Localization of a user equipment

Abstract

There is provided techniques for localization of a UE. A method is performed by the UE. The method comprises receiving a first localization signal from a network node in accordance with a first assumption of a near-far-field relation between the UE and the network node. The method comprises performing a first localization of the UE based on the first localization signal and in accordance with the first assumption. The method comprises transmitting feedback to the network node about the first localization of the UE. The method comprises receiving a second localization signal from the network node in accordance with a second assumption of the near-far-field relation between the UE and the network node and in accordance with the feedback sent to the network node. The method comprises performing a second localization of the UE based on the second localization signal and in accordance with the second assumption.

Description

[0001] LOCALIZATION OF A USER EQUIPMENT

[0002] TECHNICAL FIELD

[0003] Embodiments presented herein relate to methods, a user equipment, a network node, computer programs, and a computer program product for localization of the user equipment.

[0004] BACKGROUND

[0005] Some wireless communication networks provide localization services in diverse application areas, such as detection, ranging and tracking of vulnerable road users, automated guided vehicles, or unmanned aerial vehicles. Localization can help to improve the position estimation of both active and passive objects. For active objects, whose positions are estimated using cellular signals, localization can be used as a means to make the position estimation more precise, while for passive objects localization can either be the sole available scheme for determining its position, or sensing data can be fused by data provided by other sensors, such as inertial measurement unit (IMU), onboard light detection and ranging (LIDAR) device, etc. The present disclosure is focused on localization of active objects, such as user equipment (UE), and in particular where the UE performs the localization itself based on localization signals received from a network node.

[0006] Multiple-input multiple-output (MIMO) communication, or massive MIMO (mMIMO) communication, is one of the key physical layer technologies in fifth generation (5G) telecommunication systems. Here, a network node equipped with an antenna array comprising a large number of many antennas, such as 64 or more antennas, is capable of providing large array gains and / or performing spatial multiplexing of many UEs on the same time-frequency resources. Particularly, the received signal-to-noise ratio (SNR) increases with the number of antennas.

[0007] Implementing very large number of antennas results in fundamental changes of the electromagnetic characteristics. Generally, the electromagnetic radiation field can be divided into a far-field region and a near-field region. Here, the far-field refers to the propagation range at which the direction and channel gain are approximately the same from all elements in the antenna array to the transmitti ng / recei vi ng antenna. The amplitude depends only on the propagation distance to the center of the receiver and the phase variations only depend on the incident angle. Also, the mismatch between the polarization of an antenna and of the incident wave is approximately the same for all antennas in the far-field. On the other hand, if the receive antenna is in the near-field of the transmitter, the propagation distances are so short that there are noticeable amplitude variations over the receiver aperture. Also, the incident wave is arriving from distinctly different angular directions to different elements, thus, e.g., one must model the polarization on an element-by-element basis.

[0008] Theoretically, the boundary between these the far-field region and the near-field region is determined by the Fraunhofer distance, also referred to as the Rayleigh distance. This distance is determined based the maximum allowable phase error in the antenna array. Beyond the Fraunhofer distance (i.e., in the far-field region) the electromagnetic field can be approximately modeled by planar waves. Within the Fraunhofer distance, the near-field propagation becomes dominant, and the electromagnetic field has to be accurately modeled by spherical waves. Due to the success of mMIMO, it is expected that even larger antenna arrays will be used. In such cases and / or when using high frequencies, the electromagnetic radiation field partially needs to be modeled by near-field spherical waves. This is since the Fraunhofer distance will be larger as the size of the antenna arrays grows. As a result, it may be required to consider the near-field characteristics and not only the far-field characteristics in certain situations.

[0009] Existing localization techniques are mainly developed from far-field theories and techniques. This is intuitively because with existing networks, the Fraunhofer distance is only in the order of meters. However, as the size of the antenna arrays grows, the near-field region of a very large antenna arrays may expand by orders of magnitude and reach up to few hundred meters. In such cases, the spherical wave model and the other near-field characteristics should be taken into account, as it may affect the localization procedure.

[0010] Hence, there is a need for improved localization techniques for a UE.

[0011] SUMMARY

[0012] An object of embodiments herein is to address the above the issues and provide localization of the UE that is not impacted by the above issues, or where the above issues at least are mitigated or reduced.

[0013] A particular object is to provide localization of the UE that takes into account that the UE could be located either in the far-field or the near-field of the network node.

[0014] According to a first aspect there is presented a method for localization of a UE. The method is performed by the UE. The method comprises receiving a first localization signal from a network node in accordance with a first assumption of a near-far-field relation between the UE and the network node. The method comprises performing a first localization of the UE based on the first localization signal and in accordance with the first assumption. The method comprises transmitting feedback to the network node about the first localization of the UE. The method comprises receiving a second localization signal from the network node in accordance with a second assumption of the near-far-field relation between the UE and the network node and in accordance with the feedback sent to the network node. The method comprises performing a second localization of the UE based on the second localization signal and in accordance with the second assumption.

[0015] According to a second aspect there is presented a UE for localization. The UE comprises processing circuitry. The processing circuitry is configured to cause the UE to receive a first localization signal from a network node in accordance with a first assumption of a near-far-field relation between the UE and the network node. The processing circuitry is configured to cause the UE to perform a first localization of the UE based on the first localization signal and in accordance with the first assumption. The processing circuitry is configured to cause the UE to transmit feedback to the network node about the first localization of the UE. The processing circuitry is configured to cause the UE to receive a second localization signal from the network node in accordance with a second assumption of the near-far-field relation between the UE and the network node and in accordance with the feedback sent to the network node. The processing circuitry is configured to cause the UE to perform a second localization of the UE based on the second localization signal and in accordance with the second assumption.

[0016] According to a third aspect there is presented a UE for localization. The UE comprises a receive module configured to receive a first localization signal from a network node in accordance with a first assumption of a near-far-field relation between the UE and the network node. The UE comprises a localization module configured to perform a first localization of the UE based on the first localization signal and in accordance with the first assumption. The UE comprises a transmit module configured to transmit feedback to the network node about the first localization of the UE. The UE comprises a receive module configured to receive a second localization signal from the network node in accordance with a second assumption of the near-far-field relation between the UE and the network node and in accordance with the feedback sent to the network node. The UE comprises a localization module configured to perform a second localization of the UE based on the second localization signal and in accordance with the second assumption.

[0017] According to a fourth aspect there is presented a computer program for localization of a UE. The computer program comprises computer code which, when run on processing circuitry of the UE, causes the UE to perform actions. One action comprises the UE to receive a first localization signal from a network node in accordance with a first assumption of a near-far-field relation between the UE and the network node. One action comprises the UE to perform a first localization of the UE based on the first localization signal and in accordance with the first assumption. One action comprises the UE to transmit feedback to the network node about the first localization of the UE. One action comprises the UE to receive a second localization signal from the network node in accordance with a second assumption of the near-far-field relation between the UE and the network node and in accordance with the feedback sent to the network node. One action comprises the UE to perform a second localization of the UE based on the second localization signal and in accordance with the second assumption.

[0018] According to a fifth aspect there is presented a method for localization of a UE. The method is performed by a network node. The method comprises transmitting a first localization signal towards the UE in accordance with a first assumption of a near-far-field relation between the UE and the network node. The method comprises receiving feedback from the UE about a first localization of the UE as performed by the UE based on the first localization signal. The method comprises, in response thereto, transmitting a second localization signal towards the UE in accordance with a second assumption of the near-far-field relation between the UE and the network node, and accordance with the feedback received from the UE.

[0019] According to a sixth aspect there is presented a network node for localization of a UE. The network node comprises processing circuitry. The processing circuitry is configured to cause the network node to transmit a first localization signal towards the UE in accordance with a first assumption of a near-far-field relation between the UE and the network node. The processing circuitry is configured to cause the network node to receive feedback from the UE about a first localization of the UE as performed by the UE based on the first localization signal. The processing circuitry is configured to cause the network node to, in response thereto, transmit a second localization signal towards the UE in accordance with a second assumption of the near-far-field relation between the UE and the network node, and accordance with the feedback received from the UE.

[0020] According to a seventh aspect there is presented a network node for localization of a UE. The network node comprises a transmit module configured to transmit a first localization signal towards the UE in accordance with a first assumption of a near-far-field relation between the UE and the network node. The network node comprises a receive module configured to receive feedback from the UE about a first localization of the UE as performed by the UE based on the first localization signal. The network node comprises a transmit module configured to transmit a second localization signal towards the UE in accordance with a second assumption of the near-far-field relation between the UE and the network node, and accordance with the feedback received from the UE. According to an eighth aspect there is presented a computer program for localization of a UE. The computer program comprises computer code which, when run on processing circuitry of a network node, causes the network node to perform actions. One action comprises the network node to transmit a first localization signal towards the UE in accordance with a first assumption of a near-far-field relation between the UE and the network node. One action comprises the network node to receive feedback from the UE about a first localization of the UE as performed by the UE based on the first localization signal. One action comprises the network node to, in response thereto, transmit a second localization signal towards the UE in accordance with a second assumption of the near-far-field relation between the UE and the network node, and accordance with the feedback received from the UE.

[0021] According to a ninth aspect there is presented a computer program product comprising a computer program according to at least one of the fourth aspect and the eighth aspect and a computer readable storage medium on which the computer program is stored. The computer readable storage medium could be a non-transitory computer readable storage medium.

[0022] Advantageously, these aspects provide localization of the UE that takes into account that the UE could be located either in the far-field or the near-field of the network node.

[0023] In turn, advantageously, these aspects enable accurate localization of the UE irrespectively if the UE is located in the far-field or the near-field of the network node.

[0024] Advantageously, these aspects enable accurate tracking of the UE, especially for UEs where it is not known whether the UE is located in the far-field or the near-field of the network node and / or where the UE moves between the far-field and the near-field during the tracking.

[0025] This, in turn, improves the versatility and quality of the localization and thereby, indirectly, also the communication between the UE and the network node.

[0026] Other objectives, features and advantages of the enclosed embodiments will be apparent from the following detailed disclosure, from the attached dependent claims as well as from the drawings.

[0027] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the element, apparatus, component, means, module, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, module, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

[0028] BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The inventive concept is now described, by way of example, with reference to the accompanying drawings, in which:

[0030] Fig. 1 is a schematic diagram illustrating a communications network according to embodiments;

[0031] Figs. 2, 3, 4, and 5 are flowcharts of methods according to embodiments;

[0032] Fig. 6 is a signaling diagram of a method according to an embodiment;

[0033] Fig. 7 is a schematic diagram showing functional units of a UE according to an embodiment;

[0034] Fig. 8 is a schematic diagram showing functional modules of a UE according to an embodiment;

[0035] Fig. 9 is a schematic diagram showing functional units of a network node according to an embodiment;

[0036] Fig. 10 is a schematic diagram showing functional modules of a network node according to an embodiment; and

[0037] Fig. 11 shows one example of a computer program product comprising computer readable means according to an embodiment.

[0038] DETAILED DESCRIPTION

[0039] The inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the inventive concept are shown. This inventive concept may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Like numbers refer to like elements throughout the description. Any step or feature illustrated by dashed lines should be regarded as optional.

[0040] As disclosed above, there is a need for improved localization techniques for a UE.

[0041] In further detail, as disclosed above, the number of antennas on the transmitter or the receiver and / or the carrier frequency increases, the near-field region may reach up to a few hundred meters. Also, the electromagnetic characteristics in the near-field and far-field differ from each other significantly, which may affect the localization quality.

[0042] For this reason, the used localization method needs to be adaptive with respect to the UE position, or trajectory, with respect to the network node. This becomes especially important in the localization when the UE moves between the near-field region and the far-field region.

[0043] The embodiments disclosed herein in particular relate to techniques for localization of a UE. In order to obtain such techniques, there is provided a UE, a method performed by the UE, a computer program product comprising code, for example in the form of a computer program, that when run on processing circuitry of the UE, causes the UE 200 to perform the method. In order to obtain such techniques, there is further provided a network node, a method performed by the network node, and a computer program product comprising code, for example in the form of a computer program, that when run on processing circuitry of the network node, causes the network node 300 to perform the method.

[0044] Fig. 1 is a schematic diagram illustrating a communications network 100 where embodiments presented herein can be applied. The communications network 100 comprises a network node 300. The network node 300 could be any of a (radio) access network node, radio base station, base transceiver station, node B, evolved node B, gNB, access point, access node, integrated access and backhaul node, transmission and reception point, or the like. The network node 300 is configured to provide network access to a UE 200 over a wireless link 140. The UE 200 could be any of a portable wireless device, mobile station, mobile phone, handset, wireless local loop phone, smartphone, laptop computer, tablet computer, wireless modem, wireless sensor device, network equipped vehicle, network equipped sensor, Internet of Things device, or the like. Depending on the distance between the network node 300 and the UE 200, the UE could be located either in the near-field 110 or the far-field 120 of the network node 300. The near-field 110 and the far-field 120 are illustrated as being separated by a border 130.

[0045] Reference is now made to Fig. 2 illustrating a method for localization of a UE 200 as performed by the UE 200 according to an embodiment.

[0046] As will be disclosed below, the network node 300 transmits a first localization signal. It is assumed that the UE 200 receives this first localization signal.

[0047] S106: The UE 200 receives a first localization signal from a network node 300 in accordance with a first assumption of a near-far-field relation between the UE 200 and the network node 300. In general terms, the near-far-field relation specifies whether the UE 200 is in the near-field or the far-field of the network node 300. That is, one first assumption is that the UE 200 is in the near-field of the network node 300, and another first assumption is that the UE 200 is in the far-field of the network node 300.

[0048] The UE 200 then performs a first localization as in step S108.

[0049] S108: The UE 200 performs a first localization of the UE 200 based on the first localization signal and in accordance with the first assumption.

[0050] In this way, and as will be further disclosed below, the UE 200 understands its (rough) location, speed, trajectory, etc. and understands if the considered first assumption is correct or not.

[0051] Then, based on the obtained localization result, the UE 200 requests the network node 200 to send a second localization signal according to second assumption, which is used by the UE 200 for a second, more accurate, localization.

[0052] S110: The UE 200 transmits feedback to the network node 300 about the first localization of the UE 200.

[0053] As will be disclosed below, the network node 300 then transmits a second localization signal. It is assumed that the UE 200 receives this second localization signal.

[0054] S114: The UE 200 receives a second localization signal from the network node 300 in accordance with a second assumption of the near-far-field relation between the UE 200 and the network node 300 and in accordance with the feedback sent to the network node 300.

[0055] In general terms, the second assumption is opposite to the first assumption.

[0056] The UE 200 then performs a second localization based on the second received localization signal and the considered second assumption.

[0057] S116: The UE 200 performs a second localization of the UE 200 based on the second localization signal and in accordance with the second assumption.

[0058] In this way, the UE 200 can accurately localize itself and understand its speed / moving trajectory in different near- or far-field regions with respect to the network node 300.

[0059] It is noted that although it is disclosed that the UE 200 performs a first localization of the UE 200 and second localization of the UE 200, this does not exclude the fact that the UE 200 might perform at least one further localization of the UE 200 or even a sequence of localizations of the UE 200 in accordance with the first or second assumption. In this way, tracking of the UE 200 can be achieved.

[0060] Embodiments relating to further details of localization of a UE 200 as performed by the UE 200 will now be disclosed with continued reference to Fig. 2.

[0061] In general terms, depending on the considered assumption, the UE 200 may run different localization algorithms for the near-field and for the far-field. In particular, in some embodiments, the assumptions (i.e., the first assumption and the second assumption) impact how the UE 200 receives the localization signals and how the UE 200 performs the localizations (i.e., the first localization and the second localization). As an example, that the UE 200 is located in the near-field of the network node 300 dictates that a different channel model needs to be considered than if the UE 200 is located in the far- field of the network node 300. The far-field model, in general, yields a rank one matrix where a set of linear operations may be applied sequentially to derive, individually, spatial estimations, i.e., angle of arrival, time of flight etc. On the other hand, the spherical wavefront of the near-field propagation creates a more complicated channel model, where the angular and the range domain are not decoupled. Therefore, the localization algorithm employed for the near-field will be more complex. In addition, the network node 300 may employ beam-forming for the far-field localization scenario and beam-focusing, with each beam focusing the energy on a focal poi ntLfor the near-field localization scenario, which should be taken into account by the UE when performing the localization.

[0062] One of the differences between the assumption that the UE 200 is in the near-field of the network node 300 and the assumption that the UE 200 is in the far-field of the network node 300 from a localization perspective is the increased computational complexity for the near-field case. The planar wave assumption in the far-field detaches the distance of flight from the phase of the received elements, relative to a reference element. Therefore, the angle-of-arrival may be estimated independently for the far-field case. In the near-field, the wave curvature is not negligible and the distance to each receiving element affects the received phase considerably. As a result, the angle-of-arrival needs to be jointly estimated with the distance to the reference point of the array for the near-field case. In general, the joint estimation increases the search dimensions and thus, the computational complexity.

[0063] For instance, if using a far-field based localization algorithm for the first localization the UE 200 might deduce that the UE 200 is in, or close to, the near-field. The UE 200 then understands that the localization result of the first localization might be inaccurate. In one alternative the UE 200 uses a near- field localization algorithm for the second localization to obtain a more accurate localization result. In another alternative the UE 200 predicts that it will soon move to the near-field and for that reason uses a near-field localization algorithm for the second localization. Hence, in some embodiments, according to the first assumption the UE 200 is located in the far-field of the network node 300 when receiving the first localization signal. Then, according to the second assumption the UE 200 is located in the near-field of the network node 300 when receiving the second localization signal. However, in other embodiments, according to the first assumption the UE 200 is located in the near-field of the network node 300 when receiving the first localization signal, and according to the second assumption the UE 200 is located in the far-field of the network node 300 when receiving the second localization signal. This could be the case when tracking of the UE 200 is performed.

[0064] In some aspects, the UE 200 sends a capability report to the network node 300 to inform the network node 300 the capabilities of the UE 200 to perform localization. Therefore, in some embodiments, the UE 200 is configured to perform (optional) step S102 before receiving the first localization signal in step S106 and so that the network node 300 can adapt the first localization signal accordingly (i.e., to fit the capabilities) before the first localization signal is transmitted.

[0065] S102: The UE 200 transmits a capability report to the network node 300. The capability report is indicative of localization capabilities of the UE 200.

[0066] However, as will be further disclosed below, in other embodiments, the network node 300 may receive the capability report of the UE 200 from some other entity than the UE 200 itself.

[0067] In some non-limiting examples, the capability report indicates the number of antennas, or panels, at the UE, the size of antennas, or panels, at the UE, the capability of the UE to perform localization in the near-field and / or the far-field, supported codebook-based operations, localization capabilities, etc. In some non-limiting examples, the localization capabilities pertain to at least one of: support of single, dual or alternating polarization at the transmit and receive antenna used for localization at the UE, downli nk / uplink switching delay and accuracy for localization, support of single- or dual-directional localization, etc.

[0068] As will be further disclosed below, in some aspects, the network node 200 transmits information about the appropriate localization method to be used by the UE 200 for the first localization. Therefore, in some embodiments, the UE 200 is configured to perform (optional) step S104 before receiving the first localization signal in step S106 and so that the UE 200 can use the appropriate localization method. S104: The UE 200 receives information from the network node 300 indicative of which localization method to use when performing the first localization.

[0069] Also, prior to transmitting the first localization signal, the network node 300 may send the UE 200 configuration about how to receive the first localization signal. For instance, the configuration may indicate at which time / frequency resources the UE 200 should receive the first localization signal. The configurations to the UE 200 may be semi-persistent, semi-static and / or dynamic, and may be indicated based on radio resource control (RRC) signaling, medium access control control element (MAC-CE) signaling, and / or downlink control information (DCI) signaling.

[0070] The feedback might be sent upon the UE 200 having confirmed that the first assumption is incorrect, or at least that there is a need for the UE 200 to perform the second localization. The latter could be the case for the above disclosed scenario where the UE 200 predicts that it will soon move to the near-field (in case the first assumption is that the UE is in the far-field of the network node 300), or vice versa (in case the first assumption is that the UE is in the near-field of the network node 300).

[0071] In general terms, whether the first assumption is correct or not can be determined from different types of information. For example, in some non-limiting examples, that the first assumption is incorrect is determined from at least one of: information indicative of a position where the UE 200 is located, information indicative of a position where the network node 300 is located, a phase difference between antennas at the UE 200 as estimated for the first localization signal. The information indicative of the position where the UE 200 is located can be received from the network node 300, from a global positioning system, etc. Then if the position as deduced from the first localization differs more than some threshold value from the position given by the information received from the network node 300, from the global positioning system, etc., then the UE 200 can deduce that the first assumption is incorrect.

[0072] Further, the feedback as transmitted in step S110 might indicate that the first assumption is incorrect and / or that transmission of the second localization signal is requested. In general terms, the feedback might either explicitly or implicitly state that the assumption needs to be changed for the second localization. An example of an explicit statement is the UE 200 informing the network node 300 that the first assumption is incorrect. An example of an implicit statement is the UE 200 reporting the localization result of the first localization to the network node 300 and it is then up to the network node 300 itself to deduce that the first assumption was incorrect. Therefore, in some embodiments, the feedback comprises a localization result of the UE 200 as estimated from the first localization of the UE 200. In some examples, the feedback is transmitted as uplink control information (UCI) signaling, such as hybrid automatic repeat request acknowledgement, a scheduling request, channel state information, or be based on signaling over an uplink data channel (such as the physical uplink shared channel, PUSCH) and / or an uplink control channel (such as the physical uplink control channel, PUCCH).

[0073] As will be further disclosed below, in some aspects, the network node 200 transmits information about the appropriate localization method to be used by the UE for the second localization. Therefore, in some embodiments, the UE 200 is configured to perform (optional) step S112 before receiving the second localization signal in step S114 and so that the UE 200 can use the appropriate localization method.

[0074] S112: The UE 200 receives information from the network node 300 indicative of which localization method to use when performing the second localization.

[0075] Also, prior to transmitting the second localization signal, the network node 300 may send the UE 200 configuration about how to receive the second localization signal. For instance, the configuration may indicate at which time / frequency resources the UE 200 should receive the second localization signal. The configurations to the UE 200 may be semi-persistent, semi-static and / or dynamic, and may be indicated based on RRC, MAC-CE and / or DCI signaling.

[0076] In some aspects, the UE 200 estimates the probability that there is a line-of-sight connection between the UE 200 and the network node 300. That is, in some embodiments, performing at least one of the first localization of the UE 200 and the second localization of the UE 200 comprises estimating a probability of there being a wireless line-of-sight connection between the UE 200 and the network node 300. Then, the feedback from the UE 200 to the network node 300 may include information about this estimation.

[0077] For example, the UE 200 could estimate the probability that there is a line-of-sight connection between the UE 200 and the network node 300 by removing the multi-path component. The removal of the multipath component relies, in general, on separating and identifying individual links in the angular (angle of arrival) and range (distance of flight) domains. Estimating such parameters relies on the assumed received wavefront, as the planar wavefront enables for a decoupled parameter estimation. Moreover, if the far-field assumption is validated for the wireless link between the network node 300 and the UE 200, then the signal component due to scatterers present in the UE’s near field may be removed. In another example, estimating the probability that there is a line-of-sight connection between the UE 200 and the network node 300 is estimated based on the direction of the received beams, the timing advance and / or the estimated position of the UE 200. In some aspects, at the end of the second localization step, the UE 200 performs a final localization based on one or a combination of the first and the second localizations. Hence, in some embodiments, a final localization result of the UE 200 is determined at least based on the second localization of the UE 200 and optionally on the first localization of the UE 200. However, as disclosed above, there might also be further localizations performed after the second localization, for example if tracking of the UE 200 is performed.

[0078] The UE 200 might then inform the network node 300 about the final localization. Therefore, in some embodiments, the UE 200 is configured to perform (optional) step S118 after the second localization has been performed.

[0079] S118: The UE 200 transmits the final localization result of the UE 200 to the network node 300.

[0080] Reference is now made to Fig. 3 illustrating a method for localization of a UE 200 as performed by the network node 300 according to an embodiment.

[0081] S206: The network node 300 transmits a first localization signal towards the UE 200 in accordance with a first assumption of a near-far-field relation between the UE 200 and the network node 300.

[0082] As disclosed above, the near-far-field relation specifies whether the UE 200 is in the near-field or the far-field of the network node 300. That is, one first assumption is that the UE 200 is in the near-field of the network node 300, and another first assumption is that the UE 200 is in the far-field of the network node 300.

[0083] As further disclosed above, the UE 200 performs a first localization based on the first localization signal and transmits feedback thereof to the network node 300.

[0084] S210: The network node 300 receives feedback from the UE 200 about a first localization of the UE 200 as performed by the UE 200 based on the first localization signal.

[0085] The network node 300 can then adapt which type of localization signal, or in what way the second localization is transmitted towards the UE 200 based on the received feedback.

[0086] S216: The network node 300 in response to having received the feedback from the UE 200 transmits a second localization signal towards the UE 200 in accordance with a second assumption of the near-far- field relation between the UE 200 and the network node 300, and accordance with the feedback received from the UE 200. In general terms, the second assumption is opposite to the first assumption.

[0087] As disclosed above, the UE 200 might perform at least one further localization of the UE 200 or even a sequence of localizations of the UE 200 in accordance with the first or second assumption. Therefore, the network node 300 might be configured to transmit corresponding further localization signals.

[0088] Embodiments relating to further details of localization of a UE 200 as performed by the network node 300 will now be disclosed with continued reference to Fig. 3.

[0089] As disclosed above, the assumptions impact how the UE 200 receives the localization signals and how the UE 200 performs the localizations. Likewise, in some embodiments the assumptions (i.e., the first assumption and the second assumption) impact characteristics of the localization signals (i.e., the first localization signal and the second localization signal).

[0090] As disclosed above, in some embodiments according to the first assumption the UE 200 is located in a far-field of the network node 300. The first localization signal might therefore follow far-field characteristics. Likewise, in some embodiments according to the second assumption the UE 200 is located in a near-field of the network node 300. The second localization signal might therefore follow near-field characteristics. However, as also disclosed above, also the opposite options can be made, depending on the scenario.

[0091] In general terms, the far-field characteristics and the near-field characteristics relate to any, or any combination of the number of pilot signals included in the localization signal, which codebooks and / or beam-forming is used for transmitting the localization signal, the transmission power of the localization signal, the polarization of the transmitted localization signal, the carrier frequency of the transmitted localization signal, etc. The codebooks for the far-field might be based on beam-forming in different angles, whereas the codebooks for the near-field might be based on beam-focusing technique in which both the angle and distance are taken into account and energy of each beam is focused on a specific focal point. Moreover, depending on the UE position the transmission power may be adapted accordingly, where the transmission power is lower for the near-field than for the far-field. For example, the near-field effect may result in polarization mismatches in the receiver antenna array which can be taken into account in for the localization signal used for the near-field assumption. In addition, given the first localization result, fewer pilots may be considered in the second localization step (regardless of the firs assumption is that the UE 200 is located in the near field or the far field of the network node 300). Finally, since frequency affects the far-field distance, a different frequency band may be employed for the near-field. As disclosed above, the UE 200 sends a capability report to the network node 300 to inform the network node 300 the capabilities of the UE 200 to perform localization. However, the capability report might also be received from another entity, such as an operations, administration, and management (0AM) node or another network node. In particular, in some embodiments, the network node 300 is configured to perform (optional) step S202 before transmitting the first localization signal in step S206.

[0092] S202: The network node 300 receives a capability report indicative of localization capabilities of the UE 200. Characteristics of at least one of the first localization signal and the second localization signal are selected in accordance with the capability report.

[0093] Examples of information specified in the capability report has been disclosed and is therefore not repeated here.

[0094] As disclosed above, in some aspects, the network node 200 transmits information about the appropriate localization method to be used by the UE 200 for the first localization. Therefore, in some embodiments, the network node 300 is configured to perform (optional) step S204 before transmitting the first localization signal in step S206.

[0095] S204: The network node 300 transmits information to the UE 200 indicative of which localization method to use by the UE 200 when performing a first localization based on the first localization signal.

[0096] As disclosed above, whether the first assumption is correct or not can by the UE 300 for example be determined from information indicative of a position where the network node 300 is located. Therefore, in some embodiments, the network node 300 is configured to perform (optional) step S208.

[0097] S208: The network node 300 transmits information to the UE 200 indicative of a position where the network node 300 is located.

[0098] In some aspects, and depending on the information received in the feedback from the UE 200 in step S210, the network node 300 might estimate properties of the wireless channel between the network node 300 and the UE 200. In particular, in some embodiments, the network node 300 is configured to perform (optional) step S212.

[0099] S212: The network node 300 performs channel estimation based on the feedback received from the UE 200. Just as for the first localization, also for the second localization the network node 300 might transmit information about the appropriate localization method to be used by the UE 200 for the second localization. Therefore, in some embodiments, the network node 300 is configured to perform (optional) step S214 before transmitting the second localization signal in step S216.

[0100] S214: The network node 300 transmits information to the UE 200 indicative of which localization method to use by the UE 200 when performing a second localization based on the second localization signal.

[0101] As disclosed above, the UE 200 might inform the network node 300 about the final localization. Therefore, in some embodiments, the network node 300 is configured to perform (optional) step S218.

[0102] S218: The network node 300 receives a final localization result of the UE 200 from the UE 200.

[0103] One particular embodiment for localization of the UE 200 as performed by the UE 200 and the network node 300 based on at least some of the above disclosed embodiments will now be disclosed in detail with reference to the flowcharts of Fig. 4 and Fig. 5, as well as to the signaling diagram of Fig. 6.

[0104] 5301 , S401 , S501 : The UE 200 transmits a capability report to the network node 300. The capability report is indicative of localization capabilities of the UE 200

[0105] 5302, S402, S502: The network node 300 transmits a first localization signal towards the UE 200 in accordance with a first assumption of a near-far-field relation between the UE 200 and the network node 300.

[0106] 5303, S503: The UE 200 performs a first localization of the UE 200 based on the first localization signal and in accordance with the first assumption.

[0107] 5304, S403, S504: The UE 200 transmits feedback to the network node 300 about the first localization of the UE 200.

[0108] S404, S505: The network node 300 adapts which type of localization signal, or in what way the second localization is transmitted towards the UE 200 based on the received feedback.

[0109] S305, S405, S506: The network node 300 transmits a second localization signal towards the UE 200 in accordance with a second assumption of the near-far-field relation between the UE 200 and the network node 300, and accordance with the feedback received from the UE 200. S306, S507: The UE 200 performs a second localization of the UE 200 based on the second localization signal and in accordance with the second assumption.

[0110] S307, S406, S508: The UE 200 transmits the final localization result of the UE 200 to the network node 300.

[0111] Fig. 7 schematically illustrates, in terms of a number of functional units, the components of a UE 200 according to an embodiment. Processing circuitry 210 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions stored in a computer program product 1110a (as in Fig. 11), e.g. in the form of a storage medium 230. The processing circuitry 210 may further be provided as at least one application specific integrated circuit (ASIC), or field programmable gate array (FPGA).

[0112] Particularly, the processing circuitry 210 is configured to cause the UE 200 to perform a set of operations, or steps, as disclosed above. For example, the storage medium 230 may store the set of operations, and the processing circuitry 210 may be configured to retrieve the set of operations from the storage medium 230 to cause the UE 200 to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus the processing circuitry 210 is thereby arranged to execute methods as herein disclosed.

[0113] The storage medium 230 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory.

[0114] The UE 200 may further comprise a communications (comm.) interface 220 for communications with other entities, functions, nodes, and devices, such as the network node 300, to perform localization in accordance with the herein disclosed embodiments. As such the communications interface 220 may comprise one or more transmitters and receivers, comprising analogue and digital components.

[0115] The processing circuitry 210 controls the general operation of the UE 200 e.g. by sending data and control signals to the communications interface 220 and the storage medium 230, by receiving data and reports from the communications interface 220, and by retrieving data and instructions from the storage medium 230. Other components, as well as the related functionality, of the UE 200 are omitted in order not to obscure the concepts presented herein. Fig. 8 schematically illustrates, in terms of a number of functional modules, the components of a UE 200 according to an embodiment. The UE 200 of Fig. 8 comprises a number of functional modules; a receive module 210c configured to perform step S106, a localization module 21 Od configured to perform step S108, a transmit module 21 Oe configured to perform step S110, a receive module 21 Og configured to perform step S114, and a localization module 21 Oh configured to perform step S116. The UE 200 of Fig. 8 may further comprise a number of optional functional modules, such as any of a transmit module 21 Oa configured to perform step S102, a receive module 210b configured to perform step S104, a receive module 21 Of configured to perform step S112, and a transmit module 21 Oi configured to perform step S118.

[0116] In general terms, each functional module 210a:21 Oi may be implemented in hardware or in software. Preferably, one or more or all functional modules 210a:21 Oi may be implemented by the processing circuitry 210, possibly in cooperation with the communications interface 220 and / or the storage medium 230. The processing circuitry 210 may thus be arranged to from the storage medium 230 fetch instructions as provided by a functional module 210a:21 Oi and to execute these instructions, thereby performing any steps of the UE 200 as disclosed herein.

[0117] Fig. 9 schematically illustrates, in terms of a number of functional units, the components of a network node 300 according to an embodiment. Processing circuitry 310 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions stored in a computer program product 1110b (as in Fig. 11), e.g. in the form of a storage medium 330. The processing circuitry 310 may further be provided as at least one application specific integrated circuit (ASIC), or field programmable gate array (FPGA).

[0118] Particularly, the processing circuitry 310 is configured to cause the network node 300 to perform a set of operations, or steps, as disclosed above. For example, the storage medium 330 may store the set of operations, and the processing circuitry 310 may be configured to retrieve the set of operations from the storage medium 330 to cause the network node 300 to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus the processing circuitry 310 is thereby arranged to execute methods as herein disclosed.

[0119] The storage medium 330 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory. The network node 300 may further comprise a communications interface 320 for communications with other entities, functions, nodes, and devices, such as the UE 200, to participate in the localization of the UE 300 in accordance with the herein disclosed embodiments. As such the communications interface 320 may comprise one or more transmitters and receivers, comprising analogue and digital components.

[0120] The processing circuitry 310 controls the general operation of the network node 300 e.g. by sending data and control signals to the communications interface 320 and the storage medium 330, by receiving data and reports from the communications interface 320, and by retrieving data and instructions from the storage medium 330. Other components, as well as the related functionality, of the network node 300 are omitted in order not to obscure the concepts presented herein.

[0121] Fig. 10 schematically illustrates, in terms of a number of functional modules, the components of a network node 300 according to an embodiment. The network node 300 of Fig. 10 comprises a number of functional modules; a transmit module 310c configured to perform step S206, a receive module 31 Oe configured to perform step S210, and a transmit module 31 Oh configured to perform step S216. The network node 300 of Fig. 8 may further comprise a number of optional functional modules, such as any of a receive module 310a configured to perform step S202, a transmit module 310b configured to perform step S204, a transmit module 31 Od configured to perform step S208, an estimate module 31 Of configured to perform step S212, a transmit module 310g configured to perform step S214, and a receive module 31 Oi configured to perform step S218.

[0122] In general terms, each functional module 310a:31 Oi may be implemented in hardware or in software. Preferably, one or more or all functional modules 310a:31 Oi may be implemented by the processing circuitry 310, possibly in cooperation with the communications interface 320 and / or the storage medium 330. The processing circuitry 310 may thus be arranged to from the storage medium 330 fetch instructions as provided by a functional module 310a:31 Oi and to execute these instructions, thereby performing any steps of the network node 300 as disclosed herein.

[0123] The network node 300 may be provided as a standalone device or as a part of at least one further device. For example, the network node 300 may be provided in a node of the radio access network or in a node of the core network. Alternatively, functionality of the network node 300 may be distributed between at least two devices, or nodes. These at least two nodes, or devices, may either be part of the same network part (such as the radio access network or the core network) or may be spread between at least two such network parts. In general terms, instructions that are required to be performed in real time may be performed in a device, or node, operatively closer to the cell than instructions that are not required to be performed in real time. A first portion of the instructions performed by the network node 300 may be executed in a first device, and a second portion of the instructions performed by the network node 300 may be executed in a second device; the herein disclosed embodiments are not limited to any particular number of devices on which the instructions performed by the network node 300 may be executed. Hence, the methods according to the herein disclosed embodiments are suitable to be performed by a network node 300 residing in a cloud computational environment. Therefore, although a single processing circuitry 310 is illustrated in Fig. 9 the processing circuitry 310 may be distributed among a plurality of devices, or nodes. The same applies to the functional modules 31 Oa: 310i of Fig. 10 and the computer program 1120b of Fig. 11 .

[0124] Some (radio) access network architectures define network nodes (or gNBs) comprising multiple component parts or nodes: a central unit (CU), one or more distributed units (DUs), and one or more radio units (RUs). The protocol layer stack of the network node is divided between the CU, the DUs and the RUs, with one or more lower layers of the stack implemented in the RUs, and one or more higher layers of the stack implemented in the CU and / or DUs. The CU is coupled to the DUs via a fronthaul higher layer split (HLS) network; the CU / DUs are connected to the RUs via a fronthaul lower-layer split (LLS) network. The DU may be combined with the CU in some embodiments, where a combined DU / CU may be referred to as a CU or simply a baseband unit. A communication link for communication of user data messages or packets between the RU and the baseband unit, CU, or DU is referred to as a fronthaul network or interface. Messages or packets may be transmitted from the network node 300 in the downlink (i.e., from the CU to the RU) or received by the network node 300 in the uplink (i.e., from the RU to the CU).

[0125] Fig. 11 shows one example of a computer program product 1110a, 1110b comprising computer readable means 1130. On this computer readable means 1130, a computer program 1120a can be stored, which computer program 1120a can cause the processing circuitry 210 and thereto operatively coupled entities and devices, such as the communications interface 220 and the storage medium 230, to execute methods according to embodiments described herein. The computer program 1120a and / or computer program product 1110a may thus provide means for performing any steps of the UE 200 as herein disclosed. On this computer readable means 1130, a computer program 1120b can be stored, which computer program 1120b can cause the processing circuitry 310 and thereto operatively coupled entities and devices, such as the communications interface 320 and the storage medium 330, to execute methods according to embodiments described herein. The computer program 1120b and / or computer program product 1110b may thus provide means for performing any steps of the network node 300 as herein disclosed.

[0126] In the example of Fig. 11 , the computer program product 1110a, 1110b is illustrated as an optical disc, such as a CD (compact disc) or a DVD (digital versatile disc) or a Blu-Ray disc. The computer program product 1110a, 1110b could also be embodied as a memory, such as a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), or an electrically erasable programmable read-only memory (EEPROM) and more particularly as a non-volatile storage medium of a device in an external memory such as a USB (Universal Serial Bus) memory or a Flash memory, such as a compact Flash memory. Thus, while the computer program 1120a, 1120b is here schematically shown as a track on the depicted optical disk, the computer program 1120a, 1120b can be stored in any way which is suitable for the computer program product 1110a, 1110b.

[0127] The inventive concept has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended patent claims.

Claims

CLAIMS1 . A method for localization of a UE (200), wherein the method is performed by the UE (200), and wherein the method comprises: receiving (S106) a first localization signal from a network node (300) in accordance with a first assumption of a near-far-field relation between the UE (200) and the network node (300); performing (S108) a first localization of the UE (200) based on the first localization signal and in accordance with the first assumption; transmitting (S110) feedback to the network node (300) about the first localization of the UE (200); receiving (S114) a second localization signal from the network node (300) in accordance with a second assumption of the near-far-field relation between the UE (200) and the network node (300) and in accordance with the feedback sent to the network node (300); and performing (S116) a second localization of the UE (200) based on the second localization signal and in accordance with the second assumption.

2. The method according to claim 1, wherein the assumptions impact how the UE (200) receives the localization signals and how the UE (200) performs the localizations.

3. The method according to claim 1, wherein the second assumption is opposite to the first assumption.

4. The method according to claim 1 , wherein according to the first assumption the UE (200) is located in a far-field of the network node (300) when receiving the first localization signal.

5. The method according to claim 1, wherein according to the second assumption the UE (200) is located in a near-field of the network node (300) when receiving the second localization signal.

6. The method according to claim 1, wherein the method further comprises: transmitting (S102) a capability report to the network node (300), wherein the capability report is indicative of localization capabilities of the UE (200).

7. The method according to claim 1, wherein the method further comprises:receiving (S104) information from the network node (300) indicative of which localization method to use when performing the first localization.

8. The method according to claim 1, wherein the feedback is sent upon the UE (200) having confirmed that the first assumption is incorrect.

9. The method according to claim 8, wherein that the first assumption is incorrect is determined from at least one of:- information indicative of a position where the UE (200) is located,- information indicative of a position where the network node (300) is located, and- a phase difference between antennas at the UE (200) as estimated for the first localization signal.

10. The method according to claim 1 , wherein the feedback indicates that the first assumption is incorrect and / or that transmission of the second localization signal is requested.11 . The method according to claim 1 , wherein the feedback comprises a localization result of the UE (200) as estimated from the first localization of the UE (200).

12. The method according to claim 1 , wherein the method further comprises: receiving (S112) information from the network node (300) indicative of which localization method to use when performing the second localization.

13. The method according to claim 1 , wherein performing at least one of the first localization of the UE (200) and the second localization of the UE (200) comprises estimating a probability of there being a wireless line-of-sight connection between the UE (200) and the network node (300).

14. The method according to claim 1, wherein a final localization result of the UE (200) is determined at least based on the second localization of the UE (200) and optionally on the first localization of the UE (200).

15. The method according to claim 14, wherein the method further comprises: transmitting (S118) the final localization result of the UE (200) to the network node (300).

16. A method for localization of a UE (200), wherein the method is performed by a network node (300), and wherein the method comprises: transmitting (S206) a first localization signal towards the UE (200) in accordance with a first assumption of a near-far-field relation between the UE (200) and the network node (300); receiving (S210) feedback from the UE (200) about a first localization of the UE (200) as performed by the UE (200) based on the first localization signal; and in response thereto: transmitting (S216) a second localization signal towards the UE (200) in accordance with a second assumption of the near-far-field relation between the UE (200) and the network node (300), and accordance with the feedback received from the UE (200).

17. The method according to claim 16, wherein the assumptions impact characteristics of the localization signals.

18. The method according to claim 16, wherein the second assumption is opposite to the first assumption.

19. The method according to claim 16, wherein according to the first assumption the UE (200) is located in a far-field of the network node (300) and the first localization signal follows far-field characteristics.

20. The method according to claim 16, wherein according to the second assumption the UE (200) is located in a near-field of the network node (300) and the second localization signal follows near-field characteristics.21 . The method according to claim 16, wherein the method further comprises: receiving (S202) a capability report indicative of localization capabilities of the UE (200), and wherein characteristics of at least one of the first localization signal and the second localization signal are selected in accordance with the capability report.

22. The method according to claim 16, wherein the method further comprises: transmitting (S204) information to the UE (200) indicative of which localization method to use by the UE (200) when performing a first localization based on the first localization signal.

23. The method according to claim 16, wherein the method further comprises:transmitting (S208) information to the UE (200) indicative of a position where the network node (300) is located.

24. The method according to claim 16, wherein the method further comprises: performing (S212) channel estimation based on the feedback received from the UE (200).

25. The method according to claim 16, wherein the method further comprises: transmitting (S214) information to the UE (200) indicative of which localization method to use by the UE (200) when performing a second localization based on the second localization signal.

26. The method according to claim 16, wherein the method further comprises: receiving (S218) a final localization result of the UE (200) from the UE (200).

27. A UE (200) for localization, the UE (200) comprising processing circuitry (210), the processing circuitry being configured to cause the UE (200) to: receive a first localization signal from a network node (300) in accordance with a first assumption of a near-far-field relation between the UE (200) and the network node (300); perform a first localization of the UE (200) based on the first localization signal and in accordance with the first assumption; transmit feedback to the network node (300) about the first localization of the UE (200); receive a second localization signal from the network node (300) in accordance with a second assumption of the near-far-field relation between the UE (200) and the network node (300) and in accordance with the feedback sent to the network node (300); and perform a second localization of the UE (200) based on the second localization signal and in accordance with the second assumption.

28. A UE (200) for localization, the UE (200) comprising: a receive module (210c) configured to receive a first localization signal from a network node (300) in accordance with a first assumption of a near-far-field relation between the UE (200) and the network node (300);a localization module (21 Od) configured to perform a first localization of the UE (200) based on the first localization signal and in accordance with the first assumption; a transmit module (21 Oe) configured to transmit feedback to the network node (300) about the first localization of the UE (200); a receive module (210g) configured to receive a second localization signal from the network node (300) in accordance with a second assumption of the near-far-field relation between the UE (200) and the network node (300) and in accordance with the feedback sent to the network node (300); and a localization module (21 Oh) configured to perform a second localization of the UE (200) based on the second localization signal and in accordance with the second assumption.

29. The UE (200) according to claim 27 or 28, further being configured to perform the method according to any of claims 2 to 15.

30. A network node (300) for localization of a UE (200), the network node (300) comprising processing circuitry (310), the processing circuitry being configured to cause the network node (300) to: transmit a first localization signal towards the UE (200) in accordance with a first assumption of a near-far-field relation between the UE (200) and the network node (300); receive feedback from the UE (200) about a first localization of the UE (200) as performed by the UE (200) based on the first localization signal; and in response thereto: transmit a second localization signal towards the UE (200) in accordance with a second assumption of the near-far-field relation between the UE (200) and the network node (300), and accordance with the feedback received from the UE (200).31 . A network node (300) for localization of a UE (200), the network node (300) comprising: a transmit module (310c) configured to transmit a first localization signal towards the UE (200) in accordance with a first assumption of a near-far-field relation between the UE (200) and the network node (300); a receive module (31 Oe) configured to receive feedback from the UE (200) about a first localization of the UE (200) as performed by the UE (200) based on the first localization signal; anda transmit module (31 Oh) configured to transmit a second localization signal towards the UE (200) in accordance with a second assumption of the near-far-field relation between the UE (200) and the network node (300), and accordance with the feedback received from the UE (200).

32. The network node (300) according to claim 30 or 31 , further being configured to perform the method according to any of claims 18 to 26.

33. A computer program (1120a) for localization of a UE (200), the computer program comprising computer code which, when run on processing circuitry (210) of the UE (200), causes the UE (200) to: receive (S106) a first localization signal from a network node (300) in accordance with a first assumption of a near-far-field relation between the UE (200) and the network node (300); perform (S108) a first localization of the UE (200) based on the first localization signal and in accordance with the first assumption; transmit (S110) feedback to the network node (300) about the first localization of the UE (200); receive (S114) a second localization signal from the network node (300) in accordance with a second assumption of the near-far-field relation between the UE (200) and the network node (300) and in accordance with the feedback sent to the network node (300); and perform (S116) a second localization of the UE (200) based on the second localization signal and in accordance with the second assumption.

34. A computer program (1120b) for localization of a UE (200), the computer program comprising computer code which, when run on processing circuitry (310) of a network node (300), causes the network node (300) to: transmit (S206) a first localization signal towards the UE (200) in accordance with a first assumption of a near-far-field relation between the UE (200) and the network node (300); receive (S210) feedback from the UE (200) about a first localization of the UE (200) as performed by the UE (200) based on the first localization signal; and in response thereto: transmit (S216) a second localization signal towards the UE (200) in accordance with a second assumption of the near-far-field relation between the UE (200) and the network node (300), and accordance with the feedback received from the UE (200).

35. A computer program product (1110a, 1110b) comprising a computer program (1120a, 1120b) according to at least one of claims 33 and 34, and a computer readable storage medium (1130) on which the computer program is stored.

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