Method and apparatus for determining the position of a mobile communication device
First Claim
1. A mobile communication device capable of determining range to a reference communication device by exchanging ranging signals with the reference communication device, comprising:
- a transmitter configured to transmit to the reference communication device a sequence of outbound ranging signals at different carrier frequencies;
a receiver configured to receive from the reference communication device a sequence of reply ranging signals at the different carrier frequencies in response to the outbound ranging signals; and
a processor configured to select from among the reply ranging signals a reply ranging signal at a carrier frequency providing a highest signal timing accuracy, said processor determining a time of arrival of the selected reply ranging signal and the range to the reference communication device from a round-trip signal propagation time of the selected reply ranging signal and a corresponding outbound ranging signal.
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Abstract
A position location communication system determines the position of a mobile master radio using a round-trip messaging scheme in which the time of arrive (TOA) of ranging signals is accurately determined to yield the range estimates required to calculate the position of the mobile radio. The master radio transmits ranging signals to plural reference radios which respond by transmitting reply ranging signals. Upon reception of the reply ranging signal, the master radio determines the range to the reference radio from the signal propagation time. Any combination of fixed or mobile radios having known positions can be used as the reference radios for another mobile radio in the system. Individual radios do not need to be synchronized to a common time reference, thereby eliminating the need for highly accurate system clocks. Errors in TOA estimates are minimized by performing internal delay calibration, Doppler compensation, leading-edge-of-the-signal curve fitting and frequency diversity techniques.
219 Citations
45 Claims
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1. A mobile communication device capable of determining range to a reference communication device by exchanging ranging signals with the reference communication device, comprising:
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a transmitter configured to transmit to the reference communication device a sequence of outbound ranging signals at different carrier frequencies;
a receiver configured to receive from the reference communication device a sequence of reply ranging signals at the different carrier frequencies in response to the outbound ranging signals; and
a processor configured to select from among the reply ranging signals a reply ranging signal at a carrier frequency providing a highest signal timing accuracy, said processor determining a time of arrival of the selected reply ranging signal and the range to the reference communication device from a round-trip signal propagation time of the selected reply ranging signal and a corresponding outbound ranging signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A position location system for determining the position of a mobile communication device, comprising:
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a plurality of reference communication devices having known positions, each configured to transmit and receive ranging signals; and
a mobile communication device configured to exchange ranging signals with said reference communication devices, said mobile communication device transmitting to each reference communication device a sequence of outbound ranging signals at different carrier frequencies, each of said reference communication devices transmitting a sequence of reply ranging signals at the different carrier frequencies in response to the outbound ranging signals, wherein;
said mobile communication device determines the range to each reference communication device from a round-trip signal propagation time of a selected outbound ranging signal and a corresponding reply ranging signal transmitted at a carrier frequency providing a highest signal timing accuracy, and determines the position of said mobile communication device from the known positions of said reference communication devices and the range to each reference communication device. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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36. A transmission waveform for transporting signal acquisition information over a communication medium, comprising:
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a communication acquisition sequence comprising a plurality of first spread spectrum symbols containing information for detecting arrival of the transmission waveform, each of said first spread spectrum symbols having a predetermined number of chips; and
a time of arrival (TOA) synchronization sequence comprising a plurality of second spread spectrum symbols each having a number of chips greater than the predetermined number of chips of said first spread spectrum symbols, said second spread spectrum symbols containing information for determining a time of arrival of the transmission waveform.
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37. A method of determining the range between a mobile communication device and a reference communication device, comprising the steps of:
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(a) transmitting a sequence of outbound ranging signals at different carrier frequencies from the mobile communication device to the reference communication device;
(b) transmitting a sequence of reply ranging signals at the different carrier frequencies from the reference communication device to the mobile communication device in response to the outbound ranging signals; and
(c) determining the range between the mobile communication device and the reference communication device from a round-trip signal propagation time of a selected outbound ranging signal and a corresponding reply ranging signal transmitted at a carrier frequency providing a highest signal timing accuracy. - View Dependent Claims (38, 39, 40, 41, 42, 43, 44, 45)
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Specification