Location system and method with acquisition of accurate location parameters
First Claim
1. A method of locating a locatable unit using a locator unit which moves relative to said locatable unit, said method comprising the steps of:
- transmitting a first signal from a first one of said locator and locatable units;
receiving said first signal at a second one of said locator and locatable units;
estimating, at said second unit, a Doppler component of said received first signal, said step using a preset frequency from a preset estimate table as adjusted by subsequent signals from said first one of said locator and locatable units to said second one of said locator and locatable units, said preset frequency being an approximation of propagation characteristics of said first signal;
transmitting a second signal from said second unit, said second signal being modulated to convey data which describe said estimated Doppler component of said first signal;
receiving said second signal at said first unit;
measuring, at said first unit, a frequency offset between a frequency at which said second signal is received at said first unit and a predetermined frequency, said predetermined frequency being reserved for transmission of said second signal; and
determining a position for said locatable unit in response to said estimated Doppler component received at said first unit as transmitted in said second signal and said frequency offset as measured in said measuring step, said estimated Doppler component and said frequency offset defining a curve whereon said position is located.
3 Assignments
0 Petitions
Accused Products
Abstract
A location system relies upon a non-coherent, FDM/TDM communication scheme to measure location parameters. A locator unit moves relative to the locatable unit. A series of messages are communicated between the locator unit and the locatable unit. Through feedback provided from the locator unit to the locatable unit, the locatable unit adjusts its reference frequency and time base so that signals it transmits arrive at the locator unit on a desired frequency and at a desired time slot. The locatable unit estimates Doppler and propagation duration and transmits the estimates to the locator unit. The locator unit measures offsets between desired frequencies and time slots and actual frequencies and time slots. The offsets are combined with the locatable unit'"'"'s estimates of Doppler and propagation duration to form an integrated Doppler parameter and an integrated propagation duration parameter. The integrated Doppler and propagation duration are used to determine location.
180 Citations
26 Claims
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1. A method of locating a locatable unit using a locator unit which moves relative to said locatable unit, said method comprising the steps of:
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transmitting a first signal from a first one of said locator and locatable units; receiving said first signal at a second one of said locator and locatable units; estimating, at said second unit, a Doppler component of said received first signal, said step using a preset frequency from a preset estimate table as adjusted by subsequent signals from said first one of said locator and locatable units to said second one of said locator and locatable units, said preset frequency being an approximation of propagation characteristics of said first signal; transmitting a second signal from said second unit, said second signal being modulated to convey data which describe said estimated Doppler component of said first signal; receiving said second signal at said first unit; measuring, at said first unit, a frequency offset between a frequency at which said second signal is received at said first unit and a predetermined frequency, said predetermined frequency being reserved for transmission of said second signal; and determining a position for said locatable unit in response to said estimated Doppler component received at said first unit as transmitted in said second signal and said frequency offset as measured in said measuring step, said estimated Doppler component and said frequency offset defining a curve whereon said position is located. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of operating a locatable unit in connection with a locator unit which moves relative to said locatable unit, said method comprising the steps of:
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receiving a first signal at said locatable unit; estimating a Doppler component of said first signal, said step using a preset frequency from a preset estimate table as adjusted by subsequent signals from said first one of said locator and locatable units to said second one of said locator and locatable units, said preset frequency being an approximation of propagation characteristics of said first signal; determining a frequency at which a second signal may be transmitted from said locatable unit so that said second signal will exhibit a predetermined frequency when received at said locator unit, said predetermined frequency being reserved for transmission of said second signal; and transmitting said second signal from said locatable unit, said second signal being modulated to convey data which describe said estimated Doppler component of said first signal. - View Dependent Claims (11, 12, 13)
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14. A method of locating a locatable unit using a locator unit which resides a distance away from said locatable unit, said method comprising the steps of:
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transmitting a first signal from a first one of said locator and locatable units; receiving said first signal at a second one of said locator and locatable units; estimating, at said second unit, a propagation duration using a preset duration from said preset estimate table as adjusted by subsequent signals from said first one of said locator and locatable units to said second one of said locator and locatable units, said preset duration being an approximation of propagation characteristics required for said first signal to propagate between said first and second units; transmitting a second signal from said second unit, said second signal being modulated to convey data which describe said estimated propagation duration of said first signal; receiving said second signal at said first unit; measuring, at said first unit, a timing offset between a point in time at which said second signal is received at said first unit and a predetermined point in time; and determining a position for said locatable unit in response to said estimated propagation duration, received at said first unit as transmitted in said second signal and said timing offset as measured in said measuring step, said estimated propagation duration and said timing offset defining a propagation delay curve whereon said position is located. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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21. A method of operating a locatable unit in connection with a locator unit which moves relative to said locatable unit, said method comprising the steps of:
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receiving a first signal at said locatable unit; estimating a propagation duration using a preset duration from a preset estimate table as adjusted by subsequent signals from said first one of said locator and locatable units to said second one of said locator and locatable units, said preset duration being an approximation of propagation characteristics required for said first signal to propagate between said locator and locatable units; determining a point in time at which a second signal may be transmitted from said locatable unit so that said second signal should arrive at said locator unit at a predetermined point in time; and transmitting said second signal from said locatable unit, said second signal being modulated to convey data which describe said estimated propagation duration of said first signal. - View Dependent Claims (22)
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23. A method of operating a radio telecommunications system having at least one satellite moving in an orbit around the earth and having at least one subscriber unit located proximate the earth'"'"'s surface, said method comprising the steps of:
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transmitting a first signal from said satellite; receiving said first signal at said subscriber unit; estimating, at said subscriber unit, a Doppler component of said received first signal and a propagation duration required for said first signal to propagate between said satellite and said subscriber unit; transmitting a second signal from said subscriber unit, said second signal being modulated to convey data which describe said estimated Doppler component of said first signal and to convey data which describe said propagation duration; receiving said second signal at said satellite; measuring, at said satellite, a frequency offset between a frequency at which said second signal is received at said satellite and a predetermined frequency, and a timing offset between a point in time at which said second signal is received at said satellite and a predetermined point in time; and determining a location of said subscriber unit relative to the earth in response to said estimated Doppler component, said estimated propagation duration, said frequency offset, and said timing offset, said estimated Doppler component and said frequency offset defining a curve whereon said location is located and said estimated propagation duration and said timing offset defining a propagation delay curve whereon said location is located. - View Dependent Claims (24, 25, 26)
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Specification