Interactive video distribution systems – Video distribution system with upstream communication – Receiver
Reexamination Certificate
1997-09-16
2001-05-01
Faile, Andrew I. (Department: 2711)
Interactive video distribution systems
Video distribution system with upstream communication
Receiver
C725S116000, C725S126000
Reexamination Certificate
active
06226794
ABSTRACT:
The present invention relates to an interactive information distribution system and, more particularly, to a set top terminal for interactively communicating with the information distribution system.
BACKGROUND OF THE INVENTION
Recent advances in digital signal processing techniques and, in particular, advances in digital compression techniques, have led to a plethora of proposals for providing new digital services to a subscribers home via existing telephone and coaxial networks. For example, it has been proposed to provide hundreds of cable television channels to subscribers by compressing digital video, transmitting the compressed digital video over conventional coaxial cable television cables, and then decompressing the video at the subscriber's set top terminal. Another proposed application of this technology is a movie-on-demand system in which a subscriber communicates directly to the video service provider via telephone lines to request a particular video program from a video library and the requested video program is routed to the subscriber's home via telephone lines or via coaxial television cables for immediate viewing.
However, these present movie-on-demand video systems are not truly interactive systems wherein a subscriber can selectively access a large audio, video or data library and control the presentation of the selected information on a real time basis, as when a video program is played back using the viewer's conventional video cassette recorder. Most of the presently available systems have a simple control interface that permits the subscriber to merely order information without any further control of the presentation of the information. Typically the set top terminals in these forms of systems merely demodulate the signal from the cable network and present them to the viewer on the viewer's conventional television. Control information from the set top terminal to the service provider is typically carried by the telephone network. As such, only rudimentary commands are permitted, otherwise a dedicated telephone line would be necessary.
Therefore, there is a need in the art for a set top terminal that is capable of interacting with an interactive information distribution system to provide real time interaction with the services provided by the service provider.
SUMMARY OF THE INVENTION
The disadvantages heretofore associated with the prior art are overcome by the present invention. The present invention is a set top terminal for receiving information transmitted from a service provider, for receiving control information transmitted by a service provider, and for transmitting control information from the set top terminal to the service provider to interactively control the services that are being received. More specifically, the set top terminal receives in-band information from the service provider, e.g., menu images, data, video, audio, and the like, in a frequency band of 50-750 MHz. The control information transmitted by the set top terminal is carried in a frequency band of 15.5 to 29.5 MHz. As such, the set top terminal communicates using three independent communications channels: (a) an information channel; (2) a command channel; and (3) a back channel. The back channel information is modulated by the set top terminal using a binary phase shift key (BPSK) modulator. The command channel of control information received by the set top terminal from the network is transmitted using quadrature phase shift key (QPSK) modulation. The broadband information carried by the information channel is modulated using either quadrature amplitude modulation (QAM) or a conventional analog modulated television signal modulation scheme such as NTSC, PAL, or SECAM. Prior to being modulated into a carrier frequency, both the command channel data and the information channel data are packetized using a transport protocol such as the Moving Pictures Experts Group transport protocol, a modified version of this protocol, or some other protocol that facilitates packet addressing and routing.
More specifically, the set top terminal of the present invention contains a diplexer that is coupled at its input to an RF feed from a source of video and control information. The diplexer has a single feed path to be used by the back channel, the command channel and the information channel. The diplexer, which acts as a T filter, couples the signal from the RF feed to a signal splitter that, in turn, couples the signal to two tuners (one tuner for the command channel signals and one tuner for the information channel signals). The command channel tuner and demodulator select a particular frequency carrying command channel information for the particular set top terminal, demodulate that information, depacketize the data and provide a data stream of control information to a microprocessor that controls the set top terminal.
The tuner for the information channel selects a particular channel on which information for the set top terminal is received and converts the RF signal to an IF signal. The IF signal, if it is an analog video signal, is processed by an NTSC demodulator in a conventional manner. Parallel to the NTSC demodulator is a digital television signal demodulator that demodulates QAM modulation, extracts data packets addressed to this set top terminal using an information channel transport decoder and finally, decodes the compressed video using an MPEG decoder to produce both digital video and digital audio signals. The digital video signal is then encoded using an NTSC encoder to produce a luminance and chrominance signal that is multiplexed and modulated using an RF modulator to generate a composite video signal on channel 3/4 for reception by a conventional television. In addition, there is an S video output, a composite video output and stereo audio output. To control the information, the user manipulates an infrared remote control to send commands to the set top terminal which has an infrared receiver that digitizes the information and couples it to a data/address bus for the microprocessor. The information on the bus is processed by the microprocessor, formatted into transmittable data which is modulated onto a carrier using the BPSK back channel modulator. The output of the modulator is amplified and coupled to the diplexer such that a single path input into the set top terminal is used for both transmitting and receiving information. The power level and transmission frequency used by the set top terminal are controlled by the microprocessor.
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Anderson, Jr. Bruce J.
Drasner Sharyn L.
Greenberg Arthur L.
Lamont Nadine
Bui Kieu-Oanh
Burke William J.
Faile Andrew I.
Sarnoff Corporation
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