Method and apparatus for positioning using quasi-fingerprinting
View Patent ↗According to certain aspects, the invention provides a method of achieving near-fingerprinting accuracy without fingerprinting database costs, via parametric representation of training data. In embodiments, this is achieved by using a parametric representation for the training data and limiting the region of applicability of the parametric model in order to mimic fingerprinting. According to certain additional aspects, an algorithm according to principles of the invention includes two separate parts, training and positioning. Training encompasses the derivation of the parametric model and region of applicability. This comprises access point position, propagation model and the window of applicability. Positioning covers the use of the derived model along with a set of fresh observations to generate a position estimate.
1. A method comprising:
receiving measurement data for a wireless transmitter at a server;
calculating geographic contours of a window of applicability that circumscribes positions at which the measurement data was taken, the geographic contours defining a shape of the window of applicability;
calculating a set of signal power radii that respectively define positional contours at least partially around a nominal position of the wireless transmitter for a plurality of different signal strength values; and
producing a quasi-fingerprint for the wireless transmitter comprising the window of applicability and the set of signal power radii.
2. A method according to claim 1 , wherein the measurement data comprises a plurality of different measurements, wherein each measurement includes a signal strength value of a signal received by a wireless receiver from the wireless transmitter and a corresponding position of the wireless receiver.
3. A method according to claim 2 , wherein the wireless receivers have positioning functionality.
4. A method according to claim 3 , wherein the positioning functionality includes GNSS positioning functionality, and the corresponding position is a GNSS computed position.
5. A method according to claim 2 , wherein calculating geographic contours of the applicability window includes fitting the shape to the measurement data such that the geographic contours overlie at least one of the corresponding positions.
6. A method according to claim 2 , wherein calculating geographic contours of the applicability window includes fitting the shape to the measurement data such that the geographic contours outlie all of the corresponding positions by at least a margin.
7. A method according to claim 1 , wherein calculating geographic contours of the applicability window includes computing a covariance matrix using the measurement data and using an eigenvector determined from the covariance matrix to identify a primary axis for the shape.
8. A method according to claim 1 , wherein the shape is a rectangle.
9. A method according to claim 1 , wherein the shape is an ellipse.
10. A method according to claim 1 , wherein the wireless transmitter is a Wi-Fi access point.
11. A method according to claim 1 , further comprising calculating geographic contours of a second window of applicability that circumscribes positions at which additional measurement data was taken, the second window of applicability being disconnected from the window of applicability, wherein the quasi-fingerprint further includes the second window of applicability.
12. A server computer that implements a wireless positioning method, the method comprising:
receiving measurement data for a wireless transmitter;
calculating geographic contours of a window of applicability that circumscribes positions at which the measurement data was taken, the geographic contours defining a shape of the window of applicability;
calculating a set of signal power radii that respectively define positional contours at least partially around a nominal position of the wireless transmitter for a plurality of different signal strength values; and
producing a quasi-fingerprint for the wireless transmitter comprising the window of applicability and the set of signal power radii.
13. A server computer according to claim 12 , wherein the measurement data comprises a plurality of different measurements, wherein each measurement includes a signal strength value of a signal received by a wireless receiver from the wireless transmitter and a corresponding position of the wireless receiver.
14. A server computer according to claim 13 , wherein the wireless receivers have positioning functionality.
15. A server computer according to claim 14 , wherein the positioning functionality includes GNSS positioning functionality, and the corresponding position is a GNSS computed position.
16. A server computer according to claim 13 , wherein calculating geographic contours of the applicability window includes fitting the shape to the measurement data such that the geographic contours overlie at least one of the corresponding positions.
17. A server computer according to claim 13 , wherein calculating geographic contours of the applicability window includes fitting the shape to the measurement data such that the geographic contours outlie all of the corresponding positions by at least a margin.
18. A server computer according to claim 12 , wherein calculating geographic contours of the applicability window includes computing a covariance matrix using the measurement data and using an eigenvector determined from the covariance matrix to identify a primary axis for the shape.
19. A server computer according to claim 12 , wherein the wireless transmitter is a Wi-Fi access point.