Network node and method in a wireless communications network

Abstract

A method performed by a network node is provided The method is for tracking beams from multiple User Equipments (UEs) in a wireless communications network. The network node serves a service area. The service area is divided into a number N of sub-areas. All UEs of the multiple UEs are configured to transmit Sounding Reference Signals (SRSs) over a same set of M symbols in a time domain. The network node receives (501) SRSs from each respective UE out of the multiple UEs, as configured. For each symbol, out of the set of M symbols of the received SRSs, the network node performs the following: The network node selects (502) a sub-area one by one among the number N of sub-areas. For each selected sub-area, when one or more UEs out of the multiple UEs are located inside the selected sub-area, the network node decodes (503) SRS received from these one or more UEs for beam tracking within the service area. Additionally, or alternatively for each selected sub-area, when one or more UEs out of the multiple UEs are located outside the selected sub-area, but their respective current beams have an adjacent beam located within the selected sub-area, the network node decodes (504) SRS from these UEs for neighbor beam tracking.

Description

[0001] NETWORK NODE AND METHOD IN A WIRELESS COMMUNICATIONS NETWORK

[0002] TECHNICAL FIELD

[0003] Embodiments herein relate to a network node and methods therein in a wireless communications network. In some aspects, they relate to tracking beams from multiple User Equipments (UE)s in the wireless communications network.

[0004] BACKGROUND

[0005] In a typical wireless communication network, wireless devices, also known as wireless communication devices, mobile stations, stations (STA) and / or User Equipment (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, a Base Station (BS) or a radio base station (RBS), which in some networks may also be denoted, for example, a Base Station (BS), a NodeB, eNodeB (eNB), or gNodeB (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 a radio frequency with the wireless devices within the range of the radio network node.

[0006] 3rd Generation Partnership Project (3GPP) is the standardization body for specifying the standards for the cellular system evolution, e.g., including 3G, 4G, 5G and the future evolutions. Specifications for Evolved Universal Terrestrial Radio Access (E- UTRA) and Evolved Packet System (EPS) have been completed within the 3GPP. In 4G also called a Fourth Generation (4G) network, EPS is core network and E-UTRA is radio access network. In 5G, 5G Core (5GC) is core network, NR is radio access network. As a continued network evolution, the new release of 3GPP specifies a 5G network also referred to as 5G New Radio (NR) and 5GC.

[0007] Frequency bands for 5G NR are being separated into two different frequency ranges, Frequency Range 1 (FR1) and Frequency Range 2 (FR2). FR1 comprises sub-6 GHz frequency bands. Some of these bands are bands traditionally used by legacy standards but have been extended to cover potential new spectrum offerings from 410 MHz to 7125 MHz. FR2 comprises frequency bands from 24.25 GHz to 52.6 GHz. Bands in this millimeter wave range have shorter range but higher available bandwidth than bands in the FR1.

[0008] Multi-antenna techniques may significantly increase the data rates and reliability of a wireless communication system. For a wireless connection between a single user, such as a UE, and a base station (BS), 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. This may be referred to as Single-User (SU)-MIMO. In the scenario where MIMO techniques is used for the wireless connection between multiple users and the base station, MIMO enables the users to communicate with the base station simultaneously using the same time-frequency resources by spatially separating the users, which increases further the cell capacity. This may be referred to as Multi-User (MU)-MIMO. Note that MU-MIMO may benefit when each UE only has one antenna. The cell capacity can be increased linearly with respect to the number of antennas at the BS side. Due to that, more and more antennas are employed in BS. Such systems and / or related techniques are commonly referred to as massive MIMO.

[0009] In fifth generation (5G) New Radio (NR), millimeter wave (mmW) frequency maintaining a decent coverage for UEs is quite challenging unless there is a directed beam towards a particular UE. Beamforming enables a dynamic creation of directed beams, by changing phase and amplitude of individual antenna elements, towards a particular UE to enhance its link budget. 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.

[0010] The 3rd 3GPP has in 38.802 Section 6.1.6 defined layer 1 and layer 2 beam management procedures. Procedure 1 (P1) is the initial access procedure, P2 is for beam refinement and tracking at the Next Generation NodeB (gNB)and P3 is for UE beam refinement.

[0011] Figure 1 depicts a 5G NR beam refinement procedure, and downlink-based beam management. The procedures P1, P2 and P3 in a gNB and a UE based on Channel State Information (CSI) - Reference Signals (RS)s are illustrated in Figure 1 and are summarized as follows.

[0012] During the P1 procedure, the gNB broadcasts 11 Synchronization Signal Blocks (SSBs) in DL through wide beams. These typically cover several UEs at the same time. Via measurements the UEs identify which of the SSBs is the best for their current location. Following this, the UE transmits 12 a preamble on a Random Access Channel (RACH) occasion that corresponds to a best SSB. The gNB receives that RACH occasion using the same Wide Beams (WB) that was used for transmitting the corresponding SSB and with the preamble reception the gNB gets the information about the best wide beam for the UE at present. After the initial access is completed, the gNB triggers a beam refinement 13 or P2 procedure in order to identify the best narrow beam within the strongest SSB that was identified during P1 procedure. After the completion 14, 15, 16 of beam refinement, data transmission and reception at the gNB is performed on narrow beams. However, to account for the dynamic changes in the channel and mobility of UEs, gNB needs to track each UE by sending CSI-RS 17 per candidate narrow beam towards each UE and processing the response 18, called CSI report, from UEs to determine the best new narrow beam direction. The beam tracking may try candidate beams close to the narrow beam currently considered the strongest one.

[0013] There is in parallel also CSI reporting on SSB measurements 19, wide beam management, occasionally they would indicate a new strongest wide beam corresponding to an SSB. Then the gNB yet again would perform something similar to a beam refinement, offering the UE a set of candidate Channel State Information Reference Signal (CSI-RS)s representing narrow beams to be measured on to find out what is the strongest narrow beam within the new wide beam. CSI-RS is a reference signal (RS) that is used in the Downlink (DL) direction in 5G NR.

[0014] The P3 procedure is mainly performed 20 by the UE with some assistance from gNB to refine its transmit and receive beam if capable of beamforming.

[0015] In examples herein, a time division duplex (TDD) system is assumed, where the same frequency band is used for both uplink and downlink directions with different time periods or slots for uplink and downlink communication.

[0016] Instead of downlink-based beam management with CSI-RS to track the UE as described in Figure 1 sounding signals may be used.

[0017] Then the UE is requested to transmit a so-called Sounding Reference Signal (SRS), see 3GPP Release 18 38.211. The SRS transmitted by a UE on uplink is a specifically defined reference signal received by a base station. The base station allocates SRS resources individually for each UE. The UEs are provided with SRS resources orthogonal to each other, meaning they are differentiated with respect to frequency, resource blocks and comb pointing out specific subcarriers, and cyclic shift. The cyclic shift is a way to share a range of subcarriers. A sequence of complex phases is applied to the subcarriers as a function of subcarrier index. Each UE would have different sequences, loosely referred to as different cyclic shifts, to share the frequency resources. All in all, the aspect that each UE is provided with an individual resource means that there will always be a limit on how many SRS resources can be allocated at a given time.

[0018] To build affordable beamforming systems for high-band deployment it is possible to rely on time-domain beamforming. This means beamforming weights are applied per antenna element after the point of Inverse Fast Fourier Transform (IFFT) as seen from the downlink perspective. To have even more cost-efficient solutions only a few beam directions may be allowed, to reduce the signal processing the beamforming machinery needs to manage. Another aspect of building affordable beamforming systems for mmW is the need for many antenna elements to get enough coverage. Having digital processing chains with digital units like Analogue Digital (AD) converters for each antenna element is costly. A compromise is hybrid beamforming as shown in Figure 2. Each antenna subarray subject to analogue beamforming is connected to a digital processing chain. If there was no analogue beamforming applied this would be the same as pure digital beamforming. To the right in Figure 2 it is indicated that the antenna subarrays in this example cover two spatial sub-areas, as induced by analogue beamforming.

[0019] Assuming one of the spatial sub-areas induced by analogue beamforming in Figure 2, there is an option of digital beamforming. The digital beamforming may introduce a Grid of Beams (GoB), both in horizontal and vertical dimension. Seen from above this would look like in Figure 3, showing a GoB in the horizontal dimension. There may be several of these, one per vertical plane, such that the GoB extends in the vertical dimension as well.

[0020] A digital receiver may be used to analyse sounding signals from a UE, concluding on what narrow beams in the GoB are the dominant ones, assuming one spatial sub-area induced by analogue beamforming. This would then form the basis for uplink-based beam management, another version of the beam tracking described above using CSI-RS.

[0021] As shown in Figure 1, the UE from time to time moves from a coverage of one SSB to the coverage of another SSB. The base station would notice such event based on UE- reported SSB measurements in a CSI report. The base station would inform the UE that the coverage changed by signalling of Transmission Configuration Indicator (TCI) state for the downlink and by signalling of spatial relation for the uplink. TCI state and spatial relation may be viewed as enumerations of the wide beams connected to SSBs. There is one TCI state / spatial relation per SSB.

[0022] SUMMARY

[0023] As part of developing embodiments herein, the inventors identified some problems that first will be described.

[0024] Beam tracking based on CSI-RS in DL is costly compared to sounding, since one CSI-RS transmission per candidate beam and UE is needed. The number of simultaneously supported beam directions also limits how many CSI-RS may be multiplexed on a given symbol and therefore many P2 tracking events may be executed in parallel. Beam tracking based on sounding in combination with hybrid beamforming is more resource efficient since it involves one reference signal transmission from the UE that is spatially analysed by a digital receiver, so no need to reserve one symbol per narrow beam for CSI-RS. However, when a new best SSB for the UE is detected, additional measurements are required to evaluate the possible new candidate narrow beams corresponding to the new best SSB. This will be discussed more in detail below.

[0025] An object of embodiments herein is to improve the tracking beams from multiple UEs in a wireless communications network.

[0026] According to an aspect of embodiments herein, the object is achieved by a method performed by a network node. The method is for tracking beams from multiple User Equipments (UEs) in a wireless communications network. The network node serves a service area. The service area is divided into a number N of sub-areas. All UEs of the multiple UEs are configured to transmit Sounding Reference Signals (SRSs) over a same set of M symbols in a time domain. The network node receives from each respective UE out of the multiple UEs, SRSs as configured. For each symbol, out of the set of M symbols of the received SRSs, the network node performs the following. The network node selects a sub-area one by one among the number N of sub-areas. For each selected sub-area, when one or more UEs out of the multiple UEs are located inside the selected sub-area, the network node decodes SRS received from these one or more UEs for beam tracking within the service area. Additionally, or alternatively for each selected sub-area, when one or more UEs out of the multiple UEs are located outside the selected sub-area, but their respective current beams have an adjacent beam located within the selected sub-area, the network node decodes SRS from these UEs for neighbor beam tracking.

[0027] According to another aspect of embodiments herein, the object is achieved by a network node. The network node is configured to track beams from multiple User Equipments (UEs) in a wireless communications network. The network node is adapted to serve a service area. The service area is divided into a number N of sub-areas. All UEs of the multiple UEs are configured to transmit SRSs over a same set of M symbols. The network node is further configured to:

[0028] - Receive from each respective UE out of the multiple UEs, SRSs as configured, For each symbol, out of the set of M symbols of the received SRSs:

[0029] - Select a sub-area one by one among the number N of sub-areas, and for each selected sub-area,

[0030] - When one or more UEs out of the multiple UEs are located inside the selected sub-area, the network node is further being configured to decode SRS adapted to be received from these one or more UEs for beam tracking within the service area, and / or

[0031] - When one or more UEs out of the multiple UEs are located outside the selected sub-area, but their respective current beams have an adjacent beam located within the selected sub-area, the network node is further being configured to decode SRS from these UEs for neighbor beam tracking.

[0032] Embodiments herein may provide one or more of the following advantages: Embodiments herein e.g., provide a method and configuration for tracking narrow beams in current wide beam corresponding to current spatial state and for measuring narrow beams from adjacent wide beam corresponding to other spatial relation even when the spatial relation is related to adjacent spatial sub-areas as induced by analogue beamforming. This would otherwise have required separate and / or additional SRS resources to be configured for the UEs, which may be limited by UE capabilities for some UEs.

[0033] Embodiments herein overcome the spatial limits of hybrid beamforming by combining the use of multiple symbols with multiple spatial sub-areas and combining normal beam tracking with neighbour tracking, thus avoiding additional overheads. Multiple symbols are anyway needed for the entire service area.

[0034] Embodiments herein e.g., use one symbol only for an SRS transmission to enable a network node to do beam tracking within current spatial sub-area. This is to overcome the need of CSI-RS for downlink beam management within current spatial sub-area to occur on many symbols.

[0035] BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Examples of embodiments herein are described in more detail with reference to attached drawings in which:

[0037] Figure 1 is a combined flowchart and signaling scheme according to prior art.

[0038] Figure 2 is a schematic block diagram according to prior art.

[0039] Figure 3 is a schematic block diagram according to prior art.

[0040] Figure 4 is a schematic block diagram illustrating embodiments of a communications network.

[0041] Figure 5 is a flowchart depicting an embodiment of a method in a network node.

[0042] Figure 6 is a schematic block diagram illustrating an example embodiment of a method herein.

[0043] Figure 7 is a schematic block diagram illustrating an example embodiment of a method herein.

[0044] Figure 8 is a schematic block diagram illustrating an example embodiment of a method herein.

[0045] Figure 9 is a schematic block diagram illustrating embodiments of a network node.

[0046] DETAILED DESCRIPTION

[0047] As part of developing embodiments herein, the inventors identified some problems that will be described further below. As hinted above, beam tracking based on CSI-RS in DL is costly compared to sounding, since one CSI-RS transmission per candidate beam and UE is needed. The number of simultaneously supported beam directions also limits how many CSI-RS may be multiplexed on a given symbol and therefore how many P2 tracking events may be executed in parallel. As a result, the maximum number of connected UEs that can be served by the base station is typically smaller for DL (CSI-RS) based Beam Management (BM) than for UL (SRS) based BM. Beam tracking based on sounding in combination with hybrid beamforming is more resource efficient since it involves one reference signal transmission from the UE that is spatially analysed by a digital receiver, so no need to reserve one symbol per narrow beam for CSI-RS. However, when a new best SSB for the UE is detected, additional measurements are required to evaluate the possible new candidate narrow beams corresponding to the new best SSB.

[0048] To reduce the need for additional measurements, beam tracking may include not only narrow beams corresponding to the current SSB but also narrow beams corresponding to spatially adjacent SSBs. The detection of a new best narrow beam corresponding to an adjacent SSB may lead to a decision to switch to the corresponding TCI state / spatial relation without involving additional measurements.

[0049] Neighbour tracking in downlink-based beam management has problems with the combination of hybrid beamforming and deployment of several primary carriers. The reason for this is that the component of analogue beamforming in hybrid beamforming means a symbol is dedicated to cover the same sub-area for all frequency resources of all deployed carriers. This means each CSI-RS representing a candidate narrow beam needs to be mapped to a symbol dedicated to the correct sub-area.

[0050] Downlink based beam management reserves a number of symbols for CSI-RS. On each of these symbols a CSI-RS is transmitted representing a candidate narrow beam for the UE to measure on. Neighbour tracking is based on a sub-selection of narrow beams close to the current beam. When that sub-selection involves neighboring beams from different spatial sub-areas, as induced by analogue beamforming, it is difficult to coordinate the scheduling such that it fits all users in all carriers doing downlink beam management; recall one spatial area applies to all frequency resources. For some UEs the neighbour beams are all within one specific spatial area. For other UEs the neighbour beams are with another spatial area. For yet another group of users the neighbour beams may be from any combination of spatial sub-areas, the number of neighbour beams per spatial sub-area may also be different. This means it is complicated to coordinate the subareas for many users concurrently doing beam management measurements on CSI-RS.

[0051] For UL SRS based beam management the need to coordinate the sub-areas on all cells also applies. However, the problem is substantially mitigated because of the significant reduction of reference signal transmissions needed for the beam management procedures, only one reference signal in time-domain needed per sub-area compared to one reference signal per candidate narrow beam and sub-area.

[0052] For sounding based on SRS, the possibility of above-mentioned neighbour tracking is limited by the availability of configurable SRS resources, simply because of lack of support by the UE chipsets. It is also limited by the spatial coverage of the SRS receiver when the possible new candidate beam falls outside the current spatial sub-area area induced by analogue beamforming.

[0053] Example embodiments herein use the same multi-symbol SRS resource for both beam tracking within current spatial relation and measurement of beams from adjacent spatial area.

[0054] According to some examples, each UE is configured to perform SRS signalling with a multi-symbol SRS resource comprising M symbols, with a certain periodicity. The physical SRS signal is repeated in the M symbols. An entire service area of a cell is divided into N sub-areas such that N <= M. A network node, e.g. a gNB, providing service in the service area, receives SRS from a different spatial sub-area in each of the configured symbols, therefore it is possible to handle the entire service area within the configured symbols. A spatial sub-area when used herein is covered by a beamform induced by analogue beamforming as shown in Figure 2(b). All sub-areas are handled for each UE, since the UE repeats the SRS M times and all narrow beams are represented in the transmitted SRS. The network node resolves all the narrow beams in its digital receiver. In other words, the network node does not need to do a UE-specific subselection of sub-areas and narrow beams. Figure 4 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 communications network 100 may use 5G NR but may further use a number of other different technologies, such as, 6G, Wi-Fi, Long Term Evolution (LTE), LTE-Advanced, Wideband Code Division Multiple Access (WCDMA), Global System for Mobile communications / enhanced Data rate for GSM Evolution (GSM / EDGE), Worldwide Interoperability for Microwave Access (WiMax), or Ultra Mobile Broadband (UMB), just to mention a few possible implementations.

[0055] Network nodes, such as a network node 110, operate in the RAN of the communications network 100. The network node 110 serves a service area 115. According to embodiments herein, the service area 115 is divided into a number N of subareas 116, 117, 118. This will be explained more in detail below.

[0056] The network node 110, may be a transmission and reception point e.g. a radio access network node such as a base station, e.g. a radio base station such as a NodeB, an evolved Node B (eNB, eNode B), an NR Node B (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, a Wireless Local Area Network (WLAN) access point or an Access Point Station (AP STA), an access controller, or any other network unit capable of communicating with UEs, such as the UEs UE1 , UE2, and UE3, within a cell, e.g., served by the network node 110. The respective network node 110 may be referred to as a serving radio network node and may communicate with the UEs UE1 , UE2, and UE3 with Downlink (DL) transmissions to the UEs UE1 , UE2, and UE3 and Uplink (UL) transmissions from the UEs UE1 , UE2, and UE3.

[0057] One or more UEs operate in the wireless communication network 100, such as e.g. the UEs UE1, UE2, and UE3. The UEs UE1 , UE2, and UE3 may e.g. each be a remote UE, a wireless device, an NR device, a mobile station, a wireless terminal, an NB-loT device, an MTC device, an eMTC device, a CAT-M device, a WiFi device, an LTE device and an a non-access point (non-AP) STA, a STA, that communicates via a network node such as e.g. the network node 110, one or more Access Networks (AN), e.g. a RAN, to one or more core network (CN) nodes, in one or more CNs. The UEs UE1 , UE2, and UE3 may communicate with one or more CN nodes. It should be understood by the skilled in the art that “UE” is a non-limiting term which means any terminal, client, mobile client, IMS client, wireless communication terminal, user equipment, Device to Device (D2D) terminal, or node e.g. smart phone, laptop, mobile phone, sensor, relay, mobile tablets or even a car or any small base station communicating within a cell.

[0058] Methods according to embodiments herein are performed by the network node 110. This node may be Distributed Nodes (DN)s and functionality, e.g. comprised in a cloud 170 as shown in Figure 4.

[0059] Example embodiments herein provide M multi-symbol SRS signalling with the multiple UEs such as e.g., UE1, UE2 and UE3, where each UE is configured to transmit SRS repeatedly over the same M symbols in time domain.

[0060] The network node 110 needs only one symbol (of the configured M symbols) for estimating best narrow beam for any particular UE e.g., UE2, based on the UE2’s current wide beam. There is a hierarchical structure such that a sub-area is covered by several wide beams, and a wide beam embraces a set of narrow beams.

[0061] The network node 110 may optionally use additional symbols of the configured M symbols for estimating possible new best narrow beam from wide beams adjacent to a UE’s, such as e.g. UE1 and / or UE3s, current wide beam, even when the wide beams are related to other spatial sub-areas as induced by analogue beamforming.

[0062] Within the configured M symbols, the network node 110 goes through the entire service area of the cell, divided into spatial sub-areas, and performs the beam tracking for all UEs, e.g. UE1 , UE2 and UE3, that are configured with the same set of M symbols.

[0063] A number of embodiments will now be described, some of which may be seen as alternatives, while some may be used in combination.

[0064] A method according to embodiments will first be described in a general way as seen from the view of the network node 110 together with Figure 5, followed by examples and a more detailed description.

[0065] Embodiments herein provide methods and configuration for tracking beams such as narrow beams corresponding to the N sub-areas 116, 117, 118 corresponding to the service area 115. The method may e.g., further relate to measuring narrow beams from an adjacent wide beam corresponding to another spatial relation, even when the spatial relation is related to adjacent spatial sub-areas as induced by analogue beamforming. This will support mobility from one sub-area to another without reported SSB measurements from a UE.

[0066] Examples of embodiments herein overcome the spatial limits of hybrid beamforming by combining the use of multiple symbols with multiple sub-areas, also referred to as spatial sub-areas, and combining normal beam tracking with neighbour tracking.

[0067] Figure 5 shows exemplary embodiments of a method performed the network node 110. The method is for tracking beams from the multiple UEs, UE1, UE2, UE3 in the wireless communications network 100. The network node 110 serves the service area 115. There is a hierarchical structure such that a sub-area is covered by several wide beams, and a wide beam embraces a set of narrow beams. The service area 115 is divided into a number N of sub-areas 116, 117, 118. Each sub-area may be created by means of analog beamforming. This is e.g., to obtain good coverage without the cost that comes with digital beamforming. N may be a small number, even as small as two, (one means strictly digital beamforming). In addition to the analog frontend creating the N subareas using analog beamforming, there may also be digital beamforming, creating a grid of (narrow) beams for each of the N sub-areas 116, 117, 118. All, or at least most of the, UEs of the multiple UEs, UE1 , UE2, UE3 are configured to transmit SRSs over a same set of M symbols in a time domain. To transmit SRSs over set of M symbols e.g., means that each UE transmits a physical signal simply repeated in each of the M symbols. In this way the network node (110) may receive SRSs over this set of M symbols from each UE regardless of what sub-area it resides in. It is not needed to e.g., allocate the M symbols for each UE UE1, UE2, UE3, in a time-multiplexing fashion. All the UEs UE1, UE2, UE3 may be frequency-multiplexed over the M symbols by means of different comb offsets, cyclic shifts and PRBs.

[0068] The method comprises the following actions, which actions may be taken in any suitable order. Optional actions are referred to as dashed boxes in Figure 5.

[0069] Action 501.

[0070] The network node 110 receives from each respective UE out of the multiple UEs UE1, UE2, UE3, SRSs as configured.

[0071] The SRSs may be received from each respective UE over the same set of M symbols. The network node 110 may receive SRSs from each respective UE according to any one or more out of: Receiving from each respective UE, SRSs over the same set of M symbols, and receiving from each respective UE, SRSs over the same set of M symbols as configured from one single SRS resource configured to have M symbols repeated.

[0072] For each symbol, out of the set of M symbols of the received SRSs, the network node 110 performs the following Actions 502-504:

[0073] Action 502.

[0074] The network node 110 selects a sub-area one by one among the number N of subareas EP1, EP2, EP3.

[0075] In some embodiments, the selecting of a sub-area one by one among the number N of sub-areas EP1, EP2, EP3, is performed until any one out of: All N sub-areas 116, 117, 118 have been selected, or all N sub-areas 116, 117, 118 in which UEs are located and all sub-areas with neighbor beams of UEs have been selected.

[0076] For each selected sub-area 116, 117, 118, the network node 110 checks if any of the multiple UEs, UE1, UE2, UE3 are located inside the selected sub-area, and if any of the multiple UEs, UE1 , UE2, UE3 are located outside the selected sub-area. This is since the measurements of SRSs from the UEs UE1, UE2, UE3 are to be handled differently depending on whether they are located inside or outside of the selected sub-area, which will be explained below.

[0077] Action 503.

[0078] When one or more UEs, e.g., the second UE2, out of the multiple UEs, UE1 , UE2, UE3 are located inside the selected sub-area, the network node 110 decodes SRS received from these one or more UEs UE2 for beam tracking within the service area 115.

[0079] The network node 110 e.g., measures the signal quality for each of the narrow beams for the UEs located inside the subarea. These measurements for a specific UE will later be compared with nearby narrow beams in a different sub-area of the same UE.

[0080] Action 504.

[0081] Additionally, or alternatively, when one or more UEs UE1 , UE3 out of the multiple UEs, UE1 , UE2, UE3 are located outside the selected sub-area, but their respective current beams have an adjacent beam located within the selected sub-area, the network node 110 decodes SRS from these UEs UE1, UE3 for neighbor beam tracking. The network node 110 may e.g., measure the signal quality for each of the narrow beams for UEs out of the multiple UEs, UE1 , UE2, UE3 that are located outside of this subarea. These measurements for a specific UE may later be compared with narrow beams in the same sub-area the UE is located in.

[0082] Adjacent beams when used herein e.g. means that directions of these beams are as close to each other angularly as possible. It may also mean beams, that are two, three or n beams away from the current beam. The adjacent beams may further be referred to as nearby beams.

[0083] Action 505

[0084] In some of these embodiments, and for each UE, out of the multiple UEs UE1 , UE2, UE3, the network node 110 may select a best narrow beam. The selecting is performed based on comparing narrow beams inside the UEs sub-area with nearby narrow beams outside the sub-area of the UE. This may e.g. be performed based on comparing narrow beams of different subareas for each UE.

[0085] The selecting of the best narrow beam may comprise: Selecting a best narrow beam as a new narrow beam when for each UE: A best narrow beam inside the sub-area of the UE is better than a current narrow beam by a first margin and a new wide beam related to the best narrow beam is better than the current wide beam by a second margin. Optionally the first margin may be smaller or larger in case the best narrow beam is inside the current wide beam.

[0086] The selecting of the best narrow beam may further or as an alternative comprise: Selecting a best narrow beam as a new narrow beam when for each UE: A best narrow beam outside the sub-area of the UE is better than a current narrow beam by a third margin and a new wide beam related to the best narrow beam is better than a current wide beam by a fourth margin for the best narrow beam.

[0087] If the selected new narrow beam is outside its current wide beam, a new TCI state and / or a new spatial relation may be signaled to the UE.

[0088] For example, since the UEs are not using a correct spatial relation, in other words not the correct spatial filter, for another wide beam different than current wide beam, a special margin is used, the third and fourth margin. Also, to increase the confidence the current wide beam may be compared with the wide beam related to the best narrow beam. In some embodiments, the sub-area, as e.g., induced by analog beamforming, of the first of the M symbols are aligned with the sub-area, as induced by analog beamforming, of the symbols for a preceding transmission. That may mean that a preceding transmission may be prolonged. The same analog beamforming then applies to this prolonged transmission such that more information can be transmitted (in this subarea).

[0089] After selecting the sub-areas comprising current or adjacent beams of any UE, unused symbols out of the M symbols, may be used for any upcoming transmission.

[0090] It should be noted that for a UE, such as e.g., UE2, to be located inside the selected sub-area in fact may mean that the network node 110 considers UE2 to have a current wide beam and a current narrow beam within the selected sub-area.

[0091] Embodiments herein such as the embodiments mentioned above will now be further described and exemplified. The text below is applicable to and may be combined with any suitable embodiment described above.

[0092] Assume in the following example, that the service area 115 comprises N spatial sub-areas 116, 117, 118, and an SRS receiver of the network node 110 is capable of handling one sub-area at a time. These sub-areas 116, 117, 118 are denoted as Elevation Planes (EP)s in illustrations Figures 6, 7 and 8. In the example below the number of subareas 116, 117, 118 N=3. In this example and in the corresponding figures, the sub-area 116 is referred to as EP1 , the sub-area 117 is referred to as EP2, and the sub-area 118 is referred to as EP3.

[0093] Figures 6-8 refer to examples of applying embodiments herein to a service area that has three UEs, UE1 , UE2, and UE3.

[0094] In the illustrations in Figures 6-8, a 4-symbol SRS resource is configured, i.e. , the set of M symbols comprises 4 symbols, M=4. This is based on Radio Resource Control (RRC) parameters referred to as number of symbols (nrofSymbols) and repetition Factor (repetitionFactor) as part of SRS-Resource in 3GPP standard Release 15 38.331. 3GPP does not allow three symbols to be configured for the repetitionFactor, in release 15 only 1 , 2 and four symbols are allowed. Therefore, in this example, only the last 3 symbols will be used, as there are only 3 sub-areas. The network node 110 will be performing the following:

[0095] For each of the 3 symbols: Select a sub-area that has not been handled, and:

[0096] - If there are UEs currently located in this sub-area, decode SRS for these

[0097] UEs for beam tracking within current spatial relation,

[0098] - Else if there are UEs that are not located in this sub-area but have their adjacent SSBs located in this sub-area, decode SRS for these UEs for neighbour tracking.

[0099] Referring to Figure 6, depicting receiving of SRS for EP2.

[0100] In the 2nd symbol of the 4 configured, the network node 110, such as its SRS receiver, processes UL transmissions of SRS from the sub-area denoted as EP2. The network node 110 checks if any of the multiple UEs, UE1, UE2, UE3 are located inside the selected sub-area EP2, and if any of the multiple UEs, UE1 , UE2, UE3 are located outside the selected sub-area EP2.

[0101] UE2 is located inside EP2. The network node 110 makes beam direction estimation for UE2 based on its current spatial relation, i.e., its wide beam. The network node 110 measures the signal quality for each of the narrow beams for UE2 located inside the subarea. These measurements for the UE2 may later be compared with nearby narrow beams in a different sub-area of the same UE.

[0102] UE1 is located outside EP2 but its current wide beam has adjacent wide beams located in EP2. The network node 110 makes beam direction estimation for UE1 from a set of candidate beams that are located in EP2, beam id 284, 285, 286, 287, 288, in this example referred to in dashed section 610 in Figure 6. The network node 110 measures the signal quality for each of the nearby narrow beams for UE1 located outside of this subarea. These measurements for UE1 may later be compared with narrow beams in the same sub-area the UE1 is located in.

[0103] UE3 is located outside EP2 but its current wide beam has adjacent wide beams located in EP2. The gNB makes beam direction estimation for UE3 from a set of candidate beams that are located in EP2, beam id 169, 170, 171 , 172, 173 in this example, referred to in dashed section 620 in Figure 6.

[0104] Referring to Figure 7, depicting receiving of SRS for EP3.

[0105] In the 3rd symbol of the 4 configured, the network node 110, such as its SRS receiver, processes UL transmissions of SRS from the sub-area denoted as EP3.

[0106] UE1 is located inside EP3. The network node 110 makes beam direction estimation for UE1 based on its current spatial relation, i.e., its wide beam. No other UEs are close enough to have neighbor beams in EP3.

[0107] Referring to Figure 8, depicting receiving of SRS for EP1.

[0108] In the 4th symbol of the 4 configured, the network node 110 such as its SRS receiver, processes UL transmissions of SRS from the sub-area denoted as EP1.

[0109] UE3 is located inside EP1. The network node 110 makes beam direction estimation for UE3 based on its current spatial relation, i.e. its wide beam.

[0110] UE2 is located outside EP1 but its current wide beam has adjacent wide beams located in EP1. The network node 110 makes beam direction estimation for UE2 from a set of candidate beams that are located in EP1 , beam id 111 , 112, 113, 114, 115 in this example, referred to in dashed section 810 in Figure 8.

[0111] After the steps illustrated above, for all three UEs, UE1, UE2, and UE3 in the example, the network node 110 has a complete view of the best candidate beams including candidate beams adjacent to the UEs’ current wide beams. Note that the order of sub-areas, i.e., the mapping of sub-areas onto symbols, probed by network node 110 is not important. The important point is that each relevant sub-area 116, 117, 118, i.e., EP1, EP2, EP3 in this example, is probed, also referred to as investigated, at least once. This may allow other transmissions with a preferred sub-area to occur concurrently with reception of SRS. For instance, a Physical Uplink Shared Channel (PUSCH) transmission may include the first symbol of the repeated symbols with SRS, not with same Physical Resource Blocks (PRB)s. The sub-area, as e.g., induced by analog beamforming, of the first SRS symbol is aligned with the sub-area, as e.g., induced by analog beamforming, of the symbols for the preceding PUSCH transmission. That may mean that the preceding PUSCH transmission may be prolonged. The same analog beamforming then applies to this prolonged transmission such that more information can be transmitted (in this subarea). The SRS reception would then start with the sub-area of the PUSCH; the following symbols would cover the remaining subareas and no PUSCH.

[0112] To perform the method actions above, the network node 110 is configured to track beams from multiple User Equipments, UEs, UE1 , UE2, UE3 in a wireless communications network 100. The network node 110 is adapted to serve a service area 115. The service area 115 is divided into a number N of sub-areas 116, 117, 118. All UEs of the multiple UEs, UE1 , UE2, UE3 are configured to transmit SRSs over the same set of M symbols.

[0113] The network node 110 may comprise an arrangement depicted in Figure 9. The network node 110 may comprise an input and output interface 900 configured to communicate in the communications network 100, e.g., with the multiple UEs UE1 , UE2, UE3. The input and output interface 900 may comprise a wireless receiver not shown, and a wireless transmitter not shown.

[0114] The network node 110 is further configured to receive from each respective UE out of the multiple UEs UE1 , UE2, UE3, SRSs as configured.

[0115] The network node 110 is further configured to, for each symbol, out of the set of M symbols of the received SRSs, perform the following:

[0116] The network node 110 is further configured to: Select a sub-area one by one among the number N of sub-areas EP1, EP2, EP3, for each selected sub-area 116, 117, 118.

[0117] - When one or more UEs UE2 out of the multiple UEs, UE1, UE2, UE3 are located inside the selected sub-area, decode SRS adapted to be received from these one or more UEs UE2 for beam tracking within the service area 115, and / or

[0118] - When one or more UEs UE1 , UE3 out of the multiple UEs, UE1 , UE2, UE3 are located outside the selected sub-area, but their respective current beams have an adjacent beam located within the selected sub-area, decode SRS from these UEs UE1, UE3 for neighbor beam tracking.

[0119] In some embodiments, the network node 110 is further configured to select a subarea one by one among the number N of sub-areas EP1, EP2, EP3, until any one out of:

[0120] - all N sub-areas 116, 117, 118 have been selected, or

[0121] - all N sub-areas 116, 117, 118 in which UEs are located and all sub-areas with neighbor beams of UEs have been selected.

[0122] The network node 110 may further be configured to receive SRSs from each respective UE by any one or more out of: Receiving from each respective UE, SRSs over the same set of M symbols, and receiving from each respective UE, SRSs over the same set of M symbols as configured from one single SRS resource configured to have M symbols repeated.

[0123] In some embodiments, the network node 110 is further being configured to, for each UE, out of the multiple UEs UE1, UE2, UE3, select a best narrow beam based on comparing narrow beams inside the UEs sub-area with nearby narrow beams outside the sub-area of the UE. In some embodiments, the network node 110 is further configured to select the best narrow beam by selecting a best narrow beam as a new narrow beam when for each UE: A best narrow beam inside the sub-area of the UE is better than a current narrow beam by a first margin and a new wide beam related to the best narrow beam is better than the current wide beam by a second margin. Optionally the first margin may be smaller or larger in case the best narrow beam is inside the current wide beam.

[0124] In some embodiments, the network node 110 is further configured to select the best narrow beam by selecting a best narrow beam as a new narrow beam when for each UE: A best narrow beam outside the sub-area of the UE is better than a current narrow beam by a third margin and a new wide beam related to the best narrow beam is better than a current wide beam by a fourth margin for the best narrow beam.

[0125] In some embodiments, the network node 110 is further configured to receive SRSs from each respective UE by any one or more out of: Receiving from each respective UE, SRSs over the same set of M symbols, and receiving from each respective UE, SRSs over the same set of M symbols as configured from one single SRS resource configured to have M symbols repeated.

[0126] In some embodiments, the sub-area of the first of the M symbols are adapted to be aligned with the sub-area of a preceding transmission.

[0127] In some embodiments, the network node 110 is further being configured to: after selecting of the sub-areas comprising current or adjacent beams of any UE, use unused symbols out of the M symbols for any upcoming transmission.

[0128] Embodiments herein may be implemented through a respective processor or one or more processors, such as the respective processor 910 of a processing circuitry in the network node 110 depicted in Figure 9 with respective 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.

[0129] The network node 110 may further comprise a respective memory 920 comprising one or more memory units. The memory 920 comprises instructions executable by the processor in the network node 110. The memory 920 is arranged to be used to store e.g., media functions, indications, tags, information, data, configurations, communication data, and applications to perform the methods herein when being executed in the network node 110.

[0130] In some embodiments, a computer program 930 comprises instructions, which when executed by the respective at least one processor 910, cause the at least one processor of the network node 110 to perform the actions above.

[0131] In some embodiments, a carrier 940 comprises the computer program 930, wherein the carrier 940 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.

[0132] Those skilled in the art will appreciate that units in the network node 110 described above 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 processors described 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).

[0133] When using the word "comprise" or “comprising” it shall be interpreted as nonlimiting, i.e. meaning "consist at least of".

[0134] The embodiments herein are not limited to the preferred embodiments described above. Various alternatives, modifications and equivalents may be used.

Claims

CLAIMS1. A method performed by a network node (110) for tracking beams from multiple User Equipments, UEs, (UE1, UE2, UE3) in a wireless communications network (100), wherein the network node (110) serves a service area (115), which service area (115) is divided into a number N of sub-areas (116, 117, 118), and wherein all UEs of the multiple UEs, (UE1 , UE2, UE3) are configured to transmit Sounding Reference Signals, SRSs, over a same set of M symbols in a time domain, the method comprising: receiving (501) from each respective UE out of the multiple UEs (UE1 , UE2, UE3), SRSs as configured, for each symbol, out of the set of M symbols of the received SRSs: selecting (502) a sub-area one by one among the number N of sub-areas (EP1, EP2, EP3), and for each selected sub-area (116, 117, 118):- when one or more UEs (UE2) out of the multiple UEs, (UE1 , UE2, UE3) are located inside the selected sub-area, decoding (503) SRS received from these one or more UEs (UE2) for beam tracking within the service area (115), and / or- when one or more UEs (UE1 , UE3) out of the multiple UEs, (UE1 , UE2, UE3) are located outside the selected sub-area, but their respective current beams have an adjacent beam located within the selected sub-area, decoding (504) SRS from these UEs (UE1 , UE3) for neighbor beam tracking.

2. The method according to claim 1, wherein the selecting (502) of a sub-area one by one among the number N of sub-areas (EP1, EP2, EP3), is performed until any one out of:- all N sub-areas (116, 117, 118) have been selected, or- all N sub-areas (116, 117, 118) in which UEs are located and all sub-areas with neighbour beams of UEs have been selected.

3. The method according to any of the claims 1-2, wherein receiving (501) SRSs from each respective UE comprises any one or more out of: receiving from each respective UE, SRSs over the same set of M symbols, and receiving from each respective UE, SRSs over the same set of M symbols as configured from one single SRS resource configured to have M symbols repeated.

4. The method according to any of the claims 1-3, further comprising: for each UE, out of the multiple UEs (UE1 , UE2, UE3), selecting (505) a best narrow beam based on comparing narrow beams inside the UEs sub-area with nearby narrow beams outside the sub-area of the UE.

5. The method according to claim 4, wherein selecting (505) a best narrow beam comprises: selecting a best narrow beam as a new narrow beam when for each UE: a best narrow beam inside the sub-area of the UE is better than a current narrow beam by a first margin and a new wide beam related to the best narrow beam is better than the current wide beam by a second margin.

6. The method according to any of the claims 4-5, wherein selecting (505) a best narrow beam comprises: selecting a best narrow beam as a new narrow beam when for each UE: a best narrow beam outside the sub-area of the UE is better than a current narrow beam by a third margin and a new wide beam related to the best narrow beam is better than a current wide beam by a fourth margin for the best narrow beam.

7. The method according to any of the claims 1-6, wherein the sub-area of the first of the M symbols are aligned with the sub-area of a preceding transmission.

8. The method according to any of the claims 1-7, wherein after selecting (502) the sub-areas comprising current or adjacent beams of any UE, the unused symbols out of the M symbols, are used for any upcoming transmission.

9. A computer program (930) comprising instructions, which when executed by a processor (910), causes the processor (910) to perform actions according to any of the claims 1-8.

10. A carrier (940) comprising the computer program (930) of claim 9, wherein the carrier (940) is one of an electronic signal, an optical signal, an electromagneticsignal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium.

11. A network node (110) configured to track beams from multiple User Equipments, UEs, (UE1 , UE2, UE3) in a wireless communications network (100), wherein the network node (110) is adapted to serve a service area (115), which service area (115) is divided into a number N of sub-areas (116, 117, 118), and wherein all UEs of the multiple UEs, (UE1 , UE2, UE3) are configured to transmit Sounding Reference Signals, SRSs, over a same set of M symbols, the network node (110) further configured to: receive from each respective UE out of the multiple UEs (UE1 , UE2, UE3), SRSs as configured, for each symbol, out of the set of M symbols of the received SRSs: select a sub-area one by one among the number N of sub-areas (EP1 , EP2, EP3), and for each selected sub-area (116, 117, 118), the network node (110) further being configured to:- when one or more UEs (UE2) out of the multiple UEs, (UE1 , UE2, UE3) are located inside the selected sub-area, decode SRS adapted to be received from these one or more UEs (UE2) for beam tracking within the service area (115), and / or- when one or more UEs (UE1 , UE3) out of the multiple UEs, (UE1 , UE2, UE3) are located outside the selected sub-area, but their respective current beams have an adjacent beam located within the selected sub-area, decode SRS from these UEs (UE1 , UE3) for neighbor beam tracking.

12. The network node (110) according to claim 11 , wherein the selecting of a sub-area one by one among the number N of sub-areas (EP1 , EP2, EP3), is adapted to be performed until any one out of:- all N sub-areas (116, 117, 118) have been selected, or- all N sub-areas (116, 117, 118) in which UEs are located and all sub-areas with neighbour beams of UEs have been selected.

13. The network node (110) according to any of the claims 11-12, further being configured to receive SRSs from each respective UE by any one or more out of: receiving from each respective UE, SRSs over the same set of M symbols, andreceiving from each respective UE, SRSs over the same set of M symbols as configured from one single SRS resource configured to have M symbols repeated.

14. The network node (110) according to any of the claims 11-13, further being configured to: for each UE, out of the multiple UEs (UE1 , UE2, UE3), select a best narrow beam based on comparing narrow beams inside the UEs sub-area with nearby narrow beams outside the sub-area of the UE.

15. The network node (110) according to claim 14, further being configured to select a best narrow beam by: selecting a best narrow beam as a new narrow beam when for each UE: a best narrow beam inside the sub-area of the UE is better than a current narrow beam by a first margin and a new wide beam related to the best narrow beam is better than the current wide beam by a second margin.

16. The network node (110) according to any of the claims 14-15, further being configured to select a best narrow beam by: selecting a best narrow beam as a new narrow beam when for each UE: a best narrow beam outside the sub-area of the UE is better than a current narrow beam by a third margin and a new wide beam related to the best narrow beam is better than a current wide beam by a fourth margin for the best narrow beam.

17. The network node (110) according to any of the claims 11-16, wherein the sub-area of the first of the M symbols are adapted to be aligned with the sub-area of a preceding transmission.

18. The network node (110) according to any of the claims 11-17, further being configured to: after selecting the sub-areas comprising current or adjacent beams of any UE, using unused symbols out of the M symbols for any upcoming transmission.

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