Secure wireless user localization scheme using transmission range variation

1. A method for determining the location of a wireless device in a wireless network, comprising the steps of:

transmitting to said wireless device from a plurality of wireless network access points a plurality of encoded signals at a plurality of different transmission power levels;

receiving from said wireless device a set of encoded signals detected by said wireless device from among said plurality of transmitted encoded signals; and

determining the location of said wireless device as a function of said set of encoded signals received from said wireless device.

2. The method of claim 1 , wherein said plurality of wireless network access points comprises at least three wireless network access points.

3. The method of claim 2 , wherein said wireless network access points are deployed at the vertex of an equilateral triangle with the length of a side equal to the maximum transmission radius of an access point.

4. The method of claim 1 , wherein each of said plurality of encoded signals uniquely identifies a particular wireless network access point from which that one of said plurality of encoded signals was transmitted, and a transmission power level at which that one of said plurality of encoded signals was transmitted.

5. The method of claim 1 , wherein transmission power level and signal encoding instructions are sent to each wireless network access point by an access point controller.

6. The method of claim 5 , wherein said access point controller includes a location database storing location information of access points within said wireless network.

7. A system for determining the location of a wireless device within a wireless network, comprising:

a plurality of wireless network access points deployed at predetermined locations in said wireless network;

an access point controller having a database containing location and transmission power range capability of each of said access points; and

a router for enabling said access point controller to communicate with said access points; wherein

said access point controller issues commands to each of said access points to transmit a plurality of encoded signals at various transmission power levels within said transmission power range capability, and issues a command to said wireless device to collect detected encoded signals over a predetermined period of time and to transmit to said access point controller the collected encoded signals, whereby said access point controller determines a location of said wireless device based on the collected encoded signals received from the wireless device and information contained in said database.

8. The system of claim 7 , wherein said plurality of wireless network access points comprises at least three wireless network access points.

9. The system of claim 8 , wherein said wireless network access points are deployed at the vertex of an equilateral triangle with the length of a side equal to the maximum transmission radius of an access point.

10. The system of claim 7 , wherein each of said plurality of encoded signals uniquely identifies a particular wireless network access point from which that one of said plurality of encoded signals was transmitted, and a transmission power level at which that one of said plurality of encoded signals was transmitted.

11. The system of claim 7 , wherein transmission power level and signal encoding instructions are sent to each wireless network access point by said access point controller.

12. A method of localization of a wireless device in a wireless network, comprising the steps of:

initializing a localization query from an access point controller to said wireless device;

receiving a localization request response from said wireless device;

instructing a plurality of wireless network access points to transmit encoded transmission power level signals;

instructing said wireless device to collect detected encoded transmission power level signals over a predetermined period of time;

receiving from said wireless device a collection of detected encoded transmission power level signals after expiration of said predetermined period of time; and

estimating the location of said wireless device in said wireless network based on the received collection of encoded transmission power level signals.

13. The method of claim 12 , further comprising the step of informing said wireless device of its estimated location within said wireless network.

14. A method of localization of a wireless device in a wireless network, comprising the steps of:

receiving a localization request from said wireless device;

instructing a plurality of wireless network access points to transmit encoded transmission power level signals;

instructing said wireless device to collect detected encoded transmission power level signals over a predetermined period of time;

receiving from said wireless device a collection of detected encoded transmission power level signals after expiration of said predetermined period of time;

estimating the location of said wireless device in said wireless network based on the received collection of encoded transmission power level signals; and

informing said wireless device of its estimated location within said wireless network.

15. The method of claim 1 , wherein said step of transmitting to said wireless device from a plurality of wireless network access points a plurality of encoded signals at a plurality of different transmission power levels, includes transmitting to said wireless device from each of said plurality of wireless network access points a plurality of encoded signals at a plurality of different transmission power levels, and wherein each of said plurality of wireless network access points transmits at a plurality of different transmission power levels and transmits a plurality of different encoded signals corresponding to different ones of said transmission power levels.

16. The method of claim 15 , wherein said plurality of encoded signals include a plurality of nonces, with each nonce unique to a respective one of said wireless network access points and associated with a particular power level.

17. The method of claim 4 , wherein said step of transmitting to said wireless device from a plurality of wireless network access points a plurality of encoded signals at a plurality of different transmission power levels, includes transmitting to said wireless device from each of said plurality of wireless network access points a plurality of encoded signals at a plurality of different transmission power levels, and wherein each of said plurality of wireless network access points transmits at a plurality of different transmission power levels and transmits a plurality of different encoded signals corresponding to different ones of said transmission power levels.

18. The method of claim 17 , wherein said plurality of encoded signals include a plurality of nonces, with each nonce unique to a respective one of said wireless network access points and associated with a particular power level.

19. The method of claim 7 , wherein said access point controller issues commands to each of said access points to transmit said plurality of encoded signals, with each of said plurality of encoded signals corresponding to different ones of a plurality of transmission power levels.