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Browse Prior Art Database

Using Phase Relationships for Position Location in Cellular Systems

IP.com Disclosure Number: IPCOM000121343D
Original Publication Date: 1991-Aug-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 2 page(s) / 80K

Publishing Venue

IBM

Related People

Moore, VS: AUTHOR [+2]

Abstract

This article describes a technique wherein a receiver can use the phase relationships between two cellular telephone RF control channel signals to determine the receiver's geographic location and a further technique which uses the control channels of a cellular telephone system for this purpose.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Using Phase Relationships for Position Location in Cellular Systems

      This article describes a technique wherein a receiver can
use the phase relationships between two cellular telephone RF control
channel signals to determine the receiver's geographic location and a
further technique which uses the control channels of a cellular
telephone system for this purpose.

      If all RF control channels within a cellular system were to
begin all data transmissions at the same time, then the phase
relationships between any three signals can be used to determine a
receiver's location.  LORAN employs the same practice.  However, in
the technique disclosed herein, signals from a cellular system are
compared to determine the receiver's location in respect to the
corresponding originating signal locations.  For example, if the two
digital signals correspond exactly in time, the receiver must be
equidistant between the two transmission sources. This means the
receiver is somewhere on a locus line whose points are equidistant
from the two transmission sites. Where on this line the observer
actually sits can be found by noting the phase relationship between
one of the previous two signals and a third signal.  This observation
results in a second locus line, again equidistant between the two
specified signal transmission sites.  The intersection of the first
and second locus lines pinpoints the receiver's location.

      In operation, cell sites transmit data packets coherently.  The
phase relationship between the start of two data packets yields a
locus line between the two corresponding transmission sites on which
the receiver must reside.  A third control channel reception offers
the phase relationship needed to compute where on the locus line the
receiver actually is.  The cellular phone must be able to receive two
control carriers at one time to allow the phone's digital signal
processor (DSP) to compute the phase difference between the two
sign...