Determination of a location parameter for a user equipment

Abstract

A method carried out in a location node of a wireless network for determining a location parameter of a user equipment, UE, wherein the method comprises: obtaining (600) a normalized vector (x) based on reception, in at least three separate antenna ports of an antenna array of a radio node, of a radio signal (y) received from the UE via a coverage-enhancing device, CED; determining (605) a first distance (dUE) between the UE and the CED using a function (y) which maps the normalized vector (x) to the first distance given spatial information of the CED upon conveying the radio signal.

Description

[0001]DETERMINATION OF A LOCATION PARAMETER FOR A USER EQUIPMENT Technical field This disclosure relates to the field of wireless communication, and specifically to the task of determining a location parameter for a wireless terminal. The proposed solution is associated with the context of wireless terminals which transmit radio signals to a radio node via a coverage-enhancing device. The location parameter may be a measure of a location of the wireless terminal or a measure indicative of distance between the wireless terminal and the coverage-enhancing device. Background In wireless communication, a wireless channel is used to transfer information and data between different nodes acting as transmitter and receiver, using an electromagnetic wave signal. It is therefore beneficial if the wireless channel is designed to ensure that the signal successfully reaches the receiver. Besides applying sufficient transmit power, an advantageous technology is so-called beamforming, whereby transmitted energy may be focused and directed towards the receiver. Beamforming and beam management have been more frequently considered since the development of the so-called 5G version of wireless communication under supervision of the 3rdGeneration Partnership Project (3GPP), and particularly for use in the mm wave spectrum. A reconfigurable antenna panel comprising an array of a plurality of antenna elements, or antennas for short, may e.g., be configured at a radio node, wherein the antenna elements may be suitably fed such that a combined bearer is obtained with suitable directional properties. Another type of device of similar technology is a panel station or forwarding station, herein referred to as a coverage- enhancing device (CED), configured to forward a signal from a transmitter towards a receiver. By way of example, such a CED is sometimes referred to as a Reconfigurable Intelligent Surface (RIS), alternatively a Large Intelligent Surface (LIS) or a Network controlled Repeater (NCR)above rank 1. Such CEDs using reconfigurable panels aim to influence the wireless channel in a passive or active way, wherein its antennas, or antenna elements, arranged in an array, convey or reflect electromagnetic waves with a configurable phase shift, and possibly with gain. Such CEDs are typically designed to reflect impinging electromagnetic waves, though they can also be designed to transmit impinging electromagnetic waves or be transmissive to deflect impinging electromagnetic waves passing through the panel of the CED. In order to relay the signal from the transmitter to the receiver, the CED applies a beamforming pattern. Determining location of a wireless terminal, commonly referred to as user equipment (UE) in the field of wireless communication, is a task that may be desirable for several purposes. Various technologies have been suggested and used, mostly related to reception or transmission of signals between the UE and three or more further nodes and using trilateration. Recently, discussion has been initiated to make positioning based on carrier phase. This is typically related to systems where a radio node comprises an antenna array (also referred to as a panel array) with a plurality of antennas (antenna elements), wherein different antennas can be configured with different phase setting for shaping spatial sensitivity of the antenna array, both with regard to direction and distance (focusing). There is thus a general desire to find for improvement in the field of location determination of UEs, such as in the context of signaling over a CED. Summary A general object is to provide a mechanism for determination of a location parameter for a UE which communicates via a CED. The proposed solution is defined by the terms of the independent claims, whereas various additional features are set out in the dependent claims. According to a first aspect, a method is provided for use in a location node of a wireless network for determining a location parameter of a UE, wherein the method comprises: obtaining a normalized vector based on reception, in at least three separate antenna ports connected to an antenna array of a radio node, of a radio signal received from the UE via a CED; determining a first distance between the UE and the CED using a function which maps the normalized vector to the first distance given spatial information of the CED upon conveying the radio signal. According to a second aspect, the proposed solution relates to a method carried out in a radio node for facilitating determination of a location parameter of a UE, wherein the method comprises: receiving, in at least three separate antenna ports of an antenna array of the radio node, a radio signal from the UE via a CED; transmitting, to a location node of a wireless network, signal information indicative of a normalized vector based on the received signal, whereby the location node is configured to determine a first distance between the UE and the CED using a function which maps the normalized vector to the first distance given spatial information of the CED upon conveying the radio signal. The proposed solution stems from the realization that separate detection, using the different antenna ports in the radio node, of the same received signal, will provide sufficient input for determining the first direction given the known spatial information of the CED. The proposed solution thereby provides a mechanism for determination of a location parameter of the UE which only requires resources for one reference signal transmission. Determining the location parameter thus comprises determining the first distance, which may be combined with information of a first direction of signal reception in the CED of the radio signal from the UE to obtain a location determination. In some examples, the determination of the location parameter may be useful for configuring the CED to appropriately focus on the determined position of the UE, so as to improve channel quality. In various examples, the determination of the first distance may provide an identification of far field reception in the CED. Brief description of the drawings Various examples will be described with reference to the drawings, in which: Fig.1 schematically illustrates a radio network and a CED usable for conveying electromagnetic wave signals between an access node of the wireless network and a UE; Fig.2A schematically illustrates a context in which the CED is configured for conveying radio signals between a UE and a radio node in the form of a second UE by device-to-device (D2D) communication, such as by sidelink communication; Fig.2B schematically illustrates a context in which the CED is configured for conveying radio between a UE and a radio node in the form of an access node of a wireless network; Fig.3 schematically illustrates functional elements of a radio node in the form of an access node, configured in accordance with various examples of the proposed solution; Fig.4 schematically illustrates functional elements of a location node of a wireless network, which may be configured for determination of the location parameter in accordance with various examples of the proposed solution; and Fig.5 shows a context of receiving signals in a radio node from a UE via a CED, for determining the location parameter according to various examples of the proposed solution; Fig.6 shows a flow chart of a method carried out in a location node, in accordance with an example of the proposed solution; Fig.7 shows a flow chart of a method carried out in a radio node, in accordance with an example of the proposed solution; Fig.8A provides an illustration of an example of a function given certain spatial information of the CED, and how the normalized vector elements correlates with the distance between the UE and the CED in an example; Fig.8B provides an illustration corresponding to Fig.8A, but with a different direction of reception in the CED; Fig.9A shows the plots of Figs 8A and 8B superposed; Fig.9B is a zoomed-in image of the upper part of Fig.9A; Fig.10A shows a diagram of estimated distance between the UE and the CED compared to true distance, given different levels of signal-to-noise ratio (SNR), as a result of an optimizing process; and Fig.10B shows a diagram corresponding to that of Fig.10A for a subset of SNR values, with a misalignment in assumed direction between the UE and the CED, to indicate robustness of the proposed solution. Detailed description In the following description, for purposes of explanation and not limitation, details are set forth herein related to various examples. However, it will be apparent to those skilled in the art that the present disclosure may be practiced in other examples that depart from these specific details. In some instances, detailed descriptions of well- known devices, circuits, and methods are omitted so as not to obscure the description of the present disclosure with unnecessary detail. The functions of the various elements including functional blocks, including but not limited to those labeled or described as “computer”, “processor” or “controller”, may be provided through the use of hardware such as circuit hardware and / or hardware capable of executing software in the form of coded instructions stored on computer readable medium. Thus, such functions and illustrated functional blocks are to be understood as being either hardware-implemented and / or computer-implemented and are thus machine-implemented. In terms of hardware implementation, the functional blocks may include or encompass, without limitation, digital signal processor (DSP) hardware, reduced instruction set processor, hardware (e.g., digital or analog) circuitry including but not limited to application specific integrated circuit(s) (ASIC), and (where appropriate) state machines capable of performing such functions. In terms of computer implementation, a computer is generally understood to comprise one or more processors or one or more controllers, and the terms computer and processor and controller may be employed interchangeably herein. When provided by a computer or processor or controller, the functions may be provided by a single dedicated computer or processor or controller, by a single shared computer or processor or controller, or by a plurality of individual computers or processors or controllers, some of which may be shared or distributed. Moreover, use of the term “processor” or “controller” shall also be construed to refer to other hardware capable of performing such functions and / or executing software, such as the example hardware recited above. The drawings provide performance plots and are otherwise to be regarded as being schematic, where representations and elements illustrated in the drawings are not necessarily shown to scale. Rather, the various elements are represented such that their function and general purpose become apparent to a person skilled in the art. Any connection or coupling between functional blocks, devices, components, or other physical or functional units shown in the drawings or described herein may also be implemented by an indirect connection or coupling. A coupling between components may also be established over a wireless connection. Functional blocks may be implemented in hardware, firmware, software, or a combination thereof. Fig.1 schematically illustrates a wireless communication scenario, providing an example of a scene in which the solutions provided herein may be incorporated. A wireless network 100 comprises an access network 120, such as a 5G NR access network (Radio Access Network – RAN 120), usable for communication over an air interface with further stations, such as the UE 10. The access network 120 may comprise a plurality of access nodes or base stations, of which access node 121 is indicated, configured to provide a wireless interface for connection to, inter alia, the UE 10. For an NR implementation, the access node may be referred to as a gNB. Each access node comprises a point of transmission and reception, referred to as a Transmission and Reception Point (TRP), which coincides with an antenna array of the respective access node. Logic for operating the access node may be configured at the TRP or at another physical location. The wireless network 100 further includes a core network (CN) 110, to which the access network 120 is connected. The core network 110 is in turn connected to other communication networks 130, such as the Internet. The core network comprises interfaces 111, inter alia, for communicating with the access network 120. A location node 112 may be comprised in the core network 110 or may alternatively be a separate function connected to the core network 110. In a 5G implementation, the location node 112 may comprise a location management function (LMF), as indicated in the drawing. The UE 10 may be any device operable to wirelessly communicate with the network 100 through the base stations 121, 122, such as a mobile telephone, computer, tablet, a machine to machine (M2M) device, an IoT (Internet of Things) device, a vehicle device, or other. A CED 140, such as a RIS, is usable for conveying signals between an access node 121 of the access network 120 and further stations, such as the UE 10. The CED 140 may comprise an antenna array 141 and be configured for beamforming, i.e., to selectively configure separate elements of the antenna array to accomplish spatial sensitivity in both direction and distance. The CED 140 may be used in uplink (UL), wherein the UE 10 acts as transmitter Tx and the access node 121 acts as receiver Rx, and / or in downlink (DL), wherein the access node 121 acts as Tx and the UE 10 acts as Rx. The CED may be configured by the wireless network 100, such as by the access node 121, for accomplishing a certain spatial sensitivity. While the drawing of Fig.1 illustrates a scenario where the CED 140 is operated to convey a signal between the access node 121 and the UE 10, it shall be noted that the CED 140 may alternatively be employed for conveying a signal between two UEs, i.e., in a device-to-device (D2D) setup. This is shown by way of example in Fig.2A. In this context, the second UE 20 may act as the radio node in accordance with the proposed solution, for receiving the radio signal from the first UE 10 via the CED, for the purpose of obtaining a location determination of the first UE 10. Fig.2B shows a setup corresponding to Fig.2A, but where the radio node is the access node 121, as shown in Fig.1. Examples will be provided going forward based on this setup, whereas it shall be understood that corresponding examples may be configured with the UE 20 as the radio node. The UE 10 is positioned at a first distance ^^^and at a first spherical angle ^^^from the CED 140; note that ^^^is a tuple of azimuth and elevation angles. Similarly, the radio node (exemplified as gNB) 121 is positioned at a second distance ^^^^and at second spherical angle ^^^^from the CED 140. We assume that both ^^^^and ^^^^, which are comprised in spatial information related to the CED 140, are known in advance. In this context, it may be noted that the first and second distances are each single distances between reference points at the UE 10, the CED antenna array 141 and the radio node antenna array 314, not individual distances per antenna. In some examples, which may represent a common scenario, the access node 121 and the CED 140 belong to the same operator / deployment and are, in general, static infrastructure. A further assumption is that the radio node 121 is in the near field of the CED 140. Near field context may depend on CED size / dimension, such as the total aperture the antenna array occupiesin the CED 140. For typical CED dimensions, this would put the radio node 121 up to about 10m, or so, away from the CED 140. This is not very restrictive as it is today well understood that for a CED to make impact, it should be physically close to either the UE or the radio node (gNB). The objective of the proposed solution is to determine a location parameter of the UE 10. The location parameter may comprise an estimate of the distance ^^^. In some examples, the estimate of the first distance ^^^may comprise an estimate of whether the UE 10 is in near field or far field with respect to the CED 140. In some examples, the location parameter is a position / location of the UE 10, as given by the combination of the first distance ^^^and the first spherical angle ^^^. The proposed solution thus entails providing an estimate of the first distance ^^^. The proposed solution comprises determining the first distance given spatial information of the CED 140 upon conveying a radio signal from the UE 10 to the radio node 121. The spatial information may comprise the first direction ^^^. This information may be obtained from any legacy procedure. However, jointly ^^^and ^^^is a measure of the position of the UE 10. Put compactly, the problem to be studied is to estimate ^^^given the spatial information of the CED 140 upon conveying the radio signal, which spatial information may comprise that ^^^, ^^^^, Further, an objective is to accomplish this with minimal resource requirements. Before proceeding to the details of the examples of the proposed solution, various entities which may be configured to carry out different aspects of the proposed solution will be briefly described. Fig.3 schematically illustrates a radio node in the form of an access node 121 of the wireless network 100 as presented herein, and for carrying out various method steps as outlined. In various examples, the access node 121 is a radio base station for operation in the radio communication network 100, to serve one or more radio UEs, such as the UE 10. The access node 121 may comprise a wireless transceiver 313, such as a radio transceiver for communicating with other entities of the radio communication network 100, such as the UE 10. The transceiver 313 may thus include a radio receiver and transmitter for communicating through at least an air interface. The transceiver may comprise a radio modem. The access node 121 may further comprise, or be connected to, an antenna array 314 which comprises a plurality of antennas (antenna elements) 3141. The antenna array 314 is connected to the transceiver 313. Different antenna ports 3142 connected to the antennas 3141 may thus receive a signal with different angle of arrival (AOA). The antennas 3141 may have RF (radio frequency) chains so that all signals are accessible individually, i.e., configured for digital beamforming. In the proposed solution, the signal is thus individually received with at least three different antenna RF paths, i.e., in at least three individual antennas or at least three individual groups of antennas, with respective RF chains. In other words, the antennas 3141 may have individual or dedicated RF chains, and there may be one RF chain per antenna. In this context, hybrid beamforming is a technique used in wireless communication systems, particularly in massive MIMO (Multiple Input Multiple Output) systems, to efficiently manage the complexity and power consumption associated with using a large number of antennas for transmitting and receiving signals. Rather than traditional MIMO systems, where each antenna has its own radio frequency (RF) chain, hybrid beamforming combines both analog and digital beamforming techniques. The purpose of the analog beamforming stage is to convert, by means of analog components, a large number of analog antenna element observations into a much smaller number of analog values that may then be converted into the digital domain, the so-called RF ports. In an M RF-port implementation, each antenna element is connected to a bank of M phase shifters. The m:th digital value is constructed by combining the m:th phase shifter output across all antenna elements. It is an objective of the phase shifter configuration design that the M RF port values should represent the original analog antenna element observations as well as possible. In hybrid beamforming there would be digital beamforming as well, but this is as such not required for the proposed solution. In an example where the proposed solution is applied to an antenna array 314 configured for hybrid beamforming, the reference signal is thus received in at least three different antenna ports connected to separate RF chains, which as such may be connected to respective groups of antennas or individual antennas. The access node 121 may, inter alia, operate as a transmitter Tx for transmitting signals to be forwarded by the CED 140, and / or as a receiver Rx for receiving signals forwarded by the CED 140. The antenna array 314 may be configured for beamforming, so as to selectively transmit and receive radio signals in the direction of the CED 140. The access node 121 further comprises logic circuitry 310 configured to control the access node 121 to communicate with the UE 100 via the radio transceiver 313 on the physical channel. The logic circuitry 310 may realize a scheduler for scheduling communication of a data set according to the solutions proposed herein, and for configuring the UE to operate according to the scheduling. The logic circuitry 310 may include a processing device 311, including one or multiple processors, microprocessors, data processors, co-processors, and / or some other type of component that interprets and / or executes instructions and / or data. Processing device 311 may be implemented as hardware (e.g., a microprocessor, etc.) or a combination of hardware and software (e.g., a system-on-chip (SoC), an application- specific integrated circuit (ASIC), etc.). The processing device 311 may be configured to perform one or multiple operations based on an operating system and / or various applications or programs. The logic circuitry 310 may further include memory storage 312, which may include one or multiple memories and / or one or multiple other types of storage mediums. For example, memory storage 312 may include a random access memory (RAM), a dynamic random access memory (DRAM), a cache, a read only memory (ROM), a programmable read only memory (PROM), flash memory, and / or some other type of memory. Memory storage 312 may include a hard disk (e.g., a magnetic disk, an optical disk, a magneto-optic disk, a solid state disk, etc.). The memory storage 312 is configured for holding computer program code, which may be executed by the processing device 311, wherein the logic 310 is configured to control the access node 121 to carry out any of the method steps as provided herein. Software defined by said computer program code may include an application or a program that provides a function and / or a process. The software may include device firmware, an operating system (OS), or a variety of applications that may execute in the logic 310. In some examples, the logic circuitry may further be configured to control the CED 140 by remote signaling using the transceiver 313 or other connection. The access node 121 may further comprise an interface 315, configured for communication with the core network 110. Fig.4 schematically shows a location node 112 of (or connected to) the wireless network 100. The location node 112 comprises logic circuitry 113 configured to carry out or assist in positioning / locating UEs in the wireless network 100. The location node 112 may in various examples comprise or realize a location management function as provided for 5GC. The logic circuitry 113 may include a processing device 114, including one or multiple processors, microprocessors, data processors, co-processors, and / or some other type of component that interprets and / or executes instructions and / or data. Processing device 114 may be implemented as hardware (e.g., a microprocessor, etc.) or a combination of hardware and software (e.g., a system-on-chip (SoC), an application- specific integrated circuit (ASIC), etc.). The processing device 114 may be configured to perform one or multiple operations based on an operating system and / or various applications or programs. The logic circuitry 113 may further include memory storage 114, which may include one or multiple memories and / or one or multiple other types of storage mediums. For example, memory storage 114 may include a random access memory (RAM), a dynamic random access memory (DRAM), a cache, a read only memory (ROM), a programmable read only memory (PROM), flash memory, and / or some other type of memory. Memory storage 114 may include a hard disk (e.g., a magnetic disk, an optical disk, a magneto-optic disk, a solid state disk, etc.). The memory storage 114 is configured for holding computer program code, which may be executed by the processing device 113, wherein the logic 113 is configured to control the location node 112 to carry out any of the method steps as provided herein. Software defined by said computer program code may include an application or a program that provides a function and / or a process. The software may include device firmware, an operating system (OS), or a variety of applications that may execute in the logic 113. In some examples, the location node 112 may be realized by computer code residing in the cloud. As already stated, the proposed solution benefits from using spatial information related to the CED 140 upon conveying a radio signal from the UE 10 to the radio node 121. The spatial information comprises ^^^. Obtainment of this first direction may be carried out according to legacy procedure, but for completeness an example of such a method is provided here, with reference to Fig.5. A simple far field beam sweep will do. The gNB 121 may configure the CED 140 with a set of far-field beams, in Fig.5 denoted by B1-B4. The beam B0towards the gNB 121 itself may be pre-configured, either as a far-field beam (suboptimal), a near-field beam, etc; the type of beamforming between the CED 140 and gNB 121 is not limiting. Next, (and exemplified using DL signaling) the gNB 121 would transmit reference signals toward the CED 140, and the CED 140 is configured to apply a beam sweep. The beam in which the UE 10 reports as the best, such as the strongest RSRP (Reference Signal Receive Power), B3 in the shown example, would provide the gNB 121 with an estimate of the first direction comprises^^^. The access node 121 may convey this information to the location node 112. Methods and devices are proposed herein, which are usable for determining a location parameter of a UE 10. According to one aspect, and as shown in Fig.6, a location node 112 may comprise logic circuitry 113 configured to execute program code to carry out the following steps for determining a location parameter of a UE 10. At step 600, the location node 112 obtains a normalized vector based on reception, in at least three separate antenna ports 3142 of an antenna array 314 of a radio node 121, of a radio signal received from the UE 10 via a CED 140. In some examples, obtaining the normalized vector comprises receiving, from the radio node 121, a first vector representing the received signal, and normalizing the first vector to obtain the normalized vector. In other examples, obtaining the normalized vector comprises receiving the normalized vector from the radio node 121. At step 605, the location node determines a first distance ^^^between the UE 10 and the CED 140 using a function which maps the normalized vector to the first distance given spatial information of the CED 140 upon conveying the radio signal. In some examples, as indicated by step 610, the location node 121 may transmit a message to the radio node 121, which message is indicative of the determined location parameter given by the determined first distance. In this context, the location parameter may comprise the first distance, i.e., between the UE 10 and the CED 140, as estimated by the location node 121. In another example, the location parameter may comprise a geographical position of the UE 10, as estimated by the location node 121. The radio node 121 may thereby be set up to configure the CED 140 based on the location parameter, such as by controlling the CED antenna array 141 to obtain spatial sensitivity to the UE 10. According to another aspect, and as shown in Fig.7, a radio node 121 may comprise logic circuitry 311 configured to execute program code to carry out the following steps for facilitating determination of a location parameter of a UE 10. At step 700, the radio node receives, in at least three separate antenna ports 3142 of the antenna array 314 of the radio node, a radio signal from the UE 10 via a CED 140. In some examples, indicated by 705, the radio node normalizes a first vector representing the received signal to obtain a normalized vector. At step 710, the radio node transmits, to a location node 121 of a wireless network 100, signal information indicative of a normalized vector based on the received signal, whereby the location node is configured to determine a first distance between the UE 10 and the CED 140 using a function which maps the normalized vector to the first distance given spatial information of the CED upon conveying the radio signal. Where step 705 is included, the signal information comprises the normalized vector. In other examples, the signal information comprises a first vector representing the received signal, to be normalized in the location node 112. In some examples, as indicated by 715, the radio node 121 may obtain, from the location node, a message comprising the location parameter given by the determined first distance. As noted, the location parameter may in some examples comprise the first distance, and in some examples a determined geographical position of the UE 10. In some examples, as indicated by 720, the radio node may configure the CED 140 with a beam to the UE based on the obtained measure of the location parameter. Various alternative examples may be configured for the methods of Figs 6 and 7. In some examples, the spatial information is indicative of a first direction between the CED 140 and the UE 10, and a second distance and a second direction between the CED 140 and the radio node 121, upon conveying the radio signal. These indicated parameter values of the spatial information may, as mentioned, be determined beforehand and by legacy procedures. In some examples, the function defines a noise-free expression of the normalized vector, characterized by the first and second directions and the first and second distances. The function which maps the normalized vector to the first distance may further be fully characterized given antenna geometry of the radio node antenna array 315 and of the CED antenna array 141, such as the aperture defined by antenna disposition and spacing. The antenna array geometry information is obviously static. Various aspects and examples related to determining the first distance will now be outlined, again with the specific example of the radio node being the access node or gNB 121. The CED 140 is configured with certain spatial information for conveying a radio signal from the UE 10 to the gNB 121. In this context, the CED 140 is configured with a beam towards the UE 10 (in the first direction ^^^), i.e., beam ^^with reference to Fig.5. To elaborate a bit further, if another method than the one outlined above is used for finding^^^,beam ^^is nevertheless configured. Moreover, the CED 140 is configured with a beam ^^towards the gNB 121. As mentioned, the beam type is not limiting and needs not be the same as the one used for determining the first direction. It can also be mentioned that this may be configured jointly with ^^, as a “beam pair". The UE 10 transmits a radio signal, herein also referred to as a reference signal.By way of example, the reference signal may be an SRS (Sounding Reference Signal). Determining the location parameter based on an UL radio signal saves resources. The location node 112, making the final calculation, is upstream of the UE 10. Had the determination of the location parameter instead been based on a DL signal, more resources would be required for the reporting of the measurements back toward the location node 11.LMF. Additionally, the proposed solution involves measuring phase to / from at least 3 gNB RF paths. Doing this in DL would require transmission of 3 orthogonal pilots. According to the proposed solution, it only takes one UL transmission from the UE 10, i.e., reception with all three gNB RF paths, or antenna ports, is possible with a single resource. So, wireless resources are saved both for reference signal sounding and for reporting The reference signal will thus be conveyed by the CED 140, configured according to the spatial information, to the gNB 121. The reference signal is recorded individually at separate antenna ports 3142 of the gNB 121. All antennas have RF paths connected to the respective ports 3142 so that all signals are accessible individually. It can be noted that this concept technically requires at least 2 independent measures from different gNB antennas (or groups of antenna) 3141 to derive a measure. However at least 3 are needed to avoid unambiguous results. Therefore, a solution with at least 3 antenna ports (and RF chains) may be sufficient. At this point, the gNB 121 has recorded a signal ^, which may be represented as a first vector with ^ (or at least 3) elements, where ^ denotes the number of gNB antennas 3141 or ports 3142 (or RF chains). Said signal ^ is narrowband, and in wideband scenarios, there is one such signal per subcarrier. In the remaining exposition, the description is limited to a single subcarrier, with the remark that all subcarriers follow the same principle, and it will be straightforward to the ordinary person skilled in the art of how to deal with that case. The first vector (signal) ^ will be normalized, either in the gNB 121 or later in the location node 112. In this context, one (arbitrary) gNB antenna is selected as a reference antenna. For simplicity, antenna 1 is used as reference. The entire vector ^ is normalized with the observation at this reference antenna so that we obtain a normalized vector (signal) ^ (^ elements) as ^^= ^^ / ^^. Consequently, ^^= 1 by definition and may be discarded. The observation underlying the proposed solution is that the resulting signal ^ has a rich structure. Namely, specifically in the absence of noise in given static / constant information given by antenna geometry, this signal is fully characterized by the four parameters ^^^, ^^^, ^^^^, and ^^^^. In other words, the sought first direction ^^^in addition to the known spatial information. This may be formally expressed as ^ = ^(^^^, ^^^, ^^^^, ^^^^), for some function ^( ) that can be determined offline. Note that the three parameters ^^^, ^^^^, ^^^^are known – the first by estimation and the latter by design. Therefore, we may obtain an estimate of ^^^as This function ^( ) may be stored, e.g., in a look-up table of memory 115, or computed online. In some examples, the function (^) comprises a mapping pattern based on a machine learning model, trained to map the normalized vector (^) to the first distance. Further, it may be noted that it can be shown that for the function +( ). That is, if the UE 10 is in the far field with respect to the CED 140, its angular direction plays no role in the normalized observation ^. This offers a very elegant way to quickly and effortlessly determine whether or not the UE can be regarded as being in the far field. Namely, if ^ ≈ +(^^^^, ^^^^), it may immediately be concluded that the UE 10 is in the far field (which implies that no further beam management is necessary at the CED 140; ^^is the optimal CED configuration towards the UE 10 from a beam focus perspective, related to the distance between UE and CED. This may be under the assumption that B3 is the best FF beam, then we can say that it can't be better than this. Various examples of determination of the first distance will now be provided with reference to Figs 8A to 10B. We consider here a theoretical example of ^ = 3 antennas at the gNB 121 and 21 antennas at the CED 140. All these antennas are, for simplicity, arranged as uniform linear arrays (ULAs). Seen from a boresight direction of the CED 140, the gNB 121 is located 30 / away (array center – array center) and at a 45∘clockwise angle. The Fraunhofer distance of the CED 140 is about 220 / , so the gNB 121 is indeed in its near field. With a 3GHz carrier frequency, the gNB 121 is about 3 meters from the CED 140, a reasonable context for an indoor scenario. The CED 140 is about 1 meter long, which is again reasonable in an indoor environment (alternatively in a vehicle or in general in an “in-X” case). Finally, the UE 10 is located at a clockwise angle to the CED 140 of −25∘. In Fig.8A, the function ^(^^^, ^^^, ^^^^, ^^^^) is illustrated for this parameter setup, i.e., ^(^^^, −25∘, 30 / , 45∘). Recall that this function has three outputs, but as the first one is 1 by definition, we only consider the latter two. These two depend on ^^^and we henceforth denote them as ^$(^^^) and ^^(^^^). In the diagram, the upper “spiral” corresponds to the trajectory that ^$(^^^) undergoes as ^^^changes; the lower “spiral” thus corresponds to ^^(^^^). For each “spiral,” the black circle marks ^4(^^^≈ 0), i.e., the resulting value if the UE 10 is in the extreme near field. The black diamond marks ^4(^^^→ ∞), i.e., the resulting value if the UE 10 is in the far field. It may be pointed out that the spirals are somewhat rotated, otherwise they would coincide and clutter the figure. This is, however, “allowed” as it is deterministic. Also, the black line serves no purpose, it just shows the unit circle to give a feeling for scale of the figure. In an online situation, we would obtain two values ^$and ^^(of the normalized vector) which would fall somewhere on the two “spirals.” Then the positions along the spiral would provide the value ^^^. (This is implicitly what the optimization problem stated above does). In Fig.8B, the illustration is repeated, but for a UE 10 at a clockwise angle of 15∘. As we can see, we still have two spirals, from which we may determine the distance ^^^. In Fig.9A, the results from Figs 8A and 8B are provided in the same plot. Fig.9B is a zoom-in around the diamond of the upper spirals in Fig.9A. As is shown by Fig. 9B, the diamond coincides for both “spirals” (the spirals differ depending on the UE angle). This confirms the earlier claim that the UE angle is irrelevant in the far field. The black diamonds are in fact given by the function +(30 / , 45∘). Finally, some actual estimates of ^^^are provided. The angular setup and the value ^^^^are the same as in Figs 8A to 9B. Again, 21 CED antennas of the antenna array 141 is used, but ^ = 9 gNB antennas 3141. The true UE distance is drawn uniformly from the range [10 / , 300 / ]. The received signal ^ is now corrupted by complex Gaussian noise, with variance 9^per entry ^4. Note that since path loss is considered, the average received power per gNB antenna in a case where the CED 140 comprises a single antenna is unity. Hence, we may define the CED-free-per-antenna- SNR simply as :9;<=>= 1 / 9^. The CED 140 improves said SNR by a factor ≲ 9$, where 9 is the number of CED antennas. The reason why the CED 140 is not exactly increasing the SNR by a factor 9$, is that the CED 140 cannot focus on all gNB antennas 3141 simultaneously, as the gNB antenna array 314 is in the near field (NF) of the CED 140. In Fig.10A results of the estimation of ^^^for four different values of :9;<=>are shown. The diagram shows the results of estimation, obtained by solving the problem ^^^^= arg m!in "^ − stated above using Matlab’s built in optimization package. The results are presented as scatter plot, where the true distance is on the x-axis and the estimated one on the y-axis. As can be seen, the estimation is more precise for UEs in the near field of the CED 140, and for :9;<=>values of 30dB and more, the results are rather accurate. (An error free estimator would show up in the plot as having all markers along the diagonal “y=x”). An SNR of 30dB or more may come across as extremely high. However, the following should be kept in mind: - The plot is shown for a single subcarrier. With 9 subcarriers, the required SNR would decrease with a factor 9. A typical OFDM system may employ 1024 subcarriers, wherefore 30dB in Figure 6 actually corresponds to a per-antenna-SNR of 0dB for the wideband system. - A larger number of independent RF paths to the antennas 3141 at the gNB 121 would further reduce the required SNR. - Fig.10A is made for a single signal in time. If multiple reference signals are used in consecutive slots, the required SNR would reduce correspondingly. - In near field systems, the path losses are inherently small yielding high SNRs. To investigate the robustness of the proposed solution with respect to the preliminary estimation of ^^^, similar results to those in Fig.10A are provided in Fig. 10B, but made with a 10°misalignement of the chosen beam ^^. This beam should ideally point towards −25°counterclockwise with respect to the boresight direction of the CED 140, but here it is directed towards −35°. Hence, a full 10°misalignment. The results of the MatLab estimator shown in Fig.10B are given for :9;<=>= 30dB and :9;<=>= 40dB. As can be seen (by comparing to Fig.10A), the proposed method is fairly robust against such misalignments. Various features and explanatory basis for the proposed solution have been outlined in the foregoing. The proposed solution may take any shape as provided herein, including any combination of the elements and features of the items set out below. Item 1. A method carried out in a location node of a wireless network for determining a location parameter of a user equipment, UE, wherein the method comprises: obtaining (600) a normalized vector (^) based on reception, in at least three separate antenna ports of an antenna array of a radio node, of a radio signal (^) received from the UE via a coverage-enhancing device, CED; determining (605) a first distance (^^^)between the UE and the CED using a function (^) which maps the normalized vector (^) to the first distance given spatial information of the CED upon conveying the radio signal. Item 2. The method of item 1, wherein obtaining a normalized vector comprises: receiving, from the radio node, a first vector (^) representing the received signal; and normalizing the first vector (^) to obtain the normalized vector (^). Item 3. The method of item 1, wherein obtaining a normalized vector comprises receiving the normalized vector (^) from the radio node. Item 4. The method of any preceding item, wherein the spatial information is indicative of a first direction (^^^) between the CED and the UE, and a second distance (^^^^)and a second direction (^^^^)between the CED and the radio node. Item 5. The method of item 4, wherein said function (^) defines a noise-free expression of the normalized vector, characterized by the first and second directions and the first and second distances. Item 6. The method of item 4 or 5, wherein determining the first distance comprises: determining that the UE is in far field range to CED, based on the normalized vector corresponding to the function being independent of the first distance and the first direction. Item 7. The method of item 4, wherein said function (^) comprises a mapping pattern based on a machine learning model, trained to map the normalized vector (^) to the first distance. Item 8. The method of any preceding items, carried out based on determining that the radio node is arranged at near field range to the CED. Item 9. The method of any preceding items, wherein the radio node is access node of the wireless network. Item 10. The method of any preceding item, further comprising: transmitting (610), to the radio node, a message indicative of the location parameter given by the determined first distance. Item 11. The method of item 10, wherein said message indicates whether the UE is in far field range to the CED. Item 12. The method of any of items 1-8, wherein the radio node is a second UE. Item 13. A location node (112) of a wireless network, said location node comprising logic circuitry (113) configured to carry out any of the steps of items 1-12. Item 14. A method carried out in a radio node for facilitating determination of a location parameter of a user equipment, UE, wherein the method comprises: receiving (700), in at least three separate antenna ports of an antenna array of the radio node, a radio signal (^) from the UE via a coverage-enhancing device, CED; transmitting (710), to a location node of a wireless network, signal information indicative of a normalized vector (^) based on the received signal, whereby the location node is configured to determine a first distance (^^^) between the UE and the CED using a function (^) which maps the normalized vector (^) to the first distance(^^^)given spatial information of the CED upon conveying the radio signal. Item 15. The method of item 14, further comprising: normalizing (705) a first vector (^) representing the received signal to obtain the normalized vector (^), wherein the signal information comprises normalized vector (^). Item 16. The method of item 14, wherein the signal information comprises a first vector (^) representing the received signal. Item 17. The method of any of items 14-16, wherein the spatial information is indicative of a first direction (^^^) between the CED and the UE, and a second distance (^^^^) and a second direction (^^^^) between the CED and the radio node. Item 18. The method of item 17, wherein said function (^) defines a noise-free expression of the normalized vector, characterized by the first and second directions and the first and second distances. Item 19. The method of any of items 14-18, further comprising: obtaining (715), from the location node, a message comprising the location parameter given by the determined first distance. Item 20. The method of any of items 14-19, wherein the radio node is access node of the wireless network. Item 21. The method of item 20, comprising: configuring (720) the CED with a beam to the UE based on the obtained measure of the location parameter. Item 22. The method of any of items 14-19, wherein the radio node is a second UE. Item 23. A radio node (121, 20) of a wireless network, said radio node comprising logic circuitry (310) configured to carry out any of the steps of items 13-22.

Claims

CLAIMS 1. A method carried out in a location node of a wireless network for determining a location parameter of a user equipment, UE, wherein the method comprises: obtaining (600) a normalized vector (^) based on reception, in at least three separate antenna ports of an antenna array of a radio node, of a radio signal (^) received from the UE via a coverage-enhancing device, CED; determining (605) a first distance (^^^) between the UE and the CED using a function (^) which maps the normalized vector (^) to the first distance given spatial information of the CED upon conveying the radio signal.

2. The method of claim 1, wherein obtaining a normalized vector comprises: receiving, from the radio node, a first vector (^) representing the received signal; and normalizing the first vector (^) to obtain the normalized vector (^).

3. The method of claim 1, wherein obtaining a normalized vector comprises receiving the normalized vector (^) from the radio node.

4. The method of any preceding claim, wherein the spatial information is indicative of a first direction (^^^) between the CED and the UE, and a second distance (^^^^)and a second direction (^^^^)between the CED and the radio node.

5. The method of claim 4, wherein said function (^) defines a noise-free expression of the normalized vector, characterized by the first and second directions and the first and second distances.

6. The method of claim 4 or 5, wherein determining the first distance comprises: determining that the UE is in far field range to CED, based on the normalized vector corresponding to the function being independent of the first distance and the first direction.

7. The method of claim 4, wherein said function (^) comprises a mapping pattern based on a machine learning model, trained to map the normalized vector (^) to the first distance.

8. The method of any preceding claims, carried out based on determining that the radio node is arranged at near field range to the CED.

9. The method of any preceding claims, wherein the radio node is access node of the wireless network.

10. The method of any preceding claim, further comprising: transmitting (610), to the radio node, a message indicative of the location parameter given by the determined first distance.

11. The method of claim 10, wherein said message indicates whether the UE is in far field range to the CED.

12. The method of any of claims 1-8, wherein the radio node is a second UE.

13. A location node (112) of a wireless network, said location node comprising logic circuitry (113) configured to carry out any of the steps of claims 1-12.

14. A method carried out in a radio node for facilitating determination of a location parameter of a user equipment, UE, wherein the method comprises: receiving (700), in at least three separate antenna ports of an antenna array of the radio node, a radio signal (^) from the UE via a coverage-enhancing device, CED; transmitting (710), to a location node of a wireless network, signal information indicative of a normalized vector (^) based on the received signal, whereby the location node is configured to determine a first distance (^^^)between the UE and the CED using a function (^) which maps the normalized vector (^) to the first distance(^^^)given spatial information of the CED upon conveying the radio signal.

15. The method of claim 14, further comprising:normalizing (705) a first vector (^) representing the received signal to obtain the normalized vector (^), wherein the signal information comprises normalized vector (^).

16. The method of claim 14, wherein the signal information comprises a first vector (^) representing the received signal.

17. The method of any of claims 14-16, wherein the spatial information is indicative of a first direction (^^^)between the CED and the UE, and a second distance (^^^^) and a second direction (^^^^) between the CED and the radio node.

18. The method of claim 17, wherein said function (^) defines a noise-free expression of the normalized vector, characterized by the first and second directions and the first and second distances.

19. The method of any of claims 14-18, further comprising: obtaining (715), from the location node, a message comprising the location parameter given by the determined first distance.

20. The method of any of claims 14-19, wherein the radio node is access node of the wireless network.

21. The method of claim 20, comprising: configuring (720) the CED with a beam to the UE based on the obtained measure of the location parameter.

22. The method of any of claims 14-19, wherein the radio node is a second UE.

23. A radio node (121, 20) of a wireless network, said radio node comprising logic circuitry (310) configured to carry out any of the steps of claims 13-22.

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