CN116325599A

CN116325599A - Port selection codebook enhancement by partial channel reciprocity

Info

Publication number: CN116325599A
Application number: CN202080105243.5A
Authority: CN
Inventors: F·托萨托; 刘皓; R·阿赫麦德·萨勒姆; S·E·哈伊里
Original assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy
Current assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy
Priority date: 2020-08-07
Filing date: 2020-08-07
Publication date: 2023-06-23
Also published as: WO2022027646A1

Abstract

Embodiments of the present disclosure relate to devices, methods, apparatuses, and computer-readable storage media for port selection codebook enhancement through partial channel reciprocity. The method includes determining, at a first device, a set of beams and frequency domain components associated with a channel state information-reference signal, CSI-RS, to be transmitted from the first device to a second device; generating an indication of a mapping between at least one port selected for transmitting CSI-RS at the first device and the frequency domain component and the set of beams; and transmitting the CSI-RS including the indication to the second device. In this way, the gNB can indicate on which FD components the PMI calculation should be limited, so that PMI feedback overhead in UL can be reduced without increasing overhead cost in DL.

Description

Port selection codebook enhancement by partial channel reciprocity

Technical Field

Embodiments of the present disclosure relate generally to the field of telecommunications and, in particular, relate to an apparatus, method, device, and computer readable storage medium for port selection codebook enhancement by partial channel reciprocity.

Background

It has been approved that Multiple Input Multiple Output (MIMO) Channel State Information (CSI) feedback can be further enhanced by exploiting some channel statistics such as angle(s) and delay(s) partial uplink/downlink (UL/DL) reciprocity, mainly for FR1 (450 MHz-6000 MHz) Frequency Division Duplex (FDD) deployments.

For CSI measurements and reporting, type II Port Selection (PS) codebook enhancements may be evaluated or specified. The network device (gNodeB, gNB) may estimate information related to angle(s) and delay(s) based on Sounding Reference Signals (SRS) by exploiting the angle and delayed DL/UL reciprocity, and the remaining DL CSI is reported by terminal devices (user equipment, UEs) to achieve a better tradeoff between UE complexity, performance, and reporting overhead.

Disclosure of Invention

In general, example embodiments of the present disclosure provide a solution for port selection codebook enhancement.

In a first aspect, a first device is provided. The first device includes at least one processor; at least one memory including computer program code; the at least one memory and the computer program code are configured to, with the at least one processor, cause the first device at least to: determining a set of beams and frequency domain components associated with a channel state information reference signal (CSI-RS) to be transmitted from a first device to a second device; generating an indication of a mapping between at least one port selected for transmitting CSI-RS at the first device and the frequency domain component and the set of beams; and transmitting the CSI-RS including the indication to the second device.

In a second aspect, a second device is provided. The second device includes at least one processor; at least one memory including computer program code; the at least one memory and the computer program code are configured to, with the at least one processor, cause the second device to at least: receiving a CSI-RS from a first device; obtaining an indication of a mapping between at least one port selected for transmitting CSI-RS at a first device and a set of beams and frequency domain components associated with the CSI-RS; and generating a CSI report based on the indication.

In a third aspect, a method is provided. The method includes determining, at a first device, a set of beams and frequency domain components associated with CSI-RS to be transmitted from the first device to a second device; generating an indication of a mapping between at least one port selected for transmitting CSI-RS at the first device and the frequency domain component and the set of beams; and transmitting the CSI-RS including the indication to the second device.

In a fourth aspect, a method is provided. The method includes receiving, at a second device, a CSI-RS from a first device; obtaining an indication of a mapping between at least one port selected for transmitting CSI-RS at a first device and a set of beams and frequency domain components associated with the CSI-RS; and generating a CSI report based on the indication.

In a fifth aspect, an apparatus is provided that includes means for determining, at a first device, a set of beams and frequency domain components associated with a CSI-RS to be transmitted from the first device to a second device; means for generating an indication of a mapping between at least one port selected for transmitting CSI-RS and frequency domain components and a set of beams at a first device; and means for transmitting the CSI-RS including the indication to the second device.

In a sixth aspect, an apparatus is provided that includes means for receiving a CSI-RS from a first device; means for obtaining an indication of a mapping between at least one port selected for transmitting CSI-RS at a first device and a set of beams and frequency domain components associated with the CSI-RS; and means for generating a CSI report based on the indication.

In a seventh aspect, there is provided a computer readable medium having stored thereon a computer program which, when executed by at least one processor of a device, causes the device to perform the method according to the third aspect.

In an eighth aspect, there is provided a computer readable medium having stored thereon a computer program which, when executed by at least one processor of a device, causes the device to perform the method according to the fourth aspect.

Other features and advantages of embodiments of the present disclosure will be apparent from the following description of the particular embodiments, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the embodiments of the disclosure.

Drawings

The embodiments of the present disclosure are set forth in an illustrative sense, and the advantages thereof will be explained in more detail below with reference to the drawings, in which

FIG. 1 illustrates an example environment in which example embodiments of the present disclosure may be implemented;

fig. 2 shows a signaling diagram illustrating a port selection codebook enhancement procedure according to some example embodiments of the present disclosure;

fig. 3 illustrates an example of CSI-RS ports and port selection mechanisms for beamforming of a type II PS codebook according to some example embodiments of the present disclosure;

fig. 4 illustrates a compression operation performed by a UE in calculating an type II Precoding Matrix Indicator (PMI) according to some example embodiments of the disclosure;

FIG. 5 illustrates an example of a reciprocity enhanced eType II PS codebook according to some example embodiments of the disclosure;

fig. 6 illustrates an example of mapping beams and FD components to beamformed CSI-RS ports according to some example embodiments of the present disclosure;

Fig. 7 illustrates an example of mapping beams and FD components to beamformed CSI-RS ports according to some example embodiments of the present disclosure;

fig. 8 illustrates an example of mapping beams and FD components to beamformed CSI-RS ports according to some example embodiments of the present disclosure;

FIG. 9 illustrates a flowchart of an example method of port selection codebook enhancement according to some example embodiments of the present disclosure;

FIG. 10 illustrates a flowchart of an example method of port selection codebook enhancement according to some example embodiments of the present disclosure;

FIG. 11 illustrates a simplified block diagram of a device suitable for implementing exemplary embodiments of the present disclosure; and

fig. 12 illustrates a block diagram of an example computer-readable medium, according to some embodiments of the disclosure.

The same or similar reference numbers will be used throughout the drawings to refer to the same or like elements.

Detailed Description

Principles of the present disclosure will now be described with reference to some example embodiments. It should be understood that these embodiments are described merely for the purpose of illustrating and helping those skilled in the art understand and practice the present disclosure and are not meant to limit the scope of the present disclosure in any way. The disclosure described herein may be implemented in various other ways besides those described below.

In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

In this disclosure, references to "one embodiment," "an example embodiment," etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with an example embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

It will be understood that, although the terms "first" and "second," etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish between functions of the various elements. As used herein, the term "and/or" includes any and all combinations of one or more of the listed terms.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "has," "including," "includes" and/or "including" when used herein, specify the presence of stated features, elements, components, and/or groups thereof, but do not preclude the presence or addition of one or more other features, elements, components, and/or groups thereof.

As used in this application, the term "circuitry" may refer to one or more or all of the following:

(a) Pure hardware circuit implementations (such as implementations using only analog and/or digital circuitry), and

(b) A combination of hardware circuitry and software, such as (as applicable):

(i) Combination of analog and/or digital hardware circuit(s) and software/firmware, and

(ii) Any portion of the hardware processor(s) with software, including the digital signal processor(s), software, and memory(s), work together to cause a device, such as a mobile phone or server, to perform various functions, and

(c) Hardware circuit(s) and/or processor(s), such as microprocessor(s) or a portion of microprocessor(s), that require software (e.g., firmware)

The operation is performed, but software may not exist when the operation is not required.

The definition of circuitry is applicable to all uses of that term in this application, including in any claims. As another example, as used in this application, the term circuitry also encompasses hardware-only circuitry or a processor (or multiple processors) or an implementation of a hardware circuit or portion of a processor and its (or their) accompanying software and/or firmware. For example, if applicable to the particular claim elements, the term circuitry also encompasses a baseband integrated circuit or processor integrated circuit for a mobile device, or a similar integrated circuit in a server, a cellular network device, or other computing or network device.

As used herein, the term "communication network" refers to a network that conforms to any suitable communication standard, such as a fifth generation (5G) system, long Term Evolution (LTE), LTE-advanced (LTE-a), wideband Code Division Multiple Access (WCDMA), high Speed Packet Access (HSPA), narrowband internet of things (NB-IoT), and so forth. Furthermore, the communication between the terminal device and the network device in the communication network may be performed according to any suitable generation communication protocol, including, but not limited to, first generation (1G), second generation (2G), 2.5G, 2.75G, third generation (3G), fourth generation (4G), 4.5G, future fifth generation (5G) New Radio (NR) communication protocols, and/or any other protocol currently known or to be developed in the future. Embodiments of the present disclosure may be applied to various communication systems. In view of the rapid development of communications, there are, of course, future types of communication techniques and systems that can embody the present disclosure. The scope of the present disclosure should not be limited to only the above-described systems.

As used herein, the term "network device" refers to a node in a communication network via which a terminal device accesses the network and receives services from the network. A network device may refer to a Base Station (BS) or an Access Point (AP), e.g., a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), a NR next generation NodeB (gNB), a Remote Radio Unit (RRU), a Radio Header (RH), a Remote Radio Head (RRH), a relay, a low power node (such as femto, pico), etc., depending on the terminology and technology applied. The RAN split architecture includes a gNB-CU (centralized unit that hosts RRC, SDAP, and PDCP) that controls multiple gNB-DUs (distributed units that host RLC, MAC, and PHY). The relay node may correspond to the DU portion of the IAB node.

The term "terminal device" refers to any terminal device capable of wireless communication. By way of example, and not limitation, a terminal device may also be referred to as a communication device, user Equipment (UE), subscriber Station (SS), portable subscriber station, mobile Station (MS), or Access Terminal (AT). The terminal devices may include, but are not limited to, mobile phones, cellular phones, smart phones, voice over IP (VoIP) phones, wireless local loop phones, tablets, wearable terminal devices, personal Digital Assistants (PDAs), portable computers, desktop computers, image capture terminal devices (such as digital cameras), gaming terminal devices, music storage and playback devices, in-vehicle wireless terminal devices, wireless endpoints, mobile stations, laptop embedded devices (LEEs), laptop in-vehicle devices (LMEs), USB dongles, smart devices, wireless customer premise devices (CPE), internet of things (IoT) devices, watches or other wearable devices, head Mounted Displays (HMDs), vehicles, drones, medical devices and applications (e.g., tele-surgery), industrial devices and applications (e.g., robots and/or other wireless devices operating in the context of industrial and/or automated processing chains), consumer electronic devices, devices operating on commercial and/or industrial wireless networks, and the like. The terminal device may also correspond to a Mobile Termination (MT) portion of an Integrated Access and Backhaul (IAB) node (also referred to as a relay node). In the following description, the terms "terminal device", "communication device", "terminal", "user equipment" and "UE" may be used interchangeably.

While in various example embodiments, the functionality described herein may be performed in a fixed and/or wireless network node, in other example embodiments, the functionality may be implemented in a user equipment device (such as a cell phone or tablet or laptop or desktop or mobile IoT device or fixed IoT device). For example, the user equipment device may be suitably equipped with corresponding capabilities as described in connection with the fixed and/or wireless network node(s). The user equipment device may be a user equipment and/or a control device, such as a chipset or a processor, configured to control the user equipment when installed in the user equipment. Examples of such functions include a bootstrapping server function and/or a home subscriber server, which may be implemented in a user equipment device by providing the user equipment device with software configured to cause the user equipment device to perform from the perspective of these functions/nodes.

Fig. 1 illustrates an example communication network 100 in which embodiments of the present disclosure may be implemented. As shown in fig. 1, the communication network 100 includes a network device 110 (hereinafter also referred to as a first device 110 or a gNB 110) and a terminal device 120 (hereinafter also referred to as a second device 120 or a UE 120). Terminal device 120 may communicate with network device 110. It should be understood that the number of network devices and terminal devices shown in fig. 1 is given for illustrative purposes and is not meant to be limiting. Communication network 100 may include any suitable number of network devices and terminal devices.

Depending on the communication technology, network 100 may be a Code Division Multiple Access (CDMA) network, a Time Division Multiple Access (TDMA) network, a Frequency Division Multiple Access (FDMA) network, an Orthogonal Frequency Division Multiple Access (OFDMA) network, a single carrier frequency division multiple access (SC-FDMA) network, or any other network. The communications discussed in network 100 may conform to any suitable standard including, but not limited to, new radio access (NR), long Term Evolution (LTE), LTE evolution, LTE-advanced (LTE-a), wideband Code Division Multiple Access (WCDMA), code Division Multiple Access (CDMA), CDMA2000, global system for mobile communications (GSM), and the like. Further, these communications may be performed in accordance with any generation communication protocol currently known or to be developed in the future. Examples of communication protocols include, but are not limited to, first generation (1G), second generation (2G), 2.5G, 2.75G, third generation (3G), fourth generation (4G), 4.5G, fifth generation (5G) communication protocols. The techniques described herein may be used for the wireless networks and radio technologies described above as well as other wireless networks and radio technologies. For clarity, certain aspects of the technology are described below for LTE, and LTE terminology is used in much of the description below.

As described above, it has been approved that MIMO CSI feedback can be further enhanced by exploiting some UL/DL reciprocity of channel statistics such as angle(s) and delay(s), mainly for FR1 FDD deployment.

For CSI measurements and reporting, type II PS codebook enhancement may be evaluated or specified. The gNB may estimate information related to angle(s) and delay(s) based on SRS by exploiting DL/UL reciprocity of angle and delay, and the remaining DL CSI is reported by the UE to achieve a better tradeoff between UE complexity, performance, and reporting overhead.

It is assumed that channel reciprocity in FDD systems is only applicable to certain wideband/long-term statistics shared by UL and DL channels if the duplex distance is relatively small compared to the carrier frequency, and that frequency conversion techniques can be used to improve the accuracy of DL channel parameters based on UL channel measurements if the FDD duplex distance is greater than the carrier frequency. There are two types of partial channel reciprocity, spatial reciprocity and path delay reciprocity.

Regarding spatial reciprocity, assuming that the gNB may perform UL channel measurements on SRS received from the UE, based on the measurements, the gNB may estimate an Angular Power Spectrum (APS) or a dominant eigenvector of the UL channel.

Regarding path delay reciprocity, the gNB may also estimate the PDP of the UL channel from the SRS. The delay profile may be averaged over all SRS ports of the UE and may be calculated separately for each spatial beam associated with the UE. The propagation conditions (i.e., delay statistics) of the channel are assumed to be similar for all SRS ports and all beams associated with the angular sector of the discovery UE. In this case, the same cluster of channel multipaths is responsible for the primary path delays of the UEs for each primary beam. There is a physical correspondence between the primary path delay of the PDP measured on the UL channel and the primary Frequency Domain (FD) component measured on the DL channel.

However, no mechanism in the type II PS codebook may allow the gNB to exploit knowledge of the primary delay/FD component obtained from SRS measurements.

Accordingly, the present disclosure proposes a solution for port selection codebook enhancement. In this solution, the gNB may determine an indication of a mapping between at least one port for transmitting the CSI-RS and a frequency domain component associated with the CSI-RS and a set of beams, and transmit the CSI-RS including the indication to the second device. In this way, the gNB can indicate on which FD components the PMI calculation should be limited, so that PMI feedback overhead in UL can be reduced without increasing overhead cost in DL.

The principles and implementations of the present disclosure will be described in detail below with reference to fig. 2, which shows a signaling diagram illustrating a port selection codebook enhancement procedure according to some example embodiments of the present disclosure. For discussion purposes, process 200 will be described with reference to FIG. 1. Process 200 may involve UE 120 and gNB 110 shown in fig. 1.

As shown in fig. 2, UE 120 may send (202) an SRS to gNB 110. Based on UL channel measurements on SRS received from UE 120, gNB 110 may estimate a set of beams and FD components associated with the transmission of CSI-RS from gNB 110 to UE 120.

One aspect of the invention relates to how the gNB 110 dynamically indicates the selected beam and FD components to the UE in the CSI-RS signal. Before explaining a process of generating an indication associated with the selected beam and FD component, an example of CSI-RS ports and port selection mechanism for beamforming of a type II PS codebook will be described below with reference to fig. 3.

Fig. 3 illustrates an example of CSI-RS ports and port selection mechanisms for beamforming of a type II PS codebook according to some example embodiments of the present disclosure. Antenna array 310 has a 4 x 1 x 2 configuration in which 4 panels 311-314 are split to form 4 cross-polarized azimuth beams 321-324, each beam associated with 2 CSI-RS ports (where beam 321 is associated with ports 0 and 4, beam 322 is associated with ports 1 and 5, beam 323 is associated with ports 2 and 6, and beam 324 is associated with ports 3 and 7), for a total of P _CSI-RS =8 CSI-RS ports.

Mapping between transmit beams and ports is such that ports P and p+l (where p=0, … …, P _CSI-RS -1) representing two polarizations of the same beam. The transmit beams are designed to provide maximum gain in different azimuth directions of the cell sector. Radio Resource Control (RRC) parameters for CSI reporting settings include the number of beams L and for port selection Parameter d (where 1.ltoreq.d.ltoreq.L), which determines the port sampling step size, i.e., the set of beam patterns that the UE can select. In this example, in the case of the parameter l=d=2, the UE selects

ports

0 and 1, so the spatial component of PMI is given by:

wherein->

Beam selection is polarization common and layer common because the UE indicates a set of L beams for both polarizations and all reported layers. The UE may indicate up to 4 different layers using the type II PS codebook.

Then, for each layer l=1, … …, v, where v is the reported rank, the UE calculates a Linear Combining Coefficient (LCC) for combining N ₃ The selected ports in each of the subbands are selected to best approximate the first strongest channel eigenvector.

Fig. 4 illustrates an example of a compression operation performed by a UE when calculating an type II PMI according to some example embodiments of the disclosure. For each layer l, a DFT transform is applied to N of each selected port ₃ A (subband 410) LCC, selecting M in the transformed domain _ν A main FD component 420, where M _ν Is an RRC configuration parameter and selects a subset 430 of transformed LLC from the reduced size combining matrix for feedback. A maximum of K may be reported for each layer ₀ A non-zero coefficient, the total maximum value of all layers is K ^TOT ≤2K ₀ . In this example, N ₃ ＝13，M _ν =5. The selected main FD component forms a matrix W _f (l) While non-zero linear combination coefficients (NZC) 431-435 form a matrix

Thus, the precoder vector indicated by the eType II PS PMI for layer i is represented by:

different from W ₁ Is layer-specific, both FD-base and NZC-selection. Thus, and calculate and signal W _f (l) And

the associated overhead and complexity is much greater than W ₁ The overhead and complexity required.

The expected CSI enhancement may be achieved by UL/DL partial reciprocity to further optimize port selection PMI. As described above, in reciprocity-assisted CSI reporting, the gNB 110 may estimate the primary wideband beam and FD component from UL channel measurements on SRS received from the UE 120.

If beam selection is made at the gNB 110, the gNB 110 need not expose the UE 120 to more CSI-RS ports than are associated with the selected beam. Thus, after the strongest L2-port beams are selected for UE 120, these 2L ports are mapped into CSI-RS resources configured for that UE 120.

In general, the amount estimated by the gNB 110 from SRS is layer-common in the sense that the gNB 110 may not have full visibility of the spatial layers that the DL channel may support if, for example, SRS ports are less than or different from those used by the receiver of the UE 120. In addition, UE 120 may also have typically different transmitter and receiver antenna elements. This is not a limitation on port selection at the gNB, since port selection is also layer-common when performed on the UE side.

However, when estimating the primary DL FD component from SRS, the gNB 110 may estimate these quantities for each port, but it may not associate the primary FD component of the port with a particular layer. In fact, the layers calculated by UE 120 may generally be represented as a linear combination of ports, and this layer-specific information may be estimated by UE 120 from DL channel measurements.

When gNB exploits partial UL-DL channel reciprocity, it is possible toBeam selection and FD component selection are performed by the gNB by using SRS measurements. Typically, for each selected beam, the gNB determines a set of primary FD components. These components correspond to

The position of the non-zero coefficient (NZC). However, since the gNB has no visibility of layers, the location of the NZC cannot be assigned to a particular layer.

Fig. 5 illustrates an example of a reciprocity enhanced type II PS codebook according to some example embodiments of the present disclosure. As shown in fig. 5, at the mark

Squares 511-520 marked with darker colors in grid 510 of (c) indicate the location of these FD components of each beam. Let αK ₀ Is the total number of these components. In this example, there is αK ₀ =10 identified FD components, 2 for beam i=0, 1 for beam i=1, 3 for beam i=2, 4 for beam i=3. The parameter α is predetermined by some RRC configurations. For example, for rank restriction, α may be set to 1, allowing only the reported rank v=1; α=2 represents an unrestricted rank indicator.

Selected beamforming spatial domain basis W ₁ Which is broadband and layer-common, while the selected FD component for port i is determined by the quantity W _f (i) Indicated, where i=0, … …, 2L-1. Note that W _f (i) Is insufficient to form a layer-specific FD group W _f (l) (where l=1, … …, v) because, in general, gNB is not aware of W _f (i) To which layers the components of (c) should be mapped.

Thus, referring again to fig. 2, the gnb 110 may determine 204 how to dynamically indicate the selected beam and FD component to the UE 120 in the CSI-RS signal. That is, the gNB is to determine an indication of the mapping between at least one CSI-RS port and the selected beam and FD component.

In some example embodiments, the gNB 110 may convert αK ₀ Each of the identified components is mapped into a separate CSI-RS port, and the UE maps to each endThe port calculates a single linear combination coefficient. In this case, a greater number of UE-specific beamforming CSI-RS ports than the number of selected beams may be required, as typically αk ₀ >2L。

In this case, the gNB 110 may determine the number of selected beam sets and the corresponding cyclic shift of FD components corresponding to the beam sets. Based on the determined number of selected beam sets and the respective cyclic shifts of FD components, the gNB 110 may determine an association between frequency domain components and at least one port, wherein each of the frequency domain components is mapped to a respective one of the at least one CSI-RS ports.

In this case where each component is mapped into a separate CSI-RS port, the CSI-RS of at least one CSI-RS port is beamformed by the beamforming weights calculated by the gNB, and a cyclic shift is applied to the time domain sequence (corresponding to a phase ramp in the frequency domain) so that the UE can calculate the corresponding linear combining coefficient as FD component 0. In this case, the UE does not perform any DFT-based frequency compression, because FD component 0 is calculated by a simple sum of CSI-RS samples for a given port.

In the example where the gNB selects 2l=4 beams and m=5 FD components with indices f=0, 1, 2, 11, 12, the 2 CSI-RS ports are beamformed with weights associated with beam i=0. The CSI-RS for the first CSI-RS port is not applied with cyclic shift, while the signal for the second CSI-RS is shifted 12 because its second FD component is at a position of N ₃ The last of the set of=13.

Fig. 6 illustrates an example of mapping beams and FD components to beamformed CSI-RS ports according to some example embodiments of the present disclosure. As shown in fig. 6, 2 CSI-RS ports 621-622 are beamformed with shifts 0 and 12 by beam i=0, 1 CSI-RS port 623 is beamformed without being applied with a shift by beam i=1, 3 CSI-RS ports 624-626 are beamformed with shifts 0, 11 and 12 by beam i=2, and 4 CSI-RS ports 627-630 are beamformed with

shifts

0, 1, 2 and 12 by beam i=3, respectively. That is,

FD components

611 and 612 are mapped to CSI-

RS ports

621 and 622, respectively. FD component 613 is mapped to CSI-RS port 623.FD components 614-616 are mapped to CSI-RS ports 624-626, respectively. FD components 617-620 are mapped to CSI-RS ports 627-630, respectively.

In this case, αK ₀ It is also possible that =2lm, that is, for all beams selected, all FD components are mapped.

In some example embodiments, FD component selection may be transmitted through CSI-RS signals by using a form of sequence selection. In this case, two different CSI-RS sequences may be introduced for a subband, such that the gNB may use one CSI-RS sequence or the other CSI-RS sequence depending on whether the FD component associated with the subband is selected for the CSI-RS port.

For example, the gNB 110 may select at least one CSI-RS port and determine a respective subband associated with the at least one CSI-RS port. The gNB 110 may then determine an association between the FD component and the corresponding subband.

To generate an indication of the mapping between at least one CSI-RS port and the selected beam and FD component, the gNB 110 may obtain a reference sequence associated with the CSI-RS, which may be given as follows:

where r (m) is the QPSK reference signal sequence, quantities k ', l', w _f (k') and w _t (k') is given in the table.

The gNB 110 may then determine a cyclic shift for the reference sequence. A single cyclic shift of the CSI-RS sequence used in a sub-band or a predefined subset of Physical Resource Blocks (PRBs) of the sub-band may be used, which may be represented as a function

Based on the reference sequence and the cyclic shift, the gNB 110 may determine a target sequence associated with the CSI-RS. For example, the target sequence may be represented by the function +.>

Multiplied by a reference sequence, which can be expressed as follows:

wherein is associated with the sub-band

PRB->

Corresponding sequence->

Is applied to all resource elements (k, l) mapped to CSI-RS port p in the PRB.

As a special case of this embodiment, the gNB 110 may use the same sequence for all ports,

this corresponds to the case where the active FD component is the same for all ports. Function->

Can be defined as follows:

wherein the method comprises the steps of

……、N ₃ -1 is a subband index, N ₃ Is the number of subbands configured in the reporting band,

……n-1 is the PRB index within a subband and N is the subband size in PRB number.

Fig. 7 illustrates an example of mapping beams and FD components to beamformed CSI-RS ports by a sequence selection mechanism for CSI-RS signals in subbands to indicate selection of FD components for the CSI-RS ports, according to some example embodiments of the present disclosure.

As shown in fig. 7, this example shows mapping of CSI-RS ports in subband n and the sequence for both cases in equation (3)

Is a value of (2). Each sub-band is +. >

The PRBs (only PRB0 and +_ 710 are shown in FIG. 7)>

And each port CDM over 2 Resource Elements (REs) in each PRB. For example, in PRB0 710, CSI-

RS ports

0 and 1 are CDM over

REs

711 and 712, and CSI-

RS ports

2 and 3 are CDM over REs 713 and 714. At->

In this, CSI-

RS ports

0 and 1 are CDM over

REs

721 and 722, and CSI-

RS ports

2 and 3 are CDM over

REs

723 and 724.

In this case, FD component n is selected by gNB for port 0 and CSI-RS sequence is unchanged, ψ ₀ (n) =0. The same FD component is not selected for port 1 and in this case the CSI-RS sequence is modified by the phase ramp of slope pi.

In some example embodiments, signaling of different active FD components for each port in the CSI-RS may be performed using a mix of Zero Power (ZP) CSI-RS and non-zero power (NZP) CSI-RS.

ZP-CSI-RS is used for DL CSI acquisition and interference measurement, and is typically used as CSI interference measurement (CSI-IM) when configuring CSI reports. It also shields the REs so that they are not available for PDSCH transmission. As indicated by the name ZP, nothing is sent in the configured ZP-CSI-RS REs.

Thus, to encode information of the active FD component for each port, the gNB 110 may determine a mapping of configured ZPs and NZP-CSI-RSs over a joint of REs for channel and interference measurements in a given subband or subband group.

Since the side information required to be transmitted on the CSI-RS signal consists of a single bit per subband or subband group and a one-to-one mapping between the given subband, FD component and path delay, the encoding of the side information may be performed by shifting the mapping of ZP-CSI-RS for CSI-IM and NZP-CSI-RS for Channel Measurement Resources (CMR) in the given subband or subband group.

For example, the gNB 110 may determine respective zero power portions of CSI-RS and respective non-zero portions of CSI-RS for the selected at least one CSI-RS port based on the FD component, and generate an indication of mapping between the at least one CSI-RS port and the selected beam and FD component based on the respective zero power portions and the respective non-zero portions.

Fig. 8 shows an example of mapping beams and FD components to beamformed CSI-RS ports by using a combination of ZP-CSI-RS/NZP-CSI-RS for CSI-RS signals in subbands to indicate selection of FD components for the CSI-RS ports. As shown in fig. 8, the mapping of NZP-CSI-RS is shown as CMR and ZP-CSI-RS is shown as CSI-IM to select FD components for a particular CSI-RS port.

PRB0 810

Refers to the case where FD components are selected for all ports, while PRB0 830 and +. >

Refers to the case where FD components are selected for all ports except for

ports

0 and 1. For example, in PRB0 810, CSI-

RS ports

0 and 1 are CDM over

REs

811 and 812, and CSI-

RS ports

2 and 3 are CDM over

REs

813 and 814, a set of RE815 may represent a portion of the ZP-CSI-RS.

Since the power of the NZP-CSI-RS and ZP-CSI-RS REs are very different and they experience the same channel effects, the UE will be able to detect the offset in the ZP and NZP CSI-RS maps and then detect the selected FD component for each port.

Based on the different approaches described above, the gNB 110 may dynamically indicate the selected beam and FD components to the UE 120 in the CSI-RS signal. That is, an indication of a mapping between at least one CSI-RS port and the selected beam and FD component may be determined. Then, referring again to fig. 2, the gnb 110 may send 206 a CSI-RS to the UE 120 that includes the indication. After receiving the CSI-RS from the gNB 110, the UE 120 may determine 208 a CSI report based on the indication obtained from the CSI-RS.

In some example embodiments, UE 120 may determine a number of frequency domain components selected by gNB 110 based on the indication and determine a bitmap size based on the determined number of frequency domain components. UE 120 may then generate a CSI report having the determined bitmap size.

Referring again to fig. 5, an example of a bitmap in the reciprocity enhanced II PS PMI is also shown. UE 120 will no longer need to indicate FD groups for each reporting layer. For each of the v layers, UE 120 may report a size of ak ₀ Or smaller one-dimensional bitmaps per layer, rather than reporting a size of 2L.M _v Is of a size determined by the selected port (2L) and the selected FD component (M _ν ) Given). Size alpha K ₀ Corresponding to the total number of "active" FD components on all ports indicated by the gNB 110.

A typical bitmap size is 2l×m per layer _v The bitmap thus has a total overhead of v.2LM _v . However, with the solution proposed in the present disclosure, for a constraint of v=1 or otherwise v·2k ₀ Maximum Rank (MR) with bitmap overhead reduced to a maximum size K ₀ . In eType II CBs, K ₀ Is defined as 2LM ₁ More precisely, the score of (c), more precisely,

wherein the method comprises the steps of

The maximum number of non-zero coefficients that can be reported in all layers in the eType II PS is K when mr=1 ^TOT ≤K ₀ While in MR>K is at 1 ^TOT ≤2K ₀ . Thus, bitmap overhead may be reduced by, for example, more than 50%.

As shown in fig. 5, the point marks 521-525 in the bitmap 530 may indicate NZCs calculated by the UE 120 for a given layer l (e.g., l=1). If UE 120 does not report a port selection indication, the size of the bitmap of layer 1 may be 10×1, such as αK ₀ Either =10, or if UE 120 selects a subset of ports, its size may be smaller. In this example, if UE 120 may indicate that 5 components are selected from 10 components, the minimum bitmap size may be 5×1.

In this way, the gNB can indicate on which FD components the PMI calculation should be limited, so that PMI feedback overhead in UL can be reduced without increasing overhead cost in DL.

Further, the complexity at the UE for calculating the PMI amount as port selection and FD component selection performed at the gNB may be reduced.

Furthermore, possible performance improvements can be achieved with respect to non-reciprocity assisted eType II PS, since each layer M _ν The limitation of the individual FD components selected is no longer applicable. In fact, the gNB may select a different FD component for each port, and the total may exceed M _ν . The UE may also indicate for which layers certain FD components are most relevant and provide a corresponding non-zero LCC.

Furthermore, if the UE is configured to report only LCCs corresponding to FD component 0, the total number of FD components N may be increased ₃ Without increasing the significant complexity of the UE to achieve the potentially improved performance relative to non-reciprocity assisted type II PS. N (N) ₃ Is a parameter configured by the network corresponding to the number of configured PMI subbands, and it is defined as the number of CQI subbands N _SB R times, N ₃ ＝RN _SB Wherein R is a non-reciprocal co-agentThe median range of the assisted eType II PS is the RRC parameter of {1,2 }. In the reciprocity-assisted type II PS, the value of R may be greater than 2 without affecting the complexity of UE implementation.

Fig. 9 illustrates a flowchart of an example method 900 of port selection codebook enhancement according to some example embodiments of the present disclosure. The method 900 may be implemented at a first device 110 as shown in fig. 1. For discussion purposes, the method 900 will be described with reference to FIG. 1.

At 910, the first device determines a set of beams and frequency domain components associated with CSI-RS to be transmitted from the first device to the second device.

In some example embodiments, a first device may receive an SRS from a second device and determine a set of beams and frequency domain components based on the SRS.

At 920, the first device generates an indication of a mapping between at least one port selected at the first device for transmitting CSI-RS and the frequency domain component and the set of beams.

In some example embodiments, the first device may determine a number of beam sets and respective cyclic shifts of frequency domain components corresponding to the beam sets. The first device may also determine an association between the frequency domain components and the at least one port based on the number of beam sets and the respective cyclic shifts, wherein each of the frequency domain components is mapped to a respective one of the at least one port, and the first device may also determine a mapping based on the association.

In some example embodiments, the first device may select at least one port based on the set of beams. The first device may also determine a respective subband associated with the at least one port and determine an association between the frequency domain component and the respective subband. The first device may also generate an indication based at least on the association.

In some example embodiments, the first device may determine a reference sequence associated with the CSI-RS and determine a cyclic shift of the reference sequence based on the association. The first device may also determine a target sequence associated with the CSI-RS based on the reference sequence and the cyclic shift, and generate an indication based on the target sequence.

In some example embodiments, the first device may select at least one port based on the set of beams. The first device may also determine a respective zero power portion of the CSI-RS and a respective non-zero portion of the CSI-RS for the at least one port based on the frequency domain component, and generate an indication based on the respective zero power portion and the respective non-zero portion.

At 930, the first device transmits a CSI-RS including the indication to the second device.

Fig. 10 illustrates a flowchart of an example method 1000 of port selection codebook enhancement according to some example embodiments of the present disclosure. The method 1000 may be implemented at the second device 120 as shown in fig. 1. For discussion purposes, method 1000 will be described with reference to FIG. 1.

At 1010, the second device receives a CSI-RS from the first device.

At 1020, the second device obtains an indication of a mapping between at least one port selected at the first device for transmitting the CSI-RS and a set of beams and frequency domain components associated with the CSI-RS.

At 1030, the second device generates a CSI report based on the indication.

In some example embodiments, the second device may determine a number of frequency domain components based on the indication and determine a size of a bitmap for CSI reporting based on the number of frequency domain components. The second device may also generate a CSI report based on the size.

In some example embodiments, if the second device determines that the association between the frequency domain component and the at least one port is obtained from the indication, the second device may determine the number of the at least one port. The second device may also determine a number of frequency domain components based on the number of at least one port.

In some example embodiments, if the second device determines that the association between the frequency domain component and the at least one port is obtained from the indication, the second device may determine the number of the at least one port. The second device may also receive an indication of a number of frequency domain components to be reported via radio resource control signaling. The number of frequency domain components is uncorrelated with the number of configured subbands. The second device may also be based on at least one port An indication of the number and the number of frequency domain components, a number of linear combination coefficients to report in the CSI report is determined, and a size of the bitmap is determined based on the number of linear combination coefficients to report in the CSI report. Note that the number of frequency domain components M _ν May be configured as a fixed value, e.g., M _ν =1, and the number of configured PMI subbands N ₃ Irrespective, i.e. M _ν No longer N as in the Rel-16 II PS codebook ₃ Is a function of (2).

In some example embodiments, if the second device determines that an association between the frequency domain component and a corresponding subband associated with the at least one port is obtained from the indication, the second device may determine the number of frequency domain components based on the association.

In some example embodiments, if the second device determines that the respective zero power portion of the CSI-RS and the respective non-zero portion of the CSI-RS of the at least one port are obtained from the indication, the second device may determine the number of frequency domain components based on the respective non-zero portion of the CSI-RS.

In some example embodiments, an apparatus (e.g., implemented at the first device 110) capable of performing the method 900 may include means for performing the respective steps of the method 900. The component may be implemented in any suitable form. For example, the components may be implemented in circuitry or software modules.

In some example embodiments, the apparatus includes means for determining, at a first device, a set of beams and frequency domain components associated with a CSI-RS to be transmitted from the first device to a second device; means for generating an indication of a mapping between at least one port selected for transmitting CSI-RS and frequency domain components and a set of beams at a first device; and means for transmitting the CSI-RS including the indication to the second device.

In some example embodiments, an apparatus (e.g., implemented at the second device 120) capable of performing the method 1000 may include means for performing the respective steps of the method 1000. The component may be implemented in any suitable form. For example, the components may be implemented in circuitry or software modules.

In some example embodiments, the apparatus includes means for receiving a CSI-RS from a first device; means for obtaining an indication of a mapping between at least one port selected for transmitting CSI-RS at a first device and a set of beams and frequency domain components associated with the CSI-RS; and means for generating a CSI report based on the indication.

Fig. 11 is a simplified block diagram of a device 1100 suitable for implementing embodiments of the present disclosure. Device 1100 may be provided to enable communication devices, such as the gNB 110 and UE120 shown in FIG. 1. As shown, device 1100 includes one or more processors 1110, one or more memories 1140 coupled to processors 1110, and one or more transmitters and/or receivers (TX/RX) 1140 coupled to processor 1100.

TX/RX 1140 is used for two-way communication. TX/RX 1140 has at least one antenna to facilitate communication. The communication interface may represent any interface necessary to communicate with other network elements.

The processor 1110 may be of any type suitable to the local technical network and may include, as non-limiting examples, one or more of the following: general purpose computers, special purpose computers, microprocessors, digital Signal Processors (DSPs), and processors based on a multi-core processor architecture. The device 1100 may have multiple processors, such as an application-specific integrated circuit chip that is slaved in time to a clock that is synchronized to the master processor.

Memory 1120 may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memory include, but are not limited to, read Only Memory (ROM) 1124, electrically Programmable Read Only Memory (EPROM), flash memory, hard disk, compact Disk (CD), digital Video Disk (DVD), and other magnetic and/or optical storage. Examples of volatile memory include, but are not limited to, random Access Memory (RAM) 1122 and other volatile memory that does not persist during power failure.

Computer program 1130 includes computer-executable instructions that are executed by an associated processor 1110. Program 1130 may be stored in ROM 1120. Processor 1110 may perform any suitable actions and processes by loading program 1130 into RAM 1120.

Embodiments of the present disclosure may be implemented by program 1130 such that device 1100 may perform any of the processes of the present disclosure discussed with reference to fig. 2-10. Embodiments of the present disclosure may also be implemented in hardware or a combination of software and hardware.

In some embodiments, program 1130 may be tangibly embodied in a computer-readable medium that may be included in device 1100 (such as in memory 1120) or other storage device that device 1100 may access. Device 1100 can load program 1130 from a computer readable medium into RAM 1122 for execution. The computer readable medium may include any type of tangible, non-volatile memory, such as ROM, EPROM, flash memory, hard disk, CD, DVD, etc. Fig. 12 shows an example of a computer readable medium 1200 in the form of a CD or DVD. Program 1130 is stored on a computer readable medium.

In general, the various embodiments of the disclosure may be implemented using hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of the embodiments of the disclosure are illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product comprises computer executable instructions, such as instructions included in program modules, that are executed in a device on a target real or virtual processor to perform the methods 200 and 400 described above with reference to fig. 2 and 4. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform particular tasks or implement particular abstract data types. In various embodiments, the functionality of the program modules may be combined or split between program modules as desired. Machine-executable instructions of program modules may be executed within local or distributed devices. In a distributed device, program modules may be located in both local and remote memory storage media.

Program code for carrying out the methods of the present disclosure may be written in any combination of one or more programming languages. These program code may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus such that the program code, when executed by the processor or controller, causes the functions/operations specified in the flowchart and/or block diagram to be implemented. The program code may execute entirely on the machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

In the context of this disclosure, computer program code or related data may be carried by any suitable carrier to enable a device, apparatus, or processor to perform the various processes and operations described above. Examples of carriers include signals, computer readable media, and the like.

The computer readable medium may be a computer readable signal medium or a computer readable storage medium. The computer readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of a computer-readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

Further, while operations are described in a particular order, this should not be construed as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In some cases, multitasking and parallel processing may be advantageous. Also, while several specific implementation details are included in the above discussion, these should not be construed as limitations on the scope of the disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination.

Although the disclosure has been described in language specific to structural features and/or methodological acts, it is to be understood that the disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1. A first device, comprising:

at least one processor; and

at least one memory including computer program code;

the at least one memory and the computer program code are configured to, with the at least one processor, cause the first device at least to:

determining a set of beams and frequency domain components associated with a channel state information, CSI-RS, to be transmitted from the first device to a second device;

generating an indication of a mapping between at least one port selected at the first device for transmitting the CSI-RS and the frequency domain component and the set of beams; and

and transmitting the CSI-RS including the indication to the second device.

2. The first device of claim 1, wherein the first device is caused to determine the set of beams and the frequency domain component by:

Receiving a sounding reference signal, SRS, from the second device; and

the set of beams and the frequency domain component are determined based on the SRS.

3. The first device of claim 1, wherein the first device is further caused to:

determining a number of the set of beams;

determining respective cyclic shifts of the frequency domain components corresponding to the set of beams;

determining an association between the frequency domain components and the at least one port based on the number of beam sets and the respective cyclic shifts, wherein each of the frequency domain components is mapped to a respective one of the at least one port; and

the mapping is determined based on the association.

4. The first device of claim 1, wherein the first device is caused to generate the indication by:

selecting the at least one port based on the set of beams;

determining a respective subband associated with the at least one port;

determining an association between the frequency domain component and the respective subband; and

the indication is generated based at least on the association.

5. The first device of claim 4, wherein the first device is caused to generate the indication based at least on the association by:

Determining a reference sequence associated with the CSI-RS;

determining a cyclic shift for the reference sequence based on the association; and

determining a target sequence associated with the CSI-RS based on the reference sequence and the cyclic shift; and

the indication is generated based on the target sequence.

6. The first device of claim 1, wherein the first device is caused to generate the indication by:

selecting the at least one port based on the set of beams;

determining, based on the frequency domain components, a respective zero power portion of the CSI-RS and a respective non-zero portion of the CSI-RS for the at least one port; and

the indication is generated based on the respective zero power portion and the respective non-zero portion.

7. The first device of claim 1, wherein the first device comprises a terminal device and the second device comprises a network device.

8. A second device, comprising:

at least one processor; and

at least one memory including computer program code;

the at least one memory and the computer program code are configured to, with the at least one processor, cause the second device to at least:

Receiving channel state information-reference signal, CSI-RS, from a first device;

obtaining an indication of a mapping between at least one port selected at the first device for transmitting the CSI-RS and a set of beams and frequency domain components associated with the CSI-RS; and

and generating a CSI report based on the indication.

9. The first device of claim 8, wherein the second device is caused to generate the CSI report by:

determining a number of the frequency domain components based on the indication;

determining a size of a bitmap for the CSI report based on the number of frequency domain components; and

the CSI report is generated based on the size.

10. The first device of claim 9, wherein the second device is caused to determine the number of frequency domain components by:

determining a number of the at least one port in accordance with determining that an association between the frequency domain component and the at least one port is obtained from the indication; and

the number of frequency domain components is determined based on the number of the at least one port.

11. The first device of claim 9, wherein the second device is caused to determine the size of the bitmap by:

receiving an indication of the number of frequency domain components to be reported via radio resource control signaling, the number of frequency domain components being uncorrelated with the number of configured subbands;

determining a number of linear combination coefficients to be reported in the CSI report based on the indication of the number of the at least one port and the number of frequency domain components; and

the size of a bitmap is determined based on the number of linear combination coefficients to be reported in the CSI report.

12. The first device of claim 9, wherein the second device is caused to determine the number of frequency domain components by:

in accordance with a determination that an association between the frequency domain component and a respective subband associated with the at least one port is obtained from the indication, a number of the frequency domain components is determined based on the association.

13. The first device of claim 9, wherein the second device is caused to determine the number of frequency domain components by:

In accordance with a determination that a respective zero power portion of the CSI-RS and a respective non-zero portion of the CSI-RS for the at least one port are obtained from the indication, a number of the frequency domain components is determined based on the respective non-zero portion of the CSI-RS.

14. The first device of claim 8, wherein the first device comprises a terminal device and the second device comprises a network device.

15. A method, comprising:

determining, at a first device, a set of beams and frequency domain components associated with a channel state information-reference signal, CSI-RS, to be transmitted from the first device to a second device;

and transmitting the CSI-RS including the indication to the second device.

16. The method of claim 15, wherein determining the set of beams and the frequency domain component comprises:

receiving a sounding reference signal, SRS, from the second device; and

17. The method of claim 15, further comprising:

Determining a number of the set of beams;

the mapping is determined based on the association.

18. The method of claim 15, wherein generating the indication comprises:

selecting the at least one port based on the set of beams;

determining a respective subband associated with the at least one port;

the indication is generated based at least on the association.

19. The method of claim 18, wherein generating the indication based at least on the association comprises:

determining a reference sequence associated with the CSI-RS;

The indication is generated based on the target sequence.

20. The method of claim 15, wherein generating the indication comprises:

selecting the at least one port based on the set of beams;

21. The method of claim 15, wherein the first device comprises a terminal device and the second device comprises a network device.

22. A method, comprising:

at the second device, receiving channel state information-reference signal, CSI-RS, from the first device;

and generating a CSI report based on the indication.

23. The method of claim 22, wherein generating the CSI report comprises:

The CSI report is generated based on the size.

24. The method of claim 23, wherein determining the number of frequency domain components comprises:

25. The method of claim 23, wherein determining the size of a bitmap comprises:

26. The method of claim 23, wherein determining the number of frequency domain components comprises:

27. The method of claim 23, wherein determining the number of frequency domain components comprises:

28. The method of claim 22, wherein the first device comprises a terminal device and the second device comprises a network device.

29. An apparatus, comprising:

means for determining, at a first device, a set of beams and frequency domain components associated with a channel state information-reference signal, CSI-RS, to be transmitted from the first device to a second device;

means for generating an indication of a mapping between at least one port selected for transmitting the CSI-RS at the first device and the frequency domain component and the set of beams; and

Means for transmitting the CSI-RS including the indication to the second device.

30. An apparatus, comprising:

means for receiving channel state information, CSI, reference signals, CSI-RS, from a first device;

means for obtaining an indication of a mapping between at least one port selected at the first device for transmitting the CSI-RS and a set of beams and frequency domain components associated with the CSI-RS; and

means for generating a CSI report based on the indication.

31. A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method of any one of claims 15 to 21.

32. A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method of any one of claims 22 to 28.