Interactive video distribution systems – User-requested video program system – Video-on-demand
Reexamination Certificate
1997-03-19
2001-05-22
Miller, John W. (Department: 2611)
Interactive video distribution systems
User-requested video program system
Video-on-demand
C725S131000, C725S132000, C370S448000
Reexamination Certificate
active
06237146
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a system and method of bidirectional digital video communication over a cable that permits bidirectional communication between a cable headend and subscriber home terminals (e.g., Set-Top Boxes) with minimum message collisions.
BACKGROUND OF THE INVENTION
Cable television is becoming more popular and millions of homes use and receive analog cable signals from a cable supplier to watch favorite programs and in some instances receive other information. Typically, each subscriber has a Set-Top Box, (also referred to as a Home Terminal) that rests on the standard television and receives from the cable headend down-stream transmissions such television shows. The cable headend typically has a connection to a national programming supplier such as a television network.
Advances in communication are now making possible the use of digital video or EPPV/VOD products that allow cable suppliers to offer enhanced pay-per-view (EPPV) and video-on-demand (VOD) services while having a digital network solution. By using a digital network, the use of out-of-band signaling capabilities are now possible as well as video and audio transmission in both the uplink and downlink direction. It is now possible to have a digital video Set-Top Box or Digital Video Home Terminal that can receive downstream transmissions and transmit upstream signals as necessary.
With the use of a digital network and RF Trunk, it is possible for hundreds of Digital Video Home Terminals to reside on one RF Trunk. With the use of hundreds of Digital Video Home Terminals that can generate a message upstream to the cable headend, it is possible for message collisions to occur when two or more Digital Video Home Terminals send a message about the same time, requesting video programming or other information and services. It is therefore necessary to design a system using Digital Video Home Terminals that avoids collisions with messages generated from various Digital Video Home Terminals located at different subscriber premises. Additionally, any solution to this problem should require little processing power and memory within the Digital Video Home Terminal or Set-Top Box to reduce the cost, size and complexity of Set-Top Box. To reduce the overall cost of the system to the subscriber, it is desirable that any major processing to avoid message collision be accomplished at the cable headend.
SUMMARY OF THE INVENTION
In accordance with the present invention, a cable system now permits bidirectional digital communication between a cable headend and a plurality of subscriber Digital Video Home Terminals each located at a different subscriber location such as a subscriber residence. The cable headend includes a processor for calculating and generating a randomized back-off array for each of the plurality of subscriber Digital Video Home Terminals. An RF Trunk line interconnects the cable headend and the plurality of subscriber home terminals so that messages from a subscriber can be sent to the cable headend and digital video or other information can be sent to the subscriber.
Each subscriber Digital Video Home Terminal includes a processor which receives from the cable headend a randomized back-off array for controlling when a Digital Video Home Terminal attempts to send a message to a cable headend and then reattempts to send the message a plurality of times after a random back-off interval of time has passed after each reattempt until no collision with another message is generated from a different home terminal.
In one aspect of the present invention, each Digital Video Home Terminal includes means for initializing communication with the cable headend when the randomized back-off array is received from the cable headend. In still another aspect of the present invention, a Digital Video Home Terminal includes Random Access Memory for storing the back-off array within the Random Access Memory of the Digital Video Home Terminal. The back-off array received from the cable headend allows reattempted message transmissions after a respective time-out period has elapsed that comprises a first randomized interval of time and then allows reattempted message transmission after another time-out period that comprises a second randomized interval of time. The first randomized interval of time is calculated from a uniformly distributed retry algorithm that is part of the back-off array and the second randomized period of time is calculated from an exponential period of time. The processor cable headend can also include circuitry for generating an acknowledgment to a subscriber Digital Video Home Terminal after the cable headend has received a message from the Digital Video Home Terminal. In an another aspect of the present invention the Digital Video Home Terminal is responsive whenever an acknowledgment is not received so that the Digital Video Home Terminal reattempts a message transmission to the cable headend pursuant to the random back-off interval of time. The trunk line interconnecting the cable headend and the plurality of subscriber Digital Video Home Terminals typically comprises an RF Trunk line.
REFERENCES:
patent: 4633462 (1986-12-01), Stifle et al.
patent: 5572517 (1996-11-01), Safadi
patent: 5696765 (1997-12-01), Safadi
Buchanan William M.
Richards Claudia K.
Lucent Technologies - Inc.
Miller John W.
Morgan & Finnegan , LLP
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