Mobile radiotelephone determination using time of arrival of GPS and pilot signals
First Claim
1. A method for determining a location of a radiotelephone comprising a pilot signal receiver, a global positioning system (GPS) signal receiver, and a local clock, the radiotelephone operating in a radiotelephone system comprising a plurality of bases stations, each base station comprising a pilot signal transmitter and a GPS signal receiver, the method comprising the steps of:
- estimating a time of arrival of GPS signals at the radiotelephone GPS receiver relative to the radiotelephone clock;
estimating a time of arrival of a radiotelephone system pilot signal at the radiotelephone signal receiver relative to the radiotelephone clock; and
calibrating the time of arrival values in response to delays associated with the base station'"'"'s pilot signal transmitter and the radiotelephone'"'"'s pilot signal receiver.
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Accused Products
Abstract
The time of arrival of a global positioning system signal and the time of arrival of a code division multiple access pilot signal, from a base station, are estimated at a mobile radiotelephone. Both estimates are performed relative to a local clock in the radiotelephone. These signals are calibrated for the time delay produced by the transmitter at the base station and the time delay produced by the receiver in the radiotelephone.
54 Citations
7 Claims
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1. A method for determining a location of a radiotelephone comprising a pilot signal receiver, a global positioning system (GPS) signal receiver, and a local clock, the radiotelephone operating in a radiotelephone system comprising a plurality of bases stations, each base station comprising a pilot signal transmitter and a GPS signal receiver, the method comprising the steps of:
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estimating a time of arrival of GPS signals at the radiotelephone GPS receiver relative to the radiotelephone clock;
estimating a time of arrival of a radiotelephone system pilot signal at the radiotelephone signal receiver relative to the radiotelephone clock; and
calibrating the time of arrival values in response to delays associated with the base station'"'"'s pilot signal transmitter and the radiotelephone'"'"'s pilot signal receiver.
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2. A method for determining differential time delays through pairs of base station transmitters in a radiotelephone system comprising a plurality of base stations, the method comprising the steps of:
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a first pair of base station transmitters, of the plurality of base stations, each transmitting a signal to a common receiver;
the common receiver receiving each of the pair of transmitted signals;
determining, at the common receiver, a transmission delay of each signal of the received pair of signals; and
determining a difference between the transmission delays of each of the received signals of the pair of received signals, the difference being the time delay through the first pair of base station transmitters. - View Dependent Claims (3)
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4. A method for determining a time of arrival, at a receiver, of a received code division multiple access (CDMA) pilot signal, the time of arrival being determined relative to the receiver'"'"'s local clock, the radiotelephone signal comprising a plurality of frames, the method comprising the steps of:
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decimating each frame of the plurality of frames at a predetermined rate to generate pilot signal samples;
performing a Fast Fourier Transform on the pilot signal samples;
decimating a pilot despreading sequence at the predetermined rate;
performing a Fast Fourier Transform on a pilot despreading sequence;
multiplying the Fast Fourier Transform of the pilot signal samples by the Fast Fourier Transform of the despreading sequence to produce a product signal;
performing an inverse Fast Fourier Transform on the product signal to generate a cross correlation function of the CDMA pilot signal and the pilot despreading signal;
generating a power delay profile by summing the squared magnitude of the cross correlation function for each received pilot signal frames; and
estimating the time of arrival in response to the power delay profile.
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5. A method for determining a location of a radiotelephone comprising a transmitter and receiver, the radiotelephone operating in a radiotelephone system comprising a plurality of bases stations, each base station comprising a transmitter and receiver, the method comprising the steps of:
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receiving a predetermined number of GPS signals, each signal being transmitted from a different GPS satellite;
receiving a predetermined number of base station pilot signals, each pilot signal being transmitted from a different base station;
differentially combining each pilot signal with the remaining pilot signals of the predetermined number of base station pilot signals, the combining performed with all permutations of pairs of pilot signals;
differentially combining each GPS signal with the remaining GPS signals of the predetermined number of GPS signals, the combining performed with all permutations of pairs of GPS signals; and
combining the results of the pilot signal differential combination with the results of the GPS signal differential combination to determine the location of the radiotelephone.
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6. An apparatus for estimating a transmitter delay in a radio frequency transmitter, the apparatus comprising:
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a transmit path, coupled to an original baseband signal, comprising;
an upconverter for changing the frequency of a signal to be transmitted, thus producing an upconverted signal;
a power amplifier, coupled to the upconverter, for amplifying the upconverted signal to become an amplified signal; and
a coupler, coupled to the power amplifier, for distributing the amplified signal; and
a feedback path comprising;
a local oscillator that generates a clocking signal, the local oscillator coupled to the upconverter;
a multiplier coupled to the coupler and the local oscillator for downconverting the amplified signal to produce a reproduced baseband signal;
a filter, coupled to the multiplier, for filtering the reproduced baseband signal to produce a filtered signal; and
a correlator, coupled to the filter and the original baseband signal, for correlating the filtered signal with the original baseband signal to produce an estimate of the transmitter delay.
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7. A receiver apparatus for receiving both a code division multiple access (CDMA) signal and a global positioning system (GPS) signal, the receiver apparatus comprising:
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an antenna for receiving the CDMA and the GPS signals;
a CDMA signal receiver, coupled to the antenna, for operating on the CDMA signal;
a dual frequency synthesizer for generating a CDMA clock signal and a GPS clock signal;
a switch having a first input coupled to the CDMA clock signal, a second input coupled to the GPS clock signal, a control input, and an output for outputting either the CDMA clock signal or the GPS clock signal in response to the control input;
a switch frequency generator for generating a switching signal, the switching signal coupled to the control input of the switch;
a down-converter mixer, coupled to the antenna and the switch output, for multiplying a received signal from the antenna with either the CDMA clock signal or the GPS clock signal depending on the switching signal, the down-converter mixer outputting a commutated CDMA/GPS signal;
a narrowband filter, coupled to the down-converter mixer, for filtering the commutated CDMA/GPS signal to generate a filtered signal having a CDMA portion and a GPS portion; and
a processor, coupled to the narrowband filter and the switch frequency generator, for processing the CDMA portion of the filtered signal independently of the GPS portion of the filtered signal, the processing performed in response to the switching signal.
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Specification