Satellite Subset Selection

• US 20130002485A1
• Filed: 01/05/2012
• Published: 01/03/2013
• Est. Priority Date: 01/05/2011
• Status: Active Grant

• Current Assignee: Qualcomm technologies international, ltd. (Qualcomm, Inc.)
• Original Assignee: Cambridge Silicon Radio Limited (Qualcomm, Inc.)
• Inventors: Pratt, Anthony Richard, Jarvis, Murray Robert
• Granted Patent: US 9,158,002 B2
• Time in Patent Office: Days
• US Class Current: 342/357.67
• CPC Class Codes: G01S 19/28 Satellite selection
• CPC Class Codes: G01S 19/42 Determining position

Abstract

Apparatus for calculating the location of a receiver by means of a location algorithm that generates a receiver location in dependence on signalling events received by that receiver from a set of satellites, the apparatus being arranged to select, from a constellation of satellites visible to the receiver, the set of satellites to use in the location algorithm in dependence on an effect that it is estimated using that set of satellites will have on the capability of the location algorithm to generate an accurate location for the receiver.

Claims

1. An apparatus for calculating the location of a receiver by means of a location algorithm that generates a receiver location in dependence on signalling events received by that receiver from a set of satellites, the apparatus being arranged to select, from a constellation of satellites visible to the receiver, the set of satellites to use in the location algorithm in dependence on an effect that it is estimated using that set of satellites will have on the capability of the location algorithm to generate an accurate location for the receiver.

2. An apparatus as claimed in claim 1, wherein the apparatus is arranged to estimate the effect that using the set of satellites will have on the capability of the location algorithm to generate an accurate location for the receiver in dependence on a convergence zone associated with that set of satellites.

3. An apparatus as claimed in claim 1, wherein the location algorithm generates the receiver location in dependence on an estimated location of the receiver, the apparatus being arranged to estimate the effect that the set of satellites will have on the capability of the location algorithm to generate an accurate location for the receiver in dependence on an error associated with the estimated location.

4. An apparatus as claimed in claim 1, wherein the location algorithm generates the receiver location in dependence on an estimated transmission time of the signalling events, the apparatus being arranged to estimate the effect that the set of satellites will have on the capability of the location algorithm to generate an accurate location for the receiver in dependence on an error associated with the estimated transmission time.

5. An apparatus as claimed in claim 1, wherein the apparatus is arranged to calculate the location of the receiver by performing two or more iterations of the location algorithm, the apparatus being arranged to select a first set of satellites to use in a first iteration of the algorithm and to select a second, different set of satellites for a subsequent iteration of the algorithm.

6. An apparatus as claimed in claim 5, wherein the apparatus is arranged to, select the first set of satellites to comprise a first number of satellites and to select the second set of satellites to comprise a second number of satellites, said second number being higher than said first number.

7. An apparatus as claimed in claim 5, wherein the apparatus is arranged to select the first set of satellites to be the set associated with the maximum convergence zone achievable by means of the constellation of visible satellites.

8. An apparatus as claimed in claim 5, wherein the apparatus is arranged to select the first set of satellites to be associated with a larger convergence zone than the second set of satellites.

9. An apparatus as claimed in claim 5, wherein the apparatus is arranged to select the second set of satellites to generate a more accurate location for the receiver than the first set of satellites.

10. An apparatus as claimed in claim 1, wherein the apparatus is arranged to select the set of satellites by:

forming a candidate set comprising satellites that are visible to the receiver;

repeatedly identifying which of the satellites in the candidate set is associated with the smallest convergence zone and eliminating that satellite from the candidate set until the candidate set consists of a predetermined number of satellites; and

selecting the set of satellites to comprise the predetermined number of satellites in the candidate set.

11. An apparatus as claimed in claim 1, wherein the apparatus is arranged to select the set of satellites by:

identifying one or more candidate sets of satellites that could be formed from the constellation of satellites visible to the receiver and used to calculate a location for the receiver;

determining a convergence zone associated with each of the candidate sets; and

selecting as the set of satellites the candidate set associated with the largest convergence zone.

12. An apparatus as claimed in claim 1, wherein the apparatus is arranged to select the set of satellites to consist of a predetermined number of satellites in the set of visible satellites that have the highest levels of elevation relative to the receiver.

13. An apparatus as claimed in claim 1, wherein the apparatus is arranged to select the set of satellites to consist of a predetermined number of satellites in the set of visible satellites that have the lowest line-of-sight velocities.

14. An apparatus as claimed in claim 12, wherein the apparatus is arranged to designate one of the set of satellites as a reference satellite.

15. A method for calculating the location of a receiver by means of a location algorithm that generates a receiver location in dependence on signalling events received by that receiver from a set of satellites, the method comprising selecting, from a constellation of satellites visible to the receiver, the set of satellites to use in the location algorithm in dependence on an effect that it is estimated using that set of satellites will have on the capability of the location algorithm to generate an accurate location for the receiver.

16. A computer-readable medium encoded with instructions, that when executed by an apparatus for calculating the location of a receiver by means of a location algorithm that generates a receiver location in dependence on signalling events received by that receiver from a set of satellites causes the apparatus to select, from a constellation of satellites visible to the receiver, the set of satellites to use in the location algorithm in dependence on an effect that it is estimated using that set of satellites will have on the capability of the location algorithm to generate an accurate location for the receiver.