EP-4740029-A1 - METHOD FOR CLOCK SYNCHRONIZATION VIA DIFFERENTIAL CHANNEL STATE INFORMATION

Abstract

A method includes: based on a synchronization signal transmitted from a master node and received at a sniffer node, recording a partial channel state information characterizing a communication channel between the master node and the sniffer node for a second time period; in response to a localization signal transmitted from a target device, calculating a time bias between the master node and the sniffer node based on a transmit time of the synchronization signal, a third receive time of the synchronization signal at the sniffer node, a channel response characterizing the communication channel for a first time period, and the partial channel state information; and estimating a position of the target device based on a first receive time of the localization signal at the master node, a second receive time of the localization signal at the sniffer node, and the time bias.

Inventors

• YLAMURTO, TOMMI
• KRATZ, Philip, D.

Assignees

• Zainar, Inc.

Dates

Publication Date

20260513

Application Date

20240705

Claims (1)

1. CLAIMS I claim: 1. A method comprising: • at a first node in a set of nodes: o receiving a first signal transmitted from a target device; o recording a first receive time of the first signal at the first node; o transmitting a second signal from the first node; and o recording a transmit time of the second signal from the first node; at a second node in the set of nodes: o receiving the first signal transmitted from the target device; o recording a second receive time of the first signal at the second node; o receiving the second signal transmitted from the first node; o recording a third receive time of the second signal at the second node; and o based on the second signal, recording a first partial channel state information characterizing a communication channel between the first node and the second node for a second time period; accessing a first channel response characterizing the communication channel between the first node and the second node for a first time period preceding the second time period; in response to the first signal, calculating a time bias between the first node and the second node based on: o the transmit time of the second signal from the first node; o the third receive time of the second signal at the second node; o the first channel response; and o the first partial channel state information; and estimating a target position of the target device based on: o the first receive time of the first signal at the first node; o the second receive time of the first signal at the second node; and o the time bias. 2 The method of Claim 1, further comprising, during the first time period: at the first node: o transmitting a first ranging signal to the second node; and o recording a second transmit time of the first ranging signal from the first node; • at the second node: o in response to receiving the first ranging signal, recording a fourth receive time of the first ranging signal at the second node; o based on the first ranging signal, recording a second partial channel state information characterizing the communication channel; o transmitting a second ranging signal to the first node; and o recording a third transmit time of the second ranging signal from the second node; at the first node: o in response to receiving the second ranging signal, recording a fifth receive time of the second ranging signal at the first node; and o based on the second ranging signal, recording third partial channel state information characterizing the communication channel; and calculating the first channel response based on: o the second partial channel state information; o the third partial channel state information; o the second transmit time of the first ranging signal; o the third transmit time of the second ranging signal; o the fourth receive time of the first ranging signal; and o the fifth receive time of the second ranging signal. 3 The method of Claim 1, further comprising, during the first time period: in response to receiving a third signal from the first node, recording a second partial channel state information characterizing the communication channel based on the third signal; and calculating the first channel response based on the second partial channel state information and a first distance between the first node and the second node. 4 The method of Claim 1: further comprising: o at a third node in the set of nodes: ■ receiving the first signal transmitted from the target device; ■ recording a fourth receive time of the first signal at the third node; ■ receiving the second signal transmitted from the first node; ■ recording a fifth receive time of the second signal at the third node; and ■ based on the second signal, recording a second partial channel state information characterizing a second communication channel between the first node and the third node for the second time period; o accessing a second channel response characterizing the second communication channel between the first node and the third node for the first time period; o in response to the first signal, calculating a second time bias between the first node and the third node based on: ■ the transmit time of the second signal from the first node; ■ the fifth receive time of the second signal at the third node; ■ the second channel response; and ■ the second partial channel state information; o estimating a first time-difference-of-arrival of the first signal at the first node and the second node based on: ■ the first receive time of the first signal at the first node; ■ the second receive time of the first subset of signals at the second node; and ■ the time bias; and o estimating a second time-difference-of-arrival of the first signal at the first node and the third node based on: ■ the first receive time of the first signal at the first node; ■ the fourth receive time of the first signal at the third node; and ■ the second time bias; and wherein estimating the target position comprises estimating the target position of the target device based on: o the first time-difference-of-arrival of the first signal at the first node and the second node; and o the second time-difference-of-arrival of the first signal at the first node and the third node. The method of Claim 1: further comprising: o at the second node: ■ receiving a third signal transmitted from the target device; and ■ recording a fourth receive time of the third signal at the second node; o at a third node in the set of nodes: ■ receiving a third signal transmitted from the target device; ■ recording a fifth receive time of the third signal at the third node; ■ receiving the second signal transmitted from the first node; ■ recording a sixth receive time of the second signal at the third node; and ■ based on the second signal, recording a second partial channel state information characterizing a second communication channel between the first node and the third node for the second time period; o accessing a second channel response characterizing the second communication channel between the first node and the third node for the first time period; o calculating a second time bias between the first node and the third node based on: ■ the transmit time of the second signal from the first node; ■ the sixth receive time of the second signal at the third node; ■ the second channel response; and ■ the second partial channel state information; o estimating a first time-difference-of-arrival of the first signal at the first node and the second node based on: ■ the first receive time of the first signal at the first node; ■ the second receive time of the first subset of signals at the second node; and ■ the time bias; and o estimating a second time-difference-of-arrival of the third signal at the second node and the third node based on: ■ the fourth receive time of the third signal at the second node; ■ the fifth receive time of the third signal at the third node; and ■ the second time bias; and wherein estimating the target position comprises estimating the target position of the target device based on: o the first time-difference-of-arrival of the first signal at the first node and the second node; and o the second time-difference-of-arrival of the third signal at the second node and the third node. The method of Claim i, wherein calculating the time bias comprises calculating the time bias based on: the transmit time of the second signal from the first node; the third receive time of the second signal at the second node; and a quotient of the first partial channel state information and the first channel response. 7. The method of Claim 1, wherein calculating the time bias comprises: • calculating a first square of the first partial channel state information; • calculating a second square of the first channel response; and calculating the time bias based on: o the transmit time of the second signal from the first node; o the third receive time of the second signal at the second node; o the first square of the first channel state information; and o the second square of the first channel response. 8 The method of Claim 1, wherein calculating the time bias comprises: calculating a first duration between the second receive time, of the first signal at the second node, and the third receive time of the second signal at the second node; and calculating the time bias in response to the first duration falling below a threshold duration. 9 The method of Claim 1: wherein transmitting the second signal comprises transmitting the second signal comprising a multicast synchronization signal in response to receiving the first signal at the first node; and wherein calculating the time bias comprises calculating the time bias based on: o the transmit time of the multicast synchronization signal from the first node; o the third receive time of the multicast synchronization signal at the second node; o the first channel response; and o the first partial channel state information. 10 The method of Claim 1: wherein receiving the first signal at the first device comprises receiving the first signal comprising an acknowledgement signal responsive to the second signal transmitted from the first node; and • wherein estimating a target position comprises estimating the target position of the target device based on: o the first receive time of the acknowledgement signal at the first node; o the second receive time of the acknowledgement signal at the second node; and o the time bias. n. The method of Claim 1: wherein recording the first receive time comprises recording the first receive time of the first signal at the first node based on a first timing reference characterized by a first clock frequency; wherein recording the second receive time comprises recording the second receive time of the first signal at the second node based on a second timing reference characterized by a second clock frequency different from the first clock frequency; wherein calculating the time bias comprises calculating a clock phase difference based on: o the transmit time of the second signal from the first node; o the third receive time of the second signal at the second node; o the first channel response; and o the first partial channel state information; and wherein the target position of the target device comprises: o calculating a clock frequency offset based on the first clock frequency and the second clock frequency; and o estimating the target position of the target device based on: ■ the first receive time of the first signal at the first node; ■ the second receive time of the first signal at the second node; ■ the clock phase difference; and ■ the clock frequency offset. 12. The method of Claim 1: wherein accessing the first channel response comprises: o during a third time period preceding the second time period, storing the first channel response in the second node; and o during the second time period, accessing the first channel response at the second node; and wherein calculating the time bias comprises calculating the time bias at the second node. 13- The method of Claim 1: • further comprising selecting the first node as a master node based on a first position of the first node relative to the set of nodes; and • wherein transmitting the second signal comprises transmitting the second signal from the first node in response to selecting the first node as the master node. 14. The method of Claim 1, wherein calculating the time bias comprises: accessing a first distance between the first node and the second node; and calculating the time bias between the first node and the second node based on: o the transmit time of the second signal from the first node; o the third receive time of the second signal at the second node; o the first channel response; o the first partial channel state information; and o the first distance between the first node and the second node. 15. The method of Claim 1: wherein receiving the first signal at the second node comprises receiving a set of signals transmitted from the target device, the set of signals comprising the first signal and a third signal; wherein recording the second receive time of the first signal comprises recording a set of receive times of the set of signals at the second node, the set of receive times comprising: o the second receive time of the first signal at the second node; and o a fourth receive time of the third signal at the second node; further comprising: o based on the set of signals, recording a set of partial channel state information characterizing a second communication channel between the second node and the target device; o calculating combined partial channel state information relative to the third signal based on the set of partial channel state information; o estimating a first time difference and a first phase difference for the first signal based on the combined partial channel state information; and o calculating an adjusted second receive time of the first signal based on: ■ the second receive time of the first signal at the second node; ■ the first time difference; and ■ the first phase difference; and • wherein estimating the target position comprises estimating the target position of the target device based on: o the first receive time of the first signal at the first node; o the adjusted second receive time of the first signal; and o the time bias. 16. A method comprising: at a first node in a set of nodes: o receiving a first subset of signals in a set of signals transmitted from a target device, the first subset of signals comprising a first signal; o recording a first set of receive times of the first subset of signals at the first node, the first set of receive times comprising a first receive time of the first signal at the first node; o transmitting a second signal from the first node; and o recording a transmit time of the second signal from the first node; at a second node in the set of nodes: o receiving a second subset of signals in the set of signals transmitted from the target device, the second subset of signals comprising the first signal; o recording a second set of receive times of the second subset of signals at the second node, the second set of receive times comprising a second receive time of the first signal at the second node; o receiving the second signal transmitted from the first node; o recording a third receive time of the second signal at the second node; and o based on the second signal, recording a first partial channel state information characterizing a communication channel between the first node and the second node for a second time period; accessing a first channel response characterizing the communication channel between the first node and the second node for a first time period preceding the second time period; in response to the first signal, calculating a time bias between the first node and the second node based on: o the transmit time of the second signal from the first node; o the third receive time of the second signal at the second node; o the first channel response; and o the first partial channel state information; and • estimating a target position of the target device based on: o the first set of receive times of the first subset of signals at the first node; o the second set of receive times of the second subset of signals at the second node; and o the time bias. 17. The method of Claim 16: wherein receiving the first subset of signals at the first node comprises receiving the first subset of signals comprising the first signal and excluding a third signal; wherein receiving the second subset of signals at the second node comprises receiving the second subset of signals comprising the first signal and the third signal; wherein recording the second set of receive times comprises recording the second set of receive times comprising: o the second receive time of the first signal at the second node; and o a fourth receive time of the third signal at the second node; further comprising, at a third node in the set of nodes: o in response to receiving a third subset of signals, in the set of signals and comprising the third signal, recording a third set of receive times of the third subset of signals at the third node, the third set of receive times comprising a fifth receive time of the third signal at the third node; and o in response to receiving the second signal transmitted from the first node, recording a sixth receive time of the second signal at the third node; further comprising estimating a first time-difference-of-arrival of the first signal at the first node and the second node based on: o the first set of receive times of the first subset of signals at the first node; o the second set of receive times of the second subset of signals at the second node; and o the time bias; further comprising estimating a second time-difference-of-arrival of the third signal at the second node and the third node based on: o the second set of receive times of the second subset of signals at the second node; o the third set of receive times of the third subset of signals at the third node; o the time bias between the first node and the second node; and o a second time bias between the first node and the third node; and • wherein estimating the target position comprises estimating the target position of the target device based on: o the first time-difference-of-arrival of the first signal at the first node and the second node; and o the second time-difference-of-arrival of the third signal at the second node and the third node. 18. The method of Claim 17, further comprising: at the third node, based on the second signal, recording a second partial channel state information characterizing a second communication channel between the first node and the third node for the second time period; and calculating the second time bias between the first node and the third node based on: o the transmit time of the second signal from the first node; o the sixth receive time of the second signal at the third node; o a second channel response characterizing the second communication channel between the first node and the third node; and o the second partial channel state information. 19. A method comprising: at a sniffer node in a set of nodes: o receiving a first signal transmitted from a target device; o recording a second receive time of the first signal at the second node; o receiving a second signal transmitted from a master node in the set of nodes; o recording a third receive time of the second signal at the second node; and o based on the second signal, recording a first partial channel state information characterizing a communication channel between the first node and the second node for a second time period; accessing a first channel response characterizing the communication channel between the master node and the sniffer node for a first time period preceding the second time period; • in response to the first signal, calculating a clock phase difference between the master node and the sniffer node based on: o a transmit time of the second signal from the master node; o the third receive time of the second signal at the sniffer node; o the first channel response; and o the first partial channel state information; and • estimating a target position of the target device based on: o a first receive time of the first signal at the master node; o the second receive time of the first signal at the sniffer node; and o the clock phase difference. 20. The method of Claim 19, further comprising, during the first time period: in response to receiving a third signal from the master node, recording a fourth receive time of the third signal at the sniffer node; based on the third signal, recording a second partial channel state information characterizing the communication channel; and calculating the first channel response based on the second partial channel state information and a first distance between the master node and the sniffer node.

Description

METHOD FOR CLOCK SYNCHRONIZATION VIA DIFFERENTIAL CHANNEL STATE INFORMATION CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This Application claims the benefit of U.S. Provisional Application No. 63/527,774, filed on 19-JUL-2023, and U.S. Provisional Application No. 63/525,351, filed on 06-JUL-2023, each of which is incorporated in its entirety by this reference. TECHNICAL FIELD [0002] This invention relates generally to the field of network-based positioning and more specifically to a new and useful method for clock synchronization via differential channel state information within the field of network-based positioning. BRIEF DESCRIPTION OF THE FIGURES [0003] FIGURE 1 is a flowchart representation of a method; [0004] FIGURES 2A and 2B are flowchart representations of one variation of the method; [0005] FIGURE 3 is a flowchart representation of one variation of the method; [0006] FIGURE 4 is a flowchart representation of one variation of the method; [0007] FIGURE 5 is a flowchart representation of one variation of the method; [0008] FIGURE 6 is a flowchart representation of one variation of the method; and [0009] FIGURE 7 is a flowchart representation of one variation of the method. DESCRIPTION OF THE EMBODIMENTS [0010] The following description of embodiments of the invention is not intended to limit the invention to these embodiments but rather to enable a person skilled in the art to make and use this invention. Variations, configurations, implementations, example implementations, and examples described herein are optional and are not exclusive to the variations, configurations, implementations, example implementations, and examples they describe. The invention described herein can include any and all permutations of these variations, configurations, implementations, example implementations, and examples. 1. Methods [oon] As shown in FIGURES i, 2A, 2B, 3, 4, 5, and 6, a method S100 includes, at a first node in a set of nodes: receiving a first signal transmitted from a target device in Block S122; recording a first receive time of the first signal at the first node in Block S124; transmitting a second signal from the first node in Block S130; and recording a transmit time of the second signal from the first node in Block S132. [0012] The method S100 also includes, at a second node in the set of nodes: receiving the first signal transmitted from the target device in Block S126; recording a second receive time of the first signal at the second node in Block S128; receiving the second signal transmitted from the first node in Block S134; recording a third receive time of the second signal at the second node in Block S136; and, based on the second signal, recording a first partial channel state information characterizing a communication channel between the first node and the second node for a second time period in Block S138. [0013] The method S100 further includes: accessing a first channel response characterizing the communication channel between the first node and the second node for a first time period preceding the second time period in Block S140; in response to the first signal, calculating a time bias between the first node and the second node based on the transmit time of the second signal from the first node, the third receive time of the second signal at the second node, the first channel response, and the first partial channel state information in Block S142; and estimating a target position of the target device based on the first receive time of the first signal at the first node, the second receive time of the first signal at the second node, and the time bias in Block S146. 1.1 _ Variation: Measurement Grouping [0014] As shown in FIGURES 1, 2A, 2B, 3, 4, 5, 6, and 7, one variation of the method S100 includes, at a first node in a set of nodes: receiving a first subset of signals in a set of signals transmitted from a target device in Block S122, the first subset of signals including a first signal; recording a first set of receive times of the first subset of signals at the first node in Block S124, the first set of receive times including a first receive time of the first signal at the first node; transmitting a second signal from the first node in Block S130; and recording a transmit time of the second signal from the first node in Block S132. [0015] This variation of the method S100 also includes, at a second node in the set of nodes: receiving a second subset of signals in the set of signals transmitted from the target device in Block S126, the second subset of signals including the first signal; recording a second set of receive times of the second subset of signals at the second node in Block S128, the second set of receive times including a second receive time of the first signal at the second node; receiving the second signal transmitted from the first node in Block S134; recording a third receive time of the second signal at the second node in Block S136; and, based on the second s