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Wireless signals and techniques for determining locations of objects in multi-path environments

  • US 10,168,414 B2
  • Filed: 01/26/2015
  • Issued: 01/01/2019
  • Est. Priority Date: 07/17/2014
  • Status: Active Grant
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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