Technique for channel measurement configuration

Abstract

A technique for channel measurement configuration is described. According to one method aspect of the technique, a method (300) of a radio device (100) is provided. The method (300) comprising: determining (304) at least one value of a metric for channel coherence of a radio channel (502) between the radio device (100) and a network node (200) of a radio access network, RAN (500); and transmitting (306), to the RAN (500) or the network node (200), the determined (304) at least one value of the channel coherence metric.

Description

[0001] Technique for channel measurement configuration

[0002] Technical Field

[0003] The present disclosure generally relates to a technique for configuring radio channel measurements. More specifically, and without limitation, methods and devices are provided for configuring measurements of a radio channel of a radio access network (RAN) as well as for assisting the measurement configuration of the RAN.

[0004] Background

[0005] The Third Generation Partnership Project (3GPP) has specified radio access technologies (RATs) such as Fourth Generation (4G) LongTerm Evolution (LTE) and Fifth Generation (5G) New Radio (NR), which efficient usage of radio resources relies on measurements of the uplink (UL) and downlink (DL) channels in the frequency domain (FD). Examples of these measurements include channel state information (CSI) measurements, demodulation reference signal (DM-RS) measurements, and sounding reference signal (SRS) measurements. The Sixth Generation (6G) mobile wireless communication system will support a diverse set of use cases and a diverse set of deployment scenarios. The latter includes deployment at both low frequencies on the order of 100s of MHz and high frequencies, e.g. mm-waves in the tens of GHz.

[0006] However, as the channel bandwidth grows, measuring a radio channel by these conventional means becomes inefficient, e.g. in terms of reference signal resources over payload resources. On the other hand, measuring the radio channel coarsely in the frequency domain will miss its complex structure, resulting in disparity between the actual channel capacity and the implemented modulation and coding scheme due to a subpar channel estimate.

[0007] For example, one conventional way of monitoring the frequency domain channel variations is based on uplink sounding reference signals (UL SRS) transmission. However, using reciprocity-based downlink (DL) precoding over multiple carriers may be infeasible or inefficient in commercial systems, because the complicated SRS carrier switching schemes specified in NR do not work well in practice. For instance, the NR SRS carrier switching scheme is associated with large latency due to switching of SRS among carriers and causes a significant period of time with no transmission on the actual UL carriers. Moreover, SRS-based solutions for monitoring the frequency domain channel variations are not useful in the cases with low SNR, e.g., for cell-edge UEs, where estimates based on the SRS is not reliable. Also, SRS carrier switching may not be necessarily supported by the user equipment (UE). In all such cases, SRS-based methods may not be useable for monitoring the channel variation in the frequency domain. Furthermore, it may not be possible to use SRS or UL DM-RS for estimating the frequency domain channel variations in DL only carriers.

[0008] Summary

[0009] Accordingly, there is a need for a technique that enables accurate and resourceefficient channel measurements.

[0010] According to one method aspect, a method performed by a radio device is provided. The method comprises determining at least one value of a metric for channel coherence of a radio channel between the radio device and a network node of a radio access network (RAN). The method further comprises transmitting, to the RAN or the network node, the determined value of the channel coherence metric.

[0011] Embodiments of the method enable reliably attaining information about channel variations in the frequency domain at the network.

[0012] For example, a method of a radio device assisting configuration of a channel measurement is provided. The method comprises determining a value of a metric for channel coherence of a radio channel between the radio device and a network node of a radio access network (RAN). The method further comprises transmitting, to the RAN or the network node, the determined value of the channel coherence metric for assisting a frequency domain configuration of a subsequent measurement of the radio channel between the radio device and the network node.

[0013] At least some of these and further embodiments enable the radio access network (RAN) configuring the subsequent channel measurement to be both accurate and resource-efficient, e.g. since a granularity of the radio channel in the frequency domain is indicated by the determined and transmitted metric value beforehand when the network node or the RAN configures a frequency domain structure of the subsequent channel measurement. For example, embodiments of the technique enable a two-stage measurement process, wherein the first stage determines the value of the channel coherence metric of the radio channel and the second stage includes the ("actual") subsequent measurement of the radio channel.

[0014] Alternatively or in addition, embodiments of the method can enable the network node or the RAN to set a frequency domain granularity (e.g., UL and / or DL reference signal density in the frequency domain) for channel measurements, e.g. to balance accuracy and resource-efficiency of the channel measurements.

[0015] Herein, accurate may refer to the accuracy of the value determined for the metric and / or the subsequent channel measurement (e.g., a channel estimation).

[0016] Alternatively or in addition, resource-efficient may refer to radio resources occupied by reference signals to be measured and / or a signaling overhead for reporting measurements (e.g., compared to radio resources available for control or payload). Alternatively or in addition, frequency domain granularity may refer to a frequency density and / or a frequency domain extent, e.g. associated with uplink (UL) reference signals (UL RS, e.g., SRS and / or UL DM-RS) and / or downlink (DL) reference signals (DL RS, e.g., NZP CSI-RS and / or DL DM-RS), e.g. used in the subsequent measurement. The frequency domain granularity may be UE-specific.

[0017] At least some of these embodiments and further embodiments may take into account channel variability in the frequency domain. Thus, information regarding channel variability in the frequency domain is readily available at the network node.

[0018] While the metric value may be determined optionally in the downlink (e.g., based on downlink reference signals), the subsequent channel measurement (which frequency domain configuration may rely upon the determined and transmitted metric value) may be performed in the uplink and / or in the downlink.

[0019] The technique may be applied to multiple-input multiple-output (MIMO) channels and / or a DL-only carrier as examples of the radio channel. Alternatively or in addition, the technique may be applied to sixth generation (6G) radio access technology, e.g. 3GPP Release 20 and / or 21. Moreover, the metric may comprise a delay spread.

[0020] The one method aspect may be implemented alone or in combination with any one of the embodiments in the list of claims, particularly the claims 1 to 15. The "metric for channel coherence" (e.g., according to the one method aspect) may be also referred to as the "channel coherence metric", or briefly as "metric". The channel coherence metric may be an example of frequency domain channel properties (FDCP). The "value" of the "metric" may be briefly referred to as "metric value".

[0021] The transmitted at least one value of the metric (e.g., according to the one method aspect) may be indicative of at least one of: a radio propagation along the radio channel, optionally indicative of a multi-path radio propagation along the radio channel; and a frequency domain channel property.

[0022] Alternatively or in addition, the transmitted at least one value of the metric (e.g., according to the one method aspect) may assist the network node for frequency domain configuration, optionally for an adaptive frequency-domain resource allocation and / or dynamically assigning physical resource blocks, PRBs, to the radio device (100) in a manner that aligns with frequency domain channel properties indicated by the at least one metric value.

[0023] While embodiments of the technique may determine the at least one metric value in the frequency or time domain, the at least one metric value may assist (e.g., influence or control) a configuration in frequency domain.

[0024] By way of example, the at least one metric may comprise a coherence bandwidth, e.g. as a measure of the range of frequencies over which a response of the radio channel is (e.g., relatively) constant. The coherence bandwidth may be inversely proportional to a time delay spread of the radio channel, as another example of the metric. An increase in the coherence bandwidth (or decrease in delay spread) may assist the network node in configuring frequency domain resources responsive to a frequency-flat channel or meaning that all frequency components experience similar fading. A decrease in the coherence bandwidth (or increase in delay spread) may assist the network node in a frequency domain configuration that matches the radio channel exhibiting frequency-selective fading or different frequency components experiencing varying levels of attenuation.

[0025] Alternatively or in addition, the transmitted at least one value of the metric (e.g., according to the one method aspect) may assist a frequency domain configuration of a subsequent measurement of the radio channel between the radio device and the network node. For example, embodiments may measure channel coherence (in any domain) to optimize a frequency domain configuration of a subsequent channel measurement. Alternatively or in addition, the radio device may report a channel coherence metric (which is not necessarily measured in the frequency domain), and the network node may configure the channel measurement resources in the frequency domain based on the reported at least one metric value. Accordingly, the term "channel coherence metric" may encompass time and / or frequency domain measurements.

[0026] The "subsequent measurement of the radio channel" may be abbreviated by "subsequent channel measurement", or briefly "subsequent measurement".

[0027] Alternatively or in addition, the transmitted at least one value of the metric (e.g., according to the one method aspect) may assist or trigger at least one of: a change of an allocation of reference signal resources to reference signals in frequency domain; a change in a pattern of reference signal resources in frequency domain, optionally wherein all of the reference signal resources in the pattern carry a reference signal associated to one antenna port; and a change in a density of reference signals in frequency domain, optionally wherein a decrease in coherence bandwidth indicated by the at least one metric value triggers an increase in the density and / or wherein an increase in coherence indicated by the at least one metric value bandwidth triggers an increase in the density.

[0028] The reference signals may be transmitted from the radio device to the network node; or the reference signals may be received at the radio device from the network node.

[0029] Alternatively or in addition, the transmitted at least one value of the metric (e.g., according to the one method aspect) may assist or trigger a change of at least one of: a subband size for the radio channel, optionally a subband size of a channel state information, CSI, report for the radio channel; and a numerology or subcarrier spacing, SCS, forthe radio channel.

[0030] The determining of the at least one value of the channel coherence metric of the radio channel between the radio device and the RAN may comprise measuring the channel coherence metric, e.g. resulting in the determined at least one value or at least one intermediate value and / or computing the channel coherence metric, e.g. based on one or more other measurement values or the at least one intermediate value. The determining, the measuring and / or the computing may be performed by the radio device.

[0031] The transmitting, to the RAN, of the determined at least one value of the channel coherence metric that is assisting the frequency domain configuration may also be referred to as reporting the determined at least one value to the RAN or the network node. The network node, towards which the at least one value of the metric is determined, may be a serving network node of the radio device. The radio device may report the at least one value of the metric to its serving network node. Alternatively or in addition, the network node may provide dual connectivity to the radio device, e.g. as a secondary network node other than the serving primary network node. The radio device may report the at least one value of the metric for the channel between the radio device and the secondary network node to the primary network node.

[0032] Alternatively or in addition, the channel coherence metric assisting the frequency domain configuration may trigger the RAN, e.g., the network node, to determine (e.g., change) the frequency domain configuration and / or to transmit the determined (e.g., changed) frequency domain configuration to the radio device. Herein, the expression "frequency domain configuration" may refer to the determining of the frequency domain configuration at the network node or the RAN based on the received at least one metric value, and / or may refer to one or more configuration parameters resulting from the determining (i.e., one or more configuration parameters determined based on the received at least one metric value), and / or the configuring (e.g., providing) of the radio device with the one or more configuration parameters (i.e., the transmitting of the configuration message). The frequency domain configuration may be a change of the frequency domain configuration (i.e., a frequency domain reconfiguration).

[0033] The radio channel may be a radio channel between the radio device and a network node of the RAN. The determined at least one value of the channel coherence metric may be transmitted to the network node of the RAN.

[0034] The method (e.g., according to the one method aspect) may further comprise receiving, from the RAN or the network node, control signaling for the determining of the at least one value of the channel coherence metric and / or for the transmitting of the determined at least one value of the channel coherence metric to the RAN or the network node, optionally wherein the control signaling is indicative of a configured set of radio resources for determining the at least one value of the channel coherence metric and / or wherein the control signaling is indicative of the channel coherence metric for which the at least one value is to be determined, and / or wherein the at least one value is transmitted in a report message that is further indicative of at least one of: a selected set of radio resources used by the radio device for determining the at least one value of the channel coherence metric, and the channel coherence metric for which the at least one value is determined.

[0035] The selected set may be a (proper) subset of the configured set.

[0036] The control signaling for the determining (e.g., measuring) and / or transmitting (e.g., reporting) may be received from the network node of the RAN. Alternatively or in addition, the receiving of the control signaling may configure the radio device for, and / or trigger, the determining and / or the transmitting.

[0037] The determining of the at least one value of the channel coherence metric (e.g., according to the one method aspect) may comprise measuring the at least one value of the channel coherence metric of a radio channel between the radio device and the network node or the RAN, and / or the at least one value of the channel coherence metric is measured based on one or more downlink reference signals from the network node or the RAN and / or at least one of: one or more non-zero power channel state information reference signals, NZP CSI-RSs; one or more tracking reference signals, TRSs, from the network node (200) or the RAN (500); one or more physical downlink shared channel demodulation reference signals, PDSCH DM-RSs; one or more physical downlink control channel demodulation reference signals, PDCCH DM-RSs; one or more synchronization signals, optionally a primary synchronization signal, PSS, or a secondary synchronization signal (SSS); one or more phase tracking reference signals, PT-RSs; one or more reconfigurable intelligent surface reference signals, RIS-RSs; and one or more terahertz band demodulation reference signals, THz-DMRS.

[0038] A plurality of values of the channel coherence metric may be determined (e.g., measured) by the radio device and transmitted to the network node. Each measured and transmitted metric value may be based on a different set of (e.g., time, frequency, and / or spatial) resources of downlink reference signals (DL RS). The different DL RS resource sets may be disjoint, i.e., non-overlapping. The channel coherence metric (e.g., according to the first method aspect) may comprise, or may be based on, at least one of: a delay spread of the radio channel in time domain; a channel delay profile of the radio channel in time domain; a power density of the radio channel in time domain; one or more peaks of a channel delay profile of the radio channel in time domain; one or more sample points of a channel delay profile of the radio channel at predefined points in time domain, optionally predefined by the received control signaling; a coherence time of the radio channel; a time domain convolution between a reference signal transmitted from the network node and a signal received on the radio channel at the radio device; one or more channel variations of the radio channel in frequency domain; a coherence bandwidth of the radio channel; a Doppler spread of the radio channel in frequency domain; a frequency domain autocorrelation of the radio channel; one or more sample points of a frequency domain autocorrelation of the radio channel at predefined points in frequency domain, optionally predefined by the received control signaling; a frequency domain convolution between a reference signal transmitted from the network node and a signal received on the radio channel at the radio device; a discrete convolution between a channel measured at sub-carrier k on a reference signal received from the network node and a channel measured at sub-carrier k+ f on a reference signal received from the network node in the frequency domain; a coherence distance of the radio channel in spatial domain; one or more strongest paths from a channel delay profile of the radio channel; and an analysis of a delay profile of the radio channel (502) for identifying one or more strongest paths.

[0039] Any one of the convolution and autocorrelation may be discrete in time and / or frequency domain.

[0040] The coherence time, as measured at the radio device, may correspond to a coherence time of a downlink transmission at the RAN (e.g., the network node) minus the delay spread. Alternatively or in addition, coherence bandwidth and coherence time may be inversely proportional.

[0041] The autocorrelation may be replaced by a convolution between a received signal and a transmitted signal (e.g., a reference signal known at the radio device)

[0042] The radio channel (e.g., according to the first method aspect) may be or may comprise an uplink channel or the radio channel may be or may comprise a downlink channel, and / or the radio channel may carry a physical uplink shared channel, PUSCH, or a physical downlink shared channel, PDSCH. While the radio channel may be measured in the downlink at the radio device, the resulting at least one metric value may assist the usage of the radio channel (e.g., for data communication) in the downlink or (e.g., by virtue of channel reciprocity) in the uplink.

[0043] While the metric may relate to a physical property of radio propagation of the radio channel, the radio channel comprising a PUSCH or PDSCH may mean that the radio channel carries (i.e., is used) for transmitting the PUSCH or receivingthe PDSCH.

[0044] The method (e.g., according to the one method aspect) may further comprise: receiving a configuration message indicative of the frequency domain configuration of the subsequent measurement of the radio channel between the radio device and the RAN; and / or wherein the frequency domain configuration is dependent on the transmitted at least one value of the metric for the channel coherence; and / or wherein the frequency domain configuration comprises a density of reference signals in the frequency domain for the subsequent measurement of the radio channel; and / or wherein the frequency domain configuration is indicative of an allocation of frequency domain resources for at least one of uplink reference signals, UL RS, optionally SRS and / or UL DM-RS, and downlink reference signals, DL RS, optionally NZP CSI-RS and / or DL DM-RS; and / or wherein the frequency domain configuration is indicative of a subband size of DL RS, optionally NZP CSI-RS and / or DL DM-RS, for the subsequent measurement of the radio channel; and / or wherein the subsequent measurement of the radio channel is a CSI measurement.

[0045] The determining of the at least one value of the channel coherence metric (e.g., according to the one method aspect) may comprise a preparatory measurement that is different from the subsequent measurement, optionally wherein the subsequent measurement is based on the preparatory measurement, and / or the frequency domain configuration used by the subsequent measurement of the radio channel may depend on the determined at least one value of the channel coherence metric.

[0046] The "preparatory measurement" of the at least one value of the channel coherence metric may be referred to as "preparatory coherence measurement". The "subsequent measurement" of the radio channel may be referred to as "subsequent channel measurement". The at least one of the determining and the transmitting metric (e.g., according to the one method aspect) may be event-driven.

[0047] The received control signaling may comprise a higher layer parameter that is indicative of the radio device to determine and / or transmit the at least one metric value and / or that is indicative of an event triggering determination and / or the transmission.

[0048] Any embodiment of the one method aspect may be implemented as a method of reporting one or more frequency domain channel properties (FDCP).

[0049] The one aspect or a variant of the one aspect comprises method aspects for measuring and / or reporting of frequency domain channel properties (FDCP).

[0050] Embodiments of these aspects specify signaling details associated with the reporting. Such a report may provide the RAN, e.g., a network node (e.g., a gNB), with information about the delay spread or equivalently the time dispersion of the channel. The presented embodiments develop the configuration and signaling for the FDCP report. Moreover, same and further embodiments comprise measuring the frequency domain channel variations based on, e.g., frequency domain autocorrelation calculation, delay spread calculation, the delay profile analysis of the strongest paths, etc. In this way, the at least some embodiments address at least one of the features for 3GPP Release 20 as well as Sixth Generation (6G) radio access technology.

[0051] As to another method aspect, a method of a network node configuring a channel measurement is provided. The method comprises receiving, from a radio device, a value of a metric for channel coherence of a radio channel between the radio device and the network node of a radio access network (RAN). The method further comprises configuring, based on the received value of the channel coherence metric, a frequency domain configuration of a subsequent measurement of the radio channel between the radio device and the network node.

[0052] The other method aspect may be implemented alone or in combination with any one of the embodiments in the list of claims, particularly the claims 16 to 19.

[0053] The method (e.g., according to the another method aspect) may further comprise: transmitting, to the radio device, control signaling for determining the value of the channel coherence metric and / or for transmitting the determined value of the channel coherence metric to the network node, optionally wherein the control signaling is indicative of a configured set of radio resources for determining the value of the channel coherence metric and / or wherein the control signaling is indicative of the channel coherence metric for which the value is to be determined.

[0054] The configuring of the frequency domain may comprise transmitting a configuration message indicative of the frequency domain configuration to the radio device.

[0055] The another method aspect may further comprise any feature and / or any step disclosed in the context of the one method aspect, or a feature and / or step corresponding thereto, e.g., a receiver counterpart to a transmitter feature or step.

[0056] Without limitation, for example in a 3GPP implementation, any "radio device" may be a user equipment (UE). Any one of the method aspects may be embodied by a method of maintaining or establishing a UE connection, optionally wherein a frequency range and / or a carrier frequency of the radio channel is configured based on the metric value and / or a quality of service (QoS) required by the UE.

[0057] In any radio access technology (RAT), the technique may be implemented for a connected state and / or for UE mobility (e.g., when switching the network node that is serving the radio device) and / or for multi-connectivity (e.g., when adding or removing a radio channel to a secondary network node that is not serving the radio device).

[0058] Any radio device may be a user equipment (UE), e.g., accordingto a 3GPP specification. The radio device and the RAN may be wirelessly connected in an uplink (UL) and / or a downlink (DL) through a Uu interface. Alternatively or in addition, a sidelink (SL) may enable a direct radio communication between proximal radio devices, e.g., a remote radio device and the relay radio device, optionally using a PC5 interface.

[0059] The RAN may comprise one or more network node (e.g. base stations), at least some or each of which may perform the second method aspect. Alternatively or in addition, the radio network may be a vehicular, ad hoc and / or mesh network comprising two or more radio devices, e.g., acting as the remote radio device and / or the relay radio device and / orthe further remote radio device, and / or performingthe first and / or second method aspects. Any of the radio devices may be a 3GPP user equipment (UE) or a Wi-Fi station (STA). The radio device may be a mobile or portable station, a device for machine-type communication (MTC), a device for narrowband Internet of Things (NB-IoT) or a combination thereof. Examples for the UE and the mobile station include a mobile phone, a tablet computer and a self-driving vehicle. Examples forthe portable station include a laptop computer and a television set. Examples forthe MTC device or the NB-IoT device include robots, sensors and / or actuators, e.g., in manufacturing, automotive communication and home automation. The MTC device orthe NB-IoT device may be implemented in a manufacturing plant, household appliances and consumer electronics.

[0060] Whenever referring to the RAN, the RAN may be implemented by one or more base stations (e.g., embodiments of the network node). The radio device may be wirelessly connected or connectable (e.g., according to a radio resource control, RRC, state or active mode) with the at least one base station (e.g., the network node) of the RAN.

[0061] The network node (e.g., a base station) may encompass any station that is configured to provide radio access to any of the one or more radio devices. The network node may comprise or refer to a cell, a transmission and reception point (TRP), a central unit (CU), a distributed unit (DU), a radio access node or an access point (AP). The network node (and / or the relay radio device) may provide a data link to a host computer providing user data to the radio device or gathering user data from the radio device. Examples forthe base stations may include a 3G base station or Node B (NB), 4G base station or eNodeB (eNB), a 5G base station or gNodeB (gNB), a Wi-Fi AP and a network controller (e.g., according to Bluetooth, ZigBee or Z-Wave).

[0062] The RAN may be implemented accordingto the Global System for Mobile Communications (GSM), the Universal Mobile Telecommunications System (UMTS), 3GPP LongTerm Evolution (LTE), 3GPP New Radio (NR), 3GPP 5G advanced, and / or 3GPP 6G radio access technology (RAT).

[0063] Any aspect of the technique may be implemented on a Physical Layer (PHY), a Medium Access Control (MAC) layer, a Radio Link Control (RLC) layer, a packet data convergence protocol (PDCP) layer, and / or a Radio Resource Control (RRC) layer of a protocol stack for the radio communication. Herein, referring to a protocol of a layer may also refer to the corresponding layer in the protocol stack. Vice versa, referring to a layer of the protocol stack may also refer to the corresponding protocol of the layer. Any protocol may be implemented by a corresponding method.

[0064] As to another aspect, a computer program product is provided. The computer program product comprises program code portions for performing any one of the steps of the one and / or another method aspects disclosed herein when the computer program product is executed by one or more computing devices. The computer program product may be stored on a computer-readable recording medium. The computer program product may also be provided for download, e.g., via the radio network, the RAN, the Internet and / or the host computer. Alternatively, or in addition, the method may be encoded in a Field-Programmable Gate Array (FPGA) and / or an Application-Specific Integrated Circuit (ASIC), or the functionality may be provided for download by means of a hardware description language.

[0065] As to one device aspect, a device for assisting configuration of a channel measurement is provided. The device may be configured to perform any one of the steps of the one method aspect. Optionally, the device may comprise processing circuitry (e.g., at least one processor and a memory). Said memory comprises instructions executable by said at least one processor whereby the device is operative to perform any one of the steps of the one method aspect.

[0066] As to another device aspect, a device for configuring a channel measurement is provided. The device may be configured to perform any one of the steps of the other method aspect. Optionally, the device comprises processing circuitry (e.g., at least one processor and a memory). Said memory comprises instructions executable by said at least one processor whereby the device is operative to perform any one of the steps of the other method aspect.

[0067] As to a still further aspect a communication system including a host computer is provided. The host computer comprises a processing circuitry configured to provide user data, e.g., included in a DL transmission based on the subsequent channel measurement. The host computer further comprises a communication interface configured to forward the user data to a cellular network (e.g., the RAN and / or the base station) for transmission to a UE. A processing circuitry of the cellular network is configured to execute any one of the steps of the other method aspect. The UE comprises a radio interface and processing circuitry, which is configured to execute any one of the steps of the one method aspect.

[0068] The communication system may further include the UE. Alternatively, or in addition, the cellular network may further include one or more base stations configured for radio communication with the UE and / orto provide a data link between the UE and the host computer usingthe first and / or second method aspects.

[0069] The processing circuitry of the host computer may be configured to execute a host application, thereby providing the user data and / or any host computer functionality described herein. Alternatively, or in addition, the processing circuitry of the UE may be configured to execute a client application associated with the host application.

[0070] Any one of the devices, the UE, the network node, the base station, the communication system or any node or station for embodying the technique may further include any feature disclosed in the context of the method aspect, and vice versa. Particularly, any one of the units and modules disclosed herein may be configured to perform or initiate one or more of the steps of the method aspect.

[0071] Brief Description of the Drawings

[0072] Further details of embodiments of the technique are described with reference to the enclosed drawings, wherein:

[0073] Fig. 1 shows a schematic block diagram of an embodiment of a device for assisting configuration of a channel measurement;

[0074] Fig. 2 shows a schematic block diagram of an embodiment of a device for configuration of a channel measurement;

[0075] Fig. 3 shows a flowchart for a method of assisting configuration of a channel measurement, which method may be implementable by the device of Fig. 1;

[0076] Fig.4 shows a flowchart for a method of configuring a channel measurement, which method may be implementable by the device of Fig. 2; Fig. 5 schematically illustrates an example of a radio network comprising embodiments of the devices of Figs. 1 and 2 for performingthe methods of Figs. 3 and 4, respectively;

[0077] Fig. 6 schematically illustrates an example of a time-frequency grid of radio resources for reference signals that can be configured responsive to a value of a channel coherence metric;

[0078] Figs. 7 and 8 schematically illustrate examples of OFDM symbols comprising reference signals which extent in the frequency domain can be configured responsive to a value of a channel coherence metric;

[0079] Fig. 9 schematically illustrates example values of a channel delay profile in the time domain as an one example of the channel coherence metric or as a basis for computingthe value of a delay spread as another example of the channel coherence metric;

[0080] Fig. 10 schematically illustrates example values of an autocorrelation of a profile in the time domain as an one example of the channel coherence metric or as a basis for computingthe value of a delay spread as another example of the channel coherence metric;

[0081] Fig. 11 show a schematic block diagram of a radio device embodyingthe device of Fig. 1;

[0082] Fig. 12 shows a schematic block diagram of a network node embodying the device of Fig. 2; and

[0083] Fig. 13 schematically illustrates an example telecommunication network connected via an intermediate network to a host computer.

[0084] Detailed Description

[0085] In the following description, for purposes of explanation and not limitation, specific details are set forth, such as a specific network environment in order to provide a thorough understanding of the technique disclosed herein. It will be apparent to one skilled in the art that the technique may be practiced in other embodiments that depart from these specific details. Moreover, while the following embodiments are primarily described for a New Radio (NR) or 5G or 5G Advanced implementation, it is readily apparent that the technique described herein may also be implemented for any other radio communication technique, including a Wireless Local Area Network (WLAN) implementation according to the standard family IEEE 802.11, 3GPP LTE (e.g., LTE-Advanced or a related radio access technique such as MulteFire), for Bluetooth according to the Bluetooth Special Interest Group (SIG), particularly Bluetooth Low Energy, Bluetooth Mesh Networking and Bluetooth broadcasting, for Z-Wave according to the Z-Wave Alliance orforZigBee based on IEEE 802.15.4.

[0086] Moreover, those skilled in the art will appreciate that the functions, steps, units and modules explained herein may be implemented using software functioning in conjunction with a programmed microprocessor, an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), a Digital Signal Processor (DSP) or a general purpose computer, e.g., including an Advanced RISC Machine (ARM). It will also be appreciated that, while the following embodiments are primarily described in context with methods and devices, the invention may also be embodied in a computer program product as well as in a system comprising at least one computer processor and memory coupled to the at least one processor, wherein the memory is encoded with one or more programs that may perform the functions and steps or implement the units and modules disclosed herein.

[0087] Fig. 1 schematically illustrates a block diagram of an embodiment of a device for assisting configuration of a channel measurement. The device is generically referred to by reference sign 100.

[0088] The device 100 comprises a Channel Coherence Determination Module 104 that determines a value of a metric for channel coherence of a radio channel between the radio device and a network node (e.g., a base station) of a radio access network (RAN).

[0089] The device 100 further comprises a Coherence Metric Reporting Module 106 that transmits - to the RAN, e.g. to the network node - the determined value of the channel coherence metric for assisting a frequency domain configuration of a subsequent measurement of the radio channel between the radio device and the network node.

[0090] The device 100 may further comprise a module 102 that receives control signaling for configuringthe radio device forthe determination and the reporting of the metric value. Alternatively or in addition, the device 100 may further comprise a module 110 that receives control signaling for configuring the radio device for the subsequent channel measurement based on the determined and transmitted (i.e., reported) metric value. The preparatory measurement of the metric value for determining the frequency domain structure of the radio channel may not be confused with the subsequent channel measurement, which frequency domain configuration is dependent on the metric value.

[0091] The preparatory measurement and the subsequent channel measurement may be a two-stage measurement process that avoids allocating radio resources in the frequency domain where the radio channel is flat in the frequency domain, and / or that increases a density of reference signals for the subsequent measurement where the channel (e.g., a Channel Impulse Response, or CIR) varies steeper as a function of frequency (i.e., the frequency domain channel properties, or FDCP).

[0092] Any of the modules of the device 100 may be implemented by units configured to provide the correspondingfunctionality.

[0093] The device 100 may also be referred to as, or may be embodied by, the radio device (or user equipment, briefly: UE). The radio device 100 and the network node may be in direct radio communication, e.g., at least for the determining of the metric value. The network node may be embodied by the below-mentioned device 200.

[0094] Fig. 2 schematically illustrates a block diagram of an embodiment of a device for configuring a channel measurement. The device is generically referred to by reference sign 200.

[0095] The device 200 comprises a Coherence Metric Reception Module 206 that receives a value of a metric for a channel coherence of a radio channel between a network node and a radio device. The device 200 further comprises a Frequency Domain Configuration Module 208 that configures the radio device for a subsequent channel measurement based on the received metric value.

[0096] Any of the modules of the device 200 may be implemented by units configured to provide the correspondingfunctionality. The device 200 may further comprise a module 202 that transmits control signa ling for configuring the radio device for the determination and the reporting of the metric value. Alternatively or in addition, the device 100 may further comprise a module 210 that transmits control signaling (e.g., a configuration message) for configuring the radio device for the subsequent channel measurement based on the determined and transmitted (reported) metric value. The controlsignalingforthe preparatory measurement of the metric value for determining the frequency domain structure of the radio channel may not be confused with the configuration message triggering the subsequent channel measurement, which frequency domain configuration is dependent on the metric value.

[0097] The device 200 may also be referred to as, or may be embodied by, the network node (e.g., a base station, or briefly: gNB for 5G, or extended NodeB or xNB for 6G). The radio device and the network node 200 may be in direct radio communication, e.g., at least for the determining of the metric value. The radio device may be embodied by the above-mentioned device 100.

[0098] Fig.3 schematically illustrates a flowchart of the proposed scheme from the UE 100 perspective.

[0099] Conventional radio access technology does not provide a report from the UE for indicatingthe channel variations in the frequency domain, i.e., providingthe network with information about the delay spread experienced by a UE corresponding to a measured channel. Furthermore, relying on measurements of UL SRS will not result in accurate measurement of channel variation in the frequency domain, and SRS carrier switching may not be necessarily supported by a UE. Hence, there is a need for a report from the UE to the network providing information on channel variations in the frequency domain.

[0100] Herein, whenever referringto one or more frequency domain channel properties (FDCP), the channel coherence metric may be an embodiment of the FDCP.

[0101] Alternatively or in addition, whenever referringto the channel coherence metric, the FDCP may be an embodiment of the channel coherence metric. Furthermore, although the terminology frequency domain channel property is used in the description of the subject technology, other alternative terms such as frequency domain property (FDP), frequency domain property information (FDPI), delay domain channel property (DDCP), or delay spread information (DSI) may equivalently be used to describe a report that provide information on channel variation in frequency domain. Fig. 3 shows a flowchart of a method 300 of assisting configuration of a radio device 100 for a subsequent channel measurement.

[0102] In an optional step 302 of the method 300 of Fig. 3, the UE 100 receives control signaling from the network node 200. The control signaling provides information to the UE 100 in order for the UE 100 to perform a step 304 of determining a metric value for a channel coherence metric (or FDCP) for a radio channel between the UE 100 and the network node 200. The step 304 may be implemented by measurement 304-1 and / or calculation 304-2, yieldingthe metric value of the channel coherence metric. Alternatively or in addition, the control signaling provides information to the UE 100 in order for the UE 100 to perform a step 306 of reporting the value of the channel coherence metric (or FDCP) from the UE 100 to the network node 200.

[0103] In the method 300, the step 302 is optional, e.g. because the UE 100 may be preconfigured with parameters for performing the steps 304 and / or 306.

[0104] For brevity, in the description hereinbelow, FDCP can encompass

[0105] a channel metric that is expressly indicative of a frequency domain property of the channel, and / or

[0106] a channel metric that implies or is physically equivalent to a frequency domain property of the channel, and / or

[0107] a channel coherence metric that enables the network node 200 or the RAN 500 to configure a subsequent measurement of the radio channel, e.g. by configuring downlink reference signals (DL RS) in the frequency domain, i.e. allocating frequency resources for the DL RS, for the subsequent channel measurement.

[0108] In the optional step 302, the network node 200 configures the UE 100 with at least one downlink reference signal (DL RS) on which the UE 100 shall determine the value of the channel coherence metric, i.e. measure the FDCP. That is, the step 304 (e.g., the measurement resulting in the value of the channel coherence metric) may be based on the DL RS, e.g. tracking reference signals (TRS).

[0109] In a further optional step 310, the radio device 100 receives a frequency domain configuration for the subsequent channel measurement from the network node 200. The transmitted 306 value of the channel coherence metric (FDCP) can enable the network node 200 to configure the frequence domain resources for measuring the channel with the granularity that is appropriate for the channel. If a density of (UL or DL) reference signals is greater than needed according to the reported 306 value of the FDCP, frequency resources are wasted. If the density of (UL or DL) reference signals is less than needed accordingto the reported 306 value of the FDCP, the subsequent channel measurement becomes less accurate. The step 310 is optional, e.g. because the network node 200 may determine that the current frequency domain configuration should not be changed according to the transmitted 306 value of the channel coherence metric (FDCP).

[0110] The method 300 may be performed by the device 100. For example, the modules 102, 104, 106, and 110 may perform the steps 302, 304, 306, and 310, respectively.

[0111] In any embodiment, the preparatory coherence measurement 304-1 in the step 304 may be different from (e.g., prior to) the subsequent channel measurement. The subsequent channel measurement may be based on the preparatory coherence measurement in that the frequency domain configuration used by the subsequent measurement of the radio channel depends on the metric value resulting from the preparatory coherence measurement 304 and reported in the step 306.

[0112] While the preparatory coherence measurement 304-1 in the step 304 is different from the subsequent channel measurement, the DL RS used for the preparatory coherence measurement may also be used forthe subsequent channel measurement, or may be different from DL RS used for the subsequent channel measurement.

[0113] In one embodiment, the at least one DL RS (for the preparatory coherence measurement in the step 304) may be configured in the step 302 to the UE 100 as part of a reporting configuration for reporting FDCP in the step 306. In each of the at least one DL RS, the UE 100 performs FDCP measurements 304 and computes (i.e., calculates) an FDCP quantity (e.g., any one of the examples of the channel coherence metric) to be reported 306. In one embodiment, when more than one DL RS is configured 302 for measurement 304 of FDCP, the UE 100 measures 304-1 and computes 304-2 one FDCP per each of the at least one DL RS.

[0114] In another embodiment, the UE 100 is configured 302 by the network node 200 with NTDL RSs as part of the reporting configuration for reporting FDCP in the step 306. In one variant of this embodiment, the UE 100 selects one of the NTDL RSs to measure FDCP on and indicate this selection as part of the FDCP report. In one example, if the UE 100 is configured 302 with NT= 4 DL RSs as part of the reporting configuration for reporting FDCP, the UE may select N'T= 2 DL RSs among the NT= 4 DL-RSs for measuring FDCP. The UE then measures FDCP on the N’T= 2 DL-RSs and computes (or calculates) the FDCPs corresponding to the N’T= 2 DL-RSs. Information on the selection of the N’T= 2 DL-RSs along with the computed FDCPs corresponding to the N’T= 2 DL RSs are included as part of the FDCP report. Although the above example covers N’T= 2 DL-RSs being selected for FDCP measurement, this example is non-limiting and the UE 100 may select any number N’T= 1, 2,..., NTof DL-RS. When the UE selects all NTconfigured DL-RS(s) for FDCP measurement, the UE, in one embodiment, may include an explicit indication as part of the FDCP report that all NTconfigured DL-RS(s) have been selected for FDCP measurement. In an alternative embodiment, when the UE selects all NTconfigured DL-RS(s) for FDCP measurement, the UE includes only the computed FDCPs corresponding to all the NTconfigured DL-RS(s) and no explicit indication of the selection of a subset of DL-RS(s) is indicated in the FDCP report. The FDCP report may be periodic, semi-persistent or dynamic (aperiodic one-shot report or aperiodic burst of multiple reports).

[0115] The measurement and report configuration received 302 for FDCP reporting 306, i.e., the control signaling, may be based on radio resource control (RRC), medium access control (MAC) control element (CE), or a combination of the two. The one or more DL RSs used for FDCP measurement 304-1 may correspond to one or more transmission reception points (TRPs), one or more DL carriers, or one or more cells (which may include one or more serving cells or non-serving cell(s).

[0116] In one embodiment, the one or more DL RSs used for determining 304 the channel coherence metric or FDCP can be any one of the following types:

[0117] - one or more NZP CSI-RSs,

[0118] - one or more tracking reference signals (TRSs),

[0119] - one or more PDSCH DM-RSs,

[0120] - one or more PDCCH DM-RSs, and

[0121] - one or more further DL RSs specifically defined in 3GPP Release 20 or beyond and / or for Sixth Generation (6G) radio access technology (RAT).

[0122] A first example of a further DL RS may comprise a Reconfigurable Intelligent Surface Reference Signal (RIS-RS). With the integration of reconfigurable intelligent surfaces (RIS) expected in 6G RATs, a further reference signal may be introduced to facilitate channel estimation and / or beamforming in environments utilizing a RIS. The RIS-RS may enable optimizing signal propagation and improving coverage by dynamically adjusting the electromagnetic properties of RIS in an environment. A second example of a further DL RS may comprise Terahertz Band Demodulation Reference Signal (THz-DMRS). As 6G RAT aims to exploit higher frequency bands, including the terahertz spectrum (above 100 GHz), specialized demodulation reference signals may be necessary. The THz-DMRS may address the unique propagation characteristics and challenges associated with terahertz frequencies, such as increased path loss and molecular absorption, by enabling accurate channel estimation and synchronization at these high frequencies.

[0123] In an alternative embodiment, in place of one or more DL RSs, one or more DL RS resource sets may be used. Here, one or each DL RS resource set may comprise at least one DL RS. In this alternative embodiment, the one or more DL-RS resource sets are used to perform one or more FDCP measurements, respectively. That is, one FDCP measurement 304-1 is done on the at least one DL RS within one DL RS resource set. The at least one DL RS within each DL RS resource set may be any one of the DL RS types mentioned above.

[0124] In one embodiment, each of the one or more DL RS resource sets is configured with a higher layer parameter indicating that the one or more DL RS resources within each of the DL RS resource sets is / are to be used for FDCP measurement 304-1.

[0125] In one embodiment, the UE 100 receives 302 explicit configuration as part of the reporting configuration (i.e., the control signaling) to indicate that the UE 100 shall report one or more FDCP values (i.e., metric values) determined 304 (e.g., measured and / or calculated) as part of the report (i.e., the step 306) corresponding to the reporting configuration. In one example, a configuration of the FDCP report (i.e., the transmission of the metric value) may include a higher layer parameter as part of the reporting configuration to indicate the UE 100 to report the one or more FDCP values determined in the step 304 (e.g., measured 304-1 and / or calculated 304-2).

[0126] Alternatively or in addition, the reporting configuration may include information about the dynamic range (e.g., maximum and / or minimum value(s) of FDCP or metric that can be reported) and / or the quantization levels (e.g., the number of bits per each metric or FDCP value determined 304) for the one or more FDCP values (i.e., metric values) to be report 306. Alternatively or in addition, a dynamic range and / or a quantization level for the one or more FDCP values (i.e., the metric values) to be reported 306 are pre-specified in 3GPP specifications. In one embodiment, the FDCP report in the step 306 may have a fixed payload size. For instance, a UE may receive reporting configuration from the network node 200 (e.g., a gNB) to report a fixed number of FDCP value(s) to be measured / computed and reported corresponding to a fixed number of NTDL-RSs. In this embodiment, the UE reports 306 the determined 304 (e.g., measured and / or calculated) one or more metric (e.g., FDCP) values corresponding to the fixed number of NTDL-RS(s).

[0127] In another embodiment, the FDCP report 306 may have variable payload. In one such embodiment, the UE 100 receives configuration (e.g., via RRC) from the gNB on NTcandidate DL-RS(s) that are intended for FDCP measurement. Then, the UE receives a second signal (e.g., a MAC CE message) indicating which subset or whole set N'T(N’T< NT) of the NTcandidate DL-RS(s) the UE shall perform FDCP measurements on. The UE then performs FDCP measurements on the subset or whole set N’T(N’T< NT) of the NTcandidate DL-RS(s), and reports the N’Tmeasured / computed FDCP value(s) correspondingto the N’TDL-RS(s). Since the value of N’Tdepends on which subset or whole set of DL-RS(s) the UE is indicated, by the second signal from the gNB, to perform FDCP measurements on, the payload of the FDCP report in this embodiment is varying.

[0128] In yet another embodiment, the FDCP report may have variable payload with the UE indicating which subset or whole set N’T(N’T< NT) of the NTcandidate DL-RS(s) the UE performed FDCP measurements. The UE indication, including information on which subset or whole set N’T(N’T< NT) of the NTcandidate DL-RS(s), is included as part of the FDCP report along with the computed FDCP value(s) corresponding to the subset or whole set N’T(N’T< NT) of the NTcandidate DL-RS(s). Since the value of N’Tdepends on which subset or whole set of DL-RS(s) the UE performs FDCP measurements on, the payload of the FDCP report in this embodiment is varying.

[0129] In an alternative embodiment, the FDCP report may have two parts. A first part is composed of a fixed payload and may contain information on which subset or whole set N'T(N'T< NT) of the NTcandidate DL-RS(s) the UE 100 will perform FDCP measurements 304. The payload size of a second part is indicated in the first part. For instance, in the first part, the UE 100 indicates information on N’T. This will further indicate that the number of FDCP reports in the second part is N’T.

[0130] In the step 304 of the method 300, e.g. as illustrated in Fig. 3, the UE 100 performs measurements 304-1 and computes 304-2 the value of the metric (e.g., FDCP) according to the control signaling received from the network node 200 in the step 302. Different implementations of the method 300 may be used by the UE 100 for measuring 304-1 the channel coherence metric or FDCP, and / or for the computation 304-2. Embodiments covering different measurement and computation methods for FDCP are disclosed below.

[0131] Fig. 4 shows an example flowchart for a method 400 of configuring a channel measurement. The method 400 may be performed by a network node 100 of a radio access network (RAN). The method 400 comprises receiving 406, from a radio device 100, a value of a metric for channel coherence of a radio channel between the radio device 100 and the network node 200 of the RAN. The method 400 further comprises configuring 408, based on the received 406 value of the channel coherence metric, a frequency domain configuration of a subsequent measurement of the radio channel between the radio device 100 and the network node 200.

[0132] Optionally, in a step 404, the network node 200 transmits to a radio device 100 control signa ling for determining the value of the metric for the channel coherence of the radio channel between the radio device and the network node. Alternatively or in addition, in a step 410, the network node 200 transmit a configuration message indicative of the frequency domain configuration of the subsequent measurement of the radio channel to the radio device 100.

[0133] The method 400 may be performed by the device 200. For example, the modules 202, 206, 208, and 210 may perform the steps 402, 406, 408 and 410, respectively.

[0134] In any aspect, e.g., as schematically illustrated in Fig. 5, the technique may be applied to a radio channel 502 comprising or constituting an uplink (UL) and / or a downlink (DL) or direct communications between radio devices, e.g., device-to-device (D2D) communications or sidelink (SL) communications.

[0135] Each of the radio device 100 and network node 200 may be a mobile device or a base station. Herein, any radio device 100 may be a mobile or portable station and / or any radio device 100 wirelessly connectable to an embodiment of the network node or the RAN, or to another radio device acting as the device 200. For example, the radio device 100 may be a user equipment (UE), a device for machine-type communication (MTC) or a device for (e.g., narrowband) Internet of Things (loT). Two or more radio devices may be configured to wirelessly connect to each other, e.g., in an ad hoc radio network or via a 3GPP SL connection. Furthermore, any base station may be a station providing radio access, may be part of a radio access network (RAN) and / or may be a node connected to the RAN for controlling the radio access. For example, the base station may be an access point, for example a Wi-Fi access point.

[0136] Herein, whenever referringto the metric of the channel coherence or the FDCP, these terms may be interchanged in any context and any embodiment.

[0137] Any implementation of the configuring step 402 or the measurement 304-1 or the computation 304-2 of the channel coherence metric (e.g., FDCP) may use at least some of the following features and steps for determining 304 the following examples of the channel coherence metric.

[0138] A first example of the channel coherence metric may comprise a delay spread in time domain (Trms).

[0139] The root mean square (RMS) delay spread quantifies the extent of multipath delay spread in the time domain. The step 304 may determine

[0140]

[0141] wherein:

[0142] o Pnis the power of the n-th multipath component.

[0143] o rnis the delay of the n-th multipath component.

[0144] —

[0145] o T is the mean delay given

[0146]

[0147] A second example of the channel coherence metric may comprise a channel delay profile in time domain

[0148]

[0149] The channel delay profile may represent an impulse response of the radio channel 502 as a function of delay T. The step 304 may determine

[0150]

[0151] wherein:

[0152] o anis the amplitude of the n-th path.

[0153] o (pnis the phase shift of the n-th path.

[0154] o <?(•) is the Dirac delta function.

[0155] A third example of the channel coherence metric may comprise peaks of a channel delay profile in the time domain. The significant peaks may correspond to dominant multipath components. The step 304 may identify the peaks where ^(T) has maximum amplitudes.

[0156] A fourth example of the channel coherence metric may comprise a coherence time (Tc).

[0157] The coherence time quantifies the time duration over which the impulse response of the radio channel is considered invariant.

[0158] The step 304 may approximate this metric by:

[0159]

[0160] wherein fDis the maximum Doppler frequency shift.

[0161] A fifth example of the channel coherence metric may comprise channel variations in frequency domain.

[0162] The frequency response / i( ) of the channel varies with frequency due to multipath effects. The step 304 may determine, at least some sample points of:

[0163]

[0164] A sixth example of the channel coherence metric may comprise a coherence bandwidth (Bc).

[0165] The coherence bandwidth may be measured 304-1 as the range of frequencies over which the frequency response of the radio channel 502 is correlated. Alternatively or in addition, the step 304 may determine

[0166]

[0167] A seventh example of the channel coherence metric may comprise a Doppler spread in frequency domain (BD).

[0168] The Doppler spread quantifies the spread of the Doppler frequencies due to relative motion of the UEs 100. The step 304 may determine the metric value

[0169] BQ = 2 D,

[0170] wherein:

[0171] O

[0172]

[0173] o v is the relative velocity.

[0174] o fcis the carrier frequency.

[0175] o c is the speed of light.

[0176] An eighth example of the channel coherence metric may comprise coherence distance (dc).

[0177] The coherence distance is the spatial separation over which the characteristics of the radio channel 502 remain correlated. The step 304 may determine the metric value

[0178] dc= vTc.

[0179] ! nineth example of the channel coherence metric may comprise strongest paths from a channel delay profile.

[0180] The strongest paths are the multipath components with the highest power Pn. The step 304 may determine (identify) them ranking / ^ in $(?).

[0181] A tenth example of the channel coherence metric may comprise a frequency domain autocorrelation ( / ?( )).

[0182] The step 304 may determine, at least some sample points of, the autocorrelation function of the frequency response of the radio channel:

[0183]

[0184] wherein

[0185] o £■[•] denotes expectation.

[0186] o h*(f) is the complex conjugate of h f).

[0187] An eleventh example of the channel coherence metric may comprise a delay profile analysis of the strongest paths.

[0188] The step 304 may analyze the delays tnand powers Pnof the strongest paths as an example of the channel characteristics implying a frequency domain structure for the subsequent channel measurement.

[0189] Optionally, the following relations between different examples of the channel coherence metrics may be implemented in the step 304-2.

[0190] Delay Spread (Trms) and Coherence Bandwidth (Bc) may be inversely proportional. Doppler Spread (BD) and Coherence Time (Tc) may be inversely proportional.

[0191] Velocity (v) may imply Doppler Spread (BD), which implies Coherence Time (Tc) and Coherence Distance (dc), e.g. according to direct relationships of above formulas. Channel Impulse Response ($(?)) and Frequency Response ( i( )) are Fourier Transform pairs.

[0192] Autocorrelation Functions R Af) and

[0193]

[0194] relate to Trmsand BD, e.g. by indicating how time and frequency domain properties are interconnected.

[0195] At least some embodiments may imply or implement at least some of the following relationships:

[0196] 1. Relationship between Coherence Bandwidth and Delay Spread

[0197] The coherence bandwidth is inversely proportional to the RMS delay spread.

[0198]

[0199] This implies that a larger delay spread results in a smaller coherence bandwidth, leading to frequency-selective fading.

[0200] 2. Relationship between Coherence Time and Doppler Spread Coherence time is inversely proportional to the maximum Doppler frequency shift.

[0201]

[0202] A higher Doppler spread (due to higher relative velocities) reduces the coherence time, causing the channel to vary more rapidly over time.

[0203] 3. Relationship between Doppler Spread and Velocity

[0204] Doppler spread is directly proportional to relative velocity.

[0205]

[0206] 4. Relationship between Coherence Distance and Coherence Time Coherence distance relates spatial and temporal channel variations. dc= vTc

[0207] This means that over a distance dc, the channel’s characteristics remain correlated.

[0208] 5. Frequency Domain Autocorrelation and Delay Spread

[0209] The autocorrelation function R Af) is related to the delay power spectrum S(T) through the Fourier transform.

[0210]

[0211] The width of R Af) (i.e., Bc) is inversely related to the width of S(T) (i.e., Trms).

[0212] 6. Time Domain Autocorrelation and Doppler Spread

[0213] Similarly, the time autocorrelation function R At) relates to the Doppler power spectrum S fD).

[0214]

[0215] The width of R At) (i.e., Tc) is inversely related to BD.

[0216] 7. Channel Variations in Frequency and Delay Spread

[0217] The variation of the channel in the frequency domain is influenced by the multipath delay spread.

[0218] o Extensive delay spread causes significant frequency selectivity.

[0219] o This is characterized by rapid changes in / i( ) over frequency.

[0220] 8. Channel Variations in Time and Doppler Spread

[0221] The variation of the channel in the time domain is influenced by the Doppler spread.

[0222] o Higher Doppler spread leads to rapid temporal variations in the channel.

[0223] o This affects the stability of the channel over time.

[0224] 9. Strongest Paths and Delay Spread

[0225] The strongest paths contribute significantly to the overall delay spread.

[0226] o By analyzing these paths, one can estimate Trms.

[0227] o Filters or equalizers can be designed focusing on these dominant paths.

[0228] Furthermore, any configuration parameter that is "predefined" may encompass stored in memory (e.g., in a Subscriber Identity Module, SIM) of the UE 100, or hard- coded or hard-wired in the UE 100, or preconfigured or configured by a network node or radio access network (RAN) for the transmitting wireless device (e.g., preconfigured while in coverage prior to performing the method out of coverage, or configured while in coverage when performing the method).

[0229] The radio spectrum shared by multiple RATs may be an unlicensed spectrum.

[0230] Herein, a list of the form A, B, and / or C (also written as A, B and / or C) may correspond to at least one or each of A, B, and C, i.e., A and / or B and / or C.

[0231] Channel State Information is a first example of the subsequent measurement and / or a varying granularity of the frequency domain (FD) configuration, e.g., configured 408 responsive to the reported 406 FDCP (i.e., channel coherence metric).

[0232] In the radio access technology "New Radio" (NR) specified by the Third Generation Partnership Project (3GPP), Channel State Information (CSI) is essential for the radio access network (RAN) to understand channel conditions and adjust transmission parameters accordingly.

[0233] In NR, a UE can be configured with one or multiple CSI report configurations for DL CSI feedback by the UE (i.e., feedback on the downlink reported in the uplink). A CSI report may contain one or more of channel rank indicator (Rl), antenna precoding matrix indicator (PMI), channel quality indicator (CQI), downlink reference signal received power (RSRP) or signal to interference and noise ratio (SINR), and CSI reference signal (CSI-RS) resource indicator (CRI).

[0234] Each CSI report configuration is associated with a bandwidth part (BWP) and contains all necessary information required for a CSI report, including

[0235] - a CSI resource configuration for channel measurement;

[0236] - reporting type, i.e., aperiodic CSI (on PUSCH), periodic CSI (on PUCCH) or semi-persistent CSI (on PUCCH, and DCI activated on PUSCH); and

[0237] - report quantity specifying what to be reported, such as Rl, PMI, CQI, RSRP, etc.

[0238] A UE can be configured with one or multiple CSI resource configurations for channel measurement. Each CSI resource configuration for channel measurement can contain one or more non-zero-power (NZP) CSI-RS resource sets. For each NZP CSI- RS resource set, it can further contain one or more NZP CSI-RS resources. A NZP CSI-RS resource can be periodic, semi-persistent, or aperiodic.

[0239] Periodic CSI starts after it has been configured by radio resource control (RRC) and is reported on physical uplink control channel (PUCCH), the associated one or more NZP CSI-RS resources are also periodic.

[0240] For aperiodic CSI, it is reported on PUSCH and is activated by a CSI request bit field in downlink control information (DCI). The associated one or more NZP CSI-RS resources can be either periodic, semi-persistent, or aperiodic. The linkage between a code point of the CSI request field and a CSI report configuration is via an aperiodic CSI trigger state. A UE is configured by higher layer a list of aperiodic CSI trigger states, where each of the trigger states contains an associated CSI report configuration. The CSI request field is used to indicate one of the aperiodic CSI trigger states and thus, one CSI report configuration.

[0241] If there are more than one NZP CSI-RS resource set and / or more than one CSI interference measurement (CSI-IM) resource set are associated with a CSI report configuration, only one NZP CSI-RS resource set is selected in the aperiodic CSI trigger state. Thus, each aperiodic CSI report is based on a single NZP CSI-RS resource set.

[0242] CQI and PMI can be reported per subband or wideband. In case of wideband CQI or PMI, the CQI or PMI is for the whole bandwidth configured for CSI report. In case of subband CQI or PMI, the CQI or PMI is reported for each subband. The subband size in NR can be from 4 physical resource blocks (PRBs) to 32 PRBs, depending on the size of the BWP as shown in the table below and / or according to Table 5.2.1.4-2 in the 3GPP document TS 38.214, version 18.4.0.

[0243] Configurable subband sizes

[0244]

[0245] Channel estimation based on demodulation reference signals is a second example the subsequent measurement and / or a varying granularity of frequency domain (FD) configuration, e.g., configured 408 responsive to the reported 406 FDCP (i.e., channel coherence metric).

[0246] Demodulation reference signals (DM-RS) are used for coherent demodulation of physical layer data channels, i.e., Physical Downlink Shared Channel (PDSCH) and Physical Uplink Shared Channel (PUSCH), as well as of Physical Downlink Control Channel (PDCCH). The DM-RS is confined to physical resource blocks (PRBs) carrying the associated physical layer channel and is mapped on allocated resource elements of the time-frequency resource grid.

[0247] The mapping of DM-RS to resource elements is configurable in both frequency and time domain. In NR Release 15, there are two mapping types in the frequency domain, i.e., Type 1 and Type 2. In addition, there are two mapping types in the time domain, i.e., mapping type A and type B, which defines the symbol position of the first OFDM symbol containing DM-RS within a transmission interval.

[0248] Fig. 6 shows examples of Type 1 DM-RS in portions (a) and (b) as well as Type 2 DM-RS in portions (c) and (d), with single-symbol DM-RS in portions (a) and (c) and double-symbol DM-RS in portions (b) and (d). In each case, a time domain mapping is Type A with the first DM-RS in the third OFDM symbol of a transmission interval of 14 symbols. With Type A mapping, the initial DM-RS symbol may be always placed at the first symbol of a transmission slot comprising a scheduled physical downlink shared channel (PDSCH) and / or a physical uplink shared channel (PUSCH). This can ensure that the receiver has immediate access to DM-RS for channel estimation at the very start of the transmission, which is particularly advantageous for low-latency applications.

[0249] It can be observed from Fig. 6 that Type 1 and Type 2 differ with respect to both the mapping structure and the number of supported DM-RS code division multiplexing (CDM) groups, wherein Type 1 supports 2 CDM groups and Type 2 supports 3 CDM groups. This effectively means that the frequency density of DM-RS in frequency domain, e.g. a number of CDM groups within a physical resource block (PRB), is different for the two types of DM-RS.

[0250] Fig. 6 shows DM-RS for configuration Type 1 and Type 2 (also written as Type I and Type II, respectively) for different CDM groups indicated by different hatch patterns. Furthermore, the DM-RS are front-loaded, i.e. the reference signals are positioned at the beginning of a transmission slot in the frequency-time grid of a wireless communication frame. The term "front-loaded" signifies that the DM-RS is placed in the earlier part of the transmission period, which is especially useful in systems requiring quick channel estimation to ensure low-latency and reliable data decoding.

[0251] In NR Release 18, the number of orthogonal DM-RS ports for both PDSCH and PUSCH are doubled without increasing the DM-RS overhead (e.g., without increasing the amount of required time and frequency resources):

[0252] - For DM-RS Type 1, single-symbol DM-RS: From 4 ports to 8 ports

[0253] - For DM-RS Type 1, double-symbol DM-RS: From 8 ports to 16 ports

[0254] - For DM-RS Type 2, single-symbol DM-RS: From 6 ports to 12 ports

[0255] - For DM-RS Type 2, double-symbol DM-RS: From 12 ports to 24 ports.

[0256] Extending the number of orthogonal DM-RS ports in NR Release 18 was done by increasing the length of a frequency domain orthogonal cover code (FD-OCC) from 2 to 4.

[0257] Each of Figs. 7 and 8 schematically illustrates an example of a demodulation reference signal (DM-RS) according to Type 1. The DM-RS transmission is based on a single-symbol DM-RS for one code division multiplexing (CDM) group. Fig. 7 schematically illustrates an example of the DM-RS transmission according to 3GPP Release 15 DM-RS Type 1. The FD-OCC length is 2. Fig. 8 schematically illustrates an example of a FD-OCC length increased from 2 to 4 according to 3GPP Release 18.

[0258] With an FD-OCC of length 2, the UE can transmit 2 orthogonal DM-RS sequences on the same set of time-frequency resources, effectively doubling the number of ports. With an FD-OCC of length 4, the UE can transmit 4 orthogonal DM-RS sequences, thus quadrupling the number of effective ports.

[0259] The price for the increase in the number of ports is the extent in the frequency domain (DF). The FD-OCC length determines the required extent in the frequency domain for orthogonality. The FD-OCC length essentially defines a spread of the DM-RS across multiple subcarriers to maintain orthogonality.

[0260] One example of how this can look for DM-RS Type 1, single-symbol DM-RS for one CDM group is illustrated in Figs. 7 and 8. DM-RS Type 1 according to 3GPP Release 15 is illustrated in the Fig. 7. DM-RS according to 3GPP Release 18 is illustrated in the Fig. 8. As shown in the Fig. 8, the length-4 FD-OCC spans 7 sub- carriers in the frequency domain. In order for the orthogonality of the length-4 FD-OCC to hold, the channel needs to be invariant over 7 sub-carriers in the frequency domain. On the other hand, the length-2 FD-OCC spans 3 sub-carriers in the frequency domain, which means that the channel needs to be invariant over 3 subcarriers in the frequency domain in order for the orthogonality of the length-2 FD-OCC to hold. Hence, accuracy of channel estimation with the different types of DM-RSs (e.g., DM-RS based on FD-OCC with length 2 versus length 4) depends on the degree of channel variability in the frequency domain.

[0261] The length is a parameter of the FD-OCC code that determines the number of orthogonal cover codes available, which is a multiplier for the number of antenna ports available for the order of multiple-input multiple output (MIMO) transmissions, i.e., the number of layers or streams in the PUSCH and / or PDSCH. But for efficiently using these FD-OCC extended DM-RS on the same DM-RS resources during channel estimation, invariance of the channel is required across the FD extent of the FD-OCC extended DM-RS.

[0262] Similar to DM-RS, other reference signals such as non-zero-power CSI-RS (NZP CSI-RS) and sounding reference signals (SRS) also have different frequency densities (i.e., different number of resource elements per port per PRB) that the network can configure the UE with. The accuracy of channel estimation with the different frequency densities associated with NZP CSI-RS and / or SRS depends on the degree of channel variability in the frequency domain.

[0263] Aspects of the technique comprise methods and signaling 302 for FDCP reporting 306. Such a reporting 306 provides the network 500 with information about the delay spread and how fast the channel 502 changes in the frequency domain, without using uplink reference signals.

[0264] For conciseness and without limitation, the radio device 100 is referred to, and described as, a user equipment (UE) hereinbelow.

[0265] A method aspect 300, which is performed by the UE 100 and which may be extended by any embodiment disclosed herein, comprises:

[0266] - The UE 100 receives, from the network or RAN 500, control signaling for measurement, computation, and / or reporting a frequency domain channel property (FDCP) report or channel coherence metric. - The UE 100 measures and computes the FDCP-related measurement quantities or channel coherence metric.

[0267] - The UE 100 reports the FDCP-related quantities or channel coherence metric to the network 500.

[0268] While the description of the technique refers to a channel coherence metric in singular form, the channel coherence metric may comprise one or more quantities (e.g., a sequence of power densities associated with different delay times representing a channel delay profile). Accordingly, "a value of the channel coherence metric" may comprise multiple real and / or complex numbers.

[0269] Furthermore, while the description of the technique refers to one or more frequency domain channel properties (FDCP) or FDCP measurement quantities, such properties or quantities may be embodied by the channel coherence metric. For example, the FDCP report to the network may be embodied by a step of transmitting, to the RAN, a value of the channel coherence metric.

[0270] In this technique, different alternative FDCP measurement quantities (e.g., examples of the channel coherence metric) such as frequency domain autocorrelation, delay spread, the strongest paths from channel delay profile, etc. may be reported by the UE based on the received signaling from a network node of the RAN (e.g., the network node serving the UE). The detailed signaling (e.g., configuration information and other related signaling) may vary depending on which of the alternative FDCP measurement quantities is used for reporting of FDCP by the UE.

[0271] Embodiments of a method 300 performed by the UE 100 may combine any disclosure herein as to:

[0272] - detailed signaling related to configuration and dynamic indication from the network node 200 to the UE 100 for FDCP reporting in a step 302; and / or - details of the FDCP measurement quantity used for FDCP reporting in a step 304; and / or

[0273] - details of what the UE 100 reports as part of FDCP reporting in a step 306.

[0274] Details of the above-mentioned steps 302 and / or 306 may vary depending on which FDCP measurement quantity is determined in the step 304. Any of the following detailed embodiments may be implemented independently as described below or in combination with any of the above aspects and listed embodiments.

[0275] In one detailed embodiment, a single method (e.g., among any one of the methods disclosed below) for measurement 304-1 and computation 304-2 of FDCP is predefined in 3GPP specifications. When the UE 100 is signaled (e.g., configured via RRC, signaled via MAC CE, or a combination of the two) by the network node 200, the UE 100 measures 304-1 and computes 304-2 FDCP according to the pre-defined method in 3GPP specifications. In another embodiment, the UE 100 receives 302 signaling from the network node 200 providing information on the FDCP measurement 304-1 and computation 304-2 method as part of step 302.

[0276] In one embodiment, the FDCP or metric may be measured based on a frequency domain (FD) autocorrelation of one or more received DL-RSs. Below description uses the terms ‘autocorrelation’ and ‘correlation’ interchangeably. Let

[0277]

[0278] be the channel measured at subcarrier k based on a DL-RS at time t. Then, the amplitude of the normalized frequency domain autocorrelation used for the FDCP report can be defined as

[0279]

[0280] where K is the total number of subcarriers, and A is the frequency separation in number of subcarriers. According to the above method, normalized frequency domain autocorrelation is defined as a function of the frequency separation A. In some embodiments, the UE 100 may receive 302 signaling (e.g., configuration via RRC) of one or more frequency separations for which the UE 100 shall measure 304-1 and compute 304-2 normalized frequency domain autocorrelation for a given DL RS. The signaling of one or more frequency separations may be part of the control signaling in the step 302 in some embodiments.

[0281] For example, if the UE 100 receives one frequency separation A from the network node 200 via signaling, then the UE 100 computes normalized autocorrelation

[0282]

[0283] corresponding to frequency separation A. In some embodiments, the same frequency separation A is used for computing the normalized autocorrelation corresponding to the more than one DL-RS (e.g., either N'T DL-RSs or NTDL-RSs as defined above). In an alternative embodiment, the frequency separation A is signaled per DL RS or a group of DL RSs which are used for measurement and computing of FDCP by the UE 100.

[0284] In another example, if the UE 100 receives two frequency separations A / j and A2from the network node 200 via signaling, then the UE 100 computes two normalized autocorrelations c(A, ) and c(A2) corresponding to frequency separations A / j and A2. In some embodiments, the signaled frequency separations A / j and A2are used for computing the normalized autocorrelations c(A, ) and c(A2) corresponding to the more than one DL-RS (e.g., either N? DL-RSs or NTDL-RSs as defined above).

[0285] In practice, the DL RS is transmitted on a subset of carriers, e.g., every D subcarriers. In this case, the frequency separation A = iD,i = 0,1,..., - — 1. For a BWP of 100 RBs and D = 12, there would be 100 normalized autocorrelation values,

[0286] i.e., c(A ) = c(i£>), i = 0, 1,..., 99.

[0287] To reduce overhead of reporting 306 frequency domain normalized autocorrelation values corresponding to a large number of i values, in one embodiment, the frequency domain normalized autocorrelation values corresponding to a subset of i values are reported. In one embodiment, the UE 100 receives 302 signaling (e.g., configuration via RRC or signaling via RRC and MAC CE combined) from the network node 200 (e.g., a gNB) on which subset of i values for which the UE 100 shall report frequency domain normalized autocorrelation values for. The UE 100, in the step 306, reports the frequency domain normalized autocorrelation values for the signaled subset of i values. In another embodiment, the frequency domain normalized autocorrelation values corresponding to the signaled subset of i values are first quantized before being reported. In one example, each of the frequency domain normalized autocorrelation values corresponding to the signaled subset of i values are quantized to B > 1 bits wherein the B bits indicated one of 2Bquantized amplitude levels. In one detailed embodiment, the UE 100 receives signaling from the network node 200 on the value of B (i.e., quantization level) as part of step 302.

[0288] In some detailed embodiments, the FDCP may be measured over a time window with an averaging / filtering method. The time window and / or the averaging / filtering method may be configured by the NW, pre-defined in the specification or selected and indicated by the UE. the averaging can be in the frequency domain also. For example, considering A =12 sub-carriers, then the UE may measure multiple instances of c(A ) corresponding to A =12 sub-carriers in the frequency domain. Then, these multiple instances of c(A ) can be averaged to produce a frequency domain averaged c(A ). The FDCP report may be on PUSCH, PUCCH, UCI, etc.

[0289] In another detailed embodiment, the channel measurements {

[0290]

[0291] k = iD,i = 0,1,...,- — 1} may be converted in the time (or delay) domain via Discrete Fourier Transform (DFT) or Discrete Cosine Transform (DCT). If TV = K / D - point DFT is used, the time domain samples can be expressed in time (or delay) domain as

[0292] #(T) = IDFT{ht(k), k = iD,i = 0,1,..., N - 1}, T = 0,1,..., N - 1,

[0293]

[0294] effectively the channel impulse response. Let {|^(T) |2, T = 0,1,..., N-l] denote the channel’s power delay profile. An example is illustrated in Fig. 9, where ti represents the first channel path and t2represents the last channel path. In this example, T=t2-ti represents the channel delay spread. For subcarrier spacing g (e.g.,

[0295] 1

[0296] wherein g is given in seconds), the full time range is seconds and time delay for the nthp

[0297] rath with resp

[0298] r

[0299]

[0300] seconds.

[0301] Fig. 9 schematically illustrates an example of channel delay profile |^(T) |2.

[0302] In a variant of any embodiment, if the channel delay spread T (as an example of the metric value) equals or is greater than a cyclic prefix value (CPL), a numerology and / or subband size may be changed accordingto the step 408.

[0303] If the DL RS is transmitted over multiple OFDM symbols, let gi(r) denote the sample correspondingto the IthOFDM symbol. Then, the channel delay profiles corresponding to different OFDM symbols may be averaged over the multiple OFDM symbols as

[0304]

[0305] In one detailed embodiment, the UE receives signaling from the network node, in Step (100), to report the delay spread, T, either in unit of seconds or in unit of number of samples. In case of using seconds as the unit, the full range would be from 0 to —. Then, the UE 100 computes the delay spread, T, from the channel delay profile as illustrated by the example in Fig. 9, and the UE reports the computed delay spread during Step (120). A number of quantization levels, M, may be specified such that [log2(M)l bits may be used for quantizing each reported delay spread. The DFT / DCT size N then can be up to UE implementation. In case of using number of samples to report the delay spread, then N needs to be specified or implicitly derived for the DL-RS configuration so that the same N is used in both the UE and the network. Then, [log2(TV)l bits would be needed for the reporting. Note that in these embodiments, the FDCP reporting quantity is delay spread T, and the UE may report the delay spread(s) correspondingto the subset or whole set N'T(N'T< NT) of the NTcandidate DL-RS(s) as described previously.

[0306] In another detailed embodiment, |^(T) |2may be normalized with respect the maximum value, i.e.,,, • The normalized values for T from ti to t2are then max|5(r)F

[0307] quantized and the quantized values are reported. The quantization may be based on log scale, i.e., with a step size in dBs, e.g., 2 dB. In this case, the channel power delay profile is reported 306. In this detailed embodiment, the channel power delay profile is the FDCP reporting quantity, and the UE 100 may report the channel power delay profile(s) correspondingto the subset or whole set N'T(N'T< NT) of the NTcandidate DL RS(s) as described previously.

[0308] In another detailed embodiment, the UE 100 receives 302 configuration from the network node 200 to report 306 P strongest paths from channel delay profile corresponding to a DL RS. According to such configuration, the UE 100 may report at least one of ‘amplitude’, ‘quantized amplitude’, ‘received path power’, or ‘quantized received path power’ for (e.g., each of) the P strongest paths from a channel delay profile correspondingto a DL RS. In some embodiments, the UE 100 may also report the delay positions of the P strongest paths from channel delay profile correspondingto a DL RS. In this embodiment, at least one of ‘amplitude’, ‘quantized amplitude’, ‘received path power’, ‘quantized received path power’, and ‘delay positions’ corresponding to the P strongest path is the FDCP reporting quantity, and the UE may report such FDCP reporting quantities correspondingto the subset or whole set N'T(N'T< NT) of the NTcandidate DL-RS(s) as described previously. In a further embodiment, the UE may receive P as a configuration parameter as part of reporting configuration for FDCP reporting. Alternatively, P may be configured in terms of a percentage. That is, the UE 100 receives configuration to report FDCP reporting quantities for x% of the strongest paths where P = x · Pmaxwhere Pmaxis the maximum number of measurable paths in the channel delay profile.

[0309] In another detailed embodiment, the UE 100 receives 302 configuration from the network node 200 to report earliest and the latest among the strongest P paths from channel delay profile corresponding to a DL RS. According to such configuration, the UE 100 may report at least one of ‘amplitude’, ‘quantized amplitude’, ‘received path power’, or ‘quantized received path power’ for the earliest and the latest among the P strongest paths from channel delay profile corresponding to a DL RS. In some embodiments, the UE 100 may also report the delay positions of the earliest and the latest of the P strongest paths from channel delay profile corresponding to a DL RS. In this embodiment, at least one of ‘amplitude’, ‘quantized amplitude’, ‘received path power’, ‘quantized received path power’, and ‘delay positions’ corresponding to the earliest and the latest of the P strongest path is the FDCP reporting quantity, and the UE may report such FDCP reporting quantities correspondingto the subset or whole set N'T(N'T< NT) of the NTcandidate DL RS(s) as described previously.

[0310] In one detailed embodiment, the FDCP report may contain information about the frequency domain autocorrelation of the received one or more DL RSs, the delay spread or any other of the measurement quantities (i.e., metrics) mentioned above. Here, the FDCP may be reported according to at least one of these FDCP reporting quantities mentioned above. Particularly, the FDCP report may comprise information about one or more of:

[0311] (a) an indication of the measured frequency domain autocorrelation value; (b) an indication of the measured delay spread;

[0312] (c) an indication of one or more of the strongest paths from channel delay profile corresponding to one or more DL-RSs; (d) an indication of the delay positions of the P strongest paths from channel delay profile corresponding to one or more DL-RS(s).

[0313] (e) an indication of any one or more of ‘amplitude’, ‘quantized amplitude’, ‘received path power’, or ‘quantized received path power’ for the earliest and the latest among the P strongest paths from channel delay profile corresponding to one or more DL RS(s) and / or the delay positions of the earliest and the latest of the P strongest paths from channel delay profile corresponding to one or more DL-RS(s);

[0314] (f) an indication whether the frequency domain autocorrelation value, the delay spread or the other measurement quantities mentioned above exceed a pre-defined threshold or whether the UE has been unable to obtain a valid measurement for the considered measurement quantity; (g) an indication of the sets of DL-RSs and / or carriers used for FDCP measurement;

[0315] (h) other measurement values, e.g., SNR, SINR, RSRP, RSRQ, etc.; and (i) An indication of the recommended subband size for e.g. CSI reporting or PDSCH MIMO precoding (PMI size).

[0316] For instance, if the autocorrelation value, the delay spread or the other measurement quantities mentioned above exceed a threshold value X, the UE may indicate it to the network via an “invalid” or “out-of-range” state considered in the quantization states. Here, the threshold value may be configured by the RAN 500 or network node 200 in the step 302, pre-defined in specification or selected and indicated by the UE 100 in the step 306.

[0317] Once the UE 100 reports the FDCP report to the network node in a Step 306 of Fig. 3, the network node may take actions based on the received FDCP report. In one alternative, the action taken by the network node with respect to the received FDCP report may be configuring or re-configuring the density of reference signals in the frequency domain. Here, for instance, if the frequency domain normalized autocorrelation is above a threshold, i.e.,

[0318]

[0319] and c being the normalized frequency domain autocorrelation and the threshold, respectively, low density of references signals in the frequency domain, e.g., a density X, is considered by the network. Otherwise, with a frequency domain normalized autocorrelation below the threshold, i.e.,

[0320]

[0321] < c, high density of reference signals in the frequency domain, e.g., a density X with X> X, is considered. In another embodiment, the density of the reference signals in the frequency domains scales with the correlation value, e.g., linearly, according to a pre-defined table, etc.

[0322] Although the network action is described in terms of frequency domain normalized autocorrelation as the reporting quantity for FDCP, similar network actions may be defined for other example reporting quantities for FDCP described in other embodiments described above.

[0323] Another possible action taken by the network node with respect to the received FDCP report is configuration / re-configuration of subband size of CSI reports, where the network for example increases the subband size of a CSI report if the FDCP report indicates a large coherence bandwidth (i.e. a more frequency flat channel), and the network e.g. reduce the subband size of a CSI report if the FDCP report indicates a small coherence bandwidth (i.e., a more frequency selective channel).

[0324] In this way, the FDCP report provides the network 500 with information about the frequency domain channel variations and the delay spread. Such an information is of interest in the cases where SRS-based schemes are not feasible and / or efficient to monitor the frequency domain channel variations, e.g., in the cases with cell-edge UEs, the UEs not supporting SRS carrier switching and / or the cases with more DL carriers than the UL carriers. In this way, the proposed scheme addresses one of the topics of interest in 6G.

[0325] In one embodiment, the measurement for an early FDCP report may be based on the reference signals in one or more of the downlink transmissions during the initial access or the random access phase. In an example, a UE may report FDCP based on the reception of demodulation reference signals in the PBCH transmission which carries the master information, and / or based on SSB or similar new 6G reference signal for synchronization.

[0326] In one embodiment, the FDCP report may be event-driven, i.e., UE-initiated. Here, once an event configured by the network occurs at the UE, the UE reports the measured FDCP reports in either pre-configured UL resources or in the UL resources granted by the network per UE’s request. Here, one or more events may be considered, e.g.,

[0327] - The normalized frequency domain autocorrelation, the delay spread, the channel power delay profile, etc. of a DL-RS exceeding or dropping below a threshold value, and / or

[0328] - The difference between a current normalized frequency domain autocorrelation, a delay spread, a channel power delay profile, etc. of a DLRS and its previous measurement exceeding a threshold value.

[0329] Note that one can consider similar event definitions by considering other FDCP measurement quantities mentioned above (e.g., the delay positions of the P strongest paths, etc.). Here, the UE receives the event configuration and its corresponding threshold values, associated UL resources, etc. as a part of Step (100).

[0330] Further feature combinations

[0331] The method 300 may be realized according to at least one of the further combination of features F (e.g., steps):

[0332] F1 - A method performed by the user equipment (UE) in a wireless network, the method comprising

[0333] a- Receiving signaling from a network node for measurement, calculation and reporting of one or more frequency domain channel properties (FDCP), b- Measurement and computation of FDCP according to the signaling received in F1a,

[0334] c- Reporting the computed FDCP to the network node.

[0335] F2- F1 a and where the UE being configured with one or more DL-RS(s) or one or more DL-RS resource set(s) to measure the FDCP.

[0336] a- F2 and where the one or more DL-RS(s) or one or more DL-RS resource set(s) being configured to the UE as part of a reporting configuration for reporting FDCP. b- F2 and where one DL-RS resource set consisting of one or more DL-RS(s).

[0337] c- F2, F1 b and where one FDCP measurement being performed on the DL-RS(s) within one DL-RS resource set.

[0338] d- F2 and where each of the one or more DL-RS resource set(s) being configured with a higher layer parameter indicating that the DL-RS resource(s) within each of the DL-RS resource sets is / are to be used for FDCP measurement.

[0339] F3- F1 a, F2 and where the one or more DL-RS(s) or the one or more DL-RS resource set(s) correspond to one or more TRP(s), one or more DL carrier(s), or one or more cells (which can include serving cell(s) or non-serving cell(s)).

[0340] F4- F1 a, F2-3 and where the one or more DL-RS(s) being at least one of:

[0341] one or more NZP CSI-RS(s),

[0342] one or more tracking reference signal(s) or TRS(s),

[0343] one or more PDSCH DM-RS(s),

[0344] one or more PDCCH DM-RS(s), and

[0345] one or more new DL-RS(s) defined in 6G.

[0346] F5- F1 and where the report configuration comprising at least one of:

[0347] a- An explicit configuration indicating that the UE shall report FDCP value(s) measured / calculated as part of the report corresponding to the reporting configuration.

[0348] b- A higher layer parameter to indicate the UE to report FDCP value(s) measured / calculated.

[0349] c- Information about the dynamic range (e.g., maximum and / or minimum value(s) of FDCP that can be reported) and / or the quantization levels (e.g., the number of bits per each FDCP value measured / calculated) for the FDCP value(s) to be reported. d- An indication of the FDCP measurement and computation method / metric, e- An indication of one or more frequency separation(s) for which the UE shall measure and compute normalized frequency domain autocorrelation for a given DL-RS.

[0350] F6- F1 b and where the UE selecting a subset or the whole of the one or more configured DL-RS(s) for FDCP measurement and computation.

[0351] a- F6, 1c and where the UE indicating the selected subset of one or more DL-RS(s) as part of the FDCP report (e.g., in the cases where the subset is selected by the UE).

[0352] F7- F1 b and where the method for measurement and computation of the FDCP report being based on, any metric mentioned above and / or at least one of:

[0353] a- The normalized frequency domain autocorrelation of the DL-RS(s),

[0354] b- The delay spread (either in unit of seconds or in unit of number of samples), c- The channel power delay profile,

[0355] d- One or more of the strongest paths from the channel delay profile corresponding to one or more DL-RS(s) (e.g., ‘amplitude’, ‘quantized amplitude’, ‘received path power’, or ‘quantized received path power’ for the P strongest paths from channel delay profile corresponding to a DL-RS).

[0356] e- 7d and where the UE also reporting the delay positions of the P strongest paths from channel delay profile corresponding to one or more DL-RS(s).

[0357] f- At least one of ‘amplitude’, ‘quantized amplitude’, ‘received path power’, or ‘quantized received path power’ for the earliest and the latest among the P strongest paths from channel delay profile corresponding to one or more DL-RS and / or the delay positions of the earliest and the latest of the P strongest paths from channel delay profile corresponding to one or more DL-RS(s).

[0358] F8- F1 and where the FDCP report being periodic, semi-persistent, dynamic (aperiodic one-shot report or aperiodic burst of multiple reports), or event-driven (UE-initiated).

[0359] F9- F1 a and where the measurement, computation, and report configuration for FDCP reporting being based on RRC, MAC CE, or a combination of the two.

[0360] F10- F1 c and where FDCP report having a fixed or variable payload (e.g., on a fixed orvariable number of DL-RSs).

[0361] F11 - F10 and where, with variable payload, the UE receiving a first configuration signal (e.g., via RRC) on the candidate DL-RS(s) that are intended for FDCP measurement and a second signal (e.g., a MAC CE message) indicating which subset or whole set of the candidate DL-RS(s) the UE shall perform FDCP measurements on.

[0362] F12- F1 c and where the FDCP report having two-parts.

[0363] a- F12 and where the first part being composed of a fixed payload and containing information on which subset or whole set of the candidate DL-RS(s) the UE will perform FDCP measurements.

[0364] b- F12 and where the payload size of the second part being indicated implicitly or explicitly in the first part.

[0365] c- F12 and where the second part containing information about the FDCP measurements associated with the selected subset or whole set of the candidate DL-RS(s) indicated in the first part.

[0366] F13- F7a and where the same or different frequency separations are used for computing the normalized autocorrelation corresponding to different DL-RSs.

[0367] F14- F1 c and where the FDCP report comprising information about at least one of a- An indication of the measured frequency domain autocorrelation value(s), b- An indication of the measured delay spread value(s),

[0368] c- An indication of one or more of the strongest paths from channel delay profile corresponding to one or more DL-RS(s).

[0369] d- An indication of the delay positions of the P strongest paths from channel delay profile corresponding to one or more DL-RS(s).

[0370] e- An indication at least one of ‘amplitude’, ‘quantized amplitude’, ‘received path power’, or ‘quantized received path power’ for the earliest and the latest among the P strongest paths from channel delay profile correspondingto one or more DL-RS(s) and / or the delay positions of the earliest and the latest of the P strongest paths from channel delay profile corresponding to one or more DL- RS(s).

[0371] f- An indication whether the FDCP measurement quantity (e.g., frequency domain autocorrelation value, the delay spread etc.) exceed a pre-defined threshold or whether the UE has been unable to obtain a valid measurement for the considered measurement quantity.

[0372] g- An indication of the sets of DL-RSs and / or carriers used for FDCP measurement, h- Other measurement values, e.g., SNR, SINR, RSRP, RSRQ, etc.

[0373] i- An indication of the recommended subband size for e.g. CSI reporting or PDSCH MIMO precoding (PMI size) j- Coherence Bandwidth (i.e. a indication of the range of frequencies within which the channel frequency response remains flat, or below a certain threshold, where the threshold either can be pre-determined in specification, or configured by the network).

[0374] F15- F1 b and where the method for measurement and computation of FDCP being pre-defined in 3GPP specifications.

[0375] F16- All above and where the dynamic range and / or the quantization levels for the FDCP value(s) to be reported are pre-specified in 3GPP specifications.

[0376] F17- F8 and where with an event-driven report, once an event occurs at the UE, the UE reports the measured FDCP reports in either pre-configured UL resources or in the UL resources granted by the network per UE’s request.

[0377] a- F17 and where the event and its corresponding parameters (e.g., thresholds, associated report configuration, UL resources, etc.) are received in 1a.

[0378] b- F17 and where the event is defined as at least one of:

[0379] I. A FDCP measurement quantity (e.g., normalized frequency domain autocorrelation, the delay spread, the channel power delay profile, etc.) of a DL-RS exceeding or going below a threshold value, and

[0380] II. The difference between a current FDCP measurement quantity (e.g., normalized frequency domain autocorrelation, a delay spread, a channel power delay profile, etc.) of a DL-RS and its previous measurement exceeding a threshold value.

[0381] Fig. 11 shows a schematic block diagram for an embodiment of the device 100. The device 100 comprises processing circuitry, e.g., one or more processors 1104 for performing the method 300 and memory 1106 coupled to the processors 1104. For example, the memory 1106 may be encoded with instructions that implement at least one of the modules 104 and 106.

[0382] The one or more processors 1104 may be a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, microcode and / or encoded logic operable to provide, either alone or in conjunction with other components of the device 100, such as the memory 1106, UE functionality. For example, the one or more processors 1104 may execute instructions stored in the memory 1106. Such functionality may include providing various features and steps discussed herein, including any of the benefits disclosed herein. The expression "the device being operative to perform an action" may denote the device 100 being configured to perform the action.

[0383] As schematically illustrated in Fig. 11, the device 100 may be embodied by a radio device 1100, e.g., functioning as a UE. The radio device 1100 comprises a radio interface 1102 coupled to the device 100 for radio communication with one or more network nodes, e.g., functioning as a base station 200 of the RAN 500.

[0384] Fig. 12 shows a schematic block diagram for an embodiment of the device 200. The device 200 comprises processing circuitry, e.g., one or more processors 1204 for performing the method 400 and memory 1206 coupled to the processors 1204. For example, the memory 1206 may be encoded with instructions that implement at least one of the modules 206 and 208.

[0385] The one or more processors 1204 may be a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, microcode and / or encoded logic operable to provide, either alone or in conjunction with other components of the device 200, such as the memory 1206, network node functionality. For example, the one or more processors 1204 may execute instructions stored in the memory 1206. Such functionality may include providing various features and steps discussed herein, including any of the benefits disclosed herein. The expression "the device being operative to perform an action" may denote the device 200 being configured to perform the action.

[0386] As schematically illustrated in Fig. 12, the device 200 may be embodied by a network node 1200, e.g., functioning as a 6G base station. The network node 1200 comprises a radio interface 1202 coupled to the device 200 for radio communication with one or more radio device, e.g., functioning as UE 100.

[0387] With reference to Fig. 13, in accordance with an embodiment, a communication system 1300 includes a telecommunication network 1310, such as a 3GPP-type cellular network, which comprises an access network 1311, such as a radio access network, and a core network 1314. The access network 1311 comprises a plurality of base stations 1312a, 1312b, 1312c, such as NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 1313a, 1313b, 1313c. Each base station 1312a, 1312b, 1312c is connectable to the core network 1314 over a wired orwireless connection 1315. Afirst user equipment (UE) 1391 located in coverage area 1313c is configured to wirelessly connect to, or be paged by, the corresponding base station 1312c. A second UE 1392 in coverage area 1313a is wirelessly connectable to the corresponding base station 1312a. While a plurality of UEs 1391, 1392 are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole UE is in the coverage area or where a sole UE is connectingto the corresponding base station 1312.

[0388] Any of the base stations 1312 and the UEs 1391, 1392 may embody the devices 200 and 100, respectively.

[0389] The telecommunication network 1310 is itself connected to a host computer 1330, which may be embodied in the hardware and / or software of a standalone server, a cloud-implemented server, a distributed server or as processing resources in a server farm. The host computer 1330 may be under the ownership or control of a service provider, or may be operated by the service provider or on behalf of the service provider. The connections 1321, 1322 between the telecommunication network 1310 and the host computer 1330 may extend directly from the core network 1314 to the host computer 1330 or may go via an optional intermediate network 1320. The intermediate network 1320 may be one of, or a combination of more than one of, a public, private or hosted network; the intermediate network 1320, if any, may be a backbone network or the Internet; in particular, the intermediate network 1320 may comprise two or more sub-networks (not shown).

[0390] The communication system 1300 of Fig. 13 as a whole enables connectivity between one of the connected UEs 1391, 1392 and the host computer 1330. The connectivity may be described as an over-the-top (OTT) connection 1350. The host computer 1330 and the connected UEs 1391, 1392 are configured to communicate data and / or signaling via the OTT connection 1350, using the access network 1311, the core network 1314, any intermediate network 1320 and possible further infrastructure (not shown) as intermediaries. The OTT connection 1350 may be transparent in the sense that the participating communication devices through which the OTT connection 1350 passes are unaware of routing of uplink and downlink communications. For example, a base station 1312 need not be informed about the past routing of an incoming downlink communication with data originating from a host computer 1330 to be forwarded (e.g., handed over) to a connected UE 1391. Similarly, the base station 1312 need not be aware of the future routing of an outgoing uplink communication originating from the UE 1391 towards the host computer 1330.

[0391] By virtue of the method 300 being performed by any one of the UEs 1391 or 1392 and / or the method 400 performed by any one of the base stations 1312, the performance or range of the OTT connection 1350 can be improved, e.g., in terms of increased throughput and / or reduced latency. More specifically, the host computer 1330 may indicate to the RAN 500 (e.g., on an application layer) a QoS of the traffic, which triggers a change in the radio channel (e.g., carrier and / or bandwidth) that is measured according to the two-step procedure of method 300 and 400.

[0392] As has become apparent from above description, at least some embodiments of the technique provide the network (e.g., the RAN) with information about channel coherence, e.g. a delay spread of the radio channel and / or a measure of how fast the radio channel changes in the frequency domain, e.g., how "flat" orfrequency-selective the radio channel is, preferably without the use of uplink signals from the UE, e.g., without a sounding reference signal (SRS) transmission. In the latter case, no channel reciprocity has to be assumed.

[0393] These and further embodiments avoid the drawbacks associated with SRS-based estimation of channel variation in frequency domain. It is noted that SRS-based estimation may suffer inaccurate estimation of channel variation in frequency domain due to factors such as narrow transmission bandwidth of SRS (e.g., limited due to a maximum power of the UE and / or a path loss of the channel) and / or an unavailability of SRS in DL-only carriers (since an SRS transmission is not possible in a DL-only carrier).

[0394] Moreover, determining (e.g., measuring) the FDCP or channel coherence metric at the UE benefits from the RAN (e.g., the network node) having more transmit power than the UE, which is why the RAN (e.g., the network node) can transmit a reference signal that utilize the full bandwidth, which improves the accuracy of the reported FDCP ortransmitted value of the channel coherence metric compared to a narrowband SRS-based measurement.

[0395] In the corresponding steps 310 and 410 of the methods performed by the UE and the network, respectively, the FDCP report or value of the channel coherence metric can be used to properly configure or re-configure the density of the reference signals in the frequency domain, and / or determine the subband size of CSI reports. Many advantages of the present invention will be fully understood from the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the units and devices without departing from the scope of the invention and / or without sacrificing all of its advantages. Since the invention can be varied in many ways, it will be recognized that the invention should be limited only by the scope of the following embodiments.

Claims

Claims1. A method (300) of a radio device (100), the method (300) comprising:determining (304) at least one value of a metric for channel coherence of a radio channel (502) between the radio device (100) and a network node (200) of a radio access network, RAN (500); andtransmitting (306), to the RAN (500) or the network node (200), the determined (304) at least one value of the channel coherence metric.

2. The method of claim 1, wherein the transmitted (306) at least one value of the metric is indicative of at least one of:a radio propagation along the radio channel (502), optionally indicative of a multi-path radio propagation along the radio channel (502); anda frequency domain channel property.

3. The method of claim 1 or 2, wherein the transmitted (306) at least one value of the metric assists the network node (200) for frequency domain configuration (600), optionally for an adaptive frequency-domain resource allocation and / or dynamically assigning physical resource blocks, PRBs, to the radio device (100) in a manner that aligns with frequency domain channel properties indicated by the at least one metric value.

4. The method of any one of claims 1 to 3, wherein the transmitted (306) at least one value of the metric assists a frequency domain configuration (600) of a subsequent measurement of the radio channel (502) between the radio device (100) and the network node (200).

5. The method of any one of claims 1 to 4, wherein the transmitted (306) at least one value of the metric assists or triggers at least one of:a change of an allocation of reference signal resources to reference signals in frequency domain;a change in a pattern of reference signal resources in frequency domain, optionally wherein all of the reference signal resources in the pattern carry a reference signal associated to one antenna port; anda change in a density of reference signals in frequency domain, optionally wherein a decrease in coherence bandwidth indicated by the at least one metric value triggers an increase in the density and / or wherein an increase in coherenceindicated by the at least one metric value bandwidth triggers an increase in the density.

6. The method of claim 5, wherein the reference signals are transmitted from the radio device (100) to the network node (200); orwherein the reference signals are received at the radio device (100) from the network node (200).

7. The method of any one of claims 1 to 6, wherein the transmitted (306) at least one value of the metric assists or triggers a change of at least one of:a subband size for the radio channel (502), optionally a subband size of a channel state information, CSI, report for the radio channel (502); anda numerology or subcarrier spacing, SCS, for the radio channel (502).

8. The method (300) of any one of claims 1 to 7,further comprising receiving (302), from the RAN (500) or the network node (200), control signaling for the determining (304) of the at least one value of the channel coherence metric and / or for the transmitting (306) of the determined (304) at least one value of the channel coherence metric to the RAN or the network node (200), optionally wherein the control signaling is indicative of a configured set of radio resources for determining (304) the at least one value of the channel coherence metric and / or wherein the control signaling is indicative of the channel coherence metric for which the at least one value is to be determined (304), and / or wherein the at least one value is transmitted (306) in a report message that is further indicative of at least one of: a selected set of radio resources used by the radio device (100) for determining (304) the at least one value of the channel coherence metric, and the channel coherence metric for which the at least one value is determined (304).

9. The method (300) of any one of claims 1 to 8, wherein the determining (304) of the at least one value of the channel coherence metric comprises measuring (304-1 ) the at least one value of the channel coherence metric of a radio channel (502) between the radio device (100) and the network node (200) or the RAN (500), and / or wherein the at least one value of the channel coherence metric is measured (304-1 ) based on one or more downlink reference signals from the network node (200) or the RAN (500) and / or at least one of:one or more non-zero power channel state information reference signals, NZP CSI-RSs;one or more tracking reference signals, TRSs, from the network node (200) or the RAN (500);one or more physical downlink shared channel demodulation reference signals, PDSCH DM-RSs;one or more physical downlink control channel demodulation reference signals, PDCCH DM-RSs;one or more synchronization signals, optionally a primary synchronization signal, PSS, or a secondary synchronization signal (SSS);one or more phase tracking reference signals, PT-RSs;one or more reconfigurable intelligent surface reference signals, RIS-RSs; and one or more terahertz band demodulation reference signals, THz-DMRS.

10. The method (300) of any one of claims 1 to 9, wherein the channel coherence metric comprises, or is based on, at least one of:a delay spread of the radio channel (502) in time domain;a channel delay profile of the radio channel (502) in time domain;a power density of the radio channel (502) in time domain;one or more peaks of a channel delay profile of the radio channel (502) in time domain;one or more sample points of a channel delay profile of the radio channel (502) at predefined points in time domain, optionally predefined by the received (302) control signaling;a coherence time of the radio channel (502);a time domain convolution between a reference signal transmitted from the network node (200) and a signal received on the radio channel (502) at the radio device (100);one or more channel variations of the radio channel (502) in frequency domain;a coherence bandwidth of the radio channel (502);a Doppler spread of the radio channel (502) in frequency domain;a frequency domain autocorrelation of the radio channel (502);one or more sample points of a frequency domain autocorrelation of the radio channel (502) at predefined points in frequency domain, optionally predefined by the received (302) control signaling;a frequency domain convolution between a reference signal transmitted from the network node (200) and a signal received on the radio channel (502) at the radio device (100);a discrete convolution between a channel measured at sub-carrier k on a reference signal received from the network node (200) and a channel measured at sub-carrier k+Δf on a reference signal received from the network node (200) in the frequency domain;a coherence distance of the radio channel (502) in spatial domain;one or more strongest paths from a channel delay profile of the radio channel (502); andan analysis of a delay profile of the radio channel (502) for identifying one or more strongest paths.

11. The method (300) of any one of claims 1 to 10, wherein the radio channel (502) is or comprises an uplink channel or wherein the radio channel (502) is or comprises a downlink channel, and / orwherein the radio channel (502) carries a physical uplink shared channel, PUSCH, or a physical downlink shared channel, PDSCH.

12. The method (300) of any one of claims 1 to 11, further comprising:receiving (310) a configuration message indicative of the frequency domain configuration (600) of the subsequent measurement of the radio channel (502) between the radio device (100) and the RAN (500); and / orwherein the frequency domain configuration (600) is dependent on the transmitted (306) at least one value of the metric for the channel coherence; and / or wherein the frequency domain configuration (600) comprises a density of reference signals in the frequency domain for the subsequent measurement of the radio channel (502); and / orwherein the frequency domain configuration (600) is indicative of an allocation of frequency domain resources for at least one of uplink reference signals, UL RS, optionally SRS and / or UL DM-RS, and downlink reference signals, DL RS, optionally NZP CSI-RS and / or DL DM-RS; and / orwherein the frequency domain configuration (600) is indicative of a subband size of DL RS, optionally NZP CSI-RS and / or DL DM-RS, for the subsequent measurement of the radio channel (502); and / orwherein the subsequent measurement of the radio channel (502) is a CSI measurement.

13. The method (300) of any one of claims 1 to 12, wherein the determining (304) of the at least one value of the channel coherence metric comprises a preparatory measurement that is different from the subsequent measurement, optionally wherein the subsequent measurement is based on the preparatory measurement, and / orwherein the frequency domain configuration used by the subsequent measurement of the radio channel (502) depends on the determined (304) at least one value of the channel coherence metric.

14. The method (300) of any one of claims 1 to 13, wherein at least one of the determining (304) and the transmitting (306) is event-driven.

15. The method (300) of any one of claims 1 to 14, wherein the received (302) control signaling comprising a higher layer parameter that is indicative of the radio device (100) to determine (304) and / or transmit (306) the at least one metric value and / or that is indicative of an event triggering determination (304) and / or the transmission (306).

16. A method (400) of a network node (200) configuring a channel measurement, the method (400) comprising:receiving (406), from a radio device (100), a value of a metric for channel coherence of a radio channel (502) between the radio device (100) and the network node (200) of a radio access network, RAN (500); andconfiguring (408), based on the received (406) value of the channel coherence metric, a frequency domain configuration (600) of a subsequent measurement of the radio channel (502) between the radio device (100) and the network node (200).

17. The method (400) of claim 16, further comprising:a transmitting (402), to the radio device (100), control signaling for determining the value of the channel coherence metric and / or for transmitting the determined value of the channel coherence metric to the network node (200), optionally wherein the control signaling is indicative of a configured set of radio resources for determining the value of the channel coherence metric and / or wherein the control signaling is indicative of the channel coherence metric for which the value is to be determined.

18. The method (400) of claims 16 or 17, wherein the configuring (408) of the frequency domain comprises transmitting (410) a configuration message indicative of the frequency domain configuration to the radio device (100).

19. The method (400) of any one of claims 16 to 18, further comprising the steps or features of any one of embodiments 2 to 15 or any step or feature corresponding thereto.

20. A computer program product comprising program code portions for performing the steps of any one of the claims 1 to 15 and / or 16 to 19 when the computer program product is executed on one or more computing devices (1104; 1204), optionally stored on a computer-readable recording medium (1106; 1206).

21. A radio device (100; 1100; 1391; 1392) for assisting configuration of a channel measurement, the radio device (100; 1100; 1391; 1392) comprising memory operable to store instructions and processing circuitry operable to execute the instructions, such that the radio device (100; 1100; 1391; 1392) is operable to:determine a value of a metric for channel coherence of a radio channel (502) between the radio device (100) and a network node (200) of a radio access network, RAN (500); andtransmit, to the RAN (500) or the network node (200), the determined value of the channel coherence metric for assisting a frequency domain configuration (600) of a subsequent measurement of the radio channel (502) between the radio device (100) and the network node (200).

22. The radio device (100; 1100; 1391; 1392) of claim 21, further comprising the features and further operable to perform the steps of any one of claims 2 to 15.

23. A radio device (100; 1100; 1391; 1392) for assisting configuration of a channel measurement, the radio device (100; 1100; 1391; 1392) being configured to:determine a value of a metric for channel coherence of a radio channel (502) between the radio device (100) and a network node (200) of a radio access network, RAN (500); andtransmit, to the RAN (500) or the network node (200), the determined value of the channel coherence metric for assisting a frequency domain configuration (600) of a subsequent measurement of the radio channel (502) between the radio device (100) and the network node (200).

24. The radio device (100; 1100; 1391; 1392) of claim 23, further comprising the features and further configured to perform the steps of any one of claims 2 to 15.

25. A network node (200; 1200; 1312) for configuring a channel measurement, the network node (200; 1200; 1312) comprising memory operable to store instructions and processing circuitry operable to execute the instructions, such that the network node (200; 1200; 1312) is operable to:receive, from a radio device (100), a value of a metric for channel coherence of a radio channel (502) between the radio device (100) and the network node (200) of a radio access network, RAN (500); andconfigure, based on the received value of the channel coherence metric, a frequency domain configuration (600) of a subsequent measurement of the radio channel (502) between the radio device (100) and the network node (200).

26. The network node (200; 1200; 1312) of claim 25, further comprising the features and further operable to perform any one of the steps of any one of claims 17 to 19.

27. A network node (200; 1200; 1312) for configuring a channel measurement, the network node (200; 1200; 1312) comprising memory operable to store instructions and processing circuitry operable to execute the instructions, such that the network node (200; 1200; 1312) is configured to:receive, from a radio device (100), a value of a metric for channel coherence of a radio channel (502) between the radio device (100) and the network node (200) of a radio access network, RAN (500); andconfigure, based on the received value of the channel coherence metric, a frequency domain configuration (600) of a subsequent measurement of the radio channel (502) between the radio device (100) and the network node (200).

28. The network node (200; 1200; 1312) of claim 27, further comprising the features and further configured to perform the steps of any one of claims 17 to 19.

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