Methods and apparatuses for channel state information reporting for wireless communications

Abstract

The embodiments of the present invention relate to methods and apparatuses, in the form of a wireless device (700), and a network node (800) The method performed by the wireless device comprises receiving (401A) from the network node (800) a configuration or an indication, wherein the configuration or the indication indicates a number of a first dimension or columns and a number of a second dimension or rows of an antenna port layout at the network node, and a configuration or an indication, wherein the configuration or the indication indicates M Channel State Information – Reference Signal, CSI-RS, resources, wherein each CSI-RS resource comprises a number of antenna or CSI-RS ports, wherein the antenna or CSI-RS ports of each CSI-RS resource are mapped to a subset or proper subset of row and column indices of the antenna port layout. The method further comprises determining (402A) entries of a precoding vector per CSI-RS resource associated with a subset or proper subset of the rows and columns of the antenna port layout. The method further comprises generating (403A) a CSI report or a CSI feedback report comprising a Precoder Matrix Indicator, PMI, indicating the precoding vector, and reporting (404A), to the network node (800), the CSI report or the CSI feedback report.

Description

[0001]Methods and Apparatuses for Channel State Information Reporting for Wireless Communications TECHNICAL FIELD The present disclosure relates to the field of wireless telecommunications, and in particular to methods and apparatuses for Channel State Information (CSI) feedback reporting in an Uplink Control Channel (UCI) for a codebook-based precoding in a wireless communications network such as advanced 5G networks. BACKGROUND The radio access technology (RAT) in fifth generation (5G) mobile communications system, also known as 5G new radio (NR), provides a higher level of performance and flexibility than the previous generations of mobile communications systems.5G mobile communications has been driven by the need to provide ubiquitous connectivity for applications as diverse automotive communication, remote control with feedback, video downloads, as well as data applications for Internet-of-Things (IoT) devices, machine type communication (MTC) devices, etc.5G wireless technology brings several main benefits, such as faster speed, shorter delays and increased connectivity. The third-generation partnership project (3GPP) provides the complete system specification for the 5G network architecture, which includes at least a radio access network (RAN), core transport networks (CN) and service capabilities. Figure 1 illustrates a simplified schematic view of an example of a wireless communications network 100 including a core network (CN) 110 and a radio access network (RAN) 120. The RAN 120 is shown including a plurality of network nodes or radio base stations, which in 5G are called gNBs. Three radio base stations are depicted gNB1, gNB2 and gNB3. Each gNB serves an area called a coverage area or a cell. Figure 1 illustrates 3 cells 121, 122 and 123, each served by its own gNB, gNB1, gNB2 and gNB3, respectively. It should be mentioned that the network 100 may include any number of cells and gNBs. The radio base stations, or network nodes serve users within a cell. In 4G or LTE, a radio base station is called an eNB, in 3G or UMTS, a radio base station is called an eNodeB, and BS in other radio access technologies. A user equipment (UE) may be a wireless or a mobile terminal device or a stationary communication device. A wireless device may be a mobile terminal device, a UE, an Internet of Things (IoT) device, a Machine-type communication (MTC) device, etc. IoT devices may include wireless sensors, software, actuators, and computer devices. The IoT devices can be imbedded into mobile devices, motor vehicle, industrial equipment, environmental sensors, medical devices, aerial vehicles and more, as well as network connectivity that enables these devices to collect and exchange data across an existing network infrastructure. Referring back to Figure 1, each cell as shown includes UEs and IoT devices. gNB1 in cell 121 serves UE1121A, UE2121B and IoT device 121C. Similarly, gNB2 in cell 121 serves UE3 122A, UE4122B and IoT device 122C, and gNB3 in cell 123 serves UE5123A, UE6 123B and IoT device 123C. The wireless communications network 100 may include any number of UEs and IoT devices or any other types of devices. The devices communicate with the serving gNB(s) in the uplink and the gNB(s) communicate with the devices in the downlink. The respective base stations gNB1 to gNB3 may be connected to the CN 110, e.g., via the S1 interface, via respective backhaul links 111, 121D, 122D, 123D, which are schematically depicted in Fig.1 by the arrows pointing to “core”. The core network 110 may be connected to one or more external networks, such as the Internet. The gNBs may be connected to each other via the S1 interface or the X2 interface or the XN interface in 5G, via respective interface links 121E, 122E and 123E, which is depicted in the figure by the arrows pointing to gNBs. For data transmission, a physical resource grid may be used. The physical resource grid may comprise a set of resource elements (REs) to which various physical channels and physical signals are mapped. For example, the physical channels may include the physical downlink, uplink and / or sidelink (SL) shared channels (PDSCH, PUSCH, PSSCH) carrying user specific data, also referred to as downlink, uplink or sidelink payload data, the physical broadcast channel (PBCH) carrying for example a master information block (MIB) and a system information block (SIB), the physical downlink, uplink and / or sidelink control channels (PDCCH, PUCCH, PSCCH) carrying for example the downlink control information (DCI), the uplink control information (UCI) or the sidelink control information (SCI). For the uplink, the physical channels may further include the physical random-access channel (PRACH or RACH) used by UEs for accessing the network once a UE is synchronized and obtains the MIB and SIB. The physical signals may comprise reference signals (RS), synchronization signals (SSs) and the like. The resource grid may comprise a frame or radio frame having a certain duration, like 10 milliseconds, in the time domain and having a given bandwidth in the frequency domain. The radio frame may have a certain number of subframes of a predefined length, e.g., 2 subframes with a length of 1 millisecond. Each subframe may include two slots of a number of OFDM symbols depending on the cyclic prefix (CP) length. IN 5G, each slot consists of 14 OFDM symbols or 12 OFDM symbols based on normal CP and extended CP respectively. A frame may also consist of a smaller number of OFDM symbols, e.g., when utilizing shortened transmission time intervals (TTIs) or a mini-slot / non-slot-based frame structure comprising just a few OFDM symbols. Slot aggregation is supported in 5G NR and hence data transmission can be scheduled to span one or multiple slots. Slot format indication informs a UE whether an OFDM symbol is downlink, uplink or flexible. The wireless communications network may be any single-tone or multicarrier system using frequency-division multiplexing, like the orthogonal frequency-division multiplexing (OFDM) system, the orthogonal frequency-division multiple access (OFDMA) system, or any other Discrete Fourier Transform (DFT) based signal with or without CP, e.g., DFT-spread OFDM (DFT-s-OFDM). Other waveforms, like non-orthogonal waveforms for multiple access, e.g., filter-bank multicarrir (FBMC), generalized frequency division multiplexing (GFDM) or universal filtered multi carrier (UFMC), may also be used. The wireless communication system may operate, e.g., in accordance with the LTE-Advanced Pro standard, the 5G or NR (New Radio) standard or any other standard using any of the aforementioned waveforms. The wireless communications network system depicted in Figure 1 may be a heterogeneous network having two distinct overlaid networks, a network of macro cells with each macro cell including a macro base station, like base station gNB1 to gNB3, and a network of small cell base stations (not shown in Figure 1), like femto- or pico-base stations. In addition to the above described wireless network also non-terrestrial wireless communication networks exist including spaceborne transceivers, like satellites, and / or airborne transceivers, like unmanned aircraft systems. The non-terrestrial wireless communication network or system may operate in a similar way as the terrestrial system described above with reference to Figure 1, for example in accordance with the LTE-advanced pro standard or the 5G or NR, standard. In the wireless communications network system such as the one depicted schematically in Figure 1, multi-antenna techniques may be used, e.g., in accordance with LTE, NR or any other communication system, to improve user data rates, link reliability, cell coverage and network capacity. To support multi-stream or multi-layer transmissions, linear precoding is used in the physical layer of the communication system. Linear precoding is performed by a precoder matrix which maps layers of data to antenna ports. The precoding may be seen as a generalization of beamforming, which is a technique to spatially direct or focus a data transmission towards an intended receiver. The precoder matrix to be used at the gNB to map the data to the transmit antenna ports is decided using channel state information, CSI. In the wireless communications network system as described above, such as LTE or New Radio (5G), downlink signals convey data signals, control signals containing downlink, DL, control information (DCI), and a number of reference signals or symbols (RS) used for different purposes. A gNodeB (or gNB or base station) transmits data and downlink control information (DCI) through the so-called physical downlink shared channel (PDSCH) and physical downlink control channel (PDCCH) or enhanced PDCCH (ePDCCH), respectively. Moreover, the downlink signal(s) of the gNB may contain one or multiple types of reference signals (RSs) including a common RS (CRS) in LTE, a channel state information RS (CSI-RS), a demodulation RS (DM-RS), and a phase tracking RS (PT-RS). The CRS is transmitted over a DL system bandwidth part and used at the user equipment (UE) to obtain a channel estimate to demodulate the data or control information. The CSI-RS is transmitted with a reduced density in the time and frequency domain compared to CRS and used at the UE for channel estimation or for channel state information (CSI) acquisition. The DM-RS is transmitted only in a bandwidth part of the respective PDSCH and used by the UE for data demodulation. For signal precoding at the gNB, several CSI-RS reporting mechanisms are used such as non- precoded CSI-RS and beamformed CSI-RS reporting. For a non-precoded CSI-RS, a one-to- one mapping between a CSI-RS port and a transceiver unit, TXRU, of the antenna array at the gNB is utilized. Therefore, non-precoded CSI-RS provides a cell-wide coverage where the different CSI-RS ports have the same beam direction and beam width. For beamformed / precoded UE-specific or non-UE-specific CSI-RS, a beamforming operation is applied over a single antenna port or over multiple antenna ports to have several narrow beams with high gain in different directions and, therefore, no cell-wide coverage. In a wireless communications network employing time division duplexing, TDD, due to channel reciprocity, the CSI is available at the base station (gNB). However, when employing frequency division duplexing, FDD, due to the absence of channel reciprocity, the channel is estimated at the UE and the estimate is fed back to the gNB. Figure 2 shows a block-based model of a Multiple Input Multiple Output (MIMO) DL transmission using codebook-based- precoding in accordance with LTE release 8. Fig.2 shows schematically the base station 200, gNB, the user equipment, UE, 202 and the channel 204, like a radio channel for a wireless data communication between the base station 200 and the user equipment 202. The base station includes an antenna array ANTT having a plurality of antennas or antenna elements, and a precoder 206 receiving a data vector 208 and a precoder matrix F from a codebook 210. The term “precoder” means, without limitation, a precoding matrix or a precoder matrix. The channel 204 may be described by the channel tensor / matrix 212. The user equipment 202 receives the data vector 214 via an antenna or an antenna array ANTR having a plurality of antennas or antenna elements. A feedback channel 216 between the user equipment 202 and the base station 200 is provided for transmitting feedback information. The previous releases of 3GPP up to Release 15 support the use of several downlink reference symbols (such as CSI-RS) for CSI estimation at the UE. In FDD systems (up to Rel. 15), the estimated channel at the UE is reported to the gNB implicitly where the CSI report transmitted by the UE over the feedback channel includes the rank index (RI), the precoding matrix index (PMI) and the channel quality index (CQI) (and the CRI from Rel.13) allowing, at the gNB, to decide the precoding matrix, and the modulation order and coding scheme (MCS) of the symbols to be transmitted. The PMI and the RI are used to determine the precoding matrix from a predefined set of matrices Ω also referred to as codebook. The codebook, e.g., in accordance with LTE, may be a look-up table with matrices in each entry of the table, and the PMI and RI from the UE decide from which row and column of the table the precoder matrix to be used is obtained. The precoders and codebooks are designed up to Rel.15 for gNBs equipped with one-dimensional Uniform Linear Arrays (ULAs) having dual-polarized antennas (in total ^^= 2^^antennas or antenna ports), or with two-dimensional Uniform Planar Arrays (UPAs) having dual-polarized antennas at ^^^^positions (in total ^^= 2^^^^antennas or antenna ports). The ULA allows controlling the radio wave in the horizontal (azimuth) direction only, so that azimuth-only beamforming at the gNB is possible, whereas the UPA supports transmit beamforming on both vertical (elevation) and horizontal (azimuth) directions, which is also referred to as full-dimension (FD) MIMO. The codebook, e.g., in the case of massive antenna arrays such as FD-MIMO, may be a set of beamforming weights that forms spatially separated electromagnetic transmit / receive beams using the array response vectors of the array. The beamforming weights (also referred to as the array steering vectors) of the array are amplitude gains and phase adjustments that are applied to the signal fed to the antennas (or the signal received from the antennas) to transmit (or obtain) a radiation towards (or from) a particular direction. The components of the precoder matrix are obtained from the codebook, and the PMI and the RI are used to read the codebook and obtain the precoder. The array steering vectors may be described by the columns of a two-dimensional Discrete Fourier Transform (DFT) matrix when ULAs or UPAs are used for signal transmission. The precoder matrices used in the Type-I, Type-I multi-panel and Type-II CSI reporting schemes in 3GPP NR standards are defined by a dual-stage structure (i.e., two components codebook), ^ = ^^^^. The first component or the so-called first stage precoder or matrix, ^^, is used to select a number of beam vectors from a Discrete Fourier Transform-based (DFT- based) matrix, which is also called the spatial codebook. Moreover, the first stage precoder, ^^, corresponds to a wide-band matrix and contains a number of spatial beamforming vectors (the so-called spatial beams) selected from a DFT-based codebook matrix for the two polarizations of the antenna array. The second component or the so-called second stage precoder is used to combine the selected beam vectors. This means the second stage precoder or matrix, ^^, corresponds to a selection / combining / co-phasing matrix to select / combine / co-phase the beams defined in ^^. For rank-^ transmission, ^ contains ^ vectors, wherein ^ denotes the transmission rank, where the entries of each vector are chosen to combine single or multiple beams within each polarization. The selection of the matrices ^^and ^^is performed by the UE based on reference signals such as CSI-RS and the knowledge of the channel conditions. The selected matrices are indicated in a CSI report in the form of a RI (the RI denotes the rank of the precoding matrix) and a PMI and are used at the gNB to update the multi-user precoder for the next transmission time interval. The term ‘higher layer’ in the following, when used in isolation, denotes any communication layer above the physical layer in the protocol stack. When the term is used in connection with a specific layer, it denotes any communication in the protocol stack above said layer. The term serving cell and carrier component (CC) may be used interchangeably in this disclosure as a serving cell configured for a UE and is usually a separate physical carrier centered around a particular carrier frequency. Depending on the frequency of a component carrier / serving cell, the size of the cell and the beamformed reference signals may vary. The term ‘PDxCH’ or ‘PDXCH’ may indicate either the physical downlink shared channel (PDSCH) or the physical downlink control channel (PDCCH), while ‘PUxCH’ or ‘PUXCH’ may indicate either the physical uplink shared channel (PUSCH) or the physical uplink control channel (PUCCH). The term ‘PxxCH’ or ‘PXXCH’ may denote a PDSCH, a PDCCH, a PUSCH, a PRACH, a PBCH, a PSSCH, or a PSCCH. The phrase ‘fixed / predetermined / provided in the specifications’ in this invention disclosure may mean the following: one or more rules and / or methods and / or particulars regarding certain parameter(s) are provided in the standard specifications that the UE and / or any network node is supposed to follow or implement. The term ‘configured’ may mean the following: one or more rules and / or methods and / or particulars regarding one or more parameters as provided in the standard specifications that the UE is supposed to follow or implement are provided to the UE by one or more network entities, e.g., via higher layer signaling, like radio resource control, RRC, signaling. In the current NR standards, the number of reference signals or antenna / CSI-RS ports configured in a CSI report and used for CSI measurements by a UE is up to 32. Recently, some of the “high” FR bands, such as the NR band n104, whose frequency range is from 6.425 to 7.125 GHz, are gaining some attraction for deployments in Europe. For those frequency bands, new antenna arrays with a higher number of antenna elements or antenna ports are required to maintain the uplink / downlink coverage compared to the lower FR1 frequency bands. Hence, there is a need for such deployments to increase the number of CSI- RS ports from 32 to 64 or even 128. However, when increasing the number of antenna ports from 32 to 64 or even to 128, the complexity for estimating or measuring the antenna ports at the UE is significantly increased over the case of 32 antenna ports. In order to keep the complexity and CPU occupation for estimating or measuring the antenna or CSI-RS ports at the UE at a reasonable level, some enhancements with respect to CSI measurements and CSI reporting are needed. In this disclosure, a method, and apparatuses, for the enhancement of the CSI measurement and reporting when the number of antenna or CSI-RS ports is high, is provided. SUMMARY It is an objective of the embodiments herein to provide methods and apparatuses for CSI feedback reporting for a codebook-based precoding in a wireless communications network such as advanced 5G networks. According to an aspect of some embodiments herein, there is provided a method performed by a wireless device (e.g., a User Equipment (UE)), the method comprising: - receiving from a network node, - a configuration or an indication, wherein the configuration or the indication indicates a number of a first dimension or columns, and a number ^^of a second dimension or rows of an antenna port layout at the network node, and - a configuration or an indication, wherein the configuration or the indication indicates M Channel State Information – Reference Signal, CSI-RS, resources, wherein each CSI-RS resource comprises a number of antenna or CSI-RS ports, wherein the antenna or CSI-RS ports of each CSI-RS resource are mapped to a subset or proper subset of row and column indices of the antenna port layout, - determining entries of a precoding vector per CSI-RS resource associated with a subset or proper subset of the rows and columns of the antenna port layout, - generating a CSI report or a CSI feedback report comprising a Precoder Matrix Indicator, PMI, indicating the precoding vector, and - reporting, to the network node, the CSI report or the CSI feedback report. According to an another aspect of some embodiments herein, there is provided a method performed by a wireless device (e.g., a User Equipment (UE)), the method comprising: - receiving from a network node, - a configuration or an indication, wherein the configuration or the indication indicates a number of a first dimension or columns, and a number ^^of a second dimension or rows of an antenna port layout at the network node, and - a configuration or an indication, wherein the configuration or the indication indicates at least one Channel State Information – Reference Signal, CSI-RS, resources, and a number of subbands, wherein a CSI-RS resource comprises a number of antenna or CSI-RS ports and each antenna or CSI-RS port is associated with the number of subbands, wherein an antenna or CSI-RS port is mapped to a first entry of the antenna port layout using a first mapping scheme for a first set of subbands, and to a second entry of the antenna port layout using a second mapping scheme for a second set of subbands, - determining entries of a precoding vector associated with the antenna or CSI- RS ports, - generating a CSI report or a CSI feedback report comprising a Precoder Matrix Indicator, PMI, indicating the precoding vector, and - reporting, to the network node, the CSI report or the CSI feedback report. According to another aspect of embodiments herein, there is provided a method performed by a network node, for receiving, from a wireless device, a channel state information, CSI, report in a wireless communications network, the CSI report indicating a precoder matrix, the method comprising: o transmitting, to a wireless device - a configuration or an indication, wherein the configuration or the indication indicates a number ^^of a first dimension or columns and a number ^^of a second dimension or rows of an antenna port layout at the network node, and - a configuration or an indication, wherein the configuration or the indication indicates M Channel State Information – Reference Signal, CSI-RS, resources, wherein each CSI-RS resource comprises a number of antenna or CSI-RS ports, wherein the antenna or CSI-RS ports of each CSI-RS resource are mapped to a subset or proper subset of row and column indices of the antenna port layout, o for enabling the wireless device to: ^ determine entries of a precoding vector per CSI-RS resource associated with a subset or proper subset of the rows and columns of the antenna port layout, ^ determine a precoder matrix for RI transmission layers, wherein the precoder matrix comprises v precoding vectors, and each precoding vector has 2^^^^entries and is associated with a transmission layer, ^ generate a CSI report or a CSI feedback report for transmission to the network node comprising a Precoder Matrix Indicator, PMI, indicating the precoding vector or precoder matrix; and o receiving, from the wireless device uplink control information (UCI) including the CSI report or the CSI feedback report over an uplink, UL, channel. According to another aspect of embodiments herein, there is provided a method performed by a network node, for receiving, from a wireless device, a channel state information, CSI, report in a wireless communications network, the CSI report indicating a precoder matrix, the method comprising: o transmitting, to a wireless device - a configuration or an indication, wherein the configuration or the indication indicates a number ^^of a first dimension or columns and a number ^^of a second dimension or rows of an antenna port layout at the network node, and - a configuration or an indication, wherein the configuration or the indication indicates at least one Channel State Information – Reference Signal, CSI-RS, resources, and a number of subbands, wherein a CSI-RS resource comprises a number of antenna or CSI-RS ports and each antenna or CSI-RS port is associated with the number of subbands, wherein an antenna or CSI-RS port is mapped to a first entry of the antenna port layout using a first mapping scheme for a first set of subbands, and to a second entry of the antenna port layout using a second mapping scheme for a second set of subbands, for enabling the wireless device to: ^ determine entries of a precoding vector or precoder matrix associated with the antenna or CSI-RS ports, ^ generate a CSI report or a CSI feedback report for transmission to the network node comprising a Precoder Matrix Indicator, PMI, indicating the precoding vector or precoder matrix; and receiving, from the wireless device uplink control information (UCI) including the CSI report or the CSI feedback report over an uplink, UL, channel. According to another aspect of embodiments herein, there is also provided a wireless device comprising a processor and a memory containing instructions executable by the processor, whereby said wireless device is operative to perform any one of the embodiments presented in the detailed description related to the actions performed by the wireless device. According to yet another aspect of embodiments herein, there is also provided a network node comprising a processor and a memory containing instructions executable by the processor, whereby said network node is operative or configured to perform any one of the embodiments presented in the detailed description related to the network node. There is also provided a computer program comprising instructions which when executed on at least one processor of the wireless device, cause the at least said one processor to carry out the actions or method steps presented herein. There is also provided a computer program comprising instructions which when executed on at least one processor of the network node, cause the at least said one processor to carry out the method steps presented herein. A carrier is also provided containing the computer program, wherein the carrier is one of a computer readable storage medium, an electronic signal, optical signal, or a radio signal. An advantage of the embodiments herein is to significantly reduce the complexity and CPU occupation for estimating or measuring the antenna or CSI-RS ports at the UE when the number of antenna or CSI-RS ports is large, as described in the detailed description. Note that in this disclosure, the terms antenna port and CSI-RS port are used interchangeably. Additional advantages of the embodiments herein are provided in the detailed description of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the present invention are now described in further detail with reference to the accompanying drawings, in which: Fig.1 shows a schematic representation of a wireless communications system, wherein embodiments herein may be applied; Fig.2 shows a block-based model of a MIMO DL transmission using codebook-based- precoding in accordance with LTE Release 8; Fig.3 illustrates a flowchart of a method performed by a wireless device (e.g., a UE) according to some embodiments herein; Fig.4 illustrates a flowchart of a method performed by a network node (e.g., a gNB) according to some embodiments herein; Fig.5 illustrates an example of a structure of the antenna port layout having columns and ^^rows. Fig.6 illustrates an example of a mapping of the CSI-RS ports of ^ = 2 CSI-RS resources each associated with ^ = 3 rows and all columns of the antenna port layout with interleaving set to ‘off’. Fig.7 illustrates a mapping of the CSI-RS ports of ^ = 2 CSI-RS resources each associated with ^ = 3 rows and all columns of the antenna port layout with interleaving set to ‘on’. Fig.8 illustrates a mapping of the CSI-RS ports of ^ = 2 CSI-RS resources each associated with ^ = 4 columns and all rows of the antenna port layout with interleaving set to ‘off’. Fig.9 illustrates a mapping of the CSI-RS ports of ^ = 2 CSI-RS resources each associated with ^ = 4 columns and all rows of the antenna port layout with interleaving set to ‘on’. Fig.10 illustrates a mapping of the CSI-RS ports of ^ = 4 CSI-RS resources each associated with ^ = 4 columns and ^ = 3 rows to the antenna port layout with Interleaving set to ‘off’. Fig.11 illustrates a mapping of the CSI-RS ports of ^ = 4 CSI-RS resources each associated with ^ = 4 columns and ^ = 3 rows to the antenna port layout with Interleaving set to ‘on’. Fig.12 is a block diagram depicting a wireless device (e.g, a UE) according to exemplary embodiments herein. Fig.13 is a block diagram depicting a network node (eg. a gNB) according to exemplary embodiments herein. Fig.14 illustrates a mapping of the CSI-RS ports of ^ = 2 CSI-RS resources. Fig.15 illustrates a mapping of the CSI-RS ports of a first and a second CSI-RS port subsets of ^ = 2 CSI-RS resources. DETAILED DESCRIPTION In the following, a detailed description of the exemplary embodiments is described in conjunction with the drawings, in several scenarios to enable easier understanding of the solution(s) described herein. In certain embodiments, the parameters ^^and ^^are indicated by a network node to the UE and indicate a first dimension or columns and a second dimension or rows of the antenna port layout, respectively, at the network node. In some options, the values of ^^and ^^are configured with the higher layer parameter n1-n2. The antenna port layout comprises 2^^^^antenna ports, wherein the antenna ports 0, … , ^^^^− 1 are associated with a first polarization and the antenna ports ^^^^, … , 2^^^^− 1 are associated with a second polarization of the antenna port layout. Figure 5 shows the structure of the antenna port layout having ^^columns and ^^rows, wherein each entry of the layout represents a dual-polarized antenna element associated with two antenna ports. Each antenna port associated with the first or second polarization is associated with a row or row index, ^2, and with a column or column index, ^1, of the antenna port layout, wherein ^1 = 0, … , ^^− 1 and ^2 = 0, … , ^^− 1. Note that in the following antenna port and CSI-RS port are used interchangeably. Also, note that precoder vector and precoding vector are used interchangeably. Precoder matrix and precoding matrix are also used interchangeably. When used separately, the term “precoder” means, without limitation, a precoding matrix or a precoder matrix. In a certain embodiment, the wireless device determines a precoder or precoder vector or matrix for RI transmission layers and indicates the precoder or precoder vector or matrix in the CSI report. The symbol RI indicates the number of transmission layers. In certain embodiments, the precoding matrix comprises v precoding vectors, wherein each precoding vector has 2^^^^entries and is associated with a transmission layer. In some embodiments, the number of transmission layers is the same as the number of precoding vectors, that is, RI= v. Each precoding vector comprises one or more DFT-based vectors. In the following, the precoding vector is denoted as vector ^^,^,^,^(note that the indices ^, ^, ^, ^ of ^^,^,^,^are general indices that may not depend on a specific definition of the precoding vector). As an example, the precoding vector for the r-th layer (^ = 1, … , for the 2^^^^antenna ports of the antenna port layout is given by ^ ^^,^,^,^,^= ^^^^^^,^^, where ^^,^is an oversampled DFT-based vector, defined by where ^^=exp(√−1πn / N)represents a phase value from an 8-PSK (^ = 3) or 16-PSK (^ =4) or any higher order PSK. Here, the vector in ^^,^,^,^is associated with the first polarization and with antenna ports 0, … , ^^^^− 1 of the antenna port layout and the vector ^^^^,^in ^^,^,^,^is associated with the second polarization and with antenna ports ^^^^, … , 2^^^^− 1 of the antenna port layout. The vector ^^,^is selected from an oversampled 2D-DFT codebook of size ^^^^× ^^^^^^^^. A codebook comprises vectors or indices indicating vectors. A UE may select a vector from the codebook and indicate the selected vector or the index of the selected vector (i.e., a precoding vector) in the CSI report. Each vector in the 2D-DFT codebook is denoted by ^^,^, where ^ ∈ {0, … , ^^^^− 1} and ^ ∈ and ^^are the oversampling factors with respect to the first dimension (columns) and second dimension (rows), respectively, of the antenna port layout. In general, and ^^are positive integer values. In some examples, = 1 and / or ^^= 1. Each entry of the vector ^^is associated with a row or row index ^^of the antenna port layout. Each entry of the DFT based vector ^^,^is associated with a column / column index ^^and row / row index ^^of the antenna port layout comprising ^^columns and ^^rows. The (^^⋅ ^^+ ^^)-th entry of the vector ^^,^is associated with a column / column index ^^and row / row index ^^of the antenna port layout, wherein − 1 and ^^= 0, … , ^^− 1. As an example, the precoding vector for the ^-th layer (^ = 1, … , for the 2^^^^antenna ports of the antenna port layout is given by where ^^^,^is an oversampled DFT-based vector, defined by where ^^^= exp(√−1π^^ / N) represents a phase value from an 8-PSK or 16-PSK or any higher order PSK. Here, the vector ^^^,^in ^^,^,^,^is associated with antenna ports 0, … , ^ − 1, the vector ^ ^^^,^in ^^,^,^,^is associated with antenna ports ^ , … , ^^^^− 1, the in ^ is associated with antenna ports ^ ^^^^^^^,^,^,^ ^ ^, … , ^ − 1, and the vector ^^^^^^,^in ^^,^,^,^is associated with antenna ports^^^^^^ , … , 2^^^^− 1. The vector ^^^,^is selected from an oversampled 2D- ^^^^^^^^codebook is denoted ^^are the oversampling factors with respect to the first dimension (columns) and second dimension (rows), respectively, of the antenna port layout. Note that ^^and ^^are positive integer values. In general, ^^and ^^are equal or larger than 1. In some cases, In certain embodiments, each precoder vector or matrix of the plurality of precoder vectors or matrices is represented by a linear combination of spatial-domain components and frequency- domain components, and a set of combining / combination coefficients for combining the spatial-domain components and frequency-domain components as described herein. The plurality of precoder vectors or matrices may be indicated in the CSI report by indicating the spatial-domain components and frequency-domain and the set of linear combination coefficients. The term ´combination coefficient´ and the term ´combining coefficient´ in this disclosure can be used interchangeably. The precoder vectors or matrices may be defined over a number of subbands ^^. The bandwidth of the DL channel may be divided into a number of subbands, wherein each precoder vector or matrix is associated with a sub-band. In certain embodiments, the number of subbands of the precoder is an integer number (or a real number smaller than 1) of the number of CQI subbands configured to the wireless device. The number of subbands or the number of CQI subbands may be indicated to the wireless device via the CSI report configuration. The precoder vectors or matrices are determined by the wireless device based on measurements of the received reference signals (e.g., CSI-RS), wherein the reference signals are provided by another wireless device or the network node. The reference signals are configured to the wireless device via the CSI report configuration. The wireless device is configured to perform CSI measurements on one or more configured CSI-RS resources and to determine based on the CSI measurements the precoder vectors or matrices and to indicate them in the CSI report. Spatial domain components of the precoder In certain embodiments, the wireless device or UE is configured to determine one or more spatial domain, SD, components for the set of linear combination coefficients of the precoder. Each SD component corresponds to a basis vector. A set of SD components may correspond to a first basis set. For determining the precoder vectors or matrices, the wireless device or UE is configured to select one or more SD components from a first basis set. A basis vector from the first basis set is associated with a set of antenna ports or CSI-RS ports of the CSI- RS resources. The set of antenna ports or CSI-RS ports may be associated with a first and second polarization. A first set of antenna or CSI-RS ports may be associated with a first polarization, and a second set of antenna or CSI-RS ports may be associated with a second polarization. The selection of the one or more basis vectors (one or more SD components) from the first basis set can be polarization-common or polarization-specific. In case of polarization-common selection, the selected basis vectors from the first basis set are common to the two polarizations of the antenna or CSI-RS ports configured to the wireless device. In case of polarization-specific selection, the selected basis vectors from the first set are independently selected by the wireless device for the two polarizations of the antenna or CSI- RS ports configured to the wireless device. In an exemplary embodiment, the wireless device selects ^ basis vectors of the precoding vector or matrix from the first basis set and indicates the selected ^ basis vectors in the CSI report. In some examples, the selected ^ basis vectors are polarization-common, and hence identical for the first and second set of antenna or CSI- RS ports. In some examples, the selected ^ basis vectors are polarization-dependent, and hence possibly different to the first or second set of antenna or CSI-RS ports. In some examples, the selected ^ basis vectors are layer-dependent and differ for a subset of transmission layers or per transmission layer of the precoder. In such a case, the basis vectors are selected independently per layer subset or layer of the precoder. In some other examples, the selected ^ basis vectors are layer-independent and identical for all layers of the precoder. In certain embodiments, the first basis set is an orthogonal basis set, i.e., the basis set comprises a number of orthogonal basis vectors. For example, the first basis set is a DFT- or DCT-based basis set. In certain embodiments, the first basis set is defined by an DFT or IDFT basis set, or an oversampled DFT or IDFT basis set. In certain embodiments, the first basis set comprises a set of Discrete Cosine Transform (DCT)-based vectors. When the first basis set is defined by an DFT-based (DFT or IDFT) basis set, the first basis set is represented by a DFT- or IDFT-matrix. In certain embodiments, the first basis set is defined by a rotated DFT- based basis, wherein the indices of the DFT-based vectors are defined by ^^= ^^^^^+ ^^, be the rotation factors of the rotated DFT-based basis, and ^^denote the antenna ports with respect to a first and a second dimension, respectively, and and ^^denote the oversampling factors with respect to the first and second dimension, respectively. In such cases, the rotated DFT-based basis is selected from an oversampled DFT-based basis comprising ^^^^^^^^DFT-based vectors. The rotation factors may be selected by the wireless device, or configured to the wireless device, or reported by the wireless device as a part the CSI-report. The oversampling factors may be fixed in the 3GPP specifications and hence known to the wireless device. The two parameters ^^and ^^may depend on a CSI- RS resource and can be different for different CSI-RS resources indicated in the CSI report configuration. In certain embodiments, the first basis set is an orthogonal basis set, i.e., the basis set comprises a number of orthogonal basis vectors comprising an identity matrix. Each vector of size ^^^^^^^or ^^^^^^^ / 2 from the basis set is associated with a CSI-RS port and comprises ^^^^^^^− 1 or^^^^^^^ ^ − 1 zeros and a single one, wherein ^^^^^^^or ^^^^^^^ / 2 (e.g., per polarization of the antenna ports) is the number of antenna ports of one or multiple antenna port groups. In some examples, ^^^^^^^may depend on the CSI-RS resource and can be different for different CSI-RS resources. Frequency domain components of the precoder In certain embodiments, the wireless device or UE is configured to determine one or more frequency domain, FD, components for the set of linear combination coefficients of the precoder. Each frequency-domain, FD, component of the precoder corresponds to a basis vector. A set of FD components corresponds to a second basis set. For determining the precoder vectors or matrices, the wireless device is configured to select one or more FD components (i.e., basis vectors) from the second basis set. A basis vector from the second basis set is associated with a number of subbands, ^^, of the bandwidth of the DL channel. A subband may comprise a number of Physical Resource Blocks (PRBs). In certain embodiments, the number of subbands, ^^, is dependent on the number of CQI subbands, or on the CQI subband size configured to the wireless device. In certain embodiments, the second basis set is defined by an orthogonal basis set, i.e., the basis set comprises a number of orthogonal vectors. For example, the second basis set is a DFT- or DCT-based basis. In certain embodiments, the second basis set is defined by an DFT or IDFT basis, or an oversampled DFT or IDFT basis. In certain embodiments, the second basis set comprises a set of Discrete Cosine Transform (DCT)-based vectors. When the second basis set is defined by an DFT-based (DFT or IDFT) basis, the second basis set may be represented by a DFT- or IDFT-matrix. In certain embodiments, the second basis set is defined by a rotated DFT-based basis, wherein the indices of the DFT-based vectors are defined by ^^= ^^^^+ ^^, ^^= 0, … , ^^− 1 with ^^= 0, … , ^^− 1 be the rotation factor of the rotated DFT-based basis. In such cases, the rotated DFT-based basis is selected from an oversampled DFT-based basis comprising ^^^^DFT-based vectors. This means, the basis set corresponding to the frequency-domain components is an oversampled DFT- or DCT- based matrix comprising ^^orthogonal DFT- or DCT-based matrices. The rotation factor may be selected by the wireless device, or configured to the wireless device, or reported by the wireless device as a part the CSI-report. In certain embodiments, the number of frequency subbands defines the length (^^) of the basis vectors of the second basis set. The number of frequency subbands may be indicated to the wireless device, e.g., via a higher layer, or may be fixed in the NR specifications and known by the wireless device or selected by the wireless device and indicated in the CSI-report. In certain embodiments, the set of FD components is a basis set represented by DFT-based or DCT-based matrix or an oversampled DFT-based or DCT-based matrix, and the basis set comprises a number of basis vectors that represent the FD components, and each basis vector is a DFT- or DCT-based vector. In certain embodiments, the basis vector set of the FD components is an oversampled DFT- or DCT-based matrix comprising ^^orthogonal DFT- or DCT-based matrices. In certain embodiments, the wireless device selects ^ FD components from the second basis set for the precoding matrix or vector across ^ CSI-RS resources, wherein ^ > 1. In certain embodiments, the wireless device selects ^ FD components from the second basis set for the precoding matrix or vector per CSI-RS resource for ^ CSI-RS resources, wherein ^ > 1. In certain embodiments, the parameter ^ is configured to the wireless device, selected and reported from the wireless device to a network node, derived from another parameter such as ^^, or it is fixed in the 3GPP NR specifications and hence known to the wireless device. In the current NR specifications, the number of antenna or CSI-RS ports is limited to 32 and the supported combinations of ^^and ^^of the antenna port layout are (^^, ^^) ={(2,1),(2,2),(4,1),(3,2),(6,1),(4,2),(8,1),(4,3),(6,2),(12,1),(4,4),(8,2),(16,1)}. These configurations are mainly used for sub-6 GHz (frequency range 1, FR1) deployments. Recently, some of the “high” FR bands, such as the NR band n104, whose frequency range is from 6.425 to 7.125 GHz, are gaining some attraction for deployments in Europe. For those frequency bands, new antenna arrays or antenna port layouts with a higher number of antenna elements or antenna ports are required to maintain the uplink / downlink coverage compared to the lower FR1 frequency bands. Note that in principle the supported combinations of ^^and ^^and number of antenna ports in the current NR standards could be reused for the “high" FR1 band antenna arrays by grouping multiple antennas in a set of subarrays, wherein each subarray is associated with one or more antenna ports. However, this approach would obviously reduce the angular range coverage of the antenna array, and therefore, it is desired to increase the number of antenna ports and to introduce new antenna port layout configurations in the NR standards for the new frequency bands. When increasing the number of antenna ports from 32 to 64 or even to 128, the complexity for estimating or measuring the antenna ports at the UE is significantly increased over the case of 32 antenna ports (which is currently the maximum number of antenna ports supported in the NR specifications). In order to reduce the complexity and CPU occupation for estimating or measuring the antenna ports at the UE, it is proposed in this invention to group or segment the CSI-RS or antenna ports into a number of subsets. These subsets are further called as CSI-RS resources. The CSI-RS resources are time-division multiplexed (TDM) and / or frequency-division multiplexed (FDM) by a network node and transmitted sequentially over a number of symbols and / or slots. The UE receives and processes the TDM-ed (and / or FDM- ed) CSI-RS resources sequentially over time, so that the complexity and CPU occupation for estimating or measuring a large number of antenna ports is reduced. In this way, a UE is able to measure or estimate 64 or even 128 antenna ports. Based on the CSI measurements, the UE calculates a precoder vector or matrix and generates a CSI report that comprises a precoding matrix identifier, PMI, indicating the precoding vector or matrix. The CSI report is transmitted via an uplink transmission or channel to a network node, such as a gNB. Configuration of CSI-RS resources To reduce the complexity for the CSI calculation at the UE, it is proposed that the 2^^^^antenna or CSI-RS ports used for CSI measurements at the UE are segmented into ^ non- overlapping subsets or proper subsets, wherein each subset is associated with a CSI-RS resource. This means each CSI-RS resource contains a subset of 2^^^^antenna ports, wherein the antenna port(s) of the ^-th CSI-RS resource is / are different to the antenna port(s) of the ^-th CSI-RS resource, for ^ ≠ ^, ^ = 0, … , ^ − 1, and ^ = − 1. The antenna ports of a given CSI-RS resource are mapped to a set of row and column indices of the antenna port layout that does not overlap with or is completely different from the set of row and column indices associated with the antenna ports of any other CSI-RS resource. Alternatively, the UE is configured with P antenna or CSI-RS ports, and each CSI-RS resource is associated with the same P antenna or CSI-RS ports, or is associated with a subset or proper subset of the P antenna or CSI-RS ports. The antenna ports of a given CSI-RS resource are mapped to a set of row and column indices of the antenna port layout. In some cases, the entries (i.e., the row and column indices) associated with the antenna ports of a given CSI-RS resource do not overlap with or are completely different from the entries (i.e., the row and column indices) associated with the antenna ports of another CSI-RS resource. Here, it is assumed that the antenna port layout comprises ^^^^entries (or pairs / positions), wherein each entry (or pair / position) is associated with two antenna ports configured in a CSI- RS resource. In some examples ^ < 2^^^^. In some cases, an antenna port ^^of a first CSI- RS resource and the same antenna port ^^of a second CSI-RS resource are associated with the same entry of the antenna port layout (i.e., the same row and column index). The said antenna ports of said two CSI-RS resources may be associated with the same polarization. Note that such a configuration allows a wireless device to estimate and correct for a phase change and / or amplitude variation of the antenna ports over time. In some cases, the antenna ports of a first CSI-RS resource associated with a first polarization and the antenna ports of a second CSI-RS resource associated with a second polarization are associated with the same entries of the antenna port layout (i.e., the same row and column indices). Alternatively, the UE is configured with P antenna or CSI-RS ports, and each CSI-RS resource is associated with the same P antenna or CSI-RS ports or is associated with a subset or proper subset of the P antenna or CSI-RS ports. In one option, the antenna ports of a given CSI-RS resource are mapped to a set of entries of the precoding vector or matrix that does not overlap with or is completely different from the set of entries of the precoding vector or matrix associated with the antenna ports of any other CSI-RS resource. Here, it is assumed that the precoding vector comprises 2^^^^entries, wherein each entry is associated with one antenna port configured in a CSI-RS resource. In another option, the antenna ports of a given CSI-RS resource are mapped to a set of entries of the precoding vector or matrix which are partly identical from the set of entries of the precoding vector or matrix associated with the antenna ports of any other CSI-RS resource. Here, at least an antenna port ^^of a first CSI-RS resource and the same antenna port ^^of a second CSI-RS resource are associated with the same entry of the precoding vector. The said antenna ports of said two CSI-RS resources may be associated with the same polarization. In certain embodiments, the UE is configured with ^ CSI-RS resources or a CSI-RS resource set with ^ CSI-RS resources. A given CSI-RS resource is received by the UE in a set of one or more symbols that does not overlap or intersect with the symbol(s) in which at least one of the other ^ configured CSI-RS resources is received. In certain embodiments, the UE is configured with ^ CSI-RS resources or a CSI-RS resource set with ^ CSI-RS resources. A given CSI-RS resource is received by the UE in a set of one or more symbols that partially overlaps or intersects with the symbol(s) in which at least one of the other ^ configured CSI-RS resources is received. In certain embodiments, the UE is configured with ^ CSI-RS resources or a CSI-RS resource set with ^ CSI-RS resources. A given CSI-RS resource is received by the UE in a set of one or more symbols that does not overlap or intersect with the symbol(s) in which any of the other ^ configured CSI-RS resources are received. This means that the ^ resources are received in ^ distinct / non-overlapping sets of symbols, i.e., the ^ resources are TDMed. The ^ resources may be received over one or more slots. In an example, ^ = 4 resources are configured to the UE, wherein two resources are received in a slot ^^, and the other two resources are received in a slot ^^+ 1, wherein the ^ = 4 resources are received in ^ = 4 distinct sets of symbol(s). In another example, ^ resources are configured, wherein the ^-th resource is received in slot ^^+ ^, ^ = 0, … , ^ − 1. In certain embodiments, the ^ CSI-RS resources are received sequentially in time over a number of slots. In this way, the UE complexity for the antenna or CSI-RS ports measurement from a given resource or instant in time is reduced, as CSI measurements are performed sequentially over time. This allows the usage of “large” antenna port layouts at the network node, i.e., the usage of antenna arrays that are equipped or associated with a large number of antenna ports (e.g., 64 or 128). In certain embodiments, the antenna ports and / or CSI-resources are indicated by the network node to the UE via a higher layer (e.g., via the CSI report configuration). In certain embodiments, the number of CSI-RS or antenna ports is configured to be identical for all M CSI-RS resources. In certain embodiments, the UE is configured with one or more resource set(s) comprising ^ CSI-RS resources, wherein ^ > 1. Each ^-th CSI-RS resource (^ = 0, … , ^ − 1) is associated with a number of antenna or CSI-RS ports. In a first option, the UE is configured with an identical number of CSI-RS ports for all resources. In a second option, the number of CSI-RS ports configured for at least one resource is different to the number of CSI-RS ports configured for at least one other CSI-RS resource in the resource set. In certain embodiments, the UE is configured with ^ > 1 CSI-RS resource sets, wherein the ^-th CSI-RS resource set comprises ^^CSI-RS resources, and the ^-th CSI-RS resource in the ^-th CSI-RS resource set comprises ^ CSI-RS ports, whe ^^^ ^,^rein ^ =∑^^^ ^^and ^^,^= 2^^^^. In certain examples, the number of CSI-RS ports ^^,^is identical or non-identical across the ^ resource sets. In certain examples, the number of CSI-RS resources ^^is identical or not for the ^ resource sets. In certain embodiments, all the CSI-RS resources in a given CSI-RS resource set are assumed to be QCL-ed with the same DL RS with respect to QCL type ‘D’. In some examples, the RS may be an SSB, a CSI-RS resource configured with ‘repetition’ or a CSI-RS resource used for tracking, i.e., CSI-RS configured with ‘trsInfo’. In certain embodiments, all the CSI-RS resources in a given CSI-RS resource set are assumed to be QCL-ed with the same DL RS with respect to QCL type ‘A’ or QCL type ‘C’. In some examples, the RS may be a SSB or CSI-RS used for tracking. In certain embodiments, all the CSI-RS resources in a given CSI-RS resource set have identical TCI-State and / or QCL assumption(s). This may mean that all the CSI-RS resources are assumed to be QCL-ed with one or more DL RSs, with respect to the same QCL type(s). Mapping of antenna ports to row / column indices of the antenna port layout In certain embodiments, the CSI-RS ports of a CSI-RS resource are associated with a proper subset of the rows and columns of the antenna port layout. In some options, the CSI-RS ports of a CSI-RS resource are associated with a proper subset of columns and all rows of the antenna port layout. In some other options, the CSI-RS ports of a CSI-RS resource are associated with a proper subset of rows and all columns of the antenna port layout. The information of the mapping of the CSI-RS ports of the ^ CSI-RS resources to the ^^columns and ^^rows of the antenna port layout (i.e., the association of the antenna ports with rows and column indices of the antenna port layout) must be known by the UE, or it should be indicated to the UE (e.g., from a network node). In one option, the mapping information is indicated to the UE by RRC signaling from a network node. In another option, the mapping information is fixed in the NR specifications, and hence known to the UE. The mapping between the CSI-RS ports of the M resources to the ^^columns and ^^rows of the antenna port layout can also be determined by the UE based on one or more parameters indicated to the UE. In certain embodiments, the UE is configured with a parameter ^^denoting the number of CSI-RS ports in the first dimension or the number of columns of the antenna port layout with which a CSI-RS resource is associated with. In one option, the value of ^^is configured for each CSI-RS resource to the UE. In another option, the value of ^^is identical for all CSI-RS resources and configured once for all CSI-RS resources in a resource set. In certain embodiments, the UE is configured with a parameter ^^denoting the number of antenna ports in the second dimension or the number of rows of the antenna port layout with which a CSI-RS resource is associated with. In one option, the value of ^^is configured for each ^-th CSI-RS resource. In another option, the value of ^^is identical for all CSI-RS resources and configured once for all CSI-RS resources in a resource set. In certain embodiments, the UE is configured with the parameter ^^and ^^denoting the number of antenna ports in the first dimension or the number of columns and the number of antenna ports in the second dimension or the number of rows, respectively, with which a CSI- RS resource is associated with. In one option, the values of ^^and ^^are configured for each ^-th CSI-RS resource. In another option, the values of ^^and ^^are identical for all CSI-RS resources (in this case, ^^= ^ and ^^= ^, ∀ ^ = 0, … , ^ − 1) and configured once for all CSI-RS resources in a resource set. In certain embodiments, the UE is configured with a parameter ^^and the value of ^^is determined by the UE as ^^=^^^^. In certain embodiments, the UE is configured with a parameter ^ and the value of ^ is determined b^^^ ^y the UE as ^^=^^, where ^^is the number of CSI-RS ports of the ^-th CSI-RS resource. In certain embodiments, the UE is configured with a parameter ^^and the value of ^^is determined by the UE as ^^= ^^^^^, where ^ > 0 is a real number and ^^is the number of CSI-RS ports of the ^-th CSI-RS resource. In certain embodiments, the UE is configured with a parameter ^ and the valu^^^e of ^^is determined by the UE as ^^= ^^^. In certain examples, the value of ^ = 0.5. This may mean that ^^= 2^^⋅ ^^. In certain embodiments, the number of antenna ports in the first dimension, ^^, and the number of antenna ports in the second dimension, ^^, of the antenna port layout are identical for all ^ CSI-RS resources associated with one or more resource sets. In the following different mapping schemes to map the antenna ports of the antenna ports of the ^ CSI-RS resources to entries of the precoding vector ^^,^,^,^are proposed. In certain embodiments, each antenna port of a CSI-RS resource is associated with a value or an index 3000+^, wherein ^ > 0 is an integer value. In the following examples, a ^-th port or ^ -th antenna port hence refers to antenna port 3000+^. Configuration 1 In certain embodiments, the CSI-RS ports of each CSI-RS resource are associated with a single row and all columns of the antenna port layout. In some examples, the ^-th port of a ^ CSI-RS resource is associated with the (^^^^ ^^^^+ ^^⋅ mod(^, ^^) + ^)-th entry of vector ^^,^,^,^, wherein ^ ∈ {0, … , ^^− 1} is a CSI-RS resource index, and ^ = 0, … , 2^^− 1 are the CSI-RS port indices associated with a CSI-RS resource. Here, ^^(i.e., ^ = ^^) and 2^^denote the total number of CSI-RS resources and the total number of CSI-RS ports associated with each resource, respectively. In certain embodiments, the antenna ports of each CSI-RS resource are associated with ^ consecutive rows and all columns of the antenna port layout. In one example, the ^-th port is ated with the ⋅ ^ + mod(^, R) ^ associ + ^^⋅ mod ^^ ^ ^ , entry of vector ^^,^,^,^, wherein ^ the CSI-RS resource index and ^ = 0, … , 2^^^ − 1 are the CSI-RS port indices associated with a CSI-RS resource. In another example, the ^-th port is associated with the ^ + ^^⋅ mod(^, ^)+ mod entry of vector ^ , wherein ^ the CSI-RS resource index and ^ = 0, … , 2^^^ 1 are the CSI-RS port indices associated with a CSI-RS resource. Here,^^^ (i.e., ^ = ^^ / ^) and 2^^^ denote the total number of CSI-RS resources and the total number of CSI-RS ports associated with each resource, respectively. In some examples, ^ = 1, or ^ = 2. In some examples, ^ = ^^. Configuration 2 In certain embodiments, the CSI-RS ports of each CSI-RS resource are associated with all rows and one column of the antenna port layout. In some examples, the ^-th port of a CSI-RS resource is associated with the ^^^^+ ^^^(^, ^^) + ^^^)-th entry of vector ^ , wherein ^ ∈ {0, … , ^^− 1} is a CSI-RS resource index, and ^ = 0, … , 2^^− 1 are the CSI-RS port indices associated with a CSI-RS resource. Here, ^ (i.e., ^ = and 2^^denote total number of CSI-RS resources and the total number of CSI-RS ports associated with each resource, respectively. In certain embodiments, the antenna ports of each CSI-RS resource are associated with all rows and ^ consecutive columns of the antenna port layout. In one example, the ^-th port is associated with the^^ + ^^⋅ mod(^, ^)+ mod entry of vector ^ , wherein the CSI-RS resource index and ^ = 0, … , 2^^^ 1 are the CSI-RS port indices associated with a CSI-RS resource. In another example, the ^- th port is associated with the th entry of vector , wherein = 0, … , 2^^^ − 1 are the CSI-RS port indices associated with a CSI-RS resource. Here, (i.e., ^ = ^^ / ^) and 2^^^ denote the total number of CSI-RS resources and the total number of CSI-RS ports associated with each resource, respectively. In some examples, ^ = 1, or ^ = 2. In some examples, ^ = ^^. Configuration 3 In certain embodiments, the CSI-RS ports of each CSI-RS resource are associated with ^ consecutive rows and ^ consecutive columns of the antenna port layout, wherein ^ < ^^and ^ < ^^. In a first example, the ^-th port of a CSI-RS resource is associated with the entry of vector ^^,^,^,^. In a second example, the ^-th port of a CSI-RS resource is associated with the entry of ^^,^,^,^. In a third example, the ^-th port of a CSI-RS resource is associated with the entry of ^^,^,^,^. In a fourth example, the ^-th port of a CSI-RS resource is associated with the entry of vector ^ . Here, ^ ∈ {0, … , − 1} is a CSI-RS resource index, and ^ = 0, … , 2^^ − 1 are CSI-RS port indices associated with a CSI-RS resource, wherein ^^ and ^^ denote the total number of CSI-RS resources and the total number of CSI-RS ports associated with each resource, respectively. In some examples, the ^-th CSI-RS resource is associated with an ^-th CSI-RS resource index. In some other examples, the CSI-RS resource indices are mapped to the CSI-RS resources via a mapping or a permutation function. Until Rel.183GPP New Radio, the maximum number of antenna or CSI-RS ports associated with a CSI-RS resource has been limited to 32. So, when using an antenna port layout with antenna elements greater than 32, several CSI-RS resources each associated with a number of antenna or CSI-RS ports need to be used to sound (either in a TDM or FDM or CDM manner) all antenna ports of the antenna port layout. When using multiple CSI-RS resources for channel estimation, the CSI-RS resources may be transmitted in a TDM fashion, i.e., the CSI-RS resources are transmitted in different time slots. If the CSI-RS or antenna ports of a CSI-RS resource are mapped to consecutive antenna ports of the antenna port layout, the aperture size of each CSI-RS transmission is limited to a reduced angular range compared to the case where 2^^^^antenna ports are used for CSI-RS transmission. This may result in reduced channel estimation performance. Therefore, instead of mapping the antenna or CSI- RS ports of a CSI-RS resource to consecutive antenna ports of the antenna port layout (fixed aperture size), the aperture size of the CSI-RS transmissions in every slot can be increased or enhanced by interleaving the antenna or CSI-RS ports of the CSI-RS resources in a uniform or non-uniform fashion. In the following some examples of such a mapping with interleaving in a first dimension or second dimension or both first and second dimensions of the antenna port layout are described. Interleaving of port-mapping Interleaving option 1: Interleaving in a single dimension In certain embodiments, the UE is configured with a higher layer parameter ‘Interleaving’, which can be set to ‘on’ or ‘off ‘. In one option, the interleaving is set to ‘on’ in one dimension and set to ‘off’ in the other dimension. In another option, the interleaving is set to ‘on’ or ‘off’ for the first dimension (columns) and second dimension (rows) of the antenna port layout. Interleaving in second dimension (rows) – Configuration 1 In certain embodiments, each CSI-RS resource is associated with ^ non-consecutive rows and all columns of the antenna port layout, wherein the rows associated with a CSI-RS resource are separated by ^^rows of the antenna port layout. In one option, the value of ^^is equal to the number of CSI-RS resources configured to the UE. In another option, the value of ^^is configured to the UE or fixed in the NR specifications or determined by the UE based on one or more higher layer configured parameters. In a further option, the value of ^^is determined by the UE as ^ = ^ . In one example, for ^ = 4, ^^= 8 and ^ = 2, each CSI- RS resource is associated with the non-consecutive rows {0,4} or {1,5} or {2,6} or {3,7}, wherein the separation between the 2 rows associated with a CSI-RS resource is 4. Figure 6 illustrates the mapping of the CSI-RS ports of ^ = 2 CSI-RS resources, each associated with ^ = 3 rows and all columns of the antenna port layout when interleaving set to ‘off’. Figure 7 illustrates the mapping of the CSI-RS ports of ^ = 2 CSI-RS resources each associated with ^ = 3 rows and all columns of the antenna port layout when interleaving set to ‘on’. In certain embodiments, the antenna ports of each CSI-RS resource are associated with ^ non-consecutive rows and all columns of the antenna port layout. In one example, the ^-th ^ port is associated with the +^^^ ⋅ ^^^(^, ^)+ ^^⋅ ^^^ ^^ ^ ^ , entry of vector ^^,^,^,^, wherein ^ the CSI-RS resource index and ^ = 0, … , 2^^^ − 1 are the CSI-RS port indices associated with a CSI-RS resource. In another example, the ^- th port is associated with the ^ + ^^⋅ ^^^(^, ^^)+^^⋅ ^^^ entry of vector^ , wherein ^ ∈ is the CSI-RS resource index and ^ = 0, … , 2^^^ 1 are the CSI-RS port indices associated with a CSI-RS resource. Here,^^^ and 2^^^ denote the total number of CSI-RS resources and the total number of CSI-RS ports associated with each resource, respectively. In some examples, ^ = 1, or ^ = 2. In some examples, ^ = ^^. Interleaving in the first dimension (columns) – Configuration 2 In certain embodiments, each CSI-RS resource is associated with ^ non-consecutive columns and all rows, wherein the columns of a CSI-RS resource are separated by ^^columns. In one option, the value of ^^is equal to the number of CSI-RS resources configured to the UE. In another option, the value of ^^is configured to the UE or fixed in the specification or determined by the UE based on one or more higher layer configured parameters. In a further option, the value of is determined by the UE . In one example, for ^ = 4, ^^= 8 and ^ 2, each CSI-RS resource is associated with the non-consecutive columns {0,4} or {1,5} or {2,6} or {3,7}, wherein the separation between the two columns associated with a CSI-RS resource is four. Figure 8 illustrates the mapping of the CSI-RS ports of ^ = 2 CSI-RS resources each associated with ^ = 4 columns and all rows of the antenna port layout when interleaving set to ‘off’. Figure 9 illustrates the mapping of the CSI-RS ports of ^ = 2 CSI-RS resources each associated with ^ = 4 columns and all rows of the antenna port layout when interleaving set to ‘on’. In certain embodiments, the antenna ports of each CSI-RS resource are associated with ^ non-consecutive columns and all rows of the antenna port layout. In one example, the ^-th port is associated with the entry of vector ^^,^,^,^, wherein ^ ∈ {0, … ,^^ − 1} is the CSI-RS resource index and ^ = 0, … , 2^^^ − 1 are the CSI-RS port indices associated with a CSI-RS resource. In another example, the ^- th port is associated with the entry of vector , wherein 0, … , 2^ ^ − 1 are the CSI-RS port indices associated with a CSI-RS resource. Here, ^ 2^^^ denote the total number of CSI-RS resources and the total number of CSI-RS ports associated with each resource, respectively. In some examples, ^ = 1, or ^ = 2. In some examples, ^ = ^^. Interleaving in the first dimension (columns) – Configuration 3 In certain embodiments, each CSI-RS resource is associated with ^ consecutive rows and ^ non-consecutive columns, wherein the columns of the CSI-RS resource are separated by ^^columns. In one option, the value of ^^is equal to the number of CSI-RS resources configured to the UE. In another option, the value of ^^is configured to the UE or fixed in the specification or determined by the UE based on one or more higher layer configured parameters. In a further option, the value is dete rmined by the UE as ^^= . In one example, for ^ = 4, = and ^ = 2, each CSI-RS resource is associated with the non-consecutive columns {0,4} or {1,5} or {2,6} or {3,7}, wherein the separation between the 2 columns associated with a CSI- RS resource is 4. In certain embodiments, the CSI-RS ports of each CSI-RS resource are associated with ^ consecutive rows and ^ non-consecutive columns of the antenna port layout, wherein ^ < ^^and ^ < ^^. In a first example, the ^-th port of a CSI-RS resource is associated with the entry of ^^,^,^,^. In a second example, the ^-th port of a CSI-RS resource is associated with the entry of vector ^^,^,^,^. In a third example, the ^-th port of a CSI-RS resource is associated with the entry of vector ^^,^,^,^. In a fourth example, the ^-th port of a CSI-RS resource is associated with the entry of ^^,^,^,^. Here, ^ ∈ {0, … ,^^^^ − 1} is a CSI-RS resource index, and ^ = 0, … , 2^^ − 1 are the CSI-RS port indices associated with a CSI-RS resource, wherein ^^ and ^^ denote the total number of CSI-RS resources and the total number of CSI-RS ports associated with each resource, respectively. Interleaving in second dimension (rows) – Configuration 3 In certain embodiments, each CSI-RS resource is associated with ^ non-consecutive rows and ^ consecutive columns, wherein the rows of the CSI-RS resource are separated by ^^rows. In one option, the value of ^^is equal to the number of CSI-RS resources configured to the UE. In another option, the value of ^^is configured to the UE or fixed in the specification or determined by the UE based on one or more higher layer configured parameters. In a further option, the value of ^ is determined by the UE as ^^= In one example, for ^ = 4, ^^8 and ^ = 2, each CSI-RS resource is associated with the non-consecutive rows {0,4} or {1,5} or {2,6} or {3,7}, wherein the separation between the 2 rows associated with a CSI-RS resource is 4. In certain embodiments, the CSI-RS ports of each CSI-RS resource are associated with ^ non-consecutive rows and ^ consecutive columns of the antenna port layout, wherein ^ < ^^In a first example, the ^-th port of a CSI-RS resource is associated with ^ ⋅ ^^^(^, ^)+ ^^⋅ ^^^ entry of ^ vector ^^,^,^,^. In a second example, the ^-th port of a CSI-RS resource is associated with the entry of vector ^^,^,^,^. In a third example, the ^-th port of a CSI-RS resource is associated with the ^^,^,^,^. In a fourth example, the ^-th port of a CSI-RS resource is associated with the entry of vector ^ . Here, ^ ∈ {0, … , − 1} is a CSI-RS resource index, and ^ = 0, … , 2^^ − 1 are CSI-RS port indices associated with a CSI-RS resource, wherein ^^ and ^^ denote the total number of CSI-RS resources and the total number of CSI-RS ports associated with each resource, respectively. Interleaving option 2: Interleaving in first and second dimensions In certain embodiments, each CSI-RS resource is associated with ^ non-consecutive columns and ^ non-consecutive rows, wherein the columns of the CSI-RS resource are separated by columns and the rows of the CSI-RS resource are separated by ^^rows. In a first option, the value of ^ ^ is given as ^^= ^ . In a second option, the value of ^^is given In a third option, the value of {^^, ^^} is configured to the UE or fixed in the specification or determined by the UE based on one or more higher layer configured parameters. In a fourth option, the value of ^^is configured and the value of ^^is determined based by the UE. In a fourth option, the value of ^^is configured and the value of ^^is determined based by the UE. In one example, for ^ = 8, ^^= 8, ^^= 8 and ^ = 4, ^ = 2, each CSI-RS resource is associated with the non-consecutive columns {0,2,4,6} or {1,3,5,7} and non-consecutive rows {0,2} or {1,3} or {4,6} or {5,7} or {0,4} or {1,5} or {2,6} or {3,7}, wherein the separation between two columns of the CSI-RS resource is 4 and the separation between the rows of the CSI-RS resource is either 2 or 4. Figure 10 illustrates the mapping of the CSI-RS ports of ^ = 4 CSI-RS resources each associated with ^ = 4 columns and ^ = 3 rows of the antenna port layout with interleaving set to ‘off’. Figure 11 illustrates the mapping of the CSI-RS ports of ^ = 4 CSI-RS resources each associated with ^ = 4 columns and ^ = 3 rows of the antenna port layout with interleaving set to ‘on’. In certain embodiments, the CSI-RS ports of each CSI-RS resource are associated with ^ non- consecutive rows and ^ non-consecutive columns of the antenna port layout, wherein ^ < ^^In a first example, the ^-th port of a CSI-RS resource is associated with ^^^ ⋅ ^^^(^, ^) +^^^^^ ⋅ ^^^ entry of vector ^^,^,^,^. In a second example, the ^-th port of a CSI-RS resource is associated with entry of vector ^^,^,^,^. In a third example, the ^-th port of a CSI-RS resource is associated with the entry of vector ^^,^,^,^. In a fourth example, the ^-th port of a CSI-RS resource is associated with the entry of vector ^ . Here, ^ ∈ {0, … , − 1} is a CSI-RS resource index, and ^ = 0, … , 2^^ − 1 are CSI-RS port indices associated with a CSI-RS resource, wherein ^^ and ^^ denote the total number of CSI-RS resources and the total number of CSI-RS ports associated with each resource, respectively. In the following, mapping schemes to map the CSI-RS ports of the ^ CSI-RS resources to ^^columns and ^^rows of the antenna port layout are presented. In certain embodiments, the antenna ports of a CSI-RS resource are associated with one row and all columns of the antenna port layout, wherein the ^^CSI-RS ports associated with the first polarization are mapped to the ^^columns of the antenna port layout and the ^^CSI-RS ports associated with the second polarization are mapped to the ^^columns of the antenna port layout, and wherein ^^and 2^^are the number of CSI-RS resources and the number of CSI-RS ports associated with a CSI-RS resource, respectively. In one option, the ^-th CSI-RS resource is mapped to the ^-th row of the antenna port layout and the ^-th and ^ + th CSI-RS ports of the ^-th CSI-RS resource are mapped to the ^-th column of the antenna port layout, wherein ^ ∈ {0, … , ^^− 1} and ^ ∈ {0, … , ^^− 1}. In certain embodiments, the antenna ports of a CSI-RS resource are associated with ^ consecutive rows and all columns of the antenna port layout, wherein the ^^^ CSI-RS ports associated with the first polarization are mapped to the ^ rows and ^^columns of the antenna port layout and the ^^^ CSI-RS ports associated with the second polarization are mapped to the same ^ rows and ^ columns of the antenna port layout, an^^^d wherein and 2^^^ are the number of CSI-RS resources and the number of CSI-RS ports associated with a CSI-RS resource, respectively. In one example, the first ^^CSI-RS ports of both polarizations are mapped to the first row and ^^columns in an increasing order and the next ^^CSI-RS ports of both polarizations are mapped to the second row and ^^columns in an increasing order and so on and the last ^^CSI-RS ports of both polarizations are mapped to the last row and all ^^columns in an increasing order. In another example, the first ^ CSI-RS ports of both polarizations are mapped to the first column and ^ rows in an increasing order and the next ^ CSI-RS ports of both polarizations are mapped to the second column and ^ rows in an increasing order and so on and the last ^ CSI-RS ports of both polarizations are mapped to the last column and ^ rows in an increasing order. In certain embodiments, the CSI-RS ports of a CSI-RS resource is associated with all rows and one column of the antenna port layout, wherein the ^^CSI-RS ports associated with the first polarization are mapped to the ^^rows of the antenna port layout and the ^^CSI-RS ports associated with the second polarization are mapped to the ^^rows of the antenna port layout, and wherein ^^and 2^^are the number of CSI-RS resources and the number of CSI- RS ports associated with a CSI-RS resource, respectively. In one option, the ^-th CSI-RS resource is mapped to the ^-th column of the antenna port layout and each ^-th and ^ + ^^-th CSI-RS port of the ^-th CSI-RS resource are mapped to the ^-th row of the antenna port layout, wherein ^ ∈ {0, … , − 1} and ^ ∈ {0, … , ^^− 1}. In certain embodiments, the CSI-RS ports of a CSI-RS resource is associated with all rows and ^ consecutive columns of the antenna port layout, wherein the ^^^ CSI-RS ports associated with the first polarization are mapped to the ^^rows and ^ columns of the antenna port layout and the ^^^ CSI-RS ports associated with the second polarization are mapped to the ^^rows and ^ columns of the antenna port layout, and wherein ^^ / ^ and 2^^^ are the number of CSI-RS resources and the number of CSI-RS ports associated with a CSI-RS resource, respectively. In one example, the first ^^CSI-RS ports of both polarizations are mapped to the first column and ^^rows in an increasing order and the next ^^CSI-RS ports of both polarizations are mapped to the second column and ^^rows in an increasing order and so on and the last ^^CSI-RS ports of both polarizations are mapped to the last column and ^^rows in an increasing order. In another example, the first ^ CSI-RS ports of both polarizations are mapped to the first row and ^ columns in an increasing order and the next ^ CSI-RS ports of both polarizations are mapped to the second row and ^ columns in an increasing order and so on and the last ^ CSI-RS ports of both polarizations are mapped to the last row and ^ columns in an increasing order. In certain embodiments, the CSI-RS ports of a CSI-RS resource is associated with ^ consecutive rows and ^ consecutive columns of the antenna port layout, wherein ^ < ^^and ^ < ^^, wherein the ^^ CSI-RS ports associated with the first polarization are mapped to the ^ rows and ^ columns and the ^^ CSI-RS ports associated with the second polarization are mapped to the same ^ rows and same ^ columns of the antenna port layout, and wherein and 2^^ are the number of CSI-RS resources and the number of CSI-RS ports associated with a CSI-RS resource, respectively. In one example, ^ = 2, ^ = 4, ^^= 8, ^^= 4, the UE is configured with 4 CSI-RS resources and each CSI-RS resource comprises 16 antenna ports associated with the rows {0,1} or {2,3} or {1,2} or {3,0} and columns {0,1,2,3} or {4,5,6,7}. In certain embodiments, the CSI-RS ports of a CSI-RS resource are associated with ^ non- consecutive rows and ^ consecutive columns of the antenna port layout, wherein ^ < ^^and ^ < ^^, wherein the ^^ CSI-RS ports associated with the first polarization are mapped to the ^ rows and ^ columns and the ^^ CSI-RS ports associated with the second polarization are mapped to the same ^ rows and same ^ columns, of the antenna port layout, and wherein and 2^^ are the number of CSI-RS resources and the number of CSI-RS ports associated with a CSI-RS resource, respectively. In one example, ^ = 2, ^ = 4, ^^= 8, ^^= 4, the UE is configured with 4 CSI-RS resources and each CSI-RS resource comprises 16 antenna ports associated with the rows {0,2} or {1,3} and columns {0,1,2,3} or {4,5,6,7}. In certain embodiments, the CSI-RS ports of a CSI-RS resource is associated with ^ non- consecutive rows and ^ non-consecutive columns of the antenna port layout, wherein ^ < ^^and ^ < ^^, wherein the ^^ CSI-RS ports associated with the first polarization are mapped to the ^ rows and ^ columns and the ^^ CSI-RS ports associated with the second polarization are mapped to the same ^ rows and same ^ columns, of the antenna port layout, and wherein and 2^^ are the number of CSI-RS resources and the number of CSI-RS ports associated with a CSI-RS resource, respectively. In one example, ^ = 2, ^ = 4, ^^= 8, ^^= 4, the UE is configured with 4 CSI-RS resources and each CSI-RS resource comprises 16 antenna ports associated with the rows {0,2} or {1,3} and columns {0,2,4,6} or {1,3,5,7}. In certain embodiments, the CSI-RS ports of a CSI-RS resource is associated with ^ consecutive rows and ^ non-consecutive columns of the antenna port layout, wherein ^ < ^^and ^ < ^^, wherein the ^^ CSI-RS ports associated with the first polarization are mapped to the ^ rows and ^ columns and the ^^ CSI-RS ports associated with the second polarization are mapped to the same ^ rows and same ^ columns, of the antenna port layout, and wherein and 2^^ are the number of CSI-RS resources and the number of CSI-RS ports associated with a CSI-RS resource, respectively. In one example, ^ = 2, ^ = 4, ^^= 8, ^^= 4, the UE is configured with 4 CSI-RS resources and each CSI-RS resource comprises 16 antenna ports associated with the rows {0,1} or {2,3} or {1,2} or {3,0} and columns {0,2,4,6} or {1,3,5,7}. In one example, the first ^ CSI-RS ports of both polarizations are mapped to the first column and ^ rows in an increasing order and the next ^ CSI-RS ports of both polarizations are mapped to the second column and ^ rows in an increasing order and so on and the last ^ CSI-RS ports of both polarizations are mapped to the last column and ^ rows in an increasing order. In one example, the first ^ CSI-RS ports of both polarizations are mapped to the first row and ^ columns in an increasing order and the next ^ CSI-RS ports of both polarizations are mapped to the second row and ^ columns in an increasing order and so on and the last ^ CSI-RS ports of both polarizations are mapped to the last row and ^ columns in an increasing order. In certain embodiments, the ^ non-consecutive columns associated with a CSI-RS resource are given (^ − 1)⋅ ^^^, wherein ^ ∈ {0, … ^ − 1} is the CSI-RS resource index and ^ ∈ {0, … , ^ − 1} is the column index associated with a CSI-RS resource with ^ columns, and wherein ^^is the interleaving parameter in the first dimension. In one example, for ^ = 4, ^^= 8, ^ = 2, and = 2, each CSI-RS resource is associated with the non-consecutive columns {0,2} or or {4,6} or {5,7}, wherein the separation between the consecutive columns associated with a CSI-RS resource is ^^. In some examples, ^^= 1. In some other examples, ^^= 2. In other examples, ^^∈ ^^. In certain embodiments, the ^ non-consecutive rows associated with a CSI-RS resource are given 1)⋅ ^^^, wherein ^ ∈ {0, … ^ − 1} is the CSI-RS resource index and ^ ∈ {0, … , ^ − 1} is the row index associated with a CSI-RS resource with ^ rows, and wherein ^^is the interleaving parameter in the second dimension. In one example, for ^ = 4, ^^= 8, ^ = 2, and ^^= 2, each CSI-RS resource is associated with the non-consecutive rows {0,2} or {1,3} or {4,6} or {5,7}, wherein the separation between the consecutive rows associated with a CSI-RS resource is ^^. In some examples, ^^= 1. In some other examples, ^^= 2. In other examples, ^^∈ ^^. In certain embodiments, the ^ non-consecutive rows and ^ non-consecutive columns associated with a CSI-RS resource are given + ^^^^+ ^^^(^, ^^) +(^ − 1)⋅ ^^^, respectively, wherein ^ ∈ {0, … ^ − 1} is the CSI-RS resource index and ^ ∈ {0, … , ^ − 1} is the row index and ^ ∈ {0, … , ^ − 1} is the column index of a CSI-RS resource associated with ^ rows and ^ columns, respectively. Here, ^^is the interleaving parameter in the second dimension and ^^is the interleaving parameter in the first dimension. In one example, for ^ = 4, ^^= 8, ^^= 8, ^ = 2, ^ = 2, ^^= 2, and ^^= 2, each CSI-RS resource is associated with the non- consecutive rows {0,2} or {1,3} or {4,6} or {5,7} and non-consecutive columns {0,2} or {1,3} or {4,6} or {5,7}, wherein the separation between the consecutive rows and consecutive columns associated with a CSI-RS resource is ^^and ^^, respectively. In some examples, ^^= 1. In some other examples, ^^= 2. In other examples, ^^∈ ^^. In some examples, ^^= 1. In some other examples, ^^= 2. In other examples, ^^∈ ^^. CSI-RS resources associated with antenna ports of a single polarization In certain embodiments, the CSI-RS ports of a CSI-RS resource are mapped to the entries of the antenna port layout associated with a single polarization. Note that the first ^^^^entries (or antenna ports) associated with the ^^rows and ^^columns of the antenna port layout are associated with a first polarization and the remaining ^^^^entries (or antenna ports) associated with the ^^rows and ^^columns of the antenna port layout are associated with a ^ second polarization. In some examples, for M CSI-RS resources, ^ CSI-RS resources are mapped to the entries (or antenna ports) of the antenna port layout associated with a first ^ polarization and the remaining ^ CSI-RS resources are mapped to the entries (or antenna ports) of the antenna port layout associated with a second polarization. In the following different mapping schemes to map the antenna ports of the antenna ports of the ^ CSI-RS resources to entries of the precoding vector are proposed. Configuration 1 In certain embodiments, the antenna ports of each CSI-RS resource are associated with ^ consecutive rows and all columns of the antenna port layout. In one example, the ^-th port of ^ ^^ a CSI-RS resource is associated with the ^mod(^, R)+ ^^^ ^ ^ + ^^^^ ⋅ ^^^^+ mod ^^,^^^ ^ ⋅ ^^-th entry of the precoding vector. In another example, the ^-th port is associated with the ^ ^ ^^⋅ mod(^, ^^)+ mod ^^^^^ , ⋅ ^^^^+ mod ^^,^^^ ^ ⋅ ^^-th entry of the precoding vector. In the above examples, ^ ∈ {0, … ,^^^^ − 1} is the CSI-RS resource index and ^ = 0, … , ^ ^ − 1 are the CSI-RS port indices associate^^^^d with a CSI-RS resource. Here, ^ (i.e., ^ =^^^^ ) and ^^^ denote the total number of CSI-RS resources and the total number of CSI- RS ports associated with each resource, respectively. In some examples, ^ = 1, or ^ = 2. In some examples, ^ = ^^. Configuration 2 In certain embodiments, the antenna ports of each CSI-RS resource are associated with all rows and ^ consecutive columns of the antenna port layout. In one example, the ^-th port of ^^ a CSI-RS resource is associated with the ^^^^^ ⋅ ^^^^+ mod ⋅ ^^^ + ^^-th entry of the mod + ^^⋅ ^^^(^, ^)+⌊^ / ^⌋^-th entry of the precoding vector. In the above examples, ^ ∈ {0, … , − 1} is a CSI-RS resource index, and ^ = 0, … , ^^^ − 1 are the CSI- RS port indices associated with a CSI-RS resource. Here,^^^ ^ , (i.e., ^ = ) and ^^^ denote the total number of CSI-RS resources and the total number of CSI-RS ports associated with each resource, respectively. In some examples, ^ = 1, or ^ = 2. In some examples, ^ = ^^. Configuration 3 In certain embodiments, the CSI-RS ports of each CSI-RS resource are associated with ^ consecutive rows and ^ consecutive columns of the antenna port layout, wherein ^ < ^^and ^ < ^^. In a first example, the ^-th port of a CSI-RS resource is associated with ^ ^mod(^, ^) ^⋅^ + ^^⋅ ^ ^ ^ + ⋅ ^^^^ ^^^ + ^ ⋅ mod ^^,^^^ ^^-th entry of the precoding vector. In a second example, the ^-th port of a CSI-RS resource is associated with the ^^^⋅ mod(^, ^)+ ^ ^ ^⋅^ mod ^ ^ ^ , ^^+ ⋅ ^^^^ ^^^ + ^ ⋅ mod^^,^^^^^-th entry of the precoding vector. In the above examples, ^ ∈ {0, … ,^^^^^^^ − 1} is a CSI-RS resource index, and ^ = 0, … , ^^ − 1 are the CSI- RS port indices associated with a CSI-RS resource. Here,^^^^^^^^^^^^ , (i.e., ^ = ^^ ) and ^^ denote the total number of CSI-RS resources and the total number of CSI-RS ports associated with each resource, respectively. In the following some examples of mapping with interleaving in the first dimension or second dimension or both first and second dimension of the antenna port layout are described. Interleaving in second dimension (rows) – Configuration 1 In certain embodiments, the CSI-RS ports of each CSI-RS resource are associated with ^ non-consecutive rows and all columns of the antenna port layout, wherein ^ < ^^. In some mod(^, ^) + ^ ^^^ ^ ^ + mod ^^,^^^ ^^-th entry of the precoding vector. Here, ^ ∈ {0, … , − 1} is a CSI-RS resource index, and ^ = 0, … , ^^^ − 1 are the CSI-RS port indices associated with a CSI-RS resource. ^ , (i.e., ^ =^^^^ ) and ^^^ denote the total number of CSI-RS resources and the total number of CSI-RS ports associated with each resource, respectively. Interleaving in first dimension (columns) – Configuration 2 In certain embodiments, the CSI-RS ports of each CSI-RS resource are associated with all rows and ^ non-consecutive columns of the antenna port layout, wherein ^ < ^^. In some mod(^, ^)+ ^^^^-th entry of the precoding vector. Here, ^ ^ ∈ {0, … , − 1} is CSI-RS resource index, and ^ = 0, … , ^^^ − 1 are the CSI-RS port indices associated with a CSI-RS resource. Here,^^^ ^ , (i.e., ^ = ) and ^^^ denote the total number of CSI-RS resources and the total number of CSI-RS ports associated with each resource, respectively. Interleaving in first dimension (columns) – Configuration 2 In certain embodiments, the CSI-RS ports of each CSI-RS resource are associated with R consecutive rows and ^ non-consecutive columns of the antenna port layout, wherein ^ < ^^and In some examples, the ^-th port of a CSI-RS resource is associated ^^^ ^^^^^^^ ^^^ + mod( mod^ mod entry of the precoding vector. Here, ^ ∈ {0, … ,^^^^^^^ − 1} is a CSI-RS resource index, and ^ = 0, … , ^^ − 1 are the CSI-RS port indices associated with a CSI-RS resource. Here,^^^^^^^ , (i.e., ^ =^^^^^^^ ) and ^^ denote the total number of CSI-RS resources and the total number of CSI- RS ports associated with each resource, respectively. Interleaving in second dimension (rows) – Configuration 1 In certain embodiments, the CSI-RS ports of each CSI-RS resource are associated with R non-consecutive rows and ^ consecutive columns of the antenna port layout, wherein ^ < ^^and In some examples, the ^-th port of a CSI-RS resource is associated with entry of the precoding vector. Here, ^ ∈ {0, … ,^^^^^^^ − 1} is a CSI-RS resource index, and ^ = 0, … , ^^ − 1 are the CSI-RS port indices associated with a CSI-RS resource. Here,^^^^^^^ , (i.e., ^ =^^^^^^^ ) and ^^ denote the total number of CSI-RS resources and the total number of CSI- RS ports associated with each resource, respectively. Interleaving in first and second dimension – Configuration 3 In certain embodiments, the CSI-RS ports of each CSI-RS resource are associated with ^ non-consecutive rows and ^ non-consecutive columns of the antenna port layout, wherein ^ < ^^and ^ < ^^. In a first example, the ^-th port of a CSI-RS resource is associated with mod ^^,^^^ ^ ^-th entry of the precoding vector. Here, ^ ∈ {0, … ,^^^^^^^ − 1} is a CSI-RS resource index, and ^ = 0, … , ^^ − 1 are the CSI-RS port indices associated with a CSI-RS resource. Here,^^^^^^^^^^^^ , (i.e., ^ = ^^ ) and ^^ denote the total number of CSI-RS resources and the total number of CSI-RS ports associated with each resource, respectively. Non-uniform Interleaving In certain embodiments, the antenna port layout comprises ^^rows and ^^columns, and the UE is configured with two CSI-RS resources. Each antenna port of a CSI-RS resources is mapped to an antenna port or an entry (defined by a row index and a column index) of the antenna port layout. The mapping of the antenna ports of a CSI-RS resource to the entries of the antenna port layout follows an interleaved scheme as explained in the following. It is assumed that there are two sets ^^and ^^of different rows / row indices, whereas each set comprises^^^ non-consecutive rows / row indices. As an example, the first set comprises rows / row indices {0,2,4, … , ^^− 2} and the second set comprises rows / row indices {1,3,5, … , ^^− 1}. The entries of the antenna port layout associated with rows / row indices from the first set ^^and with a first column index are associated with antenna ports of a first CSI- RS resource. The entries of the antenna port layout associated with rows / row indices from the second set ^^and with the first column index are associated with antenna ports of a second CSI-RS resource. The entries associated with rows / row indices from the first set ^^and with a second column index are associated with antenna ports of the second CSI-RS resource. The entries associated with rows / row indices from the second set ^^and with the second column index are associated with antenna ports of the first CSI-RS resource, and so on. Fig. 14 shows as an example the association of the entries of the antenna port layout with the antenna ports of the CSI-RS resources for ^^= 4 and ^^= 8, and ^ = 2. For ^ = 2 CSI- RS resources, the entries associated with the two rows {0,2} of a first column are associated with the antenna ports of a first CSI-RS resource and the entries associated with the two rows {1,3} of the same first column are associated with the antenna ports of a second CSI-RS resource. A similar association is defined for the third, fifth and seventh column of the antenna port layout. The entries of the rows {0,2} of the second column are associated with the antenna ports of the second CSI-RS resource and the entries of rows {1,3} of the second column is associated with the first CSI-RS resource. A similar association is defined for the fourth, sixth and eighth column of the antenna port layout. Note that the interleaving distance of entries associated with the rows of the antenna port layout and with the antenna ports of a CSI-RS resource is two. In certain embodiments, the antenna port layout comprises ^^rows and ^^columns, and the UE is configured with four CSI-RS resources. Similar as described above, each antenna port of a CSI-RS resources is mapped to an antenna port or an entry (defined by a row index and a column index) of the antenna port layout. The mapping of the antenna ports of a CSI-RS resource to the entries of the antenna port layout also follows an interleaved scheme as explained in the following. It is assumed that there are four sets ^^, ^^, ^^and ^^of different rows / row indices, whereas each set comprises^^^ non-consecutive rows / row indices. As an example, the first set comprises rows / row indices {0,4, … , ^^− 4}, the second set comprises rows / row indices {1,5, … , ^^− 3}, the third set comprises rows / row indices {2,6, … , ^^− 2}, and the fourth set comprises rows / row indices {3,7, … , ^^− 1}. The entries of the antenna port layout associated with rows / row indices from the first set ^^and with a first column index are associated with the antenna ports of a first CSI-RS resource. The entries of the antenna port layout associated with rows / row indices from the second set ^^and with the first column index are associated with the antenna ports of a second CSI-RS resource. The entries of the antenna port layout associated with rows / row indices from the third set ^^and with the first column index are associated with antenna ports of a third CSI-RS resource. The entries of the antenna port layout associated with rows / row indices from the fourth set ^^and with the first column index are associated with the antenna ports of a fourth CSI-RS resource. The entries of the antenna port layout associated with rows / row indices from the first set ^^and with a second column index are associated with the antenna ports of the fourth CSI-RS resource. The entries of the antenna port layout associated with rows / row indices from the second set ^^and with the second column index are associated with the antenna ports of the first CSI- RS resource. The entries of the antenna port layout associated with rows / row indices from the third set ^^and with the second column index are associated with the antenna ports of the second CSI-RS resource. The entries of the antenna port layout associated with rows / row indices from the fourth set ^^and with the second column index are associated with the antenna ports of the third CSI-RS resource. The entries of the antenna port layout associated with rows / row indices from the first set ^^and with a third column index are associated with the antenna ports of the third CSI-RS resource. The entries of the antenna port layout associated with rows / row indices from the second set ^^and with the third column index are associated with the antenna ports of the fourth CSI-RS resource. The entries of the antenna port layout associated with rows / row indices from the third set ^^and with the third column index are associated with the antenna ports of the first CSI-RS resource. The entries of the antenna port layout associated with rows / row indices from the fourth set ^^and with the third column index are associated with the antenna ports of the second CSI-RS resource. The entries with rows / row indices from the first, the second, the third and the fourth sets ^^, ^^, ^^and ^^and with a fourth column / column index of the antenna port layout are associated with the antenna ports of the second, the third, the fourth and the first, CSI-RS resources, respectively, and so on. In certain embodiments, the antenna port layout comprises ^^rows and ^^columns, and the UE is configured with two CSI-RS resources. Each antenna port of a CSI-RS resources is mapped to an antenna port or an entry (defined by a row index and a column index) of the antenna port layout. The mapping of the antenna ports of a CSI-RS resource to the entries of the antenna port layout follows an interleaved scheme as explained in the following. It is assumed that there are two sets ^^and ^^of different columns / column indices, whereas each set comprises^^^ non-consecutive columns / column indices. As an example, the first set comprises columns / column indices {0,2,4, … , − 2} and the second set comprises columns / column indices {1,3,5, … , − 1}. The entries of the antenna port layout associated with columns / column indices from the first set ^^and with a first-row index are associated with antenna ports of a first CSI-RS resource. The entries of the antenna port layout associated with columns / column indices from the second set ^^and with the first-row index are associated with antenna ports of a second CSI-RS resource. The entries associated with columns / column indices from the first set ^^and with a second-row index are associated with antenna ports of the second CSI-RS resource. The entries associated with columns / column indices from the second set ^^and with the second-row index are associated with antenna ports of the first CSI-RS resource, and so on. In certain embodiments, the antenna port layout comprises ^^rows and ^^columns, and the UE is configured with four CSI-RS resources. Similar as described above, each antenna port of a CSI-RS resources is mapped to an antenna port or an entry (defined by a row index and a column index) of the antenna port layout. The mapping of the antenna ports of a CSI-RS resource to the entries of the antenna port layout also follows an interleaved scheme as explained in the following. It is assumed that there are four sets ^^, ^^, ^^and ^^of different columns / column indices, whereas each set comprises^^^ non-consecutive columns / column indices. As an example, the first set comprises columns / column indices {0,4, … , − 4}, the second set comprises columns / column indices {1,5, … , − 3}, the third set comprises columns / column indices {2,6, … , ^^− 2}, and the fourth set comprises columns / column indices {3,7, … , ^^− 1}. The entries of the antenna port layout associated with columns / column indices from the first set ^^and with a first-row index are associated with the antenna ports of a first CSI-RS resource. The entries of the antenna port layout associated with columns / column indices from the second set ^^and with the first-row index are associated with the antenna ports of a second CSI-RS resource. The entries of the antenna port layout associated with columns / column indices from the third set ^^and with the first-row index are associated with antenna ports of a third CSI-RS resource. The entries of the antenna port layout associated with columns / column indices from the fourth set ^^and with the first-row index are associated with the antenna ports of a fourth CSI-RS resource. The entries of the antenna port layout associated with columns / column indices from the first set ^^and with a second-row index are associated with the antenna ports of the fourth CSI-RS resource. The entries of the antenna port layout associated with columns / column indices from the second set ^^and with the second-row index are associated with the antenna ports of the first CSI- RS resource. The entries of the antenna port layout associated with columns / column indices from the third set ^^and with the second-row index are associated with the antenna ports of the second CSI-RS resource. The entries of the antenna port layout associated with columns / column indices from the fourth set ^^and with the second-row index are associated with the antenna ports of the third CSI-RS resource. The entries of the antenna port layout associated with columns / column indices from the first set ^^and with a third-row index are associated with the antenna ports of the third CSI-RS resource. The entries of the antenna port layout associated with columns / column indices from the second set ^^and with the third- row index are associated with the antenna ports of the fourth CSI-RS resource. The entries of the antenna port layout associated with columns / column indices from the third set ^^and with the third-row index are associated with the antenna ports of the first CSI-RS resource. The entries of the antenna port layout associated with columns / column indices from the fourth set ^^and with the third-row index are associated with the antenna ports of the second CSI-RS resource. The entries associated with columns / column indices from the first, the second, the third and the fourth sets ^^, ^^, ^^and ^^and with a fourth row index of the antenna port layout are associated with the antenna ports of the second, the third, the fourth and the first CSI-RS resources, respectively, and so on. In certain embodiments, the CSI-RS or antenna ports of a CSI-RS resource are segmented into multiple CSI-RS port subsets, wherein a CSI-RS port subset comprises one or more non- overlapping CSI-RS or antenna ports. The number of CSI-RS or antenna ports in the CSI-RS port subsets can be identical or different. The sum of the number of CSI-RS or antenna ports across all CSI-RS port subsets associated with a CSI-RS resource is equal to total number of CSI-RS ports associated with a CSI-RS resource. In some options, a CSI-RS resource is associated with two CSI-RS port subsets. In certain embodiments, the antenna or CSI-RS ports of a first CSI-RS port subset of a CSI- RS resource are associated with all or a proper subset of even numbered rows / row indices and with all or a proper subset of even numbered columns / column indices of the antenna port layout and the antenna or CSI-RS ports of a second CSI-RS port subset of the CSI-RS resource are associated with all or a proper subset of odd numbered rows / row indices and with all or a proper subset of odd numbered columns / column indices of the antenna port layout. In certain embodiments, the antenna or CSI-RS ports of a first CSI-RS port subset of a CSI- RS resource are associated with all or a proper subset of odd numbered rows / rows indices and with all or a proper subset of even numbered column / column indices of the antenna port layout and the antenna or CSI-RS ports of a second CSI-RS port subset of a CSI-RS resource are associated with all or a proper subset of even numbered rows / row indices and with all or a proper subset of odd numbered column / column indices of the antenna port layout. In some examples, the antenna or CSI-RS port of a CSI-RS resource associated with row index ^^and column index ^^(and a first polarization) of the antenna port layout is associated with entry{^^^^+ ^^}of the precoding vector and the antenna or CSI-RS port associated with a second polarization is associated with entry {^^^^+ ^^^^+ ^^} of the precoding vector. In some examples, for ^^= 8, ^^= 4, and ^ = 2, each CSI-RS resource comprises 32 CSI- RS or antenna ports. For a first CSI-RS resource, the CSI-RS or antenna ports of a first CSI- RS port subset are associated with rows {0,2} and columns {0,2,4,6} of the antenna port layout and the CSI-RS or antenna ports of a second CSI-RS port subset are associated with rows {1,3} and columns {1,3,5,7} of the antenna port layout. This means the CSI-RS or antenna ports of the first CSI-RS port subset are associated with entries {0,2,8,10,16,18,24,26,32,34,40,42,48,50,56,58} of the precoding vector, and the CSI-RS or antenna ports of the second CSI-RS port subset are associated with entries {5,7,13,15,21,23,29,31,37,39,45,47,53,55,61,63} of the precoding vector. For the second CSI- RS resource, the CSI-RS or antenna ports of the first CSI-RS port subset are associated with rows {1,3} and columns {0,2,4,6} of the antenna port layout and the CSI-RS or antenna ports of the second CSI-RS port subset are associated with rows {0,2} and columns {1,3,5,7}. This means the CSI-RS or antenna ports of the first CSI-RS port subset are associated with entries {1,3,9,11,17,19,25,27,33,35,41,43,49,51,57,59} of the precoding vector, and the CSI-RS or antenna ports of the second CSI-RS port subset are associated with entries {4,6,12,14,20,22,28,30,36,38,44,46,52,54,60,62} of the precoding vector. Fig.15 shows the mapping of the CSI-RS or antenna ports of the two CSI-RS port subsets of each CSI-RS resource. The antenna port layout comprises ^^= 8 columns and ^^= 4 rows and two CSI- RS resources with each CSI-RS resource comprising two CSI-RS port subsets. In some examples, for ^^= 8, ^^= 4, and ^ = 4, each CSI-RS resource comprises 16 CSI- RS or antenna ports. Two out of the four CSI-RS resources comprises antenna ports of a first polarization and the remaining two CSI-RS resources comprises antenna ports of a second polarization. For a first CSI-RS resource, the CSI-RS or antenna ports of a first CSI-RS port subset are associated with rows {0,2} and columns {0,2,4,6} of the antenna port layout and the CSI-RS or antenna ports of a second CSI-RS port subset are associated with rows {1,3} and columns {1,3,5,7} of the antenna port layout. This means the CSI-RS or antenna ports of the first CSI-RS port subset are associated with entries {0,2,8,10,16,18,24,26,32} of the precoding vector, and the CSI-RS or antenna ports of the second CSI-RS port subset are associated with entries {5,7,13,15,21,23,29,31} of the precoding vector. For the second CSI- RS resource, the CSI-RS or antenna ports of the first CSI-RS port subset are associated with rows {1,3} and columns {0,2,4,6} of the antenna port layout and the CSI-RS or antenna ports of the second CSI-RS port subset are associated with rows {0,2} and columns {1,3,5,7} This means the CSI-RS or antenna ports of the first CSI-RS port subset are associated with entries {1,3,9,11,17,19,25,27} of the precoding vector, and the CSI-RS or antenna ports of the second CSI-RS port subset are associated with entries {4,6,12,14,20,22,28,30} of the precoding vector. For the third CSI-RS resource, the CSI-RS or antenna ports of a first CSI-RS port subset are associated with rows {0,2} and columns {0,2,4,6} of the antenna port layout and the CSI-RS or antenna ports of a second CSI-RS port subset are associated with rows {1,3} and columns {1,3,5,7} of the antenna port layout. This means the CSI-RS or antenna ports of the first CSI-RS port subset are associated with entries {34,40,42,48,50,56,58} of the precoding vector, and the CSI-RS or antenna ports of the second CSI-RS port subset are associated with entries {37,39,45,47,53,55,61,63} of the precoding vector. For the fourth CSI- RS resource, the CSI-RS or antenna ports of the first CSI-RS port subset are associated with rows {1,3} and columns {0,2,4,6} of the antenna port layout and the CSI-RS or antenna ports of the second CSI-RS port subset are associated with rows {0,2} and columns {1,3,5,7} of the antenna port layout. This means the CSI-RS or antenna ports of the first CSI-RS port subset are associated with entries {33,35,41,43,49,51,57,59} of the precoding vector, and the CSI- RS or antenna ports of the second CSI-RS port subset are associated with entries {36,38,44,46,52,54,60,62} of the precoding vector. Indication of offset values The entries (indices) of the precoding vector associated with the antenna or CSI-RS ports of a first CSI-RS port subset of a first CSI-RS resource have an offset value of ‘1’ compared to the entries (indices) of the precoding vector associated with the antenna or CSI-RS ports of a first CSI-RS port subset of a second CSI-RS resource. Moreover, the entries (indices) of the precoding vector associated with the antenna or CSI-RS ports of a second CSI-RS port subset of the first CSI-RS resource have an offset value of ‘-1’ compared to the entries (indices) of the precoding vector associated with the antenna or CSI-RS ports of a second CSI-RS port subset of a second CSI-RS resource. This means the rows / row indices of the antenna port layout associated with the antenna ports of the first CSI-RS port subset of the second CSI-RS resource are given by adding an offset value of ‘+1’ to the rows / row indices of the antenna port layout associated with the antenna ports of the first CSI-RS port subset of the first CSI-RS resource. In the same manner, the rows / row indices of the antenna port layout associated with the antenna ports of the second CSI-RS port subset of the second CSI-RS resource are given by adding an offset value of ‘-1’ to the rows / row indices of the antenna port layout associated with the antenna ports of the second CSI-RS port subset of the first CSI-RS resource. In certain embodiments, the indication of the mapping or association of the antenna ports of a CSI-RS resource or of the antenna ports of the M CSI-RS resources to the row and column indices of the antenna port layout or to the entries of the precoding vector comprises an indication of one or more offset values associated with one or more CSI-RS resources of the M CSI-RS resources. Ordering of CSI-RS resources based on CSI-RS resource ID / Scrambling ID The UE is configured with M CSI-RS resources in a CSI-RS resource set. Each CSI-RS resource in the CSI-RS resource set is associated with a resource ID and a scrambling ID. When estimating the channel on a CSI-RS resource, the UE needs to perform blind decoding in a search space comprising the M CSI-RS resource IDs or scrambling IDs, wherein the UE compares every CSI-RS resource with every resource in the CSI-RS resource set. This approach has obviously a high computational complexity and can be alleviated by transmitting the CSI-RS resources of the CSI-RS resource set in a specific order. By doing so, the UE knows the order of the CSI-RS resource IDs or scrambling IDs and can perform channel estimation without the need of blind decoding which drastically reduces the complexity for channel estimation at the UE. In certain embodiments, the M CSI-RS resources configured to the UE in a CSI-RS resource set are received in the same order as the CSI-RS resource IDs or scrambling IDs configured to the UE (e.g., via the CSI report configuration). In some examples, the M CSI-RS resources configured to the UE in the CSI-RS resource set are received in an increasing or decreasing order of the CSI-RS resource IDs or scrambling IDs. Ordering of CSI-RS resources In certain embodiments, the CSI-RS resources are numbered in an increasing order across columns first and rows next. In one example, for ^ = 2, ^ = 4, ^^= 8 and ^^= 4, the first CSI-RS resource is associated with rows {0,1} and columns {0,1,2,3}, the second CSI-RS resource is associated with rows {0,1} and columns {4,5,6,7}, the third CSI-RS resource is associated with rows {2,3} and columns {0,1,2,3}, and the fourth CSI-RS resource is associated with rows {2,3} and columns {4,5,6,7}. In certain embodiments, the CSI-RS resources are numbered in an increasing order across rows first and columns next. In one example, for ^ = 2, ^ = 4, ^^= 8 and ^^= 4, the first CSI-RS resource is associated with rows {0,1} and columns {0,1,2,3}, the second CSI-RS resource is associated with rows {2,3} and columns {0,1,2,3}, the third CSI-RS resource is associated with rows {0,1} and columns {4,5,6,7}, and the fourth CSI-RS resource is associated with rows {2,3} and columns {4,5,6,7}. Indication of the association of antenna ports of a CSI-RS resource to row / column indices of the antenna port layout In certain embodiments, the UE is configured to receive an indication of the mapping or association of the antenna ports of a CSI-RS resource or of the antenna ports of the M CSI- RS resources to the row and column indices of the antenna port layout or the entries of the precoding vector. In some examples, the indication is provided from a network node via higher layer signaling. With the indication of the mapping, the UE can perform an association of an antenna port of a CSI-RS resource to a row and column index of the antenna port layout, or to an entry of the precoding vector. In certain embodiments, one or more bitmaps provide the mapping or association of the antenna ports of a CSI-RS resource or of the antenna ports of the M CSI-RS resources to the row and column indices of the antenna port layout or the entries of the precoding vector. In some examples, the UE is configured with a ^(^^+ ^^)-length bitmap for the ^ CSI-RS resources, where ^^+^^bits from the bitmap per CSI-RS resource are associated with the antenna ports of a CSI-RS resource. In some examples, the first ^^+^^bits are associated with the first CSI-RS resource (^ = 0), and the last ^^+^^bits are associated with the last CSI-RS resource (^ = ^ − 1). In some examples, ^^bits of the ^^+^^-length bitmap are associated with ^^columns of the antenna port layout and ^^bits of the ^^+^^-length bitmap are associated with the ^^rows of the antenna port layout. A ‘1’ in the ^^-th position of the ^^bit sequence indicates the ^^-th column of the antenna port layout and a ‘1’ in the ^^-th position of the ^^bit sequence indicates the ^^-th row of the antenna port layout. In some examples, ^^bits comprise ^ ’1’s and ^^− ^ ‘0’s and ^^bits comprise ^ ‘1’s and ^^− ^ ‘0’s, where ^ and ^ denote the number of columns and rows of the antenna port layout, respectively, with which the CSI-RS ports of a CSI-RS resource are associated with. In some options, the bitmap is associated with CSI-RS resources, wherein < ^, and the mapping or association of the antenna ports of (^ − ^^) CSI-RS resources is determined by the UE based on the mapping or association of the antenna ports of the CSI-RS resources. In one example = 1. In another example, ^^≥ 1. In certain embodiments, the UE is configured with one or more offset values, wherein the one or more offset values are used to determine the mapping or association of the antenna ports of (^ − ^^) CSI-RS resources to the entries of the antenna port layout. Here, is the number of CSI-RS resources for which the mapping or association of the antenna ports to the entries of the antenna port layout is configured to the UE or is known by the UE (e.g., the mapping is fixed in the NR specifications). In some examples, the number of offset values is (^ − ^^). In some other examples, the number of offset values is less than (^ − ^^). In certain embodiments, the mapping or association of the antenna or CSI-RS ports of a CSI- RS resource to the entries of the antenna port layout or the entries of the precoding vector is obtained by adding an offset value to the entries of the antenna port layout or the entries of the precoding vector with which the antenna or CSI-RS ports of a reference CSI-RS resource is associated with. In some examples, the reference CSI-RS resource is the CSI-RS resource with index ^ = 0 or the first CSI-RS resource. In some examples, each offset value is associated with an index, and the UE may be configured with ^ or ^ − 1 or less than ^ offset indices. In some examples, the UE is configured with ^ − − 1 offset values or indices. In some examples, the UE is configured with offset values or indices. Here, is the number of CSI-RS resources for which the mapping or association of the antenna ports to the antenna port layout is known to the UE or configured to the UE. In some examples, the offset values are fixed in the NR specification(s) and hence known to the UE. In certain embodiments, the offset values depend on the mapping or association of the antenna or CSI-RS ports of a reference CSI-RS resource to the entries of the antenna port layout or the entries of the precoding vector. In some examples, the antenna or CSI-RS ports of each CSI-RS resource are associated with ^ consecutive rows and all columns of the antenna port layout. The ^-th antenna or CSI-port of a reference CSI-RS resource (with index ^ ^ = 0) is associated with the ^^^^+ mod(^, R)+ ^^⋅ mod^^ ^ , entry of the ^ precoding vector, ∀ ^ = 0, … , 2^^^ − 1. The mapping of the 2^^^ antenna or CSI-RS ports associated with each of the remaining ^ − 1 CSI-RS resources (^ = 1, … , ^ − 1) to the entries of the precoding vector is obtained by adding an offset value ^ ⋅ ^ to the entries of the precoding vector associated with the reference CSI-RS resource. In some examples, the antenna or CSI-RS of each CSI-RS resource are associated with all rows and ^ consecutive columns of the antenna port layout. The ^-th antenna or CSI-RS port of the reference CSI-RS resource (with index ^ = 0) is associated with the ^^^^+ ^^⋅ () ^^ mod ^, ^ + mod ^ ^ ^ entry of the precoding vector, ∀ ^ = 0, … , 2^^^ − 1. The mapping of the 2^^^ antenna or CSI-RS ports associated with the each of the remaining ^ − 1 CSI-RS resources (^ = 1, … ,^^^ − 1) to the entries of the precoding vector is obtained by adding an offset value ^ ⋅ ^^^ to the entries of the precoding vector associated with the reference CSI-RS resource. In some examples, the antenna or CSI-RS ports of each CSI-RS resource are associated with ^ consecutive rows and ^ consecutive columns of the antenna port layout, wherein ^ < ^^and ^ . The ^-th antenna or CSI-RS port of a reference CSI-RS resource (with index ^ 0) is associated with the entry of the precoding vector, ∀^ = 0, … , 2^^ − 1. The mapping of the 2^^ antenna or CSI-RS ports associated with the each of the remaining ^ − 1 CSI-RS resources (^ = 1, … , ^^ − 1) to the entries of the precoding vector is obtained by adding an offset value to the entries of the precoding vector associated with the reference CSI-RS resource. In some examples, the antenna or CSI-RS ports of each CSI-RS resource are associated with ^ non-consecutive rows and all columns of the antenna port layout. The ^-th antenna or CSI- RS port of a reference CSI-RS resource (with index ^ = 0) is associated with the vector is obtained by adding an offset value ^ to the entries of the precoding vector associated with the reference CSI-RS resource. In some examples, the antenna or CSI-RS ports of each CSI-RS resource are associated with ^ non-consecutive columns and all rows of the antenna port layout. The ^-th antenna or CSI- RS port of a reference CSI-RS resource (with index ^ = 0) is associated with the entry of the precoding vector, ∀ ^ = 0, … , 2^^^ − 1. The mapping of the 2^^^ antenna or CSI-RS ports associated with the each of the remaining ^ − 1 CSI-RS resources (^ = 1, … ,^^^ − 1) to the entries of the precoding vector is obtained by adding an offset value ^ ⋅ ^^to the entries of the precoding vector associated with the reference CSI-RS resource. In some examples, the antenna or CSI-RS ports of each CSI-RS resource are associated with ^ consecutive rows and ^ non-consecutive columns of the antenna port layout, wherein ^ < ^^and ^ < The ^-th antenna or CSI-RS port of a reference CSI-RS resource (with index ^ = 0) is associated entry of the precoding vector, ∀^ = 0, … , 2^^ − 1. The mapping of the 2^^ antenna or CSI-RS ports associated with the each of the remaining ^ − 1 CSI-RS resources (^ = 1, … , ^^ − 1) to the entries of the precoding vector is obtained by adding an offset value to the entries of the precoding vector associated with the reference CSI-RS resource. In some examples, the antenna or CSI-RS ports of each CSI-RS resource are associated with ^ non-consecutive rows and ^ consecutive columns of the antenna port layout, wherein ^ < ^^and ^ < The ^-th antenna or CSI-RS port of a reference CSI-RS resource (with index ^ = 0) is associated with the entry of the precoding vector, ∀^ = 0, … , 2^^ − 1. The mapping of the 2^^ antenna or CSI-RS ports associated with the each of the remaining ^ − 1 CSI-RS resources (^ = 1, … , ^^ − 1) to the entries of the precoding vector is obtained by adding an offset value ^^^ ⋅ to the entries of the precoding vector associated with the reference CSI-RS resource. In some examples, the antenna or CSI-RS ports of each CSI-RS resource are associated with ^ non-consecutive rows and ^ non-consecutive columns of the antenna port layout, wherein ^ < ^^and ^ The ^-th antenna or CSI-RS port of a reference CSI-RS resource (with ^ ^ index ^ = 0) is associated with the ^^ ^^ ^ ^^^^+ ^ ⋅ ^^^^^ ^ ^ , ^^^-th entry of the precoding vector, ∀^ = 0, … , 2^^ − 1. The mapping of the 2^^ antenna or CSI-RS ports associated with the each of the remaining ^ − 1 CSI-RS resources (^ = 1, … , ^^ − 1) to the ^⋅^ entries of the precoding vector is obtained by adding an offset value ^^⋅ ^^^^ + ^^^ ^^,^^^ ^ to the entries of the precoding vector associated with the reference CSI-RS resource. In some examples, the antenna or CSI-RS ports of each CSI-RS resource are associated with ^ consecutive rows and all columns of the antenna port layout. The ^-th antenna or CSI-port of a reference CSI-RS resource (with index ^ = 0) is associated with the th entry of the precoding vector, ∀ ^ = 0, … , ^^^ − 1. The mapping of the ^^^ antenna or CSI- RS ports associated with each of the remaining ^ − 1 CSI-RS resources (^ = 1, … , ^ − 1) ^^ to the entries of the precoding vector is obtained by adding an offset value ^^^^ ⋅ ^^^^+ mod ^^,^^^ ^ ⋅ ^ to the entries of the precoding vector associated with the reference CSI-RS resource. In some examples, the antenna or CSI-RS ports of each CSI-RS resource are associated with all rows and ^ consecutive columns of the antenna port layout. The ^-th antenna or CSI-RS port of a reference CSI-RS resource (with index ^ = 0) is associated with the ^-th entry of the precoding vector, ∀ ^ = 0, … , ^^^ − 1. The mapping of the ^^^ antenna or CSI-RS ports associated with the each of the remaining ^ − 1 CSI-RS resources (^ = 1, … , − 1) to the ^^ entries of the precoding vector is obtained by adding an offset value ^^^^ ⋅ mod ⋅ ^^^ to the entries of the precoding vector associated with the reference CSI-RS resource. In some examples, the antenna or CSI-RS ports of each CSI-RS resource are associated with ^ consecutive rows and ^ consecutive columns of the antenna port layout, wherein ^ < ^^and ^ The ^-th antenna or CSI-RS port of a reference CSI-RS resource (with index ^ = ) is associated with the ^ ^ 0 mod(^, ^)+ ^^⋅ ^ ^ ^^-th entry of the precoding vector, ∀ ^ = 0, … , ^^ − 1. The mapping of the ^^ antenna or CSI-RS ports associated with the each of the remaining ^ − 1 CSI-RS resources (^ = 1, … , ^^ − 1) to the entries of the precoding vector ^⋅^ is obtained by adding an offset value ^^^ to the entries of the precoding vector associated with the reference CSI-RS resource. In some examples, the antenna or CSI-RS ports of each CSI-RS resource are associated with ^ non-consecutive rows and all columns of the antenna port layout, wherein ^ < ^^. The ^-th antenna or CSI-port of a reference CSI-RS resource (with index ^ = 0) is associated with the ()^ ⋅ mod ^, ^ + ^^^ ^ ^^-th entry of the precoding vector, ∀ ^ = 0, … , ^^^ − 1. The mapping of the antenna or CSI-RS ports associated with each of the remaining ^ − 1 CSI-RS resources (^ = 1, … ,^^^^ − 1) to the entries of the precoding vector is obtained by adding an ^^ offset value ^^^^ ^^^^+ mod ^^,^^^ ^ to the entries of the precoding vector associated with the reference CSI-RS resource. In some examples, the antenna or CSI-RS ports of each CSI-RS resource are associated with all rows and ^ non-consecutive columns of the antenna port layout, wherein ^ < ^^. The ^-th antenna or CSI-RS port of a reference CSI-RS resource (with index ^ = 0) is associated with the entry of precoding vector, ∀ ^ = 0, … , ^^^ − 1. The mapping of the ^^^ antenna or CSI-RS ports associated with the each of the remaining ^ − 1 CSI-RS resources (^ = 1, … ,^^^^ − 1) to the entries of the precoding vector is obtained by adding an offset value ^ ^^ + ^^⋅ mod ^ to the entries of the precoding vector associated the reference CSI-RS resource. In some examples, the antenna or CSI-RS ports of each CSI-RS resource are associated with ^ consecutive rows and ^ non-consecutive columns of the antenna port layout, wherein ^ < ^^and ^ < ^^. The ^-th antenna or CSI-RS port of a reference CSI-RS resource (with index ^ = 0) is associated with the entry of the precoding vector, ∀^ = 0, … , ^^ − 1. The mapping of the ^^ antenna or CSI-RS ports associated with the each of the remaining ^ − 1 CSI-RS resources (^ = 1, … , − 1) to the entries of the ^^^ precoding vector is obtained by adding an offset value ^^^^^^^^^^ + ^ ⋅ mod ^^,^^^ ^ + ^^⋅ to the entries of the precoding vector associated with the reference CSI-RS resource. In some examples, the antenna or CSI-RS ports of each CSI-RS resource are associated with ^ non-consecutive rows and ^ consecutive columns of the antenna port layout, wherein ^ < ^ and ^ < . The ^-th antenna or CSI-RS port of a reference CSI-RS resource (with ^ = 0) is associated with the ⋅ mod(^, ^)+ ^^⋅ mod entry of the precoding vector, ∀^ = 0, … , ^^ − 1. The mapping of the ^^ antenna or CSI-RS ports associated with the each of the remaining ^ − 1 CSI-RS resources (^ = 1, … , ^^ − 1) to the entries of the precoding vector is obtained by adding an offset value ^ ^^ + ^^^ to the entries of the precoding vector associated with the reference CSI-RS resource. In some examples, the antenna or CSI-RS ports of each CSI-RS resource are associated with ^ non-consecutive rows and ^ non-consecutive columns of the antenna port layout, wherein ^ < ^^and ^ The ^-th antenna or CSI-RS port of a reference CSI-RS resource (with index ^ = 0) is associated with the^^^^ ⋅ mod(^, ^) entry of the precoding vector, ∀^ = 0, … , ^^ − 1. The mapping of the ^^ antenna or CSI-RS ports associated with the each of the remaining ^ − 1 CSI-RS resources (^ = 1, … , ^^ − 1) to the entries of the precoding vector is obtained by adding an offset value ^^^^ + mod ^^,^^^ ^ to the entries of the precoding vector associated with the reference CSI-RS resource. In certain embodiments, the mapping or association of the antenna or CSI-RS ports of a CSI- RS resource to the rows and columns of the antenna port layout is obtained by adding an offset value(s) to the rows and columns of the antenna port layout associated with a reference CSI-RS resource. In some examples, the reference CSI-RS resource is the CSI-RS resource with index ^ = 0 or the first CSI-RS resource. In some examples, the antenna or CSI-RS ports of each CSI-RS resource are associated with R rows and all columns of the antenna port layout. A CSI-RS reference resource is associated with rows {^^, … , ^^^^} and all columns. Then a CSI-RS resource with index ^ is associated with rows {^^, … , ^^^^} + ^^^^ , wherein the rows associated with the CSI-RS resource with index ^ is obtained by adding an offset value^^^ ^ to the row / row indices associated with the reference CSI-RS resource. In some examples, the antenna or CSI-RS ports of each CSI-RS resource are associated with all rows and C columns of the antenna port layout. A CSI-RS reference resource is associated with columns {^ , … , and all rows. Then, the CSI-RS resource with index ^ is with the columns {^^, … , ^^^^} + ^^^^ , wherein the columns associated with a CSI-RS resource with index ^ is obtained by adding an offset value to the columns / column indices associated with the reference CSI-RS resource. In some examples, the antenna or CSI-RS ports of each CSI-RS resource are associated with R rows and C columns of the antenna port layout. A CSI-RS reference resource is associated with rows {^^, … , ^^^^} and columns {^^, … , ^^^^}. Then, the CSI-RS resource with index ^ is associated with the rows {^ , … , ^^^^^^^^} + ^ ^^^^^^^ , wherein rows associated with a CSI-RS resource with index m is obtained by adding an offset value ^ ⋅ ^^^ ^^, to the row / row indices of the CSI-RS reference resource and the column / column indices of a CSI-RS resource with index m is obtained by adding an offset value to the column / columns indices associated with the reference CSI-RS resource. In certain embodiments, the offset value(s) associated with the first dimension or columns and / or the second dimension or rows of the antenna port layout are configured to the UE or are fixed in the NR specification(s) or are determined by the UE based on the rows and columns associated with the antenna port layout of a reference CSI-RS resource. In certain embodiments, the UE is configured with multiple mappings or associations of the antenna ports of a CSI-RS resource or of the antenna ports of the M CSI-RS resources to the row and column indices of the antenna port layout or the entries of the precoding vector. Each mapping provides an association of the antenna or CSI-RS ports of a CSI-RS resource to the row and column indices or entries of the antenna port layout and / or the entries of the precoding vector of the CSI report. In some examples, the multiple mappings or associations are configured by a network node, eg., a gNB. The gNB may indicate via higher layer one of the configured mappings or associations to be used by the UE, e.g., for calculating the precoding vector used in the CSI report. The indication can be provided from the network node via higher layer signaling (e.g., RRC). In another example, the indication is provided from the network node via physical layer signaling (e.g., the downlink control channel, DCI). In some examples, the indication via a higher layer, or via the DCI is provided in form of a bitmap, wherein each bit in the bitmap is associated with a specific mapping or association. For example, when the UE is configured with N different mappings or associations, the bitmap may comprise N bits. In certain embodiments, the UE is configured to report a CSI, or a CSI report, via PUSCH or PUCCH corresponding to the ^ configured CSI-RS resources, or a resource set configured with ^ CSI-RS resources, wherein at least one of the following apply: ^ the CSI report does not comprise a CSI-RS resource indicator, ^ the CSI report is transmitted in two parts wherein the first part comprises at least a rank indicator / index and a channel quality indicator / index, ^ the CSI report is transmitted after the reception of all the ^ CSI-RS resources following the triggering of the ^ resources or the resource set (for e.g., when the CSI-RS resources are aperiodic), ^ the CSI report is transmitted after the reception of all the ^ CSI-RS resources following the start of a period of the CSI-RS (this may apply when the CSI-RS resources are periodic or semi-persistent). In certain embodiments, the wireless device is configured with a number of subbands, ^, wherein each subband is associated with a number of contiguous physical resource blocks, PRBs, or comprises a plurality of contiguous PRBs. In certain embodiments, the number of sets of subbands is either fixed in the NR specifications, or configured to the wireless device (e.g., a UE), or determined by the wireless device based on one or more parameters configured to the wireless device, or determined by the wireless device based on one or more fixed parameters in the NR specification(s). In some examples, the number of sets of subbands is dependent on the number of CSI-RS resources. In certain embodiments, the mapping of the antenna or CSI-RS ports of a CSI-RS resource to the entries of the antenna port layout is subband-dependent. A CSI-RS resource comprises a number of antenna or CSI-RS ports, wherein each antenna or CSI-RS port is mapped to an entry of the antenna port layout. Each antenna or CSI-RS port of the CSI-RS resource may be associated with the configured number of subbands ^. This means that one or more antenna or CSI-RS ports of a CSI-RS resource is / are mapped to the entries of the antenna port layout using a first mapping scheme for a first set of subbands, and the same antenna or CSI-RS port(s) of the CSI-RS resource are mapped to the entries of the antenna port layout using a second mapping scheme for a second set of subbands. Note that the first and second set of subbands may comprise different subbands. For example, when the wireless device is configured with ^ subbands, the first set may comprise subbands, 0,2, … , ^ − 2, and the second set may comprise subbands, 1,3, … , ^ − 1. In another example, the first set may comprise subbands, 0,1, … , ^ / 2 − 1, and the second set may comprise subbands, ^ / 2, … , ^ − 1.The first and / or second mapping scheme as mentioned above can be one of the mapping schemes described in the embodiments above. For example, the first and second mappings schemes can be interleaved schemes. In some examples, the first, and the second mapping schemes are identical. In some examples, the first and the second mapping schemes are different. By using such a mapping, the aperture size of the CSI-RS transmissions can be increased or enhanced. The above subband-specific mapping scheme allows a mapping of the antenna or CSI-RS ports to the entries of the antenna port layout that covers the full aperture size (all elements of the antenna port layout) of the antenna port layout using a single CSI-RS resource for a CSI-RS transmission. The wireless device may estimate the channel based on the measured antenna or CSI-RS port(s) and interpolate the measured values in space (with respect to the antenna or CSI-RS ports) and frequency domain (with respect to the subbands) to obtain a set of channel estimates for all configured subbands and antenna or CSI-RS ports of the CSI-RS resource. In some examples, it is assumed that there are two sets ^^and ^^of different rows / row indices, whereas each set comprises^^^ non-consecutive rows / row indices. As an example, the first set comprises rows / row indices {0,2,4, … , ^^− 2} and the second set comprises rows / row indices {1,3,5, … , ^^− 1}. The entries of the antenna port layout associated with rows / row indices from the first set ^^and with a first column index are associated with antenna ports of a first set of subbands. The entries of the antenna port layout associated with rows / row indices from the second set ^^and with the first column index are associated with antenna ports of a second set of subbands. The entries associated with rows / row indices from the first set ^^and with a second column index are associated with antenna ports of the second set of subbands. The entries associated with rows / row indices from the second set ^^and with the second column index are associated with antenna ports of the first set of subbands, and so on. In some examples, it is assumed that there are two sets ^^and ^^of different columns / column indices, whereas each set comprises^^^ non-consecutive columns / column indices. As an example, the first set comprises columns / column indices {0,2,4, … , − 2} and the second set comprises columns / column indices {1,3,5, … , − 1}. The entries of the antenna port layout associated with columns / column indices from the first set ^^and with a first-row index are associated with antenna ports of a first set of subbands. The entries of the antenna port layout associated with columns / column indices from the second set ^^and with the first-row index are associated with antenna ports of a second set of subbands. The entries of the antenna port layout associated with columns / column indices from the first set ^^and with a second- row index are associated with antenna ports of the second set of subbands. The entries of the antenna port layout associated with columns / column indices from the second set ^^and with the second-row index are associated with antenna ports of the first set of subbands, and so on. In some examples, there are four sets of subbands and four CSI-RS resources. This means that for a first set of subbands one or more antenna ports of a CSI-RS resource is / are mapped to the entries of the antenna port layout using a first mapping scheme, and for a second set of subbands the same antenna port(s) of the CSI-RS resource are mapped to the entries of the antenna port layout using a second mapping scheme, and for a third set of subbands the same antenna port(s) of the CSI-RS resource are mapped to the entries of the antenna port layout using a third mapping scheme, and for a fourth set of subbands the same antenna port(s) of the CSI-RS resource are mapped to the entries of the antenna port layout using a fourth mapping scheme. For example, when the wireless device is configured with ^ subbands, the first set may comprise subbands, 0, … , − 1, the second set may comprise ^ ^ ^ ^^ subbands, ^ + 1, … , ^ − 1, the third set may comprise subbands, ^ + 1, … , ^ − 1, and fourth ^^ set may comprise subbands + ^ 1, … , For example, when the wireless device is configured with ^ subbands, the first set may comprise subbands, 0,4, … , ^ − 4, the second set may comprise subbands, 1,5, … , ^ − 3, the third set may comprise subbands, 2,6, … , ^ − 2, and the fourth set may comprise subbands 3,7, … , ^ − 1. The first and / or second and / or third and / or fourth mapping scheme as mentioned above can be one of the mapping schemes described in the embodiments above. For example, the first, second, third, and fourth mappings schemes can be interleaved schemes. In some examples, the first, the second, the third and the fourth mapping schemes are identical. In some examples, the first, the second, the third and the fourth mapping schemes are different. In some examples, it is assumed that there are four sets, ^^, ^^, ^^, and ^^of different rows / row indices, whereas each set comprises^^^ non-consecutive rows / row indices. As an example, the first set comprises rows / row indices {0,4, … , ^^− 4}, the second set comprises rows / row indices {1,5, … , ^^− 3}, the third set comprises rows / row indices {2,6, … , ^^− 2}, and the fourth set comprises rows / row indices {3,7, … , ^^− 1}. The entries of the antenna port layout associated with rows / row indices from the first set ^^and with a first column index are associated with the antenna ports of a first set of subbands. The entries of the antenna port layout associated with rows / row indices from the second set ^^and with the first column index are associated with the antenna ports of a second set of subbands. The entries of the antenna port layout associated with rows / row indices from the third set ^^and with the first column index are associated with antenna ports of a third set of subbands. The entries of the antenna port layout associated with rows / row indices from the fourth set ^^and with the first column index are associated with the antenna ports of a fourth set of subbands. The entries of the antenna port layout associated with rows / row indices from the first set ^^and with a second column index are associated with the antenna ports of the fourth set of subbands. The entries of the antenna port layout associated with rows / row indices from the second set ^^and with the second column index are associated with the antenna ports of the first set of subbands. The entries of the antenna port layout associated with rows / row indices from the third set ^^and with the second column index are associated with the antenna ports of the second set of subbands. The entries of the antenna port layout associated with rows / row indices from the fourth set ^^and with the second column index are associated with the antenna ports of the third set of subbands. The entries of the antenna port layout associated with rows / row indices from the first set ^^and with a third column index are associated with the antenna ports of the third set of subbands. The entries of the antenna port layout associated with rows / row indices from the second set ^^and with the third column index are associated with the antenna ports of the fourth set of subbands. The entries of the antenna port layout associated with rows / row indices from the third set ^^and with the third column index are associated with the antenna ports of the first set of subbands. The entries of the antenna port layout associated with rows / row indices from the fourth set ^^and with the third column index are associated with the antenna ports of the second set of subbands. The entries with rows / row indices from the first, the second, the third and the fourth sets ^^, ^^, ^^and ^^and with a fourth column / column index of the antenna port layout are associated with the antenna ports of the second, the third, the fourth and the first, set of subbands, respectively, and so on. In some examples, it is assumed that there are four sets ^^, ^^, ^^and ^^of different columns / column indices, whereas each set comprises^^^ non-consecutive columns / column indices. As an example, the first set comprises columns / column indices {0,4, … , − 4}, the second set comprises columns / column indices {1,5, … , − 3}, the third set comprises columns / column indices {2,6, … , ^^− 2}, and the fourth set comprises columns / column indices {3,7, … , ^^− 1}. The entries of the antenna port layout associated with columns / column indices from the first set ^^and with a first-row index are associated with the antenna ports of a first set of subbands. The entries of the antenna port layout associated with columns / column indices from the second set ^^and with the first-row index are associated with the antenna ports of a second set of subbands. The entries of the antenna port layout associated with columns / column indices from the third set ^^and with the first-row index are associated with antenna ports of a third set of subbands. The entries of the antenna port layout associated with columns / column indices from the fourth set ^^and with the first-row index are associated with the antenna ports of a fourth set of subbands. The entries of the antenna port layout associated with columns / column indices from the first set ^^and with a second-row index are associated with the antenna ports of the fourth set of subbands. The entries of the antenna port layout associated with columns / column indices from the second set ^^and with the second-row index are associated with the antenna ports of the first set of subbands. The entries of the antenna port layout associated with columns / column indices from the third set ^^and with the second-row index are associated with the antenna ports of the second set of subbands. The entries of the antenna port layout associated with columns / column indices from the fourth set ^^and with the second-row index are associated with the antenna ports of the third set of subbands. The entries of the antenna port layout associated with columns / column indices from the first set ^^and with a third-row index are associated with the antenna ports of the third set of subbands. The entries of the antenna port layout associated with columns / column indices from the second set ^^and with the third-row index are associated with the antenna ports of the fourth set of subbands. The entries of the antenna port layout associated with columns / column indices from the third set ^^and with the third-row index are associated with the antenna ports of the first set of subbands. The entries of the antenna port layout associated with columns / column indices from the fourth set ^^and with the third-row index are associated with the antenna ports of the second set of subbands. The entries associated with columns / column indices from the first, the second, the third and the fourth sets ^^, ^^, ^^and ^^and with a fourth row index of the antenna port layout are associated with the antenna ports of the second, the third, the fourth and the first, set of subbands, respectively, and so on. In some examples, the number of sets of subbands and the number of CSI-RS resources are not equal. Referring to Figure 3, there is illustrated a method performed by a wireless device according to some of the previously described embodiments. The method comprising: - receiving (401A) from a network node, - a configuration or an indication, wherein the configuration or the indication indicates a number ^^of a first dimension or columns, and a number ^^of a second dimension or rows of an antenna port layout at the network node, and - a configuration or an indication, wherein the configuration or the indication indicates M Channel State Information – Reference Signal, CSI-RS, resources, wherein each CSI-RS resource comprises a number of antenna or CSI-RS ports, wherein the antenna or CSI-RS ports of each CSI-RS resource are mapped to a subset or proper subset of row and column indices of the antenna port layout, - determining (402A) entries of a precoding vector per CSI-RS resource associated with a subset or proper subset of the rows and columns of the antenna port layout, - generating (403A) a CSI report or a CSI feedback report comprising a Precoder Matrix Indicator, PMI, indicating the precoding vector; and - transmitting (404A) or reporting the CSI report or the CSI feedback report to the network node. In some examples, there is only a single configuration or indication that provides the number and the number ^^of the antenna port layout, and the M CSI-RS resources to the UE. In one examples, the number ^^and the number ^^of the antenna port layout, and the M CSI- RS resources are configured via a higher layer (e.g., RRC) to the UE. In another example, the number ^^and the number ^^of the antenna port layout, and the M CSI-RS resources are indicated via a downlink control channel indicator, DCI, to the UE. According to some embodiments herein, there is provided a method performed by a wireless device (e.g., a User Equipment (UE)), the method comprising: - receiving from a network node, - a configuration or an indication, wherein the configuration or the indication indicates a number ^^of a first dimension or columns, and a number ^^of a second dimension or rows of an antenna port layout at the network node, and - a configuration or an indication, wherein the configuration or the indication indicates at least one Channel State Information – Reference Signal, CSI-RS, resources, and a number of subbands, wherein a CSI-RS resource comprises a number of antenna or CSI-RS ports and each antenna or CSI-RS port is associated with the number of subbands, wherein an antenna or CSI-RS port is mapped to a first entry of the antenna port layout using a first mapping scheme for a first set of subbands, and to a second entry of the antenna port layout using a second mapping scheme for a second set of subbands, - determining entries of a precoding vector associated with the antenna ports, - generating a CSI report or a CSI feedback report comprising a Precoder Matrix Indicator, PMI, indicating the precoding vector, and - reporting, to the network node, the CSI report or the CSI feedback report. According to some embodiments herein, the first and second set of subbands comprise different subbands. For example, when the wireless device is configured with ^ subbands, the first set may comprise subbands, 0,2, … , ^ − 2, and the second set may comprise subbands, 1,3, … , ^ − 1. In another example, the first set may comprise subbands, 0,1, … , ^ / 2 − 1, and the second set may comprise subbands, ^ / 2, … , ^ − 1. The first and second set of subbands may be non-empty sets. According to some embodiments herein, the first, the second, the third and the fourth set of subbands comprise different subbands. For example, when the wireless device is configured with ^ subbands, the first set may comprise subbands, 0, … , the second set may ^ ^ ^ comprise subbands, ^ + 1, … , ^ − 1, the third set may comprise subbands, ^ + 1, … , − 1, and ^^ fourth set may comprise subbands ^ + 1, … , ^ − 1. For example, when the wireless device is configured with ^ subbands, the first set may comprise subbands, 0,4, … , ^ − 4, the second set may comprise subbands, 1,5, … , ^ − 3, the third set may comprise subbands, 2,6, … , ^ − 2, and the fourth set may comprise subbands 3,7, … , ^ − 1. According to some embodiments herein, the first and / or second mapping scheme as mentioned above can be one of the mapping schemes described in the embodiments above. For example, the first and second mappings schemes can be interleaved schemes. Note that in general, according to some embodiments herein, the first mapping scheme is different to the second mapping scheme. This means that a first mapping maps the antenna port(s) of the CSI-RS resource to a first set of entries or antenna ports of the antenna port layout and the second mapping maps the antenna ports of the CSI-RS resource to a second set of entries or antenna ports of the antenna port layout, wherein the first set of entries or antenna ports of the antenna port layout is different to the second set of entries or antenna ports of the antenna port layout. Note that the first set of entries may comprise different entries compared to the second set of entries. According to some embodiments herein, an antenna or CSI-RS port is mapped for a first set of subbands to a first entry of the antenna port layout using a first mapping scheme, and for a second set of subbands to a second entry of the antenna port layout using a second mapping scheme, wherein the first entry of the antenna port layout is different to the second entry of the antenna port layout. According to some embodiments herein, the wireless device is configured to receive a given CSI-RS resource in a set of symbols that does not overlap or intersect with the set of symbols in which any of the other ^ CSI-RS resources are received. According to some embodiments herein, the wireless device is configured with P antenna or CSI-RS ports, and each CSI-RS resource is associated with the same P antenna or CSI-RS ports, or a subset or proper subset of the P antenna or CSI-RS ports. According to some embodiments herein, the antenna or CSI-RS ports of each CSI-RS resource are associated with a number of consecutive rows, ^, and all columns of the antenna port layout, and wherein ^ ≥ 1. According to some embodiments herein, the ^-th antenna or CSI-RS port of the CSI-RS resource is associated with the (^, ^) + ^^⋅ ^^^ entry of the precoding vector, wherein the CSI-RS resource index, and ^ = 0, … , 2^^^ − 1 is the CSI-RS port index associated with the CSI-RS resource. According to some embodiments herein, the antenna or CSI-RS ports of each CSI-RS resource are associated with a number of consecutive columns, ^, and all rows of the antenna port layout, and wherein ^ ≥ 1. According to some embodiments herein, the ^-th antenna or CSI-RS port of a CSI-RS resource is associated with the entry of the precoding vector, wherein ^ ∈ {0, … , − 1} is the CSI-RS resource index, and ^ = 0, … , 2^^^ − 1 is the antenna or CSI-RS port index associated with the CSI-RS resource. According to some embodiments herein, the antenna or CSI-RS ports of each CSI-RS resource are associated with a number of consecutive or non-consecutive rows, ^, and a number of consecutive or non-consecutive columns, ^, of the antenna port layout, wherein ^ < ^^and ^ < ^^. According to some embodiments herein, the antenna or CSI-RS ports of each CSI-RS resource are associated with a number of consecutive or non-consecutive rows, ^, and a number of consecutive columns, ^, of the antenna port layout, wherein ^ < ^^and ^ < According to some embodiments herein, the ^-th antenna or CSI-RS port of a CSI-RS ^ ^⋅^ resource is associated with the , ^ + ⋅ ^^^^ ^^^ + ^ ⋅ ^^^ ^^,^^^ ^^-th entry of the precoding vector, wherein ^ ∈ {0, … ,^^^^^^ − 1} is the CSI-RS resource index, and ^ = 0, … , 2^^ − 1 is the antenna or CSI-RS port index associated with the CSI-RS resource. According to some embodiments herein, the ^-th antenna or CSI-RS port of a CSI-RS resource is associated with the^()^ ^⋅^ +^⋅ ^^^ ^, ^ + ^^⋅ ^^^ ^^ ^, ^^ + ^^^ ⋅^ ^+ ^ ^^^^^^ ^^,^^^^-th entry of the precoding vector, wherein^^^^^ ^ ∈ {0, … , ^^ − 1} is the CSI-RS resource index, and ^ = 0, … , 2^^ − 1 is the antenna or CSI-RS port index associated with the CSI-RS resource. According to some embodiments herein, the value of ^ or the value of ^ is determined by the wireless device based on one or more configured parameters or is configured to the wireless device via higher layer signaling, or is fixed in the NR specifications and known to the wireless device. According to some embodiments herein, each CSI-RS resource is associated with a CSI-RS resource index, and wherein the ^ CSI-RS resources are mapped to the CSI-RS resource indices via a mapping or a permutation function. According to some embodiments herein, the method comprises receiving an indication of the mapping or association of the antenna or CSI-RS ports of a CSI-RS resource to the row and column indices of the antenna port layout or the entries of the precoding vector. According to some embodiments herein, the CSI-RS or antenna ports of a CSI-RS resource are segmented into multiple CSI-RS port subsets, wherein a CSI-RS port subset comprises one or more non-overlapping CSI-RS or antenna ports. According to some embodiments herein, when the number of CSI-RS port subsets is two, the antenna or CSI-RS ports of a first CSI-RS port subset of a CSI-RS resource are associated with all or a proper subset of even numbered rows / row indices and with all or a proper subset of even numbered columns / column indices of the antenna port layout and the antenna or CSI- RS ports of a second CSI-RS port subset of the CSI-RS resource are associated with all or a proper subset of odd numbered rows / row indices and with all or a proper subset of odd numbered columns / column indices of the antenna port layout. According to some embodiments herein, when the number of CSI-RS port subsets is two, the antenna or CSI-RS ports of a first CSI-RS port subset of a CSI-RS resource are associated with all or a proper subset of odd numbered rows / rows indices and with all or a proper subset of even numbered column / column indices of the antenna port layout and the antenna or CSI- RS ports of a second CSI-RS port subset of a CSI-RS resource are associated with all or a proper subset of even numbered rows / row indices and with all or a proper subset of odd numbered column / column indices of the antenna port layout. According to some embodiments herein, the antenna or CSI-RS ports of a CSI-RS resource are associated with ^ consecutive rows and all columns of the antenna port layout and the ^- th antenna or CSI-RS port of a CSI-RS resource is associated with the vector. According to some embodiments herein, the CSI-RS ports of each CSI-RS resource are associated with all rows and ^ consecutive columns of the antenna port layout and the ^-th mod^⋅ ^^^ + ^^-th entry of the precoding vector. According to some embodiments herein, the antenna or CSI-RS ports of each CSI-RS resource are associated with ^ non-consecutive rows and ^ non-consecutive columns of the antenna port layout and the ^-th antenna or CSI-RS port of a CSI-RS resource is associated mod^^,^^^^-th entry of the precoding vector, wherein ^ ∈ {0, … ,^^^^^^^ − 1} is the CSI-RS resource index, and ^ = 0, … , ^^ − 1 are the antenna or CSI-RS port indices associated with a CSI-RS resource. In order to perform the previously described process or method steps performed by the wireless device or UE, there is also provided a wireless device. Figure 12 illustrates a simplified block diagram depicting a wireless device 700. The wireless device 700 comprises a processor 710 or processing circuit or a processing module or a processor means 710; a receiver circuit or receiver module 740; a transmitter circuit or transmitter module 750; a memory module 720, a transceiver circuit or transceiver module 730 which may include the transmitter circuit 750 and the receiver circuit 740. The wireless device 700 further comprises an antenna system 760 which includes antenna circuitry for transmitting and receiving signals to / from at least the network node or other wireless device(s). The antenna system employs beamforming as previously described. The wireless device may be a UE or an IoT device. The wireless device 700 may belong to any radio access technology including 4G or LTE, LTE-A, 5G, advanced 5G or a combination thereof that support beamforming technology. The wireless device comprising the processor and the memory contains instructions executable by the processor, whereby the wireless device 700 is operative or is configured to perform any one of the embodiments related to the wireless device as previously described. The processing module / circuit 710 includes a processor, microprocessor, an application specific integrated circuit (ASIC), field programmable gate array (FPGA), or the like, and may be referred to as the “processor.” The processor 710 controls the operation of the wireless device and its components. Memory (circuit or module) 720 includes a random-access memory (RAM), a read only memory (ROM), and / or another type of memory to store data and instructions that may be used by processor 710. In general, it will be understood that the wireless device 700 in one or more embodiments includes fixed or programmed circuitry that is configured to carry out the operations in any of the embodiments disclosed herein. In at least one such example, the processor 710 includes a microprocessor, microcontroller, DSP, ASIC, FPGA, or other processing circuitry that is configured to execute computer program instructions from a computer program stored in a non-transitory computer-readable medium that is in or is accessible to the processing circuitry. Here, “non-transitory” does not necessarily mean permanent or unchanging storage, and may include storage in working or volatile memory, but the term does connote storage of at least some persistence. The execution of the program instructions specially adapts or configures the processing circuitry to carry out the operations disclosed in this disclosure relating to the wireless device. Further, it will be appreciated that the wireless device 700 may comprise additional components. The wireless device 700 by means of processor 710 executes instructions contained in the memory 720 whereby the wireless device is operative to perform any one of the previously described embodiments related to the actions performed by the wireless device, some of which are presented in appended claims. There is also provided a computer program comprising instructions which when executed by the processor 710 of the wireless device cause the processor 710 to carry out the method according to any one of the previously described embodiments. Referring to Figure 4, there is illustrated a method performed by a network node 800 according to some of the previously described embodiments. The method performed by the network node 800 is used for receiving a CSI report in a wireless communications network from a wireless device 700, the CSI report indicating a precoder matrix. Figure 5 illustrates the main method steps, which comprises: o transmitting (501), to a wireless device (700), - a configuration or an indication, wherein the configuration or the indication indicates a number of a first dimension or columns, and a number ^^of a second dimension or rows of an antenna port layout at the network node, and - a configuration or an indication, wherein the configuration or the indication indicates M Channel State Information – Reference Signal, CSI-RS, resources, wherein each CSI-RS resource comprises a number of antenna or CSI-RS ports, wherein the antenna or CSI- RS ports of each CSI-RS resource are mapped to a subset or proper subset of row and column indices of the antenna port layout; o for enabling the wireless device to: o determine entries of a precoding vector per CSI-RS resource associated with a subset or proper subset of the rows and columns of the antenna port layout, o determine a precoder matrix for RI transmission layers, wherein the precoder matrix comprises v precoding vectors, and each precoding vector has 2^^^^entries and is associated with a transmission layer, o generate a CSI report or a CSI feedback report for transmission to the network node comprising a Precoder Matrix Indicator, PMI, indicating the precoding vector or precoder matrix; and o receiving (502), from the wireless device (700) an uplink control information (UCI) including the CSI report or the CSI feedback report over an uplink, UL, channel. According to another aspect of embodiments herein, there is provided a method performed by a network node, for receiving, from a wireless device, a channel state information, CSI, report in a wireless communications network, the CSI report indicating a precoder matrix, the method comprising: o transmitting, to a wireless device - a configuration or an indication, wherein the configuration or the indication indicates a number ^^of a first dimension or columns and a number ^^of a second dimension or rows of an antenna port layout at the network node, and - a configuration or an indication, wherein the configuration or the indication indicates at least one Channel State Information – Reference Signal, CSI-RS, resources, and a number of subbands, wherein a CSI-RS resource comprises a number of antenna or CSI-RS ports and each antenna or CSI-RS port is associated with the number of subbands, wherein an antenna or CSI-RS port is mapped to a first entry of the antenna port layout using a first mapping scheme for a first set of subbands, and to a second entry of the antenna port layout using a second mapping scheme for a second set of subbands, for enabling the wireless device to: ^ determine entries of a precoding vector or precoder matrix associated with the antenna or CSI-RS ports, ^ generate a CSI report or a CSI feedback report for transmission to the network node comprising a Precoder Matrix Indicator, PMI, indicating the precoding vector or precoder matrix; and receiving, from the wireless device uplink control information (UCI) including the CSI report or the CSI feedback report over an uplink, UL, channel. To perform the previously described process or method steps performed by the network node there is also provided a network node. Figure 13 illustrates a block diagram depicting a network node 800. The network node 800 comprises a processor 810 or processing circuit or a processing module or a processor means 810; a receiver circuit or receiver module 840; a transmitter circuit or transmitter module 850; a memory module 820, a transceiver circuit or transceiver module 830 which may include the transmitter circuit 850 and the receiver circuit 840. The network node 800 further comprises an antenna system 860 which includes antenna circuitry for transmitting and receiving signals to / from at least the wireless device. The antenna system employs beamforming as previously described. The network node 800 may belong to any radio access technology including 4G or LTE, LTE- A, 5G, advanced 5G or a combination thereof that support beamforming technology. The network node may be a gNB. The network device comprising the processor and the memory contains instructions executable by the processor, whereby the network node 800 is operative or is configured to perform any one of the embodiments related to the network node 800 as previously described. The processing module / circuit 810 includes a processor, microprocessor, an application specific integrated circuit (ASIC), field programmable gate array (FPGA), or the like, and may be referred to as the “processor.” The processor 810 controls the operation of the network node and its components. Memory (circuit or module) 820 includes a random-access memory (RAM), a read only memory (ROM), and / or another type of memory to store data and instructions that may be used by processor 810. In general, it will be understood that the network node in one or more embodiments includes fixed or programmed circuitry that is configured to carry out the operations in any of the embodiments disclosed herein. In at least one such example, the processor 810 includes a microprocessor, microcontroller, DSP, ASIC, FPGA, or other processing circuitry that is configured to execute computer program instructions from a computer program stored in a non-transitory computer-readable medium that is in or is accessible to the processing circuitry. Here, “non-transitory” does not necessarily mean permanent or unchanging storage, and may include storage in working or volatile memory, but the term does connote storage of at least some persistence. The execution of the program instructions specially adapts or configures the processing circuitry to carry out the operations disclosed in this disclosure relating to the wireless device. Further, it will be appreciated that the wireless device 800 may comprise additional components. The network node 800 may also be viewed as a Transmitter and Receiver Point (TRP). The network node 800 by means of processor 810 executes instructions contained in the memory 820 whereby the network node 800 is operative to perform any one of the previously described embodiments related to the actions performed by the network node, some of which are presented in appended claim 20. There is also provided a computer program comprising instructions which when executed by the processor 810 of the network node cause the processor 810 to carry out the method according to any one of claim 20. Several advantages of the described embodiments in this disclosure are achieved as previously described and which include significantly reducing the computational complexity at the wireless device for CSI measurements of codebook-based CSI reporting when the number of configured antenna or CSI-RS ports is high at the wireless device. Reference throughout this specification to “an example” or “exemplary” means that a particular feature, structure, or characteristic described in connection with the example is included in at least one embodiment of the present technology. Thus, appearances of the phrases “in an example” or the word “exemplary” in various places throughout this specification are not necessarily all referring to the same embodiment. Throughout this disclosure, the word "comprise" or “comprising” has been used in a non- limiting sense, i.e. meaning "consist at least of". Although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. The embodiments herein may be applied in any wireless systems including LTE or 4G, LTE- A (or LTE-Advanced), 5G, advanced 5G, WiMAX, WiFi, satellite communications, TV 5 broadcasting etc.

Claims

CLAIMS 1. A method performed by a wireless device (700), the method comprising: - receiving (401A) from a network node (800) - a configuration or an indication, wherein the configuration or the indication indicates a numberof a first dimension or columns, and a number ^^of a second dimension or rows of an antenna port layout at the network node, and - a configuration or an indication, wherein the configuration or the indication indicates M Channel State Information – Reference Signal, CSI-RS, resources, wherein each CSI-RS resource comprises a number of antenna or CSI-RS ports, wherein the antenna or CSI-RS ports of each CSI-RS resource are mapped to a subset or proper subset of row and column indices of the antenna port layout; - determining (402A) entries of a precoding vector per CSI-RS resource associated with a subset or proper subset of the rows and columns of the antenna port layout; - generating (403A) a CSI report or a CSI feedback report comprising a Precoder Matrix Indicator, PMI, indicating the precoding vector; and - reporting (404A), to the network node (800), the CSI report or the CSI feedback report.

2. The method of claim 1, wherein a CSI-RS resource is received in a set of symbols that does not overlap or intersect with the set of symbols in which any of the other ^ CSI- RS resources are received.

3. The method of claim 1 or 2, wherein the wireless device is configured with P antenna or CSI-RS ports, and each CSI-RS resource is associated with the P antenna or CSI- RS ports, or a subset or proper subset of the P antenna or CSI-RS ports.

4. The method of claim 1, wherein the antenna or CSI-RS ports of each CSI-RS resource are associated with a number of consecutive rows, ^, and all columns of the antenna port layout, and wherein ^ ≥ 1.

5. The method of claim 4, wherein ^^^ CSI-RS ports associated with a first polarization are mapped to the ^ rows and ^^columns of the antenna port layout and ^^^ CSI-RSports associated with a second polarization are mapped to the same ^ rows and ^^columns of the antenna port layout.

6. The method of claim 4 or 5, wherein^ and 2^^^ are the number of CSI-RS resources and the number of CSI-RS ports associated with a CSI-RS resource, respectively.

7. The method of claim 4, wherein the antenna or CSI-RS ports of a CSI-RS resource are associated with ^ consecutive rows and all columns of the antenna port layout, and the ^-th antenna or CSI-RS port of a CSI-RS resource is associated with the ^ ^ mod(^, R)+ ^^^ ^ ^ +⋅ ^^^^+ mod ^^,^^^ ^ ⋅ ^^-th entry of the precoding vector, wherein ^ ∈ {0, … ,^^^^ − 1} is the CSI-RS resource index, and ^ = 0, … , ^^^ − 1 is the antenna or CSI-RS port index associated with a CSI-RS resource.

8. The method of claim 1, wherein the CSI-RS or antenna ports of a CSI-RS resource are segmented into multiple CSI-RS port subsets, wherein a CSI-RS port subset comprises one or more non-overlapping CSI-RS or antenna ports.

9. The method of claim 8, wherein when the number of CSI-RS port subsets is two, the antenna or CSI-RS ports of a first CSI-RS port subset of a CSI-RS resource are associated with all or a subset of even numbered rows / row indices and with all or a subset of even numbered columns / column indices of the antenna port layout, and the antenna or CSI-RS ports of a second CSI-RS port subset of the CSI-RS resource are associated with all or a subset of odd numbered rows / row indices and with all or a subset of odd numbered columns / column indices of the antenna port layout.

10. The method of claim 8, wherein when the number of CSI-RS port subsets is two, the antenna or CSI-RS ports of a first CSI-RS port subset of a CSI-RS resource are associated with all or a subset of odd numbered rows / rows indices and with all or a subset of even numbered column / column indices of the antenna port layout, and the antenna or CSI-RS ports of a second CSI-RS port subset of a CSI-RS resource are associated with all or a subset of even numbered rows / row indices and with all or a subset of odd numbered column / column indices of the antenna port layout.

11. The method of claim 1, wherein the antenna or CSI-RS ports of each CSI-RS resource are associated with a number of consecutive columns, ^, and all rows of the antenna port layout, and wherein ^ ≥ 1.

12. The method of claim 11, wherein ^^^ CSI-RS ports associated with a first polarization are mapped to the ^^rows and ^ columns of the antenna port layout and ^^^ CSI-RS ports associated with the second polarization are mapped to the same ^^rows and ^ columns of the antenna port layout.

13. The method of claim 11 or 12, wherein ^^ / ^ and 2^^^ are the number of CSI-RS resources and the number of CSI-RS ports associated with a CSI-RS resource, respectively.

14. The method of claim 11, wherein the antenna or CSI-RS ports of each CSI-RS resource are associated with all rows and ^ consecutive columns of the antenna port layout and the ^-th antenna or CSI-RS port of a CSI-RS resource is associated with thevector, wherein ^ ∈ {0, … , − 1} is the CSI-RS resource index, and ^ = 0, … , ^^^ − 1 is the antenna or CSI-RS port index associated with a CSI-RS resource.

15. The method of claim 1, wherein the antenna or CSI-RS ports of each CSI-RS resource are associated with a number of consecutive or non-consecutive rows, ^, and a number of consecutive or non-consecutive columns, ^, of the antenna port layout, wherein ^ < ^^and ^ < ^^.

16. The method of claim 15, wherein the antenna or CSI-RS ports of each CSI-RS resource are associated with ^ non-consecutive rows and ^ non-consecutive columns of the antenna port layout and the ^-th port of a CSI-RS resource is associated with ^mod ^^,^^ ^ ^-th entry of the precoding vector, wherein ^ ∈ {0, … ,^^^^^^^ − 1} is the CSI-RS resource index, and ^ = 0, … , ^^ − 1 is the antenna or CSI-RS port index associated with a CSI-RS resource.

17. The method of claim 4, wherein the ^-th antenna or CSI-RS port of the CSI-RS resource is associated with the ^ ^ ^^ ^^⋅^^^^^^+ ^ ⋅ ^ + ^^^(^, ^)+ ^^⋅ ^^^ ^^^^, ^^^^-th entry of the precoding vector, wherein ^ ∈ {0, … ,− 1} is the CSI-RS resource index, and ^ = 0, … , 2^^^ − 1 is the antenna or CSI-RS port index associated with the CSI-RS resource.

18. The method of claim 11, wherein the ^-th antenna or CSI-RS port of a CSI-RS resource is associated with the entry of the precoding… ,− and ^ = 0, … , 2^^^ − 1 is the antenna or CSI-RS port index associated with the CSI- RS resource.

19. The method of claim 15, wherein the ^-th antenna or CSI-RS port of a CSI-RS resource is associated with the^^^^^,^^^^^-th entry of the precoding vector, wherein ^ ∈ {0, … ,− 1} is the CSI- RS resource index, and ^ = 0, … , 2^^ − 1 is the antenna or CSI-RS port index associated with the CSI-RS resource.

20. The method of claim 15, wherein the ^-th antenna or CSI-RS port of a CSI-RS resource is associated with the^^^^^^^^^^-th entry of the precoding vector, wherein ^ ∈ {0, … ,− 1} is the CSI- RS resource index, and ^ = 0, … , 2^^ − 1 is the antenna or CSI-RS port index associated with the CSI-RS resource.

21. The method of any preceding claim, wherein the value of ^ or the value of ^ is determined by the wireless device based on one or more configured parameters, or is configured to the wireless device via higher layer signaling, or is fixed in the NR specifications and known to the wireless device.

22. The method of preceding claims, wherein each CSI-RS resource is associated with a CSI-RS resource index, and wherein the ^ CSI-RS resources are mapped to the CSI- RS resource indices via a mapping or a permutation function.

23. The method of claim 1, wherein the method further comprises receiving an indication of a mapping or association of the antenna or CSI-RS ports of a CSI-RS resource to the row and column indices of the antenna port layout or the entries of the precoding vector.

24. The method of claim 1, wherein a mapping of the CSI-RS ports of the ^ CSI-RS resources to the ^^columns and ^^rows of the antenna port layout is indicated by the network node.

25. A method performed by a network node (800) for receiving, from a wireless device (700), a channel state information, CSI, report in a wireless communications network, the CSI report indicating a precoder matrix, the method comprising: o transmitting (501), to the wireless device (700), a configuration or an indication indicating a number ^^of a first dimension or columns and a number ^^of a second dimension or rows of an antenna port layout at the network node, and a configuration or an indication indicating M Channel State Information – Reference Signal, CSI-RS, resources, wherein each CSI-RS resource comprises a number of antenna or CSI-RS ports, wherein the antenna or CSI-RS ports of each CSI-RS resource are mapped to a subset or proper subset of row and column indices of the antenna port layout; for enabling the wireless device to: ^ determine entries of a precoding vector per CSI-RS resource associated with a subset or proper subset of the rows and columns of the antenna port layout, ^ determine a precoder matrix for RI transmission layers, wherein the precoder matrix comprises v precoding vectors, and each precoding vector has 2^^^^entries and is associated with a transmission layer, ^ generate a CSI report or a CSI feedback report for transmission to the network node comprising a Precoder Matrix Indicator, PMI, indicating the precoding vector or precoder matrix; and o receiving (502), from the wireless device (700) an uplink control information (UCI) including the CSI report over an uplink, UL, channel.

26. A network node (800) comprising a processor (810) and a memory (820) containing instructions executable by said processor (810), whereby the network node (800) is operative to perform the method according to claim 25.

27. A wireless device, (700) comprising a processor (710) and a memory (720) containing instructions executable by said processor (710), whereby the wireless device (700) is operative to perform the method according to any of claims 1-24.

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