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Method and apparatus for detecting the movement of a device that receives a signal broadcast from a relative fixed position
| Details |
Inventors: Gabber, Eran; Wool, Avishai;
Assignee: Lucent Technologies Inc. (Murray Hill, NJ)
Primary Examiner: Issing; Gregory C.
Assistant Examiner:
Attorney, Agent or Firm: Ryan, Mason & Lewis, LLP
A system for detecting the movement of a device that receives a signal broadcast from a relative fixed position, such as a set-top terminal in a Direct Broadcast Satellite (DBS) system, is disclosed, using the phase shift of the broadcast signal, as received by the device. A set-top terminal or similar mechanism restricts access to the transmitted multimedia information using stored decryption keys. If a set-top terminal is moved, the distance between the set-top terminal and the satellite will change, thereby causing a measurable phase shift in the signal received by the set-top terminal. The set-top terminal periodically or intermittently records a sequence of bits received from the satellite and provides the recorded bits to the service provider server for analysis. If the set-top terminal has been moved, the recorded bits will shift. The sequence of bits may be recorded at random intervals, triggered by an external event, shown, for example, by an accurate internal clock, a request sent by a terrestrial paging network, or a request sent by a low-earth-orbit (LEO) satellite messaging system. The service provider detects relative movements of the set-top terminals by instructing a group of set-top terminals in geographical proximity to start recording at the same time, and comparing the sequence of bits recorded by each set-top terminal. |
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DETAILED DESCRIPTION Generally, a method and apparatus are provided for detecting the movement of a device that receives a signal broadcast from a relative fixed position, such as a signal sent by a geo-synchronous satellite and received by a set-top terminal in a Direct Broadcast Satellite (DBS) system.
According to an aspect of the invention, a service provider can detect the movement of a device using the phase shift of the broadcast signal, as received by the device.
If the device is moved even by a small amount, the distance between the device and the satellite (or another relative fixed position) will change, thereby causing a measurable phase shift in the signal received by the device.
The device periodically or intermittently records a sequence of bits received from the satellite and transmits the recorded bits to the service provider server for analysis.
If the device has been moved, the recorded bits will shift.
In one illustrative implementation, the device records a sequence of bits, triggered by an external event, such as an instant of time, shown by an accurate internal clock, a request sent by a terrestrial paging network, or a request sent by a low-earth-orbit (LEO) satellite messaging system.
The recording may optionally be performed at unpredictable times, so that a person who has moved a device cannot know when the device will actually start recording.
A service provider can detect relative movements of a device by instructing a group of devices in geographical proximity to start recording at the same time, and comparing the sequence of bits recorded by each device.
The geographical proximity is derived from the legitimate location of the corresponding devices, and may be, for example, the devices of one or more neighbors, or a trusted device installed, for example, on a telephone pole in a neighborhood.
In this manner, if the reported recording from one of the devices is shifted significantly relative to the other devices in the same geographical proximity, the device has been moved
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