Forward link repeater frequency watermarking scheme
First Claim
1. A repeater for amplifying a forward link signal from a base station to a mobile station, wherein the mobile station has a frequency tracking loop, the repeater comprising:
- an amplifier for amplifying the forward link signal from the base station to the mobile station; and
a fast frequency modulator that frequency modulates the forward link signal with an identifying fast frequency watermark as it passes through the repeater, wherein said watermark has a frequency such that the frequency tracking loop substantially does not detect said watermark at said mobile station.
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Accused Products
Abstract
A forward link repeater frequency watermarking (FLRFWM) system and method that enable accurate position location of mobile stations in areas where repeaters are present by watermarking repeated signals with repeater information. A repeater watermarks a forward link signal with a (unique or non-unique) fast frequency modulation waveform watermark every time a signal passes through the repeater. A mobile station detects and/or identifies the fast frequency watermark on the forward link signal to determine repeater information that aids the network position determination entity or mobile station position location system in determining position location using AFLT and/or A-GPS systems. A forward link fast frequency watermarking system described herein achieves minimal impact on FL, AFLT, and GPS performance, good detection, identification and false alarm probabilities, short time-to-detect/identify, and good detection/identification sensitivity.
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Citations
35 Claims
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1. A repeater for amplifying a forward link signal from a base station to a mobile station, wherein the mobile station has a frequency tracking loop, the repeater comprising:
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an amplifier for amplifying the forward link signal from the base station to the mobile station; and
a fast frequency modulator that frequency modulates the forward link signal with an identifying fast frequency watermark as it passes through the repeater, wherein said watermark has a frequency such that the frequency tracking loop substantially does not detect said watermark at said mobile station. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A mobile station for receiving a plurality of forward link pilot signals and identifying the presence of a fast frequency watermark waveform to determine whether any of said forward link signals are repeated, said mobile station comprising:
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a receiver for receiving forward link signals;
a frequency tracking loop for enabling accurate demodulation of the forward link signals;
an AFLT searcher for detecting pilots and performing pilot phase measurements including measuring the times of arrival of said plurality of forward link pilot signals; and
a repeater identification system configured to detect and identify the watermark, if any, and thereby identify a repeated forward link signal, wherein said repeater identification system searches the forward link signal for the watermark to retrieve the watermark waveform that uniquely identifies the repeater, the watermark waveform having a frequency such that the frequency tracking loop substantially does not detect said watermark. - View Dependent Claims (15, 16, 17, 18, 19)
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20. A method for determining position location information of a mobile station from the forward link of a plurality of pilot signals, the method comprising:
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performing an AFLT search in the mobile station to detect pilots and measure an earliest time-of-arrival of said plurality of pilot signals;
selecting a first pilot signal located during said AFLT search;
repeater-screening said first pilot signal by performing a repeater AFLT search on said first pilot signal, including searching for a fast frequency watermark waveform that identifies a repeated signal, wherein said watermark waveform has a frequency such that a frequency tracking loop in said mobile station substantially does not detect said watermark at said mobile station;
repeating said steps of performing and repeater-screening for a plurality of other selected pilot signals until a sufficient number of repeater-screened pilot signals to determine a position location of the mobile station is obtained; and
providing pilot phase measurements and repeater information for the pilot signals obtained in said AFLT search to one of a mobile station position determining system and a network position determination entity to determine the position of said mobile station. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27)
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28. A method for retrieving repeater information from a pilot signal, if any, in a mobile station, the method comprising:
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performing a repeater identification search in the mobile station on a first pilot signal, including searching for a fast frequency watermark waveform that identifies a repeated signal on the forward link of said first pilot signal, wherein said watermark waveform has a frequency such that a frequency tracking loop in said mobile station substantially does not detect said watermark at said mobile station; and
providing pilot phase measurements and repeater information for position location determination. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35)
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Specification