WO2025040260A1

WO2025040260A1 - Mapping function for spatial characteristics of reference signals

Info

Publication number: WO2025040260A1
Application number: PCT/EP2023/073207
Authority: WO
Inventors: Ming Li; Bo Göransson
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2023-08-24
Filing date: 2023-08-24
Publication date: 2025-02-27
Anticipated expiration: 2026-02-24

Abstract

A wireless device (10) determines a first spatial characteristic of first reference signals on a first frequency. Further, the wireless device determines a second spatial characteristic of second reference signals on a second frequency from the at least one spatial characteristic of the first reference signals and based on a mapping function. The mapping function depends on the first frequency and the second frequency and maps the at least one first spatial characteristic to the at least one second spatial characteristic.

Description

Mapping function for spatial characteristics of reference signals

Technical Field

The present invention relates to methods for controlling wireless communication in a wireless communication network and to corresponding devices, systems, and computer programs.

Background

In wireless communication networks, e.g., based on the 4G (4th Generation) LTE (Long Term Evolution) or 5G (5th Generation) NR technology as specified by 3GPP (3rd Generation Partnership Project), it is known to utilize various kinds of reference signals (RS) for controlling wireless transmissions. For example, a radio access network (RAN) node, in the 4G LTE technology typically denoted as “eNodeB” or “eNB” and in the 5G NR technology typically denoted as “gNodeB” or “gNB” may transmit demodulation RS (DM-RS), channel state information (CSI) RS, synchronization signals (SS), such as PSS (Primary Synchronization Signal) or SSS (Secondary Synchronization Signal), SSBs (Synchronization Signal Blocks), and tracking reference signals (TRS). These RS may be received by a UE (user equipment) and used for various purposes, e.g., such as timing synchronization, channel estimation, demodulation, or the like.

To facilitate channel estimation at the UE, a concept denoted as QCL (Quasi-Co-Location) was introduced to the 3GPP specifications, see, e.g., 3GPP TS 38.214 V17.6.0 (2023-06). A receiver algorithm in the UE typically performs some channel analysis prior to channel estimation in order to tune the channel estimator filters and to set the correct gain of the receiver front end to utilize the full dynamic range of the receiver. For example, it is useful for a channel estimation algorithm to know the delay spread of the channel, as this a-priori information generally improves the estimation performance. Delay spread can be measured using a wide bandwidth CSI-RS and be used to demodulate a PDSCH (Physical Downlink Shared Channel) even if it is only scheduled to be transmitted in a single physical resource block (PRB). Using the PDSCH DM-RS only, for delay spread estimation purpose would lead to a poor estimate in this example since the DM-RS is only a single RB wide. Here, QCL allows to specify an association between different RSs, such as the wide bandwidth CSI-RS and the variable bandwidth PDSCH DM-RS, to make clear which channel properties estimated from one RS may be exploited to improve the estimate of a channel from another RS. According to the 3GPP specifications, different types of QCL can be defined between antenna ports of downlink transmissions, represented by large-scale channel parameters:

QCL Type A: Doppler shift, Doppler spread, average delay, delay spread QCL Type B: Doppler shift, Doppler spread QCL Type C: average delay, Doppler shift QCL Type D: Spatial Rx parameter

When two antenna ports are QCL with respect to one or more of these five parameters, then the UE may estimate those large-scale parameters for the second antenna port by a measurement on the first antenna port. When the UE, possibly at a later point in time, needs to perform channel estimation of the channel using the second antenna port, then it can base the selection of the channel estimation filter, e.g., using the estimated delay spread, on these estimated large-scale parameters. Hence, the UE can prepare the filter in advance to receiving on the antenna second port since it already knows the large-scale parameters.

Further features which have the purpose of facilitating receive (Rx) and/or transmit (Tx) processing include TCI (Transmission Configuration Indication), beam correspondence, and spatial relation:

The network may configure a UE with an active TCI state for channel reception, e.g., PDCCH (Physical Downlink Control Channel) and PDSCH, respectively. The active TCI indicates, for each channels, timing reference the UE shall assume for the downlink reception. The timing reference is defined with respect to a certain downlink RS. Different TCI states may be configured to indicate to the UE which downlink RSs can be used as QCL source for corresponding downlink reception of PDCCH or PDSCH. For example, the following RSs can be used as source RS to indicate a Tx beam for downlink: SSB blocks or CSI-RS for beam management, CSI-RS for tracking, and CSI-RS for CSI acquisition. Accordingly, a downlink RS, e.g., SSB, CSI-RS, may be regarded as corresponding to a certain downlink beam, spatial filter, spatial domain transmission filter, main lobe of the radiation pattern of antenna array, or the like. The active TCI state may thus additionally indicate to the UE which UE Rx beam to use when receiving PDCCH and/or PDSCH, since it shall use the UE Rx beam that allows best conditions for receiving the SSB index or downlink RS resource associated with the TCI state. The best UE Rx beam for a given TCI state may change over time, for example, if the orientation of the UE changes, but is often relatively static at least over short time intervals.

With beam correspondence, a transmitter can determine the Tx beam to a receiver based on the Rx beam used to receive data from this receiver. This concept is typically applied for UE beam correspondence, i.e. , by causing the UE to use the same beam for transmission as for reception.

A “spatial relation” may be defined at the UE to specify the UL transmission behavior. The purpose of such spatial relation is to facilitate network control of the UE transmission directions. A spatial relation may signaled from the network to the UE. The spatial relation may be either a relation between downlink reception and uplink transmission or a relation between two uplink transmissions. In the former case, the spatial relation instructs the UE to use the same beam for uplink transmission of a given signal as it uses for reception of a given downlink reference signal, CSI-RS or SSB. This requires that the UE also supports beam correspondence. If the spatial relation is between two uplink signals, the spatial relation instructs the UE to use the same beam for uplink transmission as it has used for transmission of a previous uplink reference signal, e.g., an SRS (Sounding Reference Signal).

The signaling of QCL and TCI is accomplished per carrier or BWP. This may result in significant signaling in cases where multiple different frequencies are used, e.g., in scenarios involving carrier aggregation or when multiple bandwidth parts (BWPs) are utilized.

Accordingly, there is a need for techniques which allow for efficiently utilizing reference signals transmitted on different frequencies.

Summary

According to an embodiment, a method of controlling wireless communication is provided. According to the method, a wireless device determines a first spatial characteristic of first reference signals on a first frequency. Further, the wireless device determines a second spatial characteristic of second reference signals on a second frequency from the at least one spatial characteristic of the first reference signals and based on a mapping function. The mapping function depends on the first frequency and the second frequency and maps the at least one first spatial characteristic to the at least one second spatial characteristic.

According to a further embodiment, a method of controlling wireless communication is provided. The method comprises configuring a wireless device with a mapping function. The mapping function enables the wireless device to determine, from a first spatial characteristic of first reference signals on a first frequency, a second spatial characteristic of second reference signals on a second frequency. The mapping function depends on the first frequency and the second frequency and maps the at least one first spatial characteristic to the at least one second spatial characteristic.

According to a further embodiment, a wireless device for operation in a wireless communication network is provided. The wireless device is adapted to determine a first spatial characteristic of first reference signals on a first frequency. Further, the wireless device is adapted to determine a second spatial characteristic for second reference signals on a second frequency from the at least one spatial characteristic of the first reference signals and a mapping function. The mapping function depends on the first frequency and the second frequency and maps the at least one first spatial characteristic to the at least one second spatial characteristic.

According to a further embodiment, a wireless device for operation in a wireless communication network is provided. The wireless device comprises at least one processor and a memory. The memory contains instructions executable by said at least one processor, whereby the wireless device is operative to determine a first spatial characteristic of first reference signals on a first frequency. Further, the memory contains instructions executable by said at least one processor, whereby the wireless device is operative to determine a second spatial characteristic for second reference signals on a second frequency from the at least one spatial characteristic of the first reference signals and a mapping function. The mapping function depends on the first frequency and the second frequency and maps the at least one first spatial characteristic to the at least one second spatial characteristic.

According to a further embodiment, a network node a wireless communication network is provided. The network node is adapted to configure a wireless device with a mapping function. The mapping function enables the wireless device to determine, from a first spatial characteristic of first reference signals on a first frequency, a second spatial characteristic of second reference signals on a second frequency. The mapping function depends on the first frequency and the second frequency and maps the at least one first spatial characteristic to the at least one second spatial characteristic.

According to a further embodiment, a network node for a wireless communication network is provided. The network node comprises at least one processor and a memory. The memory contains instructions executable by said at least one processor, whereby the network node is operative to configure a wireless device with a mapping function. The mapping function enables the wireless device to determine, from a first spatial characteristic of first reference signals on a first frequency, a second spatial characteristic of second reference signals on a second frequency. The mapping function depends on the first frequency and the second frequency and maps the at least one first spatial characteristic to the at least one second spatial characteristic.

According to a further embodiment of the invention, a computer program or computer program product is provided, e.g., in the form of a non-transitory storage medium, which comprises program code to be executed by at least one processor of a wireless device. Execution of the program code causes the wireless device to determine a first spatial characteristic of first reference signals on a first frequency. Further, execution of the program code causes the wireless device to determine a second spatial characteristic for second reference signals on a second frequency from the at least one spatial characteristic of the first reference signals and a mapping function. The mapping function depends on the first frequency and the second frequency and maps the at least one first spatial characteristic to the at least one second spatial characteristic.

According to a further embodiment of the invention, a computer program or computer program product is provided, e.g., in the form of a non-transitory storage medium, which comprises program code to be executed by at least one processor of a network node. Execution of the program code causes the network node to configure a wireless device with a mapping function. The mapping function enables the wireless device to determine, from a first spatial characteristic of first reference signals on a first frequency, a second spatial characteristic of second reference signals on a second frequency. The mapping function depends on the first frequency and the second frequency and maps the at least one first spatial characteristic to the at least one second spatial characteristic.

Details of such embodiments and further embodiments will be apparent from the following detailed description of embodiments.

Brief Description of the Drawings

Fig. 1 schematically illustrates a wireless communication network according to an embodiment of the present disclosure.

Fig. 2 schematically elements for implementing beamformed wireless transmissions in accordance with embodiments of the present disclosure. Fig. 3 schematically illustrates spatial characteristics of reference signals on different frequencies.

Fig. 4 schematically illustrates an example of a mapping function according to an embodiment of the present disclosure.

Fig. 5 schematically illustrates a further example of a mapping function according to an embodiment of the present disclosure.

Fig. 6 schematically illustrates signaling according to an embodiment of the present disclosure.

Fig. 7 shows a flowchart for schematically illustrating a method according to an embodiment.

Fig. 8 shows a flowchart for schematically illustrating a further method according to an embodiment.

Fig. 9 schematically illustrates structures of a wireless device according to an embodiment.

Fig. 10 schematically illustrates structures of a network node according to an embodiment.

Fig. 11 schematically illustrates interaction of a host and a wireless device according to an embodiment.

Detailed Description

In the following, concepts in accordance with exemplary embodiments of the invention will be explained in more detail and with reference to the accompanying drawings. The illustrated embodiments relate to controlling wireless communication in a wireless communication network. The wireless communication network may be based on the 5G NR technology specified by 3GPP. However, other technologies could be used as well, e.g., the 4G LTE technology specified by 3GPP or a future 6G (6^th Generation) technology.

In the illustrated concepts, it may be taken into account that reference signals transmitted on different frequencies may still have similar spatial characteristics. In the illustrated concepts, a mapping function is provided which enables deriving a spatial characteristic of RS on one frequency from the spatial characteristic of RS on another frequency. The different frequencies may correspond to different carriers, i.e. , be different carrier frequencies, or to different BWPs of the same carrier. The spatial characteristic may include QCL and/or TCI state. For example, for first reference signals (RS1) on a first frequency (f1) and for second reference signals (RS2) on a second frequency (f2), the mapping function may enable deriving QCL of RS2 from QCL of RS1. Similarly, the mapping function may enable deriving TCI state of RS2 from TCI state of RS1. In some scenarios, the mapping function can be determined using machine learning and training. In some cases, the mapping function could also be at least in part pre-configured. The mapping function can be configured in a wireless device, e.g., a UE, and/or in a network node, e.g.., a RAN node (such as a gNB or eNB). The configuration can be based on signaling between the network node and the wireless device.

As used herein, the term wireless device may refer to a UE or to any type of device wirelessly communicating with a network node and/or with another device in a cellular or mobile communication system. Examples of UE are a mobile device, a machine type communication (MTC) UE or UE capable of machine-to-machine (M2M) communication, a PDA (Personal Digital Assistant), a tablet, a mobile terminal, a smartphone, a laptop embedded equipment (LEE), a laptop mounted equipment (LME), a USB (Universal Serial Bus) dongle, a narrowband (NB) UE, a low-power UE, a reduced capacity (RedCap) UE, a high-power UE, or the like.

Fig. 1 illustrates exemplary structures of the wireless communication network. In particular, Fig. 1 shows UEs 10 in a cell 110 which is served by an access node 100 of the wireless communication network. Here, it is noted that the wireless communication network may actually include a plurality of access nodes 100 that may serve a number of cells within the coverage area of the wireless communication network. The access node 100 may for example correspond to an eNB of the LTE technology or to a gNB of the NR technology.

The access nodes 100 may be regarded as being part of an RAN of the wireless communication network. Further, Fig. 1 schematically illustrates a CN (Core Network) 210 of the wireless communication network. In Fig. 1 , the CN 210 is illustrated as including a GW (gateway) 220 and one or more control node(s) 240. The GW 220 may be responsible for handling user plane data traffic of the UEs 10, e.g., by forwarding user plane data traffic from a UE 10 to a network destination or by forwarding user plane data traffic from a network source to a UE 10. Here, the network destination may correspond to another UE 10, to an internal node of the wireless communication network, or to an external node which is connected to the wireless communication network. Similarly, the network source may correspond to another UE 10, to an internal node of the wireless communication network, or to an external node which is connected to the wireless communication network. The GW 220 may for example correspond to a UPF (User Plane Function) of the 5G Core (EGC) or to an SGW (Serving Gateway) or PGW (Packet Data Gateway) of the 4G EPC (Evolved Packet Core). The control node(s) 240 may for example be used for controlling the user data traffic, e.g., by providing control data to the access node 100, the GW 220, and/or to the UE 10.

As illustrated by double-headed arrows, the access nodes 100 may send DL wireless transmissions to at least some of the UEs 10, and some of the UEs 10 may send UL wireless transmissions to the access node 100. The DL transmissions and UL transmissions may be used to provide various kinds of services to the UEs 10, e.g., a voice service, a multimedia service, or some other data service. Such services may be hosted in the CN 210, e.g., by a corresponding network node. By way of example, Fig. 1 illustrates an application service platform 250 provided in the CN 210. Further, such services may be hosted externally, e.g., by an AF (application function) connected to the CN 210. By way of example, Fig. 1 illustrates one or more application servers 300 connected to the CN 210. The application server(s) 300 could for example connect through the Internet or some other wide area communication network to the CN 210. The application service platform 250 may be based on a server or a cloud computing system and be hosted by one or more host computers. Similarly, the application server(s) 300 may be based on a server or a cloud computing system and be hosted by one or more host computers. The application server(s) 300 may include or be associated with one or more AFs that enable interaction with the CN 210 to provide one or more services to the UEs 10, corresponding to one or more applications. These services or applications may generate the user data traffic conveyed by the DL transmissions and/or the UL transmissions. Accordingly, the application server(s) 300 may include or correspond to the above-mentioned network destination and/or network source for the user data traffic. In the respective UE 10, such service may be based on an application (or shortly “app”) which is executed on the UE 10. Such application may be pre-installed or installed by the user. Such application may generate at least a part of the user plane data traffic between the UEs 10 and the access node 100.

Fig. 2 schematically illustrates multi-antenna transmission between an access node 100, e.g., the access node 100 of Fig. 1 , and a UE 10, e.g., one of the UEs 10 of Fig. 1. As illustrated in Fig. 2, the access node 100 is equipped with a plurality of antenna elements 111 , 112, 113, 114, 115. As further illustrated, also the UE 10 is equipped with a plurality of antenna elements 11 , 12. It is noted that the illustrated numbers of the antenna elements of the access node 100 and of the UE 10 are exemplary and that other numbers, in particular higher numbers, could be utilized as well. The antenna elements 111 , 112, 113, 114, 115 and 11 , 12 may be used for beamformed wireless transmissions. This may involve subjecting antenna signals of the antenna elements to weighting and/or phase shifting, in particular by applying a precoding matrix to the antenna signals. The precoding matrix may in turn be calculated based on an estimate of a channel matrix of the wireless channel, e.g., by using a codebook. For example, for DL wireless transmissions from the access node 100 to the UE 10, the UE 10 may utilize RS received from the access node 100 to estimate the DL wireless channel from the access node 100 to the UE 10, and then report corresponding CSI to the access node 100. The access node 100 may then set the precoding matrix of the antenna signals of antennas 111 , 112, 113, 114, 115 based on the estimate of the DL wireless channel. For UL wireless transmissions from the UE 10 to the access node 100, the UE 10 may utilize RS received from the access node 100 to estimate the UL wireless channel from the access node 100 to the UE 10, assuming channel reciprocity, and then set the precoding matrix of the antenna signals of antennas 11 , 12 based on the estimate of the UL wireless channel.

In accordance with the illustrated concepts, beamformed wireless transmissions may be used for at least some of the UEs 10 in Fig. 1 , and the illustrated concepts may support such beamformed UL wireless transmissions by an enhanced channel estimation process for multiple frequencies. Specifically, the mapping function may be used to derive one or more spatial characteristics of RS on one frequency from corresponding spatial characteristics on another frequency. For example, if the access node 100 sends first reference signals (RS1) on a first frequency (f1) and second reference signals (RS2) on a second frequency (f2), the UE 10 may apply the mapping function to derive QCL of RS2 from QCL of RS1. Similarly, the UE 10 may apply the mapping function to derive TCI state of RS2 from TCI state of RS1. As a result, signaling related to QCL and/or TCI state may be significantly reduced in scenarios where the wireless communication between the access node 100 and the UE 10 is based on multiple frequencies, e.g., if a wireless link between the UE 10 and the access node 100 is based on aggregation or on usage of multiple BWPs, e.g., by BWP switching.

In the following, the illustrated concepts will be further explained by explaining the mapping function in examples involving usage of a first frequency (f1) and a second frequency (f2). It is however noted that extensions of the mapping function to higher number of frequencies. Further, as indicated above, each frequency, i.e. , also f1 and f2, may correspond to different carrier frequencies, associated with different cells, e.g., a primary cell (PCell) and one or more secondary cells (SCells), or may correspond to different BWPs of the same carrier, associated with the same Cell, e.g., the same PCell. In the illustrated examples, the mapping function maps the considered spatial characteristic on f2, which is in the following denoted as SC(f2) to the spatial characteristic on f 1 , which is in the following denoted as SC(f1). This may be expressed as:

where, MF denotes the mapping function. As indicated, the mapping function depends on f1 and f2.

As mentioned above, the spatial characteristic may correspond to QCL of the RS or to TCI state. However, other types of spatial characteristic could be considered as well, e.g., an antenna array pattern.

In an example, the mapping function can compensate for beam squint which is typically observed appear for large differences between f1 and f2. Here, the mapping function could map beam direction 01 of a RS at f1 to beam direction 0f2 of the RS at f2, e.g., according to:

In some cases, the mapping function may also be composed of multiple subfunction. For example, such different subfunctions could be defined per range of difference between f1 and f2. This may for example be expressed as follows:

where fTH_1 , fTH_2, and fTH3 denote limits of the different ranges of the difference between f1 and f2.

According to a further example, the mapping function maps RS indices of RS at f2 to RS indices at f1. This is done in such a way that the RS index of an RS at f1 is mapped to an RS index of an RS with similar spatial characteristic, e.g., beam direction, at f2 Fig. 3 schematically illustrates a corresponding example. In Fig. 3, spatial characteristics of RS, e.g., SSB or CSI- RS, at f1 are illustrated by solid lines, and spatial characteristics of the RS at f2 are illustrated by broken lines. At frequency f 1 , RS index a to RS index a+4 represent different spatial characteristics of the RS, and at f2, RS index b to RS index b+2 represent different spatial characteristics of the RS. As can be seen from the illustration, the spatial characteristic of RS indices a and a+1 at f1 may be regarded as similar to the spatial characteristic of RS index b at f2, the spatial characteristic of RS index a+2 at f1 may be regarded as similar to the spatial characteristic of RS index b+1 at f2, and the spatial characteristic of RS indices a+3 and a+4 at f1 may be regarded as similar to the spatial characteristic of RS index b+2 at f2. Accordingly, the mapping function could map RS indices a and a+1 at f1 to RS index b at f2, RS index a+2 at f1 to RS index b+1 at f2, and RS indices a+3 and a+4 at f1 to RS index b+2 at f2. Fig. 4 illustrates such mapping in a table format.

The RS indices may also be used to define higher-level spatial characteristics, such as QCL and/or TCI state. Based on the mapping of the RS indices at f1 to the RS indices at f2, the mapping function may thus also translate QCL at f1 to QCL at f2. Similarly, the mapping function may thus also translate TCI state at f1 to QCL at f2.

It is noted that in the above example an offset between the indices, e.g., an offset between a and b, may depend of the frequencies f1 and f2, specifically on a difference of f1 and f2. Further, the RS indices may also correspond to certain spatial ranges. For example, the range of RS index a to RS index a+4 at f1 could correspond to a full beam sweeping range of the access node 100 or of the UE 10, or to a specific subset of the beam sweeping range of the access node 100 or of the UE 10. Similarly, the range of RS index b to RS index b+2 at f2 could correspond to a full beam sweeping range of the access node 100 or of the UE 10, or to a specific subset of the beam sweeping range of the access node 100 or of the UE 10.

It is also noted that the mapping and table format illustrated in Fig. 4 is merely an example and may vary depending on the scenario considered in practice. For example, the number of RS indices may depend on UE and network configuration.

The mapping function may be defined in different ways with respect to the interpretation of two RS indices being mapped. In one example, the spatial direction corresponding to RS index a+1 at f1 is between the spatial directions of RS index b and RS index b+1 at f2. From a spatial domain filtering perspective this may indicate that if RS index a+1 at f1 is adopted in QCL or TCI state for f 1 , then the adopted beam at f2 can correspond to RS index b, without requiring any acknowledged information of measurements on reference signals at f2 and without requiring an explicit QCL or TCI state configuration for f2.

The above example of an RS index based mapping function can be generalized as illustrated in Fig. 5. As illustrates, the mapping function may be based on defining one or more sets of indices for f 1 (in the figure denoted as lndices_1 , lndices_2, and lndices_3) and one or more sets of indices for f2 (in the figure denoted as lndices_4, lndices_5, and lndices_6), with each set of indices including one or more RS indices. The mapping function may then map a set of indices for f2 to a set of indices for f1. In a further example, the mapping function could be implemented by basing the assignment of indices, e.g., RS indices or beam indices, on direction of the actually formed beam. Accordingly, the same index could be assigned to a beam or RS having a certain direction at f1 and to a beam or RS having the same direction at f2. This may involve selecting beams or RS with the same direction from a given spatial signal pattern and/or adjusting the spatial signal pattern at f1 and/or f2 to generate the beam or RS having the required direction.

In some scenarios, the mapping function can be pre-defined, e.g., as an explicit mapping or based on rules allowing to derive the mapping depending on a set of input variables. In further scenarios, the mapping function could also be obtained by training an ML (machine learning) model based on observed beam relationships between f1 and f2. For example, such ML model and its training could be based on supervised learning or on reinforcement learning.

In an exemplary implementation, the mapping function could be obtained by interaction of the access node 100 and the UE 10, e.g., in the following manner:

The access node configures two sets of RS, one on f1 and one on f2. This may be accomplished by using RRC (Radio Resource Control Signaling), e.g., using lEs (Information Elements) denoted as “CSI-MeasConfig” and “CSI-ResourceConfig”. The UE 10 may then evaluate and detect RS on f1 that have signal strength higher than a threshold and RS on f2 that have signal strengths that are higher than a threshold. In one variant, the UE 10 then determines the mapping function based on the measurement result on the detected RS, e.g., in the form of one or more of the columns in the table of Fig. 4 or in the table of Fig. 5. Then, the UE 10 may indicate the mapping function or information on validity of the mapping function to the access node 100. In another variant, the UE 10 reports measurement results on the detected RS to the access node 100. This may be accomplished in accordance with a reporting configuration defined by RRC signaling, e.g., using an IE denoted as “CSI-ReportConfig”. Based on the reported measurement results, the access node 100 may then determine the mapping function with respect to measurement result, e.g., in the form of one or more of the columns in the table of Fig. 4 or in the table of Fig. 5. The access node 100 may then signal the mapping function to the UE 10, e.g., using RRC signaling, MAC (Medium Access Control) CE (Control Element) signaling, or physical layer signaling, e.g., by DCI (Downlink Control Information). When the mapping function is available at the UE 10, e.g., after being determined locally at the UE 10 or after being signaled by the access node 100, the access node 100 may signal enablement of the mapping function to the UE 10, using RRC signaling, MAC CE signaling, or physical layer signaling, e.g., by DCI. In some cases, beam initiation or adjustment on f1 is not required. Rather, the UE 10 or access node 100 may generate the mapping function based on pre-calibration in factory or other type of pre-configuration. The UE 10 may then expect and adopts the beam on f2 based on looking up mapping function if a corresponding beam on f1 is determined and acquired by the UE 10.

It is noted that some degree of inaccuracy or vagueness of the mapping function may be acceptable. For example, in a situation like illustrated in Fig. 3., it can occur that it is only possible to map RS index b at f2 and RS index b+1 at f2 to RS index a+1 at f 1 , without being able to decide which one among RS index b and RS index b+1 at f2 shall be mapped to RS index a+1 at f1. In such case, the mapping function could still provide significant benefits in simplifying the channel estimation process, by utilizing only the partial mapping for the RS index b and RS index b+1 at f2 to RS index a+1 at f1. In practice, such usage of such partial mapping may also be utilized in the form that, if the mapping is undecided between two RS on f2, e.g., between RS index b or RS index b+1 , one of these RS, e.g., RS index b, could be adopted as serving beam and the other RS, RS index b+1 , configured as candidate beam. As a result, even if the adopted serving beam turns out to be not the best beam, resulting in beam quality being lower than a threshold or triggering of beam failure detection, then the other beam, e.g., corresponding to RS index b+1 , can be easily used as a replacement, e.g., by a beam recovery procedure.

In some scenarios, validity of the mapping function may depend on certain conditions or requirements. For example, the access node 100 may need to meet co-location requirements on f1 and f2. For example, the device infrastructure serving f1 and f2 may need to be colocated. This requirement is for example met when f1 and f2 are served using the same device infrastructure. In cases where f1 and f2 are served using at least in part different infrastructure, e.g., different antennas, it may be required that the propagation delay from the different infrastructure to the UE 10 is below a threshold.

Fig. 6 illustrates exemplary processes in accordance with the illustrated concepts. In the illustrated example, the processes involve an access node 100, e.g., corresponding to the above-mentioned access node 100, and a UE 10, e.g., corresponding to any of the above- mentioned UEs 10.

In a variant, the access node 100 determines the mapping function, as indicated by block 601. In this variant, the determination of the mapping function may be based on sending RS to the UE 10 and receiving reports of measurement results on the RS from the UE 10, e.g., as explained above. Having determined the mapping function, the access node 100 sends a mapping function indication 602 to the UE 10, thereby signaling the determined mapping function to the UE 10. The mapping function indication 602 may be conveyed by RRC signaling, MAC CE signaling, or physical layer signaling, e.g., by DCI, or any combination of such signaling types.

In another variant, the UE 10 determines the mapping function, as indicated by block 603. In this variant, the determination of the mapping function may be based on receiving RS from the access node 100 and evaluation of measurement results on the RS at the UE 10, e.g., as explained above. Having determined the mapping function, the UE 10 may send a mapping function indication 604 to the access node 100, thereby signaling the determined mapping function to the access node 100. The mapping function indication 604 may be conveyed by RRC signaling, MAC CE signaling, or physical layer signaling, e.g., by UCI (uplink control information), or any combination of such signaling types.

It is noted that in some scenarios the above two variants of determination of the mapping function by the access node 100 and determination of the mapping function by the UE 10 could be combined, e.g., by determining the mapping function in a collaborative manner. For example, the mapping function could be determined in a multi-stage process, with one stage being implemented at the UE 10 and another stage being implemented at the access node 100.

When the mapping function is determined and available at the UE 10, the access node 100 may enable usage of the mapping function by sending a mapping function enablement indication 605 to the UE 10. The mapping function enablement indication 605 may be conveyed by RRC signaling, MAC CE signaling, or physical layer signaling, e.g., by DCI, or any combination of such signaling types.

Subsequently, the access node 100 sends reference signals 606 to the UE 10. The UE 10 evaluates the reference signals by utilizing the mapping function. As explained above, the mapping function may for example be used to perform a beam sweeping process in a shortened and more resource efficient manner. In some scenarios, the UE 10 may also send a CSI report 607 based on the reference signals 606 to the access node 100.

Then, the information acquired from the reference signals 606 may be used for performing beamformed transmissions 608, 609. For example, the UE 10 may utilize CSI estimated based on the reference signals 606 for performing beamformed UL transmissions to the access node 100, or the access node 100 may utilize CSI reported by the UE 10, e.g., in CSI report 607, for performing beamformed UL transmissions to the UE 10.

Fig. 7 shows a flowchart for illustrating a method, which may be utilized for implementing the illustrated concepts. The method of Fig. 7 may be used for implementing the illustrated concepts in a wireless device. For example, such wireless device may correspond to any of the above-mentioned UEs 10.

If a processor-based implementation of the wireless device is used, at least some of the steps of the method of Fig. 7 may be performed and/or controlled by one or more processors of the wireless device. Such wireless device may also include a memory storing program code for implementing at least some of the below described functionalities or steps of the method of Fig. 7.

At step 710, the wireless device may determine a mapping function. In some scenarios, this may involve that the mapping function is at least in part configured by signaling from the wireless communication network, such as by the above-mentioned mapping function indication 602. This signaling may involve RRC signaling, MAC CE signaling, and/or physical layer signaling. In some scenarios, the signaling from the wireless communication network could also indicate one or more rules to be applied by the wireless device for determining the mapping function. In some scenarios, the mapping function can be at least in part preconfigured in the wireless device. In some scenarios, the mapping function can be at least in part learnt by training during operation of the wireless device, e.g., by training of an ML model. Having determined the mapping function, the wireless device may signal the mapping to a node of the wireless communication network, such as by the above-mentioned mapping function indication 604. This signaling may involve RRC signaling, MAC CE signaling, and/or physical layer signaling.

At step 720, the wireless device determines a first spatial characteristic of first reference signals on a first frequency. In some scenarios, the first spatial characteristic may include an indication of a spatial beam to be used for measurements on at least one of the first reference signals, e.g., in the form of a first TCI state. In some scenarios, the first spatial characteristic may include an indication that, for at least one first antenna port of the wireless device, measurements of at least one parameter performed on at least one of the first reference signals may be used for estimating the at least one parameter for at least one second antenna port of the wireless device, e.g., in the form of a first QCL mapping. In some scenarios, the first spatial characteristic may include a first set of one or more indices respectively identifying a corresponding one of the first reference signals.

In some scenarios, the wireless device may determine the first spatial characteristic based on signaling from a node of the wireless communication network, e.g., based on signaling of QCL or TCI state. Alternatively or in addition, the wireless device may determine the first spatial characteristic based on measurements on the first reference signals.

In some scenarios, the first frequency may correspond to a primary cell serving the wireless device, e.g., to a serving PCell. Further, the first frequency may correspond to a first BWP of a carrier serving the wireless device.

At step 730, the wireless device determines a second spatial characteristic of second reference signals on a second frequency. This is accomplished from the at least one spatial characteristic of the first reference signals determined at step 720 and based on a mapping function, e.g., as determined at step 710. The mapping function depends on the first frequency and the second frequency and maps the at least one first spatial characteristic to the at least one second spatial characteristic. In some scenarios the mapping function may also depend on a difference between the first frequency and the second frequency. In this case, the mapping function could also be piece-wise defined at least in a first range of the difference between the first frequency and the second frequency and a second range of the difference between the first frequency and the second frequency, e.g., as explained in connection with relations (3a) and (3b). In some scenarios, the mapping function may also depend on a first frequency range in which the first frequency is located and/or on a second frequency range in which the second frequency is located.

If the first spatial characteristic is an indication of a spatial beam to be used for measurements on at least one of the first reference signals, the second spatial characteristic may be an indication of a spatial beam to be used for measurements on the at least one of the second reference signals. If the first spatial characteristic is a first TCI state, the second spatial characteristic may be a second TCI state. The mapping function may thus map the first TCI state to the second TCI state. If the first spatial characteristic is an indication that, for at least one first antenna port of the wireless device, measurements of at least one parameter performed on at least one of the first reference signals may be used for estimating the at least one parameter for at least one second antenna port of the wireless device, the second spatial characteristic may be an indication that, for at least one first antenna port of the wireless device, measurements of at least one parameter performed on at least one of the second reference signals may be used for estimating the at least one parameter for at least one second antenna port of the wireless device. If the first spatial characteristic is a first QCL mapping, the second spatial characteristic may be a second QCL mapping. The mapping function may thus map the first QCL mapping to the second QCL mapping. If the first spatial characteristic includes a first set of one or more indices respectively identifying a corresponding one of the first reference signals, and the second spatial characteristic may include a second set of one or more indices respectively identifying a corresponding one of the second reference signals. The mapping function may then map the first set of indices to the second set of indices, e.g., as explained in connection with Figs. 4 and 5.

If the first frequency corresponds to a primary cell serving the wireless device, e.g., to a serving PCell, the second frequency may correspond to a secondary cell of the wireless device, e.g., to an SCell. If the first frequency corresponds to a first BWP of a carrier serving the wireless device, the second frequency may correspond to a second BWP of the carrier.

At step 740, the wireless device may receive reference signals. For example, the wireless device may receive reference signals on the second frequency and utilize the second spatial characteristic in the reception process and/or for evaluation of the received reference signals, e.g., for setting spatial filters.

At step 750, the wireless device may control beamforming of wireless transmissions on the second frequency. This may be based on the second spatial characteristic determined at step 730. For example, the beamforming could be controlled based on CSI evaluated from the reference signals received at step 740.

Fig. 8 shows a flowchart for illustrating a further method, which may be utilized for implementing the illustrated concepts. The method of Fig. 8 may be used for implementing the illustrated concepts in a node of a wireless communication network. For example, such node may correspond to an access node, such as the above-mentioned access node 100. The node may for example be an eNB or a gNB.

If a processor-based implementation of the node is used, at least some of the steps of the method of Fig. 8 may be performed and/or controlled by one or more processors of the node. Such wireless device may also include a memory storing program code for implementing at least some of the below described functionalities or steps of the method of Fig. 8. At step 810, the node may configure a wireless device, e.g., a UE, such as one of the above- mentioned UEs 10, with a mapping function. This may involve that the node first determines the mapping function. In some scenarios, this may involve that the node receives signaling indicating the mapping function from the wireless device, such as by the above-mentioned mapping function indication 604. This signaling may involve RRC signaling, MAC CE signaling, and/or physical layer signaling. In some scenarios, the mapping function can be at least in part pre-configured in the node. In some scenarios, the determination of the mapping function may involve that the mapping function is at least in part learnt by training during operation of the wireless device, e.g., by training of an ML model.

The mapping function enables the wireless device to determine, from a first spatial characteristic of first reference signals on a first frequency, a second spatial characteristic of second reference signals on a second frequency. The mapping function depends on the first frequency and the second frequency and maps the at least one first spatial characteristic to the at least one second spatial characteristic.

Configuring the wireless device with the mapping function may involve sending signaling indicating the mapping function to the wireless device, such as by the above-mentioned mapping function indication 602. This signaling may involve RRC signaling, MAC CE signaling, and/or physical layer signaling. In some scenarios, the signaling to the wireless device could also indicate one or more rules to be applied by the wireless device for determining the mapping function.

In some scenarios, the first spatial characteristic may include an indication of a spatial beam to be used for measurements on at least one of the first reference signals, e.g., in the form of a first TCI state. In some scenarios, the first spatial characteristic may include an indication that, for at least one first antenna port of the wireless device, measurements of at least one parameter performed on at least one of the first reference signals may be used for estimating the at least one parameter for at least one second antenna port of the wireless device, e.g., in the form of a first QCL mapping. In some scenarios, the first spatial characteristic may include a first set of one or more indices respectively identifying a corresponding one of the first reference signals.

In some scenarios, the node may signal the first spatial characteristic to the wireless device, e.g., based on signaling of QCL or TCI state. In some scenarios, the first frequency may correspond to a primary cell serving the wireless device, e.g., to a serving PCell. Further, the first frequency may correspond to a first BWP of a carrier serving the wireless device. If the first spatial characteristic is an indication of a spatial beam to be used for measurements on at least one of the first reference signals, the second spatial characteristic may be an indication of a spatial beam to be used for measurements on the at least one of the second reference signals. If the first spatial characteristic is a first TCI state, the second spatial characteristic may be a second TCI state. The mapping function may thus map the first TCI state to the second TCI state. If the first spatial characteristic is an indication that, for at least one first antenna port of the wireless device, measurements of at least one parameter performed on at least one of the first reference signals may be used for estimating the at least one parameter for at least one second antenna port of the wireless device, the second spatial characteristic may be an indication that, for at least one first antenna port of the wireless device, measurements of at least one parameter performed on at least one of the second reference signals may be used for estimating the at least one parameter for at least one second antenna port of the wireless device. If the first spatial characteristic is a first QCL mapping, the second spatial characteristic may be a second QCL mapping. The mapping function may thus map the first QCL mapping to the second QCL mapping. If the first spatial characteristic includes a first set of one or more indices respectively identifying a corresponding one of the first reference signals, and the second spatial characteristic may include a second set of one or more indices respectively identifying a corresponding one of the second reference signals. The mapping function may then map the first set of indices to the second set of indices, e.g., as explained in connection with Figs. 4 and 5.

At step 820, the node may send reference signals. For example, the node may send reference signals on the second frequency, so that the wireless device can utilize the second spatial characteristic, determined from the mapping function, in the reception process and/or for evaluation of the received reference signals, e.g., for setting spatial filters.

At step 830, the node may control beamforming of wireless transmissions on the second frequency. This may be based on the second spatial characteristic determined based on the mapping function. For example, the beamforming could be controlled based on CSI reports evaluated from the reference signals sent at step 820 utilizing the second spatial characteristic determined from the mapping function. It is noted that the methods of Figs. 7 and 8 could also be combined, e.g., in a system including at least one wireless device and a node operating according to the method of Fig. 8 to configure the at least one wireless device with the mapping function. The at least one wireless device could then operate according to the method of Fig. 7.

Fig. 9 illustrates a processor-based implementation of a wireless device 900 for operation in a wireless communication network, which may be used for implementing the above-described concepts. More specifically, the structures of the wireless device 900 may be used to implement the above-described functionalities of a UE, such as any of the above-mentioned UEs 10.

As illustrated, the wireless device 900 may include wireless interface 910, which may be used for wireless communication with one or more nodes of the wireless communication network. The wireless interface 910 could for example be based on the llu interface of the NR technology or the llu interface of the LTE technology.

Further, the wireless device 900 may include one or more processors 950 coupled to the interface 910 and a memory 960 coupled to the processor(s) 950. By way of example, the interface 910, the processor(s) 950, and the memory 960 could be coupled by one or more internal bus systems of the wireless device 900. The memory 960 may include a read-only memory (ROM), e.g., a flash ROM, a random-access memory (RAM), e.g., a dynamic RAM (DRAM) or static RAM (SRAM), a mass storage, e.g., a hard disk or solid state disk, or the like. As illustrated, the memory 960 may include software 970 and/or firmware 980. The memory 960 may include suitably configured program code to be executed by the processor(s) 950 so as to implement or configure the above-described functionalities for controlling wireless communication, such as explained in connection with Fig. 7.

It is to be understood that the structures as illustrated in Fig. 9 are merely schematic and that the wireless device 900 may actually include further components which, for the sake of clarity, have not been illustrated, e.g., further interfaces or further processors. Also, it is to be understood that the memory 960 may include further program code for implementing known functionalities of a UE in a 3GPP system. According to some embodiments, also a computer program may be provided for implementing functionalities of the wireless device 900, e.g., in the form of a physical medium storing the program code and/or other data to be stored in the memory 960 or by making the program code available for download or by streaming. Fig. 10 illustrates a processor-based implementation of a network node 1000 for operation in a wireless communication network, which may be used for implementing the above-described concepts. More specifically, the structures of the network node 1000 may be used to implement the above-described functionalities of an access node, such as the above-mentioned access node 100. The network node 1000 may for example be an eNB or a gNB.

As illustrated, the network node 1000 may include wireless interface 1010, which may be used for wireless communication with one or more wireless devices, such as the above-mentioned UEs 10. The wireless interface 1010 could for example be based on the llu interface of the NR technology or the llu interface of the LTE technology. Further, the network node 1000 may include a network interface 1020, which may be used for communication with other network nodes.

Further, the network node 1000 may include one or more processors 1050 coupled to the interfaces 1010, 1020 and a memory 1060 coupled to the processor(s) 1050. By way of example, the interfaces 1010, 1020, the processor(s) 1050, and the memory 1060 could be coupled by one or more internal bus systems of the network node 1000. The memory 1060 may include a ROM, e.g., a flash ROM, a RAM, e.g., a DRAM or SRAM, a mass storage, e.g., a hard disk or solid state disk, or the like. As illustrated, the memory 1060 may include software 1070 and/or firmware 1080. The memory 1060 may include suitably configured program code to be executed by the processor(s) 1050 so as to implement or configure the above-described functionalities for controlling wireless communication, such as explained in connection with Fig. 8.

It is to be understood that the structures as illustrated in Fig. 10 are merely schematic and that the network node 1000 may actually include further components which, for the sake of clarity, have not been illustrated, e.g., further interfaces or further processors. Also, it is to be understood that the memory 1060 may include further program code for implementing known functionalities of an eNB or a gNB in a 3GPP system. According to some embodiments, also a computer program may be provided for implementing functionalities of the network node 1000, e.g., in the form of a physical medium storing the program code and/or other data to be stored in the memory 1060 or by making the program code available for download or by streaming.

Fig. 11 shows a communication diagram of a host 1102 communicating via a network node 1104 with a UE 1106 over a partially wireless connection in accordance with some embodiments. Example implementations, in accordance with various embodiments, of the UE (such as one of the above-mentioned UEs 10), network node (such as one of the above- mentioned access nodes 100), and host (such as the above-mentioned service platform 250 or application server(s) 300) will now be described with reference to Fig. 11 .

Embodiments of host 1102 include hardware, such as a communication interface, processing circuitry, and memory. The host 1102 also includes software, which is stored in or accessible by the host 1102 and executable by the processing circuitry. The software includes a host application that may be operable to provide a service to a remote user, such as the UE 1106 connecting via an over-the-top (OTT) connection 1150 extending between the UE 1106 and host 1102. In providing the service to the remote user, a host application may provide user data which is transmitted using the OTT connection 1150.

The network node 1104 includes hardware enabling it to communicate with the host 1102 and UE 1106. The connection 1160 may be direct or pass through a core network (like core network 210 of Fig. 1) and/or one or more other intermediate networks, such as one or more public, private, or hosted networks. For example, an intermediate network may be a backbone network or the Internet.

The UE 1106 includes hardware and software, which is stored in or accessible by UE 1106 and executable by the UE’s processing circuitry. The software includes a client application, such as a web browser or operator-specific “app” that may be operable to provide a service to a human or non-human user via UE 1106 with the support of the host 1102. In the host 1102, an executing host application may communicate with the executing client application via the OTT connection 1150 terminating at the UE 1106 and host 1102. In providing the service to the user, the UE's client application may receive request data from the host's host application and provide user data in response to the request data. The OTT connection 1150 may transfer both the request data and the user data. The UE's client application may interact with the user to generate the user data that it provides to the host application through the OTT connection 1150.

The OTT connection 1150 may extend via a connection 1160 between the host 1102 and the network node 1104 and via a wireless connection 1170 between the network node 1104 and the UE 1106 to provide the connection between the host 1102 and the UE 1106. The connection 1160 and wireless connection 1170, over which the OTT connection 1150 may be provided, have been drawn abstractly to illustrate the communication between the host 1102 and the UE 1106 via the network node 1104, without explicit reference to any intermediary devices and the precise routing of messages via these devices. As an example of transmitting data via the OTT connection 1150, in step 1108, the host 1102 provides user data, which may be performed by executing a host application. In some embodiments, the user data is associated with a particular human user interacting with the UE 1106. In other embodiments, the user data is associated with a UE 1106 that shares data with the host 1102 without explicit human interaction. In step 1110, the host 1102 initiates a transmission carrying the user data towards the UE 1106. The host 1102 may initiate the transmission responsive to a request transmitted by the UE 1106. The request may be caused by human interaction with the UE 1106 or by operation of the client application executing on the UE 1106. The transmission may pass via the network node 1104, in accordance with the teachings of the embodiments described throughout this disclosure. Accordingly, in step 1112, the network node 1104 transmits to the UE 1106 the user data that was carried in the transmission that the host 1102 initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In step 1114, the UE 1106 receives the user data carried in the transmission, which may be performed by a client application executed on the UE 1106 associated with the host application executed by the host 1102.

In some examples, the UE 1106 executes a client application which provides user data to the host 1102. The user data may be provided in reaction or response to the data received from the host 1102. Accordingly, in step 1116, the UE 1106 may provide user data, which may be performed by executing the client application. In providing the user data, the client application may further consider user input received from the user via an input/output interface of the UE 1106. Regardless of the specific manner in which the user data was provided, the UE 1106 initiates, in step 1118, transmission of the user data towards the host 1102 via the network node 1104. In step 1120, in accordance with the teachings of the embodiments described throughout this disclosure, the network node 1104 receives user data from the UE 1106 and initiates transmission of the received user data towards the host 1102. In step 1122, the host 1102 receives the user data carried in the transmission initiated by the UE 1106.

The illustrated concepts may help to improve performance of OTT services provided to the UE 1106 using the OTT connection 1150, in which the wireless connection 1170 forms a segment. More precisely, the teachings of the illustrated concepts may allow for providing the wireless connection 1170, and thus also the OTT connection, with improved efficiency with respect to usage of reference signals on different frequencies, e.g., for controlling beamforming. For example, beam sweeping processes may be shortened and thereby efficiency of resource usage improved. In an example scenario, factory status information may be collected and analyzed by the host 1102. As another example, the host 1102 may process audio and video data which may have been retrieved from a UE for use in creating maps. As another example, the host 1102 may collect and analyze real-time data to assist in controlling vehicle congestion (e.g., controlling traffic lights). As another example, the host 1102 may store surveillance video uploaded by a UE. As another example, the host 1102 may store or control access to media content such as video, audio, VR or AR which it can broadcast, multicast or unicast to UEs. As other examples, the host 1102 may be used for energy pricing, remote control of non-time critical electrical load to balance power generation needs, location services, presentation services (such as compiling diagrams etc. from data collected from remote devices), or any other function of collecting, retrieving, storing, analyzing and/or transmitting data.

In some examples, a measurement procedure may be provided for the purpose of monitoring data rate, latency, and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection 1150 between the host 1102 and UE 1106, in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring the OTT connection may be implemented in software and hardware of the host 1102 and/or UE 1106. In some embodiments, sensors (not shown) may be deployed in or in association with other devices through which the OTT connection 1150 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software may compute or estimate the monitored quantities. The reconfiguring of the OTT connection 1150 may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not directly alter the operation of the network node 1104. Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling that facilitates measurements of throughput, propagation times, latency and the like, by the host 1102. The measurements may be implemented in that software causes messages to be transmitted, in particular empty or ‘dummy’ messages, using the OTT connection 1150 while monitoring propagation times, errors, etc.

As can be seen, the concepts as described above may be used for enabling enhanced efficiency in the evaluation of RS. In this way, wireless communication may be improved in various ways. Specifically, usage of the mapping function may provide significant benefits to channel estimation and related procedures, in particular in view of beamformed transmissions. For example, RS beam sweeping may be shortened and the related occupancy of timefrequency resources reduced. Accordingly, in some scenarios the mapping function may be used reduce beam sweep range and/or beam sweeping time, e.g., by sweeping just a few beams on one frequency, e.g., f2, based on the mapping instead of sweeping a full set of beams covering the whole spatial directions provided by the access node 100 and/or UE 10, utilizing previously acquired spatial information on another frequency, e.g., f1. In a specific example, the mapping function can be used when activating an SCell, e.g., on f2, to abbreviate beam sweeping, provided that the UE 10 has already acquired spatial information on another frequency, e.g., from the serving PCell on f1.

It is to be understood that the examples and embodiments as explained above are merely illustrative and susceptible to various modifications. For example, the illustrated concepts may be applied to various numbers of frequencies and to various types of reference signals. Further, the illustrated concepts may be applied in connection with various kinds of wireless communication technologies. Moreover, it is to be understood that the above concepts may be implemented by using correspondingly designed software to be executed by one or more processors of an existing device or apparatus, or by using dedicated device hardware. Further, it should be noted that the illustrated apparatuses or devices may each be implemented as a single device or as a system of multiple interacting devices or modules.

Claims

1. A method of controlling wireless communication in a wireless communication network, the method comprising: a wireless device (10; 900; 1106) determining a first spatial characteristic of first reference signals on a first frequency; and the wireless device (10; 900; 1106) determining a second spatial characteristic of second reference signals on a second frequency from the at least one spatial characteristic of the first reference signals and based on a mapping function which depends on the first frequency and the second frequency and maps the at least one first spatial characteristic to the at least one second spatial characteristic.

2. The method according to claim 1 , wherein the mapping function depends on a difference between the first frequency and the second frequency.

3. The method according to claim 1 or 2, wherein the mapping function is piece-wise defined at least in a first range of the difference between the first frequency and the second frequency and a second range of the difference between the first frequency and the second frequency.

4. The method according to any one of the preceding claims, wherein the mapping function depends on a first frequency range in which the first frequency is located and/or on a second frequency range in which the second frequency is located.

5. The method according to any one of the preceding claims, wherein the first spatial characteristic comprises an indication of a spatial beam to be used for measurements on at least one of the first reference signals, and wherein the second spatial characteristic comprises an indication of a spatial beam to be used for measurements on the at least one of the second reference signals.

6. The method according to claim 5, wherein the first spatial characteristic comprises a first Transmission Configuration Indicator, TCI, state and the second spatial characteristic comprises a second TCI state.

7. The method according to any one of the preceding claims, wherein the first spatial characteristic comprises an indication that, for at least one first antenna port of the wireless device (10; 900; 1106), measurements of at least one parameter performed on at least one of the first reference signals may be used for estimating the at least one parameter for at least one second antenna port of the wireless device (10; 900; 1106), and wherein the second spatial characteristic comprises an indication that, for at least one first antenna port of the wireless device (10; 900; 1106), measurements of at least one parameter performed on at least one of the second reference signals may be used for estimating the at least one parameter for at least one second antenna port of the wireless device (10; 900; 1106).

8. The method according to claim 7, wherein the first spatial characteristic comprises a first Quasi Co-Location, QCL, mapping and the second spatial characteristic comprises a second QCL mapping.

9. The method according to any one of the preceding claims, wherein the first spatial characteristic comprises a first set of one or more indices respectively identifying a corresponding one of the first reference signals, and the second spatial characteristic comprises a second set of one or more indices respectively identifying a corresponding one of the second reference signals.

10. The method according to any one of the preceding claims, wherein the wireless device (10; 900; 1106) determines the first spatial characteristic based on signaling from a node (100; 1000; 1104) of the wireless communication network.

11. The method according to any one of the preceding claims, wherein the mapping function is at least in part configured by signaling from the wireless communication network.

12. The method according to any one of the preceding claims, wherein the mapping function is at least in part pre-configured in the wireless device (10; 900; 1106).

13. The method according to any one of the preceding claims, wherein the mapping function is at least in part learnt by training during operation of the wireless device (10; 900; 1106).

14. The method according to any one of the preceding claims, wherein the wireless device (10; 900; 1106) signals the mapping function to a node (100; 1000;

1104) of the wireless communication network.

15. The method according to any one of the preceding claims, comprising: based on the second spatial characteristic, the wireless device (10; 900; 1106) controlling beamforming of wireless transmissions on the second frequency.

16. The method according to any one of the preceding claims, wherein the first frequency corresponds to a primary cell serving the wireless device (10; 900; 1106) and the second frequency corresponds to a secondary cell of the wireless device (10; 900; 1106).

17. The method according to any one of claims 1 to 15, wherein the first frequency corresponds to a first bandwidth part of a carrier serving the wireless device (10; 900; 1106) and the second frequency corresponds to a second bandwidth part of the carrier.

18. A method of controlling wireless communication in a wireless communication network, the method comprising: configuring a wireless device (10; 900; 1106) with a mapping function, wherein the mapping function enables the wireless device (10; 900; 1106) to determine, from a first spatial characteristic of first reference signals on a first frequency, a second spatial characteristic of second reference signals on a second frequency, wherein the mapping function depends on the first frequency and the second frequency and maps the at least one first spatial characteristic to the at least one second spatial characteristic.

19. The method according to claim 18, wherein the mapping function depends on a difference between the first frequency and the second frequency.

20. The method according to claim 18 or 19, wherein the mapping function is piece-wise defined at least in a first range of the difference between the first frequency and the second frequency and a second range of the difference between the first frequency and the second frequency.

21 . The method according to any one of claims 18 to 20, wherein the mapping function depends on a first frequency range in which the first frequency is located and/or on a second frequency range in which the second frequency is located.

22. The method according to any one of claims 18 to 21 , wherein the first spatial characteristic comprises an indication of a spatial beam to be used for measurements on at least one of the first reference signals, and wherein the second spatial characteristic comprises an indication of a spatial beam to be used for measurements on the at least one of the second reference signals.

23. The method according to claim 22, wherein the first spatial characteristic comprises a first Transmission Configuration Indicator, TCI, state and the second spatial characteristic comprises a second TCI state.

24. The method according to any one of claims 18 to 23, wherein the first spatial characteristic comprises an indication that, for at least one first antenna port of the wireless device (10; 900; 1106), measurements of at least one parameter performed on at least one of the first reference signals may be used for estimating the at least one parameter for at least one second antenna port of the wireless device (10; 900; 1106), and wherein the second spatial characteristic comprises an indication that, for at least one first antenna port of the wireless device (10; 900; 1106), measurements of at least one parameter performed on at least one of the second reference signals may be used for estimating the at least one parameter for at least one second antenna port of the wireless device (10; 900; 1106).

25. The method according to claim 24, wherein the first spatial characteristic comprises a first Quasi Co-Location, QCL, mapping and the second spatial characteristic comprises a second QCL mapping.

26. The method according to any one of claims 18 to 25, wherein the first spatial characteristic comprises a first set of one or more indices respectively identifying a corresponding one of the first reference signals, and the second spatial characteristic comprises a second set of one or more indices respectively identifying a corresponding one of the second reference signals.

27. The method according to any one claims 18 to 26, wherein the first spatial characteristic is determined based on signaling from a node (100; 1000; 1104) of the wireless communication network.

28. The method according to any one of claims 18 to 27, comprising: configuring the mapping function by signaling from the wireless communication network to the wireless device (10; 900; 1106).

29. The method according to any one of claims 18 to 28, wherein the mapping function is at least in part learnt by training during operation of the wireless device (10; 900; 1106).

30. The method according to any one of claims 18 to 29, comprising: receiving signaling indicating the mapping function from the wireless device (10; 900; 1106).

31 . The method according to any one of claims 18 to 30, wherein the first frequency corresponds to a primary cell serving the wireless device (10; 900; 1106) and the second frequency corresponds to a secondary cell of the wireless device (10; 900; 1106).

32. The method according to any one of claims 18 to 30, wherein the first frequency corresponds to a first bandwidth part of a carrier serving the wireless device (10; 900; 1106) and the second frequency corresponds to a second bandwidth part of the carrier.

33. The method according to any one of claims 18 to 32, wherein at least a part of the method is performed by a node (100; 1000; 1104) of the wireless communication network.

34. A wireless device (10; 900; 1106) for operation in a wireless communication network, the wireless device (10; 900; 1106) being adapted to: determine a first spatial characteristic of first reference signals on a first frequency; and determine a second spatial characteristic for second reference signals on a second frequency from the at least one spatial characteristic of the first reference signals and a mapping function which depends on the first frequency and the second frequency and maps the at least one first spatial characteristic to the at least one second spatial characteristic.

35. The wireless device (10; 900; 1106) according to claim 34, wherein the wireless device (10; 900; 1106) is adapted to perform a method according to any one of claims 2 to 17.

36. The wireless device (10; 900; 1106) according to claim 34 or 35, comprising: at least one processor (950), and a memory (960) containing program code executable by the at least one processor (950), whereby execution of the program code by the at least one processor (950) causes the wireless device (10; 900; 1106) to perform a method according to any one claims 1 to 15.

37. A node (100; 1000; 1104) for a wireless communication network, the node (100; 1000; 1104) being adapted to: configure a wireless device (10; 900; 1106) with a mapping function, wherein the mapping function enables the wireless device (10; 900; 1106) to determine, from a first spatial characteristic of first reference signals on a first frequency, a second spatial characteristic of second reference signals on a second frequency, wherein the mapping function depends on the first frequency and the second frequency and maps the at least one first spatial characteristic to the at least one second spatial characteristic.

38. The node (100; 1000; 1104) according to claim 37, wherein the node (100; 1000; 1104) is configured to perform a method according to any one of claims 19 to 33.

39. The node (100; 1000; 1104) according to claim 37 or 38, comprising: at least one processor (1050), and a memory (1060) containing program code executable by the at least one processor (1050), whereby execution of the program code by the at least one processor (1050) causes the node (100; 1000; 1104) to perform a method according to any one of claims 18 to 33.

40. A computer program or computer program product comprising program code to be executed by at least one processor (950) of a wireless device (10; 900; 1106) operating in a wireless communication network, whereby execution of the program code causes the wireless device (10; 900; 1106) to perform a method according to any one of claims 1 to 17.

41. A computer program or computer program product comprising program code to be executed by at least one processor (1050) of a node (100; 1000; 1104) of a wireless communication network, whereby execution of the program code causes the node (100; 1000; 1104) to perform a method according to any one of claims 18 to 33.