Subspace signature matching for location ambiguity resolution in wireless communication systems

Claim 2

In a system for wireless transmitter location finding, a method for selecting from a set of calibrated transmitter locations a set of most likely locations, the method comprising: measuring at a base station a transmitter signal signature R; calculating a difference between a function L R and each function L R .sbsb.i in a set of functions L R .sbsb.1, . . . , L R .sbsb.M, where the function L R represents how signature R compares to a set of calibrated signatures which corresponds to the set of calibrated locations, and where the functions L R .sbsb.1, . . . , L R .sbsb.M represent how each signature in a set of M calibrated signatures compares to the set of calibrated signatures; selecting a set of most likely signatures, such that, for each most likely signature R k , the calculated difference between the function L R and L R .sbsb.k is smaller than a predetermined threshold; and identifying a subset of the set of calibrated transmitter locations, wherein each location in the subset corresponds to a signature in the selected subset of most likely signatures.

Claim 3

The method of claim 1 wherein the function L R evaluated at a calibrated location i is a function of the cosines of the principle angles between a transmitter signature R and a calibrated signature U i .

Claim 4

The method of claim 1 wherein the function L R evaluated at a calibrated location i is a trace of a projection of R onto a subspace spanned by a calibrated signature U i .

Claim 5

The method of claim 1 wherein the difference between the function L R and each function L R .sbsb.i is calculated by calculating a sum of squared distances between L R and L R .sbsb.i.

Claim 6

The method of claim 1 wherein the difference between the function L R and each function L R .sbsb.i is calculated by calculating the Kullback-Liebler distance between L R and L R .sbsb.i.

Claim 7

In a system for wireless transmitter location finding, a method for selecting from a set of calibrated transmitter locations a set of most likely locations, the method comprising: measuring at a first base station a transmitter signal signature R; measuring at a second base station a transmitter signal signature R'; calculating a difference between a function L R and each function L R .sbsb.i in a set of functions L R .sbsb.1, . . . , L R .sbsb.M, where the function L R represents how signature R compares to a set of first base station calibrated signatures which corresponds to the set of calibrated locations, and where the functions L R .sbsb.1, . . . , L R .sbsb.M represent how each signature in a set of likely first calibrated signatures compares to the set of calibrated signatures; calculating a difference between a function L R' and each function L R' .sbsb.i in a set of functions L R' .sbsb.1, . . . , L R' .sbsb.M, where the function L R represents how signature R' compares to a set of second base station calibrated signatures which corresponds to the set of calibrated locations, and where the functions L R' .sbsb.1, . . . , L R' .sbsb.M represent how each signature in a set of likely second calibrated signatures compares to the set of second calibrated signatures; selecting from the sets of first and second likely signatures a subset of most likely common signatures, such that, for each most likely signature R k , and for each most likely signature R' k , an arithmetic combination of the calculated difference between the functions L R and L R .sbsb.k, and the calculated difference between the function L R and L R .sbsb.k, is smaller than a predetermined threshold; and identifying a subset of the set of calibrated transmitter locations, wherein each location in the subset corresponds to a signature in the selected subset of most likely signatures.

Claim 8

In a system for wireless transmitter location finding, a method for selecting from a set of calibrated transmitter locations a set of most likely locations, the method comprising: measuring at a first base station a transmitter signal signature R; measuring at a second base station a transmitter signal signature R'; calculating a difference between a function L R and each function L R .sbsb.i in a set of functions L R .sbsb.1, . . . , L R .sbsb.M, where the function L R represents how signature R compares to a set of first base station calibrated signatures which corresponds to the set of calibrated locations, and where the functions L R .sbsb.1, . . . , L R .sbsb.M represent how each signature in a set of likely first calibrated signatures compares to the set of calibrated signatures; calculating a difference between a function L R' and each function L R' .sbsb.i in a set of functions L R' .sbsb.1, . . . , L R' .sbsb.M, where the function L R represents how signature R' compares to a set of second base station calibrated signatures which corresponds to the set of calibrated locations, and where the functions L R' .sbsb.1, . . . , L R' .sbsb.M represent how each signature in a set of likely second calibrated signatures compares to the set of second calibrated signatures; selecting from the sets of first and second likely signatures a subset of most likely common signatures, such that, for each most likely signature R k , and for each most likely signature R' k , an arithmetic combination of the calculated difference between the functions L R and L R .sbsb.k, and the calculated difference between the function L R and L R .sbsb.k, is smaller than a predetermined threshold; and identifying a subset of the set of calibrated transmitter locations, wherein each location in the subset corresponds to a signature in the selected subset of most likely signatures.

Claim 9

The method of claim 6 wherein the function L R evaluated at a calibrated location i is a function of the cosines of the principle angles between the transmitter signature R and a calibrated signature U i .

Claim 10

The method of claim 6 wherein the function L R evaluated at a calibrated location i is a trace of a projection of R onto a subspace spanned by a calibrated signature U i .

Claim 11

The method of claim 6 wherein the difference between the function L R and each function L R .sbsb.i is calculated by calculating a sum of squared distances between L R and L R .sbsb.i.

Claim 12

The method of claim 6 wherein the difference between the function L R and each function L R .sbsb.i is calculated by calculating the Kullback-Liebler distance between L R and L R .sbsb.i.