Method and device for performing beam management on basis of channel estimation 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. The present disclosure relates to a method and device for performing beam management on the basis of channel estimation in a wireless communication system. The method performed by a terminal in a wireless communication system, according to one embodiment of the present disclosure, may comprise the steps of: receiving, from a base station, first information including information for identifying some of a plurality of precoding matrix indicator (PMI) beams among the plurality of PMI beams; receiving, from the base station, a channel state information (CSI)-reference signal (RS); transmitting, to the base station, a first report including information about a PMI beam selected, through channel estimation based on the CSI-RS, from among the some PMI beams identified on the basis of the first information; receiving, from the base station, second information for a channel estimation report based on a demodulation reference signal (DMRS); receiving, from the base station, the DMRS for a physical downlink shared channel (PDSCH) through a plurality of beams; and transmitting, to the base station, a second report including information about at least one beam selected, through channel estimation based on the DMRS, from among the plurality of beams.

Description

Method and apparatus for performing beam management based on channel estimation in a wireless communication system

[0001] The present disclosure relates to a method and apparatus for performing beam management 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 performing beam management based on channel estimation in a wireless communication system.

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

[0009] The present disclosure may provide methods performed by a terminal in a wireless communication system. A method performed by a terminal in a wireless communication system according to one embodiment of the present disclosure may include: receiving first configuration information from a base station containing information for identifying some of a plurality of PMI (precoding matrix indicator) beams; receiving a CSI (channel state information)-RS (reference signal) from the base station; transmitting to the base station a first report containing information about a PMI beam selected through channel estimation based on the CSI-RS among the portion of PMI beams identified based on the first configuration information; receiving second configuration information from the base station for a channel estimation report based on a DMRS (demodulation reference signal); receiving a PDSCH (physical downlink shared channel) from the base station through a plurality of beams; and transmitting to the base station a second report containing information about at least one beam selected through channel estimation based on DMRSs corresponding to the plurality of beams. A PDSCH transmitted through a first layer corresponding to a first beam among the plurality of beams and a PDSCH transmitted through a second layer corresponding to at least one second beam among the plurality of beams may contain the same data.

[0010] The present disclosure may provide methods performed by a base station in a wireless communication system. A method performed by a base station in a wireless communication system in one embodiment of the present disclosure may include: transmitting a first configuration information to a terminal that includes information for identifying some of the PMI beams among a plurality of PMI (precoding matrix indicator) beams; transmitting a CSI (channel state information)-RS (reference signal) to the terminal; receiving a first report from the terminal that includes information about a PMI beam selected through channel estimation based on the CSI-RS among the portion of PMI beams identified based on the first configuration information; transmitting a second configuration information to the terminal for a channel estimation report based on a DMRS (demodulation reference signal); transmitting a PDSCH (physical downlink shared channel) to the terminal through a plurality of beams; and receiving a second report from the terminal that includes information about at least one beam selected through channel estimation based on DMRSs corresponding to the plurality of beams. A PDSCH transmitted through a first layer corresponding to a first beam among the plurality of beams and a PDSCH transmitted through a second layer corresponding to at least one second beam among the plurality of beams may contain the same data.

[0011] In a wireless communication system according to one embodiment of the present disclosure, a terminal may include a memory for storing commands, 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 from a base station first configuration information containing information for identifying some of the PMI (precoding matrix indicator) beams among a plurality of PMI beams, receive a CSI (channel state information)-RS (reference signal) from the base station, transmit to the base station a first report containing information about a PMI beam selected through channel estimation based on the CSI-RS among the portion of PMI beams identified based on the first configuration information, receive from the base station second configuration information for a channel estimation report based on a DMRS (demodulation reference signal), receive a PDSCH (physical downlink shared channel) through a plurality of beams from the base station, and transmit to the base station a second report containing information about at least one beam selected through channel estimation based on DMRSs corresponding to the plurality of beams. A PDSCH transmitted through a first layer corresponding to a first beam among the plurality of beams and a PDSCH transmitted through a second layer corresponding to at least one second beam among the plurality of beams may contain the same data.

[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 to the terminal first configuration information containing information for identifying some of the PMI (precoding matrix indicator) beams among a plurality of PMI beams, transmit a CSI (channel state information)-RS (reference signal) to the terminal, receive from the terminal a first report containing information about a PMI beam selected through channel estimation based on the CSI-RS among the portion of PMI beams identified based on the first configuration information, transmit second configuration information for a channel estimation report based on a DMRS (demodulation reference signal) to the terminal, transmit a PDSCH (physical downlink shared channel) through a plurality of beams to the terminal, and receive from the terminal a second report containing information about at least one beam selected through channel estimation based on DMRSs corresponding to the plurality of beams. A PDSCH transmitted through a first layer corresponding to a first beam among the plurality of beams and a PDSCH transmitted through a second layer corresponding to at least one second beam among the plurality of beams may contain the same data.

[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 a method in which a terminal according to one embodiment of the present disclosure selects at least one PMI beam among a plurality of PMI beams.

[0020] FIG. 6 illustrates a flowchart for performing beam management based on channel estimation according to one embodiment of the present disclosure.

[0021] FIG. 7 illustrates examples of reduced PMI indices identified based on information indicating PMI indices according to one embodiment of the present disclosure.

[0022] FIG. 8 illustrates examples of reduced PMI indices identified based on information regarding the pattern of PMI indices according to one embodiment of the present disclosure.

[0023] FIG. 9 illustrates examples of reduced PMI indices identified based on information for identifying PMI index subsets according to one embodiment of the present disclosure.

[0024] FIG. 10 illustrates examples of PMI beams corresponding to a PMI index subset according to one embodiment of the present disclosure.

[0025] FIG. 11 illustrates an example of identifying reduced PMI indices based on information regarding the patterns of some of the PMI indices among a plurality of PMI indices included in a PMI index subset according to one embodiment of the present disclosure.

[0026] FIG. 12 illustrates examples of reduced PMI indices identified based on information regarding the mapping relationship between a plurality of PMI index subsets and a plurality of downlink (DL) reference signals (RS) according to one embodiment of the present disclosure.

[0027] FIG. 13 illustrates an example in which a terminal according to one embodiment of the present disclosure selects at least one PMI beam among a plurality of PMI beams based on channel estimation for PDSCH.

[0028] FIG. 14 illustrates an example in which a base station according to one embodiment of the present disclosure transmits PDSCH to a terminal through a plurality of beams.

[0029] FIG. 15 illustrates a PDSCH transmission procedure of a base station according to one embodiment of the present disclosure.

[0030] FIG. 16 illustrates a partial flowchart of a PDSCH transmission procedure of a base station including an operation to duplicate a layer according to one embodiment of the present disclosure.

[0031] FIG. 17 illustrates an example in which a terminal according to one embodiment of the present disclosure receives PDSCH through a plurality of layers including a replicated layer.

[0032] FIG. 18 illustrates a flowchart of an operation in which a terminal according to one embodiment of the present disclosure performs beam gain computation and demodulation based on DMRS channel estimation.

[0033] FIG. 19 illustrates an example of information regarding a time resource of a PDSCH to which a replicated layer is transmitted according to one embodiment of the present disclosure.

[0034] FIG. 20 illustrates an example of information regarding time resources of a PDSCH that becomes a PDSCH through a replicated layer according to one embodiment of the present disclosure, and information indicating frequency resources of a PDSCH that is transmitted through a replicated layer.

[0035] FIG. 21 illustrates an example of information regarding time resources of a PDSCH through a replicated layer and bitmap information regarding frequency resources through which a PDSCH is transmitted according to one embodiment of the present disclosure.

[0036] FIG. 22 illustrates an example of information regarding time resources of PDSCH transmitted through a replicated layer according to one embodiment of the present disclosure, and information regarding the start position and interval of frequency resources of PDSCH transmitted through a replicated layer.

[0037] FIG. 23 illustrates an example of information regarding time resources of a PDSCH transmitted through a replicated layer according to one embodiment of the present disclosure, and information regarding the starting position and length of frequency resources of a PDSCH transmitted through a replicated layer.

[0038] FIG. 24 illustrates an example of information indicating a replicated layer according to one embodiment of the present disclosure.

[0039] FIG. 25 illustrates an example of information indicating an original layer according to one embodiment of the present disclosure.

[0040] FIG. 26 illustrates a schematic diagram of a terminal according to one embodiment of the present disclosure reporting to a base station at least one beam selected based on channel estimation among a plurality of beams.

[0041] FIG. 27 illustrates a flowchart of signal transmission between a terminal and a base station in which the base station instructs the terminal to determine a set of candidate beams based on whether the wireless channel quality of a specific beam is greater than or equal to a preset difference value than the wireless channel quality of a reference beam.

[0042] FIG. 28 illustrates a flowchart of signal transmission between a terminal and a base station in the case where the base station instructs the terminal to determine a set of candidate beams based on whether the wireless channel quality of a specific beam applied to a replicated layer is greater than a specific threshold value.

[0043] FIG. 29 is a flowchart of operations performed by a terminal to perform beam management based on channel estimation according to one embodiment of the present disclosure.

[0044] FIG. 30 is a flowchart of operations performed by a base station to perform beam management based on channel estimation according to one embodiment of the present disclosure.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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."

[0053] 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.

[0054] Phrases such as "in one embodiment" appearing in various places in this disclosure do not necessarily refer to the same embodiment.

[0055] 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.

[0056] 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.

[0057] 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'.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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).

[0062] 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.

[0063] 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.

[0064] 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)).

[0065] 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).

[0066] 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.

[0067] 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).

[0068] 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.

[0069] According to various embodiments, the control unit (240) can control the base station to perform operations according to various embodiments described below.

[0070] 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.

[0071] Referring to FIG. 3, the terminal includes a communication unit (310), a storage unit (320), and a control unit (330).

[0072] 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.

[0073] 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.

[0074] 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).

[0075] 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).

[0076] 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).

[0077] According to various embodiments, the control unit (330) can control the terminal to perform operations according to various embodiments described below.

[0078] 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.

[0079] 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.

[0080] In some embodiments, the number of slots (402) constituting a single subframe (403) and the length of the slots (402) may vary depending on the subcarrier spacing. This subcarrier spacing may be referred to as numerology (μ). That is, the subcarrier spacing, the number of slots included in the subframe, the length of the slots, and the length of the subframe may 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. Additionally, 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.

[0081] In some embodiments, the subcarrier spacing, the number of slots included in a subframe, the length of the slots, and the length of the subframe may be applied variably depending on the communication system. For example, in the case of an LTE system, the subcarrier spacing is 15 kHz, and two slots constitute one subframe, where the length of the slots is 0.5 ms and the length of the subframe is 1 ms. In another example, in the case of an NR system, the subcarrier spacing (μ) may be one of 15 kHz, 30 kHz, 60 kHz, 120 kHz, or 240 kHz, and the number of slots included in one subframe according to the subcarrier spacing (μ) may be 1, 2, 4, 8, or 16.

[0082] 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.

[0083] 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.

[0084] 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).

[0085] 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.

[0086] 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).

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] In a wireless network environment, a base station (BS) can perform beam management based on a PMI (precoding matrix indicator) report from a terminal (user equipment, UE). The base station transmits a CSI-RS (channel state information reference signal) to the terminal, and the terminal can estimate the channel state based on the CSI-RS received from the base station. Based on the estimation result of the channel state, the terminal can perform CSI computation for CSI reporting to the base station. The terminal can perform CSI computation based on CSI report configuration information (CSI-ReportConfig), which is a higher-layer message received from the base station. For example, the terminal can receive information to be reported to the base station based on configuration information included in the report quantity configuration information message (reportQuantity) within the CSI-ReportConfig. For example, when reportQuantity = cri-RI-PMI-CQI, the terminal can calculate at least one of CRI (CSI-RS resource indicator), RI (rank indicator), PMI, or CQI (channel quality indicator) based on the channel estimation result. The terminal can report at least one of the calculated CRI, RI, PMI, or CQI to the base station. The terminal can determine the PMI to report to the base station based on the configuration information included in the codebook configuration information message (codebookConfig) within CSI-ReportConfig.The terminal can determine the PMI beams to perform a PMI search based on the codebook type setting information for a PMI search included in the codebookConfig and the setting information for identifying the PMI beams to perform the PMI search. For example, if the terminal is configured to receive CSI-RS through a 32-port, the codebook type setting information for a PMI search included in the codebookConfig may be indicated as codebook type = typeI-SinglePanel. For example, the setting information for identifying the PMI beams to perform a PMI search included in the codebookConfig may be indicated in a manner such as n1=8, n2=2. Here, n1 and n2 may refer to information for indicating PMI indices corresponding to the precoder matrices within the codebook.

[0093] In the example described above, the terminal can determine the PMI to report to the base station based on the channel estimation results for multiple PMI beams configured through codebookConfig. For example, the terminal can select the PMI beam with the highest channel power among the multiple PMI beams. For example, if the total number of PMI beams is defined as Q, the terminal can select the PMI beam with the highest channel power among the Q PMI beams. Here, channel power can be calculated as |Hw(i)|² where the channel matrix is ​​defined as H and the vector corresponding to PMI beam i is defined as w(i). Accordingly, the index of the PMI beam selected by the terminal Is, It can be determined as.

[0094] In the method for performing beam management based on PMI reporting by a terminal using the aforementioned CSI-RS, if the number of CSI-RS ports increases, the computational complexity for PMI reporting by the terminal may increase exponentially. That is, if the number of CSI-RS ports increases, the total number of beams increases, which may increase the computational complexity required for the terminal to perform PMI search. For example, compared to the case where the maximum number of supported CSI-RS ports is N=32 and the total number of beams for type I-SinglePanel is 256, if the number of CSI-RS ports increases to 256, the total number of beams may increase eightfold to 2048. Consequently, as the number of PMI beams to be processed and the size of the channel matrix increase, the computational complexity for PMI search by the terminal may increase exponentially. For example, when a terminal performs PMI search based on channel power, a computational complexity of O(N²) may be required due to the involvement of matrix multiplication operations. Accordingly, if the maximum number of supported CSI-RS ports increases eightfold from 32 to 256, the computational complexity for PMI search may increase by approximately 64 times. Additionally, if the number of CSI-RS ports increases, the overhead for PMI reporting by the terminal may increase due to the increase in the number of beams.

[0095] The present disclosure aims to provide a method and apparatus for efficiently reporting a PMI beam using channel estimation based on CSI-RS and channel estimation based on DMRS (demodulation reference signal) in a wireless communication system. More specifically, the present disclosure aims to provide a method and apparatus for selecting and reporting a PMI beam while reducing the computational complexity for PMI search of a terminal and the overhead for signaling associated with CSI reporting of the terminal based on CSI-RS and DM-RS.

[0096] In the present disclosure, operations performed by a terminal or base station may be described using terms distinguishing stages such as 'Phase 0' and 'Phase 1', but this is for ease of explanation only and does not imply that the operations performed by the terminal or base station are exclusively distinguished or limited.

[0097] In the present disclosure, 'PMI beam' and 'PMI index,' which refers to an index corresponding to a PMI beam, may be used interchangeably. Additionally, a subset of PMI beams composed of at least some of the PMI beams may be referred to as a 'PMI subset,' a 'PMI beam subset,' or a 'PMI index subset.'

[0098] FIG. 5 illustrates a method in which a terminal according to one embodiment of the present disclosure selects at least one PMI beam among a plurality of PMI beams.

[0099] Referring to FIG. 5, a terminal according to one embodiment of the present disclosure can select at least one PMI beam among a plurality of PMI beams corresponding to a plurality of PMI indices. An operation performed by a terminal according to one embodiment may include a step of selecting one PMI beam through a coarse PMI search on some of the PMI beams among the plurality of PMI beams (Phase 0), and a step of selecting an optimal beam among a plurality of beams determined based on the selected one PMI beam (fine PMI selection) (Phase 1).

[0100] According to one embodiment, the terminal may perform a PMI search for some of the PMI beams among a plurality of PMI beams in phase 0. 'A plurality of PMI beams' may refer to PMI beams corresponding to all PMI indices within a predetermined codebook. Referring to an example (500) of FIG. 5, the terminal may perform a PMI search for some of the PMI beams (S0) corresponding to PMI indices having values ​​of 2, 7, 12, and 15 among the plurality of PMI beams (505) corresponding to a plurality of PMI indices defined by values ​​from 0 to 15 in phase 0. 'PMI search' may refer to an operation in which the terminal selects a specific PMI beam or a specific PMI index preferred by the terminal based on channel estimation for some of the PMI beams. For example, the terminal may select a PMI beam (522) corresponding to PMI index 2 (512) among some of the PMI beams (S0) as a preferred PMI beam based on channel estimation.

[0101] In the present disclosure, some of the PMI beams (S0) among the plurality of PMI beams that are the subject of PMI search may be referred to as 'reduced PMI beams', 'reduced candidate PMI beams', or 'reduced PMI beam set'.

[0102] According to one embodiment, some PMI beams may be provided to a terminal by a base station. The base station may select some of the PMI beams among a plurality of PMI beams according to predetermined conditions (e.g., channel status, beam in use, number of antennas of the terminal or base station, terminal capability, etc.) and provide PMI index information corresponding to the selected some PMI beams to the terminal.

[0103] According to one embodiment, the base station may determine a plurality of beams (520) in phase 1 based on the PMI beam reported by the terminal in phase 0. Here, the plurality of beams (520) may include PMI beams (S1) adjacent to the PMI beam (522) reported by the terminal in phase 0. For example, if the PMI beam (522) reported by the terminal in phase 0 is a beam corresponding to PMI index 2 (512), the plurality of beams (520) may include PMI beams (S1) with PMI index values ​​of 0, 1, 3, and 4. However, the method by which the base station determines the plurality of beams (520) is not limited thereto. For example, the base station may determine the PMI beam (522) reported by the terminal in phase 0 and at least one PMI beam spaced apart from the PMI beam (522) by a predetermined distance as the plurality of beams.

[0104] According to one embodiment, the terminal can select the best beam among a plurality of beams (520) determined by the base station in phase 1. For example, referring to another example (501) of FIG. 5, the terminal can select at least one beam among the plurality of beams (520) determined by the base station in which the terminal has a relatively good channel condition based on channel estimation.

[0105] FIG. 6 illustrates a flowchart for performing beam management based on channel estimation according to one embodiment of the present disclosure.

[0106] Referring to FIG. 6, operations for performing PMI beam management performed by a terminal and a base station according to one embodiment can be understood as being divided into two stages: Phase 0 (600) and Phase 1 (610). Phase 0 (600) and Phase 1 (610) of FIG. 6 may correspond to Phase 0 and Phase 1 of FIG. 5. Phase 0 (600) can be understood as a stage for searching for an approximate optimal PMI beam or an optimal PMI index. Phase 1 (610) can be understood as a stage for selecting an optimal PMI beam or an optimal PMI index more precisely than Phase 0 (600).

[0107] According to one embodiment, in step 601, the base station may transmit first configuration information regarding a PMI beam to the terminal. The terminal may receive the first configuration information from the base station. For example, the first configuration information may be transmitted from the base station to the terminal via a control signal. The control signal may include RRC signaling, but the type of control signal is not limited thereto. For example, the control signal used to transmit the first configuration information may include DCI or MAC-CE. For example, the first configuration information may include information for the terminal to identify some of the PMI indices (e.g., some PMI indices (S0) of FIG. 5) among a plurality of PMI indices (e.g., PMI indices 0 to 15 of FIG. 5) corresponding to a plurality of PMI beams. For example, the first configuration information may include information regarding reduced PMI beams or information regarding a limited range of PMI indices for performing PMI search. Specific information included in the first setting information will be described later with reference to FIGS. 7 to 12.

[0108] According to one embodiment, information for identifying some of the PMI indices (e.g., some PMI indices (S0) of FIG. 5) among a plurality of PMI indices (e.g., PMI indices 0 to 15 of FIG. 5) corresponding to a plurality of PMI beams may be transmitted to the terminal through at least one of a CSI ReportConfig message included in RRC signaling, or a CodebookConfig message including information regarding a precoder corresponding to the plurality of PMI indices.

[0109] According to one embodiment, in step 603, the base station may transmit CSI-RS to the terminal. The terminal may receive CSI-RS from the base station. For example, the base station and the terminal may transmit and receive CSI-RS based on a preset number of CSI-RS ports. For example, the preset number of CSI-RS ports may include 256 CSI-RS ports, but the number of CSI-RS ports is not limited thereto. That is, the CSI-RS ports may include fewer or more than 256 CSI-RS ports. Additionally, according to one embodiment, the base station may transmit only the CSI-RS corresponding to the reduced PMI beams.

[0110] According to one embodiment, in step 605, the terminal may select an optimal PMI beam among the reduced PMI beams. Alternatively, the terminal may select a PMI index corresponding to the optimal PMI beam among the reduced PMI beams. For example, the terminal may identify the reduced PMI beams or PMI indices corresponding to the reduced PMI beams based on the first configuration information received from the base station in step 601. The terminal may select an optimal PMI beam through channel estimation using CSI-RS for the reduced PMI beams. For example, the terminal may select the PMI beam with the highest channel power among the reduced PMI beams as the optimal PMI beam. The terminal may identify a PMI index corresponding to the selected optimal PMI beam.

[0111] According to one embodiment, in step 607, the terminal may transmit a first report to the base station containing information about a selected optimal PMI index. The information about the selected optimal PMI index may refer to the value of the selected optimal PMI index. That is, the optimal PMI index in step 607 may include the optimal PMI index identified through channel measurement among some of the PMI indices received by the terminal in step 601. The first report may refer to a CSI report containing a PMI transmitted from the terminal to the base station, but the information that may be included in the first report is not limited to PMI. For example, in addition to PMI, the first report may include at least one of a CRI (CSI-RS resource indicator), a RI (rank indicator), or a CQI (channel quality indicator).

[0112] According to one embodiment, in step 611, the base station may determine a plurality of beams to be used for DMRS transmission for the physical downlink shared channel (PDSCH). Step 611 may correspond to the step of the base station determining the plurality of beams (520) described above with reference to the example (501) of FIG. 5. For example, the base station may determine the PMI beam selected in phase 0 and the PMI beams (S1) adjacent to the PMI beam selected in phase 0 as the plurality of beams to be used for DMRS transmission for the PDSCH.

[0113] Of course, the method by which a base station selects multiple PMI beams is not limited to the above examples, and the base station may select PMI beams that are not adjacent to the selected PMI beam, or may select a beam other than the PMI beam selected in phase 0. For example, the base station may select a beam that forms a predetermined distance or a predetermined angle with the selected PMI beam.

[0114] According to one embodiment, a plurality of beams to be used for DMRS transmission for PDSCH may include a plurality of beams applied to a plurality of layers transmitting PDSCH. For example, a base station may determine a first beam for PDSCH transmission through a first layer and at least one second beam for PDSCH transmission through at least one second layer. In the present disclosure, “at least one second layer” may mean at least one layer copied based on the first layer. For example, the first layer may be referred to as the original layer, and the second layer as the copied layer. The copied layer may be a layer corresponding to another beam to which the same data is transmitted via PDSCH.

[0115] In step 611, the base station may determine the number of at least one second layer to be generated through the replication of the first layer and a plurality of beams to be applied to each layer. The 'copied layer' or 'copy of a layer' will be explained in detail with reference to FIG. 16.

[0116] According to one embodiment, in step 613, the base station may transmit second configuration information to the terminal for reporting the terminal's channel estimation based on DMRS. The terminal may receive the second configuration information from the base station. The second configuration information may include information for identifying at least one second layer and information for the terminal to select at least one beam through channel estimation based on DMRS and to report the selected at least one beam to the base station. The 'information for identifying at least one second layer' included in the second configuration information will be described in detail with reference to FIGS. 19 to 25. The 'information for the terminal to select at least one beam through channel estimation based on DMRS and to report the selected at least one beam to the base station' included in the second configuration information will be described in detail with reference to FIGS. 26 to 28.

[0117] In one embodiment, the second setting information may be transmitted from the base station to the terminal via a control signal. The control signal may include at least one of RRC signaling, DCI, or MAC-CE.

[0118] According to one embodiment, in step 615, the base station may transmit PDSCH and corresponding DMRS to the terminal through a plurality of beams determined in step 611. The terminal may receive PDSCH and corresponding DMRS from the base station through the plurality of beams. For example, the base station may transmit PDSCH and corresponding DMRS to the terminal through a plurality of layers to which different plurality of beams are each applied. For example, the base station may perform PDSCH transmission through a plurality of layers to which different plurality of beams, each including a first layer and at least one second layer, are each applied, using a plurality of time or frequency resource units. Here, the 'time resource' may include a symbol, a slot, a subframe, etc. The 'frequency resource' may include a subcarrier, a resource block (RB), a resource block group (RB group, RBG), etc.

[0119] According to one embodiment, in step 617, the terminal can select at least one beam through channel estimation based on DMRS.

[0120] The terminal can perform channel estimation based on the DMRS of the PDSCH transmitted through a first layer and at least one second layer corresponding to a plurality of different beams. Based on the result of the channel estimation, the terminal can select at least one beam among the plurality of beams as the optimal beam. For example, when PDSCH transmission is performed through a plurality of layers in a plurality of slots, the terminal can measure the received signal strength of the DMRS port corresponding to each layer in each slot and select at least one layer with the highest received signal strength of the DMRS port.

[0121] According to one embodiment, the received signal strength of a DMRS port can be compared based on a preset radio quality indicator. For example, the radio quality indicator may include reference signal received power (RSRP), channel power, signal-to-noise ratio (SNR), signal-to-interference-plus-noise ratio (SINR), etc., but the types of radio quality indicators are not limited thereto, and other indicators for evaluating the quality of the radio channel may be used.

[0122] According to one embodiment, in step 619, the terminal may transmit to the base station a second report containing information about at least one beam selected in step 617. The base station may receive the second report from the terminal. For example, the terminal may select at least one layer with the highest received signal selected in step 617, or at least one beam corresponding to the selected at least one layer, as the layer or beam to be reported to the base station. The terminal may transmit to the base station a second report containing information about the selected layer or beam.

[0123] According to one embodiment, in step 621, the base station may update the beam for PDSCH transmission based on the second report received from the terminal in step 619. The operation of the base station updating the beam for PDSCH transmission may include the operation of determining whether to perform PDSCH transmission through the beam selected by the terminal based on information regarding at least one beam selected by the terminal included in the second report. That is, the base station may decide to perform PDSCH transmission through the beam selected by the terminal, but is not limited thereto. For example, after receiving the second report from the terminal, the base station may decide not to perform PDSCH transmission through the beam selected by the terminal in step 617, but to perform PDSCH transmission through a beam different from the beam selected by the terminal in step 617. For example, the base station may decide to perform PDSCH transmission through the beam previously used for performing PDSCH transmission, or the PMI beam selected by the terminal in step 605.

[0124] According to one embodiment, in step 623, the base station may perform PDSCH transmission using the beam updated in step 621. If the base station decides to update the beam for PDSCH transmission in step 621, it may perform PDSCH transmission using the updated beam. On the other hand, if the base station decides not to update the beam for PDSCH transmission in step 621, it may perform PDSCH transmission through the beam that was previously used.

[0125] FIG. 7 illustrates examples of reduced PMI indices identified based on information indicating PMI indices according to one embodiment of the present disclosure.

[0126] Referring to FIG. 7, the 'reduced PMI indices' are the total PMI indices (S) corresponding to the total PMI beams (or total candidate PMI beams). full It may refer to PMI indices (S0) corresponding to the reduced PMI beams (or reduced candidate PMI beams) among ). For example, the total number of PMI beams is 16, and the total PMI indices (S full In the example of FIG. 7, where ) is defined as a value from 0 to 15, the reduced PMI indices (S0) are 16 PMI indices (S full Some of the PMI indices may be included. For example, the reduced PMI indices (S0) may include PMI indices of 2, 7, 12, and 15. The reduced PMI beams may be provided to a terminal by a base station. The base station may select some of the PMI beams among the plurality of PMI beams according to predetermined conditions (e.g., channel status, beam in use, number of antennas of the terminal or base station, terminal capability, etc.) and provide the terminal with reduced PMI index information corresponding to the reduced PMI beams (selected some of the PMI beams).

[0127] As described with reference to steps 601 and 603 of FIG. 6, the terminal can perform PMI search for reduced PMI beams based on information regarding reduced PMI indices included in the first configuration information received from the base station. To this end, in one embodiment, the terminal may require information for identifying reduced PMI beams or reduced PMI indices corresponding to the reduced PMI beams.

[0128] According to one embodiment, the base station tells the terminal that the terminal has all PMI indices (S fullInformation for identifying reduced PMI indices (S0) among ) can be transmitted. For example, the base station can transmit information to the terminal for the terminal to identify some of the PMI indices among the plurality of PMI indices. The information for identifying some of the PMI indices among the plurality of PMI indices may be included in the first configuration information transmitted by the base station to the terminal in step 601 of FIG. 6.

[0129] According to one embodiment, information for a terminal to identify some of the PMI indices among a plurality of PMI indices may include information indicating a plurality of PMI indices included in the reduced PMI indices (S0). For example, referring to FIG. 7, the entire PMI indices (S full Information indicating some of the PMI indices included in the reduced PMI indices (S0) among ) can be transmitted to the terminal in the form of a PMI index or a PMI index value. For example, information indicating some of the PMI indices can be transmitted to the terminal through RRC signaling including configuration information messages such as [Table 1] and [Table 2].

[0130]

[0131] For example, referring to Table 1, the PMI index values ​​2, 7, 12, and 15 indicating the total PMI indices 0 to 15 and some PMI indices in Fig. 7 may be included in the CSI-ReportConfig message.

[0132]

[0133] For example, referring to Table 2, the PMI index values ​​2, 7, 12, and 15 indicating the total PMI indices from 0 to 15 and some PMI indices in Fig. 7 may be included in the CodebookConfig message.

[0134] FIG. 8 illustrates examples of reduced PMI indices identified based on information regarding the pattern of PMI indices according to one embodiment of the present disclosure.

[0135] According to one embodiment, information for a terminal in the first configuration information to identify some of the PMI indices among a plurality of PMI indices may include information regarding the pattern of some of the PMI indices among the plurality of PMI indices. The information regarding the pattern of some of the PMI indices may include information regarding the index value at which the terminal starts PMI search (start PMI index), information regarding the difference in index values ​​between a specific PMI index that is the target of the PMI search and a PMI index in the next sequence that is the target of the PMI search (step size), and information regarding the number of PMI indices that are the target of the PMI search (nrofIndices). For example, referring to FIG. 8, when start PMI index = 4, step size = 8, and nrofIndices = 4, the terminal may perform CSI calculations for PMI beams with PMI index values ​​of 12, 20, and 28, respectively, starting from a PMI beam with a PMI index value of 4. As a result, the terminal may perform PMI search for PMI beams within a limited range based on information regarding the pattern of some of the PMI indices among the plurality of PMI indices.

[0136] According to one embodiment, information regarding the pattern of some of the PMI indices among a plurality of PMI indices can be transmitted from a base station to a terminal through RRC signaling. For example, information regarding the pattern of some of the PMI indices can be transmitted to a terminal through RRC signaling including configuration information messages such as [Table 3] and [Table 4].

[0137]

[0138] For example, referring to Table 3, pattern information can be transmitted to the terminal as reducedPMIIndexSet setting information within CSI-ReportConfig.

[0139]

[0140] For example, referring to Table 4, pattern information can be transmitted to the terminal as reducedPMIIndexSet setting information within CodebookConfig.

[0141] According to one embodiment, a base station may transmit information to a terminal for updating reduced PMI indices. For example, the base station may transmit updated information regarding reduced PMI indices to the terminal via DCI and MAC-CE. A terminal with a high signal-to-noise ratio or a terminal with a relatively small amount of data to be received (i.e., low buffer occupancy (BO)) can satisfy a data rate requirement without searching for an accurate beam. In such cases, the base station may update the set step size to a relatively large value for the terminal. As a result, the base station can dynamically reduce the computational complexity for PMI search of the terminal.

[0142] FIG. 9 illustrates examples of reduced PMI indices identified based on information for identifying PMI index subsets according to one embodiment of the present disclosure. FIG. 10 illustrates examples of PMI beams corresponding to PMI index subsets according to one embodiment of the present disclosure. Referring to FIG. 9 and FIG. 10, a plurality of PMI index subsets may each include PMI indices having consecutive PMI index values. Each PMI index subset may include the same number of PMI indices. For example, referring to FIG. 9, if the total number of PMI indices is 32, the total PMI indices may be divided into four PMI index subsets, each containing eight PMI indices. Referring to FIG. 10, the PMI indices included in each PMI index subset may correspond to PMI beams having adjacent directions.

[0143] According to one embodiment, among the first configuration information transmitted from a base station to a terminal, the information for the terminal to identify some of the PMI indices among the plurality of PMI indices may include information regarding the plurality of PMI index subsets constituting the entire PMI index. For example, the information regarding the plurality of PMI index subsets may include information regarding the number of PMI index subsets (e.g., 4) (number of subsets), and information for the terminal to select some of the PMI index subsets among the plurality of PMI index subsets (e.g., PMI index subset 1).

[0144] According to one embodiment, information for a terminal to select some of the PMI index subsets among a plurality of PMI index subsets may include the number of PMI index subsets to be selected (Q) and information regarding a representative PMI index representing each PMI index subset. For example, referring to the example in FIG. 9, if the total number of PMI beams is 32, and the PMI beams correspond to PMI index values ​​from 0 to 32, and the representative PMI index values ​​of the first to fourth index subsets are 3, 11, 19, and 27, respectively, the information regarding the representative PMI indices representing each PMI index subset may be defined by the index values ​​of the representative PMI indices (e.g., 3, 11, 19, 27). Alternatively, the information regarding the representative PMI index representing each PMI index subset may include information regarding the relative positions of the representative PMI indices (901, 911, 921, 931) within each PMI index subset. For example, referring to FIG. 9, if the representative PMI indices (901, 911, 921, 931) are located at the 4th position within each PMI index subset, the information for the representative PMI index representing each PMI index subset can be determined as 4.

[0145] According to one embodiment, the terminal can estimate the channel state for each representative PMI index based on information regarding the representative PMI index. For example, the terminal can perform an estimation of the channel state for the PMI beam corresponding to each representative PMI index. For example, in FIG. 9, the terminal can perform a CSI calculation for the PMI beam corresponding to the representative PMI indices (901, 911, 921, 931).

[0146] According to one embodiment, the terminal may select Q PMI index subsets based on Q representative PMI indices having an optimal channel state among the representative PMI indices. For example, referring to FIG. 9, the terminal may select the first PMI index subset (910) containing the representative PMI index (911) having an optimal channel state among the representative PMI indices (901, 911, 921, 931) as the PMI index subset (910) to perform PMI search.

[0147] According to one embodiment, the terminal can perform CSI calculations for channel estimation for at least one PMI index within a selected PMI index subset (910). For example, if the terminal selects the first PMI index subset (910) as the PMI index subset to perform PMI search, the terminal can perform channel estimation for PMI beams corresponding to PMI indices within the first PMI index subset (910). For example, referring to FIGS. 9 and FIGS. 10 together, the terminal can perform CSI calculations for PMI beams corresponding to PMI indices 8 through 15 within the first PMI index subset (901). As a result, the number of PMI beams for which the terminal needs to perform CSI calculations can be reduced.

[0148] According to one embodiment, information regarding a plurality of PMI index subsets can be determined by a base station. For example, the base station may determine the number of PMI index subsets constituting the total PMI indices, a representative PMI index of each PMI index subset, and the location of the representative PMI index.

[0149] According to one embodiment, a base station may transmit information regarding multiple PMI index subsets to a terminal via RRC signaling. The terminal may receive information regarding multiple PMI index subsets from the base station via RRC signaling.

[0150] FIG. 11 illustrates an example of identifying reduced PMI indices based on information regarding the patterns of some of the PMI indices among a plurality of PMI indices included in a PMI index subset according to one embodiment of the present disclosure.

[0151] According to one embodiment, reduced PMI indices may be set for each PMI index subset. That is, information regarding multiple PMI index subsets may include information for a terminal to select some of the PMI indices among the multiple PMI indices included in the selected PMI index subset.

[0152] According to one embodiment, information for selecting some of the PMI indices among a plurality of PMI indices included in a selected PMI index subset may include information indicating reduced PMI indices (e.g., PMI index value) or information regarding the pattern of reduced PMI indices within the PMI index subset. Here, 'information regarding the pattern of reduced PMI indices within the PMI index subset' may be understood in the same way as information regarding the pattern of some of the PMI indices among a plurality of PMI indices described with reference to FIG. 8. For example, information regarding the pattern of reduced PMI indices within the PMI index subset may include information regarding the index value at which a PMI search is started for the terminal within the PMI index subsets selected by the terminal (start PMI index), information regarding the difference in index values ​​between a specific PMI index that is the target of the PMI search and the next PMI index that is the target of the PMI search (step size), and information regarding the number of PMI indices that are the target of the PMI search (nrofIndices).

[0153] According to one embodiment, a base station may transmit information to a terminal for selecting some of the PMI indices among a plurality of PMI indices included in a selected PMI index subset. For example, the base station may transmit RRC signaling to the terminal that includes a message such as [Table 5] or [Table 6].

[0154]

[0155]

[0156] Referring to [Table 5] and [Table 6], the base station may transmit to the terminal, through the CSI-ReportConfig configuration information message or CodebookConfig configuration information message within the RRC signaling, information instructing to start PMI search from the first PMI index for each subset (start PMI index per subset = 0), information instructing to perform PMI search at intervals of 3 PMI indices (step size = 3), and information instructing to perform PMI search for 3 PMI indices (nrofIndices = 3). Referring to FIG. 11, when the terminal selects Q PMI index subsets (1100, 1120) including representative PMI indices 3 and 19 based on the estimation result of channel state among four PMI index subsets, the terminal can perform CSI calculations for PMI beams corresponding to PMI indices with PMI index values ​​of 0, 3, 6, 16, 19, and 22 among each selected PMI index subset (1100, 1120).

[0157] FIG. 12 illustrates examples of reduced PMI indices identified based on information regarding the mapping relationship between a plurality of PMI index subsets and a plurality of downlink (DL) signals according to one embodiment of the present disclosure.

[0158] Referring to FIG. 9, the downlink signal may include a synchronization signal block (SSB). The mapping relationship between a plurality of PMI index subsets and a plurality of downlink signals can be determined by a base station. For example, the base station may map each PMI index subset to correspond to the order of the SSB index. For example, the base station may map PMI index subset 0 to SSB 0, PMI index subset 1 to SSB 1, PMI index subset 2 to SSB 2, and PMI index subset 3 to SSB 3, respectively. For example, the base station may map an SSB having a direction relatively similar to the PMI beams corresponding to the PMI index subset to each PMI index subset.

[0159] According to one embodiment, the terminal may select some of the PMI index subsets based on information regarding the mapping relationship between a plurality of PMI index subsets and a plurality of downlink signals. For example, the terminal may select PMI index subsets corresponding to some SSBs with relatively good channel conditions based on channel condition estimation for the SSBs. For example, referring to FIG. 12, the terminal may select PMI index subset 0 (1200) corresponding to SSB 0 with the highest RSRP and PMI index subset 1 (1210) corresponding to SSB 1 among PMI index subsets 1 to 4. The terminal may perform PMI search on the selected PMI index subset 0 (1200) and PMI index subset 1 (1210). As a result, the computational complexity performed by the terminal for PMI search in Phase 0 may be reduced. For example, the terminal may not perform CSI calculation for PMI search for the remaining PMI index subsets, excluding the PMI index subsets selected by the terminal. Additionally, the number of replicated layers in Phase 1, as described below, may be reduced. For example, in Phase 1, the base station may not perform PDSCH transmission through the replicated layers for the remaining PMI index subsets, excluding the PMI index subsets selected by the terminal.

[0160] According to one embodiment, a base station may transmit information regarding the mapping relationship between a plurality of PMI index subsets and a plurality of DL RSs to a terminal through RRC signaling. For example, the base station may transmit RRC signaling to the terminal that includes a message such as [Table 7] or [Table 8].

[0161]

[0162]

[0163] Referring to [Table 7] and [Table 8], the base station may provide the terminal with information regarding the mapping relationship between SSB indices and PMI subsets through CSI-ReportConfig configuration information messages or CodebookConfig configuration information messages within RRC signaling. Additionally, the base station may provide the terminal with information regarding the number of PMI index subsets to search for (nrofSubsetsToSearch). For example, if nrofSubsetsToSearch = 2, the terminal may perform channel state estimation for PMI index subsets corresponding to the two SSBs with the highest reference signals received power (RSRP). Additionally, the base station may provide the terminal with information instructing it to perform channel estimation for some of the PMI indices included in each PMI index subset. For example, the base station may provide the terminal with information regarding the pattern of reduced PMI indices within each PMI index subset.

[0164] Hereinafter, with reference to FIGS. 13 to 28, the operation of the terminal and base station in Phase 1 will be described.

[0165] FIG. 13 illustrates an example in which a terminal according to one embodiment of the present disclosure selects at least one PMI beam among a plurality of PMI beams based on channel estimation for PDSCH. The operation of the terminal and base station described with reference to FIG. 13 may correspond to the operation of the terminal and base station in Phase 1 of FIG. 5 and FIG. 6.

[0166] According to one embodiment, a base station may transmit PDSCH through a plurality of layers using a plurality of beams in phase 1. The plurality of beams may include a beam corresponding to a PMI index selected in phase 0. Additionally, the plurality of beams may include at least one beam for a PDSCH transmitted through at least one replicated layer. The replicated layer may include a layer created by replicating a layer to which a beam corresponding to the PMI index selected in phase 0 is applied. Furthermore, replicating a layer may refer to an operation of creating a layer having the same data as a specific layer. For example, data mapped to the first layer In this case, the base station has at least one second layer identical to the data mapped to the first layer. identical to Layer replication that maps can be performed. For example, a base station can perform layer replication according to Equation 1 below. For example, in FIG. 13, the layers to which Beam 0, Beam 1, Beam 3, and Beam 4 are applied may contain the same data as the layer to which Beam 2 is applied. Data contained within the PDSCH transmitted through the second layer is data included in the PDSCH transmitted through the first layer. It can be the same as.

[0167] Hereinafter, in the present disclosure, a layer to which a beam corresponding to a PMI index selected in phase 0 is applied may be referred to as a 'first layer,' and at least one layer created by duplicating the first layer may be referred to as 'at least one second layer.' Additionally, a beam applied to the first layer may be referred to as a 'first beam,' and a beam applied to at least one second layer may be referred to as a 'at least one second beam.'

[0168] According to one embodiment, a terminal may select at least one beam among a plurality of beams applied to a plurality of layers from a base station based on channel estimation based on DMRS. The at least one beam selected by the terminal may include a beam having a relatively good channel state estimation result among the plurality of beams. For example, referring to FIG. 13, the terminal may select a beam (Beam 3) corresponding to PMI index 3 among a plurality of beams including a first beam (Beam 2) and at least one second beam (Beam 0, Beam 1, Beam 3, Beam 4). The terminal may report information regarding PMI index 3 or the selected beam (Beam 3) to the base station.

[0169] FIG. 14 illustrates an example in which a base station according to one embodiment of the present disclosure transmits PDSCH to a terminal through a plurality of beams.

[0170] According to one embodiment, a base station may determine beams to be applied to a PDSCH transmitted through a plurality of layers based on a PMI beam reported by a terminal in phase 0. For example, when a base station performs 1-layer based PDSCH (1-layer PDSCH) transmission, the base station may determine a beam to be applied to the first layer as a first beam corresponding to the PMI index reported by the terminal in phase 0. In the present disclosure, the first layer may be referred to as a reference layer or an original layer. Additionally, the base station may determine a beam to be applied to a second layer created by duplicating the first layer as a beam different from the first beam. For example, the base station may select a beam to be applied to the second layer from among the remaining beams, excluding the first beam, among the beams corresponding to the PMI index included in the codebook. For example, the base station may select, among the beams corresponding to the PMI index included in the codebook, a beam having a directional component relatively similar to the first beam as the beam to be applied to the second layer, but is not limited thereto. For example, the base station may select a beam not included in the codebook as the beam to be applied to the second layer. Of course, the method by which the base station selects multiple PMI beams is not limited to the above examples, and the base station may select PMI beams that are not adjacent to the selected PMI beam, or may select a beam other than the PMI beam selected in phase 0. For example, the base station may select a beam that forms a predetermined distance or a predetermined angle with the selected PMI beam. For example, the beam to be applied to the second layer may include a beam determined for MU-MIMO (multi-user multiple input multiple output) transmission.

[0171] According to one embodiment, a base station may allocate DM-RS ports for a plurality of layers. For example, the base station may allocate a DM-RS port 1000 for PDSCH transmission through a first layer and a DMRS port 1001 for PDSCH transmission through a second layer. The base station may transmit PDSCH through a first layer to which a first beam (Beam 2) is applied through DMRS port 1000 to a terminal, and transmit PDSCH through a second layer to which a second beam (Beam 0), which is different from the first beam in phase 0, is applied through DMRS port 1001.

[0172] According to one embodiment, at least one second beam corresponding to at least one second layer can be divided into specific time resource units and transmitted together with the first beam. For example, referring to FIG. 9, when at least one second beam corresponds to beam 0, beam 1, beam 3, and beam 4, the base station can perform PDSCH transmission by applying beam 2 and beam 0 to slot 0, beam 2 and beam 1 to slot 1, beam 2 and beam 3 to slot 2, and beam 2 and beam 4 to slot 3.

[0173] FIG. 15 illustrates a PDSCH transmission procedure of a base station according to one embodiment of the present disclosure.

[0174] According to one embodiment, a base station may perform a series of operations including modulation, layer mapping, and antenna port mapping for PDSCH transmission.

[0175] Modulation step 1510 may refer to an operation that transforms the characteristics of the signal for PDSCH. The modulated signal is, It can be expressed as follows. The number of modulation symbols per layer is It can be expressed as, and in the case of 1-layer based PDSCH transmission, It can be defined as.

[0176] The layer mapping step 1520 may refer to the operation of mapping a modulated signal to a layer. For example, in the layer mapping step, the base station may map each layer to a radio resource element. The data of the mapped layer is, It can be defined as follows.

[0177] The antenna port mapping step 1530 may refer to the operation of mapping to logical antenna ports. For example, referring to FIG. 15, one layer is, It can be mapped to multiple (P) ports (P-ports) through matrix operations such as the one above. Here can mean the precoding matrix of PX 1.

[0178] FIG. 16 illustrates a partial flowchart of a PDSCH transmission procedure of a base station including an operation to duplicate a layer according to one embodiment of the present disclosure.

[0179] Referring to FIG. 16, the base station may perform an operation to duplicate a layer as part of the PDSCH transmission procedure. The operation of the base station to duplicate a layer may include steps 1610 and 1620 of FIG. 16.

[0180] According to one embodiment, after performing the modulation and layer mapping procedure of FIG. 15, the base station may determine whether to perform layer replication in step 1610. The base station may determine whether to perform layer replication based on preset conditions when performing PDSCH. For example, preset conditions for determining whether to perform layer replication may include that a first report by a terminal in Phase 0 is received to perform beam management using PMI reporting.

[0181] According to one embodiment, the base station may perform a layer copy in step 1620, as determined in step 1610 to perform a layer copy. The base station may determine the number of at least second layers to be copied (number of copied layers, Ncl). For example, the number of at least second layers to be copied may be determined based on information pre-set in the base station. The base station may create at least one second layer in a predetermined number by copying data (or signal) mapped to the first layer (or original layer). For example, data mapped to the first layer In this case, the base station, in step 1620, has at least one second layer identical to the data mapped to the first layer. identical to It can be mapped. For example, a base station can perform layer replication according to Equation 1 below.

[0182] [Mathematical Formula 1]

[0183]

[0184]

[0185] In mathematical formula 1, , corresponds to the first layer or the original layer, and can correspond to a replicated second layer. Here, i represents the index of the layer, and in the case of a 1-layer PDSCH transmission, i can be defined as 0. As a result, the data contained in at least one second layer can be completely identical to the data contained in the first layer.

[0186] According to one embodiment, the base station may perform antenna port mapping for each layer after the layer replication step 1620. That is, the base station may perform precoding for the data of the layer. For example, referring to FIG. 16, the number of ports is N, and the precoding matrix is In the case of (Nx2), the base station is class The multiplication operation of (i.e., Two layer signals can be mapped to N antenna ports through ).

[0187] FIG. 17 illustrates an example in which a terminal according to one embodiment of the present disclosure receives PDSCH through a plurality of layers including a replicated layer.

[0188] Referring to FIG. 17, a base station can perform PDSCH transmission through a first beam (1700) and a second beam (1710) different from the first beam (1700). The first beam (1700) and the second beam (1710) of FIG. 17 may correspond to Beam 2 and Beam 0 of FIG. 14, respectively. That is, in the example of FIG. 17, the base station performs 1-layer based PDSCH transmission, and the original layer or reference layer corresponds to beam 0 The duplicated layer corresponds to beam 1 This can be applied. Referring to FIG. 17, the original layer to which the first beam (1700) is applied may be referred to as the 'first layer', and the duplicated layer to which the second beam (1710) is applied may be referred to as the 'second layer'.

[0189] According to one embodiment, the terminal can measure the beam gain applied to each layer through a DMRS port for each layer. For example, the channel between the base station and the terminal In this case, the terminal, based on DM-RS reception through DM-RS port 1000 and port 1001, has a beam gain for the DM-RS port 1000 corresponding to the first layer ( )second As, the beam gain for DM-RS port 1001 corresponding to the second layer ( )second It can be calculated as.

[0190] FIG. 18 illustrates a flowchart of an operation in which a terminal according to one embodiment of the present disclosure performs beam gain computation and demodulation based on DMRS channel estimation. FIG. 18 can be understood as the case where the terminal receives the PDSCH transmitted by the base station in the example of FIG. 17.

[0191] According to one embodiment, the terminal can estimate the channel for each DMRS port through DMRS channel estimation in step 1810. For example, the terminal DMRS port channel for the first layer DMRS port channels for the second layer It can be estimated.

[0192] According to one embodiment, the terminal can identify, at step 1820, whether at least one of the received layers is a copied layer. For example, the terminal can identify that the second layer is a copied layer based on a copied layer indicator for identifying a copied layer received from a base station. For example, the terminal can identify that two layers transmitted to different multiple beams are layers containing the same data, rather than layers transmitted via a general 2-layer based PDSCH.

[0193] According to one embodiment, the terminal may, based on identifying that there is no duplicated layer among the layers received in step 1820, combine each DMRS port channel in step 1830 and then perform a demodulation operation on the combined DMRS port channel. Step 1830 may include step 1831 of combining each DMRS port channel and step 1833 of performing a demodulation operation.

[0194] According to one embodiment, the terminal can combine each DMRS port channel in step 1831. The signal combined by the terminal is It can be represented as. Here, corresponds to a combined DMRS port channel for the first layer for 1-layer PDSCH demodulation and a DMRS port channel for the second layer replicated from the first layer, where n may mean noise.

[0195] According to one embodiment, the terminal can perform a demodulation operation for the combined DMRS port channel in step 1833. When performing a demodulation operation for the combined DMRS port channel, the deterioration of demodulation performance caused by the layers demodulating each channel signal transmitted through the two DMRS ports can be prevented.

[0196] According to one embodiment, the terminal has an estimated DMRS port channel and Based on this, the terminal can perform demodulation for each layer individually in step 1833, based on identifying that there are no duplicated layers among the layers received in step 1820.

[0197] According to one embodiment, the terminal can determine the quality of the beam applied to the second layer based on the calculation of the beam gain in step 1840. Step 1840 may include step 1841 of calculating the beam gain and step 1843 of comparing the calculated beam gain with the beam gain of the reference layer.

[0198] According to one embodiment, the terminal can calculate the beam gains of the received layers in step 1841. The operation of the terminal calculating the beam gains of the received layers in step 1841 may correspond to the operation of calculating beam gains described with reference to FIG. 17. For example, the terminal may determine the power of the DMRS port channel for each layer as a metric of the beam gain. The terminal determines the beam gain applied to the first layer The beam gain applied to the second layer created by duplicating the first layer It can be measured as.

[0199] According to one embodiment, the terminal, in step 1843, has a beam gain of the second layer and a reference layer beam gain, ) can be compared. To this end, the terminal may receive a DMRS port index for a reference layer beam from the base station in advance. Here, the reference layer beam may be set to a beam applied to the first layer, but is not limited thereto. For example, the reference layer beam may be set to a specific threshold value in advance. As a result of comparing the beam gains, the terminal can compare the beam gain of the second layer This reference layer beam gain If it is larger, the beam of the second layer can be determined as a candidate beam to be reported to the base station.

[0200] Hereinafter, with reference to FIGS. 19 to 28, the second configuration information transmitted by the base station to the terminal described with reference to step 613 of FIG. 6 will be described in detail. According to one embodiment, the second configuration information, which is information for identifying at least one second layer, may include information regarding the time resources and frequency resources of the PDSCH transmitted through at least one second layer. FIGS. 19 to 23 illustrate examples of information regarding the time resources or frequency resources of the PDSCH transmitted through a replicated layer according to various embodiments of the present disclosure.

[0201] FIG. 19 illustrates an example of information regarding a time resource of a PDSCH to which a replicated layer is transmitted according to one embodiment of the present disclosure.

[0202] According to one embodiment, a base station may transmit information regarding the time resources of a PDSCH transmitted through a replicated layer to a terminal. For example, the base station may transmit information regarding the time resources of a PDSCH transmitted through a replicated layer to a terminal via DCI. The information regarding the time resources of a PDSCH transmitted through a replicated layer may include information indicating whether a PDSCH is transmitted through the replicated layer in the time resources of a PDSCH scheduled via DCI.

[0203] Referring to FIG. 19, the base station may transmit information to the terminal indicating whether a PDSCH through a replicated layer in slot n (1920) is transmitted via a DCI transmitted through slot 0 (1910). Slot n (1920) may represent a time resource for a PDSCH scheduled via a DCI included in slot 0 (1910). The information indicating whether a PDSCH through a replicated layer in slot n (1920) is transmitted may be expressed as Copied layer indicator = {0 (Copied layer off), 1 (Copied layer on)}. If Copied layer indicator = 1, it may indicate that a PDSCH through a replicated layer in slot n (1920) scheduled by the DCI is transmitted. If Copied layer indicator = 0, it may indicate that a replicated layer in slot n (1920) scheduled by the DCI is not transmitted. The terminal can determine whether a PDSCH is transmitted through a replicated layer for slot n (1920) scheduled by DCI based on information received from the base station.

[0204] FIG. 20 illustrates an example of information regarding time resources of a PDSCH that becomes a PDSCH through a replicated layer according to one embodiment of the present disclosure, and information indicating frequency resources of a PDSCH that is transmitted through a replicated layer. The information regarding time resources of a PDSCH that is transmitted through a replicated layer in FIG. 20 may correspond to the information regarding time resources of a PDSCH that is transmitted through a replicated layer described with reference to FIG. 19. For example, with reference to FIG. 20, a base station may transmit information to a terminal indicating whether a PDSCH through a replicated layer is transmitted in slot n (2020) through a DCI transmitted through slot 0 (2010).

[0205] According to one embodiment, a base station may transmit information regarding frequency resources of a PDSCH transmitted through a replicated layer to a terminal. For example, the base station may transmit information regarding frequency resources of a PDSCH transmitted through a replicated layer to a terminal via DCI. The information regarding frequency resources of a PDSCH transmitted through a replicated layer may include information indicating whether a PDSCH is transmitted through the replicated layer at frequency resources corresponding to a specific time resource of a PDSCH scheduled by DCI.

[0206] Referring to FIG. 20, a base station may transmit to a terminal information indicating whether a duplicated layer is transmitted in slot n (2020) scheduled by DCI, and information indicating whether a PDSCH is transmitted through a duplicated layer for frequency resources (2030) corresponding to slot n (2020) scheduled by DCI. The information indicating whether a PDSCH is transmitted through a duplicated layer in frequency resources (2030) corresponding to slot n (2020) scheduled by DCI may include information regarding whether a PDSCH through at least one second layer is transmitted only in some of the frequency resources (or in all of the frequency resources) corresponding to slot n (2020), or information indicating which of the odd-numbered frequency resources and even-numbered frequency resources a PDSCH is transmitted through a duplicated layer. For example, information indicating which frequency resources, among even-numbered frequency resources (even RB index) and odd-numbered frequency resources (odd RB index), transmit PDSCH through the replicated layer can be expressed as Copied layer RBs = {0 (even), 1 (odd)}, with reference to FIG. 20. For example, when Copied layer RBs = 0, it may be indicated that PDSCH through the replicated layer is transmitted only on even-numbered frequency resources. In this case, odd-numbered frequency resources may be used only for transmitting PDSCH through the original layer. For example, when copied layer RBs = 1, PDSCH through the replicated layer may be transmitted only on odd-numbered frequency resources, and even-numbered frequency resources may be used only for transmitting PDSCH through the original layer.

[0207] FIG. 21 illustrates an example of bitmap information regarding time resources of a PDSCH transmitted through a replicated layer and frequency resources transmitted through a replicated layer according to one embodiment of the present disclosure. The information regarding time resources of a PDSCH transmitted through a replicated layer in FIG. 21 may correspond to the information regarding time resources of a PDSCH transmitted through a replicated layer described with reference to FIG. 19. For example, with reference to FIG. 21, a base station may transmit information to a terminal indicating whether a PDSCH transmitted through a replicated layer in slot n (2120) is transmitted through a DCI transmitted through slot 0 (2110).

[0208] According to one embodiment, a base station may provide information to a terminal regarding frequency resources of a PDSCH transmitted through a replicated layer. For example, information indicating whether a PDSCH is transmitted through a replicated layer for frequency resources (2130) corresponding to a specific time resource (2120) of a PDSCH scheduled by DCI may include bitmap information representing frequency resources (RBs) or frequency resource groups (RBGs) (2140) of a PDSCH transmitted through a replicated layer. For example, the bitmap information may include a frequency-domain resource allocation (FDRA) bitmap for the PDSCH. For example, if the resource allocation (RA) type of the FDRA is type 0, the base station may be indicated, through bitmap information such as FDRA for copied layers = 10101000100010001, that PDSCH is transmitted through layers copied from RBGs (2140) corresponding to RBG indices marked with 1.

[0209] FIG. 22 illustrates an example of information regarding the time resources of a PDSCH transmitted through a replicated layer according to one embodiment of the present disclosure, and information regarding the start positions and intervals of the frequency resources of a PDSCH transmitted through a replicated layer. The information regarding the time resources of a PDSCH transmitted through a replicated layer in FIG. 22 may correspond to the information regarding the time resources of a PDSCH transmitted through a replicated layer described with reference to FIG. 19. For example, referring to FIG. 22, a base station may transmit information to a terminal indicating whether a PDSCH through a replicated layer in slot n (2220) is transmitted through a DCI transmitted through slot 0 (2210).

[0210] According to one embodiment, a base station may provide information to a terminal regarding frequency resources of a PDSCH transmitted through a replicated layer. For example, information indicating whether a PDSCH is transmitted through a replicated layer in slot n (2220) may include information regarding the starting position and interval of frequency resources or frequency resource groups (2240) of the PDSCH transmitted through the replicated layer. For example, referring to FIG. 22, information regarding the starting position of frequency resources or frequency resource groups (2240) of the PDSCH transmitted through the replicated layer may include information indicating the frequency resource or frequency resource group where the transmission of the PDSCH through the replicated layer begins. For example, start RBG index = 0 may indicate that the transmission of the PDSCH through the replicated layer begins at RBG 0 among the RBGs. Information regarding the interval of frequency resources or frequency resource groups (2240) of PDSCH transmitted through the replicated layer may include information indicating the interval of frequency resources transmitted through the replicated layer. For example, RBG step size = 3 may indicate that the RBG interval of PDSCH transmitted through the replicated layer is 3 RBG. That is, transmission of PDSCH through the replicated layer starts from RBG 0, and the RBG index to which PDSCH is transmitted through the replicated layer next is indicated as 3, 6, ...

[0211] FIG. 23 illustrates an example of information regarding the time resources of a PDSCH transmitted through a replicated layer according to one embodiment of the present disclosure, and information regarding the starting position and length of the frequency resources of a PDSCH transmitted through a replicated layer. The information regarding the time resources of a PDSCH transmitted through a replicated layer in FIG. 23 may correspond to the information regarding the time resources of a PDSCH transmitted through a replicated layer described with reference to FIG. 19. For example, referring to FIG. 22, a base station may transmit information to a terminal indicating whether a PDSCH transmitted through a replicated layer in slot n (2320) is transmitted through a DCI transmitted through slot 0 (2310).

[0212] According to one embodiment, the base station may provide information to the terminal regarding the frequency resources of the PDSCH transmitted through the replicated layer. For example, information indicating whether the PDSCH is transmitted through the replicated layer in slot n (2320) may include information regarding the starting position and length of the frequency resources or groups of frequency resources of the PDSCH transmitted through the replicated layer.

[0213] For example, a base station may transmit to a terminal, via DCI, information regarding the starting position of RBs or RBGs of a PDSCH transmitted through a replicated layer (start RB or start RBG), and information regarding the number of consecutive RBs or RBGs of a PDSCH transmitted through a replicated layer (RB length or RBG length). For example, a base station may transmit to a terminal via DCI a resource indication value (RIV), which is an FDRA indicator used in conventional RA type 1. For example, referring to FIG. 23, a base station may indicate to a terminal via DCI that a PDSCH through a replicated layer is transmitted from a total of 13 consecutive RBs from RB 127 to RB 139 by indicating RIV = 37000, or start RB = 127, and RB length = 13.

[0214] FIGS. 24 and 25 illustrate specific examples of information indicating a duplicated layer or information indicating an original layer among information for identifying a duplicated layer included in the second setting information according to various embodiments of the present disclosure.

[0215] FIG. 24 illustrates an example of information indicating a replicated layer according to one embodiment of the present disclosure.

[0216] According to one embodiment, information for identifying a replicated layer within the second configuration information may include information indicating the replicated layer. For example, the information indicating the replicated layer may include DMRS port index information for the replicated layer and ID information of the replicated layer.

[0217] According to one embodiment, a base station may transmit DMRS port index information for a layer copied via DCI and ID information of the copied layer to a terminal. For example, if the copied layer is assigned to DMRS port 1001, the base station may transmit the DMRS port index information assigned to the copied layer to the terminal in the form of DM-RS port index set = {1001}. Additionally, the base station may transmit the ID information of the copied layer to the terminal in the form of copied layer ID 2 = {1001}. In this case, the terminal can identify, based on the information received from the base station, that the ID of the copied layer transmitted from the resource scheduled by the DCI is 2 and that the copied layer is assigned to DM-RS port index 1001.

[0218] According to one embodiment, the ID of the replicated layer may be used to report to the base station the replicated layer to which the optimal beam selected by the terminal is applied when the terminal selects a beam corresponding to any one of the layers replicated with the optimal beam.

[0219] FIG. 25 illustrates an example of information indicating an original layer according to one embodiment of the present disclosure.

[0220] According to one embodiment, information for identifying a duplicated layer within the second setting information may include information indicating an original layer. For example, information indicating a duplicated layer may include DMRS port index information corresponding to the original layer. Here, the original layer may be referred to as a term designating a first layer that is not a duplicated layer, as described above.

[0221] According to one embodiment, a base station may transmit DMRS port index information corresponding to the original layer to a terminal via DCI. For example, referring to FIG. 25, when DM-RS ports 1001, 1002, and 1003 are assigned to the replicated layers, the base station may transmit information regarding DMRS port 1000 assigned to the original layer to the terminal, thereby indicating to the terminal that the remaining DM-RS ports (DMRS port index set = {1001, 1002, 1003}) excluding DMRS port 1000 are DM-RS ports for the replicated layers. In addition, in this case, the base station may transmit ID information of the replicated layers to the terminal by assigning ID 2 to the replicated layer corresponding to DMRS port 1001, assigning ID 3 to the replicated layer corresponding to DMRS port 1002, and assigning ID 4 to the replicated layer corresponding to DMRS port 1002.

[0222] FIG. 26 illustrates a method in which a terminal according to one embodiment of the present disclosure reports at least one beam selected based on channel estimation among a plurality of beams to a base station.

[0223] According to one embodiment, in phase 1, the terminal may select at least one beam among a plurality of beams received from the base station through channel estimation based on DMRS and transmit a second report to the base station containing information regarding the selected at least one beam. The example of FIG. 26 may be an example of the operation of the terminal and the base station in phase 1 when the terminal transmits a CSI report obtained based on channel estimation using CSR-RS in phase 0 to the base station, and the base station sets a PMI beam corresponding to the PMI included in the terminal's CSI report as a reference beam.

[0224] According to one embodiment, a base station can perform PDSCH transmission through replicated layers in phase 1. For example, if the IDs of the replicated layers are 0, 1, 2, and 3, the base station can perform PDSCH transmission through replicated layer 0 in slot 5, replicated layer 1 in slot 6, replicated layer 2 in slot 7, and replicated layer 3 in slot 8. In this case, the base station can transmit PDSCH through the original layer to which the reference beam is applied and one replicated layer in each slot.

[0225] According to one embodiment, the terminal can compare a reference beam with a plurality of beams applied to replicated layers received from the base station via PDSCH, based on the estimation of the DMRS port channel. For example, the terminal compares the CQI for beams (f0, f1, f2, f3) applied to replicated layers 0, 1, 2, and 3. i and reference beam(f ref CQI for ) ref You can compare.

[0226] According to one embodiment, the terminal includes a candidate beam set (candidate beam set) comprising at least one beam to be reported to the base station based on the result of comparing a plurality of beams applied to the replicated layers with a reference beam, ) can be determined. For example, the CQI for the beams (f0, f2) corresponding to replicated layer 0 and replicated layer 2, respectively, is CQI ref If it is greater than or equal to a preset threshold value (Δ0), the candidate beam set ( ) can be determined to be 0 or 2.

[0227] According to one embodiment, the terminal has a determined set of candidate beams ( Among at least one beam included in ), the optimal beam can be selected. For example, the terminal, a determined set of candidate beams ( Included in ) the beam with the largest beam gain among at least one beam ( ) can be selected as the optimal beam. Subsequently, the terminal can transmit a second report containing information about the selected optimal beam to the base station.

[0228] According to one embodiment, a base station may transmit to a terminal information for the terminal to select at least one beam among a plurality of beams, or information for the terminal to report at least one beam selected by the terminal to the base station via RRC signaling or DCI / MAC-CE. The information for the terminal to select at least one beam among a plurality of beams, or information for the terminal to report at least one beam selected by the terminal to the base station, may be included in the second setting information described with reference to step 613 of FIG. 6.

[0229] According to one embodiment, information for a terminal to select at least one beam among a plurality of beams may include information regarding criteria for selecting at least one beam based on at least one metric representing the quality of a wireless channel. Such information may be referred to as information regarding a beam selection criterion, which indicates which beam information the terminal will report to the base station. For example, information regarding a beam selection criterion may include information regarding determining the wireless channel quality of a beam applied to a replicated layer based on a certain quality metric, and determining a set of candidate beams that can be reported to the base station based on a certain criterion.

[0230] According to one embodiment, a quality indicator for wireless channel quality for a beam may include at least one of SNR, SINR, RSRP, or CQI. However, the quality indicator for wireless channel quality for a beam is not limited thereto, and various quality indicators for measuring the quality of a wireless channel may be used.

[0231] According to one embodiment, information regarding criteria for determining a candidate beam set to be reported to a base station may include information instructing that a candidate beam set be determined based on either a result of a relative comparison with the quality of a reference beam or a result of a comparison with a preset threshold value. For example, beam selection rule = 0 may indicate determining a candidate beam set based on whether the wireless channel quality of a specific beam is greater than or equal to a preset difference value (Δ0) by comparing the wireless channel quality of a specific beam with the wireless channel quality of a reference beam. In this case, the preset difference value (Δ0) may refer to the difference in channel quality values ​​expressed by any one of the aforementioned wireless channel quality indicators (e.g., SNR, SINR, RSRP, CQI). For example, beam selection rule = 1 may indicate determining a candidate beam set based on whether the wireless channel quality of a specific beam applied to a replicated layer is greater than a specific threshold value (Δ1). A specific threshold value (Δ1) may mean a value determined by a base station, expressed as any one of the aforementioned wireless channel quality indicators (e.g., SNR, SINR, RSRP, CQI).

[0232] According to one embodiment, information for reporting at least one beam selected by a terminal to a base station may include information regarding what information to report to the base station regarding the at least one selected beam (i.e., report resources). This information may be referred to as information regarding the report quantity of a second report.

[0233] For example, information regarding the reporting amount of the second report may include information regarding the number of at least one beam that the terminal reports to the base station. For example, information regarding the reporting amount of the second report may instruct to report any one of the following: an index of a layer corresponding to at least one beam selected by the terminal, a radio quality value measured by the terminal for at least one beam selected, a slot index indicating a layer corresponding to at least one beam selected, or an ID of a layer corresponding to at least one beam selected.

[0234] According to one embodiment, the base station may instruct the terminal to report the difference in relative quality indicator index of the beam applied to the replicated layer with respect to the reference beam (e.g., the PMI beam reported by the terminal in phase 0). For example, the base station may instruct the terminal to report the difference between the CQI index of the reference beam (e.g., the PMI beam reported by the terminal in phase 0) and the relative CQI index of the beam applied to the replicated layer, rather than the CQI index value. For example, the terminal may report ΔCQI = 5 to the base station when the CQI index corresponding to the reference beam (e.g., the PMI beam reported by the terminal in phase 0) is 10 and the CQI index corresponding to the beam applied to the replicated layer is 15. This may reduce the overhead for the terminal's second report.

[0235] According to one embodiment, a base station may instruct a terminal to transmit a second report including information indicating whether the terminal prefers the beam applied to the original layer. For example, if the beam of the original layer (i.e., the reference beam) is selected as the optimal beam as a result of the terminal's channel estimation, the base station may instruct the terminal to transmit a second report including information indicating that the terminal prefers the original layer beam over the beams corresponding to the replicated layers. For example, if original layer preference = 1, it may mean that the terminal prefers the original layer beam over the beams corresponding to the replicated layers, and if original layer preference = 0, it may mean that the terminal does not prefer the original layer beam.

[0236] FIGS. 27 and 28 illustrate a flowchart of signal transmission between a terminal and a base station for performing beam management based on the transmission of a PDSCH through a replicated layer according to one embodiment of the present disclosure.

[0237] FIG. 27 illustrates a flowchart of signal transmission between a terminal and a base station in which the base station instructs the terminal to determine a set of candidate beams based on whether the wireless channel quality of a specific beam is greater than or equal to a preset difference value (Δ0) than the wireless channel quality of a reference beam.

[0238] Referring to FIG. 27, in step 2710, the base station may transmit to the terminal, via RRC signaling, information for the terminal to select at least one beam among a plurality of beams, and information for the terminal to report the selected at least one beam to the base station (copied layer-based beam training information). For example, via RRC signaling, the base station may instruct the terminal to determine a candidate beam set based on whether the radio channel quality of a specific beam is greater than or equal to a preset difference value (Δ0) than the radio channel quality of a reference beam (beam selection rule = 0). Additionally, via RRC signaling, the base station may instruct the terminal to determine a candidate beam set using CQI as a quality metric (beam quality metric: CQI). Additionally, the base station may transmit to the terminal a preset difference value (Δ0) for comparing the radio channel quality of the beam applied to the replicated layer with the radio channel quality of the reference beam. Additionally, the base station may instruct the terminal to report information regarding beams corresponding to two replicated layers having high CQI values ​​via RRC signaling (Number of reported best copied layer beams = 2). Additionally, the base station may instruct the terminal to report the index of the selected beam and the difference in CQI via RRC signaling (Report quantity = {Best beam index set, CQI difference}).

[0239] According to one embodiment, in step 2720, the base station may transmit to the terminal information for the terminal to select at least one beam among a plurality of beams transmitted via RRC signaling, and information for the terminal to report at least one beam selected by the terminal to the base station, in addition to information for identifying a duplicated layer by slot via DCI. The information for identifying a duplicated layer by slot transmitted via DCI may correspond to information indicating a duplicated layer described with reference to FIG. 24 or information indicating an original layer described with reference to FIG. 25.

[0240] According to one embodiment, the terminal may receive PDSCH through beams applied to layers copied from the base station at step 2730. At step 2740, the terminal may transmit a second report (report on copied layer beams) to the base station. Referring to FIG. 27, the second report may include an index set for the optimal beam selected by the terminal and information regarding CQI differences between the reference beam and the selected beam.

[0241] FIG. 28 illustrates a flowchart of signal transmission between a terminal and a base station in the case where the base station instructs the terminal to determine a set of candidate beams based on whether the wireless channel quality of a specific beam applied to a replicated layer is greater than a specific threshold value (Δ1).

[0242] Referring to FIG. 28, in step 2810, the base station may, through RRC signaling, instruct the terminal to determine a candidate beam set based on whether the radio channel quality of a specific beam applied to a copied layer is greater than a specific threshold value (Δ1) (beam selection rule = 1). Additionally, the base station may, through RRC signaling, instruct the terminal to determine a candidate beam set using SINR as a quality metric (beam quality metric: SINR). Additionally, the base station may also transmit to the terminal a threshold value (Δ1 = 20) for evaluating the radio channel quality of a reference beam. Additionally, the base station may, through RRC signaling, instruct the terminal to report information regarding a beam corresponding to one copied layer having a high SINR value (Number of reported best copied layer beams = 1). Additionally, the base station may, through RRC signaling, instruct the terminal to report the index and CQI values ​​of the selected beam (Report quantity = {Best beam index set, CQIs}).

[0243] Steps 2820, 2830, and 2840 of FIG. 28 may correspond to steps 2720, 2730, and 2740 of FIG. 27, respectively. However, in the example of FIG. 28, the terminal may transmit a second report containing CQI values ​​(CQIs) to the base station in step 2840, unlike in FIG. 27.

[0244] FIG. 29 is a flowchart of operations performed by a terminal to perform beam management based on channel estimation according to one embodiment of the present disclosure.

[0245] According to one embodiment, at step 2910, the terminal may receive first configuration information from a base station that includes information for identifying some of the PMI beams among a plurality of PMI beams. The operation performed by the terminal at step 2910 may correspond to the operation of the terminal at step 601 of FIG. 6.

[0246] According to one embodiment, the terminal may receive CSI-RS from the base station in step 2920. The operation performed by the terminal in step 2920 may correspond to the operation of the terminal in step 603 of FIG. 6.

[0247] According to one embodiment, the terminal may, at step 2930, transmit a first report to the base station containing information indicating a PMI index. For example, the terminal may transmit a first report to the base station containing information about a PMI beam selected through channel estimation based on CSI-RS among some PMI beams identified based on the first configuration information. The operation performed by the terminal at step 2930 may include the operation of the terminal at steps 605 and 607 of FIG. 6.

[0248] According to one embodiment, in step 2940, the terminal may receive a PDSCH from a base station through a plurality of beams. The operation performed by the terminal in step 2940 may include the operation of the terminal in step 613 of FIG. 6.

[0249] According to one embodiment, in step 2950, ​​the terminal can receive a PDSCH from a base station through a plurality of beams. The operation performed by the terminal in step 2950 may correspond to the operation of the terminal in step 615 of FIG. 6.

[0250] According to one embodiment, in step 2960, the terminal may transmit to the base station a second report containing information about at least one beam selected through channel estimation based on DMRSs corresponding to a plurality of beams. The operation performed by the terminal in step 2960 may include the operation of the terminal in steps 617 and 619 of FIG. 6.

[0251] FIG. 30 is a flowchart of operations performed by a base station to perform beam management based on channel estimation according to one embodiment of the present disclosure.

[0252] According to one embodiment, in step 3010, the base station may transmit to the terminal first configuration information including information for identifying some of the PMI beams among a plurality of PMI beams. The operation performed by the base station in step 3010 may correspond to the operation of the base station in step 601 of FIG. 6.

[0253] According to one embodiment, the base station may transmit CSI-RS to the terminal in step 3020. The operation performed by the base station in step 3020 may correspond to the operation of the base station in step 603 of FIG. 6.

[0254] According to one embodiment, at step 3030, the base station may receive a first report from a terminal containing information indicating a PMI index. For example, the base station may receive a first report from a terminal containing information about a PMI beam selected through channel estimation based on CSI-RS among some PMI beams identified based on first configuration information. The operation performed by the base station at step 3030 may correspond to the operation of the base station at step 607 of FIG. 6.

[0255] According to one embodiment, the base station may, in step 3040, transmit second configuration information for a DMRS-based channel estimation report to the terminal. The operation performed by the base station in step 3040 may include the operation of the base station in steps 611 and 613 of FIG. 6.

[0256] According to one embodiment, the base station may transmit PDSCH to the terminal through a plurality of beams in step 3050. The operation performed by the base station in step 3050 may correspond to the operation of the base station in step 615 of FIG. 6.

[0257] According to one embodiment, in step 3060, the base station may receive a second report from the terminal containing information about at least one beam selected through channel estimation based on DMRSs corresponding to a plurality of beams. The operation performed by the base station in step 3060 may correspond to the operation of the base station in step 619 of FIG. 6.

[0258] Methods according to the claims or embodiments described in the specification of the present disclosure may be implemented in the form of hardware, software, or a combination of hardware and software.

[0259] When 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 within an electronic device. One or more programs include instructions that cause the electronic device to execute methods according to the claims or embodiments described in the specification of this disclosure.

[0260] 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.

[0261] 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.

[0262] 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.

[0263] Additionally, in the present disclosure, terms such as “part,” “module,” etc. may be a hardware component, such as a processor or circuit, and / or a software component executed by a hardware component, such as a processor.

[0264] "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.

[0265] 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.

[0266] 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 first configuration information from a base station, the information for identifying some of the PMI (precoding matrix indicator) beams among a plurality of PMI beams; A step of receiving a CSI (channel state information)-RS (reference signal) from the above base station; A step of transmitting to the base station a first report containing information about a PMI beam selected through channel estimation based on CSI-RS among the portion of PMI beams identified based on the first setting information; A step of receiving second configuration information for a channel estimation report based on a DMRS (demodulation reference signal) from the base station; A step of receiving a PDSCH (physical downlink shared channel) through a plurality of beams from the above base station; and The method includes the step of transmitting to the base station a second report containing information about at least one beam selected through channel estimation based on DMRSs corresponding to the plurality of beams, and A method in which a PDSCH transmitted through a first layer corresponding to a first beam among the plurality of beams and a PDSCH transmitted through a second layer corresponding to at least one second beam among the plurality of beams contain the same data.

2. In Paragraph 1, The above first setting information is received through RRC (radio resource control) signaling, and A method in which information for identifying some of the above PMI beams is received through at least one of a CSI report configuration information (CSI-ReportConfg) message included in the RRC signaling, or a codebook configuration information (CodebookConfig) message including information regarding a precoder corresponding to the plurality of PMIs.

3. In Paragraph 1, A method comprising at least one of the following: information for identifying some of the PMI beams, information indicating some of the PMI beams among some of the plurality of PMI beams, information regarding a pattern for identifying some of the PMI beams among the plurality of PMI beams, or information regarding a plurality of PMI subsets constituting the plurality of PMI beams.

4. In Paragraph 3, The information regarding the plurality of PMI subsets includes information for the terminal to select some of the PMI subsets among the plurality of PMI subsets, and Information for the terminal to select some of the PMI subsets comprises, for each of the plurality of PMI subsets, information for one PMI beam representing each PMI subset, or mapping information of indices of the plurality of PMI subsets and the plurality of downlink signals, wherein the downlink signal includes a synchronization signal block (SSB).

5. In Paragraph 3, A method in which information regarding the plurality of PMI subsets includes information regarding a pattern for identifying some of the PMI beams within the plurality of PMI subsets.

6. In Paragraph 1, The above second setting information includes information for identifying the at least one second layer, and The information for identifying the at least one second layer includes information regarding the time resources and frequency resources of the PDSCH transmitted through the at least one second layer, and information indicating the at least one second layer. A method in which the above second setting information is provided through DCI (downlink control information).

7. In Paragraph 6, The information regarding the time resource of the PDSCH transmitted through the at least one second layer includes information indicating whether the PDSCH is transmitted through the at least one second layer at the time resource of the PDSCH scheduled through the DCI, and A method comprising at least one of the following: information regarding the frequency resources of the PDSCH transmitted through the at least one second layer, wherein the information regarding whether the PDSCH is transmitted through the at least one second layer in some of the frequency resources among all frequency resources corresponding to the time resources; bitmap information representing groups of frequency resources through which the PDSCH is transmitted through the at least one second layer; information regarding the starting position and interval of the frequency resources or groups of frequency resources of the PDSCH transmitted through the at least one second layer; or information regarding the starting position and length of the frequency resources or groups of frequency resources of the PDSCH transmitted through the at least one second layer.

8. In Paragraph 6, A method comprising information indicating at least one second layer, wherein the information includes information on an index of a DMRS port corresponding to the first layer, or information on an index of a DMRS port corresponding to the at least one second layer.

9. In Paragraph 1, A method comprising: information regarding at least one metric representing the quality of a wireless channel for the terminal to select the at least one beam through channel estimation based on the DMRS; and information regarding the report quantity of the second report.

10. A method performed by a base station in a wireless communication system, A step of transmitting to a terminal first configuration information including information for identifying some of the PMI (precoding matrix indicator) beams among a plurality of PMI beams; A step of transmitting a CSI (channel state information)-RS (reference signal) to the above terminal; A step of receiving a first report from the terminal containing information about a PMI selected through channel estimation based on CSI-RS among the portion of PMIs identified based on the first setting information; A step of transmitting second configuration information for a channel estimation report based on a DMRS (demodulation reference signal) to the above terminal; A step of transmitting a PDSCH (physical downlink shared channel) to the above terminal through a plurality of beams; and The method includes the step of receiving a second report from the terminal containing information about at least one beam selected through channel estimation based on DMRSs corresponding to the plurality of beams, and A method in which a PDSCH transmitted through a first layer corresponding to a first beam among the plurality of beams and a PDSCH transmitted through a second layer corresponding to at least one second beam among the plurality of beams contain the same data.

11. In Paragraph 10, The above first setting information is received through RRC (radio resource control) signaling, and A method in which information for identifying some of the above PMI beams is received through at least one of a CSI report configuration information (CSI-ReportConfg) message included in the RRC signaling, or a codebook configuration information (CodebookConfig) message including information regarding a precoder corresponding to the plurality of PMI beams.

12. In Paragraph 10, A method comprising at least one of the following: information for identifying some of the PMI beams, information indicating some of the PMI beams among some of the plurality of PMI beams, information regarding a pattern for identifying some of the PMI beams among the plurality of PMI beams, or information regarding a plurality of PMI subsets constituting the plurality of PMI beams.

13. In Paragraph 12, The information regarding the plurality of PMI subsets includes information for the terminal to select some of the PMI subsets among the plurality of PMI subsets, and Information for the terminal to select some of the PMI subsets comprises, for each of the plurality of PMI subsets, information for a single PMI beam representing each PMI subset, or mapping information between the plurality of PMI subsets and a plurality of downlink signals, wherein the downlink signal includes a synchronization signal block (SSB).

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 first configuration information from a base station, which includes information for identifying some of the PMI (precoding matrix indicator) beams among a plurality of PMI beams, and Receive CSI (channel state information)-RS (reference signal) from the above base station, and Transmitting to the base station a first report containing information on a PMI beam selected through channel estimation based on CSI-RS among the portion of PMI beams identified based on the first setting information, and Receive second configuration information for a channel estimation report based on a DMRS (demodulation reference signal) from the above base station, and From the above base station, a PDSCH (physical downlink shared channel) is received through a plurality of beams, and The base station is configured to transmit a second report containing information about at least one beam selected through channel estimation based on DMRSs corresponding to the plurality of beams, and A terminal in which a PDSCH transmitted through a first layer corresponding to a first beam among the plurality of beams and a PDSCH transmitted through a second layer corresponding to at least one second beam among the plurality of beams contain the same data.

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 to a terminal first configuration information including information for identifying some of the PMI (precoding matrix indicator) beams among a plurality of PMI beams, and Transmit CSI (channel state information)-RS (reference signal) to the above terminal, and From the terminal, receiving a first report containing information about a PMI beam selected through channel estimation based on CSI-RS among the portion of PMI beams identified based on the first setting information, and Transmit second configuration information for a channel estimation report based on a DMRS (demodulation reference signal) to the above terminal, and Transmitting a PDSCH (physical downlink shared channel) to the above terminal through a plurality of beams, and To receive a second report from the above terminal containing information about at least one beam selected through channel estimation based on DMRSs corresponding to the plurality of beams, and A base station in which a PDSCH transmitted through a first layer corresponding to a first beam among the plurality of beams and a PDSCH transmitted through a second layer corresponding to at least one second beam among the plurality of beams contain the same data.

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