Sounding reference signal panel switching for uplink beam management

Abstract

A method in a wireless device (120) for facilitating determining a beam to be used for communication with a network, the method comprising: indicating to the network capabilities to transmit from different panels (126), each panel representing a set of associated transmit antennas; receiving an uplink reference signal, UL RS, configuration from the network, the UL RS configuration indicating at least two UL RS resources to be transmitted from different panels; transmitting a plurality of UL RSs using different panels according to the UL RS configuration; and receiving an instruction to communicate with the network using one or more beams, each beam corresponding to one of the transmitted UL RSs.

Description

Technical Field

[0001] The present disclosure relates to the field of cellular communication between multi-antenna transceivers. In particular, it proposes a technique for determining a beam suitable for communication between a network node and a wireless device equipped with multiple antenna panels. Background Art

[0002] In the high frequency range (denoted as FR2 in 3GPP NR), multiple radio frequency (RF) beams can be used to transmit and receive signals at the gNB and user equipment (UE). For each downlink (DL) transmit (Tx) beam from the gNB, there is usually an associated best UE receive (Rx) beam for receiving signals from the DL beam. The DL Tx beam and the associated UE Rx beam form a beam pair; the DL beam and the associated UE Rx beam can be imagined as being connected by a conceptual beam pair link. The beam pair can be identified by the so-called beam management process in NR.

[0003] In deployments with multiple transmission points (TRPs) or distributed multiple-input multiple-output (D-MIMO) millimeter wave (mmWave) communications, it can be beneficial to use a sounding reference signal (SRS) based beam management procedure (specifically, an uplink (UL) beam management procedure) (rather than using a DL beam management procedure) to determine a suitable beam pair link between the network and the UE. In fact, for multiple TRPs or D-MIMO mmWave deployments, the beam management overhead of the DL beam management procedure will be very high because for each UE, there are multiple different beams from multiple different TRPs or access points (APs) that need to be frequently evaluated.

[0004] A higher level of difficulty is introduced if the UE has multiple panels, which are a group of related transmit antennas. More precisely, since signals can arrive at the UE and emanate from it in all different directions, it is beneficial to implement antennas at the UE that are able to produce omni-like coverage in addition to high-gain narrow beams. One way to increase omni-directional coverage at the UE is to install multiple panels with mutually different orientations, such as Figure 4 Many commercial UEs already have multiple panels at their disposal.

[0005] For UEs served by multiple TRPs or D-MIMO mmWave deployments, the use of an UL beam management procedure would appear promising, whereby a suitable beam pair link between any TRP / AP and the UE could be determined in a cost-efficient manner. However, the current UL beam management procedure in 3GPP NR lacks precision and is therefore difficult to apply in a meaningful way. To illustrate this, assume that the network will determine a suitable UE beam from a UE with multiple transmit antenna panels, and the network configures an SRS resource set using beam management as indicated. The UE receiving this configuration will most likely select multiple beams from a single one of the UE panels for evaluation. Currently, there is no way for the network to ensure that the UE performs the beam management procedure on multiple different UE panels. Since the best beam pair link may be different depending on the UE panel used during the UL beam management procedure, there is a considerable risk of selecting a suboptimal beam pair link when using the current NR UL beam management procedure.

[0006] Similarly, if the network wishes to evaluate the beam pair links from several different APs / TRPs to the UE, there may not be enough data to make a fully informed evaluation if the UE only probes the beams associated with one of the UE panels, since different APs / TRPs may be located in many different directions relative to the UE. Therefore, current NR UL beam management procedures are not well suited for multiple TRPs and D-MIMO deployments, and updates to the UL beam management procedures may be required in upcoming releases of 3GPP NR and in the future for 6G.

[0007] Beam prediction based on machine learning (ML) or artificial intelligence (AI) is a promising and busy area of ​​development, including ongoing research projects within 3GPP NR Release 18. To facilitate AI / ML based beam prediction, it is generally beneficial to accumulate as much information as possible (and as diverse information as possible) at the gNB. This includes information used to initially train the AI / ML model as well as information to be fed to the trained model to make decisions during operation. The current NR DL beam management procedures are of limited use for AI / ML based beam prediction due to several types of uncertainty in UE beam reporting. In fact, beam reporting depends heavily on the UE implementation, e.g., which UE panel to use, which UE beam to use for the selected UE panel (e.g., wide UE beam, narrow UE beam), how far in time the performance metrics reported in the beam report should be filtered, etc., and therefore the beam reporting is not controlled by the network. For similar reasons, the current NR UL beam management procedures are also not very useful for AI / ML based beam prediction, because it is uncertain which panel the UE is using, which beams the UE is using for the selected UE panel, etc. Therefore, the need to improve the current NR UL beam management process is further emphasized by the expectation of providing more information at the gNB to facilitate AI / ML based beam prediction. Summary of the invention

[0008] One object of the present disclosure is to provide an improved way of determining beams to be used for communications between a network node and a UE having multiple panels. Another object is to make more full use of the transmission capabilities of a multi-panel UE to achieve better performance communications. Specifically, this may include using a global optimal beam instead of only using the best beam that can be sent from one of the panels of the UE to achieve communications. Another object is to propose pre-agreed signaling that allows the network to control panel switching and / or panel selection at the UE. Yet another object is to facilitate the use of ML-based beam prediction, including by providing more diverse and / or more complete data for training and making decisions.

[0009] At least some of these objectives are achieved by the invention as defined by the independent claims.The dependent claims relate to advantageous embodiments of the invention.

[0010] In a first aspect of the present disclosure, a method for facilitating determining a beam to be used for communication with a network is provided by a wireless device. The method includes: receiving an uplink reference signal (UL RS) configuration from the network, the UL RS configuration indicating at least two UL RS resources to be transmitted from different panels, each panel representing a group of related transmit antennas; transmitting multiple UL RSs using the different panels according to the UL RS configuration; and receiving an instruction to communicate with the network using one or more beams, each beam corresponding to one of the transmitted UL RSs.

[0011] In a second aspect, a wireless device (or UE) adapted to facilitate determining a beam to be used for communication with a network is provided. The wireless device has a processing circuit configured to perform the method of the first aspect.

[0012] In a third aspect of the present disclosure, a method for determining a beam to be used for communication with a wireless device, performed by a network node, is provided. The method includes: sending an uplink reference signal (UL RS) configuration to the wireless device, the UL RS configuration indicating at least two UL RS resources to be sent from different panels, and each panel represents a group of related transmit antennas; receiving multiple UL RSs from the wireless device according to the UL RS configuration; selecting one or more UL RSs from the received UL RSs; and sending an instruction for causing the wireless device to communicate with the network using a beam corresponding to the selected one or more UL RSs.

[0013] In a fourth aspect, a network node (e.g., a base station such as a gNB) adapted to determine a beam to be used for communication with a wireless device is provided. The network node has a processing circuit configured to perform the method of the third aspect.

[0014] In a fifth aspect, a computer program is provided, the computer program comprising instructions for causing a computer (or specifically, a processing circuit within a wireless device or a network node) to perform the above method. The computer program may be stored or distributed on a data carrier. As used herein, a "data carrier" may be a temporary data carrier (e.g., a modulated electromagnetic wave or light wave) or a non-temporary data carrier. Non-temporary data carriers include volatile and non-volatile memories, such as permanent and non-permanent storage media of magnetic, optical or solid-state type. Still within the scope of a "data carrier", such a memory may be fixedly mounted or portable.

[0015] The first, second, third, fourth and fifth aspects can be used to introduce a panel switching scheme that can be adopted as part of a pre-agreed protocol (specifically, a protocol within a telecommunications standard). This simplifies the network's task of determining a suitable beam pair link for the UE based on the UL beam management process. Optionally, the beam pair link selection may also include selecting a suitable AP / TRP and UE panel. This will enhance the performance of a variety of different deployments (such as D-MIMO deployments, multi-TRP deployments, millimeter wave base stations, networks with AI / ML-based beam prediction, and deployments with "uplink only" nodes) at millimeter wave frequencies.

[0016] In some embodiments, the wireless device initially indicates the ability to transmit from different panels. Specifically, the UE may indicate the ability to transmit on different UL RS resources associated with (or transmitted from) at least two different UE panels during the beam management process. The network node may utilize knowledge of this capability when determining the UL RS configuration to be sent to the wireless device. In other words, the network does not need to rely on conservative assumptions about the UE's ability to optimize the UL RS configuration based on the UE's true structural and functional characteristics. Therefore, a more complete range of beam combinations can be explored and potentially used for communication.

[0017] In a first subset of embodiments common to all aspects of the present disclosure, the faceplate of the wireless device is not associated with an explicit faceplate ID.

[0018] In a second subset of embodiments common to the first and second aspects, an explicit panel ID is associated with each of those panels of the wireless device that are in use.

[0019] Generally, unless otherwise explicitly stated herein, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field. Unless otherwise explicitly stated, all references to "a / an / the element, device, component, device, step, etc." should be openly interpreted as referring to at least one instance of an element, device, component, device, step, etc. Unless explicitly stated otherwise, the steps of any method disclosed herein do not have to be strictly performed in the exact order disclosed. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Various aspects and embodiments will now be described with reference to the accompanying drawings, in which:

[0021] Figure 1 shows a wireless device located in the coverage area of ​​a single TRP base station and a multi-TRP base station;

[0022] Figure 2 Three example beam management processes are shown;

[0023] Figure 3 Uplink beam management is shown;

[0024] Figure 4 is a perspective view of a wireless device (UE) having four panels;

[0025] Figure 5 is a schematic diagram of a wireless device having three panels oriented in orthogonal directions to improve coverage, wherein the wireless device has at its disposal one baseband chain that can be connected to one of the panels at a time;

[0026] Figure 6 Depicts an example use case of the present disclosure, namely a communication setup including a wireless device having three panels, the wireless device operating in a multi-TRP / D-MIMO mmWave deployment; and

[0027] Figure 7 is a sequence diagram illustrating a method of determining a beam to be used for communication between a network node and a wireless device. DETAILED DESCRIPTION

[0028] Aspects of the present disclosure will now be described more fully below with reference to the accompanying drawings in which certain embodiments of the present invention are shown. However, these aspects may be expressed in a variety of different forms and should not be construed as limiting; rather, these embodiments are provided by way of example so that the present disclosure will be comprehensive and complete and fully convey the various aspects of the present invention to those skilled in the art. Throughout this specification, similar reference numerals refer to similar elements.

[0029] In general, the present disclosure proposes a signaling framework and capability reporting that supports a panel switching scheme in 5G / 6G so that the network can configure the UE to send SRS from all candidate UE panels using a beam covering the entire angular interval of the UE panel.

[0030] Figure 1 Concerning the first deployment, in which the wireless device 120 is located at a base station 110 having a single TRP 115 ( Figure 1 ) and a base station 110 having two TRPs 115a and 115b ( Figure 1 The base station 110 is configured as a network node in a radio access network within a cellular telecommunication system (eg, a 3GPP NR system).

[0031] The figure schematically illustrates the components of the wireless device 120 according to an embodiment in the form of a plurality of functional units. The processing circuit 122 is provided using any combination of one or more of a suitable central processing unit (CPU), a multiprocessor, a microcontroller, a digital signal processor (DSP), etc., capable of executing software instructions stored in a computer program product 124 (e.g., in the form of a storage medium 123). The processing circuit 122 may also be provided as at least one application specific integrated circuit (ASIC) or a field programmable gate array (FPGA). Specifically, the processing circuit 122 is configured to cause the wireless device 120 to perform a set of operations or steps, as described below with reference to Figure 7 For example, the storage medium 123 may store the set of operations, and the processing circuit 122 may be configured to retrieve the set of operations from the storage medium 123 so that the wireless device 120 performs the set of operations. The set of operations may be provided as an executable instruction set. Thus, the processing circuit 122 is arranged to perform a method for facilitating determining a beam to be used when the wireless device 120 communicates with the network node 110, which will be referred to as Figure 7 The storage medium 123 may also include a persistent storage device, which may be, for example, any single memory or any combination of magnetic memory, optical memory, solid-state memory, or even remotely mounted memory.

[0032] The wireless device 120 may also include a communication interface 125 for communicating with the network node 110. Thus, the communication interface 125 may include one or more transmitters and receivers including analog components and digital components. The processing circuit 122 controls the overall operation of the wireless device 120, for example, by sending data and control signals to the communication interface 125 and the storage medium 123, by receiving data and reports from the communication interface 125, and by obtaining data and instructions from the storage medium 123. Other components of the wireless device 120 and related functions are omitted so as not to obscure the concepts presented herein.

[0033] Figure 1 Components of the network node 110 according to an embodiment are also shown in the form of a plurality of functional units. Each network node 110 includes a front end unit 111 and a TRP 115. The front end unit 111 may be co-located with the TRP 115, or located at a location remote from the TRP 115. In the front end unit 111, a processing circuit 112 is provided using any combination of one or more of a suitable CPU, a multiprocessor, a microcontroller, a DSP, etc., capable of executing software instructions stored in a computer program product 114 (e.g., in the form of a storage medium 113). The processing circuit 112 may also be provided as at least one ASIC or FPGA. Specifically, the processing circuit 112 is configured to cause each network node 110 to perform a set of operations or steps, as described below with reference to Figure 7 For example, the storage medium 113 may store the set of operations, and the processing circuit 112 may be configured to retrieve the set of operations from the storage medium 113 so that the wireless device 110 performs the set of operations. The set of operations may be provided as an executable instruction set. Thus, the processing circuit 112 is arranged to perform a method for determining a beam to be used when the network node 110 communicates with the wireless device 120, which will be referred to as Figure 7 The storage medium 113 may also include a persistent memory, as exemplified above.

[0034] The network node 110 may also include a communication interface including a TRP 115 for communicating with the wireless device 120. Thus, the communication interface may include one or more transmitters and receivers including analog and digital components. The processing circuit 112 controls the overall operation of the network node 110, for example, by sending data and control signals to the communication interface (communication interface with the TRP 115) and the storage medium 113, by receiving data and reports from the communication interface, and by retrieving data and instructions from the storage medium 113. Other components of the network node 110 and related functions are omitted so as not to obscure the concepts presented herein.

[0035] SRS

[0036] Before describing the inventors' contributions, some background concepts will be reviewed. In 3GPP NR, Sounding Reference Signal (SRS) is used to provide Channel State Indication (CSI) to the gNB in ​​the UL. Uses of SRS include, for example, deriving appropriate transmit / receive beams and / or performing link adaptation (i.e., setting transmission rank and MCS). SRS can also be used to select DL (e.g., for PDSCH transmission) and UL (e.g., for PUSCH transmission) MIMO precoding.

[0037] In LTE and NR, SRS is configured via the Radio Resource Control (RRC) protocol, where parts of the configuration can be updated via MAC-CE signaling (to reduce latency). The configuration includes, for example, the SRS resource allocation (physical mapping and sequence to use) and the time domain behavior (aperiodic, semi-persistent, or periodic). For aperiodic SRS transmission, the RRC configuration does not activate SRS transmission from the UE, but a dynamic activation trigger is sent from the gNB in ​​the DL via DCI in the PDCCH, which instructs the UE to send SRS once at a predetermined time.

[0038] When configuring SRS transmission, the gNB configures a set of SRS resources and a set of SRS resource sets through the SRS-Config IE, where each SRS resource set contains one or more SRS resources.

[0039] SRS Configuration

[0040] In RRC, each SRS resource is configured with an SRS-Resource IE. See the ASN code in 3GPP TS 38.331 version 16.1.0, clause 6.3.2.

[0041] This version of the RRC protocol allows SRS resources to be configured with respect to one or more of the following:

[0042] -The number of SRS ports (1, 2 or 4), configured by the RRC parameter nrofSRS-Ports.

[0043] - Transmission comb (i.e., mapped to every 2nd or 4th subcarrier), configured by the RRC parameter transmissionComb, which includes:

[0044] o Specify the comb offset (i.e. which of the combs should be used), configured by the RRC parameter combOffset.

[0045] o Cyclic shift, configured by the RRC parameter cyclicShift, which configures the cyclic shift for the Zadoff-Chu sequence used for SRS (for multi-port SRS resources it is port specific). The use of cyclic shift increases the number of SRS resources that can be mapped to a comb (because SRS sequences are designed to be (almost) orthogonal under cyclic shift), but there is a limit on how many cyclic shifts can be used (8 for comb 2 and 12 for comb 4).

[0046] - The time domain position within a given time slot is configured by the RRC parameter resourceMapping, which includes:

[0047] o The time domain starting position, constrained to be one of the last 6 symbols (in NR Release 15) or any of the 14 symbols in a slot (in NR Release 16), configured by the RRC parameter startPosition.

[0048] o The number of symbols of the SRS resource (which can be set to 1, 2 or 4), is configured by the RRC parameter nrofSymbols.

[0049] o Repetition factor (which can be set to 1, 2 or 4), configured by the RRC parameter repetitionFactor. When the repetition factor is greater than 1, the same frequency resource is used multiple times between symbols, which is used to improve coverage because this allows the receiver to collect more energy.

[0050] - The sounding bandwidth, frequency domain position and offset, and frequency hopping pattern (i.e., which part of the transmission bandwidth the SRS resource occupies) of the SRS resource are set through the RRC parameters freqDomainPosition, freqDomainShift, and freqHopping parameters c-SRS, b-SRS, and b-hop. The minimum possible sounding bandwidth is 4 RB.

[0051] - The RRC parameter resourceType determines whether the SRS resource is sent periodically, aperiodically (single transmission triggered by DCI), or semi-persistently (same as the periodic case except that the start and stop of periodic transmission is controlled by MAC-CE signaling instead of RRC signaling).

[0052] -RRC parameter sequenceId specifies how to initialize the SRS sequence.

[0053] - The RRC parameter spatialRelationInfo configures the spatial relationship of the SRS beam with respect to another RS ​​(which can be another SRS, SSB or CSI-RS). If an SRS resource has a spatial relationship with another SRS resource, then the SRS resource should be transmitted using the same beam as the indicated SRS resource (i.e., virtualized).

[0054] In 3GPP NR Release 16, an additional (and optional) RRC parameter resourceMapping-r16 was introduced. If resourceMapping-r16 is signaled, the UE shall ignore the RRC parameter resourceMapping. The difference between resourceMapping-r16 and resourceMapping is that the SRS resource (for which the number of OFDM symbols and repetition factor are still limited to 4) can start in any of the 14 OFDM symbols in the slot configured by the RRC parameter startPosition-r16.

[0055] In addition, in RRC, the SRS resource set is configured with SRS-ResourceSet IE. See the ASN code in 3GPP TS 38.331 version 16.1.0, clause 6.3.2.

[0056] SRS resources will be sent as part of an SRS resource set, where all SRS resources in the same SRS resource set must share the same resource type. The SRS resource set can be configured with respect to one or more of the following:

[0057] - For aperiodic SRS, the slot offset is configured by the RRC parameter slotOffset and sets the delay from the reception of the PDCCH trigger to the start of SRS transmission.

[0058] - Resource usage (which is configured by the RRC parameter usage) sets constraints and assumptions on resource properties (see 3GPP TS 38.214 for further details). An SRS resource set can be configured with one of four different usages ("antennaSwitching", "codebook", "nonCodebook" and "beamManagement"), which are assigned to the parameter "usage".

[0059] o SRS resource sets configured with purpose “antennaSwitching” are used for reciprocity based DL precoding (i.e., used to sound the channel in UL so that the gNB can use reciprocity to set an appropriate DL precoder). The UE is expected to transmit one SRS port per UE antenna port.

[0060] o SRS resource sets configured with usage "codebook" are used for codebook-based UL transmissions (i.e., for detecting different UE antennas and helping the gNB determine / signal the UL precoder, transmission rank and MCS suitable for PUSCH transmissions). There are a maximum of two SRS resources in an SRS resource set with usage "codebook". However, how the SRS ports are mapped to the UE antenna ports depends on the UE implementation and is unknown to the gNB.

[0061] o The set of SRS resources configured with usage "nonCodebook" is used for NCB based UL transmissions. Specifically, the UE sends one SRS resource per candidate beam (UE determines the appropriate candidate beam based on CSI-RS measurements in DL, so reciprocity needs to be preserved). The gNB can then determine which UL beam the wireless device should apply for PUSCH transmission by indicating a subset of these SRS resources. One UL layer will be sent for each indicated SRS resource. Note that how the UE maps SRS ports to antenna ports is up to the UE implementation and is unknown to the gNB.

[0062] o SRS resource sets configured with purpose "beamManagement" (mainly used in frequency bands above 6 GHz, i.e. for FR2) are used to evaluate different UE beams emulating a beamforming array. The UE transmits one SRS resource per emulated beam and the gNB will perform RSRP measurements for each transmitted SRS resource and in this way determine the appropriate UE beam to report to the UE.

[0063] - The associated CSI-RS for each of the possible resource types (this configuration is applicable only for NCB based UL transmissions).

[0064] o For aperiodic SRS, the associated CSI-RS resource is set by the RRC parameter csi-RS.

[0065] o For semi-persistent / periodic SRS, the associated CSI-RS resource is set by the RRC parameter associatedCSI-RS.

[0066] - PC parameters (e.g., alpha and p0 (p-zero)) are used to set the SRS transmission power. SRS has its own UL PC scheme in NR (see 3GPP TS 38.213 for further details), which specifies how the UE should divide the available output power between two or more SRS ports during one SRS transmission opportunity (SRS transmission opportunity is the time window within a slot where SRS transmission is performed).

[0067] In summary, the SRS-ResourceSet configuration can be used to determine the usage, power control, and time slot offset of the aperiodic SRS, etc. The SRS resource configuration determines the time and frequency allocation, periodicity and offset, sequence, and spatial relationship information.

[0068] SRS Antenna Switching

[0069] The gNB is expected to probe all UE antennas, where probing an antenna means transmitting SRS from that antenna, which in turn enables the gNB to estimate the channel between that UE antenna and the antenna at the gNB. However, since it is usually costly to equip a UE with many transmit ports, SRS antenna switching was introduced in 3GPP NR Release 15 for several different UE architectures where the number of receive chains is greater than the number of transmit chains. If the UE supports antenna switching, it will report this by means of UE capability signaling.

[0070] As specified in 3GPP TS 38.306, Release 15 UEs can use the IE supportsSRS-TxPortSwitch to report the following antenna switching capabilities:

[0071] - t1r2,

[0072] - t1r4,

[0073] - t2r4,

[0074] - t2r2,

[0075] -t4r4,

[0076] - t1r4–t2r4.

[0077] For example, if a UE reports t1r2 in the UE capability signaling, it means that it has two receive antennas (i.e., two receive chains) but is only able to transmit from one of these antennas at a time (i.e., one transmit chain) and supports antenna switching. In this case, the UE may be configured with two single-port SRS resources so that it can use a single transmit port to probe both receive ports, with antenna switching in between).

[0078] Additional UE capabilities were introduced in NR Release 16, where the IE supportsSRS-TxPortSwitch-r1610 can have the following values:

[0079] - t1r1–t1r2,

[0080] - t1r1–t1r2–t1r4,

[0081] - t1r1–t1r2–t2r2–t2r4,

[0082] - t1r1–t2r2,

[0083] - t1r1–t2r2–t4r4,

[0084] - t1r1–t1r2–t2r2–t1r4–t2r4.

[0085] This IE can be used to indicate support for configuring a UE with an SRS resource set with purpose "antennaSwitching", but where only a subset of all UE antennas are sounded. For example, UE capability t1r1-t1r2 indicates that the gNB can configure one single-port SRS resource per SRS resource set (same as no antenna switching capability) or two single-port SRS resources with purpose "antennaSwitching" (same as capability "t1r2" above). In this case, if the UE is configured with a single SRS resource (no antenna switching), it will only sound one of its two antennas, which will save UE power consumption, but at the expense of reduced channel knowledge at the gNB (because the gNB can only estimate the channel between itself and the UE based on one of the two UE antennas).

[0086] For SRS resources with usage "antennaSwitching", for UEs with fewer transmit chains than receive chains, a guard period must be configured between SRS resources to account for Tx switching transient times. For subcarrier spacing less than 120 kHz, the guard period is 1 OFDM symbol, while for 120 kHz spacing subcarriers, the guard period is 2 OFDM symbols. This means that, depending on the subcarrier spacing, the UE is expected to be able to switch antennas within one or two OFDM symbols.

[0087] Multi-beam operation

[0088] Beam Management Process

[0089] In the high frequency range (FR2), multiple RF beams can be used to transmit and receive signals at the gNB and UE. For each DL beam from the gNB, there is usually an associated best UE Rx beam for receiving signals from the DL beam. The DL beam and the associated UE Rx beam form a beam pair. The beam pair can be identified by the so-called beam management process in NR.

[0090] DL beams are (usually) identified by an associated DL reference signal (RS) that is sent periodically, semi-persistently, or aperiodically in the beam. The DL RS used for this purpose can be a synchronization signal (SS) and a physical broadcast channel (PBCH) block (SSB) or a channel state information RS (CSI-RS). By measuring all DL RSs, the UE can determine and report to the gNB the best DL beam for DL ​​transmission. The gNB can then send a burst of DL-RS in the reported best DL beam to let the UE evaluate the candidate UE RX beams.

[0091] Although not explicitly stated in the NR specification, beam management has been divided into three processes, such as Figure 2 As shown schematically:

[0092] P-1: Aims to find the approximate direction of UE 120 using wide gNB Tx beams 211, 212, 213 from gNB 110 covering the entire angular sector. UE 120 can use a single Rx beam 221.

[0093] P-2: Aims to refine the gNB Tx beam by performing a new beam search around the coarse direction found in P-1 (i.e., by sending regular (narrow) Tx beams 214, 215, 216). The UE 120 may use a single Rx beam 222.

[0094] P-3: For UEs with analog beamforming to let them find the appropriate UE Rx beam. In P-3, the UE 120 receives on multiple beams 223, 224, 225, while the gNB 110 transmits on a constant beam 217, which is preferably a regular (narrow) beam.

[0095] It is expected that P-1 utilizes beams with fairly large beamwidths and where beam reference signals are sent periodically and shared among all UEs in the cell. Typically, the reference signal for P-1 is a periodic CSI-RS or SSB. The UE then reports the N best beams and their corresponding RSRP values ​​to the gNB.

[0096] P-2 is expected to use aperiodic and / or semi-persistent CSI-RS transmitted in narrow beams 214, 215, 216 around the coarse direction found in P-1.

[0097] P-3 is expected to use aperiodic or semi-persistent CSI-RS that is transmitted repeatedly in one narrow gNB beam 217. An alternative approach is to let the UE determine the appropriate UE Rx beam based on periodic SSB transmissions. Since each SSB consists of four OFDM symbols, up to four UE Rx beams 223, 224, 225 can be evaluated during each SSB burst transmission. One benefit of using SSB instead of CSI-RS is that the additional overhead of CSI-RS transmission is not required.

[0098] Beam pointing

[0099] In NR, several signals can be sent from different antenna ports of the same base station. These signals can have the same large-scale characteristics, such as Doppler shift / spread, average delay spread or average delay. Therefore, these antenna ports are called quasi co-located (QCL).

[0100] If the UE knows that two antenna ports are QCL with respect to a certain parameter (e.g., Doppler spread), the UE can estimate the parameter based on one of these antenna ports and apply the estimate to receiving the signal on the other antenna port. For example, there can be a QCL relationship between the CSI-RS for Tracking RS (TRS) and the PDSCH DMRS. When the UE receives the PDSCH DMRS, it can use the measurements already made on the TRS to assist in DMRS reception.

[0101] Information about which assumptions can be made about the QCL is signaled from the network to the UE. In NR, four types of QCL relationships between the transmit source RS and the transmit target RS are defined:

[0102] Type A: {Doppler shift, Doppler spread, average delay, delay spread}

[0103] Type B: {Doppler shift, Doppler spread}

[0104] Type C: {average delay, Doppler shift}

[0105] Type D: {Spatial Rx Parameters}.

[0106] D-type QCL was introduced in 3GPP NR to facilitate beam management through analog beamforming and is called spatial QCL. There is no strict definition of spatial QCL at present, but it is understood that if two transmitted antenna ports are spatially QCL, the UE can use the same Rx beam to receive them. This is helpful for UEs that use analog beamforming to receive signals, because before receiving a certain signal, the UE needs to adjust its Rx beam in a certain direction. If the UE knows that the signal is spatially QCL with some other signal it has received before, it can also safely use the same Rx beam to receive the signal.

[0107] In NR, the spatial QCL relationship of DL or UL signals / channels can be indicated to the UE by using "beam indication". "Beam indication" is used to help the UE find a suitable Rx beam for DL ​​reception and / or a suitable Tx beam for UL transmission. In NR, the "beam indication" for DL ​​is transmitted to the UE by indicating the transmission configuration indicator (TCI) state to the UE, while in UL, the "beam indication" can be transmitted by indicating the DL-RS or UL-RS as the spatial relationship (in NR Release 15 / 16) or TCI state (in NR Release 17).

[0108] UL beam management

[0109] Some UEs may have analog beamformers with no beam correspondence or poor beam correspondence (i.e. Tx / Rx correspondence), which means that DL / UL reciprocity cannot always be used to determine the beams of these beamformers. For such UEs, the UE beam for UL cannot be derived from the beam management process based on DL reference signals as described above. To handle such UEs, UL beam management has been included in the NR standard specification since Release 15. The main difference between normal beam management and UL beam management is that UL beam management utilizes uplink reference signals instead of DL reference signals. It has been agreed that the UL reference signal used for UL beam management is the sounding reference signal (SRS).

[0110] Figure 3The two UL beam management procedures supported in NR are schematically shown: U2 and U3. The U2 procedure (upper half) is performed by the UE 120 sending a burst of SRS resources in one UE Tx beam 321 and letting the gNB's TRP 110 evaluate different TRP Rx beams 311, 312, 313, 314, 315. The U3 procedure (lower half) lets the UE find the appropriate UE Tx beam by sending different SRS resources in different UE Tx beams 322, 323, 324, 325, 326 while the TRP 110 maintains a constant beam 316.

[0111] Even if the UE has beam correspondence, UL beam management can be useful. More precisely:

[0112] - In 3GPP, some companies believe that the combined DL beam management procedure and UL beam management procedure requires less overhead and latency than using only the DL beam management procedure.

[0113] - So-called "uplink-only" node deployment is a hot topic in 3GPP to improve UL coverage in a cost-effective manner, especially at higher frequencies. "UL-only" network nodes are equipped with UL capabilities but no or only very limited downlink capabilities. In this case, since "UL-only" nodes cannot send DL reference signals, the beam pair link between the UE and the "UL-only" node must be based on the UL beam management procedure.

[0114] - In D-MIMO, there will be many different access points (APs) or transmission points (TRPs) in a small area, and each AP / TRP may be equipped with multiple different beams. The large amount of reference signal overhead required to determine the AP / TRP and corresponding AP / TRP beam suitable for a UE using DL beam management has been identified as a problem for D-MIMO. Therefore, it has been internally recommended that AP / TRP selection and corresponding beam selection should preferably be based on UL SRS transmissions from a UE (which can then be used to determine the AP / TRP and corresponding AP / TRP beam suitable for that UE).

[0115] Therefore, UL beam management will likely play a more important role in advanced 5G and 6G applications.

[0116] UE Panel

[0117] For a UE, signals can arrive and be sent from all different directions, which makes it beneficial to implement antennas at the UE that can produce omni-like coverage in addition to high-gain narrow beams. One way to increase omni-directional coverage at a UE is to install multiple panels and have them point (orient) in different directions, which is often the case for commercial UEs. However, to reduce cost and energy consumption, some of these UEs may only transmit from one UE panel at each point in time.

[0118] Figure 4 An example of an actual UE 120 with two baseband chains (one for each polarization) 122 is shown, which are used to switch between four different dual-polarization panels 126. Each panel 126 is operable to transmit a beam to the main transmission direction of the panel along a direction generally corresponding to a half-plane. More precisely, the antennas in one panel 126 can be oriented parallel to each other in a common direction. Typically (but not necessarily), the antennas in one panel 126 are physically close, for example, the mutual distance of the antennas in one panel 126 is less than the distance to the antennas in any other panel. In addition, the antennas in one panel 126 can be fed by an RF signal at a common input point, which can be commonly connected to and disconnected from the baseband chain 122.

[0119] Figure 5 A wireless device 120 is shown having three panels 126 oriented in orthogonal directions to improve spherical coverage. The wireless device has at its disposal one baseband chain 122 which can be connected to one of the panels 126 at a time. Figure 5 The analog switch in shows this capability. Referring to a similar UE structure, it is described in the following presentation how to switch between three UE panel modules M1, M2, M3 using antenna switching:

[0120] - Qualcomm Technologies, Inc., “Breaking the Wireless Barriers to Mobilize 5G NRmmWave,” May 2019, downloaded from https: / / www.qualcomm.com / content / dam / qcomm-martech / dm-assets / documents / breaking_the_wireless_barriers_to_mobilize_5g_nr_mmwave.pdf.

[0121] The UE panel of a commercial UE can generate beams with different beam widths, for example:

[0122]

[0123] Typically, commercial UEs generate wider beams by temporarily deactivating one or more power amplifiers (PAs) of the panel, which has a negative impact on the available output power. However, the output power loss when generating wide beams can be mitigated by applying dual-polarization beamforming (e.g., using array size invariant (ASI) beamforming). It is useful for the UE to generate a wide beam of the panel during the beam scanning process to first find a rough direction to the serving AP / TRP, which will enable the UE to select and activate the appropriate UE panel. In the example of Table 1, the UE can generate one wide beam, five half-wide beams, and nine narrow beams for each panel.

[0124] Beam selection method

[0125] Figure 6 A multi-TRP / D-MIMO millimeter wave deployment with five TRPs 115a, 115b, 115c, 115d, 115e is shown. A millimeter wave wireless device (or UE) 120 with three panels is located in the intersection of the coverage areas of TRPs 115a, 115b, 115c, 115d, 115e. Each panel is operable to transmit beams 621, 622, 623 to the main transmission direction of each panel along a direction generally corresponding to a half-plane. Specifically, different UE panels are associated with different TRPs / APs 115.

[0126] To implement beam-pair link selection between the wireless device 120 and the network, one option is to initially select a suitable combination of TRP / AP 115 and UE panel, and then perform narrow beam scanning to determine narrow beams for the determined UE panel and narrow beams for the determined TRP / AP 115. It is assumed that the wireless device 120 can send UL-RS in all different directions, for example, by sending UL-RS from all UE panels and wherein wide beams 621, 622, 623 are used for each UE panel. Another option is to not initially determine such a combination of TRP / AP 115 and UE panel, but to directly send SRS from each narrow beam on all UE panels; however, this will introduce an unacceptable amount of SRS overhead signaling and latency. For example, assuming that the wireless device 120 is equipped with 4 panels and each panel has 9 narrow beams, the wireless device 120 needs to scan 4×9=36 beams during each UL beam management process; because a simple wireless device 120 can usually only transmit from one beam from one panel at each time instance, such scanning will need to occupy no less than 36 OFDM symbols. In addition, in the case where the TRP / AP 115 needs to perform a TRP / AP beam scanning process to determine a suitable TRP / AP beam for the corresponding UE beam, each of the 36 SRS resources needs to be repeated. times, among which, Equal to the number of TRP / AP beams to be evaluated.

[0127] refer to Figure 7 , Figure 7 is a sequence diagram illustrating a method of determining a beam to be used for communication between a network node 110 and a wireless device 120. From the perspective of the wireless device 120, Figure 7 A method for facilitating determining a beam to be used by a wireless device 120 for communication with a network node 110 is provided. From the perspective of the network node 110, Figure 7 A method for determining a beam to be used by a wireless device 120 for communication with the wireless device 120 is provided; furthermore, the network node 110 may determine a beam for itself to use in the communication. It is understood that the beam determined to be used by the wireless device 120 is sent from a specific panel in the panel (i.e., the panel from which the UL RS selected by the network node 110 is sent).

[0128] In the optional First step 710 , the wireless device 120 indicates an ability to transmit from different panels 126. More specifically, the indicated capability may relate to transmitting on different UL RS resources associated with (or transmitting from) at least two different UE panels 126 during a beam management procedure.

[0129] This capability may be indicated by a further development of capability signaling specified in 3GPP NR. More specifically, the capability signaled by the wireless device may be referred to as "UE panel switching capability". In some embodiments, the capabilities of the wireless device indicated include one or more of the following:

[0130] 1. The number of panels;

[0131] 2. The number of panels that are sent simultaneously;

[0132] 3. Panel switching interval.

[0133] Regarding project 2, refer to Figure 5 , Figure 5 A wireless device 120 is shown having a single baseband chain 122 (which is therefore functionally limited to transmitting from one panel 126 at a time). With respect to item 3, the panel switching gap period may refer to a duration of , so that two transmissions from different panels cannot be scheduled more In other words, the first transmission must terminate at least Note that, unlike the panel switching transient time to be described below, the panel switching gap period is a global quantity that characterizes the wireless device 120 as a whole.

[0134] In some embodiments, for each panel, the capabilities of the wireless device indicated include one or more of the following:

[0135] 1. Radiated power per beam;

[0136] 2. Antenna gain per beam;

[0137] 3. Support for wide beam generation;

[0138] 4. Support for the first beam type with a single beam per panel;

[0139] 5. Support for generating half-width beams;

[0140] 6. Support for a second beam type with multiple beams per panel;

[0141] 7. Support for narrow beam generation;

[0142] 8. The number of UL RS ports that a wireless device can transmit in one beam of a given type or given width;

[0143] 9. The number of supported beam types, each associated with a different beam width;

[0144] 10. The number of beams of the supported beam type;

[0145] 11. Approximate beam widths for supported beam types;

[0146] 12. Number of transmitter ports (i.e., antenna ports, transmitter antenna ports).

[0147] Examples of items 1, 10 and 11 are disclosed in Table 1. Items 10 and 12 express an important property of the wireless device 120, namely, since there are different ways to generate beams with different widths. Specifically, if a wide beam (a beam type with a relatively large width) is generated from a panel using dual-polarization beamforming, and the wireless device has an analog beamformer on the panel, then from the panel, it is possible to send UL RS from a single port at a time. Regarding items 4 and 6, the beam type can be characterized by its width (e.g., wide, half-width, narrow), and this may be useful to implement hierarchical scanning. Regarding item 6, it is not required that the panel should be able to send the multiple beams simultaneously. Regarding item 12, the typical number of transmitter ports in the UE 120 is two.

[0148] The above embodiments may belong to the first subgroup of embodiments (without panel ID) or the second subgroup of embodiments (with panel ID). Next, some embodiments in the second subgroup of embodiments will be described.

[0149] In the embodiments in the second subgroup, the capabilities of the wireless device indicated include a panel ID associated with one of the panels 126. Specifically, each panel 126 of the wireless device 120 may carry a panel ID. Optionally, for each panel ID, the capabilities of the wireless device indicated include one or more of the following:

[0150] 1. Radiated power per beam;

[0151] 2. Antenna gain per beam;

[0152] 3. Support for wide beam generation;

[0153] 4. Support for the first beam type with a single beam;

[0154] 5. Support for generating half-width beams;

[0155] 6. Support for a second beam type with multiple beams;

[0156] 7. Support for narrow beam generation;

[0157] 8. The number of UL RS ports that a wireless device can transmit in one beam of a given type or given width;

[0158] 9. The number of supported beam types, each associated with a different beam width;

[0159] 10. The number of beams of the supported beam type;

[0160] 11. Approximate beam widths for supported beam types;

[0161] 12. Number of ports;

[0162] 13. Panel switching transient time.

[0163] Refer to the description above related to these capabilities. For item 13, the panel switching transient time can be expressed as a start transient (the time that needs to pass before a transmission from a panel with this panel ID proceeds), an end transient (the time required to end an ongoing transmission from a panel with this panel ID), or the maximum of the start transient and the end transient. This allows the total switching time between each two panels to be determined, which provides an accurate standard to be followed when configuring UL RS transmissions. Note that the panel switching transient time allows different transient times to be indicated for different panels in a single wireless device 120.

[0164] In a specific embodiment, the "UE panel switching capability" may include, for example, one or more of the following information: the number of UE panels, the maximum number of UE panels transmitting simultaneously, support for generating wide beams for each UE panel, support for generating half-width beams for each UE panel, the number of half-width beams for each UE panel, the number of narrow beams for each UE panel, the panel switching gap period, the number of ports for each UE panel, the antenna gain of each beam type (i.e., wide beam, half-width beam, and narrow beam) for each UE panel, etc. Optionally, the "UE panel switching capability" includes an explicit UE panel ID, and the above listed information may be signaled based on the UE panel ID.

[0165] In another specific embodiment, the wireless device 120 reports whether the wireless device 120 is capable of performing dual polarization beamforming when generating wide beams and / or half-wide beams from one or more UE panels (see SO Peterson, "Power-Efficient Beam Pattern Synthesis via Dual Polarization Beamforming", arXiv:1910.10015 [eess.SP], October 22, 2019, and references therein). If the capability is reported, it is assumed that the same maximum output power is available when sending SRS from the UE panel for all different kinds of UE panel beam widths (beam types). If the network knows the output power difference between different beam types during the SRS antenna switching process, the network can more easily determine whether further beam refinement is needed or whether the link budget is good enough based on the antenna switching process performed. This information can also be combined with, for example, the antenna gain for each beam type.

[0166] In a specific embodiment, the wireless device reports the antenna gain and / or output power for each beam type for one or more UE antenna panels. If the network knows the output power difference between different beam types as well as the antenna gain difference, the network can more easily determine whether further beam refinement is needed or whether the link budget is good enough based on the antenna switching process performed.

[0167] In a further specific embodiment, for one or more UE panels, the wireless device reports the EIRP of the corresponding beam type. In this way, the network can more easily determine whether further beam refinement is needed or whether the link budget is good enough based on the antenna switching process performed.

[0168] exist Second step 712 In the embodiment of the present invention, the network node 110 sends a UL RS configuration to the wireless device 120. For example, a certain beam type (e.g., one wide beam per UE panel) may be used to send (or associate) one or more UL RS resources for each UE panel. Here, each UL RS resource may consist of one or two UL RS ports. In the case of using two UL RS ports per UL RS resource, each UL RS port is typically transmitted from one of the two polarizations of the UE panel.

[0169] In some embodiments, (information in) the UL RS configuration is grouped into UL RS resource sets, each UL RS resource set being associated with a different panel of the wireless device 120 .

[0170] Specifically, the number of UL RS resource sets may be equal to the number of panels according to the indicated capabilities of the wireless device. This corresponds to configuring reference signals for the entire panel range of the wireless device 120. Optionally, the UL RS configuration specifies a gap period between consecutive UL RS resource sets, the gap period corresponding to a panel switching gap period according to the indicated capabilities of the wireless device.

[0171] Alternatively, the UL RS configuration consists of a single UL RS resource set having a plurality of UL RS resources, and each of the UL RS resources is associated with a different panel. It is understood that the UL RS configuration may optionally specify a gap period between consecutive UL RS resources in the UL RS resources, and the gap period may correspond to a panel switching gap period according to the capabilities of the indicated wireless device.

[0172] In some embodiments, the UL RS configuration includes an explicit indication of a beam width or a beam type with uniform width to be used when sending UL RS resources from the panel. That is, the UL RS configuration may indicate a nominal width of the beam or a range of nominal widths (e.g., in terms of HPBW). Alternatively, the UL RS configuration may refer to one of a plurality of pre-agreed beam types that differ in their widths, e.g., in a range from "wide" to "narrow", where the actual widths of these beam types are specified in physical units by the implementer.

[0173] In some embodiments, the UL RS configuration includes an implicit indication of the beam width or beam type with uniform width to be used when transmitting UL RS resources from the panel. For example, the (relative) beam width may be inferred from the number of UL RS resources or beams.

[0174] In these embodiments, it may be assumed that the UL RS configuration is grouped into UL RS resource sets. Thus, the implicit indication is to use for the panel a beam width or beam type that is supported by the panel according to the indicated capabilities of the wireless device and having a number of beams equal to the number of UL RS configured in the UL RS resource set for the panel. In practice, if the wireless device 120 has indicated in step 710 that it supports beam type 1, then the wireless device 120 may indicate that it supports beam type 2. beams, beam type 2 beams and beam type 3 beams, and the UL-RS resource set is configured with UL RS resources, the network expects the wireless device 120 to use beam type 2 when sending UL-RS resources. Here, it is assumed that , the three beam types may have rising nominal widths.

[0175] In a first example of implicit indication, if there is a single configured UL RS in the UL RS resource set for the panel on the one hand, and there is an indicated capability to generate a wide beam from the panel on the other hand, the wireless device 120 can infer that it should apply a wide beam when sending the UL RS.

[0176] In a second example of implicit indication, if, on the one hand, there are multiple (greater than or equal to 2) configured UL RS resources in the UL RS resource set for the panel, and on the other hand, there is an indicated capability to generate an equal number of half-width beams from the panel, the wireless device 120 can infer that it should apply a half-width beam when sending each of the UL RSs.

[0177] In a third example of implicit indication, if there is a single configured UL RS resource set with multiple UL RSs associated with different panels on the one hand, and there is an indicated capability to generate a wide beam from the panel on the other hand, the wireless device 120 can infer that it should apply a wide beam when transmitting each of the UL RSs. Optionally, the number of UL RSs in the single configured UL RS resource set is equal to the number of panels according to the indicated capability.

[0178] In some embodiments, the UL RS configuration includes a UL RS resource associated with a repetition factor. The repetition factor indicates a number of consecutive OFDM symbols that the wireless device 120 should transmit in the UL RS resource.

[0179] In some embodiments, the UL RS configuration includes a sounding reference signal (SRS) resource. The SRS resource may be included in an SRS resource set with an indicated purpose, the indicated purpose representing panel switching. With respect to the RRC protocol in 3GPP NR, the purpose may be assigned a value of "antennaSwitching" or "beamManagement". Alternatively, the purpose representing panel switching may be a new value not currently defined in the RRC protocol, such as "panelSwitching".

[0180] If the optional first step 710 has been performed, the UL RS configuration may be based on the received "UE panel switching capability". The UE panel switching configuration may be, for example, a set of UL RSs, which are configured according to the "UE panel switching capability".

[0181] In the second subgroup of embodiments, when the indicated capabilities of the wireless device include a panel ID associated with one of the panels 126, the UL RS configuration may explicitly indicate the panel ID. The panel ID may be indicated for each UL RS resource. Specifically, the UL RS configuration may be grouped into UL RS resource sets, and each UL RS resource set is associated with a different panel ID. The panel ID may refer to the panel used for transmission in these UL RS resources. Alternatively, the UL RS configuration consists of a single UL RS resource set with multiple UL RS resources, and each UL RS resource is associated with a different panel ID.

[0182] In a specific embodiment, each UL-RS is explicitly associated with a previously reported UE panel ID so that the wireless device knows which UL-RS should be sent from which UE panel. SRS resource sets, where is equal to the number of UE panels, and each SRS resource set consists of SRS resources, which is equal to the number of UE beams that should be evaluated for each UE panel. In addition, each SRS resource may consist of one or two SRS ports (i.e., transmitter antenna ports), depending on the number of Tx chains of the corresponding UE panel. In a related specific embodiment, the number of SRS resource sets that the wireless device is able to transmit simultaneously (i.e., the number of SRS resource sets that contain SRS resources that overlap each other in time) is based on the maximum number of UE panels that transmit simultaneously indicated in the "UE panel switching capability".

[0183] In method 700 Third step 714 The transmission of UL RS is triggered in the process. The trigger may be initiated actively by the network node 110, or may be a result of UL RS configuration, scheduling, etc.

[0184] exist Fourth step 716 In the embodiment, the wireless device 120 sends the UL RS when sending the UL RS according to the trigger.

[0185] In a particular embodiment, the wireless device 120 is configured to transmit one UL RS per UE panel using a wide beam for each UE panel, which can be used to determine a suitable combination of UE panel 126 and TRP / AP 115.

[0186] In a specific embodiment, the wireless device is configured with multiple UL RS from each UE panel, wherein the multiple UL-RS are transmitted using the same wide beam. In this way, the network can scan different TRP / AP Rx beams during UL-RS transmission and determine the appropriate TRP / AP beam in addition to determining the combination of UE panel and TRP / AP 115.

[0187] In a specific embodiment, the wireless device is configured with multiple UL RSs for each UE panel, wherein the multiple UL RSs are transmitted in different half-width beams or narrow beams for one or more UE panels. In this way, it can be determined which UE panel should be used and which beam to apply for the UE panel.

[0188] In a specific embodiment, the wireless device should send all SRS from all different panels (i.e., all SRS used during the panel switching process) with equal output power. In this way, it is easier for the network to compare different beam pair links between the wireless device and the network and determine the best beam pair link in this way. In NR, UL output power control is configured for each SRS resource set, so the determined UL output power may become different for different UE panels (assuming that different SRS resource sets are used for different UE panels). To alleviate this problem, in one embodiment, if the UL power control results in different UL output powers for different SRS resource sets for the panel switching process, the wireless device should overrule the configured UL power control and set the output power equally for each UE panel. More precisely, the wireless device can, for example, select the UL output power corresponding to the UE panel with the highest output power and apply it to all UE panels during the panel switching process, or the average output power can be determined based on all power control loops.

[0189] exist Fifth Step 718 In the embodiment of the present invention, the network node 110 selects a UL RS from the received UL RSs. The selection may be based on any suitable evaluation criteria. In addition, a trained ML model may be used, as described in more detail below.

[0190] In some embodiments, step 718 includes selecting two of the received UL RSs that form a beam pair to be used for subsequent communications between the wireless device 120 and the network node 110 .

[0191] It will be appreciated that the network node 110 may receive the UL RS at one or more AP / TRPs 115, thereby allowing it to determine:

[0192] - Optimize TRP / AP (per radio or per UE panel),

[0193] - Preferred beam for preferred TRP / AP (per radio or per UE panel),

[0194] - Preferentially UE Panel, and / or

[0195] - Optimize UE panel beam.

[0196] exist Sixth step 720 In the embodiment, the network node 110 transmits its selection to the wireless device 120 in the form of an instruction so that the wireless device 120 uses the beams corresponding to the selected one or more UL RSs to communicate with the network node 110. For example, the instruction may refer to one beam from the first panel and another beam from the second panel.

[0197] Further beam management processes may also be performed during this step 720. For example, if a suitable combination of UE panels and TRP / AP 115 has been determined in step 720, further beam management processes may be triggered to determine which beam to use for the selected TRP / AP 115 or to determine which beam to use for the selected UE panel, or both.

[0198] exist Seventh step 722 In the embodiment, the network node 110 and the wireless device 120 communicate through uplink and / or downlink transmission of data and signaling using the beams corresponding to the selected one or more UL RSs.

[0199] ML-based beam prediction

[0200] To facilitate AI / ML based beam prediction, it is often beneficial to accumulate as much information as possible (and as diverse information as possible) at the gNB. This includes information used to initially train the AI / ML model as well as information to be fed to the trained model to obtain decisions during operation.

[0201] In response to this need, the present disclosure also relates to a method for training an ML model, the method comprising: sending a UL RS configuration to a wireless device 120, the UL RS configuration indicating at least two UL RS resources to be transmitted from different panels 126, each panel representing a group of related transmit antennas; receiving a plurality of UL RSs from the wireless device at a network node 110 according to the UL RS configuration; and providing training data based on measurements of the received UL RSs. Optionally, the training data may also include a ground truth selection of one of the received UL RSs, the one of the UL RSs representing at least one beam suitable for communication between the network node 110 and the wireless device 120, wherein the one or more beams may have been successfully used for such communication.

[0202] In addition, the present disclosure relates to a method for applying an ML model for beam selection, the method comprising: sending a UL RS configuration to a wireless device 120, the UL RS configuration indicating at least two UL RS resources to be transmitted from different panels 126, each panel representing a group of related transmit antennas; receiving multiple UL RSs from the wireless device at a network node 110 according to the UL RS configuration; and providing decision data to a trained ML model based on measurements of the received UL RSs; obtaining a beam selection decision from the ML model; and sending instructions for causing the wireless device 120 to communicate with the network using a beam corresponding to the selected one or more UL RSs.

[0203] Aspects of the disclosure have mainly been described above with reference to a few embodiments. However, as readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.

Claims

1. A method (700) in a wireless device (120) for facilitating determining a beam to be used for communication with a network (110), the method comprising: receiving (712) an uplink reference signal (UL) RS configuration from the network, the UL RS configuration indicating at least two UL RS resources to be transmitted from different panels (126), each panel representing a group of associated transmit antennas; transmitting (716) a plurality of UL RSs using the different panels according to the UL RS configuration; and An instruction to communicate with the network using one or more beams is received (720), each beam corresponding to one of the transmitted UL RSs.

2. The method according to claim 1, further comprising: The network is indicated (710) with the capability to transmit from different panels.

3. A method (700) in a network node (110) for determining a beam to be used for communication with a wireless device (120), the method comprising: transmitting (712) an uplink reference signal (UL RS) configuration to the wireless device, the UL RS configuration indicating at least two UL RS resources to be transmitted from different panels (126), each panel representing a group of related transmit antennas; receiving (716) a plurality of UL RSs from the wireless device according to the UL RS configuration; selecting (718) one or more of the received UL RSs; and Instructions are sent (720) for causing the wireless device to communicate with the network using beams corresponding to the selected one or more UL RSs.

4. The method according to claim 3, further comprising: An indicated capability of the wireless device to transmit from a different panel (126) is obtained (710).

5. The method according to claim 3 or 4, wherein: selecting (718) at least two UL RSs among the received UL RSs, the at least two UL RSs forming a beam pair, The transmitted instructions are used to cause the wireless device to communicate with the network using the beam pair.

6. The method according to any one of claims 2, 4 and 5, wherein: The capabilities of the wireless device indicated include one or more of the following: The number of panels; The number of panels that are being sent simultaneously; Panel switching interval.

7. The method according to any one of claims 2 and 4 to 6, wherein: For each panel, the capabilities of the wireless device indicated include one or more of the following: Radiated power per beam; Antenna gain per beam; Support for wide beam generation; Support for the first beam type with a single beam; Support for generating half-width beams; Support for a second beam type with multiple beams; Support for narrow beam generation; The number of UL RS ports that the wireless device can transmit in one beam of a given type or a given width; The number of supported beam types, each associated with a different beamwidth; The number of beams of the supported beam types; The approximate beam widths for supported beam types; Number of transmitter ports.

8. A method according to any one of the preceding claims, wherein: The UL RS configurations are grouped into UL RS resource sets, each UL RS resource set being associated with a different panel.

9. The method according to claim 8, wherein: The number of UL RS resource sets is equal to the number of panels according to the indicated capabilities of the wireless device.

10. The method according to claim 8 or 9, wherein: The UL RS configuration specifies a gap period between consecutive UL RS resource sets, the gap period corresponding to a panel switching gap period according to the indicated capabilities of the wireless device.

11. The method according to any one of claims 1 to 7, wherein: The UL RS configuration consists of a single UL RS resource set having a plurality of UL RS resources, each UL RS resource being associated with a different panel.

12. A method according to any one of the preceding claims, wherein: The UL RS configuration includes an explicit indication of the beam width or beam type with uniform width to be used when transmitting UL RS resources from the panel.

13. The method according to any one of claims 1 to 11, wherein: The UL RS configuration includes an implicit indication of the beam width or beam type with uniform width to be used when transmitting UL RS resources from the panel.

14. A method according to claim 13 as dependent on claim 2 or 4, wherein: The UL RS configurations are grouped into UL RS resource sets; and The implicit indication is to use a beam width or beam type for the panel, the beam width or beam type being supported by the panel according to the indicated capabilities of the wireless device and having a number of beams equal to the number of UL RSs configured in the ULRS resource set for the panel.

15. The method according to claim 14, wherein: The combination of a single configured UL RS in a UL RS resource set for a panel on the one hand and an indicated capability to generate wide beams from the panel on the other hand indicates that the wireless device should apply wide beams when sending the UL RS.

16. The method according to claim 14 or 15, wherein: The combination of the multiple configured UL RS resources in the UL RS resource set for a panel on the one hand and the indicated capability to generate an equal number of half-width beams from the panel on the other hand indicates that the wireless device should apply a half-width beam when sending each of the UL RS.

17. The method according to claim 14, wherein: The combination of a single configured UL RS resource set with multiple UL RSs associated with different panels on the one hand and the indicated capability to generate wide beams from the panels on the other hand indicates that the wireless device should apply wide beams when transmitting each of the UL RSs.

18. The method according to claim 17, wherein: The number of UL RSs in the single configured UL RS resource set is equal to the number of panels according to the indicated capabilities.

19. A method according to any one of the preceding claims, wherein: The UL RS configuration also includes a UL RS resource associated with a repetition factor, the repetition factor indicating that the wireless device should transmit for a number of consecutive symbols in the UL RS resource.

20. A method according to any one of the preceding claims, wherein: The UL RS configuration includes a sounding reference signal SRS resource.

21. The method according to claim 20, wherein: The SRS resource is included in an SRS resource set having an indicated usage, and the indicated usage represents panel switching.

22. The method according to claim 21, wherein: The indicated usage is antenna switching or beam management.

23. A method according to any one of the preceding claims, wherein: For each UL RS resource, the UL RS configuration explicitly indicates a panel ID (126a, 126b, 126c).

24. The method of claim 23 as defined in any one of claims 2, 4 and 5, wherein: The indicated capabilities of the wireless device include a panel ID.

25. The method according to claim 23 or 24, wherein: For each panel ID, the capabilities of the wireless device indicated include one or more of the following: Radiated power per beam; Antenna gain per beam; Support for wide beam generation; Support for the first beam type with a single beam; Support for generating half-width beams; Support for a second beam type with multiple beams; Support for narrow beam generation; The number of UL RS ports that the wireless device can transmit in one beam of a given type or a given width; The number of supported beam types, each associated with a different beamwidth; The number of beams of the supported beam types; The approximate beam widths for supported beam types; The number of ports; Panel switching transient time.

26. The method according to any one of claims 23 to 25, wherein: The UL RS configurations are grouped into UL RS resource sets, each UL RS resource set being associated with a different panel ID.

27. The method according to any one of claims 23 to 25, wherein: The UL RS configuration consists of a single UL RS resource set having a plurality of UL RS resources, each UL RS resource being associated with a different panel ID.

28. A wireless device (120) for facilitating determining a beam to be used for communications with a network (110), the wireless device comprising a processing circuit (122), the processing circuit (122) being configured to: receiving an uplink reference signal (UL) RS configuration from the network, the UL RS configuration indicating at least two UL RS resources to be transmitted from different panels (126), each panel representing a group of associated transmit antennas; transmitting a plurality of UL RSs using the different panels according to the UL RS configuration; and An instruction is received to communicate with the network using one or more beams, each beam corresponding to one of the transmitted ULRS.

29. A network node (110) for determining a beam to be used for communicating with a wireless device (120), the network node comprising a processing circuit (112), the processing circuit (112) being configured to: transmitting an uplink reference signal (UL) RS configuration to the wireless device, the UL RS configuration indicating at least two UL RS resources to be transmitted from different panels (126), each panel representing a group of related transmit antennas; receiving a plurality of UL RSs from the wireless device according to the UL RS configuration; selecting one or more UL RSs among the received UL RSs; and Instructions are sent to cause the wireless device to communicate with the network using beams corresponding to the selected one or more UL RSs.

30. A computer program (124) comprising instructions which, when executed on a processing circuit (122) of a wireless device (120), cause the wireless device to perform the method (700) according to any one of claims 1, 2 and 6 to 27.

31. A computer program (114) comprising instructions which, when executed on a processing circuit (112) of a network node (110), cause the network node to perform a method (700) according to any one of claims 3 to 27.

32. A computer program product comprising a computer program (1120) according to claim 30 or 31 and a computer readable storage medium on which the computer program is stored.

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