Method and system for defining search windows based on mobile station location
First Claim
1. A method of searching for a target spread spectrum signal for a mobile station, said target spread spectrum signal having a nominal phase, said method comprising:
- said mobile station receiving a base station almanac, wherein said base station almanac identifies locations of a plurality of transmitters in a spread spectrum communication system;
said mobile station receiving a synchronization signal from a source transmitter, said synchronization signal providing information regarding a system time used by said spread spectrum communication system;
said mobile station developing a mobile station time based on said synchronization signal, wherein said mobile station time differs from said system time by a source-transmitter transmission delay;
estimating said source-transmitter transmission delay;
said mobile station obtaining a target transmitter location of a target transmitter from said base station almanac, wherein said target transmitter transmits said target spread spectrum signal;
estimating a mobile station location of said mobile station;
estimating a target-transmitter transmission delay based on at least said target transmitter location and said mobile station location;
calculating an expected phase of said target spread spectrum signal at said mobile station based on at least said nominal phase, said source-transmitter transmission delay, and said target-transmitter transmission delay; and
said mobile station searching for a spread spectrum signal having a phase at said mobile station that is within a predefined range of said expected phase.
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Accused Products
Abstract
A mobile station uses a search window to search for a target pilot signal transmitted by a target transmitter in a spread spectrum communication system. The search window may be centered on the expected phase of the target pilot signal at the mobile station. To calculate the expected phase, the mobile station estimates a transmission delay associated with the target pilot signal, based on at least the target transmitter'"'"'s location and the mobile station'"'"'s location. The transmission delay may account for the time it takes for the target pilot signal to propagate from the target transmitter to the mobile station. The expected phase of the target pilot signal may then be calculated based on at least a nominal phase of the target pilot signal (e.g., the phase when transmitted by the target transmitter) and the estimated transmission delay.
20 Citations
14 Claims
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1. A method of searching for a target spread spectrum signal for a mobile station, said target spread spectrum signal having a nominal phase, said method comprising:
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said mobile station receiving a base station almanac, wherein said base station almanac identifies locations of a plurality of transmitters in a spread spectrum communication system; said mobile station receiving a synchronization signal from a source transmitter, said synchronization signal providing information regarding a system time used by said spread spectrum communication system; said mobile station developing a mobile station time based on said synchronization signal, wherein said mobile station time differs from said system time by a source-transmitter transmission delay; estimating said source-transmitter transmission delay; said mobile station obtaining a target transmitter location of a target transmitter from said base station almanac, wherein said target transmitter transmits said target spread spectrum signal; estimating a mobile station location of said mobile station; estimating a target-transmitter transmission delay based on at least said target transmitter location and said mobile station location; calculating an expected phase of said target spread spectrum signal at said mobile station based on at least said nominal phase, said source-transmitter transmission delay, and said target-transmitter transmission delay; and said mobile station searching for a spread spectrum signal having a phase at said mobile station that is within a predefined range of said expected phase. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A mobile station, comprising:
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a communication receiver for receiving spread spectrum signals; a processor; data storage; and a plurality of program instructions stored in said data storage and executable by said processor to perform functions comprising; (a) receiving a base station almanac, wherein said base station almanac identifies locations of a plurality of transmitters in a spread spectrum communication system; (b) obtaining a target transmitter location of a target transmitter from said base station almanac; (c) estimating a target-transmitter transmission delay based on at least said target transmitter location and a mobile station location of said mobile station; (d) developing a mobile station time based on a synchronization signal received from a source transmitter in said spread spectrum communication system, wherein said mobile station time differs from a system time by a source-transmitter transmission delay; (e) estimating said source-transmitter transmission delay; (f) calculating an expected phase at said mobile station of a target spread spectrum signal transmitted by said target transmitter, wherein said expected phase is calculated based on at least a nominal phase of said target spread spectrum signal, said source-transmitter transmission delay, and said target-transmitter transmission delay; and (g) controlling said communication receiver based on said expected phase. - View Dependent Claims (12, 13, 14)
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Specification