# US 10,484,814 B2 · Direction finding and FTM positioning in wireless local area networks > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,484,814 B2 - Document ID: US10484814B2 - Status: Granted - Kind: B2 - Application number: 15/121,049 - Filed: 2015-02-24 - Published: 2016-12-15 - Granted: 2019-11-19 - Earliest claimed: 2014-02-25 - Assignees: Mediatek Inc. - Applicants: Mediatek Inc. - Inventors: James June-Ming Wang; Jianhan Liu; Thomas Edward Pare, Jr.; Tianyu Wu; Gabor Bajko; Yung-Ping Hsu - Web page: https://patentgrep.com/patent/US10484814B2 ## CPC - H04W 4/021: Services related to particular areas, e.g. point of interest [POI] services, venue services or geofences - G01S 1/08: Systems for determining direction or position line - G01S 3/14: Systems for determining direction or deviation from predetermined direction {(aerial arrangements for changing or varying the orientation or the shape of the directional pattern H01Q3/00; combinations of different interacting aerial units for giving a desired directional characteristic H01Q21/29; aerials or aerial systems providing at least two radiation patterns H01Q25/00)} - G01S 3/74: Multi-channel systems specially adapted for direction-finding, i.e. having a single antenna system capable of giving simultaneous indications of the directions of different signals (systems in which the directions of different signals are determined sequentially and displayed simultaneously G01S3/04, G01S3/14) - G01S 5/0252: {Radio frequency fingerprinting} - G01S 5/06: Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements (G01S5/12 takes precedence) - G01S 5/12: by co-ordinating position lines of different shape, e.g. hyperbolic, circular, elliptical or radial - G01S 13/825: {with exchange of information between interrogator and responder} - H04L 5/005: {of common pilots, i.e. pilots destined for multiple users or terminals} - H04W 4/023: {using mutual or relative location information between multiple location based services [LBS] targets or of distance thresholds} - H04W 4/33: for indoor environments, e.g. buildings - H04W 24/10: Scheduling measurement reports {; Arrangements for measurement reports} - H04W 64/00: Locating users or terminals {or network equipment} for network management purposes, e.g. mobility management - H04W 84/12: WLAN [Wireless Local Area Networks] - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A method of combined direction finding (DF) and fine timing measurement (FTM) positioning in a wireless location area network (WLAN) is proposed. A multiple antenna IEEE 802.11 transmitting device (AP) can transmit signal preamble containing multiple Long Training Field (LTF) symbols in a radio frame from multiple antennas, which allows a receiving device (STA) to resolve multiple DF sounding signals transmitted from the multiple antennas and thereby estimating angle of departure (AoD). On the other hand, the AP can estimate angle of arrival (AoA) from radio signals transmitted from the STA. When the radial resolution error of AoD or AoA positioning increases, DF positioning and fine-timing measurement (FTM) ranging can be jointly applied to reduce the radial resolution error and extends the AoD/AoA service area with positing accuracy. ## Claims ### Claim 1 A method comprising: (a) receiving a plurality of direction finding (DF) sounding signals transmitted from a first wireless device via multiple antenna by a second wireless device in a wireless local area network (WLAN); (b) estimating an angle of departure (AoD), which is an azimuth angle of the first wireless device from the second wireless device, based on the plurality of DF sounding signals; (c) determining a location of the second wireless device based on the estimated AoD; (d) when a radial resolution error of the AoD estimation is larger than a threshold, performing a fine-timing measurement (FTM) procedure with the first wireless device to determine a radial distance between the second wireless device and the first wireless device through transmitting an FTM request to the first wireless device by the second wireless device; and (e) updating the location of the second wireless device based on both the estimated AoD and the radial distance determined by the FTM procedure. ### Claim 2 (depends on 1) The method of claim 1, further comprising: obtaining location information, antenna platform orientation information, and antenna positions and/or spatial signature of the multiple antennas of the first wireless device. ### Claim 3 (depends on 1) The method of claim 1, further comprising: receiving a null data packet announcement (NDPA) frame from the first wireless device indicating the immediate subsequent transmission of the DF sounding signals. ### Claim 4 (depends on 1) The method of claim 1, further comprising: receiving a fine-timing measurement (FTM) frame from the first wireless device, wherein an indication field of the FTM frame is set to a predefined value. ### Claim 5 (depends on 1) The method of claim 1, wherein the radial resolution error is based on an AoD service area provided by the first wireless device. ### Claim 6 (depends on 1) The method of claim 1, wherein the radial resolution error is determined based on an offset angle of the second wireless device relative to an antenna boresight of the antenna platform of the first wireless device. ### Claim 7 (depends on 1) The method of claim 1, wherein the radial resolution error is determined based on the distance between the second wireless device and the first wireless device. ### Claim 8 (depends on 1) The method of claim 1, wherein the radial resolution error is determined based on received signal strength indicator (RSSI) information. ### Claim 9 (depends on 1) The method of claim 1, where the second wireless device first performs the FTM ranging in (d) before performing the AoD estimate in (a) and (b). ### Claim 10 (depends on 9) The method of claim 9, where FTM frames during the FTM ranging in (d) contain multiple long training field (LTF) symbols for the subsequent AoD estimate, and wherein the subsequent AoD is indicated by an indicator in an FTM frame set to a pre-determined value. ### Claim 11 A wireless station comprising: a receiver that receives a plurality of direction finding (DF) sounding signals transmitted from an access point (AP) station via multiple antennas in a wireless local area network (WLAN); a storage device, arranged to store a program code; and a processor, arranged to execute the program code; wherein when loaded and executed by the processor, the program code instructs the processor to execute the following steps: estimating an AoD, which is an azimuth angle of the station from the AP, based on the plurality of DF sounding signals; determining a location of the station based on the estimated AoD; when a radial resolution error is larger than a threshold, performing a fine-timing measurement (FTM) procedure with the AP through transmitting an FTM request to the AP to determine a radial distance between the station and the AP; and updating the location of the station based on both the estimated AoD and the radial distance determined by the FTM procedure. ### Claim 12 (depends on 11) The wireless station of claim 11, wherein the receiver obtains AP location information, AP antenna platform orientation information, and antenna position information of the multiple antennas. ### Claim 13 (depends on 11) The wireless station of claim 11, wherein the receiver also receives a null data packet announcement (NDPA) frame from the AP station indicating the immediate subsequent transmission of the DF sounding signals. ### Claim 14 (depends on 11) The wireless station of claim 11, wherein the receiver also receives a fine-timing measurement (FTM) request frame from the AP station indicating the transmission of the DF sounding signals, wherein a status indication field of the FTM request frame is set to a predefined value.