Wireless signals and techniques for determining locations of objects in multi-path environments
First Claim
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1. A method comprising:
- at a first device, receiving a probe signal sent from a second device through a multipath channel, the probe signal received at the first device having a waveform that is different from the waveform sent by the second device due to influence of the multipath channel;
estimating a channel impulse response based on the probe signal received at the first device;
determining a time-reversed signal based on the estimated channel impulse response;
computing coordinates of a position of the second device based on a combination of (i) the time-reversed signal, (ii) stored first data representing channel impulse responses derived from probe signals sent from a third device at a plurality of positions in a venue, and (iii) second data representing coordinates of the plurality of positions in the venue that are stored in a storage device, in which the second device is located at one of the plurality of positions or in a vicinity of one of the plurality of positions, and determining coordinates of the position of the second device comprising determining which of the channel impulse responses represented by the first data more closely matches the channel impulse response estimated based on the probe signal sent from the second device as compared to the other channel impulse responses represented by the first data;
for each of a plurality of positions, determining a feature value based on a function of the time-reversed signal and the stored channel impulse response associated with the position, anddetermining the position of the second device based on the position associated with a largest feature value among the feature values,wherein at least one of (i) the feature value associated with a position is a function of the stored channel impulse response or responses associated with one or more neighboring positions, (ii) the feature value associated with a position is a function of the stored channel impulse responses derived from probe signals sent from the position at a plurality of time periods, or (iii) determining the feature value associated with a position comprises calculating a convolution of the time-reversed signal and the stored channel impulse response associated with the position.
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Abstract
A time-reversal positioning system includes a storage storing first data representing channel impulse responses derived from probe signals sent from a plurality of positions and second data representing coordinates of the positions. A data processor determines a position of a terminal device based on the stored channel impulse responses and a time-reversed signal determined based on a time-reversed version of a channel impulse response that is estimated based on a channel probing signal sent from the terminal device.
60 Citations
20 Claims
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1. A method comprising:
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at a first device, receiving a probe signal sent from a second device through a multipath channel, the probe signal received at the first device having a waveform that is different from the waveform sent by the second device due to influence of the multipath channel; estimating a channel impulse response based on the probe signal received at the first device; determining a time-reversed signal based on the estimated channel impulse response; computing coordinates of a position of the second device based on a combination of (i) the time-reversed signal, (ii) stored first data representing channel impulse responses derived from probe signals sent from a third device at a plurality of positions in a venue, and (iii) second data representing coordinates of the plurality of positions in the venue that are stored in a storage device, in which the second device is located at one of the plurality of positions or in a vicinity of one of the plurality of positions, and determining coordinates of the position of the second device comprising determining which of the channel impulse responses represented by the first data more closely matches the channel impulse response estimated based on the probe signal sent from the second device as compared to the other channel impulse responses represented by the first data; for each of a plurality of positions, determining a feature value based on a function of the time-reversed signal and the stored channel impulse response associated with the position, and determining the position of the second device based on the position associated with a largest feature value among the feature values, wherein at least one of (i) the feature value associated with a position is a function of the stored channel impulse response or responses associated with one or more neighboring positions, (ii) the feature value associated with a position is a function of the stored channel impulse responses derived from probe signals sent from the position at a plurality of time periods, or (iii) determining the feature value associated with a position comprises calculating a convolution of the time-reversed signal and the stored channel impulse response associated with the position. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An apparatus comprising:
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a storage storing (i) first data representing channel impulse responses derived from probe signals that are generated and sent from a first device at a plurality of positions in a venue and received at a second device that is different from the first device, and (ii) second data representing coordinates of the plurality of positions in the venue from which the first device sent the probe signals; and a data processor configured to; compute a position of a terminal device based on a combination of the first data, the second data, and a time-reversed signal determined based on a time-reversed version of a channel impulse response that is estimated based on a channel probing signal sent from the terminal device; for each of a plurality of positions, determine a feature value based on a function of the time-reversed signal and the stored channel impulse response associated with the position, and determine the position of the terminal device based on the position associated with a largest feature value among the feature values, wherein at least one of (i) the feature value associated with a position is also a function of the stored channel impulse response or responses associated with one or more neighboring positions, (ii) the feature value associated with a position is a function of the stored channel impulse responses derived from probe signals sent from the position at a plurality of time periods, or (iii) determine the feature value associated with a position comprises calculate a convolution of the time-reversed signal and the stored channel impulse response associated with the position. - View Dependent Claims (19, 20)
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13. An apparatus comprising:
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a circuit to receive a probe signal sent from a second device through a multipath channel, the probe signal received at the apparatus having a waveform that is different from the waveform sent by the second device due to influence of the multipath channel; and a data processor configured to; estimate a channel impulse response based on the received probe signal; determine a time-reversed signal based on the estimated channel impulse response; compute coordinates of a position of the second device based on a combination of (i) the time-reversed signal, (ii) stored first data representing channel impulse responses derived from probe signals sent from a third device at a plurality of positions in a venue, and (iii) second data representing coordinates of the plurality of positions in the venue that are stored in a storage device, in which the second device is located at one of the plurality of positions or in a vicinity of one of the plurality of positions, and determine coordinates of the position of the second device comprising determine which of the plurality of positions whose coordinates are represented by the second data is closer to the position of the second device as compared to the other positions among the plurality of positions; for each of a plurality of positions, determine a feature value based on a function of the time-reversed signal and the stored channel impulse response associated with the position, and determine the position of the second device based on the position associated with a largest feature value among the feature values, wherein at least one of (i) the feature value associated with a position is also a function of the stored channel impulse response or responses associated with one or more neighboring positions, (ii) the feature value associated with a position is a function of the stored channel impulse responses derived from probe signals sent from the position at a plurality of time periods, or (iii) determine the feature value associated with a position comprises calculate a convolution of the time-reversed signal and the stored channel impulse response associated with the position. - View Dependent Claims (14, 15, 16, 17, 18)
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Specification