System and method for geolocating a wireless mobile unit from a single base station using repeatable ambiguous measurements

In a method for geolocating a mobile unit within the operating area of a single base station having a plurality of randomly located antennas wherein a range estimate of the mobile unit from the base station is available and wherein the base station and mobile unit are receiving, one from the other, communication signals and pilot signals in accordance with a known air interface protocol, the improvement including the steps of:

• (a) providing a database comprising plural sets of reference ambiguous lines of bearing indexed by range from the base station and angle of bearing from the base station, obtained by:
• (i) selectively locating a test unit at a plurality of known geographic locations within the operating area of the base station;
• (ii) receiving at a subset of the plurality of randomly located antennas at the base station a communication signal transmitted from the test unit;
• (iii) measuring the phase of the received communication signal at each of the antennas in the subset;
• and
• (iv) determining the difference in phase between pairs of antennas in the subset to thereby determine the reference ambiguous lines of bearing from the base station to the mobile unit;
• (b) determining a set of real-time ambiguous lines of bearing for the mobile unit by:
• (i) receiving at a subset of the plurality of randomly located antennas at the base station a communication signal transmitted from the mobile unit;
• (ii) measuring the phase of the received communication signal at each of the antennas in the subset;
• and
• (iii) determining the difference in phase between pairs of antennas in the subset to thereby determine the real-time ambiguous lines of bearing from the base station to the mobile unit;
• and
• (c) comparing the set of real-time ambiguous lines of bearing with the sets of reference ambiguous lines of bearing in the database to thereby determine the range and bearing of the mobile unit from the base station so as to geolocate the mobile unit.

In a method for geolocating a mobile unit from a serving base station located within a pattern of base stations wherein a range estimate of the mobile unit from the serving base station is available, and wherein the serving base station and the mobile unit are receiving, one from the other, communication signals and pilot signals in accordance with a known air interface protocol, and wherein the mobile unit is detecting a pilot signal transmitted from ones of the base stations in the pattern of base stations, the improvement including the steps of:

• (a) providing a database comprising plural sets of reference pilot signal data indexed by range from the serving base station and angle of bearing from the serving base station, obtained by:
• (i) selectively locating a test unit at a plurality of known geographic locations within the operating area of the serving base station;
• (ii) receiving at the serving base station a pilot signal transmitted from the test unit;
• and
• (iii) detecting at the serving base station the pilot signal data contained within said pilot signal to thereby determine the set of reference pilot signal data;
• (b) determining a set of real-time pilot signal data for the mobile unit by:
• (i) receiving at the serving base station a pilot signal transmitted from the mobile unit;
• and
• (ii) detecting at the serving base station the pilot signal data contained within said pilot signal to thereby determine the set of real-time pilot signal data;
• and
• (c) comparing the set of real-time pilot signal data with the sets of reference pilot signal data to thereby determine the range and bearing of the mobile unit from the serving base station so as to geolocate the mobile unit.

In a method for geolocating a mobile unit within the operating area of a single base station wherein a range estimate of the mobile unit from the base station is available and wherein the base station and mobile unit are receiving, one from the other, communication signals and pilot signals in accordance with a known air interface protocol requiring spreading, the improvement including the steps of:

• (a) providing a database comprising plural sets of reference pilot finger data indexed by range from the base station and angle of bearing from the base station, obtained by:
• (i) selectively locating a test unit at a plurality of known geographic locations within the operating area of the base station;
• (ii) receiving at the base station a communication signal transmitted from the test unit;
• and
• (iii) despreading at the base station the communication data contained within said test unit communication signal;
• and
• (iv) extracting the pilot finger data from said test unit communication data to thereby determine the set of reference pilot finger data;
• (b) determining a set of real-time pilot finger data by:
• (i) receiving at the base station a communication signal transmitted from the mobile unit;
• and
• (ii) despreading at the base station the communication data contained within said mobile unit communication signal;
• and
• (iii) extracting the pilot finger data from said mobile unit communication data to thereby determine the set of real-time pilot finger data;
• and
• (c) comparing the set of real-time pilot finger data with the sets of reference pilot finger data to thereby determine the range and bearing of the mobile unit from the base station so as to geolocate the mobile unit.

A system for geolocating a mobile unit from a single base station having a plurality of randomly located antennas wherein the base station and mobile unit are receiving, one from the other, communication signals and pilot signals in accordance with a known air interface protocol comprising:

• database means for storing plural sets of measurements selected from the group consisting of reference ambiguous lines of bearing, reference pilot signal data, and reference pilot finger data, wherein said database is indexed by range from the base station and angle of bearing from the base station;
• measurement means for determining a set of real-time measurements selected from the group consisting of real-time ambiguous lines of bearing, real-time pilot signal data, and realtime pilot finger data;
• and range estimating means for estimating the range of the mobile unit from the base station;
• comparing means for comparing the set of real-time measurements with the sets of reference measurements to thereby determine the range and bearing of the mobile unit from the base station so as to geolocate the mobile unit.