Selection of neighboring positioning devices for a client device

Abstract

Embodiments of the invention relate to positioning of a client device (100) based on a subset of neighboring positioning devices (630) selected from set of detected neighboring positioning devices (620). The client device (100) detects a set of neighboring positioning devices (620) based on a set of reference signal measurements (RSMs) obtained by measuring a set of reference signals (RSs) received from a set of possible neighboring positioning devices (610) for the client device (100) and / or a set of network nodes (300´). The client device (100) further selects a subset of neighboring positioning devices (630) in the set of detected neighboring positioning devices (620) based on at least one selection criterion and transmit a positioning report (510) to a network node (300). The positioning report (510) indicates the subset of neighboring positioning devices (630). Furthermore, embodiments of the invention also relate to the network node (300), corresponding methods and a computer program.

Description

[0001] SELECTION OF NEIGHBORING POSITIONING DEVICES FOR A CLIENT DEVICE

[0002] TECHNICAL FIELD

[0003] Embodiments of the invention relate to a client device for selection of neighboring positioning devices for the client device and a network node for determining a position of the client device. Furthermore, embodiments of the invention also relate to corresponding methods and a computer program.

[0004] BACKGROUND

[0005] Positioning methods based on artificial intelligence (Al) / machine learning (ML) can be classified into two main categories, namely, direct AI / ML positioning and AI / ML assisted positioning. The considered methods include, user equipment (UE)-based, UE- assisted / location management function (LMF)-based and next generation radio access network (NG-RAN) node assisted positioning methods.

[0006] The variants of AI / ML-based positioning include other aspects such as the location where the training, inference and monitoring are performed. The considered cases are:

[0007] • UE-based positioning with UE-side model, direct AI / ML or AI / ML assisted positioning.

[0008] • UE-assisted / LMF-based positioning with UE-side model, AI / ML assisted positioning.

[0009] • UE-assisted / LMF-based positioning with LMF-side model, direct AI / ML positioning.

[0010] • NG-RAN node assisted positioning with gNB-side model, AI / ML assisted positioning.

[0011] • NG-RAN node assisted positioning with LMF-side model, direct AI / ML positioning.

[0012] In terms of implementation and input features, multiple options are considered, including already supported positioning measurements and new measurements.

[0013] SUMMARY

[0014] An objective of embodiments of the invention is to provide a solution which mitigates or solves the drawbacks and problems of conventional solutions.

[0015] Another objective of embodiments of the invention is to provide a solution for improved selection of neighboring positioning devices used for determining a position of a client device.

[0016] The above and further objectives are solved by the subject matter of the independent claims. Further embodiments of the invention can be found in the dependent claims.

[0017] According to a first aspect of the invention, the above mentioned and other objectives are achieved with a client device configured to: measure a set of reference signals received from a set of possible neighboring positioning devices for the client device and / or a set of network nodes to obtain a set of reference signal measurements, each reference signal in the set of reference signals being associated with a possible neighboring positioning device in the set of possible neighboring positioning devices or a network node in the set of network nodes; detect a set of neighboring positioning devices based on the set of reference signal measurements; select a subset of neighboring positioning devices in the set of detected neighboring positioning devices based on at least one selection criterion; and transmit a positioning report to a network node, the positioning report indicating the subset of neighboring positioning devices.

[0018] An advantage of the client device according to the first aspect is that the client device is able to detect neighboring positioning devices based on a limited set of reference signals measurements. Subsequently, the client device can select a subset of neighboring positioning devices in an optimized manner, e.g., construct a convex hull around the client device, and report selected neighbors and associated channel measurement quantities. The report from the client device can then be used to derive its position with high accuracy and low complexity, e.g., using K-nearest neighbors, weighted K-nearest neighbors (WKNN) or convolutional neural networks.

[0019] In an implementation form of a client device according to the first aspect, the client device is further configured to: receive a reference signal configuration from the network node, the reference signal configuration indicating the set of reference signals.

[0020] An advantage with this implementation form is that the client device can be configured to measure downlink reference signals, transmitted by network nodes, or sidelink reference signals or uplink reference signals, transmitted by neighboring positioning devices. This enables substantial flexibility in conducting positioning measurements. The supported time domain behavior for such measurements can be periodic, semi-persistent, aperiodic or event- triggered.

[0021] In an implementation form of a client device according to the first aspect, the reference signal configuration further indicates a set of predetermined channel measurement values for the set of possible neighboring positioning devices. An advantage with this implementation form is that the client device can perform neighboring positioning device detection and selection based on downlink reference signals measurements and the set of predetermined channel measurements. Thereby, improving the accuracy of the position of the client device.

[0022] In an implementation form of a client device according to the first aspect, the set of predetermined channel measurement values are associated with a set of reference positions for the set of possible neighboring positioning devices.

[0023] An advantage with this implementation form is that the client device can perform neighboring positioning device detection and selection based on downlink reference signals measurements and the set of predetermined channel measurements. Additionally, the client device can derive an estimation of its own position, based on selected neighboring positioning devices.

[0024] In an implementation form of a client device according to the first aspect, the set of reference signal measurements comprises a set of measured channel measurement values.

[0025] An advantage with this implementation form is that different channel measurement quantities can be supported, e.g., channel impulse response (CIR), power delay profile (PDP), channel covariance, precoding matrix indicator (PMI), reference signal received power (RSRP), received signal strength indicator (RSSI).

[0026] In an implementation form of a client device according to the first aspect, the client device is further configured to: detect the set of neighboring positioning devices based on the set of reference signal measurements and the set of predetermined channel measurement values.

[0027] An advantage with this implementation form is that the client device can perform neighboring positioning device detection and selection based on downlink reference signals measurements. Indeed, the client device can measure downlink reference signals and derive channel measurement values. By comparing the derived measurements, e.g., compute distance or correlation, with the configured predetermined channel measurements, the client device can detect neighbors and select a subset of neighboring positioning devices based on the proximity between measurements.

[0028] In an implementation form of a client device according to the first aspect, the set of reference signals comprises a set of uplink reference signals and / or a set of sidelink reference signals. An advantage with this implementation form is that neighboring positioning devices detection and selection can be performed based on uplink and / or sidelink reference signals measurements. This enables substantial flexibility in conducting positioning measurements.

[0029] In an implementation form of a client device according to the first aspect, the client device is further configured to: detect the set of neighboring positioning devices upon receiving a detection trigger from the network node.

[0030] An advantage with this implementation form is that reference signals measurements for neighboring positioning device detection and selection can be performed in aperiodic manner, consequently avoiding a high cost that may result from performing such measurements periodically.

[0031] In an implementation form of a client device according to the first aspect, the client device is further configured to: transmit a reference signal transmission request to the network node, the reference signal transmission request indicating a request for the set of possible neighboring positioning devices to start transmitting the set of reference signals.

[0032] An advantage with this implementation form is that client device-triggered positioning and client device-side positioning can be supported.

[0033] In an implementation form of a client device according to the first aspect, the selection criterion is any of: a convex hull selection criterion thereby forming a subset of neighboring positioning devices in a convex hull around the client device; a non-straight line selection criterion thereby forming a subset of neighboring positioning devices in which three or more neighboring positioning devices are not positioned in a straight line; a maximum distance selection criterion thereby forming a subset of neighboring positioning devices having the largest average pair-wise distance in relation to each other; and / or a minimum distance selection criterion thereby forming a subset of neighboring positioning devices having the smallest average pair-wise distance in relation to the client device. An advantage with this implementation form is that different neighboring positioning devices selection methods can be supported. The selection needs to be performed in such manner that subsequent positioning can be performed with low error. Higher accuracy positioning based on neighbor detection can be achieved if the selected neighboring positioning devices construct a convex hull containing the client device. To achieve this, different criteria are proposed, with the goal of at least achieving an approximation of the convex hull condition.

[0034] In an implementation form of a client device according to the first aspect, the set of detected neighboring positioning devices comprises N neighboring positioning devices and the subset of neighboring positioning devices comprises k neighboring positioning devices where k < N.

[0035] An advantage with this implementation form is that different criteria can be supported for neighboring device selection. Additionally, by selecting a subset of neighboring positioning devices, from the set of detected neighboring positioning devices, according to an optimized criterion, positioning error can be reduced.

[0036] In an implementation form of a client device according to the first aspect, the indication of the subset of neighboring positioning devices is any of: a bitmap indicting the subset of neighboring positioning devices from a set of possible neighboring positioning devices; a combinatorial indicator indicting the subset of neighboring positioning devices from a set of possible neighboring positioning devices; and / or a set of reference signal indicators indicating the subset of neighboring positioning devices, each reference signal indicator indicating a reference signal resource transmitted by a neighboring positioning device in the subset of neighboring positioning devices.

[0037] An advantage with this implementation form is that different low overhead reporting formats can be supported. The selected neighboring positioning devices can thereby be indicated with limited signaling over the air interface.

[0038] In an implementation form of a client device according to the first aspect, the positioning report further indicates the set of reference signal measurements.

[0039] An advantage with this implementation form is that different implementations can be supported for deriving the client device position at the network node side. Indeed, the network node can use the indicated set of reference signal measurements in order to further enhance its implemented algorithm and consequently, further reducing positioning error. Additionally, these measurements can be used to construct a predetermined measurements data base for future use.

[0040] In an implementation form of a client device according to the first aspect, the set of detected neighboring positioning devices comprises client devices and / or positioning reference units.

[0041] An advantage with this implementation form is that dedicated positioning reference devices or other client devices can be used for this scheme which could reduce the cost of implementing direct ML-based positioning, according to the proposed solution.

[0042] According to a second aspect of the invention, the above mentioned and other objectives are achieved with a network node configured to: receive a positioning report from a client device, the positioning report indicating a subset of neighboring positioning devices from a set of detected neighboring positioning devices for the client device; and determine a position of the client device based on the positioning report.

[0043] An advantage of the network node according to the second aspect is that different criteria can be supported for neighboring device selection. Additionally, by selecting a subset of neighboring positioning devices, from the set of detected neighboring positioning devices, according to an optimized criterion, positioning error can be reduced. The network node can use the indicated subset of neighboring positioning devices and their known positions as input features for a direct ML-based positioning algorithm which outputs an estimate of the client device position.

[0044] In an implementation form of a network node according to the second aspect, the network node is further configured to: determine the position of the client device based on the positioning report and a machine learning model.

[0045] An advantage with this implementation form is that direct ML-based positioning can be supported in a low complexity manner. Indeed, the reported quantities indicating selected neighboring positioning devices and, in some cases, associated channel measurements have limited dimensions and can be used as input for a low complexity direct ML-based positioning algorithm such as WKNN. In an implementation form of a network node according to the second aspect, the network node is further configured to: transmit a reference signal configuration to the client device, the reference signal configuration indicating a set of reference signals for measuring a set of possible neighboring positioning devices for the client device.

[0046] An advantage with this implementation form is that the client device can perform neighboring positioning device detection and selection based on downlink reference signals, uplink reference signals or sidelink reference signals measurements. This enables substantial flexibility in conducting positioning measurements.

[0047] In an implementation form of a network node according to the second aspect, the reference signal configuration further indicates a set of predetermined channel measurement values for the set of possible neighboring positioning devices.

[0048] An advantage with this implementation form is that the client device can perform neighboring positioning device detection and selection based on downlink reference signals measurements. Additionally, the client device can derive an estimation of its own position, based on selected neighboring positioning devices.

[0049] In an implementation form of a network node according to the second aspect, the set of predetermined channel measurement values are associated with a set of reference positions for the set of possible neighboring positioning devices.

[0050] An advantage with this implementation form is that the client device can perform neighboring positioning device detection and selection based on downlink reference signals measurements. Indeed, the client device can measure downlink reference signals and derive channel measurement values. By comparing the derived measurements, e.g., compute distance or correlation, with the configured predetermined channel measurements, the client device can detect neighbors and select a subset based on the proximity between measurements. Additionally, the client device can derive an estimation of its own position, based on selected neighboring positioning devices and the known set of reference positions.

[0051] In an implementation form of a network node according to the second aspect, the network node is further configured to: transmit a detection trigger to the client device, the detection trigger instructing the client device to detect a set of neighboring positioning devices. An advantage with this implementation form is that reference signals measurements for neighboring positioning device detection and selection can be performed in aperiodic manner, consequently avoiding a high cost that may result from performing such measurements periodically.

[0052] In an implementation form of a network node according to the second aspect, the network node is further configured to: receive a reference signal transmission request from the client device, the reference signal transmission request indicating a request for the set of possible neighboring positioning devices to start transmitting the set of reference signals; and transmit a reference signal transmission trigger to the set of possible neighboring positioning devices, the reference signal transmission trigger instructing the set of possible neighboring positioning devices to transmit the set of reference signals.

[0053] An advantage with this implementation form is that client device-triggered positioning and client device-side positioning can be supported.

[0054] In an implementation form of a network node according to the second aspect, the set of detected neighboring positioning devices comprises N neighboring positioning devices and the subset of neighboring positioning devices comprises k neighboring positioning devices where k < N.

[0055] An advantage with this implementation form is that different criteria can be supported for neighboring device selection. Additionally, by selecting a subset of neighboring positioning devices, from the set of detected neighboring positioning devices, according to an optimized criterion, positioning error can be reduced.

[0056] In an implementation form of a network node according to the second aspect, the indication of the subset of neighboring positioning devices is any of: a bitmap indicting the subset of neighboring positioning devices from a set of possible neighboring positioning devices; a combinatorial indicator indicting the subset of neighboring positioning devices from a set of possible neighboring positioning devices; and / or a set of reference signal indicators indicating the subset of neighboring positioning devices, each reference signal indicator indicating a reference signal resource transmitted by a neighboring positioning device in the subset of neighboring positioning devices. An advantage with this implementation form is that different low overhead reporting formats can be supported. The selected neighboring positioning devices can thereby be indicated with limited signaling over the air interface.

[0057] In an implementation form of a network node according to the second aspect, the positioning report further indicates a set of reference signal measurements used by the client device for detecting the set of detected neighboring positioning devices.

[0058] An advantage with this implementation form is that different implementations can be supported for deriving the client device position at the network node side. Indeed, the network node can use the indicated set of reference signal measurements in order to further enhance its implemented algorithm and consequently, further reducing positioning error. Additionally, these measurements can be used to construct a predetermined measurements data base for future use.

[0059] In an implementation form of a network node according to the second aspect, the network node is a network access node or a location management function.

[0060] An advantage with this implementation form is that different possible implementations are supported, in the framework of new radio (NR) positioning protocol or future network generations.

[0061] According to a third aspect of the invention, the above mentioned and other objectives are achieved with a method for a client device, the method comprises: measuring a set of reference signals received from a set of possible neighboring positioning devices for the client device and / or a set of network nodes to obtain a set of reference signal measurements, each reference signal in the set of reference signals being associated with a possible neighboring positioning device in the set of possible neighboring positioning devices or a network node in the set of network nodes; detecting a set of neighboring positioning devices based on the set of reference signal measurements; selecting a subset of neighboring positioning devices in the set of detected neighboring positioning devices based on at least one selection criterion; and transmitting a positioning report to a network node, the positioning report indicating the subset of neighboring positioning devices. The method according to the third aspect can be extended into implementation forms corresponding to the implementation forms of the client device according to the first aspect. Hence, an implementation form of the method comprises the feature(s) of the corresponding implementation form of the client device.

[0062] The advantages of the methods according to the third aspect are the same as those for the corresponding implementation forms of the client device according to the first aspect.

[0063] According to a fourth aspect of the invention, the above mentioned and other objectives are achieved with a method for a network node, the method comprises: receiving a positioning report from a client device, the positioning report indicating a subset of neighboring positioning devices from a set of detected neighboring positioning devices for the client device; and determining a position of the client device based on the positioning report.

[0064] The method according to the fourth aspect can be extended into implementation forms corresponding to the implementation forms of the network node according to the second aspect. Hence, an implementation form of the method comprises the feature(s) of the corresponding implementation form of the network node.

[0065] The advantages of the methods according to the fourth aspect are the same as those for the corresponding implementation forms of the network node according to the second aspect.

[0066] Embodiments of the invention also relate to a computer program, characterized in program code, which when run by at least one processor causes the at least one processor to execute any method according to embodiments of the invention. Further, embodiments of the invention also relate to a computer program product comprising a computer readable medium and the mentioned computer program, wherein the computer program is included in the computer readable medium, and may comprises one or more from the group of: read-only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), flash memory, electrically erasable PROM (EEPROM), hard disk drive, etc.

[0067] Further applications and advantages of embodiments of the invention will be apparent from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] The appended drawings are intended to clarify and explain different embodiments of the invention, in which:

[0069] - Fig. 1 shows a client device according to an embodiment of the invention;

[0070] - Fig. 2 shows a flow chart of a method for a client device according to an embodiment of the invention;

[0071] - Fig. 3 shows a network node according to an embodiment of the invention;

[0072] - Fig. 4 shows a flow chart of a method for a network node according to an embodiment of the invention;

[0073] - Fig. 5 shows a communication system according to an embodiment of the invention;

[0074] - Fig. 6 shows signaling for positioning of a client device according to an embodiment of the invention; and

[0075] - Fig. 7 shows signaling for triggering positioning of a client device according to an embodiment of the invention.

[0076] DETAILED DESCRIPTION

[0077] ML-based positioning, i.e., direct AI / ML positioning and AI / ML assisted positioning, can considerably improve the accuracy of device positioning in challenging environment, especially in indoor deployments. In such environments, the accuracy of conventional positioning measurements suffers due to many multipath components.

[0078] However, also ML-based positioning comes with challenges, especially with regards to data collection for training, inference, and model performance monitoring. Indeed, ML models and cellular networks have different constraints and requirements. While an ML model typically benefits from high quality and large size data, cellular networks benefit from maintaining signaling and reference signals transmission over the air interface to a minimum.

[0079] These conflicting requirements need to be addressed with careful design so that the increase in positioning accuracy does not come at the cost of a problematic network resource utilization.

[0080] Another important design consideration is the input feature for positioning ML models. Several input features and collected data have been considered, including new and existing positioning measurements. Additionally, the number of entities providing the measurements from their perspective is an important design variable, e.g., the number of involved transmission reception points (TRPs), positioning reference units, etc. The aforementioned design aspects define the computational load, the communication overhead, the complexity of ML models and the achievable accuracy, among others. Consequently, it is important to achieve an advantageous tradeoff between accuracy and complexity / overhead.

[0081] According to embodiments of the invention an improved way of selecting neighboring positioning devices to be used for positioning of a client device is therefore provided.

[0082] Fig. 1 shows a client device 100 according to an embodiment of the invention. In the embodiment shown in Fig. 1 , the client device 100 comprises a processor 102, a transceiver 104 and a memory 106. The processor 102 is coupled to the transceiver 104 and the memory 106 by communication means 108 known in the art. The client device 100 further comprises an antenna or antenna array 110 coupled to the transceiver 104, which means that the client device 100 is configured for wireless communications in a communication system.

[0083] The processor 102 may be referred to as one or more general-purpose central processing units (CPUs), one or more digital signal processors (DSPs), one or more application-specific integrated circuits (ASICs), one or more field programmable gate arrays (FPGAs), one or more programmable logic devices, one or more discrete gates, one or more transistor logic devices, one or more discrete hardware components, or one or more chipsets. The memory 106 may be a read-only memory, a random access memory (RAM), or a non-volatile RAM (NVRAM). The transceiver 104 may be a transceiver circuit, a power controller, or an interface providing capability to communicate with other communication modules or communication devices. The transceiver 104, memory 106 and / or processor 102 may be implemented in separate chipsets or may be implemented in a common chipset.

[0084] That the client device 100 is configured to perform certain actions can in this disclosure be understood to mean that the client device 100 comprises suitable means, such as e.g., the processor 102 and the transceiver 104, configured to perform the actions.

[0085] According to embodiments of the invention the client device 100 is configured to measure a set of reference signals RSs received from a set of possible neighboring positioning devices 610 for the client device 100 and / or a set of network nodes 300' to obtain a set of reference signal measurements RSMs, each reference signal in the set of reference signals RSs being associated with a possible neighboring positioning device 612 in the set of possible neighboring positioning devices 610 or a network node in the set of network nodes 300'. The client device 100 is further configured to detect a set of neighboring positioning devices 620 based on the set of reference signal measurements RSMs and select a subset of neighboring positioning devices 630 in the set of detected neighboring positioning devices 620 based on at least one selection criterion. The client device 100 is further configured to transmit a positioning report 510 to a network node 300, the positioning report 510 indicating the subset of neighboring positioning devices 630.

[0086] Furthermore, in an embodiment of the invention, the client device 100 for a communication system 500 comprises a processor configured to: measure a set of reference signals RSs received from a set of possible neighboring positioning devices 610 for the client device 100 and / or a set of network nodes 300' to obtain a set of reference signal measurements RSMs, each reference signal in the set of reference signals RSs being associated with a possible neighboring positioning device 612 in the set of possible neighboring positioning devices 610 or a network node in the set of network nodes 300'; detect a set of neighboring positioning devices 620 based on the set of reference signal measurements RSMs; and select a subset of neighboring positioning devices 630 in the set of detected neighboring positioning devices 620 based on at least one selection criterion. The client device 100 also comprises a transceiver configured to transmit a positioning report 510 to a network node 300, the positioning report 510 indicating the subset of neighboring positioning devices 630.

[0087] Moreover, in yet another embodiment of the invention, the client device 100 for a communication system 500 comprises a processor and a memory having computer readable instructions stored thereon which, when executed by the processor, cause the processor to: measure a set of reference signals RSs received from a set of possible neighboring positioning devices 610 for the client device 100 and / or a set of network nodes 300' to obtain a set of reference signal measurements RSMs, each reference signal in the set of reference signals RSs being associated with a possible neighboring positioning device 612 in the set of possible neighboring positioning devices 610 or a network node in the set of network nodes 300'; detect a set of neighboring positioning devices 620 based on the set of reference signal measurements RSMs; select a subset of neighboring positioning devices 630 in the set of detected neighboring positioning devices 620 based on at least one selection criterion; and transmit a positioning report 510 to a network node 300, the positioning report 510 indicating the subset of neighboring positioning devices 630.

[0088] Fig. 2 shows a flow chart of a corresponding method 200 which may be executed in a client device 100, such as the one shown in Fig. 1. The method 200 comprises measuring 202 a set of reference signals RSs received from a set of possible neighboring positioning devices 610 for the client device 100 and / or a set of network nodes 300' to obtain a set of reference signal measurements RSMs, each reference signal in the set of reference signals RSs being associated with a possible neighboring positioning device 612 in the set of possible neighboring positioning devices 610 or a network node in the set of network nodes 300'. The method 200 further comprises detecting 204 a set of neighboring positioning devices 620 based on the set of reference signal measurements RSMs and selecting 206 a subset of neighboring positioning devices 630 in the set of detected neighboring positioning devices 620 based on at least one selection criterion. The method 200 further comprises transmitting 208 a positioning report 510 to a network node 300, the positioning report 510 indicating the subset of neighboring positioning devices 630.

[0089] Fig. 3 shows a network node 300 according to an embodiment of the invention. In the embodiment shown in Fig. 3, the network node 300 is a network access node. However, in embodiments the network node 300 may instead be a location management function (LMF). With reference to Fig. 3, the network node 300 comprises a processor 302, a transceiver 304 and a memory 306. The processor 302 is coupled to the transceiver 304 and the memory 306 by communication means 308 known in the art. The network node 300 may be configured for wireless and / or wired communications in a communication system. The wireless communication capability may be provided with an antenna or antenna array 310 coupled to the transceiver 304, while the wired communication capability may be provided with a wired communication interface 312 e.g., coupled to the transceiver 304.

[0090] The processor 302 may be referred to as one or more general-purpose CPU, one or more DSPs, one or more ASICs, one or more FPGAs, one or more programmable logic devices, one or more discrete gates, one or more transistor logic devices, one or more discrete hardware components, one or more chipsets. The memory 306 may be a read-only memory, a RAM, or a NVRAM. The transceiver 304 may be a transceiver circuit, a power controller, or an interface providing capability to communicate with other communication modules or communication devices, such as network nodes and network servers. The transceiver 304, the memory 306 and / or the processor 302 may be implemented in separate chipsets or may be implemented in a common chipset.

[0091] That the network access node 300 is configured to perform certain actions can in this disclosure be understood to mean that the network access node 300 comprises suitable means, such as e.g., the processor 302 and the transceiver 304, configured to perform the actions. According to embodiments of the invention the network node 300 is configured to receive a positioning report 510 from a client device 100, the positioning report 510 indicating a subset of neighboring positioning devices 630 from a set of detected neighboring positioning devices 620 for the client device 100. The network node 300 is configured to determine a position of the client device 100 based on the positioning report 510.

[0092] Furthermore, in an embodiment of the invention, the network node 300 for a communication system 500 comprises a transceiver configured to: receive a positioning report 510 from a client device 100, the positioning report 510 indicating a subset of neighboring positioning devices 630 from a set of detected neighboring positioning devices 620 for the client device 100. The network node 300 also comprises a processor configured to determine a position of the client device 100 based on the positioning report 510.

[0093] Moreover, in yet another embodiment of the invention, the network node 300 for a communication system 500 comprises a processor and a memory having computer readable instructions stored thereon which, when executed by the processor, cause the processor to: receive a positioning report 510 from a client device 100, the positioning report 510 indicating a subset of neighboring positioning devices 630 from a set of detected neighboring positioning devices 620 for the client device 100; and determine a position of the client device 100 based on the positioning report 510.

[0094] Fig. 4 shows a flow chart of a corresponding method 400 which may be executed in a network access node 300, such as the one shown in Fig. 4. The method 400 comprises receiving 402 a positioning report 510 from a client device 100, the positioning report 510 indicating a subset of neighboring positioning devices 630 from a set of detected neighboring positioning devices 620 for the client device 100. The method 400 further comprises determining 404 a position of the client device 100 based on the positioning report 510.

[0095] Fig. 5 shows a communication system 500 according to an embodiment of the invention. The communication system 500 in the disclosed embodiment comprises a client device 100 and a network node 300. In the embodiment shown in Fig. 5, the network node 300 is a network access node but in embodiments the network node 300 may instead be a core network node such as e.g., a location management function (LMF). The communication system 500 further comprises a set of possible neighboring positioning devices 610 for the client device 100 and a set of network nodes 300'. The set of possible neighboring positioning devices 610 may comprise client devices and / or positioning reference units. The positioning reference units may be fixed units and the positions of the positioning reference units may be known in the communication system 500. The set of network nodes 300 may comprise network access nodes and may or may not comprise the network node 300 when the network node 300 is a network access node.

[0096] In embodiments, the communication system 500 is an indoor environment, such as e.g., a factory floor, where there is moving devices and fixed devices. In this case, the moving device may be client devices and the fixed devices may be positioning reference units which positions are known.

[0097] The communication system 500 may be a communication system according to the 3GPP standard such as e.g., a 5G system in which case the client device 100 may be a user equipment (UE) and any network access node may be a transmission reception point (TRP), a next generation node B (gNB) or similar, but the invention is not limited thereto.

[0098] According to embodiments of the invention the client device 100 measures a set of reference signals RSs received from the set of possible neighboring positioning devices 610 for the client device 100 and / or the set of network nodes 300' to obtain a set of reference signal measurements RSMs. Based on the set of reference signal measurements RSMs, the client device 100 detects a set of neighboring positioning devices 620. From the set of detected neighboring positioning devices 620, the client device 100 selects a subset of neighboring positioning devices 630, as shown in Fig. 5. The selection is based on at least one selection criterion and enables an optimization of which neighboring positioning devices to use for determining the position of the client device 100.

[0099] With reference to Fig. 5, the client device further transmits a positioning report 510 to the network node 300. The positioning report 510 indicates the subset of neighboring positioning devices 630 selected by the client device 100. Based on the positioning report 510, the network node 300 can determine the position of the client device 100.

[0100] Fig. 6 shows signaling for determining a position of the client device 100 according to an embodiment of the invention. In the embodiment shown in Fig. 6, the client device 100 is configured with a reference signal configuration for positioning measurements by the network node 300. The network node 300 may be a network access node or an LMF.

[0101] In step I in Fig. 6, the network node 300 transmits a reference signal configuration 520 to the client device 100. The reference signal configuration 520 indicates a set of reference signals RSs for measuring a set of possible neighboring positioning devices 610 for the client device 100. Each reference signal in the set of reference signals RSs is associated with a possible neighboring positioning device in the set of possible neighboring positioning devices 610 or a network node in the set of network nodes 300'. Reference signals RSs associated with neighboring positioning devices may be uplink reference signals ULRSs and / or sidelink reference signals SLRSs, while reference signals RSs associated with network nodes may be downlink reference signals DLRSs. The set of reference signals RSs may hence comprise a set of uplink reference signals ULRSs and / or a set of sidelink reference signals SLRSs from the set of possible neighboring positioning devices 610 and / or a set of downlink reference signals DLRSs from the set of network nodes 300'. With the reference signal configuration 520, the network node 300 may configure the client device 100 with the set of reference signals RSs to measure to obtain a set of reference signal measurements RSMs.

[0102] In embodiments, the reference signal configuration 520 further indicate a set of predetermined channel measurement values for the set of possible neighboring positioning devices 610. The set of predetermined channel measurement values may be reference channel measurements previously performed by neighboring positioning devices. The set of predetermined channel measurement values may be associated with a set of reference positions RPs for the set of possible neighboring positioning devices 610. From the reference signal configuration 520, the client device 100 may hence obtain positioning information for the set of possible neighboring positioning devices 610 without having to perform measurements on their reference signals RSs.

[0103] The client device 100 receives the reference signal configuration 520 indicating the set of reference signals RSs from the network node 300. Based on the received reference signal configuration 520, the client device 100 measures the set of reference signals RSs indicated in the reference signal configuration 520, in step II in Fig. 6. Each reference signal in the set of reference signals RSs is associated with a possible neighboring positioning device in the set of possible neighboring positioning devices 610 or a network node in the set of network nodes 300'. The set of reference signals RSs may hence be received from the set of possible neighboring positioning devices 610 for the client device 100 and / or the set of network nodes 300', as shown in Fig. 6.

[0104] The set of reference signals RSs may comprise a set of uplink reference signals ULRSs and / or a set of sidelink reference signals SLRSs from the set of possible neighboring positioning devices 610 and / or a set of downlink reference signals DLRSs from the set of network nodes 300'. The set of uplink reference signals ULRSs may e.g., be sounding reference signals (SRSs) which the set of possible neighboring positioning devices 610 have been configured to transmit. The set of sidelink reference signals SLRSs may be transmitted by the set of possible neighboring positioning devices 610 over the PC5 interface. The set of downlink reference signals DLRSs may be positioning reference signals (PRSs) or channel state information reference signals (CSI-RSs) transmitted by the set of network nodes 300'.

[0105] The set of reference signals RSs may be transmitted in a periodic, semi-persistent or aperiodic manner. In embodiments, the network node 300 may trigger the set of possible neighboring positioning devices 610 and / or the set of network nodes 300' to start transmission of the set of reference signals RSs, as further described below with reference to Fig. 7.

[0106] The client device 100 measures the set of reference signals RSs to obtain a set of reference signal measurements RSMs. Thus, the set of reference signal measurements RSMs may comprise a set of measured channel measurement values. For example, the set of reference signal measurements RSMs may comprise channel measurement quantities such as e.g., precoder matrix indicator (PMI), channel covariance matrix, channel impulse response (CIR), power delay profile (PDP), reference signal received power (RSRP), received signal strength indicator (RSSI), angle of arrival (AoA), arrival time, etc.

[0107] In step III in Fig. 6, the client device 100 detects a set of neighboring positioning devices 620 based on the set of reference signal measurements RSMs. The set of detected neighboring positioning devices 620 may comprise client devices and / or positioning reference units. The client devices may be mobile, while the positioning reference units may be stationary with known positions. The client device 100 may use the set of reference signal measurements RSMs directly, e.g., the set of measured channel measurement values, or perform one or more computation based on the set of reference signal measurements RSMs. The client device 100 may e.g., compute correlation and / or distance between channel measurement quantities, distance estimates with respect to neighboring positioning devices, etc. based on the set of reference signal measurements RSMs.

[0108] The client device 100 may further detect the set of neighboring positioning devices 620 based on the set of reference signal measurements RSMs and the set of predetermined channel measurement values. In other words, the client device 100 may use both the set of reference signal measurements RSMs obtained from measurements and the set of predetermined channel measurement values obtained from the network node 300 e.g., with the reference signal configuration 520. The client device 100 may e.g., compare the set of reference signal measurements RSMs, i.e., its own measurements, with the obtained set of predetermined channel measurement values to detect the set of neighboring positioning devices 620. In embodiments, the network node 300 may trigger the client device 100 to detect a set of neighboring positioning devices 620, i.e. , to perform step III in Fig. 6. Optionally, the network node 300 may hence transmit a detection trigger 530 to the client device 100, as shown in optional step Illa in Fig. 6. The detection trigger 530 instructs the client device 100 to detect a set of neighboring positioning devices 620. The network node 300 may hence initiate positioning of the client device 100 by transmitting a detection trigger 530 to the client device 100. Upon receiving the detection trigger 530 from the network node 300, the client device 100 may initiate the detection of the set of neighboring positioning devices 620, i.e., step III in Fig. 6 may be performed based on the received detection trigger 530.

[0109] In step IV in Fig. 6, the client device 100 selects a subset of neighboring positioning devices 630 in the set of detected neighboring positioning devices 620 based on at least one selection criterion. The selection criterion may be used to identify and select the neighboring positioning devices from the set of detected neighboring positioning devices 620 which optimizes the search space. In embodiments, the set of detected neighboring positioning devices 620 comprises N neighboring positioning devices and the subset of neighboring positioning devices 630 comprises k neighboring positioning devices where k < N. Thus, the subset of neighboring positioning devices 630 may comprise fewer neighboring positioning device than the set of detected neighboring positioning devices 620.

[0110] The selection criterion may be any of: a convex hull selection criterion, a non-straight line selection criterion, a maximum distance selection criterion and / or a minimum distance selection criterion. The convex hull of a set of points S in n dimensions is the intersection of all convex sets containing S. The convex hull selection criterion forms a subset of neighboring positioning devices 630 in a convex hull around the client device 100, i.e., the selected subset of neighboring positioning devices 630 forms a convex hull in which the client device 100 is positioned. This criterion requires knowledge of the distance and angular position of neighboring positioning devices, with respect to the client device 100. While the achieved performance with this criterion is superior, it requires more computation at the client device 100 to perform proper selection, in addition to multiple antenna elements / antenna arrays. The non-straight line selection criterion forms a subset of neighboring positioning devices 630 in which three or more neighboring positioning devices are not positioned in a straight line. With the non-straight line selection criterion, selection of three or more neighbors in the same line can hence be avoided. This criterion is a simpler one which aims at approximating the convex hull criterion. It is based on computation of angle of arrival, at least in a coarse manner. The maximum distance selection criterion forms a subset of neighboring positioning devices 630 having the largest average pair-wise distance in relation to each other. This criterion is a simpler one which aims at approximating the convex hull criterion. It is based on knowledge about the pair-wise distances of neighboring positioning devices 630. The minimum distance selection criterion forms a subset of neighboring positioning devices 630 having the smallest average pair-wise distance in relation to the client device 100. This criterion aims at reducing the range of positioning error margin.

[0111] In step V in Fig. 6, the client device 100 transmits a positioning report 510 to the network node 300. The positioning report 510 indicates the subset of neighboring positioning devices 630, i.e., the subset of neighboring positioning devices 630 selected by the client device 100 in step IV in Fig. 6. The subset of neighboring positioning devices 630 may be indicated in a number of different ways, e.g., using identities of the neighboring positioning devices 630. In embodiments, the indication of the subset of neighboring positioning devices 630 may be any of:

[0112] • A bitmap indicting the subset of neighboring positioning devices 630 from a set of possible neighboring positioning devices 610'. In the bitmap, a “1” may be indicated for a selected neighboring positioning device and a “0” for a non-selected possible neighboring positioning device, etc.

[0113] • A combinatorial indicator indicting the subset of neighboring positioning devices 630 from a set of possible neighboring positioning devices 610'. Assuming a set of possible neighboring positioning devices 610' of size M. Each combinatorial indicator, for a selected neighboring positioning device, can be of bit-width log2(M). Alternately, for indicating a selection of k neighboring positioning devices from M possible neighboring positioning devices, an indicator of bit-width log2(C M, ky , where C M, k) is equal to the binomial coefficient.

[0114] • A set of reference signal indicators indicating the subset of neighboring positioning devices 630, each reference signal indicator indicating a reference signal resource transmitted by a neighboring positioning device in the subset of neighboring positioning devices 630. Given that the neighboring positioning devices are configured to transmit different reference signal resources, an association between measured reference signal resource and neighboring positioning device may be constructed. Consequently, by indicating a reference signal resource indicator, the client device indicates a specific neighboring positioning device. In this case, the overhead depends on the number of configured reference signal resources that needs to be measured.

[0115] The client device 100 may further use the selected subset of neighboring positioning devices 630 to determine its own position. For example, if the selected neighboring positioning devices are positioning reference units and the client device 100 is configured with the positions of positioning reference units, the client device 100 may be able to derive its own position based on the selected subset of neighboring positioning devices 630 and their respective positions.

[0116] To do so the client device 100 may use an instance-based algorithm such as ^-nearest neighbors or weighted ^-nearest neighbors which does not require prior training. Only the knowledge of the positions of selected positioning reference units, and in some cases, optimized weights, are sufficient for the client device 100 to derive its own position.

[0117] The network node 300 receives the positioning report 510 from the client device 100. From the positioning report 510, the network node 300 obtains the indicated subset of neighboring positioning devices 630 from the set of detected neighboring positioning devices 620 for the client device.

[0118] In step VI in Fig. 6, the network node 300 determines a position of the client device 100 based on the positioning report 510. In the determining, the network node 300 may use the information from the client device 100, i.e. , the subset of neighboring positioning devices 630 indicated in the positioning report 510, as well as other information available to the network node 300. The network node 300 may further use a ML model to determine the position of the client device 100. Thus, in embodiments, the network node 300 may determine the position of the client device 100 based on the positioning report 510 and a ML model.

[0119] In embodiments, the positioning report 510 further indicates the set of reference signal measurements RSMs, i.e., the client device 100 may indicate the set of reference signal measurements RSMs the client device 100 has obtained and used in the detection and selection of neighboring positioning devices. As previously described, the set of reference signal measurements RSMs may comprise measured quantities such as e.g., RSRP, RSSI, AoA, arrival time, compute correlation and / or distance with respect to channel measurement quantities, distance estimates with respect to neighboring positioning devices, etc. From the positioning report 510, the network node 300 may hence obtain the set of reference signal measurements RSMs used by the client device 100 for detecting the set of detected neighboring positioning devices 620. The network node 300 may use this additional information when determining the position of the client device 100 in step VI in Fig. 6.

[0120] Fig. 7 shows signaling for determining a position of the client device 100 according to an embodiment of the invention where the client device 100 initiates the positioning and triggers the transmission of reference signals. In step I in Fig. 7, the client device 100 transmits a reference signal transmission request 540 to the network node 300. The reference signal transmission request 540 indicates a request for the set of possible neighboring positioning devices 610 to start transmitting the set of reference signals RSs.

[0121] The network node 300 receive the reference signal transmission request 540 from the client device 100 and hence obtains the request for the set of possible neighboring positioning devices 610 to start transmitting the set of reference signals RSs indicated in the reference signal transmission request 540. Based on the reference signal transmission request 540, the network node 300 transmits a reference signal transmission trigger 550 to the set of possible neighboring positioning devices 610, in step II in Fig. 7. The reference signal transmission trigger 550 instructs the set of possible neighboring positioning devices 610 to transmit the set of reference signals RSs.

[0122] In step III in Fig. 7, the set of possible neighboring positioning devices 610 starts to transmit the set of reference signals RSs based on the received reference signal transmission trigger 550.

[0123] In step IV in Fig. 7, the client device 100 measures the set of reference signals RSs received from the set of possible neighboring positioning devices 610 to obtain a set of reference signal measurements RSMs. The set of reference signal measurements RSMs may be used to detect a set of neighboring positioning devices 620 and the client device 100 may then select a subset of neighboring positioning devices 630 in the set of detected neighboring positioning devices 620 based on at least one selection criterion. The measuring, detection and selection by the client device 100 may be performed as described with reference to steps II to IV in Fig. 6.

[0124] The client device 100 may then indicated the selected subset of neighboring positioning devices 630 to the network node 300 by transmitting the positioning report 510 to the network node 300, as shown in step V in Fig. 7.

[0125] The client device 100 herein may be denoted as a user device, a user equipment (UE), a mobile station, an internet of things (loT) device, a sensor device, a wireless terminal and / or a mobile terminal, and is enabled to communicate wirelessly in a wireless communication system, sometimes also referred to as a cellular radio system. The UEs may further be referred to as mobile telephones, cellular telephones, computer tablets or laptops with wireless capability. The UEs in this context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and / or data, via a radio access network (RAN), with another communication entity, such as another receiver or a server. The UE may further be a station, which is any device that contains an IEEE 802.11 -conformant media access control (MAC) and physical layer (PHY) interface to the wireless medium (WM). The UE may be configured for communication in 3GPP related long term evolution (LTE), LTE-advanced, fifth generation (5G) wireless systems, such as new radio (NR), and their evolutions, as well as in IEEE related Wi-Fi, worldwide interoperability for microwave access (WiMAX) and their evolutions.

[0126] The network access node 300 herein may also be denoted as a radio network access node, an access network access node, an access point (AP), or a base station (BS), e.g., a radio base station (RBS), which in some networks may be referred to as transmitter, “gNB”, “gNodeB”, “eNB”, “eNodeB”, “NodeB” or “B node”, depending on the standard, technology and terminology used. The radio network access nodes may be of different classes or types such as e.g., macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby the cell size. The radio network access node may further be a station, which is any device that contains an IEEE 802.11 -conformant MAC and PHY interface to the WM. The radio network access node may be configured for communication in 3GPP related LTE, LTE- advanced, 5G wireless systems, such as NR and their evolutions, as well as in IEEE related Wi-Fi, WiMAX and their evolutions.

[0127] Furthermore, any method according to embodiments of the invention may be implemented in a computer program, having code means, which when run by processing means causes the processing means to execute the steps of the method. The computer program is included in a computer readable medium of a computer program product. The computer readable medium may comprise essentially any memory, such as previously mentioned a ROM, a PROM, an EPROM, a flash memory, an EEPROM, or a hard disk drive.

[0128] Moreover, it should be realized that the client device 100 and the network node 300 comprise the necessary communication capabilities in the form of e.g., functions, means, units, elements, etc., for performing or implementing embodiments of the invention. Examples of other such means, units, elements and functions are: processors, memory, buffers, control logic, encoders, decoders, rate matchers, de-rate matchers, mapping units, multipliers, decision units, selecting units, switches, interleavers, de-interleavers, modulators, demodulators, inputs, outputs, antennas, amplifiers, receiver units, transmitter units, DSPs, TCM encoder, TCM decoder, power supply units, power feeders, communication interfaces, communication protocols, etc. which are suitably arranged together for performing the solution. Therefore, the processor(s) of the client device 100 and the network node 300 may comprise, e.g., one or more instances of a CPU, a processing unit, a processing circuit, a processor, an ASIC, a microprocessor, or other processing logic that may interpret and execute instructions. The expression “processor” may thus represent a processing circuitry comprising a plurality of processing circuits, such as e.g., any, some or all of the ones mentioned above. The processing circuitry may further perform data processing functions for inputting, outputting, and processing of data comprising data buffering and device control functions, such as call processing control, user interface control, or the like. Finally, it should be understood that the invention is not limited to the embodiments described above, but also relates to and incorporates all embodiments within the scope of the appended independent claims.

Claims

CLAIMS1. A client device (100) configured to: measure a set of reference signals (RSs) received from a set of possible neighboring positioning devices (610) for the client device (100) and / or a set of network nodes (300') to obtain a set of reference signal measurements (RSMs), each reference signal in the set of reference signals (RSs) being associated with a possible neighboring positioning device (612) in the set of possible neighboring positioning devices (610) or a network node in the set of network nodes (300'); detect a set of neighboring positioning devices (620) based on the set of reference signal measurements (RSMs); select a subset of neighboring positioning devices (630) in the set of detected neighboring positioning devices (620) based on at least one selection criterion; and transmit a positioning report (510) to a network node (300), the positioning report (510) indicating the subset of neighboring positioning devices (630).

2. The client device (100) according to claim 1 , configured to: receive a reference signal configuration (520) from the network node (300), the reference signal configuration (520) indicating the set of reference signals (RSs).

3. The client device (100) according to claim 2, wherein the reference signal configuration (520) further indicates a set of predetermined channel measurement values for the set of possible neighboring positioning devices (610).

4. The client device (100) according to claim 3, wherein the set of predetermined channel measurement values are associated with a set of reference positions (RPs) for the set of possible neighboring positioning devices (610).

5. The client device (100) according to any one of the preceding claims, wherein the set of reference signal measurements (RSMs) comprises a set of measured channel measurement values.

6. The client device (100) according to claim 5 when dependent on claim 3 or 4, configured to: detect the set of neighboring positioning devices (620) based on the set of reference signal measurements (RSMs) and the set of predetermined channel measurement values.

7. The client device (100) according to any one of the preceding claims, wherein the set of reference signals (RSs) comprises a set of uplink reference signals (ULRSs) and / or a set of sidelink reference signals (SLRSs).

8. The client device (100) according to any one of the preceding claims, configured to: detect the set of neighboring positioning devices (620) upon receiving a detection trigger (530) from the network node (300).

9. The client device (100) according to any one of the preceding claims, configured to: transmit a reference signal transmission request (540) to the network node (300), the reference signal transmission request (540) indicating a request for the set of possible neighboring positioning devices (610) to start transmitting the set of reference signals (RSs).

10. The client device (100) according to any one of the preceding claims, wherein the selection criterion is any of: a convex hull selection criterion thereby forming a subset of neighboring positioning devices (630) in a convex hull around the client device (100); a non-straight line selection criterion thereby forming a subset of neighboring positioning devices (630) in which three or more neighboring positioning devices are not positioned in a straight line; a maximum distance selection criterion thereby forming a subset of neighboring positioning devices (630) having the largest average pair-wise distance in relation to each other; and / or a minimum distance selection criterion thereby forming a subset of neighboring positioning devices (630) having the smallest average pair-wise distance in relation to the client device (100).

11. The client device (100) according to any one of the preceding claims, wherein the set of detected neighboring positioning devices (620) comprises N neighboring positioning devices and the subset of neighboring positioning devices (630) comprises k neighboring positioning devices where k < N.

12. The client device (100) according to any one of the preceding claims, wherein the indication of the subset of neighboring positioning devices (630) is any of: a bitmap indicting the subset of neighboring positioning devices (630) from a set of possible neighboring positioning devices (610');a combinatorial indicator indicting the subset of neighboring positioning devices (630) from a set of possible neighboring positioning devices (610'); and / or a set of reference signal indicators indicating the subset of neighboring positioning devices (630), each reference signal indicator indicating a reference signal resource transmitted by a neighboring positioning device in the subset of neighboring positioning devices (630).

13. The client device (100) according to any one of the preceding claims, wherein the positioning report (510) further indicates the set of reference signal measurements (RSMs).

14. The client device (100) according to any one of the preceding claims, wherein the set of detected neighboring positioning devices (620) comprises client devices and / or positioning reference units.

15. A network node (300) configured to: receive a positioning report (510) from a client device (100), the positioning report (510) indicating a subset of neighboring positioning devices (630) from a set of detected neighboring positioning devices (620) for the client device (100); and determine a position of the client device (100) based on the positioning report (510).

16. The network node (300) according to claim 15, configured to: determine the position of the client device (100) based on the positioning report (510) and a machine learning model.

17. The network node (300) according to claim 15 or 16, configured to: transmit a reference signal configuration (520) to the client device (100), the reference signal configuration (520) indicating a set of reference signals (RSs) for measuring a set of possible neighboring positioning devices (610) for the client device (100).

18. The network node (300) according to claim 17, wherein the reference signal configuration (520) further indicates a set of predetermined channel measurement values for the set of possible neighboring positioning devices (610).

19. The network node (300) according to claim 18, wherein the set of predetermined channel measurement values are associated with a set of reference positions (RPs) for the set of possible neighboring positioning devices (610).

20. The network node (300) according to any one of claims 15 to 19, configured to: transmit a detection trigger (530) to the client device (100), the detection trigger (530) instructing the client device (100) to detect a set of neighboring positioning devices (620).

21. The network node (300) according to any one of claims 17 to 20, configured to: receive a reference signal transmission request (540) from the client device (100), the reference signal transmission request indicating a request for the set of possible neighboring positioning devices (610) to start transmitting the set of reference signals (RSs); and transmit a reference signal transmission trigger (550) to the set of possible neighboring positioning devices (610), the reference signal transmission trigger (550) instructing the set of possible neighboring positioning devices (610) to transmit the set of reference signals (RSs).

22. The network node (300) according to any one of claims 15 to 21 , wherein the set of detected neighboring positioning devices (620) comprises N neighboring positioning devices and the subset of neighboring positioning devices (630) comprises k neighboring positioning devices where k < N.

23. The network node (300) according to any one of claims 15 to 22, wherein the indication of the subset of neighboring positioning devices (630) is any of: a bitmap indicting the subset of neighboring positioning devices (630) from a set of possible neighboring positioning devices (610'); a combinatorial indicator indicting the subset of neighboring positioning devices (630) from a set of possible neighboring positioning devices (610'); and / or a set of reference signal indicators indicating the subset of neighboring positioning devices (630), each reference signal indicator indicating a reference signal resource transmitted by a neighboring positioning device in the subset of neighboring positioning devices (630).

24. The network node (300) according to any one of claims 15 to 23, wherein the positioning report (510) further indicates a set of reference signal measurements (RSMs) used by the client device (100) for detecting the set of detected neighboring positioning devices (620).

25. The network node (300) according to any one of claims 15 to 24, wherein the network node (300) is a network access node or a location management function.

26. A method (200) for a client device (100), the method (200) comprises: measuring (202) a set of reference signals (RSs) received from a set of possible neighboring positioning devices (610) for the client device (100) and / or a set of network nodes (300') to obtain a set of reference signal measurements (RSMs), each reference signal in the set of reference signals (RSs) being associated with a possible neighboring positioning device (612) in the set of possible neighboring positioning devices (610) or a network node in the set of network nodes (300'); detecting (204) a set of neighboring positioning devices (620) based on the set of reference signal measurements (RSMs); selecting (206) a subset of neighboring positioning devices (630) in the set of detected neighboring positioning devices (620) based on at least one selection criterion; and transmitting (208) a positioning report (510) to a network node (300), the positioning report (510) indicating the subset of neighboring positioning devices (630).

27. A method (400) for a network node (300): receiving (402) a positioning report (510) from a client device (100), the positioning report (510) indicating a subset of neighboring positioning devices (630) from a set of detected neighboring positioning devices (620) for the client device (100); and determining (404) a position of the client device (100) based on the positioning report (510).

28. A computer program with a program code for performing a method according to claim 26 or 27 when the computer program runs on a computer.

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