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Portable hybrid location determination system

  • US 5,936,572 A
  • Filed: 02/25/1997
  • Issued: 08/10/1999
  • Est. Priority Date: 02/04/1994
  • Status: Expired due to Term
First Claim
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1. Apparatus for determining the present location of a mobile user that carries the apparatus inside or outside buildings and structures, the apparatus comprising:

  • a radio location determination (LD) module that receives radio LD signals from Q1 (Q1≧

    3) terrestrial radio LD signal sources having known locations, that determines present location of the radio LD module from knowledge of relative phases of the radio LD signals as transmitted from the radio LD signal sources, that determines a radio LD signal indicium Irad that is a measure of at least one of (i) signal strength and (ii) signal quality of each of the radio LD signals received, and that issues radio LD module present location information and the radio LD signal indicium as radio LD output signals;

    an outdoor LD module that receives outdoor LD signals from outdoor LD signal sources carried on Q2 (Q2≧

    3) satellites with known orbits, that determines present location of the outdoor LD module from the outdoor LD signals received, that determines an outdoor LD signal indicium Iout that is a measure of at least one of (i) signal strength and (ii) signal quality of each of the outdoor LD signals received, and that issues outdoor LD module present location information and the outdoor LD signal indicium as outdoor LD output signals;

    a controller mechanism, including a microprocessor, that receives the radio LD output signals and the outdoor LD output signals, that compares Irad with a selected threshold value Irad,thr, that compares Iout with a selected threshold value Iout,thr, and that selects at most one of the radio LD signal present location information and the outdoor LD signal present location information to determine a present location of a user that carries the radio LD module and the outdoor LD module, based on the comparisons of Irad and Iout ;

    where the indicium Irad is determined by strengths Sj (rad)(j=1, . . . , Q1) of signals received from the Q1 radio LD signal sources and is drawn from the class of indicia consisting of;

    ##EQU7## where the coefficients aq are selected non-negative numbers and at least one coefficient aq is positive; and

    ##EQU8## the parameters p(q) are non-negative numbers, and at least one parameter p(q) is positive; and

    where the indicium Iout is determined by strengths Sj (out)(j=1, . . . , Q2) of signals received from the Q2 outdoor LD signal sources and is drawn from the class of indicia consisting of;

    ##EQU9## where the coefficients bq are selected non-negative numbers and at least one coefficient bq is positive; and

    ##EQU10## the parameters r(q) are non-negative numbers, and at least one parameter r(q) is positive.

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