WO2024074190A1

WO2024074190A1 - Devices and methods for reduction of positioning measurements in communication systems

Info

Publication number: WO2024074190A1
Application number: PCT/EP2022/077500
Authority: WO
Inventors: Salah Eddine HAJRI; Olav Tirkkonen; Hanan Hassan AL-TOUS; Xinze Li
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2022-10-04
Filing date: 2022-10-04
Publication date: 2024-04-11

Abstract

Embodiments of the invention relate to a procedure for reduction of positioning measurements allowing a client device (100) to perform positioning measurements on a reduced number of PRS resources without negatively impacting positioning accuracy. The procedure is initiated by the client device (100) determining a channel characteristic of a radio channel for reception of a set of configured PRS resources, and based on the channel characteristic, select a subset of the received PRS resources for positioning measurements. Thereby, the power consumption in the client device (100) may be reduced, as well as the computational complexity related to positioning, since not all configured PRS resources will be measured. Moreover, positioning related delays may be reduced, as the number of measurements to derive positioning quantities are reduced. Furthermore, the invention also relates to corresponding methods and a computer program.

Description

DEVICES AND METHODS FOR REDUCTION OF POSITIONING MEASUREMENTS IN COMMUNICATION SYSTEMS

TECHNICAL FIELD

Embodiments of the invention relate to a client device and a network access node for reduction of positioning measurements in communication systems. Furthermore, embodiments of the invention also relate to corresponding methods and a computer program.

BACKGROUND

Knowledge of a position of a client device, such as a user equipment (UE) is essential for many user applications such as navigation, wayfinding, location-based digital services, augmented- reality applications, as well as emergency services, to name a few. With the proliferation of industrial internet of things (lloT) and reduced capability devices, power efficiency of positioning procedures has become an important key performance indicator (KPI).

New radio positioning protocol A (NRPPa) refers to a 5G positioning protocol which was first specified in the 3^rd generation partnership project (3GPP) Release 16 to support several location technologies, targeting both commercial and regulatory use cases. NRPPa introduced several enhancements compared to long term evolution positioning protocol (LPP). The performance of NRPPa was further improved in 3GPP Release 17 in terms of latency, power consumption and accuracy.

The new radio (NR) positioning capabilities are continuously augmented. In 3GPP Release 18, a study item for expanded and improved positioning was agreed, targeting improved accuracy, integrity and power efficiency. Additionally, machine learning-based enhancements are being studied in a 3GPP Release 18 study item on artificial intelligence (Al)/machine learning (ML) for NR air interface.

SUMMARY

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

Another objective of embodiments of the invention is to provide a solution providing decreased power consumption and increased positioning accuracy during positioning procedures in communication systems. 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.

According to a first aspect of the invention, the above mentioned and other objectives are achieved with a client device for a communication system, the client device being configured to: determine a channel characteristic of a radio channel for reception of a set of configured PRS resources; and measure a subset of PRS resources in the set of configured PRS resources based on the channel characteristic of the radio channel.

Configured PRS resources may herein be understood to be PRS resources which the client device has been configured to measure, e.g., by a network. That the client device measures a subset of PRS resources may herein refer to the client device measuring a reduced number of PRS resources compared to the set of configured PRS resources, i.e., does not measure all the PRS resources in the set of configured PRS resources. For example, the client device may perform a reduction, or skipping, of positioning measurements resulting in one or more PRS resources from the set of configured PRS resource not being measured. The subset of PRS resources may hence comprise fewer PRS resources than the set of configured PRS resources but is not limited thereto. In embodiments, the subset of PRS resources may comprise all the PRS resources in the set of configured PRS resources.

An advantage of the client device according to the first aspect is that the client device can, based on the determined channel characteristic, reduce the number of PRS resources to measure during a position estimation procedure. The positioning measurements may hereby be restricted to high quality positioning measurements, while other positioning measurements can be skipped. By not measuring all configured PRS resources, the power consumption in the client device can be reduced, as well as the computational complexity related to positioning. Additionally, as positioning measurement reduction, or skipping, can be performed depending on the expected quality of positioning measurements, increased accuracy can be achieved. Moreover, positioning related delays can be reduced, as the number of positioning measurements to derive positioning quantities are reduced. In implementations where PRS repetition is configured in the network and reduction of positioning measurements is activated in the client device, the client device may skip measuring late repetitions and instead provide measurement results based on a number of selected early PRS repetitions. This may lead to early availability of positioning measurements as the client device may not need to wait until all repetitions of PRS resources are received. If exploited appropriately, positioning measurement results could be transmitted earlier to the network compared with the case where measurement skipping is not employed.

In an implementation form of a client device according to the first aspect, the channel characteristic comprises one or more of: a signal-to-interference and noise ratio, an interference power, a reference signal received power, and a frequency shift of the radio channel.

An advantage with this implementation form is that the considered channel characteristics have an impact on the achievable quality of positioning measurements and the accuracy of the derived position.

In an implementation form of a client device according to the first aspect, the client device is configured to: measure the subset of PRS resources when the channel characteristic of the radio channel meets a channel characteristic threshold value.

An advantage with this implementation form is that positioning measurements are performed on high quality PRS resources, while other PRS resources are skipped. Hereby, an increased quality of positioning measurements and accuracy of the derived position may be achieved while reducing positioning related delays in the client device and in the network.

In an implementation form of a client device according to the first aspect, the client device is configured to: measure the subset of PRS resources based on the channel characteristic of the radio channel and when an autocorrelation for a set of previous measurements on PRS resources meets an autocorrelation threshold value.

An advantage with this implementation form is that non-informative positioning measurements can be skipped. For example, in case autocorrelation of positioning measurements exceeds a given threshold, the client device may assume that the network could utilize prior reported positioning measurements since no considerable change was detected. In an implementation form of a client device according to the first aspect, the client device is configured to: measure the subset of PRS resources based on the channel characteristic of the radio channel and when a correlation for a set of previous measurements on PRS resources meets a correlation threshold value.

The value of the correlation threshold may depend on several factors such as the network layout, the used positioning method, client device capabilities, number of antennas or antenna sub-arrays/panels, and targeted positioning accuracy.

An advantage with this implementation form is that redundant positioning measurements based on received PRS from different transmission reception points (TRPs) may be skipped. In implementations where the client device is configured to measure PRS resources transmitted by different TRPs, detecting high correlation between positioning measurements may indicate that the relative position of the client device with respect to each of the TRP is similar e.g., with respect to angle of arrival. Positioning measurements from TRPs with similar positions may thus be redundant. Skipping positioning measurements from redundant TRPs could be performed without substantial impact on the end positioning accuracy.

In an implementation form of a client device according to the first aspect, the client device is configured to: determine the channel characteristic of the radio channel jointly with one or more client device procedures in the group comprising: a link adaptation procedure, a beam management procedure, a channel equalization procedure, a phase/frequency tracking procedure, and a cross link interference measurement procedure.

An advantage with this implementation form is that the client device can reuse existing radio resource measurement procedures in order to derive the necessary channel characteristics, mitigating the need of dedicated positioning measurements. Hereby, power consumption and reduction in overhead may be achieved.

In an implementation form of a client device according to the first aspect, the client device is configured to: receive a first control signal from a network access node, the first control signal indicating a PRS resource measurement configuration comprising one or more of: a threshold value, a restriction, and a reporting format. An advantage with this implementation form is that the conditions that the client device may use to identify PRS measurements that may be skipped, can be fully or partially defined by the network. Consequently, PRS skipping conditions may be optimized according to information available at the network only, or obtainable at the client device only after request and signaling. For example, PRS skipping conditions may depend on the coarse location of the client device, more specifically, on an estimate of its relative position with respect to one or multiple TRPs, statistics collected from prior positioning measurements of other devices, position mapping models constructed and trained by the network, among others.

In an implementation form of a client device according to the first aspect, the threshold value comprises one or more of: a channel characteristic threshold value, an autocorrelation threshold value, and a correlation threshold value; and/or the restriction comprises one or more of: PRS resources allowed to be measured, a time interval during which PRS resources are allowed to be measured, and a number of PRS resources allowed to be measured.

An advantage with this implementation form is that the network can adapt positioning measurement skipping behavior based on features such as client device capabilities, network layout and constraints, learned propagation environment in the coverage area and positioning service requirements. By restricting the behavior of PRS measurement skipping, the network could use insights that are derived locally, based on different sources of information, without forcibly sharing it explicitly with the client device. For example, the network can derive conditions and restrictions for positioning measurement skipping based on the statistics it obtained from prior positioning measurements by multiple client devices. Instead of sharing the positioning measurements, the network may use the insights it derives in order to optimize PRS skipping condition and behavior, at the client device.

In an implementation form of a client device according to the first aspect, the client device is configured to: receive a second control signal from a network access node, the second control signal indicating an activation/deactivation command; and measure the subset of PRS resources based on the channel characteristic of the radio channel and when the second control signal indicates the activation command.

An advantage with this implementation form is that the network can dynamically control positioning measurement skipping behavior depending on network requirements, target positioning performance and capabilities of the client device. In an implementation form of a client device according to the first aspect, the client device is configured to: transmit a third control signal to a network access node, the third control signal indicating the subset of PRS resources and/or a reason for measuring the subset of PRS resources.

An advantage with this implementation form is that the client device may convey information that the network can use for later positioning optimizations, such as adapting PRS configuration, positioning periodicity, configured measurements, and positioning method.

In an implementation form of a client device according to the first aspect, the reason for measuring the subset of PRS resources is any in the group comprising: the channel characteristic meets a channel characteristic threshold value, an autocorrelation for a set of previous measurements on PRS resources meets an autocorrelation threshold value, a correlation for a set of previous measurements on PRS resources meets a correlation threshold value, and a relative position of the client device with respect to a transmission and reception point, TRP.

An advantage with this implementation form is that the indication transmitted by the client device can cover multiple sources of positioning errors which may enable the network to perform the appropriate positioning corrections if needed. Hereby, increased positioning accuracy may be achieved.

In an implementation form of a client device according to the first aspect, the third control signal is provided in a bitmap format.

An advantage with this implementation form is that information between the client device and the network is conveyed using a standardized format.

According to a second aspect of the invention, the above mentioned and other objectives are achieved with a network access node for a communication system, the network access node being configured to: transmit a first control signal to a client device, the first control signal indicating a PRS resource measurement configuration comprising one or more of: a threshold value, a restriction, and a reporting format; and/or transmit a second control signal to the client device, the second control signal indicating an activation/deactivation command associated with the PRS resource measurement configuration.

An advantage of the network access node according to the second aspect is that the network can dynamically control positioning measurement skipping behavior, depending on features such as network and positioning performance requirements, and capabilities of the client device.

In an implementation form of a network access node according to the second aspect, the threshold value comprises one or more of: a channel characteristic threshold value, an autocorrelation threshold value, and a correlation threshold value; and/or the restriction comprises one or more of: PRS resources allowed to be measured, a time interval during which PRS resources are allowed to be measured, and a number of PRS resources allowed to be measured.

An advantage with this implementation form is that the network can adapt PRS measurement skipping behavior based on features such as client device capabilities, network layout and constraints, learned propagation environment in the coverage area and positioning service requirements. By restricting the behavior of PRS measurements skipping, the network could use insights that it derived locally, based on different sources of information, without forcibly sharing it explicitly with the client device.

In an implementation form of a network access node according to the second aspect, the network access node is configured to receive a third control signal from the client device, the third control signal indicating a subset of measured PRS resources and/or a reason for measuring the subset of PRS resources.

An advantage with this implementation form is that the network can use the received indication related to the reason for PRS measurement skipping for later positioning optimizations, such as adapting PRS configuration, positioning periodicity, configured measurements, and positioning methods.

In an implementation form of a network access node according to the second aspect, the reason for measuring the subset of PRS resources is any in the group comprising: the channel characteristic meets a channel characteristic threshold value, an autocorrelation for a set of previous measurements on PRS resources meets an autocorrelation threshold value, a correlation for a set of previous measurements on PRS resources meets a correlation threshold value, a relative position of the client device with respect to a TRP.

An advantage with this implementation form is that the indication transmitted by the client device can cover multiple sources of positioning errors which may enable the network to perform the appropriate positioning corrections, if needed. Such corrections may include adaptation of PRS configuration, positioning method, positioning measurements restrictions, and PRS muting. A wide range of factors can impact positioning, depending on the employed positioning method. Such factors include, multipath in non-line of sight (NLoS) conditions, initial phase mismatch between transmitter and receiver, frequency shifts due to Doppler and carrier frequency offset, poor received PRS quality due to interference, shadowing or pathloss. In an example, when carrier phase-based positioning is employed, the network may define PRS skipping conditions wherein a set of PRS resources are not to be measured if it is subject to a frequency shift exceeding a given a network-defined threshold.

In an implementation form of a network access node according to the second aspect, the third control signal is provided in a bitmap format.

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 determining a channel characteristic of a radio channel for reception of a set of configured PRS resources; and measuring a subset of PRS resources in the set of configured PRS resources based on the channel characteristic of the radio channel.

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.

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. According to a fourth aspect of the invention, the above mentioned and other objectives are achieved with a method for a network access node, the method comprises transmitting a first control signal to a client device, the first control signal indicating a PRS resource measurement configuration comprising one or more of: a threshold value, a restriction, and a reporting format; and/or transmitting a second control signal to the client device, the second control signal indicating an activation/deactivation command associated with the PRS resource measurement configuration.

The method according to the fourth aspect can be extended into implementation forms corresponding to the implementation forms of the network access 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 access node.

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

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.

Further applications and advantages of embodiments of the invention will be apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

- Fig. 3 shows a network access node according to an embodiment of the invention; - Fig. 4 shows a flow chart of a method for a network access node according to an embodiment of the invention;

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

- Fig. 6 shows signaling between a client device and network access nodes for a positioning procedure according to an embodiment of the invention;

- Fig. 7 shows example of PRS resource subset bitmap indication;

- Fig. 8 shows a flowchart of a method according to an embodiment of the invention;

- Fig. 9 shows a flowchart of a method according to an embodiment of the invention; and

- Fig. 10 shows signaling between a client device, a network access node and a network node for a positioning procedure according to an embodiment of the invention.

DETAILED DESCRIPTION

According to conventional solutions, a position of a client device, such as a UE, is determined by a network entity based on measurements performed by the client device on positioning reference signal (PRS) resources broadcasted by neighboring network access nodes such as a next generation node B (gNB) with one or multiple TRPs. For example, the client device may measure time differences in received PRS signals and since the positions of the gNBs/TRPs are known, the observed time differences may be used to calculate the location of the client device.

Conventional solutions for reduced power consumption in client devices mainly focus on low capability client device positioning and client device positioning during radio resource control inactive state (RRCJNACTIVE) and idle state (RRCJDLE). Power saving during positioning is not limited to low capability client devices and should be supported also during radio resource control connected state (RRC_CONNECTED).

Achieving increased positioning accuracy with decreased power consumption may be challenging. Typically, a straightforward approach to increase positioning accuracy could be to increase positioning measurements and positioning related quantities, e.g., by measuring additional channel taps/paths. However, that would be detrimental to power consumption at the client device side, network side, or both since increased number of positioning measurements would typically induce larger delays and more processors occupancy in the client devices and increased signalling over the network. Thus, reducing positioning measurements without hindering positioning accuracy would improve the network performance. One way of reducing positioning measurements is by using PRS muting. PRS muting is specified in both long term evolution (LTE) and 5G NR to improve PRS hearability and reduce PRS interference. PRS muting is network centric and comprises semi-statically configured PRS muting patterns which reduce their reactivity to constantly changing channel conditions, especially in medium and high-speed mobility scenarios.

Given the drawbacks of conventional solutions, further enhancements of positioning procedures focusing on decreased power consumption and increased positioning accuracy are needed.

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.

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.

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.

According to embodiments of the invention, the client device 100 is configured to determine a channel characteristic of a radio channel for reception of a set of configured PRS resources and measure a subset of PRS resources in the set of configured PRS resources based on the channel characteristic of the radio channel. Furthermore, in an embodiment of the invention, the client device 100 for a communication system 500 comprises a processor configured to: determine a channel characteristic of a radio channel for reception of a set of configured PRS resources and measure a subset of PRS resources in the set of configured PRS resources based on the channel characteristic of the radio channel.

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: determine a channel characteristic of a radio channel for reception of a set of configured PRS resources and measure a subset of PRS resources in the set of configured PRS resources based on the channel characteristic of the radio channel.

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 202 determining a channel characteristic of a radio channel for reception of a set of configured PRS resources. The method further comprises 204 measuring a subset of PRS resources in the set of configured PRS resources based on the channel characteristic of the radio channel.

Fig. 3 shows a network access node 300 according to an embodiment of the invention. In the embodiment shown in Fig. 3, the network access 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 access 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.

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.

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 access node 300 is configured to transmit a first control signal 510 to a client device 100, the first control signal 510 indicating a PRS resource measurement configuration comprising one or more of: a threshold value, a restriction, and a reporting format; and/or transmit a second control signal 520 to the client device 100, the second control signal 520 indicating an activation/deactivation command associated with the PRS resource measurement configuration.

Furthermore, in an embodiment of the invention, the network access node 300 for a communication system 500 comprises a transceiver configured to: transmit a first control signal 510 to a client device 100, the first control signal 510 indicating a PRS resource measurement configuration comprising one or more of: a threshold value, a restriction, and a reporting format; and/or transmit a second control signal 520 to the client device 100, the second control signal 520 indicating an activation/deactivation command associated with the PRS resource measurement configuration.

Moreover, in yet another embodiment of the invention, the network access 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: transmit a first control signal 510 to a client device 100, the first control signal 510 indicating a PRS resource measurement configuration comprising one or more of: a threshold value, a restriction, and a reporting format; and/or transmit a second control signal 520 to the client device 100, the second control signal 520 indicating an activation/deactivation command associated with the PRS resource measurement configuration.

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. 3. The method 400 comprises transmitting 402 a first control signal 510 to a client device 100, the first control signal 510 indicating a PRS resource measurement configuration comprising one or more of: a threshold value, a restriction, and a reporting format; and/or transmitting 404 a second control signal 520 to the client device 100, the second control signal 520 indicating an activation/deactivation command associated with the PRS resource measurement configuration.

Fig. 5 shows a communication system 500 according to an embodiment of the invention. The communication system 500 in the disclosed example comprises a client device 100 and a plurality of network access nodes 300 configured to communicate and operate in the communication system 500. It should be noted that the communication system 500 may comprise any number of client devices 100 and any number of network access nodes 300 without deviating from the scope of the invention. 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 UE and the network access node 300 may be a gNB/TRP but embodiments of the invention is not limited thereto.

The communication system 500 may moreover include a network (NW) comprising a plurality of network nodes. A network node may be a network node in a core network such as a location management function (LMF) 600 and may communicate with the client device 100 via one or more network access nodes 300 for example during a positioning procedure.

With reference to Fig. 5, during a positioning procedure, the LMF 600 may request location information from the client device 100. The client device 100 may be configured to receive a plurality of reference signals 550 in a plurality of radio channels 560 from the plurality of radio access nodes 300 over a radio interface, such as a llu interface. The plurality of reference signals 550 may comprise PRS resources broadcasted by each of the radio access node 300 in a comb pattern covering the whole bandwidth domain to reduce the risk of interference and to enable accurate timing estimation. The client device 100 may be configured to perform positioning measurements, and to provide positioning measurement information to a network node, such as the LMF 600, through one or more network access nodes 300. Typically, the client device 100 may be configured to receive and measure PRS resources broadcasted by the network access node 300 serving the client device 100, such as a serving gNB/TRP as well as a number of neighboring network access nodes 300, such as neighboring gNBs/TRPs.

According to conventional solutions, the PRS resources measured by the client device 100 are configured by the network. This means that all the configured PRS resources, i.e. , the set of configured PRS resources, are measured by the client device 100. Thus, the client device 100 may be configured to measure positioning quantities on PRS resources that are subject to high interference or to detrimental Doppler and multi-path impact. In such scenarios, additional positioning measurements may actually be counter-productive, from a positioning accuracy perspective. Simulations of distance error in 2D localization based on signaling from a plurality of base stations (BS) have shown that the localization error may increase when more BSs are added. Consequently, adding more time of arrival (ToA) measurements, without considering their quality, may degrade localization performance.

The positioning measurements that would provide optimal positioning performance may depend on a plurality of features such as received signal strength indicator (RSSI) or reference signal received power (RSRP), PRS interference, line of sight (LoS)/non-line of sight (NLoS), velocity of the client device 100, frequency offsets due to Doppler shift and carrier frequency offset, initial phase mismatch between transmit (TX) and receive (RX) oscillator, path-loss, and shadowing. In other words, features related to PRS signal quality and the quality of the relevant radio channels.

Based on the above, reducing the number of positioning measurements without negatively impacting positioning accuracy would reduce the power consumption and computational complexity at the client device 100 during positioning measurements. This may be achieved by a client device 100 capable of predicting the quality of positioning measurements before performing them.

Thus, according to embodiments of the invention, the client device 100 may be configured for reduction of positioning measurements. This means that the client device 100 may be enabled to determine the channel characteristic of a radio channel for reception of the set of configured PRS resources and to decide a subset of the set of configured PRS resources to measure and which configured PRS resources to not measure, i.e., which positioning measurements to skip. The client device 100 may base the decision on the determined channel characteristic, as well as one or more threshold values and/or restrictions. The one or more threshold values and/or restrictions may here be referred to as PRS selection and/or PRS skipping conditions. The client device 100 may estimate a quality of positioning measurements, a priori, based on the derived channel characteristics, which may be estimated based on previous positioning measurements on PRS resources or other downlink reference signals (DL RS) such as channel state information - reference signal (CSI-RS), tracking reference signal (TRS), synchronization signal block (SSB), or demodulation reference signal (DMRS). The client device 100 may hereby be provided with an additional degree of freedom (DoFs) in selecting the measurements that need to be performed and/or reported, since it has a better appreciation of the downlink (DL) channel and interference conditions compared to the network, especially in frequency division duplex (FDD) systems. The positioning measurements may hereby be restricted to high quality measurements, while low quality positioning measurements may be skipped resulting in higher positioning accuracy, decreased computational complexity and reduced power consumption in the client device 100.

Fig. 6 shows a signaling sequence between a client device 100 and a plurality of network access nodes 300a, 300b, 300c for reduction of positioning measurements according to an embodiment of the invention. The client device 100 may be a UE, the network access node 300a may be a serving gNB/TRP and the network access nodes 300b and 300c may be neighboring gNBs/TRPs but are not limited thereto.

In step I in Fig. 6, the network access node 300a transmits a first control signal 510 to the client device 100. The first control signal 510 may indicate a PRS resource measurement configuration and specify PRS selection and/or PRS skipping conditions that may be used by the client device 100 when reducing/skipping positioning measurements during a positioning procedure. The PRS resource measurement configuration may be included in a radio resource control (RRC) configuration message provided by the network to the client device 100, e.g., via the network access node 300a. The RRC configuration message may moreover contain RRC configuration specifying the set of configured PRS resources, i.e., the PRS resources that the client device 100 is configured to receive and measure. The PRS resource measurement configuration may comprise one or more of a threshold value, a restriction and/or a reporting format. The threshold value and/or restriction may be used by the client device 100 when deciding the subset of configured PRS resources to measure and/or the PRS resource measurements that are skipped. The format for reporting of the PRS subset selection, i.e., for reporting which PRS resources have been measured, may comprise a bitmap format.

In embodiments, the threshold value may comprise a channel characteristic threshold value, an autocorrelation threshold value, and/or a correlation threshold value. The threshold value may, in embodiments, represent a value related to a feature which is acceptable for PRS resources selected for measurements. The restriction may, in embodiments, comprise one or more of: PRS resources allowed to be measured, a time interval during which PRS resources are allowed to be measured, and a number of PRS resources allowed to be measured.

The client device 100 may thus be configured to perform reduction of positioning measurements based on network defined PRS selection and/or PRS skipping conditions received from the network access node 300a in the first control signal 510. The PRS selection and/or PRS skipping conditions may comprise considerations related to the quality of one or more radio channels such as a received power, signal-to-interference and noise ratio (SINR), and/or frequency and time synchronization. Moreover, the PRS selection and/or PRS skipping conditions may further comprise considerations related to measurement uniqueness, such as autocorrelation of measurements on the same reference signal (RS) resource and/or correlation between measurements on different RS resources.

Additionally, the client device 100 may define its own PRS selection and/or PRS skipping conditions which may be used during positioning measurements. Client device defined PRS selection and/or PRS skipping conditions may depend on the implementation or configuration of the client device 100. The client device 100 may use machine learning models based on previous positioning measurements and positioning procedures. For example, previous radio resource measurements (RRM)/channel state information (CSI) measurements performed for link adaptation, beam management, channel equalization, and/or cross link reference measurements may be used to provide input features related to channel characteristics, such as frequency shift (Doppler) and SINR to the client device-based model. In implementations, where results from frequency shift (Doppler) and SINR measurements can be obtained before starting the reception of PRS resources, the client device 100 may use such results to determine which PRS resources to measure and which to skip.

Additionally, the client device defined PRS selection and/or PRS skipping conditions may be based on the capabilities of the client device 100 which may affect the accuracy of relevant positioning procedures. Examples of such capabilities may include hardware capabilities restricting positioning accuracy, supported bandwidth, power class oscillator accuracy and/or number of antenna ports. Indeed, the accuracy of timing estimations may increase with the supported bandwidth, and the accuracy of angle of arrival (AoA) may increase with the number of client device antennas. During positioning measurements the client device 100 may use network defined conditions, client device defined conditions or both depending on the configuration of the client device 100.

In step II in Fig. 6, upon reception of the PRS resource measurement configuration, the client device 100 may be configured to perform reduction of positioning measurements. In other words, when receiving the first control signal 510, the client device 100 is enabled to maintain PRS measurements on the radio interfaces to a minimum such that the target positioning requirements in terms of accuracy, complexity and delay can be achieved.

In step III in Fig. 6, the network access node 300a transmits a second control signal 520 to the client device 100. The second control signal 520 may be an activation command associated with the PRS resource measurement configuration to increase power efficiency. In that case, when the client device 100 receives the second control signal 520 in step IV in Fig. 6, the reduction of positioning measurement is activated in the client device 100.

Generally, activation of the client device 100 based reduction of positioning measurement may be performed when:

• The client device 100 is capable of deriving the metrics it needs to determine PRS measurements that can be skipped, with less computations and power consumption, compared to performing the actual configured positioning measurements and computations.

• The needed insights can be derived by the client device 100 before the time of reception of the PRS resources that would not be measured. Practically, this refers to the ability of the client device 100 to determine relevant channel characteristics, evaluate PRS skipping conditions, and determine the PRS resources that may be excluded from PRS measurements, before receiving the PRS resources in question.

• The skipped positioning measurements will not improve position or mobility related quantities, e.g., velocity and direction of movement.

• In case a machine learning model is being used to select the positioning measurements to skip, the model may be matching the ongoing propagation conditions, i.e., model inference performance is satisfactory, depending on the network or service KPIs.

The second control signal 520 may further be a deactivation command associated with the PRS resource measurement configuration. In that case, when the client device 100 receives the second control signal 520 in step IV in Fig. 6, the reduction of positioning measurement is deactivated in the client device 100. Thus, positioning measurements are performed according to conventional methods until an activation command is received by the client device 100. A deactivation of the reduction of positioning measurement may be done due to data collection, client device 100 model drift, and change in the traffic.

The second control signal 520 may be transmitted via dynamic signaling, for example via downlink control information (DCI) or medium access control (MAC) control element (CE). The second control signal 520 may further be transmitted by means of RRC signaling or positioning protocol messages.

Steps V - VIII in Fig. 6 apply to the case when an activation command has been received by the client device 100. In step V in Fig. 6, when the second control signal 520 indicates the activation command and the reduction of positioning measurement is activated, the client device 100 may, as previously explained, determine a channel characteristic of a radio channel for reception of a set of configured PRS resources. The set of configured PRS resources may be the PRS resources the client device 100 is configured to measure. Client device configuration may, as previously explained, be received from the network in a RRC configuration message. The RRC configuration message may comprise PRS configuration specifying the set of configured PRS resources. The client device 100 may be configured to measure PRS resources associated with the network access node 300a serving the client device 100, as well as one or more neighboring network access nodes 300b, 300c.

In embodiments, the channel characteristic may comprise a SINR, an interference power, a reference signal received power, and/or a frequency shift of the radio channel. The channel characteristic may be determined by means of measurements or by means of predictions. Measurement of the channel characteristic may be performed on dedicated resources or from reference signals transmitted for other radio resource measurements such as channel state information, beam management, cross link interference measurements. Prediction of the channel characteristics may be performed using prediction algorithms, such as Kalman filters, neural networks, based on cached measurements, over a configured or client device-selected measurement window.

In an embodiment, the channel characteristic of the radio channel may be determined jointly with one or more client device procedures in the group comprising: a link adaptation procedure, a beam management procedure, a channel equalization procedure, a phase/frequency tracking procedure, and a cross link interference measurement procedure. According to an example, TRS measurements for phase tracking can be used in order to estimate the Doppler shift that is impacting the transmitted PRS signals. In another example, measurement for CSI reporting, on channel or channel and interference measurement resources, can be utilized in order to approximate the achievable SINR during the reception of PRS resources.

In step VI in Fig. 6, the client device 100 may measure a subset of PRS resources in the set of configured configured PRS resources. The subset of PRS resources may be measured based on the determined channel characteristic of the radio channel for reception of the set of configured PRS resources.

The client device 100 may be configured to select PRS resources from the set of configured PRS resources that are skipped and to select a subset of PRS resources from the set of configured PRS resources that are measured. The selection may be done by comparing the determined channel characteristic of the radio channel with a threshold value associated with the determined channel characteristic. Moreover, the selection may be done based on a restriction. As previously explained, the threshold value and the restriction may be comprised in the PRS resource measurement configuration which may be received in the first control signal 510.

In embodiments, the client device 100 may measure the subset of PRS resources when the channel characteristic of the radio channel meets a channel characteristic threshold value. The channel characteristic threshold value may indicate an acceptable value of the radio channel characteristic such as the SI NR, an interference power, a reference signal received power or a frequency shift of the radio channel. Thus, the channel characteristic of the radio channel may be determined to meet the channel characteristic threshold value if the channel characteristic of the radio channel is above or below the threshold value.

In embodiments, the client device 100 may measure the subset of PRS resources based on the channel characteristic of the radio channel and when an autocorrelation for a set of previous measurements on PRS resources meets an autocorrelation threshold value. The threshold value may indicate an acceptable value of autocorrelation. Thus, the autocorrelation for a set of previous measurements on PRS resources may be determined to meet an autocorrelation threshold value if it is above or below the threshold value.

In embodiments, the client device 100 may measure the subset of PRS resources based on the channel characteristic of the radio channel and when a correlation for a set of previous measurements on PRS resources meets a correlation threshold value. The threshold value may indicate an acceptable value of correlation. Consequently, the correlation for a set of previous measurements on PRS resources may be determined to meet a correlation threshold value if it is above or below the threshold value. In other words, positioning measurements may be skipped if strong autocorrelation/correlation over time is detected. Such may be the case, if the client device 100 is still in previously reported beam coverage area if the difference in time of arrival is negligible or if the client device model for measurement prediction is able to provide accurate prediction. In another example, positioning measurements may be skipped based on a relative position of the client device 100 with respect to different TRPs or based on L1- signal to SINR measured from PRS only or PRS and other DL-RS, taken as interference measurement resources (IMR). Further examples of client device based reduction of positioning measurements that may be applied in embodiments of the invention will be described with reference to Fig. 8 and Fig. 9. In step VII in Fig. 6, the client device 100 may transmit a third control signal 530 to the network access node 300a. The third control signal 530 is received by the network access node 300a in step VIII in Fig. 6.

The client device 100 may, in the third control signal 530, indicate the subset of PRS resources and/or a reason for measuring the subset of PRS resources which corresponds to indicate which positioning measurements were not measured, i.e. , skipped. In embodiments, the third control signal 530 may be a positioning measurement skipping indication indicating which measurements were skipped/not measured. The third control signal 530 may be transmitted for each of the skipped positioning measurements, or for groups of skipped positioning measurements. When the client device 100 indicates a reason for skipped positioning measurements, client device configuration or specifications may define an association between a codepoint and a reason for skipping. An example of such an association is given in the Table 1.

Table 1

The reason for measuring the subset of PRS resources may comprise that the channel characteristic meets a channel characteristic threshold value, an autocorrelation for a set of previous measurements on PRS resources meets an autocorrelation threshold value, a correlation for a set of previous measurements on PRS resources meets a correlation threshold value, and/or a relative position of the client device 100 with respect to a network access node 300.

In embodiments, the third control signal 530 may be provided in a bitmap format. The bitmap may indicate which PRS resources were measured or skipped. In the considered framework, a bitmap may correspond to a mapping between a specific domain and bits. A sequence of locations within an array or a sequence of variables may be indicated in a straightforward way in a binary format by means of an index. Fig. 7 shows an example of PRS resource subset bitmap indication. Here, the case of PRS resource set with 2 PRS resources and PRS repetition is illustrated. The skipped PRS resources #1 and #2 are indicated in bitmap form wherein the index of a bit in the bitmap corresponds to a transmitted resource, where “1” denotes a resource that was measured and “0” denotes a resource that was skipped. As shown in Fig. 7, positioning measurement skipping may be different from one slot to the other. The client device 100 may report a bitmap per slot or a combined bitmap for multiple slots.

Figs. 8 - 9 are used to illustrate examples of different scenarios where the client device 100 determines a subset of PRS resources in the set of configured PRS resources for positioning measurements. The scenarios are set in a NR/LTE context thus, 3GPP 5G terminology, definitions, expressions, and system architecture will be used. Therefore, the client device 100 can be considered as a UE and the network access node 300 as a gNB/TRP. However, embodiments of the invention are not limited thereto.

Fig. 8 shows a flow chart of an embodiment for a UE 100 performing channel state information CSI based resource wise PRS measurement skipping. CSI measurements are performed to help the network assess the channel quality, derive optimal TX/RX beams, modulation and coding scheme (MCS) index and frequency selective or wideband precoder. While CSI-RS, DMRS and SSB do not have the same design as PRS, non-negligible insights can be derived for future positioning measurements selection. In the following, possible variants for CSI-based PRS skipping conditions are presented.

The method starts in step I in Fig. 8. In step II in Fig 8, the UE 100 performs CSI measurements and channel estimation for a time sample tj. The CSI measurements may be performed on signals such as CSI-RS, synchronization signals (SS) and/or DMRS. In step III in Fig 8, the CSI measurements are processed.

In step IV in Fig 8, the CSI measurements for time sample tj are compared to CSI measurements for previous time samples. The comparison may be performed to check if at least one measurement condition is met. The UE 100 may decide to skip fully or partially a PRS measurement occasion depending on network configured and/or UE 100 defined measurement/measurement skipping conditions. Examples of measurement conditions may for example include measurement autocorrelation over time, threshold on channel or precoding matrix indicator (PMI), autocorrelation over time and/or threshold on Doppler shift. If the measurement condition is met, the method continues to step V in Fig. 8 where measurements on DL-PRS are performed. If the measurement condition is not met, the measurement is skipped, and the method continues to step VI where the time sample is incremented to ti=ti +1. Thereafter the method continues to step II in Fig. 8 where the CSI is measured at the incremented time sample.

Fig. 9 shows a flow chart of an example of CSI based TRP wise PRS measurement skipping.

The method starts in step I in Fig. 9. In step II in Fig 9, measurements and channel estimation are performed for downlink reference signals (DL-RSs) received from a plurality of TRPs at time sample tj. The DL-RSs may include for example CSI, RS, SS and/or DMRS. In step III in Fig 9, computation of RSSI for TRPs and CSI correlation between TRPs is performed.

In step IV in Fig. 9, N number of TRPs are selected, i.e. , the TSP with the strongest RSSI and N-1 other TRPs. The selected TRPs have small CSI correlation. The UE 100 may consider the CSI correlation between TRPs in order to derive which PRS measurements can be skipped, without loss of accuracy. Depending on the relative position of the UE 100 and TRPs, PRS measurements may vary greatly in terms of the additional information it may provide for accurate positioning. The UE 100 may consider conditions such as, correlation of the delay and/or spatial support of the respective channels, SI NR of DL-RS of the respective TRPs and/or transmission configuration indicator (TCI) states of DL-RS from different TRPs.

In step V in Fig. 9, DL-PRS measurements on the selected N number of TRPs are performed. In step VI in Fig. 9, the time sample is incremented to ti=ti +1. Thereafter the method continues to step II in Fig. 9 where the CSI is measured at the incremented time sample.

Fig. 10 shows a signaling diagram for a positioning procedure with reduction of positioning measurements according to an embodiment of the invention in an exemplary 3GPP implementation. The signaling diagram involves a UE 100, a first gNB/TRP 300a, a second gNB/TRP 300b, a third gNB/TRP 300c and a LMF 600. In the shown embodiment it is assumed that the first gNB/TRP 300a is a serving gNB/TRP.

In step I in Fig. 10, a TRP configuration information exchange between the LMF 600 and the gNB/TRPs 300a, 300b, 300c is performed, followed by a positioning capability transfer between the UE 100 and the LMF 600 in step II in Fig. 10. The TRP configuration information exchange may include configuration of downlink positioning reference resources DL PRS. The positioning capability transfer may refer to one or multiple supported positioning methods. In step III in Fig. 10, the UE 100 receives from the LMF 600 a set of assistance data that is needed by the subsequent positioning procedure, e.g., TRP location information. The UE 100 is hereby configured for positioning procedures. The UE 100 may be configured to receive a set of PRS resources and to perform reduction of positioning measurements based on PRS resource measurement configuration as described with reference to Fig. 6.

The positioning procedure in the UE 100 is initiated in step IV in Fig. 10, by the LMF 600 transmitting a location information request.

In step V in Fig. 10, the UE 100 receives a set of configured PRS resources from the gNB/TRPs 300a, 300b, 300c based on the configuration provided by the network and performs positioning measurements on the received PRS resources. The positioning measurements are transmitted to the LMF 600 in step VI in Fig 10, as measurement information.

In step VII in Fig 10, the UE 100 receives the second control signal 520 comprising an activation command for activating the reduction of positioning measurement in the UE 100, as described with reference to Fig. 6. The activation of the reduction of positioning measurement may, in an example, be conveyed from the LMF 600 to the UE 100 as part of positioning protocol messages. In another example, the serving gNB/TRP 300a may use dynamic L1/L2, RRC or positioning protocol signaling to activate, or deactivate, reduction of positioning measurement.

In step VIII in Fig. 10, the UE 100 receives downlink reference signaling DL-RS from neighboring gNBs/TRPs 300a, 300b, 300c and determines in step IX in Fig. 10 a subset of PRS resources for positioning measurements as described with reference to Fig. 6. The UE performs step IX based on channel characteristics derived from the received DL RS. The UE 100 may alternatively use measurements from other DL-RS, such as CSI-RS for CSI reporting/mobility, DM RS and/or SSB to derive the subset of PRS resources for positioning measurements, as previously explained with reference to Fig. 8.

In step X in Fig. 10, the UE 100 receives a set of configured PRS resources and measures the subset of PRS resources determined in step IX in Fig.10, as described with reference to Fig. 6.

In the embodiment shown in Fig 10, the UE 100 in step XI transmits a third control signal 530 to the LMF 600 The third control signal 530 indicates the subset of PRS resources and/or a reason for measuring the subset of PRS resources, as described in Fig. 6, as well as measurement information related to the subset of PRS resources.

The client device 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.

The network access node 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.

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. Moreover, it should be realized that the client device and the network access node 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 and the network access node 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

1. A client device (100) for a communication system (500), the client device (100) being configured to: determine a channel characteristic of a radio channel for reception of a set of configured PRS resources; and measure a subset of PRS resources in the set of configured PRS resources based on the channel characteristic of the radio channel.

2. The client device (100) according to claim 1 , wherein the channel characteristic comprises one or more of: a signal-to-interference and noise ratio, an interference power, a reference signal received power, and a frequency shift of the radio channel.

3. The client device (100) according to claim 1 or 2, configured to: measure the subset of PRS resources when the channel characteristic of the radio channel meets a channel characteristic threshold value.

4. The client device (100) according to any one of the preceding claims, configured to: measure the subset of PRS resources based on the channel characteristic of the radio channel and when an autocorrelation for a set of previous measurements on PRS resources meets an autocorrelation threshold value.

5. The client device (100) according to any one of the preceding claims, configured to: measure the subset of PRS resources based on the channel characteristic of the radio channel and when a correlation for a set of previous measurements on PRS resources meets a correlation threshold value.

6. The client device (100) according to any one of the preceding claims, configured to: determine the channel characteristic of the radio channel jointly with one or more client device procedures in the group comprising: a link adaptation procedure, a beam management procedure, a channel equalization procedure, a phase/frequency tracking procedure, and a cross link interference measurement procedure.

7. The client device (100) according to any one of the preceding claims, configured to: receive a first control signal (510) from a network access node (300), the first control signal (510) indicating a PRS resource measurement configuration comprising one or more of: a threshold value, a restriction, and a reporting format.

8. The client device (100) according claim 7, wherein the threshold value comprises one or more of: a channel characteristic threshold value, an autocorrelation threshold value, and a correlation threshold value; and/or the restriction comprises one or more of: PRS resources allowed to be measured, a time interval during which PRS resources are allowed to be measured, and a number of PRS resources allowed to be measured.

9. The client device (100) according to any one of the preceding claims, configured to: receive a second control signal (520) from a network access node (300), the second control signal (520) indicating an activation/deactivation command; and measure the subset of PRS resources based on the channel characteristic of the radio channel and when the second control signal (520) indicates the activation command.

10. The client device (100) according to any one of the preceding claims, configured to: transmit a third control signal (530) to a network access node (300), the third control signal (530) indicating the subset of PRS resources and/or a reason for measuring the subset of PRS resources.

11 . The client device (100) according to claim 10, wherein the reason for measuring the subset of PRS resources is any in the group comprising: the channel characteristic meets a channel characteristic threshold value, an autocorrelation for a set of previous measurements on PRS resources meets an autocorrelation threshold value, a correlation for a set of previous measurements on PRS resources meets a correlation threshold value, and a relative position of the client device (100) with respect to a transmission and reception point, TRP.

12. The client device (100) according to claim 10 or 11 , wherein the third control signal (530) is provided in a bitmap format.

13. A network access node (300) for a communication system (500), the network access node being configured to: transmit a first control signal (510) to a client device (100), the first control signal (510) indicating a PRS resource measurement configuration comprising one or more of: a threshold value, a restriction, and a reporting format; and/or transmit a second control signal (520) to the client device (100), the second control signal (520) indicating an activation/deactivation command associated with the PRS resource measurement configuration.

14. The network access node (300) according claim 13, wherein the threshold value comprises one or more of: a channel characteristic threshold value, an autocorrelation threshold value, and a correlation threshold value; and/or the restriction comprises one or more of: PRS resources allowed to be measured, a time interval during which PRS resources are allowed to be measured, and a number of PRS resources allowed to be measured.

15. The network access node (300) according to claim 13 or 14, configured to receive a third control signal (530) from the client device (530), the third control signal (530) indicating a subset of measured PRS resources and/or a reason for measuring the subset of PRS resources.

16. The network access node (300) according to claim 15, wherein the reason for measuring the subset of PRS resources is any in the group comprising: the channel characteristic meets a channel characteristic threshold value, an autocorrelation for a set of previous measurements on PRS resources meets an autocorrelation threshold value, a correlation for a set of previous measurements on PRS resources meets a correlation threshold value, a relative position of the client device (100) with respect to a TRP.

17. The network access node (300) according to claim 15 or 16, wherein the third control signal (530) is provided in a bitmap format.

18. A method (200) for a client device (100), the method (200) comprising: determining (202) a channel characteristic of a radio channel for reception of a set of configured PRS resources; and measuring (204) a subset of PRS resources in the set of configured PRS resources based on the channel characteristic of the radio channel.

19. A method (400) for a network access node (300), the method (400) comprising: transmitting (402) a first control signal (510) to a client device (100), the first control signal

(510) indicating a PRS resource measurement configuration comprising one or more of: a threshold value, a restriction, and a reporting format; and/or transmitting (404) a second control signal (520) to the client device (100), the second control signal (520) indicating an activation/deactivation command associated with the PRS resource measurement configuration.

20. A computer program with a program code for performing a method according to claim 18 or 19 when the computer program runs on a computer.