Multiplex communications – Communication over free space – Repeater
Patent
1995-07-03
1998-04-28
Safourek, Benedict V.
Multiplex communications
Communication over free space
Repeater
370492, 370522, 380 10, 371 691, H04L 108, H04L 918, H04N 7167
Patent
active
057454825
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to repeating devices and, particularly, to a repeating device which is used in a CATV (Community Antenna TV, Cable TV) and combined listening/receiving system or the like which individually receives concealment broadcasting from an antenna through a cable.
BACKGROUND TECHNOLOGY
In recent years, concealment broadcasting (broadcasting in which programming is provided only for specific viewers) has started, and a receiving device for receiving the concealment broadcasting has been popularized. The arrangement is such that the concealment broadcasting which uses a concealment broadcasting device is arranged such that a broadcasting station codes or enciphers video and audio signals (hereinafter referred to as "scramble") to transmit the signals so that persons (hereinafter referred to as "non-contractor") other than selected viewers (hereinafter referred to as "contracted viewers") cannot view the program. Further, the contracted viewers are capable of using decoding devices (hereinafter referred to as "decoder"), each decoder having a descrambler for conducting the decoding (hereinafter referred to as "descramble") in which the scrambled signal is returned to the original video and audio signals, so the contracted viewers can view the program. Meanwhile, the arrangement is such that the non-contractors cannot conduct the descramble so that they cannot view the program.
An example of such a concealment broadcasting system will be described as an example of a COATEC (COATEC: Conditional Access Technology Research Institute) system, which is one of several chargeable satellite broadcasting systems presently employed or operated in Japan. FIG. 6 shows an arrangement of a transmitter 100 of the broadcasting station on the transmission side in the COATEC system.
The transmitter 100 uses scramblers 101 and 105 to scramble the video and audio signals. Moreover, a scramble flag is used so that a program received on the receiving side can be judged as being scrambled broadcasting or non-scrambled broadcasting. In the COATEC system, the scramble flag corresponds to the eighth bit (hereinafter referred to as "R#8") of a range bit which is multiplexed upon the audio signal and the twelfth bit of the control code (a video scramble flag, hereinafter referred to as "VS").
The arrangement is such that the transmitter 100 transmits the scramble flag such that the scramble flag is continuously sent (hereinafter referred to as "successive sending"), a plurality of times, by a successive-sending control part 111. The scramble flag is multiplexed upon the scramble audio signal by a multiplexing part 123 and is transmitted, such that the scramble flag is judged in majority by a majority judgment part of the decoder on the receiving side to protect against errors. Furthermore, the transmitter 100 inputs the scramble flag into the scramblers 101 and 105 to conduct an ON/OFF control of the scramble of the video and audio signals.
Furthermore, in the system, in order to send a PN (Pseudorandom Noise) signal (pseudorandom signal) for conducting scramble and descramble from the transmitter 100 to the decoder, the transmitter 100 and the decoder have respective PN generators thereof for generating the same PN signal, and the same PN initial value (cipher key) KS is set to the PN generator with the same timing with respect to the video and audio signals to acquire the wholly identical PN signal.
As a timing signal which sets the PN initial value KS, there is a scramble timing TS. In order to be able to judge, in majority, the scramble timing TS by a majority judgment part of the decoder to protect against the errors, the transmitter 100 is arranged to successively send the scramble timing TS by a successive-sending control part 109, and to multiplex the scramble timing upon the scramble audio signal by the multiplexing part 123 for transmission. Further, the transmitter 100 inputs the scramble timing TS into PN generators 103 and 107 to set the PN initial value KS at the same timing as the PN gene
REFERENCES:
patent: 4937821 (1990-06-01), Boulton
patent: 5151782 (1992-09-01), Farraro
patent: 5339315 (1994-08-01), Maeda et al.
patent: 5359601 (1994-10-01), Wasilewski et al.
patent: 5421031 (1995-05-01), De Bey
patent: 5506615 (1996-04-01), Awaji
Electric Communication Technology Deliberative Council Report, Nov. 1963.
Japan Ministry of Posts and Telecommunications, Ministerial Ordinance No. 77, and a Notification No. 803.
Nishiura Masaaki
Ooi Shinichi
Kabushiki Kaisha Toshiba
Rao Seema S.
Safourek Benedict V.
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