Port Selection Codebook Enhancement via Partial Channel Reciprocity

Abstract

Embodiments of the present disclosure relate to an apparatus, method, device, and computer-readable storage medium for enhancing a port selection codebook through partial channel reciprocity. The method includes determining, at a first device, a beam set and a frequency-domain component 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 at the first device for transmitting the CSI-RS, the frequency-domain component, and the beam set; and transmitting, to the second device, the CSI-RS including the indication. In this way, the gNB can indicate on which FD components the PMI calculation should be restricted, so that the PMI feedback overhead in the UL can be reduced without increasing the additional overhead cost in the DL.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to the field of telecommunications, and more particularly to devices, methods, apparatuses, and computer-readable storage media for enhancing a port selection codebook through partial channel reciprocity. Background Art

[0002] It has been approved that, mainly for FR1 (450 MHz - 6000 MHz) frequency division duplex (FDD) deployments, by leveraging partial uplink / downlink (UL / DL) reciprocity of certain channel statistics such as (multiple) angles and (multiple) delays, the multi-input multi-output (MIMO) channel state information (CSI) feedback can be further enhanced.

[0003] For CSI measurement and reporting, type-II port selection (PS) codebook enhancement can be evaluated or specified. A network device (gNodeB, gNB) can estimate information related to (multiple) angles and (multiple) delays based on a sounding reference signal (SRS) by leveraging the DL / UL reciprocity of angles and delays, and the remaining DL CSI is reported by a terminal device (user equipment, UE) to achieve a better trade-off among UE complexity, performance, and reporting overhead. Summary of the Invention

[0004] Generally, example embodiments of the present disclosure provide a solution for enhancing a port selection codebook.

[0005] In a first aspect, a first device is provided. The first device includes 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, together with the at least one processor, cause the first device to at least: determine a beam set and a frequency domain component associated with a channel state information reference signal (CSI-RS) to be sent from the first device to a second device; generate an indication of a mapping between at least one port selected at the first device for sending the CSI-RS, the frequency domain component, and the beam set; and send the CSI-RS including the indication to the second device.

[0006] In a second aspect, a second device is provided. The second device includes 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, together with the at least one processor, cause the second device to at least: receive the CSI-RS from the first device; obtain an indication of a mapping between at least one port selected at the first device for sending the CSI-RS and a beam set and a frequency domain component associated with the CSI-RS; and generate a CSI report based on the indication.

[0007] In a third aspect, a method is provided. The method includes determining, at a first device, a beam set and a frequency-domain component associated with a 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, the frequency-domain component, and the beam set; and transmitting, to the second device, the CSI-RS including the indication.

[0008] 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 at the first device for transmitting the CSI-RS and a beam set and a frequency-domain component associated with the CSI-RS; and generating a CSI report based on the indication.

[0009] In a fifth aspect, an apparatus is provided. The apparatus includes means for determining, at a first device, a beam set and a frequency-domain component 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 at the first device for transmitting the CSI-RS, the frequency-domain component, and the beam set; and means for transmitting, to the second device, the CSI-RS including the indication.

[0010] In a sixth aspect, an apparatus is provided. 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 at the first device for transmitting the CSI-RS and a beam set and a frequency-domain component associated with the CSI-RS; and means for generating a CSI report based on the indication.

[0011] In a seventh aspect, a computer-readable medium having stored thereon a computer program is provided. The computer program, when executed by at least one processor of a device, causes the device to perform the method according to the third aspect.

[0012] In an eighth aspect, a computer-readable medium having stored thereon a computer program is provided. The computer program, when executed by at least one processor of a device, causes the device to perform the method according to the fourth aspect.

[0013] When read in conjunction with the accompanying drawings, other features and advantages of embodiments of the present disclosure will also become apparent from the following detailed description of specific embodiments, which illustrate, by way of example, the principles of embodiments of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Embodiments of the present disclosure are presented by way of example, and their advantages will be explained in more detail below with reference to the accompanying drawings, in which

[0015] Figure 1Shows an example environment in which example embodiments of the present disclosure may be implemented;

[0016] Figure 2 Shows a signaling diagram illustrating a port selection codebook enhancement process according to some example embodiments of the present disclosure;

[0017] Figure 3 Shows 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;

[0018] Figure 4 Shows a compression operation performed by a UE when calculating an eType-II precoding matrix indicator (PMI) according to some example embodiments of the present disclosure;

[0019] Figure 5 Shows an example of a reciprocity-enhanced eType-II PS codebook according to some example embodiments of the present disclosure;

[0020] Figure 6 Shows an example of mapping beams and FD components to beamformed CSI-RS ports according to some example embodiments of the present disclosure;

[0021] Figure 7 Shows an example of mapping beams and FD components to beamformed CSI-RS ports according to some example embodiments of the present disclosure;

[0022] Figure 8 Shows an example of mapping beams and FD components to beamformed CSI-RS ports according to some example embodiments of the present disclosure;

[0023] Figure 9 Shows a flowchart of an example method for port selection codebook enhancement according to some example embodiments of the present disclosure;

[0024] Figure 10 Shows a flowchart of an example method for port selection codebook enhancement according to some example embodiments of the present disclosure;

[0025] Figure 11 Shows a simplified block diagram of a device suitable for implementing example embodiments of the present disclosure; and

[0026] Figure 12 Shows a block diagram of an example computer-readable medium according to some embodiments of the present disclosure.

[0027] Throughout the drawings, the same or similar reference numerals denote the same or similar elements. Detailed Description

[0028] The principles of the present disclosure will now be described with reference to some example embodiments. It should be understood that the description of these embodiments is only for illustration and to assist those skilled in the art in understanding and implementing the present disclosure, and does not represent any limitation on the scope of the present disclosure. The disclosure described herein can be implemented in a variety of other ways than those described below.

[0029] In the following description and claims, unless otherwise defined, 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 pertains.

[0030] In the present disclosure, references to "one embodiment", "an embodiment", "example embodiment", etc. indicate that the described embodiment may include a particular feature, structure, or characteristic, but not every embodiment must include the particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an example embodiment, it is within the knowledge of those skilled in the art to effect such feature, structure, or characteristic in combination with other embodiments, whether or not explicitly described.

[0031] It should be understood that although terms such as "first" and "second" may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish the functions of various elements. As used herein, the term "and / or" includes any and all combinations of one or more of the listed terms.

[0032] The terms used herein are only for describing particular embodiments and are not intended to limit the example embodiments. The singular forms "a", "an", and "the" used herein also include the plural forms unless the context clearly dictates otherwise. Further understood, the terms "comprises", "comprising", "has", "having", "includes", and / or "including" when used herein specify the presence of the stated features, elements, and / or components, etc., but do not preclude the presence or addition of one or more other features, elements, components, and / or combinations thereof.

[0033] As used in this application, the term "circuitry" can refer to one or more or all of the following:

[0034] (a) A pure hardware circuit implementation (such as an implementation using only analog and / or digital circuitry), and

[0035] (b) A combination of hardware circuitry and software, such as, where applicable:

[0036] (i) A combination of (one or more) analog and / or digital hardware circuits and software / firmware, and

[0037] (ii) Any portion of (one or more) hardware processors with software (including (one or more) digital signal processors, software, and (one or more) memories), which work together to enable a device, such as a mobile phone or a server, to perform various functions, and

[0038] (c) (One or more) hardware circuits and / or (one or more) processors, such as (one or more) microprocessors or a portion of (one or more) microprocessors, which require software (e.g., firmware)

[0039] to operate, but the software can be absent when not required to operate.

[0040] This definition of circuitry is suitable for all uses of the term in this application, including in any claim. As another example, as used in this application, the term circuitry also encompasses an implementation of only a hardware circuit or a processor (or processors) or a portion of a hardware circuit or a processor and its (or their) accompanying software and / or firmware. For example, if applicable to a particular claim element, the term circuitry also encompasses a baseband integrated circuit or a processor integrated circuit for a mobile device, or a similar integrated circuit in a server, a cellular network device, or other computing or network devices.

[0041] As used herein, the term "communication network" refers to a network that follows 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), etc. In addition, the communication between a terminal device and a network device in a communication network can be performed according to any suitable generation of communication protocol, including but not limited to the 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 protocol, and / or any other protocol known currently or to be developed in the future. Embodiments of the present disclosure can be applied to various communication systems. Considering the rapid development of communication, of course, there will also be future types of communication technologies and systems that can embody the present disclosure. The scope of the present disclosure should not be limited to the above systems.

[0042] As used herein, the term "network device" refers to a node in a communication network through which a terminal device accesses the network and receives services from the network. The network device may refer to a base station (BS) or an access point (AP), for example, Node B (NodeB or NB), evolved Node B (eNodeB or eNB), NR next generation Node B (gNB), remote radio unit (RRU), radio header (RH), remote radio head (RRH), relay, 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 part of the IAB node.

[0043] The term "terminal device" refers to any terminal device capable of wireless communication. By way of example and not limitation, the 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 device may include, but is not limited to, mobile phones, cellular phones, smart phones, IP voice (VoIP) phones, wireless local loop phones, tablets, wearable terminal devices, personal digital assistants (PDA), portable computers, desktop computers, image capture terminal devices (such as digital cameras), game terminal devices, music storage and playback devices, in-vehicle wireless terminal devices, wireless endpoints, mobile stations, laptop embedded devices (LEE), laptop in-vehicle devices (LME), USB dongles, smart devices, wireless customer premise equipment (CPE), Internet of Things (IoT) devices, watches or other wearable devices, head-mounted displays (HMD), vehicles, drones, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in the context of an industrial and / or automation processing chain), consumer electronic devices, devices operating on commercial and / or industrial wireless networks, etc. The terminal device may also correspond to the mobile termination (MT) part 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.

[0044] Although in various example embodiments, the functions described herein may be performed in fixed and / or wireless network nodes, in other example embodiments, the functions may be implemented in user equipment devices such as a mobile phone or a tablet or a laptop or a desktop computer or a mobile IoT device or a fixed IoT device. For example, the user equipment device may be suitably equipped with corresponding capabilities as described in connection with (multiple) fixed and / or wireless network nodes. The user equipment device may be a user equipment and / or a control device such as a chipset or a processor that is 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 the user equipment device by providing software to the user equipment device that is configured to cause the user equipment device to perform from the perspective of these functions / nodes.

[0045] Figure 1 FIG. 4 shows an example communication network 100 in which embodiments of the present disclosure may be implemented. As Figure 1 shown, the communication network 100 includes a network device 110 (hereinafter also referred to as the first device 110 or gNB 110) and a terminal device 120 (hereinafter also referred to as the second device 120 or UE 120). The terminal device 120 may communicate with the network device 110. It should be understood that Figure 1 the number of network devices and terminal devices shown is given for illustrative purposes and without any limitation. The communication network 100 may include any suitable number of network devices and terminal devices.

[0046] According to the communication technology, the 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 communication discussed in the network 100 may conform to any suitable standard, including but not limited to New Radio Access (NR), Long-Term Evolution (LTE), LTE Evolution, Advanced LTE (LTE-A), Wideband Code Division Multiple Access (WCDMA), Code Division Multiple Access (CDMA), cdma2000, and Global System for Mobile Communications (GSM), etc. In addition, these communications may be performed according to any generation of communication protocols known currently or to be developed in the future. Examples of communication protocols include but are not limited to the 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 above-mentioned wireless networks and radio technologies as well as other wireless networks and radio technologies. For clarity, certain aspects of the techniques are described below for LTE, and LTE terminology is used in most of the following description.

[0047] As described above, it has been approved that, mainly for FR1 FDD deployment, by leveraging the partial UL / DL reciprocity of certain channel statistics such as (multiple) angles and (multiple) delays, MIMO CSI feedback can be further enhanced.

[0048] For CSI measurement and reporting, type-II PS codebook enhancements can be evaluated or specified. The gNB can estimate the information related to (multiple) angles and (multiple) delays based on the SRS by leveraging the DL / UL reciprocity of angles and delays, and the remaining DL CSI is reported by the UE to achieve a better trade-off among UE complexity, performance, and reporting overhead.

[0049] It is assumed that if the duplex distance is relatively small compared to the carrier frequency, the channel reciprocity in an FDD system only applies to certain wideband / long-term statistical characteristics shared by the UL and DL channels, and if the FDD duplex distance is greater than the carrier frequency, frequency conversion techniques can be used to improve the accuracy of DL channel parameters based on UL channel measurements. There are two types of partial channel reciprocity, namely, spatial reciprocity and path delay reciprocity.

[0050] Regarding spatial reciprocity, it is assumed that the gNB can perform UL channel measurements on the SRS received from the UE, and based on this measurement, the gNB can estimate the angular power spectrum (APS) or the principal eigenvector of the UL channel.

[0051] Regarding path delay reciprocity, the gNB can also estimate the PDP of the UL channel based on the SRS. This delay distribution can be averaged over all SRS ports of the UE and can be calculated separately for each spatial beam associated with the UE. It is assumed that the propagation conditions of the channel (i.e., delay statistics) are similar for all SRS ports and all beams associated with the angular sector where the UE is discovered. In this case, the same cluster of channel multipaths is responsible for the main path delay of the UE for each main beam. There is a physical correspondence between the main path delay of the PDP measured on the UL channel and the main frequency domain (FD) component measured on the DL channel.

[0052] However, there is no mechanism in the type-II PS codebook that allows the gNB to utilize the knowledge of the main delay / FD component obtained from SRS measurements.

[0053] Accordingly, the present disclosure proposes a solution for enhancing the port selection codebook. In this solution, the gNB can determine an indication of the mapping between at least one port used for transmitting CSI-RS and the frequency domain components and beam sets associated with the CSI-RS, and send the CSI-RS including this indication to the second device. In this way, the gNB can indicate on which FD components the PMI calculation should be restricted, thereby reducing the PMI feedback overhead in the UL without increasing the additional overhead cost in the DL.

[0054] The principles and implementations of the present disclosure will be described in detail below with reference to Figure 2 and will be illustrated by Figure 2 FIG. shows a signaling diagram illustrating a port selection codebook enhancement process according to some example embodiments of the present disclosure. For the purpose of discussion, reference will be made to Figure 1 to describe process 200. Process 200 may involve Figure 1 the UE 120 and gNB 110 shown in

[0055] As shown in Figure 2 , the UE 120 may send (202) SRS to the gNB 110. Based on the UL channel measurements on the SRS received from the UE 120, the gNB 110 may estimate the beam sets and FD components associated with the transmission of CSI-RS from the gNB 110 to the UE 120.

[0056] One aspect of the present invention relates to how the gNB 110 dynamically indicates the selected beams and FD components to the UE in the CSI-RS signal. Before explaining the process of generating an indication associated with the selected beams and FD components, reference will be made to Figure 3 to describe an example of the CSI-RS ports and port selection mechanism for beamforming using a type-II PS codebook.

[0057] Figure 3 FIG. shows an example of the CSI-RS ports and port selection mechanism for beamforming using a type-II PS codebook according to some example embodiments of the present disclosure. The antenna array 310 has a 4×1×2 configuration, where 4 panels 311-314 are split to form 4 cross-polarized azimuth beams 321-324, each beam being 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.

[0058] The mapping between the transmit beams and the ports is such that ports p and p+L (where p = 0,..., P CSI-RS-1) represents two polarizations of the same beam. The transmit beam is designed to provide maximum gain in different azimuth directions of the cell sector. The radio resource control (RRC) parameters for CSI reporting settings include the number of beams L for port selection and the parameter d (where 1 ≤ d ≤ L), and the parameter d determines the port sampling step, that is, the set of beam patterns that the UE can select. In this example, when the parameters L = d = 2, the UE selects ports 0 and 1, so the spatial component of the PMI is given by:

[0059] where

[0060] 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 can use the eType II PS codebook to indicate up to 4 different layers.

[0061] Then, for each layer l = 1,..., ν, where ν is the reported rank, the UE calculates the linear combination coefficient (LCC), which is used to combine the selected ports in each of the N 3 subbands to best approximate the l-th strongest channel eigenvector.

[0062] Figure 4 Shows an example of the compression operation performed by the UE when calculating the eType II PMI according to some example embodiments of the present disclosure. For each layer l, the DFT transform is applied to the N 3 (subband 410) LCCs of each selected port, and M ν main FD components 420 in the transformed domain are selected, where M ν is an RRC configuration parameter, and a subset 430 of the transformed LLCs from the reduced-size combination matrix is selected for feedback. Up to K 0 non-zero coefficients can be reported for each layer, and the total maximum for all layers is K TOT ≤ 2K 0 . In this example, N 3 = 13, M ν = 5. The selected main FD components form the matrix W f (l), and the non-zero linear combination coefficients (NZCs) 431 - 435 form the matrix Therefore, the precoder vector indicated by the eType II PS PMI for layer l is represented by:

[0063]

[0064] Different from W 1The spatial beam (which is layer common), FD basis, and NZC selection are all layer specific. Thus, the overhead and complexity associated with calculating and signaling W f (l) and are much greater than the overhead and complexity required by W 1 .

[0065] It is expected that CSI enhancement can be achieved through UL / DL partial reciprocity to further optimize port selection PMI. As described above, in reciprocity-assisted CSI reporting, gNB 110 can estimate the main broadband beam and FD components based on UL channel measurements on the SRS received from UE 120.

[0066] If beam selection is performed at gNB 110, gNB 110 does not need to expose UE 120 to more CSI-RS ports than the CSI-RS ports associated with the selected beam. Thus, after selecting the strongest L two-port beams for UE 120, these 2L ports are mapped into the CSI-RS resources configured for that UE 120.

[0067] Typically, the quantities estimated by gNB 110 based on the SRS are layer common, in the sense that if, for example, the SRS ports are fewer or different from the ports used by the receiver of UE 120, gNB 110 may not have full visibility of the spatial layers that the DL channel can support. Additionally, UE 120 may also have typically different transmitter and receiver antenna elements. This is not a limitation on port selection at the gNB, as port selection is also layer common when performed on the UE side.

[0068] However, when estimating the main DL FD components from the SRS, gNB 110 can estimate these quantities for each port, but it may not associate the main FD components of the ports with a specific layer. In fact, the layers calculated by UE 120 can typically be represented as a linear combination of ports, and this layer-specific information can be estimated by UE 120 based on DL channel measurements.

[0069] When the gNB utilizes partial UL-DL channel reciprocity, beam selection and FD component selection can be performed by the gNB using SRS measurements. Typically, for each selected beam, the gNB determines a set of main FD components. These components correspond to the positions of the non-zero coefficients (NZC) in

[0070] Figure 5 shows an example of a reciprocity-enhanced eType II PS codebook according to some example embodiments of the present disclosure. AsFigure 5 As shown, the squares 511 - 520 marked in a darker color in the grid 510 marked as indicate the positions of these FD components of each beam. Let αK 0 be the total number of these components. In this example, there are αK 0 = 10 identified FD components, 2 for beam i = 0, 1 for beam i = 1, 3 for beam i = 2, and 4 for beam i = 3. The parameter α is predetermined by some RRC configurations. For example, for rank restriction, α can be set to 1, allowing only the reported rank ν = 1; α = 2 indicates an unrestricted rank indicator.

[0071] The selected beamforming spatial domain basis W 1 , which is common to broadband and layers, and the selected FD components for port i are indicated by the quantity W f (i), where i = 0, ……, 2L - 1. Note that the information in W f (i) is not sufficient to form the layer - specific FD basis W f (l) (where l = 1, ……, ν), because generally, the gNB does not know which layers the components of W f (i) should be mapped to.

[0072] Therefore, referring again to Figure 2 , the gNB 110 can determine how to dynamically indicate the selected beams and FD components to the UE 120 in the CSI - RS signal. That is, the gNB will determine an indication of the mapping between at least one CSI - RS port and the selected beams and FD components.

[0073] In some example embodiments, the gNB 110 can map each of the αK 0 identified components to a separate CSI - RS port, and the UE calculates a single linear combination coefficient for each port. In this case, the number of CSI - RS ports for UE - specific beamforming may need to be greater than the number of selected beams, because generally αK 0 > 2L.

[0074] In this case, the gNB 110 can determine the number of sets of selected beams and the corresponding cyclic shifts of the FD components corresponding to that beam set. Based on the determined number of sets of selected beams and the corresponding cyclic shifts of the FD components, the gNB 110 can determine the association between the frequency - domain components and at least one port, where each of the frequency - domain components is mapped to a corresponding one of the at least one CSI - RS port.

[0075] In the case where each component is mapped to 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 the phase ramp in the frequency domain) so that the UE can calculate the corresponding linear combination 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 the simple sum of the CSI-RS samples of a given port.

[0076] In an example where the gNB selects 2L = 4 beams and M = 5 FD components with indices f = 0, 1, 2, 11, 12, the CSI-RS of 2 CSI-RS ports is beamformed by the weights associated with beam i = 0. No cyclic shift is applied to the CSI-RS for the first CSI-RS port, while the signal for the second CSI-RS is shifted by 12 because the position of its second FD component is the last one in the set where N 3 = 13.

[0077] Figure 6 An example of mapping beams and FD components to beamformed CSI-RS ports according to some example embodiments of the present disclosure is shown. As Figure 6 shown, the 2 CSI-RS ports 621-622 are beamformed by beam i = 0 with shifts 0 and 12 respectively, 1 CSI-RS port 623 is beamformed by beam i = 1 without applying a shift, 3 CSI-RS ports 624-626 are beamformed by beam i = 2 with shifts 0, 11 and 12 respectively, and 4 CSI-RS ports 627-630 are beamformed by beam i = 3 with shifts 0, 1, 2 and 12 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.

[0078] In this case, αK 0 = 2LM is also possible, that is, for all the selected beams, all FD components are mapped.

[0079] In some example embodiments, the FD component selection can be signaled via CSI-RS signals in the form of sequence selection. In this case, two different CSI-RS sequences can be introduced for a subband such that the gNB can use one CSI-RS sequence or the other CSI-RS sequence according to whether the FD component associated with the CSI-RS port is selected for the subband.

[0080] For example, gNB 110 can select at least one CSI-RS port and determine the corresponding subband associated with the at least one CSI-RS port. Then, gNB 110 can determine the association between the FD component and the corresponding subband.

[0081] To generate an indication of the mapping between at least one CSI-RS port and the selected beam and FD component, gNB 110 can obtain a reference sequence associated with the CSI-RS, which can be given as follows:

[0082]

[0083] where r(m) is a QPSK reference signal sequence, and the quantities k′, l′, w f (k′) and w t (k′) are given by a table.

[0084] Then, gNB 110 can determine the cyclic shift for the reference sequence. A single cyclic shift of the CSI-RS sequence used in a subband or a predefined subset of the physical resource blocks (PRBs) of the subband can be used, which can be expressed as a function Based on the reference sequence and the cyclic shift, gNB 110 can determine the target sequence associated with the CSI-RS. For example, the target sequence can be represented by multiplying the reference sequence by a function which can be expressed as follows:

[0085]

[0086] where the sequence corresponding to the PRB in the subband is applied to all resource elements (k, l) mapped to the CSI-RS port p in that PRB.

[0087] As a special case of this embodiment, gNB 110 can use the same sequence for all ports, which corresponds to the case where the active FD components for all ports are the same. The function can be defined as follows:

[0088]

[0089] wherein ……, N 3 -1 is a subband index, and N 3 is the number of subbands configured in the reporting band, ……, N - 1 are PRB indices within the subband, and N is the subband size expressed in terms of the number of PRBs.

[0090] Figure 7 illustrates an example of mapping a beam and FD component to a beamformed CSI-RS port through a sequence selection mechanism for CSI-RS signals in a subband according to some example embodiments of the present disclosure to indicate the selection of the FD component for the CSI-RS port.

[0091] As Figure 7 shown, this example illustrates the mapping of the CSI-RS ports in subband n and the sequences for these two cases in Equation (3). Each subband has PRBs ( Figure 7 only PRB0 710 and are shown in and CDM is performed for each port over 2 resource elements (REs) in each PRB. For example, in PRB0 710, CSI-RS ports 0 and 1 perform CDM over REs 711 and 712, and CSI-RS ports 2 and 3 perform CDM over REs 713 and 714. In CSI-RS ports 0 and 1 perform CDM over REs 721 and 722, and CSI-RS ports 2 and 3 perform CDM over REs 723 and 724.

[0092] In this case, the gNB selects FD component n for port 0 and the CSI-RS sequence remains 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 a phase ramp with a slope of π.

[0093] In some example embodiments, a mixture of zero-power (ZP) CSI-RS and non-zero-power (NZP) CSI-RS can be used to signal different active FD components for each port in CSI-RS.

[0094] 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 reporting. It also masks REs so that they are not available for PDSCH transmission. As the name ZP indicates, nothing is transmitted in the configured ZP-CSI-RS REs.

[0095] Thus, to encode the information of the active FD component for each port, gNB 110 may determine the mapping of the configured ZP and NZP-CSI-RS over the union of REs for channel and interference measurements in a given subband or subband group.

[0096] Since the side information to be sent on the CSI-RS signal consists of a single bit for each subband or subband group, and there is a one-to-one mapping between a given subband, FD component, and path delay, the encoding of the side information can be performed by shifting the mapping of the ZP-CSI-RS for CSI-IM and the NZP-CSI-RS for channel measurement resource (CMR) in a given subband or subband group.

[0097] For example, gNB 110 may determine the corresponding zero-power part of the CSI-RS and the corresponding non-zero part of the CSI-RS for at least one selected CSI-RS port based on the FD component, and generate an indication of the mapping between at least one CSI-RS port and the selected beam and FD component based on the corresponding zero-power part and the corresponding non-zero part.

[0098] Figure 8 Shows an example of mapping a beam and an FD component to a beamformed CSI-RS port by using a combination of ZP-CSI-RS / NZP-CSI-RS for a CSI-RS signal in a subband to indicate the selection of the FD component for the CSI-RS port. As Figure 8 shown, the mapping of the NZP-CSI-RS is shown as CMR, and the ZP-CSI-RS is shown as CSI-IM to select the FD component for a specific CSI-RS port.

[0099] PRB0 810 and refer to the case where the FD component is selected for all ports, while PRB0 830 and refer to the case where the FD component is selected for all ports except ports 0 and 1. For example, in PRB0810, CSI-RS ports 0 and 1 perform CDM over REs 811 and 812, and CSI-RS ports 2 and 3 perform CDM over REs 813 and 814, and a set of REs 815 may represent a part of the ZP-CSI-RS.

[0100] Since the power difference between the NZP-CSI-RS and ZP-CSI-RS REs is large and they experience the same channel effects, the UE will be able to detect the offset in the ZP and NZP CSI-RS mappings and subsequently detect the selected FD component for each port.

[0101] Based on the different ways described above, gNB 110 can dynamically indicate the selected beam and FD component to UE 120 in the CSI-RS signal. That is, an indication of the mapping between at least one CSI-RS port and the selected beam and FD component can be determined. Then, referring again to Figure 2 , gNB 110 can send 206 the CSI-RS including the indication to UE 120. After receiving the CSI-RS from gNB 110, UE 120 can determine 208 the CSI report based on the indication obtained from the CSI-RS.

[0102] In some example embodiments, UE 120 can determine the number of frequency-domain components selected by gNB 110 based on the indication, and determine the bitmap size based on the determined number of frequency-domain components. Then, UE 120 can generate a CSI report with the determined bitmap size.

[0103] Referring again to Figure 5 , an example of the bitmap in the reciprocity-enhanced II PS PMI is also shown. UE 120 will no longer need to indicate the FD basis for each reporting layer. For each of the ν layers, UE 120 can report a one-dimensional bitmap of size αK 0 or smaller per layer, instead of reporting a two-dimensional bitmap of size 2L·M v (the dimensions of which are given by the selected ports (2L) and the selected FD components (M ν ). The size αK 0 corresponds to the total number of "active" FD components on all ports indicated by gNB 110.

[0104] The typical bitmap size is 2L×M per layer v , so the total overhead of the bitmap is v·2LM v . However, with the solution proposed in the present disclosure, for the maximum rank (MR) limited to ν = 1 or otherwise v·2K 0 , the bitmap overhead is reduced to a maximum size of K 0 . In eType II CBs, K 0 is defined as a fraction of 2LM 1 , more precisely, where the maximum number of non-zero coefficients that can be reported in all layers in eType II PS is K TOT ≤ K 0 when MR = 1, and K TOT ≤ 2K 0 when MR > 1. Therefore, the bitmap overhead can be reduced by more than 50% for example.

[0105] AsFigure 5 As shown, the dot markers 521-525 in the bitmap 530 may indicate the NZC calculated by the UE 120 for a given layer l (e.g., l = 1). If the UE 120 does not report a port selection indication, the size of the bitmap for layer 1 may be 10×1, such as αK 0 = 10, or if the UE 120 selects a subset of ports, its size may be smaller. In this example, if the UE 120 can indicate selecting 5 components from 10 components, the minimum bitmap size may be 5×1.

[0106] In this way, the gNB can indicate on which FD components the PMI calculation should be restricted, so that the PMI feedback overhead in the UL can be reduced without increasing the additional overhead cost in the DL.

[0107] In addition, the complexity at the UE for calculating the PMI amount for port selection and FD component selection performed at the gNB can be reduced.

[0108] In addition, with respect to non-reciprocity-assisted eType II PS, possible performance improvements can be achieved because the limit of M ν selected FD components per layer no longer applies. In fact, the gNB can select different FD components for each port, and the total number can exceed M ν . The UE can also indicate which FD components are most relevant for which layers and provide corresponding non-zero LCCs.

[0109] In addition, if the UE is configured to report only the LCC corresponding to FD component 0, possible improved performance relative to non-reciprocity-assisted eType II PS can be achieved by increasing the total number N 3 of FD components without increasing the significant complexity of the UE. N 3 is a parameter configured by the network corresponding to the number of configured PMI subbands, and it is defined as R times the number N SB of CQI subbands, i.e., N 3 = RN SB , where R is an RRC parameter with a value range of {1, 2} in non-reciprocity-assisted eType II PS. In reciprocity-assisted eType II PS, the value of R can be greater than 2 without affecting the complexity of UE implementation.

[0110] Figure 9 shows a flowchart of an example method 900 for port selection codebook enhancement according to some example embodiments of the present disclosure. The method 900 may be implemented at the first device 110 as shown Figure 1 . For the purpose of discussion, the method 900 will be described with reference to Figure 1 .

[0111] At 910, the first device determines a beam set and frequency domain components associated with the CSI-RS to be sent from the first device to the second device.

[0112] In some example embodiments, the first device may receive SRS from the second device and determine the beam set and frequency domain components based on the SRS.

[0113] At 920, the first device generates an indication of a mapping between at least one port selected at the first device for transmitting the CSI-RS, the frequency domain components, and the beam set.

[0114] In some example embodiments, the first device may determine the number of beam sets and the respective cyclic shifts of the frequency domain components corresponding to the beam sets. The first device may also determine the association between the frequency domain components and at least one port based on the number of beam sets and the respective cyclic shifts, where 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 the mapping based on the association.

[0115] In some example embodiments, the first device may select at least one port based on the beam set. The first device may also determine the respective subbands associated with the at least one port and determine the association between the frequency domain components and the respective subbands. The first device may also generate the indication based at least on the association.

[0116] In some example embodiments, the first device may determine a reference sequence associated with the CSI-RS and determine the 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 the indication based on the target sequence.

[0117] In some example embodiments, the first device may select at least one port based on the beam set. The first device may also determine the respective zero-power portions and the respective non-zero portions of the CSI-RS for the at least one port based on the frequency domain components and generate the indication based on the respective zero-power portions and the respective non-zero portions.

[0118] At 930, the first device transmits the CSI-RS including the indication to the second device.

[0119] Figure 10 A flowchart of an example method 1000 for port selection codebook enhancement according to some example embodiments of the present disclosure is shown. Method 1000 may be implemented at a second device 120 as shown in Figure 1 For purposes of discussion, method 1000 will be described with reference to Figure 1 describe method 1000.

[0120] At 1010, the second device receives CSI-RS from the first device.

[0121] At 1020, the second device obtains an indication of a mapping between at least one port selected at the first device for transmitting CSI-RS and a beam set and frequency domain components associated with the CSI-RS.

[0122] At 1030, the second device generates a CSI report based on the indication.

[0123] In some example embodiments, the second device may determine the number of frequency domain components based on the indication and determine the size of a bitmap for the CSI report based on the number of frequency domain components. The second device may also generate a CSI report based on the size.

[0124] In some example embodiments, if the second device determines that the association between the frequency domain components and at least one port is obtained from the indication, the second device may determine the number of at least one port. The second device may also determine the number of frequency domain components based on the number of at least one port.

[0125] In some example embodiments, if the second device determines that the association between the frequency domain components and at least one port is obtained from the indication, the second device may determine the number of at least one port. The second device may also receive an indication of the number of frequency domain components to be reported via radio resource control signaling. The number of frequency domain components is not related to the number of configured subbands. The second device may also determine the number of linear combination coefficients to be reported in the CSI report based on the number of at least one port and the indication of the number of frequency domain components, and determine the size of the bitmap based on the number of linear combination coefficients to be reported 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, regardless of the number N 3 of configured PMI subbands, i.e., M ν is no longer a function of N as in the Rel-16 type-II PS codebook. 3

[0126] In some example embodiments, if the second device determines that the association between the frequency domain components and corresponding subbands associated with at least one port is obtained from the indication, the second device may determine the number of frequency domain components based on the association.

[0127] In some example embodiments, if the second device determines that the corresponding zero-power part and the corresponding non-zero part of the CSI-RS of at least one port are obtained from the indication, the second device may determine the number of frequency domain components based on the corresponding non-zero part of the CSI-RS.

[0128] ​In some example embodiments, an apparatus (e.g., implemented at a first device 110) capable of performing method 900 may include components for performing the corresponding steps of method 900. The components may be implemented in any suitable form. For example, the components may be implemented in circuitry or software modules.

[0129] In some example embodiments, the apparatus includes components for determining, at a first device, a beam set and frequency-domain components associated with a CSI-RS to be transmitted from the first device to a second device; for 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 components and the beam set; and for transmitting to the second device a CSI-RS including the indication.

[0130] In some example embodiments, an apparatus (e.g., implemented at a second device 120) capable of performing method 1000 may include components for performing the corresponding steps of method 1000. The components may be implemented in any suitable form. For example, the components may be implemented in circuitry or software modules.

[0131] In some example embodiments, the apparatus includes components for receiving a CSI-RS from a first device; for obtaining an indication of a mapping between at least one port selected at the first device for transmitting the CSI-RS and a beam set and frequency-domain components associated with the CSI-RS; and for generating a CSI report based on the indication.

[0132] Figure 11 is a simplified block diagram of a device 1100 suitable for implementing embodiments of the present disclosure. The device 1100 may be provided to implement a communication device, such as Figure 1 the gNB 110 and UE120 shown. As shown, the device 1100 includes one or more processors 1110, one or more memories 1140 coupled to the processors 1110, and one or more transmitters and / or receivers (TX / RX) 1140 coupled to the processor 1100.

[0133] The TX / RX 1140 is for two-way communication. The TX / RX 1140 has at least one antenna to facilitate communication. The communication interface may represent any interface necessary for communicating with other network elements.

[0134] The processor 1110 may be of any type suitable for a local technical network and, by way of non-limiting example, may include one or more of the following: a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture. The device 1100 may have multiple processors, such as an application-specific integrated circuit chip that is subordinate in time to a clock synchronized with a main processor.

[0135] The memory 1120 may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memories 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 storage and / or optical storage. Examples of volatile memories include, but are not limited to, random access memory (RAM) 1122 and other volatile memories that do not persist during a power outage.

[0136] The computer program 1130 includes computer-executable instructions executed by the associated processor 1110. The program 1130 may be stored in the ROM 1120. The processor 1110 may perform any suitable actions and processes by loading the program 1130 into the RAM 1120.

[0137] Embodiments of the present disclosure may be implemented by the program 1130 such that the device 1100 may execute any process of the present disclosure referred to Figures 2 - 10 in the discussion. Embodiments of the present disclosure may also be implemented by hardware or a combination of software and hardware.

[0138] In some embodiments, the program 1130 may be tangibly embodied in a computer-readable medium, which may be included in the device 1100 (such as in the memory 1120) or in other storage devices accessible by the device 1100. The device 1100 may load the program 1130 from the computer-readable medium into the 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. Figure 12 An example of a computer-readable medium 1200 in the form of a CD or DVD is shown. The program 1130 is stored on the computer-readable medium.

[0139] In general, various embodiments of the present disclosure may be implemented using hardware or dedicated circuits, software, logic, or any combination thereof. Some aspects may be implemented using hardware, while other aspects may be implemented using firmware or software that may be executed by a controller, microprocessor, or other computing device. Although aspects of the embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other graphical representation, it should be understood that, by way of non-limiting example, the blocks, devices, systems, techniques, or methods described herein may be implemented using hardware, software, firmware, dedicated circuits or logic, general hardware or a controller or other computing device, or some combination thereof.

[0140] 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 includes computer-executable instructions, such as instructions included in program modules, which are executed in a device on a target real or virtual processor to perform the methods 200 and 400 described above with reference to Figure 2 and Figure 4 the methods 200 and 400. 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 functions of the program modules may be combined or split among the program modules as needed. The machine-executable instructions of the program modules may be executed within a local or distributed device. In a distributed device, the program modules may be located in both local and remote storage media.

[0141] The program code for performing the methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general-purpose computer, a special-purpose computer, or other programmable data processing device, such that the program codes, when executed by the processor or controller, cause the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code may be executed entirely on the machine, partially on the machine, as a stand-alone software package, partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0142] In the context of the present disclosure, the computer program code or related data may be carried by any suitable carrier such that a device, apparatus, or processor can perform the various processes and operations described above. Examples of carriers include signals, computer-readable media, etc.

[0143] The computer-readable media may be a computer-readable signal medium or a computer-readable storage medium. The computer-readable media may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatuses, or devices, or any suitable combination of the foregoing. More specific examples of the computer-readable storage medium will include an electrical connection having one or more wires, a portable computer floppy disk, 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.

[0144] Moreover, although the operations are described in a particular order, this should not be construed as requiring that the operations be performed in the particular order shown or in sequential order, or that all of the illustrated operations be performed to obtain the desired result. In some cases, multitasking and parallel processing may be advantageous. Also, although several specific implementation details are included in the foregoing discussion, these should not be construed as limitations on the scope of the present 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 may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented separately or in any suitable sub-combination in multiple embodiments.

[0145] Although the present 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 above specific features and acts are disclosed as example forms of implementing the claims.

Claims

1. A first device for communication, 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, together with the at least one processor, cause the first device to at least: determine a beam set and a frequency domain component associated with a channel state information-reference signal CSI-RS to be sent from the first device to a second device; determine the number of the beam set; determine corresponding cyclic shifts of the frequency domain components corresponding to the beam set; based on the number of the beam set and the corresponding cyclic shifts, determine the association between the frequency domain components and at least one port, wherein each of the frequency domain components is mapped to a corresponding one of the at least one port; based on the association, determine the mapping between the at least one port selected for sending the CSI-RS at the first device, the frequency domain components, and the beam set; generate an indication of the mapping; and send the CSI-RS including the indication to the second device.

2. The first device according to claim 1, wherein the first device is caused to determine the beam set and the frequency domain component by: receiving a sounding reference signal SRS from the second device; and determining the beam set and the frequency domain component based on the SRS.

3. The first device according to claim 1, wherein the first device is caused to generate the indication by: selecting the at least one port based on the beam set; determining corresponding subbands associated with the at least one port; determining the association between the frequency domain components and the corresponding subbands; and generating the indication based at least on the association.

4. The first device according to claim 3, 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 based on the reference sequence and the cyclic shift, determining a target sequence associated with the CSI-RS; and generating the indication based on the target sequence.

5. The first device according to claim 1, wherein the first device is caused to generate the indication by: selecting the at least one port based on the beam set; based on the frequency domain components, determining corresponding zero-power portions and corresponding non-zero portions of the CSI-RS for the at least one port; and generating the indication based on the corresponding zero-power portions and the corresponding non-zero portions.

6. The first device according to claim 1, wherein the first device includes a terminal device and the second device includes a network device.

7. A second device for communication, 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, together with the at least one processor, cause the second device to at least: Receive channel state information-reference signal CSI-RS from a first device; Obtain an indication of a mapping between at least one port selected at the first device for transmitting the CSI-RS, a beam set, and a frequency domain component associated with the CSI-RS; And Generate a CSI report based on the indication, wherein generating the CSI report includes: Determine the number of the frequency domain components based on the indication; Determine the size of a bitmap for the CSI report based on the number of the frequency domain components; and Generate the CSI report based on the size.

8. The second device according to claim 7, wherein the second device is caused to determine the number of the frequency domain components by: Determine the number of the at least one port according to that an association between the frequency domain component and the at least one port is obtained from the indication; and Determine the number of the frequency domain components based on the number of the at least one port.

9. The second device according to claim 7, wherein the second device is caused to determine the size of the bitmap by: Determine the number of the at least one port according to that an association between the frequency domain component and the at least one port is obtained from the indication ； And Receive, via radio resource control signaling, an indication of the number of the frequency domain components to be reported, the number of the frequency domain components being not related to the number of configured subbands; Determine the number of linear combination coefficients to be reported in the CSI report based on the number of the at least one port and the indication of the number of the frequency domain components; And Determine the size of the bitmap based on the number of the linear combination coefficients to be reported in the CSI report.

10. The second device according to claim 7, wherein the second device is caused to determine the number of the frequency domain components by: Based on an association determined from the indication of an association between the frequency domain component and a corresponding subband associated with the at least one port, determine the number of the frequency domain components.

11. The second device according to claim 7, wherein the second device is caused to determine the number of the frequency domain components by: Based on a corresponding zero-power part of the CSI-RS for the at least one port and a corresponding non-zero part of the CSI-RS obtained from the indication, determine the number of the frequency domain components based on the corresponding non-zero part of the CSI-RS.

12. The second device according to claim 7, wherein the first device includes a terminal device and the second device includes a network device.

13. A method for communication, including: At a first device, determine a beam set and a frequency domain component associated with channel state information-reference signal CSI-RS to be transmitted from the first device to a second device; Determine the number of the beam sets; Determine a corresponding cyclic shift of the frequency domain component corresponding to the beam set; Determine the association between the frequency domain components and at least one port based on the number of the beam sets and the corresponding cyclic shifts, wherein each of the frequency domain components is mapped to a corresponding one of the at least one port; Based on the association, determine the mapping between the at least one port selected at the first device for transmitting the CSI-RS, the frequency domain components, and the beam sets; Generate an indication of the mapping; and Transmit the CSI-RS including the indication to the second device.

14. The method according to claim 13, wherein determining the beam sets and the frequency domain components comprises: Receiving a sounding reference signal SRS from the second device; and Determining the beam sets and the frequency domain components based on the SRS.

15. The method according to claim 13, wherein generating the indication comprises: Selecting the at least one port based on the beam sets; Determining the corresponding subbands associated with the at least one port; Determining the association between the frequency domain components and the corresponding subbands; and Generating the indication based at least on the association.

16. The method according to claim 15, wherein generating the indication based at least on the association comprises: 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 Generating the indication based on the target sequence.

17. The method according to claim 13, wherein generating the indication comprises: Selecting the at least one port based on the beam sets; Determining the corresponding zero-power part and the corresponding non-zero part of the CSI-RS for the at least one port based on the frequency domain components; and Generating the indication based on the corresponding zero-power part and the corresponding non-zero part.

18. The method according to claim 13, wherein the first device includes a terminal device and the second device includes a network device.

19. A method for communication, comprises: At a second device, receiving a channel state information-reference signal CSI-RS from a first device; Obtaining an indication of the mapping between the at least one port selected at the first device for transmitting the CSI-RS, the beam sets associated with the CSI-RS, and the frequency domain components; and Generating a CSI report based on the indication, wherein generating the CSI comprises: Determining the number of the frequency domain components based on the indication; Determining the size of a bitmap for the CSI report based on the number of the frequency domain components; and Generating the CSI report based on the size.

20. The method according to claim 19, wherein determining the number of the frequency domain components comprises: Determining the number of the at least one port according to being obtained from the indication for determining the association between the frequency domain components and the at least one port; and Determining the number of the frequency domain components based on the number of the at least one port.

21. The method according to claim 19, wherein determining the size of the bitmap comprises: determining the number of the at least one port according to the association between the determined frequency domain component and the at least one port obtained from the indication; and receiving, via radio resource control signaling, an indication of the number of the frequency domain components to be reported, the number of the frequency domain components being independent of the number of configured subbands; determining the number of linear combination coefficients to be reported in the CSI report based on the number of the at least one port and the indication of the number of the frequency domain components; and determining the size of the bitmap based on the number of the linear combination coefficients to be reported in the CSI report.

22. The method according to claim 19, wherein determining the number of the frequency domain components comprises: determining the number of the frequency domain components based on the association between the determined frequency domain component and the corresponding subband associated with the at least one port obtained from the indication.

23. The method according to claim 19, wherein determining the number of the frequency domain components comprises: determining the number of the frequency domain components based on the corresponding non-zero part of the CSI-RS according to the corresponding zero-power part of the CSI-RS for the at least one port and the corresponding non-zero part of the CSI-RS obtained from the indication.

24. The method according to claim 19, wherein the first device comprises a terminal device and the second device comprises a network device.

25. A device for communication, comprising: means for determining, at a first device, a beam set and frequency domain components associated with a channel state information-reference signal (CSI-RS) to be sent from the first device to a second device; means for determining the number of the beam set; means for determining corresponding cyclic shifts of the frequency domain components corresponding to the beam set; means for determining an association between the frequency domain components and at least one port based on the number of the beam set and the corresponding cyclic shifts, wherein each of the frequency domain components is mapped to a corresponding one of the at least one port; means for determining, based on the association, a mapping between the at least one port selected at the first device for sending the CSI-RS, the frequency domain components, and the beam set; means for generating an indication of the mapping; and means for sending, to the second device, the CSI-RS including the indication.

26. A device for communication, comprising: means for receiving a channel state information-reference signal (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 sending the CSI-RS, a beam set associated with the CSI-RS, and frequency domain components; and means for generating a CSI report based on the indication, wherein generating the CSI report comprises: determining the number of the frequency domain components based on the indication; Determine the size of the bitmap for the CSI report based on the number of the frequency domain components; and Generate the CSI report based on the size.

27. A non-transitory computer-readable medium, comprising program instructions for causing a device to at least execute the method according to any one of claims 13 to 18.

28. A non-transitory computer-readable medium, comprising program instructions for causing a device to at least execute the method according to any one of claims 19 to 24.

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