Method and network node for beam management in a wireless communication network

Abstract

Disclosed is a method for network node beam management performed by a network node (130). When a second wide beam is determined to have higher signal quality than a first wide beam having a narrow beam on which data communication with a UE (140) is currently performed, the network node instructs the UE (140) to transmit an uplink reference signal with a spatial relation corresponding to the second wide beam. The network node (130) evaluates the received uplink reference signal to determine which narrow beam within the second wide beam that has the highest signal quality. Thereafter, the network node continues the data communication with the UE using the determined narrow beam of the second wide beam. The uplink reference signal may be sent on a probing communication resource that is different from communication resources used for uplink reference signals used within the data communication on the narrow beam within the first wide beam.

Description

METHOD AND NETWORK NODE FOR BEAM MANAGEMENT IN A WIRELESS COMMUNICATION NETWORKTECHNICAL FIELD

[0001] The present disclosure relates generally to methods and network nodes for beam management, more specifically for management of network node beams. The present disclosure further relates to computer programs and carriers corresponding to the above methods, devices and nodes.BACKGROUND

[0002] In recent versions of wireless communication networks, such as Long Term Evolution (LTE) networks, also called 4thGeneration (4G) networks, and New Radio (NR) networks, also called 5thGeneration (5G) networks, the network nodes can be provided with a plurality of antenna elements for transmission and / or reception of signals from / to wireless communication devices, also called User Equipment (UE). One purpose with such plurality of antennas at the network node is the possibility to form reception / transmission beams at the network node by sending / receiving the same signal from / to each antenna element with mutually different phase shifts and possibly also amplitude selected in a smart way in order to form a beam directed towards a UE of interest. Such beams formed at the network node can be called network node beams. To account for the dynamic changing of the channel conditions and UE mobility, it is necessary to regularly measure and evaluate different beam directions and pick the one best serving the communication with a base station. The network node beams can be formed as wider or narrower beams in terms of transmission / reception angle seen from the network node. Each wide network node beam then covers a plurality of narrow network node beams. It may also be possible that UEs are provided with a plurality of antennas for enabling beamforming also at the UE side, so called UE beams.

[0003] In order to select beams to use for a communication with one or more UEs and to communicate such selections in the network, beam management procedures need to be defined. The 3rdGeneration Partnership Project (3GPP) has defined layer 1 and layer 2 beam management procedures in TR 38.802,Version 14.2.0, dated September 2017, Section 6.1 .6. Procedure 1 (P1 ) is an initial access procedure whereas Procedure 2 (P2) is for network node beam management and Procedure 3 (P3) is for UE beam management, in case the UE is equipped with a plurality of antennas enabling beam management.

[0004] In P1 , the network node broadcasts Synchronization Signal Blocks (SSBs) in downlink in different wide network node beams. The UE measures signal strength on the received SSBs in the different network node beams and sends a random-access preamble related to the strongest SSB. SSBs are transmitted over wide network node beams to cover several UEs at the same time. After the initial access is completed for one UE, the network node triggers the P2 procedure in order to identify the best narrow network node beam for the UE within the wide network node beam of the strongest SSB that was identified during P1 . In P2, the network node transmits Channel State information Reference Signals (CSI-RS) in the different narrow network node beams within the wide network node beam of the strongest SSB. The UE measures signal strength for each received CSI-RS, one CSI-RS per narrow network node beam within the detected wide network node beam and sends a CSI report to the network node in return. From the measurements of the CSI report, the network node determines which narrow network node beam should be used for the transmission and reception of data between the UE and the network node. After the completion of the beam refinement in P2, data transmission towards the UE and reception from the UE is then performed on the determined narrow network node beam.

[0005] However, to account for dynamic changes in channel quality and for mobility of UEs, the network node needs to track the UE during ongoing transmission and / or reception of data between the network node and the UE over the determined narrow network node beam. Such tracking is performed by sending CSI-RSs per candidate narrow network node beam towards the UE and by processing the CSI response from the UE to determine the best new narrow network node beam direction. The beam tracking may try candidate beams close to the narrow network node beam currently considered the strongest one. This tracking is called P2 tracking. An example of the P2 tracking procedure is shown infig. 1 for a network node (gNB) 10 and a LIE 20. In this example, there are three wide network node beams, where SSBi is sent in wide network node beam 1 , SSB2 is sent in wide network node beam 2 and SSB3 is sent in wide network node beam 3. Wide network node beam 1 is the wide network node beam selected for the UE and within wide network node beam 1 there are three narrow network node beams 4, 5 and 6. In the P2 procedure, the gNB 10 selected narrow network node beam 6 for the communication with the UE 20. The UE is then instructed to transmit and receive data using a spatial relation, i.e. , a UE beam corresponding to the wide network node beam 1 . In the P2 tracking procedure, the network node sends CSI-RS in each narrow network node beam in the same wide network node beam as the selected narrow network node beam 6, in fig. 1 this means in narrow network node beams 4, 5 and 6 and determines from the received measurement results, whether any of narrow network node beams 4 and 5 have become stronger than beam 6.

[0006] In parallel to the P2 tracking procedure, the gNB 10 sends SSBs on different wide network node beams and the UE 20 measures on them and sends the measurements back to the gNB 10. Occasionally, those measurements indicate a new wide network node beam is stronger than the selected wide network node beam. Then the gNB 10 would again perform something similar to a network node beam refinement procedure, offering the UE a set of candidate CSI- RSs, each representing a different narrow beam to be measured on to find out what is the strongest narrow network node beam within the new wide network node beam. This is called a P2 probing procedure and is illustrated by the example of fig. 2, which has the same setup as the example of fig. 1. In this example, the ongoing communication of data takes place on narrow beam 6 within wide beam 1 . Suddenly, SSB measurements on the wide network node beams 1 , 2 and 3 indicates that wide network node beam 2 has become stronger than wide network node beam 1 . The gNB 10 then sends CSI-RS on each of the narrow network node beams 7, 8 and 9 of the wide network node beam 2, and based on the received CSI reports from the UE 20 determines that narrow network node beam 8 is the strongest. The UE 20 is then instructed to transmit and receive data with the gNB 10 using a UE beam that has a spatial relation corresponding to thewide network node 2. Further, the gNB 10 communicates data with the LIE 20 using the narrow network node beam 8.

[0007] Such beam tracking procedure based on CSI-RS sent by the network node downlink (DL) is costly when it comes to network resources as it requires one CSI-RS transmission per candidate beam and UE to be tracked. Also, a CSI report of the measurements on the candidate beams performed by the UE needs to be transmitted to the network node. Consequently, there is a need for a beam tracking procedure that is less costly.SUMMARY

[0008] It is an object of embodiments of the invention to address at least some of the problems and issues outlined above. It is an object of embodiments of the invention to provide a beam management procedure that is more efficient than prior art procedures, such as the one using CSI-RS described in the Background. It is another object of embodiment to provide a P2 probing procedure that is more network resource efficient than prior art procedures. It is possible to achieve at least of one of these objects by using methods and network nodes as defined in the attached independent claims.

[0009] According to one aspect, a method is provided for beam management performed by a network node of a wireless communication network. The network node has a plurality of antenna elements. The method comprises, for a UE that is assigned a spatial relation corresponding to a first wide network node beam for communication with the network node, wherein the network node uses a narrow network node beam within the first wide network node beam for communication with the UE, determining, from measurements on reference signals, that a narrow network node beam of a plurality of narrow network node beams within a second wide network node beam may experience higher signal quality than the narrow network node beam of the first wide network node beam used for communication. The method further comprises transmitting, to the UE, in response to the determining that a narrow network node beam within the second wide network node beam experiences higher signal quality than the narrow network node beamwithin the first wide network node beam used for communication, an instruction to transmit a UL reference signal assigned with a spatial relation corresponding to the second wide network node beam, and receiving, from the UE, the UL reference signal assigned with the spatial relation corresponding to the second wide network node beam. The method further comprises determining, from measurements performed by the network node on the received UL reference signal, which of the plurality of narrow network node beams within the second wide network node beam that has the highest signal quality, and communicating with the UE using the narrow network node beam within the second wide network node beam that was determined to have the highest signal quality, and wherein the UE is assigned a spatial relation corresponding to the second wide network node beam for the communication

[0010] According to another aspect, a network node is provided that is configured to operate in a wireless communication network, the network node having a plurality of antenna elements. The network node comprises a processing circuitry and a memory. Said memory containing instructions executable by said processing circuitry, whereby the network node is operative for, for a UE that is assigned a spatial relation corresponding to a first wide network node beam for communication with the network node, wherein the network node uses a narrow network node beam within the first wide network node beam for communication with the UE, determining, from measurements on reference signals, that a narrow network node beam of a plurality of narrow network node beams within a second wide network node beam may experience higher signal quality than the narrow network node beam of the first wide network node beam used for communication. The network node is further operative for transmitting, to the UE, in response to the determining that a narrow network node beam within the second wide network node beam experiences higher signal quality than the narrow network node beam within the first wide network node beam used for communication, an instruction to transmit a UL reference signal assigned with a spatial relation corresponding to the second wide network node beam. The network node is further operative for receiving, from the UE, the UL reference signal assigned with the spatial relation corresponding to the second wide network node beam, determining, frommeasurements performed by the network node on the received LIL reference signal, which of the plurality of narrow network node beams within the second wide network node beam that has the highest signal quality, and communicating with the UE using the narrow network node beam within the second wide network node beam that was determined to have the highest signal quality, and wherein the UE is assigned a spatial relation corresponding to the second wide network node beam for the communication.

[0011] According to other aspects, computer programs and carriers are also provided, the details of which will be described in the claims and the detailed description.

[0012] Further possible features and benefits of this solution will become apparent from the detailed description below.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The solution will now be described in more detail by means of exemplary embodiments and with reference to the accompanying drawings, in which:

[0001] Fig. 1 is a schematic diagram of a P2 tracking procedure according to prior art.

[0015] Fig. 2 is a schematic diagram of a P2 probing procedure according to prior art.

[0016] Fig 3 is a schematic block diagram of a wireless communication network in which the present invention may be used.

[0017] Fig. 4 is a flow chart illustrating a method performed by a network node, according to possible embodiments.

[0018] Fig. 5 is a schematic diagram of a P2 tracking procedure according to prior art.

[0019] Fig. 6 is a schematic diagram of a P2 probing procedure according to possible embodiments.

[0020] Fig. 7 is a block diagram illustrating a network node in more detail, according to further possible embodiments.DETAILED DESCRIPTION

[0021] Briefly described and according to some embodiments, a solution is provided that achieves a more efficient P2 probing procedure by using uplink reference signals such as Sounding Reference Signals in the P2 probing procedure instead of CSI-RS. When data communication between a UE and a network node uses a narrow network node beam within a first wide network node beam and it is determined that a narrow network node beam within a second wide network node beam may experience higher signal quality than the narrow network node beam within the first wide network node beam used for the data communication, the network node instructs the UE to transmit an uplink (UL) reference signal with a spatial relation that corresponds to the second wide network node beam. When receiving the UL reference signal having a spatial relation corresponding to the second wide network node beam from the UE, the network node determines from measurements performed on the UL reference signal which of the narrow network node beams within the second wide network node beam that has the highest signal quality. Thereafter, the network node communicates data with the UE using the determined narrow network node beam within the second wide network node beam. By using UL reference signals instead of DL reference signals in the P2 probing procedure, only one reference signal can be transmitted for one wide beam instead of one DL reference signal per narrow beam of the one wide beam.

[0022] Fig. 3 shows a wireless communication network 100 comprising a radio access network (RAN) node aka network node 130 that is in, or is adapted for, wireless communication with a wireless communication device aka wireless device or User Equipment (UE) 140. The network node 130 provides radio access in a cell 150 covering a geographical area. The network node 130 may be connected to other network nodes of a radio access network (RAN) and nodes of a core network (CN), schematically marked with 160 in fig. 3.

[0023] The wireless communication network 100 may be any kind of wireless communication network that can provide radio access to wireless devices.Example of such wireless communication networks are networks based on Global System for Mobile communication (GSM), Enhanced Data Rates for GSM Evolution (EDGE), Universal Mobile Telecommunications System (UMTS), Code Division Multiple Access 2000 (CDMA 2000), Long Term Evolution (LTE), LTE Advanced, Wireless Local Area Networks (WLAN), Worldwide Interoperability for Microwave Access (WiMAX), WiMAX Advanced, as well as fifth generation (5G) wireless communication networks based on technology such as New Radio (NR), and any possible future sixth generation (6G) wireless communication network.

[0024] The network node 130 may be any kind of network node that can provide wireless access to a wireless device 140 alone or in combination with another network node. Examples of network nodes 130 are a base station (BS), a radio BS, a base transceiver station, a BS controller, a network controller, a Node B (NB), an evolved Node B (eNB), a gNodeB (gNB), a Multi-cell / multicast Coordination Entity, a relay node, an access point (AP), a radio AP, a remote radio unit (RRU), a remote radio head (RRH) and a multi-standard BS (MSR BS).

[0025] The wireless device 140 may be any type of device capable of wirelessly communicating with a network node 130 using radio signals. For example, the wireless device 140 may be a User Equipment (UE), a machine type UE or a UE capable of machine to machine (M2M) communication, a sensor, a tablet, a mobile terminal, a smart phone, a laptop embedded equipped (LEE), a laptop mounted equipment (LME), a USB dongle, a Customer Premises Equipment (CPE), an Internet of Things (loT) device, etc.

[0026] Fig. 4 describes a method for beam management performed by a network node 130 of a wireless communication network 100, the network node having a plurality of antenna elements. The method comprises, for a UE 140 that is assigned a spatial relation corresponding to a first wide network node beam for communication with the network node 130, wherein the network node 130 uses a narrow network node beam within the first wide network node beam forcommunication with the LIE 140, determining 202, from measurements on reference signals, that a narrow network node beam of a plurality of narrow network node beams within a second wide network node beam may experience higher signal quality than the narrow network node beam of the first wide network node beam used for communication. The method further comprises transmitting 204, to the UE 140, in response to the determining 202 that a narrow network node beam within the second wide network node beam experiences higher signal quality than the narrow network node beam within the first wide network node beam used for communication, an instruction to transmit an uplink, UL, reference signal assigned with a spatial relation corresponding to the second wide network node beam, and receiving 208, from the UE 140, the UL reference signal assigned with the spatial relation corresponding to the second wide network node beam. The method further comprises determining 210, from measurements performed by the network node 130 on the received 208 UL reference signal, which of the plurality of narrow network node beams within the second wide network node beam that has the highest signal quality, and communicating 214 with the UE 140 using the narrow network node beam within the second wide network node beam that was determined 210 to have the highest signal quality, and wherein the UE 140 is assigned a spatial relation corresponding to the second wide network node beam for the communication.

[0027] The method is applicable for a Time Division Duplex (TDD) based communication system. In a TDD based system, the same frequency band is used for both uplink and downlink communication with different time periods or slots for uplink and downlink communication. A network node beam is a beam that the network node uses for receiving signals from the UE and for transmitting signals to the UE. The term “Communicating with the UE” involves the network node transmitting signals to the UE and / or receiving signals from the UE. That the UE is assigned a spatial relation corresponding to a certain wide network node beam allows the UE to use a certain UE beam it has previously found to work well with the certain wide network node beam, the certain UE beam being one of a plurality of different UE beams that the UE is able to produce. “Communicating with the UE” mav signify data communication, i.e. traffic data.

[0028] According to an embodiment, the determining that a narrow network node beam within the second wide network node beam may experience higher signal quality than the narrow network node beam of the first wide network node beam used for communication is a determination that a narrow network node beam within the second wide network node beam may experience higher signal quality than the narrow network node beam of the first wide network node beam used for communication by a margin. In other words, the determination needs to indicate that the signal quality is a certain amount higher than the signal quality experienced by the narrow network node beam of the first wide network node beam used for communication before the network node transmits 204 an instruction to the UE to transmit an UL reference signal assigned with a spatial relation corresponding to the second wide network node beam. The margin, or certain amount may be e.g. 1-3dB. Alternatively, the margin may be that the signal quality indicates at least e.g. 10-20 % higher than the signal quality of the narrow network node beam of the first wide network node beam used for communication.

[0029] According to an embodiment, the first wide network node beam and the second wide network node beam are separate beams covering separate transmission / reception angles. There may be a slight overlap between the first and second wide network node beams, however, they are essentially two separate beams. Each of the first and second wide network node beam comprises a plurality of separate narrow network node beams. For example, if a wide network node beam covers a transmission / reception angle of 3a and there are 3 narrow network node beams per wide network node beam, the narrow network node beams each covers a transmission / reception angle of a.

[0030] The measurements on reference signals, from which it is determined 202 that a narrow network node beam within the second wide network node beam may experience higher signal quality than the narrow network node beam within the first wide network node beam used for communication may be measurements performed by the UE on downlink (DL) reference signals transmitted by the network node, or measurements performed by the network node on UL reference signals transmitted by the UE. According to an embodiment, when the referencesignals are DL reference signals, the measurements on DL reference signals are performed by the UE 140 on a first DL measurement signal transmitted by the network node 130 on the first wide network node beam and on a second DL measurement signal transmitted by the network node on the second wide network node beam. The first DL measurement signal may be a Synchronization Signal Block (SSB). The second DL measurement signal may be an SSB. The measurements performed by the UE may be transmitted to the network node in a downlink reference signal measurement report. According to another embodiment, when the reference signals are UL reference signals, the UL reference signals can be received and measured by the first and the second wide network node beams even though the UE transmits the UL reference signals in the UE beam that is assigned the spatial relation corresponding to the first wide network node beam. A third embodiment, when the reference signals are UL reference signals, the UL reference signals can be received and measured by a grid of narrow network node beams within the first and the second wide network node beams even though the UE transmits the UL reference signals in the UE beam that is assigned the spatial relation corresponding to the first wide network node beam. This is possible when still considerable energy is received in the second wide network node beam or in the third embodiment, in a narrow network node beam within the second wide network node beam, so that the network node can indicate this spatial relation is of interest and worth investigating by instructing the UE to transmit the UL reference signal assigned with the spatial relation corresponding to the second wide network node beam. The UL reference signal transmitted with a spatial relation corresponding to the first wide network node beam is not ideal for evaluating narrow network node beams outside of the first wide network node beam, so therefore a new UL reference signal having a spatial relation corresponding to the second wide network node beam should be sent to determine whether this narrow network node beam in the second wide network node beam or another one in the second wide network node beam actually has higher signal quality than the narrow network node beam of the first wide network node beam that is in use for communication. In a variant of the third embodiment, a narrow network node beam determined to have high enough signal quality in a grid of narrow network nodebeams within the second wide network node beam is used directly for communication with the UE without instructing the UE to transmit the UL reference signal assigned the spatial relation corresponding to the second wide network node beam. In this variant of the third embodiment, one may for robustness compare reported wide network node beam measurements from the UE. If the signal quality of the second wide network node beam is not lower than a margin of for example 1-2 dB compared to the first wide network beam, one may allow using the narrow network node beam of the second wide network node beam directly. These wide network node beam measurements may be SSB measurements.

[0031] Regarding the communication in step 214, as well as the communication in steps 206 and 216 which will be described below, when the communication is UL communication, the network node instructs the UE to transmit in a scheduled communication resource and to assign to the communication on the scheduled communication resource, the spatial relation of the wide network node beam embracing the determined narrow network node beam. Thereafter, the UE transmits the communication to the UE. When communication is DL communication, the network node assigns the communication the TCI state of the wide network node beam embracing the determined narrow network node beam and informs the UE of a scheduled communication resource of the communication, before transmitting the communication to the UE.

[0032] By the above method, as the network node can evaluate signal quality in its different narrow network node beams from a reference signal transmitted by the UE assigned with a spatial relation corresponding to the second wide network node beam, only one UL reference signal needs to be transmitted for the determination of narrow network node beam within the second wide network node beam compared to one DL reference signal per narrow network node beam of the second wide network node beam which is needed for evaluation in prior art. As a result, a beam management procedure that is more efficient than prior art is achieved, i.e. that is less costly when it comes to usage of network resources.

[0033] According to an embodiment, the determining 202 that a narrow network node beam within the second wide network node beam may experience higher signal quality than the narrow network node beam within the first wide network node beam used for communication is from measurements by the UE 140 indicating that the second wide network node beam has higher signal quality than the first wide network node beam. The measurements by the UE may be received by the network node as a CSI report including SSB measurements.

[0034] According to another embodiment, the determining 202 that a narrow network node beam within the second wide network node beam may experience higher signal quality than the narrow network node beam within the first wide network node beam used for communication is from measurements by the network node 130 on UL reference signals assigned a spatial relation corresponding to the first wide network node beam indicating a narrow network node beam of the second wide network node beam experiencing higher signal quality than the narrow network node beam within the first wide network node beam used for communication.

[0035] According to an embodiment, the UL reference signal assigned with the spatial relation corresponding to the second wide network node beam received 208 from the UE 140 is assigned a probing communication resource that is different to communication resources assigned for other UL reference signals assigned with a spatial relation corresponding to the first wide network node beam.

[0036] “Communication resources” here means time-frequency communication resources. The UL reference signal assigned with the spatial relation corresponding to the second wide network node beam is here assigned a so called probing communication resource, which is a different communication resource than used for the other UL reference signals that are transmitted by the UE during the data communication with the network. This probing communication resource is a communication resource for an UL reference signal that is separate from a communication resource set of UL reference signals assigned to the ongoing communication. As the communication resource set of UL referencesignals are assigned to the ongoing data communication they have to be transmitted assigned with the same spatial relation as the current data communication. The probing communication resource on the other hand is not within the communication resource set of UL reference signals and then the spatial relation for the probing communication resource can be selected freely. As a result, by using such a probing communication resource for an UL reference signal, this UL reference signal can be assigned with the spatial relation corresponding to the second wide network node beam even though ongoing UL data communication on e.g. a Physical Uplink Shared Channel (PUSCH) or a Physical Uplink Control Channel (PUCCH) is performed on a spatial relation corresponding to the first wide network node beam. Supporting such extra communication resource is subject to UE capabilities reported by UEs. It would benefit the transmission of UL reference signals in other beams during an ongoing data communication as the spatial relation of this UL reference signal received in step 208 can be assigned independently from the spatial relation of the UL reference signals used for the ongoing communication. The “other UL reference signals” mentioned here are used by the network node for checking the signal quality on the different narrow network node beams within the first wide network node beams.

[0037] According to an embodiment, the UL reference signal assigned with the spatial relation corresponding to the second wide network node beam that is received 208 from the UE 140 is a Sounding Reference Signal (SRS).

[0038] According to another embodiment, the instruction to the UE 1 0 to transmit a UL reference signal assigned with a spatial relation corresponding to the second wide network node beam is transmitted 204 in a Physical Downlink Control Channel (PDCCH). The message containing the instruction in the PDCCH is referred to as a Downlink control information (DCI). The scheduling of the UL reference signal by a DCI is referred to as aperiodic, meaning the transmission happens once. It is also possible to have the UL reference signal transmitted in a so called semi-persistent way. Then the transmissions occur periodically when activated by a Medium Access Control - Control Element (MAC-CE), part ofPDSCH, and continues until deactivated by another MAC-CE. A third way, so called periodic, is to have the periodic transmissions occur for the duration of the connection without any explicit activation / deactivation. In addition to scheduling the transmissions of UL reference signal, it is needed to ensure the intended spatial relation is assigned. This can be done by a PDSCH, i.e. updating the UE with the relevant spatial relation for the UL reference signal using an instruction transmitted in a MAC-CE. The update of the spatial relation may also be done using a DCI.

[0039] According to an embodiment, the method further comprises communicating 206 with the UE 140 using the narrow network node beam within the first wide network node beam used for communication, after the transmitting 204 of the instruction to the UE to transmit the UL reference signal assigned with the spatial relation corresponding to the second wide network node beam and before the communicating 214 with the UE 140 using the narrow network node beam within the second wide network node beam that was determined 210 to have the highest signal quality.

[0040] So, even if the UE has been instructed to transmit the UL reference signal assigned with the spatial relation corresponding to the second wide network node beam, the network node can carry on receiving or transmitting communication with the UE using the narrow network node beam of the first wide network node beam used for the communication at least until the network node determines to start communicating 214 with the UE 140 using the narrow network node beam within the second wide network node beam that was determined 210 to have the highest signal quality.

[0041] According to another embodiment, the network node 130 has a digital receiver and wherein the UL reference signal assigned with the spatial relation corresponding to the second wide network node beam is received 208 by the digital receiver. A digital receiver has the ability to analyze from the received UL reference signal assigned with the spatial relation of the second wide networknode beam, which of the plurality of narrow network node beams within the second wide network node beam that has the highest signal quality.

[0042] According to yet another embodiment, the method further comprises determining 212 whether the determined 210 narrow network node beam within the second wide network node beam experiences higher signal quality than the narrow network node beam within the first wide network node beam used for the communication. Further, only when the determined 210 narrow network node beam within the second wide network node beam was determined 212 to have higher signal quality than the narrow network node beam within the first wide network node beam used for the communication, the communicating 214 with the UE 140 using the determined 210 narrow network node beam within the second wide network node beam is performed. Hereby, it is confirmed that the narrow network node beam within the new second wide network node beam experiences higher signal quality than the narrow network node beam that is in use for the communication before any change of narrow network node beam for the communication is actually performed. Hereby, an unnecessary change of network node beam for the communication can be avoided.

[0043] According to another embodiment, when the determined 210 narrow network node beam within the second wide network node beam was determined 212 to have same or lower signal quality than the narrow network node beam within the first wide network node beam used for communication, do not perform the communicating 214 with the UE using the determined 210 narrow network node beam within the second wide network node beam but instead communicating 216 with the UE using the narrow network node beam within the first wide network node beam used for the communication. Thus, it is defined that the communication will stay on the narrow network node beam of the first wide network node beam in case the signal quality was actually not higher on the narrow network node beam of the second wide network node beam than the signal quality of the narrow network node beam of the first wide network node beam already in use.

[0044] According to yet another embodiment, the method further comprises determining, based on the measurements performed on the received 208 UL reference signal having a spatial relation corresponding to the second wide network node beam, signal quality of narrow network node beams outside of the second wide network node beam as well as signal quality of the narrow network node beam within the second wide network node beam that was determined 210 to have the highest signal quality. Further, when it is determined that a first of the narrow network node beams outside the second wide network node beam has a higher signal quality than the narrow network node beam within the second wide network node that was determined to have the highest signal quality, transmitting, to the UE 140, an instruction to transmit an UL reference signal assigned with a spatial relation corresponding to the wide network node beam of the first narrow network node beam.

[0045] In other words, when any narrow network node beam outside of the second wide network node beam was determined to have a higher signal quality than the narrow network node beams inside the second wide network node beam, the procedure of transmitting instructions to the UE to transmit an UL reference signal is performed again but this time for the UE to transmit with a spatial relation that corresponds to the wide network node beam of that narrow network node beam that was outside of the second wide network node beam. In other words, the procedure can be seen as retaken from step 204 of fig. 2 but where the UE is instructed to transmit an UL reference signal with a spatial relation corresponding to the wide network node beam of the narrow network node beam that was outside of the second wide network node beam. For example, if a narrow network node beam of a third wide network node beam experienced higher signal quality from the UL reference signal transmitted by the UE with a spatial relation corresponding to the second wide network node than the narrow network node beam of the second wide network node, the UE will be instructed to transmit a new UL reference signal, this time with a spatial relation corresponding to the third wide network node beam. The UL reference signal transmitted with a spatial relation corresponding to the second wide network node beam is not ideal for evaluating narrow network node beams outside of the second wide network node beam, sotherefore a new UL reference signal having a spatial relation corresponding to the third wide network node beam should be sent to determine whether this narrow network node beam in the third wide network node beam or another one in the third wide network node beam actually has higher signal quality than the one in use.

[0046] In the 3GPP standard of today, see TS 38.213, 38.214 and 38.331 , the UL data transmission from the UE 20, for example on a PUSCH (see 6.1.1.1 in 38.214, release 15 and onwards) or a PUCCH (see 9.2.2 in 38.213, release 15 and onwards), is expected to use the same spatial relation as an SRS resource assigned to an SRS resource set with ‘usage’ set to codebook. This means that the SRS resources in the SRS set, which are the SRS resources available to the UE need to use the same spatial relation as the data transmitted UL. In other words, it is not possible, or at least difficult, to support ongoing UL data transmission and at the same time perform P2 probing using a different spatial relation than for the UL data transmission. Also, in case an SSB measurement indicates that a different, second, wide network node beam than the wide (first) beam currently used for the data communication has a higher signal quality than the first wide beam, it is not for sure that any of the narrow beams of the second wide network node beam turns out to be strong enough for a narrow beam change from the narrow beam of the first wide beam to the narrow beam of the second wide beam to happen. If a change of the data communication from a narrow network node beam within the first wide network node beam to a narrow network node beam within the second wide beam would then be performed before the P2 probing has been performed, the data communication may then be subject to a spatial relation that is underperforming. Also then, an unnecessary change of data communication from the first wide network node beam to the second wide network node beam may have been performed, which consumes resources.

[0047] This problem is alleviated by scheduling a special probing SRS communication resource whenever a different wide network node beam is determined to be stronger than the existing wide network node beam based on the SSB measurements, or based on UL reference signals as explained above. Thespecial probing SRS resource would be independent from the SRS resource set with usage set to codebook. Thus, the probing SRS resource can be assigned a spatial relation corresponding to the new, second wide network node beam even though the data is transmitted during the same time period UL on resources assigned a spatial relation corresponding to the first wide network node beam. In other words, the UE may utilize a distinct UE beam to transmit the SRS on the probing SRS resource, distinct to the UE beam the UE currently uses for UL data transmissions This designated UE beam for transmission of the SRS on the probing communication resource may be the same one that the UE determined to be the optimal UE beam for receiving the SSB signal that represents the latest, strongest wide network node beam. This differs from downlink-based beam management in which as many CSI-RS resources as there are narrow beams within the SSB coverage needs to be transmitted.

[0048] As described in relation to fig. 1 , there are ongoing measurements on SSBs, i.e. on wide network node beams during an ongoing data communication. When such SSB measurements indicate a dominant SSB different from the current one, i.e., a wide network node beam different from the network node beam used for the current data communication, it is at this point unclear which specific narrow network node beam is the most optimal for the UE in the new dominant SSB, i.e. which narrow network node beam within the new wide network node beam that has the highest signal quality, e.g. highest signal strength or highest Signal to Noise Ratio. Additionally, it is unknown whether this optimal narrow network node beam would outperform the currently utilized narrow beam belonging to the coverage of the current SSB. Therefore, an additional probing SRS resource different from the one used for P2 tracking is scheduled to be transmitted from the UE in the P2 probing.

[0049] Fig. 5 shows P2 Tracking, which is performed as in prior art. Here user data and any possible SRS are sent by UE 320 on the first same spatial relation corresponding to narrow beam 6’ of first wide network node beam T, which is the narrow beam used for the ongoing communication at the network node. The SRSs are here using a resource of an SRS resource set 340 within “usage” set tocodebook. In fig. 6 on the other hand, the new P2 probing procedure is shown. Here gNB 310 has determined from the SSB measurements on the first, second and third wide network node beams 1 ', 2', 3' that the second wide network node beam 2' experiences a higher signal quality than the first wide network node beam 1 'on which the ongoing communication is performed using narrow beam 6'. In response, the gNB 310 instructs the UE 320 to transmit an SRS on a probing SRS resource 330, which is not within the SRS resource set 340 with “usage” set to codebook. The SRS can hereby be transmitted with a second spatial relation corresponding to the second wide network node beam 2' even though data transmission is performed DL on the narrow beam 6' of the first wide network node beam 1 ' and / or UL with the first spatial relation corresponding to the narrow beam 6' of the first wide network node beam 1 '.

[0050] By receiving the transmission of the SRS on the probing SRS resource by a digital receiver, the network node can fully analyze which narrow network node within the second wide network node beam that has the highest signal quality and possibly also whether the signal quality is dominant enough to be used for upcoming data transmissions, e.g., higher than the signal quality of the narrow network node currently used for the data transmission.

[0051] When hybrid beamforming is used at the network node, a combination of digital and analog beamforming is used. In such hybrid beamforming, the plurality of antenna elements is divided into a plurality of antenna sub-arrays where each such antenna subarray comprises a subgroup of the total amount of antenna elements so that the number of antenna subarrays of the network node is fewer than the number of antenna elements. The antenna elements of an antenna subarray are subject to analogue beamforming whereas each antenna subarray is connected to a digital processing chain. An antenna subarray would cover a certain geographic subarea of the whole coverage area of the network node. Within this geographic subarea, the received SRS can be analyzed in the digital processing chain, which comprises the digital receiver. The geographic subarea may cover a plurality of wide network node beams.

[0052] A "digital receiver" can be explained according to the following: The received UL signal can be processed via digital beam forming in order to identify the best candidate beam out of a multitude of beams. In practice that means the received signal is processed multiple times in parallel, where each processing chain represents a certain candidate beam. The received reference signal quality from the different beams can then be compared with each other to identify the best candidate beam. In order to make this digital beamforming (DBF) processing feasible, especially for FR2, it is an option to limit the bandwidth for these processed signals in frequency domain. So, the digital receiver is the part of the system that is capable of DBF in the UL. The digital receiver operates after an Analog-to-Digital converter as seen from a network node reception perspective. It is then possible for the digital receiver to store the samples digitally and perform in parallel a number of beamforming operations, each corresponding to one beam in a grid of beams. The network node can compare which of the beams achieved the highest signal quality.

[0053] The network node may inform the UE of the SRS resource it has scheduled for the UE using a PDCCH. This is called an aperiodic SRS. The network node may then freely assign the UE a “test” spatial relation aligned with the reported dominant SSB, without jeopardizing the PUSCH / PUCCH transmissions, which are always using a spatial relation based on the SRS resource being part of SRS resource set with ‘usage’ assigned to codebook.

[0054] In fig. 6, the signal quality of the narrow network node beams 7', 8', 9' within the second wide network node beam 2' are analyzed by the gNB 310, i.e. the network node by a digital receiver. According to another variant, also narrow network node beams outside of the second wide network node beam 2' can be analyzed by the digital receiver, such as narrow network node beam 5'or 6', as long as the narrow network node beams are within the subarea covered by the antenna subarray, i.e. so that they have the same digital receiver chain. One strategy may be to select narrow network node beams close to the second wide network node beam 2', however up to all narrow network node beams within the subarea can be analyzed.

[0055] Typically, the probing SRS would be assigned the spatial relation associated with the detected dominant SSB, i.e. , in fig. 6, the second wide network node beam 2'. This means narrow network node beams related to other wide netork node beams would be less accurately evaluated since they would otherwise be subject to other spatial relations. Still the evaluations for narrow network node beams outside the detected dominant network node beam can be useful. It could in fact trigger a third round of P2 probing procedure.

[0056] Fig. 7, in conjunction with fig. 3, describes a network node 130 configured to operate in a wireless communication network 100, the network node having a plurality of antenna elements. The network node 130 comprises a processing circuitry 603 and a memory 604. Said memory containing instructions executable by said processing circuitry, whereby the network node 130 is operative for, for a UE 140 that is assigned a spatial relation corresponding to a first wide network node beam for communication with the network node 130, wherein the network node 130 uses a narrow network node beam within the first wide network node beam for communication with the UE 140, determining, from measurements on reference signals, that a narrow network node beam of a plurality of narrow network node beams within a second wide network node beam may experience higher signal quality than the narrow network node beam of the first wide network node beam used for communication. The network node 130 is further operative for transmitting, to the UE 140, in response to the determining that a narrow network node beam within the second wide network node beam experiences higher signal quality than the narrow network node beam within the first wide network node beam used for communication, an instruction to transmit a UL reference signal assigned with a spatial relation corresponding to the second wide network node beam. The network node 130 is further operative for receiving, from the UE 140, the UL reference signal assigned with the spatial relation corresponding to the second wide network node beam, determining, from measurements performed by the network node 130 on the received UL reference signal, which of the plurality of narrow network node beams within the second wide network node beam that has the highest signal quality, and communicating with the UE 140 using the narrow network node beam within the second wide networknode beam that was determined to have the highest signal quality, and wherein the UE 140 is assigned a spatial relation corresponding to the second wide network node beam for the communication.

[0057] According to an embodiment, the network node 130 is operative for the determining that a narrow network node beam within the second wide network node beam may experience higher signal quality than the narrow network node beam within the first wide network node beam used for communication from measurements by the UE 1 0 indicating that the second wide network node beam has higher signal quality than the first wide network node beam.

[0058] According to another embodiment, the network node 130 is operative for the determining that a narrow network node beam within the second wide network node beam may experience higher signal quality than the narrow network node beam within the first wide network node beam used for communication is from measurements by the network node 130 on UL reference signals assigned a spatial relation corresponding to the first wide network node beam indicating a narrow network node beam of the second wide network node beam experiencing higher signal quality than the narrow network node beam within the first wide network node beam used for communication.

[0059] According to another embodiment, the network node 130 is operative for the receiving of the UL reference signal assigned with the spatial relation corresponding to the second wide network node beam from the UE 140 assigned a probing communication resource that is different to communication resources assigned for other UL reference signals assigned with a spatial relation corresponding to the first wide network node beam.

[0060] According to another embodiment, the network node 130 is operative for the receiving of the UL reference signal assigned with the spatial relation corresponding to the second wide network node beam from the UE 140 as a Sounding Reference Signal, SRS.

[0061] According to another embodiment, the network node 130 is operative for the transmitting of the instruction to the UE 140 to transmit a UL reference signal assigned with a spatial relation corresponding to the second wide network node beam in a Physical Downlink Control Channel, PDCCH.

[0062] According to yet another embodiment, the network node 130 is further operative for communicating with the UE 1 0 using the narrow network node beam within the first wide network node beam used for communication, after the transmitting of the instruction to the UE to transmit the UL reference signal assigned with the spatial relation corresponding to the second wide network node beam and before the communicating with the UE 140 using the narrow network node beam within the second wide network node beam that was determined to have the highest signal quality.

[0063] According to yet another embodiment, the network node 130 has a digital receiver. Further, the network node 130 is operative for receiving the UL reference signal assigned with the spatial relation corresponding to the second wide network node beam by the digital receiver.

[0064] According to yet another embodiment, the network node 130 is further operative for determining whether the determined narrow network node beam within the second wide network node beam experiences higher signal quality than the narrow network node beam within the first wide network node beam used for communication. Further, only when the determined narrow network node beam within the second wide network node beam was determined to have higher signal quality than the narrow network node beam within the first wide network node beam used for communication, perform the communicating with the UE 140 using the determined narrow network node beam within the second wide network node beam.

[0065] According to yet another embodiment, when the determined narrow network node beam within the second wide network node beam was determined to have same or lower signal quality than the narrow network node beam within the first wide network node beam used for communication, the network node isoperative for not performing the communicating with the LIE using the determined narrow network node beam within the second wide network node beam but instead communicating with the UE using the narrow network node beam within the first wide network node beam used for communication.

[0066] According to still another embodiment, the network node 130 is further operative for determining based on the measurements performed on the received UL reference signal having a spatial relation corresponding to the second wide network node beam, signal quality of narrow network node beams outside of the second wide network node beam as well as signal quality of the narrow network node beam within the second wide network node beam that was determined to have the highest signal quality. Further, when it is determined that a first of the narrow network node beams outside the second wide network node beam has a higher signal quality than the narrow network node beam within the second wide network node that was determined to have the highest signal quality, transmitting, to the UE 140, an instruction to transmit an UL reference signal assigned with a spatial relation corresponding to the wide network node beam of the first narrow network node beam.

[0067] According to other embodiments, the network node 130 may further comprise a communication unit 602, which may be considered to comprise conventional means for wireless communication with the UE 140, such as a transceiver for wireless transmission and reception of signals in the communication network. The communication unit 602 may also comprise conventional means for communication with other network nodes 160 of the wireless communication network 100. The instructions executable by said processing circuitry 603 may be arranged as a computer program 605 stored e.g. in said memory 604. The processing circuitry 603 and the memory 604 may be arranged in a sub-arrangement 601. The sub-arrangement 601 may be a microprocessor and adequate software and storage therefore, a Programmable Logic Device, PLD, or other electronic component(s) / processing circuit(s) configured to perform the methods mentioned above. The processing circuitry 603 may comprise one or more programmable processor, application-specific integratedcircuits, field programmable gate arrays or combinations of these adapted to execute instructions.

[0068] The computer program 605 may be arranged such that when its instructions are run in the processing circuitry 603, the instructions cause the network node 130 to perform the steps described in any of the described embodiments of the network node 130 and its method. The computer program 605 may be carried by a computer program product connectable to the processing circuitry 603. The computer program product may be the memory 604, or at least arranged in the memory. The computer program product may be called a computer-readable storage medium. The memory 604 may be realized as for example a Random-access memory (RAM), Read-Only Memory (ROM) or an Electrical Erasable Programmable ROM (EEPROM). In some embodiments, a carrier may contain the computer program 605. The carrier may be one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or computer readable storage medium. The computer-readable storage medium may be e.g., a CD, DVD or flash memory, from which the program could be downloaded into the memory 604. Alternatively, the computer program 605 may be stored on a server or any other entity to which the network node 130 has access via the communication unit 602. The computer program 605 may then be downloaded from the server into the memory 604.

[0069] Although the description above contains a plurality of specificities, these should not be construed as limiting the scope of the concept described herein but as merely providing illustrations of some exemplifying embodiments of the described concept. It will be appreciated that the scope of the presently described concept fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the presently described concept is accordingly not to be limited. Reference to an element in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more." All structural and functional equivalents to the elements of the abovedescribed embodiments that are known to those of ordinary skill in the art areexpressly incorporated herein by reference and are intended to be encompassed hereby. Moreover, it is not necessary for an apparatus or method to address each and every problem sought to be solved by the presently described concept, for it to be encompassed hereby. In the exemplary figures, a broken line generally signifies that the feature within the broken line is optional.

Claims

CLAIMS1 . A method for beam management performed by a network node (130) of a wireless communication network (100), the network node having a plurality of antenna elements, the method comprising: for a User Equipment, UE (140), that is assigned a spatial relation corresponding to a first wide network node beam for communication with the network node (130), wherein the network node (130) uses a narrow network node beam within the first wide network node beam for communication with the UE (140), determining (202), from measurements on reference signals, that a narrow network node beam of a plurality of narrow network node beams within a second wide network node beam may experience higher signal quality than the narrow network node beam of the first wide network node beam used for communication, transmitting (204), to the UE (140), in response to the determining (202) that a narrow network node beam within the second wide network node beam experiences higher signal quality than the narrow network node beam within the first wide network node beam used for communication, an instruction to transmit an uplink, UL, reference signal assigned with a spatial relation corresponding to the second wide network node beam, receiving (208), from the UE (140), the UL reference signal assigned with the spatial relation corresponding to the second wide network node beam, determining (210), from measurements performed by the network node (130) on the received (208) UL reference signal, which of the plurality of narrow network node beams within the second wide network node beam that has the highest signal quality, and communicating (214) with the UE (140) using the narrow network node beam within the second wide network node beam that was determined (210) to have the highest signal quality, and wherein the UE (140) is assigned a spatial relation corresponding to the second wide network node beam for the communication.

2. Method according to claim 1 , wherein the determining (202) that a narrow network node beam within the second wide network node beam mayexperience higher signal quality than the narrow network node beam within the first wide network node beam used for communication is from measurements by the UE (140) indicating that the second wide network node beam has higher signal quality than the first wide network node beam.

3. Method according to claim 1 , wherein the determining (202) that a narrow network node beam within the second wide network node beam may experience higher signal quality than the narrow network node beam within the first wide network node beam used for communication is from measurements by the network node (130) on UL reference signals assigned a spatial relation corresponding to the first wide network node beam indicating a narrow network node beam of the second wide network node beam experiencing higher signal quality than the narrow network node beam within the first wide network node beam used for communication.

4. Method according to any of the preceding claims, wherein the UL reference signal assigned with the spatial relation corresponding to the second wide network node beam received (208) from the UE (140) is assigned a probing communication resource that is different to communication resources assigned for other UL reference signals assigned with a spatial relation corresponding to the first wide network node beam.

5. Method according to any of the preceding claims, wherein the UL reference signal assigned with the spatial relation corresponding to the second wide network node beam that is received (208) from the UE (140) is a Sounding Reference Signal, SRS.

6. Method according to any of the preceding claims, wherein the instruction to the UE (140) to transmit a UL reference signal assigned with a spatial relation corresponding to the second wide network node beam is transmitted (204) in a Physical Downlink Control Channel, PDCCH.

7. Method according to any of the preceding claims, further comprising:communicating (206) with the LIE (140) using the narrow network node beam within the first wide network node beam used for communication, after the transmitting (204) of the instruction to the UE to transmit the UL reference signal assigned with the spatial relation corresponding to the second wide network node beam and before the communicating (214) with the UE (140) using the narrow network node beam within the second wide network node beam that was determined (210) to have the highest signal quality.

8. Method according to any of the preceding claims, wherein the network node (130) has a digital receiver and wherein the UL reference signal assigned with the spatial relation corresponding to the second wide network node beam is received (208) by the digital receiver.

9. Method according to any of the preceding claims, further comprising: determining (212) whether the determined (210) narrow network node beam within the second wide network node beam experiences higher signal quality than the narrow network node beam within the first wide network node beam used for communication, and only when the determined (210) narrow network node beam within the second wide network node beam was determined (212) to have higher signal quality than the narrow network node beam within the first wide network node beam used for communication, perform the communicating (214) with the UE (140) using the determined (210) narrow network node beam within the second wide network node beam.

10. Method according to claim 9, wherein when the determined (210) narrow network node beam within the second wide network node beam was determined (212) to have same or lower signal quality than the narrow network node beam within the first wide network node beam used for communication, do not perform the communicating (214) with the UE using the determined (210) narrow network node beam within the second wide network node beam but instead communicating (216) with the UE using the narrow network node beam within the first wide network node beam used for communication.

11. Method according to any of the preceding claims, further comprising:determining based on the measurements performed on the received (208) UL reference signal having a spatial relation corresponding to the second wide network node beam, signal quality of narrow network node beams outside of the second wide network node beam as well as signal quality of the narrow network node beam within the second wide network node beam that was determined (210) to have the highest signal quality, and when it is determined that a first of the narrow network node beams outside the second wide network node beam has a higher signal quality than the narrow network node beam within the second wide network node that was determined to have the highest signal quality, transmitting, to the LIE (140), an instruction to transmit an UL reference signal assigned with a spatial relation corresponding to the wide network node beam of the first narrow network node beam.

12. A network node (130) configured to operate in a wireless communication network (100), the network node having a plurality of antenna elements, the network node (130) comprising a processing circuitry (603) and a memory (604), said memory containing instructions executable by said processing circuitry, whereby the network node (130) is operative for: for a User Equipment, UE (140), that is assigned a spatial relation corresponding to a first wide network node beam for communication with the network node (130), wherein the network node (130) uses a narrow network node beam within the first wide network node beam for communication with the UE (140), determining, from measurements on reference signals, that a narrow network node beam of a plurality of narrow network node beams within a second wide network node beam may experience higher signal quality than the narrow network node beam of the first wide network node beam used for communication, transmitting, to the UE (140), in response to the determining that a narrow network node beam within the second wide network node beam experiences higher signal quality than the narrow network node beam within the first wide network node beam used for communication, an instruction to transmit an uplink, UL, reference signal assigned with a spatial relation corresponding to the second wide network node beam,receiving, from the LIE (140), the LIL reference signal assigned with the spatial relation corresponding to the second wide network node beam, determining, from measurements performed by the network node (130) on the received UL reference signal, which of the plurality of narrow network node beams within the second wide network node beam that has the highest signal quality, and communicating with the UE (140) using the narrow network node beam within the second wide network node beam that was determined to have the highest signal quality, and wherein the UE (140) is assigned a spatial relation corresponding to the second wide network node beam for the communication.

13. Network node (130) according to claim 12, operative for the determining that a narrow network node beam within the second wide network node beam may experience higher signal quality than the narrow network node beam within the first wide network node beam used for communication from measurements by the UE (140) indicating that the second wide network node beam has higher signal quality than the first wide network node beam.

14. Network node (130) according to claim 12, operative for the determining that a narrow network node beam within the second wide network node beam may experience higher signal quality than the narrow network node beam within the first wide network node beam used for communication is from measurements by the network node (130) on UL reference signals assigned a spatial relation corresponding to the first wide network node beam indicating a narrow network node beam of the second wide network node beam experiencing higher signal quality than the narrow network node beam within the first wide network node beam used for communication.

15. Network node (130) according to any of claims 12-14, operative for the receiving of the UL reference signal assigned with the spatial relation corresponding to the second wide network node beam from the UE (140) assigned a probing communication resource that is different to communication resourcesassigned for other UL reference signals assigned with a spatial relation corresponding to the first wide network node beam.

16. Network node (130) according to any of claims 12-15, operative for the receiving of the UL reference signal assigned with the spatial relation corresponding to the second wide network node beam from the UE (140) as a Sounding Reference Signal, SRS.

17. Network node (130) according to any of claims 12-16, operative for the transmitting of the instruction to the UE (140) to transmit a UL reference signal assigned with a spatial relation corresponding to the second wide network node beam in a Physical Downlink Control Channel, PDCCH.

18. Network node (130) according to any of claims 12-17, further being operative for: communicating with the UE (140) using the narrow network node beam within the first wide network node beam used for communication, after the transmitting of the instruction to the UE to transmit the UL reference signal assigned with the spatial relation corresponding to the second wide network node beam and before the communicating with the UE (140) using the narrow network node beam within the second wide network node beam that was determined to have the highest signal quality.

19. Network node (130) according to any of claims 12-18, wherein the network node (130) has a digital receiver, and wherein the network node (130) is operative for receiving the UL reference signal assigned with the spatial relation corresponding to the second wide network node beam by the digital receiver.

20. Network node (130) according to any of claims 12-19, further being operative for: determining whether the determined narrow network node beam within the second wide network node beam experiences higher signal quality than the narrow network node beam within the first wide network node beam used for communication, and only when the determined narrow network node beam withinthe second wide network node beam was determined to have higher signal quality than the narrow network node beam within the first wide network node beam used for communication, perform the communicating with the UE (140) using the determined narrow network node beam within the second wide network node beam.21 . Network node (130) according to claim 20, wherein when the determined narrow network node beam within the second wide network node beam was determined to have same or lower signal quality than the narrow network node beam within the first wide network node beam used for communication, the network node is operative for not performing the communicating with the UE using the determined narrow network node beam within the second wide network node beam but instead communicating with the UE using the narrow network node beam within the first wide network node beam used for communication.

22. Network node (130) according to any of claims 12-21 , further being operative for: determining based on the measurements performed on the received UL reference signal having a spatial relation corresponding to the second wide network node beam, signal quality of narrow network node beams outside of the second wide network node beam as well as signal quality of the narrow network node beam within the second wide network node beam that was determined to have the highest signal quality, and when it is determined that a first of the narrow network node beams outside the second wide network node beam has a higher signal quality than the narrow network node beam within the second wide network node that was determined to have the highest signal quality, transmitting, to the UE (140), an instruction to transmit an UL reference signal assigned with a spatial relation corresponding to the wide network node beam of the first narrow network node beam.

23. A computer program (605) comprising instructions, which, when executed by at least one processing circuitry of a network node (130) of a wireless communication network (100), the network node having a plurality of antenna elements, causes the network node (130) to perform the following steps: for a User Equipment, UE (140), that is assigned a spatial relation corresponding to a first wide network node beam for communication with the network node (130), wherein the network node (130) uses a narrow network node beam within the first wide network node beam for communication with the UE (140), determining, from measurements on reference signals, that a narrow network node beam of a plurality of narrow network node beams within a second wide network node beam may experience higher signal quality than the narrow network node beam of the first wide network node beam used for communication, transmitting, to the UE (140), in response to the determining that a narrow network node beam within the second wide network node beam experiences higher signal quality than the narrow network node beam within the first wide network node beam used for communication, an instruction to transmit an uplink, UL, reference signal assigned with a spatial relation corresponding to the second wide network node beam, receiving, from the UE (140), the UL reference signal assigned with the spatial relation corresponding to the second wide network node beam, determining, from measurements performed by the network node (130) on the received UL reference signal, which of the plurality of narrow network node beams within the second wide network node beam that has the highest signal quality, and communicating with the UE (140) using the narrow network node beam within the second wide network node beam that was determined to have the highest signal quality, and wherein the UE (140) is assigned a spatial relation corresponding to the second wide network node beam for the communication.

24. A carrier containing the computer program (605) according to claim 23, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, an electric signal or a computer readable storage medium.

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