Method and device for selecting transmission port subset on basis of channel state information report in wireless communication system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a data transmission rate higher than that of a 4G communication system such as LTE. A method performed by a terminal in a wireless communication system, according to the present disclosure, may comprise the steps of: receiving, from a base station, RRC signaling including candidate port subset search configuration information and report condition configuration information; transmitting, to the base station, information related to at least one first port subset selected on the basis of the candidate port subset search configuration information and the report condition configuration information; receiving, from the base station, information related to a port subset determined for downlink signal reception; and receiving, from the base station, the downlink signal using the determined port subset.

Description

Method and apparatus for selecting a transmitting port subset based on channel state information reporting in a wireless communication system

[0001] The present disclosure relates to a terminal and a base station in a wireless communication system. Specifically, the present disclosure relates to a method and apparatus for selecting a transmission port subset based on a channel state information report in a wireless communication system.

[0002] Looking back at the evolution of wireless communication through successive generations, technologies have been developed primarily for human-oriented services, such as voice, multimedia, and data. Following the commercialization of 5G (5th Generation) communication systems, connected devices, which have been increasing explosively, are expected to be connected to communication networks. Examples of networked objects include vehicles, robots, drones, home appliances, displays, smart sensors installed in various infrastructures, construction machinery, and factory equipment. Mobile devices are expected to evolve into various form factors, such as augmented reality glasses, virtual reality headsets, and holographic devices. In the 6G (6th Generation) era, efforts are underway to develop improved 6G communication systems to connect hundreds of billions of devices and objects to provide diverse services. For this reason, 6G communication systems are being referred to as "beyond 5G" systems.

[0003] In the 6G communication system predicted to be realized around 2030, the maximum transmission speed is tera (i.e., 1,000 gigabit) bps (bit per second), and the wireless latency is 100 microseconds (μsec). In other words, compared to the 5G communication system, the transmission speed in the 6G communication system is 50 times faster, and the wireless latency is reduced to one-tenth.

[0004] To achieve such high data transmission speeds and ultra-low latency, 6G communication systems are being considered for implementation in the terahertz (THz) band (e.g., the 95 gigahertz (GHz) to 3 terahertz (3THz) band). Due to more severe path loss and atmospheric absorption phenomena compared to the millimeter wave (mmWave) band introduced in 5G, the importance of technologies capable of guaranteeing signal reach, or coverage, is expected to increase in the terahertz band. As key technologies to ensure coverage, new waveforms, beamforming, and multi-antenna transmission technologies such as massive Multiple-Input and Multiple-Output (MIMO), Full Dimensional MIMO (FD-MIMO), array antennas, and large-scale antennas, which are superior in terms of coverage compared to RF (Radio Frequency) devices, antennas, and OFDM (Orthogonal Frequency Division Multiplexing), must be developed. In addition, new technologies such as metamaterial-based lenses and antennas, high-dimensional spatial multiplexing technology using Orbital Angular Momentum (OAM), and Reconfigurable Intelligent Surface (RIS) are being discussed to improve the coverage of terahertz band signals.

[0005] In addition, to improve frequency efficiency and system network, development is underway in 6G communication systems for full duplex technology, in which uplink and downlink simultaneously utilize the same frequency resources at the same time; network technology that integrates satellites and HAPS (High-Altitude Platform Stations); network structure innovation technology that supports mobile base stations and enables network operation optimization and automation; dynamic spectrum sharing technology through collision avoidance based on spectrum usage prediction; AI-based communication technology that utilizes AI (Artificial Intelligence) from the design stage and internalizes end-to-end AI support functions to realize system optimization; and next-generation distributed computing technology that realizes services of complexity exceeding the limits of terminal computing capabilities by utilizing ultra-high performance communication and computing resources (Mobile Edge Computing (MEC), cloud, etc.). In addition, attempts are continuing to further strengthen connectivity between devices, further optimize networks, promote the softwareization of network entities, and increase the openness of wireless communication through the design of new protocols to be used in 6G communication systems, the implementation of hardware-based security environments, the development of mechanisms for the safe utilization of data, and the development of technologies regarding privacy maintenance methods.

[0006] Due to the research and development of such 6G communication systems, it is expected that a new dimension of hyper-connected experience will become possible through the hyper-connectivity of 6G communication systems, which encompasses not only connections between objects but also connections between people and objects. Specifically, it is projected that 6G communication systems will enable the provision of services such as truly immersive extended reality (XR), high-fidelity mobile holograms, and digital replicas. Furthermore, services such as remote surgery, industrial automation, and emergency response, which are provided through 6G communication systems with enhanced security and reliability, will be applied in various fields including industry, healthcare, automotive, and home appliances.

[0007] Based on the discussion above, the present disclosure aims to provide a method and apparatus for selecting a transmitting port subset based on channel state information reporting in a wireless communication system.

[0008] The technical problems to be solved in this document are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art to which this invention belongs from the description below.

[0009] A method performed by a terminal in a wireless communication system according to one embodiment of the present disclosure may include: receiving RRC signaling from a base station, the signaling including candidate port subset search setting information for identifying at least one candidate port subset comprising some of the CSI-RS ports among a plurality of CSI (channel state information)-RS (reference signal) ports, and reporting condition setting information for selecting at least one first port subset to report information regarding the port subset to the base station based on the search for the at least one candidate port subset; transmitting information regarding the at least one first port subset selected based on the candidate port subset search setting information and the reporting condition setting information to the base station; receiving information regarding a port subset determined for receiving a downlink (DL) signal from the base station; and receiving the downlink signal using the determined port subset from the base station.

[0010] A method performed by a base station in a wireless communication system according to one embodiment of the present disclosure may include: transmitting RRC signaling to a terminal, the signaling including candidate port subset search setting information for identifying at least one candidate port subset comprising some of the CSI-RS ports among a plurality of CSI (channel state information)-RS (reference signal) ports, and reporting condition setting information for selecting at least one first port subset to report information regarding the port subset to the base station based on the search for the at least one candidate port subset; receiving from the terminal information regarding the at least one first port subset selected based on the candidate port subset search setting information and the reporting condition setting information; transmitting to the terminal information regarding a port subset determined for transmitting a downlink signal; and transmitting to the terminal the downlink signal using the determined port subset.

[0011] In a wireless communication system according to one embodiment of the present disclosure, a terminal may include a memory for storing instructions, a transceiver, and a controller connected to the memory and the transceiver. When executed by the above commands, the above controller may cause the terminal to receive RRC signaling from a base station, the signaling including candidate port subset search setting information for identifying at least one candidate port subset comprising some of the CSI-RS ports among a plurality of CSI (channel state information)-RS (reference signal) ports, and reporting condition setting information for selecting at least one first port subset to report information regarding the port subset to the base station based on the search for the at least one candidate port subset; transmit information regarding the at least one first port subset to the base station based on the candidate port subset search setting information and the reporting condition setting information; receive information regarding the port subset determined for receiving a downlink signal from the base station; and receive the downlink signal using the determined port subset from the base station.

[0012] In a wireless communication system according to one embodiment of the present disclosure, a base station may include a memory for storing instructions, a transceiver, and a controller connected to the memory and the transceiver. When executed by the above commands, the controller may cause the base station to transmit RRC signaling to the terminal, the signaling including candidate port subset search setting information for identifying at least one candidate port subset comprising some of the CSI-RS ports among a plurality of CSI (channel state information)-RS (reference signal) ports, and reporting condition setting information for selecting at least one first port subset to report information regarding the port subset to the base station based on the search for the at least one candidate port subset; receive from the terminal information regarding the at least one first port subset selected based on the candidate port subset search setting information and the reporting condition setting information; transmit information regarding the determined port subset to the terminal for downlink signal transmission; and cause the terminal to transmit the downlink signal using the determined port subset.

[0013] The present disclosure provides an apparatus and method capable of effectively providing services in a wireless communication system.

[0014] The effects obtainable in the present disclosure are not limited to those mentioned in the various embodiments, and other unmentioned effects will be clearly understood by those skilled in the art to which the present disclosure pertains from the description below.

[0015] FIG. 1 illustrates a wireless environment network in a wireless communication system according to one embodiment of the present disclosure.

[0016] FIG. 2 illustrates the functional configuration of a base station in a wireless communication system according to one embodiment of the present disclosure.

[0017] FIG. 3 illustrates the functional configuration of a terminal in a wireless communication system according to one embodiment of the present disclosure.

[0018] FIG. 4 illustrates an example of a wireless resource area in a wireless communication system according to one embodiment of the present disclosure.

[0019] FIG. 5 illustrates an example of determining some ports to be used for PDSCH based on a report of a port subset according to one embodiment of the present disclosure.

[0020] FIG. 6 illustrates a schematic diagram of a base station according to one embodiment of the present disclosure receiving a report regarding a port subset from a terminal based on configuration information.

[0021] FIG. 7 illustrates a conceptual diagram of a CSI-RS port according to one embodiment of the present disclosure.

[0022] FIG. 8 illustrates an example of a method for configuring a port subset based on a CDM group according to one embodiment of the present disclosure.

[0023] FIG. 9 illustrates an example of a method for configuring a port subset based on search interval information according to one embodiment of the present disclosure.

[0024] FIG. 10 illustrates an example of stopping the search for a candidate port subset based on candidate port subset search setting information according to one embodiment of the present disclosure.

[0025] FIG. 11 illustrates an example of a method for configuring a port subset based on a CSI-RS index according to one embodiment of the present disclosure.

[0026] FIG. 12 illustrates a flowchart of an operation for reporting a port subset based on reporting condition information according to one embodiment of the present disclosure.

[0027] FIG. 13 illustrates an example of information indicating a threshold value regarding a downlink received signal strength according to one embodiment of the present disclosure.

[0028] FIG. 14 illustrates a flowchart of an operation for updating reporting conditions according to one embodiment of the present disclosure.

[0029] FIG. 15 illustrates mapping information transmitted to a terminal to update a threshold value for a downlink received signal strength according to one embodiment of the present disclosure.

[0030] FIG. 16 illustrates mapping information of adjustment values ​​transmitted to a terminal to update a threshold value for a downlink received signal strength according to one embodiment of the present disclosure.

[0031] FIG. 17 illustrates an example for explaining a method for a base station to determine a port subset for PDSCH transmission according to one embodiment of the present disclosure.

[0032] FIG. 18 illustrates a flowchart of an operation for reselecting a port subset for PDSCH performed by a terminal and a base station according to one embodiment of the present disclosure.

[0033] FIG. 19 illustrates an example in which a base station according to one embodiment of the present disclosure instructs a terminal to search for a port subset consisting of a number of ports greater than the number of ports currently in use.

[0034] FIG. 20 illustrates an example in which a base station according to one embodiment of the present disclosure instructs a terminal to search for a port subset consisting of a number of ports equal to or less than the number of ports currently in use.

[0035] FIG. 21 is a flowchart of an operation performed by a terminal to select a transmission port subset based on RRC signaling according to one embodiment of the present disclosure.

[0036] FIG. 22 is a flowchart of an operation performed by a base station to select a transmission port subset based on RRC signaling according to one embodiment of the present disclosure.

[0037] Hereinafter, embodiments are described in detail with reference to the attached drawings so that those skilled in the art can easily implement the contents of the present disclosure. However, the disclosed embodiments may be implemented in various different forms and are not limited to the embodiments described herein. Furthermore, in order to clearly explain the present disclosure in the drawings, parts unrelated to the explanation have been omitted, and similar parts throughout the specification have been given similar reference numerals.

[0038] The terms used in this disclosure are described in their current, general form considering the functions mentioned herein; however, they may refer to various other terms depending on the intent of those skilled in the art, case law, the emergence of new technologies, etc. Accordingly, the terms used in this disclosure should not be interpreted solely by their names, but should be interpreted based on the meaning of the terms and the overall content of this disclosure.

[0039] Additionally, terms such as 'first', 'second', etc., may be used to describe various components, but the components are not limited by these terms. These terms are used for the purpose of distinguishing one component from another.

[0040] In the present disclosure, when a part is described as being "connected" to another part, this includes not only cases where they are "directly connected," but also cases where they are "electrically connected" or "operationally connected" with other elements interposed between them. Furthermore, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0041] The terms used in this disclosure are used merely to describe specific embodiments and are not intended to limit the scope of other embodiments. A singular expression may include a plural expression unless the context clearly indicates otherwise. Terms used, including technical or scientific terms, may have the same meaning as generally understood by those skilled in the art described in this disclosure. Terms used in this disclosure that are defined in a general dictionary may be interpreted as having the same or similar meaning as they have in the context of the relevant technology, and are not to be interpreted in an ideal or overly formal sense unless explicitly defined in this disclosure. In some cases, even terms defined in this disclosure are not to be interpreted to exclude the embodiments of this disclosure.

[0042] In the various embodiments of the present disclosure described below, a hardware-based approach is described as an example. However, since the various embodiments of the present disclosure include techniques using both hardware and software, the various embodiments of the present disclosure do not exclude a software-based approach. Furthermore, terms referring to network entities, terms referring to device components, etc., are illustrative for the convenience of explanation. Accordingly, the present disclosure is not limited to the terms described below, and other terms having equivalent technical meanings may be used.

[0043] Additionally, the present disclosure describes various embodiments using terms defined in some communication standards (e.g., 3GPP (3rd generation partnership project), ETSI (European Telecommunication Standards Institute)), but this is merely illustrative. Various embodiments of the present disclosure can be easily modified and applied to other communication systems.

[0044] Additionally, in this disclosure, expressions such as "greater than" or "less than" may be used to determine whether a specific condition is satisfied or fulfilled; however, this is merely for the purpose of expressing an example and does not exclude descriptions such as "greater than" or "less than." Conditions described as "greater than" may be replaced with "greater than," conditions described as "less than" may be replaced with "less than," and conditions described as "greater than and less than" may be replaced with "greater than and less than."

[0045] Terms referring to signals, channels, control information, network entities, and device components used in the following description are examples provided for the convenience of explanation. Accordingly, the present disclosure is not limited to the terms described below, and other terms having equivalent technical meanings may be used.

[0046] Phrases such as "in one embodiment" appearing in various places in this disclosure do not necessarily refer to the same embodiment.

[0047] FIG. 1 illustrates a wireless environment network in a wireless communication system according to one embodiment of the present disclosure. FIG. 1 illustrates a base station (110), a first terminal (120), and a second terminal (130) as some of the nodes using a wireless channel in the wireless communication system. FIG. 1 illustrates only one base station, but other base stations identical or similar to the base station (110) may be additionally included.

[0048] A base station (110) is a network infrastructure that provides wireless access to terminals (120, 130). The base station (110) has coverage defined as a certain geographical area based on the distance at which it can transmit signals. In addition to being a base station, the base station (110) may be referred to as an 'access point (AP)', 'eNodeB (eNB)', '5G node (5th generation node)', 'next generation nodeB (gNB)', 'wireless point', 'transmission / reception point (TRP)', or other terms having an equivalent technical meaning.

[0049] Each of the first terminal (120) and the second terminal (130) is a device used by a user and performs communication with the base station (110) via a wireless channel. In some cases, at least one of the first terminal (120) and the second terminal (130) may be operated without user involvement. That is, at least one of the first terminal (120) and the second terminal (130) is a device that performs machine type communication (MTC) and may not be carried by the user. Each of the first terminal (120) and the second terminal (130) may be referred to as 'user equipment (UE)', 'mobile station', 'subscriber station', 'remote terminal', 'wireless terminal', or 'user device', or other terms having an equivalent technical meaning, in addition to 'terminal'.

[0050] A base station (110), a first terminal (120), and a second terminal (130) can transmit and receive wireless signals in a millimeter wave (mmWave) band (e.g., 28 GHz, 30 GHz, 38 GHz, 60 GHz). At this time, to improve channel gain, the base station (110), the first terminal (120), and the second terminal (130) can perform beamforming. Here, beamforming may include transmission beamforming and reception beamforming. That is, the base station (110), the first terminal (120), and the second terminal (130) can impart directivity to the transmission signal or the reception signal. To this end, the base station (110) and the terminals (120, 130) can select serving beams through a beam search or beam management procedure. After serving beams are selected, subsequent communication can be performed through a resource that is in a quasi-co-located (QCL) relationship with the resource that transmitted the serving beams.

[0051] If large-scale characteristics of the channel transmitting the symbol on the first antenna port can be inferred from the channel transmitting the symbol on the second antenna port, the first antenna port and the second antenna port may be evaluated to have a QCL relationship. For example, the large-scale characteristics may include at least one of a delay spread, a Doppler spread, a Doppler shift, an average gain, an average delay, and a spatial receiver parameter.

[0052] FIG. 2 illustrates the functional configuration of a base station in a wireless communication system according to one embodiment of the present disclosure. The configuration exemplified in FIG. 2 can be understood as the configuration of a base station (110). Terms such as '... unit', '... unit' used below refer to a unit that processes at least one function or operation, and this can be implemented in hardware or software, or a combination of hardware and software.

[0053] Referring to FIG. 2, the base station may include a wireless communication unit (210), a backhaul communication unit (220), a storage unit (230), and a control unit (240).

[0054] The wireless communication unit (210) performs functions for transmitting and receiving signals through a wireless channel. For example, the wireless communication unit (210) performs a conversion function between a baseband signal and a bit sequence according to the physical layer specifications of the system. For example, when transmitting data, the wireless communication unit (210) generates complex symbols by encoding and modulating the transmitted bit sequence. Also, when receiving data, the wireless communication unit (210) restores the received bit sequence by demodulating and decoding the baseband signal.

[0055] Additionally, the wireless communication unit (210) upconverts a baseband signal into an RF (radio frequency) band signal and transmits it through an antenna, and downconverts the RF band signal received through the antenna into a baseband signal. To this end, the wireless communication unit (210) may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC (digital to analog converter), an ADC (analog to digital converter), etc. Additionally, the wireless communication unit (210) may include a plurality of transmission and reception paths. Furthermore, the wireless communication unit (210) may include at least one antenna array composed of a plurality of antenna elements.

[0056] In terms of hardware, the wireless communication unit (210) may be composed of a digital unit and an analog unit, and the analog unit may be composed of a plurality of sub-units depending on operating power, operating frequency, etc. The digital unit may be implemented as at least one processor (e.g., a digital signal processor (DSP)).

[0057] The wireless communication unit (210) transmits and receives signals as described above. Accordingly, all or part of the wireless communication unit (210) may be referred to as a 'transmitter', a 'receiver', or a 'transceiver'. Furthermore, in the following description, transmission and reception performed through a wireless channel are used to mean that processing as described above is performed by the wireless communication unit (210).

[0058] The backhaul communication unit (220) provides an interface for communicating with other nodes within the network. That is, the backhaul communication unit (220) converts a bit sequence transmitted from a base station to another node, e.g., another connection node, another base station, an upper node, a core network, etc., into a physical signal, and converts a physical signal received from another node into a bit sequence.

[0059] The storage unit (230) stores data such as basic programs, application programs, and configuration information for the operation of the base station. The storage unit (230) may be composed of volatile memory, non-volatile memory, or a combination of volatile memory and non-volatile memory. Additionally, the storage unit (230) provides the stored data upon request from the control unit (240).

[0060] A control unit (240) (e.g., a controller) controls the overall operations of the base station. For example, the control unit (240) transmits and receives signals through the wireless communication unit (210) or through the backhaul communication unit (220). Additionally, the control unit (240) writes and reads data to and from the storage unit (230). Furthermore, the control unit (240) can perform the functions of a protocol stack required by the communication standard. According to other implementation examples, the protocol stack may be included in the wireless communication unit (210). To this end, the control unit (240) may include at least one processor.

[0061] According to various embodiments, the control unit (240) can control the base station to perform operations according to various embodiments described below.

[0062] FIG. 3 illustrates the functional configuration of a terminal in a wireless communication system according to one embodiment of the present disclosure. The configuration exemplified in FIG. 3 can be understood as the configuration of a terminal (120, 130). Terms such as '...part', '...unit' used below refer to a unit that processes at least one function or operation, and this may be implemented in hardware or software, or a combination of hardware and software.

[0063] Referring to FIG. 3, the terminal includes a communication unit (310), a storage unit (320), and a control unit (330).

[0064] The communication unit (310) performs functions for transmitting and receiving signals through a wireless channel. For example, the communication unit (310) performs a conversion function between a baseband signal and a bit sequence according to the physical layer specifications of the system. For example, when transmitting data, the communication unit (310) generates complex symbols by encoding and modulating the transmitted bit sequence. Also, when receiving data, the communication unit (310) restores the received bit sequence by demodulating and decoding the baseband signal. Additionally, the communication unit (310) upconverts the baseband signal into an RF band signal and transmits it through an antenna, and downconverts the RF band signal received through the antenna into a baseband signal. For example, the communication unit (310) may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc.

[0065] Additionally, the communication unit (310) may include a plurality of transmission and reception paths. Furthermore, the communication unit (310) may include at least one antenna array composed of a plurality of antenna elements. In terms of hardware, the communication unit (310) may be composed of a digital circuit and an analog circuit (e.g., a radio frequency integrated circuit (RFIC)). Here, the digital circuit and the analog circuit may be implemented as a single package. Additionally, the communication unit (310) may include a plurality of RF chains. Furthermore, the communication unit (310) may perform beamforming.

[0066] The communication unit (310) transmits and receives signals as described above. Accordingly, all or part of the communication unit (310) may be referred to as a 'transmitter', a 'receiver', or a 'transmitter / receiver'. Additionally, in the following description, transmission and reception performed via a wireless channel are used to mean that processing as described above is performed by the communication unit (310).

[0067] The storage unit (320) stores data such as basic programs, application programs, and setting information for the operation of the terminal. The storage unit (320) may be composed of volatile memory, non-volatile memory, or a combination of volatile memory and non-volatile memory. Additionally, the storage unit (320) provides the stored data upon the request of the control unit (330).

[0068] The control unit (330) (e.g., controller) controls the overall operations of the terminal. For example, the control unit (330) transmits and receives signals through the communication unit (310). Additionally, the control unit (330) writes and reads data to and from the storage unit (320). Furthermore, the control unit (330) can perform the functions of the protocol stack required by the communication standard. To this end, the control unit (330) may include at least one processor or microprocessor, or be part of a processor. Additionally, part of the communication unit (310) and the control unit (330) may be referred to as a communication processor (CP).

[0069] According to various embodiments, the control unit (330) can control the terminal to perform operations according to various embodiments described below.

[0070] FIG. 4 illustrates an example of a radio resource domain in a wireless communication system according to one embodiment of the present disclosure. In various embodiments of the present disclosure, the radio resource domain may include a structure in a time-frequency domain. According to one embodiment, the wireless communication system may include an NR communication system.

[0071] Referring to FIG. 4, in the wireless resource domain, the horizontal axis represents the time domain and the vertical axis represents the frequency domain. The length of the wireless frame (404) is 10 ms. The wireless frame (404) may be a time domain segment consisting of 10 subframes. The length of the subframe (403) is 1 ms. The unit of composition in the time domain may be an OFDM (orthogonal frequency division multiplexing) and / or DFT-s-OFDM (DFT (discrete Fourier transform)-spread-OFDM) symbol, and N-symb OFDM and / or DFT-s-OFDM symbols (401) may be combined to form a single slot (402). In various embodiments, the OFDM symbol may include a symbol for transmitting and receiving a signal using the OFDM multiplexing method, and the DFT-s-OFDM symbol may include a symbol for transmitting and receiving a signal using the DFT-s-OFDM or SC-FDMA (single carrier frequency division multiple access) multiplexing method. The minimum transmission unit in the frequency domain is a subcarrier, and the carrier bandwidth constituting the resource grid can be composed of a total of NscBW subcarriers (405). Additionally, for convenience of explanation, an embodiment regarding downlink signal transmission and reception is described in this disclosure, but this is also applicable to an embodiment regarding uplink signal transmission and reception.

[0072] In some embodiments, the number of slots (402) constituting one subframe (403) and the length of the slots (402) may vary depending on the subcarrier spacing. This subcarrier spacing is a numerology ( It can be referred to as ). That is, the subcarrier spacing, the number of slots included in the subframe, the length of the slot, and the length of the subframe can be configured variably. For example, in an NR communication system, when the subcarrier spacing (SCS) is 15 kHz, one slot (402) constitutes one subframe (403), and the lengths of the slot (402) and the subframe (403) may each be 1 ms. Also, for example, when the subcarrier spacing is 30 kHz, two slots may constitute one subframe (403). In this case, the length of the slot is 0.5 ms and the length of the subframe is 1 ms.

[0073] In some embodiments, the subcarrier spacing, the number of slots included in a subframe, the slot length, and the subframe length may be applied variably depending on the communication system. For example, in the case of an LTE (long-term evolution) system, the subcarrier spacing is 15 kHz, and two slots constitute one subframe, wherein the slot length may be 0.5 ms and the subframe length may be 1 ms. As another example, in the case of an NR system, the subcarrier spacing ( ) can be one of 15kHz, 30kHz, 60kHz, 120kHz, or 240kHz, and the subcarrier interval ( Depending on ), the number of slots included in one subframe can be 1, 2, 4, 8, or 16.

[0074] In the time-frequency domain, the basic unit of a resource may be a resource element (RE) (406), and the resource element (406) may be represented by an OFDM symbol index and a subcarrier index. A resource block may include multiple resource elements. In an NR system, a resource block (RB) (or physical resource block (PRB)) (407) may be defined as N_SCRB consecutive subcarriers in the frequency domain. The number of subcarriers N_SCRB may be 12. The frequency domain may include common resource blocks (CRBs). A physical resource block (PRB) may be defined in the bandwidth part (BWP) in the frequency domain. The CRB and PRB numbers may be determined differently depending on the subcarrier interval. In an LTE system, an RB may be defined as Nsymb consecutive OFDM symbols in the time domain and N_SCRB consecutive subcarriers in the frequency domain.

[0075] In NR and / or LTE systems, scheduling information for downlink data or uplink data may be transmitted from a base station (110) to a terminal (120) via downlink control information (DCI). In various embodiments, DCI may be defined according to various formats, each format may indicate whether the DCI includes scheduling information for uplink data (e.g., UL grant), scheduling information for downlink data (DL resource allocation), whether it is a compact DCI with a small size of control information, whether it is a fall-back DCI, whether spatial multiplexing using multiple antennas is applied, and / or whether it is a DCI for power control. For example, NR DCI format 1_0 or NR DCI format 1_1 may include scheduling for downlink data. Additionally, for example, NR DCI format 0_0 or NR DCI format 0_1 ​​may include scheduling for uplink data.

[0076] As described above, FIG. 4 illustrates an example of a downlink and uplink slot structure in a wireless communication system. In particular, FIG. 4 illustrates the structure of a resource grid in a 3GPP NR system. Referring to FIG. 4, a slot may include multiple orthogonal frequency division multiplexing (OFDM) symbols in the time domain and multiple resource blocks (RBs) in the frequency domain. A signal may consist of part or all of the resource grid. Additionally, the number of OFDM symbols generally included in a single slot may vary depending on the length of the cyclic prefix (CP). In FIG. 4, for convenience of explanation, a case in which a single slot consists of 14 OFDM symbols is illustrated, but the configuration of symbols is not specified for the signal referred to in this disclosure. In addition, the modulation method of the generated signal is not limited to a specific value of QAM (Quadrature Amplitude Modulation) and can follow modulation methods of various communication standards such as BPSK (Binary phase-shift keying) and QPSK (Quadrature Phase Shift Keying).

[0077] Various embodiments of the present disclosure are described based on LTE communication systems or NR communication systems, but the contents of the present disclosure are not limited thereto and can be applied to various wireless communication systems for transmitting downlink or uplink control information. Furthermore, it is understood that the contents of the present disclosure can be applied to unlicensed bands in addition to licensed bands as needed.

[0078] In the present disclosure, the higher layer signaling or higher signal may be a signal transmission method transmitted from a base station (110) to a terminal (120) using a physical layer downlink data channel, or from a terminal (120) to a base station (110) using a physical layer uplink data channel. According to one embodiment, the higher layer signaling may include at least one of radio resource control (RRC) signaling, signaling according to an F1 interface between a centralized unit (CU) and a distributed unit (DU), or a signal transmission method transmitted through a media access control (MAC) control element (MAC CE). Additionally, according to one embodiment, the higher layer signaling or higher signal may include system information, such as a system information block (SIB), that is commonly transmitted to a plurality of terminals (120).

[0079] In a 5G wireless communication system, a synchronization signal block (SSB) (also referred to as an SS block, SS / PBCH block, etc.) may be transmitted for initial access, and the synchronization signal block may consist of a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a physical broadcast channel (PBCH). In the initial access phase, when a terminal first connects to the system, the terminal can obtain downlink time and frequency domain synchronization from the synchronization signal and obtain a cell identity (cell ID) through a cell search procedure. The synchronization signal may include the PSS and the SSS. The terminal can receive a PBCH containing a master information block (MIB) from the base station to obtain system information related to transmission and reception, such as system bandwidth or related control information, as well as basic parameter values. Based on the received PBCH, the terminal can obtain a system information block (SIB) by performing decoding on the PDCCH (physical downlink control channel) and PDSCH (physical downlink shared channel). Subsequently, the terminal can exchange identity with the base station through a random access step and initially connect to the network after going through steps such as registration and authentication.

[0080] As described above, one slot can contain 14 symbols, and in a 5G communication system, the uplink-downlink configuration of symbols and / or slots can be set in three stages.

[0081] As a first method, the uplink-downlink of symbols and / or slots can be established semi-statically at the symbol level through cell-specific configuration information derived from system information. More specifically, the cell-specific uplink-downlink configuration information derived from system information may include uplink-downlink pattern information and reference subcarrier information. The uplink-downlink pattern information may indicate the pattern periodicity, the number of consecutive downlink slots and the number of symbols in the next slot from the start of each pattern, the number of consecutive uplink slots and the number of symbols in the next slot from the end of the pattern. Slots and symbols not designated as uplink or downlink may be determined as flexible slots / symbols.

[0082] In a second method, through user-specific configuration information via dedicated upper-level signaling, a flexible slot or a slot containing a flexible symbol can be indicated by the number of consecutive downlink symbols from the start symbol of the slot and the number of consecutive uplink symbols from the end of the slot, respectively, or can be indicated by the entire slot downlink or the entire slot uplink.

[0083] As a third method, to dynamically change the downlink and uplink signal transmission intervals, symbols designated as flexible symbols in each slot (e.g., symbols not designated as downlink and uplink) can be indicated as downlink symbols, uplink symbols, or flexible symbols through a Slot Format Indicator (SFI) included in the downlink control channel. The Slot Format Indicator can select an index from a pre-configured table (e.g., 3GPP TS 38.213 Table 11.1.1-1) for the uplink-downlink configuration of 14 symbols within a single slot.

[0084] FIG. 5 illustrates an example of determining some ports to be used for PDSCH based on a report of a port subset according to one embodiment of the present disclosure.

[0085] In 6G (6th generation) wireless communication systems, to improve the performance of MU-MIMO (multiple user-multiple input multiple output), an extreme massive MIMO (E-MIMO) system is intended to be provided that uses a greater number of ports than the number of base station ports in LTE and 5G. For example, in 6G wireless communication systems, a technology is intended to be provided to perform PDSCH transmission using 256 ports. When the number of ports used by a base station increases, the amount of power required for beamforming may also increase. Therefore, to efficiently manage power, the base station may perform signal transmission using only some of the total ports of the base station.

[0086] Referring to FIG. 5, the base station can perform PDSCH transmission using some of the CSI-RS ports among the total CSI (channel state information)-RS (reference signal) ports (510). For example, some of the CSI-RS ports (520) among the total CSI-RS ports (510) may not be used, and PDSCH transmission may be performed using only the remaining CSI-RS ports (530). That is, the base station can manage the power consumption of the base station by adjusting the number of ports used for PDSCH transmission according to the channel state.

[0087] Meanwhile, if a base station performs downlink (DL) transmission using only some of its total ports, the power consumption of the base station may be reduced, but it may fail to satisfy the terminal's quality of service (QoS) requirements. For example, if at least 12 ports need to be used for downlink transmission to satisfy the terminal's QoS requirements, a problem may arise where the terminal's QoS requirements cannot be satisfied because the base station performs downlink transmission using only 4 of its total ports.

[0088] The base station may instruct the terminal to perform CSI reporting on multiple candidate port subsets containing different numbers of CSI-RS ports in order to identify the minimum number of ports required to satisfy the terminal's QoS requirements. However, as the total number of available ports increases, the number of possible candidate port subsets also increases. This can lead to a problem where not only does the complexity of the CSI calculations performed by the terminal to search for the optimal port subset increase, but the overhead for the terminal's CSI reporting also increases.

[0089] The present disclosure aims to provide a method and apparatus for selecting a transmission port subset based on a channel state information (CSI) report in a wireless communication system.

[0090] In addition, the present disclosure can provide a method and apparatus that minimizes the increase in overhead for CSI calculation complexity and CSI reporting of a terminal and satisfies the QoS requirements of a terminal by adaptively determining the number of ports used for PDSCH transmission according to the transmission environment in a wireless communication system.

[0091] In the present disclosure, 'port subset' and 'port subset index' corresponding to the port subset may be used interchangeably.

[0092] In the present disclosure, the operation of 'searching' for a port subset may mean the operation of identifying a port subset that satisfies a reporting condition among candidate port subsets.

[0093] FIG. 6 illustrates a schematic diagram of a base station according to one embodiment of the present disclosure receiving a report regarding a port subset from a terminal based on configuration information.

[0094] Referring to FIG. 6, the base station may transmit configuration information to the terminal for reporting information regarding a port subset. For example, referring to the configuration information (601) of Example 601 and the configuration information (620) of Example 602 in FIG. 6, the configuration information for reporting regarding a port subset may include candidate port subset search configuration information and report condition configuration information.

[0095] According to one embodiment, the candidate port subset search configuration information may include configuration information for a terminal to identify at least one candidate port subset. A 'port subset' may include some CSI-RS ports among a plurality of CSI (channel state information)-RS (reference signal) ports. Additionally, a 'candidate port subset' may refer to a candidate port subset for which the terminal will perform channel estimation to report to a base station. The candidate port subset search configuration information may be information that instructs the terminal to identify only some of the CSI-RS port subsets among the combinable CSI-RS port subsets as candidate port subsets for CSI reporting. That is, the candidate port subset search configuration information may be understood as configuration information for the terminal to search for a candidate port subset among the combinable CSI-RS port subsets.

[0096] According to one embodiment, the candidate port subset search setting information may include information indicating a method for configuring at least one candidate port subset by selecting some CSI-RS ports to constitute at least one candidate port subset. Hereinafter, in the present disclosure, the information indicating a method for configuring at least one candidate port subset by selecting some CSI-RS ports to constitute at least one candidate port subset may be referred to as 'search mode information'. The search mode information may include information indicating any one of the methods for configuring a port subset for CSI operations of the terminal. The information indicating the search mode may be expressed as search mode = CDM (code division multiplexing) group, search mode = step size, search mode = CSI-RS index, but the method for configuring the port subset and the term indicating the method for configuring the port subset are not limited thereto. A method for the terminal to configure a port subset based on the information indicating each of the search modes described above will be explained in detail with reference to FIGS. 8 to 11.

[0097] According to one embodiment, the candidate port subset search setting information may include information regarding the number of CSI-RS ports in a subset constituting at least one candidate port subset. For example, the information regarding the number of CSI-RS ports in a subset constituting at least one candidate port subset may include information regarding the maximum and minimum number of CSI-RS ports in a subset constituting at least one candidate port subset. Hereinafter, in the present disclosure, the maximum number of CSI-RS ports in a subset constituting at least one candidate port subset is P maxIt can be expressed as. Also, the minimum number of some CSI-RS ports constituting at least one candidate port subset is P min It can be expressed as. For example, P max = 32 and P min In the case where = 16, the terminal can identify a port subset containing 16 or more ports and 32 or fewer ports as a candidate port subset.

[0098] According to one embodiment, the candidate port subset search setting information may include information regarding a condition for stopping the search of at least one candidate port subset. For example, the information regarding a condition for stopping the search of at least one candidate port subset may include information regarding the maximum number of port subsets that the terminal reports to the base station. The maximum number of port subsets that the terminal reports to the base station is Q max It can be expressed as. For example, Q max When = 1, the terminal may stop determining whether the remaining candidate port subsets satisfy the reporting conditions by identifying one port subset among the candidate port subsets that satisfies the set reporting conditions. Additionally, information regarding the conditions for stopping the search for at least one candidate port subset may include information regarding the minimum number of port subsets that the terminal reports to the base station.

[0099] According to one embodiment, the candidate port subset search setting information may include information regarding the order of searching at least one candidate port subset. For example, the information regarding the order of searching at least one candidate port subset may include information instructing to determine whether at least one candidate port subset satisfies a set reporting condition sequentially according to the number of ports included in at least one candidate port subset. Hereinafter, in the present disclosure, the information instructing to determine whether at least one candidate port subset satisfies a set reporting condition sequentially according to the number of ports included in at least one candidate port subset may be referred to as search direction information. Hereinafter, 'search direction' refers to P max A search method for determining whether a reporting condition is satisfied, set in descending order starting from a port subset containing CSI-RS ports, or P min It may refer to a search method for determining whether a reporting condition is satisfied, set in ascending order starting from a port subset containing CSI-RS ports. Information regarding the order of constituting at least one candidate port subset is, depending on the number of ports included in at least one candidate port subset, the maximum number of at least one port subsets (Q max It may include information instructing to determine whether a condition is met by sequentially reporting only until ) is satisfied. For example, if Search direction = 0, the terminal, the number of CSI-RS ports is P min Reporting condition determinations for the in port subsets can be performed first. For example, when Search direction = 1, the terminal has P number of CSI-RS ports. max First, perform reporting condition evaluation for the port subsets corresponding to , and Q max If satisfied, the condition evaluation of the port subset can be stopped.

[0100] According to one embodiment, the reporting condition setting information may include information for selecting at least one port subset to report information regarding the port subset to the base station based on the search for at least one candidate port subset. The reporting condition setting information may mean setting information regarding criteria for selecting at least one port subset to be reported by the terminal to the base station. For example, the reporting condition setting information may include information indicating a threshold value for the state of a downlink (DL) received signal or a channel state. For example, the reporting condition setting information may include information indicating a threshold value expressed as at least one of RSRP (reference signal received power), CQI (channel quality indicator), or SINR (signal to interference noise ratio). Of course, the method for expressing the threshold value that may be included in the reporting condition setting information is not limited thereto. For example, the reporting condition setting information may include information indicating a threshold value expressed as RSRQ (reference signal received quality). The reporting condition information may include at least one of UE-specific setting information or cell-specific setting information. For example, the reporting condition information may include both UE-specific configuration information and cell-specific configuration information. The terminal can determine whether the channel measurement value for a candidate port subset is greater than or equal to a threshold value included in the reporting condition information. If the channel measurement value for a candidate port subset is greater than or equal to the threshold value included in the reporting condition information, the terminal can determine that candidate port subset as a reportable port subset.

[0101] Additionally, for the sake of convenience of explanation, the candidate port subset discovery configuration information and the reporting condition configuration information have been listed separately; however, the candidate port subset discovery configuration information and the reporting condition configuration information may be included within a single configuration information or within a single message (e.g., a single RRC message, or a single DCI, MAC message, etc.), and information described as being included within the candidate port subset discovery configuration information may be included within the reporting condition configuration information, and information described as being included within the reporting condition configuration information may be included within the candidate port subset discovery configuration information.

[0102] According to one embodiment, the candidate port subset search configuration information may include information indicating whether the candidate port subset search configuration information is terminal-specific (UE-specific) configuration information or cell-specific configuration information. The candidate port subset search configuration information may include UE-specific or cell-specific configuration information. Accordingly, the base station may transmit to the terminal information indicating whether the candidate port subset search configuration information is of the type UE-specific or cell-specific. Hereinafter, in the present disclosure, the information indicating whether the candidate port subset search configuration information is terminal-specific configuration information or cell-specific configuration information may be referred to as 'search type information'.

[0103] Referring to Example 601 in FIG. 6, when the search type is UE-specific, the candidate port subset search setting information (610) may include information instructing each terminal to report a port subset that satisfies a reporting condition among the candidate port subsets identified by the terminal. For example, a first terminal (e.g., UE 1 in FIG. 6) may report to a base station information regarding a port subset (613) that satisfies a reporting condition among the candidate port subsets identified by the first terminal. Based on the information regarding the port subset (613) received from the first terminal, the base station may determine a resource for performing SU-MIMO (single user MIMO) transmission to the first terminal. For example, a second terminal (e.g., UE 2 in FIG. 6) may report to a base station information regarding a port subset (614) that satisfies a reporting condition among the candidate port subsets identified by the second terminal. The base station can determine the resources (612) for performing SU-MIMO transmission to the first terminal based on information regarding the port subset (614) received from the second terminal.

[0104] Referring to Example 602 in FIG. 6, when the search type is Cell-specific, the candidate port subset search setting information (610) may instruct the terminals to report a port subset that satisfies the reporting conditions among the common port subsets that the base station has commonly set for the terminals. For example, the first terminal (e.g., UE 1 in FIG. 6) may report to the base station information regarding at least one port subset (623) that satisfies the reporting conditions among the common port subsets set by the base station. For example, the second terminal (e.g., UE 2 in FIG. 6) may report to the base station information regarding at least one port subset (624) that satisfies the reporting conditions among the common port subsets set by the base station. The base station may determine resources (621) for performing MU-MIMO (multi-user MIMO) transmission to the first terminal and the second terminal based on information regarding at least one port subset (623) received from the first terminal and information regarding at least one port subset (624) received from the second terminal. Table 1 is an example of information included in RRC signaling transmitted by the base station to the terminal when the search type is cell-specific.

[0105]

[0106] Referring to Table 1, when the search type is cell-specific, the candidate port subset search configuration information transmitted via RRC signaling may include information (portSubsetIndicator) indicating common port subsets that are commonly configured for multiple terminals. The terminal may determine the common port subsets as candidate port subsets. The terminal may determine whether reporting conditions are satisfied for the common port subsets determined as candidate port subsets. The terminal may report information regarding CSI-RS port subsets satisfying reporting conditions to the base station. When the search type is cell-specific, unlike when the search type is UE-specific, P min or P max Information may be omitted within the candidate port subset search configuration information. Additionally, when the search type is cell-specific, unlike when the search type is UE-specific, the base station is configured to report information to the terminal regarding all port subsets among the common port subsets that satisfy the reporting conditions (Q max = All) can be done. As a result, the base station can determine a port subset that can commonly satisfy the QoS requirements of multiple terminals, rather than a port subset preferred by a specific terminal.

[0107] According to one embodiment, a base station may transmit candidate port subset configuration information to a terminal using at least one of radio resource control (RRC) signaling, a media access control element (MAC-CE), or downlink control information (DCI). For example, the base station may transmit information such as that shown in Tables 2 and 3 to the terminal. Of course, the terms representing candidate port subset configuration information are not limited to the examples listed in Tables 2 and 3, and other terms having the same or similar meaning may be used.

[0108]

[0109]

[0110] Tables 2 and 3 can be understood as examples of a base station transmitting to a terminal candidate port subset configuration information additionally included within the general CSI report configuration and CSI report subconfiguration information. For example, the base station transmits to the terminal the minimum and maximum number of CSI-RS ports (P min , P max ), number of maximum reportable port subsets (Q maxInformation regarding the search direction, etc., can be transmitted via RRC or MAC-CE / DCI signaling. For example, referring to Table 2, the base station can transmit candidate port subset configuration information and report condition configuration information to the terminal via RRC signaling, including them within the csi-ReportSubConfigRestriction information. For example, referring to Table 3, the base station can transmit candidate port subset configuration information and report condition configuration information to the terminal via MAC-CE or DCI signaling, including them within the csi-ReportSubConfigRestriction information.

[0111] According to one embodiment, a base station may transmit reporting condition setting information to a terminal using at least one of RRC signaling, MAC-CE, or DCI. For example, the base station may transmit information such as that in Tables 4 and 5 to the terminal. Of course, the terms representing reporting condition setting information are not limited to the examples listed in Tables 4 and 5, and other terms having the same or similar meaning may be used.

[0112]

[0113]

[0114] Tables 4 and 5 can be understood as examples of a base station transmitting to a terminal additionally including report condition setting information within general CSI report configuration and CSI report subconfiguration information. For example, referring to Table 4, the base station may transmit to the terminal via RRC signaling information regarding the report condition criteria and threshold values ​​within the csi-ReportCondition. For example, referring to Table 5, the base station may transmit to the terminal via MAC-CE and DCI information including the report condition criteria and threshold values ​​within the csi-ReportCondition.

[0115] FIG. 7 illustrates a conceptual diagram of a CSI-RS port according to one embodiment of the present disclosure.

[0116] A base station according to one embodiment can transmit CSI-RS to a terminal using a plurality of CSI-RS ports. For convenience of explanation, the plurality of CSI-RS ports (700) may be represented as a plurality of ports arranged to have a first number (N1) in a first direction (710) and a second number (N2) in a second direction (720). In the present disclosure, the first direction (710) may be referred to as a horizontal direction or an x-axis direction, and the second direction (720) may be referred to as a vertical direction or a y-axis direction.

[0117] FIG. 7 may include a plurality of CSI-RS ports (700). According to one embodiment, the plurality of CSI-RS ports may include a total of 32 ports composed of a plurality of codes; however, this is for convenience of explaining the operation to be described later and does not mean that the total number or arrangement of ports of the base station is limited as shown in FIG. 7. For example, the total number of ports may be 16, which is fewer than the 32 ports shown in FIG. 7. For example, the total number of ports may be 256, which is more than the 32 ports shown in FIG. 7.

[0118] Hereinafter, with reference to FIGS. 8 to 11, a method for a terminal to identify a candidate port subset based on candidate port subset search configuration information will be described.

[0119] FIG. 8 illustrates an example of a method for configuring a candidate port subset based on a code division multiplexing (CDM) group according to one embodiment of the present disclosure. The plurality of ports (800) of FIG. 8 may correspond to the plurality of CSI-RS ports (700) of FIG. 7.

[0120] Referring to FIG. 8, when the candidate port subset search configuration information received from the base station is as shown in Table 6 below, the terminal can configure a candidate port subset based on CDM groups. Herein, CDM may refer to at least two groups distinguished using at least two orthogonal codes that are mutually orthogonal. Below, an operation for searching for a candidate port subset will be described in the case where the terminal receives candidate port subset search configuration information as shown in Table 6 from the base station.

[0121]

[0122] A terminal according to one embodiment, when candidate port subset search configuration information received from a base station is as shown in Table 6, has a minimum number (P) of CSI-RS ports constituting a candidate port subset. min ) is 16, and the maximum number of CSI-RS ports constituting the candidate port subset (P max Since ) is 32, the terminal can identify candidate port subsets for determining reporting conditions, ranging from a port subset with 16 CSI-RS ports to a port subset with 32 CSI-RS ports. For example, also in Table 6, since the search direction is set to 0, the terminal can perform a search starting from a port subset with 16 CSI-RS ports.

[0123] Referring to FIG. 8, a plurality of ports may be divided into a plurality of CDM group units. For example, a plurality of ports (800) comprising a total of 32 ports may be divided into 4 CDM group units corresponding to each of the 8 ports. For example, a first CDM group (CDM group 0) (820) may include 8 CSI-RS ports classified by a first code, which are depicted as being located in the first area (811) of FIG. 8 among the plurality of ports (800). For example, a second CDM group (CDM group 1) (821) may include 8 CSI-RS ports classified by a first code, which are located in the second area (812) among the plurality of ports (800). For example, the third CDM group (CDM group 2) (822) may include eight CSI-RS ports that are placed in the first area (811) among the plurality of ports (800) and distinguished by the second code. For example, the fourth CDM group (CDM group 3) (823) may include eight CSI-RS ports that are placed in the second area (812) among the plurality of ports (800) and distinguished by the second code. The plurality of CDM groups (820, 821, 822, 823) may each correspond to a plurality of frequency areas (830, 831, 832, 833) in the frequency domain allocation area (801).

[0124] A terminal according to one embodiment may configure a candidate port subset comprising a specific number of CSI-RS ports based on a CDM group. For example, referring to FIG. 8, the terminal may configure a total of 16 ports corresponding to a first CDM group (820) or a third CDM group (822) as one candidate port subset (841). For example, the terminal may configure a total of 16 ports corresponding to a second CDM group (821) or a fourth CDM group (823) as another candidate port subset. Of course, the method of configuring the candidate port subset by the terminal described with reference to FIG. 8 is not limited to the examples described above.

[0125] According to one embodiment, the terminal can determine reporting conditions for candidate port subsets configured using CDM group units. For example, the terminal can determine that a candidate port subset (841) composed of a total of 16 ports corresponding to the first CDM group (820) or the third CDM group (822) does not satisfy the set reporting conditions. For example, the terminal can determine that a candidate port subset (842) composed of a total of 16 ports corresponding to the second CDM group (821) or the fourth CDM group (823) satisfies the set reporting conditions.

[0126] According to one embodiment, the terminal has a maximum number of port subsets (Q) that the terminal reports to the base station. max Based on information regarding ), at least one candidate port subset to report to the base station among the candidate port subsets can be determined. For example, referring to FIG. 8, as shown in Table 6, the maximum number of port subsets that the terminal reports to the base station (Q maxWhen ) is set to 1, information regarding one of the candidate port subsets can be reported to the base station. For example, the terminal does not report information regarding the candidate port subset (841) to the base station as it determines that the candidate port subset (841) consisting of a total of 16 ports corresponding to the first CDM group (820) or the third CDM group (822) does not satisfy the set reporting conditions, and can report information regarding the candidate port subset (842) to the base station as it determines that the candidate port subset (842) consisting of a total of 16 ports corresponding to the second CDM group (821) or the fourth CDM group (823) satisfies the set reporting conditions. Unlike the example in FIG. 8, if both the candidate port subset (841) corresponding to the first CDM group (820) or the third CDM group (822) and the candidate port subset (842) corresponding to the second CDM group (821) or the fourth CDM group (823) satisfy the reporting conditions, the terminal may select one of the two candidate port subsets that has a better channel estimation result and report information regarding the selected port subset to the base station.

[0127] Unlike the example in FIG. 8, if there is no port subset satisfying the reporting condition among the candidate port subsets consisting of 16 ports, the terminal can sequentially determine whether the reporting condition is satisfied for candidate port subsets containing a number greater than 16 ports. The terminal [reports] the maximum number of port subsets (Q) to be reported to the base station. max The process described above can be repeated until a subset of candidate ports satisfying the reporting conditions of ) is found.

[0128] FIG. 9 illustrates an example of a method for configuring a port subset based on search interval information according to one embodiment of the present disclosure. Table 7 below is an example of candidate port subset search configuration information associated with the example of FIG. 9.

[0129]

[0130] In one embodiment, when a terminal receives candidate port subset search configuration information such as Search type= UE-specific, search mode= Step size-based, search direction= 0, Pmax= 16, Pmin= 8, Qmax= 1 of Table 7, the terminal, the number of CSI-RS ports is the minimum number (P min Starting from port subsets where = 8), the number of CSI-RS ports is the maximum number (P max Port subsets up to = 16) can be identified as candidate port subsets. Based on search direction = 0, which indicates ascending order, the terminal has a minimum number of CSI-RS ports (P min Reporting conditions can be determined starting from the candidate port subsets where = 8). The terminal is instructed to the base station that the maximum number of port subsets to report information regarding the port subsets is 1 (Q max Based on = 1), information regarding up to 1 port subset among the candidate port subsets that satisfies the reporting condition can be reported to the base station.

[0131] According to one embodiment, when the search mode is indicated as step size-based as in Table 7, the terminal can configure a candidate port subset based on reference CSI-RS index information and step size information. For example, the terminal can configure candidate port subsets (921, 922) based on step size information, based on a reference port (910) indicated by the reference CSI-RS index information.

[0132] According to one embodiment, the reference CSI-RS index information may refer to information indicating a single CSI-RS port that serves as a reference when configuring a candidate port subset to include a predetermined number of consecutive CSI-RS ports for at least two orthogonal directions. Hereinafter, in the present disclosure, a single CSI-RS port determined by the reference CSI-RS index information may be referred to as a 'reference port'. For example, referring to FIG. 9, a reference port (910) determined by candidate port subset search setting information such as Table 7 may correspond to a single CSI-RS port indicated by the reference CSI-RS index information (reference CSI-RS index = {3004, 3020}).

[0133] According to one embodiment, the search interval information comprises a parameter (Δ) defined for each direction in configuring a candidate port subset to include a predetermined number of consecutive CSI-RS ports for at least two orthogonal directions. n...can mean ). For example, the number of ports (N1) along the horizontal axis and the number of ports (N2) along the vertical axis based on the reference port (910) can be defined as N1 = L1Δ1 and N2 = L2Δ2, respectively. Here, L1 and L2 are natural numbers and may represent variables used by the terminal to determine the number of ports corresponding to each direction. For example, if L1 is determined as 1 and L2 as 2, the number of ports along the horizontal axis based on the reference port (910) can be determined as N1 = L1Δ1 = 2 and the number of ports along the vertical axis as N2 = L2Δ2 = 2. For example, if L1 is determined as 2 and L2 = 1, the number of ports along the horizontal axis based on the reference port (910) can be determined as N1 = L1Δ1 = 4. The number of ports on the vertical axis N2 = L2Δ2 = 1 can be determined. The terminal can configure a candidate port subset specified by the number of ports on the horizontal axis (N1 = L1Δ1) based on the reference port (910), the number of ports on the vertical axis (N2 = L2Δ2) based on the reference port (910), and direction information based on the reference port (910). For example, referring to FIG. 9, based on the reference port (910), α1 = 0 and 1 indicate the left and right directions, respectively, and α2 = 0 and 1 indicate the up and down directions, respectively. The terminal can configure candidate port subsets (921, 922) including four ports specified by the combination of N1 = L1Δ1, N2 = L2Δ2, α1, and α2.

[0134] According to one embodiment, a terminal may transmit information regarding L1, L2, α1, and α2 to a base station as information regarding a port subset among candidate port subsets that satisfies a reporting condition. For example, referring to FIG. 9, if a candidate port subset (922) satisfies a reporting condition, the terminal may have L1=1, L2=1, α1=0, and α2 Information regarding = 0 or 1 can be reported to the base station as information regarding the candidate port subset (922). In cases where the candidate port subset (922) can be identified with only L1= 1, L2= 1, and α1= 0, as in the case of the candidate port subset (922) of FIG. 9, information regarding α2 reported to the base station may be omitted. Based on the information regarding the port subset reported from the terminal, the base station can identify that information regarding the port subset has been reported, consisting of four consecutive ports in the left direction including the reference port (910) and one consecutive port including the reference port (910) based on the reference port (910).

[0135] FIG. 10 illustrates an example of stopping the search for a candidate port subset based on candidate port subset search setting information according to one embodiment of the present disclosure. Table 8 below is an example of candidate port subset search setting information associated with the example of FIG. 10.

[0136]

[0137] In one embodiment, when a terminal receives candidate port subset search configuration information such as Search type= UE-specific, search mode = Step size-based, search direction = 1, Pmax = 24, Pmin = 8, Qmax = 2 of Table 8, the terminal, wherein the number of CSI-RS ports is the maximum number (P max From port subsets where = 24), the minimum number of CSI-RS ports (Pmin Port subsets up to = 8) can be identified as candidate port subsets. Based on search direction = 1, which indicates descending order, the terminal has a maximum number of CSI-RS ports (P max Reporting conditions can be determined starting from a candidate port subset (1021) that is = 24). The terminal is instructed to report information regarding the port subset to the base station that the maximum number of port subsets is 2 (Q max Based on = 2), information regarding up to 2 port subsets among the candidate port subsets that satisfy the reporting conditions can be reported to the base station.

[0138] According to one embodiment, when the search mode is indicated as step size-based as shown in Table 8, the terminal can configure a candidate port subset based on reference CSI-RS index information and step size information. The method by which the terminal configures a candidate port subset based on reference CSI-RS index information and step size information can be understood in the same way as the example described with reference to FIG. 9. For example, the terminal, based on a reference port (1010) indicated by reference CSI-RS index information, the step size information ( = 2, Candidate port subsets (1021, 1022, 1023) can be configured based on = 1).

[0139] According to one embodiment, the terminal has a maximum number of port subsets (Q) to report information regarding the port subsets. max If a candidate port subset of ) is determined, the determination of reporting conditions for the remaining candidate port subsets may be stopped. For example, referring to FIG. 9, according to Table 8, the maximum number of port subsets to report information regarding the port subsets is Q maxWhen set to 2, the terminal may stop determining the reporting condition for subsequent candidate port subsets consisting of 16 ports as it determines that candidate port subset (1021) and candidate port subset (1023) satisfy the reporting condition. For example, the terminal may report information to the base station regarding two candidate port subsets (1021, 1023) that satisfy the reporting condition without performing the determination of the reporting condition for candidate port subsets consisting of 8 ports.

[0140] FIG. 11 illustrates an example of a method for configuring a port subset based on a CSI-RS index according to one embodiment of the present disclosure. Table 9 below is an example of candidate port subset search configuration information associated with the example of FIG. 11.

[0141]

[0142] In one embodiment, when a terminal receives candidate port subset search configuration information such as Search type= UE-specific, search mode = CSI-RS index-based, search direction = 0, Pmax = 24, Pmin = 16, Qmax = 1 of Table 9, the terminal, wherein the number of CSI-RS ports is a minimum number (P min Starting from port subsets where = 16), the number of CSI-RS ports is the maximum number (P max Port subsets up to = 24) can be identified as candidate port subsets. Based on search direction = 0, which indicates ascending order, the terminal has a minimum number of CSI-RS ports (P min Reporting conditions can be determined starting from candidate port subsets where = 16). The terminal is instructed to the base station that the maximum number of port subsets to report information regarding the port subsets is 2 (Q maxBased on = 1), information regarding up to 1 port subset among the candidate port subsets that satisfies the reporting condition can be reported to the base station.

[0143] In one embodiment, when the search mode is set to search mode = CSI-RS index-based, the terminal can configure a candidate port subset based on a CSI-RS port index. For example, the terminal can configure candidate port subsets including a specified number (e.g., 16) of ports per CSI-RS port index.

[0144] According to one embodiment, the terminal has a maximum number (Q) according to Table 9. max If a candidate port set satisfying the reporting conditions of ) is identified, the search for the port subset can be stopped.

[0145] According to one embodiment, the terminal may transmit to the base station information regarding a port subset among candidate port subsets that satisfies reporting conditions. For example, the terminal may transmit to the base station information regarding a CSI-RS port index corresponding to 16 ports constituting a port subset among candidate port subsets that satisfies reporting conditions (CSI-RS index = {3000, 3005, 3006, 3009, 3010, 3011, 3012, 3015, 3016, 3021, 3022, 3025, 3026, 3027, 3028, 3031}).

[0146] According to one embodiment, a base station can identify a port subset reported by a terminal based on information regarding a port subset received from the terminal. For example, the base station can identify 16 ports constituting the reported port subset based on information regarding a CSI-RS port index (CSI-RS index = {3000, 3005, 3006, 3009, 3010, 3011, 3012, 3015, 3016, 3021, 3022, 3025, 3026, 3027, 3028, 3031}).

[0147] FIG. 12 illustrates a flowchart of an operation for reporting a port subset based on reporting condition setting information according to one embodiment of the present disclosure.

[0148] According to one embodiment of the present disclosure, in step 1210, the base station may transmit report condition setting information to the terminal. In step 1210, the terminal may receive report condition setting information from the base station. Here, the report condition setting information may correspond to the report condition setting information described with reference to FIG. 6. For example, the report condition setting information may include information for selecting at least one port subset to report information regarding the port subset to the base station based on a search for at least one candidate port subset. For example, the report condition setting information may include information indicating a threshold value for the state of a downlink (DL) received signal or a channel state. For example, the base station may transmit to the terminal CSI report setting information (CSI-ReportConfig) expressed as in Table 9 below as report condition setting information.

[0149]

[0150] Referring to Table 10, the reporting condition setting information may include information indicating a threshold expressed as at least one of RSRP (reference signal received power), CQI (channel quality indicator), or SINR (signal to interference noise ratio). For example, a base station may set an RSRP threshold as a cell-specific reporting condition and set a CQI threshold or a SINR threshold as a UE-specific reporting condition to a terminal. For example, a base station may, through RRC signaling, RSRP to a terminal th = -100 dBm, CQI th = 10 (CQI index), SINR th At least one threshold value associated with channel state or received signal strength, expressed as 15 dB, can be set. Of course, the specific numerical value of the threshold value or the index indicating the threshold value may be set differently from the example described above. For example, the threshold value may include at least one of the modulation coding scheme (MCS) index, channel quality indicator (CQI) index, signal-to-noise-ratio (SNR) value, signal-to-interference-plus-noise-ratio (SINR) value, reference signal received power (RSRP) value, reference signal received quality (RSRQ) value, or received signal strength indicator (RSSI) value.

[0151] According to one embodiment of the present disclosure, in step 1220, the terminal may search for a port subset that satisfies a reporting condition set by the reporting condition setting information. The 'search' of the port subset may include an operation of identifying a port subset that satisfies the reporting condition among candidate port subsets. The operation of 'identifying' a port subset that satisfies the reporting condition may include an operation of determining whether the candidate subset satisfies the reporting condition. Step 1220 may include an operation of determining whether to perform a port subset search based on the RSRP value of the CSI-RS resource instructed by the base station. For example, the terminal may perform a port subset search if the RSRP value of the CSI-RS resource instructed by the base station is greater than or equal to a set RSRP threshold. On the other hand, if the RSRP value of the CSI-RS resource instructed by the base station is less than the set RSRP threshold, the terminal may perform CSI reporting based on all CSI-RS ports rather than a port subset search for the candidate port subset. The terminal can determine the reporting conditions for candidate port subsets based on received signal strength if the RSRP value of the CSI-RS resource instructed by the base station is greater than or equal to the set RSRP threshold. For example, the terminal can identify candidate port subsets having a received signal strength greater than the set threshold among the candidate port subsets identified based on candidate port subset search configuration information. The terminal determines the maximum number (Q) of port subsets to report information regarding port subsets to the base station for port subsets satisfying the reporting conditions. max If you have searched up to ), you can stop searching for a subset of ports that satisfy the reporting conditions.

[0152] According to one embodiment of the present disclosure, a terminal may transmit a report regarding a CSI-RS port subset to a base station in step 1230. A base station may receive a report regarding a CSI-RS port subset from the terminal in step 1230. For example, the terminal may transmit information regarding a port subset satisfying the reporting conditions searched in step 1220 to the base station. The information regarding a port subset transmitted by the terminal to the base station in step 1230 may be determined differently depending on the search mode of the candidate port subset search setting information. For example, if the search mode is set to CDM group based, the information regarding a port subset transmitted by the terminal to the base station may include information regarding the index of a CDM group corresponding to a port subset satisfying the reporting conditions. For example, if the search mode is set to step size-based, the information regarding a port subset transmitted by the terminal to the base station may include information about L1, L2, α1, and α2 for identifying a port subset satisfying a reporting condition among candidate port subsets. For example, if the search mode is set to CSI-RS index-based, the information regarding a port subset transmitted by the terminal to the base station may include information about the indices of ports included in a port subset satisfying a reporting condition among candidate port subsets. Of course, the above examples are not limited, and the information regarding a port subset transmitted by the terminal to the base station may include all information indicating a port subset satisfying a reporting condition.

[0153] FIG. 13 illustrates an example of information indicating a threshold value for a downlink (DL) received signal strength according to one embodiment of the present disclosure.

[0154] In one embodiment, the reporting condition setting information may include information indicating at least one threshold value related to downlink received signal strength. The information indicating at least one threshold value related to downlink received signal strength may include mapping information of a plurality of threshold values ​​and a plurality of indices corresponding to each threshold value. For example, the information indicating at least one threshold value related to downlink received signal strength may include at least one of mapping information (1310) of RSRP threshold values ​​and a plurality of indices corresponding to each RSRP threshold value, mapping information (1320) of CQI index values ​​and a plurality of indices corresponding to each CQI index value, or mapping information (1330) of SINR threshold values ​​and a plurality of indices corresponding to each SINR threshold value.

[0155] Additionally, information indicating at least one threshold value related to downlink received signal strength may include information indicating a threshold value among a plurality of indices corresponding to each threshold value. For example, information indicating a threshold value for downlink received signal strength may include RSRP within the mapping information (1310) of RSRP threshold values ​​and a plurality of indices corresponding to each RSRP threshold value. th It may include information regarding an RSRP index (1311) indicating = -102 [dBm]. For example, information indicating a threshold value for downlink received signal strength may include CQI within mapping information (1320) of CQI index values ​​and a plurality of indices corresponding to each CQI index value. th = 8 [index] may include information regarding a CQI index (1321) indicating [index]. For example, information indicating a threshold value for downlink received signal strength may include SINR within mapping information (1330) of SINR threshold values ​​and a plurality of indices corresponding to each SINR threshold value. thIt may include information regarding a CQI index (1331) indicating = 9 [dB].

[0156] According to one embodiment, a base station may transmit mapping information of a plurality of threshold values ​​and a plurality of indices corresponding to each threshold value to a terminal through RRC signaling. Additionally, the base station may transmit information regarding one index indicating a threshold value among a plurality of indices corresponding to each threshold value to the terminal through RRC signaling. For example, the base station may transmit CSI-ReportConfig information (CSI-ReportConfig) as shown in Table 11 below to the terminal.

[0157]

[0158] According to one embodiment, the terminal can receive a threshold value that serves as a criterion for determining a reporting condition based on mapping information of a plurality of threshold values ​​received from a base station and a plurality of indices corresponding to each threshold value, and information regarding a single index indicating a threshold value among the plurality of indices corresponding to each threshold value.

[0159] FIG. 14 illustrates a flowchart of an operation for updating reporting conditions according to one embodiment of the present disclosure.

[0160] According to one embodiment, the base station may transmit to the terminal, in step 1410, total mapping information associated with a threshold value for determining a reporting condition. The terminal may receive the total mapping information from the base station in step 1410. For example, the total mapping information may be transmitted from the base station to the terminal via RRC signaling. The 'total mapping information' transmitted by the base station to the terminal via RRC signaling in step 1410 of FIG. 14 may correspond to the mapping information of a plurality of threshold values ​​and a plurality of indices corresponding to each threshold value, as described above with reference to FIG. 13.

[0161] According to one embodiment, the base station may transmit reduced mapping information to the terminal in step 1420. The terminal may receive reduced mapping information from the base station in step 1420. For example, the reduced mapping information may be transmitted from the base station to the terminal via MAC-CE. Here, the reduced mapping information may refer to mapping information corresponding to a portion of the total mapping information transmitted in step 1410. For example, if the number of indices regarding threshold values ​​included in the total mapping information is 16, the reduced mapping information may include only 4 mapping information among the mapping information of the 16 threshold values ​​and indices. Although step 1420 is shown as being performed after step 1410 in FIG. 14, in one embodiment, step 1420 may be omitted.

[0162] According to one embodiment, at step 1430, the base station may transmit to the terminal information regarding an index indicating a threshold value within the mapping information via DCI. At step 1430, the terminal may receive from the base station information regarding an index indicating a threshold value within the mapping information via DCI. For example, at step 1430, the base station may transmit to the terminal information regarding an index indicating a threshold value different from the threshold value within the reporting condition information received by the terminal at step 1210 of FIG. 12, among a plurality of indices within the overall mapping information transmitted at step 1410. For example, if the base station transmits reduced mapping information to the terminal as it performs step 1420, the base station may transmit at step 1430 information regarding an index indicating a threshold value different from the threshold value within the reporting condition information received by the terminal at step 1210 of FIG. 12, among a plurality of indices within the reduced mapping information.

[0163] According to one embodiment, the terminal may, at step 1440, update a threshold value for a reporting condition based on information for updating a reporting condition received from a base station. For example, the terminal may update the threshold value for a reporting condition to a threshold value corresponding to an index received from a base station at step 1430.

[0164] According to one embodiment, the information transmitted from the base station to the terminal in steps 1410 to 1430 may include UE-specific or Cell-specific setting information.

[0165] According to one embodiment, by updating the reporting conditions according to operations 1410 to 1430 of FIG. 14, the base station can adaptively adjust the number of ports to be used for PDSCH transmission according to the amount of data to be transmitted to the terminal. In the present disclosure, PDSCH transmission may be referred to as an example of a downlink (DL) signal.

[0166] FIG. 15 illustrates mapping information transmitted to a terminal to update a threshold value for a downlink received signal strength according to one embodiment of the present disclosure. The full mapping table of FIG. 15 may correspond to the full mapping information transmitted to the terminal in operation 1410 of FIG. 14. The reduced mapping table of FIG. 15 may correspond to the reduced mapping information transmitted to the terminal in operation 1420 of FIG. 14.

[0167] According to one embodiment, a base station may select some of the indices (1511) among a plurality of indices included in the overall mapping information (1510). For example, the base station may select some of the indices (1511) among the plurality of indices included in the overall mapping information (1510) that correspond to candidate threshold values ​​to be used for updating the threshold value for determining reporting conditions. For example, the base station may select a number of some indices (e.g., L = 4) that is less than the total number of indices included in the overall mapping information (e.g., 16).

[0168] According to one embodiment, a base station may generate reduced mapping information (1530) based on information regarding some selected indices (1511). For example, referring to FIG. 15, the base station may generate mapping information of selected indices indicated by 1 and threshold values ​​indicated by the selected indices based on bit string information indicating four selected indices. The reduced mapping information (1530) may include mapping information regarding four selected indices and threshold values.

[0169] According to one embodiment, a base station may transmit reduced mapping information (1530) to a terminal via MAC-CE. Additionally, the base station may transmit information indicating one index (1531) among L indices within the reduced mapping information (1530) to the terminal via DCI. For example, the base station may transmit 2 of the four indices within the reduced mapping information (1530) to the terminal via DCI. The terminal may update the SINR threshold value to 19 dB, which corresponds to index 2 within the reduced mapping information (1530) and corresponds to index 11 within the full mapping information (1510).

[0170] FIG. 16 illustrates mapping information of an adjustment value transmitted to a terminal to update a threshold value for a downlink received signal strength according to one embodiment of the present disclosure. In the present disclosure, the adjustment value may be referred to as an adjustment factor.

[0171] According to one embodiment, a base station may transmit information regarding an adjustment value of a threshold to a terminal as information for updating reporting conditions. For example, the base station may transmit mapping information between the adjustment values ​​of the threshold and indices to the terminal via RRC signaling.

[0172] According to one embodiment, the mapping information between the adjustment values ​​of the threshold and the indices may include information regarding the difference value of the threshold to be updated with respect to the existing threshold for determining reporting conditions. For example, referring to FIG. 16, the mapping information between the adjustment values ​​of the threshold and the indices includes the adjustment value (Δ) for the RSRP threshold. RSRP Mapping information (1610) of the ) and indices, adjustment value (Δ) for the CQI threshold CQI Mapping information (1620) of the ) and indices, or adjustment value (Δ) for the SINR threshold value SINR It may include at least one of the mapping information (1630) of the ) and the indices.

[0173] According to one embodiment, information regarding the adjustment value of the threshold value may include information indicating one of the indices within the mapping information of the adjustment values ​​of the threshold value and the indices. For example, a base station may transmit to a terminal, via DCI and MAC-CE, information indicating one of the indices within the mapping information (1610, 1620, 1630) of the adjustment values ​​and the indices. The terminal may update the threshold value for determining reporting conditions based on the information regarding the adjustment value of the threshold value received from the base station. For example, if the terminal receives information regarding the adjustment value of the RSRP threshold value from the base station, the terminal may update the RSRP threshold value for determining reporting conditions, RSRP th = RSRP th + Δ RSRP It can be updated to. For example, if the terminal receives information from the base station regarding the adjustment value of the CQI threshold, the terminal, the CQI threshold for determining the reporting condition, CQI th = CQI th + Δ CQI It can be updated to. For example, if the terminal receives information from the base station regarding the adjustment value of the SINR threshold, the terminal, the SINR threshold for determining the reporting condition, SINR th = SINR th + Δ SINR It can be updated to.

[0174] FIG. 17 illustrates an example for explaining a method for a base station to determine a port subset for PDSCH transmission according to one embodiment of the present disclosure.

[0175] According to one embodiment, the base station, in determining a port subset for PDSCH transmission based on information regarding a port subset satisfying a reporting condition received from a terminal, may include the operation of determining the number of ports to be used for PDSCH transmission and the operation of selecting one port subset among port subsets including the determined number of ports.

[0176] According to one embodiment, the base station, based on information regarding port subsets satisfying reporting conditions reported by a plurality of terminals, determines the number of ports (P) to be used for PDSCH transmission. ES ) can be determined. For example, the base station can identify the smallest number of ports among the number of ports included in the port subsets reported by each terminal. For example, referring to FIG. 17, the base station identifies the smallest number (P) among the number of ports included in the port subsets corresponding to port subset indices 0, 1, and 2 reported by the first terminal. min,1 ) can identify 128. For example, the base station can identify the smallest number (P) among the number of ports included in port subsets corresponding to port subset indices 0 to 6 reported from the second terminal. min,2 ) can identify 32. The base station identifies the largest number (max) among the 'number of the fewest ports' identified through the process described above for multiple terminals. The number of ports to use for PDSCH transmission (P) is 128. ES It can be decided as ).

[0177] According to one embodiment, the base station has a number of ports (P) to be used for a determined PDSCH transmission. ES Based on ), a port subset to use for PDSCH transmission can be determined. For example, the base station, P ESAmong port subsets including ports, one port subset with the best received signal strength can be selected as the port subset to be used for PDSCH transmission. For example, referring to FIG. 17, the base station, number of ports (P) to be used for PDSCH transmission ES Among the port subsets containing 128 ports, the port subset with the highest average SINR value can be selected as the port subset to be used for PDSCH transmission. Of course, the indicator regarding channel condition that serves as the criterion for determining the port subset is not limited to the average SINR value. For example, the base station can determine the port subset based on the CQI value.

[0178] According to one embodiment, a base station may transmit information regarding a port subset determined for PDSCH transmission to a terminal. The terminal may receive information regarding a port subset determined for PDSCH transmission from the base station. For example, the base station may transmit information regarding a port subset determined for PDSCH transmission to the terminal via DCI or MAC-CE. The information regarding a port subset determined includes the number of ports (P) included in the port subset determined. ES It may include information regarding a port subset index corresponding to ) or a port subset.

[0179] According to one embodiment, a base station may transmit a PDSCH to a terminal using a determined port subset. The terminal may receive a PDSCH from the base station using a determined port subset.

[0180] With reference to FIG. 17, an example of an operation in which a base station selects a port subset based on information regarding a port subset received from a terminal has been described, but the base station is not limited to being bound by information regarding a port subset reported by the terminal and having to select a port subset for PDSCH. For example, the base station may select a port subset composed of ports different from the ports included in the port subset reported by the terminal as a port subset for PDSCH.

[0181] FIG. 18 illustrates a flowchart of an operation for reselecting a port subset for PDSCH performed by a terminal and a base station according to one embodiment of the present disclosure.

[0182] According to one embodiment, in step 1810, the base station may transmit a PDSCH to the terminal using a determined port subset. Here, the 'determined port subset' may correspond to a port subset for the PDSCH determined based on information reported by the terminal, as described above with reference to FIG. 17.

[0183] According to one embodiment, at step 1820, the base station may identify that a condition for reselecting a port subset is satisfied. The condition for reselecting a port subset may mean a preset condition associated with channel conditions. For example, the condition for reselecting a port subset may mean that the average block error rate (BLER) or resource block (RB) usage is above or below a preset threshold.

[0184] According to one embodiment, at step 1830, the base station may transmit configuration information to the terminal for reselecting a port subset. The terminal may receive configuration information for reselecting a port subset from the base station. The configuration information for reselecting a port subset may include information instructing the terminal to search for at least one port subset among port subsets containing CSI-RS ports that are greater than, equal to, or less than the number of ports currently in use by the base station. The ports currently in use by the base station may correspond to the ports included in the port subset used by the base station for PDSCH at step 1810. The base station may have a BLER ratio at a specific threshold value (BLER th If the value is greater than ), it is determined that the number of ports used for PDSCH is insufficient to satisfy the requirements for downlink data transmission to the terminal, and information may be transmitted to the terminal instructing it to search for at least one port subset among port subsets containing a number of CSI-RS ports greater than the number of ports currently in use by the base station. Conversely, the base station, when the BLER ratio reaches a specific threshold value (BLER th If the number of ports used for PDSCH is greater than ) it is determined that the number of ports used for PDSCH is excessively large compared to the requirements for downlink data transmission for the terminal, information instructing the terminal to search for at least one port subset among port subsets including CSI-RS ports less than or equal to the number of ports currently in use by the base station may be transmitted.

[0185] According to one embodiment, in step 1840, the base station may transmit CSI-RS to the terminal. The terminal may receive CSI-RS from the base station.

[0186] According to one embodiment, the terminal may search for a port subset based on the configuration information for port subset reselection received in step 1830 at step 1850. The operation of the terminal searching for a port subset based on the configuration information for port subset reselection will be described in detail with reference to FIGS. 19 and 20.

[0187] According to one embodiment, at step 1860, the terminal may transmit information regarding the port subset discovered at step 1850 to the base station. The base station may receive information regarding the port subset from the terminal.

[0188] According to one embodiment, the base station may, at step 1870, re-select a port subset based on information regarding a port subset received from the terminal at step 1860. For example, the base station may select a port subset containing a greater number of ports than the number of ports included in the port subset used for PDSCH at step 1810 as the port subset to be used for PDSCH. For example, the base station may select a port subset containing a number of ports equal to or less than the number of ports included in the port subset used for PDSCH at step 1810 as the port subset to be used for PDSCH.

[0189] According to one embodiment, the base station may transmit a PDSCH to the terminal in step 1880 using the port subset re-selected in step 1870. The terminal may receive a PDSCH from the base station using the port subset re-selected in step 1870.

[0190] FIG. 19 illustrates an example in which a base station according to one embodiment of the present disclosure instructs a terminal to search for a port subset consisting of a number of ports greater than the number of ports currently in use.

[0191] The operation 1910 of FIG. 19 may include the operation of the base station transmitting CSI-RS to the terminal to search for a port subset that satisfies a reporting condition based on candidate port subset search setting information and reporting condition setting information.

[0192] Operation 1920 of FIG. 19 may include an operation in which the terminal reports a port subset satisfying a reporting condition to the base station. For example, operation 1920 of FIG. 19 may correspond to the operation of the terminal in step 1230 of FIG. 12.

[0193] Operations 1930 to 1950 of FIG. 19 may correspond to operations performed by the terminal and base station in step 1820 of FIG. 18. For example, operations 1930 to 1950 may include a specific observation window ( During the period, it can be understood as an operation for determining conditions regarding the BLER ratio. For example, in operation 1930 of FIG. 19, the base station may periodically transmit CSI-RS to the terminal using the port subset determined by the base station described in FIG. 17. In operation 1940 of FIG. 19, the terminal may transmit a CSI report for the port subset determined by the base station. In operation 1950 of FIG. 19, the base station, based on the CSI report received from the terminal, determines that the BLER ratio is greater than or equal to a specific BLER threshold value while performing PDSCH transmission according to the predetermined port subset (BLER BLER th Can identify ).

[0194] According to one embodiment, a specific observation window ( During ), the BLER ratio reaches a specific BLER threshold (BLER th) If greater than , the base station may, in operation 1960, transmit configuration information to the terminal for reselecting a port subset. Operation 1960 may correspond to step 1830 of FIG. 18. For example, the base station, a specific observation window ( During ), the BLER ratio reaches a specific BLER threshold (BLER th If it is greater than ), it is determined that the number of ports in use does not satisfy the QoS requirements of the terminals, so the terminal [is not provided with] the number of ports currently in use (P ES,0 Information instructing to search for information regarding port subsets (1900) containing a number of ports greater than ) can be transmitted. For example, referring to FIG. 19, in one embodiment, a base station may transmit a control signal to a terminal via DCI or MAC-CE that includes search direction information such as port subset search direction = 0. Based on the search direction information indicated by port subset search direction = 0, the terminal [describes] the number of currently used ports (P ES,0 Port subsets (1900) containing a number of ports greater than 64 can be identified as candidate port subsets. Additionally, in one embodiment, the base station may transmit port subset search direction = 0 and a reference number of reference ports or a reference port subset index to the terminal via DCI or MAC-CE as search direction information. The terminal can identify port subsets (1900) containing a number of ports greater than the number of ports corresponding to the reference number of ports or the reference port subset index as candidate port subsets. The number of ports corresponding to the reference number of ports or the reference port subset index is the number of ports currently in use (P ES,0It can correspond to ).

[0195] According to one embodiment, the terminal can determine whether the identified candidate port subset satisfies the reporting conditions in operation 1970. In operation 1970, the terminal can receive CSI-RS transmitted from the base station using all ports. After receiving the CSI-RS, the terminal can determine the reporting conditions for the identified candidate port subsets (1900) based on the configuration information received in operation 1960.

[0196] According to one embodiment, in operation 1980, the terminal may transmit information to the base station regarding up to M0 port subsets satisfying the reporting condition. The base station may receive information from the terminal regarding up to M0 port subsets satisfying the reporting condition. M0 may mean a number smaller than the number (M) of candidate port subsets (1900).

[0197] According to one embodiment, a base station may re-select a port subset based on information about port subsets received from a terminal. The number of ports included in the re-selected port subset may be greater than the number of ports currently in use. The base station may transmit information about the re-selected port subset to the terminal.

[0198] FIG. 20 illustrates an example in which a base station according to one embodiment of the present disclosure instructs a terminal to search for a port subset consisting of a number of ports equal to or less than the number of ports currently in use.

[0199] Operation 2010 of FIG. 20 may correspond to operation 1910 of FIG. 19. For example, operation 2010 of FIG. 20 may include an operation in which a base station transmits CSI-RS to a terminal to search for a port subset satisfying a reporting condition based on candidate port subset search setting information and reporting condition setting information.

[0200] Operation 2020 of FIG. 20 may correspond to operation 1920 of FIG. 19. For example, operation 2020 may include an operation in which a terminal reports a port subset satisfying a reporting condition to a base station.

[0201] Operations 2030 to 2050 of FIG. 20 may correspond to operations performed by the terminal and base station in step 1820 of FIG. 18. For example, operations 2030 to 2050 may include a specific observation window ( It can be understood as an operation that determines conditions regarding the BLER ratio during the period. For example, in operation 2050, the base station determines that the BLER ratio is below a specific BLER threshold (BLER BLER th Can identify ).

[0202] According to one embodiment, a specific observation window ( During ), the BLER ratio reaches a specific BLER threshold (BLER th If ) is less than , the base station may, in operation 2060, transmit configuration information to the terminal for reselecting a port subset. Operation 2060 may correspond to step 1830 of FIG. 18. For example, the base station, a specific observation window ( During ), the BLER ratio reaches a specific BLER threshold (BLER th If it is less than ), as it is determined that the number of ports in use sufficiently satisfies the QoS requirements of the terminals, the number of currently used ports (P) to the terminal ES,0Information instructing to search for information regarding port subsets (2000) including ports less than or equal to ) can be transmitted. For example, referring to FIG. 20, in one embodiment, a base station may transmit a control signal to a terminal via DCI or MAC-CE that includes search direction information such as port subset search direction = 1. Based on the search direction information indicated by port subset search direction = 1, the terminal [describes] the number of currently used ports (P ES,0 Port subsets (2000) containing 64 or fewer ports can be identified as candidate port subsets. Additionally, in one embodiment, the base station may transmit port subset search direction = 1 and a reference number of reference ports or a reference port subset index to the terminal via DCI or MAC-CE as search direction information. The terminal may identify port subsets (2000) containing fewer than the number of ports corresponding to the reference number of ports or the reference port subset index as candidate port subsets. The number of ports corresponding to the reference number of ports or the reference port subset index is the number of ports currently in use (P ES,0 It can correspond to ).

[0203] According to one embodiment, the terminal can determine, in operation 2070, whether the identified candidate port subset satisfies the reporting condition. The base station can transmit CSI-RS to the terminal using port subsets having the number of ports included in the port subset used for PDSCH from the base station in operation 1970. After receiving the CSI-RS, the terminal can determine the reporting condition for the identified candidate port subsets (2000) based on the configuration information received in operation 2060.

[0204] According to one embodiment, in operation 2080, the terminal may transmit information about up to M1 port subsets satisfying the reporting condition to the base station. The base station may receive information about up to M1 port subsets satisfying the reporting condition from the terminal. M1 may mean a number smaller than the number (M) of candidate port subsets (2000).

[0205] According to one embodiment, a base station may re-select a port subset based on information about port subsets received from a terminal. The number of ports included in the re-selected port subset may be less than or equal to the number of ports currently in use. The base station may transmit information about the re-selected port subset to the terminal.

[0206] FIG. 21 is a flowchart of an operation performed by a terminal to select a transmission port subset based on RRC signaling according to one embodiment of the present disclosure.

[0207] According to one embodiment, at step 2110, the terminal may receive RRC signaling from a base station that includes candidate port subset search setting information and reporting condition setting information. For example, the terminal may receive RRC signaling from a base station that includes candidate port subset search setting information for identifying at least one candidate port subset comprising some of the CSI-RS ports among a plurality of CSI-RS ports, and reporting condition setting information for selecting at least one port subset to report information regarding the port subset to the base station based on the search for at least one candidate port subset.

[0208] According to one embodiment, at step 2120, the terminal may transmit information regarding at least one port subset to the base station. For example, the terminal may select at least one port subset based on candidate port subset search setting information and reporting condition setting information received from the base station at step 2110. The terminal may transmit information regarding the selected at least one port subset.

[0209] According to one embodiment, at step 2130, the terminal may receive information from the base station regarding a port subset determined for receiving a downlink signal. For example, the port subset determined for receiving a downlink signal may mean a port subset determined based on information regarding at least one port subset transmitted by the terminal to the base station at 2120.

[0210] According to one embodiment, the terminal can receive a downlink signal using a determined port subset from the base station at step 2140.

[0211] FIG. 22 is a flowchart of an operation performed by a base station to select a transmission port subset based on RRC signaling according to one embodiment of the present disclosure.

[0212] According to one embodiment, in step 2210, the base station may transmit RRC signaling to the terminal, including candidate port subset search setting information and reporting condition setting information. For example, the base station may transmit RRC signaling to the terminal, including candidate port subset search setting information for identifying at least one candidate port subset comprising some of the CSI-RS ports among a plurality of CSI-RS ports, and reporting condition setting information for selecting at least one port subset to report information regarding the port subset to the base station based on the search for at least one candidate port subset.

[0213] According to one embodiment, the base station may receive information regarding at least one port subset from the terminal in step 2220. For example, the information regarding at least one port subset may include information regarding at least one port subset selected based on candidate port subset search setting information and reporting condition setting information transmitted to the terminal in step 2210.

[0214] According to one embodiment, in step 2230, the base station may transmit information regarding a port subset determined for downlink signal transmission to the terminal. For example, the base station may determine a port subset for downlink signal transmission based on information regarding at least one port subset received from the terminal. The base station may transmit information regarding the determined port subset for PDSCH transmission to the terminal.

[0215] According to one embodiment, the base station may transmit a downlink signal using a determined port subset to the terminal in step 2240.

[0216] The present disclosure may provide a method and apparatus for selecting a transmission port subset based on a channel state information (CSI) report in a wireless communication system.

[0217] In addition, the present disclosure can provide a method and apparatus that minimizes the increase in the complexity of CSI calculation and overhead for CSI reporting of a terminal and satisfies the requirements for QoS of a terminal by adaptively determining the number of ports used for downlink signal (e.g., PDSCH) transmission according to the transmission environment in a wireless communication system.

[0218] When a method according to various embodiments of the present disclosure is implemented in software, a computer-readable storage medium may be provided for storing one or more programs (software modules). One or more programs stored in the computer-readable storage medium are configured for execution by one or more processors in an electronic device. One or more programs include instructions that cause the electronic device to execute methods according to the embodiments described in the claims or specification of the present disclosure.

[0219] In the present disclosure, the function or operation performed by an electronic device may be performed by one or more processors executing one or more instructions stored in memory. The function or operation of the electronic device mentioned in the present disclosure may be performed by a single processor executing one or more instructions, or by a combination of multiple processors executing one or more instructions. A processor mentioned in the present disclosure is understood to include a circuit for performing operations or controlling other components of the electronic device. For example, the one or more processors may include a central processing unit (CPU), a micro-processor unit (MPU), an application processor (AP), a communication processor (CP), a neural processing unit (NPU), a system on chip (SoC), or an integrated circuit (IC) configured to execute one or more instructions. The one or more processors may be configured to perform the operation of the electronic device described above.

[0220] In the present disclosure, a program (software module, software) may be stored in a random access memory, a non-volatile memory including flash memory, a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), a magnetic disc storage device, a compact disc-ROM (CD-ROM), digital versatile discs (DVDs), or other forms of optical storage devices, or a magnetic cassette. Alternatively, it may be stored in a memory composed of some or all of these. The memory may be composed of a single storage medium or a combination of multiple storage media. The one or more instructions may be stored in a single storage medium or distributed across multiple storage media.

[0221] Additionally, the above program may be stored on an attachable storage device that can be accessed via a communication network such as the Internet, Intranet, LAN (local area network), WLAN (wide LAN), or SAN (storage area network), or a combination thereof. Such a storage device may be connected to a device performing an embodiment of the present disclosure through an external port. Additionally, a separate storage device on a communication network may be connected to a device performing an embodiment of the present disclosure.

[0222] Additionally, in the present disclosure, terms such as "part," "module," etc. may be hardware components such as a processor or circuit, and / or software components executed by hardware components such as a processor.

[0223] "Parts" and "modules" may be implemented by a program that is stored on an addressable storage medium and can be executed by a processor. For example, "parts" and "modules" may be implemented by components such as software components, object-oriented software components, class components, and task components, as well as by processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables.

[0224] The specific embodiments described in this disclosure are merely examples and do not limit the scope of this disclosure in any way. For the sake of brevity, descriptions of prior electronic configurations, control systems, software, and other functional aspects of said systems may be omitted.

[0225] Meanwhile, although specific embodiments have been described in the detailed description of the present disclosure, it is understood that various modifications are possible within the scope of the present disclosure. Therefore, the scope of the present disclosure should not be limited to the described embodiments, but should be defined by the claims set forth below as well as equivalents thereof.

Claims

1. A method performed by a terminal in a wireless communication system, A step of receiving RRC signaling from a base station, comprising candidate port subset search setting information for identifying at least one candidate port subset including some of the CSI-RS ports among a plurality of CSI (channel state information)-RS (reference signal) ports, and reporting condition setting information for selecting at least one first port subset to report information regarding the port subset to the base station based on the search for the at least one candidate port subset; A step of transmitting to the base station information regarding the at least one first port subset selected based on the candidate port subset search setting information and the reporting condition setting information; A step of receiving information regarding a port subset determined for receiving a downlink (DL) signal from the base station; and A method comprising the step of receiving a downlink signal using the determined port subset from the base station.

2. In Paragraph 1, The above candidate port subset search configuration information comprises: information indicating whether the candidate port subset search configuration information is terminal-specific (UE-specific) configuration information or cell-specific configuration information; information indicating a method for configuring the at least one candidate port subset by selecting the portion of CSI-RS ports included in the at least one candidate port subset; information regarding the number of the portion of CSI-RS ports configuring the at least one candidate port subset; information regarding a condition for stopping the search of the at least one candidate port subset; and information regarding the order of searching the at least one candidate port subset.

3. In Paragraph 2, Information for a method of configuring the at least one candidate port subset by selecting the CSI-RS ports included in the at least one candidate port subset comprises any one of the following: information for instructing to select the CSI-RS ports based on a code division multiplexing (CDM) group; information for instructing to select a predetermined number of consecutive CSI-RS ports in at least two orthogonal directions relative to a specific CSI-RS port; or information for instructing to select the CSI-RS ports based on an index of the CSI-RS port. A method in which information regarding the number of CSI-RS ports in the part constituting the at least one candidate port subset further includes information regarding the maximum and minimum number of CSI-RS ports in the part constituting the at least one candidate port subset.

4. In Paragraph 2, The information regarding the condition for stopping the search of the at least one candidate port subset includes information regarding the maximum or minimum number of the at least one first port subset that the terminal reports to the base station, and The information regarding the order constituting the at least one candidate port subset comprises information instructing to determine whether the at least one candidate port subset satisfies a reporting condition in the reporting condition setting information sequentially according to the number of ports included in the at least one candidate port subset.

5. In Paragraph 1, The above-mentioned reporting condition setting information includes information regarding conditions for reporting the at least one candidate port subset to the base station, and A method comprising information regarding conditions for reporting at least one candidate port subset to the base station, wherein the information includes at least one threshold value related to downlink (DL) received signal strength.

6. In Paragraph 5, Information indicating the at least one threshold value related to the downlink reception signal strength is It is expressed as at least one of the indices indicating the at least one threshold value among the at least one threshold value or a plurality of threshold values ​​and a plurality of indices corresponding to the plurality of threshold values, and A method in which at least one threshold value comprises at least one of an MCS (modulation coding scheme) index, a CQI (channel quality indicator) index, an SNR (signal-to-noise-ratio) value, a SINR (signal-to-interference-plus-noise-ratio) value, an RSRP (reference signal received power) value, an RSRQ (reference signal received quality) value, or an RSSI (received signal strength indicator) value.

7. In claim 5, the above method is, A method further comprising the step of receiving control information from the base station that directs an update of the reporting condition, wherein the control information includes information for changing at least one of the at least one threshold value to a different value.

8. In claim 1, the step of transmitting to the base station the information regarding the at least one first port subset based on the candidate port subset search setting information and the reporting condition setting information, A step of receiving CSI-RS from the above base station; Based on the channel estimation result regarding the above CSI-RS, the step of determining the at least one first port subset among the at least one candidate port subset that satisfies the reporting condition included in the reporting condition setting information; and A method comprising the step of transmitting to the base station the information regarding at least one first port subset determined above.

9. In claim 1, the above method is, A step of receiving configuration information for reselecting a port subset from the base station when a condition for reselecting a port subset is satisfied; A step of receiving CSI-RS from the above base station; and The method includes the step of transmitting to the base station information regarding at least one second port subset based on the setting information for reselecting the port subset, and The method for reselecting the above port subset includes information instructing the terminal to search for at least one second port subset among port subsets that include CSI-RS ports, which are either greater than the number of ports currently in use by the base station or equal to or less than the number of ports currently in use.

10. A method performed by a base station in a wireless communication system, A step of transmitting RRC signaling to a terminal, comprising candidate port subset search setting information for identifying at least one candidate port subset including some of the CSI-RS ports among a plurality of CSI (channel state information)-RS (reference signal) ports, and reporting condition setting information for selecting at least one first port subset to report information regarding the port subset to the base station based on the search for the at least one candidate port subset; A step of receiving information regarding the at least one first port subset selected from the terminal based on the candidate port subset search setting information and the reporting condition setting information; A step of transmitting to the terminal information regarding a port subset determined for transmitting a downlink (DL) signal; and A method comprising the step of transmitting the downlink signal using the determined port subset to the terminal.

11. In Paragraph 10, The above candidate port subset search configuration information comprises: information indicating whether the candidate port subset search configuration information is terminal-specific (UE-specific) configuration information or cell-specific configuration information; information indicating a method for configuring the at least one candidate port subset by selecting the portion of CSI-RS ports included in the at least one candidate port subset; information regarding the number of the portion of CSI-RS ports configuring the at least one candidate port subset; information regarding a condition for stopping the search of the at least one candidate port subset; and information regarding the order of searching the at least one candidate port subset.

12. In Paragraph 11, Information for a method of configuring the at least one candidate port subset by selecting the CSI-RS ports included in the at least one candidate port subset comprises any one of the following: information for selecting the CSI-RS ports based on a code division multiplexing (CDM) group; information for selecting the CSI-RS ports that are consecutive by a predetermined number in at least two orthogonal directions relative to a specific CSI-RS port; or information for selecting the CSI-RS ports based on an index of the CSI-RS port. A method in which information regarding the number of CSI-RS ports in the part constituting the at least one candidate port subset further includes information regarding the maximum and minimum number of CSI-RS ports in the part constituting the at least one candidate port subset.

13. In Paragraph 11, The information regarding the condition for stopping the search of the at least one candidate port subset includes information regarding the maximum or minimum number of the at least one first port subset that the terminal reports to the base station, and The information regarding the order constituting the at least one candidate port subset comprises information instructing to determine whether the at least one candidate port subset satisfies a reporting condition in the reporting condition setting information sequentially according to the number of ports included in the at least one candidate port subset.

14. In a terminal of a wireless communication system, Memory for storing instructions; transceiver; and It includes a controller connected to the memory and the transceiver, and the controller, when executed by the instructions, causes the terminal: Receiving RRC signaling from a base station, comprising candidate port subset search setting information for identifying at least one candidate port subset including some of the CSI-RS ports among a plurality of CSI (channel state information)-RS (reference signal) ports, and reporting condition setting information for selecting at least one first port subset to report information regarding the port subset to the base station based on the search for the at least one candidate port subset, To the base station, information regarding the at least one first port subset is transmitted based on the candidate port subset search setting information and the reporting condition setting information, and Receive information regarding a port subset determined for receiving a downlink (DL) signal from the above base station, and A terminal that receives the downlink signal using the determined port subset from the base station.

15. In a base station of a wireless communication system, Memory for storing instructions; transceiver; and It includes a controller connected to the memory and the transceiver, and the controller, when executed by the instructions, causes the base station: Transmitting RRC signaling to a terminal, comprising candidate port subset search setting information for identifying at least one candidate port subset including some of the CSI-RS ports among a plurality of CSI (channel state information)-RS (reference signal) ports, and reporting condition setting information for selecting at least one first port subset to report information regarding the port subset to the base station based on the search for the at least one candidate port subset. From the terminal, information regarding the at least one first port subset selected based on the candidate port subset search setting information and the reporting condition setting information is received, and Transmit information regarding a port subset determined for transmitting a downlink (DL) signal to the above terminal, and A base station that enables the terminal to transmit the downlink signal using the determined port subset.

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