Systems and methods for multicarrier phase-based localization

Abstract

To provide a new and useful method for multicarrier phase-based localization in the field of radio frequency localization.SOLUTION: The method includes: accessing a multicarrier reference signal; receiving a multicarrier uplink signal transmitted from a user device, the multicarrier uplink signal including a subcarrier uplink signal for each subcarrier frequency in a set of subcarrier frequencies; for each subcarrier frequency in the set of subcarrier frequencies, calculating a phase difference, in a set of phase differences, between a subcarrier reference signal for the subcarrier frequency and the subcarrier uplink signal for the subcarrier frequency; calculating a time-of-arrival of the multicarrier uplink signal at a transceiver based on a set of adjusted phase differences; and transmitting the time-of-arrival of the multicarrier uplink signal to a remote server.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No. 63 / 152,780, filed February 23, 2021, and U.S. Provisional Application No. 63 / 053,509, filed July 17, 2020, each of which is incorporated by reference in its entirety.

[0002] The present invention relates generally to the field of radio frequency location, and more particularly to a novel and useful method for multi-carrier phase-based location in the field of radio frequency location. [Brief explanation of the drawings]

[0003] [Figure 1] FIG. 1 is a flow chart diagram of the first method. [Figure 2] FIG. 2 is a flow chart diagram of the second method. [Figure 3] FIG. 3 is a flow chart diagram of the third method. [Figure 4] FIG. 4 is a schematic diagram of the network. [Figure 5] FIG. 5 is a flow chart of a variation of the first method. [Figure 6] FIG. 6 is a flow chart of a variation of the first method. [Figure 7A] FIG. 7A is a flowchart of a variation of the first and second methods. [Figure 7B] FIG. 7B is a flowchart of a variation of the first and second methods. [Figure 7C] FIG. 7C is a flowchart of a variation of the first and second methods. [Figure 7D] FIG. 7D is a flowchart of a variation of the first and second methods. [Figure 7E] FIG. 7E is a flowchart of a variation of the first and second methods. [Figure 8]FIG. 8 is a flow chart of a variation of the second method. [Figure 9] FIG. 9 is a flowchart of a variation of the second and third methods. DETAILED DESCRIPTION OF THE INVENTION

[0004] The following description of embodiments of the present invention is not intended to limit the invention to these embodiments, but rather to enable those skilled in the art to make and use the present invention. The variations, configurations, implementations, exemplary implementations, and examples described herein are optional and are not exclusive to the variations, configurations, implementations, exemplary implementations, and examples they describe. The present invention described herein may include any and all permutations of these variations, configurations, implementations, exemplary implementations, and examples.

[0005] 1. How to calculate the arrival time at the transmitter and receiver 1, a transceiver is configured to perform a method S100 for calculating a time of arrival of a multicarrier uplink signal. The method S100 includes, in block S110, accessing a multicarrier reference signal, the multicarrier reference signal defining a set of subcarrier frequencies and including a subcarrier reference signal for each subcarrier frequency in the set of subcarrier frequencies, receiving a multicarrier uplink signal transmitted from a user device, the multicarrier uplink signal defining a set of subcarrier frequencies and including a subcarrier uplink signal for each subcarrier frequency in the set of subcarrier frequencies, and accessing a calibration function for the transceiver, in block S130, that represents a relationship between subcarrier frequencies and phase offset. Method S100 also includes, for each subcarrier frequency in the set of subcarrier frequencies, calculating a phase difference between a subcarrier reference signal for the subcarrier frequency and a subcarrier uplink signal for the subcarrier frequency in Block S140, and adjusting the phase difference by a frequency-dependent phase offset based on the subcarrier frequency and a calibration function of the transceiver to generate an adjusted phase difference among the set of adjusted phase differences in Block S150. Method S100 further includes calculating a time of arrival of the multicarrier uplink signal at the transceiver based on the set of adjusted phase differences in Block S160, and transmitting the time of arrival of the multicarrier uplink signal to a remote server in Block S170.

[0006] A variation of method S100 further includes, in block S162, for each pair of subcarrier frequencies in the set of subcarrier frequencies, calculating a time of arrival estimate in the set of time of arrival estimates based on a first phase difference for a first subcarrier frequency in the pair of subcarrier frequencies and a second phase difference for a second subcarrier frequency in the pair of subcarrier frequencies, and in block S164, calculating a time of arrival of the multicarrier uplink signal at the transceiver based on the set of time of arrival estimates.

[0007] 2. Uplink Method for Calculating User Device Location 2, the location management server is configured to perform a method S200 for calculating a location of a user device. In block S210, the method S200 includes, for each transceiver in the set of transceivers, accessing a time of arrival at the transceiver of a multi-carrier uplink signal transmitted from the user device. For method S200, the arrival time of the multicarrier uplink signal for each transceiver in a set of transceivers is calculated by: accessing a multicarrier reference signal, the multicarrier reference signal defining a set of subcarrier frequencies and including a subcarrier reference signal for each subcarrier frequency in the set of subcarrier frequencies; receiving a multicarrier uplink signal defining a set of subcarrier frequencies, the multicarrier uplink signal including a subcarrier uplink signal for each subcarrier frequency in the set of subcarrier frequencies; accessing a calibration function for the transceiver representing a relationship between subcarrier frequencies and phase offsets; calculating, for each subcarrier frequency in the set of subcarrier frequencies, a phase difference between the subcarrier reference signal for the subcarrier frequency and the subcarrier uplink signal for the subcarrier frequency, adjusting the phase difference by a frequency dependent phase offset based on the subcarrier frequency and the calibration function of the transceiver to generate an adjusted phase difference in a set of adjusted phase differences for the multicarrier uplink signal; and calculating the arrival time of the multicarrier uplink signal at the transceiver based on the set of adjusted phase differences for the multicarrier uplink signal. The method S200 also includes, in block S220, calculating a set of time differences of arrival based on the arrival times of the multi-carrier uplink signals for each transceiver in the set of transceivers, and, in block S230, calculating an uplink position estimate for the user device by multilateration based on the set of time differences of arrival and the known positions of each transceiver in the set of transceivers.

[0008] 3. Downlink Method for Calculating User Device Location 3, a user device is configured to perform a method S300 for localizing the user device relative to a set of transceivers. The method S300 includes, in block S310, accessing a multicarrier reference signal, the multicarrier reference signal defining a set of subcarrier frequencies and including a subcarrier reference signal for each subcarrier frequency in the set of subcarrier frequencies, and receiving, in block S320, a set of multicarrier downlink signals, each multicarrier downlink signal in the set of multicarrier downlink signals being transmitted by a transceiver in the set of transceivers and defining a set of subcarrier frequencies and including a subcarrier downlink signal for each subcarrier frequency in the set of subcarrier frequencies. The method S300 also includes, for each multicarrier downlink signal in the set of multicarrier downlink signals, calculating, for each subcarrier frequency in the set of subcarrier frequencies, a phase difference between a subcarrier reference signal for the subcarrier frequency and a subcarrier downlink signal for the subcarrier frequency in Block S330, calculating, for each pair of subcarrier frequencies in the set of subcarrier frequencies, a time of arrival estimate in a set of time of arrival estimates based on a first phase difference for a first subcarrier frequency in the pair of subcarrier frequencies and a second phase difference for a second subcarrier frequency in the pair of subcarrier frequencies in Block S340, and calculating a time of arrival of the received multicarrier signal at the receiving device based on the set of time of arrival estimates in Block S350. The method S300 further includes calculating a downlink position estimate for the user device based on the time of arrival of each received multicarrier signal in the set of received multicarrier signals and a set of known locations of the set of transceivers in Block S360.

[0009] 4. Application Generally, a network (e.g., a telecommunications network, a local area wireless network) includes a location management server, a set of transceivers (e.g., base stations, wireless nodes, cell sites), and at least one user device (e.g., user equipment such as an IoT device, a network-enabled smartphone, a tablet, a laptop computer, etc.), and is configured to cooperatively perform method S100 in each of the set of transceivers and method S200 in the location management server to calculate a location estimate for the user device with high accuracy (e.g., to within one meter). Additionally or alternatively, a user device in the network can perform method S300 to calculate a location estimate for itself relative to the set of transceivers (characterized by similar accuracy) and can report this downlink position estimate to the location management server.

[0010] The network utilizes a multicarrier-based communication protocol (via methods S100, S200, and S300), such as orthogonal frequency division multiplexing (hereinafter "OFDM"), as used in fourth-generation (hereinafter "4G") or fifth-generation (hereinafter "5G") mobile telecommunications networks, to localize any user device operating on the network based on multicarrier phase information extracted from a multicarrier uplink signal transmitted from the user device and received by a set of transceivers (for methods S100 and S200) and / or multicarrier phase information extracted from a multicarrier downlink signal transmitter from a set of transceivers and received by the user device (for method S300). Thus, the network can perform phase-based location of user devices operating on the network without occupying additional bandwidth due to radio frequency (hereinafter "RF") carrier frequency hopping, without modifications to transceiver or user device hardware, and without requiring substantial modifications or additions to the network's communication protocol.

[0011] In particular, each transceiver in a set of transceivers can perform method S100 upon receiving a multicarrier uplink signal from a user device to estimate the time of arrival (hereinafter "TOA") of the multicarrier uplink signal accurately (e.g., within 10 nanoseconds) at the transceiver. More specifically, for each subcarrier signal of the multicarrier uplink signal, the transceiver can calculate a subcarrier phase difference between a subcarrier uplink signal and a subcarrier reference signal at the same subcarrier frequency and adjust the subcarrier phase difference to account for the frequency-dependent phase offset introduced by the transceiver's receive chain. The transceiver can then calculate a TOA estimate for each unique pair of subcarrier phase differences by canceling out the constant phase offset that affects both subcarrier phase differences in the pair. Because the transceiver can generate many TOA estimates for the multicarrier uplink signal, the transceiver can detect and eliminate frequency-selective phase distortion (hereinafter "phase distortion") from these estimates through statistical estimation (e.g., regression, averaging, weighted averaging), thereby further improving the accuracy of the resulting TOA estimate. Thus, by performing the blocks of method S100, each transceiver can cancel or otherwise mitigate source phase offsets that reduce the accuracy of TOA estimates.

[0012] After each transceiver has calculated the TOA of the subcarrier uplink signal according to method S100, the location management server may execute block S200 to access the TOA from each transceiver in the set of transceivers and calculate a set of time differences of arrival (hereinafter "TDOA") between the transceivers, thereby offsetting additional phase offsets caused by, for example, sampling time offsets between the user device and the set of transceivers. After calculating the set of TDOAs (e.g., three or four TDOAs) for the multi-carrier uplink signal, the location management server may calculate the location (in two-dimensional or three-dimensional space) of the user device by TDOA multilateration based on the set of known locations of the transceivers and the set of TDOAs.

[0013] Because each transceiver can extract phase information from baseband subcarrier signals of a multicarrier signal instead of RF carrier signals, each transceiver can extract a large amount of phase information (e.g., proportional to the number of subcarrier signals comprising the multicarrier signal) from a single multicarrier uplink signal, which requires a large number of consecutive signals characterized by variable RF carrier frequencies in a frequency-hopping localization scheme. Thus, method S100 can be performed within a short time frame (e.g., a single signal duration plus processing time) and a small bandwidth (e.g., the bandwidth occupied by a single multicarrier signal).

[0014] Furthermore, as described above, by extracting various simultaneous (or short, consecutive, within a few microseconds) phase differences from a set of subcarrier signals comprising a multicarrier signal, each transceiver can mitigate the impact of phase distortion in these subcarrier signals on TOA estimation. For example, a single multicarrier signal in a network communication protocol such as 5G may include 1,200 upstream subcarrier signals within the single multicarrier signal, while the transceiver can calculate the TOA for the multicarrier signal based on only two subcarrier phase differences. Thus, the system can calculate multiple TOA estimates for the multicarrier signal, each of which may be affected by phase distortion in the underlying phase difference measurements, and combine these TOAs into a single, more accurate TOA for each transceiver.

[0015] Additionally, by leveraging scheduled multi-carrier signals specified by the network's communication protocol, the network can perform methods S100, S200, and / or S300 without any additional overhead in the required communication protocol. For example, the network may be a 5G telecommunications network that includes a location management server that executes a location management function (hereinafter "LMF") that incorporates the blocks of method S200 and interfaces with a set of 5G base stations (i.e., gNBs, radio nodes) that operate as a set of transceivers to perform the blocks of method S100. In this example, the network may leverage radio resource control (hereinafter "RRC") signaling, such as a sounding reference signal (hereinafter "SRS") transmitted from a 5G-enabled user device to the set of 5G base stations as a multi-carrier uplink signal, to transmit TOA data (e.g., τ m ), phase data (e.g., θ meas,n,m), and / or communicate raw waveform data to the LMF for processing according to the blocks of method S200. Thus, in this example, the 5G network may enable sub-1 meter positioning of user devices on the 5G network by using TOA data elements supported in NRPPa to transfer phase data and / or raw waveform data between the 5G base station and the location management server, or by minimally modifying NRPPa, and updating the software of the LMF to perform method S200.

[0016] In another example, a network is configured to locate a user device in the network based on downlink signals by executing the blocks of method S300 at the user device. For example, in a 5G telecommunications network, the user device may utilize downlink signals such as positioning reference signals (hereinafter "PRS") (transmitted to the user device from base stations in the 5G network on different frequency-time resources). The user device may then execute the blocks of method S300 to calculate its position relative to the base station, or may transmit relative TDOA data, phase data, and / or waveform data (e.g., by reference signal time difference (hereinafter RSTD)) to the LMF via the LTE Positioning Protocol (hereinafter "LPP") or LPP Extension (hereinafter "LPPe") for further processing via the blocks of method S100.

[0017] In yet another example, the network can operate according to both the uplink (S100 and S200) and downlink (S300) variations described above. The network can then perform a super-resolution algorithm (based on the frequency separation between the uplink and downlink signals) to further improve localization accuracy.

[0018] Thus, a network may adapt existing mobile communication protocols and network infrastructure to perform the blocks of methods S100, S200, and S300 by modifying the existing protocols to support additional data fields for TOA data, phase data, and / or waveform data generated in accordance with the blocks of methods S100, S200, and S300.

[0019] Generally, the blocks of method S100 are described herein as being performed by a transceiver in a set of transceivers. However, in some variations, the blocks of method S100 may be performed by another entity in the network (e.g., one or more remote servers) where the transceiver transmits pre-requisite data describing the multi-carrier uplink signal to be transmitted by the user device to each transceiver in the set of transceivers.

[0020] Generally, the blocks of method S200 are described herein as being performed by a remote server or location management server, however, in some variations, the blocks of method S200 may be performed by multiple remote servers or by reader transceivers operating in a network.

[0021] Generally, the blocks of method S300 are described herein as being performed by a user device operating in the network. However, in some variations, the blocks of method S300 can be performed by a remote server, such as a location management server or reader transceiver, when the user device transmits pre-requisite data describing the multi-carrier downlink signal to the remote server.

[0022] Generally, the blocks of methods S100, S200, and S300 are described herein with respect to the TOAs of various signals at various devices. However, as used herein, TOA may also include known, scheduled, or characterized transmission delays (e.g., between downlink signals transmitted by separate transceivers in a set of transceivers). Thus, in blocks of methods S200 and S300 that include calculating TDOA based on a set of TOAs, the location management server and the user device, respectively, may take into account the difference in transmission times between the signals for which the TOAs are calculated before calculating the TDOA.

[0023] 5. User Devices Generally, the transceivers perform the blocks of method S100 to calculate a position estimate for a user device, and the location management server performs the blocks of method S200 to locate a user device operating within a network based on multi-carrier uplink signals transmitted from the user device and received at a set of transceivers. More specifically, the user device may be any computing device including a transceiver capable of transmitting multi-carrier signals according to the network's communication protocol. For example, the network may locate a user device such as an Internet of Things (IoT) device, a smartphone, a smartwatch, a tablet, a laptop computer, or any other network-enabled computing device.

[0024] In one implementation, the user device includes a network-enabled transceiver that does not include a Global Navigation Satellite System (GNSS) chip, and in this implementation, the network can locate the user device based on a multi-carrier uplink signal transmitted by the user device without utilizing GNSS.

[0025] In another implementation, a user device may include any computing device capable of operating within a network in accordance with the network's wireless communication protocol. More specifically, a user device may include any user equipment capable of transmitting multi-carrier uplink signals that are received by the minimum number of base stations in the network required for multilateration (e.g., three transceivers for two-dimensional positioning, four transceivers for three-dimensional positioning).

[0026] In one example, the user device includes any class of user equipment (UE) operating within a 5G network and communicating with at least three base stations (i.e., gNBs).

[0027] 6. Transmitter / Receiver As shown in FIG. 4, the network includes a set of transceivers that communicate with a particular user device to obtain raw multicarrier waveform data describing the multicarrier uplink signal transmitted from the user device, such that the network can locate the user device by executing the blocks of method S100 in each transceiver and by executing the blocks of method S200 in a location management server. Furthermore, each transceiver in the set can transmit (directly or via another network protocol) calculated TOA estimates, phase information, and / or raw waveform data associated with the multicarrier uplink signal to the location management server. More specifically, each transceiver in the set can include a wireless node or base station of the network. Thus, the set of transceivers can provide telecommunications services to the user device in addition to executing the blocks of method S100, as referenced herein.

[0028] In one implementation, to locate a user device according to block S100 of method, a set of transceivers may be time-synchronized to within 10 nanoseconds (e.g., by GPS time synchronization) and may include a precise clock capable of maintaining this level of time synchronization.

[0029] In another implementation, the set of transceivers can include a set of user devices served by the network. In this implementation, the set of transceivers can receive multi-carrier sidelink signals from transmitting user devices in the network and can communicate with a location management server according to the blocks of methods S100 and S200 to thereby locate the transmitting user devices in the network. In this implementation, the location management server can continuously track the location of each transceiver performing this sidelink variant of method S100 to effectively locate the transmitting user devices in the network.

[0030] 6.1 Time Synchronization and Sampling Time Offset Generally, each transceiver in a set of transceivers that receives the multicarrier uplink signal and executes the blocks of method S100 may include a time synchronization clock. More specifically, each transceiver in the set may execute a time synchronization protocol (e.g., via GPS time synchronization, two-way ranging and time synchronization protocol, or the time synchronization protocol described in U.S. Patent Application No. 10,833,840). Furthermore, each transceiver in the set may have access to a calibrated sampling time offset that characterizes the transceiver's sampling time offset relative to a reference time. Thus, each transceiver in the set may adjust the calculated TOA for the multicarrier reference signal for phase offsets caused by sampling time differences between the transceiver and other transceivers in the network.

[0031] 7. Location Management Server 4, the network includes a location management server in communication with multiple transceivers and configured to perform the blocks of method S200. More specifically, the location management server may include multiple remote servers that cooperate to calculate location estimates for user devices based on the TOAs of multi-carrier uplink signals calculated by a set of transceivers. The location management server is thus configured to compile these TOAs to generate location estimates for user devices and / or track the locations of user devices over time.

[0032] In one implementation, the location management server operates within a 5G telecommunications network and performs a location management function (hereinafter "LMF") in accordance with the 5G standard. By performing the LMF, the location management server can receive TOA data (e.g., a TOA, a set of TOA estimates, and / or raw waveform data) from each transceiver in the set of transceivers via the NRPPa protocol. Thus, each transceiver can transmit a TOA calculated by the transceiver associated with the multicarrier uplink signal to a location management server configured to calculate a location of the user device by multilateration and based on the set of TOAs of the multicarrier uplink signals at the set of transceivers that includes the transceiver, wherein the set of times of arrival includes the times of arrival of the multicarrier uplink signals at the transceivers.

[0033] 8. Uplink Protocol Generally, the network can implement an uplink location protocol that includes blocks of method S100 executed by each transceiver in a set of transceivers, and blocks of method S200 executed by a location management server, which is further described below.

[0034] In one implementation, the location management server can initiate the uplink protocol by accessing a prior position estimate of the user device and selecting a set of transceivers within a threshold distance of the prior position estimate based on the known positions of each transceiver in the set (e.g., calculated based on the reception range of the multi-carrier uplink signal transmitted by the user device). The location management server can then request TOA data associated with the multi-carrier uplink signal from the selected set of transceivers.

[0035] Once the set of transceivers is selected, each transceiver in the set can select a channel (e.g., an Orthogonal Frequency Division Multiple Access (OFDMA) resource) in a radio protocol implemented by the transceiver that receives the multi-carrier uplink signal from the user device, and the network can communicate the selected channel information to the user device.

[0036] In one implementation, the location management server can prompt the user device and the set of transceivers to initiate an uplink protocol periodically or on a predetermined schedule. In one example where the location management server is running LMF in accordance with the 5G standard, the location management server can request location measurements from the set of transceivers (i.e., gNBs) in response to receiving a location request for a particular user device from an Access and Mobility Management Function (hereinafter, "AMF"). The location management server can then receive TOA, TOA estimates, and / or raw waveform data from the set of transceivers associated with a multi-carrier uplink signal transmitted by the user device. In this example, upon calculating a location estimate for the user device, the location management server can transmit the location in response to the AMF.

[0037] Generally, the blocks of method S100 are described below from the perspective of a single transceiver in a set of transceivers, however, each transceiver selected to receive the multi-carrier uplink signal can independently perform the blocks of method S100 to calculate the TOA for the multi-carrier uplink signal at the transceiver.

[0038] Generally, the blocks of method S200 are described below from the perspective of a location management server communicating (directly or indirectly) with a set of transceivers, although a set of transceivers may also refer to a subset of transceivers in a network that receive a multi-carrier uplink signal transmitted by a single client device.

[0039] Generally, the blocks of methods S100 and S200 are described herein as being performed by a transceiver and a location management server, respectively. However, blocks S120, S130, S140, S150, and S160 may be performed by the location management server upon receiving raw or partially processed waveform data from each transceiver in the set of transceivers.

[0040] 8.1 Multi-carrier reference signals Generally, in block S110, the transceiver can define a set of subcarrier frequencies and access a multicarrier reference signal including a subcarrier reference signal for each subcarrier frequency in the set of subcarrier frequencies. More specifically, the transceiver can access a multicarrier modulated signal including a set of subcarrier signals, each characterized by a subcarrier frequency separated from spectrally adjacent subcarrier frequencies by a frequency spacing Δf. Furthermore, the transceiver can access a multicarrier reference signal encoding a sequence of digital symbols identifying the user device in response to a request by the location management server for the location of the user device to access a multicarrier reference signal that matches the multicarrier uplink signal transmitted by the user device, thereby enabling the transceiver to identify the user device located by execution of the block of method S100. Alternatively, the transceiver can maintain an identifier table that associates user device identifiers with the particular channel or slot on which the transceiver receives each multicarrier uplink signal. In this implementation, the transceiver can access a multicarrier reference signal corresponding to a device identifier before receiving the corresponding multicarrier uplink signal, without needing to interpret the user device identifier from the multicarrier uplink signal itself. Thus, the transceiver can disambiguate multicarrier uplink signals received from multiple user devices and match each multicarrier uplink signal to a corresponding multicarrier reference signal to generate a set of phase differences between the multicarrier uplink signals and the multicarrier reference signals, as described further below.

[0041] In one example, the transceiver accesses an RRC reference signal or pilot signal in a 5G communication protocol, such as SRS, transmitted from a user device. In this example, the signal is an OFDM reference signal with a Δf of 15 kilohertz. However, the transceiver can access any other multicarrier reference signal, including those at different frequencies within the passband.

[0042] In general, a multicarrier reference signal is a digital symbol with a subcarrier frequency f n A sum of N subcarrier reference signals n containing complex sinusoids of

[0043] TIFF0007771245000001.tif19148, but A n is the amplitude, and θ n is an additional phase of each subcarrier reference signal. Thus, as used herein, n refers to a specific subcarrier reference signal, subcarrier uplink signal, or subcarrier downlink signal in a set of subcarrier signals N.

[0044] 8.2 Multi-carrier uplink signals Generally, in block S120, the transceiver can receive a multicarrier uplink signal transmitted from a user device, the multicarrier uplink signal defining a set of subcarrier frequencies and including a subcarrier uplink signal for each subcarrier frequency in the set of subcarrier frequencies. More specifically, in block S120, the transceiver can receive (e.g., by transmission from a user device) a multicarrier uplink signal including a set of subcarrier uplink signals that include the same sequence of digital symbols as a multicarrier reference signal and are characterized by the same subcarrier frequencies as the set of reference subcarrier frequencies. In particular, the multicarrier uplink signal is a copy of the multicarrier reference signal that has been upconverted to an RF carrier frequency and transmitted by the user device over a wireless channel during a scheduled time slot. Thus, the transceiver can directly compare each subcarrier phase of the multicarrier uplink signal with the corresponding subcarrier phase of the multicarrier reference signal, as further described below.

[0045] During transmission between a user device and a transceiver m in a set of transceivers M, the multi-carrier uplink signal has some propagation time (or TOA) τ m Therefore, the phase difference θ between each subcarrier uplink signal in the set of subcarrier uplink signals and the corresponding subcarrier reference signal in the set of subcarrier reference signals is τ,n,m By extracting τ m and for each set of M transceivers receiving the multi-carrier uplink signal from the user device, τ m Once calculated, the user device is subsequently localized (by block S200).

[0046] In general, the multi-carrier uplink signal at transceiver m is

[0047] It can be modeled as TIFF0007771245000002.tif18157 (A n (The following is omitted for simplicity of explanation.) Furthermore, the multi-carrier uplink signal r m (t) may be affected by multipath delays, and therefore the signal model is

[0048] TIFF0007771245000003.tif10155, where I represents the total number of paths and ρ i represents the amplitude of each multipath signal,

[0049] TIFF0007771245000004.tif9170 represents the phase delay caused by the propagation delay of a multipath signal, and θ i represents the additional phase that arises not from propagation delay (e.g., due to reflection and / or diffraction). Thus, I=1, τ1=τ m , and in the ideal condition where θ1=0, τ m is, for any subcarrier signal n, However, even under the ideal conditions described above, the measured phase difference θ meas,n,m is θ τ,n,m Instead, θ meas,n,m but, TIFF0007771245000006.tif13155, where θ fc represents the RF carrier phase offset, and θ c represents a constant frequency-independent phase offset, and θ d,m represents the deterministic frequency-dependent phase offset introduced by analog hardware components, software, and / or firmware (e.g., digital filters) of transceiver m, and θ u,m represents the phase offset caused by the sampling offset between the user device and the transceiver m, and θ D,ncan be randomly and symmetrically distributed across a set of subcarrier frequencies, or f n represents the frequency selective phase distortion, which may be nonlinear with respect to

[0050] Therefore, in order to accurately calculate the TOA of the multi-carrier uplink signal at the transceiver, thereby enabling localization of the user device according to the blocks of method S200, the transceiver can characterize or eliminate each of these phase offsets according to the blocks of method S100.

[0051] In one example, the multi-carrier uplink signal is a received baseband signal of a sounding reference signal transmitted according to a 5G telecommunications protocol. Thus, in this example, the transceiver can receive a sounding reference signal in a wireless telecommunications protocol transmitted by a user device.

[0052] In another example, the multi-carrier uplink signal is a received baseband signal of an OFDM signal. More specifically, in this example, the transceiver can receive the multi-carrier uplink signal including the OFDM signal. Thus, in this example, the multi-carrier uplink signal defines a set of subcarrier frequencies that are orthogonal to one another.

[0053] In yet another example, the multicarrier uplink signal can be divided across multiple OFDMA subslots, and different subcarrier uplink signals of the multicarrier uplink signal can therefore arrive at the transceiver in separate groups according to the subslot in which each group of subcarrier uplink signals was transmitted by the user device. In this implementation, the location management server can assume that the velocity of the user device is zero during the time period in which the multicarrier uplink signal was transmitted. Alternatively, the location management server can access motion data for the user device during the time period in which the subcarrier uplink signals of the multicarrier uplink signal were transmitted and compensate for this motion during TDOA multilateration.

[0054] In another implementation where the transceiver is a base station in a wireless network, the base station receives a multi-carrier uplink signal from a user device served by the base station such that a wireless channel over which the multi-carrier uplink signal is transmitted is characterized by sufficient fidelity. More specifically, the base station is configured to receive a multi-carrier uplink signal transmitted from a user device served by the base station in the wireless network.

[0055] Alternatively, the base station can receive multicarrier uplink signals from user devices served by other base stations in the wireless network. More specifically, the base station is configured to receive multicarrier uplink signals transmitted from user devices served by a second base station in the wireless network. Thus, the base station in the wireless network can listen to the multicarrier uplink signals and calculate TOAs for these multicarrier uplink signals despite a suboptimal wireless channel between the base station and the transmitting user devices.

[0056] 8.3 Accessing Device Calibration Functions Generally, the transceiver has access to a calibration function that represents the relationship between the subcarrier frequency and the phase offset in block S130. More specifically, the transceiver can calculate the phase offset for an input subcarrier frequency f n The output phase offset θ for transmitter / receiver m d,m Thus, by first calibrating each transceiver (according to a calibration procedure described further below), the transceiver can account for any critical frequency-dependent phase offsets caused by the transceiver's specific analog hardware components, software, and / or firmware.

[0057] In one implementation, the set of transceivers includes a set of base stations. Each transceiver and / or location management server can access a calibration function associated with an individual transceiver in the set based on the transceiver's unique identifier. Alternatively, each transceiver and / or location management server may access a calibration function associated with the make and model of each base station. Thus, in this alternative implementation, each calibration function is not specific to an individual base station or transceiver, but instead is descriptive of each type or model of base station.

[0058] In another implementation where the set of transceivers includes a set of user devices, each user device and / or location management server may have access to a calibration function associated with the make and model of the user device. Alternatively, the user device and / or location management server may have access to a calibration function associated with the International Mobile Equipment Identity number of the user device.

[0059] 8.4 Phase difference calculation Generally, the transceiver may calculate, for each subcarrier frequency in the set of subcarrier frequencies, a phase difference between a subcarrier reference signal for the subcarrier frequency and a subcarrier uplink signal for the subcarrier frequency in block S140. More specifically, upon receiving a multicarrier uplink signal transmitted by a user device, the transceiver may calculate, in block S140, a measured phase difference θ between each subcarrier uplink signal n of the multicarrier uplink signal and a corresponding subcarrier reference signal characterized by the same subcarrier frequency as the subcarrier uplink signal. meas,n,m Thus, the transceiver can calculate a phase difference for each subcarrier frequency included in the multicarrier signal, and in subsequent blocks of method S100, refine these phase differences to eliminate or compensate for the various phase offsets mentioned above.

[0060] More specifically, the transceiver may receive a set of digital samples representing a downconverted waveform of the multi-carrier uplink signal, calculate a discrete Fourier transform (hereinafter "DFT") based on the set of digital samples, apply a passband filter or other digital filter to the set of digital samples and / or other distortion reduction techniques, and calculate a set of phase differences between the multi-carrier uplink signal and a multi-carrier reference signal for each valid (i.e., characterized by sufficiently low distortion) subcarrier signal included in the multi-carrier uplink signal. Alternatively, the transceiver may perform any of the aforementioned processes before transmitting the waveform representation of the received multi-carrier uplink signal to the location management server for further processing according to the blocks of method S200.

[0061] In one implementation, the transceiver can calculate a phase difference for a subset of subcarrier frequencies of the multicarrier uplink signal and the multicarrier reference signal. More specifically, the transceiver can select a subset of subcarrier frequencies defined by the multicarrier uplink signal and the multicarrier reference signal that are unlikely to exhibit a phase difference greater than 2π radians. In this implementation, the transceiver can estimate a distance of the user device relative to the transceiver (e.g., based on a priori position estimate for the user device or based on a GNSS-based position estimate for the user device), estimate a phase shift of each subcarrier signal in a set of subcarrier signals of the multicarrier uplink signal during propagation over the estimated distance between the user device and the transceiver, and exclude those subcarrier signals that exhibit an estimated phase shift greater than 2π radians over the estimated distance. Thus, the transceiver can exclude inaccurate phase measurements from its TOA estimate.

[0062] 8.4.1 Cyclic Prefix Usage In an application where the communication protocol of the network is an OFDM communication scheme, the transceiver may utilize a terminal portion of a cyclic prefix of each symbol in the multicarrier uplink signal to further improve the accuracy of the phase difference calculation referred to in block S140 above. As shown in FIG. 6, in this implementation, the transceiver is configured to calculate, for each symbol of the subcarrier uplink signal, a phase difference between a subcarrier reference signal for a subcarrier frequency and a subcarrier uplink signal for a subcarrier frequency based on a sampling window that includes the terminal portion of the cyclic prefix of the symbol and excludes the terminal region of the symbol. In particular, the transceiver may be configured to calculate the duration of the terminal portion of the cyclic prefix based on a delay spread of the received subcarrier frequency and to calculate the duration of the terminal region of the symbol based on a roll-off factor of the user device.

[0063] Generally, multicarrier OFDM communication protocols introduce waveform distortion toward the terminal regions of each symbol (due to the roll-off factor of the raised cosine DAC reconstruction filter). While this terminal distortion does not meaningfully affect the receiver's interpretation of each symbol of the multicarrier signal, this terminal distortion introduces nonlinear, frequency-dependent errors into the phase difference calculation of each subcarrier signal of the multicarrier signal during execution of block S140. However, instead, the transceiver can sample the terminal portions of the cyclic prefix, which are characterized by less distortion than the terminal regions of the symbols. Therefore, the transceiver can shift and extend the sampling window per symbol forward to include the terminal portions of the cyclic prefix for each subcarrier signal of the multicarrier signal to avoid distortion within the terminal regions of the symbols of the subcarrier signal.

[0064] Furthermore, the transceiver characterizes the channel's current delay spread (based on the expected propagation delay and expected clock bias of the signal between the user device and the transceiver) and excludes an initial portion of the cyclic prefix equal to the delay spread plus a buffer period to avoid distortion in the cyclic prefix caused by multipath fading of previous symbols. Because the duration of the cyclic prefix for the communication protocol is set based on the estimated worst-case delay spread for the subcarrier signal, this terminal portion of the cyclic prefix exists, unaffected by multipath fading. Therefore, in most cases, a significant portion of the cyclic prefix can be utilized to calculate the phase difference between the subcarrier uplink signal and the subcarrier reference signal. For example, if the cyclic prefix for the communication protocol is 4 microseconds and the delay spread is equal to 1 microsecond, the transceiver can utilize up to 3 microseconds of the terminal portion of the cyclic prefix within the period (minus the buffer to account for propagation delay and clock bias). Therefore, the transceiver can calculate the phase difference of the subcarrier uplink signal relative to the subcarrier reference signal based on a sampling window that includes the terminal portion of the cyclic prefix and excludes the terminal region of each data symbol in the subcarrier signal.

[0065] More specifically, for each subcarrier uplink signal in the set of subcarrier signals, the transceiver performs instantaneous channel estimation, statistical channel estimation, and / or super-resolution methods (e.g., a multiple signal classification algorithm) to calculate a current delay spread of the subcarrier signal, calculates a usable period of a terminal portion of a cyclic prefix of the subcarrier signal based on the current delay spread, and calculates a phase difference θ between the subcarrier uplink signal n and a corresponding subcarrier reference signal characterized by the same subcarrier frequency based on a sampling window that includes the terminal portion of each cyclic prefix of the subcarrier signal and excludes the terminal region of each data symbol of the subcarrier uplink signal. meas,n,m can be calculated.

[0066] In one implementation, the transceiver can estimate the delay spread of the subcarrier signal based on the pilot sequence. Alternatively, the transceiver can estimate the delay spread of the channel using the content of the cyclic prefix. In these implementations, the transceiver can execute a channel estimation-based algorithm to generate a power delay profile based on a known reference signal and the received signal. Given the power delay profile for the channel, the transceiver can calculate the delay spread of the channel (i.e., the root-mean-square delay spread).

[0067] Having calculated the delay spread for each subcarrier signal in the set of subcarrier signals, the transceiver can subtract the delay spread value (plus a buffer period) from the cyclic prefix to calculate a usable period for the terminal portion of the cyclic prefix. For example, for a channel characterized by a cyclic prefix having a period of 4 microseconds, a calculated delay spread of 2.5 microseconds, and a buffer period of 0.5 microseconds, the transceiver can calculate a usable period for the terminal portion of the cyclic prefix of 1 microsecond.

[0068] In an alternative implementation, the transceiver can employ a super-resolution algorithm such as Multiple Signal Classification (hereinafter "MUSIC") to generate a multipath profile for the channel and the power of each identified multipath component in the multipath profile (as described in further detail in U.S. Provisional Application No. 63 / 105,822). Running the MUSIC algorithm, the transceiver can calculate the delay spread as the delay between the LOS component and the most recent significant multipath component identified by the MUSIC power spectrum.

[0069] In addition to identifying the terminal portion of the cyclic prefix for use in the phase difference calculation, the transceiver can also exclude terminal regions of each symbol of the subcarrier signal that are affected by waveform distortion by the DAC reconstruction filter. The transceiver can calculate the excluded period of this terminal region of each symbol based on the roll-off factor β of the reconstruction filter utilized by the transmitter (i.e., the user device for uplink signals and the wireless node or base station for downlink signals). In one example, the transceiver can exclude terminal regions of symbols characterized by the excluded period t = 2T / β, where T is the sampling rate of the DAC at the transmitter. Thus, (as shown in FIG. 6) the transceiver can identify regions of the symbols and cyclic prefix of the multicarrier signal that include terminal portions of the cyclic prefix characterized by usable periods and exclude terminal regions of symbols characterized by excluded periods.

[0070] In this implementation, the transceiver can set a buffer period for calculating the usable portion of the cyclic prefix based on an estimate of the total DAC delay and an estimate of the propagation delay between the transmitter and receiver of the signal (e.g., based on an estimated line-of-sight distance between the transmitter and receiver in the network). In one example, the buffer period also accounts for an estimated time bias between the transmitter and receiver.

[0071] In this implementation, the transceiver can periodically recalculate the delay spread of the channel and therefore the usable duration of the terminal portion of the cyclic prefix. Thus, the transceiver can modify the sampling window of each subcarrier signal in the set of subcarrier signals used in the phase difference calculation over time as the delay spread of the channel changes.

[0072] Furthermore, in this implementation, the transceiver has access to the tail portions of the multicarrier waveform that may otherwise be discarded at the physical layer prior to the guard interval removal step of the communication protocol, and thus the transceiver can extract digital samples from the cyclic prefix of the multicarrier signal.

[0073] 8.5 Frequency-Dependent Phase Adjustment Generally, the transceiver, in block S150, calculates a frequency-dependent phase offset θ based on a corresponding subcarrier frequency and a calibration function of the transceiver to generate an adjusted phase difference in a set of adjusted phase differences. d,m (f n ) can adjust the calculated phase difference for each subcarrier uplink signal by θ. More specifically, the transceiver identifies a subcarrier frequency associated with the subcarrier uplink signal, calculates a corresponding frequency-dependent phase offset based on the subcarrier frequency according to a calibration function, and calculates a corresponding frequency-dependent phase offset based on the subcarrier frequency according to a calibration function. meas,n,m This frequency dependent phase offset can be subtracted from θ meas,n,m Eliminates the impact of the transceiver hardware, software, and / or firmware on θ for each subcarrier uplink signal n as in TIFF0007771245000007.tif13168 τ,n,m can be separated.

[0074] In one implementation, the transceiver has access to a linear calibration function for the transceiver, in which case the frequency dependent phase offset is calculated as a frequency dependent delay τ d,m (f n However, the transceiver may have access to a calibration function that describes some mathematical relationship between the frequency-dependent phase offset and the subcarrier frequency.

[0075] 8.6 Arrival time estimation In general, the transceiver may estimate the TOA of the multicarrier uplink signal at the transceiver based on a set of adjusted phase differences for each subcarrier reference signal in the set of subcarrier reference signals in block S160. As shown in FIG. 5, in block S162, the transceiver may calculate, for each pair of subcarrier frequencies in the set of subcarrier frequencies, a TOA estimate in the set of TOA estimates based on a first phase difference for a first subcarrier frequency in the pair of subcarrier frequencies and a second phase difference for a second subcarrier frequency in the pair of subcarrier frequencies. In particular, the transceiver may:

[0076] τ in TIFF0007771245000008.tif14170 m A TOA estimate in the set of TOA estimates can be calculated for each pair of subcarrier frequencies in the set of subcarrier frequencies by solving for m represents the TOA estimation,

[0077] TIFF0007771245000009.tif7170 represents a first phase difference for a first subcarrier frequency,

[0078] TIFF0007771245000010.tif7170 represents the second phase difference for the second subcarrier frequency,

[0079] TIFF0007771245000011.tif8170 represents the first subcarrier frequency,

[0080] TIFF0007771245000012.tif8170 represents the second subcarrier frequency.

[0081] Therefore, (e.g., the formula τ m =-θ τ,n,m / 2πf n TOA τ for multicarriers received at transmitter / receiver m by a single phase measurement (by mInstead of calculating

[0082] TIFF0007771245000013.tif9170 is a set of subcarrier frequencies in the uplink signal N.

[0083] TIFF0007771245000014.tif8170 and

[0084] Based on any two adjusted phase differences from any two subcarrier uplink signals n1 and n2 corresponding to TIFF0007771245000015.tif8170, it can be calculated as follows:

[0085] TIFF0007771245000016.tif14170 Therefore, based on the two phase differences extracted from the two subcarrier uplink signals

[0086] By calculating TIFF0007771245000017.tif9170, the transmitter and receiver can calculate (θ D = 0) the following expansion

[0087] As shown in TIFF0007771245000018.tif66151, the phase offset affecting both subcarriers of the uplink signal can be cancelled.

[0088] As a result of adding the combined phase distortion for TIFF0007771245000019.tif9170, Eq.

[0089] Return to TIFF0007771245000020.tif12170.

[0090] Therefore, block S160 is executed,

[0091] TIFF0007771245000021.tif9170 and θ cBy eliminating the term, the transceiver can obtain τ by executing the subsequent blocks of method S100. m can be further separated.

[0092] Furthermore, by performing the above calculations for each unique pair of subcarrier frequencies in the set of subcarrier frequencies, the transceiver may calculate the phase distortion θ such that the transceiver or location management server can aggregate this set of TOA estimates to reduce noise in the overall TOA calculation, as described further below. D A set of TOA estimates, each affected by

[0093] TIFF0007771245000022.tif8170 can be generated.

[0094] In one implementation, the transceiver may be configured to determine the maximum frequency difference between a pair of subcarrier frequencies.

[0095] TIFF0007771245000023.tif8170, which the transceiver uses to calculate a set of TOA estimates. In this implementation, the transceiver has access to an approximate distance from the user device (e.g., based on a prior position estimate for the user device) and calculates a threshold frequency difference such that no phase difference of one factor 2π occurs over that distance during propagation of the multi-carrier uplink signal from the user device to the transceiver.

[0096] 8.7 Phase distortion mitigation for TOA estimation Generally, the transceiver may calculate the TOA of the multi-carrier uplink signal at the transceiver based on a set of TOA estimates in block S164 to reduce the effect of phase distortion on the TOA calculation. More specifically, the transceiver may:

[0097] Phase distortion in the TOA calculations can be mitigated before transmitting the TOA calculations to the location management server by averaging TOA estimates calculated based on various eigenpairs of subcarrier frequencies in a set of subcarrier frequencies of the multi-carrier uplink signal, such as according to the formula in u,m represents the sampling time offset of transceiver m and user device, where

[0098] Alternatively, the transmitter and receiver may use any set of N-1 or fewer TOA estimates.

[0099] TIFF0007771245000026.tif11170 may be averaged, provided that n i , n j ∈N (e.g., TOA estimates computed from a set of non-contiguous subcarrier frequency pairs),

[0100] TIFF0007771245000027.tif15170. Therefore, the transmitter and receiver must use the sampling time offset τ u,m The average of a set of TOA estimates can be calculated to calculate a single distortion-mitigated TOA value for a multi-carrier uplink signal at the transceiver that is still offset by the sampling time offset τ. u,m are cancelled out in block S220 performed by the location management server, as further described below.

[0101] Additionally, the transceiver may average a subset of TOA estimates from the set of all possible TOA estimates calculated by the transceiver in block S160. For example, the transceiver may discard TOA estimates that may be affected by a factor of 2π of the phase difference used by the transceiver to calculate the TOA estimate.

[0102] In one implementation, the transceiver may calculate a weighted average of TOA estimates to calculate the TOA of the multicarrier uplink signal. More specifically, the transceiver may calculate a weighted average of the set of TOA estimates for each TOA estimate in the set of TOA estimates based on a first phase distortion associated with a first subcarrier frequency for the TOA estimate and a second phase distortion associated with a second subcarrier frequency for the TOA estimate. In particular, the transceiver may perform a phase distortion measurement for each subcarrier frequency defined by the multicarrier uplink signal, and subsequently increase the weight of the TOA estimate obtained from the subcarrier uplink signal with lower distortion on average. For example, the transceiver may:

[0103] The weighted average can be calculated according to the formula in TIFF0007771245000028.tif20142, where w n is the subcarrier frequency f n represents the weights corresponding to P. However, the transceiver may calculate a weighted average of the TOA estimates according to any weighting scheme and based on any measurement characterizing the subcarrier frequencies of the multicarrier uplink signal. Alternatively, the system may calculate a weighted average over a set of P discrete TOA estimates.

[0104] After calculating the TOAs for the multi-carrier uplink signal and transmitting the TOAs to the location management server, the location management server then calculates a single TDOA between each pair of transceivers in the set of transceivers M according to the blocks of method S200, as described further below.

[0105] In contrast to TOA estimation for each combination of subcarrier uplink signals in a set of subcarrier uplink signals, a single value τ can be calculated over the network by the transceiver. m Therefore, the averaged TOAτ can be transmitted before sending to the location management server. mBy calculating , the transceiver reduces the amount of data transmitted over the network (e.g., in the 5G protocol by NRPPa).

[0106] Alternatively, the transceiver can transmit a complete set of TOA estimates to a location management server, which can perform the phase distortion mitigation described above, thereby reducing the processing burden on the transceiver. More specifically, the transceiver can be configured to transmit a set of time of arrival estimates to a remote server.

[0107] 8.8 Deterministic Frequency-Dependent Phase Offset Calibration In one implementation, before performing the blocks of method S100 described above, the transceiver (or another entity in the network) calculates the deterministic frequency-dependent phase offset θ of transceiver m. d,m More specifically, the transceiver may perform a set of calibrations to calculate θ . More specifically, the transceiver may perform method S100 as described above using a known user device location (selected to avoid multipath or other environmental scenarios that are unfavorable to localization accuracy) and calculate the location uncertainty using the transceiver's θ d,m (f n ) The transceiver can then calculate a best-fit function that characterizes the dependence of the deterministic frequency-dependent phase offset on the subcarrier frequency.

[0108] In one example, a transceiver can perform method S100 with a calibration device acting as a user device located at a known location that has LOS to two or more transceivers.

[0109] TIFF0007771245000030.tif10170, the transmitter and receiver calculate this using a pre-calculated ideal distance m between the calibration device and the transmitter and receiver m given the known distance between these devices.

[0110] It can be compared with TIFF0007771245000031.tif9170.

[0111] TIFF0007771245000032.tif9170 and calculated during the calibration procedure

[0112] This difference between TIFF0007771245000033.tif10170 is then the frequency

[0113] θ about TIFF0007771245000034.tif9170 d,m (f n ) can then be set equal to the subcarrier frequency f n θ for d,m To map the dependence of n The process may be repeated for

[0114] In another example, the transceiver may select calibration points by rasterizing the target area into three-dimensional pixels, performing a signal propagation simulation to detect a subset of these three-dimensional pixels that represent locations where the signal is LOS and characterized by being greater than a threshold signal-to-noise ratio in two or more transceivers, generating a raster mask of densely populated or unpopulated locations within the target area, and detecting overlap between the raster mask and these three-dimensional pixels of the detected subset, on which the transceiver may perform a calibration process.

[0115] 8.9 TOA Transmission and Access As shown in FIG. 7E, the TOA (τ m +τ u,mUpon calculating ( ), the transceiver may transmit the TOA of the multicarrier uplink signal at the transceiver to a remote server, such as a location management server (e.g., via NRPPa in a 5G protocol), in block S170. Alternatively, the transceiver may transmit the TOA of the multicarrier uplink signal at the transceiver to another server in the network, from which the location management server may continuously access the TOA of the multicarrier uplink signal. Thus, after each transceiver in the set of transceivers that received the multicarrier uplink signal transmits the TOA of the multicarrier uplink signal to the location management server, the location management server may perform the blocks of method S200 to locate the user device based on the set of TOAs.

[0116] Accordingly, the location management server can access, for each transceiver in the set of transceivers, the TOA at the transceiver of the multi-carrier uplink signal transmitted from the user device in block S210. In one implementation, the location management server can receive the TOA of the multi-carrier uplink signal directly from each transceiver in the set of transceivers (e.g., via NRPPa).

[0117] 7C and 7D, instead of accessing a single TOA of the multi-carrier uplink signal for each transceiver in the set of transceivers, the location management server can instead access or receive a set of TOA estimates for each transceiver in the set of transceivers, and then perform block S164 to mitigate phase distortion in the calculation of the TOA of the multi-carrier uplink signal for each transceiver. More specifically, the location management server can be configured to access a set of TOA estimates for each transceiver in the set of transceivers, where each TOA estimate is based on a pair of subcarrier frequencies in the set of subcarrier frequencies, and to calculate the TOA at the transceiver of the multi-carrier uplink signal for each transceiver in the set of transceivers based on the set of TOA estimates.

[0118] In one implementation, as shown in Figure 7B, the location management server can access, for each transceiver in the set of transceivers, the phase difference for each subcarrier frequency in the set of subcarrier frequencies of the multi-carrier uplink signal. In this implementation, the location management server can perform blocks S162 and S164 of method S100 in addition to blocks S100, thereby further reducing the computational overhead for each transceiver in the set of transceivers while increasing the computational overhead for the location management server.

[0119] In another implementation in which the location management server accesses a set of TOA estimates for each transceiver in the set of transceivers, as shown in Figure 7C, the location management server can calculate a weighted average of the set of time of arrival estimates for each transceiver in the set of transceivers based on the signal-to-noise ratio of the multi-carrier uplink signal as measured by the transceiver. In this implementation, the location management server performs the weighted average equation described above. However, in this implementation,

[0120] TIFF0007771245000035.tif7170 is the subcarrier frequency

[0121] represents a weight based on the signal-to-noise ratio of the first subcarrier uplink signal for TIFF0007771245000036.tif9170;

[0122] TIFF0007771245000037.tif9170 is the subcarrier frequency

[0123] TIFF0007771245000038.tif7170 represents a weight based on the signal-to-noise ratio of the second subcarrier uplink signal.

[0124] In yet another implementation shown in FIG. 7A, the transceiver can transmit raw waveform data describing the multi-carrier uplink signal to a location management server, and the location management server can perform all additional blocks of both method S100 and method S200.

[0125] 8.10 Calculating time difference of arrival Generally, the location management server may calculate a set of TDOAs based on the TOAs of the multi-carrier uplink signal for each transceiver in the set of transceivers in block S220. For example, for a group of three transceivers, the location management server may calculate two TDOAs (or three for redundancy) to fully determine the relative TOA differences in the set of transceivers. By calculating TDOAs, the location management server can eliminate constant and / or frequency-dependent time offsets that affect each TOA equally, which may result from phase offsets due to sampling time offsets between the transceivers and the user device, and / or phase offsets due to analog hardware components, software, and / or firmware in the user device. More specifically, sufficient time synchronization (

[0126] TIFF0007771245000039.tif9170), assuming M, the location management server calculates the sampling time offset τ u,m To eliminate this, the TDOA for the two TOAs can be calculated.

[0127] TIFF0007771245000040.tif12170 where m1 and m2 are the individual transceivers in the set of M transceivers. Therefore, the location management server can calculate τ u,m

[0046] This can eliminate the effect of , thereby eliminating the additional frequency dependent phase offset due to the TDOA calculation, as well as the effect of poor time synchronization between the user device and the pair of transceivers.

[0128] In one implementation, the location management server calculates a set of TDOAs for each pair of transceivers in the set of transceivers corresponding to each unique pair of subcarrier frequencies in the set of subcarrier frequencies. Thus, by calculating the TDOA based on a pair of TOAs calculated based on the pair of subcarrier frequencies, the location management server can calculate τ u,m However, in this implementation, the location management server performs a set of TDOA-based phase mitigation similar to the phase distortion mitigation described above for TOA.

[0129] 8.10.1 TDOA Phase Distortion Mitigation In one implementation shown in FIG. 7C, where a pair of transceivers in block S170 each transmits a pair of TOA estimates to a location management server, the location management server then receives a phase distortion estimate in block S222.

[0130] The location management server can correct the TDOA for a pair of transceivers for TIFF0007771245000041.tif8170. More specifically, the location management server can perform multiple iterations of blocks S150, S160, and S220 based on various combinations of subcarrier uplink signals in a set of subcarrier uplink signals and perform statistical noise reduction techniques to reduce the effects of phase distortion. For example, in OFDM 5G transmission, the multicarrier uplink signal can include 1,200 upstream subcarrier uplink signals. Therefore, the location management server can further improve the accuracy of the TDOA by repeatedly calculating the TDOA between the pair of transceivers based on the subcarrier frequencies of unique pairs of the multicarrier uplink signals.

[0131] In one implementation, the location management server averages a set of TDOA estimates to obtain

[0132] TIFF0007771245000042.tif60170, where for all m1 and m2 in M, and for all n in N,

[0133] TIFF0007771245000043.tif9170, but

[0134] The file is TIFF0007771245000044.tif9170.

[0135] Alternatively, the location management server may perform the above averaging formula for some subset of the N-1 subcarrier frequency pairs. In another alternative implementation, the location management server may calculate a weighted average of the TDOA based on a phase noise related factor such as the signal-to-noise ratio of each multi-carrier uplink signal.

[0136] However, the location management server may perform any other statistical analysis and / or phase distortion correction to reduce the phase distortion affecting each calculated TDOA.

[0137] 8.11 Arrival Time Difference Multilateration Generally, after correcting each TDOA in the set of TDOAs for phase distortion as described above, the location management server calculates an uplink position estimate for the user device by multilateration in block S230 based on the set of TDOAs and the known positions of each transceiver in the set of transceivers. More specifically, given the known positions for each transceiver and TDOA representing the relative arrival times of multi-carrier uplink signals for each transceiver in the set of M transceivers, the location management server can execute a TDOA multilateration algorithm to calculate the user device's position. For example, given two TDOAs between three transceivers, the location management server can calculate a two-dimensional user device position. In another example, given three TDOAs between four transceivers, the location management server can calculate a three-dimensional user device position. Additionally or alternatively, for an overdetermined system of four or more TDOAs between five or more transceivers, the location management server can perform a least-squares method to statistically calculate a three-dimensional user device position.

[0138] 9. Downlink Protocol As shown in Figure 3, the network is configured to execute a downlink location protocol in which a user device performs steps similar to the blocks of methods S100 and S200, including the block of method S300 described further below, to locate itself relative to a set of transceivers (or globally given known locations of the set of transceivers). More specifically, the set of transceivers can each transmit a multicarrier downlink signal that is received by the user device. The user device can then calculate a subcarrier phase difference for each multicarrier downlink signal relative to a multicarrier reference signal.

[0139] Thus, in this variation, the user device can locate itself independently of the location management server and subsequently report its downlink position estimate to the location management server. Alternatively, the user device can communicate waveform data, subcarrier phase data, TDOA estimates (e.g., relative to a master TOA, such as a TOA associated with a multicarrier downlink signal transmitted by a serving base station), or any other form of intermediate data to the location management server, which can then complete the calculation of a downlink position estimate for the user device.

[0140] In a step similar to block S110 of method S100, the user device may determine a set of subcarrier frequencies and access a multicarrier reference signal including a subcarrier reference signal for each subcarrier frequency in the set of subcarrier frequencies in block S310. In one implementation in which the user device is operating in a 5G network, the user device may access a multicarrier reference signal, such as a PRS specified by the 5G standard. Thus, the user device may identify a multicarrier downlink signal intended for user device location.

[0141] In a step similar to block S120 of method S100, a user device can receive a set of multicarrier downlink signals in block S320, where each multicarrier downlink signal in the set of multicarrier downlink signals is transmitted by a transceiver in the set of transceivers and defines a set of subcarrier frequencies, including a subcarrier downlink signal for each subcarrier frequency in the set of subcarrier frequencies. Assuming that the user device remains substantially stationary (e.g., within a few meters) while receiving each multicarrier downlink signal and that negligible clock fluctuations (e.g., less than 10 nanoseconds) occur in the user device, the user device can perform the subsequent blocks of method S300 to localize itself relative to the set of transceivers.

[0142] In a step similar to block S140 of method S100, the user device may calculate, in block S330, for each multicarrier downlink signal in the set of multicarrier downlink signals and for each subcarrier frequency in the set of subcarrier frequencies, a phase difference between a subcarrier reference signal for the subcarrier frequency and a subcarrier downlink signal for the subcarrier frequency. More specifically, the user device may calculate a set of phase differences for the set of subcarrier frequencies according to the steps described above with respect to block S140. Thus, the user device may generate a set of phase differences for each multicarrier downlink signal received at the user device.

[0143] In steps similar to blocks S160 and S162 of method S100, the user device may, in block S340, calculate a TOA estimate in the set of TOA estimates for each multicarrier downlink signal received at the user device and for each pair of subcarrier frequencies in the set of subcarrier frequencies based on a first phase difference for a first subcarrier frequency in the pair of subcarrier frequencies and a second phase difference for a second subcarrier frequency in the pair of subcarrier frequencies. Thus, as described below with respect to block S162, the user device may calculate a constant frequency-independent phase offset θ c , and RF carrier phase offset

[0144] TIFF0007771245000045.tif9170 is the TOA estimation τ m can be offset from the calculation.

[0145] In a step similar to block S164 of method S100, the user device may calculate, in block S350, the TOA of the multicarrier downlink signals at the receiving device based on a set of TOA estimates for each multicarrier downlink signal received at the user device to mitigate phase distortion affecting each multicarrier downlink signal, such as by calculating an average or weighted average of the TOA estimates. Alternatively, in a step similar to block S222, the user device may calculate the TDOA based on the TOA estimates associated with the same pair of subcarrier frequencies to generate a TDOA estimate for each pair of subcarrier frequencies in the set of subcarrier frequencies. In this alternative implementation, the user device may then perform an average or weighted average of this set of TDOA estimates to calculate a TDOA estimate between a pair of multicarrier downlink signals received by the user device.

[0146] In steps similar to blocks S220 and S230 of method S200, the user device may calculate a downlink position estimate for the user device in block S360 based on the TOA of each multicarrier downlink signal in the set of multicarrier downlink signals and a set of known locations of the set of transceivers. In one implementation, in a step similar to block S220, the user device generates a set of TDOAs based on the set of TOAs corresponding to each multicarrier downlink signal received by the user device. Then, in a step similar to block S230, the user device may calculate a downlink position estimate based on TDOA multilateration. Alternatively, the user device may perform TOA multilateration to calculate a downlink position estimate.

[0147] 10. Uplink-Downlink Hybrid Variation In another variation, the location management server can implement a hybrid uplink-downlink variation to further improve the accuracy of location calculations for users by leveraging the frequency diversity of uplink and downlink signals. In some network protocols, uplink and downlink signals are separated in frequency (e.g., by hundreds of megahertz), and therefore, these signals may experience significantly different multipath and noise environments. Thus, by utilizing both types of signals, the location management server can increase the accuracy of location estimates for user devices.

[0148] In this variation, the set of transceivers and the location management server can perform the blocks of methods S100 and S200, respectively, to generate an uplink position estimate for the user device. Concurrently or within a short period of time (e.g., within one TDMA time slot), the user device can perform the blocks of method S300 to generate a downlink position estimate. The user device can then transmit the downlink position estimate to the location management server, which can then average or otherwise combine the uplink and downlink position estimates (via a super-resolution algorithm) into a hybrid position estimate for the user device. More specifically, the location management server can access from the user device a downlink position estimate for the user device calculated by the user device based on a set of multi-carrier downlink signals transmitted from the set of transceivers to the user device, and can calculate a hybrid position estimate based on the uplink and downlink position estimates.

[0149] As shown in FIG. 9, the location management server can access a downlink position estimate for a user device from the user device, where the downlink position estimate is calculated by the user device based on a set of multi-carrier downlink signals transmitted to the user device from a set of transceivers.

[0150] 8, the user device may utilize a GNSS positioning system to generate the downlink position estimate (in addition to or instead of calculating the downlink position estimate according to the blocks of method S300). Thus, the location management server may have access from the user device to the downlink position estimate calculated by the user device based on a global positioning satellite system in communication with the user device.

[0151] The systems and methods described herein may be embodied and / or implemented at least in part as a machine configured to accept a computer-readable medium storing computer-readable instructions. The instructions may be executed by a computer-executable component integrated with an application, applet, host, server, network, website, communication service, communication interface, hardware / firmware / software elements of a user computer or mobile terminal, wristband, smartphone, or any suitable combination thereof. Other systems and methods of embodiments may be embodied and / or implemented at least in part as a machine configured to receive a computer-readable medium storing computer-readable instructions. The instructions may be executed by a computer-executable component integrated with the types of equipment and networks described above. The computer-readable medium may be stored on any suitable computer-readable medium, e.g., RAM, ROM, flash memory, EEPROM, optical device (CD or DVD), hard drive, floppy drive, or any other suitable device. The computer-executable component may be a processor, although any suitable dedicated hardware device may (alternatively or additionally) execute the instructions.

[0152] Those skilled in the art will recognize from the foregoing detailed description and from the drawings and claims that modifications and variations may be made to the embodiments of the invention without departing from the scope of the invention, which is defined in the following claims.

Claims

1. 1. A method for calculating a time of arrival of a multi-carrier uplink signal, comprising: receiving the multicarrier uplink signal transmitted from a user device, the multicarrier uplink signal including a subcarrier uplink signal for each subcarrier frequency in a set of subcarrier frequencies; accessing a calibration function for a transceiver, the calibration function representing a relationship between a subcarrier frequency in the set of subcarrier frequencies and a phase offset associated with the transceiver; For each subcarrier frequency in the set of subcarrier frequencies: calculating a phase difference between a Subcarrier Uplink Signal for the subcarrier frequency and a corresponding Subcarrier Reference Signal for the subcarrier frequency; calculating a frequency dependent phase offset based on a subcarrier frequency associated with the subcarrier uplink signal and the calibration function; generating an adjusted phase difference among a set of adjusted phase differences based on the phase difference and the frequency-dependent phase offset; calculating a time of arrival estimate from a set of time of arrival estimates based on a pair of adjusted phase differences from the set of adjusted phase differences corresponding to a pair of subcarrier frequencies from the set of subcarrier frequencies; calculating a time of arrival of the multi-carrier uplink signal based on the set of time of arrival estimates.

2. 10. The method of claim 1, generating an adjusted phase difference among the set of adjusted phase differences comprises generating an adjusted phase difference among the set of adjusted phase differences by reducing a phase difference between the subcarrier uplink signal for the subcarrier frequency and a corresponding subcarrier reference signal for the subcarrier frequency by the frequency dependent phase offset.

3. The method of claim 1 further comprising: calculating, for each pair of subcarrier frequencies in the set of subcarrier frequencies, a time of arrival estimate in the set of time of arrival estimates; a first adjusted phase difference for a first subcarrier frequency in the pair of subcarrier frequencies; a second adjusted phase difference for a second subcarrier frequency in the pair of subcarrier frequencies, and calculating a time of arrival estimate based on the second adjusted phase difference for a second subcarrier frequency in the pair of subcarrier frequencies.

4. The method of claim 1 further comprising: calculating a combination of the set of time of arrival estimates, a first phase distortion associated with a first subcarrier frequency in the pair of subcarrier frequencies for the time of arrival estimate; and calculating the set of combined time of arrival estimates based on a second phase distortion associated with a second subcarrier frequency in the pair of subcarrier frequencies for the time of arrival estimate; 10. The method of claim 9, wherein calculating a time of arrival of the multi-carrier uplink signal comprises calculating a time of arrival of the multi-carrier uplink signal based on a combination of the set of time of arrival estimates.

5. The method of claim 1 further comprising: transmitting a time of arrival of the multi-carrier uplink signal to a location management server configured to calculate a location of the user device.

6. The method of claim 1 further comprising: a calibration signal, transmitted from a calibration device at a known distance from the transceiver; receiving a calibration signal comprising a calibration subcarrier signal for each subcarrier frequency in the set of subcarrier frequencies; For each subcarrier frequency in the set of subcarrier frequencies: calculating a target calibration phase difference between the calibration subcarrier signal for the subcarrier frequency and a subcarrier reference signal for the subcarrier frequency based on the known distance; calculating a calibration phase difference between the calibration subcarrier signal for the subcarrier frequency and the subcarrier reference signal for the subcarrier frequency; calculating a frequency-dependent phase offset for the subcarrier frequency in a set of frequency-dependent phase offsets based on a difference between the target calibration phase difference and the calibration phase difference; generating the calibration function based on the set of frequency dependent phase offsets.

7. 10. The method of claim 1, The method, wherein accessing a calibration function for the transceiver includes accessing a calibration function associated with a base station and representative of a type of base station.

8. 1. A method for calculating a time of arrival of a multi-carrier uplink signal by a transceiver, comprising: receiving a multi-carrier uplink signal transmitted from a user device, the multi-carrier uplink signal including a subcarrier uplink signal for each subcarrier frequency in a set of subcarrier frequencies; For each subcarrier frequency in the set of subcarrier frequencies: calculating a phase difference between a subcarrier reference signal, each subcarrier frequency, and a corresponding subcarrier uplink signal for said subcarrier frequency; adjusting a phase difference due to a frequency-dependent phase offset based on the subcarrier frequency and a calibration function to generate an adjusted phase difference within a set of adjusted phase differences, the calibration function representing a relationship between a subcarrier frequency within the set of subcarrier frequencies and a phase offset associated with the transceiver; calculating a time of arrival of the multi-carrier uplink signal based on the set of adjusted phase differences; transmitting the time of arrival of the multi-carrier uplink signal to a remote server configured to calculate the location of the user device by multilateration.

9. The method of claim 8 further comprising: accessing a multi-carrier reference signal, the multi-carrier reference signal comprising: specifying a multi-carrier modulated signal; comprising a set of subcarrier signals, each subcarrier signal in the set of subcarrier signals characterized by a subcarrier frequency; encoding a set of digital symbols characteristic of the user device.

10. The method of claim 9 further comprising: receiving the multi-carrier uplink signal during a time window of interest; 10. The method of claim 9, wherein receiving the multicarrier uplink signal comprises receiving a copy of the multicarrier reference signal scaled by a radio frequency carrier signal and transmitted by the user device over a wireless channel during the time window of interest.

11. The method of claim 8 further comprising: For each subcarrier frequency in the set of subcarrier frequencies: calculating a frequency dependent phase offset based on a transceiver specific calibration function based on a subcarrier frequency and an identifier corresponding to said transceiver; and reducing a phase difference between a subcarrier reference signal, each subcarrier frequency, and a corresponding subcarrier uplink signal for the subcarrier frequency by the frequency dependent phase offset to generate an adjusted phase difference among a set of adjusted phase differences.

12. 1. A transceiver for calculating arrival times of multi-carrier signals, comprising: accessing a multi-carrier uplink signal from a user device, the multi-carrier uplink signal including a subcarrier uplink signal for each subcarrier frequency in a set of subcarrier frequencies; accessing a calibration function for the transceiver, the calibration function representing a relationship between a subcarrier frequency in the set of subcarrier frequencies and a phase offset associated with the transceiver; For each subcarrier frequency in the set of subcarrier frequencies: calculating a phase difference between a subcarrier reference signal for the subcarrier frequency and a corresponding subcarrier uplink signal for the subcarrier frequency; calculating a frequency dependent phase offset based on the subcarrier frequency and the calibration function; adjusting the phase difference by the frequency dependent phase offset to generate an adjusted phase difference among a set of adjusted phase differences; calculating a time of arrival estimate from a set of time of arrival estimates based on the set of adjusted phase differences; for each time of arrival estimate in the set of time of arrival estimates, calculating a weighted average of the set of time of arrival estimates based on a pair of phase distortions associated with a pair of subcarrier frequencies for each time of arrival estimate; calculating a time of arrival of the multi-carrier uplink signal based on a set of time of arrival estimates based on a weighted average of the set of time of arrival estimates; transmitting the arrival time of the multi-carrier uplink signal to a remote server; A transceiver characterized by being configured as follows.

13. The transceiver of claim 12 further comprising:

10. A transceiver configured to access a multicarrier reference signal including a subcarrier reference signal for each subcarrier frequency in the set of subcarrier frequencies.

14. The transceiver of claim 12 further comprising: For each pair of subcarrier frequencies in the set of subcarrier frequencies, calculating a first adjusted phase difference for a first subcarrier frequency in the pair of subcarrier frequencies; calculating a second adjusted phase difference for a second subcarrier frequency in the pair of subcarrier frequencies; and calculating a time of arrival estimate in the set of time of arrival estimates based on the first adjusted phase difference and the second adjusted phase difference.

15. The transceiver of claim 12 further comprising: a transceiver configured to transmit, to a location management server configured to calculate a location of the user device, a time of arrival of the multicarrier uplink signal based on a set of arrival times of the multicarrier uplink signal at a set of transceivers including the transceiver;

16. In the method, accessing a calibration function for a transceiver, the calibration function representing a relationship between a subcarrier frequency in a set of subcarrier frequencies and a phase offset associated with the transceiver; receiving a multi-carrier uplink signal from a device, the multi-carrier uplink signal including a set of subcarrier uplink signals for each set of subcarrier frequencies; accessing a multicarrier reference signal representative of the device, the multicarrier reference signal characterizing a set of subcarrier reference signals for each of the set of subcarrier frequencies; For each subcarrier frequency in the set of subcarrier frequencies: calculating a phase difference between a subcarrier uplink signal for the subcarrier frequency and a subcarrier reference signal for the subcarrier frequency; calculating a frequency dependent phase offset based on the subcarrier frequency and the calibration function; calculating an adjusted phase difference in a set of adjusted phase differences based on the phase difference and the frequency-dependent phase offset; calculating a time of arrival estimate from a set of time of arrival estimates based on the set of adjusted phase differences; calculating a time of arrival of the multi-carrier uplink signal based on the set of time of arrival estimates.

17. In the method, accessing a calibration function for a transceiver, the calibration function representing a relationship between a subcarrier frequency in a set of subcarrier frequencies and a phase offset associated with the transceiver; receiving a multi-carrier uplink signal from a device, the multi-carrier uplink signal including a set of subcarrier uplink signals for each set of subcarrier frequencies; For each subcarrier frequency in the set of subcarrier frequencies: calculating a phase difference for the subcarrier frequency based on a subcarrier uplink signal in the set of subcarrier uplink signals; calculating a frequency dependent phase offset based on the subcarrier frequency and the calibration function; calculating an adjusted phase difference in a set of adjusted phase differences based on the phase difference and the frequency-dependent phase offset; calculating a time of arrival estimate from a set of time of arrival estimates based on the set of adjusted phase differences; calculating a time of arrival of the multi-carrier uplink signal based on the set of time of arrival estimates.

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