Position location signaling method apparatus and system utilizing orthogonal frequency division multiplexing
First Claim
1. A method of transmitting position location signals, the method comprising:
- defining a plurality (Q) of orthogonal frequencies, wherein each of the Q orthogonal frequencies are separated from one another by a multiple of a fixed frequency spacing (w);
selecting a first subset of orthogonal frequencies from the plurality of orthogonal frequencies;
generating a first Orthogonal Frequency Division Multiplex (OFDM) symbol based on the first subset of orthogonal frequencies and substantially orthogonal to a second OFDM symbol generated from a second subset of orthogonal frequencies from the plurality of orthogonal frequencies; and
transmitting a position location signal containing said first OFDM symbol from a first geographical location distinct from a second geographical location from which the second OFDM symbol is transmitted.
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Abstract
Position location signaling system, apparatus, and method are disclosed. Position location beacons can each be configured to transmit a frequency interlaced subset of orthogonal frequencies spanning substantially an entire channel bandwidth. The orthogonal frequencies can be pseudorandomly or uniformly spaced, and each beacon can be allocated an equal number of orthogonal frequencies. Each frequency of the interlaced subset of orthogonal frequencies can be modulated with an element of a predetermined data sequence. A mobile device can receive one or more of the beacon signals and determine a position using a position location algorithm that determines position in part on an arrival time of the beacon signal. Where the mobile device can receive three or more beacon signals, the mobile device can perform position location by trilateration to the beacon positions based, for example, on a time difference of arrival.
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Citations
55 Claims
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1. A method of transmitting position location signals, the method comprising:
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defining a plurality (Q) of orthogonal frequencies, wherein each of the Q orthogonal frequencies are separated from one another by a multiple of a fixed frequency spacing (w);
selecting a first subset of orthogonal frequencies from the plurality of orthogonal frequencies;
generating a first Orthogonal Frequency Division Multiplex (OFDM) symbol based on the first subset of orthogonal frequencies and substantially orthogonal to a second OFDM symbol generated from a second subset of orthogonal frequencies from the plurality of orthogonal frequencies; and
transmitting a position location signal containing said first OFDM symbol from a first geographical location distinct from a second geographical location from which the second OFDM symbol is transmitted. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. A method of transmitting position location signals, the method comprising:
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defining a plurality (Q) of orthogonal frequencies;
defining a number (M) of distinct position location signals;
generating M disjoint subsets of orthogonal frequencies from the plurality of orthogonal frequencies;
generating at least two Orthogonal Frequency Division Multiplex (OFDM) symbols corresponding to at least two of the M subsets; and
transmitting one of the at least two OFDM symbols periodically from a first geographical location over a wireless communication channel, the first geographical location distinct from a second geographical location from which the second of the at least two OFDM symbols is transmitted. - View Dependent Claims (27, 28)
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29. A method of transmitting position location signals, the method comprising:
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generating a first frequency interlaced Orthogonal Frequency Division Multiplex (OFDM) signal from a first subset of orthogonal frequencies;
synchronizing the first frequency interlaced OFDM signal to a time reference;
generating a second frequency interlaced OFDM signal from a subset of orthogonal frequencies disjoint from said first subset;
synchronizing the second frequency interlaced OFDM signal to the time reference; and
wirelessly transmitting the first and the second frequency interlaced OFDM signals from two different geographical locations.
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30. A position location signal generating apparatus, the apparatus comprising:
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means for generating at least two out of a total of M subsets of orthogonal frequencies from a plurality of Q orthogonal frequencies;
means for generating at least two Orthogonal Frequency Division Multiplex (OFDM) symbols, each of said symbols constructed from a different subset from the M subsets;
means for transmitting one of said OFDM symbols periodically over a first wireless communications link; and
means for transmitting a second of said OFDM symbols periodically over a second wireless communications link.
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31. A position location signal generating apparatus, the apparatus comprising:
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means for generating at least two frequency interlaced Orthogonal Frequency Division Multiplex (OFDM) signals from a subset of orthogonal frequencies;
means for synchronizing each of said frequency interlaced OFDM signals to a time reference; and
means for concurrently transmitting each of said frequency interlaced OFDM signals from each of two different geographical locations.
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32. A position location signal generating apparatus, the apparatus comprising:
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an orthogonal signal generator configured to generate at least a subset of orthogonal carriers out of a larger set of Q orthogonal frequency carriers;
a modulation data module configured to generate a pseudorandom data sequence;
a modulator coupled to the modulation data module and configured to modulate the subset of orthogonal carriers based in part on a pseudorandom data sequence;
an Orthogonal Frequency Division Multiplex (OFDM) modulator having an input coupled to the orthogonal signal generator, and configured to generate a first OFDM symbol based in part on the subset of orthogonal carriers; and
a transmitter coupled to the OFDM modulator and configured to wirelessly transmit the first OFDM symbol from a first geographical location distinct from a second geographical location from which a second OFDM symbol, orthogonal to the first OFDM symbol, is transmitted. - View Dependent Claims (33, 34, 35, 36, 37, 38, 39, 40)
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41. A method of position location, the method comprising:
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receiving an Orthogonal Frequency Division Multiplex (OFDM) signal;
performing a cross-correlation operation of said received OFDM signal against a reference signal;
determining a presence of a received OFDM symbol from said cross-correlation operation; and
determining a location based at least in part on the OFDM symbol. - View Dependent Claims (42, 43, 44, 45, 46, 47, 48, 49, 50, 51)
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52. A mobile device configured for position location, the device comprising:
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means for receiving an Orthogonal Frequency Division Multiplex (OFDM) signal;
means for cross-correlating at least a portion of the OFDM signal to one of a predetermined number of OFDM symbols; and
means for determining a location based at least in part on a result of said cross correlation operation.
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53. A mobile device configured for position location, the device comprising:
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a receiver configured to receive an Orthogonal Frequency Division Multiplex (OFDM) signal;
a correlator configured to correlate the received OFDM signal against a plurality of frequency interlaced OFDM symbols; and
a position location module configured to determine a location based in part on an output of the correlator if at least one frequency interlaced OFDM symbol correlates with the received OFDM signal by greater than a predetermined correlation threshold. - View Dependent Claims (54, 55)
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Specification