WO2024158317A1

WO2024158317A1 - Network node and method in a wireless communications network

Info

Publication number: WO2024158317A1
Application number: PCT/SE2023/050056
Authority: WO
Inventors: Anders Landström; Niklas WERNERSSON; Karl Werner; Kjell Larsson
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2023-01-23
Filing date: 2023-01-23
Publication date: 2024-08-02

Abstract

A method performed by a network node for selecting a precoder for a data transmission in a radio channel between the network node and a User Equipment, UE, in a wireless communications network is provided. The network node obtains (201) a first set 5of candidate beams and a second set of candidate beams. The first set of candidate beams is obtained based on a first Channel State Information, CSI, relating to a first frequency band. The second set of candidate beams is obtained based on a second CSI relating to a second frequency band. Based on evaluating (202) CSI related to the first set of candidate beams and CSI related to the second set of candidate beams, the network 10node determines (203) a third set of beams for acquiring CSI for the first frequency band. The third set of beams is based on at least one of the first set of candidate beams and the second set of candidate beams. The network node obtains (204) third CSI for the first frequency band for the radio channel between the network node and the UE based on the third set of beams. The network node selects (205) a precoder for a data transmission to 15the UE based on the obtained third CSI.

Description

NETWORK NODE AND METHOD IN A WIRELESS COMMUNICATIONS NETWORK

TECHNICAL FIELD

Embodiments herein relate to a network node and a method therein. In some aspects, they relate to selecting a precoder for a data transmission in a radio channel between a User Equipment and the network node in a wireless communications network.

BACKGROUND

In a typical wireless communication network, wireless devices, also known as wireless communication devices, mobile stations, stations (STA) and/or User Equipments (UE), communicate via a Wide Area Network or a Local Area Network such as a Wi-Fi network or a cellular network comprising a Radio Access Network (RAN) part and a Core Network (CN) part. The RAN covers a geographical area which is divided into service areas or cell areas, which may also be referred to as a beam or a beam group, with each service area or cell area being served by a radio network node such as a radio access node e.g., a Wi-Fi access point or a radio base station (RBS), which in some networks may also be denoted, for example, a NodeB, eNodeB (eNB), or gNB as denoted in Fifth Generation (5G) telecommunications. A service area or cell area is a geographical area where radio coverage is provided by the radio network node. The radio network node communicates over an air interface operating on radio frequencies with the wireless device within range of the radio network node.

3GPP is the standardization body for specifying the standards for a cellular system evolution, e.g., including 3G, 4G, 5G and future evolutions. Specifications for the Evolved Packet System (EPS), also called a Fourth Generation (4G) network, have been completed within the 3rd Generation Partnership Project (3GPP). As a continued network evolution, new releases of 3GPP specify a 5G network also referred to as 5G New Radio (NR).

Multi-antenna techniques may significantly increase the data rates and reliability of a wireless communication system. The performance is in particular improved if both the transmitter and the receiver are equipped with multiple antennas, which results in a Multiple-Input Multiple-Output (MIMO) communication channel. Such systems and/or related techniques are commonly referred to as MIMO. In addition to faster peak Internet connection speeds, 5G planning aims at higher capacity than current 4G, allowing higher number of mobile broadband users per area unit, and allowing consumption of higher or unlimited data quantities in gigabyte per month and user. This would make it feasible for a large portion of the population to stream high-definition media many hours per day with their mobile devices, when out of reach of Wi-Fi hotspots. 5G research and development also aims at improved support of machine to machine communication, also known as the Internet of things, aiming at lower cost, lower battery consumption and lower latency than 4G equipment.

At higher frequency bands e.g., millimeter wave (mmW) bands, analog beamforming is typically used. This means that at any time only a limited set of beams may be formed by an antenna panel, yielding high overhead for beam sweeping at highband frequencies. At midband frequencies digital beamforming is typically used. This allows the radio to direct beams towards multiple directions simultaneously. Dual frequency measurements analysis suggests that similar paths are often used for midband and mmW bands, even in Non Line of Sight (NLoS). Midband beam selection could hence often, although not always, be used as a basis for mmW beam selection without much performance degradation.

MmW radios rely on time domain beamforming with limited degrees of freedom, e.g., analog beamforming, and may likely do so for a foreseeable time. This may mean that the radio can only use one beam, or a set of beams, at a given time. Obtaining knowledge about the channel between a gNB and a User Equipment (UE) for a set of gNB receiving (Rx), and/or transmitting (Tx), beams may therefore be a time, and overhead, consuming process.

SUMMARY

As part of developing embodiments herein a problem was identified by the inventor and will first be discussed.

As mentioned above, obtaining knowledge about the channel between a gNB and a UE for a set of gNB Rx, and/or transmitting Tx, beams may be a time and overhead consuming process. This is since it is needed to alternate between different beams and/or set of beams, at different time instants, and then perform transmissions and/or receptions to acquire Channel State Information (CSI). A large set of gNB candidate Rx and/or Tx beams may therefore cause a high overhead which may imply a cost in terms of resources. Using a limited set of gNB candidate Rx and/or Tx beams may imply that not the spatial directions may be covered to the same degree as if using an unlimited set of gNB candidate Rx and/or Tx beams. The term covering is here quite general, but may e.g., mean that a spatial direction is covered if the obtained beamforming gain from the best beam from the limited set of gNB candidate Rx and/or Tx beams is within X dB of the best possible beam, given an unlimited set of gNB candidate Rx and/or Tx beams.

An object of embodiments herein is to improve the performance of the wireless communications network by providing a more efficient beam management.

According to an aspect of embodiments herein, the object is achieved by a method performed by a network node for selecting a precoder for a data transmission in a radio channel between the network node and a User Equipment, UE, in a wireless communications network.

The network node obtains a first set of candidate beams and a second set of candidate beams. The first set of candidate beams is obtained based on a first Channel State Information, CSI, relating to a first frequency band. The second set of candidate beams is obtained based on a second CSI relating to a second frequency band.

Based on evaluating CSI related to the first set of candidate beams and CSI related to the second set of candidate beams, the network node determines a third set of beams for acquiring CSI for the first frequency band. The third set of beams is based on at least one of the first set of candidate beams and the second set of candidate beams.

The network node obtains third CSI for the first frequency band for the radio channel between the network node and the UE based on the third set of beams.

The network node selects a precoder for a data transmission to the UE based on the obtained third CSI.

According to another aspect of embodiments herein, the object is achieved by a network node configured to select a precoder for a data transmission in a radio channel between the network node and a User Equipment, UE, in a wireless communications network. The network is further configured to:

- Obtain a first set of candidate beams and a second set of candidate beams, wherein the first set of candidate beams is adapted to be obtained based on a first Channel State Information, CSI, adapted to be related to a first frequency band, and the second set of candidate beams is adapted to be obtained based on a second CSI adapted to be related to a second frequency band,

- based on an evaluation of CSI adapted to be related to the first set of candidate beams and CSI adapted to be related to the second set of candidate beams, determine a third set of beams for acquiring CSI for the first frequency band, which third set of beams is adapted to be based on at least one of the first set of candidate beams and the second set of candidate beams, and

- obtain third CSI for the first frequency band for the radio channel between the network node and the UE based on the third set of beams, and

- select a precoder for a data transmission to the UE based on the obtained third CSI.

In this way, a more efficient beam management is achieved. This is since when obtaining the first and second set of candidate beams, and determining a third set of beams based on an evaluation CSI related the first and second sets of candidate beams, a precoder for data transmission may be selected based on CSI obtained based on the third set of beams. Embodiments herein e.g., brings the advantages of achieving an efficient beam management by obtaining a first and second set of candidate beams, where the first and second set of beams are related to different frequency bands, and selecting a precoder based on CSI obtained for a third set of beams which is related to a first frequency band and obtained from at least one or the first and second set of candidate beams. Thus, the network node may adaptively decide the third set of beams based on either, or both, of the first and second set of beams, which results in an improved performance of the wireless communications network by a more efficient beam management.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of embodiments herein are described in more detail with reference to attached drawings in which:

Figure 1 is a schematic block diagram illustrating embodiments of a wireless communications network.

Figure 2 is a flowchart depicting embodiments of a method in a network node. Figure 3 is a schematic block diagram illustrating examples of embodiments herein.

Figure 4 is a schematic block diagram illustrating examples of embodiments herein.

Figure 5 is a schematic block diagram illustrating embodiments of a network node.

Figure 6 schematically illustrates a telecommunication network connected via an intermediate network to a host computer.

Figure 7 is a generalized block diagram of a host computer communicating via a base station with a user equipment over a partially wireless connection.

Figures 8-11 are flowcharts illustrating methods implemented in a communication system including a host computer, a base station, and a user equipment.

DETAILED DESCRIPTION

Embodiments herein relate to a wireless communications network and the selection of a precoder for data transmission between a UE and a network node in a wireless communications network.

As mentioned above, an object of embodiments herein is to improve the performance of a wireless communications network by providing a more efficient beam management.

This may e.g., be achieved by alternating between two different schemes for selecting candidate Rx and/or Tx beams, such as gNB candidate Rx and/or Tx beams, to use when obtaining mmW CSI.

In one scheme, e.g., referred to as midband-based scheme, a smaller set of candidate Rx and/or Tx beams, such as gNB candidate Rx and/or Tx beams, may be derived based on midband CSI. As an example, the mmW gNB candidate Rx and/or Tx beams may be based on the N best midband beams identified by CSI Reference Signal Receive Power (CSI-RSRP) reporting or Sounding Reference Signal (SRS) reception at midband.

In another scheme, e.g., referred to as mmW-based scheme, a larger set of candidate Rx and/or Tx beams, such as gNB candidate Rx and/or Tx beams, may be derived through e.g., standard mmW beam management procedures.

Further, the object may be achieved by e.g., deciding how to alternate between the two schemes based on midband CSI and mmW CSI. As an example, based on both midband CSI and mmW CSI, the network node, e.g., a gNB, may assess in a periodic and/or aperiodic manner whether a UE has moved to a position where the N strongest midband beams corresponds poorly to the M strongest mmW beams.

If the bands are aligned, e.g., the N strongest midband beams corresponds well to the M strongest mmW beams, these N beams may be used to derive the candidate Rx and/or Tx beams, such as gNB candidate Rx and/or Tx beams, to acquire mmW CSI. Hence the midband-based scheme may be used.

If the bands are not aligned, e.g., the N best midband beams corresponds poorly to the M best mmW beams, a larger set of candidate Rx and/or Tx beams, such as gNB candidate Rx and/or Tx beams, may be used to acquire mmW CSI. Hence the mmW- based scheme may be used.

Consequently, this may result in fewer candidate Rx and/or Tx beams, such as gNB candidate Rx and/or Tx beams, being used at many UE locations, while maintaining mmW beam management at more challenging UE positions.

Figure 1 is a schematic overview depicting a wireless communications network 100 wherein embodiments herein may be implemented. The wireless communications network 100 comprises one or more RANs and one or more CNs. The wireless communications network 100 may use a number of different technologies, such as Wi-Fi, Long Term Evolution (LTE), LTE-Advanced, 5G, New Radio (NR), 6G, Wideband Code Division Multiple Access (WCDMA), Global System for Mobile communications/enhanced Data rate for GSM Evolution (GSM/EDGE), or Ultra Mobile Broadband (UMB), just to mention a few possible implementations. Embodiments herein relate to recent technology trends that are of particular interest in a 5G context, however, embodiments are also applicable in further development of the existing wireless communication systems such as e.g. WCDMA and LTE.

A number of RAN nodes operate in the communications network 100 such as e.g., the network node 110. The network node 110 provides radio coverage in a number of cells which may also be referred to as a beam or a beam group of beams, such as a cell 11 and a cell 12.

The network node 110 may be any of an NG-RAN node, a transmission and reception point e.g. a base station, a radio access network node such as a Wireless Local Area Network (WLAN) access point or an Access Point Station (AP STA), an access controller, a base station, e.g. a radio base station such as a NodeB, an evolved Node B (eNB, eNode B), a gNB, a base transceiver station, a radio remote unit, an Access Point Base Station, a base station router, a transmission arrangement of a radio base station, a stand-alone access point or any other network unit capable of communicating with a UE, such as e.g., a UE 121, within the service area served by the network node 110 depending e.g. on the radio access technology and terminology used. The network node 110 may be referred to as a serving RAN node and communicates with UEs such as the UE 121 , with Downlink (DL) transmissions to the UE121 , and in Uplink (UL) transmissions from the UE 121.

A number of UEs, such as e.g., the UE 121 , operate in the wireless communication network 100. The UE 121 may also be referred to as an loT device, a mobile station, a non-access point (non-AP), a STA, and/or a wireless terminal. It should be understood by the skilled in the art that “UE” is a non-limiting term which means any terminal, wireless communication terminal, user equipment, Machine Type Communication (MTC) device, Device to Device (D2D) terminal, a radio device in a vehicle, or node e.g., smart phone, laptop, mobile phone, sensor, relay, mobile tablets or even a small base station communicating within a cell.

Methods herein may be performed by the network node 110. As an alternative, a Distributed Node (DN) and functionality, e.g. comprised in the cloud 150 as shown in Figure 1 , may be used for performing or partly performing the methods herein.

According to examples of embodiments herein, a method and network node 110 for selecting a precoder, or a set of precoders, for data transmission between the UE 121 and the network node 110 is provided. E.g., the method may comprise alternating between a larger set, such as a first set, and a smaller set, such as a second set, of candidate Rx and/or Tx beams at e.g., mmW to obtain CSI. Further, at least the smaller set may be derived from CSI from different frequency band compared to the larger set. Which set to use may be selected, or obtained, based on joint CSI processing of CSI from the first frequency band and second frequency band. According to embodiments herein, a gNB, such as the network node 110, which may adaptively decide when to balance the number of gNB candidate Rx and/or Tx beams in one frequency band, typically using analog beamforming, based on measurements in another frequency band, typically using digital beamforming, may be provided. This may, e.g., bring the advantage of avoiding unnecessary waste of resources whenever possible without unnecessary loss of signal quality. Avoiding unnecessary beams avoids unnecessary overhead, saving energy and UE battery life. Further, embodiment herein may e.g., bring the advantage of faster beam management which may provide shorter delays, improved user experience and improved overall network performance.

A number of embodiments will now be described, some of which may be seen as alternatives, while some may be used in combination.

The embodiments of a method will be generally described in view of the network node 110 together with Figure 2. This will be followed by a more detailed description.

A method according to embodiments herein will now be described from the view of the network node 110, together with Figure 2. Figure 2 depicts example embodiments of a method performed by the network node 110 for selecting a precoder for a data transmission in a radio channel between the network node 110 and the UE 121 in the wireless communications network 100. The radio channel may e.g., be a radio channel on the first frequency band. The method comprises the following actions, which actions may be taken in any suitable order. Actions that are optional are presented in dashed boxes in Figure 2.

Action 201

The network node 110 obtains a first set of candidate beams and a second set of candidate beams. The first set of candidate beams is obtained based on a first CSI relating to a first frequency band. The second set of candidate beams is obtained based on a second CSI relating to a second frequency band. Obtaining the first and second sets of candidate beams may mean determining the first and second sets of candidate beams based on the first and second CSI. The first set of candidate beams may e.g. be determined from CSI originating from beam management procedures related to the first frequency band, such as the first CSI. These procedures may e.g., be based on a grid of beam search or by sweeping a selected set of beams. In some examples, the first set of candidate beams may correspond to the full grid of beams, while in other examples a subset of beams may be selected for the first set of candidate beams, e.g., based on the first CSI.

The second set of beams may e.g. be determined from CSI originating from CSI acquisition procedures related to the second frequency band, such as the second CSI. This CSI may be used to determine the second set of beams corresponding to a set of strong directions identified from the second CSI.

The first and second set of candidate beams may comprise one or more beams. The first set of candidate beams may comprise a larger set of beams than the second set of candidate beams. E.g., the second set of candidate beams may be subset of the first set of candidate beams in the sense of the spatial direction of the beams. This may mean the spatial direction of the beams comprised in the second set of candidate beams corresponds, at least partly, to the spatial direction of one or more of the beams in the first set of candidate beams.

In some embodiments, prior to obtaining the first and second sets of candidate beams, the network node 110 obtains the first CSI and the second CSI. The obtaining may comprise obtaining the first and second CSI using a CSI acquisition scheme comprising one or more out of: An SRS based CSI acquisition, a CSI -RS based CSI acquisition, and a beam sweeping based CSI acquisition. In other words, the network node may, in some examples, first obtain the first CSI and the second CSI, and then obtain, such as e.g., determine, the first set of candidate beams and the second set of candidate beams. The first CSI may be obtained based on the first set of candidate beams and the second CSI may be obtained based on the second set of candidate beams. Obtaining CSI based on a set of beams when used herein, may e.g., mean that the CSI is obtained, such as determined, estimated, received and/or calculated, for each respective beam in the set of beams. Hence, in some examples, CSI for a set of beams may comprise CSI for each respective beam in the set of beams. The CSI may e.g., indicate the RSRP of a respective beam.

The first frequency band and the second frequency band may comprise different frequency bands. In some embodiments, the first frequency band comprises a capacity frequency band and the second frequency band comprises an anchor or coverage frequency band. The first frequency band, such as e.g., the capacity frequency band, may e.g., a mmW frequency band. The first frequency band may also be referred to as a Frequency Range 2 (FR2) frequency band. The second frequency band, such as e.g., the anchor or coverage frequency band, may e.g., be a midband frequency band, or sub-6 frequency band. A midband or sub-6 frequency band may also be referred to as a FR1 frequency band. A sub-6 frequency band, which may also be referred to as a sub-6 GHz frequency band, and may mean a frequency band below 6 GHz.

Action 202

In some embodiments, the network node 110 evaluates CSI related to the first set of candidate beams and CSI related to the second set of candidate beams. The evaluation may comprise determining a frequency band alignment status.

A frequency band alignment status when used herein may be referred to as an indication indicating whether or not two or more frequency bands, such as e.g., the first frequency band and the second frequency band, are aligned e.g., in the sense of strong spatial directions. Referring to embodiments herein, aligned strong spatial directions may e.g., mean that the CSI related to the first set of candidate beams and the CSI related to the second set of candidate indicates that the characteristics of the two bands are similar, e.g., that strong spatial directions in the first band sufficiently well corresponds to strong spatial direction of the second band.

The evaluation may comprise evaluating the CSI related to the first set of candidate beams and the CSI related to the second set of candidate beams. In some examples, the CSI related to the first set of candidate beams comprises the first CSI and the CSI related to the second set of candidate beams comprises the second CSI.

In some embodiments, determining a frequency band alignment status comprises determining whether a strong spatial direction of the first frequency band corresponds to a strong spatial direction of the second frequency band. In an example, the first frequency band and the second frequency band may be considered to be aligned. This may e.g., mean that the N strongest spatial directions from the first set of candidate beams corresponds to the N strongest spatial directions from second set candidate beams. The N strongest spatial directions may e.g., mean the N beams with the strongest RSRP. In another example, the first frequency band and the second frequency band may be considered to be non-aligned. This may e.g., mean that the N strongest spatial directions from the first set of candidate beams do not correspond to the N strongest spatial directions from second set candidate beams.

In some embodiments, evaluating the CSI related to the first set of candidate beams and the CSI related to the second set of candidate beams by comprises obtaining fourth CSI for the first set of candidate beams and fifth CSI for the second set candidate beams. The fourth CSI is related to the first frequency band and the fifth CSI is related to the second frequency band.

The evaluation may comprise comparing the fourth CSI and the fifth CSI. I.e., the network node 110 may evaluate the fourth CSI and the fifth CSI by comparing the fourth CSI and the fifth CSI. In some examples.

The frequency band alignment status may indicate that the first frequency band and the second frequency band are aligned when e.g., the difference in RSRP of a beam X from the first set of candidate beams and a beam X’ from the second set of candidate beams is less than a first threshold. Beam X and beam X’ may be related to the same spatial direction. Beam X may be the beam with the strongest RSRP in the first set of candidate beams. Beam X’ may be the beam with the strongest RSRP in the second set of candidate beams.

Correspondingly, the frequency band alignment status may indicate that the first frequency band and the second frequency band are non-aligned when e.g., the difference in RSRP of a beam X from the first set of candidate beams and a beam X’ from the second set of candidate beams is greater than a second threshold. Beam X and beam X’ may be related to the same spatial direction. Beam X may be the beam with the strongest RSRP in the first set of candidate beams. Beam X’ may be the beam with the strongest RSRP in the second set of candidate beams.

Action 203

Based on evaluating CSI related to the first set of candidate beams and CSI related to the second set of candidate beams, the network node 110 determines a third set of beams for acquiring CSI for the first frequency band. The third set of beams is based on the first set of candidate beams and the second set of candidate beams. The third set of beams may comprise one or more beams. E.g., the third set of beams may comprise all or a subset of the first set of candidate beams. Alternatively, the third set of beams may comprise all or a subset of the second set of beams.

In some embodiments, when the frequency band alignment status indicates a strong spatial direction of the first frequency band corresponds to a strong spatial direction of the second frequency band, the third set of beams may comprise all or a subset of the second set of candidate beams. The third set of beams may comprise at least the N beams from the second set of candidate beams with the strongest RSRP.

In some embodiments, when the frequency band alignment status does not indicate a strong spatial direction of the first frequency band corresponds to a strong spatial direction of the second frequency band, the third set of beams may comprise all or a subset of the first set of candidate beams. The third set of beams may comprise at least the N’ beams from the first set of candidate beams with the strongest RSRP.

Action 204

The network node 110 obtains third CSI for the first frequency band for the radio channel between the network node 110 and the UE 121 based on the third set of beams.

As mentioned above, the first frequency band may comprise a capacity frequency band. Therefore, in some embodiments, the network node obtains the third CSI for first frequency band which comprises the capacity band.

In some embodiments, obtaining the third CSI for the first frequency band comprises that the network node 110 obtains the CSI using a CSI acquisition scheme. The CSI acquisition scheme may comprise one or more out of: An SRS based CSI acquisition, a CSI-RS based CSI acquisition, and a beam sweeping based CSI acquisition.

Action 205

The network node 110 selects a precoder for a data transmission to the UE 121 based on the obtained third CSI. The selected precoder may in some embodiments be selected for PDSCH transmissions. The selected precoder may comprise one or more precoders. The respective one or more precoders may correspond to respective beams in the third set of beams. In some embodiments, the network node 110 selects the precoder for data transmission on the first frequency band.

In some embodiments, precoder, or precoders, corresponding to the beam, or beams, with the highest quality is selected. The quality may e.g., be expressed in terms of RSRP. In other words, the precoder, or precoders, corresponding to the beam, or beams, with the strongest RSRP may be selected.

Embodiments mentioned above will now be further described and exemplified. The embodiments below are applicable to and may be combined with any suitable embodiment described above.

Although examples embodiments herein are applicable for cases where there are at least two frequency bands, it will in the following be exemplified for the case of two frequency bands. It will furthermore be assumed that the two bands correspond to mmW and midband and that CSI related information from the midband is used in the mmW band, although examples embodiments herein are applicable also when the roles of the bands are exchanged. Furthermore, examples embodiments herein are applicable for both DL transmission as well as UL reception. For a DL transmission, examples embodiments may provide methods to find, and/or maintain, a set of DL precoders, whereas for UL reception, examples embodiments herein may provide methods to find, and/or maintain, a set of UL receiver weights. In the following, the case of DL transmission will be exemplified. In Figure 3 a gNB 110, such as the network node 110, according to an example of embodiments herein is depicted. The network node 110 may e.g., comprise any one or more of the following:

- A midband CSI acquisition unit 301. The midband CSI acquisition unit 301 may output CSI based on midband transmission/s and/or reception/s.

- A precoder generator 302. The precoder generator 302 may, based on the midband and mmW CSI output two sets of precoders: i. A first set of precoders that may be used for mmW DL transmission. ii. A second set of precoders that may cover only a subset of the spatial directions covered by the first set of precoders.

- A mmW CSI acquisition unit 303. the mmW CSI acquisition unit 303 may, based on mmW transmission/s and/or reception/s output mmW CSI. The mmW acquisition unit may depend on the first set of precoders, the second set of precoders and the band alignment status.

- A monitoring unit 304. The monitoring unit 304 may operate on CSI obtained both from the midband CSI acquisition unit 301 as well as the mmW CSI acquisition unit 303 and may output a band alignment status.

- A PDSCH transmission unit 305. The PDSCH transmission unit 305 may perform PDSCH transmission/s based on CSI acquired from the mmW acquisition unit.

In one example of embodiments herein, these components may be located in the gNB 110, such as the network node 110, and may be interacting with a UE, such as the UE 121 , according to Figure 4.

It is noted that for the CSI acquisition units they may e.g., be based on at least one of the following:

- The entire or a portion of the carrier bandwidth, e.g., using a narrowband receiver.

- Second order statistics of the channel, such as e.g., a covariance matrix, which may be derived from a channel estimate. - Wideband channel estimate, but measured on only a subset of UE ports.

- A channel estimate constrained to a linear subspace.

Midband CSI acquisition unit

The midband CSI may be obtained based on an UL transmission, e.g., Sounding Reference signal (SRS), Demodulation Reference Signal (DMRS) and/or Physical Uplink Shared Channel (PUSCH), and/or on a DL transmission, e.g., CSI Reference Signal (CSI- RS) and/or Synchronization Signaling Block (SSB). The midband CSI constitutes information related to the midband channel. This information may be “rich” in the sense that it contains detailed information of the channel, e.g., the channel matrix, covariance matrix etc., but it may also be more condensed, e.g., describing the set of N strongest spatial directions and/or RSRP of the spatial directions.

Precoder generator:

The first set of precoders, such as the first set of beams, may be predefined and may e.g., correspond to a grid of beams spanning all spatial directions of the channel. The first set of precoders may also be a subset of the full grid of beams, selected based on mmW CSI, e.g., SSB RSRP or CSI-RSRP reported by the UE.

The first set of precoders may however also depend on the midband CSI. In some examples, a set of “strong” directions at midband are identified and the first set of precoders are chosen, such as selected or obtained, in such a way that they jointly cover the set of strong directions. It is here emphasized that it may require multiple precoders, such as beams, in mmW to cover one strong direction in midband since a mmW beam typically is narrower than a midband beam. A spatial direction is considered “strong” if a transmission from the network node 110 that is using a beam directed in the spatial direction is expected to result in a relatively large received power at the UE 121 side compared to other spatial directions.

Based on the midband CSI a second set of precoders, such as the second set of beams, that may cover only a subset of the spatial directions covered by the first set of precoders, is chosen, such as selected or obtained.

In some examples, a set of “strong” directions at midband are identified and the second set of precoders are chosen in such a way that they jointly cover the set of strong directions. This may e.g., be done in a best effort manner given that the second set of precoders should have a certain size. In another example of an embodiment the selection is instead carried out to guarantee that some condition is met, such as e.g., all spatial directions in midband where the channel is within X dB of the strongest spatial direction should be covered by the second set of precoders, and the size of the second set is adjusted to meet this condition.

In some examples, the second set of precoders may have a cardinality less than the cardinality of the first set of precoders and in one such example the second set of precoders is a proper subset of the first set of precoders. Hence, there may be at least one precoder in the first set of precoders that is not a member of the second set of precoders. Some examples, the term proper subset is used in a general sense and may imply that a proper subset of the spatial directions that are covered by the first set of precoders are covered by the second set of precoders. This may mean that there may exist precoders in the second set of precoders that do not exist in the first set of precoders.

MmW CSI acquisition unit

The mmW CSI may be obtained based on UL transmission/s, e.g., SRS, DMRS, and/or PLISCH. The mmW CSI may further be obtained by based on DL transmission/s, e.g., CSI-RS or SSB. The DL transmission, or UL reception, may carried out using either the first set of precoders or otherwise the second set of precoders. Which set that is used may in turn depend on the band alignment status. If the monitoring unit 304 estimates that the bands are aligned, in the sense that e.g., the strong spatial direction/s at midband also corresponds to the strong spatial direction/s at mmW, the second set of the precoders may be used for the CSI acquisition. Otherwise, when the bands are not aligned, the first set of precoders may be used for the CSI acquisition.

In some examples, beam management procedures are used for obtaining mmW CSI. This procedure may involve fewer beams in the case that the bands are aligned than in the case when the bands are not aligned, thereby reducing the amount of overhead required to obtain mmW CSI, e.g., in case the cardinality of the second set of precoders has a cardinality less than the cardinality of the first set of precoders. In some examples, the cardinality of the two sets is equal but the resolution from the second set of precoders is instead finer, e.g., since they will cover a smaller set of spatial directions of the channel.

Monitoring unit

The monitoring unit 304 may take midband CSI as well as mmW CSI as input and analyze to what extent the two bands are aligned in the sense that e.g., the strong spatial direction/s at midband also corresponds to the strong spatial direction/s at mmW. In some examples, the RSRP from the strongest, and/or set of strongest, directions from midband is compared to from the strongest, and/or set of strongest, directions as obtained at mmWwhen using with the first or second set of precoders. If the channel profile appears “similar” from this perspective the bands are considered aligned.

In some examples, the mmW CSI may be acquired using the first set of precoders in a periodic manner and this CSI is used to assess to what extent the bands are aligned or not. In some examples, the mmW CSI is acquired using the first set of precoders in an aperiodic manner. This process may for instance be triggered when it is detected that the bands are not aligned when comparing midband CSI and mmW CSI obtained when using the second set of precoders.

In some examples, the RSRP from the strongest, and/or set of strongest, directions as obtained at mmWwhen using with the first set of precoders may be compared to the strongest, and/or set of strongest, directions as obtained at mmWwhen using the second set of precoders. If the channel profile appears “similar” from this perspective the bands are considered aligned.

Below is pseudo code examples regarding the band alignment status, assuming that RSRP( ) corresponds to RSRP for precoder /:

In another example this following pseudo code is instead used:

• If ( max (RSRP(J.)) - max RSRP i)') ] < T3, then band_alignment

\iesecond set iemidband_precoders )

- true;

PDSCH transmission

Based on the mmW CSI a precoder may be chosen, such as selected, and used for PDSCH transmission on the mmW frequency band, such as the first frequency band.

Figure 5 shows an example of arrangement in the network node 110. The network node 110 may comprise an input and output interface 500 configured to communicate with each other. The input and output interface 500 may comprise a receiver, e.g. wired and/or wireless, (not shown) and a transmitter, e.g. wired and/or wireless, (not shown).

The network node 110 is configured to select a precoder for a data transmission in a radio channel between the network node 110 and the UE 121 in the wireless communications network 100

The network node 110 obtains a first set of candidate beams and a second set of candidate beams. The first set of candidate beams is adapted to be obtained based on the first CSI. The first CSI is adapted to be related to the first frequency band. The second set of candidate beams is adapted to be obtained based on the second CSI. The second CSI is adapted to be related to the second frequency band.

Based on an evaluation of CSI adapted to be related to the first set of candidate beams and CSI adapted to be related to the second set of candidate beams, the network node 110 determines a third set of beams for acquiring CSI for the first frequency band. The third set of beams is adapted to be based on at least one of the first set of candidate beams and the second set of candidate beams.

The network node 110 obtains the third CSI for the first frequency band for the radio channel between the network node 110 and the UE 121 based on the third set of beams.

The network node 110 selects a precoder for a data transmission to the UE 121 based on the obtained third CSI.

In some embodiments, to evaluate the CSI related to the first set of candidate beams and the CSI related to the second set of candidate beams is adapted to comprise to determine a frequency band alignment status.

In some embodiments, to determine a frequency band alignment status is adapted to comprise to determine whether a strong spatial direction of the first frequency band corresponds to a strong spatial direction of the second frequency band.

In some embodiments, to evaluate the CSI related to the first set of candidate beams and the CSI related to the second set of candidate beams is adapted to comprise obtain: - Fourth CSI for the first set of candidate beams, the fourth CSI adapted to be related to the first frequency band, and

- fifth CSI for the second set candidate beams, the fifth CSI adapted to be related to the second frequency band.

The evaluation may be adapted to comprise comparing the fourth CSI and the fifth CSI.

In some embodiments, to obtain the third CSI for the first frequency band is adapted to comprise to obtain the CSI using a CSI acquisition scheme adapted to comprise one or more out of:

- An SRS based CSI acquisition,

- an CSI-RS based CSI acquisition, and

- a beam sweeping based CSI acquisition.

In some embodiments, the first frequency band and the second frequency band are adapted to comprise different frequency bands.

In some embodiments, any one or more out of:

- The first frequency band is adapted to comprise a capacity frequency band, and

- the second frequency band is adapted to comprise a reference frequency band.

The embodiments herein may be implemented through a respective processor or one or more processors, such as at least one processor 510 of a processing circuitry in the network node 110 depicted in Figure 5, together with computer program code for performing the functions and actions of the embodiments herein. The program code mentioned above may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing the embodiments herein when being loaded into the network node 110. One such carrier may be in the form of a CD ROM disc. It is however feasible with other data carriers such as a memory stick. The computer program code may furthermore be provided as pure program code on a server and downloaded to the network node 110.

The network node 110 may further comprise respective a memory 520 comprising one or more memory units. The memory 520 comprises instructions executable by the processor 510 in the network node 110. The memory 520 is arranged to be used to store instructions, data, configurations, identifiers, indications, notifications, radio channels, CSI, beams, frequency bands, frequency band alignment status, spatial directions, and applications to perform the methods herein when being executed in the network node 110.

In some embodiments, a computer program 530 comprises instructions, which when executed by the at least one processor 510, cause the at least one processor 510 of the network node 110 to perform the actions above.

In some embodiments, a respective carrier 540 comprises the respective computer program 530, wherein the carrier 540 is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium.

Those skilled in the art will also appreciate that the functional modules in the network node 110, described below may refer to a combination of analog and digital circuits, and/or one or more processors configured with software and/or firmware, e.g. stored in the network node 110, that when executed by the respective one or more processors such as the at least one processor 510 described above cause the respective at least one processor 510 to perform actions according to any of the actions above. One or more of these processors, as well as the other digital hardware, may be included in a single Application-Specific Integrated Circuitry (ASIC), or several processors and various digital hardware may be distributed among several separate components, whether individually packaged or assembled into a system-on-a-chip (SoC).

Further Extensions and Variations

With reference to Figure 6, in accordance with an embodiment, a communication system includes a telecommunication network 3210, such as a 3GPP-type cellular network, which comprises an access network 3211 , such as a radio access network, and a core network 3214. The access network 3211 comprises a plurality of base stations 3212a, 3212b, 3212c, e.g. the network node 110, such as AP STAs NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 3213a, 3213b, 3213c. Each base station 3212a, 3212b, 3212c is connectable to the core network 3214 over a wired or wireless connection 3215. A first user equipment (UE) such as the UE 121 and/or a Non-AP STA 3291 located in coverage area 3213c is configured to wirelessly connect to, or be paged by, the corresponding base station 3212c. A second UE 3292 and/or a Non-AP STA in coverage area 3213a is wirelessly connectable to the corresponding base station 3212a. While a plurality of UEs 3291 , 3292 are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole UE is in the coverage area or where a sole UE is connecting to the corresponding base station 3212.

The telecommunication network 3210 is itself connected to a host computer 3230, which may be embodied in the hardware and/or software of a standalone server, a cloud- implemented server, a distributed server or as processing resources in a server farm. The host computer 3230 may be under the ownership or control of a service provider, or may be operated by the service provider or on behalf of the service provider. The connections 3221, 3222 between the telecommunication network 3210 and the host computer 3230 may extend directly from the core network 3214 to the host computer 3230 or may go via an optional intermediate network 3220. The intermediate network 3220 may be one of, or a combination of more than one of, a public, private or hosted network; the intermediate network 3220, if any, may be a backbone network or the Internet; in particular, the intermediate network 3220 may comprise two or more sub-networks (not shown).

The communication system of Figure 6 as a whole enables connectivity between one of the connected UEs 3291 , 3292 and the host computer 3230. The connectivity may be described as an over-the-top (OTT) connection 3250. The host computer 3230 and the connected UEs 3291 , 3292 are configured to communicate data and/or signaling via the OTT connection 3250, using the access network 3211 , the core network 3214, any intermediate network 3220 and possible further infrastructure (not shown) as intermediaries. The OTT connection 3250 may be transparent in the sense that the participating communication devices through which the OTT connection 3250 passes are unaware of routing of uplink and downlink communications. For example, a base station 3212 may not or need not be informed about the past routing of an incoming downlink communication with data originating from a host computer 3230 to be forwarded (e.g., handed over) to a connected UE 3291. Similarly, the base station 3212 need not be aware of the future routing of an outgoing uplink communication originating from the UE 3291 towards the host computer 3230.

Example implementations, in accordance with an embodiment, of the UE, base station and host computer discussed in the preceding paragraphs will now be described with reference to Figure 7. In a communication system 3300, a host computer 3310 comprises hardware 3315 including a communication interface 3316 configured to setup and maintain a wired or wireless connection with an interface of a different communication device of the communication system 3300. The host computer 3310 further comprises processing circuitry 3318, which may have storage and/or processing capabilities. In particular, the processing circuitry 3318 may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The host computer 3310 further comprises software 3311 , which is stored in or accessible by the host computer 3310 and executable by the processing circuitry 3318. The software 3311 includes a host application 3312. The host application 3312 may be operable to provide a service to a remote user, such as a UE 3330 connecting via an OTT connection 3350 terminating at the UE 3330 and the host computer 3310. In providing the service to the remote user, the host application 3312 may provide user data which is transmitted using the OTT connection 3350.

The communication system 3300 further includes a base station 3320 provided in a telecommunication system and comprising hardware 3325 enabling it to communicate with the host computer 3310 and with the UE 3330. The hardware 3325 may include a communication interface 3326 for setting up and maintaining a wired or wireless connection with an interface of a different communication device of the communication system 3300, as well as a radio interface 3327 for setting up and maintaining at least a wireless connection 3370 with a UE 3330 located in a coverage area (not shown in Figure 7) served by the base station 3320. The communication interface 3326 may be configured to facilitate a connection 3360 to the host computer 3310. The connection 3360 may be direct or it may pass through a core network (not shown in Figure 7) of the telecommunication system and/or through one or more intermediate networks outside the telecommunication system. In the embodiment shown, the hardware 3325 of the base station 3320 further includes processing circuitry 3328, which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The base station 3320 further has software 3321 stored internally or accessible via an external connection.

The communication system 3300 further includes the UE 3330 already referred to. Its hardware 3335 may include a radio interface 3337 configured to setup and maintain a wireless connection 3370 with a base station serving a coverage area in which the UE 3330 is currently located. The hardware 3335 of the UE 3330 further includes processing circuitry 3338, which may comprise one or more programmable processors, applicationspecific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The UE 3330 further comprises software 3331, which is stored in or accessible by the UE 3330 and executable by the processing circuitry 3338. The software 3331 includes a client application 3332. The client application 3332 may be operable to provide a service to a human or non-human user via the UE 3330, with the support of the host computer 3310. In the host computer 3310, an executing host application 3312 may communicate with the executing client application 3332 via the OTT connection 3350 terminating at the UE 3330 and the host computer 3310. In providing the service to the user, the client application 3332 may receive request data from the host application 3312 and provide user data in response to the request data. The OTT connection 3350 may transfer both the request data and the user data. The client application 3332 may interact with the user to generate the user data that it provides. It is noted that the host computer 3310, base station 3320 and UE 3330 illustrated in Figure 7 may be identical to the host computer 3230, one of the base stations 3212a, 3212b, 3212c and one of the UEs 3291 , 3292 of Figure 6, respectively. This is to say, the inner workings of these entities may be as shown in Figure 7 and independently, the surrounding network topology may be that of Figure 6.

In Figure 7, the OTT connection 3350 has been drawn abstractly to illustrate the communication between the host computer 3310 and the use equipment 3330 via the base station 3320, without explicit reference to any intermediary devices and the precise routing of messages via these devices. Network infrastructure may determine the routing, which it may be configured to hide from the UE 3330 or from the service provider operating the host computer 3310, or both. While the OTT connection 3350 is active, the network infrastructure may further take decisions by which it dynamically changes the routing (e.g., on the basis of load balancing consideration or reconfiguration of the network).

The wireless connection 3370 between the UE 3330 and the base station 3320 is in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improve the performance of OTT services provided to the UE 3330 using the OTT connection 3350, in which the wireless connection 3370 forms the last segment. More precisely, the teachings of these embodiments may improve the [select the applicable RAN effect: data rate, latency, power consumption] and thereby provide benefits such as [select the applicable corresponding effect on the OTT service: reduced user waiting time, relaxed restriction on file size, better responsiveness, extended battery lifetime],

A measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection 3350 between the host computer 3310 and UE 3330, in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring the OTT connection 3350 may be implemented in the software 3311 of the host computer 3310 or in the software 3331 of the UE 3330, or both. In embodiments, sensors (not shown) may be deployed in or in association with communication devices through which the OTT connection 3350 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software 3311, 3331 may compute or estimate the monitored quantities. The reconfiguring of the OTT connection 3350 may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not affect the base station 3320, and it may be unknown or imperceptible to the base station 3320. Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling facilitating the host computer’s 3310 measurements of throughput, propagation times, latency and the like. The measurements may be implemented in that the software 3311 , 3331 causes messages to be transmitted, in particular empty or ‘dummy’ messages, using the OTT connection 3350 while it monitors propagation times, errors etc.

Figure 8 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to Figure 6 and Figure 7. For simplicity of the present disclosure, only drawing references to Figure 8 will be included in this section. In a first step 3410 of the method, the host computer provides user data. In an optional substep 3411 of the first step 3410, the host computer provides the user data by executing a host application. In a second step 3420, the host computer initiates a transmission carrying the user data to the UE. In an optional third step 3430, the base station transmits to the UE the user data which was carried in the transmission that the host computer initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In an optional fourth step 3440, the UE executes a client application associated with the host application executed by the host computer.

Figure 9 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to Figure 6 and Figure 7. For simplicity of the present disclosure, only drawing references to Figure 9 will be included in this section. In a first step 3510 of the method, the host computer provides user data. In an optional substep (not shown) the host computer provides the user data by executing a host application. In a second step 3520, the host computer initiates a transmission carrying the user data to the UE. The transmission may pass via the base station, in accordance with the teachings of the embodiments described throughout this disclosure. In an optional third step 3530, the UE receives the user data carried in the transmission.

Figure 10 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to Figure 6 and Figure 7. For simplicity of the present disclosure, only drawing references to Figure 10 will be included in this section. In an optional first step 3610 of the method, the UE receives input data provided by the host computer. Additionally, or alternatively, in an optional second step 3620, the UE provides user data. In an optional substep 3621 of the second step 3620, the UE provides the user data by executing a client application. In a further optional substep 3611 of the first step 3610, the UE executes a client application which provides the user data in reaction to the received input data provided by the host computer. In providing the user data, the executed client application may further consider user input received from the user. Regardless of the specific manner in which the user data was provided, the UE initiates, in an optional third substep 3630, transmission of the user data to the host computer. In a fourth step 3640 of the method, the host computer receives the user data transmitted from the UE, in accordance with the teachings of the embodiments described throughout this disclosure.

Figure 11 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station such as an AP STA, and a UE such as a Non-AP STA which may be those described with reference to Figure 6 and Figure 7. For simplicity of the present disclosure, only drawing references to Figure 11 will be included in this section. In an optional first step 3710 of the method, in accordance with the teachings of the embodiments described throughout this disclosure, the base station receives user data from the UE. In an optional second step 3720, the base station initiates transmission of the received user data to the host computer. In a third step 3730, the host computer receives the user data carried in the transmission initiated by the base station.

When using the word "comprise" or “comprising” it shall be interpreted as nonlimiting, i.e. meaning "consist at least of".

The embodiments herein are not limited to the above described preferred embodiments. Various alternatives, modifications and equivalents may be used.

Claims

1. A method performed by a network node (110) for selecting a precoder for a data transmission in a radio channel between the network node (110) and a User Equipment, UE, (121) in a wireless communications network (100), the method comprising: obtaining (201) a first set of candidate beams and a second set of candidate beams, wherein the first set of candidate beams is obtained based on a first Channel State Information, CSI, relating to a first frequency band, and the second set of candidate beams is obtained based on a second CSI relating to a second frequency band, based on evaluating (202) CSI related to the first set of candidate beams and CSI related to the second set of candidate beams, determining (203) a third set of beams for acquiring CSI for the first frequency band, which third set of beams is based on at least one of the first set of candidate beams and the second set of candidate beams, and obtaining (204) third CSI for the first frequency band for the radio channel between the network node (110) and the UE (121) based on the third set of beams, and selecting (205) a precoder for a data transmission to the UE (121) based on the obtained third CSI.

2. The method according to claim 1, wherein evaluating (202) the CSI related to the first set of candidate beams and the CSI related to the second set of candidate beams comprises determining a frequency band alignment status.

3. The method according to claim 2, wherein determining a frequency band alignment status comprises determining whether a strong spatial direction of the first frequency band corresponds to a strong spatial direction of the second frequency band.

4. The method according to any of claims 1-3, wherein evaluating (202) the CSI related to the first set of candidate beams and the CSI related to the second set of candidate beams comprises obtaining:

- fourth CSI for the first set of candidate beams, the fourth CSI relating to the first frequency band, and

- fifth CSI for the second set candidate beams, the fifth CSI relating to the second frequency band, and wherein the evaluating comprises comparing the fourth CSI and the fifth CSI.

5. The method according to any of claims 1-4, wherein obtaining (204) the third CSI for the first frequency band comprises obtaining the CSI using a CSI acquisition scheme comprising one or more out of:

- a Sounding Reference Signal, SRS, based CSI acquisition,

- a CSI Reference Signal, CSI-RS, based CSI acquisition, and

- a beam sweeping based CSI acquisition.

6. The method according to any of claims 1-5, wherein the first frequency band and the second frequency band comprise different frequency bands.

7. The method according to any of claims 1-6, wherein any one or more out of:

- the first frequency band comprises a capacity frequency band, and

- the second frequency band comprises an anchor or coverage frequency band.

8. A computer program (530) comprising instructions, which when executed by a processor (510), causes the processor (510) to perform actions according to any of the claims 1-7.

9. A carrier (540) comprising the computer program (530) of claim 8, wherein the carrier (540) is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer- readable storage medium.

10. A network node (110) configured to select a precoder for a data transmission in a radio channel between the network node (110) and a User Equipment, UE, (121) in a wireless communications network (100), the network is further configured to: obtain a first set of candidate beams and a second set of candidate beams, wherein the first set of candidate beams is adapted to be obtained based on a first Channel State Information, CSI, adapted to be related to a first frequency band, and the second set of candidate beams is adapted to be obtained based on a second CSI adapted to be related to a second frequency band, based on an evaluation of CSI adapted to be related to the first set of candidate beams and CSI adapted to be related to the second set of candidate beams, determine a third set of beams for acquiring CSI for the first frequency band, which third set of beams is adapted to be based on at least one of the first set of candidate beams and the second set of candidate beams, and obtain third CSI for the first frequency band for the radio channel between the network node (110) and the UE (121) based on the third set of beams, and select a precoder for a data transmission to the UE (121) based on the obtained third CSI.

11. The network node (110) according to claim 10, wherein to evaluate the CSI related to the first set of candidate beams and the CSI related to the second set of candidate beams is adapted to comprise to determine a frequency band alignment status.

12. The network node (110) according to claim 11 , wherein determining a frequency band alignment status is adapted to comprise to determine whether a strong spatial direction of the first frequency band corresponds to a strong spatial direction of the second frequency band.

13. The network node (110) according to any of claims 10-12, wherein to evaluate the CSI related to the first set of candidate beams and the CSI related to the second set of candidate beams is adapted to comprise obtain:

- fourth CSI for the first set of candidate beams, the fourth CSI adapted to be related to the first frequency band, and

- fifth CSI for the second set candidate beams, the fifth CSI adapted to be related to the second frequency band, and wherein the evaluation is adapted to comprise comparing the fourth CSI and the fifth CSI.

14. The network node (110) according to any of claims 10-13, wherein to obtain the third CSI for the first frequency band is adapted to comprise to obtain the CSI using a CSI acquisition scheme comprising one or more out of:

- a Sounding Reference Signal, SRS, based CSI acquisition,

- a CSI Reference Signal, CSI-RS, based CSI acquisition, and

- a beam sweeping based CSI acquisition.

15. The network node (110) according to any of claims 10-14, wherein the first frequency band and the second frequency band are adapted to comprise different frequency bands.

16. The network node (110) according to any of claims 10-15, wherein any one or more out of:

- the first frequency band is adapted to comprise a capacity frequency band, and - the second frequency band is adapted to comprise an anchor or coverage frequency band.