Method and apparatus for adaptive antenna scaling in a communication system

Abstract

The method of the terminal includes: receiving first configuration information regarding a first CSI-RS resource from a base station; receiving second configuration information for a CSI reporting operation from the base station; receiving CSI-RS through M (M is a natural number less than or equal to L) CSI-RS antenna ports, which are a first subset of L CSI-RS antenna ports corresponding to the first CSI-RS resource, based on the first configuration information and the second configuration information; determining a first PMI based on the M CSI-RS antenna ports; and transmitting a CSI report including the first PMI to the base station, wherein the determining the first PMI is performed based on a codebook having at least first and second dimensions with sizes N1 and N2, respectively, and N1 and N2 may each be determined as a divisor of M.

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for adaptive antenna scaling in a communication system, and more particularly to a method and apparatus for adaptively scaling antennas in a wireless communication system to increase network power efficiency, and a corresponding method and apparatus for transmitting channel state information-reference signal (CSI-RS). [Background technology]

[0002] Mobile communication systems are a core infrastructure driving the development of the ICT industry and are evolving while overcoming the shortcomings and limitations of existing communication methods. Mobile communication systems can provide advanced services in usage scenarios such as eMBB (enhanced Mobile Broadband), URLLC (Ultra Reliable Low Latency Communication), mMTC (massive Machine Type Communication), ultra-low power, ultra-precise, and ultra-wide coverage. In addition, to achieve various performance indicators, mobile communication systems are exploring new communication frequency bands in the mid-band and high-band and are more actively utilizing multiple antenna technologies.

[0003] As a result, communication performance and processing power of communication nodes may increase, but there may be a problem that power consumption of communication nodes constituting a mobile communication system also increases. In particular, due to recent global efforts to achieve carbon neutrality and to reduce the operating costs of communication operators, there is a demand for technology that reduces power consumption not only of terminals but also of networks, i.e., base stations. Summary of the Invention [Problem to be solved by the invention]

[0004] In order to solve the above problems, an object of the present invention is to provide a method and apparatus for adaptively scaling antennas to increase power efficiency of a network, and a method and apparatus for transmitting CSI-RS accordingly. [Means for solving the problem]

[0005] To achieve the above object, one embodiment of the present invention is a method for a terminal, the method including: receiving first configuration information regarding a first channel state information-reference signal (CSI-RS) resource from a base station; receiving second configuration information for a CSI reporting operation from the base station; receiving CSI-RS through M (M is a natural number less than or equal to L) CSI-RS antenna ports, which are a first subset of L (L is a natural number) CSI-RS antenna ports corresponding to the first CSI-RS resource, based on the first configuration information and the second configuration information; determining a first precoding matrix indicator (PMI) based on the M CSI-RS antenna ports; and transmitting a CSI report including the first PMI to the base station, wherein determining the first PMI is performed based on a codebook having at least first and second dimensions with sizes N1 and N2, respectively, and N1 and N2 may each be determined as a divisor of M.

[0006] The second configuration information may include configuration information regarding multiple CSI reporting sub-configurations, the first CSI-RS resource may be referenced by a first CSI reporting sub-configuration included in the multiple CSI reporting sub-configurations, and the first PMI may be a CSI corresponding to the first CSI reporting sub-configuration.

[0007] A second CSI-RS resource is additionally referenced by the first CSI reporting sub-configuration, and the CSI corresponding to the first CSI reporting sub-configuration includes a CSI-RS resource indicator (CRI), which may be an index of the first CSI-RS resource or the second CSI-RS resource.

[0008] The second CSI-RS resources correspond to L CSI-RS antenna ports and may belong to the same CSI-RS resource set as the first CSI-RS.

[0009] The M CSI-RS antenna ports may be represented by a bitmap having a length of L, and the bitmap may be included in the second configuration information and transmitted from the base station to the terminal.

[0010] The antenna port numbers of the M CSI-RS antenna ports are reassigned in ascending order with consecutive values ​​from P to (P+M-1), where P is 0 or a natural number, and the first PMI may be determined based on the reassigned antenna port numbers.

[0011] M=2*N1*N2, where N1 is a value based on the number of CSI-RS antenna ports corresponding to the first dimension, and N2 is a value based on the number of CSI-RS antenna ports corresponding to the second dimension.

[0012] M=2*N1*N2*Ng, where N1 is a value based on the number of CSI-RS antenna ports corresponding to the first dimension, N2 is a value based on the number of CSI-RS antenna ports corresponding to the second dimension, Ng is the number of antenna panels, and the codebook may be a codebook for a multi-panel consisting of Ng panels.

[0013] The method may further include: receiving CSI-RS through M2 CSI-RS antenna ports, which are a second subset of the L CSI-RS antenna ports; and determining a second PMI based on the M2 CSI-RS antenna ports.

[0014] The second PMI may be included in the CSI report and transmitted to the base station based on an instruction from an upper layer message.

[0015] The first CSI-RS resource may be referenced by a second CSI reporting sub-configuration included in the plurality of CSI reporting sub-configurations, and the second PMI may be a CSI corresponding to the second CSI reporting sub-configuration.

[0016] Another embodiment of the present invention to achieve the above object is a method for a base station, comprising the steps of: transmitting first configuration information regarding a first channel state information-reference signal (CSI-RS) resource to a terminal; transmitting second configuration information for a CSI report to the terminal; transmitting CSI-RS to the terminal through all or some of L (L is a natural number) CSI-RS antenna ports corresponding to the first CSI-RS resource; and receiving from the terminal a CSI report including a first precoding matrix indicator (PMI) determined based on M (M is a natural number less than or equal to L) CSI-RS antenna ports, which is a first subset of the L CSI-RS antenna ports determined by the first configuration information and the second configuration information, wherein the first PMI is performed based on a codebook having at least first and second dimensions with sizes N1 and N2, respectively, and N1 and N2 may each be determined as a divisor of M.

[0017] The second configuration information may include configuration information regarding multiple CSI reporting sub-configurations, the first CSI-RS resource may be referenced by a first CSI reporting sub-configuration included in the multiple CSI reporting sub-configurations, and the first PMI may be a CSI corresponding to the first CSI reporting sub-configuration.

[0018] A second CSI-RS resource is additionally referenced by the first CSI reporting sub-configuration, and the CSI corresponding to the first CSI reporting sub-configuration includes a CSI-RS resource indicator (CRI), which may be an index of the first CSI-RS resource or the second CSI-RS resource.

[0019] The second CSI-RS resources correspond to L CSI-RS antenna ports and may belong to the same CSI-RS resource set as the first CSI-RS.

[0020] The M CSI-RS antenna ports may be represented by a bitmap having a length of L, and the bitmap may be included in the second configuration information and transmitted from the base station to the terminal.

[0021] The antenna port numbers of the M CSI-RS antenna ports are reassigned in ascending order with consecutive values ​​from P to (P+M-1), where P is 0 or a natural number, and the first PMI may be determined based on the reassigned antenna port numbers.

[0022] M=2*N1*N2, where N1 is a value based on the number of CSI-RS antenna ports corresponding to the first dimension, and N2 is a value based on the number of CSI-RS antenna ports corresponding to the second dimension.

[0023] M=2*N1*N2*Ng, where N1 is a value based on the number of CSI-RS antenna ports corresponding to the first dimension, N2 is a value based on the number of CSI-RS antenna ports corresponding to the second dimension, Ng is the number of antenna panels, and the codebook may be a codebook for a multi-panel consisting of Ng panels.

[0024] Another embodiment of the present invention to achieve the above object is a terminal, the terminal including a processor, configured to cause the terminal to perform: receiving first configuration information regarding a first channel state information-reference signal (CSI-RS) resource from a base station; receiving second configuration information for a CSI reporting operation from the base station; receiving CSI-RS through M (M is a natural number less than or equal to L) CSI-RS antenna ports, which are a first subset of L (L is a natural number) CSI-RS antenna ports corresponding to the first CSI-RS resource, based on the first configuration information and the second configuration information; determining a first precoding matrix indicator (PMI) based on the M CSI-RS antenna ports; and transmitting a CSI report including the first PMI to the base station, wherein determining the first PMI is performed based on a codebook having at least first and second dimensions with sizes N1 and N2, respectively, where N1 and N2 may each be determined as a divisor of M. [Effects of the Invention]

[0025] When using the method and apparatus of the present invention as described above, the antennas used for communication can be adaptively scaled to increase the power efficiency of the network. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a conceptual diagram illustrating a first embodiment of a communication system.

[0027] [Figure 2] 1 is a block diagram illustrating a first embodiment of the device;

[0028] [Figure 3] FIG. 1 is a conceptual diagram illustrating a first embodiment of a method for mapping resources to CSI-RS antenna ports.

[0029] [Figure 4] FIG. 1 is a conceptual diagram illustrating a first embodiment of a mapping method between CSI-RS antenna ports and TXRUs or physical antenna elements.

[0030] [Figure 5a] FIG. 1 is a conceptual diagram illustrating a first embodiment of a TXRU muting method. [Figure 5b] FIG. 10 is a conceptual diagram illustrating a second embodiment of the TXRU muting method.

[0031] [Figure 6] FIG. 1 is a conceptual diagram illustrating a first embodiment of a CSI reporting method based on multiple CSI-RS antenna port sets.

[0032] [Figure 7] FIG. 1 is a conceptual diagram illustrating a first embodiment of a method for configuring multiple CSI-RS antenna port sets.

[0033] [Figure 8] FIG. 10 is a conceptual diagram illustrating a second embodiment of a method for configuring multiple CSI-RS antenna port sets.

[0034] [Figure 9] FIG. 10 is a conceptual diagram illustrating a second embodiment of a CSI reporting method based on multiple CSI-RS antenna port sets.

[0035] [Figure 10] FIG. 2 is a conceptual diagram illustrating a first embodiment of a resource mapping method for CSI-RS antenna port sets.

[0036] [Figure 11] FIG. 10 is a conceptual diagram illustrating a second embodiment of a resource mapping method for CSI-RS antenna port sets.

[0037] [Figure 12] FIG. 10 is a conceptual diagram illustrating a third embodiment of a resource mapping method for CSI-RS antenna port sets. DETAILED DESCRIPTION OF THE INVENTION

[0038] Since the present invention can be modified in various ways and has various embodiments, a specific embodiment will be illustrated in the drawings and described in detail. However, it is not intended to limit the present invention to the specific embodiment, and it should be understood that the present invention includes all modifications, equivalents, and alternatives that fall within the spirit and technical scope of the present invention.

[0039] Terms such as "first," "second," etc. may be used to describe various components, but the components should not be limited by these terms. These terms are used only to distinguish one component from another. For example, a first component may be termed a "second component," and similarly, a second component may be termed a "first component" without departing from the scope of the present invention. The term "and / or" includes a combination of multiple associated listed items or any of multiple associated listed items.

[0040] In the examples of this application, "at least one of A and B" may mean "at least one of A or B" or "at least one of a combination of one or more of A and B." Also, in the examples of this application, "one or more of A and B" may mean "one or more of A or B" or "one or more of a combination of one or more of A and B."

[0041] When a component is said to be "coupled" or "connected" to another component, it should be understood that it may be directly coupled or connected to the other component, but that there may be other components in between. Conversely, when a component is said to be "directly coupled" or "directly connected" to another component, it should be understood that there are no other components in between.

[0042] The terms used in this application are merely used to describe specific embodiments and are not intended to limit the present invention. The singular expressions include the plural expressions unless the context clearly dictates otherwise. In this application, the terms "comprise" or "have" are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and should be understood not to preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0043] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms as defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning they have in the context of the relevant art, and should not be interpreted in an idealized or overly formal sense unless expressly defined in this application.

[0044] Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings. In describing the present invention, the same reference numerals will be used to refer to the same components in the drawings, and redundant descriptions of the same components will be omitted, in order to facilitate overall understanding.

[0045]

[0046] A communication system to which an embodiment of the present invention is applied will now be described. The communication system may be a 4G communication system (e.g., a long-term evolution (LTE) communication system, an LTE-A communication system), a 5G communication system (e.g., a new radio (NR) communication system), a 6G communication system, etc. The 4G communication system can support communication in a frequency band below 6 GHz, and the 5G communication system can support communication in a frequency band above 6 GHz as well as a frequency band below 6 GHz. The communication system to which the embodiment of the present invention is applied is not limited to the content described below, and the embodiment of the present invention may be applied to various communication systems. Here, the term "communication system" may be used interchangeably with "communication network," and "LTE" may refer to a "4G communication system," an "LTE communication system," or an "LTE-A communication system," and "NR" may refer to a "5G communication system" or an "NR communication system."

[0047] In embodiments, "an operation (e.g., a transmission operation) is configured" may mean that "configuration information (e.g., information element, parameter) for the corresponding operation" and / or "information instructing the execution of the corresponding operation" is signaled. "An information element (e.g., a parameter) is configured" may mean that the corresponding information element is signaled. "A resource (e.g., a resource region) is configured" means that configuration information for the corresponding resource is signaled. The signaling may be at least one of system information (SI) signaling (e.g., transmission of a system information block (SIB) and / or a master information block (MIB)), RRC signaling (e.g., transmission of RRC parameters and / or higher layer parameters), MAC control element (CE) signaling, or PHY signaling (e.g., transmission of downlink control information (DCI), uplink control information (UCI), and / or sidelink control information (SCI)).

[0048] FIG. 1 is a conceptual diagram illustrating a first embodiment of a communication system.

[0049] 1, the communication system 100 may include a plurality of communication nodes 110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6. The communication system 100 may further include a core network (e.g., a serving-gateway (S-GW), a packet data network (PDN)-gateway (P-GW), and a mobility management entity (MME)). When the communication system 100 is a 5G communication system (e.g., a new radio (NR) system), the core network may include an access and mobility management function (AMF), a user plane function (UPF), a session management function (SMF), etc.

[0050] The plurality of communication nodes 110 to 130 can support communication protocols (eg, LTE communication protocol, LTE-A communication protocol, NR communication protocol, etc.) defined in the 3GPP (3rd generation partnership project) standard. The communication nodes 110 to 130 may support code division multiple access (CDMA), wideband CDMA (WCDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal frequency division multiplexing (OFDM), filtered OFDM, cyclic prefix (CP)-OFDM, discrete Fourier transform-spread-OFDM (DFT-s-OFDM), orthogonal frequency division multiple access (OFDMA), single carrier (SC)-FDMA, non-orthogonal multiple access (NOMA), generalized frequency division multiplexing (GFDM), filter bank multi-carrier (FBMC), universal filtered multi-carrier (UFMC), space division multiple access (SDMA), and the like. Each of the communication nodes may refer to an apparatus or device. The embodiments may be performed by an apparatus or device. The structure of the apparatus (eg, device) may be as follows.

[0051] FIG. 2 is a block diagram illustrating a first embodiment of the device.

[0052] 2, the device 200 may include at least one processor 210, a memory 220, and a transceiver 230 that is connected to a network to perform communication. The device 200 may further include an input interface 240, an output interface 250, a storage device 260, etc. Each component included in the device 200 is connected to a bus 270 to perform communication.

[0053] The processor 210 can execute program commands stored in at least one of the memory 220 and the storage device 260. The processor 210 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods according to embodiments of the present invention are performed. The memory 220 and the storage device 260 may each be composed of at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 220 may be composed of at least one of a read-only memory (ROM) and a random access memory (RAM).

[0054] 1, the communication system 100 may include multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2, and multiple terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6. The first base station 110-1, the second base station 110-2, and the third base station 110-3 may each form a macro cell. The fourth base station 120-1 and the fifth base station 120-2 may each form a small cell. The fourth base station 120-1, the third terminal 130-3, and the fourth terminal 130-4 may belong to the cell coverage of the first base station 110-1. The second terminal 130-2, the fourth terminal 130-4, and the fifth terminal 130-5 may belong within the cell coverage of the second base station 110-2. The fifth base station 120-2, the fourth terminal 130-4, the fifth terminal 130-5, and the sixth terminal 130-6 may belong within the cell coverage of the third base station 110-3. The first terminal 130-1 may belong within the cell coverage of the fourth base station 120-1. The sixth terminal 130-6 may belong within the cell coverage of the fifth base station 120-2.

[0055] Here, the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be referred to as NodeBs (NBs), evolved NodeBs (eNBs), gNBs, advanced base stations (ABSs), high reliability-base stations (HR-BSs), base transceiver stations (BTSs), radio base stations, radio transceivers, access points, access nodes, radio access stations (RASs), mobile multihop relay-base stations (MMR-BSs), relay stations (RSs), advanced relay stations (ARSs), high reliability-relay stations (HR-RSs), home NodeBs (HNBs), home eNodeBs (HeNBs), road side units (RSUs), radio remote heads (RRHs), transmission points (TPs), transmission and reception points (TRPs), etc.

[0056] The multiple terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 may each be referred to as a UE (user equipment), TE (terminal equipment), AMS (advanced mobile station), HR-MS (high reliability-mobile station), terminal, access terminal, mobile terminal, station, subscriber station, mobile station, portable subscriber station, node, device, OBU (on board unit), etc.

[0057] Meanwhile, the base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may operate in different frequency bands or the same frequency band. The base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to each other via an ideal backhaul link or a non-ideal backhaul link, and may exchange information via the ideal backhaul link or the non-ideal backhaul link. The base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to the core network via an ideal backhaul link or a non-ideal backhaul link. Each of the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can transmit signals received from the core network to the corresponding terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6, and can transmit signals received from the corresponding terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 to the core network.

[0058] In addition, the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can each support MIMO transmission (e.g., single user (SU)-MIMO, multi user (MU)-MIMO, massive MIMO, etc.), coordinated multipoint (CoMP) transmission, carrier aggregation (CA) transmission, transmission in unlicensed bands, device to device communication (D2D) (or proximity services (ProSe)), Internet of Things (IoT) communication, dual connectivity (DC), etc. Here, the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 may perform operations corresponding to and supported by base stations 110-1, 110-2, 110-3, 120-1, and 120-2, respectively. For example, the second base station 110-2 may transmit a signal to the fourth terminal 130-4 based on the SU-MIMO scheme, and the fourth terminal 130-4 may receive a signal from the second base station 110-2 based on the SU-MIMO scheme. Alternatively, the second base station 110-2 can transmit signals to the fourth terminal 130-4 and the fifth terminal 130-5 based on the MU-MIMO scheme, and the fourth terminal 130-4 and the fifth terminal 130-5 can each receive signals from the second base station 110-2 using the MU-MIMO scheme.

[0059] The first base station 110-1, the second base station 110-2, and the third base station 110-3 can each transmit signals to the fourth terminal 130-4 based on the CoMP scheme, and the fourth terminal 130-4 can receive signals from the first base station 110-1, the second base station 110-2, and the third base station 110-3 based on the CoMP scheme. The multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can each transmit and receive signals to and from terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 within their own cell coverage based on the CA scheme. The first base station 110-1, the second base station 110-2, and the third base station 110-3 can each control D2D between the fourth terminal 130-4 and the fifth terminal 130-5, and the fourth terminal 130-4 and the fifth terminal 130-5 can perform D2D under the control of the second base station 110-2 and the third base station 110-3, respectively.

[0060] The numerology applied to physical signals and channels in a communication system (e.g., an NR communication system or a 6G communication system) may be variable. The numerology may be variable to meet various technical requirements of the communication system. In a communication system using a cyclic prefix (CP)-based OFDM waveform technology, the numerology may include subcarrier spacing and CP length (or CP type). Table 1 may be a first embodiment of a numerology configuration method for a CP-OFDM-based communication system. Adjacent subcarrier spacings may have a power-of-two relationship, and the CP length may be scaled at the same ratio as the length of the OFDM symbol. At least some of the numerologies in Table 1 may be supported depending on the frequency band in which the communication system operates. In addition, the communication system may additionally support numerology(s) not listed in Table 1. For a specific subcarrier spacing (e.g., 60 kHz), CP type(s) not listed in Table 1 (e.g., extended CP) may additionally be supported.

[0061] Table 1 relates to a first embodiment of a numerology configuration method for a CP-OFDM based communication system.

[0062] [Table 1]

[0063] The frame structure of a communication system will be described below. Elements constituting the frame structure in the time domain may include subframes, slots, minislots, symbols, etc. A subframe may be used as a unit of transmission, measurement, etc., and the length of a subframe may have a fixed value (e.g., 1 ms) regardless of the subcarrier spacing. A slot may include consecutive symbols (e.g., 14 OFDM symbols). The length of a slot may be variable and different from the length of a subframe. For example, the length of a slot may be inversely proportional to the subcarrier spacing.

[0064] A slot may be used as a unit of transmission, measurement, scheduling, resource configuration, timing (e.g., scheduling timing, hybrid automatic repeat request (HARQ) timing, channel state information (CSI) measurement and reporting timing, etc.). The length of the actual time resource used for transmission, measurement, scheduling, resource configuration, etc. may not match the length of a slot. A minislot may include consecutive symbol(s), and the length of a minislot may be shorter than the length of a slot. A minislot may be used as a unit of transmission, measurement, scheduling, resource configuration, timing, etc. A minislot (e.g., minislot length, minislot boundaries, etc.) may be predefined in a technical standard. Alternatively, a minislot (e.g., minislot length, minislot boundaries, etc.) may be configured (or indicated) to a terminal. The terminal may be configured (or indicated) to use a minislot when certain conditions are met.

[0065] A base station can schedule a data channel (e.g., a physical downlink shared channel (PDSCH), a physical uplink shared channel (PUSCH), or a physical sidelink shared channel (PSSCH)) using some or all of the symbols constituting a slot. In particular, a data channel can be transmitted using a portion of a slot for URLLC transmission, unlicensed band transmission, transmission in a coexistence situation between an NR communication system and an LTE communication system, multi-user scheduling based on analog beamforming, etc. In addition, a base station can schedule data channels using multiple slots. In addition, a base station can schedule data channels using at least one minislot.

[0066] Elements constituting a frame structure in the frequency domain may include resource blocks (RBs), subcarriers, etc. One RB may include consecutive subcarriers (e.g., 12 subcarriers). The number of subcarriers constituting one RB may be constant regardless of numerology. In this case, the bandwidth occupied by one RB may be proportional to the subcarrier spacing of the numerology. RBs may be used as transmission and resource allocation units for data channels, control channels, etc. Resource allocation for data channels may be performed in units of RBs or RB groups (e.g., resource block groups (RBGs)). One RBG may include one or more consecutive RBs. Resource allocation for control channels may be performed in units of control channel elements (CCEs). One CCE in the frequency domain may include one or more RBs.

[0067] In a communication system, a slot (e.g., a slot format) may be composed of a combination of one or more intervals from a downlink (DL) interval, a flexible interval (or unknown interval), and an uplink (UL) interval. The downlink interval, flexible interval, and uplink interval may each be composed of one or more consecutive symbols. The flexible interval may be located between the downlink interval and the uplink interval, between the first downlink interval and the second downlink interval, between the first uplink interval and the second uplink interval, etc. When a flexible interval is inserted between the downlink interval and the uplink interval, the flexible interval may be used as a guard interval.

[0068] A slot may include one or more flexible intervals. Alternatively, a slot may not include a flexible interval. The UE may perform a predefined operation in the flexible interval. Alternatively, the UE may perform an operation configured by the base station semi-statically or periodically in the flexible interval. For example, operations configured by the base station periodically may include a physical downlink control channel (PDCCH) monitoring operation, a synchronization signal / physical broadcast channel (SS / PBCH) block reception and measurement operation, a channel state information-reference signal (CSI-RS) reception and measurement operation, a downlink semi-persistent scheduling (SPS) PDSCH reception operation, a sounding reference signal (SRS) transmission operation, a physical random access channel (PRACH) transmission operation, a periodically configured physical uplink control channel (PUCCH) transmission operation, a PUSCH transmission operation according to a configured grant, etc. Flexible symbols may be overridden by downlink symbols or uplink symbols. When a flexible symbol is overridden by a downlink or uplink symbol, the terminal can perform a new operation instead of an existing operation on the corresponding flexible symbol (e.g., the overridden flexible symbol).

[0069] Meanwhile, in this disclosure, SSB may refer to a signal set including a synchronization signal and / or a broadcast channel. The synchronization signal may include a PSS, SSS, etc., and the broadcast channel may include a physical broadcast channel (PBCH). The SSB may also include a reference signal. The reference signal may refer to a demodulation reference signal (DM-RS), CSI-RS, tracking reference signal (TRS), positioning reference signal (PRS), phase tracking reference signal (PT-RS), etc. for decoding the PBCH. In an NR communication system, SSB may refer to a synchronization signal / physical broadcast channel (SS / PBCH) block. The SSB may be transmitted periodically, and one or more SSBs may be repeatedly transmitted per period.

[0070]

[0071] The format of a unit time resource (hereinafter referred to as "slot format") may be semi-statically configured by higher layer signaling (e.g., radio resource control (RRC) signaling). Information indicating the semi-static slot format may be included in system information, and the semi-static slot format may be configured cell-specifically. Alternatively, the semi-static slot format may be additionally configured for each UE through UE-specific higher layer signaling (e.g., RRC signaling). Flexible symbols in a cell-specific configured slot format may be overridden with downlink or uplink symbols by UE-specific higher layer signaling. Alternatively, the slot format may be dynamically indicated by physical layer signaling (e.g., a slot format indicator (SFI) included in downlink control information (DCI)). The semi-statically configured slot format may be overridden by a dynamically indicated slot format. For example, semi-statically configured flexible symbols may be overridden with downlink or uplink symbols by the SFI.

[0072] A base station and a terminal can perform downlink, uplink, sidelink, etc., operations in a bandwidth part. A bandwidth part can be defined as a collection of RBs (e.g., physical resource blocks (PRBs)) having a specific numerology. The RBs constituting one bandwidth part can be contiguous in the frequency domain. One numerology can be used for signal transmission (e.g., transmission of a control channel or a data channel) in one bandwidth part. In the embodiments, "signal" can refer to any physical signal and channel when used in a broad sense. A terminal performing an initial access procedure can obtain configuration information of an initial bandwidth part from the base station through system information. A terminal operating in an RRC connected state can obtain configuration information of a bandwidth part from the base station through terminal-specific upper layer signaling.

[0073] The bandwidth portion configuration information may include numerology (e.g., subcarrier spacing and / or CP length) applied to the bandwidth portion. In addition, the bandwidth portion configuration information may further include information indicating the position of the starting RB (e.g., starting PRB) of the bandwidth portion and information indicating the number of RBs (e.g., PRBs) constituting the bandwidth portion. At least one bandwidth portion among the bandwidth portion(s) configured in the terminal may be activated. For example, one uplink bandwidth portion and one downlink bandwidth portion may be activated within one carrier. In a time division duplex (TDD)-based communication system, a pair of an uplink bandwidth portion and a downlink bandwidth portion may be activated. A base station may configure multiple bandwidth portions within one carrier to a terminal and switch the active bandwidth portion of the terminal.

[0074] Meanwhile, in the embodiments, "a certain frequency band (e.g., a carrier, a bandwidth portion, an RB set, an LBT (listen before talk) subband, a guard band, etc.) is activated" may mean "a state in which a base station or a terminal can transmit and receive signals using the corresponding frequency band." Also, "a certain frequency band is activated" may mean "a state in which an RF (radio frequency) filter (e.g., a bandpass filter) of a transceiver operates including the frequency band."

[0075] In an embodiment, RB may refer to a CRB (common RB). Alternatively, RB may refer to a PRB or VRB (virtual RB). In a communication system, CRB may refer to an RB constituting a set of contiguous RBs (e.g., a common RB grid) based on a reference frequency (e.g., point A). Carriers, bandwidth portions, etc. may be arranged on the common RB grid. That is, carriers, bandwidth portions, etc. may be composed of CRB(s). RBs or CRBs constituting a bandwidth portion may be referred to as PRBs, and within a bandwidth portion, a CRB index may be appropriately converted to a PRB index. In an embodiment, RB may refer to an IRB (interlaced RB).

[0076] The PDCCH may be used to transmit DCI or a DCI format to a terminal. The smallest resource unit constituting the PDCCH may be a resource element group (REG). A REG may consist of one PRB (e.g., 12 subcarriers) in the frequency domain and one OFDM symbol in the time domain. Therefore, one REG may include 12 resource elements (REs). A demodulation reference signal (DM-RS) for decoding (or demodulating) the PDCCH may be mapped to three REs among the 12 REs constituting the REG, and control information (e.g., modulated DCI) may be mapped to the remaining nine REs. One PDCCH candidate may consist of one CCE or aggregated CCEs. One CCE may consist of multiple REGs. An NR communication system can support CCE aggregation levels 1, 2, 4, 8, 16, etc., and one CCE may consist of six REGs.

[0077] A CORESET (control resource set) can be a resource region in which a terminal performs blind decoding (or blind demodulation) of a PDCCH. A CORESET can consist of multiple REGs. A CORESET can consist of one or more PRBs in the frequency domain and one or more symbols (e.g., OFDM symbols) in the time domain. The symbols constituting one CORESET can be contiguous in the time domain. The PRBs constituting one CORESET can be contiguous or discontinuous in the frequency domain. One DCI (e.g., one DCI format, one PDCCH) can be transmitted within one CORESET. Multiple CORESETs can be configured from a cell perspective or a terminal perspective, and multiple CORESETs can overlap with each other in time-frequency resources.

[0078] CORESET can be configured in a terminal by the PBCH (e.g., system information transmitted over the PBCH, master information block (MIB)). The ID (identifier) ​​of the CORESET configured by the PBCH may be 0. That is, the CORESET configured by the PBCH may be referred to as CORESET#0. A terminal operating in an RRC idle state can perform a monitoring operation with CORESET#0 to receive the first PDCCH in the initial connection procedure. Not only a terminal operating in an RRC idle state but also a terminal operating in an RRC connected state can perform a monitoring operation with CORESET#0. CORESET can be configured in a terminal by other system information (e.g., system information block type 1 (SIB1)) in addition to system information transmitted over the PBCH. For example, in order to receive a random access response (or Msg2) in a random access procedure, the terminal can receive SIB1 including configuration information for CORESET. CORESET can also be configured in a terminal by terminal-specific upper layer signaling (e.g., RRC signaling).

[0079] The search space may be a set of PDCCH candidate(s) or a set of resource regions occupied by the PDCCH candidate(s). The UE may perform blind decoding on each PDCCH candidate within the predefined search space. The UE may determine whether a PDCCH has been transmitted to itself by performing a cyclic redundancy check (CRC) on the blind decoding result. If it is determined that the PDCCH is the PDCCH for the UE, the UE may receive the PDCCH.

[0080]

[0081] One or more search spaces may constitute a search space set. The search space may be defined / configured for each CCE aggregation level, and the search space set may refer to the search space for each CCE aggregation level or the sum of the search spaces for all CCE aggregation levels. For each CCE aggregation level, PDCCH candidates may be composed of CCE(s) selected by a predefined hash function within a CORESET or search space occasion. In some embodiments, the term "search space set" may refer to the "search space."

[0082] A search space set may be logically associated with or correspond to one CORESET. One CORESET may be logically associated with or correspond to one or more search space sets. A search space set for transmitting common DCI or group common DCI may be referred to as a common search space set (hereinafter referred to as a "CSS set"). The common DCI or group common DCI may include at least one of PDSCH resource allocation information for transmitting system information, paging, power control command, SFI, or preemption indicator. In an NR communication system, the common DCI may correspond to DCI formats 0_0, 1_0, etc., and the cyclic redundancy check (CRC) of the common DCI may be scrambled and transmitted in a system information-radio network temporary identifier (SI-RNTI), paging-RNTI (P-RNTI), random access-RNTI (RA-RNTI), temporary cell-RNTI (TC-RNTI), etc. The group-common DCI may correspond to DCI format 2_X (X = 0, 1, 2, ...), etc., and the CRC of the group-common DCI may be scrambled and transmitted in SFI-RNTI (slot format indicator-RNTI), etc. The CSS set may include Type 0, Type 0A, Type 1, Type 2, and Type 3 CSS sets.

[0083] A search space set for transmitting UE-specific DCI may be referred to as a UE-specific search space set (hereinafter referred to as a "USS set"). The UE-specific DCI may include scheduling and resource allocation information for PDSCH, PUSCH, PSSCH, etc. In an NR communication system, the UE-specific DCI may correspond to DCI formats 0_1, 0_2, 1_1, 1_2, 3_0, 3_1, etc., and the CRC of the UE-specific DCI may be scrambled and transmitted in C-RNTI, CS-RNTI (configured scheduling-RNTI), MCS-C-RNTI (modulation and coding scheme-C-RNTI), etc. Considering scheduling flexibility and fallback transmission, the UE-specific DCI may also be transmitted in a CSS set. In this case, the UE-specific DCI may be transmitted according to a DCI format corresponding to the common DCI. For example, the UE may monitor a PDCCH (eg, DCI format 0_0, 0_1) in which the CRC is scrambled with C-RNTI, CS-RNTI, MCS-C-RNTI, etc. in the CSS set.

[0084] The Type 0 CSS set may be used to receive DCI scheduling PDSCH including SIB1 and may be configured via PBCH or cell-specific RRC signaling. The ID of the Type 0 CSS set may be assigned or configured as 0. The Type 0 CSS set may be logically associated with CORESET #0.

[0085] A terminal can improve channel estimation performance or form transmit / receive beams by utilizing large-scale propagation characteristics of a wireless channel. The large-scale propagation characteristics of the wireless channel experienced by a first signal and a second signal transmitted between communication nodes may be identical. If the large-scale propagation characteristics of a first signal and a second signal transmitted from a base station to a terminal are identical, a quasi-co-location (QCL) relationship may be established between the first signal and the second signal. The large-scale propagation characteristics of the wireless channel may also be defined as QCL parameters. For example, QCL parameters may include delay spread, Doppler spread, Doppler shift, average gain, average delay, spatial Rx parameters, etc. The spatial Rx parameters may correspond to characteristics of a receive beam, receive channel spatial correlation, receive spatial filter, transmit / receive beam pair, etc. In this disclosure, the spatial Rx parameters may be referred to as "spatial QCL" for convenience. A set of one or more QCL parameter(s) may be referred to as a QCL type. QCL types used in NR communication systems may include at least Type A, Type B, Type C, and Type D. A Type D QCL may include spatial reception parameters and may correspond to a spatial QCL.

[0086] The base station may signal a "TCI state" or "TCI" to the terminal. In the present disclosure, the terms "TCI state" and "TCI" may be used interchangeably. The TCI state may include information indicating a QCL relationship between a QCL source signal (e.g., a first signal) and a QCL target signal (e.g., a second signal). Specifically, the TCI state may include one or more pieces of information designating the QCL source signal (e.g., source signal type, source signal ID, etc.) and information regarding the QCL parameter(s) (e.g., QCL type(s)) that establishes the QCL relationship. In addition, the TCI state information may be included in configuration information of the QCL target signal, and the terminal may recognize the QCL target signal based on the inclusion relationship. The QCL source signal may include an SSB, a synchronization signal, a reference signal (e.g., CSI-RS, DM-RS), a physical channel, etc. The QCL target signal may include a reference signal, a physical channel, a DM-RS for the physical channel, etc. The QCL source signal and the QCL target signal may be a downlink physical signal or channel or an uplink physical signal or channel. The transmission directions of the QCL source signal and the QCL target signal may be the same or different, and the terminal may assume that the large-scale propagation characteristics of the first signal apply equally to the second signal based on the TCI status signaling information.

[0087] A QCL relationship may be established for the PDCCH monitored by the UE. The UE may assume that the PDCCH (i.e., PDCCH DM-RS) has a QCL relationship with some signal (i.e., QCL source signal). The QCL relationship may be determined based on the signaling of the TCI information described above. Alternatively, the QCL relationship may be determined by a method predefined in a technical standard. The UE may perform beamforming operations, channel estimation operations, etc. for PDCCH monitoring and reception based on the QCL relationship.

[0088] The same TCI or QCL relationship may be applied within one CORESET. That is, the UE can perform monitoring (or reception) operations for all search space sets or all PDCCH candidates belonging to the same CORESET based on the same QCL relationship. The TCI or QCL relationship applied to each CORESET may be configured by the base station or induced according to a predefined rule. The QCL relationship for a specific CORESET may be determined based on the initial access or random access procedure of the UE. For example, CORESET 0 may have a QCL relationship with the SSB selected in the initial access procedure, the PRACH most recently transmitted in the random access procedure, etc. When a CORESET pool is configured in the UE, the same QCL relationship may be established for all CORESETs belonging to the same CORESET pool. Alternatively, the TCI or QCL relationship may be applied per search space set. In this case, different TCIs or different QCL relationships may be applied to monitoring multiple search space sets within the same CORESET.

[0089]

[0090] A link adaptation technique may be used in a communication system. That is, when a transmitting node attempts to transmit a data channel, a control channel, etc., it may adaptively change the number of transmission layers, modulation and coding (MCS), precoding or beamforming, transmit beams, receive beams, etc. For example, when transmitting a PDSCH to a terminal, a base station may instantaneously determine a modulation scheme, a channel code rate, etc. to be applied to the PDSCH, and form one or more transmission layers by applying appropriate precoding to the PDSCH. The above-mentioned link adaptation parameters may be included in scheduling information for the PDSCH, or may be included in DCI scheduling the PDSCH or SPS configuration information and transmitted to the terminal.

[0091] The link adaptation technique may be performed based on CSI reported from the UE to the base station. The base station may transmit signals (e.g., SSB, CSI-RS, TRS, DM-RS) to the UE for the UE to measure CSI. The UE may receive the signals and calculate CSI based on the received signals. CSI or CSI types may include channel quality indicator (CQI), precoding matrix indicator (PMI), rank indicator (RI), layer indicator (LI), beam index, CSI-RS resource indicator (CRI), SSB resource indicator (SSBRI), etc. In a broad sense, CSI may also include beam quality measurements (e.g., layer 1-received signal received power (L1-RSRP), layer 1-signal-to-interference-plus-noise ratio (L1-SINR), etc.). The UE may report the calculated CSI to the base station via an uplink channel (e.g., PUCCH, PUSCH).

[0092] To receive CSI measurement reports from a terminal, a base station can transmit CSI resource configuration information to the terminal. The CSI resource configuration can include configuration information for "CSI-RS resource(s)." For example, the CSI resource configuration can include configuration information for one or more "CSI resource sets." The CSI resource set can include CSI-RS resource set(s) and / or SSB resource set(s) for channel measurement, and can include CSI-IM (CSI-interference measurement) resource set(s) for interference measurement. Here, a CSI-RS resource set can refer to a set including one or more CSI-RS resource(s). If necessary, multiple CSI resource configuration(s) can be configured in a terminal. In an NR communication system, the CSI resource configuration can be referred to as a "CSI resource setting."

[0093]

[0094] In this disclosure, CSI-RS resources may refer to physical resources on which CSI-RS is transmitted. They may also refer to CSI-RS resource configuration parameter(s) or CSI-RS resource configuration units. Two types of CSI-RS resources may be configured for a terminal. The first is a non-zero-power (NZP) CSI-RS resource where the base station actually transmits CSI-RS to the terminal, and the second is a zero-power (ZP) CSI-RS resource where the base station does not actually transmit CSI-RS to the terminal. Hereinafter, unless otherwise specified, CSI-RS resources may be understood to refer to NZP CSI-RS resources. CSI-RS resources may correspond to CSI-RS or CSI-RS sequences.

[0095] CSI-RS resources can be configured as periodic, semi-persistent, or aperiodic. Periodic CSI-RS resources or activated semi-persistent CSI-RS resources appear periodically, and the resource location can be determined by a periodicity and an offset. Aperiodic CSI-RS resources can be dynamically allocated by DCI. Up to M CSI-RS antenna ports can be mapped to each CSI-RS resource (M is a natural number). In an NR communication system, M can be 32.

[0096]

[0097] FIG. 3 is a conceptual diagram illustrating a first embodiment of a method for mapping resources to CSI-RS antenna ports.

[0098] Referring to Figure 3, a terminal can receive CSI-RS resource configuration information from a base station and can receive CSI-RS based on the configuration information. The CSI-RS resources can be configured with up to 16 CSI-RS antenna ports. The 16 CSI-RS antenna ports can be mapped according to a predetermined pattern within one slot and one resource block (RB), as illustrated in Figure 3. If the CSI-RS transmission bandwidth includes multiple RBs, the CSI-RS can be mapped to multiple RBs using the same pattern. Here, RB may refer to a physical resource block (PRB).

[0099] In this embodiment, it is assumed that the indices (or numbers) of the CSI-RS antenna ports are assigned in ascending order starting from 0. Accordingly, the 16 CSI-RS antenna ports may be assigned indices from 0 to 15. However, the indices are merely identifiers for distinguishing different antenna ports, and any other numbers may be used instead of 0 to 15. For example, in an NR communication system, the indices of the CSI-RS antenna ports may be assigned in ascending order starting from 3000. The indices from 0 to 15 illustrated in FIG. 3 may correspond to indices from 3000 to 3015 in an NR communication system. The antenna port numbers of the CSI-RS antenna ports for determining CSI (e.g., PMI), which will be described later, may be reassigned in ascending order with consecutive values ​​starting from P (P is an integer, e.g., P=3000).

[0100] The CSI-RS antenna ports may be multiplexed in the form of time division multiplexing (TDM), frequency division multiplexing (FDM), and / or code division multiplexing (CDM) and mapped to resource elements (REs).

[0101] Referring to FIG. 3, TDM, FDM, and CDM can all be applied to multiplexing the 16 CSI-RS antenna ports. For example, CSI-RS antenna ports 0 to 3 may be mapped to the 5th to 6th symbols and the 3rd to 4th subcarriers, CSI-RS antenna ports 4 to 7 may be mapped to the 5th to 6th symbols and the 9th to 10th subcarriers, CSI-RS antenna ports 8 to 11 may be mapped to the 9th to 10th symbols and the 3rd to 4th subcarriers, and CSI-RS antenna ports 12 to 15 may be mapped to the 9th to 10th symbols and the 9th to 10th subcarriers. In this case, CSI-RS antenna ports 0 to 3 and CSI-RS antenna ports 4 to 7 may be FDM-multiplexed on the same symbol. Also, CSI-RS antenna ports 0 to 3 and CSI-RS antenna ports 8 to 11 may be TDM-multiplexed on the same subcarrier. Furthermore, four CSI-RS antenna ports mapped to four adjacent REs can be CDM-modulated to form CDM groups. For example, CSI-RS antenna ports 0 to 3, CSI-RS antenna ports 4 to 7, CSI-RS antenna ports 8 to 11, and CSI-RS antenna ports 12 to 15 can form CDM group 0, CDM group 1, CDM group 2, and CDM group 3, respectively.

[0102] The CDM-modulated antenna ports may be distinguished by different orthogonal cover codes (OCCs). The four different CSI-RS antenna ports of the CDM group having a size of 4 may be distinguished by a time-domain (TD)-OCC having a length of 2 and a frequency-domain (FD)-OCC having a length of 2. The order in which the CSI-RS antenna ports are mapped to the CSI-RS REs may follow a predefined rule. In this embodiment, the CSI-RS antenna port indices may be assigned first within the CDM group, second in ascending order in the frequency domain (i.e., in the direction of increasing subcarrier index), and finally in ascending order in the time domain (i.e., in the direction of increasing symbol index).

[0103] The CSI-RS mapping pattern shown in FIG. 3 is merely one example, and CSI-RS resource mapping can be implemented in various forms. The UE can receive configuration information from the base station regarding the number of CSI-RS antenna ports constituting the CSI-RS resources, the size of the CDM groups, the number of CDM groups, the location of each CDM group, the frequency-domain CSI-RS transmission density, the time-domain period, and the offset, etc., and can determine the mapping location of each CSI-RS antenna port in the CSI-RS resources based on the configuration information and receive each CSI-RS antenna port at the determined mapping location. The base station can also map the CSI-RS antenna ports to the CSI-RS resources based on the configuration information and transmit the CSI-RS antenna ports to the UE. Hereinafter, "the UE receives CSI-RS antenna port(s)" can be interpreted as meaning the UE receives CSI-RS through the corresponding CSI-RS antenna port(s). Furthermore, the base station transmitting the CSI-RS antenna port(s) may be interpreted as the base station transmitting the CSI-RS through the corresponding CSI-RS antenna port(s).

[0104] A base station transmit signal may be processed by a transceiver unit (TXRU), and the processed output signal may be beamformed by an antenna module composed of physical antenna elements, converted into electromagnetic waves, and radiated into space. The TXRU of the signal transmitter may also be referred to as a transmitter unit (TXU), RF (radio frequency) chain, etc. The TXRU(s) and physical antenna elements may be mapped to each other in a pre-implemented manner according to the desired beam shape, and the mapping may be controlled and changed by the base station if necessary. This mapping may be referred to as antenna virtualization.

[0105] According to the above operation, each CSI-RS antenna port constituting the CSI-RS resource can be mapped to one or more TXRU(s). Also, according to the TXRU-physical antenna element mapping, each CSI-RS antenna port can be mapped to one or more physical antenna element(s).

[0106] FIG. 4 is a conceptual diagram illustrating a first embodiment of a mapping method between CSI-RS antenna ports and TXRUs or physical antenna elements.

[0107] Referring to FIG. 4, a two-dimensional planar antenna panel may be used for signal transmission, and the two-dimensional planar antenna panel may be configured with physical antenna elements arranged to have cross-polarization. The physical antenna elements may be arranged on a two-dimensional plane configured in a first direction (e.g., horizontal) and a second direction (e.g., vertical), and each physical antenna element may be arranged to have a first polarization or a second polarization. Furthermore, each TXRU may be mapped to a physical antenna element having a specific polarization. For convenience, a TXRU mapped to a physical antenna element having a first polarization (or a second polarization) may be referred to as a TXRU having a first polarization (or a second polarization).

[0108] A base station may transmit CSI-RS resources consisting of 16 CSI-RS antenna ports to a terminal. The 16 CSI-RS antenna ports may be mapped to 32 TXRUs. As shown in FIG. 4, 16 of the 32 TXRUs may have a first polarization, and the remaining 16 TXRUs may have a second polarization. In this case, each CSI-RS antenna port may have the same polarization and may be mapped to two TXRUs adjacent in a second direction (e.g., vertical direction). The order in which the CSI-RS antenna ports are mapped in the first domain (e.g., horizontal domain), second domain (e.g., vertical domain), and polarization domain may be determined based on the CSI codebook structure used for PMI feedback. For example, if a dual codebook W applied to a polarized antenna and having a structure of W = W1 * W2 is used, the CSI-RS antenna ports may be numbered in ascending order: first in the second domain (e.g., vertical domain), second in the first domain (e.g., horizontal domain), and finally in the polarization domain. As a result, CSI-RS antenna ports 0 to 7 may be mapped to two TXRUs each having a first polarization, and CSI-RS antenna ports 8 to 15 may be mapped to two TXRUs each having a second polarization. In this embodiment, the TXRUs may be considered physical antenna elements. That is, the concept illustrated in FIG. 4 may be interpreted as 16 CSI-RS antenna ports mapped to 32 physical antenna elements. In this case, the mapping relationship related to the TXRUs may be defined separately. For example, there may be a one-to-one correspondence between TXRUs and physical antenna elements, or there may be a one-to-one correspondence between CSI-RS antenna ports and TXRUs.

[0109] Meanwhile, the CSI reporting (or CSI feedback) operation of the terminal may be performed based on a "CSI reporting configuration" configured by the base station. The CSI reporting configuration may include configuration information regarding the type of CSI (or report quantity) that the terminal reports to the base station, the frequency range, whether wideband / narrowband is used, the time domain periodicity, the CSI codebook, etc. The CSI reporting operation may be performed periodically, semi-permanently, or aperiodically. The CSI report may be transmitted via the PUCCH or PUSCH. The CSI reporting configuration may be associated with a CSI resource configuration. The terminal may perform a CSI calculation operation based on not only the CSI resource configuration but also the CSI reporting configuration associated with the CSI resource configuration. In an NR communication system, the CSI reporting configuration may be referred to as a "CSI reporting setting."

[0110]

[0111] Meanwhile, as communication systems become more sophisticated, technologies for increasing network power efficiency are gaining attention. A network (i.e., a base station) can operate in a low-power mode by opportunistically entering a sleep mode in which it does not perform transmission or reception operations, or by performing transmission or reception operations using only a portion of the transceiver, thereby reducing network power consumption. In this disclosure, a method for dynamically scaling spatial elements will be described as a method for reducing power consumption in the spatial domain. Here, spatial elements may refer to antenna ports (e.g., CSI-RS antenna ports), TXRUs, RF chains, physical antenna elements, antenna panels, etc.

[0112] One method for scaling spatial elements is muting some of the spatial elements. For example, a base station can dynamically mute or turn off some of the TXRUs in a certain interval, allowing signals to be transmitted using only the unmuted or on TXRUs. Muting a TXRU can include muting the physical antenna element to which the TXRU is mapped. Alternatively, the base station can dynamically mute some of the physical antenna elements in a certain interval without muting the TXRUs, allowing signals to be transmitted using only the unmuted physical antenna elements. According to the above method, the base station can maximize spatial multiplexing benefits by activating all TXRUs in an interval with heavy traffic (hereinafter referred to as "interval 1"), and can opportunistically activate only a small number of TXRUs in an interval with light traffic (hereinafter referred to as "interval 2") to operate in a low-power mode. This can increase the power efficiency of the network without a loss of transmission capacity.

[0113] As described above, the CSI-RS antenna port may be mapped to the TXRU. Therefore, when a TXRU muting operation is performed, the CSI-RS antenna port corresponding to the muted TXRU may also be muted depending on the mapping scheme or muting pattern. This will be described in detail through the following embodiments.

[0114] FIG. 5a is a conceptual diagram illustrating a first embodiment of a TXRU muting method, and FIG. 5b is a conceptual diagram illustrating a second embodiment of a TXRU muting method.

[0115] 5a and 5b, similar to the first embodiment of FIG. 4, 32 TXRUs having first and second polarizations may be arranged in a two-dimensional space. In this disclosure, "TXRUs arranged in space" may mean "physical antenna elements to which the TXRUs are mapped are arranged in space." Furthermore, each CSI-RS antenna port may have the same polarization and be mapped to two TXRUs adjacent in the vertical direction. In this case, some TXRUs may be muted using the method described above.

[0116] In the first embodiment of FIG. 5a, 16 TXRUs in columns 3 and 4 can be muted. The base station can transmit signals using the remaining 16 TXRUs. In the case of CSI-RS transmission, 8 CSI-RS antenna ports can be mapped to the remaining 16 TXRUs, and these CSI-RS antenna ports can be transmitted to the UE. Compared to the first embodiment of FIG. 4, which does not yet have TXRU muting applied, this can be considered as 8 of the 16 CSI-RS antenna ports being muted. Although the number of CSI-RS antenna ports has been scaled, assuming the antenna virtualization method remains the same, the beam pattern formed by each CSI-RS antenna port can be maintained (i.e., the TXRUs connected to each CSI-RS antenna port remain unchanged). The above method may be referred to as a first TXRU muting method.

[0117] In the second embodiment of FIG. 5b, the 16 TXRUs in rows 2 and 4 can be muted. The base station can transmit signals using the remaining 16 TXRUs. In the case of CSI-RS transmission, 16 CSI-RS antenna ports can be mapped to the remaining 16 TXRUs, and these CSI-RS antenna ports can be transmitted to the UE. When compared with the first embodiment of FIG. 4, which shows the state before TXRU muting is applied, it can be seen that the number of CSI-RS antenna ports available for transmission is not affected by TXRU muting in the case of this TXRU muting pattern. However, the number of TXRUs mapped to each CSI-RS antenna port is reduced from two to one, and therefore, even if the antenna virtualization method is the same, the beam pattern formed by each CSI-RS antenna port may change. This method may be referred to as a second TXRU muting method.

[0118] In the following, the adaptive scaling or muting method of the CSI-RS antenna ports will be described in more detail.

[0119]

[0120] FIG. 6 is a conceptual diagram illustrating a first embodiment of a CSI reporting method based on multiple CSI-RS antenna port sets.

[0121] Referring to FIG. 6, a terminal can receive CSI-RS resource configuration information from a base station. t = 16 CSI-RS antenna ports. The CSI-RS resources may be periodically repeated.

[0122] According to the proposed method, the UE can additionally receive first configuration information from the base station and can configure multiple (or one or more) CSI-RS antenna port sets based on the first configuration information. Here, the first configuration information can be configuration information for the CSI-RS antenna port set(s). As will be described later, the first configuration information can be replaced by codebook configuration information or can be considered as codebook configuration information. Alternatively, the first configuration information can be transmitted separately, or can be included in CSI-RS resource configuration information or CSI report configuration information and transmitted to the UE. Each CSI-RS antenna port set is configured as the L t The first CSI-RS antenna port set may be configured with at least a portion (i.e., a subset) of L1 = L2 = 16 CSI-RS antenna ports. That is, multiple CSI-RS antenna port sets may be induced within the same CSI-RS resource. In this embodiment, the UE may configure a first CSI-RS antenna port set and a second CSI-RS antenna port set based on the first configuration information. The first CSI-RS antenna port set is L1 = L2 = 16. t The first CSI-RS antenna port set may include 16 CSI-RS antenna ports, and the second CSI-RS antenna port set may include L2=4 CSI-RS antenna ports. t 16 CSI-RS antenna ports. For example, each CSI-RS antenna port set may be referred to as a CSI-RS sub-resource, a CSI-RS resource sub-configuration, etc., and may be configured in the terminal as a subordinate parameter of the CSI-RS resource. In the present disclosure, each CSI-RS antenna port set (or subset) may correspond to a respective spatial element pattern. Also, the above description in which multiple CSI-RS antenna port sets are configured by one CSI-RS resource is merely an example, and as described below, multiple CSI-RS antenna port sets may be configured by multiple CSI-RS resources. In this case, each CSI-RS antenna port set may correspond to a respective CSI-RS resource. Multiple CSI-RS resources may belong to the same CSI-RS resource set.

[0123] The UE may receive CSI reporting configuration information from the base station and perform a CSI reporting operation. The UE may report multiple CSIs to the base station. The multiple CSIs may correspond to multiple CSI-RS antenna port sets (i.e., multiple spatial element patterns). In this embodiment, the CSI report from the UE may include a first CSI and a second CSI. The first CSI may be CSI calculated based on the first CSI-RS antenna port set, i.e., the 16 received CSI-RS antenna ports, and the second CSI may be CSI calculated based on the second CSI-RS antenna port set, i.e., L2=4 CSI-RS antenna ports among the 16 received CSI-RS antenna ports. As described above, the first CSI and the second CSI may include CQI, PMI, RI, LI, CRI, SSBRI, beam quality measurement, etc., respectively. The above method may be referred to as (method 100).

[0124] Multiple CSIs may be transmitted to the base station based on one CSI reporting configuration. For example, a CSI reporting configuration may include multiple CSI reporting sub-configurations. Each CSI reporting sub-configuration may include configuration information for reporting each CSI derived based on the respective CSI-RS antenna port set. In other words, each CSI reporting sub-configuration may correspond to a respective CSI-RS antenna port set (or each spatial element pattern). Multiple CSIs may be transmitted together via the same uplink transmission (e.g., PUCCH, PUSCH). The above-mentioned method may be referred to as a first CSI reporting method or a multiple CSI reporting method. Alternatively, multiple CSIs may be transmitted to the base station based on multiple CSI reporting configurations. For example, each CSI reporting configuration may include configuration information for reporting each CSI derived based on the respective CSI-RS antenna port set. In this case, multiple CSIs may be transmitted via different uplink resources at different transmission timings. Alternatively, multiple CSIs may be transmitted via the same uplink resource at the same transmission timing. The above-mentioned method may be referred to as a second CSI reporting method or a single CSI reporting method.

[0125] In the first CSI reporting method, the number of CSI reporting sub-configurations belonging to the CSI reporting configuration may be referred to as A. Also, the number of CSI-RS antenna port sets configured for spatial element adaptation (e.g., one CSI-RS resource or one CSI-RS antenna port set belonging to one CSI-RS resource set) may be referred to as B. The CSI-RS resources or CSI-RS resource sets may be associated with the CSI reporting configuration. In this case, each CSI reporting sub-configuration may correspond to one or at most one CSI-RS antenna port set, and generally, A may have a value equal to or less than B. That is, the CSI report of the UE may include a CSI report for each of all spatial element patterns configured for the UE, or may include a CSI report for some of the spatial element patterns configured for the UE. In an embodiment, A may be 1, which may correspond to a second CSI reporting method. In an embodiment, B may be 1, which may correspond to a conventional CSI-RS transmission method in which the CSI-RS antenna port adaptation technique is not applied.

[0126] The UE may transmit all A CSI report(s) corresponding to the A CSI reporting sub-configurations to the BS. Alternatively, to reduce uplink control information (UCI) overhead, the UE may determine A1 CSI reporting sub-configurations from the A CSI reporting sub-configurations and transmit A1 CSI report(s) for the determined A1 CSI reporting sub-configurations to the BS (where A1 is a natural number less than or equal to A). The A1 CSI reporting sub-configurations may be determined based on configuration information received from the BS. The above-described CSI overhead reduction techniques may or may not be applied depending on the configured CSI reporting periodicity. Furthermore, the above-described CSI overhead reduction techniques may be configured in the UE based on different signaling procedures depending on the configured CSI reporting periodicity. For example, the configuration information may be included in an RRC message and may be included in or transmitted together with CSI reporting configuration information including the CSI reporting sub-configuration.

[0127] Simultaneously or separately, the CSI reporting sub-configuration(s) may be dynamically indicated to the UE based on a physical layer signaling procedure. The base station may indicate the CSI reporting sub-configuration(s) to be reported by the UE through DCI. For example, the DCI may be a group-common DCI. That is, a DCI including information on the CSI reporting sub-configuration(s) may be transmitted to a UE group, and the UE receiving the DCI may change or maintain its CSI reporting behavior based on the indication information included in the DCI. The indication information included in the group-common DCI may be common to all UEs receiving the group-common DCI. Alternatively, the group-common DCI may include multiple indication information for multiple UEs or multiple UE groups (or subgroups) receiving the group-common DCI. The multiple indication information may correspond to different fields or different bits (or bit sequences) in the same field. To monitor the group-common DCI, the UE may receive a type 3 CSS set, a group-common RNTI, etc. from the base station.

[0128] As another example, the DCI may be a scheduling DCI. For example, the CSI reporting operation for the CSI reporting sub-configuration(s) may be triggered aperiodically by the scheduling DCI. In this case, the scheduling DCI may include indication information regarding the CSI reporting sub-configuration(s), and the UE may determine A1 CSI reporting sub-configuration(s) to report to the base station based on the indication information and perform the aperiodic CSI reporting operation including the corresponding A1 CSI(s). The indication information may additionally include other information required to perform the aperiodic CSI reporting operation. For example, the indication information may include uplink TCI, uplink spatial relation information, etc. for transmit beamforming of an uplink signal through which the aperiodic CSI report is transmitted. The indication information may also include information regarding an uplink resource through which the aperiodic CSI report is transmitted.

[0129] Alternatively, the CSI reporting operation for the CSI reporting sub-configuration(s) may be performed semi-persistently or periodically. The UE may receive an instruction to activate or deactivate the CSI reporting operation from the base station through DCI (e.g., scheduling DCI) or MAC layer signaling (e.g., MAC CE). In this case, the DCI or the MAC layer signaling may include instruction information for the CSI reporting sub-configuration(s) along with CSI reporting activation instruction information, and the UE may perform a semi-persistent CSI reporting operation including the indicated CSI reporting sub-configuration(s). A predetermined time gap (e.g., slot offset and / or symbol offset) may be ensured between the time (e.g., slot, symbol) at which the UE performs a CSI report transmission operation reflecting the dynamically indicated CSI reporting sub-configuration(s) and the time (e.g., slot, symbol) at which the UE receives the dynamic instruction (e.g., DCI, MAC CE). As described above, if the CSI reporting sub-configuration corresponds to a CSI-RS antenna port set (or spatial element pattern), the above method may correspond to the operation described below, i.e., a method of dynamically indicating some CSI-RS antenna port set(s) via DCI.

[0130] Alternatively, the A1 CSI reporting sub-configuration(s) may be selected autonomously by the UE. For example, the UE may select the A1 CSI report(s) (or corresponding CSI reporting sub-configuration(s)) that provides the highest channel quality. The channel quality may be determined by a metric (e.g., CQI, etc.) defined in a technical standard. In one embodiment, A1=1. In this case, the first CSI reporting method may correspond to a CSI reporting operation including a single CSI, and UCI overhead may be maintained at a low level.

[0131] When a terminal reports multiple CSIs for multiple spatial element patterns according to the above-described method, the multiple CSIs may be correlated with each other. That is, the CSI for one spatial element pattern may be calculated based on the CSI for the other spatial element patterns. For example, the terminal may report first and second CSIs for a first CSI-RS antenna port set and a second CSI-RS antenna port set to the base station. The first and second CSIs may be reported based on a first CSI reporting sub-configuration and a second CSI reporting sub-configuration, respectively. In this case, the first CSI may be determined based on the second CSI. Alternatively, the second CSI may be determined based on the first CSI. For example, a first CQI derived based on the first CSI-RS antenna port set may be a differential CQI expressed as a difference from a second CQI derived based on the second CSI-RS antenna port set. As another example, a first PMI or a second RI derived based on a first CSI-RS antenna port set may be a differential PMI or a differential RI expressed as a difference from a second PMI or a second RI derived based on a second CSI-RS antenna port set. In this case, the second CQI may have a value (or index) corresponding to a higher quality than the first CQI. Also, a CQI derived based on the second PMI and / or the second RI may have a value (or index) corresponding to a higher quality than a CQI derived based on the first PMI and / or the first RI. The differential CSI may be represented with fewer bits, and the CSI payload may be reduced by the above-described method. When the CSI is transmitted over a PUCCH, as the size of the total payload of CSI transmitted over the PUCCH decreases, the size of the resources to which the PUCCH is mapped (e.g., the number of PRBs) may decrease, and the PUCCH format may also be changed. The above-described operations may be performed only when the first CSI reporting method is used. That is, the multiple CSIs may correspond to CSI reporting sub-configurations belonging to one CSI reporting configuration.

[0132] As another method for reducing CSI overhead, the terminal may report A2 CSI(s) representing the A CSI reporting sub-configuration(s) or the selected A1 CSI reporting sub-configuration(s) to the base station. A2 may be a natural number less than or equal to A or a natural number less than or equal to A1. The A2 CSI(s) may be calculated based on the A CSI reporting sub-configuration(s) or the selected A1 CSI reporting sub-configuration(s). Alternatively, the terminal may select A2 CSI reporting sub-configuration(s) from the A or A1 CSI reporting sub-configuration(s) and calculate the A2 CSI(s) based on the selected A2 CSI reporting sub-configuration(s).

[0133] In some embodiments, A2=1. For example, the UE may derive one CSI (e.g., CQI, PMI, RI, CRI, SSBRI, and / or L1-RSRP) for A or A1 CSI reporting sub-configuration(s) and report it to the base station. The one CSI may be a value derived based on any one CSI reporting sub-configuration. For example, the UE may calculate CSI for each of multiple CSI reporting sub-configurations, select one CSI (e.g., an optimal CSI) from the calculated CSI, and then report it. The one CSI may represent channel quality corresponding to an optimal spatial element pattern (i.e., an optimal CSI-RS antenna port muting pattern). Alternatively, the one CSI may be a value (e.g., a jointly coded value) derived based on multiple CSI reporting sub-configurations (i.e., multiple CSI-RS antenna port muting patterns). The CSI may include information on which CSI reporting sub-configuration the CSI is based on. For example, the information may include an index (or number) of a CSI reporting sub-configuration on which the CSI is based. For example, the information may be referred to as a sub-configuration indicator, a CSI reporting sub-configuration indicator, etc. The information may be distinguished from a CRI. That is, a CRI refers to information on a CSI-RS resource (e.g., a CSI-RS resource index) that a UE intends to selectively report within a given sub-configuration, while a sub-configuration indicator may refer to information on a sub-configuration that a UE intends to selectively report. Generally, when A2 CSIs are reported, A2 corresponding sub-configuration indicator(s) may also be reported.

[0134] In other embodiments, A2 = A1. For example, the terminal may calculate A1 CSI(s) based on the configured A CSI reporting sub-configuration(s), or may select A1 CSI reporting sub-configuration(s) from the A CSI reporting sub-configuration(s), and then calculate A1 CSI(s) based on the selected A1 CSI reporting sub-configuration(s) and report the A1 CSI(s) to the base station.

[0135] In the above-described method, the number of CSIs reported may vary for each CSI type. A UE's CSI report for A or A1 CSI reporting sub-configuration(s) may include A2 of a specific CSI type(s) and A or A1 of another CSI type(s). For example, a UE's CSI report may include one CQI and the remaining CSI types (e.g., PMI, RI, CRI, SSBRI, etc.) may be included in the number of CSI reporting sub-configuration(s), i.e., A or A1. The one CQI may be a (best) CQI selected from multiple CQIs derived for multiple CSI reporting sub-configuration(s).

[0136] The above-described CSI overhead reduction techniques may also be applied when a terminal reports multiple CSI based on a second CSI reporting method. For example, a first CSI reporting configuration and a second CSI reporting configuration may be configured for the terminal. A first CSI calculated based on a first CSI-RS antenna port set may be reported for the first CSI reporting configuration, and a second CSI calculated based on a second CSI-RS antenna port set may be reported for the second CSI reporting configuration. The transmission timing (e.g., transmission slot) and / or transmission resource (e.g., PUCCH, PUSCH) of the first CSI and the second CSI may be consistent.

[0137] In this case, the CSI reporting operation for the first CSI reporting configuration and the second CSI reporting configuration may be performed based on the above-described CSI overhead reduction technique. For example, the first CSI may be determined based on the second CSI. As another example, one of the first CSI and the second CSI may be selected, and the selected CSI may be reported to the base station. Alternatively, one CSI (e.g., joint CSI) may be calculated based on both the first CSI reporting configuration and the second CSI reporting configuration, and the CSI may be reported to the base station. In this case, the multiple CSI reporting configurations may be configured to have the same time characteristic. For example, if the first CSI reporting configuration is configured to be periodic, semi-persistent, or aperiodic, the second CSI reporting configuration may also be configured to be periodic, semi-persistent, or aperiodic, respectively. The UE may not expect to receive an instruction to apply the above-described CSI overhead reduction technique to multiple CSI reporting configurations having different time characteristics.

[0138] In the case of aperiodic CSI reporting, the DCI triggering the aperiodic CSI reporting may include information indicating a CSI reporting configuration to be processed and transmitted (e.g., CSI reporting configuration index(es)), and the UE may perform a CSI reporting operation based on the above-described method for the indicated CSI reporting configuration. In the case of semi-persistent CSI reporting, the DCI or MAC CE instructing activation of semi-persistent CSI reporting may include information indicating a CSI reporting configuration to be processed and transmitted (e.g., CSI reporting configuration index(es)), and the UE may perform a CSI reporting operation based on the above-described method for the indicated CSI reporting configuration.

[0139] Meanwhile, the reporting timing (e.g., transmission slot) of the first CSI may not coincide with the reporting timing (e.g., transmission slot) of the second CSI. Even in this case, the above-described CSI processing and reporting operations may be performed in the same manner. However, the timing of transmitting the finally determined CSI to the base station may be determined according to a rule predefined in a technical standard. For example, the final CSI may be transmitted in one of the first CSI transmission slot and the second CSI transmission slot (e.g., a later slot or an earlier slot). As another example, the final CSI may be transmitted in a slot other than the first CSI transmission slot and the second CSI transmission slot. Considering the time required to calculate the final CSI, the other slot may be a slot that is not earlier than the first CSI transmission slot and the second CSI transmission slot. The UE may receive from the base station the slot in which the final CSI is transmitted. For example, a slot offset between the slot in which the final CSI is transmitted and the first CSI or the second CSI transmission slot may be transmitted to the UE.

[0140]

[0141] On the other hand, if a terminal calculates multiple CSIs for multiple spatial element patterns and reports them to a base station, the CSI calculation complexity may increase. The terminal's CSI calculation capability may be indexed by a CSI processing unit (CPU). A terminal can simultaneously process up to N_CPU CSIs at a time (e.g., a specific symbol) and report the N_CPUs to the base station as its terminal capability. In this case, it can be said that the terminal has N_CPU CPUs for the CSI reporting operation. Generally, one CSI-RS resource referenced by a CSI report can occupy one CPU.

[0142] When the above-described network power reduction method is used, one CSI-RS resource may be referenced by one CSI reporting configuration, and the one CSI reporting configuration may be associated with A or A1 selected CSI reporting sub-configurations. In this case, the one CSI-RS resource may be referenced by A or A1 selected CSI reporting sub-configurations belonging to the one CSI reporting configuration. The UE may calculate A1 (or A2, further selected by the above-described method) CSIs corresponding to different spatial element patterns (e.g., different CSI-RS antenna port sets) based on the one CSI-RS resource. Therefore, the CSI calculation complexity of the UE based on the one CSI-RS resource may correspond to the CSI calculation complexity based on A1 (or A2) CSI-RS resources. Therefore, the one CSI-RS resource may occupy A1 (or A2) CPUs. Alternatively, the one CSI-RS resource may be counted A1 times. Equivalently, the one CSI-RS resource may be considered as A1 (or A2) active CSI-RS resources. Alternatively, the one CSI-RS resource may be considered as Ar active CSI-RS resources, where Ar may be determined to be one of the values ​​between 1 and A1 (or A2). In an embodiment, Ar may be a natural number.

[0143] Furthermore, the CSI calculation complexity of the UE may be limited by the number of active CSI-RS antenna ports. In this case, the number of active CSI-RS antenna ports for one CSI-RS resource may be considered as the sum of the number of CSI-RS antenna ports corresponding to the A1 (or A2) CSI reporting sub-configurations referring to the one CSI-RS resource. That is, any one CSI-RS antenna port constituting the CSI-RS resource may be counted multiple times. For example, any one CSI-RS antenna port constituting the CSI-RS resource under the configuration may correspond to the number of A1 (or A2) active CSI-RS antenna ports. The UE may transmit the number of active CSI-RS antenna ports that it can simultaneously process at one time to the base station as UE capability information.

[0144] If the number K of CPUs configured for processing by the UE at a certain time (e.g., a certain symbol) exceeds N_CPUs, the UE may not calculate or report CSI for the excess CPUs to the base station. If the K CPUs include a CPU for the CSI-RS resource described above, the UE may select some CSI reporting subconfigurations according to a priority rule from among multiple CSI reporting subconfigurations that refer to the CSI-RS resource, and perform a CSI reporting operation for the selected CSI reporting subconfiguration(s). In this case, the CSI reporting operation for the remaining CSI reporting subconfigurations may be omitted. For example, a higher priority may be assigned to a CSI reporting subconfiguration with a lower (or higher) index. According to the above operation, the UE may report only some of the multiple CSIs associated with the same CSI-RS resource to the base station. The multiple CSIs may correspond to multiple CSI reporting subconfigurations, respectively.

[0145] Meanwhile, multiple CSI-RS resources are referred to by one CSI reporting configuration, and the CSI for one CSI-RS resource among the multiple CSI-RS resources and the ID of the one CSI-RS resource (i.e., CRI (CSI-RS resource ID)) are reported. A CSI-RS resource may be reported from the UE to the base station. Similarly, each CSI-RS resource may be associated with multiple CSI reporting sub-configurations. In this case, the CSI reporting operation of the UE within the CSI processing capacity limit may be performed based on the priority among the CSI reporting sub-configurations, and the priority may be assigned in ascending or descending order of CSI reporting sub-configuration index. When the number of CSI reporting sub-configurations and the number of CSI-RS resources associated with the CSI reporting sub-configurations are P and Q, respectively, the CPU corresponding to the CSI reporting operation may be P*Q times. Among these, when the number of CSI reporting sub-configurations selected according to the priority is P1, the corresponding CPU may be reduced to P1*Q times. The UE may sequentially include the CSI reporting sub-configurations one by one in the measurement and reporting targets based on the CSI reporting sub-configuration index until P1*Q does not exceed N_CPU.

[0146] In the above case, that is, when each CSI reporting sub-configuration is associated with multiple CSI-RS resources, the UE may select one CSI-RS resource associated with each CSI reporting sub-configuration and report CSI for the selected CSI-RS resource to the base station. Here, according to the TXRU muting scheme, all CSI reporting sub-configurations may be associated with the same CSI-RS resource, or each CSI reporting sub-configuration may be associated with a different CSI-RS resource. In this case, the CSI may include a CRI, and the CRI may include information (e.g., an index) indicating the selected CSI-RS resource. When the number of configured or activated sub-configurations for one CSI report is A (or A1), the number of CSIs to be reported may also be A (or A1). In this case, the A (or A1) CRIs corresponding to the A (or A1) sub-configurations may all be the same. That is, for multiple subsets, the terminal can select a common CSI-RS resource and calculate and report CSI for the selected CSI-RS resource for each subset. At this time, the CRI corresponding to the common CSI-RS resource can be included in each CSI and transmitted. That is, the CRI can be transmitted A times (or A1 times). Alternatively, to reduce the CSI payload, the CRI can be transmitted once without duplication. At this time, the CRI can be included in the CSI for any one subset. The any one subset can be predefined in a technical standard. For example, the CRI can be transmitted by being included in the CSI for the subset with the lowest (or highest) subset index. The CRI can be a CSI with high priority or importance, and therefore can be considered the payload of CSI Part 1.

[0147] Alternatively, A (or A1) CRIs corresponding to A (or A1) sub-configurations may be determined independently. That is, the UE may select CSI for different CSI-RS resources for multiple sub-configurations and report the selected CSI to the base station. According to this method, the UE may select the CSI with the highest channel quality and the corresponding CSI-RS resource for each CSI reporting sub-configuration, and the information may be shared with the base station and used for scheduling.

[0148] In (Method 100), the base station can transmit at least the CSI-RS antenna ports that constitute a CSI-RS antenna port subset among the CSI-RS antenna ports that constitute the CSI-RS resources, i.e., the CSI-RS antenna ports that are required for the UE's CSI calculation. If there are remaining CSI-RS antenna ports that the UE does not receive (or receives but does not actually use), these do not necessarily need to be transmitted. In this embodiment, since the first CSI-RS antenna port set includes all CSI-RS antenna ports that constitute the CSI-RS resources, the base station can transmit L t = 16 CSI-RS antenna ports. t = 16 CSI-RS antenna ports and can calculate the first CSI and the second CSI.

[0149] The base station can perform adaptive downlink scheduling based on multiple CSIs reported from the terminal. Referring to FIG. 6, the base station can transmit a PDSCH using a large number of TXRUs (e.g., 32 TXRUs) based on the first CSI in a first time period with heavy traffic. Downlink transmission performance can be maximized in the first time period. Also, the base station can transmit a PDSCH using a small number of TXRUs (e.g., 4 TXRUs) based on the second CSI in a second time period with light traffic. Network power efficiency can be increased in the second time period. According to method 100, unlike a data channel transmission period, the number of TXRUs used in a CSI-RS transmission period (e.g., symbols in which CSI-RS is transmitted, slots in which CSI-RS is transmitted, etc.) can be fixed. In this embodiment, the base station allocates L of CSI-RS resources for each period. t = 16 CSI-RS antenna ports can transmit, and therefore 32 corresponding TXRUs can operate in the CSI-RS transmission period.

[0150]

[0151] FIG. 7 is a conceptual diagram illustrating a first embodiment of a method for configuring multiple CSI-RS antenna port sets.

[0152] In this embodiment, the mapping operation between CSI-RS antenna ports, TXRUs, and physical antenna elements may directly follow the operation described in the first embodiment of FIG. 4. Referring to FIG. 7, the first CSI-RS antenna port set may include all L1 = Lt = 16 CSI-RS antenna ports, which may be mapped to all 32 TXRUs. For example, a UE may receive the 16 CSI-RS antenna ports using the 16 REs shown in FIG. 3 and derive the first CSI based on a CSI codebook corresponding to the received 16 CSI-RS antenna ports. The CSI codebook may be a 2D codebook with dimensions (N1, N2) = (4, 2) or (N1, N2, P) = (4, 2, 2). Here, N1, N2, and P may represent the number of antenna ports in a first direction (e.g., horizontal direction), the number of antenna ports in a second direction (e.g., vertical direction), and the number of polarizations (e.g., P = 2), respectively. The first CSI may be derived based on the indexes assigned to the CSI-RS antenna ports (i.e., indexes 0 to 15 shown in FIG. 7) according to the above rules. The 2D codebook may be a codebook formed by the Kronecker product of two matrices. The two matrices may be matrices formed by codewords corresponding to the first direction and the second direction, and the size and elements of each matrix may be determined based on N1 and N2.

[0153] Referring to FIG. 7, the second CSI-RS antenna port set may include L2=4 CSI-RS antenna ports mapped to one row of eight TXRUs. The second CSI-RS antenna port set may be determined based on the first configuration information described above. For example, the first configuration information may be information regarding a CSI-RS antenna port muting pattern. In this disclosure, the CSI-RS antenna port muting pattern may be used as a term to refer to a set of CSI-RS antenna ports to be muted (or not muted) or information indicating the set. In this embodiment, the first configuration information may indicate 12 CSI-RS antenna ports mapped to the TXRUs in the three rightmost rows (i.e., rows 2, 3, and 4). Based on the CSI-RS antenna port muting pattern, the UE may configure a second CSI-RS antenna port set with the remaining four CSI-RS antenna ports that do not belong to the muting pattern. As another example, the first configuration information may be information regarding a CSI-RS antenna port set (or a subset). The first configuration information may include a CSI-RS antenna port set, i.e., non-muted CSI-RS antenna ports, or information indicating these. In this embodiment, the first configuration information may indicate four CSI-RS antenna ports mapped to a TXRU in one column (i.e., one column) on the left. The four CSI-RS antenna ports may be CSI-RS antenna ports 0, 1, 8, and 9.

[0154] The UE can receive the four CSI-RS antenna ports and derive the second CSI based on a CSI codebook corresponding to the four received CSI-RS antenna ports. The CSI codebook may be a 2D codebook with dimensions (N1, N2) = (1, 2) or (N1, N2, P) = (1, 2, 2). Compared to the codebook applied to the first CSI, the size of the codebook is reduced to 1 in a first direction (e.g., horizontal direction) due to the muting.

[0155] If the CSI-RS antenna port set configured by the above method is smaller than the CSI-RS antenna ports configuring the CSI-RS resources, the indices of the CSI-RS antenna ports may be reassigned to the CSI-RS antenna port set. For example, the above-described numbering rule (i.e., second direction-->first direction-->polarization direction) may be applied to the CSI-RS antenna ports configuring the CSI-RS antenna port set. In this embodiment, the indices of CSI-RS antenna ports 0, 1, 8, and 9 included in the second CSI-RS antenna port set may be changed to 0, 1, 2, and 3, respectively, according to the above rule. Based on the changed (or reassigned) indices, the UE may derive the corresponding CSI, i.e., second CSI. Even if the CSI-RS antenna port indices are reassigned, the resource locations to which the CSI-RS antenna ports are mapped may not be changed. That is, mapping or demapping of CSI-RS antenna ports may be performed based on the index before the change (e.g., the index assigned based on all CSI-RS antenna ports constituting the CSI-RS resources). Even if CSI-RS antenna ports 8 and 9 are re-assigned indexes 2 and 3, they may still be transmitted in their positions among the 16 CSI-RS antenna ports (i.e., the four REs corresponding to CDM group 2 in FIG. 3).

[0156] In (method 100), the muting described above may be virtual muting. That is, the muted CSI-RS antenna ports are merely excluded from the corresponding CSI-RS antenna port set and / or CSI, and may actually be transmitted from the base station to the terminal. In this embodiment, the 12 CSI-RS antenna ports muted for the second CSI-RS resource set configuration may be CSI-RS that are not muted in terms of the first CSI-RS resource set, and therefore, the 12 CSI-RS antenna ports may be transmitted to the terminal. However, for a certain CSI-RS resource, if the muted CSI-RS antenna port is a CSI-RS that is muted for all CSI-RS antenna port sets configured for the terminal, the terminal may not receive the CSI-RS antenna port.

[0157] One or more CSI-RS antenna port sets may be configured for one CSI-RS resource. The multiple CSI-RS antenna port sets may be distinguished from each other by different indexes. The configuration information for the CSI-RS resource may include first configuration information corresponding to each CSI-RS antenna port set. Like the first CSI-RS resource set in the above embodiment, a specific CSI-RS antenna port set may consist of all CSI-RS antenna ports constituting the CSI-RS resource. That is, the specific CSI-RS antenna port set may be the entire set. In this case, the corresponding muting pattern may not include any CSI-RS antenna ports. That is, the corresponding muting pattern may consist of zero CSI-RS antenna ports. The index of the specific CSI-RS antenna port set may be predefined in the technical specifications. For example, the index may be 0.

[0158] The CSI-RS antenna port set may be determined based on the structure (or size) of the associated CSI codebook. For example, if CSI is derived using the aforementioned 2D codebook, the CSI-RS antenna port set may be determined based on information about the antenna port(s) constituting a first direction (e.g., horizontal direction) and / or information about the antenna port(s) constituting a second direction (e.g., vertical direction). That is, the information may be included in the first configuration information. The information about the antenna port(s) constituting the first direction may be information related to N1, the size of the codebook in the first direction, and the information about the antenna port(s) constituting the second direction may be information related to N2, the size of the codebook in the second direction. Simultaneously or separately, the first configuration information may be determined based on information about the antenna port(s) constituting a third direction (or polarization direction), which may be information related to P, the size of the codebook in the third direction (or polarization direction). In an embodiment, P may be 2, or P may be a natural number greater than or equal to 2. The above method may be referred to as (method 110).

[0159] FIG. 8 is a conceptual diagram illustrating a second embodiment of a method for configuring multiple CSI-RS antenna port sets.

[0160] Referring to FIG. 8, a UE may receive CSI-RS resources including 16 CSI-RS antenna ports from a base station. In this embodiment, the mapping operation between the CSI-RS antenna ports, the TXRU, and the physical antenna elements may be the same as that described in the first embodiment of FIG. 4. That is, the CSI-RS antenna ports may be arranged in a first direction (e.g., vertical direction), a second direction (e.g., horizontal direction), and a polarization direction. In addition, the UE may be configured with a CSI-RS antenna port set (i.e., a subset) consisting of some or all of the 16 CSI-RS antenna ports for CSI reporting for scaled CSI-RS resources. The first CSI-RS antenna port set may include all 16 CSI-RS antenna ports. Conversely, the second to sixth CSI-RS antenna port sets may consist of some of the 16 CSI-RS antenna ports. The remaining CSI-RS antenna ports not included in the CSI-RS antenna port set may be considered muted. The terminal may calculate CSI(s) for the CSI-RS antenna port set(s) and report the calculated CSI(s) to the base station. The CSI(s) may be calculated based on a 2D codebook.

[0161] When the CSI-RS antenna ports constituting a first direction (e.g., horizontal direction) and a second direction (e.g., vertical direction) are represented as a two-dimensional matrix, the positions of the CSI-RS antenna ports in each direction may be represented by column and row indices. In this embodiment, the second CSI-RS antenna port set may be composed of eight CSI-RS antenna ports corresponding to row 1 and all columns, and the fourth CSI-RS antenna port set may be composed of eight CSI-RS antenna ports corresponding to all rows and columns 3 and 4.

[0162] A CSI-RS antenna port set may be indicated by (method 110). The first configuration information may include information indicating columns corresponding to CSI-RS antenna port(s) configuring a first direction and / or information indicating rows corresponding to CSI-RS antenna port(s) configuring a second direction. Alternatively, the first configuration information may include information indicating columns corresponding to CSI-RS antenna port(s) to be muted in the first direction and / or information indicating rows corresponding to CSI-RS antenna port(s) to be muted in the second direction.

[0163] As a specific method, the information may be expressed as a set of row indexes (α) and / or a set of column indexes (α). According to this method, the configuration information of the first CSI-RS antenna port set may include a row index set {0, 1} and a column index set {0, 1, 2, 3}, the configuration information of the second CSI-RS antenna port set may include a row index set {0} and a column index set {0, 1, 2, 3}, and the configuration information of the fourth CSI-RS antenna port set may include a row index set {0, 1} and a column index set {2, 3}. Alternatively, the configuration information of the first CSI-RS antenna port set may include a muted row index set Φ and a muted column index set Φ, the configuration information of the second CSI-RS antenna port set may include a muted row index set {1} and a muted column index set Φ, and the configuration information of the fourth CSI-RS antenna port set may include a muted row index set Φ and a muted column index set {0, 1}, where Φ may represent an empty set.

[0164] Alternatively, the information may be expressed as (start row index, end row index) and / or (start column index, end column index). According to this method, the configuration information of the first CSI-RS antenna port set may include (start row, end row) = (0, 1) and (start column, end column) = (0, 3), the configuration information of the second CSI-RS antenna port set may include (start row, end row) = (0, 0) and (start column, end column) = (0, 3), and the configuration information of the fourth CSI-RS antenna port set may include (start row, end row) = (0, 1) and (start column, end column) = (2, 3). Alternatively, the configuration information of the first CSI-RS antenna port set may include information indicating that no rows are to be muted (e.g., (start row, end row) = (0, 0)) and that no columns are to be muted (e.g., (start column, end column) = (0, 0)), the configuration information of the second CSI-RS antenna port set may include information indicating that (start row, end row) = (1, 1) and that no columns are to be muted (e.g., (start column, end column) = (0, 0)), and the configuration information of the fourth CSI-RS antenna port set may include information indicating that no rows are to be muted (e.g., (start row, end row) = (0, 0)) and that (start column, end column) = (0, 1).

[0165] Alternatively, the information may be expressed as (starting row index, number of consecutive rows) and / or (starting column index, number of consecutive columns). According to this method, the configuration information of the first CSI-RS antenna port set may include (starting row, number of rows) = (0, 2) and (starting column, number of columns) = (0, 4), the configuration information of the second CSI-RS antenna port set may include (starting row, number of rows) = (0, 1) and (starting column, number of columns) = (0, 4), and the configuration information of the fourth CSI-RS antenna port set may include (starting row, number of rows) = (0, 2) and (starting column, number of columns) = (2, 2). Alternatively, the configuration information of the first CSI-RS antenna port set may include information indicating that no rows are to be muted (e.g., (start row, number of rows) = (0, 0) or (A, 0), where A is any possible setting value) and no columns are to be muted (e.g., (start column, number of columns) = (0, 0) or (A, 0)), the configuration information of the second CSI-RS antenna port set may include information indicating that (start row, number of rows) = (1, 1) and no columns are to be muted (e.g., (start column, number of columns) = (0, 0) or (A, 0)), and the configuration information of the fourth CSI-RS antenna port set may include information indicating that no rows are to be muted (e.g., (start row, number of rows) = (0, 0) or (A, 0)) and (start column, number of columns) = (0, 2).

[0166]

[0167] According to the above method, all consecutive CSI-RS antenna ports in each domain may be indicated by the first configuration information. That is, the first to sixth CSI-RS antenna port sets may be indicated by the first configuration information. Meanwhile, there may be CSI-RS antenna port sets that provide the same CSI measurement effect within one CSI-RS resource. In the above embodiment, the third CSI-RS antenna port set and the fourth CSI-RS antenna port set may provide the same effect, and the fifth CSI-RS antenna port set and the sixth CSI-RS antenna port set may provide the same effect. In this case, allowing both the third CSI-RS antenna port set and the fourth CSI-RS antenna port set, or allowing both the fifth CSI-RS antenna port set and the sixth CSI-RS antenna port set, may cause unnecessary duplication and increase the signaling overhead of the first configuration information.

[0168] To solve the above problem, a method of fixing the position of the starting CSI-RS antenna port in each transmission direction may be applied. For example, the positions of the CSI-RS antenna ports constituting each CSI-RS antenna port set may start from row 1 (i.e., the row with index 0) in the second direction (e.g., the vertical direction) and from column 1 (i.e., the column with index 0) in the first direction (e.g., the horizontal direction). Furthermore, each CSI-RS antenna port set may include at least the CSI-RS antenna ports corresponding to row 1 and column 1. A CSI-RS antenna port set consisting of CSI-RS antenna ports that satisfy the above condition may be configured in the terminal. In the above embodiment, the first, second, third, and fifth CSI-RS antenna port sets may satisfy the above condition and may be configured in the terminal for CSI measurement and reporting. However, the fourth and sixth CSI-RS antenna port sets do not include the CSI-RS antenna ports in row 1 and column 1, and therefore may not satisfy the above condition and may be considered invalid configurations.

[0169] According to the method, the first configuration information may be expressed as an index of an end row and / or an index of an end column. That is, the first configuration information may not include an index of a start row or an index of a start column. According to the method, the configuration information of the first CSI-RS antenna port set may include (end row) = (1) and (end column) = (3), and the configuration information of the second CSI-RS antenna port set may include (end row) = (0) and (end column) = (3). Alternatively, the configuration information of the first CSI-RS antenna port set may include information indicating that no row is to be muted (e.g., (end row) = (0)) and information indicating that no column is to be muted (e.g., (end column) = (0)), and the configuration information of the second CSI-RS antenna port set may include information indicating that (end row) = (1) and no column is to be muted (e.g., (end column) = (0)). Conversely, the fourth CSI-RS antenna port set and the sixth CSI-RS antenna port set may be considered invalid configurations.

[0170] Alternatively, the first configuration information may be expressed as the number of consecutive rows and / or the number of consecutive columns. That is, the first configuration information does not need to include a starting row index or a starting column index. According to this method, the configuration information of the first CSI-RS antenna port set may include (number of rows) = (2) and (number of columns) = (4), and the configuration information of the second CSI-RS antenna port set may include (number of rows) = (1) and (number of columns) = (4). Alternatively, the configuration information of the first CSI-RS antenna port set may include information indicating that no rows are to be muted (e.g., (number of rows) = (0)) and information indicating that no columns are to be muted (e.g., (number of columns) = (0)), and the configuration information of the second CSI-RS antenna port set may include information indicating that (number of rows) = (1) and no columns are to be muted (e.g., (number of columns) = (0)). On the other hand, the fourth CSI-RS antenna port set and the sixth CSI-RS antenna port set may be considered invalid configurations.

[0171]

[0172] In the above-described method, the number of rows and the number of columns may correspond to N2 and N1, respectively, which are configuration information indicating the size of the 2D codebook. In other words, the first configuration information may include N1 and N2, which are configuration information indicating the size of the 2D codebook. For example, the configuration information of the first CSI-RS antenna port set may include (N1, N2) = (4, 2) or (N1, N2, P) = (4, 2, 2), and the configuration information of the second CSI-RS antenna port set may include (N1, N2) = (1, 2) or (N1, N2, P) = (1, 2, 2). Alternatively, the configuration information of the first CSI-RS antenna port set may include information indicating that there are no muted rows and no muted columns (e.g., (N1, N2) = (0, 0) or (N1, N2, P) = (0, 0, 2)), and the configuration information of the second CSI-RS antenna port set may include information indicating the number of muted rows (e.g., N2 = 2) and information indicating that there are no muted columns (e.g., N1 = 0), or (N1, N2, P) = (0, 2, 2). Similarly, the fourth CSI-RS antenna port set and the sixth CSI-RS antenna port set may be considered invalid configurations.

[0173] According to the above-described method, the first configuration information may include configuration information of a codebook (e.g., a 2D codebook) associated with a CSI-RS antenna port set. Alternatively, the first configuration information may be replaced by or considered as the codebook configuration information. Furthermore, the first configuration information may be included in CSI reporting configuration information, rather than CSI-RS resource configuration information, and transmitted to the UE. For example, the first configuration information may be included in CSI reporting configuration information or CSI reporting sub-configuration information associated with a CSI-RS antenna port set. In this case, the first configuration information may be expressed in the form of codebook configuration information. The UE may find (or confirm) the CSI-RS antenna port(s) constituting the CSI-RS antenna port set based on the codebook configuration information (e.g., N1 and N2) included in the CSI reporting configuration or CSI reporting sub-configuration. In this case, the CSI-RS resource configuration does not need to include separate first configuration information for the CSI-RS antenna port set. Alternatively, the CSI-RS resource configuration may include second configuration information other than the first configuration information (e.g., codebook configuration information, N1 and N2) included in the CSI reporting configuration. For example, the second configuration information may include information regarding the number of CSI-RS antenna ports constituting the CSI-RS antenna port set. The UE may find the CSI-RS antenna port subset using only the first configuration information included in the CSI reporting configuration, or may find the CSI-RS antenna port subset using both the first configuration information included in the CSI reporting configuration and the second configuration information included in the CSI-RS resource configuration. As another example, both the first configuration information and the second configuration information may be included in the CSI reporting configuration information. Alternatively, both the first configuration information and the second configuration information may be included in the CSI-RS resource configuration information.

[0174] According to an embodiment, the first CSI reporting configuration may be correlated with the first CSI-RS resource. Or equivalently, the first CSI reporting configuration may refer to the first CSI-RS resource. The first CSI-RS resource may be configured with C CSI-RS antenna ports and may be mapped to D REs based on a CSI-RS resource mapping rule configured in the UE. For example, D=C. The first CSI reporting configuration may include codebook configuration information corresponding to the C CSI-RS antenna ports constituting the first CSI-RS resource. The codebook configuration information may include codebook sizes (N1, N2). Here, N1 and N2 may be natural numbers satisfying 2*N1*N2=C. For convenience, the codebook corresponding to the CSI reporting configuration may be referred to as a parent codebook.

[0175] The first CSI reporting configuration may be associated with multiple (e.g., A) CSI reporting sub-configurations. The a-th CSI reporting sub-configuration may include information on C(a) CSI-RS antenna ports, which are a subset of C CSI-RS antenna ports constituting the first CSI-RS resource, and / or codebook configuration information corresponding to the C(a) CSI-RS antenna ports (where 1≦a≦A). The codebook configuration information may include codebook sizes (N1(a), N2(a)). Here, N1(a) and N2(a) may be natural numbers satisfying 2*N1(a)*N2(a)=C(a). For convenience, the codebook corresponding to each CSI reporting sub-configuration may be referred to as a child codebook.

[0176] There may be a relationship between the parent codebook and the child codebook. According to the above concept, an inclusion relationship may be established between the CSI-RS resource (i.e., the antenna ports constituting the CSI-RS resource) and the CSI-RS antenna port set (i.e., a subset). Based on this, the size of each dimension of the child codebook may be determined to be a value that does not exceed the size of each dimension of the parent codebook. In other words, for a given a, the relationships N1(a)≦N1 and N2(a)≦N2 may be established.

[0177] The codebook configuration information may include other information in addition to N1 and N2. For example, the codebook configuration information may include the number of panels to which the CSI-RS antenna ports are mapped. The UE may derive CSI using only a portion of the codewords in the codebook. Codebook subset restriction information, which indicates a set of codewords that the UE may or may not use for CSI reporting, may also be included in the codebook configuration information.

[0178] The above-described method may be applied to a Type-1 CSI codebook. The Type-1 CSI codebook may include a single-panel codebook and a multi-panel codebook. In the case of a single-panel codebook, the size of the codebook may be given by N1 and N2. In the case of a multi-panel codebook, the size of the codebook may be given by N1, N2, and the number of panels (or coherence groups formed by antenna panels) (e.g., Ng). In the case of a multi-panel codebook, if the number of polarizations (P) is additionally considered, as described above, the size of the codebook may be given by N1, N2, the number of panels (or coherence groups), and the number of polarizations (P). The above-described method may also be applied to a Type-2 CSI codebook. For Type-1 CSI codebooks and Type-2 CSI codebooks, oversampling may be applied when generating codewords constituting each dimension based on a DFT matrix or DFT vector. The combination of oversampling factors (O1, O2) may be determined based on (N1, N2) and / or the number of CSI-RS antenna ports. Alternatively, the combination of oversampling factors (O1, O2) may be determined by (N1, N2, Ng) and / or the number of CSI-RS antenna ports. That is, the terminal can determine (O1, O2) to apply to the codebook based on a predefined rule without relying on signaling from the base station. In the above embodiment, (O1, O2) may be an oversampling factor for the parent codebook. In the case of a child codebook, the oversampling factor of the child codebook corresponding to the a-th CSI reporting sub-configuration may be referred to as (O1(a), O2(a)). Unlike the case of the parent codebook, (O1(a), O2(a)) to be applied to each child codebook may be signaled from the base station to the terminal. For example, information about (O1(a), O2(a)) may be included in the configuration information of the a-th CSI reporting sub-configuration. Alternatively, (O1(a), O2(a)) to be applied to each child codebook may be determined based on (N1(a), N2(a)) and / or the number of CSI-RS antenna ports C(a).

[0179] Simultaneously or separately, the CSI-RS antenna port set corresponding to each CSI reporting configuration may be represented by a bitmap. The length of the bitmap may be C. The C bits constituting the bitmap may indicate whether or not each CSI-RS antenna port constituting the CSI-RS resource is muted. For example, a CSI-RS antenna port corresponding to a bit with a value of '1' (or '0') may be included in the CSI-RS antenna port set, and a CSI-RS antenna port corresponding to a bit with a value of '0' (or '1') may be considered not to be included in the CSI-RS antenna port set. In the bitmap corresponding to the a-th CSI reporting sub-configuration, the values ​​of the bits corresponding to the C(a) CSI-RS antenna ports may be set to '1' (or '0'). That is, the number of bits set to '1' may be C(a). C(a) may correspond to the value 2*N1(a)*N2(a). The bitmap or information about the bitmap may be included in configuration information for each CSI reporting sub-configuration and transmitted to the UE.

[0180] According to an embodiment, each bit in a bitmap may be determined independently regardless of the value of other bit(s). That is, the bitmap may be configured with any bit sequence, and a spatial element pattern may be configured on any antenna port(s) among the CSI-RS antenna ports constituting the CSI-RS resource. For example, a CSI-RS antenna port subset indicated by the bitmap may be mapped to a single-polarized antenna. As another example, the CSI-RS antenna port subset indicated by the bitmap may have a non-uniform pattern in the horizontal and / or vertical domains. Meanwhile, in a communication system (e.g., an NR communication system), a CSI codebook may be designed to have optimal performance in a uniform two-dimensional planar array antenna structure with cross-polarization. In such a case, when a spatial element pattern is configured according to the above examples, CSI accuracy may be reduced.

[0181] According to another embodiment, multiple bits mapped to specific positions in a bitmap may have the same value. For example, two CSI-RS antenna ports mapped to two sets of antenna elements at the same location but with different polarizations may be muted or transmitted together (i.e., not muted). The bits corresponding to the two CSI-RS antenna ports may have the same value (e.g., all 1s or all 0s). Specifically, when the length of the bitmap is P, the i-th bit and the (i+P / 2)-th bit of the bitmap may correspond to two CSI-RS antenna ports at the same spatial location but with different polarizations, and these bits may have the same value. That is, the first P / 2 bit string and the last P / 2 bit string of the bitmap may be the same.

[0182] Meanwhile, the CSI-RS antenna ports constituting the CSI-RS resources may be mapped to multiple panels. In this case, in addition to the cross-polarization structure, the patterns (e.g., the number and mapping structure) of the CSI-RS antenna ports mapped to the multiple panels may be identical to each other. For example, if the number of panels is two (Ng=2), the first P / 2 bits of the bitmap may correspond to the CSI-RS antenna port mapped to the first panel, and the last P / 2 bits may correspond to the CSI-RS antenna port mapped to the second panel. In this case, the first P / 2 bit string and the last P / 2 bit string may be identical. Also, the first P / 4 bits of the bitmap may correspond to the CSI-RS antenna port corresponding to the first polarization of the first panel, the second P / 4 bits may correspond to the CSI-RS antenna port corresponding to the second polarization of the first panel, the third P / 4 bits may correspond to the CSI-RS antenna port corresponding to the first polarization of the second panel, and the last P / 4 bits may correspond to the CSI-RS antenna port corresponding to the second polarization of the second panel. In this case, the first P / 4 bit string and the second P / 4 bit string may be the same. Also, the third P / 4 bit string and the last P / 4 bit string may be the same. That is, all four bit strings may match. The base station may determine a bitmap taking the above constraints into consideration and may configure a CSI-RS antenna port subset for a CSI reporting sub-configuration by signaling the determined bitmap to the UE. The UE may expect that a bitmap that satisfies the above conditions will be configured. If the bitmap does not satisfy the above conditions, the UE may ignore the configuration and may omit a CSI reporting procedure corresponding to the configuration (e.g., a CSI report for the corresponding CSI reporting sub-configuration or all CSI reports to which the corresponding CSI reporting sub-configuration belongs).

[0183] A certain spatial element pattern (e.g., a certain CSI reporting sub-configuration) may be configured with two CSI-RS antenna ports. For example, the base station may instruct the UE that the size of the codebook corresponding to the CSI reporting sub-configuration is (N1, N2) = (1, 1) or (N1(a), N2(a)) = (1, 1). The configuration information of the CSI reporting sub-configuration may include the codebook configuration information. As another example, the configuration information of the CSI reporting sub-configuration may explicitly include the number of CSI-RS antenna ports in the corresponding CSI-RS antenna port set being two. The UE may derive CSI based on the corresponding two CSI-RS antenna ports. The two CSI-RS antenna ports may be antenna ports corresponding to a specific row (e.g., the first row) and a specific column (e.g., the first column) in the spatial mapping structure of the CSI-RS antenna ports. In this case, the CSI may be calculated based on a separate codebook, i.e., a codebook defined in the technical specification to be used when the number of CSI-RS antenna ports is two. The codebook may not be a codebook configured using the Kronecker product of two matrices. Alternatively, spatial element patterns (e.g., CSI reporting sub-configurations) configured with two CSI-RS antenna ports in the above-described manner may be excluded. The terminal may not expect the same configuration as the above example.

[0184]

[0185] An inclusion relationship may be established between the CSI-RS antenna port sets configured in the UE. In the above embodiment, an inclusion relationship may be established between any two CSI-RS antenna port sets among the first, second, and fifth CSI-RS antenna port sets, and the CSI-RS antenna port sets may be simultaneously configured in the UE for the same CSI-RS resource. On the other hand, an inclusion relationship may not be established between the second and third CSI-RS antenna port sets, and the CSI-RS antenna port sets that do not have an inclusion relationship may not be configured to be associated with the same CSI-RS resource. Similarly, an inclusion relationship may be established between CSI-RS muting patterns (i.e., CSI-RS antenna port sets to be muted) configured in the UE, and the UE may simultaneously be configured with CSI-RS muting patterns that have an inclusion relationship for the same CSI-RS resource. CSI-RS muting patterns that do not have an inclusion relationship may not be configured to be associated with the same CSI-RS resource.

[0186]

[0187] Furthermore, an inclusion relationship may be established between CSI-RS antenna port sets and associated codebooks within the same CSI-RS resource, or between codebooks associated with the same CSI-RS resource. In the above embodiment, CSI corresponding to a first CSI-RS antenna port set may be derived based on a 2D codebook having a structure of (N1, N2) = (4, 2) or (N1, N2, P) = (4, 2, 2), and CSI corresponding to a second CSI-RS antenna port set may be derived based on a 2D codebook having a structure of (N1, N2) = (4, 1) or (N1, N2, P) = (4, 1, 2). The latter 2D codebook may be configured as a part of the former 2D codebook and may have a length smaller than or equal to (or not larger than) the former 2D codebook in each transmission direction (or domain). The length of the polarization direction (or domain) of the codebooks associated with the CSI-RS antenna port set, i.e., P, may be the same. In the above embodiment, the former 2D codebook and the latter 2D codebook may both have P=2.

[0188]

[0189] Within each CSI-RS antenna port set, the CSI-RS antenna port numbers may be numbered in ascending order starting from 0 (or 3000 in an NR communication system). In the above embodiment, the eight CSI-RS antenna ports constituting the third CSI-RS antenna port set may have antenna port numbers 0, 1, 2, 3, 8, 9, 10, and 11 in terms of total CSI-RS resources before muting is applied. However, these may be renumbered from 0 to 7 within the CSI-RS antenna port set. The terminal may calculate CSI (e.g., PMI, CQI, RI) based on the indexed numbers within the CSI-RS antenna port set.

[0190]

[0191] Configuration information regarding the CSI codebook to be applied to CSI calculation may be included in the CSI reporting configuration information and may be associated with each CSI report. In the second CSI reporting method, CSI codebook configuration information may be included in each CSI reporting sub-configuration information and may be used for a CSI report corresponding to each CSI reporting sub-configuration. When the UE receives the above-described CSI-RS reception and CSI measurement operations based on the CSI-RS resources, the UE may use the codebook configuration information included in the CSI report associated with the CSI-RS resources. Alternatively, information regarding the CSI codebook may be included in the CSI resource configuration information and associated with each CSI resource or each CSI-RS resource. The 2D codebook configuration information may include at least N1 and / or N2. The 2D codebook configuration information may additionally include P. In the first embodiment of FIG. 8, (N1, N2) = (4, 2) or (N1, N2, P) = (4, 2, 2), and the UE may assume the CSI-RS antenna port configuration shown in the drawing based on the information.

[0192]

[0193] According to (method 100), the base station may transmit all CSI-RS antenna ports constituting the CSI-RS resources to the terminal in the CSI-RS resources of each period. Alternatively, the base station may transmit the union of all CSI-RS antenna port sets configured for the CSI-RS resources to the terminal in the CSI-RS resources of each period. That is, until the CSI-RS resources are reconfigured, the terminal can receive the same number of CSI-RS antenna ports in the CSI-RS resources of each period (e.g., each CSI-RS occasion).

[0194] Meanwhile, some CSI-RS antenna port set(s) among the CSI-RS antenna port sets configured for the UE may be dynamically indicated to the UE. The dynamic indication may be performed by DCI. The DCI may include information regarding the ID or index of the CSI-RS antenna port set(s) to be indicated to the UE. Simultaneously or separately, as described above, some of the CSI reporting configurations or CSI reporting sub-configurations configured for the UE may be dynamically indicated to the UE. The DCI may include information regarding the ID or index of the CSI reporting configuration(s) or CSI reporting sub-configuration(s) to be indicated to the UE, and may indicate the corresponding CSI reporting operation. The UE may perform CSI measurement and reporting operations for the indicated CSI-RS antenna port set(s) and / or the indicated CSI reporting configuration(s) (or CSI reporting sub-configuration(s)). The UE may not perform CSI measurement and reporting operations for the not-instructed CSI-RS antenna port set(s) and / or the not-instructed CSI reporting configuration(s) (or CSI reporting sub-configuration(s)).

[0195] Alternatively, the UE may transmit CSI reports for all configured CSI-RS antenna port sets and / or all CSI reporting configurations (or all CSI reporting sub-configurations) to the base station, regardless of whether or not there is a dynamic indication of the CSI-RS antenna port set(s) and / or CSI reporting configuration(s) (or CSI reporting sub-configuration(s)). In this case, CSI reports corresponding to non-instructed CSI-RS antenna port sets and / or non-instructed CSI reporting configuration(s) (or CSI reporting sub-configurations) may have dummy values. In this way, the size of the CSI report information may be maintained constant regardless of the dynamic indication.

[0196] FIG. 9 is a conceptual diagram illustrating a second embodiment of a CSI reporting method based on multiple CSI-RS antenna port sets.

[0197] Referring to FIG. 9, the UE can receive CSI-RS resource configuration information from the base station. t = 16 CSI-RS antenna ports. The CSI-RS resources may be periodically repeated.

[0198] The UE may be configured or instructed by the base station to select a CSI-RS antenna port to receive on the CSI-RS resource, i.e., a CSI-RS antenna port set (i.e., a subset). In this embodiment, the UE may receive the first DCI and, based on the first DCI, determine L1=L on the CSI-RS resource. tThe terminal may be instructed to receive (i.e., activate) a first CSI-RS antenna port set consisting of L2=16 CSI-RS antenna ports. During a first time interval during which the terminal receives the first CSI-RS antenna port set, the terminal may measure CSI based on the first CSI-RS antenna port set and report the first CSI corresponding to the first CSI-RS antenna port set to the base station. The terminal may also receive a second DCI and, based on the second DCI, may be instructed to receive a second CSI-RS antenna port set consisting of L2=4 CSI-RS antenna ports on the CSI-RS resources. During a second time interval during which the terminal receives the second CSI-RS antenna port set, the terminal may measure CSI based on the second CSI-RS antenna port set and report the second CSI corresponding to the second CSI-RS antenna port set to the base station. The above method may be referred to as (method 200).

[0199] As a specific method for indicating a CSI-RS antenna port set, the UE can configure multiple CSI-RS antenna port sets based on configuration information received from the base station. The configuration information can be transmitted based on higher layer signaling (e.g., RRC signaling, MAC CE). The UE can receive indication of one (or more) CSI-RS antenna port set from the multiple CSI-RS antenna port sets through DCI. The DCI can include an ID or index of the CSI-RS antenna port set to be indicated. Alternatively, CSI-RS antenna port set configuration information can be directly included in DCI, and the UE can configure the CSI-RS antenna port set based on the DCI and receive the CSI-RS antenna port set. Alternatively, the CSI-RS antenna port set can be indicated only through higher layer signaling (e.g., RRC signaling, MAC CE) without a DCI transmission procedure.

[0200] Alternatively, as described above, the UE may receive a CSI reporting configuration including multiple CSI reporting sub-configurations from the base station. Each CSI reporting sub-configuration may correspond to a spatial element pattern, i.e., a CSI-RS antenna port set. The UE may be indicated one (or more) CSI reporting sub-configuration(s) through DCI, receive CSI-RS antenna port set(s) corresponding to the CSI reporting sub-configuration(s), and perform corresponding CSI measurement and reporting operations according to the method described above. The UE may omit the operation of receiving CSI-RS antenna ports that are not included in the indicated CSI-RS antenna port set(s) among the CSI-RS resources or CSI-RS antenna ports belonging to a CSI-RS resource set.

[0201] If there are multiple indicated CSI reporting sub-configurations, the above-described codebook inclusion relationship may be established for the multiple CSI reporting sub-configurations. For example, the configuration information of the first codebook of the first CSI reporting sub-configuration and the second codebook of the second CSI reporting sub-configuration indicated by the DCI may include (N1(1), N2(1)) and (N1(2), N2(2)), respectively. In this case, the horizontal and vertical domain codeword lengths of the first codebook may be smaller than or equal to those of the second codebook, respectively. That is, N1(1)≦N1(2) and N2(1)≦N2(2) may be satisfied.

[0202]

[0203] To increase the effective power efficiency of a base station, the above-described CSI-RS antenna port scaling or muting method can be commonly applied to multiple terminals communicating with a base station. Accordingly, information indicating the CSI-RS antenna port set and / or configuration information of the CSI-RS antenna port set can be transmitted to a terminal (or a terminal group) based on a group-common DCI. In an NR communication system, the group-common DCI may conform to DCI format 2_X (X is an integer equal to or greater than 0). A terminal can monitor the group-common DCI using a CSS set (e.g., a type 3 CSS set). The CSS set can be associated with any CORESET. If a DRX operation is configured in a terminal, the group-common DCI can be monitored during a DRX active time (or on duration). Furthermore, the group-common DCI may further include information indicating a DRX operation of the terminal (or a cell DTX operation, or a terminal DRX operation corresponding to the cell DTX operation). For example, the group-common DCI may additionally include information instructing the UE to wake up in the next active time (or on-duration) and perform a PDCCH monitoring operation, a downlink signal reception operation, etc., information instructing the UE to enter a sleep mode in the next inactive time and omit (at least part of) downlink signal reception, etc. For the wake-up instruction, the UE may monitor the group-common DCI (or a corresponding search space set, CORESET) in a period outside the DTX active time (or inactive time).

[0204] Similarly, as in the above-described method, CSI reporting sub-configuration(s) may be indicated by the group-common DCI. Each CSI reporting sub-configuration may correspond to a respective spatial element pattern, i.e., a respective CSI-RS antenna port set. A terminal may be indicated one (or more) CSI reporting sub-configuration(s) through the group-common DCI, may receive CSI-RS antenna port set(s) corresponding to the CSI reporting sub-configuration(s), and may perform corresponding CSI measurement and reporting operations in the above-described manner.

[0205] In the CSI-RS resource reception operation and the corresponding CSI measurement and reporting operation, the UE can receive CSI-RS resources (i.e., the applied CSI-RS antenna port set(s)) by applying the CSI-RS antenna port set(s) indicated by the DCI from a first time point. The first time point can be determined based on the time point at which the DCI is received. For example, the first time point can be determined to be a time point at which a certain time offset has elapsed from the time point at which the DCI is received. The first time point can be indicated by a slot. The first time point can be any slot after the slot at which the DCI is received. For example, the first time point can be determined to be the slot to which a symbol A symbols after the symbol at which the DCI is received (e.g., the last symbol) belongs, or the next slot (A is a natural number). A can be predefined in a technical standard. A can be determined based on the UE's PDCCH reception capability. When activation and deactivation operations are applied to CSI-RS resources or CSI-RS antenna port sets, the CSI-RS antenna port set(s) indicated by the DCI may be considered to be activated from the time the DCI is received or the first time point. Also, the CSI-RS antenna port set(s) indicated by the DCI may be considered to be activated by default (i.e., even without a separate activation instruction). When the indicated CSI-RS antenna port set(s) are activated, the previous CSI-RS antenna port set(s) may be deactivated.

[0206]

[0207] When the (activated) CSI-RS antenna port set is changed by the above-described method, the UE may reset the CSI measurement operation. The UE may reset the CSI measurement operation based on the time point at which the indicated CSI-RS antenna port set is applied, i.e., the first time point. Accordingly, the CSI corresponding to the indicated CSI-RS antenna port set may be calculated based on the CSI-RS resource(s) (or CSI-RS occasion(s)) received in the time interval from the first time point (e.g., the slot corresponding to the first time point) to the CSI reference resource (e.g., the corresponding slot). The CSI-RS resource(s) (or CSI-RS occasion(s)) received before the first time point (e.g., the slot corresponding to the first time point) may not be used to derive the CSI corresponding to the indicated CSI-RS antenna port set. Through the above-described reset operation, one CSI (i.e., one CSI instance, one CSI reporting instance) reported to the base station can be calculated based on the CSI-RS resource(s) (or CSI-RS occasion(s)) received for one CSI antenna port set, and CSI accuracy can still be guaranteed. The CSI reference resource can be determined to be any one slot that is sufficiently preceding the CSI reporting time (e.g., slot) by a reference value. The CSI reference resource can be a downlink slot. Alternatively, the CSI reference resource can be a slot including at least one downlink symbol or flexible symbol.

[0208]

[0209] The operation of the UE configuring the CSI-RS antenna port set may be performed by the above-described method. First configuration information may be transmitted to the UE, and the first configuration information may include information about CSI-RS antenna ports configuring the CSI-RS antenna port set or information about muted CSI-RS antenna ports excluded from the CSI-RS antenna port set. Furthermore, the information may be expressed as information about the positions of CSI-RS antenna ports in each dimension of the 2D codebook (e.g., information indicating the positions of elements in a matrix) based on (method 110).

[0210]

[0211] According to method 200, the number of CSI-RS antenna ports (or CSI-RS antenna port set) received by a terminal for the same CSI-RS resource may vary over time. Also, the number of TXRUs used to transmit CSI-RS may vary over time. In the above embodiment, 32 TXRUs may be used for CSI-RS transmission in a first time interval in which a first CSI-RS antenna port set is transmitted. Conversely, 8 TXRUs may be used for CSI-RS transmission in a second time interval in which a second CSI-RS antenna port set is transmitted. The number of TXRUs used for CSI-RS transmission may be the same as the number of TXRUs used to transmit other signals (e.g., PDSCH) within the same time interval. Therefore, the base station may operate only a small number of TXRUs in a second time interval that includes a CSI-RS transmission symbol (i.e., a symbol in which CSI-RS is transmitted). As a result, (method 200) may be advantageous for low-power operation compared to (method 100), which requires higher power consumption in the CSI-RS transmission symbol and the sections before and after it. Also, according to (method 200), the UE can measure and transmit only one CSI report per CSI reporting instance, which may improve the UE's computational complexity and uplink resource efficiency compared to (method 100), which transmits multiple CSI reports each time.

[0212]

[0213] A specific method for mapping a CSI-RS antenna port set to a CSI-RS resource according to an embodiment of the present invention will be described below. The following embodiments (methods 310 to 330) and their detailed embodiments may be applied to the above-described method 100 or method 200.

[0214] FIG. 10 is a conceptual diagram illustrating a first embodiment of a resource mapping method for CSI-RS antenna port sets.

[0215] 10, the first and second CSI-RS antenna port sets of the above embodiment may be mapped to TXRUs (i.e., corresponding physical antenna elements) arranged in a first direction (e.g., horizontal direction), a second direction (e.g., vertical direction), and a third direction (e.g., polarization direction) using the method described above. Also, the first and second CSI-RS antenna port sets may be indicated based on two-dimensional matrix information corresponding to the first and second directions (or three-dimensional matrix information corresponding to the first, second, and third directions) using the method described above.

[0216] Each CSI-RS antenna port set may be mapped to a CSI-RS resource for transmission. The first CSI-RS antenna port set may consist of all CSI-RS antenna ports constituting the CSI-RS resource. Therefore, the first CSI-RS antenna port set may follow the RE mapping pattern configured for all CSI-RS antenna ports indicated by the CSI-RS resource configuration. That is, the 16 CSI-RS antenna ports constituting the first CSI-RS antenna port set may be mapped to 16 REs, as shown in FIG. 3. On the other hand, the second CSI-RS antenna port set may consist of some of the CSI-RS antenna ports constituting the CSI-RS resource. In this case, several methods for mapping the four CSI-RS antenna ports constituting the second CSI-RS antenna port set to CSI-RS resources may be considered.

[0217] In the first method shown in FIG. 10, the CSI-RS antenna ports constituting the CSI-RS antenna port set may follow the RE mapping pattern defined for all CSI-RS antenna ports indicated by the CSI-RS resource configuration. In this embodiment, four CSI-RS antenna ports 0 to 3 may correspond to the previous index numbers 0, 1, 8, and 9, and may be mapped to four REs of CDM group 0, four REs of CDM group 2, and four REs of CDM group 2, respectively, in the overall mapping pattern consisting of the 16 CSI-RS antenna ports before muting is applied. Different codes (e.g., different OCCs) may be applied to CSI-RS antenna ports belonging to the same CDM group. As a result, the four CSI-RS antenna ports may be mapped to eight REs, and the eight REs may occupy four symbols and two subcarriers. The remaining 8 REs (i.e., 4 REs of CDM group 1 and 4 REs of CDM group 3) to which the 4 CSI-RS antenna ports are not mapped in the overall mapping pattern may be muted. That is, the remaining 8 REs may not be used for transmitting the CSI-RS resources. The above method may be referred to as (method 310).

[0218] According to (method 310), even if the CSI-RS antenna port set is scaled and the CSI-RS antenna ports are re-indexed, the mapping relationship between the CSI-RS antenna ports and the REs can be maintained. Therefore, the implementation complexity of the UE may be relatively low. Furthermore, a common mapping pattern can be used between UEs receiving CSI-RS antenna port sets to which different scaling has been applied, and CSI-RS resources can be shared among the UEs. However, in the above embodiment, eight REs, which is twice the minimum number of REs required, are used to transmit the four CSI-RS antenna ports constituting the second CSI-RS antenna port set, which may result in reduced resource efficiency and increased CSI-RS transmission latency.

[0219] As a second method, the CSI-RS antenna ports constituting the CSI-RS antenna port set may be sequentially mapped onto the CSI-RS resources based on newly assigned antenna port numbers within the CSI-RS antenna port set, while still following the RE mapping pattern configured for all CSI-RS antenna ports as indicated by the CSI-RS resource configuration. The above method may be referred to as (Method 320).

[0220] FIG. 11 is a conceptual diagram illustrating a second embodiment of a resource mapping method for CSI-RS antenna port sets.

[0221] Referring to FIG. 11, a CSI-RS antenna port set may be mapped to CSI-RS resources by (method 320). The four CSI-RS antenna ports constituting the second CSI-RS antenna port set may have newly assigned indices 0 to 3 within the CSI-RS antenna port set and may be mapped to REs according to the CSI-RS resource mapping rule shown in FIG. 1 based on the indices. That is, CSI-RS antenna ports 0 to 3 may be mapped to the four REs constituting CDM group 0 according to the rule that they are mapped in ascending order first within the CDM group, and different codes (e.g., different OCCs) may be applied to each RE. The remaining 12 REs may not be used for transmitting the CSI-RS resources. Compared to the first embodiment, according to this embodiment, the second CSI-RS antenna port set may occupy a smaller number of REs and a smaller number of symbols for transmission. This may improve resource efficiency and transmission delay.

[0222] As a third method, the CSI-RS antenna ports constituting the CSI-RS antenna port set may be mapped to the CSI-RS resources according to a separate RE mapping pattern. The separate RE mapping pattern may be determined according to a rule predefined in a technical standard. Alternatively, the separate RE mapping pattern may be transmitted from the base station to the terminal through a signaling procedure. The above method may be referred to as (method 330).

[0223] FIG. 12 is a conceptual diagram illustrating a third embodiment of a resource mapping method for CSI-RS antenna port sets.

[0224] Referring to FIG. 12, a CSI-RS antenna port set may be mapped to CSI-RS resources by (method 330). The four CSI-RS antenna ports constituting a second CSI-RS antenna port set may have newly assigned indices 0 to 3 within the CSI-RS antenna port set and may be mapped to REs according to a separate CSI-RS mapping pattern. The separate mapping pattern may consist of two CDM groups, each of which may consist of two REs adjacent in the frequency domain, and the two CDM groups may be mapped to the same symbol. CSI-RS antenna ports 0 to 3 may be mapped to two REs of CDM group 0, two REs of CDM group 1, and two REs of CDM group 1, respectively, according to an ascending indexing rule, first within the CDM group and second in the frequency domain. Different codes (e.g., different OCCs) may be applied to CSI-RS antenna ports belonging to the same CDM group. As a result, four CSI-RS antenna ports can be mapped onto four REs and one symbol. Compared to the first embodiment, according to this embodiment, the second CSI-RS antenna port set can be transmitted occupying a smaller number of REs and a smaller number of symbols. Also, compared to the second embodiment, according to this embodiment, the second CSI-RS antenna port set can be transmitted occupying a smaller number of symbols. Therefore, resource efficiency and transmission delay time can be improved.

[0225] In this embodiment, resources (i.e., a set of REs) constituting a separate RE mapping pattern for a CSI-RS antenna port set may be included in the CSI-RS resources (i.e., a set of REs constituting the CSI-RS resources) before muting is applied. Referring to FIG. 12, the four REs to which the second CSI-RS antenna port set is mapped may be a subset of the 16 REs constituting the CSI-RS resources. That is, an overlapping structure may be established between the CSI-RS resources and the resources to which the CSI-RS antenna port sets associated with the CSI-RS resources are mapped. At the same time, the separate RE mapping pattern may be determined based on resource mapping configuration information configured by the base station. For example, at least some of the configuration information regarding the size of the CDM group applied to the separate RE mapping pattern, the number of CDM groups, the symbol(s) on which each CDM group is allocated, the subcarrier(s) on which each CDM group is allocated, etc. may be signaled from the base station to the UE. At least some of the information may be signaled to the UE separately from the resource mapping configuration information for the CSI-RS resources. For example, the size of the CDM group for the CSI-RS antenna port aggregation (2 in the above embodiment) may be different from the size of the CDM group configured for the CSI-RS resource (4 in the above embodiment).

[0226] According to another embodiment, the resources (i.e., a set of REs) constituting a separate RE mapping pattern for a CSI-RS antenna port set may include other resources (i.e., other RE(s)) than the CSI-RS resources before muting is applied (i.e., the set of REs constituting the CSI-RS resources). For example, the CSI-RS antenna ports constituting the second CSI-RS antenna port set may be mapped to a symbol (e.g., the third symbol) other than the symbol to which the CSI-RS resources are mapped. As another example, the CSI-RS antenna ports constituting the second CSI-RS antenna port set may be mapped to a subcarrier (e.g., the first subcarrier) other than the subcarrier to which the CSI-RS resources are mapped.

[0227] In addition to or separately from the above embodiment, resources (i.e., a set of REs) constituting a separate RE mapping pattern for a set of CSI-RS antenna ports may be arranged in the same time resource unit (e.g., the same slot, the same subframe, the same subslot, etc.) as the CSI-RS resources (i.e., the set of REs constituting the CSI-RS resources) before muting is applied, and may have the same resource period and time offset. By using the above method, the CSI-RS reception period and time point of the UE can be maintained even if the number of CSI-RS antenna ports is dynamically changed.

[0228] According to this embodiment, the CSI-RS may not be transmitted in some RE(s) constituting the CSI-RS resource due to the CSI-RS muting operation. Referring to Figure 10, the CSI-RS antenna port may not be mapped to the 8 REs indicated on the 9th and 10th subcarriers, and the CSI-RS may not be transmitted in these REs. Referring to Figure 12, the CSI-RS antenna port may not be mapped to the 12 REs indicated on the 6th, 9th, and 10th symbols, and the CSI-RS may not be transmitted in these REs.

[0229] In this case, the RE(s) may be used to transmit other signals. The UE may receive other downlink signals other than the CSI-RS resources in the RE(s). The downlink signals may include a PDSCH. That is, the UE may receive the PDSCH in resources including RE(s) to which the CSI-RS is not mapped. In other words, the PDSCH does not need to be rate-matched to RE(s) to which the CSI-RS is not mapped. The UE may receive the PDSCH in resources other than the RE(s) to which the CSI-RS is actually mapped (i.e., RE(s) to which the activated CSI-RS antenna port set is mapped) among the REs constituting the CSI-RS resources. That is, the PDSCH may be rate-matched around the RE(s) to which the CSI-RS is actually mapped (i.e., RE(s) to which the activated CSI-RS antenna port set is mapped) among the REs constituting the CSI-RS resources. The above-described rate matching operation may be referred to as a first rate matching operation. Whether or not to perform the above-described PDSCH rate matching operation may be determined based on the time relationship between when the UE receives the scheduling of the PDSCH (e.g., when it receives a scheduling DCI) and when it receives an instruction to receive the CSI-RS antenna port set (e.g., when it receives a DCI or MAC CE instructing to receive the CSI-RS antenna port set). If the UE receives the scheduling of the PDSCH not earlier (or later) than when it receives an instruction to receive the CSI-RS antenna port set, it can receive the PDSCH based on the above-described rate matching operation.

[0230]

[0231] Alternatively, even if CSI-RS is not actually transmitted in the RE(s), the UE can receive the PDSCH in a resource region excluding the RE(s). That is, the PDSCH can be rate-matched for all RE(s) constituting the CSI-RS resource. In the above embodiment, regardless of whether CSI-RS muting is enabled, the PDSCH can be received in a resource region excluding 16 REs constituting the CSI-RS resource. The above-mentioned rate matching operation may be referred to as a second rate matching operation. The first rate matching operation and the second rate matching operation may be selectively performed. The base station may instruct the UE to perform one of the first rate matching operation and the second rate matching operation. The instruction information may be transmitted from the base station to the UE based on a signaling procedure (e.g., RRC signaling, DCI, MAC CE) in the UE. Alternatively, the UE may select one of the first rate matching operation and the second rate matching operation based on a rule predefined in a technical standard and perform the selected operation. For example, the predefined rule may be defined based on the time relationship between the time when the UE receives the PDSCH schedule and the time when the UE receives the instruction to receive the CSI-RS antenna port set. If the time when the UE receives the PDSCH schedule is not earlier (or later) than the time when the UE receives the instruction to receive the CSI-RS antenna port set, the UE can receive the PDSCH based on a first rate matching operation; otherwise, the UE can receive the PDSCH based on a second rate matching operation.

[0232] Alternatively, the downlink signal may include a PDCCH. The UE may receive CSI-RS resource configuration information and CORESET configuration information that allow the CSI-RS resources and the CORESET to overlap. The UE may monitor PDCCH candidates that are mapped to resources including RE(s) to which the CSI-RS is not mapped among PDCCH candidates belonging to the CORESET (or a corresponding search space set), and may receive the PDCCH on the corresponding resources.

[0233] Furthermore, the UE can transmit uplink signals in the RE(s). For example, the RE(s) may be REs on a flexible symbol, and the UE can transmit uplink signals in a resource region including the RE(s). To this end, the CSI-RS resource and the uplink resource may be configured in the UE to overlap. For example, the CSI-RS resource may overlap with the SRS resource on the same symbol and / or in the same RE(s). As another example, the CSI-RS resource may overlap with the PUCCH resource on the same symbol and / or in the same RE(s). The overlap between the CSI-RS resource and the uplink resource may be permitted only for the flexible symbol configured in the UE.

[0234]

[0235] In (method 200), a terminal can receive multiple CSI-RS antenna port sets in a certain CSI-RS resource period (or time interval). For example, a base station can instruct a terminal to receive multiple CSI-RS antenna port sets via DCI. The terminal can calculate CSI based on the multiple CSI-RS antenna port sets. For example, the terminal can calculate CSI for each of the multiple CSI-RS antenna port sets. The calculated CSI(s) can be reported to the base station. That is, (method 200) can be implemented in combination with (method 100).

[0236]

[0237] According to the above embodiment, multiple (or one or more) CSI-RS antenna port sets may be configured or indicated for one CSI-RS resource. The CSI(s) derived based on the multiple CSI-RS antenna port sets are the CSI(s) corresponding to the CSI-RS resources and may be reported to the base station based on the CSI reporting configuration corresponding to the CSI-RS resources. However, the above resource configurations are merely examples, and the concept of the present disclosure is not limited to the above resource configurations and may be implemented in various forms. For example, in the above embodiment, "one CSI-RS resource corresponds to one or more CSI-RS antenna port sets" may be interpreted as "one CSI-RS resource set corresponds to one or more CSI-RS resources." That is, the CSI-RS resource may correspond to a CSI-RS resource set, and the CSI-RS antenna port set may correspond to a CSI-RS resource. As another example, in the above embodiment, "one CSI-RS resource corresponds to one or more CSI-RS antenna port sets" may be interpreted as "one CSI resource set corresponds to one or more CSI-RS resource sets." That is, the CSI-RS resource may correspond to a CSI resource set, and the CSI-RS antenna port set may correspond to a CSI-RS resource set. In this case, the above-described CSI-RS antenna port set configuration operation and association operation with a CSI report may be interpreted as an operation of configuring a CSI-RS resource or a CSI-RS resource set and association operation with the corresponding CSI report. For example, the first configuration information, a CSI-RS muting pattern, etc. may be configured for each CSI-RS resource or each CSI-RS resource set. The terminal may generate CSI report information for each CSI-RS resource or each CSI-RS resource set and transmit the generated CSI report(s) to the base station.

[0238]

[0239] Meanwhile, a terminal can simultaneously transmit and receive from multiple TRPs. In the downlink, a terminal can receive a PDSCH from multiple TRPs. Multiple TRPs can transmit different layers of the PDSCH on the same resource. Alternatively, multiple TRPs can transmit different PDSCHs to a terminal. In this case, the PDSCH resources transmitted from the multiple TRPs may or may not overlap. This method may be referred to as non-coherent joint transmission (NCJT).

[0240] The NCJT transmission scheme can be dynamically switched between the NCJT transmission scheme and the single TRP transmission scheme. Therefore, the UE can measure CSI under the multiple TRP transmission hypothesis (i.e., the NCJT hypothesis). This may be referred to as the NCJT measurement hypothesis. The UE can also measure CSI under the single TRP transmission hypothesis. This may be referred to as the single TRP measurement hypothesis. The CSI according to the NCJT measurement hypothesis and the CSI according to the single TRP measurement hypothesis can be reported to the base station through a single CSI report. For example, the UE can select either the CSI(s) according to the NCJT measurement hypothesis or the CSI(s) according to the single TRP measurement hypothesis (e.g., the CSI corresponding to the largest CQI value) and report the selected CSI to the base station. Alternatively, the UE can report both the CSI(s) according to the NCJT measurement hypothesis and the CSI(s) according to the single TRP measurement hypothesis to the base station. The CSI-RS resource set configured in the UE for the above-mentioned CSI reporting operation may include multiple CSI-RS resources, among which the CSI-RS resource pair(s) used for NCJT transmission may be configured separately in the UE. Each CSI-RS resource may include unique TCI status information. For example, each CSI-RS resource may correspond to a respective TRP.

[0241] In this case, to improve network power efficiency, the TRP can transmit and receive signals by applying a TXRU muting method. Similarly, each TXRU muting pattern may correspond to a CSI reporting sub-configuration, and the UE may be configured with a CSI reporting configuration including multiple sub-configurations. In this case, each CSI-RS resource may be associated with the multiple sub-configurations and may correspond to at least one of the NCJT measurement hypothesis and the single-TRP measurement hypothesis. For example, a first CSI-RS resource and a second CSI-RS resource belonging to the same CSI-RS resource set may be configured as a CSI resources for channel measurement (CMR) pair, and the UE can perform CSI measurement and reporting operations based on the NCJT measurement hypothesis. At the same time, a third CSI-RS resource is not configured as a CMR pair and may be referenced for CSI measurement and reporting based on a single-TRP measurement hypothesis. In this case, each sub-configuration constituting the CSI reporting may be associated with all CSI-RS resources and all CMR pairs constituting the CSI-RS resource set. In the above example, each sub-configuration may be associated with a CMR pair consisting of a first CSI-RS resource and a second CSI-RS resource, and a third CSI-RS resource. The UE may measure CSI according to the NCJT measurement hypothesis based on the CMR pair for each sub-configuration, and may measure CSI according to the single TRP measurement hypothesis based on the third CSI-RS resource. The UE may select one or more CSI(s) from among these according to the above-mentioned method and report the selected CSI(s) to the base station. The CRI corresponding to the CSI-RS resource(s) or CMR pair(s) on which the selected CSI(s) are based may also be reported.

[0242]

[0243] The above-described CSI-RS scaling method or CSI-RS muting method may correspond to the first TXRU muting method. Meanwhile, as described above, when a TXRU is scaled using the second TXRU muting method, the number of corresponding CSI-RS antenna ports may not change. That is, even if the number of TXRUs to which CSI-RS antenna ports are mapped changes dynamically, the UE can receive the same CSI-RS antenna ports in the CSI-RS resources for each period. In the embodiment of FIG. 5b, the UE can receive the same 16 CSI-RS antenna ports before and after TXRU muting. That is, the 16 CSI-RS antenna ports constituting the CSI-RS resources may be transmitted through a first TXRU set at a first time point and through a second TXRU set at a second time point.

[0244]

[0245] When a TXRU is scaled from the first TXRU set to the second TXRU set using the second TXRU muting method, the mapping between each CSI-RS antenna port and a physical antenna element may change, and as a result, the beam pattern formed by each CSI-RS antenna port, coverage (or signal reach or area), etc. may change. Therefore, downlink measurement values, measurement quality, etc. based on CSI-RS resources transmitted through the first TXRU set may differ from downlink measurement values, measurement quality, etc. based on CSI-RS resources transmitted through the second TXRU set.

[0246] Accordingly, if the set of TXRUs used to transmit CSI-RS resources is changed, the base station can instruct the terminal to change the downlink measurement operation based on the CSI-RS resources. For example, the base station can instruct the terminal to reset the downlink measurement operation based on the CSI-RS resources. When the terminal receives the reset instruction, it can measure CSI based on the remaining CSI-RS resource(s) excluding the CSI-RS resource(s) received before the reset application time (the first slot in which the reset is applied) and report the measured CSI. At the same time, the terminal can measure and report CSI based on the CSI-RS resource(s) received in resources not later than the CSI reference resource(s). By combining the above operations, the CSI report can be calculated based on the CSI-RS resource(s) received between the reset application time (e.g., the corresponding slot) and the CSI-RS reference resource (e.g., the corresponding slot). The reset instruction can be dynamically performed by DCI. For example, the DCI can be a group-common DCI.

[0247] Furthermore, the DCI may be a DCI indicating a CSI-RS antenna port set in (method 200) or a DCI corresponding thereto. In this case, the UE may be instructed to the same CSI-RS antenna port set(s) as before by the DCI. If the same CSI-RS antenna port set(s) as before are indicated, the UE may regard this as TXRU scaling according to the second TXRU muting method occurring and may reset the CSI measurement and / or reporting operation according to the above-mentioned method. Alternatively, the reset instruction may be performed by higher layer signaling (e.g., RRC signaling, MAC CE).

[0248] In a similar manner, a terminal may be configured with multiple CSI-RS antenna port sets having the same number of antenna ports and / or antenna port configurations (e.g., N1 and N2 parameters). For example, a CSI-RS resource or CSI-RS resource set may include a first CSI-RS antenna port set and a second CSI-RS antenna port set, and the first CSI-RS antenna port set and the second CSI-RS antenna port set configuration may be identical. That is, the first CSI-RS antenna port set and the second CSI-RS antenna port set may be configured with the same number of antenna ports and / or antenna ports according to the same configuration (e.g., the same N1 and N2 values). Here, the first CSI-RS antenna port set and the second CSI-RS antenna port set may refer to multiple different CSI-RS resources. The multiple CSI-RS resources may be included in the CSI-RS resource set. Alternatively, the first CSI-RS antenna port set and the second CSI-RS antenna port set may correspond to multiple CSI reporting sub-configurations corresponding to the same CSI-RS resource. The number of CSI-RS antenna ports in the first CSI-RS antenna port set and the second CSI-RS antenna port set may be the same as the number of CSI-RS antenna ports in the CSI-RS resource.

[0249]

[0250] The UE may perform a CSI reporting operation based on the first CSI-RS antenna port set or a CSI reporting configuration (or CSI reporting sub-configuration) associated therewith during the first time period. At this time, the UE may receive an instruction from the base station to perform a CSI reporting operation based on the second CSI-RS antenna port set or a CSI reporting configuration (or CSI reporting sub-configuration) associated therewith. For example, the instruction may be performed by a DCI. When the UE receives an instruction to switch from the first CSI-RS antenna port set (or corresponding CSI reporting configuration or CSI reporting sub-configuration) to the second CSI-RS antenna port set (or corresponding CSI reporting configuration or CSI reporting sub-configuration), the UE may reset a CSI measurement or calculation operation. Alternatively, the UE may distinguish between a first CSI measurement and reporting operation for the first CSI-RS antenna port set (or corresponding CSI reporting configuration or CSI reporting sub-configuration) and a second CSI measurement and reporting operation for the second CSI-RS antenna port set (or corresponding CSI reporting configuration or CSI reporting sub-configuration). The first CSI measurement and reporting operation may correspond to first CSI-RS antenna port virtualization or beamforming, and the second CSI measurement and reporting operation may correspond to second CSI-RS antenna port virtualization or beamforming. By using the above-mentioned method, the terminal and the base station can handle beam or coverage changes caused by the second TXRU muting method.

[0251]

[0252] For example, a UE may be configured with a CSI reporting configuration including a first CSI reporting sub-configuration and a second CSI reporting sub-configuration. The first CSI reporting sub-configuration may indicate CSI measurement and reporting operations for a set of CSI-RS antenna ports transmitted by a first virtualization or a first TXRU set, and the second CSI reporting sub-configuration may indicate CSI measurement and reporting operations for a set of CSI-RS antenna ports transmitted by a second virtualization or a second TXRU set. To this end, the first CSI reporting sub-configuration and the second CSI reporting sub-configuration may be associated with a first CSI-RS resource and a second CSI-RS resource, respectively. In the above-described manner, the first CSI-RS resource and the second CSI-RS resource may be included in the same CSI-RS resource set and configured with the same number of CSI-RS antenna ports. The transmission period and periodicity of the first CSI-RS resource and the second CSI-RS resource may be the same.

[0253]

[0254] On the other hand, the set of REs to which the CSI-RS resources are mapped and the mapping pattern may differ between the first CSI-RS resource and the second CSI-RS resource. Specifically, the first CSI-RS resource and the second CSI-RS resource may be mapped to REs according to mapping patterns based on independent CSI-RS resource configurations. However, considering the above-mentioned second TXRU muting operation, it may be sufficient for the first CSI-RS resource and the second CSI-RS resource to be mapped to the same resource according to the same mapping pattern. For example, the first CSI-RS resource and the second CSI-RS resource may be configured to completely overlap, and the set of REs to which the CSI-RS resources are mapped and the RE mapping pattern may also be the same. That is, the first CSI-RS resource and the second CSI-RS resource may not be physically distinguishable, but may be distinguished only logically by being referenced by different CSI reporting sub-configurations.

[0255]

[0256] As described above, multiple different CSI resources may be counted in terms of CPU resources. Accordingly, the first CSI-RS resource and the second CSI-RS resource may occupy two CPUs. However, considering the second TXRU muting method, the UE may not simultaneously perform CSI measurement and reporting operations for the first CSI-RS resource and the second CSI-RS resource. That is, the UE may receive the first CSI-RS resource for CSI measurement in the first time interval and the second CSI-RS resource for CSI measurement in the second time interval. The first time interval and the second time interval may not overlap. Switching from the first time interval to the second time interval or from the second time interval to the first time interval may be instructed to the UE by the signaling method described above. In this case, the CSI calculation complexity of the UE in each of the first and second time intervals may correspond to the CSI measurement operation corresponding to one CSI-RS resource. That is, the actual CSI measurement operation of the terminal in the first time period can occupy one CPU, and similarly, the actual CSI measurement operation of the terminal in the second time period can occupy one CPU.

[0257]

[0258] Accordingly, in the proposed method, the first CSI-RS resource and the second CSI-RS resource can occupy one CPU. That is, the first CSI-RS resource and the second CSI-RS resource can be counted only once in terms of CPU usage, rather than being counted individually. Alternatively, only one of the first CSI-RS resource and the second CSI-RS resource can occupy the CPU. For example, the one CSI-RS resource can be determined based on a CSI-RS resource index or an associated CSI reporting sub-configuration index. The method can be applied only when the above-mentioned condition is satisfied, i.e., when the first CSI-RS resource and the second CSI-RS resource are referenced by different CSI reporting sub-configurations. The different CSI reporting sub-configurations can be sub-configurations included in the same CSI reporting configuration. Furthermore, application conditions for the method may additionally include a condition that the first CSI-RS resource and the second CSI-RS resource overlap (e.g., completely overlap), a condition that the RE mapping patterns of the first CSI-RS resource and the second CSI-RS resource are the same, etc. According to the proposed method, the CPU of the UE may be calculated reflecting the actual CSI calculation complexity of the UE, and the UE may use the remaining CPU to perform additional CSI measurement and reporting operations in a corresponding interval, for example, CSI measurement and reporting operations for a third CSI-RS resource. The third CSI-RS resource may be referenced by the first CSI reporting sub-configuration or the second CSI reporting sub-configuration. Alternatively, the third CSI-RS resource may be referenced by another CSI reporting sub-configuration other than the first CSI reporting sub-configuration and the second CSI reporting sub-configuration or another CSI reporting configuration.

[0259] Similarly, the CSI-RS antenna port constituting the first CSI-RS resource and the CSI-RS antenna port constituting the second CSI-RS resource are active CSI-RS antenna ports and may not be duplicate-counted. That is, when the first CSI-RS resource and the second CSI-RS resource are composed of R CSI-RS antenna ports, the number of corresponding active CSI-RS antenna ports may be R rather than 2*R. For example, only the CSI-RS antenna port constituting either one of the first CSI-RS resource and the second CSI-RS resource may be counted as an active CSI-RS antenna port. Similarly, the either one of the CSI-RS resources may be determined based on a CSI-RS resource index or a CSI reporting sub-configuration index associated with each other.

[0260]

[0261] On the other hand, if the UE is configured to limit the CSI measurement resource, it can measure CSI based on a single CSI-RS resource (or CSI-RS instance). In this case, even if the TXRU connected to the CSI-RS antenna port is changed, the UE's CSI measurement and reporting operations can be performed in the same manner without change. In light of this, a second TXRU muting method can be considered as a method for limiting the use of CSI measurement resources when the UE performs CSI measurement operations with limited CSI measurement resources.

[0262]

[0263] The above-described CSI-RS scaling muting method can basically be applied to periodic CSI-RS and semi-persistent CSI-RS. Furthermore, the corresponding above-described CSI reporting method can be applied to periodic CSI reporting, semi-persistent CSI reporting, and aperiodic CSI reporting procedures. In the case of aperiodic CSI-RS, a UE may be configured with multiple CSI-RS resources for a CSI-RS resource set and may be dynamically instructed to receive one of the multiple CSI-RS resources via DCI. In this case, each CSI-RS resource may correspond to the above-described CSI-RS antenna port set.

[0264]

[0265] The above-described CSI-RS scaling or muting method may be performed in the same or similar manner for ZP CSI-RS and CSI-IM. For example, in the above embodiment, the CSI-RS resource may refer to the ZP CSI-RS resource, and the CSI-RS antenna port set may refer to the ZP CSI-RS antenna port set. Using the above-described method, the UE can configure the ZP CSI-RS antenna port set(s) for the ZP CSI-RS resource and perform a rate matching operation (e.g., a PDSCH rate matching operation) on the ZP CSI-RS antenna port set(s). That is, the PDSCH may be mapped to resources other than the RE to which the ZP CSI-RS antenna port set is mapped, and transmitted to the UE. As another example, in the above embodiment, the CSI-RS resource may refer to the CSI-IM resource (or the NZP CSI-IM resource), and the CSI-RS antenna port set may refer to the CSI-IM antenna port set (or the NZP CSI-IM antenna port set). The terminal can perform interference measurement operations on the CSI-IM antenna port set.

[0266]

[0267] The operations of the methods according to the embodiments of the present invention may be embodied as a computer-readable program or code stored in a computer-readable recording medium. The computer-readable recording medium includes all types of storage devices that store information that can be read by a computer system. The computer-readable recording medium may also be distributed across computer systems connected to a network, so that the computer-readable program or code may be stored and executed in a distributed manner.

[0268] Additionally, the computer-readable recording medium may include a hardware device specially configured to store and execute program instructions, such as a ROM, RAM, flash memory, etc. The program instructions may include not only machine language code, such as that produced by a compiler, but also high-level language code that can be executed by a computer using an interpreter, etc.

[0269] Although some aspects of the invention have been described in the context of an apparatus, they may also be described in terms of a corresponding method, where the blocks or apparatus correspond to method steps or features of the method steps. Similarly, aspects described in the context of a method may also be described in terms of the corresponding blocks or items or features of the corresponding apparatus. Some or all of the method steps may be performed by (or using) a hardware device, such as, for example, a microprocessor, a programmable computer, or electronic circuitry. In some embodiments, at least one or more of the most significant method steps may be performed by such a device.

[0270] In some embodiments, a programmable logic device (e.g., a field programmable gate array) may be used to perform some or all of the functions of the methods described herein. In some embodiments, a field programmable gate array may operate in conjunction with a microprocessor to perform one of the methods described herein. In general, it is preferred that the methods be performed by some hardware device.

[0271] Although the present invention has been described above with reference to preferred embodiments, it will be understood by those skilled in the art that various modifications and variations of the present invention may be made without departing from the spirit and scope of the present invention as set forth in the following claims.

Claims

1. 1. A method of a terminal, comprising: receiving first configuration information regarding a first channel state information-reference signal (CSI-RS) resource from the base station; receiving second configuration information for a CSI reporting operation from the base station; receiving a CSI-RS through M (M is a natural number equal to or less than L) CSI-RS antenna ports that are a first subset of L (L is a natural number) CSI-RS antenna ports corresponding to the first CSI-RS resource based on the first configuration information and the second configuration information; determining a first precoding matrix indicator (PMI) based on the M CSI-RS antenna ports; and transmitting a CSI report including the first PMI to the base station; The step of determining the first PMI is performed based on a codebook having at least first and second dimensions of N1 and N2, respectively, where N1 and N2 are determined by sub-multiples of M.

2. 2. The method of claim 1, wherein the second configuration information includes configuration information regarding a plurality of CSI reporting sub-configurations, the first CSI-RS resource is referenced by a first CSI reporting sub-configuration included in the plurality of CSI reporting sub-configurations, and the first PMI is a CSI corresponding to the first CSI reporting sub-configuration.

3. 3. The method of claim 2, wherein a second CSI-RS resource is additionally referenced by the first CSI reporting sub-configuration, and the CSI corresponding to the first CSI reporting sub-configuration includes a CSI-RS resource indicator (CRI), and the CRI is an index of the first CSI-RS resource or the second CSI-RS resource.

4. The method of claim 3 , wherein the second CSI-RS resource corresponds to L CSI-RS antenna ports and belongs to the same CSI-RS resource set as the first CSI-RS.

5. The method of claim 1, wherein the M CSI-RS antenna ports are represented by a bitmap having a length L, and the bitmap is included in the second configuration information and transmitted from the base station to the terminal.

6. 2. The method of claim 1, wherein antenna port numbers of the M CSI-RS antenna ports are reassigned in ascending order with consecutive values ​​from P to (P+M-1), where P is 0 or a natural number, and the first PMI is determined based on the reassigned antenna port numbers.

7. 2. The method of claim 1, wherein M=2*N1*N2, N1 being a value based on the number of CSI-RS antenna ports corresponding to the first dimension, and N2 being a value based on the number of CSI-RS antenna ports corresponding to the second dimension.

8. 2. The method of claim 1, wherein M=2*N1*N2*Ng, N1 is a value based on the number of CSI-RS antenna ports corresponding to the first dimension, N2 is a value based on the number of CSI-RS antenna ports corresponding to the second dimension, Ng is the number of antenna panels, and the codebook is a codebook for a multi-panel consisting of Ng panels.

9. receiving the CSI-RS through M2 CSI-RS antenna ports, which are a second subset of the L CSI-RS antenna ports; and The method of claim 2 , further comprising determining a second PMI based on the M2 CSI-RS antenna ports.

10. The method of claim 9, wherein the second PMI is included in the CSI report and transmitted to the base station based on an instruction by an upper layer message.

11. 10. The method of claim 9, wherein the first CSI-RS resource is referenced by a second CSI reporting sub-configuration included in the plurality of CSI reporting sub-configurations, and the second PMI is a CSI corresponding to the second CSI reporting sub-configuration.

12. 1. A method of a base station, comprising: transmitting first configuration information regarding a first channel state information-reference signal (CSI-RS) resource to the terminal; transmitting second configuration information for CSI reporting to the terminal; transmitting a CSI-RS to the terminal through all or some of L (L is a natural number) CSI-RS antenna ports corresponding to the first CSI-RS resource; and receiving, from the terminal, a CSI report including a first precoding matrix indicator (PMI) determined based on M (M is a natural number equal to or less than L) CSI-RS antenna ports that are a first subset of the L CSI-RS antenna ports determined by the first configuration information and the second configuration information; The first PMI is performed based on a codebook having at least first and second dimensions of N1 and N2, respectively, where N1 and N2 are determined by sub-multiples of M.

13. 13. The method of claim 12, wherein the second configuration information includes configuration information regarding a plurality of CSI reporting sub-configurations, the first CSI-RS resource is referenced by a first CSI reporting sub-configuration included in the plurality of CSI reporting sub-configurations, and the first PMI is a CSI corresponding to the first CSI reporting sub-configuration.

14. 14. The method of claim 13, wherein a second CSI-RS resource is additionally referenced by the first CSI reporting sub-configuration, and the CSI corresponding to the first CSI reporting sub-configuration includes a CSI-RS resource indicator (CRI), and the CRI is an index of the first CSI-RS resource or the second CSI-RS resource.

15. The method of claim 14 , wherein the second CSI-RS resource corresponds to L CSI-RS antenna ports and belongs to the same CSI-RS resource set as the first CSI-RS.

16. The method of claim 12, wherein the M CSI-RS antenna ports are represented by a bitmap having a length L, and the bitmap is included in the second configuration information and transmitted from the base station to the terminal.

17. 13. The method of claim 12, wherein antenna port numbers of the M CSI-RS antenna ports are reassigned in ascending order with consecutive values ​​from P to (P+M-1), where P is 0 or a natural number, and the first PMI is determined based on the reassigned antenna port numbers.

18. 13. The method of claim 12, wherein M=2*N1*N2, N1 is a value based on the number of CSI-RS antenna ports corresponding to the first dimension, and N2 is a value based on the number of CSI-RS antenna ports corresponding to the second dimension.

19. 13. The method of claim 12, wherein M=2*N1*N2*Ng, N1 is a value based on the number of CSI-RS antenna ports corresponding to the first dimension, N2 is a value based on the number of CSI-RS antenna ports corresponding to the second dimension, Ng is the number of antenna panels, and the codebook is a codebook for a multi-panel consisting of Ng panels.

20. On the device, the terminal includes a processor; The processor is configured to configure the terminal to: receiving first configuration information regarding a first channel state information-reference signal (CSI-RS) resource from the base station; receiving second configuration information for a CSI reporting operation from the base station; receiving a CSI-RS through M (M is a natural number equal to or less than L) CSI-RS antenna ports that are a first subset of L (L is a natural number) CSI-RS antenna ports corresponding to the first CSI-RS resource based on the first configuration information and the second configuration information; determining a first precoding matrix indicator (PMI) based on the M CSI-RS antenna ports; and transmitting a CSI report including the first PMI to the base station; The step of determining the first PMI is performed based on a codebook having at least first and second dimensions of N1 and N2, respectively, where N1 and N2 are determined by sub-multiples of M.

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