5 109 286 describes a cable television system having two diplexers for separating the transmission path between a headend and a subscriber into downstream or forward and upstream or reverse transmission paths.
  • This object is obtained by locating a switch on the line between the splitting point and each subscriber, or a number of switches in the splitting point, one for each subscriber.
  • the switch is controlled by the splitting point, which in turn can be controlled by a unit for system control for " example located in the headend, so that all traffic to and from a subscriber which transmits interfering signals to the headend can be switched off.
  • the transmission path between subscribers and a splitting point is provided with diplex filters or other means for separating the downstream and upstream signals. Separate switches then independently can switch off the signals in the different directions, i.e. all signalling to a subscriber including the television signals can be switched off independently of the signalling from the subscriber to the headend and vice versa. Also, all diplex filters and switches can be located in the splitting point. DESCRIPTION OF THE DRAWINGS
  • Fig. 1 is a general block diagram illustrating a cable television system and the signal path from a headend to a subscriber.
  • FIG. 2 is a block diagram illustrating the transmission path between a subscriber and a headend according to a preferred embodi ent.
  • Fig. 1 a general block diagram illustrating a cable television system and the signal path from a headend to a subscriber is shown.
  • different television programs are received by the headend 101, e.g. by means of antennas 103 and receivers 105.
  • the different television programs are then modulated by modulators 107 and transmitted in clear on a broadband transmission line 109 after being amplified by an amplifier 111.
  • On the transmission line 109 intermediate amplifiers 113 can be located.
  • the signal received by a splitting point, in this case called an Addressable Delivery Unit (ADU) 115 then comprises all television programs in clear, i.e. not jammed.
  • ADU Addressable Delivery Unit
  • the ADU 115 then usually jams the channels which a certain subscriber does not subscribe for, before the television channels are finally distributed to the different subscribers 117 connected to that particular ADU 115.
  • the ADU 115 is controlled by a unit for system control, in this case called System Control Unit (SCU) 123, located, for instance, in the headend. All control data communication transmitted from the SCU 123 for controlling the ADU 115 is also transmitted on the line 109.
  • SCU System Control Unit
  • the switch is used for disconnecting the signals to and from the subscriber. This can be useful in many cases, for example if the subscriber intentionally or unintentionally transmits an interfering signal on the line back to the headend all or part of the traffic from the subscribers connected to the same headend can be jammed, or if a subscriber has not payed his bills, all television channels can be closed for that particular subscriber.
  • the switch can be any type of switch, but in a preferred embodiment the switch is an electronic transistor switch, which is controlled by a micro processor (not shown) located inside the ADU 115. Also in a preferred embodiment the switches are located inside the ADU 115.
  • the line 119 between the ADU 115 and each subscriber 117 is equipped with diplex filters or similar means, by means of which the signals to and from the subscriber 117 are separated from each other.
  • Fig. 2 shows a part of the ADU 115 in more detail.
  • the forward traffic (F) from the headend is fed to a first diplex filter 201 and transmitted onwards separately to a second diplex filter 203.
  • a switch 205 is located on the line between the two diplex filters 201 and 203.
  • the switch can also in this case be any type of switch, but preferably the switch is an electronic transistor switch, which is controlled by a micro processor (not shown) also located inside the ADU. From the diplex filter 201 the signal is the transmitted to the subscriber.
  • the reverse traffic (R) is transmitted via the diplex filter
  • a second switch 207 is located, which preferably is of the same kind as the switch 205 .
  • the signals going in opposite directions can then be switched off and on independently by the switches 205 and 207, which preferably are controlled by a micro processor located inside the corresponding ADU.
  • the switches 205 and 207 which preferably are controlled by a micro processor located inside the corresponding ADU.
  • the signalling to a particular subscriber can be switched off if, for example, the subscriber has not paid his bills, and/or the signalling from that particular subscriber can be switched off in the case he/she is interfering the reverse signalling to the headend, and the switching can be performed independently.
  • all diplex filters and switches are located inside the ADU 115.
  • the switch 205 is not provided. This would take away the possibility to switch off all channels for a subscriber, which would be an advantage in countries where it is forbidden to switch off all television channels.
  • a method and a device by means of which traffic to and from different individual subscribers in a cable television system can be switched on and off has been described.
  • the method and device accomplish that the signalling to and/or from an individual subscriber can be switched on and off, without affecting other subscribers in the cable television system.
  • This is particularly useful when a subscriber transmits a signal which is jamming the entire or parts of the signalling between other subscribers and the headend in the cable television system, which has been found to occur from time to time.

Abstract

In a cable television system switches (119) are located between the splitting point (115) and the subscribers (117), or in the splitting point (115). The switches (119) are used for switching off the signals to and/or from subscribers (117) which intentionally or unintentionally transmit signals to the system and thereby jamming the system for other subscribers. The switches (119) can also be used for effectively disconnecting a particular subscriber permanently or temporarily.

Description

CONTROL SYSTEM FOR CABLE TELEVISION
TECHNICAL FIELD
The present invention relates to a method and a device for signal control in a cable television system.
BACKGROUND OF THE INVENTION AND PRIOR ART
In a cable television subscriber network of type star-net, the television signal is usually transmitted on a broadband line from headends of the cable television system to different splitting points. The television signal is divided into different frequency bands or channels on which different television programs are transmitted by means of an amplitude modulated signal. Different subscribers are then connected to these splitting points, which deliver the television channels for which the subscriber subscribes, and jam the other channels, in particular premium television channels.
On the broadband line also other types of traffic can exist simultaneously, provided that the entire bandwidth is not used for transmission of television signals. Such other traffic can consist of two way data communication traffic for control of the splitting points and also of data traffic generated by different interactive subscriber services.
At the headend of the cable television system there is usually provided a unit for controlling the system and managing all data traffic between the headend and the splitting points, which for example can comprise interdiction apparatuses, and giving instructions to the splitting points.
However, since there usually is only one transmission line between the headend and a splitting point, severe problems has been found to occur if an interfering signal is transmitted onto this transmission line by a subscriber, intentionally or unintentionally. In the worst case it has been found that some or all of the signalling between the other subscribers or splitting points and the headend connected to the same cable television network of type star- net can be jammed, and thereby causing a malfunctioning of the system.
The US patent No 4 912 760 describes a cable television interdiction apparatus having means for controlling a plurality of voltage controlled oscillators for selectively jamming only unauthorized premium programming transmitted in clear from a headend to a particular subscriber.
Also, the US patent No 5 109 286 describes a cable television system having two diplexers for separating the transmission path between a headend and a subscriber into downstream or forward and upstream or reverse transmission paths.
SUMMARY OF THE INVENTION
It is an object of the present invention to overcome some of the problems caused by an interfering signal in the present star net type cable television systems and to prevent that such interfering signals are transmitted onto the broadband line between a subscriber and a headend.
This object is obtained by locating a switch on the line between the splitting point and each subscriber, or a number of switches in the splitting point, one for each subscriber. The switch is controlled by the splitting point, which in turn can be controlled by a unit for system control for " example located in the headend, so that all traffic to and from a subscriber which transmits interfering signals to the headend can be switched off.
In a preferred embodiment, the transmission path between subscribers and a splitting point is provided with diplex filters or other means for separating the downstream and upstream signals. Separate switches then independently can switch off the signals in the different directions, i.e. all signalling to a subscriber including the television signals can be switched off independently of the signalling from the subscriber to the headend and vice versa. Also, all diplex filters and switches can be located in the splitting point. DESCRIPTION OF THE DRAWINGS
The present invention will now be described in more detail by way of non-limiting examples and with reference to the accompanying drawings, in which: - Fig. 1 is a general block diagram illustrating a cable television system and the signal path from a headend to a subscriber.
-Fig. 2 is a block diagram illustrating the transmission path between a subscriber and a headend according to a preferred embodi ent.
DESCRIPTION OF PREFERRED EMBODIMENTS
In Fig. 1 a general block diagram illustrating a cable television system and the signal path from a headend to a subscriber is shown. Thus, different television programs are received by the headend 101, e.g. by means of antennas 103 and receivers 105. The different television programs are then modulated by modulators 107 and transmitted in clear on a broadband transmission line 109 after being amplified by an amplifier 111. On the transmission line 109 intermediate amplifiers 113 can be located. The signal received by a splitting point, in this case called an Addressable Delivery Unit (ADU) 115, then comprises all television programs in clear, i.e. not jammed.
The ADU 115 then usually jams the channels which a certain subscriber does not subscribe for, before the television channels are finally distributed to the different subscribers 117 connected to that particular ADU 115.
The ADU 115 is controlled by a unit for system control, in this case called System Control Unit (SCU) 123, located, for instance, in the headend. All control data communication transmitted from the SCU 123 for controlling the ADU 115 is also transmitted on the line 109.
On the line 121 between the ADU 115 and each subscriber 117 a switch 119 is located. The switch is used for disconnecting the signals to and from the subscriber. This can be useful in many cases, for example if the subscriber intentionally or unintentionally transmits an interfering signal on the line back to the headend all or part of the traffic from the subscribers connected to the same headend can be jammed, or if a subscriber has not payed his bills, all television channels can be closed for that particular subscriber. The switch can be any type of switch, but in a preferred embodiment the switch is an electronic transistor switch, which is controlled by a micro processor (not shown) located inside the ADU 115. Also in a preferred embodiment the switches are located inside the ADU 115.
In another preferred embodiment the line 119 between the ADU 115 and each subscriber 117 is equipped with diplex filters or similar means, by means of which the signals to and from the subscriber 117 are separated from each other. By then locating a switch on each of the signal paths, i.e. both on the signal path to the subscriber and from the subscriber, the signals going in opposite directions can be switched off and on independently.
Such a configuration is shown in Fig. 2, which shows a part of the ADU 115 in more detail. Thus, the forward traffic (F) from the headend is fed to a first diplex filter 201 and transmitted onwards separately to a second diplex filter 203. On the line between the two diplex filters 201 and 203, a switch 205 is located. The switch can also in this case be any type of switch, but preferably the switch is an electronic transistor switch, which is controlled by a micro processor (not shown) also located inside the ADU. From the diplex filter 201 the signal is the transmitted to the subscriber.
In a corresponding manner the traffic from the subscriber, the reverse traffic (R) is transmitted via the diplex filter
203 from which it is transmitted separate from the forward traffic (F) to the first diplex filter 201. On the line between the two diplex filters 203 and 201, a second switch 207 is located, which preferably is of the same kind as the switch 205 .
The signals going in opposite directions can then be switched off and on independently by the switches 205 and 207, which preferably are controlled by a micro processor located inside the corresponding ADU. With this type of configuration the signalling to a particular subscriber can be switched off if, for example, the subscriber has not paid his bills, and/or the signalling from that particular subscriber can be switched off in the case he/she is interfering the reverse signalling to the headend, and the switching can be performed independently. In a preferred embodiment all diplex filters and switches are located inside the ADU 115.
Also, in an additional preferred embodiment the switch 205 is not provided. This would take away the possibility to switch off all channels for a subscriber, which would be an advantage in countries where it is forbidden to switch off all television channels.
Thus, a method and a device by means of which traffic to and from different individual subscribers in a cable television system can be switched on and off has been described. The method and device accomplish that the signalling to and/or from an individual subscriber can be switched on and off, without affecting other subscribers in the cable television system. This is particularly useful when a subscriber transmits a signal which is jamming the entire or parts of the signalling between other subscribers and the headend in the cable television system, which has been found to occur from time to time.

Claims

1. A cable television system comprising at least one splitting point to which a number of subscribers are connected, characterized by means for switching on and off signals to and from an individual subscriber connected to a headend of the cable television system.
2. A cable television system according to claim l, characterized by means for switching on and off the signals to and/or from the subscriber separately.
3. A cable television system according to any of claims 1 - 2, said cable television system being configured as a star- net, characterized in that the means for switching on and off the signals to and from an individual subscriber are located in a splitting point located on the signal path between the subscriber and the headend.
4. A cable television system of type star-net comprising at least one splitting point to which a number of subscribers are connected, characterized by at least two diplex filters in said at least one splitting point and switches located between said diplex filters arranged to selectively switching on and off signals to and from an individual subscriber connected to a headend of the cable television system in response to control signals transmitted from said headend.
5. A method of disconnecting signals to and from an individual subscriber in a cable television system, the subscriber being connected to the cable television system via a splitting point located on the signal path between the subscriber and the headend, characterized in switching off the line between the subscriber and the splitting point.
6. A method according to claim 5, characterized in that forward traffic and reverse traffic are transmitted separated from each other, and that the signals to and from the individual subscriber are switched off separately.
7. A method according to any of claims 5 - 6, characterized in that the switching off is performed inside the splitting point.
PCT/SE1997/001131 1996-07-05 1997-06-24 Control system for cable television WO1998001998A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU34704/97A AU3470497A (en) 1996-07-05 1997-06-24 Control system for cable television

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9602680A SE9602680D0 (en) 1996-07-05 1996-07-05 Cable television control system
SE9602680-2 1996-07-05

Publications (1)

Publication Number Publication Date
WO1998001998A1 true WO1998001998A1 (en) 1998-01-15

Family

ID=20403307

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1997/001131 WO1998001998A1 (en) 1996-07-05 1997-06-24 Control system for cable television

Country Status (3)

Country Link
AU (1) AU3470497A (en)
SE (1) SE9602680D0 (en)
WO (1) WO1998001998A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001099425A1 (en) * 2000-06-19 2001-12-27 Roax B.V. Communication system
US9598341B2 (en) 2012-11-05 2017-03-21 Gfbiochemicals Limited Process to prepare levulinic acid

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4367557A (en) * 1975-08-09 1983-01-04 Stern Joseph L Wired broadcasting systems
EP0231120A2 (en) * 1986-01-29 1987-08-05 Global Technologies Inc. Control and metering system for pay television over a cable network
US5109286A (en) * 1988-03-10 1992-04-28 Scientific-Atlanta, Inc. CATV reverse path manifold system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4367557A (en) * 1975-08-09 1983-01-04 Stern Joseph L Wired broadcasting systems
EP0231120A2 (en) * 1986-01-29 1987-08-05 Global Technologies Inc. Control and metering system for pay television over a cable network
US5109286A (en) * 1988-03-10 1992-04-28 Scientific-Atlanta, Inc. CATV reverse path manifold system

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001099425A1 (en) * 2000-06-19 2001-12-27 Roax B.V. Communication system
NL1015473C2 (en) * 2000-06-19 2001-12-28 Roax Bv Communication system.
US9598341B2 (en) 2012-11-05 2017-03-21 Gfbiochemicals Limited Process to prepare levulinic acid

Also Published As

Publication number Publication date
AU3470497A (en) 1998-02-02
SE9602680D0 (en) 1996-07-05

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