Estimating a location of a mobile device

1. A method for estimating a location of a mobile device in a network, the method comprising:

identifying two or more uniquely identifiable radio frequency sources of the network from signals received by the mobile device at the location;

receiving approximate locations of two or more transmit areas from the uniquely identifiable radio frequency sources;

determining for each signal received by the mobile device one or more parameters that are proportional to a distance between the frequency source originating the signal and the mobile device; and

estimating the location of the mobile device from the approximate locations and the one or more parameters,

wherein at least one of the parameters is a transmit power of the mobile device at the time one of the signals was received.

2. The method of claim 1 , wherein at least one of the parameters is a signal strength measurement (RSSI) of one of the signals, the method further comprising:

receiving a maximal RSSI measurement measured by another mobile device from one of the two or more uniquely identifiable radio frequency sources; and

taking into account the maximal RSSI measurement in estimating the location of the mobile device.

3. The method of claim 2 , wherein the approximate locations are provided as coordinates on axes and estimating the location from the approximate locations and the one or more parameters comprises:

estimating the location as a weighted average of the coordinates on each of the axes, where weights used in calculating the weighted average are linear functions of signal strength measurements of signals from which the mobile device identified the uniquely identifiable radio frequency sources.

4. The method of claim 1 , wherein at least one of the parameters is a time offset gleaned from one of the signals.

5. The method of claim 1 wherein the network is a cellular network, the uniquely identifiable radio frequency sources are base stations of the cellular network having directional antennae, and the transmit areas are directed cells of the cellular network.

6. The method of claim 1 wherein the network is a cellular network, the uniquely identifiable radio frequency sources are base stations of the cellular network having omnidirectional antennae, and the transmit areas are entire cells of the cellular network.

7. The method of claim 1 wherein the network is a wireless local area network, the uniquely identifiable radio frequency sources are access points of the wireless local area network, and the transmit areas are the coverage areas of the access points.

8. A method for assisting a mobile device to estimate its location in a network, the method comprising:

receiving from mobile devices location reports that include locations of the mobile devices, an identification of a uniquely identifiable radio frequency source in the network identified by the mobile devices at the locations, and transmit powers of the mobile devices to the uniquely identifiable radio frequency source at the locations;

constructing from the location reports a radio frequency source profile for the uniquely identifiable radio frequency source, the radio frequency source profile including information based on the transmit powers and including an approximate location of a transmit area for the uniquely identifiable radio frequency source;

receiving from the mobile device a query that identifies the uniquely identifiable radio frequency source; and

in response to the query, transmitting the radio frequency source profile to the mobile device to enable the mobile device to use the approximate location and the information in estimating its location.

9. The method of claim 8 , wherein the information comprises a maximal transmit power of the transmit powers.

10. The method of claim 8 , wherein the information comprises a statistical characteristic of the transmit powers.

11. The method of claim 8 , further comprising:

determining the approximate location as a set of coordinates on perpendicular axes, wherein the set of coordinates represents statistical characteristics of the locations.

12. The method of claim 8 , wherein the network is a cellular network, the uniquely identifiable radio frequency source is a base station of the cellular network having directional antennae, and the transmit area is a directed cell of the cellular network.

13. The method of claim 8 , wherein the network is a cellular network, the uniquely identifiable radio frequency source is a base station of the cellular network having an omnidirectional antenna, and the transmit area is an entire cell of the cellular network.

14. The method of claim 8 , wherein the network is a wireless local area network, the uniquely identifiable radio frequency source is an access point of the wireless local area network, and the transmit area is a coverage area of the access point.

15. A location approximation system comprising:

a database to store a radio frequency source profile for a uniquely identifiable radio frequency source of a first network, the radio frequency source profile including an approximate location of a transmit area for the uniquely identifiable radio frequency source, wherein the uniquely identifiable radio frequency source is able to communicate with an infrastructure network;

a server coupled to the database; and

means for communicating with the infrastructure network,

wherein the server is arranged to receive from mobile devices location reports that include locations of the mobile devices, an identification of the uniquely identifiable radio frequency source identified by the mobile devices at the locations, and transmit powers of the mobile devices to the uniquely identifiable radio frequency source at the locations,

wherein the server is further arranged to construct the radio frequency source profile from the location reports,

wherein the radio frequency source profile includes information related to the transmit powers, and

wherein, in response to receipt by the server of a query from a mobile device identifying the uniquely identifiable radio frequency source, the server is arranged to transmit the radio frequency source profile to the mobile device to enable the mobile device to use the approximate location and the information in estimating its location.

16. The location approximation system of claim 15 , wherein the information comprises a maximal transmit power of the transmit powers.

17. The location approximation system of claim 15 , wherein the information comprises a statistical characteristic of the transmit powers.

18. The location approximation system of claim 15 , wherein the server is further adapted to determine the approximate location as a set of coordinates on perpendicular axes, wherein the set of coordinates represents statistical characteristics of the locations.

19. The location approximation system of claim 15 , wherein the network is a cellular network, the uniquely identifiable radio frequency source is a base station of the cellular network having directional antennae, and the transmit area is a directed cell of the cellular network.

20. The location approximation system of claim 15 , wherein the network is a cellular network, the uniquely identifiable radio frequency source is a base station of the cellular network having an omnidirectional antenna, and the transmit area is an entire cell of the cellular network.

21. The location approximation system of claim 15 , wherein the network is a wireless local area network, the uniquely identifiable radio frequency source is an access point of the wireless local area network, and the transmit area is a coverage area of the access point.