Claims
- 1. In a system for wireless transmitter location finding, a method for calculating a set of likely locations of a transmitter, the method comprising:
- (a) measuring at a base station a signal covariance R associated with the transmitter;
- (b) evaluating a function B(.theta.) that measures an energy of the signal covariance R in an angular direction .theta. relative to the base station, wherein the evaluation of B(.theta.) uses an antenna array vector a(.theta.);
- (c) calculating a distance G between the function B(.theta.) and a function B.sub.k (.theta.), where B.sub.k (.theta.) measures an energy of a calibrated signal covariance R.sub.k in the angular direction .theta. relative to the base station, wherein the evaluation of B(.theta.) uses an antenna array vector a(.theta.), and wherein R.sub.k is a calibrated signal covariance associated with a location index k; and
- (d) selecting a set of location indices k such that the distance G between B and B.sub.k is small.
- 2. The method of claim 1 wherein B(.theta.)=a(.theta.).sup.H R a(.theta.) and B.sub.k (.theta.)=a(.theta.).sup.H R.sub.k a(.theta.).
- 3. The method of claim 1 wherein B(.theta.)=a(.theta.).sup.H UU.sup.H a(.theta.) and B.sub.k (.theta.)=a(.theta.).sup.H U.sub.k U.sub.k.sup.H a(.theta.).
- 4. The method of claim 1 wherein the distance G is the squared difference between B and B.sub.k.
- 5. The method of claim 1 wherein the distance G is the Kullback-Liebler distance between B and B.sub.k.
- 6. An apparatus for location finding in a wireless communications system, the apparatus comprising:
- (a) a multichannel receiver for coherently receiving signals originating from a transmitter;
- (b) a signal processor connected to the multichannel receiver for determining a set of likely locations from the received signals; and
- (c) a memory device accessible by the processor for storing signal signature calibration data;
- wherein the signal processor determines the set of likely locations from the received signals in accordance with the following procedure:
- i) determining a signal covariance R from the signals received at the multichannel receiver;
- ii) evaluating a function B(.theta.) that measures an energy of the signal covariance R in an angular direction .theta. relative to the apparatus, wherein the evaluation of B(.theta.) uses an antenna array vector a(.theta.);
- iii) calculating a distance G between the function B(.theta.) and a function B.sub.k (.theta.), where B.sub.k (.theta.) measures an energy of a calibrated signal covariance R.sub.k in the angular direction .theta. relative to the apparatus, wherein an evaluation of B(.theta.) uses an antenna array vector a(.theta.), and wherein R.sub.k is a calibrated signal covariance associated with a location index k; and
- iv) selecting a set of location indices k such that the distance G between B and B.sub.k is small.
- 7. The apparatus of claim 6 wherein B(.theta.)=a(.theta.).sup.H R a(.theta.) and B.sub.k (.theta.)=a(.theta.).sup.H R.sub.k a(.theta.).
- 8. The apparatus of claim 6 wherein B(.theta.)=a(.theta.).sup.H UU.sup.H a(.theta.) and B.sub.k (.theta.)=a(.theta.).sup.H U.sub.k U.sub.k.sup.H a(.theta.).
- 9. The apparatus of claim 6 wherein the distance G is the squared difference between B and B.sub.k.
- 10. The apparatus of claim 6 wherein the distance G is the Kullback-Liebler distance between B and B.sub.k.
Parent Case Info
This application is a continuation-in-part of U.S. patent application Ser. No. 08/780,565, filed Jan. 8, 1997 now U.S. Pat. No. 6,026,304, which is incorporated herein by reference.
US Referenced Citations (11)
Continuation in Parts (1)
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780565 |
Jan 1997 |
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