# US 11,906,649 B2 · Systems and methods for precise radio frequency localization of wireless nodes including a wireless arbitrary device using time difference of arrival > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,906,649 B2 - Document ID: US11906649B2 - Status: Granted - Kind: B2 - Application number: 17/371,987 - Filed: 2021-07-09 - Published: 2023-01-12 - Granted: 2024-02-20 - Earliest claimed: 2021-07-09 - Assignees: ZaiNar, Inc. - Applicants: ZaiNar, Inc. - Inventors: Mark Bilstad; Tommi Ylamurto; Manu Seth - Web page: https://patentgrep.com/patent/US11906649B2 ## CPC - 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 5/10: Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements {, e.g. omega or decca systems}(G01S5/12 takes precedence {; beacons and receivers cooperating therewith G01S1/306, G01S1/308}) - G01S 5/017: {Detecting state or type of motion} - G01S 5/02216: {Timing or synchronisation of the receivers} - G01S 5/0284: {Relative positioning} - H04W 64/006: {with additional information processing, e.g. for direction or speed determination} - G01S 5/02: using radio waves (using satellite radio beacon systems for determining position G01S19/00) - G01S 5/0205: {Details} - H04W 84/12: WLAN [Wireless Local Area Networks] - 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 - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract In one embodiment, an asynchronous wireless system for localization of nodes comprises a first wireless node being configured to receive a first communication from a third wireless node having an unknown location, to determine time difference of arrival (TDoA) information of the reception of the first communication between each of the first and a second wireless node, to determine TDoA ranging including a relative or absolute position of the third wireless node using the time difference of arrival information, and to synchronize the first and second wireless nodes based on a second communication with the synchronization being decoupled in time from the first communication. In another embodiment, a computer implemented method comprises receiving, with first and second wireless anchor nodes, packets from a wireless arbitrary device and performing time difference of arrival ranging upon reception of the packets between each of the first and the second wireless anchor nodes. ## Claims ### Claim 1 A computer implemented method for a time difference of arrival (TDoA) ranging of wireless nodes in a wireless network architecture, comprising: creating multiple distance estimate candidates between a tracker device have an unknown location and a first wireless node by using a known signal travel time between the first wireless node and a second wireless node; obtaining, with the first wireless node, a receive time stamp of reception of a transmission from the tracker device; obtaining, with the second wireless node, a receive time stamp of reception of the transmission from the tracker device; obtaining, with the first wireless node, a receive time stamp of reception of a transmission from the second wireless node; and generating a clock frequency offset estimation from the first wireless node and a receiver state dependent delay of the first wireless node. ### Claim 2 (depends on 1) The computer implemented method of claim 1, further comprising: obtaining first channel state information of the first wireless node upon reception of the transmission from the tracker device; obtaining second channel state information of the first wireless node upon reception of the transmission from the second wireless node; and generating a combined channel state information based on the first and second channel state information from the reception of the transmissions from the tracker device and the second wireless node. ### Claim 3 (depends on 1) The computer implemented method of claim 1, wherein a correct direct path from the second wireless node to the first wireless node is estimated using the known signal travel time between the first and second wireless nodes, the receive time stamp of the first wireless node, a transmit time stamp for a transmission of the second wireless node, and a measured history of a clock offset between the first and second wireless nodes. ### Claim 4 (depends on 1) The computer implemented method of claim 1, wherein some of the distance estimate candidates are removed when the distance estimate candidates are not between predetermined limits. ### Claim 5 (depends on 4) The computer implemented method of claim 4, wherein predetermined limits are calculated from known locations of the first and second wireless nodes and from a shape of a space where the tracker device is known to be. ### Claim 6 (depends on 2) The computer implemented method of claim 2, wherein the combined channel state information is formed from a list of path distances from the second wireless node ordered from shortest to longest and containing only elements near a strongest path element from the first wireless node, from list of path distances from the tracker device ordered from shortest to longest and containing only elements near the strongest path element from the second wireless node, and from list of possible distances between the second wireless node and the tracker device. ### Claim 7 (depends on 1) The computer implemented method of claim 1, wherein receiver and transceiver delays for the second wireless node are taken from a table containing delays previously measured for all transceiver states. ### Claim 8 (depends on 1) The computer implemented method of claim 1, further comprising: reporting, with the tracker device, an identifier that can be used to find previously measured transmitter or receiver frequency responses in a list. ### Claim 9 (depends on 8) The computer implemented method of claim 8, wherein the identified transmitter or receiver frequency response is used to adjust channel state information of the first and second wireless nodes.