Abstract: Methods and apparatus are disclosed for determining a confidence ellipse (CEP) that encompasses possible locations of one or more target devices, which is a condition that may exist when a wireless device (WD) is initially travelling on an effectively straight path. The method includes calculating the deviation from the straight line path for the WD. If it is determined that the path is effectively a straight line, the calculation of the sum of squared residuals (SSRs) is extended so as to encompass two possible minima. A grid is then derived comprising all ground plane points, where the SSR values are (i) less than a boundary value and (ii) include the SSRs corresponding to the two possible minima. The grid is converted into a polygon, which is further converted into an ellipse displayed as the CEP. The CEP encompasses two possible locations of a target device.

Abstract: A method for determining an angle of arrival (AoA) of a radio frequency (RF) signal received at an antenna array. The method includes determining theoretical signals to be received at an antenna array having first and second antenna pairs. Antennas of the first antenna pair are offset from each other by a first offset angle and antennas of the second antenna pair are offset from each other by a second offset angle. A look-up table is generated based on the theoretical signals. An RF signal is received at each antenna pair and the antenna outputs in each antenna pair are combined to produce first and second difference values. The first and second difference values are compared to theoretical difference values in the look-up table. A measured AoA of the RF signal is determined based on the comparison of the first and second difference values to the theoretical difference values.

Abstract: A method for determining a geo-location of a target station. The method includes transmitting a plurality of ranging packets to a target station and receiving a plurality of response packets transmitted by the target station in response. A plurality of round-trip times (RTTs) are determined based on the ranging packets and the response packets. A plurality of angles of arrival (AOAs) are determined based on the response packets. First and second pluralities of squared residuals are calculated for the plurality of RTTs and the plurality of AOAs, respectively. A third plurality of squared residuals is generated by summing the first and second pluralities. A minimum of a sum of the third plurality is calculated to identify best-fit location parameters for the target station. A circular error probability (CEP) ellipse is generated using the best-fit location parameters and a geo-location of the target station is determined based on the CEP ellipse.

Abstract: A method for determining a geo-location of a target station. The method includes transmitting a plurality of ranging packets to a target station and receiving a plurality of response packets transmitted by the target station in response. A plurality of round-trip times (RTTs) are determined based on the ranging packets and the response packets. A plurality of angles of arrival (AOAs) are determined based on the response packets. First and second pluralities of squared residuals are calculated for the plurality of RTTs and the plurality of AOAs, respectively. A third plurality of squared residuals is generated by summing the first and second pluralities. A minimum of a sum of the third plurality is calculated to identify best-fit location parameters for the target station. A circular error probability (CEP) ellipse is generated using the best-fit location parameters and a geo-location of the target station is determined based on the CEP ellipse.

Abstract: A method and devices are disclosed for geo-location of wireless local area network (WLAN) devices. According to one aspect, a method for determining a corrected round trip times (RTT) resulting from communication with a WD is provided. The WD is configured with one or two short interframe spacings (SIFS). The method includes performing RTT measurements at successive times. The method includes determining a presence of one or two modes based at least in part on peaks of a kernel density estimation (KDE) surface. The KDE surface is determined from the RTT measurements. When there is only one mode, a corrected RTT is determined based on the RTT measurements and a first SIFS. When there are two modes, a corrected RTT is determined based on the RTT measurements and the first SIFS plus an SIFS offset (?), ? being based at least in part on a difference between the two modes.

Abstract: A method and devices are disclosed for geo-location of wireless local area network (WLAN) devices. According to one aspect, a method for determining a corrected round trip times (RTT) resulting from communication with a WD is provided. The WD is configured with one or two short interframe spacings (SIFS). The method includes performing RTT measurements at successive times. The method includes determining a presence of one or two modes based at least in part on peaks of a kernel density estimation (KDE) surface. The KDE surface is determined from the RTT measurements. When there is only one mode, a corrected RTT is determined based on the RTT measurements and a first SIFS. When there are two modes, a corrected RTT is determined based on the RTT measurements and the first SIFS plus an SIFS offset (?), ? being based at least in part on a difference between the two modes.

Abstract: A method for determining a geo-location of a target station. The method includes transmitting a plurality of ranging packets to a target station and receiving a plurality of response packets transmitted by the target station in response. A plurality of round-trip times (RTTs) are determined based on the ranging packets and the response packets. A plurality of angles of arrival (AOAs) are determined based on the response packets. First and second pluralities of squared residuals are calculated for the plurality of RTTs and the plurality of AOAs, respectively. A third plurality of squared residuals is generated by summing the first and second pluralities. A minimum of a sum of the third plurality is calculated to identify best-fit location parameters for the target station. A circular error probability (CEP) ellipse is generated using the best-fit location parameters and a geo-location of the target station is determined based on the CEP ellipse.

Abstract: A method for determining a geo-location of a target station. The method includes transmitting a plurality of ranging packets to a target station and receiving a plurality of response packets transmitted by the target station in response. A plurality of round-trip times (RTTs) are determined based on the ranging packets and the response packets. A plurality of angles of arrival (AOAs) are determined based on the response packets. First and second pluralities of squared residuals are calculated for the plurality of RTTs and the plurality of AOAs, respectively. A third plurality of squared residuals is generated by summing the first and second pluralities. A minimum of a sum of the third plurality is calculated to identify best-fit location parameters for the target station. A circular error probability (CEP) ellipse is generated using the best-fit location parameters and a geo-location of the target station is determined based on the CEP ellipse.

Abstract: A method of determining a location of a wireless device. The method includes receiving a plurality of beacons, via a measuring station, transmitted from the wireless device. For each beacon, a Times of Arrival (TOA), a Times of Departure (TOD), and a location of the measuring station is identified. A plurality of split time candidates are calculated based on an orbit period of the measuring station and a plurality of cluster modes are calculated for the identified TOAs. A plurality of optimal split times are selected based on the plurality of split time candidates, the plurality of cluster modes, and a beacon drift. A plurality of circular error probability (CEP) ellipses are generated corresponding to the plurality of optimal split times. The plurality of CEP ellipses are merged and a location of the wireless device is determined based, at least in part, on the merged CEP ellipse.

Abstract: A method of determining a location of a wireless device. The method includes receiving a plurality of beacons, via a measuring station, transmitted from the wireless device. For each beacon, a Times of Arrival (TOA), a Times of Departure (TOD), and a location of the measuring station is identified. A plurality of split time candidates are calculated based on an orbit period of the measuring station and a plurality of cluster modes are calculated for the identified TOAs. A plurality of optimal split times are selected based on the plurality of split time candidates, the plurality of cluster modes, and a beacon drift. A plurality of circular error probability (CEP) ellipses are generated corresponding to the plurality of optimal split times. The plurality of CEP ellipses are merged and a location of the wireless device is determined based, at least in part, on the merged CEP ellipse.

Abstract: A method for determining a geo-location of a target station includes transmitting a plurality of ranging packets to a target station and receiving a plurality of response packets transmitted by the target station. A plurality of round-trip times (RTTs) are determined based on the ranging packets and the response packets. A plurality of angles of arrival (AOAs) are determined based on the response packets. First location vectors are determined based on the pluralities of RTTs and AOAs. Second location vectors are determined based on location parameters of the measuring station and the target station. Squared residual vectors are generated based on the first and second pluralities. A minimum of a sum of the squared residual vectors is calculated to identify best-fit location parameters for the target station. A circular error probability (CEP) ellipse is generated using the best-fit location parameters and a geo-location of the target station is determined.

Abstract: A method and apparatus for measuring the angle of arrival AOA of Wi-Fi packets, using a switched beam antenna SBA is described. Wide antenna beams, quadrants, are selected in turn and a burst of packets is transmitted on each quadrant. The quadrant with the highest average signals strength is selected. Then the narrow antenna beams that make up that selected quadrant are selected, in sequence, and the average signal strength for each narrow beam is recorded. The narrow beam with the highest average signal strength is returned as the AOA. Based upon which narrow beam recorded the highest signal strength, the next sequence of antenna beams is selected. When the SBA is mounted on a mobile platform, the parameters of the transmission bursts are chosen such that the angular error due to cornering of the platform is negligible.

Abstract: A method and devices are disclosed for geo-location of wireless local area network (WLAN) devices. According to one aspect, a method for determining a corrected round trip times (RTT) resulting from communication with a WD is provided. The WD is configured with one or two short interframe spacings (SIFS). The method includes performing RTT measurements at successive times. The method includes determining a presence of one or two modes based at least in part on peaks of a kernel density estimation (KDE) surface. The KDE surface is determined from the RTT measurements. When there is only one mode, a corrected RTT is determined based on the RTT measurements and a first SIFS. When there are two modes, a corrected RTT is determined based on the RTT measurements and the first SIFS plus an SIFS offset (?), ? being based at least in part on a difference between the two modes.

Abstract: A method and apparatus for measuring confidence in the angle of arrival AOA of Wi-Fi packets, from a target station, using a switched beam antenna SBA is described. AOAs can be inaccurate due to reflections and multipaths. To assess the confidence of an AOA, each AOA is first converted to relative north, AOAt, and checked that at least M AOAs have been received in time T. If so, the standard deviation is calculated for of all the AOAs received during previous time T. If the standard deviation is less than a preset value, and the receiving station is not stationary, then the AOAt is considered to have high confidence and may be used to calculate the target station location. A vector display of the AOA uses the standard deviation to display the AOA vector as a varying length or a varying beamwidth corresponding to the standard deviation.

Abstract: A method in a first wireless device (WD) is described. The method includes determining one round trip time (RTT) of a first set of RTTs. The method also includes, at set intervals (TK), determining a set of mode peaks of the first set of RTTs, determining that the first SIFS mode has the highest mode peak of the set of mode peaks, determining that the second SIFS mode has the second highest peak of the set of mode peaks, determining a mode difference (TD), and adjusting the second subset of RTTs at least by adding or subtracting TD to each RTT of the second subset of RTTs. The method also includes determining a second set of RTTs comprising the first subset of RTTs and the adjusted second subset of RTTs, the second set of RTTs corresponding to the adjusted single SIFS mode.

Abstract: A method in a first wireless device (WD) is described. The method includes determining one round trip time (RTT) of a first set of RTTs. The method also includes, at set intervals (TK), determining a set of mode peaks of the first set of RTTs, determining that the first SIFS mode has the highest mode peak of the set of mode peaks, determining that the second SIFS mode has the second highest peak of the set of mode peaks, determining a mode difference (TD), and adjusting the second subset of RTTs at least by adding or subtracting TD to each RTT of the second subset of RTTs. The method also includes determining a second set of RTTs comprising the first subset of RTTs and the adjusted second subset of RTTs, the second set of RTTs corresponding to the adjusted single SIFS mode.

Abstract: A method and apparatus for measuring confidence in the angle of arrival AOA of Wi-Fi packets, from a target station, using a switched beam antenna SBA is described. AOAs can be inaccurate due to reflections and multipaths. To assess the confidence of an AOA, each AOA is first converted to relative north, AOAt, and checked that at least M AOAs have been received in time T. If so, the standard deviation is calculated for of all the AOAs received during previous time T. If the standard deviation is less than a preset value, and the receiving station is not stationary, then the AOAt is considered to have high confidence and may be used to calculate the target station location. A vector display of the AOA uses the standard deviation to display the AOA vector as a varying length or a varying beamwidth corresponding to the standard deviation.

Abstract: A method and apparatus for measuring the angle of arrival AOA of Wi-Fi packets, using a switched beam antenna SBA is described. Wide antenna beams, quadrants, are selected in turn and a burst of packets is transmitted on each quadrant. The quadrant with the highest average signals strength is selected. Then the narrow antenna beams that make up that selected quadrant are selected, in sequence, and the average signal strength for each narrow beam is recorded. The narrow beam with the highest average signal strength is returned as the AOA. Based upon which narrow beam recorded the highest signal strength, the next sequence of antenna beams is selected. When the SBA is mounted on a mobile platform, the parameters of the transmission bursts are chosen such that the angular error due to cornering of the platform is negligible.

Abstract: A method and apparatus for measuring the angle of arrival AOA of Wi-Fi packets, using a switched beam antenna SBA is described. Wide antenna beams, quadrants, are selected in turn and a burst of packets is transmitted on each quadrant. The quadrant with the highest average signals strength is selected. Then the narrow antenna beams that make up that selected quadrant are selected, in sequence, and the average signal strength for each narrow beam is recorded. The narrow beam with the highest average signal strength is returned as the AOA. Based upon which narrow beam recorded the highest signal strength, the next sequence of antenna beams is selected. When the SBA is mounted on a mobile platform, the parameters of the transmission bursts are chosen such that the angular error due to cornering of the platform is negligible.

Abstract: A method and devices are disclosed that locate a target station moving at a constant velocity. A method and devices are disclosed for producing an RTT vector that is based upon the changes in position of the airborne measuring station position and the relative change in position of the target station. In one embodiment, the target station is an access point or station conforming to the IEEE 802.11 Standard and the airborne measuring station may also be a device that conforms to the IEEE 802.11 Standard.