Interactive television and data transmission system
First Claim
1. A bidirectional wireless digital communication system comprisinga broadcast station for transmitting a video signal at least including horizontal blanking intervals and associated horizontal sync signals on a video carrier;
- broadcast means for controllably transmitting downlink digital data signals;
a plurality of subscriber receiver-transmitters, each subscriber receiver-transmitter having a subscriber receiving means for receiving said video signal and detecting said horizontal sync signals, and for receiving and detecting said downlink digital data signals, each subscriber receiver-transmitter also having a subscriber transmitting means coupled to said subscriber receiving means for transmitting uplink digital data signals only during at least some of the horizontal blanking intervals of the received video signal; and
at least one central receiver, each said central receiver being a means for receiving and detecting said uplink digital data signals transmitted by each subscriber transmitting means.
1 Assignment
0 Petitions
Accused Products
Abstract
A spread spectrum system provides bidirectional digital communication on a vacant television (TV) channel for simultaneous use by more than 75,000 subscribers using time and frequency division multiplex signals locked to horizontal and vertical sync pulses of an adjacent channel Host TV station. The system, whose operation is analogous to a radar system, comprises: (1) the Host TV station to send down-link sync and data pulses to subscribers during the horizontal blanking interval (HBI), (2) subscriber "transponders" which detect those signals and transmits up-link "echo" data pulses only during the HBI to eliminate interference to TV viewers, and (3) a central receiver which also uses the host TV sync pulses to trigger range gates to detect the up-link data pulses. In a preferred embodiment the central receiver employs directional antennas to determine direction to transponders and to define angular sectors partitioning the service area into pie-link "cells" which permit frequency re-use in non-contiguous sectors (like cellular radio). The system thus operates like a radar to measure elapsed time between receipt of TV sync pulses and receipt of transponder response pulses and measures bearing to transponders to thereby determine the location of fixed or mobile subscribers as well as provide data links to them. Transponders may share user'"'"'s existing TV antenna or may operate on cable TV and could be packaged and "RF modems" for personal computers, as transceivers for mobile or portable use, or they may be integrated with a TV receiver to provide "interactive television".
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Citations
63 Claims
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1. A bidirectional wireless digital communication system comprising
a broadcast station for transmitting a video signal at least including horizontal blanking intervals and associated horizontal sync signals on a video carrier; -
broadcast means for controllably transmitting downlink digital data signals; a plurality of subscriber receiver-transmitters, each subscriber receiver-transmitter having a subscriber receiving means for receiving said video signal and detecting said horizontal sync signals, and for receiving and detecting said downlink digital data signals, each subscriber receiver-transmitter also having a subscriber transmitting means coupled to said subscriber receiving means for transmitting uplink digital data signals only during at least some of the horizontal blanking intervals of the received video signal; and at least one central receiver, each said central receiver being a means for receiving and detecting said uplink digital data signals transmitted by each subscriber transmitting means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 36)
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26. A bidirectional wireless digital communication system comprising
a television broadcast station for transmitting ordinary television programming including vertical sync and horizontal sync signals and associated blanking intervals on a preassigned television channel and associated video carrier; -
broadcast means for controllably transmitting downlink digital data signals; a plurality of subscriber receiver-transmitters distributed about an area within the broadcast range of said television broadcast station and said broadcast means, each subscriber receiver-transmitter having a subscriber receiving means for receiving said video signal and detecting sync signals, and for receiving and detecting said downlink digital data signals, each subscriber receiver transmitter having modulating means for modulating uplink digital data signals on an uplink carrier of a frequency within the frequency band of a television channel adjacent said preassigned television channel, each subscriber transmitting means coupled to said subscriber receiving means for transmitting the modulated uplink digital data signals during at least some of the blanking intervals of the received video signal; and a plurality of central receivers, each central receiver being located and having a directional antenna to predominately receive the modulated uplink digital data signals from a respective subarea within said area, each said central receiver being a means for receiving and detecting said uplink digital data signals transmitted by the respective subscriber transmitting means within the respective subarea. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34, 35, 37, 38)
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39. A method of information communication within an area utilizing the frequency band of a television channel adjacent that of a television channel serving the same area and broadcasting ordinary television programming, including horizontal and vertical sync signals and associated blanking intervals, comprising the steps of:
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(a) modulating information on a carrier within the frequency band of the television channel adjacent that of the television channel broadcasting ordinary television programming; (b) transmitting the modulated information only during the horizontal blanking intervals of the ordinary television programming; (c) receiving the transmitted modulated information at a distant location and detecting the information therein. - View Dependent Claims (40, 41, 42, 43, 44)
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45. A method of communicating information from a plurality of remote locations to a central location served by a television station broadcasting ordinary television programming in the frequency band of a first preassigned television channel, the television programming including horizontal and vertical sync signals and associated blanking intervals, comprising the steps of:
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(i) at each remote location; (a) receiving the ordinary television programming and detecting the horizontal sync signals thereof, (b) modulating the information to be communicated from each remote location onto a carrier having a frequency in the frequency band of a preassigned television channel adjacent the frequency band of the first preassigned television channel, (c) transmitting the modulated information during at least some of the horizontal blanking intervals of the received television programming, and (ii) at at least one central location (d) receiving the transmissions of step (c) and detecting the information therein. - View Dependent Claims (46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57)
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58. In an interactive television system, a method of communicating information from a plurality of remote receiver locations, each connected to a cable television system, to a central location, the cable television system receiving ordinary television programming over the air and providing the same over a cable having amplifiers at various points along the cable, each serving a plurality of remote locations, comprising the steps of:
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(i) at each remote location; (a) modulating the information to be communicated from each remote location onto a carrier having a frequency in the frequency band of an unused cable television channel; (b) transmitting the modulated information on the cable only during at least some of the horizontal blanking intervals of an adjacent cable channel carrying ordinary television programming; (ii) adjacent each cable amplifier (c) detecting the horizontal sync signals of a television channel broadcasting ordinary television programming over the air (d) transmitting the modulated information received on the cable over the air and in the frequency band of a television channel adjacent the channel referred to in step (c) only during at least some of the horizontal blanking intervals associated with the detected horizontal sync signals of the channel referred to in step (c); and (iii) at at least one central location (e) receiving the transmissions of step (d) and detecting the information therein.
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59. A method of information communication within an area utilizing the frequency band of a television channel adjacent to as well as that of a television channel serving the same area and broadcasting ordinary television programming, the programming including horizontal and vertical sync signals and associated blanking intervals, comprising the steps of:
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(a) modulating information on a plurality of subcarriers; (b) modulating the modulated information of step (a) onto the carrier of the television channel broadcasting the ordinary television programming, the subcarriers causing the modulation of this step (b) to result in frequency components within the frequency band of the television channel adjacent that of the television channel broadcasting ordinary television programming; (c) broadcasting the modulated information only during the horizontal blanking intervals of the ordinary television programming; (d) receiving the transmitted modulated information at a distant location and detecting the information therein. - View Dependent Claims (60, 61)
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62. A method of determining the location of a mobile unit within an area utilizing the frequency band of a television channel adjacent to or the same as that of a television channel serving the same area and broadcasting ordinary television programming, including horizontal and vertical sync signals and associated blanking intervals, comprising the steps of:
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(a) modulating identification information on a carrier within the frequency band of the television channel adjacent to or the same as that of the television channel broadcasting ordinary television programming; (b) transmitting the modulated information only during the horizontal blanking intervals of the ordinary television programming; (c) receiving the transmitted modulated information at the mobile unit and transponding the received information; and (d) receiving the transponded informtion and the television programming at at least two different central locations and determining the location of the mobile unit by differences in the transmission times of the received signals. - View Dependent Claims (63)
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Specification