# US 11,442,137 B2 · Systems and methods for determining locations of wireless sensor nodes based on radio frequency communications between the nodes and various RF-enabled devices > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,442,137 B2 - Document ID: US11442137B2 - Status: Granted - Kind: B2 - Application number: 16/283,465 - Filed: 2019-02-22 - Published: 2020-07-02 - Granted: 2022-09-13 - Earliest claimed: 2018-12-26 - Assignees: Locix, Inc. - Applicants: Locix, Inc. - Inventors: Manu Seth; Lingkai Kong; Tommi Ylamurto - Web page: https://patentgrep.com/patent/US11442137B2 ## CPC - G01S 5/0278: {involving statistical or probabilistic considerations (G01S5/0252, G01S5/0294 take precedence)} - G01S 5/14: Determining absolute distances from a plurality of spaced points of known location - G01S 5/0205: {Details} - G01S 5/0273: {using multipath or indirect path propagation signals in position determination} - G01S 5/0284: {Relative positioning} - G01S 5/0289: {of multiple transceivers, e.g. in ad hoc networks} - G01S 11/08: using synchronised clocks - H04B 17/21: for calibration; for correcting measurements - H04L 43/0864: Round trip delays - H04W 4/029: Location-based management or tracking services - H04W 4/33: for indoor environments, e.g. buildings - H04W 4/38: for collecting sensor information - H04W 24/10: Scheduling measurement reports {; Arrangements for measurement reports} - H04W 56/004: {compensating for timing error of reception due to propagation delay} - H04W 64/003: {locating network equipment} - H04W 84/005: {Moving wireless networks} - H04B 17/14: of the whole transmission and reception path, e.g. self-test loop-back - H04B 17/391: Modelling the propagation channel - H04W 56/0065: {using measurement of signal travel time} - H04W 64/006: {with additional information processing, e.g. for direction or speed determination} - 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 - H04B: TRANSMISSION - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract Systems, apparatuses, and methods for determining locations of wireless nodes in a network architecture are disclosed herein. In one example, a system includes a first wireless node having a wireless device with one or more processing units and RF circuitry for transmitting and receiving communications in the wireless network architecture including a first RF signal having a first packet. A second wireless node having a wireless device with a transmitter and a receiver enables bi-directional communications with the first wireless node in the wireless network architecture including a second RF signal with a second packet. The one or more processing units of the first wireless node are configured to execute instructions to determine a round trip time estimate of the first and second packets, to determine channel state information (CSI) of the first and second wireless nodes, and to calibrate hardware to determine hardware delays of the first and second wireless nodes. ## Claims ### Claim 1 A system for localization of nodes in a wireless network architecture, comprising: a first wireless node having a wireless device with one or more processing units and RF circuitry for transmitting and receiving communications in the wireless network architecture including a first RF signal having a first packet; a second wireless node having a wireless device with a transmitter and a receiver to enable bi-directional communications with the first wireless node in the wireless network architecture including a second RF signal with a second packet, wherein the one or more processing units of the first wireless node or the second wireless node are configured to execute instructions to determine a round trip time estimate of the first and second packets, to determine channel state information (CSI) of the first and second wireless nodes, to calibrate hardware to determine hardware delays of the first and second wireless nodes, to apply the hardware delays to the CSI as a linear phase shift to generate corrected CSI, and to divide the corrected CSI by a calibration CSI to remove hardware delays and filter responses of the first and second wireless nodes, wherein the hardware delays are removed to correct the round trip time estimate of the first and second packets. ### Claim 2 (depends on 1) The system of claim 1, wherein the first wireless node has a first reference clock signal and the second wireless node has a second reference clock signal. ### Claim 3 (depends on 1) The system of claim 1, wherein the round trip time estimate of the first and second packets is based on a first time when the first wireless node sends the first packet, a second time when the second wireless node receives the first packet, a third time when the second wireless node sends the second packet, and a fourth time when the first wireless node receives the second packet. ### Claim 4 (depends on 1) The system of claim 1, wherein the channel state information of the first wireless node comprises a first measurement of a channel response of the second packet and the channel state information of the second wireless node comprises a second measurement of a channel response of the first packet. ### Claim 5 (depends on 4) The system of claim 4, further comprising: a remote device to enable bi-directional communications with the first and second wireless nodes, wherein at least one of the remote device, the first wireless node, and the second wireless node to determine a delay due to phase drift between reference clocks of the first and second wireless nodes based on the CSI of the first and second wireless nodes. ### Claim 6 (depends on 5) The system of claim 5, wherein the hardware delays of the first and second wireless nodes comprise automatic gain control (AGC) and low-noise amplifier delays. ### Claim 7 (depends on 6) The system of claim 6, wherein the AGC and low-noise amplifier delays are removed to correct a round trip time estimate of the first and second packets, wherein at least one of the remote device, the first wireless node, and the second wireless node to apply phase drift delay and hardware delays to the CSI as a linear phase shift to generate corrected CSI. ### Claim 8 (depends on 7) The system of claim 7, wherein at least one of the remote device, the first wireless node, and the second wireless node to compute averages of the corrected CSI for a plurality of packets. ### Claim 9 (depends on 8) The system of claim 8, wherein at least one of the remote device, the first wireless node, and the second wireless node to divide the corrected CSI by a calibration CSI to remove hardware delays. ### Claim 10 (depends on 9) The system of claim 9, wherein at least one of the remote device, the first wireless node, and the second wireless node to execute an algorithm to extract delays and complex amplitudes of the paths that combine to create an averaged CSI, wherein non-physical paths may be eliminated using path amplitude, distance, RSSI, and other relevant data as filtering criteria. ### Claim 11 (depends on 1) The system of claim 1, wherein the nodes in the wireless network architecture comprise anchor nodes to be selected for localization when an error metric that is associated with each distance estimate between an anchor node having a known location and a wireless sensor node having an unknown location is less than or equal to an error threshold. ### Claim 12 (depends on 11) The system of claim 11, wherein at least one anchor node to be eliminated for localization when the error metric is greater than or equal to the error threshold. ### Claim 13 (depends on 1) The system of claim 1, wherein at least one of the first and second wireless nodes comprises a moveable robot that changes positions during localization. ### Claim 14 An apparatus, comprising: a memory for storing instructions; one or more processing units to execute instructions for controlling a plurality of sensor nodes in a wireless network architecture and determining locations of the plurality of sensor nodes; and radio frequency (RF) circuitry to transmit communications to and receive communications from the plurality of sensor nodes each having a wireless device with a transmitter and a receiver to enable bi-directional communications with the RF circuitry of the apparatus in the wireless network architecture, wherein the one or more processing units of the apparatus are configured to execute instructions to transmit a first RF signal having a first packet to a sensor node, to receive a second RF signal with a second packet from the sensor node, to determine a round trip time estimate of the first and second packets, to determine channel state information (CSI), to calibrate hardware to determine hardware delays of at least one of the apparatus and the sensor node, to apply the hardware delays to the CSI as a linear phase shift to generate corrected CSI, and to divide the corrected CSI by a calibration CSI to remove hardware delays and filter responses of the apparatus and the sensor node, wherein the hardware delays are removed to correct the round trip time estimate of the first and second packets. ### Claim 15 (depends on 14) The apparatus of claim 14, wherein the apparatus has a first reference clock signal and the sensor node has a second reference clock signal. ### Claim 16 (depends on 14) The apparatus of claim 14, wherein the round trip time estimate of the first and second packets is based on a first time when the apparatus sends the first packet, a second time when the sensor node receives the first packet, a third time when the sensor node sends the second packet, and a fourth time when the apparatus receives the second packet. ### Claim 17 (depends on 16) The apparatus of claim 16, wherein determining CSI comprises a first measurement of a channel response of the second packet and a second measurement of a channel response of the first packet. ### Claim 18 (depends on 14) The apparatus of claim 14, wherein the hardware delays of at least one of the apparatus and the sensor node comprise automatic gain control (AGC) and low-noise amplifier delays. ### Claim 19 (depends on 18) The apparatus of claim 18, wherein the AGC and low-noise amplifier delays are removed to correct the round trip time estimate of the first and second packets. ### Claim 20 (depends on 14) The apparatus of claim 14, wherein the apparatus to apply phase drift delay and hardware delays to the CSI as a linear phase shift to generate corrected CSI. ### Claim 21 (depends on 14) The apparatus of claim 14, wherein the one or more processing units of the apparatus are configured to execute instructions to measure first channel state information of a first frequency channel of the first RF signal; measure second channel state information of a second frequency channel of the first RF signal with the first and second frequency channels being non-contiguous or discontinuous channels; and determine delay profile estimation between the apparatus and sensor node based on the first and second channel state information without phase alignment. ### Claim 22 (depends on 21) The apparatus of claim 21, wherein the delay profile estimation is determined without channel state information for a frequency band gap between the first and second frequency channels. ### Claim 23 A method for localization of wireless nodes comprising: transmitting a first RF signal from a first wireless node to a second wireless node; receiving a second RF signal with the first wireless node from the second wireless node; obtaining channel state information (CSI) for the first and second wireless nodes; obtaining internal delays including automatic gain control (AGC) delays from an automatic gain control circuit of RF circuitry and Low-noise amplifier (LNA) delays from a low-noise amplifier circuit of the RF circuitry for each of the first and second wireless nodes; removing the AGC delays and the Low-noise amplifier (LNA) delays to correct a coarse time of flight estimate of a first packet sent with the first RF signal and a second packet sent with the second RF signal; and applying the corrections including the AGC delays and the LNA delays to the CSI as a linear phase shift to generate corrected CSI. ### Claim 24 (depends on 23) The method of claim 23, further comprising: removing edges of a frequency spectrum including highest and lowest subcarriers of the first and second RF signals. ### Claim 25 (depends on 23) The method of claim 23, further comprising: determining a delay due to phase drift between the first and second wireless nodes by dividing a forward CSI by a reverse CSI. ### Claim 26 (depends on 25) The method of claim 25, further comprising: obtaining internal delays including AGC delay and Low-noise amplifier (LNA) delay for the first and second wireless nodes; summing corrections for phase drift, AGC gain, and the coarse time of flight estimate; and applying these corrections to the CSI as a linear phase shift.