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US 5,321,514 AGranted
Interactive television and data transmission system
AssigneeRadio Telecom & Technology, Inc.
InventorLouis Martinez
Life of this patent
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AssigneeRadio Telecom & Technology, Inc.
InventorLouis Martinez
Estimating the term…
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-like "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 as "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".
A wireless digital communication system comprising:
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 and having amplifiers at various points along the cable, each amplifier serving a plurality of remote locations, comprising the steps of:
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 blanking intervals, wherein the mobile unit communicates with a first base station in a first cell within said area, the method comprising the steps of:
A digital communication system comprising:
Dependencies are inferred from the claim text.