Positioning measurement

Abstract

Disclosed herein are systems, methods, and / or computer programs for determining time-based and / or angle-based measurements for position determination. The apparatus may include components for: receiving reference signals associated with positioning at multiple antennas; and determining cross-correlation values, the cross-correlation values ​​including cross-correlations between the reference signals received at each antenna and known reference signals associated with positioning. Components for: estimating a channel response of a reference antenna in the multiple antennas using the cross-correlation values, the known reference signals, and antenna correlations, the antenna correlations including a known relationship between the channel response of each antenna in the multiple antennas and the channel response of the reference antenna; and determining a time of arrival and / or angle of arrival of a received reference signal based on the estimated channel response of the reference antenna.

Description

Technical Field

[0001] Example embodiments may be directed to systems, methods and / or computer programs for determining time and / or angle based measurements for position determination, such as for reference signal based position determination of a user equipment (UE). Background Art

[0002] In a radio access network (RAN), the position of a UE can be determined using a variety of methods. One method is for the UE to estimate time of arrival (ToA) and / or angle of arrival (AoA) measurements using received downlink (DL) positioning reference signals (PRS) transmitted by each of a plurality of transmission reception points (TRPs). The estimates may be reported to a network function of the RAN, such as a location management function (LMF) residing in the core infrastructure, to calculate the position of the UE using known multi-lateration positioning techniques. Alternatively, the UE may calculate its own position using assistance information from the RAN, also using known multi-lateration positioning techniques. Position determination may be used, for example, for optimization of radio resources, provision of location-based radio or data services, and / or emergency positioning. Summary of the invention

[0003] The scope of protection sought by various embodiments of the present invention is defined by the independent claims. Embodiments and features described in this specification that do not belong to the scope of the independent claims, if any, are to be interpreted as examples useful for understanding various embodiments of the present invention.

[0004] According to a first aspect, an apparatus is described, the apparatus comprising means for:

[0005] receiving, at a plurality of antennas, reference signals associated with positioning;

[0006] determining a cross-correlation value comprising a cross-correlation between a reference signal received at each antenna and a known reference signal associated with positioning;

[0007] estimating a channel response of a reference antenna among the plurality of antennas using the cross-correlation value, the known reference signal, and an antenna correlation including a known relationship between the channel response of each antenna among the plurality of antennas and the channel response of the reference antenna; and

[0008] The time of arrival and / or angle of arrival of the received reference signal is determined based on the estimated channel response of the reference antenna.

[0009] The component for determining the arrival time of the received reference signal can be configured to: determine the arrival time of the received reference signal based on a time delay at which a maximum power associated with an estimated channel response of the reference antenna occurs; and / or determine the arrival angle of the received reference signal based on a phase of the estimated channel response at which a maximum power associated with the estimated channel response occurs.

[0010] The component for determining the arrival time of the received reference signal can be configured to: determine the arrival time of the received reference signal based on a time delay for an estimated power associated with an estimated channel response to reach a predetermined threshold; and / or determine the arrival angle of the received reference signal based on a phase of an estimated channel response for an estimated power associated with an estimated channel response to reach a predetermined threshold.

[0011] The means for estimating the channel response of the reference antenna may be configured to perform channel estimation based on a function that minimizes a difference between the cross-correlation value and the product of a projection matrix and the channel response of the reference antenna, wherein the projection matrix encodes the known reference signal and antenna correlation.

[0012] The component for estimating the channel response of the reference antenna may also be configured to estimate a set of L multipath channel response complex gains representing the estimated channel response of the received reference signal, where L is the number of multipath components received by each antenna.

[0013] The means for determining the arrival time of the received reference signal may be configured to: select a multipath channel response complex gain having a maximum power from the set of L multipath channel response complex gains; and determine a time delay associated with the selected multipath channel response complex gain.

[0014] The component for determining the arrival time of the received reference signal can be configured to: select the earliest multipath channel response complex gain whose power reaches a predetermined threshold from the group of L multipath channel response complex gains; and determine the time delay associated with the selected multipath channel response complex gain.

[0015] The means for determining the angle of arrival of the received reference signal may be configured to determine the phase of the selected multipath channel response complex gain.

[0016] In some embodiments, r s may be a vector of cross-correlation values ​​corresponding to a plurality of antennas receiving a reference signal at time index s; V may be a projection matrix based on antenna correlations between a channel response of each of the plurality of antennas and a channel response of the reference antenna, and autocorrelation values ​​of a known reference signal associated with the plurality of antennas and the L multipath components; and may be a vector of the set of L multipath channel response complex gains, representing the channel response of the reference antenna for time index s; and wherein the means for estimating the channel response of the reference antenna is configured to solve based on To estimate the channel response of the reference antenna.

[0017] The means for estimating the channel response of the reference antenna may be configured to use an iterative minimization technique based on at least one of: a minimum mean square error; a least square error; and a method for solving Any other minimization technique.

[0018] In some embodiments, the means for estimating the channel response of the reference antenna may be configured to estimate the channel response using an iterative minimization technique based on: initializing the residual signal to r s and the noise level is greater than 0;

[0019] For each iteration, up to the maximum number of iterations, iteratively estimate complex tap gain: applying a filter based on V to the residual signal; determining a component whose power is greater than the noise level in the filtered residual signal, and storing the index of the determined component in the index set; based on V and r s Update the corresponding index set The selection of the complex tap gain based on the updated The complex tap gain, r s , V and the number of samples N to update the noise level estimate; and based on the index set, the updated The complex tap gain, r s and V to update the residual signal; When the iterative estimation of the complex tap gain is terminated, the output is the estimated The complex tap gain of .

[0020] The means for determining the time of arrival of the received reference signal may be configured to: Determine the arrival time of the received reference signal by determining the index of the complex tap gain with the maximum power value among the complex tap gains, and estimate the time delay based on the product of the determined index and the sampling time Ts; and / or determine the arrival angle of the received reference signal based on estimating the phase of the estimated determined complex tap gain.

[0021] The means for determining the time of arrival of the received reference signal may be configured to: Determine the arrival time of the received reference signal by determining the minimum index of the complex tap gains whose power values ​​are higher than a predetermined threshold among the estimated complex tap gains, and estimate the time delay based on the product of the determined minimum index and the sampling time Ts; and / or determine the arrival angle of the received reference signal based on estimating the phase of the estimated determined complex tap gain.

[0022] Noise Level Can be based on Updated in each i-th iteration, where const. is a predetermined constant > 0.

[0023] Noise Level Can be based on Updated in each i-th iteration, where z i =const.×δ i , δ i ∈{i,i 2 , ...}, const. is a predetermined constant > 0.

[0024] In some embodiments, for a number A of multiple antennas, where 1≤a≤A, where antenna a=1 is a reference antenna, the component for estimating the channel response of the reference antenna may be configured to iteratively solve based on at time s To estimate the channel response gain vector of the reference antenna, it is expressed as in in is the vector of cross-correlation values ​​between the N samples of the received reference signal for antenna a and the known reference signal; the matrix V = [Γ T , c(2)Γ T , ...c(A)Γ T ] T , where c(a) is the antenna correlation between the reference antenna and antenna a, where 2≤a≤A; Γ is the autocorrelation matrix, where Γ(n,l)=γ((nl)T s ), γ is the autocorrelation function of the known reference signal for sample n and multipath component l, where 1≤n≤N and 1≤n≤N, where N is the number of samples in the received reference signal, L is the number of multipath components, and Ts is the sampling time of the system; is the L multipath channel response at time index s and reference antenna a=1, where is the complex gain of the -lth multipath component, where 1≤l≤L.

[0025] In some embodiments, the means for estimating the channel response of the reference antenna may be configured to instantiate the projection matrix V with a dynamic delay resolution d and a range R based on the following equation:

[0026]

[0027] l = R / d.

[0028] In some embodiments, the means for estimating the channel response of the reference antenna may be configured to estimate and track the delay profile of a predetermined number of components of the channel response estimate and terminate the estimation of the channel response when the delay profile has not changed compared to a previous channel response estimate.

[0029] In some embodiments, a component for receiving a reference signal associated with positioning at multiple antennas may be configured to receive a sample set of the reference signal for a current time index s at multiple antennas of a user device, and to concatenate a current set of received samples with one or more past sets of received samples received at the multiple antennas to form a supersequence of received samples of the reference signal for estimating the channel response of the reference antenna.

[0030] In some embodiments, means for receiving a reference signal associated with positioning at multiple antennas may be configured to receive a plurality of samples N of the reference signal at the multiple antennas, where N is proportional to the channel coherence time.

[0031] In some embodiments, the reference signal associated with positioning is an orthogonal frequency division multiplexing (OFDM) signal, and the component for receiving the reference signal at multiple antennas is configured to perform OFDM demodulation on an OFDM sample set of the OFDM reference signal at a current time index s for each of the multiple antennas, and to concatenate the current received sample set with one or more past received OFDM sample sets received at the multiple antennas for estimating the channel response of the reference antenna.

[0032] In some embodiments, the apparatus and the plurality of antennas may be associated with a user equipment, and the received reference signal associated with positioning may be a positioning reference signal PRS.

[0033] In some embodiments, the apparatus and the plurality of antennas may be associated with a base station, and the received reference signal associated with positioning may be a sounding reference signal, SRS.

[0034] According to a second aspect, a method is described, the method comprising: receiving a reference signal associated with positioning at multiple antennas; determining a cross-correlation value, the cross-correlation value comprising a cross-correlation between the reference signal received at each antenna and a known reference signal associated with positioning; estimating a channel response of a reference antenna among the multiple antennas using the cross-correlation value, the known reference signal, and antenna correlation, the antenna correlation comprising a known relationship between the channel response of each antenna among the multiple antennas and the channel response of the reference antenna; and determining an arrival time and / or arrival angle of the received reference signal based on the estimated channel response of the reference antenna.

[0035] Determining the arrival time of a received reference signal may include: determining the arrival time of the received reference signal based on a time delay at which a maximum power associated with an estimated channel response of a reference antenna occurs; and / or determining an arrival angle of the received reference signal based on a phase of an estimated channel response at which a maximum power associated with the estimated channel response occurs.

[0036] Determining the arrival time of a received reference signal may include: determining the arrival time of the received reference signal based on a time delay for an estimated power associated with an estimated channel response to reach a predetermined threshold; and / or determining the arrival angle of the received reference signal based on a phase of an estimated channel response for an estimated power associated with an estimated channel response to reach a predetermined threshold.

[0037] Estimating the channel response of the reference antenna may include performing channel estimation based on a function that minimizes a difference between the cross-correlation value and a product of a projection matrix and the channel response of the reference antenna, wherein the projection matrix encodes the known reference signal and antenna correlation.

[0038] Estimating the channel response of the reference antenna may include estimating a set of L multipath channel response complex gains representing the estimated channel response of the received reference signal, where L is the number of multipath components received by each antenna.

[0039] Determining the arrival time of the received reference signal may include: selecting a multipath channel response complex gain having a maximum power from the set of L multipath channel response complex gains; and determining a time delay associated with the selected multipath channel response complex gain.

[0040] Determining the arrival time of the received reference signal may include: selecting the earliest multipath channel response complex gain whose power reaches a predetermined threshold from the set of L multipath channel response complex gains; and determining a time delay associated with the selected multipath channel response complex gain.

[0041] Determining the angle of arrival of the received reference signal may include determining a phase of a selected multipath channel response complex gain.

[0042] In some embodiments, r s may be a vector of cross-correlation values ​​corresponding to a plurality of antennas receiving a reference signal at time index s; V may be a projection matrix based on antenna correlations between a channel response of each of the plurality of antennas and a channel response of the reference antenna, and autocorrelation values ​​of a known reference signal associated with the plurality of antennas and the L multipath components; and may be a vector of the set of L multipath channel response complex gains, representing the channel response of the reference antenna for time index s; and wherein estimating the channel response of the reference antenna comprises solving based on To estimate the channel response of the reference antenna.

[0043] Estimating the channel response of the reference antenna may include using an iterative minimization technique based on at least one of: minimum mean square error; least square error; and solving for Any other minimization technique.

[0044] Estimating the channel response of the reference antenna may include estimating the channel response using an iterative minimization technique based on: initializing the residual signal to r s and the noise level is greater than 0; for each iteration, up to the maximum number of iterations, iteratively estimate complex tap gain: applying a filter based on V to the residual signal; determining a component whose power is greater than the noise level in the filtered residual signal, and storing the index of the determined component in the index set; based on V and r s Update the corresponding index set The selection of the complex tap gain based on the updated The complex tap gain, r s , V and the number of samples N to update the noise level estimate; and based on the index set, the updated The complex tap gain, r s and V to update the residual signal; When the iterative estimation of the complex tap gain is terminated, the output is the estimated The complex tap gain of .

[0045] Determining the arrival time of the received reference signal may include: Determine the arrival time of the received reference signal by determining the index of the complex tap gain with the maximum power value among the complex tap gains, and estimate the time delay based on the product of the determined index and the sampling time Ts; and / or determine the arrival angle of the received reference signal based on estimating the phase of the estimated determined complex tap gain.

[0046] Determining the arrival time of the received reference signal may include: Determine the arrival time of the received reference signal by determining the minimum index of the complex tap gains whose power values ​​are higher than a predetermined threshold among the estimated complex tap gains, and estimate the time delay based on the product of the determined minimum index and the sampling time Ts; and / or determine the arrival angle of the received reference signal based on estimating the phase of the estimated determined complex tap gain.

[0047] Noise Level Can be based on Updated in each i-th iteration, where const. is a predetermined constant > 0.

[0048] Noise Level Can be based on Updated in each i-th iteration, where z i =const.×δ i , δ i ∈{i,i 2 , ...}, const. is a predetermined constant > 0.

[0049] In some embodiments, for a number A of multiple antennas, where 1≤a≤A, where antenna a=1 is a reference antenna, estimating the channel response of the reference antenna may include iteratively solving based on at time s To estimate the channel response gain vector of the reference antenna, it is expressed as in in is the vector of cross-correlation values ​​between the N samples of the received reference signal for antenna a and the known reference signal; the matrix V = [Γ T , c(2)Γ T , ...c(A)Γ T ] T , where c(a) is the antenna correlation between the reference antenna and antenna a, where 2≤a≤A; Γ is the autocorrelation matrix, where Γ(n,l)=γ((nl)T s ), γ is the autocorrelation function of the known reference signal for sample n and multipath component l, where 1≤n≤N and 1≤l≤L, where N is the number of samples in the received reference signal, L is the number of multipath components, and Ts is the sampling time of the system; is the L multipath channel response at time index s and reference antenna a=1, where is the complex gain of the -lth multipath component, where 1≤l≤L.

[0050] In some embodiments, estimating the channel response of the reference antenna may include instantiating a projection matrix V with a dynamic delay resolution d and a range R based on the following equation:

[0051]

[0052] l = R / d.

[0053] In some embodiments, estimating the channel response of the reference antenna may include estimating and tracking a delay profile of a predetermined number of components of the channel response estimate, and terminating the estimation of the channel response when the delay profile has not changed compared to a previous channel response estimate.

[0054] In some embodiments, receiving a reference signal associated with positioning at multiple antennas may include receiving a sample set of the reference signal for a current time index s at multiple antennas of a user device, and concatenating the current received sample set with one or more past received sample sets received at the multiple antennas to form a supersequence of received samples of the reference signal for estimating the channel response of the reference antenna.

[0055] In some embodiments, receiving a reference signal associated with positioning at multiple antennas may include receiving a plurality of samples N of the reference signal at the multiple antennas, where N is proportional to a channel coherence time.

[0056] In some embodiments, the reference signal associated with positioning is an orthogonal frequency division multiplexing (OFDM) signal, and receiving the reference signal at multiple antennas may include, for each of the multiple antennas, performing OFDM demodulation on a set of OFDM samples of the OFDM reference signal at a current time index s, and concatenating the current set of received samples with one or more past sets of received OFDM samples received at the multiple antennas for estimating the channel response of the reference antenna.

[0057] In some embodiments, the method may be associated with a user equipment, and the received reference signal associated with positioning may be a positioning reference signal PRS.

[0058] In some embodiments, the method may be associated with a base station, and the received reference signal associated with positioning may be a sounding reference signal SRS.

[0059] According to a third aspect, there is provided a computer program product comprising a set of instructions which, when executed on an apparatus, are configured to cause the apparatus to perform a method according to any preceding method definition.

[0060] According to a fourth aspect, a non-transitory computer-readable medium is provided, the medium including program instructions stored thereon for executing a method, the method including: receiving a reference signal associated with positioning at multiple antennas; determining a cross-correlation value, the cross-correlation value including a cross-correlation between the reference signal received at each antenna and a known reference signal associated with positioning; estimating a channel response of a reference antenna among the multiple antennas using the cross-correlation value, the known reference signal, and antenna correlation, the antenna correlation including a known relationship between the channel response of each antenna among the multiple antennas and the channel response of the reference antenna; and determining an arrival time and / or arrival angle of the received reference signal based on the estimated channel response of the reference antenna.

[0061] The program instructions of the fourth aspect may also perform operations defined according to any of the aforementioned methods of the second aspect.

[0062] According to a fifth aspect, a device is provided, comprising: at least one processor; and at least one memory comprising computer program code, which, when executed by the at least one processor, causes the device to: receive reference signals associated with positioning at multiple antennas; determine a cross-correlation value, the cross-correlation value comprising a cross-correlation between the reference signal received at each antenna and a known reference signal associated with positioning; estimate a channel response of a reference antenna among the multiple antennas using the cross-correlation value, the known reference signal, and antenna correlation, the antenna correlation comprising a known relationship between the channel response of each antenna among the multiple antennas and the channel response of the reference antenna; and determine an arrival time and / or an arrival angle of the received reference signal based on the estimated channel response of the reference antenna.

[0063] The computer program code of the fifth aspect may also perform operations defined according to any of the aforementioned methods of the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Example embodiments will now be described by way of non-limiting examples with reference to the accompanying drawings, in which:

[0065] Figure 1 is a schematic diagram of a user equipment with respect to multiple transit receiving points, which is helpful for understanding the example embodiments;

[0066] Figure 2 is a flowchart indicating processing operations according to some example embodiments;

[0067] Figure 3 is a schematic diagram of a system architecture according to some example embodiments;

[0068] Figure 4 is an indication that you can use e.g. Figure 3 A functional diagram of the operations performed by the system architecture;

[0069] Figure 5 is a graph indicating analysis results related to the magnitude of channel frequency response;

[0070] Figure 6 is a graph indicating analytical results related to arrival time detection errors;

[0071] Figure 7 is a block diagram of an apparatus that may be configured to operate in accordance with an example embodiment; and

[0072] Figure 8 is an example of a non-transitory medium on which a computer program for performing operations according to example embodiments may be stored. DETAILED DESCRIPTION

[0073] Example embodiments may be directed to systems, methods, and / or computer programs for determining time and / or angle-based measurements for position determination, such as for position determination of a user equipment (UE) based on reference signals. Such reference signals may include, but are not limited to, a positioning reference signal (PRS) transmitted from each of a plurality of transmission points (TRPs) on a corresponding downlink (DL).

[0074] As will be appreciated, in the (RAN), the position of the UE may be determined using a variety of methods. One method is for the UE to estimate time of arrival (ToA) and / or angle of arrival (AoA) measurements for the received DL PRS transmitted by each of the multiple TRPs. The estimates may be reported to a network function of the RAN, such as a location management function (LMF) resident in the core infrastructure, to calculate the position of the UE using known multilateration techniques. Alternatively, the UE may calculate its own position using assistance information from the RAN, also using known multilateration techniques.

[0075] Positioning can be used, for example, for optimization of radio resources, provision of location-based radio or data services, and / or emergency positioning. Positioning may also become a driving force for emerging use cases, such as in indoor industrial environments and / or to supplement satellite-based positioning. For example, a UE as referred to herein may be an automated guided vehicle (AGV) that needs to be tracked based on the latest location. This larger form of UE may carry an antenna array consisting of multiple elements and have sufficient power to power the antenna array consisting of multiple elements. Using an antenna comprising multiple elements can improve the effectiveness of measuring reference signals (e.g., PRS), and thereby obtain a more accurate estimate of ToA and / or AoA, which in turn can improve the overall positioning accuracy.

[0076] Figure 1In the schematic diagram, a UE 102 is shown with an associated radio frequency (RF) antenna 104 for wireless communication. The UE 102 may include, for example, a mobile phone, a laptop, a tablet, a digital assistant, a wearable computing device, a vehicle or aircraft with communication capabilities, and indeed any form of mobile device or system with communication capabilities that enables it to receive radio signals from one or more TRPs (e.g., base stations) at least via a downlink (DL). The UE 102 is shown as having a spatial relationship with multiple base stations (i.e., a first base station 106, a second base station 108, and a third base station 110). The first base station 106, the second base station 108, and the third base station 110 may include, but are not limited to, gNBs.

[0077] The first base station 106, the second base station 108 and the third base station 110 have respective first known locations, second known locations and third known locations and may communicate signals directly or indirectly with a management system 120 associated with the RAN, which may be a location management function (LMF) or the like.

[0078] The management system 120 may store or access a first known location, a second known location, and a third known location associated with the first base station 106, the second base station 108, and the third base station 110. Each of the first base station 106, the second base station 108, and the third base station 110 may transmit a PRS, which may be received by the UE 102. The ToA indicates the time taken for the PRS to reach the UE 102, and also indicates the distance between the corresponding first base station 106, the second base station 108, and the third base station 110 and the UE. Based on the assistance data indicating the first known location, the second known location, and the third known location associated with the first base station 106, the second base station 108, and the third base station 110, etc., the UE 102 may determine its own location. Alternatively, the UE 102 may provide the ToA measurement to the management system 120 for calculation. Related positioning techniques known in the art may be based on received signal time difference (RSTD) and angle of arrival (AoA) methods using similar multi-lateration principles. In AoA, the PRSs from the respective first base station 106, second base station 108, and third base station 110 may be measured based on the propagation direction of the wave incident on the antenna array of antenna 104. For example, AoA may be calculated by measuring the carrier arrival phase between the individual elements 112 of the antenna array. Also, based on the AoA measurements, the UE 102 may determine its own position using assistance data, or provide the AoA measurements to the management system 120 for calculation.

[0079] For the sake of completeness, it should also be mentioned that PRS can be transmitted to UE 102 via other forms of TRPs (i.e., other UEs in the vicinity) via links referred to as sidelinks. This is sometimes referred to as sidelink positioning. For the avoidance of doubt, references to TRPs and base stations herein are considered to cover not only gNBs, but also other UEs connected to UE 102 using corresponding sidelinks.

[0080] Example embodiments are directed to a method for using a system utilizing an antenna having multiple elements, such as Figure 1 Systems, methods, and / or computer programs for providing improved positioning accuracy for a UE) using multiple elements 112 of antenna 104 as shown.

[0081] Example embodiments may involve using knowledge of the geometry and related properties of a UE antenna architecture comprising multiple elements. Example embodiments may involve using knowledge of a channel property called delay domain sparsity, which may be preserved across multiple elements. Example embodiments achieve improved positioning accuracy using ToA and / or AoA calculations, which, as will become clear, is not based solely on averaging, for example, ToA and / or AoA estimates or power estimates over multiple elements.

[0082] Figure 2 is a flow chart according to one or more example embodiments, which shows that an indication may be provided by, for example Figure 1 The processing operations may be performed by hardware, software, firmware, or a combination thereof. In some embodiments, the processing operations may be performed by one or more controllers or processors of the UE 102, possibly under the control of computer-readable instructions (software code) stored on a memory. In some cases, at least some of the processing operations may be performed by other systems besides the UE 102, and in fact by any system having an antenna including multiple elements (i.e., antennas) where determining ToA and / or AoA based on a reference signal is necessary. Positioning is one such example.

[0083] A first operation 201 may include receiving, at a plurality of antennas, reference signals associated with positioning.

[0084] A second operation 202 may include determining a cross-correlation value including a cross-correlation between a reference signal received at each antenna and a known reference signal associated with positioning.

[0085] The third operation 203 may include estimating a channel response of a reference antenna among the plurality of antennas using the cross-correlation value, the known reference signal, and an antenna correlation including a known relationship between a channel response of each of the plurality of antennas and a channel response of the reference antenna.

[0086] A fourth operation 204 may include determining a time of arrival (ToA) and / or an angle of arrival (AoA) of the received reference signal based on the estimated channel response of the reference antenna.

[0087] The multiple antennas may include multiple elements 100 of antennas on the UE 102, such as Figure 1 A plurality of elements 100 of an antenna 104 are shown.

[0088] Reference signals associated with positioning may include PRS received on the DL from one or more of the first base station 106, the second base station 108, and the third base station 110 via sidelink(s), and / or possibly from one or more other UEs.

[0089] In other embodiments, the multiple antennas may include elements of an antenna array on a base station. In this case, the reference signal associated with positioning may include a sounding reference signal (SRS) received on an uplink (UL) by a base station or any form of TRP.

[0090] Determining the ToA of the received reference signal may be based on an estimated time delay, which is a time delay at which a maximum power associated with the estimated channel response of the reference antenna occurs. Determining the received AoA (of the reference signal) may be based on an estimated phase, which is a phase of the estimated channel response at which a maximum power associated with the estimated channel response occurs.

[0091] Alternatively or additionally, determining the ToA of the received reference signal may be based on an estimated time delay, which is a time delay at which a power associated with the estimated channel response reaches a predetermined threshold. Determining the received AoA (of the reference signal) may be based on an estimated phase, which is a phase (i.e., an instantaneous phase or angle) of the estimated channel response at which a power associated with the estimated channel response reaches a predetermined threshold.

[0092] In some embodiments, estimating the channel response of the reference antenna may include performing channel estimation based on a function that minimizes a difference between the cross-correlation value and the product of a projection matrix and the channel response of the reference antenna, wherein the projection matrix encodes the known reference signal and antenna correlation.

[0093] Additionally or alternatively, estimating the channel response of the reference antenna may include estimating a set of L multipath channel response complex gains, the set of L multipath channel response complex gains representing the estimated channel response of the received reference signal, where L is the number of multipath components received by each antenna. In this case, determining the ToA of the received reference signal may include: selecting the multipath channel response complex gain with the maximum power from the set of L multipath channel response complex gains; and determining the time delay associated with the selected multipath channel response complex gain. Alternatively or additionally, determining the ToA of the received reference signal may include: selecting the earliest multipath channel response complex gain whose power reaches a predetermined threshold from the set of L multipath channel response complex gains; and determining the time delay associated with the selected multipath channel response complex gain. In either case, determining the AoA of the received reference signal may include determining the phase of the selected multipath channel response complex gain.

[0094] In terms of the symbols that can be used in this article:

[0095] r s may be a vector of cross-correlation values ​​corresponding to a plurality of antennas receiving a reference signal at time index s;

[0096] V may be a projection matrix based on antenna correlation between a channel response of each of the plurality of antennas and a channel response of a reference antenna, and autocorrelation values ​​of known reference signals associated with the plurality of antennas and the L multipath components; and

[0097] It can be a vector of complex gains of the set of L multipath channel responses, where the vector represents the channel response of the reference antenna for time index s.

[0098] Estimating the channel response of the reference antenna may include solving To estimate the channel response of the reference antenna. For example, estimating the channel response of the reference antenna may involve using an iterative minimization technique based on at least one of the following: minimum mean square error, least square error, and for solving Any other minimization technique.

[0099] Reference now Figure 3 , a hardware architecture 300 for the execution of one or more example embodiments is shown. The hardware architecture 300 may be implemented by hardware, software, firmware, or a combination thereof. In some embodiments, the processing operations may be performed by one or more controllers or processors, possibly under the control of computer-readable instructions (software code) stored on a memory.

[0100] The architecture 300 may include a plurality of antennas 302, each coupled to an analog-to-digital converter (ADC) 304, which provides an output to a vectorization module 306. The vectorization module 306 may be configured to, among other things, determine a cross-correlation value including a cross-correlation between a reference signal received at each antenna and a known reference signal associated with positioning. The vectorization module 306 may be coupled to a channel response module 308. The channel response module 308 may be configured to estimate a channel response of a reference antenna in the plurality of antennas 302 using, among other things, the cross-correlation values ​​provided by the vectorization module 306, the known reference signal, and an antenna correlation including a known relationship between a channel response of each antenna in the plurality of antennas and a channel response of a reference antenna in the plurality of antennas.

[0101] For example, the reference antenna may be the first antenna among the plurality of antennas 302 .

[0102] The channel response module 308 may be coupled to a ToA / AoA calculation module 310, which may be configured to determine the ToA and / or AoA of the received reference signal based on the estimated channel response of the reference antenna.

[0103] The determined ToA and AoA may be provided to the positioning module 312, which may determine, for example Figure 2 The geographic location of UE 102 is shown. This may require ToA and / or AoA to be correlated with reference signals from other TRPs (e.g., other base stations or nearby UEs) via sidelinks.

[0104] Now it will give Figure 3 A more detailed explanation of the module.

[0105] In the vectorization module 306, for the number A of the plurality of antennas 302 (where the antenna index is a and 1≤a≤A), N reference signal samples for a given time index s are collected, for example, by a column vector It can be calculated for each antenna 302 The cross-correlation between the known reference signal (e.g., the transmission sequence) and the result is stored in the vector We can say that a=1:A. Γ(n,1)=γ((nl)T s ). γ is the autocorrelation function of the transmitted sequence and is therefore known. We denote L the multipath channel impulse response (CIR) at time index s and antenna a. The lth entry in the vector (i.e., ) may correspond to the complex gain of the lth multipath component, which is assumed to be delayed by lT sreaches the receiver, where T s is the sampling time of the system. We can assume that the delay can be mapped to the resolution T s and length LT s of grid.

[0106] vector The observed signal PRS s at antenna a is collected after cross-correlation. From the expression, we can see that the vector Includes the contribution of the CIR observed by antenna a and the contribution of additive white Gaussian noise (AWGN)ξ (a) From CIR to vector The mapping of can be achieved through a matrix Γ, which collects the known autocorrelations of the transmitted sequence.

[0107] Without loss of generality, we can regard antenna a=1 of antenna 302 as the reference antenna, so we can set α (1) is considered as the reference multipath CIR. Therefore, the CIR at all other antennas is a phase-rotated version of the reference CIR, with the rotation depending on the antenna correlation (and the distance between elements), i.e., α (a≠1) =c(a)α (1) , where c is the known receiver antenna correlation coefficient vector.

[0108] In other words, the CIR at antenna a depends on the CIR at antenna a=1, where the dependence is defined by the correlation coefficient c between antenna a and antenna a=1.

[0109] The received signals across all antennas 302 are then concatenated across the columns into This vector r s Now contains the signal seen by all A antennas 302 and contains the contribution of all CIRs. Since we represent each CIR as a function of the antenna correlation c and the reference CIR, we can rewrite r s To highlight the contribution of the reference CIR to the received signal: Here, we define a new projection matrix V = [Γ T ...c(A)Γ T ] T .

[0110] By doing this, we obtain a mapping between the received signals at all antennas 302 and the unknown CIR at the reference antenna a=1. What remains now is to calculate an estimate of the reference CIR from which we can directly extract ToA and / or AoA information. This can be performed by the channel response module 308 using one or more different calculation methods.

[0111] As described above, one approach is to use an iterative minimization technique based on at least one of: least mean square error; least squares error; and Any other minimization technique.

[0112] Reference now Figure 4 . Figure 4 is based on Figure 3 With reference to the functional diagram 400 of the architecture 300, an example processing method for the channel response module 308 will now be described. Figure 3 similar, Figure 4 The diagram of FIG. 400 includes multiple antennas or antenna arrays 402, each of which is coupled to an ADC 404, which provides signal samples as described above, which are then vectorized in operation 406. Block 408 indicates that the signal samples may be vectorized by Figure 3 Example operations performed by the channel response module 308.

[0113] An example operation may involve an iterative minimization technique as follows.

[0114] In a first operation 420, the residual signal may be initialized to r s And the noise level is initialized to be greater than 0.

[0115] Operation 422 indicates performing the following iterative step i, until a maximum number of iterations I, or until some other metric has converged.

[0116] The second operation 424 may include the following processing: filtering the residual and applying a threshold. For example, this may include estimating (iteratively) A complex tap gain of: applying a filter based on V to the residual signal; and determining a component in the filtered residual signal having a power greater than a noise level, and storing an index of the determined component in an index set.

[0117] The third operation 426 may include based on V and r s Update the corresponding index set Selection of complex tapped gains.

[0118] The fourth operation 428 may include: The complex tap gain, r s , V and the number of samples N to update the noise level estimate.

[0119] The fifth operation 430 may include: The complex tap gain, r s and V to refresh or update the residual signal.

[0120] This operation process may be performed until operation 422 determines that the termination criteria are met, at which point the estimated The complex tap gains of are output to the ToA / AoA calculation module 310 or process 410 .

[0121] In some embodiments, the noise level Can be based on Updated in each i-th iteration, where const. is a predetermined constant > 0 and I i is a set of channel indices whose associated powers are detected.

[0122] Reference now Figure 3 ToA / AoA calculation module 310 in (and similarly Figure 4 In the ToA / AoA calculation process 410), in an example embodiment, determining the ToA of the received reference signal can be based on the estimated An index of a complex tap gain having a maximum power value is determined from among the complex tap gains of , and a time delay is estimated based on a product of the determined index and a sampling time Ts.

[0123] Determining the AoA of the received reference signal may be based on estimating the phase of the estimated determined complex tap gains across multiple antenna array elements.

[0124] Additionally or alternatively, determining the ToA of the received reference signal may be based on estimating A minimum index of the complex tap gains having power values ​​higher than a predetermined threshold is determined among the complex tap gains, and a time delay is estimated based on a product of the determined minimum index and a sampling time Ts.

[0125] Determining the AoA of the received reference signal may be based on estimating a phase of the estimated determined complex tap gain.

[0126] Afterwards, Figure 3 The positioning module 312 in (and similarly Figure 4 The positioning operation 412 in the example may be performed for a corresponding base station (such as Figure 1 Each of the multiple reference signals of the first base station 106, the second base station 108 and the third base station 110 shown performs multi-lateration positioning using the determined ToA / AoA.

[0127] With respect to the channel response module 308, another embodiment may involve early stopping of the iterative process. In summary, this may involve estimating and tracking the delay profiles of a predetermined number of components of the channel response estimate, and terminating the estimation of the channel response when the delay profiles have not changed compared to the previous channel response estimate.

[0128] With respect to the channel response module 308, another embodiment may involve using a set of past and current samples in the CIR estimation process. In this case, the UE 102 may generate a supersequence of received samples by concatenating samples collected at time instances, where the time instances may be OFDM symbols s=0, 1, ...S, subframes, etc. Here, the UE 102 evaluates how many time instances should be processed jointly. For example, a static UE 102 may select a large number of samples S, e.g., tens of symbols, while a fast-moving UE may bundle several or no symbols. Typically, the UE 102 may combine a number of samples N that is proportional to the channel coherence time, i.e., inversely proportional to the maximum Doppler shift fD: N≈4 / fD / Tofdm. The value of fD may be calculated using velocity information v from an internal sensor: fD=(v / c)fc, where c=3e8m / s and fc is the carrier frequency. Having selected N, the UE 102 may generate the observed supersignal r=[V T ...V T ] T α (1) +ξ.

[0129] By replacing Figure 4 The previously described method can be directly applied:

[0130] r s ←r;

[0131] V←[V T ,..V T ] T .

[0132] More succinctly, the channel response module 308 may receive a sample set of a reference signal for a current time index s, and concatenate the current received sample set with one or more received sample sets received in the past at multiple antennas to form a supersequence of received samples of the reference signal for estimating the channel response of the reference antenna. The number of samples N of the reference signal may be proportional to the channel coherence time.

[0133] With respect to the channel response module 308, another embodiment may involve estimating the channel response of the reference antenna by instantiating the projection matrix V with a dynamic delay resolution d and a range R based on the following equation:

[0134]

[0135] l = R / d.

[0136] In any of the above embodiments, the reference signal associated with positioning can be an OFDM signal, and thus, receiving the reference signal at multiple antennas can involve, for each of the multiple antennas, performing OFDM demodulation on an OFDM sample set of the OFDM reference signal at a current time index s, and concatenating the current received sample set with one or more past received OFDM sample sets received at the multiple antennas for estimating the channel response of the reference antenna.

[0137] As described above, although the example embodiments focus on the position determination of UE 102 based on DL PRS signals, the same principles can be applied for UL positioning at the base station (or TRP) side. For example, the reference signal can be SRS instead of PRS.

[0138] In evaluating the effectiveness of the above-described embodiments, a test scenario involved using an antenna array comprising two antennas, a bandwidth of 256 subcarriers for a signal-to-noise ratio (SNR) range of [-6,3] dB. Figure 5 and Figure 6 , Figure 5 and Figure 6 indicate the channel frequency response amplitude and ToA detection error, respectively, using the selected parameter settings, iteration I = 20, cost. = 1e4, and The results show that an improvement of about 10 dB can be achieved compared to that provided by using conventional methods, even in low and medium SNR situations. This indicates that the accuracy of ToA estimation is twice that of using conventional methods.

[0139] In general, systems, methods and / or computer programs for improved ToA and / or AoA determination are described, which may be used for radio positioning. Example embodiments achieve this by utilizing reference signals received at multiple antennas, using techniques other than simple averaging of power estimates or ToA, which make certain assumptions that typically do not hold well in, for example, medium to low SNR regimes, such as far from cell centers and / or for UEs with non-negligible spatial correlation and / or large size factors.

[0140] Example Device

[0141] Figure 7 An apparatus according to some example embodiments is shown, which may include but is not limited to Figure 1The user terminal 102 shown. The device can be configured to perform the operations described herein, such as the operations described with reference to any disclosed process. The device includes at least one processor 700 and at least one memory 720 directly or closely connected to the processor. The memory 720 includes at least one random access memory (RAM) 722A and at least one read-only memory (ROM) 722B. Computer program code (software) 725 is stored in ROM 722B. The device can be connected to a transmitter (TX) and a receiver (RX). The device can optionally be connected to a user interface (UI) for indicating the device and / or for outputting data. At least one processor 700 is arranged to cause the device to perform at least a method according to any of the aforementioned processes together with at least one memory 720 and computer program code 725, such as as described above.

[0142] Figure 8 A non-transitory medium 800 according to some embodiments is shown. The non-transitory medium 800 is a computer readable storage medium. It may be, for example, a CD, a DVD, a USB stick, a Blu-ray disc, etc. The non-transitory medium 800 stores computer program code that causes the apparatus to perform a method of any of the aforementioned processes, for example, as disclosed with respect to the flow charts and their related features.

[0143] The names of network elements, protocols and methods are based on current standards. In other versions or other technologies, the names of these network elements and / or protocols and / or methods may be different, as long as they provide the corresponding functionality. For example, embodiments may be deployed in 2G / 3G / 4G / 5G networks and other generations of 3GPP, but may also be deployed in non-3GPP radio networks such as WiFi.

[0144] The memory can be volatile or non-volatile. It can be, for example, RAM, SRAM, flash memory, FPGA blockram, DCD, CD, USB memory stick and Blu-ray disc.

[0145] If not otherwise stated or clear from the context, stating that two entities are different means that they perform different functions. This does not necessarily mean that they are based on different hardware. That is, each entity described in this specification can be based on different hardware, or some or all entities can be based on the same hardware. This does not necessarily mean that they are based on different software. That is, each entity described in this specification can be based on different software, or some or all entities can be based on the same software. Each entity described in this specification can be embodied in the cloud.

[0146] As non-limiting examples, implementation of any of the above blocks, devices, systems, techniques or methods includes implementation as hardware, software, firmware, dedicated circuits or logic, general purpose hardware or controllers or other computing devices, or some combination thereof. Some embodiments may be implemented in the cloud.

[0147] It should be understood that what has been described above is what is presently considered to be the preferred embodiment. However, it should be noted that the description of the preferred embodiment is given by way of example only and that various modifications may be made without departing from the scope defined by the appended claims.

Claims

1. An apparatus for communication, comprising means for: receiving, at a plurality of antennas of a user equipment, a reference signal associated with positioning; determining a cross-correlation value comprising a cross-correlation between the reference signal received at each antenna and a known reference signal associated with positioning; estimating a channel response of a reference antenna among the plurality of antennas using the cross-correlation value, the known reference signal, and an antenna correlation comprising a known relationship between a channel response of each antenna among the plurality of antennas and a channel response of the reference antenna; as well as determining a time of arrival and / or angle of arrival of the received reference signal based on the estimated channel response of the reference antenna; wherein the means for estimating the channel response of the reference antenna is configured to perform the estimation based on a function that minimizes a difference between the cross-correlation value and a product of a projection matrix and the channel response of the reference antenna, wherein the projection matrix encodes the known reference signal and the antenna correlation.

2. The apparatus of claim 1 , wherein the means for determining the time of arrival of the received reference signal is configured to: determining the time of arrival of the received reference signal based on estimating a time delay at which a maximum power associated with the estimated channel response of the reference antenna occurs; and / or The angle of arrival of the received reference signal is determined based on a phase of the estimated channel response at which a maximum power associated with the estimated channel response is estimated to occur.

3. The apparatus of claim 1 , wherein the means for determining the time of arrival of the received reference signal is configured to: determining the arrival time of the received reference signal based on estimating a time delay for a power associated with the estimated channel response to reach a predetermined threshold; and / or The angle of arrival of the received reference signal is determined based on estimating a phase of the estimated channel response at which a power associated with the estimated channel response reaches a predetermined threshold.

4. An apparatus according to claim 1 or 2, wherein the component for estimating the channel response of the reference antenna is also configured to estimate a set of L multipath channel response complex gains, wherein the set of L multipath channel response complex gains represents the estimated channel response of the received reference signal, where L is the number of multipath components received by each antenna.

5. The apparatus of claim 4, wherein the means for determining the time of arrival of the received reference signal is configured to: Selecting a multipath channel response complex gain having a maximum power from the set of L multipath channel response complex gains; and A time delay associated with the selected multipath channel response complex gain is determined.

6. The apparatus of claim 4, wherein the means for determining the time of arrival of the received reference signal is configured to: Selecting the earliest multipath channel response complex gain whose power reaches a predetermined threshold from the group of L multipath channel response complex gains; and A time delay associated with the selected multipath channel response complex gain is determined.

7. The apparatus according to any one of claims 5 or 6, wherein the means for determining the angle of arrival of the received reference signal is configured to determine the phase of the selected multipath channel response complex gain.

8. The device according to claim 4, wherein: r s is a vector of the cross-correlation values ​​corresponding to the plurality of antennas receiving the reference signal at time index s; V is a projection matrix based on the antenna correlation between the channel response of each of the plurality of antennas and the channel response of the reference antenna, and autocorrelation values ​​of the known reference signals associated with the plurality of antennas and L multipath components; as well as is a vector of the set of L multipath channel response complex gains, representing the channel response of the reference antenna for time index s; as well as The means for estimating the channel response of the reference antenna is configured to be based on solving to estimate the channel response of the reference antenna.

9. The apparatus of claim 8, wherein the means for estimating the channel response of the reference antenna is configured to use an iterative minimization technique based on at least one of: Minimum mean square error; Least squares error; and Used to solve Any other minimization technique.

10. The apparatus of claim 8, wherein the means for estimating the channel response of the reference antenna is configured to estimate the channel response using an iterative minimization technique based on: Initialize the residual signal to r s and the noise level is greater than 0; For each iteration, up to the maximum number of iterations, iteratively estimate The complex tap gain of: Applying a V-based filter to the residual signal; Determine a component in the filtered residual signal whose power is greater than the noise level, and store an index of the determined component in an index set; Based on V and r s To update the pair corresponding to the index set Selection of complex tap gain; Based on the updated The complex tap gain, r s , V, and the number of samples N to update the noise level estimate; and Based on the index set, the updated The complex tap gain, r s , and V, to update the residual signal; Among them When the iterative estimation of the complex tap gain is terminated, the output is the estimated The complex tap gain of .

11. The apparatus of claim 10, wherein the means for determining the time of arrival of the received reference signal is configured to: Based on the estimated Determining the index of the complex tap gain having the maximum power value from the complex tap gains of the received reference signal, and estimating the time delay based on the product of the determined index and the sampling time Ts to determine the arrival time of the received reference signal; and / or The angle of arrival of the received reference signal is determined based on estimating a phase of the estimated determined complex tap gain.

12. The device according to claim 8, wherein: For the number A of the plurality of antennas, 1≤a≤A, where antenna a=1 is the reference antenna, the means for estimating the channel response of the reference antenna is configured to iteratively solve based on To estimate the channel response gain vector of the reference antenna, it is expressed as in in is a vector of cross-correlation values ​​between the N samples of the reference signal received for antenna a and the known reference signal; matrix V = [Γ T , c(2)Γ T , ...c(A)Γ T ] T , where c(a) is the antenna correlation between the reference antenna and the antenna a, where 2≤a≤A; Γ is the autocorrelation matrix, where Γ(n, l) = γ((Nl)T s ), γ is the autocorrelation function of the known reference signal for sample n and multipath component l, where 1≤n≤N and 1≤l≤L, where N is the number of samples in the received reference signal, L is the number of multipath components, and Ts is the sampling time; is the L multipath channel response at time index s and reference antenna a=1, where is the complex gain of the -lth multipath component, where 1≤l≤L.

13. An apparatus according to claim 1 or 2, wherein the component for estimating the channel response of the reference antenna is configured to estimate and track the delay distribution of a predetermined number of components of the channel response estimate, and terminate the estimation of the channel response when the delay distribution has not changed compared to a previous channel response estimate.

14. A method for communication, comprising: receiving, at a plurality of antennas of a user equipment, a reference signal associated with positioning; determining a cross-correlation value comprising a cross-correlation between the reference signal received at each antenna and a known reference signal associated with positioning; estimating a channel response of a reference antenna among the plurality of antennas using the cross-correlation value, the known reference signal, and an antenna correlation comprising a known relationship between a channel response of each antenna among the plurality of antennas and the channel response of the reference antenna; determining a time of arrival and / or angle of arrival of a received reference signal based on an estimated channel response of the reference antenna; Wherein estimating the channel response of the reference antenna comprises: performing the estimation based on a function that minimizes a difference, wherein the difference is a difference between the cross-correlation value and a product of a projection matrix and the channel response of the reference antenna, wherein the projection matrix encodes the known reference signal and the antenna correlation.

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