An apparatus and a computer program

Abstract

A user equipment comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the user equipment at least to perform: for individual multiple-input-multiple-output, MIMO, layers of a plurality of MIMO layers: receiving an eigen vector representing the MIMO layer, wherein eigen vectors representing the MIMO layers of the plurality of MIMO layers are comprised in a matrix, and determining an eigen value of the eigen vector representing the MIMO layer; determining an indication of a power imbalance between two or more MIMO layers of the plurality of MIMO layers; modifying the matrix; and transmitting, to a network node, the indication of a power imbalance between the two or more MIMO layers of the plurality of MIMO layers.

Description

[0001] TITLE

[0002] An apparatus and a computer program

[0003] TECHNOLOGICAL FIELD

[0004] Examples of the disclosure relate to an apparatus and a computer program. Some relate to an apparatus and a computer program in multiple-input-multiple-output systems.

[0005] BACKGROUND

[0006] For multiple-input-multiple-output (MIMO) systems with a rank greater than 1 (having two or more data streams), spatial separation between beams means that the attenuation, scattering and channel conditions experienced by different MIMO layers and / or beams varies.

[0007] BRIEF SUMMARY

[0008] According to various, but not necessarily all, examples there is provided a user equipment comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the user equipment at least to perform: for individual multiple-input-multiple-output, MIMO, layers of a plurality of MIMO layers: receiving an eigen vector representing the MIMO layer, wherein eigen vectors representing the MIMO layers of the plurality of MIMO layers are comprised in a matrix, and determining an eigen value of the eigen vector representing the MIMO layer; determining an indication of a power imbalance between two or more MIMO layers of the plurality of MIMO layers; modifying the matrix; and transmitting, to a network node, the indication of a power imbalance between the two or more MIMO layers of the plurality of MIMO layers.

[0009] In some but not necessarily all examples, the indication of power is an indication of power perceived at the user equipment.

[0010] In some but not necessarily all examples, determining an indication of a power imbalance between two or more MIMO layers of the plurality of MIMO layers is based at least on an eigen value having a highest value and an eigen value having a lowest value.

[0011] In some but not necessarily all examples, determining an indication of a power imbalance comprises determining a difference between the eigen value having the highest value and the eigen value having the lowest value.In some but not necessarily all examples, the instructions, when executed by the at least one processor, further cause the user equipment at least to perform: modifying the matrix to produce a matrix indicating the power imbalance; and transmitting, to the network node, the matrix indicating the power imbalance.

[0012] In some but not necessarily all examples, modifying the matrix comprises, for the individual Ml MO layers of the plurality of Ml MO layers, multiplying the eigen vector beam by its eigen value.

[0013] In some but not necessarily all examples, modifying the matrix comprises multiplying the first eigen vector in the matrix by the indication of a power imbalance.

[0014] In some but not necessarily all examples, modifying the matrix comprises joint encoding one of: the eigen values; or the indication of the power imbalance values with the matrix.

[0015] In some but not necessarily all examples, the instructions, when executed by the at least one processor, further cause the user equipment at least to perform: encoding the matrix indicating the power imbalance to obtain an encoded matrix; and transmitting, to the network node, the encoded matrix.

[0016] In some but not necessarily all examples, encoding the matrix is performed by a channel state information, CSI, auto-encoder.

[0017] According to various, but not necessarily all, examples there is provided a network node comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the user equipment at least to perform: receiving, from a user equipment, an indication of a power imbalance between two or more multiple-input-multiple-output, MIMO, layers of a plurality of MIMO layers; and in dependence upon the indication of a power imbalance, determining a power split ratio for transmission of the plurality of MIMO layers.

[0018] In some but not necessarily all examples, the instructions that, when executed by the at least one processor, cause the network node at least to perform: receiving, from the user equipment, a matrix indicating the power imbalance; and obtaining the indication of a power imbalance from the matrix.In some but not necessarily all examples, the matrix comprises, for individual MIMO layers of the plurality of MIMO layers, an eigen vector representing the individual MIMO layer, multiplied by an eigen value of the eigen vector; and obtaining the indication of a power imbalance from the matrix comprises obtaining norms of the plurality of eigen vectors to obtain the eigen values.

[0019] In some but not necessarily all examples, obtaining the indication of a power imbalance from the matrix further comprises determining, based on an eigen value having a highest value and an eigen value having a lowest value, an indication of a power imbalance between two or more MIMO layers of the plurality of MIMO layers.

[0020] In some but not necessarily all examples, the matrix comprises, for individual MIMO layers of the plurality of MIMO layers, an eigen vector representing the individual MIMO layer, and wherein the first eigen vector in the matrix is multiplied by the indication of the power imbalance; and obtaining the indication of the power imbalance from the matrix comprises obtaining norm of the first eigen vector to obtain the indication of the power imbalance.

[0021] In some but not necessarily all examples, obtaining the indication of the power imbalance from the matrix comprises decoding a joint encoded matrix.

[0022] In some but not necessarily all examples, the matrix is an encoded matrix, and wherein the instructions, when executed by the processor, further cause the network node to perform decoding of the encoded matrix to obtain the matrix.

[0023] In some but not necessarily all examples, decoding the matrix is performed by a channel state information, CSI, auto-encoder.

[0024] According to various, but not necessarily all, examples there is provided a method comprising: for individual multiple-input-multiple-output, MIMO, layers of a plurality of MIMO layers: receiving an eigen vector representing the MIMO layer, wherein eigen vectors representing the MIMO layers of the plurality of MIMO layers are comprised in a matrix, and determining an eigen value of the eigen vector representing the MIMO layer; determining an indication of a power imbalance between two or more MIMO layers of the plurality of MIMO layers; modifying the matrix; and transmitting, to a network node, the indication of a power imbalance between the two or more MIMO layers of the plurality of MIMO layers.According to various, but not necessarily all, examples there is provided a method comprising: receiving, from a user equipment, an indication of a power imbalance between two or more multiple-input-multiple-output, MIMO, layers of a plurality of MIMO layers; and in dependence upon the indication of a power imbalance, determining a power split ratio for transmission of the plurality of MIMO layers.

[0025] According to various, but not necessarily all, embodiments there is provided an apparatus comprising

[0026] at least one processor; and

[0027] at least one memory;

[0028] the at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to perform at least a part of one or more methods described herein.

[0029] According to various, but not necessarily all, embodiments there is provided an apparatus comprising means for performing at least part of one or more methods described herein. The description of a function and / or action should additionally be considered to also disclose any means suitable for performing that function and / or action. Functions and / or actions described herein can be performed in any suitable way using any suitable method.

[0030] According to various, but not necessarily all, embodiments there is provided examples as claimed in the appended claims.

[0031] While the above examples of the disclosure and optional features are described separately, it is to be understood that their provision in all possible combinations and permutations is contained within the disclosure. It is to be understood that various examples of the disclosure can comprise any or all the features described in respect of other examples of the disclosure, and vice versa. Also, it is to be appreciated that any one or more or all the features, in any combination, may be implemented by / comprised in / performable by an apparatus, a method, and / or instructions as desired, and as appropriate. The description of a function should additionally be considered to also disclose any means suitable for performing that function

[0032] BRIEF DESCRIPTION

[0033] Some examples will now be described with reference to the accompanying drawings in which: FIG. 1 shows an example of the subject matter described herein;

[0034] FIG. 2 shows another example of the subject matter described herein;FIG. 3 shows another example of the subject matter described herein;

[0035] FIG. 4 shows another example of the subject matter described herein;

[0036] FIG. 5 shows another example of the subject matter described herein;

[0037] FIG. 6 shows another example of the subject matter described herein;

[0038] FIG. 7 shows another example of the subject matter described herein;

[0039] FIG. 8 shows another example of the subject matter described herein;

[0040] FIG. 9A, 9B show another example of the subject matter described herein;

[0041] FIG. 10 shows another example of the subject matter described herein;

[0042] FIG. 11 shows another example of the subject matter described herein;

[0043] FIG. 12 shows another example of the subject matter described herein;

[0044] FIG. 13 shows another example of the subject matter described herein; and

[0045] FIGs 14A and 14B show another example of the subject matter described herein.

[0046] The figures are not necessarily to scale. Certain features and views of the figures can be shown schematically or exaggerated in scale in the interest of clarity and conciseness. For example, the dimensions of some elements in the figures can be exaggerated relative to other elements to aid explication. Similar reference numerals are used in the figures to designate similar features. For clarity, all reference numerals are not necessarily displayed in all figures.

[0047] DETAILED DESCRIPTION

[0048] For massive multiple-input-multiple-output (MIMO) systems, beam forming and spatial multiplexing are used to improve spectral efficiency.

[0049] In some MIMO systems, a gNB assumes that the sounding reference signal (SRS) channel has reciprocity between downlink (DL) and uplink (UL) channels when deriving UE specific beams for DL transmissions. The gNB selects a beam or a pair of beams for transmitting MIMO spatial layers, either by selecting a suitable pair of teams from a pre-defined grid of beams using the SRS channel, or by computing eigenvectors or zero forcing (2F) beamformers using the SRS channel.

[0050] In some MIMO systems, the gNB transmits CSI reference signals (CSI-RS) using sector beams; the UE measures and reports a precoding matrix indicator (PMI) as part of CSI feedback. The gNB combines the reported PMI with sector beams for transmitting the DL data.For MIMO systems with a rank greater than 1 (having two or more data streams), spatial separation between beams means that the attenuation, scattering and channel conditions experienced by different MIMO layers and / or beams varies. This causes an imbalance in the signal-to-interference-plus-noise ratio (SIN Rs) of the MIMO beams measured at the UE. This can cause high block error rate (BLER) and reduced spectral efficiency.

[0051] Thus, equal power distribution across MIMO layers and / or beams may lead to reduced spectral efficiency.

[0052] By changing the power split ratio to be allotted to the beams, improved spectral efficiency may be provided.

[0053] The optimal power split ratio to be allotted to the beams may depend on one or more of: the modulation and coding scheme (MOS), the MIMO rank, and the beam power imbalance. Thus, knowledge of the beam power imbalance enables determination of an improved power split ratio.

[0054] In SRS-based beamforming, a beam selection algorithm outputs selected beams and their corresponding reference signal received powers (RSRPs) with reference to an SRS covariance matrix. The RSRP difference between the selected beams is taken to be the power imbalance. The calculation of power imbalance does not take into consideration intercell or inter-layer interference at the user equipment (UE). Further, the post equalized SINR per MIMO layer depends on UE implementation. Thus, the actual power imbalance seen at the UE may be different from the power imbalance that is calculated and used in a power balancing algorithm at the gNB.

[0055] In CSI-RS based beam forming, power imbalance is not available at the gNB because the beams are chosen by the UE using CSI-RS.

[0056] Various examples disclosed herein provide for improved determination of power imbalance.

[0057] Fig. 1 illustrates an example of a network 100 comprising a plurality of network entities including terminal apparatus 110, node apparatus 120 and one or more network apparatus 130. The terminal apparatus 110 and node apparatus 120 communicate 124 with each other. The one or more network apparatus 130 communicate 128 with the node apparatus 120.In some examples the one or more network apparatus 130 communicate with the terminal apparatus 110. The one or more network apparatus 130 can, in some examples, communicate with each other. The one or more node apparatus 120 can, in some examples, communicate 126 with each other.

[0058] The network 100 can be a cellular network comprising a plurality of cells 122 each served by a node apparatus 120. In this example, the interface between the terminal apparatus 110 and a node apparatus 120 defining a cell 122 is a wireless interface 124.

[0059] The node apparatus 120 comprises one or more cellular radio transceivers. The terminal apparatus 110 comprises one or more cellular radio transceivers.

[0060] In the example illustrated the cellular network 100 is a third generation Partnership Project (3GPP) network in which the terminal apparatus 110 are user equipment (UE) and the node apparatus 120 can be access nodes such as base stations.

[0061] A user equipment comprises a mobile equipment. Where reference is made to user equipment that reference includes and encompasses, wherever possible, a reference to mobile equipment.

[0062] In some examples, during operation, a user equipment 110 comprises a mobile equipment comprising a smart card for authentication / encryption etc. such as a Subscriber Identity Module (SIM). In some examples, during operation, a user equipment 110 comprises mobile equipment comprising circuitry embedded as part of the user equipment 110 for authentication / encryption such as software SIM.

[0063] The node apparatus 120 can be any suitable access node such as a base station or transmission reception point. The node apparatus 120 can be a network element responsible for radio transmission and reception in one or more cells 122, to or from the UE 110. The node apparatus 120 can be a network element in a Radio Access Network (RAN), an Open-Radio Access Network (O-RAN) or any other suitable type of network.

[0064] The network apparatus 130 can be part of a core network. The network apparatus 130 can be configured to manage functions relating to connectivity for the UEs 110. For example, the network apparatus 130 can be configured to manage functions such as connectivity, mobility, authentication, authorization and / or other suitable functions. In some examples the networkapparatus 130 can comprise an Access and Mobility management Function (AMF) and / or a User Plane Function (UPF) or any other suitable entities.

[0065] In the example of Fig. 1 the network apparatus 130 is shown as a single entity. In some examples the network apparatus 130 could be distributed across a plurality of entities. For example, the network apparatus 130 could be cloud based or distributed in any other suitable manner. The network apparatus 130 can be a core network node.

[0066] The network 100 can be a 4G or 5G network, for example. It can for example be a New Radio (NR) network that uses gNB or eNB as access nodes 120. New Radio is the 3GPP name for 5G technology. In such cases the node apparatus 120 can comprise gNodeBs (gNBs) 120 configured to provide user plane and control plane protocol terminations towards the UE 110 and / or to perform any other suitable functions. The gNBs 120 are interconnected with each other by means of an X2 / Xn interface 126. The gNBs are also connected by means of the N2 interface 128 to the network apparatus 130. The gNBs can be connected to an AMF or any other suitable network apparatus 130. Other types of networks and interfaces could be used in other examples. Other types of network could comprise next generation mobile and communication network, for example, a 6G network.

[0067] FIG. 2 illustrates an example of a method 200.

[0068] In examples, FIG. 2 can be considered to illustrate a plurality of methods. For example, FIG.

[0069] 2 illustrates one or more actions at a plurality of actors / entities, and, in examples, FIG. 2 can be considered to illustrate a plurality of methods performed by the individual actors / entities.

[0070] One or more of the features discussed in relation to FIG. 2 can be found in one or more of the other FIGs.

[0071] In the example of FIG. 2, a plurality of apparatuses transmit and / or receive one or more signals and / or one or more messages across and / or via and / or using a network. In examples, any suitable form of communication in any suitable network can be used. For example, at least a portion of the network 100 of FIG. 1 can be used.

[0072] Accordingly, in examples, the plurality of apparatuses in FIG. 2 form at least a portion of network 100 as described in relation to FIG. 1.In the illustrated example, a terminal node 110 and an access node 120 transmit and / or receive one or more signals and / or one or more messages. The access node can comprise a gNodeB (gNB) and the terminal node 110 can comprise a UE.

[0073] In examples, communications and / or transmissions between elements illustrated in FIG. 2 can proceed via any number of intervening elements, including no intervening elements.

[0074] Although one terminal node 110 is illustrated in the example of FIG. 2, in examples any suitable number of terminal nodes 110, for example UEs, can be included. Similarly, in examples, any suitable number of access nodes 120 can be included.

[0075] As described herein, a description of a function and / or action should also be considered to disclose enabling, and / or causing, and / or controlling that function and / or action. For example, a description of transmitting information should also be considered to disclose enabling, and / or causing, and / or controlling transmitting / transmission of information.

[0076] For example, a description of an apparatus, such as a UE, transmitting information should also be considered to disclose at least one controller of the apparatus enabling, and / or causing, and / or controlling the apparatus to transmit the information.

[0077] In the illustrated example, the location of blocks indicates the entity performing the functions(s) and / or action(s).

[0078] Because FIG. 2 illustrates one or more actions / features of transmitting, FIG. 2 illustrates the corresponding receiving / enabling and / or causing receiving action(s) / feature(s).

[0079] For the further discussion of FIG. 2 it will be considered that the terminal node 110 is a UE 140.

[0080] The preceding statements should be understood to apply to other FIGs described herein, for example FIGs 3, 6 and 9.

[0081] From the point of view of the UE, at block 202, the method 200 comprises, determining an indication of power for individual MIMO layers of a plurality of MIMO layers and, optionally, determining an indication of power imbalance between two or more layers of the plurality of MIMO layers.In some, but not necessarily all, examples, the indication of power is an indication of power perceived at the UE. In some, but not necessarily all, examples, the indication of a power imbalance indicates interference between the two or more MIMO layers of the plurality of MIMO layers. In some, but not necessarily all, examples, the indication of a power imbalance between spatial beams, layers, groups of layers, ports, or groups of ports includes interference measured in the same beam direction.

[0082] At block 204, the method 200 comprises transmitting, to a network node, the indications of power of the plurality of MIMO layers and / or the indication of a power imbalance between two or more layers of the plurality of MIMO layers.

[0083] Consequently, FIG. 2 illustrates a method 200 comprising:

[0084] at block 202, determining an indication of power for individual MIMO layers of a plurality of MIMO layers and, optionally, determining an indication of power imbalance between two or more layers of the plurality of MIMO layers; and

[0085] at block 204, transmitting, to a network node, the indications of power of the plurality of MIMO layers and / or the indication of a power imbalance between two or more layers of the plurality of MIMO layers.

[0086] From the point of view of the network node, at block 204, the method 200 comprises receiving, from the UE, the indications of power and / or the indication of a power imbalance.

[0087] At block 206, the method 200 comprises determining a power split ration based at least in part on the indication of a power imbalance.

[0088] In some examples in which indications of power, and not an indication of a power imbalance, is received, block 206 further comprises determining the indication of a power imbalance between two or more MIMO layers of the plurality of MIMO layers, based at least in part on the received indications of power.

[0089] In some examples, block 206 further comprises causing transmission of the plurality of MIMO layers in dependence upon the determined power split ratio for transmission of the plurality of MIMO layers.

[0090] Optionally, at block 208, the method 200 comprises causing transmission of the plurality of MIMO layers in dependence upon the determined power split ratio for transmission of the plurality of MIMO layers.Consequently, FIG. 2 illustrates a method 200 comprising:

[0091] at block 204, receiving, from the UE, indications of power and / or an indication of a power imbalance;

[0092] at block 206 determining a power split ratio based at least in part on the indication of a power imbalance; and, optionally,

[0093] at block 208, causing transmission of the plurality of MIMO layers in dependence upon the determined power split ratio for transmission of the plurality of MIMO layers.

[0094] Described herein is a user equipment comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the user equipment at least to perform: for individual multiple-input-multiple-output, MIMO, layers of a plurality of MIMO layers, determining an indication of power; determining an indication of a power imbalance between two or more MIMO layers of the plurality of MIMO layers, based at least on: an indication of power which has the highest value; and an indication of power which has the lowest value; and transmitting, to a network node, the indication of a power imbalance between the two or more MIMO layers of the plurality of MIMO layers.

[0095] FIG. 3 illustrates an example of a method 300.

[0096] From the point of view of the UE, at block 302, the method 300 comprises, for individual MIMO layers of a plurality of MIMO layers, determining an indication of power.

[0097] In some, but not necessarily all, examples, an indication of power of a MIMO layer indicates at least one of: a signal-to-interference-plus-noise ratio, SINR, of the MIMO layer; a signal power component of the SINR of the MIMO layer corresponding to a precoding matrix indicator (PMI); an average reference signal received power (RSRP) of one or more reference signal ports transmitting the MIMO layer; a signal power component of the SINR of the MIMO layer corresponding to a demodulation reference signal (DMRS) port; or a SINR of a DMRS port.

[0098] In some, but not necessarily all, examples, determining an indication of power of a MIMO layer comprises measuring a signal, the signal being one of: a channel state information (CSI) reference signal; a demodulation (DM) reference signal; or a spatial division multiplexing (SD) vector corresponding to a spatial beam of a precoding matrix.In some, but not necessarily all, examples, determining an indication of power comprises computing a Ml MO rank, precoder, and / or corresponding channel quality indicator (CQI) of the measured signal. This may be performed when determination of the indication of power is based on cell-specific CSI-RS, or UE-specific CSI-RS.

[0099] In some, but not necessarily all, examples, determining an indication of power of a MIMO layer comprises determining a SINR of the MIMO layer.

[0100] In some, but not necessarily all, examples, determining an indication of power of a MIMO layer comprises determining a signal power of the MIMO layer.

[0101] In some, but not necessarily all, examples, determining an indication of power of a MIMO layer comprises determining an RSRP of a port transmitting the MIMO layer. This may be performed when determination of the indication of power is based on UE-specific CSI-RS.

[0102] The computation of RSRP of a port is dependent upon UE implementation. One example method of computing RSRP of a port is averaging the received power over all receive antennas at the UE.

[0103] At block 304, the method 300 comprises determining an indication of a power imbalance between two or more MIMO layers of the plurality of MIMO layers, based at least on: an indication of power which has the highest value; and an indication of power which has the lowest value.

[0104] In some, but not necessarily all examples, determining an indication of a power imbalance comprises determining a difference between the largest SINR and the smallest SINR. If S1, S2, ... , SR represent the SINRs (in dB) of the MIMO layers or beams 1, 2, ... , R respectively, where R is the MIMO rank or the number of selected beams, the power imbalance PI (in dB) may be calculated as:

[0105] PI = Max{S1, S2, ... , SR} - Min{S1, S2, ... , SR}.

[0106] In some, but not necessarily all, examples, determining an indication of a power imbalance comprises determining a difference between the largest signal power and the smallest signal power. If P1, P2, ... , PR represent the signal powers (in dBm) of the MIMO layers or beams 1, 2, ... , R respectively, the power imbalance PI (in dBm) may be calculated as:PI = Max{P1, P2, , PR} - Min{P1, P2, ... , PR}

[0107] In some, but not necessarily all, examples a SINR Sn and / or a signal power Pn may be associated with a CQI measurement and calculated under the assumption that only the PDSCH layers associated with beam n are transmitted through the ports.

[0108] In some, but not necessarily all, examples, determining an indication of a power imbalance comprises determining an indication of a power imbalance between a first beam on which one or more MIMO layers are transmitted and a second beam one which one or more MIMO layers are transmitted, comprising determining a difference between an average RSRP of the first beam and an average RSRP of the second beam.

[0109] As an example, four ports, for example CSI-RS ports, may be formed by two beams. The two beams are UE-specific and may be derived from SRS assuming reciprocity. Two ports (referred to below as port 1 and port 3) belonging to a first cross-pole element are beamformed using a first beam, and two ports (referred to below as port 2 and port 4) belonging to a second cross-pole element are beamformed using a second beam. The RSRPs of ports 1, 2, 3 and 4 may be represented as R1, R2, R3 and R4.

[0110] In some, but not necessarily all, examples, determining an indication of a power imbalance comprises determining an indication of a power imbalance between the first beam and the second beam. Determining an indication of power imbalance between the first beam and the second beam comprises determining a difference between an average RSRP of the first beam and an average RSRP of the second beam:

[0111] PI = abs(f(R1, R3) - f(R2, R4))

[0112] The averaging function f() may be determined by the UE. Thus, in this example, the power imbalance is the absolute difference between the average RSRPs of the first beam and the second beam.

[0113] In some, but not necessarily all, examples, determining an indication of a power imbalance for MIMO Rank 2 comprises determining a lowest power imbalance between the first beam and the second beam:

[0114] PI = min(abs(R1 - R3), abs(R2 - R4)The power imbalance of a single best beam is thus provided. In some examples, the MIMO rank R = 2 and a single beam is used for transmitting all of the MIMO layers.

[0115] In some, but not necessarily all, examples, determining an indication of power comprises measuring a SINR, a signal power, and / or an RSRP of multiple ports or groups of ports of a DM reference signal. The power imbalance between said ports or groups of ports is determined in the same way as the power imbalance between two or more MIMO layers of the plurality of MIMO layers, set out above.

[0116] By determining a power imbalance between ports or groups of ports of a DM-RS resource, the UE may determine a power imbalance between layers or groups of layers, whose precoding is calculated by the gNB based on SRS, without the need for transmission and measuring of UE-specific CSI-RS.

[0117] In some, but not necessarily all, examples, the power imbalance is quantized to obtain the indication of a power imbalance. In some such examples, the power imbalance may be referred to as an intermediate power imbalance, and the intermediate power imbalance is quantized to obtain the indication of a power imbalance.

[0118] In some, but not necessarily all, examples, the power imbalance is quantized using a lookup table-based method. A lookup table may be constructed with parameters Imin, Imax and Isize, wherein Imin is the minimum power imbalance that is supported for reporting; Imax is the maximum imbalance that is supported for reporting; and Isize is the table size.

[0119] In some, but not necessarily all, examples, Imin, Imax and Isize may be configured at the network level. In other examples, Imin, Imax and Isize have a UE-specific configuration. The UE-specific configuration may be determined based on UE capabilities.

[0120] Table 1 provides an illustrative example of a lookup table in which Imin = 3, Imax = 17 and Isize = 8.

[0121]

[0122] Table 1

[0123] Quantizing the power imbalance using the lookup table comprises mapping the determined beam power imbalance to the nearest value in the lookup table and reporting the corresponding bits.

[0124] At block 306, the method 300 comprises transmitting, to a network node, the indication of a power imbalance between the two or more Ml MO layers of the plurality of Ml MO layers.

[0125] In some, but not necessarily all, examples, the indications of power and / or the indication of a power imbalance are transmitted within a radio resource controller, RRC, message. In some such examples, the indications of power and / or the indication of a power imbalance are transmitted as a reportQuantity parameter contained in a CSI-ReportConfig RRC message.

[0126] The CSI-ReportConfig RRC message, not including the indication of a power balance, may be represented as follows:

[0127] reportQuantity CHOICE {

[0128] none NULL,

[0129] cri-RI-PMI-CQI NULL,

[0130] cri-RI-il NULL,

[0131] cri-RI-il-CQI SEQUENCE {

[0132] PDSCH-BundleSizeForCSI ENUMERATED {n2, n4} OPTIONAL

[0133] },

[0134] cri-RI-CQI NULL,

[0135] cri-RSRP NULL,

[0136] ssb-lndex-RSRP NULL,

[0137] cri-RI-LI-PMI-CQI NULL,The CSI-ReportConfig RRC message may be modified to include the indication of a power imbalance as shown below:

[0138] reportQuantity CHOICE {

[0139] none NULL,

[0140] cri-RI-PMI-CQI-Powerlmbalance NULL,

[0141] cri-RI-il-Powerlmbalance NULL,

[0142] cri-RI-il-CQI-Powerlmbalance SEQUENCE {

[0143] PDSCH-BundleSizeForCSI ENUMERATED {n2, n4} OPTIONAL

[0144] },

[0145] cri-RI-CQI-Powerlmbalance NULL,

[0146] cri-RSRP-Powerlmbalance NULL,

[0147] ssb-lndex-RSRP-Powerlmbalance NULL,

[0148] cri-RI-LI-PMI-CQI-Powerlmbalance NULL,

[0149] }

[0150] Consequently, FIG. 3 illustrates a method 300 comprising:

[0151] at block 302, for individual MIMO layers of a plurality of MIMO layers, determining an indication of power;

[0152] at block 304, determining an indication of a power imbalance between two or more MIMO layers of the plurality of MIMO layers, based at least on: an indication of power which has the highest value; and an indication of power which has the lowest value; and

[0153] at block 306, transmitting, to a network node, the indication of a power imbalance between the two or more MIMO layers of the plurality of MIMO layers

[0154] From the point of view of the network node, at block 306, the method 300 comprises receiving, from the user equipment, an indication of a power imbalance between two or more multiple-input-multiple-output, MIMO, layers of a plurality of MIMO layers.

[0155] At block 308, the method 300 comprises, in dependence upon the indication of a power imbalance, determining a power split ratio for transmission of the plurality of MIMO layers.

[0156] Consequently, FIG. 3300 illustrates a method 300 comprising:

[0157] at block 306, receiving, from the user equipment, an indication of a power imbalance between two or more MIMO layers of a plurality of MIMO layers; andat block 308, in dependence upon the indication of a power imbalance, determining a power split ratio for transmission of the plurality of Ml MO layers.

[0158] FIG. 4 illustrates an example of a method 400.

[0159] The method 400 can be performed by any suitable apparatus comprising any suitable means for performing the method, for example an apparatus as described in relation to FIG. 12.

[0160] In examples, the method 400 can be performed by a terminal node 110, such as a UE 140.

[0161] At block 402, the method 400 comprises, for individual MIMO layers of a plurality of MIMO layers, determining an indication of power.

[0162] At block 404, the method 400 comprises determining an indication of a power imbalance between two or more MIMO layers of the plurality of MIMO layers, based at least on: an indication of power which has the highest value; and an indication of power which has the lowest value.

[0163] At block 406, the method 400 comprises transmitting, to a network node, the indication of a power imbalance between the two or more MIMO layers of the plurality of MIMO layers

[0164] Consequently, FIG. 4 illustrates a method 400 comprising:

[0165] at block 402, for individual MIMO layers of a plurality of MIMO layers, determining an indication of power;

[0166] at block 404, determining an indication of a power imbalance between two or more MIMO layers of the plurality of MIMO layers, based at least on: an indication of power which has the highest value; and an indication of power which has the lowest value; and

[0167] at block 406, transmitting, to a network node, the indication of a power imbalance between the two or more MIMO layers of the plurality of MIMO layers.

[0168] FIG. 5 illustrates an example of a method 500.

[0169] The method 500 can be performed by any suitable apparatus comprising any suitable means for performing the method, for example an apparatus as described in relation to FIG. 12.

[0170] In examples, the method 500 can be performed by an access node 120, such as a gNB.At block 502, the method 500 comprises receiving, from the user equipment, an indication of a power imbalance between two or more MIMO layers of a plurality of MIMO layers.

[0171] At block 504, the method 500 comprises, in dependence upon the indication of a power imbalance, determining a power split ratio for transmission of the plurality of MIMO layers.

[0172] Consequently, FIG. 5 illustrates an example of a method 500 comprising:

[0173] at block 502, receiving, from the user equipment, an indication of a power imbalance between two or more MIMO layers of a plurality of MIMO layers; and

[0174] at block 504, in dependence upon the indication of a power imbalance, determining a power split ratio for transmission of the plurality of MIMO layers.

[0175] Described herein is a user equipment comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the user equipment at least to perform: for individual multiple-input-multiple-output, MIMO, layers of a plurality of MIMO layers: determining an indication of power; and processing the indication of power to determine a processed indication of power, wherein the processing is dependent on indications of power of one or more other MIMO layers of the plurality of MIMO layers; and transmitting, to a network node, the processed indications of power.

[0176] FIG. 6 illustrates an example of a method 600.

[0177] From the point of view of the UE, at block 602, the method 600 comprises, for individual MIMO layers of a plurality of MIMO layers: determining an indication of power.

[0178] In some, but not necessarily all, examples, determining an indication of power is performed following one of the example methods described with reference to FIG. 2.

[0179] At block 604, the method 600 comprises, for individual MIMO layers of a plurality of MIMO layers, processing the indication of power to determine a processed indication of power, wherein the processing is dependent on indications of power of one or more other MIMO layers of the plurality of MIMO layer.

[0180] In some, but not necessarily all, examples, processing an indication of power comprises quantizing the indication of power to obtain the processed indication of power. In some, but not necessarily all, examples, quantizing an indication of power is performed following one of the example methods described with reference to FIG. 2.In some, but not necessarily all, examples, processing an indication of power comprises normalizing the indication of power with respect to the maximum indication of power to obtain a normalized indication of power.

[0181] In some, but not necessarily all, examples, the signal power Si of a layer i is normalized with respect to the maximum value as follows:

[0182]

[0183] In some, but not necessarily all, examples, the normalized indication of power is quantized to obtain the processed indication of power. In some, but not necessarily all, examples, quantizing a normalized indication of power is performed following one of the example methods described with reference to FIG. 2.

[0184] In some, but not necessarily all, examples, the normalized indications of power for the plurality of Ml MO layers are sorted in descending order of size to obtain a sorted list.

[0185] In some, but not necessarily all, examples, processing an indication of power comprises, for the normalized indication of power within the sorted list, computing a differential indication of power based on a position of the normalized indication of power within the sorted list.

[0186] Table 2 provides an illustrative example of a table from which differential indications of power may be obtained.

[0187]

[0188] Table 2

[0189] In some, but not necessarily all, examples, the differential indication of power is quantized to obtain the processed indication of power. In some, but not necessarily all, examples,quantizing a differential indication of power is performed following one of the example methods described with reference to FIG. 2.

[0190] In some, but not necessarily all, examples, the processed indication of power which has the highest value is not transmitted to the network node.

[0191] In some, but not necessarily all, examples, the UE transmits an indication of the MIMO layer which has the processed indication of power having the highest value.

[0192] In some, but not necessarily all, examples, the UE transmits an indication of the order of the sorted list.

[0193] At block 606, the method 600 comprises transmitting, to a network node, the processed indications of power.

[0194] Consequently, FIG. 6 illustrates a method 600 comprising

[0195] at block 602, for individual MIMO layers of a plurality of MIMO layers: determining an indication of power;

[0196] at block 604, for individual MIMO layers of a plurality of MIMO layers, processing the indication of power to determine a processed indication of power, wherein the processing is dependent on indications of power of one or more other MIMO layers of the plurality of MIMO layer; and

[0197] at block 606, transmitting, to a network node, the processed indications of power.

[0198] From the point of view of the network node, at block 606, the method 600 comprises receiving, from the user equipment, and for individual MIMO layers of a plurality of MIMO layers, processed indications of power.

[0199] At block 608, the method 600 comprises determining a power imbalance between two or more MIMO layers of the plurality of MIMO layers, based at least on the processed indications of power.

[0200] In some, but not necessarily all, examples, determining a power imbalance between two or more MIMO layers of the plurality of MIMO layers is performed following one of the example methods described with reference to FIG. 2.At block 610, the method 600 comprises, in dependence upon the determined power imbalance, determining a power split ratio for transmission of the plurality of MIMO layers.

[0201] Consequently, FIG. 6 illustrates a method 600 comprising:

[0202] at block 606, receiving, from the user equipment, and for individual MIMO layers of a plurality of MIMO layers, processed indications of power.

[0203] At block 608, determining a power imbalance between two or more MIMO layers of the plurality of MIMO layers, based at least on the processed indications of power.

[0204] At block 610, in dependence upon the determined power imbalance, determining a power split ratio for transmission of the plurality of MIMO layers.

[0205] FIG. 7 illustrates an example of a method 700.

[0206] The method 700 can be performed by any suitable apparatus comprising any suitable means for performing the method, for example an apparatus as described in relation to FIG. 12.

[0207] In examples, the method 700 can be performed by a terminal node 110, such as a UE 140.

[0208] At block 702, the method 700 comprises, for individual MIMO layers of a plurality of MIMO layers: determining an indication of power.

[0209] At block 704, the method 700 comprises, for individual MIMO layers of a plurality of MIMO layers, processing the indication of power to determine a processed indication of power, wherein the processing is dependent on indications of power of one or more other MIMO layers of the plurality of MIMO layer.

[0210] At block 706, the method 700 comprises transmitting, to a network node, the processed indications of power.

[0211] Consequently, FIG. 7 illustrates a method 700 comprising

[0212] at block 702, for individual MIMO layers of a plurality of MIMO layers: determining an indication of power;

[0213] at block 704, for individual MIMO layers of a plurality of MIMO layers, processing the indication of power to determine a processed indication of power, wherein the processing is dependent on indications of power of one or more other MIMO layers of the plurality of MIMO layer; and

[0214] at block 706, transmitting, to a network node, the processed indications of power.FIG. 8 illustrates an example of a method 800.

[0215] The method 800 can be performed by any suitable apparatus comprising any suitable means for performing the method, for example an apparatus as described in relation to FIG. 12.

[0216] In examples, the method 800 can be performed by an access node 120, such as a gNB.

[0217] A block 802, the method 800 comprises receiving, from the user equipment, and for individual MIMO layers of a plurality of MIMO layers, processed indications of power.

[0218] At block 804, the method 800 comprises determining a power imbalance between two or more MIMO layers of the plurality of MIMO layers, based at least on the processed indications of power.

[0219] At block 806, the method 800 comprises, in dependence upon the determined power imbalance, determining a power split ratio for transmission of the plurality of MIMO layers.

[0220] Consequently, FIG. 8 illustrates a method 800 comprising:

[0221] at block 802, receiving, from the user equipment, and for individual MIMO layers of a plurality of MIMO layers, processed indications of power;

[0222] at block 804, determining a power imbalance between two or more MIMO layers of the plurality of MIMO layers, based at least on the processed indications of power; and at block 806, in dependence upon the determined power imbalance, determining a power split ratio for transmission of the plurality of MIMO layers.

[0223] In some, but not necessarily all, examples, an AI / ML-based air interface is used for transmission between the UE and the network node.

[0224] Described herein is a user equipment comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the user equipment at least to perform: for individual multiple-input-multiple-output, MIMO, layers of a plurality of MIMO layers: receiving an eigen vector representing the MIMO layer, and determining an eigen value of the eigen vector representing the MIMO layer; determining, based at least on an eigen value having a highest value and an eigen value having a lowest value, an indication of a power imbalance between two or more MIMO layers of the pluralityof Ml MO layers; and transmitting, to a network node, the indication of a power imbalance between the two or more Ml MO layers of the plurality of Ml MO layers.

[0225] FIG. 9A illustrates an example of a method 900.

[0226] From the point of view of the UE, at block 902, the method 900 comprises, for individual MIMO layers of a plurality of MIMO layers, receiving an eigen vector representing the MIMO layer.

[0227] In some, but not necessarily all, examples, the indication of a power imbalance is a matrix indicating a power imbalance.

[0228] The eigen vectors representing the MIMO layers of the plurality of layers are comprised in a matrix V, for example a CSI matrix Vt. Vt may be represented as follows:

[0229]

[0230] Where v , v2, ...,vRare the eigen vector beams and R is the MIMO rank.

[0231] At block 904, the method 900 comprises, for individual MIMO layers of the plurality of MIMO layers, determining an eigen value of the eigen vector representing the MIMO layer. The eigen values of the eigen vector beams 1, 2, ... , R may be represented (in dB) as e1, e2, ... , eR.

[0232] At block 906, the method 900 comprises determining, based at least on an eigen value having a highest value and an eigen value having a lowest value, an indication of a power imbalance between two or more MIMO layers of the plurality of MIMO layers.

[0233] In some, but not necessarily all, examples, determining an indication of a power imbalance comprises determining a difference between the eigen value having the highest value and the eigen value having the lowest value:

[0234] Pj = Max{e ,e2, ■ ■■,eR] — Min{e1,e2, ...,eR]

[0235] In some, but not necessarily all, examples, determining an indication of a power imbalance comprises modifying the matrix to produce the matrix indicating the power imbalance.In some, but not necessarily all, examples, the eigen vectors are unit norm vectors and cannot, by themselves, convey the power imbalance. The matrix indicating the power imbalance explicitly includes the power imbalance.

[0236] In some, but not necessarily all, examples, modifying the matrix comprises, for the individual Ml MO layers of the plurality of Ml MO layers, multiplying the eigen vector beam by its eigen value:

[0237]

[0238] In some, but not necessarily all, examples, modifying the matrix comprises multiplying the first eigen vector in the matrix by the indication of a power imbalance:

[0239]

[0240] In some, but not necessarily all, examples, the eigen values or power imbalance value are joint encoded with the matrix to produce the matrix indicating a power imbalance.

[0241] At block 908, the method 900 comprises transmitting, to a network node, the indication of a power imbalance between the two or more Ml MO layers of the plurality of Ml MO layers.

[0242] In some, but not necessarily all, examples, the matrix indicating a power imbalance is encoded to obtain an encoded matrix and the encoded matrix is transmitted to the network node. In some, but not necessarily all, examples, the encoding is a compression by a CSI auto-encoder.

[0243] FIG. 9B illustrates an example CSI auto-encoding system. In FIG. 9B, a portion of the system comprised in the UE is provided on the left side of the dotted line and a portion of the system comprised in a network node is provided on the right side of the dotted line.

[0244] As illustrated by FIG. 9B, the matrix Vt is encoded into bit vector bt using SF (Spatial Frequency) encoder and recurrent quantizer. Bit vector bt is transmitted to the gNB.

[0245] Consequently, FIG. 9A illustrates a method 900 comprising:

[0246] at block 902, for individual MIMO layers of a plurality of MIMO layers, receiving an eigen vector representing the MIMO layer;

[0247] at block 904, for individual MIMO layers of the plurality of MIMO layers, determining an eigen value of the eigen vector representing the MIMO layer;at block 906, determining, based at least on an eigen value having a highest value and an eigen value having a lowest value, an indication of a power imbalance between two or more Ml MO layers of the plurality of Ml MO layers; and

[0248] at block 908, transmitting, to a network node, the indication of a power imbalance between the two or more MIMO layers of the plurality of MIMO layers.

[0249] From the point of view of the network node, at block 908, the method 900 comprises receiving, from a user equipment, an indication of a power imbalance between two or more MIMO layers of a plurality of MIMO layers.

[0250] In some, but not necessarily all, examples, the indication of a power imbalance comprises a matrix indicating a power imbalance.

[0251] At block 910, the method 900 comprises, in dependence upon the indication of a power imbalance, determining a power split ratio for transmission of the plurality of MIMO layers.

[0252] In some, but not necessarily all, examples, determining a power split ratio comprises determining a power imbalance between two or more MIMO layers of the plurality of MIMO layers. The power imbalance may be obtained from the matrix indicating a power imbalance.

[0253] In some, but not necessarily all, examples, the matrix comprises, for each MIMO layer of the plurality of MIMO layers, an eigen vector multiplied by an eigen value. Obtaining the indication of a power imbalance from the matrix comprises obtaining norms of the plurality of eigen vectors to obtain the eigen values. The power imbalance may be obtained using the eigen values using the method described above.

[0254] In some, but not necessarily all, examples, the matrix comprises, for individual MIMO layers of the plurality of MIMO layers, an eigen vector representing the individual MIMO layer, in which the first eigen vector in the matrix is multiplied by the indication of the power imbalance. Obtaining the indication of a power imbalance from the matrix comprises obtaining norm of the first eigen vector to obtain the indication of the power imbalance.

[0255] In some, but not necessarily all, examples, the matrix comprises the eigen values or the indication of the power imbalance joint encoded with the matrix. Obtaining the indication of a power imbalance comprises decoding the joint encoded matrix.In some, but not necessarily all, examples, the matrix is an encoded matrix. The encoded matrix is decoded to obtain the matrix. In some, but not necessarily all, examples, the decoding is performed by a CSI auto-encoder.

[0256] Returning to FIG. 9B, the gNB reconstructs the Vt matrix from bt using recurrent invert quantizer and Sf decoder. From the reconstructed matrix, gNB obtains the PI from first eigen vector or in the other alternative gNB obtains all the eigen values and derives the PI on its own.

[0257] Consequently, FIG. 9A illustrates a method 900 comprising:

[0258] at block 908, receiving, from a user equipment, an indication of a power imbalance between two or more MIMO layers of a plurality of MIMO layers; and

[0259] at block 910, dependence upon the indication of a power imbalance, determining a power split ratio for transmission of the plurality of MIMO layers.

[0260] FIG. 10 illustrates an example of a method 1000.

[0261] The method 1000 can be performed by any suitable apparatus comprising any suitable means for performing the method, for example an apparatus as described in relation to FIG.

[0262] 12.

[0263] In examples, the method 1000 can be performed by a terminal node 110, such as a UE 140.

[0264] At block 1002, the method 1000 comprises, for individual MIMO layers of a plurality of MIMO layers, receiving an eigen vector representing the MIMO layer.

[0265] At block 1004, the method 1000 comprises, for individual MIMO layers of the plurality of MIMO layers, determining an eigen value of the eigen vector representing the MIMO layer.

[0266] At block 1006, the method 1000 comprises determining, based at least on an eigen value having a highest value and an eigen value having a lowest value, an indication of a power imbalance between two or more MIMO layers of the plurality of MIMO layers.

[0267] At block 1008, the method 1000 comprises transmitting, to a network node, the indication of a power imbalance between the two or more MIMO layers of the plurality of MIMO layers.

[0268] Consequently, FIG. 10 illustrates a method 1000 comprising:at block 1002, for individual MIMO layers of a plurality of MIMO layers, receiving an eigen vector representing the MIMO layer;

[0269] at block 1004, for individual MIMO layers of the plurality of MIMO layers, determining an eigen value of the eigen vector representing the MIMO layer;

[0270] at block 1006, determining, based at least on an eigen value having a highest value and an eigen value having a lowest value, an indication of a power imbalance between two or more MIMO layers of the plurality of MIMO layers; and

[0271] at block 1008, transmitting, to a network node, the indication of a power imbalance between the two or more MIMO layers of the plurality of MIMO layers.

[0272] FIG. 11 illustrates an example of a method 1100.

[0273] The method 1100 can be performed by any suitable apparatus comprising any suitable means for performing the method, for example an apparatus as described in relation to FIG.

[0274] 12.

[0275] In examples, the method 1100 can be performed by an access node 120, such as a gNB.

[0276] At block 1102, the method 1100 comprises receiving, from a user equipment, an indication of a power imbalance between two or more MIMO layers of a plurality of MIMO layers.

[0277] At block 1104, the method 1100 comprises, in dependence upon the indication of a power imbalance, determining a power split ratio for transmission of the plurality of MIMO layers.

[0278] Consequently, FIG. 11 illustrates a method 1100 comprising:

[0279] at block 1102, receiving, from a user equipment, an indication of a power imbalance between two or more MIMO layers of a plurality of MIMO layers; and

[0280] at block 1104, dependence upon the indication of a power imbalance, determining a power split ratio for transmission of the plurality of MIMO layers.

[0281] For massive MIMO systems, beamforming / spatial multiplexing are important techniques for improving spectral efficiency. In some examples, the gNB utilizes the reciprocity properties of the SRS channel in deriving UE specific beams for DL transmissions. For DL transmissions, the gNB selects a beam or a pair of beams for transmitting the MIMO spatial layers.

[0282] • GoB method: The gNB selects a suitable pair of beams from the pre-defined grid of beams (e. g., over-sampled DFT beams) using the SRS channel.EVD / ZF method: The gNB computes the eigenvectors or the ZF beamformers using the SRS channel.

[0283] In some examples, gNB transmits CSI-RS using sector beams and UE measure and reports the PMI as part of CSI feedback. gNB combines this PMI with sector beams for transmitting the DL data.

[0284] For MIMO rank > 1, the attenuation experienced by MIMO layers or beams will vary because the beams are spatially separated. This spatial separation results in different scattering and channel conditions, leading to an imbalance in the SINRs of the MIMO layers received by the UE. In such case, equal power distribution across MIMO layers / beams might lead to high BLER and ultimately brings down the spectral efficiency.

[0285] The impact of beam power imbalance has been studied and found out that the optimal power split ratio to be allotted to the beams depends on the MOS, Rank, and the beam power imbalance.

[0286] Now, let us understand the accuracy and availability of beam power imbalance in the current framework of SRS based beamforming and CSI-RS based PMI-beamforming.

[0287] SRS based beamforming: In this scenario, the beam selection algorithm outputs the selected beams and their corresponding RSRPs. The RSRP difference b / w these two beams is treated as the beam power imbalance. In the current approach, the power imbalance calculation does not take into consideration of inter cell & inter layer interference at UE. Also, the post equalized SINR per MIMO layer depends on UE implementation. Because of these reasons, the actual beam power imbalance seen at UE might be different from what is calculated and used in the power balancing algorithm at gNB. So, there is a need to obtain accurate and original beam power imbalance of the UE to determine optimal power split ratio at gNB.

[0288] CSI-RS based PMI-beamforming: In this scenario, beam power imbalance will not be available at gNB as the beams are decided by the UE using CSI-RS.

[0289] We aim to bring support to get the accurate power imbalance to the gNB observed at UE for providing an optimal power split ratio for the beams.

[0290] The current CSI feedback report in 3GPP does not have the capability to report power imbalance to the gNB. The contents of the "re port Quantity' field in the "CSI-ReportConfig," which is used for reporting CSI feedback, are shown in Fig. 14A.

[0291] As part of the standardization, 3GPP is introducing an AI / ML-based air interface. Within this effort, autoencoder-based CSI compression at the UE and regeneration at the gNB to convey both implicit and explicit channel state information are being explored.

[0292] We propose to introduce a new measurement and reporting quantity, with related UE capability, indicating power imbalance between beams (i.e. spatial-domain vectors), layers, or ports, for SRS based beamforming and CSI-RS-based PMI-beamforming. The availabilityof power imbalance across the beams at the UE side is a major advantage as it helps to allocate the optimal power split ratio to be allotted to the beams. The power imbalance reporting is NOT required when the MIMO rank is one.

[0293] The calculation of power imbalance across MIMO layers / beams may not require additional computation resources as it can be derived by using the intermediatory values that will be computed as part of the regular CSI feedback computation such as CQI, PMI, Rank, LI, etc. The details of computing power imbalance and reporting by the UE are provided below for legacy method as well as auto-encoder based method.

[0294] Power Imbalance calculation:

[0295] For cell / UE specific CSI-RS:

[0296] In a first embodiment example, a UE is configured to calculate the power imbalance between spatial domain (SD) vectors corresponding to selected spatial beams from a PMI (precoding matrix indicator) codebook, or between layers of the reported PMI. The UE computes the MIMO rank, precoder, and corresponding CQI by measuring the cell-specific CSI-RS resource. LetS1,S2, ...,SRbe the SINRs (in dB) or signal powers (in dBm, the signal part in SINR) of the MIMO layers / beams 1, 2, ...,R respectively of the precoder, where R is the MIMO rank or the number of selected beams. The quantity SLmay also be associated to a CQI measurement and calculated under the assumption that only the PDSCH layers associated with beam i are transmitted through the CSI-RS ports. The power imbalance across the MIMO layers / beams can be calculated as described below.

[0297] Power imbalance (in dB) F) = Max{S1,S2, ...,SR} - Min[S1,S2, ...,SR

[0298] For UE-specific CSI-RS (SRS based):

[0299] Let us consider a 4 port UE-specific CSI-RS scenario.

[0300] The beams for this scenario are UE specific and may be derived from SRS assuming reciprocity. The 4 CSI-RS ports are created using these beams. In general, ports belonging to one cross-pole element are beamformed using same beam. That means, to form 4 CSI-RS ports, gNB derives two beams for the UE, beaml and beam2. Ports 1 & 3 are beamformed using beaml and ports 2 & 4 are beamformed using beam2.

[0301] In a second embodiment example, a UE is configured to measure and report power imbalance between ports or groups of ports of a CSI-RS resource for channel measurement. Now, let us assume SltS2,S3, and S4are RSRPs of CSI-RS ports 1, 2, 3, and 4. The computation of RSRP of a CSI-RS port is up to UE’s implementation. However, in general, RSRP of a CSI-RS port can be computed by averaging the received power over all the receive antennas at UE. The beam power imbalance in this case be calculated as shown below.

[0302] Beam power imbalance

[0303]

[0304] Here, (.) is an averaging function which depends on UE’s implementation. So, the beam power imbalance is the absolute difference between the average RSRPs of the CSI-RS beams.

[0305] In case of Ml MO rank R = 2 and a single beam is used for transmitting the Ml MO layers, then the power imbalance can be calculated as shown below.

[0306] power imbalance

[0307]

[0308] This way, the UE will be able to convey the power imbalance across the MIMO layers within a single best beam.

[0309] In a third embodiment example, a UE in configured to measure and report power imbalance between ports or groups of ports of a DM-RS resource. This solution allows a UE to measure the imbalance between layers or groups of layers, whose precoding is calculated by the gNB based on SRS, and without transmitting UE-specific CSI-RS. The calculation of the power imbalance may follow the same methods described for UE-specific CSI-RS.

[0310] Note that in all three embodiment examples above, the definition of power imbalance between spatial beams, layers or groups of layers, ports or group of ports may include interference measured in the same beam direction, layers of ports.

[0311] Reporting through legacy method (CSI-ReportConfigY

[0312] A UE can report the computed power balance, or it can report all the signal powers of beams / layers and gNB will select the beams based on the reported beam signal powers. a) Reporting power imbalance:

[0313] The following example explains the process of reporting the power imbalance by UE.

[0314] The will be quantized and will be reported as part of the “reportQuantity’ in “CSI-ReportConfig" . A lot of quantization methods are available. For exemplary purpose, a lookup table-based method is described for quantization process. A lookup table can be constructed using the following parameters.

[0315] Imin: Minimum imbalance that is supported for reporting

[0316] Imax: Maximum imbalance that is supported for reporting

[0317] Isize: Imbalance table size

[0318] The parameters Imin, Imax, and Isizecan be configured at network level or can be made UE specific configuration based on UE capabilities.

[0319] UE computes the beam power imbalance and maps it to the nearest value in the look up table and reports the corresponding bits as part of the CSI feedback. The “reportQuantity” filed in “CSI-ReportConfig” RRC message is modified to include the power imbalance parameter bits like shown in FIG. 14B.

[0320] b) Reporting beam powers

[0321] In this case, all the quantized beam powers are reported either in absolute form or as normalized values. Further, they can also be reported as differential values w.r.to themaximum value. Let S ,S2, -,SRbe the beam powers that need to be reported, here R could be MIMO Rank or number of CSI-RS ports in case of UE specific CSI-RS.

[0322] Normalization:

[0323] Signal powers are normalized w.r.to the maximum value like shown below.

[0324]

[0325] The quantized values of normalized S s can be reported as is or the differential powers can be reported as shown in the table below. For reporting the differential powers, first the signal powers are sorted in descending order before proceeding to computing the differential values. In order to enable the gNB to rearrange the signal powers in original order, the UE will report the sorted order alongside the differential values. This would reduce the feedback overhead.

[0326] Table 3: Differential powers

[0327]

[0328] Quantization of the normalized powers or differential powers can be done like the method proposed before. Another optional mechanism is that when reporting all the normalized powers, the maximum power value need not be reported and instead the position of the maximum value can be reported.

[0329] Power imbalance reporting through auto-encoder based CSI feedback:

[0330] CSI compression using auto-encoders and decoders enables the UE to feedback the eigen vectors (beams) to the gNB. This provides gNB the actual beams to be used for transmission. The example system of CSI feedback based on auto-encoder and decoders is shown in Fig. 9B.

[0331] The CSI matrix Vtin Fig. 3 contains the eigen vector beams to be feedback to the gNB. Vtcan be represented as given below.

[0332] Vt= [^1 v2...vR]

[0333] Where v , v2, ...,vRbe the eigen vector beams and R is the MIMO rank. Vtis compressed by the UE using the ML based auto-encoder and quantizes it and feedback to the gNB. Later, gNB do the inverse quantization and recovers the beams using ML based auto-decoder. However, it is important to note that the eigen vector beams are unit norm vectors and they alone cannot convey the power imbalance that is present among them. So, the powerimbalance must be explicitly included in the CSI matrix Vt. For this, we are proposing the following alternatives.

[0334] Alternative 1 :

[0335] The power imbalance of eigen vectors is governed by their eigen values. Let e1;e2, ..., eRbe eigen values (in dB) of the eigen vector beams. The power imbalance of these eigen vector beams can be calculated as given below.

[0336] Power imbalance P, = Max{e , e2, ... , eR} — Min{e , e2, ..., eR}

[0337] By including the eigen values in Vt, gNB will be able to calculate the power imbalance from the reconstructed matrix Vtas shown below.

[0338] Proposed modified matrix Vt= [e1v1e2v2... eRvR]

[0339] The eigen vector beams of matrix Vtare multiplied by their corresponding eigen values at the UE side. gNB can obtain the eigen values by just taking the norms of the eigen vector beams from reconstructed matrix Vtand can calculate the power imbalance

[0340]

[0341] as shown before. Alternative 2:

[0342] In this case, instead of including all the eigen values in matrix Vt, only the power imbalance Pfis included. The proposed modified Vtmatrix is given below.

[0343] Vt = [Pi^i v2...vR]

[0344] Here, only the first eigen vector is multiplied by the power imbalance value P, at the UE side. The gNB reconstructs the Vtmatrix and by taking norm of the first eigen vector it can recover the power imbalance value P, directly.

[0345] Alternative 3:

[0346] The eigen values or the power imbalance values are joint encoded with the Vtmatrix.

[0347] The FIGs illustrate methods performed by a system comprising interaction between different system entities. The FIGs also illustrate a collection of separate methods performed separately by the different system entities.

[0348] There are present different sets of numbered paragraphs A1.1 , A1.2; A2.1 , A2.2; B1.1 , B1.2; B2.1, B2.2, .... The first paragraph in any of these sets of paragraphs could form the basis for an independent claim. Features present in one set of paragraphs can be combined with features present in other sets of paragraphs.

[0349] A1.1. A user equipment comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the user equipment at least to perform: for individual multiple-input-multiple-output, MIMO, layers of a plurality of MIMO layers, determining an indication of power; determining an indication of a power imbalance between two or more MIMO layers of the plurality of MIMO layers, based at leaston: an indication of power which has the highest value; and an indication of power which has the lowest value; and transmitting, to a network node, the indication of a power imbalance between the two or more Ml MO layers of the plurality of Ml MO layers.

[0350] A1.2. A user equipment as defined in paragraph A1.1, wherein the indication of power is an indication of power perceived at the user equipment.

[0351] A1.3. A user equipment as defined in paragraph A1.1 or paragraph A1.2, wherein the indication of a power imbalance indicates interference between the two or more Ml MO layers of the plurality of M IMO layers.

[0352] A1.4. A user equipment as defined in any of paragraphs A1.1 to A1.3, wherein an indication of power of a Ml MO layer indicates at least one of: a signal-to-interference-plus-noise ratio, SINR, of the MIMO layer; a signal power component of the SINR of the MIMO layer corresponding to a precoding matrix indicator (PMI); an average reference signal received power (RSRP) of one or more reference signal ports transmitting the MIMO layer; a signal power component of the SINR of the MIMO layer corresponding to a demodulation reference signal (DMRS) port; or a SINR of a DMRS port.

[0353] A1.5. A user equipment as defined in any of paragraphs A1.1 - A1.4, wherein determining an indication of power of a MIMO layer comprises determining a SINR of the MIMO layer.

[0354] A1.6. A user equipment as defined in any of paragraphs A1.1 - A1.5, wherein determining an indication of power of a MIMO layer comprises determining a signal power of the MIMO layer.

[0355] A1.7. A user equipment as defined in any of paragraphs A1.1 - A1.6, wherein determining an indication of power of a MIMO layer comprises determining an RSRP of a port transmitting the MIMO layer.

[0356] A1.8. A user equipment as defined in any of paragraphs A1.1 - A1.7, wherein determining an indication of power of a MIMO layer comprises measuring a signal, the signal being one of: a channel state information (CSI) reference signal; a demodulation (DM) reference signal; or a spatial division multiplexing (SD) vector corresponding to a spatial beam of a precoding matrix.A1.9. A user equipment as defined in any of paragraphs A1.4 - A1.8, wherein determining an indication of a power imbalance comprises determining a difference between the largest SINR and the smallest SINR.

[0357] A1.10. A user equipment as defined in any of paragraphs A1.4 - A1.9, wherein determining an indication of a power imbalance comprises determining a difference between the largest signal power and the smallest signal power.

[0358] A1.11. A user equipment as defined in any of paragraphs A1.4 -A1.10, wherein determining an indication of a power imbalance comprises determining an indication of a power imbalance between a first beam on which one or more MIMO layers are transmitted and a second beam on which one or more MIMO layers are transmitted, comprising determining a difference between an average RSRP of the first beam and an average RSRP of the second beam.

[0359] A1.12. A user equipment as defined in paragraph A1.11, wherein determining an indication of a power imbalance comprises determining a lowest power imbalance between the first beam and the second beam.

[0360] A1.13. A user equipment as defined in any of paragraphs A1.1 - A1.12, wherein determining the indication of a power imbalance comprises: determining an intermediate indication of a power imbalance based at least on the indication of power which has the highest value and the indication of power which has the lowest value; and quantizing the intermediate indication of a power imbalance to obtain the indication of a power imbalance.

[0361] A1.14. A user equipment as defined in paragraph A1.13, wherein quantizing the intermediate indication of a power imbalance comprises obtaining the indication of a power imbalance from a lookup table.

[0362] A1.15. A user equipment as defined in any of paragraphs A1.1 - A1.14, wherein the indication of a power imbalance is transmitted within a radio resource controller, RRC, message.

[0363] A1.16. A user equipment as defined in paragraph A1.15, wherein the indication of a power imbalance is transmitted as a reportQuantity parameter contained in a CSI-ReportConfig RRC message.A2.1. A network node comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the network node at least to perform: receiving, from a user equipment, an indication of a power imbalance between two or more multiple-input-multiple-output, MIMO, layers of a plurality of MIMO layers; and in dependence upon the indication of a power imbalance, determining a power split ratio for transmission of the plurality of MIMO layers.

[0364] A2.2. A network node as defined in paragraph A2.1, wherein the instructions, when executed by the at least one processor, further cause the user equipment at least to perform causing transmission of the plurality of MIMO layers in dependence upon the determined power split ratio for transmission of the plurality of MIMO layers.

[0365] A3.1. A method comprising: for individual multiple-input-multiple-output, MIMO, layers of a plurality of MIMO layers, determining an indication of power; determining an indication of a power imbalance between two or more MIMO layers of the plurality of MIMO layers, based at least on: an indication of power which has the highest value; and an indication of power which has the lowest value; and transmitting, to a network node, the indication of a power imbalance between the two or more MIMO layers of the plurality of MIMO layers.

[0366] A4.1. A method comprising: receiving, from a user equipment, an indication of a power imbalance between two or more multiple-input-multiple-output, MIMO, layers of a plurality of MIMO layers; and in dependence upon the indication of a power imbalance, determining a power split ratio for transmission of the plurality of MIMO layers.

[0367] B1.1. A user equipment comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the user equipment at least to perform: for individual multiple-input-multiple-output, MIMO, layers of a plurality of MIMO layers: determining an indication of power; and processing the indication of power to determine a processed indication of power, wherein the processing is dependent on indications of power of one or more other MIMO layers of the plurality of MIMO layers; and transmitting, to a network node, the processed indications of power.

[0368] B1.2. A user equipment as defined in paragraph B1.1, wherein the indication of power is an indication of power perceived at the user equipment.

[0369] B1.3. A user equipment as defined in any of paragraphs B1.1 - B1.2, wherein an indication of power of a MIMO layer indicates at least one of: a signal-to-interference-plus-noise ratio,SI NR, of the MIMO layer; a signal power component of the SINR of the MIMO layer corresponding to a precoding matrix indicator (PMI); an average reference signal received power (RSRP) of one or more reference signal ports transmitting the MIMO layer; a signal power component of the SINR of the MIMO layer corresponding to a demodulation reference signal (DMRS) port; or a SINR of a DMRS port.

[0370] B1.4 A user equipment as defined in any of paragraphs B1.1 - B1.3, wherein determining an indication of power of a MIMO layer comprises determining a SINR of the MIMO layer.

[0371] B1.5. A user equipment as defined in any of paragraphs B1.1 - B1.4, wherein determining an indication of power of a MIMO layer comprises determining a signal power of the MIMO layer.

[0372] B1.6. A user equipment as defined in any of paragraphs B1.1 - B1.5, wherein determining an indication of power of a MIMO layer comprises determining an RSRP of a port transmitting the MIMO layer.

[0373] B1.7. A user equipment as defined in any of paragraphs B1.1 - B1.6, wherein determining an indication of power of a MIMO layer comprises measuring a signal, the signal being one of: a channel state information (CSI) reference signal; a demodulation (DM) reference signal; or a spatial division multiplexing (SD) vector corresponding to a spatial beam of a precoding matrix.

[0374] B1.8. A user equipment as defined in any of paragraphs B1.1 - B1.7, wherein processing an indication of power comprises quantizing the indication of power to obtain the processed indication of power.

[0375] B1.9. A user equipment as defined in any of paragraphs B1.1 - B1.7, wherein processing an indication of power comprises: normalizing the indication of power with respect to the maximum indication of power to obtain a normalized indication of power; quantizing the normalized indication of power to obtain the processed indication of power.

[0376] B1.10. A user equipment as defined in any of paragraphs B1.1 - B1.7, wherein processing an indication of power comprises normalizing the indication of power with respect to the maximum indication of power to obtain a normalized indication of power; and wherein the instructions, when executed by the at least one processor, further cause the apparatus at least to perform processing the plurality of normalized indications of powers to obtain theprocessed indications of powers, comprising: sorting the plurality of normalized indications of power in descending order of size to obtain a sorted list for each normalized indication of power, computing a differential indication of power based on a position of the normalized indication of power within the sorted list; and quantizing the differential indications of power to obtain the processed indications of power.

[0377] B1.11. A user equipment as defined in any of paragraphs B1.1 - B1.10, wherein the processed indication of power which has the highest value is not transmitted to the network node.

[0378] B1.12. A user equipment as defined in any of paragraphs B1.1 - B1.11, wherein the instructions, when executed by the at least one processor, further cause the apparatus at least to perform transmitting an indication of the MIMO layer which has the processed indication of power having the highest value.

[0379] B1.13. A user equipment as defined in any of paragraphs B1.10 - B1.12, wherein the instructions, when executed by the at least one apparatus, further cause the apparatus at least to perform transmitting an indication of the order of the sorted list.

[0380] B1.14. A user equipment as defined in any of paragraphs B1.1 - B1.13, wherein quantizing an indication of power, a normalized indication of power and / or a differential indication of power comprises obtaining the processed indication of power from a lookup table.

[0381] B1.15. A user equipment as defined in any of paragraphs B1.1 - B1.14, wherein the processed indications of power are transmitted within a radio resource controller, RRC, message.

[0382] B1.16. A user equipment as defined in paragraph B1.15, wherein the processed indications of power are transmitted as a reportQuantity parameter contained in a CSI-ReportConfig RRC message.

[0383] B2.1. A network node comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the network node at least to perform: receiving, from a user equipment, and for individual multiple-input-multiple-output, MIMO, layers of a plurality of MIMO layers, processed indications of power; determining a power imbalance between two or more MIMO layers of the plurality of MIMO layers, based at least on the processed indications of power; and in dependence upon thedetermined power imbalance, determining a power split ratio for transmission of the plurality of Ml MO layers.

[0384] B2.2. A network node as defined in paragraph B2.1, wherein the instructions, when executed by the at least one processor, further cause the user equipment at least to perform causing transmission of the plurality of MIMO layers in dependence upon the determined power split ratio for transmission of the plurality of MIMO layers.

[0385] B3.1. A method comprising: for individual multiple-input-multiple-output, MIMO, layers of a plurality of MIMO layers: determining an indication of power; and processing the indication of power to determine a processed indication of power, wherein the processing is dependent on indications of power of one or more other MIMO layers of the plurality of MIMO layers; and transmitting, to a network node, the processed indications of power.

[0386] B4.1. A method comprising: receiving, from a user equipment, and for individual multiple-input-multiple-output, MIMO, layers of a plurality of MIMO layers, processed indications of power; determining a power imbalance between two or more MIMO layers of the plurality of MIMO layers, based at least on the processed indications of power; and in dependence upon the determined power imbalance, determining a power split ratio for transmission of the plurality of MIMO layers.

[0387] FIG. 12 illustrates an example of a controller 1202 suitable for use in an apparatus 1212. Implementation of a controller 1202 may be as controller circuitry. The controller 1202 may be implemented in hardware alone, have certain aspects in software including firmware alone or can be a combination of hardware and software (including firmware).

[0388] As illustrated in FIG. 12 the controller 1202 may be implemented using instructions that enable hardware functionality, for example, by using executable instructions 1208 in a general-purpose or special-purpose processor 1204 that may be stored on a machine readable storage medium (disk, memory etc.) to be executed by such a processor 1204.

[0389] The processor 1204 is configured to read from and write to the memory 1206. The processor 1204 may also comprise an output interface via which data and / or commands are output by the processor 1204 and an input interface via which data and / or commands are input to the processor 1204.The memory 1206 stores instructions, program, or code 1208 that controls the operation of the apparatus 1212 when loaded into the processor 1204. The instructions, program, or code 1208, provide the logic and routines that enables the apparatus 1212 to perform the methods illustrated in the accompanying FIGs. The processor 1204 by reading the memory 1206 is configured to load and execute the instructions, program, or code 1208.

[0390] The apparatus 1212 comprises:

[0391] at least one processor 1204; and

[0392] at least one memory 1206 storing instructions that, when executed by the at least one processor 1204, cause the apparatus at least to:

[0393] for individual multiple-input-multiple-output, MIMO, layers of a plurality of MIMO layers: receive an eigen vector representing the MIMO layer, wherein eigen vectors representing the MIMO layers of the plurality of MIMO layers are comprised in a matrix, and determine an eigen value of the eigen vector representing the MIMO layer;

[0394] determine an indication of a power imbalance between two or more MIMO layers of the plurality of MIMO layers; modifying the matrix; and

[0395] transmit, to a network node, the indication of a power imbalance between the two or more MIMO layers of the plurality of MIMO layers.

[0396] In some examples, there is a (computer implemented) system comprising:

[0397] for individual multiple-input-multiple-output, MIMO, layers of a plurality of MIMO layers: controlling reception of an eigen vector representing the MIMO layer, wherein eigen vectors representing the MIMO layers of the plurality of MIMO layers are comprised in a matrix, and controlling determination of an eigen value of the eigen vector representing the MIMO layer; controlling determination of an indication of a power imbalance between two or more MIMO layers of the plurality of MIMO layers; modifying the matrix; and

[0398] controlling transmission, to a network node, of the indication of a power imbalance between the two or more MIMO layers of the plurality of MIMO layers.

[0399] As illustrated in FIG. 13, the instructions, program, or code 1208 may arrive at the apparatus 1212 via any suitable delivery mechanism 1210. The delivery mechanism 1210 may be, for example, a machine readable medium, a computer-readable medium, a non-transitory computer-readable storage medium, a computer program product, a memory device, a record medium such as a solid-state memory, an article of manufacture that comprises or tangibly embodies the instructions 1208. The delivery mechanism may be a signal configured to reliably transfer the instructions 1208. The apparatus 1212 may propagate or transmit the instructions 1208 as a data signal.The term “non-transitory” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal ) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

[0400] The instructions 1208 cause an apparatus to perform at least the following:

[0401] for individual multiple-input-multiple-output, MIMO, layers ofa plurality of MIMO layers: causing reception of an eigen vector representing the MIMO layer, wherein eigen vectors representing the MIMO layers of the plurality of MIMO layers are comprised in a matrix, and causing determination of an eigen value of the eigen vector representing the MIMO layer; causing determination of an indication of a power imbalance between two or more MIMO layers of the plurality of MIMO layers; modifying the matrix; and

[0402] causing transmission, to a network node, of the indication of a power imbalance between the two or more MIMO layers of the plurality of MIMO layers.

[0403] The instructions 1208 may be comprised in a computer program, a non-transitory computer readable medium, a computer program product, a machine readable medium. In some but not necessarily all examples, the instructions 1208 may be distributed over more than one computer program.

[0404] Although the memory 1206 is illustrated as a single component / circuitry it may be implemented as one or more separate components / circuitry some or all of which may be integrated / removable and / or may provide permanent / semi-permanent / dynamic / cached storage.

[0405] Although the processor 1204 is illustrated as a single component / circuitry it may be implemented as one or more separate components / circuitry some or all of which may be integrated / removable. The processor 1204 may be a single core or multi-core processor.

[0406] References to ‘computer-readable storage medium’, ‘computer program product’, ‘tangibly embodied computer program’ etc. or a ‘controller’, ‘computer’, ‘processor’ etc. should be understood to encompass not only computers having different architectures such as single / multi- processor architectures and sequential (Von Neumann) / parallel architectures but also specialized circuits such as field-programmable gate arrays (FPGA), application specific circuits (ASIC), signal processing devices and other processing circuitry including quantum processing circuitry. References to computer program, instructions, code etc. should be understood to encompass software for a programmable processor or firmware such as, for example, the programmable content of a hardware device whether instructions for aprocessor, or configuration settings for a fixed-function device, gate array or programmable logic device etc.

[0407] As used in this application, the term ‘circuitry’ may refer to one or more or all the following: (a) hardware-only circuitry implementations (such as implementations in analog, digital and / or quantum circuitry) and

[0408] (b) combinations of hardware circuit(s) and software, such as (as applicable):

[0409] i. a combination of analog, digital and / or quantum hardware circuit(s) with software / firmware and

[0410] ii. any or all portions of hardware processor(s) (including digital and / or quantum processor(s)) with software, and memory(ies) that work together to cause an apparatus, such as a mobile device, computing device or server, to perform various functions and

[0411] (c) any or all portions of hardware circuit(s), such as a microprocessor(s) and / or quantum processors , that requires software (for example, firmware) for operation, but the software may not be present when it is not needed for operation.

[0412] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in a server, a cellular network device, or other computing or network device.

[0413] The blocks illustrated in the accompanying Figs may represent steps in a method and / or sections of code in the instructions 1208. The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some blocks to be omitted.

[0414] As used here ‘module’ refers to a unit or apparatus that excludes certain parts / components that would be added by an end manufacturer or a user. The apparatus 1212 can, for example be a module. A controller 1202 of the apparatus 1212 can, for example be a module.Where a structural feature has been described, it may be replaced by means for performing one or more of the functions of the structural feature whether that function or those functions are explicitly or implicitly described.

[0415] The above-described examples find application as enabling components of:

[0416] automotive systems; telecommunication systems; electronic systems including consumer electronic products; distributed computing systems; media systems for generating or rendering media content including audio, visual and audio visual content and mixed, mediated, virtual and / or augmented reality; personal systems including personal health systems or personal fitness systems; navigation systems; user interfaces also known as human machine interfaces; networks including cellular, non-cellular, and optical networks; ad-hoc networks; the internet; the internet of things; virtualized networks; and related software and services.

[0417] The apparatus can be provided in an electronic device, for example, a mobile terminal, according to an example of the present disclosure. It should be understood, however, that a mobile terminal is merely illustrative of an electronic device that would benefit from examples of implementations of the present disclosure and, therefore, should not be taken to limit the scope of the present disclosure to the same. While in certain implementation examples, the apparatus can be provided in a mobile terminal, other types of electronic devices, such as, but not limited to: mobile communication devices, hand portable electronic devices, wearable computing devices, portable digital assistants (PDAs), pagers, mobile computers, desktop computers, televisions, gaming devices, laptop computers, cameras, video recorders, GPS devices and other types of electronic systems, can readily employ examples of the present disclosure. Furthermore, devices can readily employ examples of the present disclosure regardless of their intent to provide mobility.

[0418] The term ‘comprise’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X may comprise only one Y or may comprise more than one Y. If it is intended to use ‘comprise’ with an exclusive meaning then it will be made clear in the context by referring to ‘comprising only one...’ or by using ‘consisting.’

[0419] In this description, the wording ‘connect’, ‘couple’ and ‘communication’ and their derivatives mean operationally connected / coupled / in communication. It should be appreciated that any number or combination of intervening components can exist (including no intervening components), i.e. , to provide direct or indirect connection / coupling / communication. Any such intervening components can include hardware and / or software components.As used herein, the term "determine / determining" (and grammatical variants thereof) can include, not least: calculating, computing, processing, deriving, measuring, investigating, identifying, looking up (for example, looking up in a table, a database, or another data structure), ascertaining and the like. Also, "determining" can include receiving (for example, receiving information), accessing (for example, accessing data in a memory), obtaining and the like. Also, " determine / determining" can include resolving, selecting, choosing, establishing, and the like.

[0420] In this description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term ‘example’ or ‘for example’ or ‘can’ or ‘may’ in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some of or all other examples. Thus ‘example’, ‘for example’, ‘can’, or ‘may’ refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a sub-class of the class that includes some but not all the instances in the class. It is therefore implicitly disclosed that a feature described with reference to one example but not with reference to another example, can where possible be used in that other example as part of a working combination but does not necessarily have to be used in that other example.

[0421] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or” mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0422] Although examples have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the claims.

[0423] Features described in the preceding description may be used in combinations other than the combinations explicitly described above.

[0424] Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

[0425] The description of a feature, such as an apparatus or a component of an apparatus, configured to perform a function, or for performing a function, should additionally beconsidered to also disclose a method of performing that function. For example, description of an apparatus configured to perform one or more actions, or for performing one or more actions, should additionally be considered to disclose a method of performing those one or more actions with or without the apparatus.

[0426] Although features have been described with reference to certain examples, those features may also be present in other examples whether described or not.

[0427] The term ‘a’, ‘an’ or ‘the’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising a / an / the Y indicates that X may comprise only one Y or may comprise more than one Y unless the context clearly indicates the contrary. If it is intended to use ‘a’, ‘an’ or ‘the’ with an exclusive meaning then it will be made clear in the context. In some circumstances the use of ‘at least one’ or ‘one or more’ may be used to emphasis an inclusive meaning but the absence of these terms should not be taken to infer any exclusive meaning.

[0428] The presence of a feature (or combination of features) in a claim is a reference to that feature or (combination of features) itself and to features that achieve substantially the same technical effect (equivalent features). The equivalent features include, for example, features that are variants and achieve substantially the same result in substantially the same way. The equivalent features include, for example, features that perform substantially the same function, in substantially the same way to achieve substantially the same result.

[0429] In this description, reference has been made to various examples using adjectives or adjectival phrases to describe characteristics of the examples. Such a description of a characteristic in relation to an example indicates that the characteristic is present in some examples exactly as described and is present in other examples substantially as described.

[0430] As used herein, the terms “the at least one” and “the one or more” mean “any one of the at least one” and “any one of the one or mor” respectively.

[0431] The above description describes some examples of the present disclosure however those of ordinary skill in the art will be aware of possible alternative structures and method features which offer equivalent functionality to the specific examples of such structures and features described herein above and which for the sake of brevity and clarity have been omitted from the above description. Nonetheless, the above description should be read as implicitly including reference to such alternative structures and method features which provideequivalent functionality unless such alternative structures or method features are explicitly excluded in the above description of the examples of the present disclosure.

[0432] Whilst endeavoring in the foregoing specification to draw attention to those features believed to be of importance the Applicant may seek protection via the claims in respect of any patentable feature or combination of features hereinbefore referred to and / or shown in the drawings whether or not emphasis has been placed thereon.

[0433] l / we claim:

Claims

46CLAIMS1. A user equipment comprising:at least one processor; andat least one memory storing instructions that, when executed by the at least one processor, cause the user equipment at least to perform:for individual multiple-input-multiple-output, MIMO, layers of a plurality of MIMO layers:receiving an eigen vector representing the MIMO layer, wherein eigen vectors representing the MIMO layers of the plurality of MIMO layers are comprised in a matrix, and determining an eigen value of the eigen vector representing the MIMO layer; determining an indication of a power imbalance between two or more MIMO layers of the plurality of MIMO layers;modifying the matrix; andtransmitting, to a network node, the indication of a power imbalance between the two or more MIMO layers of the plurality of MIMO layers.

2. A user equipment as claimed in claim 1 , wherein the indication of power is an indication of power perceived at the user equipment.

3. A user equipment as claimed in any preceding claim, wherein determining an indication of a power imbalance between two or more MIMO layers of the plurality of MIMO layers is based at least on an eigen value having a highest value and an eigen value having a lowest value.

4. A user equipment as claimed in any preceding claim, wherein determining an indication of a power imbalance comprises determining a difference between the eigen value having the highest value and the eigen value having the lowest value.

5. A user equipment as claimed in any of claims 3 - 4, wherein the instructions, when executed by the at least one processor, further cause the user equipment at least to perform:modifying the matrix to produce a matrix indicating the power imbalance; and transmitting, to the network node, the matrix indicating the power imbalance.

6. A user equipment as claimed in claim 5, wherein modifying the matrix comprises, for the individual MIMO layers of the plurality of MIMO layers, multiplying the eigen vector beam by its eigen value.

477. A user equipment as claimed in claim 5, wherein modifying the matrix comprises multiplying the first eigen vector in the matrix by the indication of a power imbalance.

8. A user equipment as claimed in claim 5, wherein modifying the matrix comprises joint encoding one of: the eigen values; or the indication of the power imbalance values with the matrix.

9. A user equipment as claimed in any of claims 5 - 8, wherein the instructions, when executed by the at least one processor, further cause the user equipment at least to perform: encoding the matrix indicating the power imbalance to obtain an encoded matrix; and transmitting, to the network node, the encoded matrix.

10. A user equipment as claimed in claim 9, wherein encoding the matrix is performed by a channel state information, CSI, auto-encoder.

11. A network node comprising:at least one processor; andat least one memory storing instructions that, when executed by the at least one processor, cause the user equipment at least to perform:receiving, from a user equipment, an indication of a power imbalance between two or more multiple-input-multiple-output, MIMO, layers of a plurality of MIMO layers; andin dependence upon the indication of a power imbalance, determining a power split ratio for transmission of the plurality of MIMO layers.

12. A network node as claimed in claim 11, wherein the instructions that, when executed by the at least one processor, cause the network node at least to perform:receiving, from the user equipment, a matrix indicating the power imbalance; and obtaining the indication of a power imbalance from the matrix.

13. A network node as claimed in claim 12, wherein:the matrix comprises, for individual MIMO layers of the plurality of MIMO layers, an eigen vector representing the individual MIMO layer, multiplied by an eigen value of the eigen vector; andobtaining the indication of a power imbalance from the matrix comprises obtaining norms of the plurality of eigen vectors to obtain the eigen values.4814. A network node as claimed in claim 13, wherein obtaining the indication of a power imbalance from the matrix further comprises determining, based on an eigen value having a highest value and an eigen value having a lowest value, an indication of a power imbalance between two or more Ml MO layers of the plurality of Ml MO layers.

15. A network node as claimed in claim 12, wherein:the matrix comprises, for individual Ml MO layers of the plurality of Ml MO layers, an eigen vector representing the individual Ml MO layer, and wherein the first eigen vector in the matrix is multiplied by the indication of the power imbalance; andobtaining the indication of the power imbalance from the matrix comprises obtaining norm of the first eigen vector to obtain the indication of the power imbalance.

16. A network node as claimed in claim 12, wherein obtaining the indication of the power imbalance from the matrix comprises decoding a joint encoded matrix.

17. A network node as claimed in claim 12, wherein the matrix is an encoded matrix, and wherein the instructions, when executed by the processor, further cause the network node to perform decoding of the encoded matrix to obtain the matrix.

18. A network node as claimed in claim 17, wherein decoding the matrix is performed by a channel state information, CSI, auto-encoder.

19. A method comprising:for individual multiple-input-multiple-output, MIMO, layers of a plurality of MIMO layers:receiving an eigen vector representing the MIMO layer, wherein eigen vectors representing the MIMO layers of the plurality of MIMO layers are comprised in a matrix, and determining an eigen value of the eigen vector representing the MIMO layer; determining an indication of a power imbalance between two or more MIMO layers of the plurality of MIMO layers;modifying the matrix; andtransmitting, to a network node, the indication of a power imbalance between the two or more MIMO layers of the plurality of MIMO layers.

20. A method comprising:receiving, from a user equipment, an indication of a power imbalance between two or more multiple-input-multiple-output, MIMO, layers of a plurality of MIMO layers; andin dependence upon the indication of a power imbalance, determining a power split ratio for transmission of the plurality of MIMO layers.

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