WO2025027477A1

WO2025027477A1 - Csi feedback for large antenna arrays by aggregating multiple csi-rs resources

Info

Publication number: WO2025027477A1
Application number: PCT/IB2024/057262
Authority: WO
Inventors: Shiwei Gao; Xinlin ZHANG; Siva Muruganathan
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2023-07-28
Filing date: 2024-07-26
Publication date: 2025-02-06
Anticipated expiration: 2026-01-28

Abstract

Systems and methods are disclosed for Channel State Information (CSI) feedback. In one embodiment, a method performed by a User Equipment (UE) comprises receiving, from a network node, a configuration for CSI feedback based on a codebook for P_CSI-RS > 32 antenna ports, the configuration comprising M>1 CSI Reference Signal (CSI-RS) resources, each with N ≤ 32 CSI-RS ports, for channel measurement, wherein the P_CSI-RS antenna ports comprise N₁ ports in a first dimension and N₂ ports in a second dimension, wherein P_CSI-RS = 2N₁N₂ = M ∙N. The method further comprises determining a port mapping between each of the P_CSI-RS antenna ports and one of the CSI-RS ports of one of the M CSI-RS resources, performing measurements on downlink channels associated to the P_CSI-RS antenna ports based on the M CSI-RS resources and the determined port mapping, computing a precoding matrix based thereon, and sending, to the network node, an associated precoding matrix indicator (PMI).

Description

CSI FEEDBACK FOR LARGE ANTENNA ARRAYS BY AGGREGATING MULTIPLE CSI-RS RESOURCES RELATED APPLICATIONS [0001] This application claims the benefit of provisional patent application serial number 63/516,364, filed July 28, 2023, the disclosure of which is hereby incorporated herein by reference in its entirety. TECHNICAL FIELD [0002] The present disclosure relates to a cellular communications system and, more specifically, to Channel State Information (CSI) feedback in a cellular communications system. BACKGROUND NR Frame Structure and Resource Grid [0003] 3^rd Generation Partnership Project (3GPP) New Radio (NR) uses Cyclic Prefix Orthogonal Frequency Division Multiplexing (CP-OFDM) in both downlink (DL) (i.e., from a network node, next generation NodeB (gNB), or base station, to a user equipment (UE)) and uplink (UL) (i.e., from UE to gNB). Discrete Fourier Transform (DFT) spread Orthogonal Frequency Division Multiplexing (OFDM) is also supported in the uplink. In the time domain, NR downlink and uplink are organized into equally sized subframes of 1 millisecond (ms) each. A subframe is further divided into multiple slots of equal duration. The slot length depends on subcarrier spacing. For subcarrier spacing of ∆^ = 15 kilohertz (kHz), there is only one slot per subframe, and each slot consists of 14 OFDM symbols. [0004] Data scheduling in NR is typically in slot basis, an example is shown in Figure 1 with a 14-symbol slot, where the first two symbols contain Physical Downlink Control Channel (PDCCH) and the rest contains physical shared data channel, either Physical Downlink Shared Channel (PDSCH) or Physical Uplink Shared Channel (PUSCH). [0005] Different subcarrier spacing values are supported in NR. The supported subcarrier spacing values (also referred to as different numerologies) are given by ∆^ = (15 × 2^{^}) ^^^ where ^ ∈ {0,1,2,3,4} . ∆^ = 15^^^ is the basic subcarrier spacing. The slot durations at different subcarrier spacings is given by ^{^} ^_^ ^^. [0006] In the frequency domain, a

bandwidth is divided into Resource Blocks (RBs), each corresponds to 12 contiguous subcarriers. The RBs are numbered starting with 0 from one end of the system bandwidth. The basic NR physical time-frequency resource grid is illustrated in Figure 2, where only one RB within a 14-symbol slot is shown. One OFDM subcarrier during one OFDM symbol interval forms one Resource Element (RE). Codebook-Based Precoding [0007] Multi-antenna techniques can significantly increase the data rates and reliability of a wireless communication system. The performance is improved if both the transmitter and the receiver are equipped with multiple antennas, which results in a Multiple-Input Multiple-Output (MIMO) communication channel. Such systems and/or related techniques are commonly referred to as MIMO systems. [0008] A core component of NR is the support of MIMO related techniques. NR supports up to 8-layer spatial multiplexing for up to 32 transmit antenna ports at the gNB with channel dependent precoding. Figure 3 shows an example of data transmission with spatial multiplexing where the information carrying symbol vector ^ = ^{^}^_^, ^_^, … , ^_^ ^! is first multiplied (or precoded) by a precoding matrix " ∈ #^$%×& before being sent over NT antenna ports. Each symbol in s is associated to a data layer and r is the number of data layers or rank, which is a property of the wireless channel between the transmitter and the receiver. " serves to beamform each data layer towards the UE such that Signal to Interference plus Noise Ratio (SINR) is maximized and cross layer interference is minimized at the UE receiver. Spatial multiplexing is achieved since multiple symbols can be transmitted simultaneously in a same time and frequency RE. [0009] The received N_R x 1 signal vector ' at the UE quipped with N_R receive antennas can ^{be expressed as} '_{= ("^ + *} where ( ∈ #^$+×$% is the MIMO channel between the transmit and receive antennas, e is a noise plus interference vector due to receiver noise and interference. [0010] The precoder matrix " is chosen to match the characteristics of the N_RxN_T MIMO channel matrix ( resulting in so-called channel dependent precoding. The precoder " can be a wideband precoder, i.e., the same over a whole bandwidth, or a subband procoder, i.e., optimized per subband. " is typically selected from a codebook of precoding matrices by the UE and reported to the gNB in terms of a Precoding Matrix Indicator (PMI). [0011] One example method for a UE to select a precoder matrix " can be to select the "_, ^{from a codebook that maximizes the Frobenius norm of the hypothesized equivalent channel:} m_^ _{,ax 0(1 ",02} where • (¹ is a channel estimate, and • "_, is a hypothesized precoder matrix with index k. [0012] In addition to " feedback, a UE typically also feedback a Rank Indicator (RI) and Channel Quality Indicator(s) (CQI) as part of Channel State Information (CSI) feedback. Given the CSI feedback from the UE, the eNB can determine the transmission parameters to use for data transmissions to the UE. [0013] For channel estimation purpose, a so-called Channel State Information Reference Signal (CSI-RS) is typically transmitted to the UE. 2D Antenna Arrays [0014] The antennas with NT antenna ports discussed above can be either a linear antenna array or two dimension (2D) plenary antenna array. A linear antenna array is a special case of a 2D antenna array. A 2D antenna array can be described by 3₄ columns, corresponding to the horizontal dimension, 3₅ rows, corresponding to the vertical dimension, and 3₆ polarizations. ^{The total number of antenna ports is thus 3 = 343536. An example of a cross polarized (i.e.,} _{36 = 2 ) antenna array with (34, 35) = (4,4) is illustrated in Figure 4.} [0015] Note that the 2D antenna array could be rotated at any angle. In this case, the row and columns may no longer correspond to vertical and horizontal directions. To reflect this more general case in NR, a 2D antenna array is simply defined by a number of antenna ports in each of ^{two dimensions, i.e., 3^ and 3^, and 36 is always 2. Thus, the total number of antenna ports is} _{3 = 23^3^.} [0016] The concept of an antenna port is non-limiting in the sense that it can refer to any virtualization (e.g., linear mapping) of the physical antenna elements. For example, pairs of physical sub-elements could be fed the same signal, and hence share the same virtualized antenna port. CSI-RS [0017] In NR, for downlink channel measurement by a UE, a reference signal is transmitted at each antenna port. The reference signal is referred to as Non-Zero Power Channel State Information Reference Signal (NZP CSI-RS). NZP CSI-RS is configured in terms of NZP CSI- RS resources. For simplicity, “NZP” may be omitted in the following discussions. A NZP CSI- RS resource supports up to 32 antenna ports. The antenna ports are also referred to as CSI-RS antenna ports, CSI-RS ports, or antenna ports. Different CSI-RS antenna ports in a CSI-RS resource are allocated with different REs and/or different Code Division Multiplexing (CDM) codes so that the downlink channel associated to each antenna port can be individually measured and estimated. [0018] Three densities are supported, i.e., 7 = ½, 1, and 3.7 is the number REs per RB per CSI-RS port. 7 = ½ means one RE per port in every other RB, e.g., in even or odd numbered RBs.7 = 3 is only supported for single port CSI-RS resource. [0019] In a CSI-RS resource, there can be multiple CDM groups. A CDM group consists of 2, 4, or 8 REs, corresponding to length 8 = 2, 4, or 8 CDM codes, respectively. The CDM codes used can be either length 2 or length 4 Time Domain Orthogonal Cover Codes (TD-OCC), i.e., TD-OCC2 or TD-OCC4, or length 2 Frequency Domain Orthogonal Cover Code (FD-OCC), i.e., FD-OCC2, or both TD-OCC and FD-OCC. The CDM groups are numbered in order of increasing frequency domain allocation first and then increasing time domain allocation. An example of a CSI-RS resource for 32 antenna ports are shown in Figure 5, where CSI-RS REs in one RB is shown. In this case, there are 8 CDM groups each with 4 REs. The CDM codes are TD-OCC2 plus FD-OCC2. [0020] Each antenna port is mapped to one of the CDM groups. Antenna ports are mapped in CDM group first, then frequency, and then time. Within each CDM group, antenna ports are multiplexed via CDM codes or sequences. CSI-RS antenna ports are numbered according to p=3000+s + jL ; =0,1,...,N L − 1

CDM code index given in 3GPP Technical Specification (TS) 38.211 (see, e.g., 17.5.0), 8 ∈ ^{1,2,4,8^} is the CDM group size, and 3 is the number of CSI-RS ports. NR Type I Single Panel Codebook [0021] The NR Type I single panel codebook is based on DFT beams or precoders and is for cross polarized 2D antenna arrays, where a DFT beam is selected for each MIMO layer. The same DFT beam is applied to antenna ports at both polarizations. A co-phasing factor is applied at antenna ports of one of the two polarizations. The details of Type I single panel codebook can be found in 3GPP TS 38.214 (see, e.g., V17.5.0). [0022] For example, for a CSI-RS resource with :_CSI-RS = 23_^3_^ antenna ports, rank 1 precoding matrix for codebook mode 1 is given by " = ^{^ >?,@} D = … E_^3_^ − ^ = 0,1, … , E_^3_^ − 1

precoding vector for beam index (D, ^) and is _H ^{^K? ^K?(N P^) !} ^>?,@ ^{= = J J M} @_I ^LM^NM_{H@ ... I} ^LM^NM ^H@^C ^{and H@ = Q1 IJ RST} ^{URVR the 3^ dimension. E^}

^and _{E are sampling f JKB⁄ ^} _{^ actor in the dimension 3^ and 3^ , respectively. YB = I is a co-} phasing The supported ⁽3_^, 3_^ ⁾ and are given in Table 5.2.2.2.1-2 of 3GPP TS 38.214, which is reproduced below as Table 1:

^{Table 1: Reproduction of Table 5.2.2.2.1-2 of 3GPP TS 38.214 ( “Supported configurations of} _{($[, $\) and (][, ]\)”)} Number of (N₁, N₂ ) (O₁ ,O₂ ) CSI-RS antenna ports, ^{P CSI-RS} 4 (2,1) (4,1) (2,2) (4,4) 8 (4,1) (4,1) (3,2) (4,4) 12 (6,1) (4,1) (4,2) (4,4) 16 (8,1) (4,1) (4,3) (4,4) 24 (6,2) (4,4) (12,1) (4,1) (4,4) (4,4) 32 (8,2) (4,4) (16,1) (4,1) [0023] A type I single panel codebook based precoding matrix is a two-stage precoder and can ^{be express as} "_{= "^"^} where "_^ contains the selected DFT beams and "_^ contains co-phasing factors. For the above rank 1 precoding "_^ = ^{^} _^ ^>?,@ "_^ = _^ ¹ . DFT beams { >_?,@} are also referred to as Spatial

^{[0024] According to 3GPP NR specification, precoded PDSCH signals ^ = ^^ !} ^{^, ^^, … , ^^ by} _{" (i.e., "^) are equivalent to corresponding symbols transmitted on the CSI-RS antenna ports} _{3000, … , 3000 + :` abPca − 1 as given by} e^{(fggg) ^^} d ⋯ n = " o^⋯ _p. The above q_?,@ based " ports for a 2D antenna array

with 23_^3_^ ports need to be index along the 3_^ dimension first and then increasing along the 3_^ dimension at a first polarization and then repeat the above for the other polarization. An example is shown in Figure 6 for a 2D antenna with 32 ports: SUMMARY [0025] Systems and methods are disclosed for Channel State Information (CSI) feedback for large antenna arrays by aggregating multiple CSI Reference Signal (CSI-RS) resources. In one embodiment, a method performed by a User Equipment (UE) comprises receiving, from a network node, a configuration for CSI feedback based on a codebook for :` _abPca > 32 antenna ports, the configuration comprising s>1 CSI-RS resources, each with 3 ≤ 32 CSI-RS ports, for channel measurement, wherein the :` _abPca antenna ports comprise N₁ ports in a first dimension and N₂ ports in a second dimension, wherein :` _abPca = 23_^3_^ = s ∙ 3. The method further comprises determining a port mapping between each of the :` _abPca antenna ports and one of the CSI-RS ports of one of the M CSI-RS resources and performing measurements on downlink channels associated to the :` _abPca antenna ports based on the M CSI-RS resources and the determined port mapping. The method further comprises computing a precoding matrix based on the measurements and the codebook and sending, to the network node, a precoding matrix indicator (PMI) associated to the computed precoding matrix as part of CSI feedback. In this manner, codebook-based CSI feedback for more than 32 antenna ports is provided without a need to design a new CSI-RS resource with more than 32 ports. [0026] In one embodiment, the method further comprises receiving, from the network node, information that indicates a port mapping type, wherein determining the port mapping comprises determining the port mapping based on the indicated port mapping type. [0027] In one embodiment, each of the M CSI-RS resources has a first number, v_^, of ports in ^{the first dimension and a second number, v} _^ ^{, of ports in the second dimension, wherein 3 =} _2v^v^. [0028] In one embodiment, the port mapping type is either a first port mapping type in which the M CSI-RS resources are aggregated in the first dimension or a second port mapping type in which the M CSI-RS resources are aggregated in the second dimension. [0029] In one embodiment, each of the M CSI-RS resources has an associated CSI-RS resource index and the M CSI-RS resources are ordered according to their associated CSI-RS resource index values. [0030] In one embodiment, the M CSI-RS resources are ordered in increasing order of the CSI-RS resource index value, wherein the first CSI-RS resource has the smallest CSI-RS resource index value, and the last CSI-RS resource has the largest CSI-RS index value among the M CSI- RS resources. [0031] In one embodiment, the M CSI-RS resources are ordered in decreasing order of the CSI-RS resource index value, wherein the first CSI-RS resource has the largest CSI-RS resource index value, and the last CSI-RS resource has the smallest CSI-RS index value among the M CSI- RS resources. [0032] In one embodiment, for the first port mapping type, the :` _abPca antenna ports are mapped to the CSI-RS ports of the M CSI-RS resources sequentially starting from the ports of a first polarization of the M CSI-RS resources, followed by the ports of a second polarization of the M CSI-RS resources, so that antenna ports w = (0,1, … , :` _abPca /2 − 1) for the :` _abPca antenna ^{ports are mapped to the first polarization and the antenna ports ( :` abPca /2, :` abPca /2 +} _{1, … , :` abPca − 1) for the :` abPca antenna ports are mapped to the second polarization.} [0033] In one embodiment, for the first port mapping type, port mapping between the :` _abPca antenna ports and the CSI-RS ports of the M CSI-RS resources is given by: w^{@ + (^ − 1)3/2; 0 ≤ w@ ≤ 3/2 − 1} 1 :` _abPca CSI-RS antenna

(^ ∈ 1, 2, … , s) CSI-RS resource among the M CSI-RS resources . [0034] In one embodiment, for the second port mapping type, the :` _abPca antenna ports are mapped to the CSI-RS ports of the M CSI-RS resources sequentially in increasing order: • in a first polarization, along the second (3_^) dimension first for each of the M CSI-RS resources and then in increasing order along the first (3_^) dimension for each of the M CSI-RS resources, and • in a second polarization, along the second (3_^) dimension first for each of the M CSI- RS resources and then in increasing order along the first (3_^) dimension for each of the M CSI-RS resources, so that antenna ports w = (0,1, … , :` _abPca /2 − 1) for the :` _abPca antenna ports are mapped to the first polarization and antenna ports (:` _abPca /2, :` _abPca /2 + 1, … , :` _abPca − 1) are mapped to the second polarization. ^{[0035] In one embodiment, for the second port mapping type, port mapping between the} _{:` abPca antenna ports and the CSI-RS ports of the M CSI-RS resources is given by:} 3^{^} ^{s (w@ + ^ − 1); w@ = 2^, ^ = 0,1, … , N/2} 0_{,1, … , N/2} ^{where w ∈ an antenna port in the}

_{:` abPca antenna ports w@ ∈ … , − a port index of the ^} ^{4 _{(^ ∈} _{1,2, … , s) CSI-RS resource among the M CSI-RS resources.} [0036] In one embodiment, the determined port mapping for the :` _abPca 32 antenna ports ensures that the antenna ports are: first indexed in increasing order along the second (3_^ ) dimension first and then in increasing order along the first (3_^) dimension for a first of two polarizations; and second indexed in increasing order along the second (3_^) dimension first and then in increasing order along the first (3_^) dimension for a second of two polarizations. [0037] In one embodiment, the port mapping provides a one-to-one mapping between each antenna port, w ∈ (0,1, … ,23_^3_^ − 1), of the :` _abPca antenna ports and one of the CSI-RS ports of one of the M CSI-RS resources, w_@ ∈ (0,1, … , 3 − 1), ^ = 1,2, … , s. ^{[0038] In one embodiment, each row of the precoding matrix is associated to one of the} _{:` abPca antenna ports and the rows are arranged in increasing order of antenna port indices of the} _{:` abPca antenna ports with a first row being associated to port index w = 0.} [0039] In one embodiment, the M CSI-RS resources have a same Code Division Multiplexing, CDM, group size. [0040] In one embodiment, the M CSI-RS resources have a same CSI-RS port layout with a first number, v_^, of ports in the first dimension and a second number, v_^, of ports in the second dimension at

of the two polarizations, wherein 3 = 2v_^v_^. [0041] In one embodiment, determining the antenna port mapping for the :` _abPca > 32 antenna ports for codebook based CSI feedback comprises determining (1504) the antenna port mapping for the :` _abPca antenna ports for codebook based CSI feedback based on a permutation matrix. [0042] In one embodiment, M equals to one of two, three, and four. [0043] In one embodiment, 3 ≤ 32. [0044] In one embodiment, 3 ∈ (16, 24, 32). [0045] Corresponding embodiments of a UE are also disclosed. In one embodiment, a UE is adapted to receive, from a network node, a configuration for CSI feedback based on a codebook ^{for :` abPca > 32 antenna ports, the configuration comprising s>1 CSI-RS resources, each with} _{3 ≤ 32 CSI-RS ports, for channel measurement, wherein the :` abPca antenna ports comprising} ^{N1 ports in a first dimension and N2 ports in a second dimension, wherein :` abPca = 23^3^ =} _{s ∙ 3. The UE is further adapted to determine a port mapping between each of the :` abPca} antenna ports and one of the CSI-RS ports of one of the M CSI-RS resources and perform measurements on downlink channels associated to the :` _abPca antenna ports based on the M CSI- RS resources and the determined port mapping. The UE is further adapted to compute a precoding matrix based on the measurements and the codebook and send, to the network node, a PMI associated to the computed precoding matrix as part of CSI feedback. [0046] In one embodiment, a UE comprises a communication interface comprising a transmitter and a receiver, and processing circuitry associated with the communication interface. The processing circuitry is configured to cause the UE to receive, from a network node, a configuration for CSI feedback based on a codebook for :` _abPca > 32 antenna ports, the configuration comprising s>1 CSI-RS resources, each with 3 ≤ 32 CSI-RS ports, for channel measurement, wherein the :` _abPca antenna ports comprising N1 ports in a first dimension and N2 ports in a second dimension, wherein :` _abPca = 23_^3_^ = s ∙ 3. The processing circuitry is further configured to cause the UE to determine a port mapping between each of the :` _abPca antenna ports and one of the CSI-RS ports of one of the M CSI-RS resources and perform measurements on downlink channels associated to the :` _abPca antenna ports based on the M CSI- RS resources and the determined port mapping. The processing circuitry is further configured to cause the UE to compute a precoding matrix based on the measurements and the codebook and send, to the network node, a PMI associated to the computed precoding matrix as part of CSI feedback. [0047] Embodiments of a method performed by a network node are also disclosed. In one embodiment, a method performed by a network node comprises sending to a UE a configuration for CSI feedback based on a codebook for :` _abPca > 32 antenna ports, the configuration comprising s>1 CSI-RS resources, each with 3 ≤ 32 CSI-RS ports, for channel measurement, wherein the :` _abPca antenna ports comprise N1 ports in a first dimension and N2 ports in a second dimension, wherein :` _abPca = 23_^3_^ = s ∙ 3. The method further comprises receiving, from the UE as part of CSI feedback, a PMI associated to a precoding matrix that is based on a port mapping between each of the :` _abPca antenna ports and one of the CSI-RS ports of one of the M CSI-RS resources, and performing one or more actions based on the received PMI. [0048] Corresponding embodiments of a network node are also disclosed. In one embodiment, a network node is adapted to send to a UE a configuration for CSI feedback based on a codebook for :` _abPca > 32 antenna ports, the configuration comprising s>1 Channel State Information Reference Signal, CSI-RS, resources, each with 3 ≤ 32 CSI-RS ports, for channel measurement, wherein the :` _abPca antenna ports comprise N1 ports in a first dimension and N2 ports in a second dimension, wherein :` _abPca = 23_^3_^ = s ∙ 3. The network node is further adapted to receive, from the UE as part of CSI feedback, a PMI associated to a precoding matrix that is based on a port mapping between each of the :` _abPca antenna ports and one of the CSI-RS ports of one of the M CSI-RS resources, and perform one or more actions based on the received PMI. [0049] In one embodiment, a network node comprises processing circuitry configured to cause ^{the network node to send to a UE a configuration for CSI feedback based on a codebook for} _{:` abPca > 32 antenna ports, the configuration comprising s >1 Channel State Information} Reference Signal, CSI-RS, resources, each with 3 ≤ 32 CSI-RS ports, for channel measurement, wherein the :` _abPca antenna ports comprise N1 ports in a first dimension and N2 ports in a second dimension, wherein :` _abPca = 23_^3_^ = s ∙ 3. The processing circuitry is further configured to cause the network node to receive, from the UE as part of CSI feedback, a PMI associated to a precoding matrix that is based on a port mapping between each of the :` _abPca antenna ports and one of the CSI-RS ports of one of the M CSI-RS resources, and perform one or more actions based on the received PMI. BRIEF DESCRIPTION OF THE DRAWINGS [0050] The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure. [0051] Figure 1 illustrates an example NR time-domain structure with 15kHz subcarrier spacing; [0052] Figure 2 illustrates a NR physical resource grid; [0053] Figure 3 illustrates data transmission with spatial multiplexing; [0054] Figure 4 is an illustration of a two-dimensional antenna array of cross-polarized antenna elements ( 3_< = 2) , with 3₄ = 4 horizontal antenna elements and 3₅ = 4 vertical antenna elements; [0055] Figure 5 illustrates an example of a CSI-RS resource for 32 antenna ports with 8 CDM groups; [0056] Figure 6 illustrates an example of a valid mapping of CSI-RS antenna ports to a 2D antenna with 32 ports; [0057] Figure 7 illustrates 32 ports antenna arrays supported in NR; [0058] Figure 8 illustrates possible layouts of 64 antenna ports; [0059] Figure 9 illustrates an example embodiment of port aggregation in the 3_^ dimension; [0060] Figure 10 illustrates an example embodiment of port aggregation in the 3_^ dimension;

[0061] Figure 11 illustrates an example embodiment of antenna port mapping for the 64 antenna ports with the first aggregation type; [0062] Figure 12 illustrates an example embodiment of antenna port mapping for the 64 antenna ports with the second aggregation type; [0063] Figure 13 illustrates an example embodiment of antenna port mapping for the 64 antenna ports with the second aggregation type; [0064] Figure 14 illustrates an example embodiment of antenna port mapping for the 96 antenna ports with a first aggregation type; [0065] Figure 15 is a flow chart that illustrates the operation of a UE in accordance with at least some of embodiments of the present disclosure; [0066] Figure 16 is a flow chart that illustrates the operation of network node (e.g., a RAN node such as, e.g., a base station such as, e.g., a gNB) in accordance with at least some embodiments of the present disclosure; [0067] Figure 17 shows an example of a communication system in accordance with some embodiments of the present disclosure; [0068] Figure 18 shows a User Equipment device (UE) in accordance with some embodiments of the present disclosure; [0069] Figure 19 shows a network node in accordance with some embodiments of the present disclosure; [0070] Figure 20 is a block diagram of a host, which may be an embodiment of the host of Figure 17, in accordance with various aspects of the present disclosure described herein; [0071] Figure 21 is a block diagram illustrating a virtualization environment in which functions implemented by some embodiments of the present disclosure may be virtualized; and [0072] Figure 22 shows a communication diagram of a host communicating via a network node with a UE over a partially wireless connection in accordance with some embodiments of the present disclosure. DETAILED DESCRIPTION [0073] The embodiments set forth below represent information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure. [0074] Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art. [0075] There currently exist certain challenge(s). With carrier frequencies becoming available above 6 Gigahertz (GHz), for a same antenna size, more antenna elements can be accommodated at such higher frequencies than at carrier frequencies below 6GHz, which are widely deployed today. In NR, the maximum number of supported antenna ports for Type I single panel codebook based CSI feedback is 32. A straightforward solution to deal with a larger number of antenna elements (i.e., larger than 32) would be to increase the antenna subarray size, i.e., to map an antenna port to multiple antenna elements and keep the maximum number of antenna ports to 32. However, this would reduce the angular coverage if there were many antenna elements in a subarray because the subarray (or the antenna port) antenna beam pattern would be much narrower than that of each antenna element, which typically has an antenna pattern covering the whole serving cell. [0076] Another solution is to extend the existing NR type I codebook to support more than 32 ports, such as 64 ports or 128 ports. The extension should be straight forward. However, this would require a new design of CSI-RS resources with more than 32 ports, which is not straightforward. Alternatively, multiple existing CSI-RS resources may be aggregated to support more than 32 ports. However, how to aggregate the antenna ports in the multiple CSI-RS resources to support more than 32 antenna ports is a problem. More specifically, how an antenna port in each of the multiple CSI-RS resources is mapped to an antenna port of the aggregated larger antenna is a problem. [0077] Certain aspects of the disclosure and their embodiments may provide solutions to these or other challenges. Embodiments of a method is proposed for determining an antenna port mapping for a 2D antenna array configured with two polarizations and with (3_^, 3_^) ports in two dimensions per polarization for codebook based CSI feedback when M>1 CSI-RS resources, each with :` _abPca ≤ 32 CSI-RS ports, are configured for channel measurement, where the M CSI-RS ^{resources are aggregated to form an equivalent CSI-RS resource for the 2D antenna array with} _{23^3^ = s:` abPca antenna ports. In one embodiment, the method includes the following:} • (Optional) A UE receives, from a network node (e.g., a Radio Access Network (RAN) node such as a base station or gNB), an indication of one of two aggregation types, i.e., aggregation in either N1 or N2 dimension, to be used. o As an example alternative, the one of the two aggregation types may be pre- determined (e.g., defined in a 3GPP specification). • The UE determines, based on the aggregation type, an antenna port layout with :` _abPca ports associated to the M CSI-RS resources •^{The UE determines a one-to-one mapping between each CSI-RS port, w ∈} (_{0,1, … ,23^3^ − 1), of the aggregated CSI-RS resource for the 2D antenna array and a} CSI-RS port, w_@ ∈ (0,1, … , :` _abPca − 1) , ^ = 1,2, … , s , of one of the M>1 CSI-RS resources based on the determined antenna port layout with :` _abPca ports, the aggregation type, and (3_^, 3_^) • The UE obtains downlink channels associated to the 2D antenna array based on the determined one-to-one mapping and channels measured on the M CSI-RS resources • The UE computes a precoding matrix based on the obtained downlink channels, where elements of each column of the precoding matrix are arranged according to the order of the antenna port indices of the aggregated CSI-RS resource with the first element being associated to port index w = 0. • The UE sends (i.e., feeds back), to the network node, a precoding matrix indicator (PMI) associated to the computed precoding matrix [0078] In one embodiment, the method includes the following: • (Optional) A UE receives, from a network node, an indication (e.g., signaling) of one of two aggregation types when s (s = 2,3, … ) CSI-RS resources each with :` _abPca (≤ 32) p^{orts are configured for type I codebook-based CSI feedback for an antenna}

^with 3_{= 23^3^ = s:` abPca (3 > 32) antenna ports.} o In one example alternative, the one of the two aggregation types is predefined (e.g., by a 3GPP specification). • The UE determines, based on the aggregation type, an antenna port layout with :` _abPca ports associated to the M CSI-RS resources • The UE determines, based on the determined antenna port layout and the aggregation type, a one-to-one mapping between antenna port, w ∈ (0,1, … , 3 − 1), of the antenna array ^{(or an equivalent aggregated CSI-RS resource with N ports) and a CSI-RS port, w@ ∈} (_{0,1, … , :` {} _{abPca − 1) of the ^ 4 (^ = 1,2, … , s) CSI-RS resource} • The UE computes a precoding matrix based on channels measured on the s CSI-RS resources, where element of each column of the precoding matrix is arranged in increasing order of antenna port w with the first element being associated to port w = 0. [0079] Certain embodiments may provide one or more of the following technical advantage(s). Embodiments of the present disclosure may enable a simple extension of the existing type I codebook-based CSI feedback to more than 32 antenna ports without designing a new CSI-RS resource with more than 32 ports. 1 Extension of Type I Single Panel Codebook to 64 Antenna Ports [0080] It is assumed that for type I single panel codebook-based CSI feedback for 64 antenna ports, two CSI-RS resources each with 32 antenna ports are configured. The 64 antenna ports are an aggregation of the two 32 antenna ports in the two CSI-RS resources. [0081] In NR, the supported 32 ports antenna layouts are shown Figure 7, where “X” represents two antenna ports with cross polarizations. As in the NR convention, 3_^ and 3_^ are the number of antenna ports for each of the two cross polarizations in two respectively.

The total number of antenna ports in both polarizations are 23_^3_^. [0082] For 64 antenna ports, the port layout may be constructed by aggregating two 32 antenna ports. The possible layouts of 64 antenna ports are shown in Figure 8. For each of the 64 antenna ports layouts shown in Figure 8, there are two possible aggregation types of two 32 antenna ports. Note that these aggregation types may also be referred to herein as “port mapping types”. In a ^{first aggregation type, the two 32 ports CSI-RS resources are aggregated in the 3^ dimension (i.e.,} _{3^=2*3^′) as shown in Figure 9, where 3^ is the same for the 32 ports and the 64 ports antenna} layouts. In a second aggregation, the two 32 ports are aggregated in the 3_^ dimension as shown ^{in Figure 10, where 3^ is the same for the 32 ports and the 64 ports antenna layouts, while} 3_^=23_^′. It can be observed that the two aggregated 32 ports have the same dimension, i.e., (3_^, _{3^). To distinguish (3^, 3^) between the 32 ports and the 64 ports, we use (3^’, 3^’) for the 32} ^{ports and (3^, 3^) for the aggregated 64 ports. Then, for the first aggregation type, 3^=23^’,} _{3^=3^’. For the second aggregation type, 3^=3^’, and 3^=23^’.} 1.1 Flexible Aggregation Types [0083] In one embodiment, when type I codebook is configured with (3_^, 3_^) for 64 ports and two 32 antenna ports CSI-RS resources in a CSI-RS resource set are configured for channel measurement, the aggregation type is also signaled to the UE so that the correct 32 ports layout can be determined by the UE. [0084] Let w ∈ (0,1, … ,63) be the antenna port index of the 64 antenna ports (i.e., an equivalent CSI-RS resource with 64 ports) and w_^ ∈ (0,1, … ,31) and w_^ ∈ (0,1, … ,31) be the antenna port indices for the corresponding first and the second 32 antenna port CSI-RS resources, respectively. Then, the relationship between w, w_^ and w_^ can be determined according to the aggregation type. Note that the antenna ports are indexed along the 3_^ dimension first and then

the 3_^ dimension for each polarization. Also, that in NR, the CSI-RS antenna port index for codebook-based CSI feedback starts from 3000 for the purpose of distinguishing from antenna for other channels or signals. For simplicity, the offset 3000 is removed here but it is understood that the idea is not limited to the port index values used here. [0085] For the first aggregation type, for a given (3_^, 3_^) for 64 ports, the UE can determine the 32 ports layout (i.e., 3′_^, 3′_^) ) as shown in Figure 9. The mapping between w, w_^ and w_^ can then be determined according to Figure 11. This mapping ensures that ports are

indexed in increasing order along the 3_^ dimension first and then in increasing order along the 3_^ dimension for each polarization, so that ports w = (0,1, … ,31) are mapped to one polarization and ports (32, 33, …63) are mapped to the other polarization. Downlink channel associated to port w is measure on a corresponding CSI-RS port in one of the two CSI-RS resources according to the port mapping. [0086] For the second aggregation type, the mapping between w, w_^ and w_^ is summarized in Figure 12 for (3_^, 3_^) = (8,4) port layout and Figure 13 for

= (16,2) port layout. As illustrated in Figure 12, this mapping ensures that the antenna ports for the aggregated CSI-RS resource are indexed in increasing order along the 3_^ dimension first and then in increasing order along the 3_^ dimension for each polarization, so that ports w = ⁽0,1⁾ of the aggregated CSI-RS resource are mapped to ports w_^ = (0,1) of the first CSI-RS resource for the first polarization, ports w = (2,3) of the

CSI-RS resource are mapped to ports w_^ = (0,1) of the second CSI-RS resource for the first polarization ports, ports w = (4,5) of the aggregated CSI-RS resource are mapped to ports w_^ = (2,3) of the first CSI-RS resource for the first polarization, ports w = ⁽6,7⁾ of the

CSI-RS resource are mapped to ports w_^ = ⁽2,3⁾ of the second ^{CSI-RS resource for the first polarization, and so on. Then, for the second polarization, ports w =} _{(32,33) of the aggregated CSI-RS resource are mapped to ports w^ = (16,17) of the first CSI-RS} resource for the second polarization, ports w = (34,35) of the aggregated CSI-RS resource are mapped to ports w_^ = (16,17) of the second CSI-RS resource for the second polarization ports, ports w = (36,37) of the aggregated CSI-RS resource are mapped to ports w_^ = (18,19) of the first CSI-RS resource for the second polarization, ports w = (38,39) of the aggregated CSI-RS resource are mapped to ports w_^ = (18,19) of the second CSI-RS resource for the second polarization, and so on. [0087] With the above antenna port mappings, the UE can measure the downlink channels associated to the 64 antenna ports via the two 32 ports CSI-RS resources and compute a precoding matrix based on a 64-port codebook. The 64-port codebook can be a simple extension of the ^{existing NR type-I single panel codebook with two new configurations of (3^ , 3^) = (8,4) and} _{(3^ , 3^) = (16,2) for 64 ports as shown Table 2 below.} Table 2: Supported configurations of (3_^, 3_^) and (E_^, E_^) for 64 antenna ports Number of C_{SI-RS antenna ports, $ = \$} ^{(N1, N2 ) (O1,O2 )} [_$\ (8,4) (4,4) 64 (16,2) (4,4) 1.2 Predefined Aggregation Type [0088] Alternative to the embodiment in Section 1.1 (where aggregation type is signaled from the network (e.g., from the gNB) to the UE), in this embodiment, one of the two aggregation types (i.e., one of the aggregation types described in Figure 11 or Figure 12/Figure 13) is predefined, e.g., in 3GPP specifications. For a given (3_^, 3_^) configuration for 64 antenna ports and two 32 ports CSI-RS resources configured for channel measurement, the UE determines the 32 port layout according to the predefined aggregation type. [0089] The antenna ports of the aggregated 64 port for example can be predefined according to the first aggregation type shown in Figure 11 as follows: • first, index antenna ports along the 3_^ dimension and then along the 3_^ dimension of the first polarization of the first aggregated CSI-RS resource

• next, index antenna ports along the 3_^ dimension and then along the 3_^ dimension of the first polarization of the second aggregated CSI-RS resource

• next, index antenna ports along the 3_^ dimension and then along the 3_^dimension of the second polarization of the first aggregated CSI-RS resource

• finally, index antenna ports along the 3_^ dimension and then along the 3_^ dimension of the second polarization of the second aggregated CSI-RS resource

[0090] In general, when s (s = 2,3, … ) CSI-RS resources each with :` _abPca (≤ 32) ports are configured for type I codebook based CSI feedback for an antenna array with 3 = 23_^3_^ = s:` _abPca (3 > 32) antenna ports and for the first aggregation type, the mapping between the antenna port w ∈ (0,1, … ,23_^3_^ − 1) of the aggregated antenna array (or an aggregated CSI-RS resource ) and the CSI-RS port, w_@ ∈ (0,1, … , :` _abPca − 1), of the ^^{4 (^ ∈ (1,2, … , s)) CSI- RS resource is given below. w^{@ + (^ − 1):` abPca/2; 0 ≤ w@ ≤ :` abPca/2 − 1} w_{= y (s + ^ − 1):` abPca} [0091] For

s^{(w@ + ^ − 1); w@ = 2^, ^ = 0,1, … , :` abPca/2} ,_{:` abPca/2}

^{[0092] In 3GPP TS 38.211 V17.5.0, the antenna port index for CSI-RS is defined as follows:} w_{= 3000 + ^ + ^8;} _{^ = 0,1, ... , 3⁄ 8 − 1} _{^ = 0,1, ... , 8 − 1;} where ^ is the CDM group index, 8 ∈ {1,2,4,8} is the number of ports within each CDM group, and ^ is the sequence indexing within each CDM group as defined in Tables 7.4.1.5.3-2 to 7.4.1.5.3-5 of 3GPP TS 38.211 for different CDM group sizes. [0093] In one embodiment, when two 32 port CSI-RS resources are aggregated to form a 64 port CSI-RS resource, it is predefined in 3GPP specifications that the two aggregated 32 port CSI- RS resources have the same CDM group size (i.e., the same 8 value). Furthermore, the two aggregated 32 port CSI-RS resources have the same port layout (3_^’, 3_^’). For the 64 port CSI- RS resource, the total number of ports in the above port indexing formula is then 3 = 2 × 23_^ ^{^}3_^ ^{^}. [0094] Let us denote the CDM group index corresponding to the first aggregated 32 port CSI- RS resource as ^_^ and the CDM group index corresponding to the second aggregated 32 port CSI- RS resource

[0095] Let us assume port indexing is according to the aggregation type in Figure 11 and the value of 8 = 8 (i.e., there are four CDM groups of size 8 in each of the aggregated 32 port CSI- RS resource). The CDM group indices for the aggregated 64 port CSI-RS can be mapped to the ^{CDM group indices in the two 32 port CSI-RS resources as follows:} ^_{^^ ^^} 0 0 1 1 2 0 3 1 4 2 5 3 6 2 7 3 [0096] Alternatively, the relationship between ^, ^_^, and ^_^ can be written as follows: ^^{^} ^{ì 3} ^{^^, ^^^ ^^ = 0, … , ^3^} ^{8 − 1} ¹ Note that in aggregated 64 port

^^{NM^ N^} ^{resource is ^ = 0, 1, … , R} ^{^ − 1. The above equation is valid for any CDM group size 8 ∈} _{{1,2,4,8}. Once the values of ^^, and ^^ are mapped to ^, the port index of the aggregated 64 port} resource can be determined using w = 3000 + ^ + ^8. 2 Extension of Type I Single Panel Codebook to More than 64 Antenna Ports [0097] Multiple CSI-RS resources can also be aggregated to form more than 64 ports. 2.1 Port Indexing Using CDM Group Index for 96 Ports [0098] In one embodiment, three 32 ports CSI-RS resources are aggregated to form a 96 ports CSI-RS resource. In this embodiment, it is predefined in 3GPP specifications that the three aggregated 32 ports CSI-RS resources have the same CDM group size (i.e., the same 8 value). Furthermore, the three aggregated 32 ports CSI-RS resources have the same port layout (3^{^} _^, 3_^ ^{^}). For the 96 ports CSI-RS resource, the total number of ports is given by 3 = 3 × 23_^ ^{^}3_^ ^{^} . [0099] It is assumed that the mapping type of Figure 14 is applicable where w ∈ (0,1, … ,95) ^{is the antenna port index of the 96 antenna ports; w^ ∈ (0,1, … ,31), w^ ∈ (0,1, … ,31) and wf ∈} _{(0,1, … ,31) respectively denote the antenna port}

_{for the corresponding first, second and the} third 32 antenna ports. [0100] Let us denote the following: ^{• the CDM group index corresponding to the first aggregated 32 port CSI-RS resource as} ^_^, •^{the CDM group index corresponding to the second aggregated 32 port CSI-RS resource as} ^_{^, and} •^{the CDM group index corresponding to the third aggregated 32 port CSI-RS resource as} ^_f. [0101] Let us further assume the value of 8 = 8 (i.e., there are four CDM groups of size 8 in each of the aggregated 32 port CSI-RS resource). The CDM group indices for the aggregated 96 port CSI-RS can be mapped to the CDM group indices in the three 32 port CSI-RS resources as ^follows: ^_{^^ ^^ ^^} 0 0 1 1 2 0 3 1 4 0 5 1 6 2 7 3 8 2 9 3 10 2 11 3 [0102] Alternatively, the relationship between ^, ^_^, ^_^ and ^_f can be written as follows: ^^{^^ ^} _^ ^{3^3^} ^{^ ^ − 1} ¹ ¹

Note that in the above equation, the range of values for CDM group of the aggregated 96port …^{, ^NM^ N^} ^{resource is ^ = 0, 1, R} ^{^ − 1. The above equation is valid for any CDM group size 8 ∈} _{{1,2,4,8}. Once the values of ^^, ^^ and ^f are mapped to ^, the port index of the aggregated 96}

port resource can be determined using w = 3000 + ^ + ^8. 3 Alternative Embodiment: Port Remapping via a Permutation Matrix [0103] In an alternative embodiment, port numbering is the same regardless of the aggregation type, so that the ports are numbered firstly within each resource as in legacy, and then numbered across resources. With the above examples, it means that w = w_^ , for w_^ = 0, …, 23_^ ^{^}3_^ ^{^}-1, while w = w_^ + 23_^ ^{^}3_^ ^{^}, for w_^ = 0, …, 23_^ ^{^}3_^ ^{^} – 1. In this case, a permutation matrix can be used, which should be used for remapping the port index when determining and applying a PMI. [0104] Take the NR Type I single panel codebook as an example, when 64 ports are obtained by aggregating two 32 ports. Denote the selected spatial domain (SD) basis vector as "_^ ∈ ℂ^{^^×^}, ^{then, both the gNB and the UE shall assume a permutation matrix "6^^@ ∈ ℝ^^×^^ is applied to} _{"^, so the effective "^ is given by "6^^@"^. A permutation matrix is a square matrix obtained} by permuting the rows or columns of an identity matrix. For a permutation matrix, each column and each row contains exactly one element equal to 1, and all other elements are 0. [0105] In one embodiment, a set of permutation matrices are pre-defined, e.g., in 3GPP specifications. Each of the pre-defined permutation matrices may be suitable for a given aggregation type. gNB configures the UE which permutation matrix to use via an index, where each index corresponds to a unique permutation matrix. [0106] Note that the proposed extension to 64 ports with port aggregation applies to all codebooks parameterized by 3_^ and 3_^, such as the Type I single panel codebook, and variants of Type II codebooks. [0107] Even though 64 ports are used as an example above, the idea can be easily extended to more than 64 ports. 4 Further Description [0108] Figure 15 is a flow chart that illustrates the operation of a UE in accordance with at least some of the embodiments described above. Optional steps are represented by dashed lines/boxes. Note that not all of the details described above are repeated in the description of Figure 15; however, the details described above are applicable to the respective steps of the process of Figure 15. As illustrated, the UE receives, from a network node, information that configures the UE with s>1 CSI-RS resources, each with :` _abPca ≤ 32 CSI-RS antenna ports (step 1500). The M CSI-RS resources are aggregated to form an aggregated CSI-RS resource for a 2D antenna array configured with two polarizations and having a size N₁ x N₂ per polarization where N₁ is a size of the 2D antenna array in a first dimension and N2 is a size of the 2D antenna array in a second dimension. The aggregated CSI-RS resource for the 2D antenna array has 2N₁N₂ =MP_CSI- RS CSI-RS resources, and M > 1. [0109] The UE determines an antenna port layout with :` _abPca CSI-RS antenna ports associated to the M CSI-RS resources (step 1502). More specifically, in one embodiment, the UE receives, from the network node, information that indicates an aggregation type to be used to aggregate the M CSI-RS resources to form the aggregated CSI-RS resource for the 2D antenna array (step 1502A-1) and determines the antenna port layout based on the indicated aggregation type (step 1502A-2). In one embodiment, the aggregation type is either a first aggregation type in which the M CSI-RS resources are aggregated in the first dimension or a second aggregation type in which the M CSI-RS resources are aggregated in the second dimension, and the information that indicates the aggregation type indicates either the first aggregation type or the second aggregation type. In one embodiment, the aggregation type is the first aggregation type. In one embodiment, the first aggregation type is such that the CSI-RS antenna port mapping for the 2D antenna array ensures that the CSI-RS antenna ports are indexed in increasing order along the 3_^ dimension first and then in increasing order along the 3_^ dimension for each polarization, so that CSI-RS antenna ports w = (0,1, … ,31) for the aggregated CSI-RS resource are mapped to one polarization and CSI-RS antenna ports (32, 33, …63) for the aggregated CSI-RS resource are mapped to the other polarization. [0110] In another embodiment, the UE determines the antenna port layout based on a predefined aggregation type (step 1502B). In one embodiment, the predefined aggregation type is a first aggregation type in which the M CSI-RS resources are aggregated in the first dimension. In one embodiment, the M CSI-RS resources consist of a first CSI-RS resource and a second CSI- RS resource, and the first aggregation type is such that the CSI-RS antenna ports of the aggregated CSI-RS resource are indexed as follows: • first, index antenna ports along the 3_^ dimension and then along the 3_^ dimension of the first polarization of the first CSI-RS resource of the M CSI-RS

• next, index antenna ports along the 3_^ dimension and then along the 3_^ dimension of the first polarization of the second CSI-RS resource of the M CSI-RS

• next, index antenna ports along the 3_^ dimension and then along the 3_^dimension of the second polarization of the first CSI-RS resource of the M CSI-RS resources, • finally, index antenna ports along the 3_^ dimension and then along the 3_^ dimension of the second polarization of the second CSI-RS resource of the M CSI-RS resources. [0111] In another embodiment, the first aggregation type is such that the CSI-RS antenna port mapping for the 2D antenna array is given by: w^{@ + (^ − 1):` abPca/2; 0 ≤ w@ ≤ :` abPca/2 − 1} w_{= y (s + ^ − 1):` abPca} [0112] In aggregation type in which the M

In one embodiment, the second aggregation type is such that the CSI-RS antenna port mapping for the 2D antenna array is given by: 3^{^} ^{s (w@ + ^ − 1); w@ = 2^, ^ = 0,1, … , :` abPca/2} ,_{:` abPca/2} [0113] the 2D antenna array for

codebook based CSI feedback (step 1504). The CSI-RS antenna port mapping provides a one-to- one mapping between each CSI-RS antenna port of the aggregated CSI-RS resource and one of the CSI-RS antenna ports of one of the M CSI-RS resources. In one embodiment, the UE determines the CSI-RS antenna port mapping for the 2D antenna array based on the antenna port layout determined in step 1502. In one embodiment, the CSI-RS antenna port mapping provides a one-to-one mapping between each CSI-RS antenna port, w ∈ (0,1, … ,23_^3_^ − 1) , of the aggregated CSI-RS resource and one of the CSI-RS antenna ports of one of the M CSI-RS resources, w_@ ∈ (0,1, … , :` _abPca − 1), ^ = 1,2, … , s. [0114] The UE performs measurements on

channels associated to the 2D antenna array based on the determined CSI-RS antenna port mapping for the 2D antenna array (step 1506). The UE computes a precoding matrix based on the measurements (step 1508) and sends, to the network node, a PMI associated to the computed precoding matrix (step 1510). In one embodiment, elements of each column of the precoding matrix are arranged according to an order of antenna port indices of the aggregated CSI-RS resource with a first element being associated to port index w = 0. [0115] In one embodiment, the M CSI-RS resources aggregated to form the aggregated CSI- RS resource have a same CDM group size. [0116] In one embodiment, the M CSI-RS resources aggregated to form the aggregated CSI- RS resource have a same CSI-RS antenna port layout. [0117] In one embodiment, the CSI-RS antenna port mapping is defined via a permutation matrix. [0118] In one embodiment, M is an integer value that is greater than 1. In one embodiment, M=2. In one embodiment, M=3. [0119] In one embodiment, :` _abPca ≤ 32. In one embodiment, :` _abPca = 32. [0120] Figure 16 is a flow chart that illustrates the operation of network node (e.g., a RAN node such as, e.g., a base station such as, e.g., a gNB) in accordance with at least some of the embodiments described above. Optional steps are represented by dashed lines/boxes. Note that not all of the details described above are repeated in the description of Figure 16; however, the details described above are applicable to the respective steps of the process of Figure 16. As illustrated, the network node sends (e.g., transmits), to a UE, information that configures the UE with s>1 CSI-RS resources, each with :` _abPca ≤ 32 CSI-RS antenna ports (step 1600). The M CSI-RS resources are aggregated to form an CSI-RS resource for a 2D antenna array

configured with two polarizations and having a size N1 x N2 per polarization where N1 is a size of the 2D antenna array in a first dimension and N₂ is a size of the 2D antenna array in a second dimension. The aggregated CSI-RS resource for the 2D antenna array has 2N1N2 =MPCSI-RS CSI- RS resources, and M > 1. [0121] The network node receives, from the UE, a PMI associated to a precoding matrix that is based on a CSI-RS antenna port mapping for the 2D antenna array for codebook based Channel State Information, CSI, feedback, wherein the CSI-RS antenna port mapping provides a one-to- one mapping between each CSI-RS antenna port of the aggregated CSI-RS resource and one of the CSI-RS antenna ports of one of the M CSI-RS resources (step 1602). The network node performs one or more actions based on the received PMI (step 1604). [0122] Figure 17 shows an example of a communication system 1700 in accordance with some embodiments. [0123] In the example, the communication system 1700 includes a telecommunication network 1702 that includes an access network 1704, such as a Radio Access Network (RAN), and a core network 1706, which includes one or more core network nodes 1708. The access network 1704 includes one or more access network nodes, such as network nodes 1710A and 1710B (one or more of which may be generally referred to as network nodes 1710), or any other similar Third Generation Partnership Project (3GPP) access nodes or non-3GPP Access Points (APs). Moreover, as will be appreciated by those of skill in the art, a network node is not necessarily limited to an implementation in which a radio portion and a baseband portion are supplied and integrated by a single vendor. Thus, it will be understood that network nodes include disaggregated implementations or portions thereof. For example, in some embodiments, the telecommunication network 1702 includes one or more Open-RAN (ORAN) network nodes. An ORAN network node is a node in the telecommunication network 1702 that supports an ORAN specification (e.g., a specification published by the O-RAN Alliance, or any similar organization) and may operate alone or together with other nodes to implement one or more functionalities of any node in the telecommunication network 1702, including one or more network nodes 1710 and/or core network nodes 1708. [0124] Examples of an ORAN network node include an Open Radio Unit (O-RU), an Open Distributed Unit (O-DU), an Open Central Unit (O-CU), including an O-CU Control Plane (O- CU-CP) or an O-CU User Plane (O-CU-UP), a RAN intelligent controller (near-real time or non- real time) hosting software or software plug-ins, such as a near-real time control application (e.g., xApp) or a non-real time control application (e.g., rApp), or any combination thereof (the adjective “open” designating support of an ORAN specification). The network node may support a specification by, for example, supporting an interface defined by the ORAN specification, such as an A1, F1, W1, E1, E2, X2, Xn interface, an open fronthaul user plane interface, or an open fronthaul management plane interface. Moreover, an ORAN access node may be a logical node in a physical node. Furthermore, an ORAN network node may be implemented in a virtualization environment (described further below) in which one or more network functions are virtualized. For example, the virtualization environment may include an O-Cloud computing platform orchestrated by a Service Management and Orchestration Framework via an O-2 interface defined by the O-RAN Alliance or comparable technologies. The network nodes 1710 facilitate direct or indirect connection of User Equipment (UE), such as by connecting UEs 1712A, 1712B, 1712C, and 1712D (one or more of which may be generally referred to as UEs 1712) to the core network 1706 over one or more wireless connections. [0125] Example wireless communications over a wireless connection include transmitting and/or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and/or other types of signals suitable for conveying information without the use of wires, cables, or other material conductors. Moreover, in different embodiments, the communication system 1700 may include any number of wired or wireless networks, network nodes, UEs, and/or any other components or systems that may facilitate or participate in the communication of data and/or signals whether via wired or wireless connections. The communication system 1700 may include and/or interface with any type of communication, telecommunication, data, cellular, radio network, and/or other similar type of system. [0126] The UEs 1712 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and/or operable to communicate wirelessly with the network nodes 1710 and other communication devices. Similarly, the network nodes 1710 are arranged, capable, configured, and/or operable to communicate directly or indirectly with the UEs 1712 and/or with other network nodes or equipment in the telecommunication network 1702 to enable and/or provide network access, such as wireless network access, and/or to perform other functions, such as administration in the telecommunication network 1702. [0127] In the depicted example, the core network 1706 connects the network nodes 1710 to one or more hosts, such as host 1716. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts. The core network 1706 includes one more core network nodes (e.g., core network node 1708) that are structured with hardware and software components. Features of these components may be substantially similar to those described with respect to the UEs, network nodes, and/or hosts, such that the descriptions thereof are generally applicable to the corresponding components of the core network node 1708. Example core network nodes include functions of one or more of a Mobile Switching Center (MSC), Mobility Management Entity (MME), Home Subscriber Server (HSS), Access and Mobility Management Function (AMF), Session Management Function (SMF), Authentication Server Function (AUSF), Subscription Identifier De-Concealing Function (SIDF), Unified Data Management (UDM), Security Edge Protection Proxy (SEPP), Network Exposure Function (NEF), and/or a User Plane Function (UPF). [0128] The host 1716 may be under the ownership or control of a service provider other than an operator or provider of the access network 1704 and/or the telecommunication network 1702, and may be operated by the service provider or on behalf of the service provider. The host 1716 may host a variety of applications to provide one or more service. Examples of such applications include live and pre-recorded audio/video content, data collection services such as retrieving and compiling data on various ambient conditions detected by a plurality of UEs, analytics functionality, social media, functions for controlling or otherwise interacting with remote devices, functions for an alarm and surveillance center, or any other such function performed by a server. [0129] As a whole, the communication system 1700 of Figure 17 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system 1700 may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: Global System for Mobile Communications (GSM); Universal Mobile Telecommunications System (UMTS); Long Term Evolution (LTE), and/or other suitable Second, Third, Fourth, or Fifth Generation (2G, 3G, 4G, or 5G) standards, or any applicable future generation standard (e.g., Sixth Generation (6G)); Wireless Local Area Network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi); and/or any other appropriate wireless communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax), Bluetooth, Z-Wave, Near Field Communication (NFC) ZigBee, LiFi, and/or any Low Power Wide Area Network (LPWAN) standards such as LoRa and Sigfox. [0130] In some examples, the telecommunication network 1702 is a cellular network that implements 3GPP standardized features. Accordingly, the telecommunication network 1702 may support network slicing to provide different logical networks to different devices that are connected to the telecommunication network 1702. For example, the telecommunication network 1702 may provide Ultra Reliable Low Latency Communication (URLLC) services to some UEs, while providing enhanced Mobile Broadband (eMBB) services to other UEs, and/or massive Machine Type Communication (mMTC)/massive Internet of Things (IoT) services to yet further UEs. [0131] In some examples, the UEs 1712 are configured to transmit and/or receive information without direct human interaction. For instance, a UE may be designed to transmit information to the access network 1704 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the access network 1704. Additionally, a UE may be configured for operating in single- or multi-Radio Access Technology (RAT) or multi-standard mode. For example, a UE may operate with any one or combination of WiFi, New Radio (NR), and LTE, i.e. being configured for Multi-Radio Dual Connectivity (MR-DC), such as Evolved UMTS Terrestrial RAN (E-UTRAN) NR - Dual Connectivity (EN-DC). [0132] In the example, a hub 1714 communicates with the access network 1704 to facilitate indirect communication between one or more UEs (e.g., UE 1712C and/or 1712D) and network nodes (e.g., network node 1710B). In some examples, the hub 1714 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding UEs. For example, the hub 1714 may be a broadband router enabling access to the core network 1706 for the UEs. As another example, the hub 1714 may be a controller that sends commands or instructions to one or more actuators in the UEs. Commands or instructions may be received from the UEs, network nodes 1710, or by executable code, script, process, or other instructions in the hub 1714. As another example, the hub 1714 may be a data collector that acts as temporary storage for UE data and, in some embodiments, may perform analysis or other processing of the data. As another example, the hub 1714 may be a content source. For example, for a UE that is a Virtual Reality (VR) headset, display, loudspeaker or other media delivery device, the hub 1714 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which the hub 1714 then provides to the UE either directly, after performing local processing, and/or after adding additional local content. In still another example, the hub 1714 acts as a proxy server or orchestrator for the UEs, in particular if one or more of the UEs are low energy IoT devices. [0133] The hub 1714 may have a constant/persistent or intermittent connection to the network node 1710B. The hub 1714 may also allow for a different communication scheme and/or schedule between the hub 1714 and UEs (e.g., UE 1712C and/or 1712D), and between the hub 1714 and the core network 1706. In other examples, the hub 1714 is connected to the core network 1706 and/or one or more UEs via a wired connection. Moreover, the hub 1714 may be configured to connect to a Machine-to-Machine (M2M) service provider over the access network 1704 and/or to another UE over a direct connection. In some scenarios, UEs may establish a wireless connection with the network nodes 1710 while still connected via the hub 1714 via a wired or wireless connection. In some embodiments, the hub 1714 may be a dedicated hub – that is, a hub whose primary function is to route communications to/from the UEs from/to the network node 1710B. In other embodiments, the hub 1714 may be a non-dedicated hub – that is, a device which is capable of operating to route communications between the UEs and the network node 1710B, but which is additionally capable of operating as a communication start and/or end point for certain data channels. [0134] Figure 18 shows a UE 1800 in accordance with some embodiments. As used herein, a UE refers to a device capable, configured, arranged, and/or operable to communicate wirelessly with network nodes and/or other UEs. Examples of a UE include, but are not limited to, a smart phone, mobile phone, cell phone, Voice over Internet Protocol (VoIP) phone, wireless local loop phone, desktop computer, Personal Digital Assistant (PDA), wireless camera, gaming console or device, music storage device, playback appliance, wearable terminal device, wireless endpoint, mobile station, tablet, laptop, Laptop Embedded Equipment (LEE), Laptop Mounted Equipment (LME), smart device, wireless Customer Premise Equipment (CPE), vehicle, vehicle-mounted or vehicle embedded/integrated wireless device, etc. Other examples include any UE identified by the 3GPP, including a Narrowband Internet of Things (NB-IoT) UE, a Machine Type Communication (MTC) UE, and/or an enhanced MTC (eMTC) UE. [0135] A UE may support Device-to-Device (D2D) communication, for example by implementing a 3GPP standard for sidelink communication, Dedicated Short-Range Communication (DSRC), Vehicle-to-Vehicle (V2V), Vehicle-to-Infrastructure (V2I), or Vehicle- to-Everything (V2X). In other examples, a UE may not necessarily have a user in the sense of a human user who owns and/or operates the relevant device. Instead, a UE may represent a device that is intended for sale to, or operation by, a human user but which may not, or which may not initially, be associated with a specific human user (e.g., a smart sprinkler controller). Alternatively, a UE may represent a device that is not intended for sale to, or operation by, an end user but which may be associated with or operated for the benefit of a user (e.g., a smart power meter). [0136] The UE 1800 includes processing circuitry 1802 that is operatively coupled via a bus 1804 to an input/output interface 1806, a power source 1808, memory 1810, a communication interface 1812, and/or any other component, or any combination thereof. Certain UEs may utilize all or a subset of the components shown in Figure 18. The level of integration between the components may vary from one UE to another UE. Further, certain UEs may contain multiple instances of a component, such as multiple processors, memories, transceivers, transmitters, receivers, etc. [0137] The processing circuitry 1802 is configured to process instructions and data and may be configured to implement any sequential state machine operative to execute instructions stored as machine-readable computer programs in the memory 1810. The processing circuitry 1802 may be implemented as one or more hardware-implemented state machines (e.g., in discrete logic, Field Programmable Gate Arrays (FPGAs), Application Specific Integrated Circuits (ASICs), etc.); programmable logic together with appropriate firmware; one or more stored computer programs, general purpose processors, such as a microprocessor or Digital Signal Processor (DSP), together with appropriate software; or any combination of the above. For example, the processing circuitry 1802 may include multiple Central Processing Units (CPUs). [0138] In the example, the input/output interface 1806 may be configured to provide an interface or interfaces to an input device, output device, or one or more input and/or output devices. Examples of an output device include a speaker, a sound card, a video card, a display, a monitor, a printer, an actuator, an emitter, a smartcard, another output device, or any combination thereof. An input device may allow a user to capture information into the UE 1800. Examples of an input device include a touch-sensitive or presence-sensitive display, a camera (e.g., a digital camera, a digital video camera, a web camera, etc.), a microphone, a sensor, a mouse, a trackball, a directional pad, a trackpad, a scroll wheel, a smartcard, and the like. The presence-sensitive display may include a capacitive or resistive touch sensor to sense input from a user. A sensor may be, for instance, an accelerometer, a gyroscope, a tilt sensor, a force sensor, a magnetometer, an optical sensor, a proximity sensor, a biometric sensor, etc., or any combination thereof. An output device may use the same type of interface port as an input device. For example, a Universal Serial Bus (USB) port may be used to provide an input device and an output device. [0139] In some embodiments, the power source 1808 is structured as a battery or battery pack. Other types of power sources, such as an external power source (e.g., an electricity outlet), photovoltaic device, or power cell, may be used. The power source 1808 may further include power circuitry for delivering power from the power source 1808 itself, and/or an external power source, to the various parts of the UE 1800 via input circuitry or an interface such as an electrical power cable. Delivering power may be, for example, for charging of the power source 1808. Power circuitry may perform any formatting, converting, or other modification to the power from the power source 1808 to make the power suitable for the respective components of the UE 1800 to which power is supplied. [0140] The memory 1810 may be or be configured to include memory such as Random Access Memory (RAM), Read Only Memory (ROM), Programmable ROM (PROM), Erasable PROM (EPROM), Electrically EPROM (EEPROM), magnetic disks, optical disks, hard disks, removable cartridges, flash drives, and so forth. In one example, the memory 1810 includes one or more application programs 1814, such as an operating system, web browser application, a widget, gadget engine, or other application, and corresponding data 1816. The memory 1810 may store, for use by the UE 1800, any of a variety of various operating systems or combinations of operating systems. [0141] The memory 1810 may be configured to include a number of physical drive units, such as Redundant Array of Independent Disks (RAID), flash memory, USB flash drive, external hard disk drive, thumb drive, pen drive, key drive, High Density Digital Versatile Disc (HD-DVD) optical disc drive, internal hard disk drive, Blu-Ray optical disc drive, Holographic Digital Data Storage (HDDS) optical disc drive, external mini Dual In-line Memory Module (DIMM), Synchronous Dynamic RAM (SDRAM), external micro-DIMM SDRAM, smartcard memory such as a tamper resistant module in the form of a Universal Integrated Circuit Card (UICC) including one or more Subscriber Identity Modules (SIMs), such as a Universal SIM (USIM) and/or Internet Protocol Multimedia Services Identity Module (ISIM), other memory, or any combination thereof. The UICC may for example be an embedded UICC (eUICC), integrated UICC (iUICC) or a removable UICC commonly known as a ‘SIM card.’ The memory 1810 may allow the UE 1800 to access instructions, application programs, and the like stored on transitory or non-transitory memory media, to off-load data, or to upload data. An article of manufacture, such as one utilizing a communication system, may be tangibly embodied as or in the memory 1810, which may be or comprise a device-readable storage medium. [0142] The processing circuitry 1802 may be configured to communicate with an access network or other network using the communication interface 1812. The communication interface 1812 may comprise one or more communication subsystems and may include or be communicatively coupled to an antenna 1822. The communication interface 1812 may include one or more transceivers used to communicate, such as by communicating with one or more remote transceivers of another device capable of wireless communication (e.g., another UE or a network node in an access network). Each transceiver may include a transmitter 1818 and/or a receiver 1820 appropriate to provide network communications (e.g., optical, electrical, frequency allocations, and so forth). Moreover, the transmitter 1818 and receiver 1820 may be coupled to one or more antennas (e.g., the antenna 1822) and may share circuit components, software, or firmware, or alternatively be implemented separately. [0143] In the illustrated embodiment, communication functions of the communication interface 1812 may include cellular communication, WiFi communication, LPWAN communication, data communication, voice communication, multimedia communication, short- range communications such as Bluetooth, NFC, location-based communication such as the use of the Global Positioning System (GPS) to determine a location, another like communication function, or any combination thereof. Communications may be implemented according to one or more communication protocols and/or standards, such as IEEE 802.11, Code Division Multiplexing Access (CDMA), Wideband CDMA (WCDMA), GSM, LTE, NR, UMTS, WiMax, Ethernet, Transmission Control Protocol/Internet Protocol (TCP/IP), Synchronous Optical Networking (SONET), Asynchronous Transfer Mode (ATM), Quick User Datagram Protocol Internet Connection (QUIC), Hypertext Transfer Protocol (HTTP), and so forth. [0144] Regardless of the type of sensor, a UE may provide an output of data captured by its sensors, through its communication interface 1812, via a wireless connection to a network node. Data captured by sensors of a UE can be communicated through a wireless connection to a network node via another UE. The output may be periodic (e.g., once every 15 minutes if it reports the sensed temperature), random (e.g., to even out the load from reporting from several sensors), in response to a triggering event (e.g., when moisture is detected an alert is sent), in response to a request (e.g., a user initiated request), or a continuous stream (e.g., a live video feed of a patient). [0145] As another example, a UE comprises an actuator, a motor, or a switch related to a communication interface configured to receive wireless input from a network node via a wireless connection. In response to the received wireless input the states of the actuator, the motor, or the switch may change. For example, the UE may comprise a motor that adjusts the control surfaces or rotors of a drone in flight according to the received input or to a robotic arm performing a medical procedure according to the received input. [0146] A UE, when in the form of an IoT device, may be a device for use in one or more application domains, these domains comprising, but not limited to, city wearable technology, extended industrial application, and healthcare. Non-limiting examples of such an IoT device are a device which is or which is embedded in: a connected refrigerator or freezer, a television, a connected lighting device, an electricity meter, a robot vacuum cleaner, a voice controlled smart speaker, a home security camera, a motion detector, a thermostat, a smoke detector, a door/window sensor, a flood/moisture sensor, an electrical door lock, a connected doorbell, an air conditioning system like a heat pump, an autonomous vehicle, a surveillance system, a weather monitoring device, a vehicle parking monitoring device, an electric vehicle charging station, a smart watch, a fitness tracker, a head-mounted display for Augmented Reality (AR) or VR, a wearable for tactile augmentation or sensory enhancement, a water sprinkler, an animal- or item-tracking device, a sensor for monitoring a plant or animal, an industrial robot, an Unmanned Aerial Vehicle (UAV), and any kind of medical device, like a heart rate monitor or a remote controlled surgical robot. A UE in the form of an IoT device comprises circuitry and/or software in dependence of the intended application of the IoT device in addition to other components as described in relation to the UE 1800 shown in Figure 18. [0147] As yet another specific example, in an IoT scenario, a UE may represent a machine or other device that performs monitoring and/or measurements and transmits the results of such monitoring and/or measurements to another UE and/or a network node. The UE may in this case be an M2M device, which may in a 3GPP context be referred to as an MTC device. As one particular example, the UE may implement the 3GPP NB-IoT standard. In other scenarios, a UE may represent a vehicle, such as a car, a bus, a truck, a ship, an airplane, or other equipment that is capable of monitoring and/or reporting on its operational status or other functions associated with its operation. [0148] In practice, any number of UEs may be used together with respect to a single use case. For example, a first UE might be or be integrated in a drone and provide the drone’s speed information (obtained through a speed sensor) to a second UE that is a remote controller operating the drone. When the user makes changes from the remote controller, the first UE may adjust the throttle on the drone (e.g., by controlling an actuator) to increase or decrease the drone’s speed. The first and/or the second UE can also include more than one of the functionalities described above. For example, a UE might comprise the sensor and the actuator and handle communication of data for both the speed sensor and the actuators. [0149] Figure 19 shows a network node 1900 in accordance with some embodiments. As used herein, network node refers to equipment capable, configured, arranged, and/or operable to communicate directly or indirectly with a UE and/or with other network nodes or equipment in a telecommunication network. Examples of network nodes include, but are not limited to, APs (e.g., radio APs), Base Stations (BSs) (e.g., radio BSs, Node Bs, evolved Node Bs (eNBs), NR Node Bs (gNBs)), and O-RAN nodes or components of an O-RAN node (e.g., O-RU, O-DU, O-CU). [0150] Base stations may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. A base station may be a relay node or a relay donor node controlling a relay. A network node may also include one or more (or all) parts of a distributed radio base station such as centralized digital units, distributed units (e.g., in an O-RAN access node), and/or Remote Radio Units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such RRUs may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a Distributed Antenna System (DAS). [0151] Other examples of network nodes include multiple Transmission Point (multi-TRP) 5G access nodes, Multi-Standard Radio (MSR) equipment such as MSR BSs, network controllers such as Radio Network Controllers (RNCs) or BS Controllers (BSCs), Base Transceiver Stations (BTSs), transmission points, transmission nodes, Multi-Cell/Multicast Coordination Entities (MCEs), Operation and Maintenance (O&M) nodes, Operations Support System (OSS) nodes, Self-Organizing Network (SON) nodes, positioning nodes (e.g., Evolved Serving Mobile Location Centers (E-SMLCs)), and/or Minimization of Drive Tests (MDTs). [0152] The network node 1900 includes processing circuitry 1902, memory 1904, a communication interface 1906, and a power source 1908. The network node 1900 may be composed of multiple physically separate components (e.g., a NodeB component and an RNC component, or a BTS component and a BSC component, etc.), which may each have their own respective components. In certain scenarios in which the network node 1900 comprises multiple separate components (e.g., BTS and BSC components), one or more of the separate components may be shared among several network nodes. For example, a single RNC may control multiple NodeBs. In such a scenario, each unique NodeB and RNC pair may in some instances be considered a single separate network node. In some embodiments, the network node 1900 may be configured to support multiple RATs. In such embodiments, some components may be duplicated (e.g., separate memory 1904 for different RATs) and some components may be reused (e.g., a same antenna 1910 may be shared by different RATs). The network node 1900 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node 1900, for example GSM, WCDMA, LTE, NR, WiFi, Zigbee, Z-wave, Long Range Wide Area Network (LoRaWAN), Radio Frequency Identification (RFID), or Bluetooth wireless technologies. These wireless technologies may be integrated into the same or different chip or set of chips and other components within the network node 1900. [0153] The processing circuitry 1902 may comprise a combination of one or more of a microprocessor, controller, microcontroller, CPU, DSP, ASIC, FPGA, or any other suitable computing device, resource, or combination of hardware, software, and/or encoded logic operable to provide, either alone or in conjunction with other network node 1900 components, such as the memory 1904, to provide network node 1900 functionality. [0154] In some embodiments, the processing circuitry 1902 includes a System on a Chip (SOC). In some embodiments, the processing circuitry 1902 includes one or more of Radio Frequency (RF) transceiver circuitry 1912 and baseband processing circuitry 1914. In some embodiments, the RF transceiver circuitry 1912 and the baseband processing circuitry 1914 may be on separate chips (or sets of chips), boards, or units, such as radio units and digital units. In alternative embodiments, part or all of the RF transceiver circuitry 1912 and the baseband processing circuitry 1914 may be on the same chip or set of chips, boards, or units. [0155] The memory 1904 may comprise any form of volatile or non-volatile computer- readable memory including, without limitation, persistent storage, solid state memory, remotely mounted memory, magnetic media, optical media, RAM, ROM, mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD), or a Digital Video Disk (DVD)), and/or any other volatile or non-volatile, non-transitory device- readable, and/or computer-executable memory devices that store information, data, and/or instructions that may be used by the processing circuitry 1902. The memory 1904 may store any suitable instructions, data, or information, including a computer program, software, an application including one or more of logic, rules, code, tables, and/or other instructions capable of being executed by the processing circuitry 1902 and utilized by the network node 1900. The memory 1904 may be used to store any calculations made by the processing circuitry 1902 and/or any data received via the communication interface 1906. In some embodiments, the processing circuitry 1902 and the memory 1904 are integrated. [0156] The communication interface 1906 is used in wired or wireless communication of signaling and/or data between a network node, access network, and/or UE. As illustrated, the communication interface 1906 comprises port(s)/terminal(s) 1916 to send and receive data, for example to and from a network over a wired connection. The communication interface 1906 also includes radio front-end circuitry 1918 that may be coupled to, or in certain embodiments a part of, the antenna 1910. The radio front-end circuitry 1918 comprises filters 1920 and amplifiers 1922. The radio front-end circuitry 1918 may be connected to the antenna 1910 and the processing circuitry 1902. The radio front-end circuitry 1918 may be configured to condition signals communicated between the antenna 1910 and the processing circuitry 1902. The radio front-end circuitry 1918 may receive digital data that is to be sent out to other network nodes or UEs via a wireless connection. The radio front-end circuitry 1918 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of the filters 1920 and/or the amplifiers 1922. The radio signal may then be transmitted via the antenna 1910. Similarly, when receiving data, the antenna 1910 may collect radio signals which are then converted into digital data by the radio front-end circuitry 1918. The digital data may be passed to the processing circuitry 1902. In other embodiments, the communication interface 1906 may comprise different components and/or different combinations of components. [0157] In certain alternative embodiments, the network node 1900 does not include separate radio front-end circuitry 1918; instead, the processing circuitry 1902 includes radio front-end circuitry and is connected to the antenna 1910. Similarly, in some embodiments, all or some of the RF transceiver circuitry 1912 is part of the communication interface 1906. In still other embodiments, the communication interface 1906 includes the one or more ports or terminals 1916, the radio front-end circuitry 1918, and the RF transceiver circuitry 1912 as part of a radio unit (not shown), and the communication interface 1906 communicates with the baseband processing circuitry 1914, which is part of a digital unit (not shown). [0158] The antenna 1910 may include one or more antennas, or antenna arrays, configured to send and/or receive wireless signals. The antenna 1910 may be coupled to the radio front-end circuitry 1918 and may be any type of antenna capable of transmitting and receiving data and/or signals wirelessly. In certain embodiments, the antenna 1910 is separate from the network node 1900 and connectable to the network node 1900 through an interface or port. [0159] The antenna 1910, the communication interface 1906, and/or the processing circuitry 1902 may be configured to perform any receiving operations and/or certain obtaining operations described herein as being performed by the network node 1900. Any information, data, and/or signals may be received from a UE, another network node, and/or any other network equipment. Similarly, the antenna 1910, the communication interface 1906, and/or the processing circuitry 1902 may be configured to perform any transmitting operations described herein as being performed by the network node 1900. Any information, data, and/or signals may be transmitted to a UE, another network node, and/or any other network equipment. [0160] The power source 1908 provides power to the various components of the network node 1900 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). The power source 1908 may further comprise, or be coupled to, power management circuitry to supply the components of the network node 1900 with power for performing the functionality described herein. For example, the network node 1900 may be connectable to an external power source (e.g., the power grid or an electricity outlet) via input circuitry or an interface such as an electrical cable, whereby the external power source supplies power to power circuitry of the power source 1908. As a further example, the power source 1908 may comprise a source of power in the form of a battery or battery pack which is connected to, or integrated in, power circuitry. The battery may provide backup power should the external power source fail. [0161] Embodiments of the network node 1900 may include additional components beyond those shown in Figure 19 for providing certain aspects of the network node’s functionality, including any of the functionality described herein and/or any functionality necessary to support the subject matter described herein. For example, the network node 1900 may include user interface equipment to allow input of information into the network node 1900 and to allow output of information from the network node 1900. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for the network node 1900. [0162] Figure 20 is a block diagram of a host 2000, which may be an embodiment of the host 1716 of Figure 17, in accordance with various aspects described herein. As used herein, the host 2000 may be or comprise various combinations of hardware and/or software including a standalone server, a blade server, a cloud-implemented server, a distributed server, a virtual machine, container, or processing resources in a server farm. The host 2000 may provide one or more services to one or more UEs. [0163] The host 2000 includes processing circuitry 2002 that is operatively coupled via a bus 2004 to an input/output interface 2006, a network interface 2008, a power source 2010, and memory 2012. Other components may be included in other embodiments. Features of these components may be substantially similar to those described with respect to the devices of previous figures, such as Figures 18 and 19, such that the descriptions thereof are generally applicable to the corresponding components of the host 2000. [0164] The memory 2012 may include one or more computer programs including one or more host application programs 2014 and data 2016, which may include user data, e.g. data generated by a UE for the host 2000 or data generated by the host 2000 for a UE. Embodiments of the host 2000 may utilize only a subset or all of the components shown. The host application programs 2014 may be implemented in a container-based architecture and may provide support for video codecs (e.g., Versatile Video Coding (VVC), High Efficiency Video Coding (HEVC), Advanced Video Coding (AVC), Moving Picture Experts Group (MPEG), VP9) and audio codecs (e.g., Free Lossless Audio Codec (FLAC), Advanced Audio Coding (AAC), MPEG, G.711), including transcoding for multiple different classes, types, or implementations of UEs (e.g., handsets, desktop computers, wearable display systems, and heads-up display systems). The host application programs 2014 may also provide for user authentication and licensing checks and may periodically report health, routes, and content availability to a central node, such as a device in or on the edge of a core network. Accordingly, the host 2000 may select and/or indicate a different host for Over-The-Top (OTT) services for a UE. The host application programs 2014 may support various protocols, such as the HTTP Live Streaming (HLS) protocol, Real-Time Messaging Protocol (RTMP), Real-Time Streaming Protocol (RTSP), Dynamic Adaptive Streaming over HTTP (DASH or MPEG-DASH), etc. [0165] Figure 21 is a block diagram illustrating a virtualization environment 2100 in which functions implemented by some embodiments may be virtualized. In the present context, virtualizing means creating virtual versions of apparatuses or devices which may include virtualizing hardware platforms, storage devices, and networking resources. As used herein, virtualization can be applied to any device described herein, or components thereof, and relates to an implementation in which at least a portion of the functionality is implemented as one or more virtual components. Some or all of the functions described herein may be implemented as virtual components executed by one or more Virtual Machines (VMs) implemented in one or more virtual environments 2100 hosted by one or more of hardware nodes, such as a hardware computing device that operates as a network node, UE, core network node, or host. Further, in embodiments in which the virtual node does not require radio connectivity (e.g., a core network node or host), then the node may be entirely virtualized. In some embodiments, the virtualization environment 2100 includes components defined by the O-RAN Alliance, such as an O-Cloud environment orchestrated by a Service Management and Orchestration Framework via an O-2 interface. [0166] Applications 2102 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) are run in the virtualization environment 2100 to implement some of the features, functions, and/or benefits of some of the embodiments disclosed herein. [0167] Hardware 2104 includes processing circuitry, memory that stores software and/or instructions executable by hardware processing circuitry, and/or other hardware devices as described herein, such as a network interface, input/output interface, and so forth. Software may be executed by the processing circuitry to instantiate one or more virtualization layers 2106 (also referred to as hypervisors or VM Monitors (VMMs)), provide VMs 2108A and 2108B (one or more of which may be generally referred to as VMs 2108), and/or perform any of the functions, features, and/or benefits described in relation with some embodiments described herein. The virtualization layer 2106 may present a virtual operating platform that appears like networking hardware to the VMs 2108. [0168] The VMs 2108 comprise virtual processing, virtual memory, virtual networking, or interface and virtual storage, and may be run by a corresponding virtualization layer 2106. Different embodiments of the instance of a virtual appliance 2102 may be implemented on one or more of the VMs 2108, and the implementations may be made in different ways. Virtualization of the hardware is in some contexts referred to as Network Function Virtualization (NFV). NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which can be located in data centers and customer premise equipment. [0169] In the context of NFV, a VM 2108 may be a software implementation of a physical machine that runs programs as if they were executing on a physical, non-virtualized machine. Each of the VMs 2108, and that part of the hardware 2104 that executes that VM, be it hardware dedicated to that VM and/or hardware shared by that VM with others of the VMs 2108, forms separate virtual network elements. Still in the context of NFV, a virtual network function is responsible for handling specific network functions that run in one or more VMs 2108 on top of the hardware 2104 and corresponds to the application 2102. [0170] The hardware 2104 may be implemented in a standalone network node with generic or specific components. The hardware 2104 may implement some functions via virtualization. Alternatively, the hardware 2104 may be part of a larger cluster of hardware (e.g., such as in a data center or CPE) where many hardware nodes work together and are managed via management and orchestration 2110, which, among others, oversees lifecycle management of the applications 2102. In some embodiments, the hardware 2104 is coupled to one or more radio units that each include one or more transmitters and one or more receivers that may be coupled to one or more antennas. Radio units may communicate directly with other hardware nodes via one or more appropriate network interfaces and may be used in combination with the virtual components to provide a virtual node with radio capabilities, such as a RAN or a base station. In some embodiments, some signaling can be provided with the use of a control system 2112 which may alternatively be used for communication between hardware nodes and radio units. [0171] Figure 22 shows a communication diagram of a host 2202 communicating via a network node 2204 with a UE 2206 over a partially wireless connection in accordance with some embodiments. Example implementations, in accordance with various embodiments, of the UE (such as the UE 1712A of Figure 17 and/or the UE 1800 of Figure 18), the network node (such as the network node 1710A of Figure 17 and/or the network node 1900 of Figure 19), and the host (such as the host 1716 of Figure 17 and/or the host 2000 of Figure 20) discussed in the preceding paragraphs will now be described with reference to Figure 22. [0172] Like the host 2000, embodiments of the host 2202 include hardware, such as a communication interface, processing circuitry, and memory. The host 2202 also includes software, which is stored in or is accessible by the host 2202 and executable by the processing circuitry. The software includes a host application that may be operable to provide a service to a remote user, such as the UE 2206 connecting via an OTT connection 2250 extending between the UE 2206 and the host 2202. In providing the service to the remote user, a host application may provide user data which is transmitted using the OTT connection 2250. [0173] The network node 2204 includes hardware enabling it to communicate with the host 2202 and the UE 2206. The connection 2260 may be direct or pass through a core network (like the core network 1706 of Figure 17) and/or one or more other intermediate networks, such as one or more public, private, or hosted networks. For example, an intermediate network may be a backbone network or the Internet. [0174] The UE 2206 includes hardware and software, which is stored in or accessible by the UE 2206 and executable by the UE’s processing circuitry. The software includes a client application, such as a web browser or operator-specific “app” that may be operable to provide a service to a human or non-human user via the UE 2206 with the support of the host 2202. In the host 2202, an executing host application may communicate with the executing client application via the OTT connection 2250 terminating at the UE 2206 and the host 2202. In providing the service to the user, the UE's client application may receive request data from the host's host application and provide user data in response to the request data. The OTT connection 2250 may transfer both the request data and the user data. The UE's client application may interact with the user to generate the user data that it provides to the host application through the OTT connection 2250. [0175] The OTT connection 2250 may extend via the connection 2260 between the host 2202 and the network node 2204 and via a wireless connection 2270 between the network node 2204 and the UE 2206 to provide the connection between the host 2202 and the UE 2206. The connection 2260 and the wireless connection 2270, over which the OTT connection 2250 may be provided, have been drawn abstractly to illustrate the communication between the host 2202 and the UE 2206 via the network node 2204, without explicit reference to any intermediary devices and the precise routing of messages via these devices. [0176] As an example of transmitting data via the OTT connection 2250, in step 2208, the host 2202 provides user data, which may be performed by executing a host application. In some embodiments, the user data is associated with a particular human user interacting with the UE 2206. In other embodiments, the user data is associated with a UE 2206 that shares data with the host 2202 without explicit human interaction. In step 2210, the host 2202 initiates a transmission carrying the user data towards the UE 2206. The host 2202 may initiate the transmission responsive to a request transmitted by the UE 2206. The request may be caused by human interaction with the UE 2206 or by operation of the client application executing on the UE 2206. The transmission may pass via the network node 2204 in accordance with the teachings of the embodiments described throughout this disclosure. Accordingly, in step 2212, the network node 2204 transmits to the UE 2206 the user data that was carried in the transmission that the host 2202 initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In step 2214, the UE 2206 receives the user data carried in the transmission, which may be performed by a client application executed on the UE 2206 associated with the host application executed by the host 2202. [0177] In some examples, the UE 2206 executes a client application which provides user data to the host 2202. The user data may be provided in reaction or response to the data received from the host 2202. Accordingly, in step 2216, the UE 2206 may provide user data, which may be performed by executing the client application. In providing the user data, the client application may further consider user input received from the user via an input/output interface of the UE 2206. Regardless of the specific manner in which the user data was provided, the UE 2206 initiates, in step 2218, transmission of the user data towards the host 2202 via the network node 2204. In step 2220, in accordance with the teachings of the embodiments described throughout this disclosure, the network node 2204 receives user data from the UE 2206 and initiates transmission of the received user data towards the host 2202. In step 2222, the host 2202 receives the user data carried in the transmission initiated by the UE 2206. [0178] One or more of the various embodiments improve the performance of OTT services provided to the UE 2206 using the OTT connection 2250, in which the wireless connection 2270 forms the last segment. More precisely, the teachings of these embodiments may improve, e.g., data rate and/or latency and thereby provide benefits such as, e.g., reduced user waiting time, relaxed restriction on file size, improved content resolution, better responsiveness, and/or extended battery lifetime. [0179] In an example scenario, factory status information may be collected and analyzed by the host 2202. As another example, the host 2202 may process audio and video data which may have been retrieved from a UE for use in creating maps. As another example, the host 2202 may collect and analyze real-time data to assist in controlling vehicle congestion (e.g., controlling traffic lights). As another example, the host 2202 may store surveillance video uploaded by a UE. As another example, the host 2202 may store or control access to media content such as video, audio, VR, or AR which it can broadcast, multicast, or unicast to UEs. As other examples, the host 2202 may be used for energy pricing, remote control of non-time critical electrical load to balance power generation needs, location services, presentation services (such as compiling diagrams etc. from data collected from remote devices), or any other function of collecting, retrieving, storing, analyzing, and/or transmitting data. [0180] In some examples, a measurement procedure may be provided for the purpose of monitoring data rate, latency, and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection 2250 between the host 2202 and the UE 2206 in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring the OTT connection 2250 may be implemented in software and hardware of the host 2202 and/or the UE 2206. In some embodiments, sensors (not shown) may be deployed in or in association with other devices through which the OTT connection 2250 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or by supplying values of other physical quantities from which software may compute or estimate the monitored quantities. The reconfiguring of the OTT connection 2250 may include message format, retransmission settings, preferred routing, etc.; the reconfiguring need not directly alter the operation of the network node 2204. Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling that facilitates measurements of throughput, propagation times, latency, and the like by the host 2202. The measurements may be implemented in that software causes messages to be transmitted, in particular empty or ‘dummy’ messages, using the OTT connection 2250 while monitoring propagation times, errors, etc. [0181] Although the computing devices described herein (e.g., UEs, network nodes, hosts) may include the illustrated combination of hardware components, other embodiments may comprise computing devices with different combinations of components. It is to be understood that these computing devices may comprise any suitable combination of hardware and/or software needed to perform the tasks, features, functions, and methods disclosed herein. Determining, calculating, obtaining, or similar operations described herein may be performed by processing circuitry, which may process information by, for example, converting the obtained information into other information, comparing the obtained information or converted information to information stored in the network node, and/or performing one or more operations based on the obtained information or converted information, and as a result of said processing making a determination. Moreover, while components are depicted as single boxes located within a larger box or nested within multiple boxes, in practice computing devices may comprise multiple different physical components that make up a single illustrated component, and functionality may be partitioned between separate components. For example, a communication interface may be configured to include any of the components described herein, and/or the functionality of the components may be partitioned between the processing circuitry and the communication interface. In another example, non-computationally intensive functions of any of such components may be implemented in software or firmware and computationally intensive functions may be implemented in hardware. [0182] In certain embodiments, some or all of the functionality described herein may be provided by processing circuitry executing instructions stored in memory, which in certain embodiments may be a computer program product in the form of a non-transitory computer- readable storage medium. In alternative embodiments, some or all of the functionality may be provided by the processing circuitry without executing instructions stored on a separate or discrete device-readable storage medium, such as in a hardwired manner. In any of those particular embodiments, whether executing instructions stored on a non-transitory computer-readable storage medium or not, the processing circuitry can be configured to perform the described functionality. The benefits provided by such functionality are not limited to the processing circuitry alone or to other components of the computing device, but are enjoyed by the computing device as a whole and/or by end users and a wireless network generally. [0183] Some example embodiments of the present disclosure are as follows: Group A Embodiments [0184] Embodiment 1: A method performed by a User Equipment, UE, comprising any one or more of the following: • receiving (1500), from a network node, information that configures the UE with s>1 Channel State Information Reference Signal, CSI-RS, resources, each with :` _abPca ≤ 32 CSI-RS antenna ports, wherein: o the M CSI-RS resources are aggregated to form an aggregated CSI-RS resource for a two-dimensional, 2D, antenna array configured with two polarizations and having a size N₁ x N₂ per polarization where N₁ is a size of the 2D antenna array in a first dimension and N2 is a size of the 2D antenna array in a second dimension; and o the aggregated CSI-RS resource for the 2D antenna array has 2N1N2 =MPCSI-RS CSI-RS ports; o • determining (1504) a CSI-RS antenna port mapping for the 2D antenna array for codebook based Channel State Information, CSI, feedback, wherein the CSI-RS antenna port mapping provides a one-to-one mapping between each CSI-RS antenna port of the aggregated CSI-RS resource and one of the CSI-RS antenna ports of one of the M CSI- RS resources; • performing (1506) measurements on downlink channels associated to the 2D antenna array based on the determined CSI-RS antenna port mapping for the 2D antenna array; • computing (1508) a precoding matrix based on the measurements; • sending (1510), to the network node, a precoding matrix indicator, PMI, associated to the computed precoding matrix. [0185] Embodiment 2: The method of embodiment 1, further comprising determining (1502) an antenna port layout with :` _abPca CSI-RS antenna ports associated to the M CSI-RS resources, wherein determining (1504) the CSI-RS antenna port mapping for the 2D antenna array comprises determining (1504) the CSI-RS antenna port mapping for the 2D antenna array based on the determined antenna port layout. [0186] Embodiment 3: The method of embodiment 2, further comprising: receiving (1502A- 1), from the network node, information that indicates an aggregation type to be used to aggregate the M CSI-RS resources to form the aggregated CSI-RS resource for the 2D antenna array; wherein determining (1502) the antenna port layout comprises determining (1502A-2) the antenna port layout based on the indicated aggregation type. [0187] Embodiment 4: The method of embodiment 3, wherein the aggregation type is either a first aggregation type in which the M CSI-RS resources are aggregated in the first dimension or a second aggregation type in which the M CSI-RS resources are aggregated in the second dimension, and the information that indicates the aggregation type indicates either the first aggregation type or the second aggregation type. [0188] Embodiment 5: The method of embodiment 4, wherein the aggregation type is the first aggregation type. [0189] Embodiment 6: The method of embodiment 5, wherein the first aggregation type is such that the CSI-RS antenna port mapping for the 2D antenna array ensures that the CSI-RS antenna ports are indexed in increasing order along the 3_^ dimension first and then in increasing order along the 3_^ dimension for each polarization, so that CSI-RS antenna ports w = (0,1, … ,31) for the aggregated CSI-RS resource are mapped to one polarization and CSI-RS antenna ports (32, 33, …63) for the aggregated CSI-RS resource are mapped to the other polarization. [0190] Embodiment 7: The method of embodiment 2, wherein determining (1502) the antenna port layout comprises determining (1502B) the antenna port layout based on a predefined aggregation type. [0191] Embodiment 8: The method of embodiment 7, wherein the predefined aggregation type is a first aggregation type in which the M CSI-RS resources are aggregated in the first dimension. [0192] Embodiment 9: The method of embodiment 8, wherein the M CSI-RS resources consist of a first CSI-RS resource and a second CSI-RS resource, and the first aggregation type is such that the CSI-RS antenna ports of the aggregated CSI-RS resource are indexed as follows: • first, index antenna ports along the 3_^ dimension and then along the 3_^ dimension of the first polarization of the first CSI-RS resource of the M CSI-RS

• next, index antenna ports along the 3_^ dimension and then along the 3_^dimension of the second polarization of the first CSI-RS resource of the M CSI-RS

• finally, index antenna ports along the 3_^ dimension and then along the 3_^ dimension of the second polarization of the second CSI-RS resource of the M CSI-RS resources. [0193] Embodiment 10: The method of embodiment 8, wherein the first aggregation type is such that the CSI-RS antenna port mapping for the 2D antenna array is given by (where w_@ is the CSI-RS port index of the mth (m=1,2,…,M) CSI-RS resource) : w^{@ + (^ − 1):` abPca/2; 0 ≤ w@ ≤ :` abPca/2 − 1} [0194]

aggregation type is a second aggregation type in which the M CSI-RS resources are aggregated in the second dimension. [0195] Embodiment 12: The method of embodiment 11, wherein the second aggregation type is such that the CSI-RS antenna port mapping for the 2D antenna array is given by (where w_@ is the CSI-RS port index of the mth (m=1,2,…,M) CSI-RS resource): 3^{^} ^{(w@ + ^ − 1); w@ = 2^, ^ = 0,1, … , :` abPca/2} ^{= s} ,_{:` abPca/2} [0196] 12, wherein the CSI-RS ^antenna

a^{one- one CSI-RS antenna port, w ∈} _{(0,1, … ,23^3^ − 1), of the aggregated CSI-RS resource and one of the CSI-RS antenna ports of} one of the M CSI-RS resources, w_@ ∈ (0,1, … , :` _abPca − 1), ^ = 1,2, … , s. [0197] Embodiment 14: The method of any of embodiments 1 to 13, wherein elements of each column of the precoding matrix are arranged in increasing order of antenna port indices of the aggregated CSI-RS resource with a first element being associated to port index w = 0. [0198] Embodiment 15: The method of any of embodiments 1 to 14, wherein the M CSI-RS resources aggregated to form the aggregated CSI-RS resource have a same Code Division Multiplexing, CDM, group size. [0199] Embodiment 16: The method of any of embodiments 1 to 15, wherein the M CSI-RS resources aggregated to form the aggregated CSI-RS resource have a same CSI-RS antenna port layout. [0200] Embodiment 17: The method of embodiment 1, wherein the CSI-RS antenna port mapping is defined via a permutation matrix. [0201] Embodiment 18: The method of any of embodiments 1 to 17, wherein M is an integer value is that greater than 1. [0202] Embodiment 19: The method of any of embodiments 1 to 17, wherein M=2. [0203] Embodiment 20: The method of any of embodiments 1 to 17, wherein M=3. [0204] Embodiment 21: The method of any of embodiments 1 to 19, wherein :` _abPca ≤ 32. [0205] Embodiment 22: The method of any of embodiments 1 to 19, wherein :` _abPca = 32. [0206] Embodiment 23: The method of any of the previous embodiments, further comprising: providing user data; and forwarding the user data to a host via the transmission to the network node. Group B Embodiments [0207] Embodiment 24: A method performed by a network node, comprising any one or more of the following: • sending (1600), to a UE, information that configures the UE with s>1 Channel State Information Reference Signal, CSI-RS, resources, each with :` _abPca ≤ 32 CSI-RS antenna ports, wherein:

o the M CSI-RS resources are aggregated to form an CSI-RS resource for a two-dimensional, 2D, antenna array configured with two polarizations and having a size N1 x N2 per polarization where N1 is a size of the 2D antenna array in a first dimension and N2 is a size of the 2D antenna array in a second dimension; and o the aggregated CSI-RS resource for the 2D antenna array has 2N1N2 =MPCSI-RS CSI-RS ports; • receiving (1602), from the UE, a precoding matrix indicator, PMI, associated to a precoding matrix that is based on a CSI-RS antenna port mapping for the 2D antenna array for codebook based Channel State Information, CSI, feedback, wherein the CSI-RS antenna port mapping provides a one-to-one mapping between each CSI-RS antenna port of the aggregated CSI-RS resource and one of the CSI-RS antenna ports of one of the M CSI-RS resources; • performing (1604) one or more actions based on the received PMI. [0208] Embodiment 25: The method of any of the previous embodiments, further comprising: obtaining user data; and forwarding the user data to a host or a user equipment. Group C Embodiments [0209] Embodiment 26: A user equipment comprising: processing circuitry configured to perform any of the steps of any of the Group A embodiments; and power supply circuitry configured to supply power to the processing circuitry. [0210] Embodiment 27: A network node comprising: processing circuitry configured to perform any of the steps of any of the Group B embodiments; and power supply circuitry configured to supply power to the processing circuitry. [0211] Embodiment 28: A user equipment (UE) comprising: an antenna configured to send and receive wireless signals; radio front-end circuitry connected to the antenna and to processing circuitry, and configured to condition signals communicated between the antenna and the processing circuitry; the processing circuitry being configured to perform any of the steps of any of the Group A embodiments; an input interface connected to the processing circuitry and configured to allow input of information into the UE to be processed by the processing circuitry; an output interface connected to the processing circuitry and configured to output information from the UE that has been processed by the processing circuitry; and a battery connected to the processing circuitry and configured to supply power to the UE. [0212] Embodiment 29: A host configured to operate in a communication system to provide an over-the-top (OTT) service, the host comprising: processing circuitry configured to provide user data; and a network interface configured to initiate transmission of the user data to a network node in a cellular network for transmission to a user equipment (UE), the network node having a communication interface and processing circuitry, the processing circuitry of the network node configured to perform any of the operations of any of the Group B embodiments to transmit the user data from the host to the UE. [0213] Embodiment 30: The host of the previous embodiment, wherein: the processing circuitry of the host is configured to execute a host application that provides the user data; and the UE comprises processing circuitry configured to execute a client application associated with the host application to receive the transmission of user data from the host. [0214] Embodiment 31: A method implemented in a host configured to operate in a communication system that further includes a network node and a user equipment (UE), the method comprising: providing user data for the UE; and initiating a transmission carrying the user data to the UE via a cellular network comprising the network node, wherein the network node performs any of the operations of any of the Group B embodiments to transmit the user data from the host to the UE. [0215] Embodiment 32: The method of the previous embodiment, further comprising, at the network node, transmitting the user data provided by the host for the UE. [0216] Embodiment 33: The method of any of the previous 2 embodiments, wherein the user data is provided at the host by executing a host application that interacts with a client application executing on the UE, the client application being associated with the host application. [0217] Embodiment 34: A communication system configured to provide an over-the-top (OTT) service, the communication system comprising a host comprising: processing circuitry configured to provide user data for a user equipment (UE), the user data being associated with the over-the-top service; and a network interface configured to initiate transmission of the user data toward a cellular network node for transmission to the UE, the network node having a communication interface and processing circuitry, the processing circuitry of the network node configured to perform any of the operations of any of the Group B embodiments to transmit the user data from the host to the UE. [0218] Embodiment 35: The communication system of the previous embodiment, further comprising: the network node; and/or the UE. [0219] Embodiment 36: A host configured to operate in a communication system to provide an over-the-top (OTT) service, the host comprising: processing circuitry configured to initiate receipt of user data; and a network interface configured to receive the user data from a network node in a cellular network, the network node having a communication interface and processing circuitry, the processing circuitry of the network node configured to perform any of the operations of any of the Group B embodiments to receive the user data from a user equipment (UE) for the host. [0220] Embodiment 37: The host of the previous 2 embodiments, wherein: the processing circuitry of the host is configured to execute a host application that receives the user data; and the host application is configured to interact with a client application executing on the UE, the client application being associated with the host application. [0221] Embodiment 38: The host of the any of the previous 2 embodiments, wherein the initiating receipt of the user data comprises requesting the user data. [0222] Embodiment 39: A method implemented by a host configured to operate in a communication system that further includes a network node and a user equipment (UE), the method comprising: at the host, initiating receipt of user data from the UE, the user data originating from a transmission which the network node has received from the UE, wherein the network node performs any of the steps of any of the Group B embodiments to receive the user data from the UE for the host. [0223] Embodiment 40: The method of the previous embodiment, further comprising at the network node, transmitting the received user data to the host. [0224] Embodiment 41: A host configured to operate in a communication system to provide an over-the-top (OTT) service, the host comprising: processing circuitry configured to provide user data; and a network interface configured to initiate transmission of the user data to a cellular network for transmission to a user equipment (UE), wherein the UE comprises a communication interface and processing circuitry, the communication interface and processing circuitry of the UE being configured to perform any of the operations of any of the Group A embodiments to receive the user data from the host. [0225] Embodiment 42: The host of the previous embodiment, wherein the cellular network further includes a network node configured to communicate with the UE to transmit the user data to the UE from the host. [0226] Embodiment 43: The host of the previous 2 embodiments, wherein: the processing circuitry of the host is configured to execute a host application, thereby providing the user data; and the host application is configured to interact with a client application executing on the UE, the client application being associated with the host application. [0227] Embodiment 44: A method implemented by a host operating in a communication system that further includes a network node and a user equipment (UE), the method comprising: providing user data for the UE; and initiating a transmission carrying the user data to the UE via a cellular network comprising the network node, wherein the UE performs any of the operations of any of the Group A embodiments to receive the user data from the host. [0228] Embodiment 45: The method of the previous embodiment, further comprising: at the host, executing a host application associated with a client application executing on the UE to receive the user data from the host application. [0229] Embodiment 46: The method of the previous embodiment, further comprising: at the host, transmitting input data to the client application executing on the UE, the input data being provided by executing the host application, wherein the user data is provided by the client application in response to the input data from the host application. [0230] Embodiment 47: A host configured to operate in a communication system to provide an over-the-top (OTT) service, the host comprising: processing circuitry configured to provide user data; and a network interface configured to initiate transmission of the user data to a cellular network for transmission to a user equipment (UE), wherein the UE comprises a communication interface and processing circuitry, the communication interface and processing circuitry of the UE being configured to perform any of the steps of any of the Group A embodiments to transmit the user data to the host. [0231] Embodiment 48: The host of the previous embodiment, wherein the cellular network further includes a network node configured to communicate with the UE to transmit the user data from the UE to the host. [0232] Embodiment 49: The host of the previous 2 embodiments, wherein: the processing circuitry of the host is configured to execute a host application, thereby providing the user data; and the host application is configured to interact with a client application executing on the UE, the client application being associated with the host application. [0233] Embodiment 50: A method implemented by a host configured to operate in a communication system that further includes a network node and a user equipment (UE), the method comprising: at the host, receiving user data transmitted to the host via the network node by the UE, wherein the UE performs any of the steps of any of the Group A embodiments to transmit the user data to the host. [0234] Embodiment 51: The method of the previous embodiment, further comprising: at the host, executing a host application associated with a client application executing on the UE to receive the user data from the UE. [0235] Embodiment 52: The method of the previous 2 embodiments, further comprising: at the host, transmitting input data to the client application executing on the UE, the input data being provided by executing the host application, wherein the user data is provided by the client application in response to the input data from the host application. [0236] Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein.

Claims

CLAIMS 1. A method performed by a User Equipment, UE, the method comprising: • receiving (1500), from a network node, a configuration for Channel State Information, CSI, feedback based on a codebook for :` _abPca > 32 antenna ports, the configuration comprising s>1 Channel State Information Reference Signal, CSI-RS, resources, each with 3 ≤ 32 CSI-RS ports, for channel measurement, wherein: o the :` _abPca antenna ports comprise N₁ ports in a first dimension and N₂ ports in a second dimension, wherein :` _abPca = 23_^3_^ = s ∙ 3; • determining (1504) a port mapping the :` _abPca antenna ports and one of

the CSI-RS ports of one of the M CSI-RS resources; • performing (1506) measurements on downlink channels associated to the :` _abPca antenna ports based on the M CSI-RS resources and the determined port mapping; • computing (1508) a precoding matrix based on the measurements and the codebook; and • sending (1510), to the network node, a precoding matrix indicator, PMI, associated to the computed precoding matrix as part of CSI feedback.

2. The method of claim 1, further comprising: receiving (1502A-1), from the network node, information that indicates a port mapping type ; wherein determining (1504) the port mapping comprises determining (1504) the port mapping based on the indicated port mapping type.

3. The method of claim 1, wherein each of the M CSI-RS resources has a first number, v_^, of ports in the first dimension and a second number, v_^, of ports in the second dimension, wherein 3 = 2v_^v_^.

4. The method of claim 2, wherein the port mapping type is either a first port mapping type in which the M CSI-RS resources are aggregated in the first dimension or a second port mapping type in which the M CSI-RS resources are aggregated in the second dimension.

5. The method of any of claims 1 to 4, where each of the M CSI-RS resources has an associated CSI-RS resource index and the M CSI-RS resources are ordered according to their associated CSI-RS resource index values.

6. The method of any claims 1 to 5, the M CSI-RS resources are ordered in increasing order of the CSI-RS resource index value, wherein the first CSI-RS resource has the smallest CSI-RS resource index value, and the last CSI-RS resource has the largest CSI-RS index value among the M CSI-RS resources.

7. The method of any claims 1 to 5, the M CSI-RS resources are ordered in decreasing order of the CSI-RS resource index value, wherein the first CSI-RS resource has the largest CSI-RS resource index value, and the last CSI-RS resource has the smallest CSI-RS index value among the M CSI-RS resources.

8. The method of claim 2, wherein for the first port mapping type, the :` _abPca antenna ports are mapped to the CSI-RS ports of the M CSI-RS resources sequentially starting from the ports of a first polarization of the M CSI-RS resources, followed by the ports of a second polarization of the M CSI-RS resources, so that antenna ports w = ⁽0,1, … , :` _abPca /2 − 1⁾ for the :` _abPca ^{antenna ports are mapped to the first polarization and the antenna ports (:` abPca /2, :` abPca /2 +} _{1, … , :` abPca − 1) for the :` abPca antenna ports are mapped to the second polarization.}

9. The method of claims 2 to 8, wherein for the first port mapping type , port mapping between the :` _abPca antenna ports and the CSI-RS ports of the M CSI-RS resources is given by: w^{@ + (^ − 1)3/2; 0 ≤ w@ ≤ 3/2 − 1} w_{= y (s + ^ )} _{w@ + − 1 N} _{2 ; N/2 ≤ w@ ≤ N − 1} where w ∈ ⁽0,1, … ,23_^3_^ − 1⁾ is an CSI-RS antenna port index of the :` _abPca CSI-RS antenna ports and w_@ ∈ (0,1, … , 3 − 1) is a CSI-RS antenna port index of the ^^{4 (^ ∈ 1, 2, … , s) CSI-RS resource among the M CSI-RS resources . 10. The method of claim 2, wherein for the second port mapping type, the :` _abPca antenna ports are mapped to the CSI-RS ports of the M CSI-RS resources sequentially in increasing order: • in a first polarization, along the second (3_^) dimension first for each of the M CSI-RS resources and then in increasing order along the first (3_^) dimension for each of the M CSI-RS resources, and • in a second polarization, along the second (3_^) dimension first for each of the M CSI-RS resources and then in increasing order along the first (3_^) dimension for each of the M CSI-RS resources, so that antenna ports w = ⁽0,1, … , :` _abPca /2 − 1⁾ for the :` _abPca antenna ports are mapped to the first polarization and antenna ports (:` _abPca /2, :` _abPca /2 + 1, … , :` _abPca − 1) are mapped to the second polarization. 11. The method of claim 2, wherein for the second port mapping type, port mapping between the :` _abPca antenna ports and the CSI-RS ports of the M CSI-RS resources is given by: 3^{^} ^{s (w@ + ^ − 1); w@ = 2^, ^ = 0,1, … , N/2} 0_{,1, … , N/2} ^{where w ∈ an antenna port in the}

_{:` abPca antenna ports w@ ∈ … , − a port index of the ^} ^{4 _{(^ ∈} _{1,2, … , s) CSI-RS resource among the M CSI-RS resources.} ^{12. The method of any claims 1 to claim 11, wherein the determined port mapping for the} _{:` abPca 32 antenna ports ensures that the antenna ports are:} first indexed in increasing order along the second (3_^) dimension first and then in increasing order along the first (3_^) dimension for a first of two polarizations; and second indexed in increasing order along the second (3_^) dimension first and then in increasing order along the first (3_^) dimension for a second of two polarizations 13. The method of any of claims 1 to 12, wherein the port mapping provides a one-to-one mapping between each antenna port, ^{w ∈ (0,1, … ,23} _^ ³ _^ ^{− 1),} of the :` _abPca antenna ports and one of the CSI-RS ports of one of the M CSI-RS resources, w_@ ∈ (0,1, … , 3 − 1), ^ = 1,2, … , s. 14. The method of any of claims 1 to 13, wherein each row of the precoding matrix is associated to one of the :` _abPca antenna ports and the rows are arranged in increasing order of ^{antenna port indices of the :`} _abPca ^{antenna ports with a first row being associated to port index} _{w = 0.} 15. The method of any of claims 1 to 14, wherein the M CSI-RS resources have a same Code Division Multiplexing, CDM, group size. 16. The method of any of claims 1 to 15, wherein the M CSI-RS resources have a same CSI- RS port layout with a first number, v_^, of ports in the first dimension and a second number, v_^, of ports in the second dimension at each of the two polarizations, wherein 3 = 2v_^v_^. ^{17. The method of claim 1, wherein determining (1504) the antenna port mapping for the} _{:` abPca > 32 antenna ports for codebook based CSI feedback comprises determining (1504) the} antenna port mapping for the :` _abPca antenna ports for codebook based CSI feedback based on a permutation matrix. 18. The method of any of claims 1 to 17, wherein M equals to one of two, three, and four. 19. The method of any of claims 1 to 18, wherein 3 ≤ 32. 20. The method of any of claims 1 to 18, wherein 3 ∈ (16, 24, 32). 21. A User Equipment, UE, adapted to: • receive (1500), from a network node, a configuration for Channel State Information, CSI, feedback based on a codebook for :` _abPca > 32 antenna ports, the configuration comprising s>1 Channel State Information Reference Signal, CSI-RS, resources, each with 3 ≤ 32 CSI-RS ports, for channel measurement, wherein: o the :` _abPca antenna ports comprising N₁ ports in a first dimension and N₂ ports in a second dimension, wherein :` _abPca = 23_^3_^ = s ∙ 3; • determine (1504) a port mapping between each of the :` _abPca antenna ports and one of the CSI-RS ports of one of the M CSI-RS resources; • perform (1506) measurements on downlink channels associated to the :` _abPca antenna ports based on the M CSI-RS resources and the determined port mapping; • compute (1508) a precoding matrix based on the measurements and the codebook; and • send (1510), to the network node, a precoding matrix indicator, PMI, associated to the computed precoding matrix as part of CSI feedback. 22. The UE of claim 21 further adapted to perform the method of any of claims 2 to 20. 23. A User Equipment, UE, (1800) comprising: • a communication interface (1812) comprising a transmitter (1818) and a receiver (1820); and • processing circuitry (1802) associated with the communication interface (1812), the processing circuitry (1802) configured to cause the UE (1800) to: o receive (1500), from a network node, a configuration for Channel State Information, CSI, feedback based on a codebook for :` _abPca > 32 antenna ports, the configuration comprising s>1 Channel State Information Reference Signal, CSI-RS, resources, each with 3 ≤ 32 CSI-RS ports, for channel measurement, wherein: ^ the :` _abPca antenna ports comprising N1 ports in a first dimension and N2 ports in a second dimension, wherein :` _abPca = 23_^3_^ = s ∙ 3; o determine (1504) a port mapping between each of the :` _abPca antenna ports and one of the CSI-RS ports of one of the M CSI-RS resources; o perform (1506) measurements on downlink channels associated to the :` _abPca antenna ports based on the M CSI-RS resources and the determined port mapping; o compute (1508) a precoding matrix based on the measurements and the codebook; and o send (1510), to the network node, a precoding matrix indicator, PMI, associated to the computed precoding matrix as part of CSI feedback. 24. The UE (1800) of claim 23, wherein the processing circuitry (1802) is further configured to cause the UE (1800) to perform the method of any of claims 2 to 20. 25. A method performed by a network node, the method comprising: • sending (1600) to a User Equipment, UE, a configuration for Channel State Information, CSI, feedback based on a codebook for :` _abPca > 32 antenna ports, the configuration comprising s>1 Channel State Information Reference Signal, CSI-RS, resources, each with 3 ≤ 32 CSI-RS ports, for channel measurement, wherein: o the :` _abPca antenna ports comprise N1 ports in a first dimension and N2 ports in a second dimension, wherein :` _abPca = 23_^3_^ = s ∙ 3; • receiving (1602), from the UE as part of CSI feedback, a precoding matrix indicator, PMI, associated to a precoding matrix that is based on a port mapping between each of the :` _abPca antenna ports and one of the CSI-RS ports of one of the M CSI-RS resources; • performing (1604) one or more actions based on the received PMI. 26. The method of claim 25, further comprising: sending, to the UE, information that indicates a port mapping type.. 27. The method of claim 25, wherein each of the M CSI-RS resources has a first number, v_^, of ports in the first dimension and a second number, v_^, of ports in the second dimension, wherein 3 = 2v_^v_^. 28. The method of claim 26, wherein the port mapping type is either a first port mapping type in which the M CSI-RS resources are aggregated in the first dimension or a second port mapping type in which the M CSI-RS resources are aggregated in the second dimension. 29. The method of any of claims 25 to 28, where each of the M CSI-RS resources has an associated CSI-RS resource index and the M CSI-RS resources are ordered according to their associated CSI-RS resource index values. 30. The method of any claims 25 to 29, the M CSI-RS resources are ordered in increasing order of the CSI-RS resource index value, wherein the first CSI-RS resource has the smallest CSI-RS resource index value, and the last CSI-RS resource has the largest CSI-RS index value among the M CSI-RS resources. 31. The method of any claims 25 to 29, the M CSI-RS resources are ordered in decreasing order of the CSI-RS resource index value, wherein the first CSI-RS resource has the largest CSI- RS resource index value, and the last CSI-RS resource has the smallest CSI-RS index value among the M CSI-RS resources. 32. The method of claim 26, wherein for the first port mapping type, the :` _abPca antenna ports are mapped to the CSI-RS ports of the M CSI-RS resources sequentially starting from the ports of a first polarization of the M CSI-RS resources, followed by the ports of a second polarization of the M CSI-RS resources, so that antenna ports w = (0,1, … , :` _abPca /2 − 1) for the :` _abPca antenna ports are mapped to the first polarization and the antenna ports (:` _abPca /2, :` _abPca /2 + 1, … , :` _abPca − 1) for the :` _abPca antenna ports are mapped to the second polarization. 33. The method of claim 26 to 32, wherein for the first port mapping type , port mapping between the :` _abPca antenna ports and the CSI-RS ports of the M CSI-RS resources is given by: ^{w@ + (^ − 1)3/2; 0 ≤ w@ ≤ 3/2 − 1} w_{= y (s + ^ − 1)N} _{+ ≤ ≤ − 1} where w ∈ (0,1, … :` _abPca CSI-RS antenna ports and w ∈ (0,1,

@ … , − (^ ∈ 1, 2, … , s) CSI-RS resource among the M CSI-RS resources . 34. The method of claim 26, wherein for the second port mapping type, the :` _abPca antenna ports are mapped to the CSI-RS ports of the M CSI-RS resources sequentially in increasing order: • in a first polarization, along the second (3_^) dimension first for each of the M CSI-RS resources and then in increasing order along the first (3_^) dimension for each of the M CSI-RS resources, and • in a second polarization, along the second (3_^) dimension first for each of the M CSI-RS resources and then in increasing order along the first (3_^) dimension for each of the M CSI-RS resources, so that antenna ports w = (0,1, … , :` _abPca /2 − 1) for the :` _abPca antenna ports are mapped to the first polarization and antenna ports (:` _abPca /2, :` _abPca /2 + 1, … , :` _abPca − 1) are mapped to the second polarization. 35. The method of claim 26, wherein for the second port mapping type, port mapping between the :` _abPca antenna ports and the CSI-RS ports of the M CSI-RS resources is given by: 3^{^} ^{+ ^ − ; w@ = 2^, ^ = 0,1, … , N/2} 0_{,1, … , N/2} ^{where w ∈}

^{an antenna port in the} _{:` abPca antenna ports and w@ ∈ (0,1, … , 3 − 1) is a CSI-RS port index of the ^} ^{4 _{(^ ∈} _{1,2, … , s) CSI-RS resource among the M CSI-RS resources.} 36. A network node adapted to: • send (1600) to a User Equipment, UE, a configuration for Channel State Information, CSI, feedback based on a codebook for :` _abPca > 32 antenna ports, the configuration comprising s>1 Channel State Information Reference Signal, CSI-RS, resources, each with 3 ≤ 32 CSI-RS ports, for channel measurement, wherein: o the :` _abPca antenna ports comprise N₁ ports in a first dimension and N₂ ports in a second dimension, wherein :` _abPca = 23_^3_^ = s ∙ 3; • receive (1602), from the UE as part of CSI feedback, a precoding matrix indicator, PMI, a^{ssociated to a precoding matrix that is based on a port mapping between each of the} :_{` abPca antenna ports and one of the CSI-RS ports of one of the M CSI-RS resources;} • perform (1604) one or more actions based on the received PMI. 37. The network node of claim 36 further adapted to perform the method of any of claims 26 to 35. 38. A network node (1900) comprising processing circuitry (1902) configured to cause the network node (1900) to: • send (1600) to a User Equipment, UE, a configuration for Channel State Information, CSI, feedback based on a codebook for :` _abPca > 32 antenna ports, the configuration comprising s>1 Channel State Information Reference Signal, CSI-RS, resources, each with 3 ≤ 32 CSI-RS ports, for channel measurement, wherein: o the :` _abPca antenna ports comprise N₁ ports in a first dimension and N₂ ports in a second dimension, wherein :` _abPca = 23_^3_^ = s ∙ 3; • receive (1602), from the UE as part of CSI feedback, a precoding matrix indicator, PMI, a^{ssociated to a precoding matrix that is based on a port mapping between each of the} :_{` abPca antenna ports and one of the CSI-RS ports of one of the M CSI-RS resources;} • perform (1604) one or more actions based on the received PMI. 39. The network node (1900) of claim 38, wherein the processing circuitry (1902) is further configured to cause the network node (1900) to perform the method of any of claims 26 to 35.