# US 12,222,434 B2 · Node positioning > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,222,434 B2 - Document ID: US12222434B2 - Status: Granted - Kind: B2 - Application number: 17/847,176 - Filed: 2022-06-23 - Published: 2022-12-29 - Granted: 2025-02-11 - Earliest claimed: 2021-06-24 - Assignees: Iiwari Tracking Solutions Oy - Applicants: Iiwari Tracking Solutions Oy - Inventors: Jukka Kämäräinen; Pertti Erkkilä - Web page: https://patentgrep.com/patent/US12222434B2 ## CPC - 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 5/02216: {Timing or synchronisation of the receivers} - 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: 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 ## Abstract According to an example aspect of the present invention, there is provided a method comprising obtaining a first length of time, a second length of time, a third length of time, a fourth length of time and a fifth length of time, and determining a time difference of arrival of a signal from a wireless tag between the first and second non-master base stations based on the determined lengths of time. ## Claims ### Claim 1 A method comprising: obtaining a first length of time, limited by receipt of a second message in a first non-master base station and by receipt of a signal from a wireless tag in the first non-master base station, obtaining a second length of time, limited by receipt of the second message in the first non-master base station and by receipt of a first message in the first non-master base station; obtaining a third length of time, limited by receipt of the second message in a second non-master base station and by receipt of the signal from the wireless tag in the second non-master base station, obtaining a fourth length of time, limited by receipt of the second message in the second non-master base station and by receipt of the first message in the second non-master base station and obtaining a fifth length of time, limited by a time of transmission of the first message from a master base station and a time of transmission of the second message, of a same type as the first message, from the master base station, and determining a time difference of arrival of the signal from the wireless tag between the first and second non-master base stations as the third length of time multiplied by a ratio of the fifth length of time and the fourth length of time, to which is added a time of flight at light speed from the master base station to the second non-master base station and from which is subtracted a product of the first length of time and a ratio of the fifth length of time and the second length of time, and from which is subtracted a time of flight at light speed from the master base station to the first non-master base station. ### Claim 2 (depends on 1) The method according to claim 1, wherein the signal from the wireless tag has a spectral width of at least 500 megahertz. ### Claim 3 (depends on 1) The method according to claim 1, further comprising multiplying the determined time difference of arrival of the signal with a time unit. ### Claim 4 (depends on 3) The method according to claim 3, further comprising determining a second and a third time difference of arrival of the signal, between a third and fourth, and a fifth and sixth, non-master base station, respectively. ### Claim 5 (depends on 4) The method according to claim 4, further comprising determining a position estimate of the wireless tag based at least in part on the time difference of arrival of the signal and the second and third time differences of arrival of the signal. ### Claim 6 (depends on 3) The method according to claim 3, wherein the signal from the wireless tag has a spectral width of at least 500 megahertz. ### Claim 7 (depends on 1) The method according to claim 1, further comprising determining a second and a third time difference of arrival of the signal, between a third and fourth, and a fifth and sixth, non-master base station, respectively. ### Claim 8 (depends on 7) The method according to claim 7, wherein the signal from the wireless tag has a spectral width of at least 500 megahertz. ### Claim 9 (depends on 7) The method according to claim 7, further comprising determining a position estimate of the wireless tag based at least in part on the time difference of arrival of the signal and the second and third time differences of arrival of the signal. ### Claim 10 (depends on 9) The method according to claim 9, wherein the signal from the wireless tag has a spectral width of at least 500 megahertz. ### Claim 11 (depends on 1) A non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least: perform the method of claim 1. ### Claim 12 A method comprising: obtaining a first length of time, limited by transmission of a second message from a master base station and by receipt of a signal from a wireless tag in the master base station, obtaining a second length of time, limited by a time of transmission of a first message from a master base station and a time of transmission of the second message, of a same type as the first message, from the master base station; obtaining a third length of time, limited by receipt of the second message in a non-master base station and by receipt of the signal from the wireless tag in the non-master base station, and obtaining a fourth length of time, limited by receipt of the second message in the non-master base station and by receipt of the first message in the non-master base station and obtaining a ratio between the second length of time and the fourth length of time; and determining a time difference of arrival of the signal from the wireless tag between the master base station and the non-master base station as the first length of time from which is subtracted the third length of time multiplied by the ratio, from which is subtracted a time of flight at light speed from the master base station to the non-master base station. ### Claim 13 (depends on 12) The method according to claim 12, further comprising multiplying the determined time difference of arrival of the signal with a time unit. ### Claim 14 (depends on 13) The method according to claim 13, further comprising determining a second and a third time difference of arrival of the signal, between the master base station and a second and third non-master base station, respectively. ### Claim 15 (depends on 14) The method according to claim 14, further comprising determining a position estimate of the wireless tag based at least in part on the time difference of arrival of the signal and the second and third time differences of arrival of the signal. ### Claim 16 (depends on 12) The method according to claim 12, further comprising determining a second and a third time difference of arrival of the signal, between the master base station and a second and third non-master base station, respectively. ### Claim 17 (depends on 16) The method according to claim 16, further comprising determining a position estimate of the wireless tag based at least in part on the time difference of arrival of the signal and the second and third time differences of arrival of the signal. ### Claim 18 (depends on 12) An apparatus comprising at least one processing core, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processing core, cause the apparatus at least to: perform the method of claim 12. ### Claim 19 (depends on 12) A non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least: perform the method of claim 12. ### Claim 20 An apparatus comprising at least one processing core, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processing core, cause the apparatus at least to: obtain a first length of time, limited by receipt of a second message in a first non-master base station and by receipt of a signal from a wireless tag in the first non-master base station, obtain a second length of time, limited by receipt of the second message in the first non-master base station and by receipt of a first message in the first non-master base station; obtain a third length of time, limited by receipt of the second message in a second non-master base station and by receipt of the signal from the wireless tag in the second non-master base station, obtain a fourth length of time, limited by receipt of the second message in the second non-master base station and by receipt of the first message in the second non-master base station and obtain a fifth length of time, limited by a time of transmission of the first message from a master base station and a time of transmission of the second message, of a same type as the first message, from the master base station, and determine a time difference of arrival of the signal from the wireless tag between the first and second non-master base stations as the first length of time multiplied by a ratio of the fifth length of time and the second length of time, to which is added a time of flight at light speed from the master base station to the first non-master base station and from which is subtracted a product of the third length of time and a ratio of the fifth length of time and the fourth length of time, and from which is subtracted a time of flight at light speed from the master base station to the second non-master base station.