Method and apparatus for beam management in communication system

Abstract

A method for a base station according to the present disclosure comprises the steps of: sharing first information and prior information for beamforming with a terminal; on the basis of the prior information, identifying whether or not the terminal is located in a near-field area; if it is identified that the terminal is located in the near-field area, determining, on the basis of the first information, grids to transmit each of near-field beams for beam sweeping and beam focusing; and transmitting a reference signal by beam sweeping each of the near-field beams so that the near-field beams are respectively focused on the determined grids.

Description

Method and device for beam management in a communication system

[0001] The present disclosure relates to improved communication technologies, and more particularly to technologies for beam management.

[0002] Communication networks (e.g., 5G communication networks, 6G communication networks, etc.) are being developed to provide improved communication services compared to existing communication networks (e.g., long term evolution (LTE), advanced LTE-A (LTE-A), etc.). 5G communication networks (e.g., new radio (NR) communication networks) can support frequency bands above 6 GHz as well as frequency bands below 6 GHz. That is, 5G communication networks can support FR1 bands and / or FR2 bands. 5G communication networks can support various communication services and scenarios compared to LTE communication networks. For example, usage scenarios of 5G communication networks can include enhanced Mobile Broadband (eMBB), Ultra Reliable Low Latency Communication (URLLC), massive Machine Type Communication (mMTC), etc.

[0003] Compared to 5G, 6G communication networks can support a wider range of communication services and scenarios. 6G communication networks can meet requirements for ultra-high performance, ultra-high bandwidth, ultra-high space, ultra-high precision, ultra-intelligence, and / or ultra-reliability. 6G communication networks can support diverse and wide frequency bands and be applied to various usage scenarios (e.g., terrestrial communications, non-terrestrial communications, sidelink communications, etc.).

[0004] Currently, 5G NR supports communications using the first frequency band (FR1) (e.g., 410-7125 MHz) and the second frequency band (FR2) (e.g., 24250-52600 MHz). When using the FR2 band, which is a millimeter wave band, the 5G NR system utilizes a massive multiple-input and multiple-output (MIMO) system and an appropriate beamforming technique that uses a large number of antennas to transmit information in a desired direction while compensating for high path attenuation. In the future, 6G communication systems are expected to utilize the terahertz band, which is a frequency band higher than millimeter waves, and accordingly, in order to compensate for the increased path attenuation, 6G communication systems are considering antenna structures that widely deploy a very large number of antennas, such as an extra-large scale massive MIMO (XL-MIMO) system. For XL-MIMO systems, the use of higher frequency bands and larger antenna sizes compared to existing 5G NR systems increases the Rayleigh distance, which marks the boundary between the near field and the far field. Furthermore, this increase in Rayleigh distance may cause the communication area previously defined as the far field to become the near field.

[0005] In the near field region of an XL-MIMO system, new procedures for beam sweeping and beam management are required at the transmitting nodes of the network, e.g., the base station.

[0006] The purpose of the present disclosure to solve the above problems is to provide a method and device for beam management in a near field region in a communication system using XL-MIMO.

[0007] According to a first embodiment of the present disclosure for achieving the above object, a method of a base station may include: sharing first information and prior information for beam forming with a terminal; determining whether the terminal is located in a near field region based on the prior information; determining grids to transmit each of the near field beams for beam sweeping and beam focusing based on the first information when it is determined that the terminal is located in the near field region; transmitting a reference signal by beam sweeping each of the near field beams so that the near beams are focused on the determined grids; receiving a first measurement report message for the reference signal from the terminal; and determining a near field beam for communicating with the terminal based on the first measurement report message.

[0008] The above first information includes information on the number of distance rings for distinguishing the near field, and the number of distance rings may be two or more.

[0009] The above-mentioned prior information may include a distance value from the base station to the terminal, and each of the near-field beams may use a spherical wave beam.

[0010] The method may further include a step of transmitting far field beams to the terminal by beam sweeping when the terminal is located in a far field area, a step of transmitting beam indices for identifying the reference signal and each of the far field beams through each of the far field beams, a step of receiving a second measurement report message including a measurement value for the reference signal and far beam index information from the terminal, and a step of determining a far field beam for communicating with the terminal based on the second measurement report message.

[0011] Each of the above-mentioned far-field beams can be a plane wave beam.

[0012] If the above-mentioned prior information further includes angle information of the terminal, the beam sweeping area of ​​the far field beams can be determined based on the angle information of the terminal.

[0013] Each of the above grids can be determined based on the distance rings determined based on the beam direction beamforming to the terminal and predetermined separation distances from the base station.

[0014] When the above-described prior information further includes angle information of the terminal, when determining the grids to be transmitted for beam sweeping and beam focusing of each of the near-field beams, the grids to be transmitted can be determined based on the angle information of the terminal.

[0015] The above first information may further include reception power threshold information.

[0016] When the first measurement report message includes two or more measured reference signal reception power values ​​having a reception power threshold value or higher and beam indices corresponding to each of the two or more measured reference signal reception power values, the near-field beam for communicating with the terminal may be selected as a beam having a beam index corresponding to the highest measured reception power value among the two or more measured reference signal reception power values.

[0017] When the first measurement report message includes two or more measured reference signal reception power values ​​having a reception power threshold value or greater and beam indices corresponding to each of the two or more measured reference signal reception power values, the near-field beam for communicating with the terminal may be determined by considering at least one of interference with other communication nodes or a load of the base station.

[0018] The above-mentioned prior information may be obtained from additional information indirectly obtained from the location service of the terminal or determined based on delay information of a signal received from the terminal.

[0019] The method may further include: a step of transmitting the reference signal by sweeping far field beams over the entire sweeping area of ​​the far field area when it is impossible to confirm whether the terminal is located in the near field area based on the above-mentioned prior information; a step of receiving a third measurement report message from the terminal; and a step of setting the far field beam having the reception power greater than or equal to a preset threshold value as a beam for communicating with the terminal when the reception power value included in the third measurement report message is a far field beam having the reception power greater than or equal to a preset threshold value.

[0020] The method may further include: determining grids for near-field beam sweeping and focusing based on the distance ring to be set in a beam direction corresponding to the far-field beam when the received power value included in the third measurement report message is not the far-field beam having the received power greater than or equal to the preset threshold value; transmitting the reference signal through near-field beam sweeping with the determined grids; receiving a fourth measurement report message including the received power value for the reference signal transmitted through the near-field beam sweeping from the terminal; and determining a near-field beam having the highest received power value among the near-field beams as a near-field beam for communicating with the terminal based on the fourth measurement report message.

[0021] A base station according to one embodiment of the present disclosure comprises at least one processor, wherein the at least one processor comprises:

[0022] A method for transmitting a reference signal by sharing first information and prior information for beam forming with a terminal; determining whether the terminal is located in a near field region based on the prior information; determining grids to transmit each of the near field beams for beam sweeping and beam focusing based on the first information when the terminal is determined to be located in the near field region; transmitting a reference signal by beam sweeping each of the near field beams so that the near beams are focused on the determined grids; receiving a first measurement report message for the reference signal from the terminal; and determining a near field beam for communicating with the terminal based on the first measurement report message.

[0023] The above first information includes information on the number of distance rings for distinguishing the near field, and the number of distance rings may be two or more.

[0024] The above-mentioned prior information may include a distance value from the base station to the terminal, and each of the near-field beams may use a spherical wave beam.

[0025] The at least one processor of the base station:

[0026] When the terminal is located in a far field area, the far field beams are beam-swept and transmitted to the terminal, and beam indices for identifying each of the reference signal and the far field beams are transmitted through each of the far field beams; a second measurement report message including a measurement value for the reference signal and far beam index information is received from the terminal; and a far field beam for communicating with the terminal is determined based on the second measurement report message.

[0027] Each of the above-mentioned far-field beams can be a plane wave beam.

[0028] If the above-mentioned prior information further includes angle information of the terminal, the beam sweeping area of ​​the far field beams can be determined based on the angle information of the terminal.

[0029] Each of the above grids can be determined based on the distance rings determined based on the beam direction beamforming to the terminal and predetermined separation distances from the base station.

[0030] When the above-described prior information further includes angle information of the terminal, when determining the grids to be transmitted for beam sweeping and beam focusing of each of the near-field beams, the grids to be transmitted can be determined based on the angle information of the terminal.

[0031] The at least one processor of the base station:

[0032] If it is impossible to confirm whether the terminal is located in the near field area based on the above-mentioned prior information, the reference signal is transmitted by sweeping the far field beams over the entire sweeping area of ​​the far field area; receiving a third measurement report message from the terminal; and if the reception power value included in the third measurement report message is a far field beam having a reception power greater than or equal to a preset threshold value, the far field beam having a reception power greater than or equal to the preset threshold value may be further caused to be set as a beam for communicating with the terminal.

[0033] The at least one processor of the base station:

[0034] The method may further cause the terminal to determine grids for sweeping and focusing a near-field beam based on the distance ring to be set in a beam direction corresponding to the far-field beam when the reception power value included in the third measurement report message is not the far-field beam having the reception power greater than or equal to the preset threshold value; to transmit the reference signal through near-field beam sweeping with the determined grids; to receive a fourth measurement report message including the reception power value for the reference signal transmitted through the near-field beam sweeping from the terminal; and to determine, based on the fourth measurement report message, a near-field beam having the highest reception power value among the near-field beams as a near-field beam for communicating with the terminal.

[0035] According to the present disclosure, a base station having an XL-MIMO antenna panel can determine a beam to use by distinguishing between a far field region and a near field region, which are electromagnetic wave regions, when beamforming to a terminal. In particular, when there is prior information, the base station can quickly find an optimal beam for communicating with a terminal in the near field region based on the prior information. When the prior information is angle information, the number of far field beams for transmitting a reference signal for determining a far field beam can be reduced. In addition, the number of near field beams for determining a near field beam can be reduced. When the prior information is distance information, the base station can quickly determine whether a terminal is located in the far field region or the near field region.

[0036] Figure 1 is a conceptual diagram illustrating a first embodiment of a communication system.

[0037] Figure 2 is a block diagram illustrating a first embodiment of a communication node constituting a communication system.

[0038] Figure 3 is a block diagram illustrating a first embodiment of communication nodes performing communication.

[0039] Figure 4a is a block diagram illustrating a first embodiment of a transmission path.

[0040] Figure 4b is a block diagram illustrating a first embodiment of a receiving path.

[0041] Figure 5 is a conceptual diagram illustrating a first embodiment of a system frame in a communication system.

[0042] Figure 6 is a conceptual diagram illustrating a first embodiment of a subframe in a communication system.

[0043] Figure 7 is a conceptual diagram illustrating a first embodiment of a slot in a communication system.

[0044] Figure 8 is a conceptual diagram illustrating a first embodiment of time-frequency resources in a communication system.

[0045] Figure 9 is a conceptual diagram illustrating a case in which communication is performed with a terminal using a near-field beam and a far-field beam from a base station.

[0046] Figure 10 is a flowchart of a procedure for beam management when a base station has no prior information about a terminal.

[0047] FIG. 11a is a conceptual diagram illustrating a method of transmitting far-field beams by beam sweeping at a base station having an XL MIMO antenna.

[0048] Figure 11b is a conceptual diagram illustrating an area in which beam sweeping is to be performed based on the number of distance rings and the size of the set of angle candidates.

[0049] Figure 11c is a conceptual diagram illustrating a case where a beam is formed to a terminal by an XL-MIMO antenna.

[0050] Figure 12 is a flowchart of a procedure for beam management when a base station has distance information from a terminal.

[0051] Figure 13 is a conceptual diagram for explaining a method of transmitting near-field beams by beam sweeping when distance information from a terminal is known at a base station having an XL MIMO antenna.

[0052] Figure 14 is a flowchart of a procedure for beam management when a base station has relative angle information with a terminal.

[0053] Figure 15 is a conceptual diagram for explaining a method of transmitting near-field beams by beam sweeping when angle information with respect to a terminal is known at a base station having an XL MIMO antenna.

[0054] Figure 16 is a flowchart of a procedure for beam management when a base station has location information of a terminal.

[0055] Figure 17 is a conceptual diagram illustrating a method for transmitting near-field beams by beam sweeping when a base station having an XL MIMO antenna knows the location information of a terminal.

[0056] FIG. 18a is a flowchart that simplifies the procedure for selecting an optimal beam between a base station and a terminal according to the first embodiment of the present disclosure.

[0057] FIG. 18b is a flowchart that simplifies the procedure for selecting an optimal beam between a base station and a terminal according to the second embodiment of the present disclosure.

[0058] FIG. 18c is a flowchart that simplifies the procedure for selecting an optimal beam between a base station and a terminal according to the third embodiment of the present disclosure.

[0059] FIG. 18d is a flowchart that simplifies the procedure for selecting an optimal beam between a base station and a terminal according to the fourth embodiment of the present disclosure.

[0060] This disclosure may be subject to various modifications and various embodiments. Specific embodiments are illustrated and described in detail in the drawings. However, this is not intended to limit the disclosure to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the disclosure.

[0061] While terms such as "first" and "second" may be used to describe various components, these components should not be limited by these terms. These terms are used solely to distinguish one component from another. For example, without departing from the scope of the present disclosure, a first component could be referred to as a "second component," and similarly, a second component could also be referred to as a "first component." The term "and / or" may refer to a combination of multiple related items described herein or to any of multiple related items described herein.

[0062] In the present disclosure, “at least one of A and B” may mean “at least one of A or B” or “at least one of combinations of one or more of A and B.” Additionally, in the present disclosure, “at least one of A and B” may mean “at least one of A or B” or “at least one of combinations of one or more of A and B.”

[0063] In the present disclosure, (re)transmission may mean “transmission,” “retransmission,” or “transmission and retransmission,” (re)setting may mean “setting,” “resetting,” or “setting and resetting,” (re)connection may mean “connection,” “reconnection,” or “connection and reconnection,” and (re)connection may mean “connection,” “reconnection,” or “connection and reconnection.”

[0064] When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components intervening. Conversely, when a component is referred to as being "directly connected" or "connected" to another component, it should be understood that there are no other components intervening.

[0065] The terminology used in this disclosure is only used to describe specific embodiments and is not intended to limit the present disclosure. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this disclosure, it should be understood that the terms "comprises" or "has" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0066] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which this disclosure pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and shall not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0067] Hereinafter, preferred embodiments of the present disclosure will be described in more detail with reference to the attached drawings. In order to facilitate an overall understanding in describing the present disclosure, the same reference numerals will be used for identical components in the drawings, and redundant descriptions of identical components will be omitted. In addition to the embodiments explicitly described in the present disclosure, operations may be performed according to combinations of embodiments, extensions of embodiments, and / or modifications of embodiments. The performance of some operations may be omitted, and the order of operation may be changed.

[0068] In an embodiment, even if a method (e.g., transmitting or receiving a signal) performed by a first communication node among communication nodes is described, a corresponding second communication node can perform a method (e.g., receiving or transmitting a signal) corresponding to the method performed by the first communication node. That is, if an operation of a UE (user equipment) is described, a corresponding base station can perform an operation corresponding to the operation of the UE. Conversely, if an operation of a base station is described, a corresponding UE can perform an operation corresponding to the operation of the base station.

[0069] A base station may be referred to as a NodeB, an evolved NodeB, a gNodeB (next generation node B), a gNB, a device, an apparatus, a node, a communication node, a BTS (base transceiver station), a RRH (radio remote head), a TRP (transmission reception point), a RU (radio unit), an RSU (road side unit), a radio transceiver, an access point, an access node, etc. A UE may be referred to as a terminal, a device, an apparatus, a node, a communication node, an end node, an access terminal, a mobile terminal, a station, a subscriber station, a mobile station, a portable subscriber station, an OBU (on-broad unit), etc.

[0070] In the present disclosure, signaling may be at least one of upper layer signaling, MAC signaling, or PHY (physical) signaling. A message used for upper layer signaling may be referred to as an "upper layer message" or an "upper layer signaling message." A message used for MAC signaling may be referred to as a "MAC message" or a "MAC signaling message." A message used for PHY signaling may be referred to as a "PHY message" or a "PHY signaling message." Upper layer signaling may refer to a transmission and reception operation of system information (e.g., a master information block (MIB), a system information block (SIB)) and / or an RRC message. MAC signaling may refer to a transmission and reception operation of a MAC control element (CE). PHY signaling may refer to a transmission and reception operation of control information (e.g., downlink control information (DCI), uplink control information (UCI), sidelink control information (SCI)).

[0071] In the present disclosure, “an operation (e.g., a transmission operation) is set” may mean that “setting information for the operation (e.g., an information element, a parameter)” and / or “information instructing the performance of the operation” is signaled. “An information element (e.g., a parameter) is set” may mean that the information element is signaled. In the present disclosure, “a signal and / or a channel” may mean a signal, a channel, or “a signal and a channel,” and a signal may be used to mean “a signal and / or a channel.”

[0072] The communication networks to which the embodiments are applied are not limited to those described below, and the embodiments may be applied to various communication networks (e.g., 4G communication networks, 5G communication networks, and / or 6G communication networks). Here, the term "communication network" may be used interchangeably with the term "communication system."

[0073] Figure 1 is a conceptual diagram illustrating a first embodiment of a communication system.

[0074] Referring to FIG. 1, the communication system (100) may include a plurality of communication nodes (110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, 130-6). In addition, the communication system (100) may further include a core network (e.g., a serving-gateway (S-GW), a packet data network (PDN)-gateway (P-GW), a mobility management entity (MME)). If the communication system (100) is a 5G communication system (e.g., a new radio (NR) system), the core network may include an access and mobility management function (AMF), a user plane function (UPF), a session management function (SMF), etc.

[0075] A plurality of communication nodes (110 to 130) can support a communication protocol (e.g., LTE communication protocol, LTE-A communication protocol, NR communication protocol, etc.) specified in the 3GPP (3rd generation partnership project) standard. The plurality of communication nodes (110 to 130) may support CDMA (code division multiple access) technology, WCDMA (wideband CDMA) technology, TDMA (time division multiple access) technology, FDMA (frequency division multiple access) technology, OFDM (orthogonal frequency division multiplexing) technology, Filtered OFDM technology, CP (cyclic prefix)-OFDM technology, DFT-s-OFDM (discrete Fourier transform-spread-OFDM) technology, OFDMA (orthogonal frequency division multiple access) technology, SC (single carrier)-FDMA technology, NOMA (non-orthogonal multiple access) technology, GFDM (generalized frequency division multiplexing) technology, FBMC (filter bank multi-carrier) technology, UFMC (universal filtered multi-carrier) technology, SDMA (space division multiple access) technology, etc. Each of the plurality of communication nodes may have the following structure.

[0076] Figure 2 is a block diagram illustrating a first embodiment of a communication node constituting a communication system.

[0077] Referring to FIG. 2, a communication node (200) may include at least one processor (210), a memory (220), and a transmission / reception device (230) that is connected to a network and performs communication. In addition, the communication node (200) may further include an input interface device (240), an output interface device (250), a storage device (260), etc. Each component included in the communication node (200) may be connected by a bus (270) and communicate with each other.

[0078] The processor (210) can execute program commands stored in at least one of the memory (220) and the storage device (260). The processor (210) may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor in which the methods according to embodiments of the present disclosure are performed. Each of the memory (220) and the storage device (260) may be configured with at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory (220) may be configured with at least one of a read-only memory (ROM) and a random access memory (RAM).

[0079] Referring again to FIG. 1, the communication system (100) may include a plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) and a plurality of terminals (130-1, 130-2, 130-3, 130-4, 130-5, 130-6). Each of the first base station (110-1), the second base station (110-2), and the third base station (110-3) may form a macro cell. Each of the fourth base station (120-1) and the fifth base station (120-2) may form a small cell. The fourth base station (120-1), the third terminal (130-3), and the fourth terminal (130-4) may be within the cell coverage of the first base station (110-1). The second terminal (130-2), the fourth terminal (130-4), and the fifth terminal (130-5) may be within the cell coverage of the second base station (110-2). The fifth base station (120-2), the fourth terminal (130-4), the fifth terminal (130-5), and the sixth terminal (130-6) may be within the cell coverage of the third base station (110-3). The first terminal (130-1) may be within the cell coverage of the fourth base station (120-1). The sixth terminal (130-6) may be within the cell coverage of the fifth base station (120-2).

[0080] Here, each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) may be referred to as a NodeB (NB), an evolved NodeB (eNB), a gNB, an advanced base station (ABS), a high reliability-base station (HR-BS), a base transceiver station (BTS), a radio base station, a radio transceiver, an access point, an access node, a radio access station (RAS), a mobile multihop relay-base station (MMR-BS), a relay station (RS), an advanced relay station (ARS), a high reliability-relay station (HR-RS), a home NodeB (HNB), a home eNodeB (HeNB), a road side unit (RSU), a radio remote head (RRH), a transmission point (TP), a transmission and reception point (TRP), etc.

[0081] Each of the plurality of terminals (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) may be referred to as a user equipment (UE), terminal equipment (TE), advanced mobile station (AMS), high reliability-mobile station (HR-MS), terminal, access terminal, mobile terminal, station, subscriber station, mobile station, portable subscriber station, node, device, on board unit (OBU), etc.

[0082] Meanwhile, each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) may operate in a different frequency band or may operate in the same frequency band. Each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) may be connected to each other via an ideal backhaul link or a non-ideal backhaul link, and may exchange information with each other via the ideal backhaul link or the non-ideal backhaul link. Each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) may be connected to the core network via the ideal backhaul link or the non-ideal backhaul link. Each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) can transmit a signal received from the core network to the corresponding terminal (130-1, 130-2, 130-3, 130-4, 130-5, 130-6), and can transmit a signal received from the corresponding terminal (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) to the core network.

[0083] Additionally, each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) may support MIMO transmission (e.g., single user (SU)-MIMO, multi user (MU)-MIMO, massive MIMO, etc.), coordinated multipoint (CoMP) transmission, carrier aggregation (CA) transmission, transmission in an unlicensed band, sidelink communication (e.g., device to device communication (D2D), proximity services (ProSe)), Internet of Things (IoT) communication, dual connectivity (DC), etc. Here, each of the plurality of terminals (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) can perform an operation corresponding to the base station (110-1, 110-2, 110-3, 120-1, 120-2) and an operation supported by the base station (110-1, 110-2, 110-3, 120-1, 120-2). For example, the second base station (110-2) can transmit a signal to the fourth terminal (130-4) based on the SU-MIMO scheme, and the fourth terminal (130-4) can receive a signal from the second base station (110-2) by the SU-MIMO scheme. Alternatively, the second base station (110-2) can transmit signals to the fourth terminal (130-4) and the fifth terminal (130-5) based on the MU-MIMO method, and each of the fourth terminal (130-4) and the fifth terminal (130-5) can receive signals from the second base station (110-2) based on the MU-MIMO method.

[0084] Each of the first base station (110-1), the second base station (110-2), and the third base station (110-3) can transmit a signal to the fourth terminal (130-4) based on the CoMP scheme, and the fourth terminal (130-4) can receive a signal from the first base station (110-1), the second base station (110-2), and the third base station (110-3) based on the CoMP scheme. Each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) can transmit and receive a signal with terminals (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) within its cell coverage based on the CA scheme. Each of the first base station (110-1), the second base station (110-2), and the third base station (110-3) can control sidelink communication between the fourth terminal (130-4) and the fifth terminal (130-5), and each of the fourth terminal (130-4) and the fifth terminal (130-5) can perform sidelink communication under the control of the second base station (110-2) and the third base station (110-3), respectively.

[0085] Meanwhile, communication nodes performing communication in a communication network may be configured as follows. The communication node illustrated in Fig. 3 may be a specific embodiment of the communication node illustrated in Fig. 2.

[0086] Figure 3 is a block diagram illustrating a first embodiment of communication nodes performing communication.

[0087] Referring to FIG. 3, each of the first communication node (300a) and the second communication node (300b) may be a base station or a UE. The first communication node (300a) may transmit a signal to the second communication node (300b). The transmission processor (311) included in the first communication node (300a) may receive data (e.g., a data unit) from a data source (310). The transmission processor (311) may receive control information from the controller (316). The control information may include at least one of system information, RRC configuration information (e.g., information configured by RRC signaling), MAC control information (e.g., MAC CE), or PHY control information (e.g., DCI, SCI).

[0088] The transmitting processor (311) may perform a processing operation on data (e.g., an encoding operation, a symbol mapping operation, etc.) to generate data symbol(s). The transmitting processor (311) may perform a processing operation on control information (e.g., an encoding operation, a symbol mapping operation, etc.) to generate control symbol(s). In addition, the transmitting processor (311) may generate synchronization / reference symbol(s) for a synchronization signal and / or a reference signal.

[0089] The Tx MIMO processor (312) may perform a spatial processing operation (e.g., a precoding operation) on data symbol(s), control symbol(s), and / or synchronization / reference symbol(s). The output (e.g., a symbol stream) of the Tx MIMO processor (312) may be provided to modulators (MODs) included in the transceivers (313a to 313t). The modulators (MODs) may perform a processing operation on the symbol stream to generate modulation symbols, and may perform an additional processing operation (e.g., an analog conversion operation, an amplification operation, a filtering operation, an upconversion operation) on the modulation symbols to generate signals. The signals generated by the modulators (MODs) of the transceivers (313a to 313t) may be transmitted via the antennas (314a to 314t).

[0090] Signals transmitted by the first communication node (300a) may be received by antennas (364a to 364r) of the second communication node (300b). Signals received by the antennas (364a to 364r) may be provided to demodulators (DEMODs) included in transceivers (363a to 363r). The demodulator (DEMOD) may perform a processing operation (e.g., a filtering operation, an amplification operation, a downconversion operation, a digital conversion operation) on the signal to obtain samples. The demodulator (DEMOD) may perform an additional processing operation on the samples to obtain symbols. The MIMO detector (362) may perform a MIMO detection operation on the symbols. The receiving processor (361) may perform a processing operation (e.g., a deinterleaving operation, a decoding operation) on the symbols. The output of the receiving processor (361) may be provided to a data sink (360) and a controller (366). For example, data may be provided to the data sink (360), and control information may be provided to the controller (366).

[0091] Meanwhile, the second communication node (300b) can transmit a signal to the first communication node (300a). The transmitting processor (368) included in the second communication node (300b) can receive data (e.g., data units) from a data source (367) and perform a processing operation on the data to generate data symbol(s). The transmitting processor (368) can receive control information from the controller (366) and perform a processing operation on the control information to generate control symbol(s). In addition, the transmitting processor (368) can perform a processing operation on a reference signal to generate reference symbol(s).

[0092] The Tx MIMO processor (369) may perform spatial processing operations (e.g., precoding operations) on data symbol(s), control symbol(s), and / or reference symbol(s). The output (e.g., symbol stream) of the Tx MIMO processor (369) may be provided to modulators (MODs) included in the transceivers (363a to 363t). The modulators (MODs) may perform processing operations on the symbol streams to generate modulation symbols, and may perform additional processing operations (e.g., analog conversion operations, amplification operations, filtering operations, upconversion operations) on the modulation symbols to generate signals. The signals generated by the modulators (MODs) of the transceivers (363a to 363t) may be transmitted via the antennas (364a to 364t).

[0093] Signals transmitted by the second communication node (300b) may be received by the antennas (314a to 314r) of the first communication node (300a). The signals received by the antennas (314a to 314r) may be provided to demodulators (DEMODs) included in the transceivers (313a to 313r). The demodulator (DEMOD) may perform a processing operation (e.g., a filtering operation, an amplification operation, a downconversion operation, a digital conversion operation) on the signal to obtain samples. The demodulator (DEMOD) may perform an additional processing operation on the samples to obtain symbols. The MIMO detector (320) may perform a MIMO detection operation on the symbols. The receiving processor (319) may perform a processing operation (e.g., a deinterleaving operation, a decoding operation) on the symbols. The output of the receiving processor (319) may be provided to a data sink (318) and a controller (316). For example, data may be provided to the data sink (318) and control information may be provided to the controller (316).

[0094] Memories (315 and 365) can store data, control information, and / or program code. Scheduler (317) can perform scheduling operations for communication. The processors (311, 312, 319, 361, 368, 369) and controllers (316, 366) illustrated in FIG. 3 may be the processor (210) illustrated in FIG. 2 and may be used to perform the methods described in the present disclosure.

[0095] FIG. 4a is a block diagram illustrating a first embodiment of a transmission path, and FIG. 4b is a block diagram illustrating a first embodiment of a reception path.

[0096] Referring to FIGS. 4A and 4B, a transmission path (410) may be implemented in a communication node that transmits a signal, and a reception path (420) may be implemented in a communication node that receives a signal. The transmission path (410) may include a channel coding and modulation block (411), an S-to-P (serial-to-parallel) block (512), an N IFFT (Inverse Fast Fourier Transform) block (413), a P-to-S (parallel-to-serial) block (414), a CP (cyclic prefix) addition block (415), and an UC (up-converter) (UC) (416). The receiving path (420) may include a DC (down-converter) (421), a CP removal block (422), an S-to-P block (423), an N FFT block (424), a P-to-S block (425), and a channel decoding and demodulation block (426). Here, N may be a natural number.

[0097] In the transmission path (410), information bits may be input to a channel coding and modulation block (411). The channel coding and modulation block (411) may perform a coding operation (e.g., a low-density parity check (LDPC) coding operation, a polar coding operation, etc.) and a modulation operation (e.g., a quadrature phase shift keying (QPSK), a quadrature amplitude modulation (QAM), etc.) on the information bits. The output of the channel coding and modulation block (411) may be a sequence of modulation symbols.

[0098] The S-to-P block (412) can convert modulation symbols in the frequency domain into parallel symbol streams to generate N parallel symbol streams. N can be an IFFT size or an FFT size. The N IFFT block (413) can perform an IFFT operation on the N parallel symbol streams to generate signals in the time domain. The P-to-S block (414) can convert the output (e.g., parallel signals) of the N IFFT block (413) into a serial signal to generate a serial signal.

[0099] The CP addition block (415) can insert a CP into a signal. The UC (416) can up-convert the frequency of the output of the CP addition block (415) to an RF (radio frequency) frequency. Additionally, the output of the CP addition block (415) can be filtered at the baseband before up-conversion.

[0100] A signal transmitted from a transmission path (410) may be input to a reception path (420). An operation in the reception path (420) may be the reverse operation of the operation in the transmission path (410). A DC (421) may down-convert the frequency of the received signal to a baseband frequency. A CP removal block (422) may remove a CP from a signal. The output of the CP removal block (422) may be a serial signal. An S-to-P block (423) may convert the serial signal into parallel signals. An N FFT block (424) may perform an FFT algorithm to generate N parallel signals. A P-to-S block (425) may convert the parallel signals into a sequence of modulation symbols. A channel decoding and demodulation block (426) may perform a demodulation operation on the modulation symbols and perform a decoding operation on the result of the demodulation operation to restore data.

[0101] In FIGS. 4A and 4B , Discrete Fourier Transform (DFT) and Inverse DFT (IDFT) may be used instead of FFT and IFFT. Each of the blocks (e.g., components) in FIGS. 4A and 4B may be implemented by at least one of hardware, software, or firmware. For example, some of the blocks in FIGS. 4A and 4B may be implemented by software, and the remaining blocks may be implemented by hardware or a “combination of hardware and software.” In FIGS. 4A and 4B , a block may be subdivided into multiple blocks, multiple blocks may be integrated into a single block, some blocks may be omitted, and blocks supporting other functions may be added.

[0102] Figure 5 is a conceptual diagram illustrating a first embodiment of a system frame in a communication system.

[0103] Referring to FIG. 5, time resources in a communication system can be divided into frame units. For example, system frames can be set consecutively in the time domain of the communication system. The length of a system frame can be 10 ms (milliseconds). The system frame number (SFN) can be set from #0 to #1023. In this case, 1024 system frames can be repeated in the time domain of the communication system. For example, the SFN of the system frame after system frame #1023 can be #0.

[0104] A system frame may include two half frames. A half frame may be 5 ms long. A half frame located at the beginning of the system frame may be referred to as "half frame #0," and a half frame located at the end of the system frame may be referred to as "half frame #1." A system frame may include 10 subframes. A subframe may be 1 ms long. The 10 subframes within a system frame may be referred to as "subframes #0-9."

[0105] Figure 6 is a conceptual diagram illustrating a first embodiment of a subframe in a communication system.

[0106] Referring to FIG. 6, one subframe may include n slots, where n may be a natural number. Accordingly, one subframe may be composed of one or more slots.

[0107] Figure 7 is a conceptual diagram illustrating a first embodiment of a slot in a communication system.

[0108] Referring to Figure 7, a single slot may include one or more symbols. A single slot illustrated in Figure 7 may include 14 symbols. The length of a slot may vary depending on the number and length of symbols contained in the slot. Alternatively, the length of a slot may vary depending on the numerology.

[0109] In a communication system, the numerology applied to physical signals and channels may be variable. The numerology may be variable to meet various technical requirements of the communication system. In a communication system applying CP (cyclic prefix)-based OFDM waveform technology, the numerology may include subcarrier spacing and CP length (or CP type). Table 1 may be a first embodiment of a method for configuring a numerology for a CP-OFDM-based communication system. At least some of the numerologies in Table 1 may be supported depending on the frequency band in which the communication system operates. In addition, the communication system may additionally support numerologies not listed in Table 1.

[0110] Subcarrier spacing 15 kHz 30 kHz 60 kHz 120 kHz 240 kHz 480 kHz OFDM symbol length [μs] 66.733.316.78.34.22.1 CP length [μs] 4.762.381.190.600.300.151 Number of OFDM symbols in ms 142856112224448

[0111] When the subcarrier spacing is 15 kHz (e.g., μ=0), the slot length can be 1 ms. In this case, one system frame can contain 10 slots. When the subcarrier spacing is 30 kHz (e.g., μ=1), the slot length can be 0.5 ms. In this case, one system frame can contain 20 slots.

[0112] When the subcarrier spacing is 60 kHz (e.g., μ=2), the slot length can be 0.25 ms. In this case, one system frame can contain 40 slots. When the subcarrier spacing is 120 kHz (e.g., μ=3), the slot length can be 0.125 ms. In this case, one system frame can contain 80 slots. When the subcarrier spacing is 240 kHz (e.g., μ=4), the slot length can be 0.0625 ms. In this case, one system frame can contain 160 slots.

[0113] A symbol may be configured as a downlink (DL) symbol, a flexible (FL) symbol, or an uplink (UL) symbol. A slot consisting solely of DL symbols may be referred to as a "DL slot," a slot consisting solely of FL symbols may be referred to as an "FL slot," and a slot consisting solely of UL symbols may be referred to as a "UL slot."

[0114] The slot format can be semi-statically configured by higher layer signaling (e.g., RRC signaling). Information indicating the semi-static slot format can be included in the system information, and the semi-static slot format can be configured cell-specifically. In addition, the semi-static slot format can be additionally configured for each terminal through terminal-specific higher layer signaling (e.g., RRC signaling). The flexible symbol of the cell-specifically configured slot format can be overridden to a downlink symbol or an uplink symbol by terminal-specific higher layer signaling. In addition, the slot format can be dynamically indicated by physical layer signaling (e.g., a slot format indicator (SFI) included in DCI). The semi-statically configured slot format can be overridden by a dynamically indicated slot format. For example, the semi-statically configured flexible symbol can be overridden to a downlink symbol or an uplink symbol by the SFI.

[0115] The reference signal may be a channel state information-reference signal (CSI-RS), a sounding reference signal (SRS), a demodulation-reference signal (DM-RS), a phase tracking-reference signal (PT-RS), etc. The channel may be a physical broadcast channel (PBCH), a physical downlink control channel (PDCCH), a physical downlink shared channel (PDSCH), a physical uplink control channel (PUCCH), a physical uplink shared channel (PUSCH), a physical sidelink control channel (PSCCH), a physical sidelink shared channel (PSSCH), etc. In the present disclosure, a control channel may mean a PDCCH, a PUCCH, or a PSCCH, and a data channel may mean a PDSCH, a PUSCH, or a PSSCH.

[0116] Figure 8 is a conceptual diagram illustrating a first embodiment of time-frequency resources in a communication system.

[0117] Referring to FIG. 8, a resource consisting of one symbol (e.g., an OFDM symbol) in the time domain and one subcarrier in the frequency domain may be defined as a "RE (resource element)". Resources consisting of one OFDM symbol in the time domain and K subcarriers in the frequency domain may be defined as a "REG (resource element group)". A REG may include K REs. A REG may be used as a basic unit for resource allocation in the frequency domain. K may be a natural number. For example, K may be 12. N may be a natural number. In the slot illustrated in FIG. 7, N may be 14. N OFDM symbols may be used as a basic unit for resource allocation in the time domain.

[0118] In the present disclosure, RB may mean CRB (common RB). Alternatively, RB may mean PRB or VRB (virtual RB). In a communication system, CRB may mean RB that constitutes a set of consecutive RBs (e.g., a common RB grid) based on a reference frequency (e.g., point A). Carriers and / or bandwidth portions may be arranged on the common RB grid. That is, the carrier and / or bandwidth portions may be composed of CRB(s). RBs or CRBs that constitute the bandwidth portions may be referred to as PRBs, and within the bandwidth portions, the CRB index may be appropriately converted to the PRB index.

[0119] Downlink data can be transmitted via the PDSCH. The base station can transmit PDSCH configuration information (e.g., scheduling information) to the terminal via the PDCCH. The terminal can obtain the PDSCH configuration information by receiving the PDCCH (e.g., downlink control information (DCI)). For example, the PDSCH configuration information can include the MCS (modulation coding scheme) used for transmitting and receiving the PDSCH, time resource information of the PDSCH, frequency resource information of the PDSCH, feedback resource information for the PDSCH, etc. The PDSCH can refer to a radio resource through which downlink data is transmitted and received. Alternatively, the PDSCH can refer to the downlink data itself. The PDCCH can refer to a radio resource through which downlink control information (e.g., DCI) is transmitted and received. Alternatively, the PDCCH can refer to the downlink control information itself.

[0120] A terminal can perform a monitoring operation on the PDCCH to receive a PDSCH transmitted from a base station. The base station can inform the terminal of the configuration information for the PDCCH monitoring operation using a higher layer message (e.g., an RRC (radio resource control) message). The configuration information for the PDCCH monitoring operation can include CORESET (control resource set) information and search space information.

[0121] CORESET information may include PDCCH DMRS (demodulation reference signal) information, PDCCH precoding information, PDCCH occasion information, etc. The PDCCH DMRS may be a DMRS used to demodulate the PDCCH. The PDCCH occasion may be a region where the PDCCH can exist. That is, the PDCCH occasion may be a region where DCI can be transmitted. The PDCCH occasion may be referred to as a PDCCH candidate. The PDCCH occasion information may include time resource information and frequency resource information of the PDCCH occasion. In the time domain, the length of the PDCCH occasion may be indicated in symbol units. In the frequency domain, the size of the PDCCH occasion may be indicated in RB units (e.g., in PRB (physical resource block) units or CRB (common resource block) units).

[0122] The search space information may include a coreset identifier (ID) associated with the search space, a period of PDCCH monitoring, and / or an offset. The period and offset of PDCCH monitoring may each be indicated on a slot-by-slot basis. In addition, the search space information may further include an index of the symbol at which the PDCCH monitoring operation begins.

[0123] A base station can configure a bandwidth part (BWP) for downlink communication. The BWP can be configured differently for each terminal. The base station can inform the terminal of the BWP configuration information using higher layer signaling. The higher layer signaling can mean "transmission operation of system information" and / or "transmission operation of RRC (radio resource control) message." The number of BWPs configured for one terminal can be one or more. The terminal can receive BWP configuration information from the base station and check the BWP(s) configured by the base station based on the BWP configuration information. When multiple BWPs are configured for downlink communication, the base station can activate one or more BWPs among the multiple BWPs. The base station can transmit the configuration information of the activated BWP(s) to the terminal using at least one of higher layer signaling, a medium access control (MAC) control element (CE), or DCI. The base station can perform downlink communication using the activated BWP(s). The terminal can identify the activated BWP(s) by receiving configuration information of the activated BWP(s) from the base station, and perform a downlink reception operation in the activated BWP(s).

[0124] Meanwhile, 5G NR supports communications utilizing the first frequency band (frequency range, FR1) (e.g., 410-7125 MHz) and the second frequency band (frequency range, FR2) (e.g., 24250-52600 MHz). When using the FR2 band, which is a millimeter wave band, the 5G NR system utilizes a massive multiple-input and multiple-output (MIMO) system and an appropriate beamforming technique that uses a large number of antennas to transmit information in a desired direction while compensating for high path attenuation. In the future, 6G communication systems are expected to utilize the terahertz band, which is a frequency band higher than millimeter waves, and accordingly, in order to compensate for the increased path attenuation, 6G communication systems are considering antenna structures that widely deploy a very large number of antennas, such as an extra-large scale massive MIMO (XL-MIMO) system. For XL-MIMO systems, the use of higher frequency bands and larger antenna sizes compared to existing 5G NR systems increases the Rayleigh distance, which marks the boundary between the near field and the far field. Furthermore, this increase in Rayleigh distance may cause the communication area previously defined as the far field to become the near field.

[0125] Below, the 6G communication system is described as a terahertz system. Therefore, the 6G communication system may be a terahertz system. However, the 6G communication system according to the present disclosure can also be applied to a gigahertz system. However, for ease of understanding, it should be noted that the 6G communication system is assumed to be a gigahertz system.

[0126] In the far-field region considered in existing 5G NR, assuming that electromagnetic waves are plane waves, the phase of the electromagnetic waves observed at each antenna can be expressed as a linear function of the antenna index. In this case, beam steering, which adjusts the beam angle in the angular domain, can be used to perform beam sweeping, as in existing 5G NR.

[0127] However, in the near-field region, which will be newly considered in 6G communication systems, the propagation shape of electromagnetic waves can be modeled as spherical waves rather than plane waves. When electromagnetic waves are modeled as spherical waves, the phase of the electromagnetic wave observed at each antenna element constituting the antenna system can be expressed as a nonlinear function that reflects not only the antenna index but also the incident angle of the electromagnetic wave and the distance between the base station and the terminal. Consequently, unlike 5G NR, 6G communication systems must consider these spherical electromagnetic waves. Therefore, the antenna phase must be adjusted to focus the beam at a specific location by considering not only the relative angle of the terminal to the base station but also the distance between the base station and the terminal. This is called beam focusing. Therefore, in the near-field communication region, beam sweeping through beam focusing in the angle-distance domain is essential to achieve higher communication performance, rather than the angular domain beam sweeping process of the existing 5G NR.

[0128] When considering near-field beam focusing, measuring performance for all beam candidates, similar to the beam management process in 5G NR, requires significantly more time resources and computational complexity. This can be broadly categorized into three reasons.

[0129] First, when beam sweeping is performed for a terminal located in the near-field region, in the case of the existing 5G NR system, beam sweeping is performed in the angular domain in the beam search space, but in the case of the 6G communication system, beam sweeping is expanded to the angular-distance domain, so the number of candidate beams for which performance must be measured increases.

[0130] Second, since the existing 5G NR communication system uses a larger number of antennas to form a highly directional beam, the beam width becomes narrower, so the 6G communication system must measure performance for a larger number of candidate beams.

[0131] Third, unlike the far-field, where beamforming vectors are calculated solely using terminal angle information, 6G communication systems must calculate the phases of each antenna based on both terminal angle and distance information between the terminal and the base station to derive near-field beamforming vectors. Therefore, beam sweeping through beam focusing in the near-field requires higher computational complexity than beam sweeping in the far-field.

[0132] The present disclosure provides a novel beam management process (or procedure or device) capable of reducing time resources and computational complexity to address the issues arising in near-field environments, as described above. Furthermore, the present disclosure, described below, defines a beam management process with low complexity in a near-field environment, defines parameters for the same, and provides a method for using the defined parameters.

[0133] The electromagnetic wave region is divided into a near-field region called the Fresnel region and a far-field region called the Fraunhofer region, and the boundary between the two regions is the Raleigh distance, which is expressed as in the following mathematical equation 1 for the maximum allowable phase error, the size of the antenna array D, and the wavelength λ=c / f corresponding to the communication frequency f. In addition, the size of the antenna array is the size of the antenna array of the base station (D BS ) and the antenna array size of the terminal (D UE ) can be calculated as the sum of the antenna array size (D BS and D UE ) represents the length along the axis with the largest value in a given antenna array.

[0134]

[0135] Here, the maximum allowable phase error φ represents the maximum phase difference between two different antennas in a given antenna array. If the maximum allowable phase error is greater than ð / 8, the Fraunhofer approximation, which is the far-field diffraction equation for propagation in the far-field region, does not hold. Since the Fraunhofer approximation does not hold when the maximum allowable phase error is greater than π / 8, it is difficult to approximate and model it as a planar wave, which has been assumed and used as the far-field region in existing communication systems. Therefore, when the maximum allowable phase error is greater than π / 8, it is impossible to express the phase of the electromagnetic wave observed at each antenna as a linear function of the antenna index, and the phase of the antenna must be expressed as a nonlinear function that reflects the antenna index, the incidence angle, and the distance between the base station and the terminal.

[0136] Therefore, applying the same beamforming techniques in the near-field region as in the far-field region may not achieve the expected communication performance in the far-field region. Furthermore, utilizing communication techniques such as initial access, beam management, and resource allocation used in the far-field region may result in performance degradation in the near-field region.

[0137] For the case where the maximum allowable phase error φ=π / 8, the boundary of the electromagnetic wave region in mathematical expression 1 is based on the far field, that is, the Rayleigh distance R can be expressed in a simplified form as in mathematical expression 2 below.

[0138]

[0139] If we interpret the physical meaning of mathematical expression 2, 2D 2 This can mean that the phase difference between different antennas is guaranteed to not exceed π / 8 for signals received from objects that are / λ or farther away. In other words, when performing beamforming to a terminal located farther away than the Rayleigh distance R, the base station can use the plane wave assumption for the beam for beamforming.

[0140] In the 5G NR standard, which is currently being commercialized and standardized, the beam management procedure consists of three steps: initial beam establishment, beam adjustment, and beam failure recovery. The initial beam establishment and beam adjustment steps use beam sweeping to select the beam combination with the highest reference signal received power (RSRP) among possible transmit-receive beam combinations. Beam sweeping in 5G NR assumes that the terminal is in the far field region. The base station forms beams in the angular domain through beam steering and then receives RSRP values ​​for each beam from the terminal. The base station can then compare the received RSRP values ​​to select the optimal transmit or receive beam.

[0141] However, in 6G communication systems, which use higher frequencies and larger antennas than those used in 5G NR, the Rayleigh distance increases. Therefore, in 6G communication systems, the communication area is defined as the near field and the far field. In the near field area, unlike the far field area, not only the angle of the electromagnetic wave but also the distance between the transmitter and receiver must be considered. In other words, in the near field area, a beam focusing technique that focuses the beam to a single area in space can be used to perform a beam sweeping process that considers both the angular domain and the distance domain.

[0142] When the beam sweeping method used in the electromagnetic field is divided into far-field and near-field, the distinction between the near-field beam sweeping method and the far-field beam sweeping can be distinguished by whether the array response vector used to calculate the beamforming vector includes distance information between the transmitter and receiver. Here, the array response vector is a vector that represents the phases of the signal transmitted (or received) by each antenna element of the transmitting (or receiving) antenna. If the array response vector is expressed using only propagation direction information without distance information, the far-field beamforming vector can be calculated to perform far-field beam sweeping. On the other hand, if each antenna element of the array response vector includes distance information as well as propagation direction, the near-field beamforming vector can be calculated to perform near-field beam sweeping.

[0143] The current 5G NR standard does not consider near-field beam sweeping. Therefore, when performing beam management in future 6G communication systems, a procedure is needed to select an electromagnetic wave region that matches the current terminal environment and requirements, considering the characteristics of the far-field and near-field regions, and then select an appropriate beam sweeping method.

[0144] Figure 9 is a conceptual diagram illustrating a case in which communication is performed with a terminal using a near-field beam and a far-field beam from a base station.

[0145] Referring to FIG. 9, a base station (not shown in FIG. 9) may include an XL-MIMO antenna panel (910). The XL-MIMO antenna panel (910) may include a large number of antenna elements (911). One antenna element may be an X-Pol antenna, or a pole antenna. Since the XL-MIMO antenna panel (910) has a large number of antenna elements, various types of arrangements are possible. For example, various arrangements are possible, such as on the wall of a large shopping mall, an airport, or the wall of a sports stadium. The base station described in FIG. 9 may include all or part of the configuration described in FIG. 2, or may further include additional configurations. For example, the base station may further include one or more of an interface for communicating with a specific network function (NF) of a core network, an interface for communicating with another adjacent base station, and an interface for communicating with other nodes that may be connected below the base station.

[0146] In addition, the terminals (921, 922, 931, 932) illustrated in FIG. 9 may include all or part of the configuration illustrated in FIG. 2. As another example, the terminals (921, 922, 931, 932) illustrated in FIG. 9 may further include additional configurations in addition to all or part of the configuration illustrated in FIG. 2. For example, at least one of the terminals (921, 922, 931, 932) may further include a user interface and / or sensor for user convenience.

[0147] Referring to FIG. 9, the direction perpendicular to the XL-MIMO antenna panel (910) is defined as the X-axis, and the plane direction of the XL-MIMO antenna panel (910) is defined as the Y-axis. The terminals (921, 922, 931, 932) may be located in a far field region or a near field region from the XL-MIMO antenna panel (910). Therefore, an area outside the range of concentric circles spaced apart from the X-axis direction by a certain distance, for example, the Rayleigh distance R (901), may be a far field region, and an area inside the concentric circles spaced apart by the Rayleigh distance R (901) may be a near field region. Therefore, the Rayleigh distance R (901) may be a line dividing the far field region and the near field region. In the example of FIG. 9, the first terminal (921) and the second terminal (922) may be terminals located in a short-range field region, and the third terminal (931) and the fourth terminal (932) may be terminals located in a long-range field region. Each of the terminals (921, 922, 931, 932) may receive a downlink signal, for example, at least one channel among a broadcast channel, a control channel, and a data channel, via a beam formed by the XL-MIMO antenna panel (910) of the base station. In addition, the terminals (921, 922, 931, 932) may transmit an uplink signal to the base station.

[0148] For example, a first terminal (921) located within a near field region can receive a signal from a base station through a first beam (941) based on a near field beamforming scheme, and a second terminal (922) can also receive a signal from the base station through a second beam (942) based on a near field beamforming scheme. In addition, a third terminal (931) located within a far field region can receive a signal from the base station through a third beam (951) based on a far field beamforming scheme, and a fourth terminal (932) can receive a signal from the base station through a fourth beam (952) based on a far field beamforming scheme.

[0149] When the terminal is located in the far field region, the base station can perform beam steering for the far field region through a beamforming vector corresponding to the far field region. On the other hand, when the terminal is located in the near field region, the base station can perform beam steering for the near field region and beam focusing for the near field region. The base station performs beam steering and beam focusing for the terminal in the near field region, and in particular, since the beam focusing must be performed corresponding to the location of the terminal, the distance between the base station and the terminal may be an important factor. In Fig. 9, the first terminal (921) in the near field region can receive the first beam (941) from the base station. In Fig. 9, the hatching of the first beam (941) at the location of the first terminal (921) is expressed in dark shades, which may mean that the energy of the first beam (941) is high at the distance where the first terminal (921) is located. Similarly, the hatching of the second beam (942) expressed in a darker shade at the location of the second terminal (922) may mean that the energy of the second beam (942) is high at the distance where the second terminal (922) is located.

[0150] On the other hand, beams (951, 952) transmitted to the far field region do not exhibit high energy only at specific locations depending on the distance. In other words, the third beam (951) and the fourth beam (952) transmitted to the far field region only have the general characteristic of being inversely proportional to the square of the distance and the transmission power transmitting the beam from the base station.

[0151] Therefore, for beams (951, 952) transmitted to the far field region, only the power according to the signal transmission distance needs to be considered, so only the angle of the beam needs to be adjusted according to the location of the terminal. However, for beams transmitted to the near field region, since the energy is concentrated at a specific location of the beam, the location of the terminal, that is, the angle and distance between the base station and the terminal, must be considered together.

[0152] In the near-field beamforming vector, the phase of each antenna is expressed as a nonlinear function that reflects not only the antenna index but also the incident angle of the electromagnetic wave, the distance between the base station and the terminal, etc. Therefore, the distance at which the beam energy is concentrated in the near-field beam can be adjusted based on a nonlinear function called a "distance ring." In a polar coordinate system defined by the relative angle θ from the base station or XL-MIMO antenna panel (910) located at the origin and the distance r from the base station, the distance ring can be expressed as in the following mathematical equation 3.

[0153]

[0154] In mathematical expression 3, the constant α may be the size of the range ring. The range ring size value may be determined to be two or more values ​​based on the near-field range (area) of the base station. In this case, when there are two or more range ring size values, a range ring index i may be assigned according to the size of each range ring. The range ring size may refer to a parameter that determines how far a near-field beam can be formed from the base station or XL-MIMO antenna panel (910), which is the origin. In a 6G communication system, the base station must be able to form multiple range rings and adjust the position at which the near-field beam is focused.

[0155] The present disclosure proposes a beam management procedure that can be generally used when a terminal is located in a far field area or a near field area.

[0156] If the terminal is located in a far-field area, the base station can divide the service area (the signal transmission range of the base station in the far-field area) into multiple parts based on the angular range of beams that the base station can generate. Then, the base station can calculate a far-field beamforming vector corresponding to the divided angles and continuously form a beam, thereby performing far-field beam sweeping.

[0157] If the terminal is located in the near-field region, the base station can divide the service area according to the angle of the beam that can be generated and the range of the range ring. Therefore, even for beams with the same angle, two or more beams must be formed according to the number of range rings. The base station can calculate the near-field beamforming vector based on each angle and range. Using the calculated values, the base station can generate beams and perform near-field beam sweeping on the generated beams.

[0158] For a base station located in the near-field region, beam sweeping across all angles and distance combinations, in the same manner as beam sweeping in 5G NR, requires significant time resources. For example, near-field beam sweeping requires beam focusing at different distances for the same angle, requiring more time resources than beam sweeping in 5G NR. Therefore, a beam management procedure that can address this issue is needed.

[0159] In the present disclosure, the entire beam sweeping process can be divided into two steps as follows to reduce the time resources and computational complexity required in the beam management process.

[0160] First, long-range field beam steering can be performed. Then, short-range field beam focusing can be performed.

[0161] Let's first look at far-field beam steering. The base station can perform beam sweeping using multiple far-field beams. In other words, it can form far-field beams in the same manner as used in 5G NR and transmit each beam by sweeping it. Accordingly, the terminal can receive the far-field beams swept and transmitted by the base station and sort the received beams in descending order of performance, starting with the best beam. Here, beam performance can be determined based on, for example, RSRP or an equivalent power value. The terminal can select a predetermined number of beams from the beams sorted by beam performance. The terminal can then report information about the selected beams to the base station. Therefore, the base station can obtain information about the best few beams through far-field beam steering.

[0162] If the terminal is located in the near field region, the base station can perform near field beam focusing. At this time, the base station may perform beam focusing based on the angle acquired through far field beam steering, rather than performing near field beam focusing for all angles and all distances. Accordingly, the base station can perform near field beam focusing for beams corresponding to angles below a predetermined value for which communication performance is determined. The terminal can receive beams from the base station based on the near field beam focusing. Then, the terminal can select the most optimal beam. The terminal can report the selected optimal beam to the base station. Through this, the base station can determine the optimal beam in the angle-distance domain.

[0163] The procedure described above eliminates the need for near-field beam sweeping for beams at angles where communication performance deteriorates during the far-field beam steering process. Consequently, the beam search space can be significantly reduced. Additionally, if the base station has prior information about the terminal's location, the beam search space can be further reduced.

[0164] The prior information that the base station can use to determine the location of the terminal is as follows.

[0165] 1) Distance between base station and terminal

[0166] 2) Relative angle between base station and terminal

[0167] 3) Distance between base station and terminal and relative angle between base station and terminal

[0168] There may be several ways for a base station to determine the distance between itself and a terminal. For example, the base station can infer (or estimate) the distance between the base station and the terminal from the propagation delay information of the physical random access channel (PRACH) preamble. As another example, the distance between the base station and the terminal can be measured using a timing-based reference signal, such as the positioning reference signal (PRS) or sounding reference signal (SRS) used in the 5G NR system. As another example, the base station can obtain distance information between the base station and the terminal in the form of side information from the positioning service of the terminal. Here, the side information may be information indirectly obtained from information obtained from the terminal, the base station, and / or the network in order for the base station to provide the terminal location service. For example, it may be timing information based on PRS, SRS, and / or location information of the terminal acquired by the terminal using the Global Positioning System (GPS). The side information mentioned in the present disclosure may be referred to as additional information.

[0169] In the methods described above, the base station can find the optimal beam by performing beam sweeping over a specific angular range and distance range among angle-distance domain grids using prior information. The angle-distance domain grids are described in detail in the drawings described below.

[0170] At this time, beam sweeping can be performed by selecting far-field or near-field beam sweeping appropriate for the electromagnetic wave region of the terminal. The base station can measure the angle between the base station and the terminal by transmitting and / or receiving a reference signal capable of measuring the relative angle information between the base station and the terminal. As an example of the reference signal, the downlink angle of departure (DL-AoD) can be measured using PRS and / or the uplink angle of arrival (UL-AoA) can be measured using SRS. As another method of measuring the angle between the base station and the terminal, the base station can obtain it in the form of side information from the location service. The side information may be referred to as additional information as described above. In this way, if the base station knows the distance and angle between the base station and the terminal through prior information, the base station can find the optimal beam by performing far-field beam steering and near-field beam focusing for the angle-distance domain.

[0171] Finally, if the base station knows the distance and relative angle between the base station and the terminal, it can use this distance information to determine whether the terminal is in the far field or the near field. If the base station determines that the terminal is in the far field, it can perform far-field beam sweeping to find the optimal beam. If the base station determines that the terminal is in the near field, it can perform near-field beam sweeping on a grid of angles and distances near the location known through prior information to find the optimal beam.

[0172] In the examples described in this disclosure, RSRP was considered as a communication performance indicator for final selection of beams between the base station and terminal during the base station and terminal beam selection process. However, other similar information can be utilized. Examples of performance indicators that can be used instead of RSRP include Reference Signal Received Quality (RSRQ) and Channel Quality Indicator (CQI). In addition, various types of reference signals that can determine channel quality can be utilized, and no special restrictions are placed on the signals that can be utilized as performance indicators in this disclosure.

[0173] The present disclosure, described below, describes a procedure for selecting an optimal beam for wireless communication between a base station and a terminal. Furthermore, when selecting the optimal beam, a beam management procedure that can be generally used by the base station regardless of whether the terminal is located in the far field or the near field is described. Furthermore, the beam management procedure described in the present disclosure can actively utilize prior information about the terminal's location held by the base station. By utilizing prior information about the terminal's location, the time required for beam sweeping and the complexity of calculations can be minimized.

[0174] To this end, the present disclosure describes suitable beam sweeping procedures for each of the following four cases. The cases that can be assumed in the present disclosure are as follows.

[0175] (1) If there is no prior information about the location of the terminal,

[0176] (2) If only the distance information between the base station and the terminal is known,

[0177] (3) When only the relative angle information between the base station and the terminal is known, or

[0178] (4) When the location information of the terminal, i.e. the relative angle and distance information between the base station and the terminal, is known.

[0179] The more prior information a base station has about the location of a terminal, the more it can reduce the number of beam candidates for which it must measure performance during beam sweeping.

[0180] Meanwhile, each of the four scenarios assumed above assumes downlink beamforming, where the base station forms a beam toward the terminal. However, the beam management process must consider both downlink beamforming, which is the base station beam, and uplink beamforming, which is the terminal beam.

[0181] Unlike existing 5G systems, where base stations and terminals could only form far-field beams, 6G systems can assume situations where both base stations and terminals can form both far-field and near-field beams. Therefore, to form appropriate transmission and reception beams corresponding to the electromagnetic wave range between the base station and terminal, the base station needs to convey electromagnetic wave range determination information to the terminal before the beam formation process.

[0182] For example, if a base station can determine an electromagnetic wave region through prior information, the base station can transmit the determined electromagnetic wave region information to the terminal before the terminal forms a beam. There may be various ways in which the base station can transmit electromagnetic wave region information to the terminal. For example, the base station can provide electromagnetic wave region information to the terminal using a reference signal such as a Channel State Information-Reference Signal (CSI-RS). As another example, the base station can newly define RRC signaling to transmit electromagnetic wave region information and transmit the electromagnetic wave region information to the terminal through the newly defined RRC signaling.

[0183] The terminal can perform its own beamforming process based on electromagnetic wave domain information received from the base station. If the terminal supports near-field beam sweeping, it can selectively use far-field beam sweeping and near-field beam sweeping, similar to the base station's beamforming process, to find the optimal terminal beam. As another example, if the terminal does not support near-field beam sweeping, it can form the optimal terminal beam through far-field beam sweeping, similar to existing 5G systems.

[0184] [Example 1: When there is no prior information about the terminal's location]

[0185] Hereinafter, a beam management method is described when a base station does not have prior information about a terminal. The prior information about the terminal described below may include at least one of an angle from an XL-MIMO antenna of the base station to the terminal or a distance from the XL-MIMO antenna of the base station to the terminal. Therefore, in the first embodiment of the present disclosure, there may be a case where the base station does not have information about either the angle from the XL-MIMO antenna of the base station to the terminal or the distance from the XL-MIMO antenna of the base station to the terminal.

[0186] When the base station does not have prior information about the terminal, the beam management method according to the present disclosure can be divided into two stages as described above. First, the optimal beam is searched through long-range field beam sweeping. If short-range field beam sweeping is required, the optimal beam to be transmitted to the terminal can be selected through short-range beam sweeping. If short-range field beam sweeping is not required, the optimal beam to be transmitted to the terminal can also be selected during the long-range beam sweeping stage. The specific operations for this will be described with reference to the attached drawings.

[0187] Figure 10 is a flowchart of a procedure for beam management when a base station has no prior information about a terminal.

[0188] Before explaining with reference to FIG. 10, the base station may be a base station having an XL-MIMO antenna panel. The configuration of the base station may include all or part of the configuration of FIG. 2 as described above, and the transceiver (230) may include an XL-MIMO antenna panel. In addition to the configuration illustrated in FIG. 2, the base station may further include additional configurations. For example, the base station may further include an interface for communicating with an NF of a core network, an interface for communicating with adjacent base stations, and an interface for communicating with a communication node connected below the base station.

[0189] The terminal described in FIG. 10 may include all or part of the configuration of FIG. 2. Additionally, the terminal may further include other configurations not illustrated in FIG. 2. For example, the terminal may further include various interfaces, sensors, etc. for user convenience.

[0190] In step S1000, the base station can share with the terminal information necessary for beam formation. For example, the base station can transmit RSRP threshold information to the terminal in advance. The RSRP threshold information may be information for determining beam suitability when setting a far-field beam and / or a near-field beam. When the base station uses the two-step beam management method according to the present disclosure, if the RSRP threshold is not satisfied, the base station can provide the terminal with information on the number of RSRP values ​​to be reported among the RSRP values ​​that are not satisfied. In addition, the base station can provide the terminal with information on the number of distance rings that the base station can use. Since the base station knows the size information of the XL-MIMO antenna panel, if the antenna panel size information of the terminal is known, the base station can calculate and store a Rayleigh distance value that can distinguish the far field and the near field. In addition, the base station can also provide the terminal with the Rayleigh distance value in advance. The Rayleigh distance can be calculated by the mathematical formula 1 or 2 described above, and the following description assumes the use of mathematical formula 2.

[0191] In step S1000, the information transmitted from the base station to the terminal may be transmitted to the terminal via one or more of upper layer signaling, for example, radio resource control (RRC) signaling messages, media access control-control information (MAC-CE), or system information blocks (SIB). For example, if the base station can perform beamforming by distinguishing between near and far fields, the number of range rings that the base station can use may be transmitted via an SIB or RRC signaling message.

[0192] Two or more RSRP thresholds may be set based on the requirements of the service provided to the terminal and / or the load of the base station. If two or more RSRP thresholds are used, the base station can transmit the two or more RSRP thresholds to the terminal via an RRC signaling message. In addition, the base station can notify, configure, or indicate to the terminal via MAC-CE which of the two or more RSRP thresholds it wants to use at a specific point in time.

[0193] In addition to the information described above, additional information may be shared between the base station and the terminal. Information to be shared between the base station and the terminal may be transmitted from the base station to the terminal and / or from the terminal to the base station in step S1000. In this case, the information to be shared between the base station and the terminal may be further transmitted from the base station to the terminal via various signaling messages and / or the physical downlink control channel (PDCCH) described above.

[0194] In step S1002, the base station can transmit the CSI-RS to the terminal through each of the far field beams using a beam sweeping method. At this time, the base station can transmit a beam index or beam identifier for identifying each of the far field beams together. The beam index or beam identifier can be configured in two ways. First, when the distance ring index is not used, in order to identify whether the transmitted beam is a far field beam or a near field beam, if the most significant bit (MSB) is "zero", it can be set as a far field beam, and if it is a near field beam, the MSB can be set to "1". If the distance ring index is used, if the transmitted beam includes the distance ring index, the beam can be identified as a near field beam, and if the distance ring index is not included, the beam can be identified as a far field beam.

[0195] Accordingly, the terminal can receive the CSI-RS transmitted by the base station in step S1002 through each of the far-field beams. The terminal can identify the beams through the beam index or beam identifier, and measure the RSRP value for the CSI-RS transmitted by the base station. The terminal can map and store the beam index or beam identifier and the measured RSRP value. Then, the RSRP value and beam index to be included in the first report message can be determined based on the RSRP threshold information set in step S1000. In all embodiments described below, the first report message is described assuming that measurement report information for the far-field beam is transmitted. In addition, the measurement report for the near-field beam described below is described assuming that it is included in the second report message. The distinction between the first report message and the second report message is merely an assumption to help understanding the invention, and should not be construed as a limiting factor of the present disclosure. The first report message and the second report message may use the same message, or different messages. Specific examples thereof will be described below.

[0196] For example, if there is an RSRP value higher than the RSRP threshold value received in step S1000 among the RSRP values ​​measured for the CSI-RS received from the base station, the terminal may include information mapping the RSRP value higher than the RSRP threshold value and the beam index information corresponding to the RSRP value in the first report message. If there are two or more RSRP values ​​higher than the RSRP threshold value, only the highest RSRP value may be included in the first report message. As another example, if there are two or more RSRP values ​​higher than the RSRP threshold value, m RSRP values ​​starting from the highest RSRP value may be included in the first report message. Here, m may be a natural number, and if m is 1, only the highest RSRP value may be included. If m is 2 or more, m RSRP values ​​having the highest RSRP value among the RSRP values ​​higher than the RSRP threshold value and the beam index information corresponding to the RSRP value may be mapped and included in the first report message. The value of m may be preset in step S1000.

[0197] Meanwhile, if there is no RSRP value higher than the RSRP threshold value received in step S1000 among the RSRP values ​​measured for the CSI-RS received from the base station, the terminal may include in the first report message the RSRP values ​​corresponding to the beam indexes and the n number of RSRP values ​​instructed to be reported in step S1000 mapped to the beam indexes corresponding to the RSRP values. At this time, the RSRP values ​​included in the first report message may be included in descending order starting from the highest RSRP value among the measured RSRP values. Meanwhile, since the terminal has received the RSRP performance information required in advance from the base station, if there is a measured RSRP value higher than the required RSRP value among the measured RSRP values, the terminal may set the parameter notifying the termination of the beam management procedure to true and transmit it. In this case, the base station and the terminal may check whether the beam management procedure is terminated only with the parameter notifying the termination of the beam management procedure.

[0198] In step S1004, the base station may receive a first report message including RSRP value(s) for the far field beam(s) from the terminal.

[0199] In step S1006, the base station can check whether the RSRP value measured at the terminal included in the first report message includes an RSRP value higher than the RSRP threshold. If the RSRP value measured at the terminal includes an RSRP value higher than the RSRP threshold, it may be the case that a beam that satisfies the communication performance exists. If a beam that satisfies the communication performance exists based on the verification result of step S1006, the base station can proceed to step S1020. If a beam that satisfies the communication performance does not exist based on the verification result of step S1006, the base station can proceed to step S1010.

[0200] In step S1020, the base station may determine one of the beams satisfying the communication performance as the beam for communication. As described above, if only one RSRP value higher than the RSRP threshold is included in the first report message, the base station may determine the far-field beam to be used for communication with the terminal through the beam index corresponding to the RSRP value.

[0201] If the first report message includes two or more RSRP values ​​higher than the RSRP threshold, the base station may determine the optimal far-field beam by considering one of various conditions. For example, the optimal beam may be selected based on various conditions such as interference with other terminals, interference with adjacent base stations, interference with remote transmitting nodes connected downstream of the base station, or load of the base station. Although not illustrated in FIG. 10, if the first report message includes two or more RSRP values, the base station may provide information on the final selected beam to the terminal.

[0202] When proceeding from step S1006 to step S1020, the terminal is located within the base station's far-field beam area. In other words, the terminal is located within the Rayleigh distance based on mathematical equation 2 or greater, and the distance between the base station or the XL antenna panel and the terminal may be greater than the Rayleigh distance. Therefore, the beam to be used between the base station and the terminal can be determined through the procedure described above.

[0203] Meanwhile, the case where the process proceeds from step S1006 to step S1010 is when the terminal is located in the near-field beam area of ​​the base station. In other words, the distance between the base station or the XL antenna panel and the terminal may be within the Rayleigh distance.

[0204] In step S1010, the base station can determine a set of angle candidates for beam sweeping and beam focusing of near-field beams. The set of angle candidates can be determined based on the RSRP values ​​included in the first report message and the mapped beam indices. For example, if there is no beam among the RSRP values ​​measured in step S1000 in which the RSRP value is greater than or equal to the RSRP threshold, the base station can configure the n RSRP values ​​with the highest RSRP values ​​to be mapped and transmitted. Accordingly, the terminal can include n RSRP values ​​and the beam indices corresponding to the RSRP values ​​in descending order from the highest RSRP value among the measured RSRP values ​​in the first report message. Accordingly, the base station can identify n beams starting from the beam with the highest RSRP value measured by the terminal. The set of angle candidates can be determined using the n beams identified in this way.

[0205] Typically, the RSRP values ​​measured at the terminal are the beam with the highest RSRP value and the RSRP values ​​of its adjacent beams, which have the next highest RSRP value. Therefore, the base station can determine the beam with the highest RSRP value and its adjacent beams as the angle candidate set. In other words, the steering angles of the beam with the highest RSRP value and its adjacent beams can be determined as the angle candidate set.

[0206] In step S1012, the base station can determine an angle-distance domain grid for the set of angle candidates. As described above, the near-field beam is focused to a specific region based on the distance from the base station and / or the XL-MIMO antenna panel. Therefore, the near-field region can be configured with grids that focus on each distance for each beam. For example, the distance section from the XL-MIMO antenna panel to r1 for the first beam can be designated as the first grid, the distance section from r1 to r2 for the first beam can be designated as the second grid, and in the same manner, the distance section from the XL-MIMO antenna panel to r2 to r3 for the first beam can be designated as the third grid. Each grid for the first beam is based on a separation distance, which can be a range ring as described above. Therefore, for one beam, there are as many grids as the number of range rings. Therefore, a distance-based grid is determined only for a specific beam corresponding to the set of angle candidates based on the beam reported from the terminal.

[0207] In step S1012, the base station can transmit the CSI-RS to the terminal via the near-field beam for each determined grid. Since the grid for each range is determined only for the angle candidates of specific beams, a significant time saving effect can be achieved compared to transmitting the CSI-RS via the beam with grids for all beams. At this time, the base station can transmit the near-field beam index together with the near-field beam. As described above, the near-field beam index can be applied in two ways. The first way is to use the MSB of the near-field beam index to distinguish between the near-field beam and the far-field beam. In this case, as described above, by setting the MSB to "1", the beam transmitted by the base station can be notified that it is a near-field beam. The second way is to use the range ring index, and the identifier for distinguishing between the near-field beam and the far-field beam may not be included. The far-field beam does not include the range ring index. On the other hand, the near-field beam may include the range ring index. Additionally, the distance ring index can be used to identify the distance range of the transmitted beam.

[0208] In step S1012, the terminal can receive the CSI-RS transmitted through a specific short-range beam for each grid. The terminal can measure the RSRP of the received CSI-RS. Then, the terminal can map and store the measured RSRP value and the beam index. The terminal can generate a second report message including an RSRP value exceeding the RSRP threshold received in advance in step S1000 among the measured RSRP values ​​and the beam index corresponding thereto. At this time, if there are two or more RSRP values ​​exceeding the RSRP threshold, the second report message may include information mapping the two or more RSRP values ​​and the beam index corresponding to each RSRP value based on the m value described above. Then, the terminal can transmit the second report message to the base station.

[0209] In step S1014, the base station may receive a second report message including an RSRP value for the near field beam(s) from the terminal.

[0210] In step S1016, the base station may determine a near-field beam based on the RSRP value(s) included in the second report message. At this time, if there are two or more RSRP values ​​included in the second report message, the base station may determine an optimal near-field beam by considering one or more of various conditions. For example, the optimal beam may be selected based on various conditions such as interference with other terminals, interference with remote transmission nodes connected downstream of the base station, or load of the base station. In addition, although not illustrated in FIG. 10, if two or more RSRP values ​​are reported in the second report message, the base station may provide information on the final selected beam to the terminal.

[0211] Meanwhile, in Fig. 10, a step for checking whether a beam satisfying communication performance exists after step S1014 is not configured to be included. This is because, as a result of the inspection in steps S1002 to S1006, the beam to be transmitted to the terminal is not a suitable far-field beam. Therefore, a beam suitable for the terminal is a near-field beam, and generally, at least one of the measurement results of the CSI-RS transmitted through each grid within the set of angle candidates satisfies the RSRP threshold or higher.

[0212] However, even if the CSI-RS is transmitted using beams within the angle candidate set through grids within the angle candidate set, there may be cases where an RSRP greater than the RSRP threshold is not measured. Therefore, to prevent such cases, a step of checking whether a beam satisfying the communication performance exists in the second report message between steps S1014 and S1016 may be further included. If a beam satisfying the communication performance does not exist in the second report message, a step of configuring an angle-distance domain grid for other beams within the near-field region and retransmitting the CSI-RS for each grid may be further included.

[0213] The embodiment of FIG. 10 described above illustrates an example in which a far-field beam and a near-field beam transmit CSI-RS. However, the CSI-RS is merely an example for ease of understanding, and other reference signals may be used. In particular, when the present disclosure is applied to a 6G communication system, if a new reference signal is defined for selecting a far-field beam and a near-field beam, the newly defined reference signal may be used. Furthermore, in addition to the reference signal, a synchronization signal block (SSB) may be used during the initial connection procedure between a terminal and a base station.

[0214] The operation described above with reference to FIG. 10 is described in more detail with reference to FIGS. 11a to 11c and the tables exemplified below.

[0215] First, the base station may have information as shown in Table 2 below.

[0216] Required RSRP performance RSRP threshold = 90 dBm Number of range rings that a base station can form 4 Size of the set of angular candidates for near-field beam sweeping 3

[0217] The "required RSRP performance" illustrated in Table 2 may be information provided by the base station to the terminal in step S1000, and may be a value used to confirm communication performance satisfaction in step S1004 of FIG. 10. In the example of Table 2, a case where the RSRP threshold is 90 dBm is illustrated. Accordingly, if the RSRP value of the CSI-RS received through a specific beam is greater than 90 dBm, the terminal and / or base station may determine that the communication performance is satisfied.

[0218] In Table 2, the "number of distance rings that the base station can form" may be the number for beam focusing in the short-range region. In other words, it may be the number of distance rings that can be formed in the distance domain when performing short-range field beam sweeping. Information on the number of distance rings may be provided to the terminal in step S1000 described above. The example in Table 2 illustrates a case where the number of distance rings that the base station can form is assumed to be 4. Therefore, a grid may be formed based on 4 distance rings for each beam.

[0219] Finally, the "size of the angular candidate set for near-field beam sweeping" may also be a value configured by the base station in the terminal in step S1000. The "size of the angular candidate set for near-field beam sweeping" may be the n value described in step S1000, and may be the number of RSRP values ​​that the terminal is configured to report when none of the RSRP values ​​measured for the far-field beams satisfy the required RSRP performance. In the example of Table 2, it is assumed that the "size of the angular candidate set for near-field beam sweeping" is three.

[0220] Table 2 considers a situation where the size of the angular candidate set is determined to a specific value prior to the beam sweeping process. However, the size of the angular candidate set may be determined flexibly based on various criteria, such as the RSRP value measured during the far-field beam sweeping process described below in Table 3, or the latency requirement among the data requirements to be provided to the terminal.

[0221] If the size of the angular candidate set is not determined before the beam sweeping process, an additional procedure for determining the size of the angular candidate set may be implemented to be performed before the near-field beam sweeping process after the far-field beam sweeping process. For example, if there is no beam larger than the RSRP threshold during the far-field beam sweeping process, the base station can designate a angular candidate set and perform near-field beam sweeping only for the corresponding angles. In this way, performing beam sweeping only within the angular candidate set during near-field beam sweeping has the advantage of reducing the time for determining a beam to be communicated through beam sweeping compared to performing beam sweeping for all near-field beams.

[0222] FIG. 11a is a conceptual diagram illustrating a method of transmitting far-field beams by beam sweeping at a base station having an XL MIMO antenna.

[0223] Referring to Fig. 11a, an example of a case in which a base station has an XL-MIMO antenna panel (1110) is illustrated. In the example of Fig. 11a, the X-axis illustrates the direction in which the XL-MIMO antenna panel (1110) faces when the base station radiates a beam through the XL-MIMO antenna panel (1110), and the Y-axis illustrates the direction parallel to the plane of the XL-MIMO antenna panel (1110).

[0224] According to the example of FIG. 11A, the base station can sequentially transmit ten beams (1111, 1112, 1113, 1114, 1115, 1116, 1117, 1118, 1119, 1120). In other words, the base station can transmit the ten beams by beam sweeping. As a more specific example, the base station can sweep the beams in the following order: first beam (1111) -> second beam (1112) -> third beam (1113) -> fourth beam (1114) -> fifth beam (1115) -> sixth beam (1116) -> seventh beam (1117) -> eighth beam (1118) -> ninth beam (1119) -> tenth beam (1120) and transmit them to the terminal (1130). As another example, the base station may sweep the beams in order from the 10th beam (1120) to the 1st beam (1111) and transmit them to the terminal (1130). In addition, the far field beams transmitted in FIG. 11A may each transmit a CSI-RS and may further include a beam index for identifying each of the far field beams.

[0225] In the example of Fig. 11a, the number of beams being swept is assumed to be 10, but this is only for the convenience of understanding, and the number of beams being swept may be more than 10.

[0226] In the example of FIG. 11A, it is assumed that the terminal (1130) is located within the area of ​​the fourth beam (1114). The terminal (1130) can measure the RSRP value of the CSI-RS transmitted through each beam. In other words, the terminal (1130) can measure the RSRP value for the CSI-RS transmitted through the first beam (1111) to the tenth beam (1120). Based on the result of measuring the RSRP for the CSI-RS transmitted through the first beam (1111) to the tenth beam, the terminal (1130) can determine whether there is a beam that satisfies the required RSRP performance (having an RSRP value of 90 dBm or more in the case of Table 2). If there is one or more beams that satisfy the threshold, the terminal (1130) can transmit to the base station a first report message that includes information mapping the identifiers of the beam(s) above the threshold and the measured RSRP values.

[0227] If the RSRP value measured by the terminal (1130) for the CSI-RS received through the fourth beam (1114) satisfies the required RSRP performance, the base station may determine the fourth beam (1114) as a far-field beam for communicating with the terminal (1130) as described in step S1020 of FIG. 10.

[0228] If there is no beam that satisfies the required RSRP performance, the terminal (1130) may transmit a first report message to the base station that includes measurement information that maps a predetermined number of n RSRP values ​​sequentially from the highest RSRP value among the received beams and the identifier of the beam(s) corresponding to each of the RSRP values.

[0229] An example of a case in which none of the RSRP values ​​measured for the CSI-RS transmitted through the first beam (1111) to the tenth beam (1120) described in FIG. 11a meet the required RSRP performance can be illustrated as in Table 3 below.

[0230] BS far-field beam (beam index) Comparison result of RSRP measured by terminal and RSRP threshold Whether to select an angle candidate set BS far-field beam #1 (00000) RSRP_37 < RSRP threshold Not selected (False) BS far-field beam #2 (00001) RSRP_55 < RSRP threshold Not selected (False) BS far-field beam #3 (00010) RSRP_77 > RSRP threshold Selected (True) BS far-field beam #4 (00011) RSRP_86 > RSRP threshold Selected (True) BS far-field beam #5 (00100) RSRP_81 > RSRP threshold Selected (True) BS far-field beam #6 (00101) RSRP_61 < RSRP threshold Not selected (False) BS far-field beam #7 (00110) RSRP_49 < RSRP threshold Not selected (False) BS far-field beam #8(00111)RSRP_35 < RSRP threshold not selected(False)BS far-field beam #9(01000)RSRP_29 < RSRP threshold not selected(False)BS far-field beam #10(01001)RSRP_23 < RSRP threshold not selected(False)

[0231] In Table 3, the far-field beam index may be an identifier for identifying the far-field beams of the base station. In addition, the result of comparing the RSRP measured by the terminal and the RSRP threshold in Table 3 may mean the result of comparing the required RSRP performance as exemplified in Table 2 with the RSRP value measured by the terminal. Lastly, in Table 3, the selection of the angle candidate set may be a field indicating whether it is included in the first report message. The example in Table 3 may be beam indices selected based on the size of the angle candidate set for near-field beam sweeping as exemplified in Table 2 because the RSRP values ​​measured by the terminal for the CSI-RS transmitted through all far-field beams do not satisfy the required RSRP performance. Therefore, according to the example in Table 2, three beams may be selected, and beam indices having three RSRPs sequentially starting from the highest RSRP value among the RSRP values ​​measured by the terminal may be included.

[0232] Meanwhile, in Table 3, the far field beam index can be transmitted through a resource indicator such as the CSI-RS resource indicator (CRI). As another example, the far field beam index can also be transmitted to the terminal by a newly defined RRC signaling message to deliver the far field beam index to the terminal. The number of far field beams of the base station is n far In this case, the number of bits used to distinguish the long-distance field beams can be the number of bits calculated by the mathematical expression 4 below.

[0233]

[0234] However, n far= 1, 2 bits can be used. In Table 3, the MSB of the BS far field beam index can be a bit to indicate that the far field beam is used. Therefore, since the number of far field candidate beams used by the base station in the sweeping process is 10, 4 bits can be used to distinguish each candidate beam. The reason for adding the value "1" in Equation 4 means that one bit is added to distinguish between the near field beam and the far field beam. Therefore, as explained above, the MSB of each beam index can use the value "0" to inform the terminal (1130) that the beam on which the current CSI-RS is transmitted is a far field beam. Therefore, this can be an example of using a total of 5 bits to identify beams.

[0235] When a base station transmits a CSI-RS through a specific beam, the base station may transmit information about the beam through which the CSI-RS is transmitted, i.e., the base station far field beam index transmitting the CSI-RS, to the terminal through at least one of a DCI, MAC-CE, or RRC reconfiguration message. As another method of transmitting the beam index to the terminal, if the base station defines a new RRC signaling message for transmitting the base station far field beam index for the beam through which the CSI-RS is transmitted, the newly defined RRC signaling message may be used.

[0236] Therefore, the terminal can identify through which transmission beam the base station transmitted the CSI-RS based on the DCI, MAC-CE, RRC reconfiguration message, or newly defined RRC signaling message.

[0237] Additionally, if the RSRP measurement values ​​illustrated in Table 3 and the n value described in step S1000 of FIG. 10 are 3 as illustrated in Table 2 above, the first report message may include mapped information as illustrated in Table 4 below.

[0238] RSRP value measured by candidate beam index terminal 00010RSRP_7700011RSRP_8600100RSRP_81

[0239] In Table 4, the MSB of the candidate beam index is set to zero (0) to identify the far field beam as described above. However, as described in the example of FIG. 10, when 10 far beams are used, 4 bits are enough to identify 10 beams. When only 4 bits are used for the beam index, the first report message may further include distance ring index information. As in the example of Table 2, when 4 distance rings are used, the distance ring information can be expressed using 2 bits. However, as described in Equation 4, one more bit may be required to distinguish the far field beams for which the distance ring is not used. Therefore, when indicating that the distance ring is not used together with the distance ring indices, 3 bits of information may be used. Table 5 below may be an example of information included in the first report message when the distance ring index is used.

[0240] Distance ring index candidate beam index RSRP value measured by terminal 1110010RSRP_77 1110011RSRP_86 1110100RSRP_81

[0241] The distance ring index being represented as "111" may mean that the distance ring index is not used. And for the first distance ring, the distance ring index may be set to "000", for the second distance ring, the distance ring index may be set to "001", for the third distance ring, the distance ring index may be set to "010", and for the fourth distance ring, the distance ring index may be set to "011".

[0242] The following description assumes that information such as Table 4 is used. The base station receives a first report message including information such as Table 4 from the terminal (1130), and based on the candidate beam index information included in the first report message, the base station can determine that among the RSRP values ​​measured for the CSI-RS received by the terminal (1130), the RSRP value measured for the CSI-RS transmitted through the fourth beam (1114) has the highest RSRP value, the beam having the second highest RSRP value is the fifth beam (1115), and the beam having the third highest RSRP value is the third beam (1113). In addition, since the RSRP values ​​measured by the terminal (1130) are reported together, the base station can also determine that none of the third beam (1113), the fourth beam (1114), and the fifth beam (1115) satisfy the required RSRP performance.

[0243] The first report message described above may utilize various types of messages. For example, the terminal (1130) may transmit RSRP and beam index information of the CSI-RS to the base station through the CSI-RS reporting process of uplink control information (UCI). As another example, the RSRP reporting process of the CSI-RS transmitted through the base station candidate beam may be such that the base station first transmits information regarding the performance report instruction of the candidate beam of the base station to the terminal (1130) through a UE information request (UEInformationRequest) in RRC signaling, and the terminal (1130) may receive this and transmit RSRP information regarding the candidate beam of the base station through a UEInformationResponse. As another example, information regarding the performance report instruction of the candidate beam of the base station may be transmitted to the terminal through a SIB or a new RRC signaling message. Then, the terminal (1130) may report using a Measurement Report message, UE Assistance Information in response to a report instruction received from the base station, or, if a new RRC signaling message is defined for reporting information according to the present disclosure, using a newly defined RRC signaling message.

[0244] Figure 11b is a conceptual diagram illustrating an area in which beam sweeping is to be performed based on the number of distance rings and the size of the set of angle candidates.

[0245] Fig. 11b may be a conceptual diagram illustrating only the near field region. Therefore, it is assumed that the far field region is not illustrated. Referring to Fig. 11b, a case in which the number of range rings is 4 is illustrated as illustrated in Table 2. More specifically, Fig. 11b illustrates a first range ring (1140) closest to the base station, a second range ring (1150) second closest to the base station, a third range ring (1160) third closest to the base station, and a fourth range ring (1170) farthest from the base station. In this case, grids for beam sweeping can be determined as follows.

[0246] As described above in FIG. 11a, let us assume that the angular candidate sets for performing beam sweeping in the near field region are the third beam (1113), the fourth beam (1114), and the fifth beam (1115). In this case, three grids can be formed for each of the third beam (1113), the fourth beam (1114), and the fifth beam (1115) within the first distance ring (1140) region. More specifically, the region for transmitting CSI-RS using the third beam (1113) within the first distance ring (1140) region will be referred to as the 1-3 region, the region for transmitting CSI-RS using the fourth beam (1114) within the first distance ring (1140) region will be referred to as the 1-4 region, and the region for transmitting CSI-RS using the fifth beam (1115) within the first distance ring (1140) region will be referred to as the 1-5 region. As above, each of the 1-3 regions, the 1-4 regions, and the 1-5 regions can be one angle-distance grid.

[0247] Additionally, three grids for beam sweeping can be formed using the third beam (1113), the fourth beam (1114), and the fifth beam (1115) for the second distance ring (1150). The region in which the CSI-RS is transmitted using the third beam (1113) within the second distance ring (1150) region is referred to as the 2-3 region, the region in which the CSI-RS is transmitted using the fourth beam (1114) within the second distance ring (1150) region is referred to as the 2-4 region, and the region in which the CSI-RS is transmitted using the sixth beam (1115) within the second distance ring (1150) region is referred to as the 2-5 region. As described above, each of the 2-3 region, the 2-4 region, and the 2-5 region can be one angle-distance grid.

[0248] In the same manner, three grids for beam sweeping can be formed for the third distance ring (1160) using the third beam (1113), the fourth beam (1114), and the fifth beam (1115). The region for transmitting CSI-RS using the third beam (1113) within the third distance ring (1160) region will be referred to as the 3-3 region, the region for transmitting CSI-RS using the fourth beam (1114) within the third distance ring (1160) region will be referred to as the 3-4 region, and the region for transmitting CSI-RS using the sixth beam (1115) within the third distance ring (1160) region will be referred to as the 3-5 region. As described above, each of the 3-3 region, the 3-4 region, and the 3-5 region can also be one angle-distance grid.

[0249] Finally, for the fourth range ring (1170), which is the furthest distance from the base station in the short-range area, three grids for beam sweeping can be formed using the third beam (1113), the fourth beam (1114), and the fifth beam (1115). The area in which the CSI-RS is transmitted using the third beam (1113) within the fourth range ring (1170) area is referred to as the 4-3 area, the area in which the CSI-RS is transmitted using the fourth beam (1114) within the fourth range ring (1170) area is referred to as the 4-4 area, and the area in which the CSI-RS is transmitted using the sixth beam (1115) within the fourth range ring (1170) area is referred to as the 4-5 area. As described above, each of the 4-3 area, the 4-4 area, and the 4-5 area can also be a single angular-range grid.

[0250] Therefore, the total number of grids that a base station must search can be determined by the product of the number of range rings that the base station can form and the size of the set of angular codes for near-field beam sweeping. In other words, the base station can determine 12 angle-range grids.

[0251] As previously described in step S1008 of FIG. 10, the base station can transmit CSI-RS to the terminal by beam-sweeping the determined angle-distance grids. Accordingly, the terminal can receive the CSI-RS via the beam directed to the angle-distance grids. Furthermore, the terminal can measure the RSRP for the received CSI-RS.

[0252] Referring to FIG. 11b, a case where a beam is focused to a specific grid is described. For example, beamforming can be performed to concentrate energy in a specific area based on angle and distance. For example, the base station can perform beam focusing to concentrate energy in the 2-5 area (1153). The 2-5 area (1153) may be an area where a signal is transmitted using the second distance ring (1150) and the fifth beam (1115).

[0253] As described above in FIG. 9, in the case of the near-field region, since the region where the beam energy is concentrated is generated based on the angle and distance, even if the beam has the same angle, the RSPR value measured by the CSI-RS at the terminal may vary greatly if the distance between the base station and the terminal is different. In other words, in the case of the near-field beam, even if beamforming is performed using the same fifth beam (1115), the energy concentration may vary greatly depending on the distance variable, that is, the value of the distance ring. When the base station forms the beam so that the beam is focused in the 2-5 region (1153), the energy in the region corresponding to beams of different distances using the same 5th beam (1115), for example, the 5th beam (1115) and the 1st distance ring (1140), may have a very low value compared to the energy in the 2-5 region (1153). For the same reason, when the base station forms the beam so that the beam is focused in the 2-5 region (1153), the energy in the region corresponding to the 5th beam (1115) and the 3rd distance ring (1160) may have a very low value compared to the energy in the 2-5 region (1153).

[0254] Similarly, if the base station performs beam focusing in the 3rd-4th area (1162), the energy in the area of ​​another distance ring where the signal is transmitted using the same 4th beam (1114) may be very low. Here, the very low energy may mean that the RSRP value measured by the terminal that received the CSI-RS signal transmitted by the base station through the corresponding beam is very low.

[0255] The base station can form a beam to be swept with different candidate beams based on the above-mentioned range rings and angle candidate sets so as to be focused from a range ring area close to the base station. In other words, beam sweeping can be performed by beam sweeping the third beam (1113), the fourth beam (1114), and the fifth beam (1115) so as to be focused in the range of the first range ring (1140), and then beam sweeping the third beam (1113), the fourth beam (1114), and the fifth beam (1115) so as to be focused in the range of the second range ring (1150).

[0256] At this time, the terminal (1130) may be located in the 3rd-4th area (1162) as illustrated in Fig. 11b. The 3rd-4th area (1162) may be in the range from the distance r1 to the distance r2 as separately indicated at the bottom of Fig. 11b.

[0257] Therefore, when a CSI-RS signal is transmitted across 12 grids, the terminal can measure the RSRP value for the CSI-RS transmitted across each grid. An example of the RSRP measurement values ​​for the CSI-RS across the 12 grids, along with each beam index, is shown in Table 6 below.

[0258] Candidate beam (beam index) of base station RSRP value Candidate beam (beam index) of base station RSRP value BS Near field beam #1 (10000) RSRP_82BS Near field beam #7 (10110) RSRP_104BS Near field beam #2 (10001) RSRP_89BS Near field beam #8 (10111) RSRP_100BS Near field beam #3 (10010) RSRP_92BS Near field beam #9 (11000) RSRP_79BS Near field beam #4 (10011) RSRP_91BS Near field beam #10 (11001) RSRP_88BS Near field beam #5 (10100) RSRP_84BS Near field beam #11 (11010) RSRP_96BS Near field beam #6 (10101) RSRP_99BS Near field beam #12(11011)RSRP_85

[0259] In Table 6, the MSB of the candidate beam of the base station being 1 may be a bit indicating that the beam transmitted from the base station is a near field beam, as explained above. In addition, the near field beam index may be transmitted through a resource indicator such as CRI. As another example, the near field beam index may be transmitted to the terminal by a newly defined RRC signaling message to deliver the near field beam index to the terminal. The number of far field beams of the base station is n near In this case, the number of bits used to distinguish the near-field beams can be the number of bits calculated by the mathematical expression 5 below.

[0260]

[0261] n mear= 1, 2 bits can be used. In Table 6, the MSB of the BS near-field beam index can be a bit to indicate that the near-field beam is used. Therefore, since the number of near-field candidate beams used by the base station during the sweeping process is 12, 4 bits can be used to distinguish each candidate beam. The reason for adding the value "1" in Equation 5 means that one bit is added to distinguish between the near-field beam and the far-field beam. Therefore, as explained above, the MSB of each beam index can use the value "1" to inform the terminal (1130) that the beam on which the current CSI-RS is transmitted is a near-field beam. Therefore, this can be an example of using a total of 5 bits to identify beams.

[0262] When a base station transmits a CSI-RS through a specific beam, the base station may transmit information about the beam through which the CSI-RS is transmitted, i.e., the base station near-field beam index transmitting the CSI-RS, to the terminal through a DCI, MAC-CE, or RRC reconfiguration message. As another method of transmitting the beam index to the terminal, the base station may define a new RRC signaling message for transmitting the base station far-field beam index for the beam through which the CSI-RS is transmitted, and the newly defined RRC signaling message may be used.

[0263] Therefore, the terminal can identify through which transmission beam the base station transmitted the CSI-RS based on the DCI, MAC-CE, RRC reconfiguration message, or newly defined RRC signaling message.

[0264] Meanwhile, a second report message may be transmitted to the base station. The second report message may include m beam indices and RSRP measurement values ​​corresponding to RSRPs measured above the RSRP threshold required in Table 6. In this case, when m is 1, the second report message may include only the highest RSRP measurement value and one beam index corresponding to it. However, when m is 2 or greater, m RSRP measurement values ​​and beam indices corresponding to each of the RSRP measurement values ​​may be included in descending order from the highest RSRP measurement value among the measured RSRP values. In this case, the beam index may be determined as a value based on the far-field beam index and the range ring as exemplified in Table 5 above.

[0265] The second report message described above may utilize various types of messages. For example, the terminal (1130) may transmit RSRP and beam index information of the CSI-RS to the base station through the CSI-RS reporting process of uplink control information (UCI). As another example, the RSRP reporting process of the CSI-RS transmitted through the base station candidate beam may be such that the base station first transmits information regarding the performance report instruction of the candidate beam of the base station to the terminal (1130) through a UE information request (UEInformationRequest) in RRC signaling, and the terminal (1130) may receive this and transmit RSRP information regarding the candidate beam of the base station through a UEInformationResponse. As another example, information regarding the performance report instruction of the candidate beam of the base station may be transmitted to the terminal through a SIB or a new RRC signaling message. Then, the terminal (1130) may report using a Measurement Report message, UE Assistance Information in response to a report instruction received from the base station, or, if a new RRC signaling message is defined for reporting information according to the present disclosure, using a newly defined RRC signaling message.

[0266] If other factors are not taken into consideration, the base station can determine the base station near field beam #7 as the optimal beam for communicating with the terminal (1130) based on Table 6. In addition, if the value of m is 1, the terminal (1130) can report to the base station only the beam index and the measured RSRP value for the near field beam #7 in the second report message.

[0267] Figure 11c is a conceptual diagram illustrating a case where a beam is formed to a terminal by an XL-MIMO antenna.

[0268] As illustrated in FIG. 11c, when the base station is located between distances r1 and r2, a beam can be formed toward the terminal (1130) via XL-MIMO antenna elements. The configuration illustrated in FIG. 11c may correspond to an example in which the terminal (1130) is located in the near field, as previously described in FIG. 11b.

[0269] [Example 2: When there is prior information about the distance between the base station and the terminal]

[0270] Below, a beam management method is described when a base station has prior information about a terminal, such as distance information from the base station or the base station's XL-MIMO antenna to the terminal. The base station can use the distance information between the base station and the terminal to determine the electromagnetic wave region in which the terminal is located. In other words, the base station can use the distance information between the base station and the terminal to determine whether the terminal is located within the near field region or the far field region. Based on this determination, the base station can perform a beam management procedure with the terminal. The specific operation thereof will be described with reference to the attached drawings.

[0271] Figure 12 is a flowchart of a procedure for beam management when a base station has distance information from a terminal.

[0272] Before describing with reference to FIG. 12, the base station may be a base station having an XL-MIMO antenna panel. The base station may have a configuration similar to that described above in FIG. 10. The terminal may also have a configuration similar to that described above in FIG. 10.

[0273] In step S1200, the base station may share with the terminal prior information necessary for beam formation. For example, the base station may transmit RSRP threshold information to the terminal in advance. The RSRP threshold information may be information for determining beam suitability when setting a far-field beam and / or a near-field beam. The base station may also provide the terminal with information on the number of distance rings that the base station can use. Since the base station knows the size information of the XL-MIMO antenna panel, if the antenna panel size information of the terminal is known, the base station may calculate and store a Rayleigh distance value that can distinguish the far field and the near field. In addition, the base station may provide the terminal with the Rayleigh distance value in advance. The Rayleigh distance may be calculated by the mathematical expression 1 or mathematical expression 2 described above, and the following description assumes the use of mathematical expression 2. The Rayleigh distance in the present disclosure is an example to help understanding the present disclosure, and if another index that can replace the Rayleigh distance can be set, the alternative index may be utilized.

[0274] In step S1200, the information transmitted from the base station to the terminal may be transmitted to the terminal via one or more of upper layer signaling, for example, a radio resource control (RRC) signaling message, media access control-control information (MAC-CE), or a system information block (SIB). For example, the number of range rings that the base station can use may be transmitted via an SIB or an RRC signaling message.

[0275] The RSRP threshold may be set based on the requirements of the service provided to the terminal and / or the load of the base station. The RSRP threshold may be transmitted to the terminal via an RRC signaling message. Alternatively, the base station may notify, configure, or indicate the RSRP threshold to the terminal via MAC-CE.

[0276] In step S1202, the base station can obtain distance information between the base station and the terminal as prior information. As described above, the base station can obtain distance information between the base station and the terminal based on the propagation delay information of the PRACH preamble, or can obtain the distance between the terminal and the base station based on the PRS and / or SRS in which the timing-based reference signal is transmitted, or can obtain distance information between the base station and the terminal as side information (or additional information) for the location service when the terminal's location service is provided. In addition, in step S1202, the base station can compare the obtained distance between the base station and the terminal with the Rayleigh distance. Here, comparing the obtained distance between the base station and the terminal with the Rayleigh distance may mean calculating the difference between the two values. In addition, as described above, the Rayleigh distance can be calculated by mathematical formula 2, and therefore, further explanation will be omitted. In the example of Fig. 12, it is assumed that the Rayleigh distance is calculated at the base station. However, the Rayleigh distance can also be calculated at the terminal.

[0277] If the Rayleigh distance is calculated at the base station, information on the size of the XL-MIMO antenna panel of the base station and the size of the antenna array of the terminal may be required, as described in Equations 1 and 2 above. Accordingly, the base station may receive information on the size of the antenna array of the terminal from the terminal in step S1200. The method for the base station to receive information on the size of the antenna array of the terminal from the terminal may utilize at least one of various methods.

[0278] For example, a terminal can transmit information about the antenna array size of the terminal to a base station via UCI.

[0279] As another example, a base station may transmit an instruction to a terminal to report information about the size of its antenna array via a UE Information Request message. Then, the terminal may transmit information about the size of its antenna array to the base station via a UE Information Response message in response to the UE Information Request message.

[0280] As another example, if UE capability information is defined to include information on the antenna array size of the terminal, the base station may obtain information on the antenna array size of the terminal by transmitting a UE capability information request message to the terminal, and the terminal may transmit the UE capability information to the base station.

[0281] As another example, the base station may transmit information to the terminal via a SIB or a new RRC signaling message, instructing the terminal to report information about the size of the terminal's antenna array. Upon receiving this, the terminal may transmit information about the terminal's antenna array size to the base station via a measurement report message, a UE Assistance Information message, or a new RRC signaling message.

[0282] If the Rayleigh distance is calculated at the terminal, the terminal may transmit the calculated Rayleigh distance information to the base station at step S1200.

[0283] In step S1204, the base station can check whether it is possible to determine the field area to which the terminal belongs. For example, the base station can determine the distance between the base station and the terminal obtained as prior information by d priorLet R be the Rayleigh distance. At this time, the distance d between the base station and the terminal obtained by the base station as prior information prior may contain errors rather than exact values. Therefore, it is necessary to check whether the difference between the two values ​​is within a preset margin range, as in mathematical expression 6 below.

[0284]

[0285] The distance d between the base station and the terminal obtained by the base station as prior information within the range of mathematical expression 6 prior In the case where there is a terminal, it may be difficult for the base station to accurately determine whether the terminal's location is included in the near field region or the far field region based on the Rayleigh distance R. Therefore, if it is impossible to determine the field region to which the terminal belongs based on the verification result of step S1204, the process may proceed to step S1230. Step S1230 may be a method according to the first embodiment described above using FIG. 10.

[0286] On the other hand, if it is possible to confirm the field area to which the terminal belongs based on the verification result of step S1204, the base station can proceed to step S1206 to confirm whether the terminal is located in the remote field area. If the terminal is located in the remote field area, the distance d between the base station and the terminal in the Rayleigh distance R prior The difference between the base station and the terminal may be negative. In other words, the distance d between the base station and the terminal prior This may be the case if the value is greater than the Rayleigh distance R.

[0287] If the terminal is located in the near field region, the distance d between the base station and the terminal is the Rayleigh distance R. prior The difference between the base station and the terminal may be positive. In other words, the distance d between the base station and the terminal prior This may be the case if the value is smaller than the Rayleigh distance R.

[0288] If it is determined that the terminal is located in the far field area based on the verification result of step S1206, the base station may perform step S1210. On the other hand, if it is determined that the terminal is located in the near field area based on the verification result of step S1206, the base station may perform step S1220.

[0289] Meanwhile, the above assumes that the base station determines whether the terminal is located in the near field region or the far field region. However, the terminal can also perform Rayleigh distance calculation and region determination simultaneously. In other words, if the terminal determines whether the terminal is located in the near field region or the far field region using the above method, the terminal can provide the determined information to the base station. In addition, the terminal must receive XL-MIMO antenna panel size information from the base station to calculate the Rayleigh distance.

[0290] Therefore, the base station can transmit XL-MIMO antenna panel size information to the terminal through downlink control information (DCI), MAC-CE, and RRC signaling messages. At this time, the base station may additionally provide frequency information used for communication. If additional frequency information is not provided, the terminal may utilize frequency information used in the procedure for obtaining downlink synchronization with the base station. The terminal can transmit to the base station the electromagnetic wave area determination information described above, that is, information on whether the terminal is located in the near field area or the far field area, or whether determination of the near field area / far field area is impossible.

[0291] Information transmitted by the terminal to the base station may utilize, for example, fields newly defined in UCI.

[0292] As another example, a base station may instruct a terminal to report electromagnetic range determination information via a terminal information request message. In this case, the terminal may determine its electromagnetic range using the above method and transmit the determined information to the base station via a terminal information response message.

[0293] In step S1210, the base station may transmit CSI-RS to the terminal through each of the far-field beams using a beam sweeping method. At this time, the base station may also transmit a beam index or beam identifier for identifying each of the far-field beams. The method for configuring the beam index or beam identifier may be the same as that described in the embodiment of FIG. 10, and therefore, a duplicate description will be omitted.

[0294] In step S1210, the terminal can receive the CSI-RS transmitted by the base station through the far field beams. The terminal can identify the beams through the beam index or beam identifier and measure the RSRP value for the CSI-RS transmitted by the base station. The terminal can map the beam index or beam identifier and the measured RSRP value and store it. In addition, the RSRP value and beam index to be included in the first report message can be determined based on the RSRP threshold information set in step S1200.

[0295] For example, the first report message may include information mapping RSRP values ​​higher than or equal to the RSRP threshold among the RSRP values ​​measured for the CSI-RS received from the base station and beam index information corresponding to the RSRP values. If there are two or more RSRP values ​​higher than or equal to the RSRP threshold, the first report message may include only the highest RSRP value. As another example, if there are two or more RSRP values ​​higher than or equal to the RSRP threshold, the first report message may include m RSRP values ​​starting from the highest RSRP value. Here, m may be a natural number, and if m is 1, only the highest RSRP value may be included. If m is 2 or more, m RSRP values ​​having the highest RSRP values ​​among the RSRP values ​​higher than the RSRP threshold and beam index information corresponding to the RSRP values ​​may be mapped and included in the first report message. The value of m may be preset in step S1000.

[0296] In step S1212, the base station may receive a first report message including RSRP value(s) for the far field beam(s) from the terminal.

[0297] In step S1214, the base station can determine a far-field beam for communication based on the first report message. If the first report message includes only one RSRP value, that is, if only one RSRP value having the highest RSRP value among the measured RSRP values ​​that are greater than or equal to the RSRP threshold and a beam identifier corresponding to the highest RSRP value are reported, the base station can set the beam as a beam for communication with the terminal in the far-field region.

[0298] On the other hand, if there are two or more RSRP values ​​included in the first report message, the base station can determine the optimal far-field beam by considering one of various conditions. For example, the optimal beam can be selected based on various conditions such as interference with other terminals, interference with adjacent base stations, interference with remote transmitting nodes connected downstream of the base station, or the load of the base station. Although not illustrated in FIG. 12, if there are two or more RSRP values ​​reported in the first report message, the base station can provide information on the final selected beam to the terminal.

[0299] Meanwhile, when proceeding from step S1206 to step S1220, the base station can determine a grid for beam sweeping and beam focusing of near-field beams based on distance information between the base station and the terminal. At this time, the grid can be determined based on the beam and distance ring as described above in FIG. 11b.

[0300] In step S1222, the base station can transmit CSI-RS to the terminal through beam sweeping and beam focusing for each determined grid. At this time, the base station can identify the grids using the distance ring index and beam index as described above in FIG. 10, or can transmit an identifier for the near field beam that is distinguished from the far field beam for each grid.

[0301] The method of transmitting a beam to a near field region according to the present disclosure has the advantage of significantly reducing the time required compared to a case where beams are transmitted to grids for all distance rings of all beams, because the distance information between the base station and the terminal is known and the grid to which the beam is to be transmitted is determined by utilizing the distance information.

[0302] In step S1222, the terminal can receive the CSI-RS transmitted for each grid and measure the RSRP of the received CSI-RS. The terminal can store the measured RSRP value by mapping each beam identifier, or can store the measured RSRP value by mapping it together with the distance ring index and the beam index. In addition, the terminal can transmit to the base station the highest RSRP value among the measured RSRP value(s) having a value greater than or equal to the RSRP threshold among the measured RSRP values ​​and the beam identifier corresponding to the highest RSRP value in a second report message. The second report message may also include two or more measured RSRP values ​​and beam index information corresponding to each of the measured RSRP values, as described above.

[0303] In step S1224, the base station may receive a second report message including RSRP value(s) for near field beams from the terminal.

[0304] In step S1226, the base station may determine a near-field region beam for communicating with the terminal based on the second report message. If the second report message includes only the highest RSRP value among the measured RSRP value(s) and the beam identifier corresponding to the highest RSRP value, the base station may select the corresponding beam. If the second report message includes two or more measured RSRP values ​​among the measured RSRP value(s) and beam identifiers corresponding to each of the measured RSRP values, the base station may determine an optimal near-field beam by considering one or more of various conditions. For example, the optimal beam may be selected based on various conditions such as interference with other terminals, interference with remote transmitting nodes connected downstream of the base station, or the load of the base station. In addition, although not illustrated in FIG. 12, if two or more RSRP values ​​are reported in the second report message, the base station may provide information on the finally selected beam to the terminal.

[0305] The embodiment of FIG. 12 described above illustrates an example in which a far-field beam and a near-field beam transmit CSI-RS. However, the CSI-RS is merely an example for ease of understanding, and other reference signals may be used. In particular, when the present disclosure is applied to a 6G communication system, if a new reference signal is defined for selecting a far-field beam and a near-field beam, the newly defined reference signal may be used. Furthermore, in addition to the reference signal, a synchronization signal block (SSB) may be used in the initial connection procedure between a terminal and a base station.

[0306] The operation of the present disclosure is described in more detail with reference to FIG. 13 and the tables exemplified below, as described above with reference to FIG. 12.

[0307] Figure 13 is a conceptual diagram for explaining a method of transmitting near-field beams by beam sweeping when distance information from a terminal is known at a base station having an XL MIMO antenna.

[0308] Referring to Fig. 13, an example of a case in which a base station has an XL-MIMO antenna panel (1310) is illustrated. In the example of Fig. 13, the X-axis represents the direction in which the XL-MIMO antenna panel (1310) faces when the base station radiates a beam through the XL-MIMO antenna panel (1310), and the Y-axis represents the direction parallel to the plane of the XL-MIMO antenna panel (1310).

[0309] This case assumes that the base station knows the distance between the terminal (1330) and the base station through prior information. Furthermore, it is assumed that the terminal (1330) is located within the near-field region. The number of beams and range rings that the base station can form can be set as shown in Table 7 below.

[0310] The number of beams that a base station can form (angle index) 10 (j = 1, 2, …, 10) The number of range rings that a base station can form (range ring index) 4 (i = 1, 2, 3, 4)

[0311] Fig. 13 may be a case where the number of distance rings that a base station can form is 4, as exemplified in Table 7. More specifically, it exemplifies a case where a first distance ring (1341) closest to the base station, a second distance ring (1342) second closest to the base station, a third distance ring (1343) third closest to the base station, and a fourth distance ring (1344) farthest from the base station are formed.

[0312] Additionally, the base station can form a first beam (1311), a second beam (1312), a third beam (1313), a fourth beam (1314), a fifth beam (1315), a sixth beam (1316), a seventh beam (1317), an eighth beam (1318), a ninth beam (1319), and a tenth beam (1320) as illustrated in Table 7.

[0313] In Fig. 13, the distance between the base station and the terminal (1330) is represented by a radius, and a semicircle (1301) with the center of the XL-MIMO antenna panel (1310) of the base station as the center point is illustrated by a dotted line. Accordingly, the semicircle (1301) indicated by a dotted line in Fig. 13 may be a line connecting points where the terminal (1330) may be present.

[0314] Accordingly, the base station can identify grids overlapping with a semicircle (1301) connecting points where a terminal (1330) may exist, as shown in FIG. 13. In FIG. 13, grids overlapping with a beam among the points through which the semicircle (1301) connecting points where a terminal (1330) may exist passes are indicated with hatching. This can be calculated as shown in the following mathematical equation (7).

[0315]

[0316] α in Equation 7i In , α represents the distance ring size, and i represents the distance ring index. d prior As explained above, it can be the distance between the base station and the terminal obtained by the base station as prior information. Also, θ j may be a beam index that a base station can form. Specific examples of grids that satisfy the condition of mathematical expression 7. In other words, the grids where the terminal (1330) can be located are as follows.

[0317] A grid set by the first beam (1311) and the fourth distance ring (1344), a grid set by the second beam (1312) and the third distance ring (1343), a grid set by the second beam (1312) and the fourth distance ring (1344), a grid set by the third beam (1313) and the third distance ring (1343), a grid set by the fourth beam (1314) and the third distance ring (1343), a grid set by the fifth beam (1315) and the third distance ring (1343), a grid set by the sixth beam (1316) and the third distance ring (1343), a grid set by the seventh beam (1317) and the third distance ring (1343), a grid set by the eighth beam (1318) and the third distance ring (1343), a ninth beam (1319) and the third distance The grid set by the ring (1343), the grid set by the ninth beam (1319) and the fourth distance ring (1344), the grid set by the tenth beam (1320) and the third distance ring (1343), and the grid set by the tenth beam (1320) and the fourth distance ring (1344) may be a grid. The number of grids as above may be a total of 12 grids, and in the present disclosure, the above grids will be referred to as a distance-based candidate grid set.

[0318] In the example of Fig. 13, when determining a range-based candidate grid set, only near-field beams corresponding to the prior range information are included. However, additional grids may be included, or a smaller number of near-field beams may be included in the range-based candidate grid set, based on the number of range rings that the base station can form and / or the latency requirements of the terminal.

[0319] The base station may sequentially sweep the beams of the grids listed above in the distance-based candidate grid set. As another example, the base station may sequentially sweep the beams of the closest third distance ring (1343) and the plurality of beams (1312-1319), and then perform beam sweeping on the fourth distance ring (1344) and the plurality of beams (1311, 1312, 1319, 1320). As another example, beam sweeping may be performed sequentially on each grid for a single beam. For example, the second beam (1312) may transmit the beam for the third distance ring (1343) and then transmit the beam for the fourth distance ring.

[0320] In the present disclosure, transmitting a beam may mean transmitting a signal, such as CSI-RS or SSB, that enables the terminal to measure RSRP through the beam, as described above. In addition, a beam identifier may be transmitted together with each beam.

[0321] When the base station transmits CSI-RS through each beam, it can inform the terminal of information about the beam through which the CSI-RS is transmitted. In other words, the base station can inform the terminal of the near field beam index of the base station transmitting the CSI-RS. At this time, the near field beam index information can be provided to the terminal through DCI, MAC-CE, RRC reset message, or newly defined RRC signaling message to inform the near field beam index of the base station.

[0322] When a base station transmits a CSI-RS through a beam, it can inform the terminal of the beam index through a resource indicator, such as the CRI of the CSI-RS, as a method of informing the terminal of the beam index. At this time, the total number of bits of the beam index can be determined using the method described in Equation 5 above.

[0323] Therefore, the terminal can determine through which transmission beam the base station transmitted the CSI-RS based on the message received from the base station.

[0324] As illustrated in FIG. 13, if a base station can obtain distance information from a terminal as prior information, beam sweeping can be performed only on grids based on the distance between the base station and the terminal, rather than beam sweeping on all beams and all range rings according to the present disclosure. In other words, the beam search space used for near-field beam sweeping can be reduced. Consequently, the time required to find an optimal beam between the base station and the terminal can be reduced.

[0325] The terminal can measure the CSI-RS transmitted by focusing the beams on each grid and store the measured RSRP by mapping it to a beam index. The measured RSRP and the measured RSRP values ​​of the near-field candidate beams are exemplified in Table 8 below.

[0326] Candidate beam (beam index) of base station RSRP value Candidate beam (beam index) of base station RSRP value BS Near field beam #1 (0000) RSRP_43BS Near field beam #7 (0110) RSRP_67BS Near field beam #2 (0001) RSRP_55BS Near field beam #8 (0111) RSRP_59BS Near field beam #3 (0010) RSRP_61BS Near field beam #9 (1000) RSRP_50BS Near field beam #4 (0011) RSRP_84BS Near field beam #10 (1001) RSRP_44BS Near field beam #5 (0100) RSRP_97BS Near field beam #11 (1010) RSRP_35BS Near field beam #6 (0101) RSRP_82BS Near field beam #12 (1011) RSRP_29

[0327] In Table 8, since there are 12 beams selected as the distance-based candidate grid set as illustrated in FIG. 13, the base station can use 12 near-field candidate beams. Since the number of near-field candidate beams used by the base station is 12, 4 bits can be allocated to distinguish each candidate beam. Comparing Table 8 with the first embodiment described above, since in the second embodiment of the present disclosure, there is no need to distinguish between the base station near-field beam and the far-field beam, the beam index of the base station's candidate beam may be a case where the one bit of MSB described in the first embodiment is not set. If it is necessary to distinguish between the near-field beam and the far-field beam, one bit of MSB can be additionally set.

[0328] The terminal can store the RSRP values ​​measured for the CSI-RS transmitted for each grid, as shown in Table 8. Furthermore, the terminal can map the beam index of the base station candidate beam corresponding to each of the stored RSRP values ​​and store them together.

[0329] The terminal can transmit measured RSRP and beam index information for CSI-RS to the base station via a second report message. The second report message can take the form of one of various messages. For example, the second report message can be configured as a UCI. If the second report message is configured as a UCI, the UCI can be transmitted to the base station during the CSI-RS reporting process.

[0330] As another example, the second report message may be reported in response to a reporting instruction from the base station. For example, if the base station is instructed to report beam performance through a UE information request (UEInformationRequest) in an RRC signaling message, the terminal may transmit the measured RSRP value and corresponding beam index information to the base station through a UEInformationResponse.

[0331] As another example of a response to a request from a base station, the base station may indicate reporting of measured RSRP values ​​in a SIB or new RRC signaling. In such a case, the terminal may respond to the reporting indication by using a newly defined RRC signaling message for reporting measurement reports, terminal assistance information, or measured RSRP values, and report the measured RSRP value and the beam index corresponding to the measured RSRP value to the base station.

[0332] At this time, the measured RSRP value may be reported as the highest RSRP value among RSRP values ​​above the RSRP threshold value and the beam index corresponding to it, as described in Fig. 12. As another example, a predetermined number of RSRP values ​​above the RSRP threshold value and the beam index corresponding to each of the RSRP values ​​may be reported.

[0333] [Example 3: When there is prior information about the angle between the base station and the terminal]

[0334] Hereinafter, a beam management method is described when a base station has angular information from the base station or the XL-MIMO antenna of the base station to the terminal as prior information about the terminal. The base station can determine a beam to use for communication with the terminal by utilizing relative angular information from the base station and / or the XL-MIMO antenna of the base station to the terminal. The method of utilizing relative angular information from the base station and / or the XL-MIMO antenna of the base station to the terminal according to the present disclosure may be a method in which the base station efficiently finds the location of the terminal by using far-field beam sweeping and / or near-field beam sweeping by utilizing only beams in directions corresponding to angles, rather than all beams. In the method according to the present disclosure, the far-field beam sweeping may be performed first, and then the near-field beam sweeping may be performed to select an optimal beam. Additionally, when hierarchical beam sweeping can be performed, a beam with higher performance can be found by repeatedly performing more detailed beam sweeping on an angle-distance domain area corresponding to the beam selected in the previous step. At this time, when performing hierarchical beam sweeping, the number of layers (the number of times a segmented beam is used) can be determined by considering the latency requirements of the service provided to the terminal. The specific operation thereof will be examined with reference to the attached drawing.

[0335] Figure 14 is a flowchart of a procedure for beam management when a base station has relative angle information with a terminal.

[0336] Before describing with reference to FIG. 14, the base station may be a base station having an XL-MIMO antenna panel. The configuration of the base station may have the configuration described above in FIG. 10. The terminal may also have the configuration described above in FIG. 10.

[0337] In step S1400, the base station may share with the terminal information necessary for beam formation. For example, the base station may transmit RSRP threshold information to the terminal in advance. The RSRP threshold information may be information for determining beam suitability when setting a far-field beam and / or a near-field beam. The base station may also provide the terminal with information on the number of distance rings that the base station can use. Since the base station knows the size information of the XL-MIMO antenna panel, if the antenna panel size information of the terminal is known, the base station may calculate and store a Rayleigh distance value that can distinguish the far field and the near field. In addition, the base station may provide the Rayleigh distance value to the terminal in advance. The Rayleigh distance may be calculated by the mathematical expression 1 or mathematical expression 2 described above, and the following description assumes the use of mathematical expression 2. The Rayleigh distance in the present disclosure is an example to help understanding the present disclosure, and if another index that can replace the Rayleigh distance can be set, the alternative index may be utilized.

[0338] In step S1400, the information transmitted by the base station to the terminal may be transmitted to the terminal via one or more of upper layer signaling, for example, a radio resource control (RRC) signaling message, media access control-control information (MAC-CE), or a system information block (SIB). For example, the number of range rings that the base station can use may be transmitted via an SIB or RRC signaling message. An RSRP threshold may be set based on requirements for services provided to the terminal and / or the load of the base station. If so, the RSRP threshold may be transmitted to the terminal via an RRC signaling message. As another example, the base station may notify, configure, or indicate the RSRP threshold to the terminal via MAC-CE.

[0339] In step S1402, the base station can obtain angle information between the terminal and the base station. For convenience of explanation, FIG. 14 illustrates a procedure for the base station to obtain angle information between the base station and the terminal in step S1402. However, the base station may also obtain angle information between the base station and the terminal in step S1400 as prior information. As described above, the angle information between the base station and the terminal may be measured through a reference signal capable of measuring the angle, such as PRS (DL-AoD) or SRS (UL-AoA). As another example, the base station may obtain angle information between the base station and the terminal as side information (or additional information) for the positioning service. In the following description, obtaining angle information between the base station and the terminal in step S1402 is explained on the assumption that the base station reads information that it has in advance as prior information.

[0340] In step S1402, the base station can determine the number of far field beams to be transmitted to the terminal based on the angle information stored as prior information. When the base station determines the number of far field beams based on the angle information, the base station can select n-1 far field beams adjacent to (or closest to) the far field beams on the angle including the terminal, including the far field beams corresponding to the angle information at which the terminal is located, as a prior angle-based candidate set. At this time, the size n of the prior angle-based candidate set can be determined based on various criteria, such as the latency requirement of the service to be provided to the terminal or the beam width that the base station can form.

[0341] For example, based on the angles acquired through prior information, the base station can set the number of far-field beams included in the prior-angle-based candidate set to 1. In this case, the prior-angle-based candidate set can only include one far-field beam corresponding to the angle information at which the terminal is located.

[0342] As another example, the base station may set the number of far-field beams included in the pre-angle-based candidate set to two based on the angles acquired as prior information. In this case, in addition to one far-field beam corresponding to the angle information at which the terminal is located, the pre-angle-based candidate set may also include one far-field beam corresponding to the angle information at which the terminal is located and one far-field beam closest to the same.

[0343] As another example, the base station may set the number of far-field beams included in the pre-angle-based candidate set to three based on the angles acquired as prior information. In this case, in addition to one far-field beam corresponding to the angle information at which the terminal is located, another far-field beam corresponding to the angle information at which the terminal is located, one closest far-field beam, and another far-field beam that is the second closest may be included in the pre-angle-based candidate set.

[0344] The number of candidate sets based on the angle of incidence can be determined based on the accuracy of the angle information and the location of the terminal. If the angle information is determined to be highly accurate, the base station can transmit only one beam. Even if the angle information is accurate, if the location is at the edge of the beam width that the base station can form, the base station can decide to additionally transmit another beam adjacent to the location of the terminal. As another example, if the accuracy of the angle information is low, the base station can select as transmission beams the far-field beam that can be formed based on the location of the terminal and two adjacent far-field beams.

[0345] In step S1404, the base station can transmit the CSI-RS by sweeping the determined far-field beams, i.e., the far-field beams within the pre-angle-based candidate set. At this time, the base station can transmit a beam index or beam identifier for identifying each of the far-field beams together. The method for configuring the beam index or beam identifier may be the same as that described in the embodiment of FIG. 10, and therefore, a duplicate description will be omitted.

[0346] In step S1404, the terminal can receive the CSI-RS transmitted by the base station through the far field beams. The terminal can identify the beams through the beam index or beam identifier and measure the RSRP value for the CSI-RS transmitted by the base station. The terminal can map the beam index or beam identifier and the measured RSRP value and store it. In addition, based on the RSRP threshold information set in step S1200, the RSRP value and beam index to be included in the first report message can be determined.

[0347] For example, the first report message may include information mapping RSRP values ​​higher than or equal to the RSRP threshold among the RSRP values ​​measured for the CSI-RS received from the base station and beam index information corresponding to the RSRP values. If there are two or more RSRP values ​​higher than or equal to the RSRP threshold, the first report message may include only the highest RSRP value. As another example, if there are two or more RSRP values ​​higher than or equal to the RSRP threshold, the first report message may include m RSRP values ​​starting from the highest RSRP value. Here, m may be a natural number, and if m is 1, only the highest RSRP value may be included. If m is 2 or more, m RSRP values ​​having the highest RSRP values ​​among the RSRP values ​​higher than the RSRP threshold and beam index information corresponding to the RSRP values ​​may be mapped and included in the first report message. The value of m may be preset in step S1400.

[0348] In step S1406, the base station may receive a first report message including RSRP value(s) for the far field beam(s) from the terminal.

[0349] In step S1406, the base station can determine whether there is a beam that satisfies the communication performance based on the RSRP measurement value included in the first report message. If, based on the inspection result of step S1406, there is a beam that satisfies the communication performance, the base station can proceed to step S1420.

[0350] Meanwhile, if there are one or more RSRP values ​​included in the first report message, and all RSRP values ​​included in the first report message are below the RSRP threshold, the base station may determine that there is no beam that satisfies the communication performance. If there is no beam that satisfies the communication performance based on the inspection result of step S1406, the base station may proceed to step S1410.

[0351] In step S1420, the base station can determine a far-field beam for communicating with the terminal. For example, if there is one RSRP value included in the first report message and it is greater than or equal to the RSRP threshold, the base station can determine that there is a beam that satisfies the communication performance. If there are two or more RSRP values ​​included in the first report message and all RSRP values ​​included in the first report message are greater than or equal to the RSRP threshold, the base station can determine the optimal far-field beam by considering one of various conditions. The various conditions can be, for example, interference with other terminals, interference with adjacent base stations, interference with remote transmission nodes connected downstream of the base station, or load of the base station. Although not illustrated in FIG. 14, if two or more RSRP values ​​are reported in the first report message, the base station can provide information on the finally selected beam to the terminal.

[0352] In step S1410, the base station may determine grids for transmitting CSI-RS to the terminal based on the first report message and the angle information, which is the prior information according to the third embodiment. The grids for transmitting CSI-RS to the terminal may be determined based on the number of beams and the number of range rings. The number of beams may be determined based on the RSRP measurement value(s) and the angle information included in the first report message. The RSRP measurement value included in the first report message may be reported with only one RSRP measurement value included, or may include two or more RSRP measurement values. When only one RSRP measurement value is included, only one near-field beam may be determined as a transmission beam in the same manner as determining a far-field beam, or the number of two or more near-field beams may be determined.

[0353] If the first report message includes two or more RSRP measurement values, the base station may determine the number of near-field beams by considering both the RSRP measurement values ​​and the angle information, which is prior information. As another example, the base station may determine the number of near-field beams by considering only the angle information, without considering the RSRP values ​​included in the first report message.

[0354] Once the number of near-field beam(s) is determined, the gratings that can form the near-field beams can be determined based on the number of range rings that can be set at the base station.

[0355] In step S1412, the base station can transmit CSI-RS to the terminal by sweeping the near-field beams with the determined grids. As described above in FIG. 10, the base station can identify the grids using the distance ring index and beam index, or transmit an identifier for the near-field beam that distinguishes it from the far-field beam for each grid.

[0356] The method of transmitting near-field region beams according to the present disclosure has the advantage of significantly reducing the time required compared to the case of transmitting beams to grids for all distance rings of all beams, because it knows the angular information between the base station and the terminal and uses this to determine the grids to transmit the beams.

[0357] In step S1412, the terminal can receive the CSI-RS transmitted for each grid through the near-field beams, and can measure the RSRP of the received CSI-RS. The terminal can store the measured RSRP value by mapping it with the near-field beam identifier, or can store the measured RSRP value by mapping it with the distance ring index and the beam index. In addition, the terminal can transmit to the base station the highest RSRP value among the measured RSRP value(s) having a value greater than or equal to the RSRP threshold value and the beam identifier corresponding to the highest RSRP value in a second report message. The second report message may include two or more measured RSRP values ​​and beam index information corresponding to each of the measured RSRP values, as described above.

[0358] In step S1414, the base station may receive a second report message including RSRP value(s) for near field beams from the terminal.

[0359] In step S1416, the base station may determine a near-field region beam for communicating with the terminal based on the second report message. If the second report message includes only the highest RSRP value among the measured RSRP value(s) and the beam identifier corresponding to the highest RSRP value, the base station may select the corresponding beam. If the second report message includes two or more measured RSRP values ​​and beam identifiers corresponding to each of the measured RSRP values, the base station may determine an optimal near-field beam by considering one or more of various conditions. For example, the optimal beam may be selected based on various conditions such as interference with other terminals, interference with remote transmitting nodes connected downstream of the base station, or the load of the base station. In addition, although not illustrated in FIG. 14, if two or more RSRP values ​​are reported in the second report message, the base station may provide information on the final selected beam to the terminal.

[0360] The embodiment of FIG. 14 described above illustrates an example in which a far-field beam and a near-field beam transmit CSI-RS. However, the CSI-RS is merely an example for ease of understanding, and other reference signals may be used. In particular, when the present disclosure is applied to a 6G communication system, if a new reference signal is defined for selecting a far-field beam and a near-field beam, the newly defined reference signal may be used. Furthermore, in addition to the reference signal, a synchronization signal block (SSB) may be used during the initial connection procedure between a terminal and a base station.

[0361] The operation of the present disclosure is described in more detail with reference to FIG. 15 and the tables exemplified below, as described above with reference to FIG. 14.

[0362] Figure 15 is a conceptual diagram for explaining a method of transmitting near-field beams by beam sweeping when angle information with respect to a terminal is known at a base station having an XL MIMO antenna.

[0363] Referring to Fig. 15, an example of a case in which a base station has an XL-MIMO antenna panel (1510) is illustrated. In the example of Fig. 15, the X-axis illustrates the direction in which the XL-MIMO antenna panel (1510) faces when the base station radiates a beam through the XL-MIMO antenna panel (1510), and the Y-axis illustrates the direction parallel to the plane of the XL-MIMO antenna panel (1510).

[0364] This case assumes that the base station knows the angle information between the terminal (1530) and the base station through prior information. Furthermore, it is assumed that the terminal (1330) is located within the near-field region. The number of beams and range rings that the base station can form can be set as shown in Table 8 below.

[0365] Relative angle information θ between the base station and the terminal prior Required RSRP performance RSRP threshold = 90 dBm Number of range rings that a base station can form 4 Size of candidate set based on pre-angle 3

[0366] The minimum communication performance required in Table 9 is exemplified using the RSRP value, assuming that the RSRP threshold is 90 dBm. The base station transmits each beam by sweeping the far field beam, and can transmit CSI-RS through each beam. Although the example in Fig. 15 is of near field beams, it can be assumed that the far field beams also transmit the same beams. If the far field beams are beamformed in the same way as the near field beams, the number of beams that the base station can form in the far beam direction is 10 (1511, 1512, 1513, 1514, 1515, 1516, 1517, 1518, 1519, 1520). Since the angle of the terminal (1530) is spaced apart by a certain angle in the upper direction of the X-axis as illustrated in FIG. 15, far-field beams can be formed in three near-field beam directions (1513, 1514, 1515).

[0367] The terminal can measure the RSRP for the CSI-RS transmitted through the far field beams and report the result to the base station by including it in the first report message. The base station can determine whether communication is possible through the far field beams by checking whether there is a beam with an RSRP value higher than the RSRP threshold among the measured RSRP values ​​based on the first report message received from the terminal. In other words, it can determine whether the terminal is located in the far field area.

[0368] If the first report message does not contain information about beams above the RSRP threshold, the base station can determine a candidate set based on the pre-angle based on the method described in Fig. 14. In the example of Fig. 15, the pre-angle information θ between the base station and the terminal prior An example is provided where the two far-field beams closest to the corresponding beam are set as a pre-angle-based candidate set for near-field beam sweeping.

[0369] According to the example of FIG. 15, the near-field beams can form ten (1511, 1512, 1513, 1514, 1515, 1516, 1517, 1518, 1519, 1520) near-field beams identically to the far-field beams. The base station can select the directions (1513, 1514, 1515) of the far-field beams as a pre-angle-based candidate set for near-field beam sweeping, and this situation is exemplified in FIG. 15.

[0370] In addition, the base station assumes that the number of range rings that can be formed in the range domain during near-field beam sweeping is four (1541, 1542, 1543, 1544). As described in Fig. 14, the size of the candidate set based on the pre-angle can be determined based on various criteria such as the width of the beam that the base station can form or the delay requirements of the terminal. By appropriately selecting the size of the candidate set based on the pre-angle, the time and computational complexity used for beam steering are reduced.

[0371] According to the beam management process described in the first embodiment, where the base station does not have prior information about the terminal's location, the base station must transmit all possible far-field beams during the far-field beam sweeping process. However, according to the third embodiment, far-field beams can be swept only for a set of candidates based on the prior angle, thereby reducing the consumption of time resources compared to sweeping all far-field beams.

[0372] Candidate beam (Beam index) of base station Comparison result between measured RSRP and RSRP threshold BS Far field beam #1 (000) RSRP_41 < RSRP threshold BS Far field beam #2 (001) RSRP_76 < RSRP threshold BS Far field beam #3 (010) RSRP_45 < RSRP threshold

[0373] Table 10 illustrates the results of comparing the indexes for each far field beam and the RSRP values ​​measured at the terminal when the third far field beam direction (1513) is determined as BS far field beam #1, the fourth far field beam direction (1514) is determined as BS far field beam #2, and the fifth far field beam direction (1515) is determined as BS far field beam #3.

[0374] Since the base station transmits only three far-field beams, it can be configured to have only three beam indices. In this case, the MSB is set to a value of "zero" to indicate that it is a far-field beam.

[0375] Therefore, RSRP for CSI-RS received through three far-field beams of the terminal can be measured. And each beam index and RSRP values ​​can be stored as shown in Table 10. Table 10 exemplifies a case where all measured RSRP values ​​are lower than the RSRP threshold. In other words, this exemplifies a case where the terminal (1530) is located in a near field area, not a far field area. However, when located in a far field area, at least one RSRP value among the RSRP values ​​may have a value higher than the RSRP threshold.

[0376] The beam index for the far field beam can be transmitted from the base station to the terminal through a resource indicator such as the CRI of the CSI-RS, or can be transmitted from the base station to the terminal using a newly defined RRC signaling message that defines and transmits the index for the far field beam. The index for identifying the far field beams that the base station can utilize can be determined using the same method as in Equation 4 described above.

[0377] When a base station transmits a CSI-RS, information about the beam through which the CSI-RS is transmitted, i.e. the far field beam index of the base station transmitting the CSI-RS, can be transmitted to the terminal together with the information via DCI, MAC-CE, RRC reset message, or newly defined RRC signaling message. Accordingly, the terminal can determine through which transmission beam the base station transmitted the CSI-RS based on the far field beam index.

[0378] The measured RSRP and RSRP threshold comparison results in Table 10 may be information obtained from the terminal. As another example, the measured RSRP and RSRP threshold comparison results in Table 10 may be included in the first report message and transmitted to the base station. As another example, only one bit of information indicating that the far field beam cannot be used based on the measured RSRP and RSRP threshold comparison results may be included in the first report message and transmitted to the base station.

[0379] The base station can determine whether the terminal is located in the far field area based on the first report message received from the terminal. In cases such as Table 10, the terminal may be located in the near field area. On the other hand, if any of the measured RSRP values ​​in Table 10 has an RSRP value greater than or equal to the RSRP threshold, the terminal may be located in the far field area. If the terminal is located in the far field area, the base station can determine the far field beam corresponding to the RSRP value greater than or equal to the RSRP threshold as the far field beam to be used for communication with the terminal.

[0380] As illustrated in Table 10, if the measured RSRP values ​​for the CSI-RS transmitted through all far-field beams are less than the RSRP threshold, the base station can determine the beam to communicate with the terminal through the near-field beam.

[0381] The first report message can contain various types of information or be reported to the base station using various message formats. First, let's examine the structure of the first report message.

[0382] For example, the first report message may include RSRP measurements for all far field beams and beam indices for each beam.

[0383] As another example, the first report message may include the highest RSRP measurement value among the RSRP measurement values ​​and the corresponding beam index. In this case, information indicating the availability of the far field beam may or may not be included.

[0384] As another example, the first report message may include a predetermined number of RSRP values, starting from the highest RSRP value among the RSRP measurement values, and the corresponding beam index values. In this case, information indicating the availability of the far field beam may or may not be included.

[0385] In the present disclosure, among the various forms of the first report message mentioned above, an example will be described in which the first report message includes the highest RSRP measurement value among RSRP measurement values ​​and a beam index corresponding thereto, and includes information indicating whether a far field beam is available.

[0386] The terminal may select BS far field beam #2, which is the far field beam with the largest RSRP in Table 10, as a beam for near field beam sweeping, and report the index of BS far field beam #2 and the RSRP measurement value for CSI-RS transmitted through far field beam #2 to the base station in a first report message. In addition, the first report message may further include a parameter indicating whether the far field beam is suitable or whether the beam management procedure is terminated. According to the example of Table 10, the suitability of the far field beam may be set to unsuitable. According to the example of Table 10, the termination of the beam management procedure may indicate an impossible state. The impossibility of terminating the beam management procedure may mean that a beam management procedure using the near field beam must be additionally performed.

[0387] This first report message may be composed of UCI. If the first report message is composed of UCI, the RSRP and beam index information of the CSI-RS may be transmitted to the base station during the CSI-RS reporting process.

[0388] The RSRP reporting process for CSI-RS transmitted via far-field beams can be performed by the base station transmitting performance reporting instruction information for the far-field beams of the base station to the terminal via a terminal information request (UEInformationRequest) in an RRC signaling message. The terminal can receive the terminal information request in the RRC signaling message and transmit RSRP information for the far-field beams via a terminal information response (UEInformationResponse).

[0389] As another example, performance reporting indication information for the far field beams of the base station can be transmitted to the terminal via a SIB or a new RRC signaling message. The terminal can report the measured information to the base station via a measurement report, UE Assistance Information, or a new RRC signaling message in response to the performance reporting indication for the far field beams.

[0390] If the terminal indicates the unavailability of the far field beams with one bit in the first report message, the base station may determine beams in the same direction as the far field beams as the direction of the near field beams. The base station may also determine the grid based on the number of range rings as set in Table 9.

[0391] Referring to FIG. 15, three grids can be determined in the first far field beam direction (1513), the second far field beam direction (1514), and the third far field beam direction (1515) within the first distance ring (1541). In addition, three grids can be determined in the first far field beam direction (1513), the second far field beam direction (1514), and the third far field beam direction (1515) within the second distance ring (1542) which is larger than the first distance ring (1541). Three grids can be determined in the first far field beam direction (1513), the second far field beam direction (1514), and the third far field beam direction (1515) within a third distance ring (1543) that is larger than the second distance ring (1542), and finally, three grids can be determined in the first far field beam direction (1513), the second far field beam direction (1514), and the third far field beam direction (1515) within a fourth distance ring (1544) that is larger than the third distance ring (1543). Therefore, the base station can determine a total of 12 grids as grids to form near field beams to the terminal.

[0392] As another example, grids can be generated based on range rings for only one beam direction based on the first report message reported by the terminal. In the example of Table 10 above, the terminal can report to the base station only the RSRP value for BS far field beam #2 in the first report message. The base station can then determine grids for four range rings for BS far field beam #2. In other words, one grid can be determined in the second far field beam direction (1514) within the first distance ring (1541), one grid can be determined in the second far field beam direction (1514) within a second distance ring (1542) that is larger than the first distance ring (1541), one grid can be determined in the second far field beam direction (1514) within a third distance ring (1543) that is larger than the second distance ring (1542), and finally one grid can be determined in the second far field beam direction (1514) within a fourth distance ring (1544) that is larger than the third distance ring (1543). Therefore, the base station can determine a total of four grids to form near field beams to the terminal.

[0393] In the following, we will explain assuming that four grids are determined.

[0394] Table 11 illustrates an example of RSRP measurement values ​​and corresponding beam index mapping for CSI-RS received by a terminal through near-field beams when a base station transmits CSI-RS through near-field beams with determined grids.

[0395] Base station candidate beam (Beam index)RSRP valueBase station near field beam #1 (100)RSRP_40Base station near field beam #2 (101)RSRP_65Base station near field beam #3 (110)RSRP_94Base station near field beam #4 (111)RSRP_71

[0396] As illustrated in Table 11, the base station near-field beams may be in the direction of a near-field beam corresponding to the fourth far-field beam (1514) among the far-field beams, and the beam index may be determined based on the range rings (1541, 1542, 1543, 1544). Accordingly, the base station may transmit a CSI-RS through four near-field beams. The terminal may measure RSRP values ​​for the CSI-RS received from the base station through the near-field beams, and store the measured RSRP values ​​corresponding to the indices of the near-field beams as illustrated in Table 11.

[0397] The indices of the near-field beams can be transmitted from the base station to the terminal via resource indicators, such as the CRI of the CSI-RS, or via newly defined RRC signaling. The number of bits in the near-field beam indices can be determined as shown in Equation 5 above. Additionally, as in the example described above, the MSB can be set to 1 to indicate to the terminal that it is a near-field beam.

[0398] When transmitting a CSI-RS, the base station can transmit information about the beam through which the CSI-RS is transmitted, i.e., the near-field beam index of the base station transmitting the CSI-RS, to the terminal through a DCI, MAC-CE, RRC reset message, or a newly defined RRC signaling message. Therefore, the terminal can confirm which transmission beam the CSI-RS is transmitted through by receiving the beam index information from the base station.

[0399] The terminal can determine whether there is a near-field beam having an RSRP measurement value greater than or equal to the RSRP threshold as exemplified in Table 9 by measuring the RSRP values ​​of the near-field beams. In the example of Table 9, the RSRP threshold is set to 90 dBm, so in Table 11, the near-field beam having an RSRP measurement value greater than or equal to the RSRP threshold can be the base station near-field beam #3. Accordingly, the terminal can report a second report message including the measured RSRP value and beam index information for the CSI-RS to the base station.

[0400] The second report message may be transmitted from the terminal to the base station when reporting a CSI-RS in UCI. Alternatively, the second report message may be transmitted to the base station based on a request and response from the base station.

[0401] For example, RSRP reporting of CSI-RS can be performed by the base station transmitting beam performance report indication information to the terminal through a UE information request (UEInformationRequest) in an RRC signaling message. The terminal can transmit measured RSRP information to the base station through a UE information response (UEInformationResponse) based on the UE information request in the RRC signaling message.

[0402] As another example, the base station may instruct the UE to report beam performance through a SIB or a newly defined RRC signaling message to indicate beam performance reporting. The UE, upon receiving the SIB or the newly defined RRC signaling message, may report beam performance information to the base station using a measurement report, UE support information, or the newly defined RRC signaling message.

[0403] According to the third embodiment described above, the number of beams for which beam sweeping must be performed is very large compared to the case where all beams are swept without any prior information, so beam sweeping may not be performed for a very large number of beams. Therefore, there is an advantage in that the time for the beam management procedure for finding the optimal beam through beam sweeping can be shortened.

[0404] [Example 4: When there is prior information about the location between the base station and the terminal]

[0405] Hereinafter, a beam management method is described when a base station has location information about a terminal as prior information about the terminal. The base station can utilize the location information of the terminal to determine the beam to use for communication with the terminal. The method of utilizing the location information of the terminal according to the present disclosure can determine whether to perform beam sweeping using a far-field beam or a near-field beam based on the location information. Furthermore, when the terminal is located in the near-field region, beam sweeping and beam focusing are performed by limiting the grids to the vicinity of the terminal's location during near-field beam sweeping, thereby quickly finding the optimal beam. Additionally, when hierarchical beam sweeping can be performed, a beam with higher performance can be found by repeatedly performing more detailed beam sweeping on the angle-distance domain region corresponding to the beam selected in the previous step. In this case, during hierarchical beam sweeping, the number of layers (the number of times the detailed beams are used) can be determined in consideration of the latency requirements of the service provided to the terminal, etc. The specific operation thereof will be described with reference to the attached drawings.

[0406] Figure 16 is a flowchart of a procedure for beam management when a base station has location information of a terminal.

[0407] Before describing with reference to FIG. 16, the base station may be a base station having an XL-MIMO antenna panel. The configuration of the base station may be as described above in FIG. 10. The terminal may also have a configuration as described above in FIG. 10.

[0408] In step S1600, the base station may share with the terminal information necessary for beam formation. For example, the base station may transmit RSRP threshold information to the terminal in advance. The RSRP threshold information may be information for determining beam suitability when setting a far-field beam and / or a near-field beam. The base station may also provide the terminal with information on the number of distance rings that the base station can use. Since the base station knows the size information of the XL-MIMO antenna panel, if the antenna panel size information of the terminal is known, the base station may calculate and store a Rayleigh distance value that can distinguish the far field and the near field. In addition, the base station may provide the Rayleigh distance value to the terminal in advance. The Rayleigh distance may be calculated by the mathematical expression 1 or mathematical expression 2 described above, and the following description assumes the use of mathematical expression 2. The Rayleigh distance in the present disclosure is an example to help understanding the present disclosure, and if another index that can replace the Rayleigh distance can be set, the alternative index may be utilized.

[0409] In step S1602, the base station can obtain the location information of the terminal. For convenience of explanation, FIG. 16 illustrates a procedure in which the base station obtains angle information between the base station and the terminal in step S1602. However, the base station may also obtain the location information of the terminal in step S1600 as prior information. The location information of the base station and the terminal may include information on the distance from the base station to the terminal and the relative angle from the base station to the terminal. The location information of the terminal can be obtained by the base station as side information (additional information) for the positioning service. In the following description, obtaining the location information of the terminal in step S1602 is explained on the assumption that the base station reads information that it has in advance as prior information.

[0410] In step S1602, the base station can compare the distance information of the terminal with the Rayleigh distance. In step S1604, the base station can determine whether the terminal is located in the far field area or the near field area based on the comparison result between the distance information of the terminal and the Rayleigh distance. If the result of the check in step S1604 indicates that the terminal is located in the far field area, the base station can proceed to step S1610. If the result of the check in step S1604 indicates that the terminal is located in the near field area, the base station can proceed to step S1620.

[0411] In step S1610, the base station can determine beams to be transmitted to the terminal based on the relative angle from the base station or the XL-MIMO antenna of the base station to the terminal. At this time, since the beams are determined based on the angle, they can be determined using the same method as described in the third embodiment.

[0412] In step S1612, the base station can sweep the determined beams to transmit CSI-RS to the terminal. At this time, each beam may include beam indices as described above. The beam indices may be determined by either a method of distinguishing between far-field beams and near-field beams using the MSB or a method of determining the indices based on whether or not a distance ring index value is included.

[0413] In step S1612, the terminal can measure the RSRP for the CSI-RS received through the beams transmitted by the base station. Then, the measured RSRP value can be mapped and stored with the corresponding beam index. The terminal can generate a first report message including the beam index and the measured RSRP value for a beam that is greater than or equal to the RSRP threshold among the measured RSRP values. Then, the terminal can report the first report message to the base station.

[0414] In step S1614, the base station can receive a first report message from the terminal.

[0415] In step S1616, the base station can determine a long-range field beam to be used for communication with the terminal based on the first report message received from the terminal.

[0416] When proceeding to step S1620, it may be the case that the terminal is located in the near field area of ​​the base station as described above. In step S1620, the base station may determine the number of hierarchical beam sweeping steps. Hierarchical beam sweeping may be a procedure for finding an optimal beam through two or more steps. For example, when two-step beam sweeping is performed, the base station may identify the approximate location of the terminal by beam sweeping using a relatively wide beam. In addition, the base station may find a more precise location of the terminal by using a more detailed beam based on the location of the terminal acquired through the wide beam.

[0417] Let us first examine the case where the number of hierarchical beam sweeping steps is set as shown in Table 12 below.

[0418] Electromagnetic wave domain judgment information Whether hierarchical beam sweeping of near-field terminals is supported True Number of steps of hierarchical beam sweeping 2

[0419] Whether beam sweeping is supported or not may depend on various factors, such as the latency requirement information of the service provided to the terminal, the beam width that the base station can transmit, the load level of the base station, and whether the terminal supports hierarchical beam sweeping. Information on whether the terminal supports hierarchical beam sweeping may be received in advance from the terminal in step S1600 described above.

[0420] Since the base station according to the fourth embodiment of the present disclosure knows both the distance between terminals and the relative angle information from the base station to the terminal, it can use other methods besides the Rayleigh distance-based determination technique to determine the electromagnetic wave range of the terminal. For example, the base station can determine the electromagnetic wave range by selecting any one of the Rayleigh distance-based determination technique, the phase difference-based determination technique, and the reference signal received path power (RSRPP)-based determination technique.

[0421] In the example in Table 12, the first row is set to True, indicating that the terminal supports hierarchical beam sweeping. If the service provided to the terminal is highly delay-sensitive, this can be set to False, indicating that hierarchical beam sweeping is not supported, even if both the terminal and base station support hierarchical beam sweeping.

[0422] In the example of Table 12, the number of hierarchical beam sweeping steps is determined as two steps. In this case, the base station can determine the number of hierarchical beam sweeping steps based on the information received from the terminal and the information held by the base station when determining the number of hierarchical beam sweeping steps. For example, the shorter the delay requirement of the terminal, the less time it is difficult to spend on the hierarchical beam sweeping process, so the number of steps in the hierarchical beam sweeping process can be set to a small number.

[0423] In addition, the base station can set a large number of hierarchical beam sweeping steps because the angle-distance domain can be subdivided as the beam width (width) that can be formed at the base station is narrow and the number of operable range rings is large. The base station can transmit information on the number of steps of the determined hierarchical beam sweeping process to the terminal in advance. The information on the number of steps of the hierarchical beam sweeping process can be transmitted in advance in step S1600 described above. Alternatively, the information on the number of steps of the hierarchical beam sweeping process can be provided to the terminal by the base station through separate signaling when it is determined to be located in a short-range area (not shown in FIG. 16).

[0424] The step number information of the hierarchical beam sweeping process can be transmitted from the base station to the terminal in various message formats. For example, the step number information of the hierarchical beam sweeping process can be transmitted to the terminal via a SIB, DCI, or a newly defined RRC signaling message that transmits the step number information of the hierarchical beam sweeping process.

[0425] If a base station changes the number of steps of a hierarchical beam sweeping process dynamically depending on the total traffic volume, etc., the base station can provide information on the number of steps of the hierarchical beam sweeping process to a terminal using a defined DCI format.

[0426] When utilizing the new DCI format, the base station can preset the maximum number of steps in the hierarchical beam sweeping process to the terminal via MAC-CE or RRC signaling messages. Furthermore, the number of steps in the hierarchical beam sweeping process can be determined for each situation based on DCI within the maximum number of steps in the hierarchical beam sweeping process.

[0427] The example of Fig. 16 may be an exemplary drawing assuming that the hierarchical beam sweeping step is determined as step 1. In the case where the hierarchical beam sweeping step is set to step 2, the modified contents of Fig. 16 will be additionally explained below.

[0428] In step S1622, the base station can determine grids for beam sweeping and beam focusing of near-field beams based on distance information and angle information. For example, if the base station exists at angles of the direction of the first beam and the direction of the second beam that can be beamformed based on the location information of the terminal, and exists at positions of the second range ring and the third range ring based on the range ring, the base station can set four grids. More specifically, two grids can be determined for the first beam direction and the second beam direction in the range of the second range ring, and two grids can be determined for the first beam direction and the second beam direction in the range of the third range ring.

[0429] In step S1624, the base station can transmit the CSI-RS to the terminal by beam-sweeping the near-field beams in the direction of the determined grids. At this time, the near-field beams can be assigned a beam index for each grid. Therefore, the terminal can receive the CSI-RS transmitted through the near-field beams by sweeping the near-field beams by the base station in step S1624. The terminal can measure the RSRP value for the received CSI-RS. The terminal can map and store the measured RSRP value and the beam index corresponding to the measured RSRP value. The terminal can compare the RSRP threshold set in step S1600 with the measured RSRP value to determine the highest RSRP value and the beam index corresponding to it among the RSRP value(s) greater than or equal to the RSRP threshold. The terminal can transmit a second report message including the highest RSRP value and the beam index corresponding to it among the RSRP value(s) greater than or equal to the RSRP threshold to the base station.

[0430] In step S1626, the base station may receive a second report message from the terminal. At this time, if the number of hierarchical beam sweeping steps of the base station is 2 or more, the hierarchical beam sweeping count value may be increased by 1 and the process may proceed to step S1622. In step S1622, the determined grid may be further divided into 2 or more grids to determine the detailed grids to be beam swept.

[0431] In step S1624, the base station can transmit CSI-RS by sweeping beams corresponding to the determined grids. The procedures up to step S1626 can be performed in the same manner. In addition, if the count value is equal to the number of hierarchical beam sweeping steps, step S1628 can be performed.

[0432] In step S1628, the base station may determine the selected short-range field beam as a beam for communicating with the terminal based on the second report message.

[0433] The operation described above with reference to FIG. 16 is described with reference to FIG. 17 and the tables exemplified below.

[0434] Figure 17 is a conceptual diagram illustrating a method for transmitting near-field beams by beam sweeping when a base station having an XL MIMO antenna knows the location information of a terminal.

[0435] Referring to Fig. 17, an example of a case in which a base station has an XL-MIMO antenna panel (1710) is illustrated. In the example of Fig. 17, the X-axis represents the direction in which the XL-MIMO antenna panel (1710) faces when the base station radiates a beam through the XL-MIMO antenna panel (1710), and the Y-axis represents the direction parallel to the plane of the XL-MIMO antenna panel (1710).

[0436] It is assumed that the base station knows the location information of the terminal (1730) as prior information. Furthermore, it is assumed that the terminal (1730) is located within the short-range field area. When the terminal's location information is prior information, the size of the candidate set based on the prior location can be determined as shown in Table 13 below.

[0437] Pre-information (location information) between base station and terminal prior , θ prior Ring and far field beam index closest to the terminal i prior , j prior Size of the set of near-field beam candidates based on prior information9

[0438] Table 13 is an example of a case where the pre-information between the base station and the terminal is the terminal's location. In Table 13, d prior is the distance information from the base station or the XL-MIMO antenna panel of the base station to the terminal, and θ prior may be relative angle information from the base station to the terminal. In Table 13, i prior can be the index of the closest distance ring to the terminal, and j priormay be a far-field beam index corresponding to the direction of the terminal.

[0439] When determining the size of the candidate set based on prior information, including the near-field beam corresponding to the terminal location and the grids adjacent to the terminal location, the number of grids adjacent to the terminal location can be eight. Accordingly, the size of the candidate set of near-field beams based on prior information, including the near-field beam corresponding to the terminal location, can be nine grids. In the fourth embodiment, the prior information is location information, and the grids described in FIG. 17 can mean near-field candidate beams.

[0440] The size of the near-field beam candidate set based on location information can be determined by various criteria, such as the beam width (or widths) that the base station can form and / or the delay requirements of the terminal. By appropriately selecting the size of the near-field beam candidate set based on prior information and the number of steps of hierarchical beam sweeping, the time resources and computational complexity used for beam adjustment can be reduced, or the beams can be formed more finely to improve communication performance. For example, the smaller the delay requirements of the service provided to the terminal, the smaller the size of the near-field candidate set based on prior information can be set, reducing the time required for the beam sweeping process. As another example, the larger the antenna array size of the base station and the more detailed the spacing between adjacent near-field beams and range rings, the larger the size of the near-field candidate set based on prior information can be. In this way, when the candidate set size increases, communication performance can be measured for various combinations of near-field beams, allowing for the selection of an optimal beam.

[0441] The size of the near-field beam candidate set based on prior information can be set to be the same at all stages of hierarchical beam sweeping. Alternatively, the size of the near-field beam candidate set based on prior information can be set flexibly at each stage of hierarchical beam sweeping, taking into account the spacing between the near-field beams and the range rings that the base station can subdivide.

[0442] A case where the size of the near-field candidate set based on prior information is 9 is illustrated in FIG. 17. According to the example of FIG. 17, the base station can perform beam sweeping in ten directions: a first direction (1711), a second direction (1712), a third direction (1713), a fourth direction (1714), a fifth direction (1715), a sixth direction (1716), a seventh direction (1717), an eighth direction (1718), a ninth direction (1719), and a tenth direction (1720). Also, the distance rings illustrated in FIG. 17 are exemplified as a first distance ring (1741) closest to the XL-MIMO antenna panel (1710), a second distance ring (1742) second closest to the XL-MIMO antenna panel (1710), a third distance ring (1743) third closest to the XL-MIMO antenna panel (1710), a fourth distance ring (1744) fourth closest from the XL-MIMO antenna panel (1710), and a fifth distance ring (1745) farthest from the XL-MIMO antenna panel (1710).

[0443] The terminal (1730) is exemplified as being located in the fifth grid having a beam in the fourth direction (1741) and a range of the third distance ring (1743). The grids closest to the grid where the terminal is located can be eight grids as shown below.

[0444] In FIG. 17, the eight grids may be a first grid having a range of a second distance ring (1742) in a third direction (1713), a second grid having a range of a third distance ring (1743) in a third direction (1713), a third grid having a range of a fourth distance ring (1744) in a third direction (1713), a fourth grid having a range of a second distance ring (1742) in a fourth direction (1714), a sixth grid having a range of a fourth distance ring (1744) in a fourth direction (1714), a seventh grid having a range of a second distance ring (1742) in a fifth direction (1715), an eighth grid having a range of a third distance ring (1743) in a fifth direction (1715), and a ninth grid having a range of a fourth distance ring (1744) in a fifth direction (1715). The numbers of the grids may also be set in a different manner than above. The grid numbers may be assigned for convenience of description of the present disclosure.

[0445] Accordingly, the base station can transmit the CSI-RS to the terminal (1730) through beam sweeping so that the beam is focused into nine grids. The terminal can receive the CSI-RS through the nine beams and measure the RSRP for the received CSI-RS. The terminal can map and store the measured RSRP value and the base station beam indices. At this time, when hierarchical beam sweeping is performed, it can be determined whether the corresponding grid, or the corresponding beam, can be used for the next hierarchical beam sweeping. The threshold for determining the beam that can be used for hierarchical beam sweeping may use the previously described communicable RSRP threshold as it is, or a new RSRP threshold may be used. The threshold for determining the beam that can be used for hierarchical beam sweeping may be the highest RSRP threshold rather than the new RSRP threshold. The reason why the highest RSRP threshold can be used is because the beam is swept using the terminal's location information, so the beams to be used by the base station are determined to be either near-field beams or far-field beams based on distance information.

[0446] Table 14 below is a table illustrating RSRP values ​​measured at a terminal according to the present disclosure, along with beam index and availability for hierarchical beam sweeping.

[0447] Base station candidate beam (Beam index)RSRP measured by terminalWhether hierarchical beam sweeping is possibleBase station near field beam #1 (0000)RSRP_32FalseBase station near field beam #2 (0001)RSRP_44FalseBase station near field beam #3 (0010)RSRP_56FalseBase station near field beam #4 (0011)RSRP_63FalseBase station near field beam #5 (0100)RSRP_75TrueBase station near field beam #6 (0101)RSRP_66FalseBase station near field beam #7 (0110)RSRP_51FalseBase station near field beam #8 (0111)RSRP_40FalseBase station Near Field Beam #9 (1000)RSRP_28False

[0448] During the near-field beam sweeping process, the base station can map the near-field beam index to the near-field candidate beam and then transmit the CSI-RS along with the near-field beam index to the terminal. The terminal can receive the CSI-RS transmitted through the near-field beam and measure the RSRP for the received CSI-RS. The terminal can map and store the near-field beam index and the RSRP values ​​measured for the CSI-RS at the terminal, as illustrated in Table 14.

[0449] And the terminal can select the optimal beam based on the RSRP measured for the CSI-RS received through each beam. According to the example of Table 14, the terminal can select the near field beam #5 with the highest RSRP value. Therefore, when the hierarchical beam sweeping step is applied, the terminal can perform hierarchical beam sweeping by further subdividing the beams for the near field beam #5. The near field beam #5 may be a beam corresponding to the fifth grid where the terminal is located in the example of Fig. 17.

[0450] The near-field beam index described above can be transmitted to the terminal via a resource indicator, such as the CRI of the CSI-RS. Alternatively, the near-field beam index can be transmitted to the terminal using a newly defined RRC signaling message to indicate the near-field beam index. Furthermore, the number of bits of the near-field beam index can be determined using the method described in Equation 5 above.

[0451] In Table 13, the size of the set of candidate near-field beams based on prior information is determined to be 9, so the number of near-field beams that the base station can form during the near-field beam sweeping process can also be 9. Table 14 illustrates an example where 4 bits are allocated to distinguishing each candidate beam because the number of near-field beams is 9.

[0452] When transmitting a CSI-RS, the base station can transmit to the terminal information about the beam through which the CSI-RS is transmitted, i.e., the near-field beam index of the base station transmitting the CSI-RS. At this time, the near-field beam index of the base station can be indicated using DCI, MAC-CE, RRC reset, or a newly defined RRC signaling message according to the present disclosure. Through this, the terminal can confirm which beam transmitted the received CSI-RS.

[0453] The terminal can report to the base station a second report message including measurement results for the beam that transmitted the received CSI-RS. This second report message can be reported in various formats. For example, the second report message can utilize UCI and transmit the RSRP and beam index information of the CSI-RS to the base station through the CSI-RS reporting process.

[0454] As another example, the base station may instruct the UE to report RSRP of CSI-RS via a UE information request (UEInformationRequest) in an RRC signaling message. The UE may then report the information included in the second report message to the base station via a UE information response (UEInformationResponse).

[0455] As another example, the base station may indicate to the UE information regarding the beam performance report instruction via a SIB or a newly defined RRC signaling message that indicates the performance report. In response to the SIB or the newly defined RRC signaling message, the UE may report information in a second report message to the base station using a measurement report, UE Assistance Information, or a newly defined RRC signaling message.

[0456] Assuming that the number of hierarchical beam sweeping steps is set to 2 in Table 12 above, the base station can complete the hierarchical beam sweeping process by repeating the procedures in Tables 13 and 14 in the angle-distance domain corresponding to the base station near-field beam #5 based on the information included in the second report message.

[0457] The operations according to the first to fourth embodiments described above can be simplified and expressed as in FIGS. 18a to 18d.

[0458] FIG. 18a is a flowchart that simplifies the procedure for selecting an optimal beam between a base station and a terminal according to the first embodiment of the present disclosure.

[0459] Before referring to FIG. 18a, the first embodiment may be a case where there is no prior information about the terminal. Accordingly, the base station may not have information about the terminal's location, the distance from the base station to the terminal, or the relative angle from the base station to the terminal.

[0460] In step S1811, the base station can determine the size of the candidate set of angles from which the base station will transmit beams to the terminal. The size of the candidate set of angles from which the base station will transmit beams can be determined based on Table 2 described in FIG. 12.

[0461] In step S1812, the base station or the terminal may transmit far-field candidate beams. At this time, the candidate beams may include reference signals capable of measuring the quality of beams such as CSI-RS. In addition, they may include identifiers capable of identifying each candidate beam. Since this has been described in detail in the first embodiment, a duplicate description is omitted. The terminal may receive a CSI-RS through the far-field candidate beams, and measure an RSRP value for the received CSI-RS. The measured RSRP values ​​may be reported to the base station through a first report message together with a beam index. The base station may determine the selection of an angular code set based on the first report message, as described in Table 3. At this time, if a far-field candidate beam is determined, step S1813 may not be performed. To indicate that step S1813 may not be performed, the arrow from step S1812 to step S1813 is illustrated as a dotted line.

[0462] In step S1813, the base station can transmit a near-field candidate beam to the terminal. The candidate beams can include a reference signal capable of measuring the quality of beams such as CSI-RS. In addition, each candidate beam can include an identifier capable of identifying the candidate beam. Since this has been described in detail in the first embodiment, a duplicate description is omitted. The terminal can measure the RSRP for the CSI-RS received through the near-field candidate beam. The measured RSRP and the corresponding beam index can be reported to the base station via a second report message. The base station can select an optimal beam based on the second report message. This selection procedure can be determined as described in Table 6.

[0463] FIG. 18b is a flowchart that simplifies the procedure for selecting an optimal beam between a base station and a terminal according to the second embodiment of the present disclosure.

[0464] Before referring to FIG. 18b, the second embodiment may be a case where there is prior information about the terminal. In the second embodiment, the prior information may be distance information between the base station and the terminal.

[0465] In step S1821, the base station can determine the electromagnetic wave range based on distance information. The electromagnetic wave range may be a near-field range or a far-field range. This can be determined based on the mathematical expression 1 or 2 described above.

[0466] In step S1822, the base station can determine the size of the code set to set a beam to the terminal based on the distance information from the base station to the terminal obtained as prior information.

[0467] In step S1823, the base station may transmit a near-field candidate beam. Note that the case of transmitting a far-field beam is not illustrated in FIG. 18b. The base station may transmit a near-field candidate beam to the terminal. At this time, the near-field candidate beams may include a reference signal capable of measuring the quality of beams such as CSI-RS. Additionally, each candidate beam may include an identifier capable of identifying the candidate beam. Since this has been described in detail in the first and second embodiments, a duplicate description will be omitted. The base station may receive a CSI-RS from the terminal through the near-field candidate beams, and measure an RSRP value for the received CSI-RS. The measured RSRP values ​​may be reported to the base station through a second report message together with a beam index. The base station may determine the selection of an angular code set based on the first report message, as described in Table 3. At this time, if a far-field candidate beam is determined, step S1813 may not be performed. The arrow from step S1812 to step S1813 is illustrated with a dotted line to indicate that step S1813 may not be performed.

[0468] In step S1813, the base station can transmit a near-field candidate beam. The candidate beams can include a reference signal capable of measuring the quality of beams such as CSI-RS. In addition, each candidate beam can include an identifier capable of identifying the candidate beam. Since this has been described in detail in the first embodiment, a redundant description is omitted. The terminal can measure the RSRP for the CSI-RS received through the near-field candidate beam. The measured RSRP and the corresponding beam index can be reported to the base station via a second report message. The base station can select an optimal beam based on the second report message. This selection procedure can be determined as described in Table 8.

[0469] FIG. 18c is a flowchart that simplifies the procedure for selecting an optimal beam between a base station and a terminal according to the third embodiment of the present disclosure.

[0470] Before referring to FIG. 18c, the third embodiment may be a case where there is prior information about the terminal. In the third embodiment, the prior information may be information about the relative angle from the base station to the terminal.

[0471] In step S1831, the base station can determine the size of the beam candidate set based on the angle information, which is prior information to be transmitted to the terminal. This can be set in the manner described in Table 9.

[0472] In step S1832, the base station may first transmit the far field candidate beams. At this time, the far field candidate beams may include reference signals capable of measuring the quality of beams such as CSI-RS. In addition, they may include identifiers capable of identifying each candidate beam. Since this has been described in detail in the first to third embodiments, redundant description is omitted. The terminal may receive CSI-RS through each beam and measure an RSRP value for the received CSI-RS. The optimal beam may be selected using the measured RSRP values. If there is an RSRP threshold value or higher among the RSRP values ​​measured for the CSI-RS received through the far field candidate beams, the optimal beam selection procedure may be terminated. If there is no RSRP value or higher than the RSRP threshold value among the RSRP values ​​measured for the CSI-RS received through the far field candidate beams, the base station proceeds to step S1833. Therefore, since the progression from step S1832 to step S1833 is determined by the result of step S1832, the connecting arrow is indicated by a dotted line.

[0473] In step S1833, the base station can transmit the near-field candidate beams to the terminal. At this time, the near-field candidate beams can include reference signals capable of measuring the quality of beams such as CSI-RS. In addition, the base station can include identifiers capable of identifying each candidate beam. Since this has been described in detail in the first to third embodiments, a duplicate description is omitted. The base station can receive the CSI-RS from the terminal through the near-field candidate beams and measure the RSRP value for the received CSI-RS. The measured RSRP values ​​can be reported to the base station through a second report message together with the beam index. The base station can determine the near-field candidate beams as described in Table 11.

[0474] FIG. 18d is a flowchart that simplifies the procedure for selecting an optimal beam between a base station and a terminal according to the fourth embodiment of the present disclosure.

[0475] Before referring to FIG. 18d, the fourth embodiment may be a case where the terminal has prior information. In the fourth embodiment, the prior information may be location information of the terminal. The location information of the terminal may include relative angle information from the base station to the terminal and distance information of the terminal from the base station.

[0476] In step S1841, the base station can determine the electromagnetic wave region in which the terminal is located based on distance information. This determination can be made based on the Rayleigh distance, as described above. Other cases that do not utilize the Rayleigh distance have been described in the fourth embodiment, so a duplicate description will be omitted. The base station can determine whether the terminal is located in the far-field region or the near-field region based on distance information between the terminal and the base station.

[0477] The example of Fig. 18d may be an embodiment for a case where the terminal is located in the near field region. Accordingly, the base station may determine the hierarchical beam sweeping step in step S1841. The hierarchical beam sweeping step may be performed once or more times. Since the method for determining the number of hierarchical beam sweeping steps has been described above in the fourth embodiment, a redundant description will be omitted.

[0478] In step S1842, the base station can determine the size of the candidate set for transmitting the near-field beams based on the location information among the prior information. The candidate set for transmitting the near-field beams is described in Table 13 of the fourth embodiment, so a description of the same content is omitted.

[0479] In step S1843, the base station can transmit the near-field candidate beams to the terminal. At this time, the near-field candidate beams can include reference signals capable of measuring the quality of beams such as CSI-RS. In addition, the base station can include identifiers capable of identifying each candidate beam. Since this has been described in detail in the first to fourth embodiments, a duplicate description is omitted. The base station can receive the CSI-RS from the terminal through the near-field candidate beams and measure the RSRP value for the received CSI-RS. The measured RSRP values ​​can be reported to the base station through a second report message together with the beam index. The base station can determine whether to perform hierarchical beam sweeping based on the near-field beam information as described in Table 14.

[0480] In step S1844, the base station can repeat step S1843 as many times as the number of hierarchical beam sweeping steps set in step S1841.

[0481] The operations of the method according to the present disclosure can be implemented as a computer-readable program or code on a computer-readable recording medium. A computer-readable recording medium includes any type of recording device that stores information readable by a computer system. Furthermore, a computer-readable recording medium can be distributed across network-connected computer systems, allowing the computer-readable program or code to be stored and executed in a distributed manner.

[0482] Additionally, the computer-readable recording medium may include hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, etc. The program instructions may include not only machine language codes produced by a compiler, but also high-level language codes that can be executed by a computer using an interpreter, etc.

[0483] While some aspects of the present disclosure have been described in the context of a device, they may also represent a description of a corresponding method, wherein a block or device corresponds to a method step or a feature of a method step. Similarly, aspects described in the context of a method may also be described as a corresponding block or item or a feature of a corresponding device. Some or all of the method steps may be performed by (or using) a hardware device, such as, for example, a microprocessor, a programmable computer, or an electronic circuit. In some embodiments, at least one or more of the most significant method steps may be performed by such a device.

[0484] A programmable logic device (e.g., a field-programmable gate array) may be used to perform some or all of the functions of the methods described in the present disclosure. The field-programmable gate array may operate in conjunction with a microprocessor to perform one of the methods described in the present disclosure. In general, the methods are preferably performed by some hardware device.

[0485] Although the present disclosure has been described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various modifications and changes may be made to the present disclosure without departing from the spirit and scope of the present disclosure as set forth in the claims below.

Claims

1. In the method of the base station, A step of sharing first information and prior information for terminal and beam forming; A step of confirming whether the terminal is located in a short-range field area based on the above-mentioned prior information; A step of determining gratings to transmit each of the near field beams for beam sweeping and beam focusing based on the first information when it is confirmed that the terminal is located in the near field region; A step of transmitting a reference signal by beam sweeping each of the near-field beams so that the near-field beams are each focused by the determined grids; A step of receiving a first measurement report message for the reference signal from the terminal; and A step of determining a near field beam for communicating with the terminal based on the first measurement report message, The above first information includes information on the number of distance rings for distinguishing the near field, and the number of distance rings is 2 or more. Method of base station.

2. In claim 1, The above-mentioned prior information includes a distance value from the base station to the terminal, Each of the above near-field beams uses a spherical wave beam, Method of base station.

3. In claim 1, A step of transmitting far field beams to the terminal by beam sweeping when the terminal is located in a far field area, wherein the reference signal and beam indices for identifying each of the far field beams are transmitted through each of the far field beams; A step of receiving a second measurement report message including measurement values ​​and remote beam index information for the reference signal from the terminal; and Further comprising a step of determining a far field beam for communicating with the terminal based on the second measurement report message; Each of the above distant field beams is a plane wave beam, Method of base station.

4. In claim 3, If the above-mentioned prior information further includes angle information of the terminal, the beam sweeping area of ​​the far-field beams is determined based on the angle information of the terminal. Method of base station.

5. In claim 1, Each of the above grids is determined based on the distance rings, which are determined based on the beam direction beamformed to the terminal and the predetermined distances from the base station. Method of base station.

6. In claim 1, When the above-mentioned prior information further includes angle information of the terminal, when determining the grids to be transmitted for beam sweeping and beam focusing of each of the near-field beams, the grids to be transmitted are determined based on the angle information of the terminal. Method of base station.

7. In claim 1, The above first information further includes reception power threshold information, Method of base station.

8. In claim 7, If the first measurement report message includes two or more measured reference signal reception power values ​​having a reception power threshold value or higher and beam indices corresponding to each of the two or more measured reference signal reception power values, the near-field beam for communicating with the terminal is selected as a beam having a beam index corresponding to the highest measured reception power value among the two or more measured reference signal reception power values. Method of base station.

9. In claim 7, If the first measurement report message includes two or more measured reference signal reception power values ​​having a reception power threshold value or higher and beam indices corresponding to each of the two or more measured reference signal reception power values, the short-range field beam for communicating with the terminal is determined by considering at least one of interference with another communication node or a load of the base station. Method of base station.

10. In claim 1, The above-mentioned prior information is obtained from additional information indirectly obtained from the location service of the terminal or is determined based on the delay information of the signal received from the terminal. Method of base station.

11. In claim 1, A step of transmitting the reference signal by sweeping the far field beams over the entire sweeping area of ​​the far field area when it is impossible to confirm whether the terminal is located in the near field area based on the above-mentioned prior information; A step of receiving a third measurement report message from the terminal; and If the reception power value included in the third measurement report message is a far-field beam having a reception power greater than or equal to a preset threshold value, the method further comprises the step of setting the far-field beam having the reception power greater than or equal to the preset threshold value as a beam for communicating with the terminal. Method of base station.

12. In claim 11, A step of determining grids for near field beam sweeping and focusing based on the distance ring to be set in a beam direction corresponding to the far field beam when the received power value included in the third measurement report message is not the far field beam having the received power greater than or equal to the preset threshold value; A step of transmitting the reference signal through short-range beam sweeping with the above-determined grids; A step of receiving a fourth measurement report message including a reception power value for the reference signal transmitted through the short-range beam sweeping from the terminal; and Further comprising a step of determining a near-field beam having the highest reception power value among the near-field beams based on the fourth measurement report message as a near-field beam for communicating with the terminal. Method of base station.

13. At the base station, At least one processor, wherein the at least one processor comprises: Sharing first information and prior information for terminal and beam forming; Based on the above-mentioned prior information, it is confirmed whether the terminal is located in the near field area; If it is confirmed that the terminal is located in the near field region, the gratings to be transmitted for beam sweeping and beam focusing of each of the near field beams are determined based on the first information; Transmitting a reference signal by beam sweeping each of the near-field beams so that the near-field beams are each focused by the determined grids; Receive a first measurement report message for the reference signal from the terminal; and Causing to determine a near field beam for communicating with the terminal based on the first measurement report message; The above first information includes information on the number of distance rings for distinguishing the near field, and the number of distance rings is 2 or more. Base station.

14. In claim 13, The above-mentioned prior information includes a distance value from the base station to the terminal, Each of the above near-field beams uses a spherical wave beam, Base station.

15. In claim 13, At least one processor of the base station: When the terminal is located in a far field area, the far field beams are beam-swept and transmitted to the terminal, and the beam indices for identifying the reference signal and each of the far field beams are transmitted through each of the far field beams; Receive a second measurement report message including measurement values ​​and remote beam index information for the reference signal from the terminal; and Further causing the remote field beam for communication with the terminal to be determined based on the second measurement report message; Each of the above distant field beams is a plane wave beam, Base station.

16. In claim 15, If the above-mentioned prior information further includes angle information of the terminal, the beam sweeping area of ​​the far-field beams is determined based on the angle information of the terminal. Base station.

17. In claim 13, Each of the above grids is determined based on the distance rings, which are determined based on the beam direction beamformed to the terminal and the predetermined distances from the base station. Base station.

18. In claim 13, When the above-mentioned prior information further includes angle information of the terminal, when determining the grids to be transmitted for beam sweeping and beam focusing of each of the near-field beams, the grids to be transmitted are determined based on the angle information of the terminal. Base station.

19. In claim 13, At least one processor of the base station: If it is impossible to confirm whether the terminal is located in the near field area based on the above-mentioned prior information, the reference signal is transmitted by sweeping the far field beams over the entire sweeping area of ​​the far field area; Receiving a third measurement report message from the terminal; and If the reception power value included in the third measurement report message is a far-field beam having a reception power greater than or equal to a preset threshold value, further causing the far-field beam having the reception power greater than or equal to the preset threshold value to be set as a beam for communicating with the terminal. Base station.

20. In claim 19, At least one processor of the base station: If the received power value included in the third measurement report message is not the far field beam having the received power greater than or equal to the preset threshold value, grids for near field beam sweeping and focusing are determined based on the distance ring to be set in the beam direction corresponding to the far field beam; Transmitting the reference signal through short-range beam sweeping with the above-determined grids; Receiving a fourth measurement report message including a reception power value for the reference signal transmitted through the short-range beam sweeping from the terminal; and Further causing the near-field beam having the highest reception power value among the near-field beams to be determined as the near-field beam for communicating with the terminal based on the fourth measurement report message. Base station.

Images