System and method of passive and active scanning of WLAN-enabled access points to estimate position of a WLAN positioning device
Systems and methods of passive and active scanning of WLAN-enabled access points to estimate position of a WLAN positioning device. A device estimates the position of itself. The device includes a WLAN radio module for receiving WLAN signals, extraction logic for extracting information from said received WLAN signals to identify the WLAN APs, and logic to cooperate with a WLAN-based positioning system. The WLAN radio module includes a phase for active scanning of WLAN APs in range of said device and a phase of passive scanning of WLAN APs in range of said device, and the passive scanning phase scans only a pre-determined and selected subset of WLAN channels. Under certain embodiments, the WLAN radio module includes a passive scanning phase that simultaneously scans multiple WLAN channels.
1. A device for estimating the position of itself in response to gathering wireless signal information from WLAN access points (APs), said device comprising: a WLAN radio module for receiving WLAN signals transmitted by WLAN APs in range of said device; scan logic to cause the WLAN radio module to scan for WLAN signals transmitted by WLAN APs in range of said device, wherein the scan logic stops the scanning after detecting at least a threshold number of WLAN APs to locate the device, wherein the threshold number is selected based on a desired position estimate accuracy; extraction logic for extracting information from received WLAN signals to identify the WLAN APs; and logic to cooperate with a WLAN based positioning system to estimate the position of the device based at least in part on the extracted information identifying the WLAN APs in the range of said device.
2. The device of claim 1 , wherein the WLAN APs are capable of transmitting on a set of WLAN channels and said WLAN radio module scans multiple WLAN channels in parallel during the scanning.
3. The device of claim 1 , wherein the scan logic causes the scanning to be performed when the device is not associated with any WLAN AP.
4. The device of claim 1 , wherein the scan logic causes a frequency of the scan to be reduced to minimize power consumption when the device is associated with a WLAN AP.
5. A device for estimating the position of itself in response to gathering wireless signal information from WLAN access points (APs), said device comprising:
a WLAN radio module for receiving WLAN signals transmitted by WLAN APs in range of said device, wherein the WLAN APs are capable of transmitting on a set of WLAN channels;
scan logic to cause the WLAN radio module to scan for WLAN signals transmitted by WLAN APs in range of said device, wherein the scan logic conducts the scanning based on how commonly a WLAN channel is used in at least one selected geographical region;
extraction logic for extracting information from received WLAN signals to identify the WLAN APs; and
logic to cooperate with a WLAN-based positioning system to estimate the position of the device based at least in part on the extracted information identifying the WLAN APs in the range of said device.
6. The method of claim 5 , wherein the scan logic scans more commonly used WLAN channels more frequently than WLAN channels less commonly used in the at least one selected geographic region.
7. The method of claim 5 , wherein the scan logic causes the WLAN radio module to perform a scanning sequence which includes:
an initial phase in which the WLAN radio module scans only a subset of said set of WLAN channels, wherein the WLAN channels of the subset are based on WLAN channels that are most commonly used in the at least one selected geographic region, and
a subsequent phase following the initial phase in which the WLAN radio module scans WLAN channels in addition to those in the subset of WLAN channels.
8. The device of claim 5 , wherein said WLAN radio module scans multiple WLAN channels in parallel during the scanning.
9. The device of claim 5 , wherein the scan logic causes the scanning to be performed when the device is not associated with any WLAN AP.
10. The device of claim 5 , wherein the scan logic causes a frequency of the scan to be reduced to minimize power consumption when the device is associated with a WLAN AP.