KR20230028152A - Beam management method using hierarchical beams, and apparatus therefor - Google Patents

Abstract

A beam management method performed by a terminal comprises the steps of: receiving one or more SSBs belonging to a first hierarchy from a base station; receiving one or more SSBs belonging to a second hierarchy from the base station; determining valid SSBs among the one or more SSBs belonging to the first hierarchy and the SSBs belonging to the second hierarchy; selecting at least one first SSB belonging to a hierarchy with the higher priority of the first hierarchy and the second hierarchy among the valid SSBs; and reporting the selected first SSB to the base station and using a beam, which has been used to receive the first SSB, as an initial beam for communication with the base station. Therefore, the performance of a communication system can be improved.

Description

Beam management method using hierarchical beams and apparatus therefor

The present invention relates to a beam management method in an ultra-high frequency band communication system, and more particularly, to a beam management method utilizing hierarchical beams in an ultra-high frequency band communication system and devices therefor.

Communication systems are continuously evolving to expand communication infrastructure for the realization of a hyper-connected society. For example, the NR communication system may support a frequency band up to around 100 GHz as well as a frequency band of 6 GHz or less, and compared to a conventional communication system (eg, a long-term evolution (LTE) communication system) More diverse services and scenarios can be supported. For example, a usage scenario of the NR communication system may include enhanced mobile broadband (eMBB), ultra reliable low latency communication (URLLC), and massive machine type communication (mMTC). In addition, the 6G communication system being discussed recently is expected to enable more diverse services and user experiences by utilizing THz frequency band, artificial intelligence, satellite communication, and quantum technology. There are various requirements in the industry that these communication systems must satisfy, and advanced communication technology is required to achieve them.

An object of the present invention to solve the above problems is to provide a method for managing beams of a terminal using hierarchical beams in an ultra-high frequency band communication system.

Another object of the present invention to solve the above problem is to provide a configuration of a terminal performing the method and a base station supporting the terminal performing the method.

A beam management method performed in a terminal according to an embodiment of the present invention for achieving the above object includes: receiving at least one synchronization signal block (SSB) belonging to a first layer from a base station; Receiving at least one SSB belonging to a second layer from the base station; determining valid SSBs from among at least one SSB belonging to the first layer and at least one SSB belonging to the second layer; selecting at least one first SSB belonging to a layer having a higher priority among the first layer and the second layer from among the available SSBs; and reporting the selected first SSB to the base station and using a beam used for receiving the first SSB in an initial access procedure for communication with the base station, wherein each SSB includes a synchronization signal and broadcasting It may include at least one of the channels.

The valid SSBs may be SSBs received by the terminal with received signal strength greater than or equal to a predetermined threshold.

The priority between the first layer and the second layer may be determined based on configuration information received from the base station.

When the first layer has a higher priority than the second layer, the number of SSBs belonging to the first layer may be smaller than the number of SSBs belonging to the second layer, and the second layer is the first layer. When having a higher priority, the number of SSBs belonging to the second layer may be smaller than the number of SSBs belonging to the first layer.

The first SSB may be an SSB having the highest received signal strength among the effective SSBs.

The terminal may report the selected first SSB to the base station by transmitting a random access preamble to the base station in the uplink resource(s) associated with the selected first SSB.

The step of using the beam used to receive the first SSB in the initial access procedure for communication with the base station includes receiving a downlink signal for initial access based on the beam and initial access based on the beam. It may include at least one of the operations of transmitting an uplink signal for.

A beam management method performed in a terminal according to another embodiment of the present invention for achieving the above object includes: receiving at least one SSB belonging to a first layer from a base station; Receiving at least one SSB belonging to a second layer from the base station; determining valid SSBs from among at least one SSB belonging to the first layer and at least one SSB belonging to the second layer; selecting a first SSB belonging to the first layer and a second SSB belonging to the second layer from among the available SSBs; and reporting the selected first SSB and the selected second SSB to the base station, and at least one of a first beam used to receive the first SSB and a second beam used to receive the second SSB and using a beam for an initial access procedure for communication with the base station, and each SSB may include at least one of a synchronization signal and a broadcast channel.

The valid SSBs may be SSBs received by the terminal with received signal strength greater than or equal to a predetermined threshold.

The first SSB may be an SSB having the highest received signal strength among valid SSBs belonging to the first layer, and the second SSB may be an SSB having the highest received signal strength among valid SSBs belonging to the second layer. there is.

The terminal may report the selected first SSB to the base station by transmitting a random access preamble to the base station on the uplink resource (s) associated with the selected first SSB, and the uplink associated with the selected second SSB A random access preamble may be transmitted to the base station in the link resource(s) to report the selected second SSB to the base station.

At least one beam used in the initial access procedure among the first beam and the second beam may be determined based on a predefined rule in a technical standard or configuration information received from the base station.

A beam width of the primary beam may be wider than that of the secondary beam.

To achieve the above object, a beam management method performed in a base station according to another embodiment of the present invention includes: transmitting at least one SSB belonging to a first layer; Transmitting at least one SSB belonging to a second layer; and receiving a report from a terminal of a first SSB selected by the terminal and using a beam used to transmit the first SSB in an initial access procedure for communication with the terminal, wherein the first SSB includes the first SSB. An SSB belonging to a layer having a higher priority among the first layer and the second layer among valid SSBs among at least one SSB belonging to the layer and at least one SSB belonging to the second layer, and each SSB may include at least one of a synchronization signal and a broadcast channel.

The valid SSBs may be SSBs received by the terminal with received signal strength greater than or equal to a predetermined threshold.

The beam management method may further include transmitting configuration information used to determine priorities between the first layer and the second layer to the terminal.

When the first layer has a higher priority than the second layer, the number of SSBs belonging to the first layer may be smaller than the number of SSBs belonging to the second layer, and the second layer is the first layer. When having a higher priority, the number of SSBs belonging to the second layer may be smaller than the number of SSBs belonging to the first layer.

The first SSB may be an SSB having the highest received signal strength among the effective SSBs.

The selected first SSB may be reported from the terminal by receiving a random access preamble from the terminal on the uplink resource (s) combined with the first SSB.

Within an SSB transmission period, SSBs belonging to the first layer are disposed before SSBs belonging to the second layer, or SSBs belonging to the first layer and SSBs belonging to the second layer intersect within the SSB transmission period. can be arranged in an interlaced manner.

According to the embodiments of the present invention, an efficient beam management method for preventing frequent serving beam change in an ultra-high frequency band communication system using hierarchical beams can be provided. Accordingly, the performance of the communication system can be improved.

1 is a conceptual diagram illustrating a first embodiment of a communication system.
Figure 2 is a block diagram showing a first embodiment of a device.
3 is a conceptual diagram illustrating a first embodiment of an initial access method based on association between downlink resources and uplink resources.
4 is a conceptual diagram for explaining a serving beam change of a terminal due to terminal mobility.
5 is a conceptual diagram for explaining a first embodiment of a signal transmission method using hierarchical beams.
6 is a conceptual diagram for explaining a second embodiment of a signal transmission method using hierarchical beams.
7 is a conceptual diagram for explaining mutual coupling and QCL relationships between SSBs.
FIG. 8 is a conceptual diagram for explaining a first embodiment of arrangement of SSB resources and mutual coupling between SSB resources, and FIG. 9 is a conceptual diagram for explaining a second embodiment of arrangement of SSB resources and mutual coupling between SSB resources. am.
10 is a conceptual diagram for explaining a first embodiment of a method for determining and reporting an initial beam according to (method 200).
11 is a conceptual diagram for explaining a first embodiment of a method for determining and reporting an initial beam by (method 210).

Since the present invention can make various changes and have various embodiments, specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. These terms are only used for the purpose of distinguishing one component from another. For example, a first element may be termed a second element, and similarly, a second element may be termed a first element, without departing from the scope of the present invention. The term "and/or" includes any combination of a plurality of related listed items or any of a plurality of related listed items.

In embodiments of the present application, “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”. Also, in the embodiments of the present application, “one or more of A and B” may mean “one or more of A or B” or “one or more of combinations of one or more of A and B”.

It is understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may exist in the middle. It should be. On the other hand, when an element is referred to as “directly connected” or “directly connected” to another element, it should be understood that no other element exists in the middle.

Terms used in this application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, the terms "include" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in this application, they should not be interpreted in an ideal or excessively formal meaning. don't

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

A communication system to which embodiments according to the present invention are applied will be described. The communication system may be a 4G communication system (eg, a long-term evolution (LTE) communication system, an LTE-A communication system), a 5G communication system (eg, a new radio (NR) communication system), a 6G communication system, and the like. there is. The 4G communication system can support communication in a frequency band of 6 GHz or less, and the 5G communication system can support communication in a frequency band of 6 GHz or more as well as a frequency band of 6 GHz or less. A communication system to which embodiments according to the present invention are applied is not limited to the contents described below, and embodiments according to the present invention can be applied to various communication systems. Here, the communication system may be used in the same sense as a communication network, "LTE" may indicate "4G communication system", "LTE communication system" or "LTE-A communication system", and "NR" may indicate "5G communication system" or "NR communication system".

In an embodiment, “setting an operation (eg, transmission operation)” means “setting information for the corresponding operation (eg, information element, parameter)” and/or “performing the corresponding operation”. It may mean that the "instructing information" is signaled. "Setting an information element (eg, parameter)" may mean that a corresponding information element is signaled. "Configuring a resource (eg, a resource region)" may mean that configuration information of a corresponding resource is signaled. Signaling is system information (SI) signaling (eg, transmission of system information block (SIB) and / or master information block (MIB)), RRC signaling (eg, transmission of RRC parameters and / or higher layer parameters) , MAC control element (CE) signaling, or PHY signaling (eg, transmission of downlink control information (DCI), uplink control information (UCI), and/or sidelink control information (SCI)).

1 is a conceptual diagram illustrating a first embodiment of a communication system.

Referring to FIG. 1, a communication system 100 includes 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 includes a core network (eg, a serving-gateway (S-GW), a packet data network (PDN)-gateway (P-GW), and a mobility management entity (MME)). can include more. When the communication system 100 is a 5G communication system (eg, a new radio (NR) system), the core network includes an access and mobility management function (AMF), a user plane function (UPF), a session management function (SMF), and the like. can include

The plurality of communication nodes 110 to 130 may support communication protocols (eg, LTE communication protocol, LTE-A communication protocol, NR communication protocol, etc.) defined in the 3rd generation partnership project (3GPP) standard. The plurality of communication nodes 110 to 130 are 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. can support Each of the plurality of communication nodes may mean an apparatus or a device. Embodiments may be performed by an apparatus or device. The structure of the device (eg, device) may be as follows.

Figure 2 is a block diagram showing a first embodiment of a device.

Referring to FIG. 2 , an apparatus 200 may include at least one processor 210, a memory 220, and a transceiver 230 connected to a network to perform communication. In addition, the device 200 may further include an input interface device 240 , an output interface device 250 , a storage device 260 , and the like. Each component included in the device 200 may be connected by a bus 270 to communicate with each other.

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

Referring back to FIG. 1, the communication system 100 includes a plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2), 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 belong to the cell coverage of the first base station 110-1. The second terminal 130-2, the fourth terminal 130-4, and the fifth terminal 130-5 may belong to the cell coverage of the second base station 110-2. The fifth base station 120-2, the fourth terminal 130-4, the fifth terminal 130-5, and the sixth terminal 130-6 may belong to the cell coverage of the third base station 110-3. there is. The first terminal 130-1 may belong to the cell coverage of the fourth base station 120-1. The sixth terminal 130-6 may belong to the cell coverage of the fifth base station 120-2.

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

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

Meanwhile, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may operate in different frequency bands or may operate in the same frequency band. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to each other through an ideal backhaul link or a non-ideal backhaul link, and , information can be exchanged with each other through an ideal backhaul link or a non-ideal backhaul link. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to the core network through an ideal backhaul link or a non-ideal backhaul link. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 transmits a signal received from the core network to a corresponding terminal 130-1, 130-2, 130-3, and 130 -4, 130-5, 130-6), and signals received from corresponding terminals 130-1, 130-2, 130-3, 130-4, 130-5, 130-6 are transmitted to the core network can be sent to

In addition, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 transmits MIMO (eg, single user (SU)-MIMO, multi-user (MU)- MIMO, massive MIMO, etc.), coordinated multipoint (CoMP) transmission, carrier aggregation (CA) transmission, transmission in an unlicensed band, direct communication between devices (device to device communication, D2D) (or , proximity services (ProSe)), Internet of Things (IoT) communication, dual connectivity (DC), etc. may be supported. Here, each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 is a base station 110-1, 110-2, 110-3, 120-1 , 120-2) and operations supported by the base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be performed. 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 uses the SU-MIMO scheme. A signal may be received from the second base station 110-2. Alternatively, the second base station 110-2 may transmit a signal to the fourth terminal 130-4 and the fifth terminal 130-5 based on the MU-MIMO scheme, and the fourth terminal 130-4 And each of the fifth terminal 130-5 may receive a signal from the second base station 110-2 by the MU-MIMO method.

Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 may transmit a signal to the fourth terminal 130-4 based on the CoMP scheme, and The terminal 130-4 may receive signals from the first base station 110-1, the second base station 110-2, and the third base station 110-3 by CoMP. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 includes a terminal 130-1, 130-2, 130-3, and 130-4 belonging to its own cell coverage. , 130-5, 130-6) and a CA method. Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 controls D2D 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 may perform D2D under the control of the second base station 110-2 and the third base station 110-3, respectively. .

The present invention relates to an initial access method of a terminal in a communication system, and more particularly, to a method for performing initial access by a terminal using a hierarchical beam in an ultra-high frequency band communication system and a method for supporting it by a base station. In addition, the present invention relates to a method for performing beam management using hierarchical beams in the communication system. The following embodiments can be applied to an NR communication system, and can also be applied to other communication systems (eg, LTE communication system, 5G (fifth generation) communication system, 6G (sixth generation) communication system, etc.) in addition to the NR communication system.

Numerology applied to physical signals and channels in a communication system (eg, NR communication system, 6G communication system) may be variable. The numerology can be varied to meet the various technical requirements of a communication system. In a communication system to which a cyclic prefix (CP) based OFDM waveform technology is applied, the numerology may include a subcarrier interval and a CP length (or CP type). Table 1 may be a first embodiment of a numerology configuration method for a CP-OFDM based communication system. Adjacent subcarrier intervals may have an exponential multiplication of 2 with each other, and the CP length may be scaled by the same ratio as the OFDM symbol length. At least some of the numerologies of Table 1 may be supported according to the frequency band in which the communication system operates. In addition, numerology(s) not listed in Table 1 may be further supported in the communication system. For a specific subcarrier interval (eg, 60 kHz), CP type(s) (eg, extended CP) not listed in Table 1 may be additionally supported.

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

subcarrier spacing 15 kHz 30 kHz 60 kHz 120 kHz 240 kHz 480 kHz OFDM
Symbol length [μs] 66.7 33.3 16.7 8.3 4.2 2.1 CP length [us] 4.76 2.38 1.19 0.60 0.30 0.15 Number of OFDM symbols in 1 ms 14 28 56 112 224 448

Below, the frame structure of the communication system will be explained. Elements constituting a frame structure in the time domain may include subframes, slots, mini-slots, symbols, and the like. A subframe may be used as a unit of transmission or measurement, and the length of a subframe may have a fixed value (eg, 1 ms) regardless of a subcarrier interval. A slot may contain contiguous symbols (eg, 14 OFDM symbols). The length of the slot may be variable, different from the length of the subframe. For example, the length of a slot may be inversely proportional to the subcarrier spacing.

A slot may be used as a unit of transmission, measurement, scheduling, resource configuration, timing (eg, scheduling timing, hybrid automatic repeat request (HARQ) timing, channel state information (CSI) measurement and reporting timing, etc.). The length of an actual time resource used for transmission, measurement, scheduling, resource configuration, etc. may not match the length of a slot. A minislot may contain consecutive symbol(s), and the length of a minislot may be shorter than the length of a slot. A minislot may be used as a unit of transmission, measurement, scheduling, resource configuration, timing, and the like. The mini-slot (eg, the length of the mini-slot, the boundary of the mini-slot, etc.) may be predefined in the technical specification. Alternatively, the mini-slot (eg, mini-slot length, mini-slot boundary, etc.) may be set (or instructed) in the terminal. When a specific condition is satisfied, the use of the mini-slot may be set (or instructed) in the terminal.

The base station may schedule a data channel (eg, physical downlink shared channel (PDSCH), physical uplink shared channel (PUSCH), physical sidelink shared channel (PSSCH)) using some or all of the symbols constituting the slot. . In particular, a data channel may be transmitted using a portion of a slot for URLLC transmission, unlicensed band transmission, transmission in a coexistence situation between an NR communication system and an LTE communication system, and multi-user scheduling based on analog beamforming. Also, the base station may schedule a data channel using a plurality of slots. Also, the base station may schedule a data channel using at least one minislot.

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

In a communication system, a slot (eg, slot format) is one or more of a downlink (DL) section, a flexible section (or unknown section), and an uplink (UL) section It may consist of a combination of Each of the downlink period, flexible period, and uplink period may consist of one or more consecutive symbols. The flexible period may be located between a downlink period and an uplink period, between a first downlink period and a second downlink period, between a first uplink period and a second uplink period, and the like. When a flexible period is inserted between a downlink period and an uplink period, the flexible period may be used as a guard period.

A slot may contain one or more flexible intervals. Alternatively, a slot may not include a flexible section. The terminal may perform a predefined operation in the flexible period. Alternatively, the terminal may perform semi-static or periodically set operations by the base station in the flexible period. For example, the operations periodically configured by the base station include a physical downlink control channel (PDCCH) monitoring operation, a synchronization signal/physical broadcast channel (SS/PBCH) block reception and measurement operation, and a channel state information-reference signal (CSI-RS) Reception and measurement operation, downlink SPS (semi-persistent scheduling) PDSCH reception operation, SRS (sounding reference signal) transmission operation, PRACH (physical random access channel) transmission operation, and PUCCH (physical uplink control channel) transmission operation configured periodically , a PUSCH transmission operation according to a configured grant, and the like. A flexible symbol may be overridden with a downlink symbol or an uplink symbol. When a flexible symbol is overridden by a downlink or uplink symbol, the terminal can perform a new operation instead of an existing operation in the corresponding flexible symbol (eg, the overridden flexible symbol).

The slot format may be set semi-fixedly by higher layer signaling (eg, radio resource control (RRC) signaling). Information indicating the semi-static slot format may be included in system information, and the semi-static slot format may be set cell-specifically. In addition, the semi-static slot format may be additionally configured for each UE through UE-specific higher layer signaling (eg, RRC signaling). A flexible symbol of a cell-specific slot format may be overridden with a downlink symbol or an uplink symbol by UE-specific higher layer signaling. In addition, the slot format may be dynamically indicated by physical layer signaling (eg, a slot format indicator (SFI) included in downlink control information (DCI)). A slot format set semi-fixedly can be overridden by a dynamically indicated slot format. For example, a semi-fixed flexible symbol may be overridden by a downlink symbol or an uplink symbol by SFI.

The base station and the terminal may perform a downlink operation, an uplink operation, a sidelink operation, and the like in a bandwidth part. The bandwidth portion may be defined as a set of RBs (eg, physical resource blocks (PRBs)) having a specific numerology. RBs constituting one bandwidth portion may be continuous in the frequency domain. One numerology may be used for signal transmission (eg control channel or data channel transmission) in one bandwidth portion. In embodiments, "signal" may refer to any physical signal and channel when used in a broad sense. A terminal performing an initial access procedure may obtain configuration information of an initial bandwidth part from a base station through system information. A UE operating in an RRC connected state may obtain configuration information of a bandwidth part from a base station through UE-specific higher layer signaling.

The setting information of the bandwidth part may include numerology (eg, subcarrier spacing and/or CP length) applied to the bandwidth part. In addition, the setting information of the bandwidth part further includes information indicating the location of the starting RB (eg, starting PRB) of the bandwidth part and information indicating the number of RBs (eg, PRBs) constituting the bandwidth part. can do. At least one bandwidth part among the bandwidth part(s) set in the terminal may be activated. For example, one uplink bandwidth portion and one downlink bandwidth portion may each be activated within one carrier. In a time division duplex (TDD) based communication system, a pair of an uplink bandwidth portion and a downlink bandwidth portion may be activated. The base station can set a plurality of bandwidth parts to the terminal within one carrier, and can switch the active bandwidth part of the terminal.

In embodiments, RB may mean a common RB (CRB). Alternatively, RB may mean PRB or virtual RB (VRB). In a communication system, a CRB may refer to an RB constituting a set of consecutive RBs (eg, a common RB grid) based on a reference frequency (eg, point A). Carriers, bandwidth portions, etc. may be placed on a common RB grid. That is, the carrier, bandwidth portion, etc. may be composed of CRB(s). An RB or CRB constituting the bandwidth portion may be referred to as a PRB, and a CRB index within the bandwidth portion may be appropriately converted to a PRB index. In an embodiment, RB may mean an interlace RB (IRB).

The smallest resource unit constituting the PDCCH may be a resource element group (REG). A REG may consist of one PRB (eg, 12 subcarriers) in the frequency domain and one OFDM symbol in the time domain. Accordingly, one REG may include 12 resource elements (REs). A demodulation reference signal (DM-RS) for decoding (or demodulation) of the PDCCH may be mapped to 3 REs among 12 REs constituting the REG, and control information (eg, modulated DCI) may be It can be mapped to the remaining 9 REs.

One PDCCH candidate may consist of one CCE or aggregated CCEs. One CCE may consist of a plurality of REGs. The NR communication system may support CCE aggregation levels 1, 2, 4, 8, 16, etc., and one CCE may consist of 6 REGs.

A control resource set (CORESET) may be a resource region in which a terminal performs blind decoding (or blind demodulation) of a PDCCH. CORESET may consist of a plurality of REGs. CORESET may consist of one or more PRBs in the frequency domain and one or more symbols (eg, OFDM symbols) in the time domain. Symbols constituting one CORESET may be consecutive in the time domain. PRBs constituting one CORESET may be continuous or discontinuous in the frequency domain. One DCI (eg, one DCI format, one PDCCH) may be transmitted within one CORESET. A plurality of CORESETs may be configured from a cell point of view or a terminal point of view, and the plurality of CORESETs may overlap each other in time-frequency resources.

CORESET may be set in the terminal by PBCH (eg, system information transmitted through PBCH, master information block (MIB)). ID (identifier) of CORESET set by PBCH may be 0. That is, CORESET set by PBCH may be referred to as CORESET #0. A UE operating in an RRC idle state may perform a monitoring operation in CORESET #0 to receive an initial PDCCH in an initial access procedure. Not only a terminal operating in an RRC idle state, but also a terminal operating in an RRC connected state can perform a monitoring operation in CORESET #0. CORESET may be set in the terminal by other system information (eg, system information block type 1 (SIB1)) in addition to system information transmitted through the PBCH. For example, in order to receive a random access response (or Msg2) in a random access procedure, the terminal may receive SIB1 including configuration information of CORESET. In addition, CORESET may be configured in the UE by UE-specific higher layer signaling (eg, RRC signaling).

One or more CORESETs for each downlink bandwidth portion may be configured for the UE. The UE may monitor the PDCCH candidate(s) for the CORESET set in the corresponding bandwidth portion in the downlink active bandwidth portion. Alternatively, the UE may monitor PDCCH candidate(s) for a CORESET (eg, CORESET #0) set in a downlink bandwidth portion other than the corresponding bandwidth portion in the downlink active bandwidth portion. The initial downlink active bandwidth part may include CORESET #0 and may be combined with CORESET #0. CORESET having a quasi co-location (QCL) relationship with the SS/PBCH block in the primary cell (PCell), secondary cell (SCell), and/or primary secondary cell (PSCell) #0 may be set for the terminal. In the secondary cell, CORESET #0 may not be set for the UE.

A search space may be a set of PDCCH candidate(s) or a set of resource regions occupied by the PDCCH candidate(s). The UE may perform blind decoding on each of the PDCCH candidates within a predefined search space. The UE can determine whether the PDCCH has been transmitted to itself by performing a cyclic redundancy check (CRC) on the blind decoding result. When it is determined that the PDCCH is a PDCCH for the UE, the UE may receive the PDCCH. The terminal may periodically monitor the search space, and may monitor the search space at one or more time positions (eg, PDCCH monitoring location, CORESET) within one period.

The PDCCH candidate may consist of CCE(s) selected by a predefined hash function within a CORESET or search space occasion. The search space may be defined/configured for each CCE aggregation level. In this case, the sum of search spaces for all CCE aggregation levels may be referred to as a search space set. A "search space" may mean a "search space set", and a "search space set" may mean a "search space".

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

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

A type 0 CSS set may be used for reception of DCI scheduling a PDSCH including SIB1 and may be configured through PBCH or cell-specific RRC signaling. The ID of a type 0 CSS set may be given or set to 0. A type 0 CSS set can be logically combined with CORESET #0.

The UE may assume that the PDCCH DM-RS has a QCL relationship with a certain signal (eg, SS/PBCH block, CSI-RS, PDSCH DM-RS, PDCCH DM-RS, etc.). In addition, since the PDCCH has the same antenna port as the PDCCH DM-RS, the PDCCH and the PDCCH DM-RS may have a QCL relationship with each other. Therefore, the UE can obtain information on the large-scale propagation characteristics of the radio channel experienced by the PDCCH and the PDCCH DM-RS through the QCL assumption, and use the information on the large-scale propagation characteristics for channel estimation and reception beam formation. etc. can be used. The QCL parameter is at least one of delay spread, Doppler spread, Doppler shift, average gain, average delay, or spatial Rx parameter. can include The spatial reception parameter may correspond to at least one characteristic of a reception beam, a reception channel spatial correlation, or a transmission/reception beam pair. For convenience, the spatial reception parameter may be referred to as "spatial QCL". PDCCH may be used in the meaning of including PDCCH DM-RS, and that the PDCCH has a QCL relationship with a certain signal may include the meaning that the DM-RS of the PDCCH has a QCL relationship with the certain signal. A signal or resource having a PDCCH and QCL relationship may be referred to as a QCL source, a QCL source signal, or a QCL source resource.

PDCCHs transmitted in the same CORESET (and corresponding search space set, PDCCH monitoring occasion, etc.) may have the same QCL relationship. That is, an aggregation unit in which the UE assumes the same QCL may be a CORESET, and QCL assumptions in each of the CORESETs may be independent. In an embodiment, QCL, QCL source, etc. of a certain CORESET may mean QCL, QCL source, etc. of a PDCCH received through a corresponding CORESET, respectively. Exceptionally, different QCL assumptions may be applied to search space sets corresponding to one CORESET. For example, a search space set for monitoring RA-RNTI (eg, a type 1 CSS set) and other search space sets may have different QCL relationships.

The QCL relationship or QCL assumption (eg, QCL source, QCL type, etc.) of CORESET may be determined by a predefined method. For example, in a terminal, a PDCCH DM-RS received through a certain CORESET or a certain search space set is selected in the course of performing an initial access or random access procedure, and a SS/PBCH block and/or CSI-RS and a predefined QCL type It can be assumed to have a QCL relationship for . Here, the QCL type may mean a set of one or more QCL parameter(s). Alternatively, the QCL relationship or QCL assumption (eg, QCL source, QCL type, etc.) of the CORESET is signaled from the base station to the terminal (eg, RRC signaling, medium access control (MAC) control element (CE) signaling, DCI signaling) , a combination of the above signaling, etc.). That is, the base station may set a transmission configuration information (TCI) state for CORESET in the terminal. In general, a TCI state is an ID of a signal having a QCL relationship with a DM-RS (eg, PDCCH DM-RS) of a physical channel to which TCI is applied (eg, a QCL source and a QCL source resource of PDCCH DM-RS) And / or may include at least one QCL type therefor. For example, the base station may configure one or more TCI state candidates for each CORESET through RRC signaling to the UE, and MAC signaling (or DCI Signaling) can be instructed or set to the terminal. If there is one TCI state candidate configured by RRC signaling, the MAC signaling procedure (or DCI signaling procedure) may be omitted. The terminal may perform PDCCH monitoring and reception operations for the corresponding CORESET based on the TCI state configuration information received from the base station.

Beam operation of a high frequency band and a low frequency band in a communication system may be different from each other. In a low-frequency band (eg, a band of 6 GHz or less), since path loss of a signal due to a channel is relatively small, a signal may be transmitted and received using a beam having a wide beamwidth. In particular, in the case of a control channel, the entire coverage of a cell (or sector) can be covered even with a single beam. However, in a high-frequency band (eg, a band of 6 GHz or higher) in which a signal path loss is large, beamforming using a large-scale antenna may be used to increase a signal reach. In addition, beamforming may be applied not only to data channels but also to common signal and control channels. A communication node (eg, a base station) may form a beam having a small beam width through multiple antennas, and use a plurality of beams having different directivity to cover the entire spatial area of a cell (or sector). Thus, the signal can be transmitted and received multiple times. An operation of repeatedly transmitting a signal on a plurality of time resources using a plurality of beams may be referred to as a beam sweeping operation. A system that transmits a signal using a plurality of beams having a narrow beam width may be referred to as a multi-beam system.

For multi-beam system operation, the base station can manage transmission/reception beams of the terminal. In addition, the UE can manage its transmission/reception beams. The terminal may measure beam quality of a signal (eg, SSB, CSI-RS, etc.) transmitted from a base station or a transmission and reception point (TRP), and may report a beam quality measurement result to the base station. For example, the UE calculates beam quality measurement values such as reference signal received power (RSRP) and signal-to-interference-plus-noise ratio (SINR) for each beam (eg, each signal and each resource). and report the optimal beam(s) and the measurement value(s) corresponding thereto to the base station. The base station may determine a transmission beam for the terminal based on beam quality measurement information received from the terminal. In addition, the base station provides information (e.g., PDCCH, PDSCH, CSI-RS, PUCCH, PUSCH, SRS, PRACH, etc.) For example, QCL information, TCI state information, etc.) may be set in the terminal. In embodiments, unless otherwise specified, “beam” may mean “transmit beam”, “receive beam”, and/or “transmit/receive beam pair”. In addition, "beam", "transmission beam", "reception beam", "transmission/reception beam pair", etc. may have common meanings. Hereinafter, "transmission beam" may correspond to "precoder", "beamformer", "transmission spatial filter", etc., and information about transmission beams may correspond to information about a precoder, beamformer, transmission spatial filter, etc. , transmission spatial relationship information, spatial transmission parameters, and the like. In addition, the "receive beam" may correspond to a "receive filter", a "receive spatial filter", a "receive beamformer", and the like, and the information about the receive beam includes information about the receive filter, the receive spatial filter, the receive beamformer, and the like. It may mean information about QCL, information about QCL type D, reception spatial relationship information, spatial reception parameters, and the like. Also, hereinafter, “multiple beams” may mean at least one beam(s).

In embodiments, a base station or serving cell may include one TRP, and downlink and uplink coverage may be formed by the TRP. The terminal may perform both an operation of receiving a downlink signal from the TRP and an operation of transmitting an uplink signal to the TRP. In this case, beamforming may be applied to downlink reception and uplink transmission. For example, the TRP may apply the first beam to transmission/reception of signals with the terminal, and the terminal may apply the second beam to transmission/reception of signals with the TRP (or base station). The transmit beam (or transmit spatial filter) of the terminal may be generated based on the receive beam (or receive spatial filter, beam quality measurement of the received signal) of the terminal. Also, the transmission beam (or transmission spatial filter) of the base station may be generated based on the reception beam (or reception spatial filter, beam quality measurement of the received signal) of the base station. That is, beam correspondence may be established between a transmission beam and a reception beam of a communication node. Hereinafter, for convenience of explanation, when a communication node transmits or receives a beam, it may mean that a signal is transmitted or received through a corresponding beam.

A base station (or TRP) may transmit a synchronization signal, broadcast information, and the like to the terminal (s) using multiple beams. For example, one or more resources may be defined or configured for transmission of PSS, SSS, PBCH, SSB, PDCCH, PDSCH, etc., and the signals in the one or more resources may be repeatedly transmitted through a beam sweeping operation. . These signals may be referred to as initial access signals. In addition, a set of signals including a synchronization signal may be transmitted together to the terminal (s), which may be referred to as a synchronization signal block (SSB). Signals constituting the SSB may be predefined in technical specifications. The SSB may further include the above-described signals in addition to the synchronization signal, and may be repeatedly transmitted through a beam sweeping operation as described above. In an NR communication system, SSB may mean SS/PBCH block, and SSB resource may mean SS/PBCH block resource.

The terminal may determine a resource for receiving an initial access signal from among the one or more resources and/or a beam corresponding thereto, and receive an initial access signal from the determined resource (based on the determined beam). For example, the terminal may determine a resource having the largest received signal strength measurement value (eg, reference signal received power (RSRP) or L1-RSRP) of an initial access signal as a reception resource, and use a beam corresponding thereto as a 'downlink link'. It can be determined as 'initial beam'. The downlink initial beam may be a transmission beam of a base station. The terminal may receive an initial access signal and obtain cell ID, downlink timing, broadcast information or system information (eg, master information block (MIB), system information block (SIB), etc.). For example, the initial access signal may be SSB. The terminal may perform a random access procedure based on the reception resource and/or beam of the initial access signal.

3 is a conceptual diagram illustrating a first embodiment of an initial access method based on association between downlink resources and uplink resources.

Referring to FIG. 3, downlink resource(s) (eg, downlink resource(s) for initial access) and uplink resources (eg, uplink resource(s) for random access) are can be associated with each other. For example, downlink resource(s) may be SSB transmission resources. Also, the uplink resource(s) may be transmission resources of PRACH. As described above, the base station may repeatedly transmit an initial access signal through multiple beams using downlink resource(s). In this embodiment, the UE is downlink resource #1 (eg, SSB resource #1, CSI-RS resource), which is one of four downlink resources (eg, SSB resources, CSI-RS resources). RS resource #1) may receive an initial access signal (eg, SSB, CSI-RS).

The terminal may receive configuration of the downlink resource(s) and the uplink resource(s) from the base station (eg, receive configuration information of the downlink resource(s) and the uplink resource(s), ), information on a mutual coupling relationship between the uplink resource(s) and the downlink resource(s) may be received. Each of the uplink resource(s) may be combined with one or more downlink resource(s). That is, downlink resource(s) and uplink resource(s) may correspond one-to-one or many-to-one. Alternatively, a plurality of uplink resource(s) may be combined with one downlink resource. That is, downlink resource(s) and uplink resource(s) may correspond one-to-many. Referring to FIG. 3, a UE may be configured with 4 SSB resources and 4 PRACH resources. In addition, a mutual coupling relationship may be established between 4 SSB resources and 4 PRACH resources. For example, SSB resources #0, #1, #2, and #3 may be combined with PRACH resources #0, #1, #2, and #3, respectively.

The UE may transmit the PRACH on uplink resources mutually combined with downlink resources on which the initial access signal is received. Referring to FIG. 3, a UE mutually combines with downlink resource #1 (eg, SSB resource #1, CSI-RS resource #1) having received an initial access signal (eg, SSB or CSI-RS). PRACH can be transmitted on the designated PRACH resource #1. At this time, the transmit beam of the PRACH may be generated based on the receive beam of the initial access signal (eg, SSB or CSI-RS). In addition, resources or beams of other uplink signals for random access (eg, Msg3 PUSCH, MsgA PUSCH, PUCCH including a HARQ response message for Msg4, etc.) It may be determined based on the downlink resource or beam through which the CSI-RS is received (or the uplink resource or beam through which the UE transmits the PRACH). For example, the uplink transmission beam and the downlink reception beam of the terminal may have the same or similar directivity. The base station can successfully receive a PRACH from the terminal using beams having the same or similar direction for transmission and reception of the mutually coupled downlink resource and the uplink resource, and the downlink resource selected by the terminal based on the mutual coupling relationship (e.g. , SSB resource or SSB) and downlink initial beam. That is, the terminal may report the initial beam to the base station in an implicit manner through the above-described method. An uplink beam corresponding to the downlink initial beam may be referred to as an uplink initial beam.

In this specification, PRACH resources may mean PRACH occasions (or PRACH occasion resources). A random access preamble (or sequence) may be mapped to the PRACH resource one or more times, and the PRACH resource may further include a cyclic prefix (CP) and a guard period. A PRACH resource or PRACH occasion may be located in one or more slot(s) in the time domain and may include one or more symbol(s). Also, a PRACH resource or PRACH occasion may include one or more RB(s) or subcarrier(s) in the frequency domain.

Meanwhile, the path loss of a signal has a positive correlation with a frequency band (ie, a frequency value) in which the corresponding signal is transmitted. In ultra-high frequency band (eg, millimeter wave band, terahertz band) communication, since the path loss of a signal is very large, an ultra-fine beam having a very small beam width may be used to provide target coverage. However, as the beam width decreases, the beam reach distance increases, but beam quality may deteriorate rapidly even with a small movement of a terminal or a small channel change, and frequent beam changes may be required.

4 is a conceptual diagram for explaining a serving beam change of a terminal due to terminal mobility.

Referring to FIG. 4 , a base station may transmit and receive a signal using a plurality of beams having a very small beam width. For example, an initial access signal (eg, SSB) may be repeatedly transmitted using the plurality of beams. Similarly, the base station can receive a random access uplink signal (eg, PRACH) of the terminal using the plurality of beams. In addition, the base station may transmit a signal to the terminal using some of the multi-beams (eg, best transmission beams) and use some of the multi-beams (eg, best reception beams). Thus, the signal transmitted from the terminal can be received. An optimum transmission beam or reception beam for a terminal may be referred to as a serving beam. At this time, when the terminal moves as shown in FIG. 4 (eg, when moving in a direction orthogonal to the beam direction), the serving beam of the terminal may be frequently changed due to beams having a narrow beam width. In addition, assuming that the terminals move the same distance, the serving beam of the terminal located in the center of the cell or the terminal located relatively close to the base station (hereinafter referred to as "cell UE") is located at the cell boundary Alternatively, it may be changed more frequently than the serving beam of a terminal located relatively far from the base station (hereinafter, referred to as an "edge UE"). Frequent change of the serving beam may increase a beam management load, and degrade signal reception performance due to increased instability of beam quality. In particular, frequent change of control channel beams may have a great adverse effect on system performance.

[Mutual coupling between SSBs]

As a method for solving the above problem, beams having different beam widths may be used for signal transmission. For example, beams with a narrow beam width and beams with a wide beam width may be used. Beams with narrow beam widths may be used for cell edge terminals and cell center terminals, and beams with wide beam widths may be used for cell center terminals. Beams with different beam widths may be referred to as layered or hierarchical beams, heterogeneous beams, and the like.

5 is a conceptual diagram for explaining a first embodiment of a signal transmission method using hierarchical beams.

Referring to FIG. 5, a base station may transmit and receive a signal using multiple beams having different beam widths. For example, some beams may have a first beamwidth and some other beams may have a second beamwidth. Without loss of generality, the first beamwidth may be considered wider than the second beamwidth. An initial access signal (eg, SSB) may be repeatedly transmitted using beams having a first beam width and beams having a second beam width. Also, the random access uplink signal (eg, PRACH) of the UE may be received using beams having a first beamwidth and beams having a second beamwidth. Narrow beams having a second beamwidth (ie, narrow beamwidth) may be used for cell edge terminals and cell center terminals, and broad beams having a first beamwidth (ie, wide beamwidth) may be used for cell center terminals. can be used for Referring to FIG. 5, a first beam having a first beam width and a second beam having a second beam width may be used as serving beams of a cell center terminal, and a third beam having a second beam width may be used as a serving beam of a cell edge terminal. can be used as

When the cell center terminal uses the first beam having a wide beam width as a serving beam, the beam management load of the cell center terminal can be relieved. However, according to the above-described method, the cell center terminal may determine the first beam or the second beam as the initial downlink beam based on the received signal strength measurement values of the initial access signals (eg, SSBs), and the second beam When the received signal strength of is greater, the second beam may be selected as the initial beam. Typically, since the beamforming gain of the second beam with a narrow beamwidth is greater than the beamforming gain of the first beam with a wide beamwidth, when both the directivity of the first beam and the second beam are aligned with the position of the terminal, the terminal It may be more likely that the second beam will be selected as the serving beam. Accordingly, it may be difficult to utilize beams having the first beam width and the above-described beam management problem may not be solved.

Therefore, there is a need for a method by which the terminal can select a beam having a specific beam width (eg, a first beam width, a wide beam width) (as an initial beam) and report the selected beam to the base station. Hereinafter, specific methods for this are described. In the following embodiments, SSB and PRACH will be mainly considered as initial access signals, but the proposed method is easy to apply to other signals to which beam sweeping is applied (eg, other initial access signals, signals other than initial access signals). can be applied Meanwhile, in the following description, selecting a certain beam as an 'initial beam' may mean that the corresponding beam is used for an 'initial access procedure'. In addition, an operation performed in an initial access procedure using a certain beam is at least one of receiving a downlink signal for initial access based on a corresponding beam and transmitting an uplink signal for initial access based on the beam. First, SSB layers (or groups or sets) may be defined as a method for classifying beams having different beam widths. A plurality of SSB layers may be defined or configured, and each SSB may correspond to or belong to any one of the plurality of SSB layers. For example, SSBs having a first beamwidth may belong to a first SSB layer, and SSBs having a second beamwidth may belong to a second SSB layer. SSBs belonging to the first SSB layer may be referred to as a first SSB set, a first SSB group, and the like, and SSBs belonging to the second SSB layer may be referred to as a second SSB set, a second SSB group, and the like.

6 is a conceptual diagram for explaining a second embodiment of a signal transmission method using hierarchical beams.

Referring to FIG. 6, the base station can transmit SSBs 20 times using different beams. SSB #n (ie, an SSB having an index of n) may correspond to beam #n (ie, a beam having an index of n) (n is an integer greater than or equal to 0). For example, SSB #0 to SSB #3 may correspond to beam #0 to beam #3, respectively, and the beams may have a wide beam width. Also, SSB #4 to SSB #19 may correspond to beams #4 to #19, respectively, and the beams may have narrow beam widths. At this time, SSBs may be classified into a plurality of SSB layers. For example, SSBs #0 to #3 may belong to a first SSB layer (or a first SSB set, a first SSB group, etc.), and SSBs #4 to #19 may belong to a second SSB layer (or a second SSB group). SSB set, second SSB group, etc.). The first SSB layer may include N ₁ =4 SSBs corresponding to beams with a wide beamwidth, and the second SSB layer may include N ₂ =16 SSBs corresponding to beams with a narrow beamwidth ( N ₁ , N ₂ are natural numbers or integers greater than or equal to 0).

A plurality of SSBs may be mutually coupled. A quasi-co-location (QCL) relationship may be established between mutually coupled SSBs. For example, the UE may assume that a spatial QCL relationship (eg, spatial reception parameter, QCL type D, etc.) is established between the mutually coupled first SSB and second SSB. Based on the above assumption, the UE can receive the first SSB and the second SSB using the same Rx beam. From the receiving point of view of the terminal, the first SSB and the second SSB may be simultaneously received. That is, the UE can receive both the first SSB and the second SSB in the same symbol(s). It can also be assumed that other types of QCL relationships (eg, delay spread, Doppler spread, Doppler shift, average gain, average delay) hold between mutually coupled SSBs. Alternatively, the other type of QCL relationship (eg, delay spread, Doppler spread, Doppler shift, average gain, average delay) may not be established between mutually coupled SSBs.

CORESETs corresponding to the plurality of mutually coupled SSBs may be mutually coupled. For example, a first SSB and a second SSB may be coupled to each other, and a first CORESET corresponding to the first SSB and a second CORESET corresponding to the second SSB may be coupled to each other. The first CORESET and the second CORESET may be CORESETs (eg, CORESET #0) having the same ID, and the resource locations of the first CORESET and the second CORESET are respectively the resource locations of the first SSB and the second SSB and/or the second CORESET. It may be determined based on information indicated from the first SSB and the second SSB. The CORESET may include a CSS set, and the CSS set may include type 0, 0A, 1, and 2 PDCCH CSS sets. The terminal may assume that a QCL relationship (eg, spatial QCL, spatial reception parameter, QCL type D) is established between mutually coupled CORESETs, and based on the assumption, monitors the mutually coupled CORESETs using the same Rx beam. and receive. From the receiving point of view of the terminal, the terminal may simultaneously receive mutually combined CORESETs in the same symbol (s).

A plurality of SSBs belonging to different SSB layers may be combined with each other. In the above embodiment, SSBs belonging to the first SSB layer and SSBs belonging to the second SSB layer may be combined with each other. In addition, the SSB corresponding to a beam having a wide beam width and the SSB corresponding to a beam having a narrow beam width may be mutually coupled. The UE can receive a plurality of SSBs belonging to different SSB layers using the same Rx beam based on the mutual coupling relationship or the QCL relationship. That is, the terminal can receive a beam having a wide beamwidth (ie, the transmission beam of the base station) and a beam having a narrow beamwidth (ie, the transmission beam of the base station) using the same reception beam. Hereinafter, the above-described method may be referred to as (method 100).

In this specification, the establishment of a QCL relationship between the first SSB and the second SSB means that a signal constituting the first SSB (eg, PSS / SSS, PBCH DM-RS, CSI-RS, etc.) or channel (eg, PBCH) It may mean that it can be used as a QCL source of a signal constituting the second SSB (eg, PSS/SSS, PBCH DM-RS, CSI-RS, etc.) or channel (eg, PBCH). Simultaneously or separately, the establishment of a QCL relationship between the first SSB and the second SSB means that a signal (eg, PSS/SSS, PBCH DM-RS, CSI-RS, etc.) or a channel (eg, PSS/SSS, PBCH DM-RS, CSI-RS, etc.) or channels (eg, PBCH) may be used as a QCL source of a signal constituting the first SSB (eg, PSS/SSS, PBCH DM-RS, CSI-RS, etc.) or channel (eg, PBCH). Simultaneously or separately, the establishment of a QCL relationship between the first SSB and the second SSB means that the signal constituting the first SSB (eg, PSS/SSS, PBCH DM-RS, CSI-RS, etc.) and the second SSB It may mean that configuring signals (eg, PSS/SSS, PBCH DM-RS, CSI-RS, etc.) share the same QCL source for specific QCL parameter(s). In addition, the terminal may receive a first signal having a QCL relationship with the first SSB and a second signal having a QCL relationship with the second SSB. In this case, the terminal may receive the first signal based on the second SSB as well as the first SSB, and may receive the second signal based on the first SSB as well as the second SSB. In addition, the terminal may assume that a QCL relationship is established between the first signal and the second signal.

Here, the first SSB and the second SSB may be SSBs belonging to the same serving cell. The first SSB and the second SSB may include the same physical layer cell ID or information corresponding thereto. The first SSB and the second SSB may be mapped on the same (active) bandwidth portion and transmitted to the UE. The first SSB and the second SSB may be cell-defining SSBs (SSBs) defining a cell. Alternatively, only some of the first SSB and the second SSB may be used as SSBs defining a cell for at least some UEs.

7 is a conceptual diagram for explaining mutual coupling and QCL relationships between SSBs.

Referring to FIG. 7 , SSBs may be classified into a first SSB layer and a second SSB layer, and SSBs belonging to the first SSB layer and SSBs belonging to the second SSB layer may be combined with each other. For example, SSB #0 belonging to the first SSB layer may be combined with SSB #4 to SSB #7 belonging to the second SSB layer, respectively. In addition, a QCL relationship may be established between mutually coupled SSBs. For example, SSB #0 may be QCLed with SSBs #4 to SSB #7, respectively. This may not necessarily mean that SSB #4 to SSB #7 have a QCL relationship with each other. For example, based on the mutual coupling relationship, the UE may not assume that SSB #4 and SSB #5 are QCL.

Information about the above-described SSB layer (or SSB set, SSB group), information indicating a mutual coupling relationship (or QCL relationship) between SSBs, etc. may be used in a signaling procedure (eg, RRC signaling, MAC signaling, DCI, or the signaling Combinations of) may be configured in the terminal from the base station. For example, the information may be included in system information (eg, SIB-1, SIB, MIB, etc.) and transmitted to the terminal. Alternatively, at least part of the information may be defined in technical specifications and shared between the base station and the terminal in advance. For example, the UE may determine the SSB layer to which a certain SSB belongs based on the SSB index of the corresponding SSB. For example, SSBs corresponding to the lowest N ₁ indices may belong to a first SSB layer, and SSBs corresponding to the highest N ₂ indices may belong to a second SSB layer. In this case, the base station may inform the terminal of information about N ₁ and N ₂ .

At least part of the information may be derived based on other information without being directly signaled to the terminal. According to an embodiment, information about the SSB layer (or SSB set or SSB group) may not be directly signaled to the UE. The UE can find out the SSB layer configuration from the mutual coupling relationship (or QCL relationship) between SSBs. For example, the UE may regard the combined SSBs as belonging to different SSB layers (or SSB set or SSB group). For example, the base station may indicate to the terminal that SSB #0 is combined with SSB #4 to SSB #7, and the terminal based on this indicates the SSB layer to which SSB #0 belongs and the SSB #4 to SSB #7 to which it belongs. SSB layers can be considered different.

According to another embodiment, the mutual coupling relationship (or QCL relationship) between SSBs may not be directly signaled to the UE. The UE can find out the mutual coupling relationship between SSBs from information on the configuration of SSB layers (or SSB set or SSB group). For example, the UE may receive information about the number N ₁ of SSBs belonging to the first SSB layer and the number N ₂ of SSBs belonging to the second SSB layer from the base station. In this case, each SSB belonging to the first SSB layer may be combined with N ₂ /N ₁ SSBs belonging to the second SSB layer. This can be established when N ₂ ≥N ₁ . Alternatively, each SSB belonging to the second SSB layer may be combined with N ₁ /N ₂ SSBs belonging to the first SSB layer. This can be established when N ₁ ≥N ₂ . According to the above embodiment, N ₁ =4 and N ₂ =16. For example, each SSB belonging to the first SSB layer may be combined with 4 (= N ₂ /N ₁ ) SSBs belonging to the second SSB layer. The mapping may be applied in ascending (or descending) order of SSB indexes within each SSB layer. For example, SSB #0 of the first SSB layer may be combined with SSBs #4 to SSB #7 of the second SSB layer, and SSB #1 of the first SSB layer may be SSBs #8 to SSB #8 of the second SSB layer. It can be combined with SSB #11, and the same rule can be repeatedly applied to the remaining SSBs.

In a method different from (method 100), the above-described mutual coupling relationship between SSBs may be applied regardless of the SSB layer (or SSB set or SSB group) or regardless of the SSB layer. For example, the terminal may receive configuration information about a mutual coupling relationship and a QCL relationship between N ₁ SSBs and N ₂ SSBs from the base station. The UE assumes that each of the N ₁ SSBs is combined with N ₂ /N ₁ SSBs according to the above method without applying the SSB layer concept, or each of the N ₂ SSBs is combined with N ₁ /N ₂ SSBs. It can be assumed that it is mutually coupled with . Similarly, a QCL relationship may be established between mutually coupled SSBs.

Each SSB (or each SSB resource) may belong to one SSB layer (or SSB set or SSB group). Alternatively, each SSB (or SSB resource) may belong to a plurality of SSB layers (or SSB sets or SSB groups). For example, an SSB with a wide beamwidth (eg, SSB #0) may belong to both the first SSB layer and the second SSB layer, and an SSB with a narrow beamwidth (eg, SSB #4) may belong only to the second SSB layer. can belong That is, the first SSB layer may include all SSBs belonging to the second SSB layer. In this case, even if the SSBs belong to the same SSB layer, a mutual coupling relationship and a QCL relationship may be established between the SSBs.

In embodiments, an SSB layer may mean an SSB group, SSB set, etc., and each SSB layer may include one or more SSB(s). Alternatively, in order to achieve a special purpose, some SSB layers may be configured not to include SSBs at all.

FIG. 8 is a conceptual diagram for explaining a first embodiment of arrangement of SSB resources and mutual coupling between SSB resources, and FIG. 9 is a conceptual diagram for explaining a second embodiment of arrangement of SSB resources and mutual coupling between SSB resources. am.

Referring to FIGS. 8 and 9 , a plurality (eg, 20) SSB resources may be deployed for SSB transmission based on beam sweeping. SSB resources can be multiplexed in the time domain and mapped to the same frequency domain. SSB resources may have indices numbered in chronological order. That is, SSB resources mapped to earlier symbols within the same SSB transmission period may have a lower SSB index. Each SSB resource may belong to one of a plurality of SSB layers, that is, a first SSB layer and a second SSB layer.

Referring to FIG. 8 , SSB resources belonging to the first SSB layer (or the second SSB layer) may be deployed first, and SSB resources belonging to the second SSB layer (or the first SSB layer) may be deployed later. For example, SSB resources corresponding to the lowest 4 (=N ₁ ) indices may belong to the first SSB layer, and SSB resources corresponding to the highest 16 (=N ₂ ) indices may belong to the second SSB layer. can belong to a hierarchy. As described above, the UE may determine a mutual coupling relationship and a QCL relationship between SSB resources or SSBs. For example, SSB resource #0 may be combined with SSB resources #4 to #7, respectively. This can be established when N ₂ ≥N ₁ . Based on the rule and values of N ₁ and N ₂ , the UE can find out the mutual coupling relationship between SSBs and/or the configuration of the SSB layer.

Referring to FIG. 9 , SSB resources belonging to the first SSB layer and SSB resources belonging to the second SSB layer may be interlaced. For example, SSB resource #0, which is the first SSB resource, may belong to the first SSB layer, and SSB resources #1 to #4, which are the next four (=N ₂ /N ₁ ) SSB resources, belong to the second SSB layer. can belong SSB resource #0, which is the first SSB resource, may be combined with SSB resources #1 to #4, respectively, which are the four (=N ₂ /N ₁ ) SSB resources. The same rule may be repeatedly applied to the remaining SSB resources. That is, SSB resource #5, which is the next one SSB resource, may belong to the first SSB layer, and SSB resources #6 to #9, which are the next 4 (=N ₂ /N ₁ ) SSB resources, may belong to the second SSB layer. can belong to SSB resource #5, which is one SSB resource, may be combined with SSB resources #6 to #9, respectively, which are four (=N ₂ /N ₁ ) SSB resources. Based on the rule and values of N ₁ and N ₂ , the UE can find out the mutual coupling relationship between SSBs and/or the configuration of the SSB layer.

In the above embodiments, SSB resources may be resources on which SSB is actually transmitted. Alternatively, some of the SSB resources may be resources on which the SSB is not actually transmitted. The base station may inform the terminal of SSB resources in which the SSB is actually transmitted (or SSB resources in which the SSB is not actually transmitted) through a signaling procedure. Based on the signaling from the base station, the UE can perform rate matching on each SSB resource where the SSB is actually transmitted to receive the PDSCH, and can receive the PDSCH in a resource region including each SSB resource where the SSB is not actually transmitted. (ie, PDSCH may not be rate matched to SSB resources).

SSB resources belonging to a plurality of SSB layers may be mapped within a predetermined time interval. For example, the SSB resources may be mapped within a half-radio frame (eg, 5 ms). For another example, the SSB resources may be mapped within an SSB transmission window. SSB mapping or transmission and reception operations based on the SSB transmission window may be used in a specific frequency band (eg, an unlicensed band). A time gap or time interval may exist between SSB resources, and the time gap may consist of one or more symbol(s). A time gap may be used for a beam switching operation between SSBs.

The random access and beam reporting method by mutual coupling between downlink resources and uplink resources described above may be applied to the above embodiments. For example, a mutual coupling relationship between SSB resources (or SSBs) and PRACH resources (or PRACHs, PRACH occasions) may be configured in the UE. In this case, mutual coupling between SSB and PRACH may be independent of SSB layer or mutual coupling between SSBs. In the above embodiment, each of the 20 SSB resources may be combined with one or more PRACH resources regardless of which SSB layer they belong to. For example, 20 SSB resources may have a one-to-one correspondence with 20 PRACH resources. Alternatively, mutual coupling between the SSB and the PRACH may be determined by which SSB layer the SSB belongs to or a mutual coupling relationship between the SSBs. For example, mutually combined SSBs (eg, an SSB belonging to the first SSB layer and an SSB belonging to the second SSB layer) may be mutually combined with the same PRACH resource(s) (or the same PRACH occasion(s)). can

[Initial beam determination and reporting]

As described above, an SSB belonging to the first SSB layer (eg, a wide SSB) and an SSB belonging to the second SSB layer received by a terminal (eg, a cell center terminal) in a system in which a plurality of fine beams are used (eg, a cell center terminal) When all SSBs with a narrow width) satisfy the beam quality condition, the UE selects an SSB belonging to the first SSB layer (eg, an SSB with a wide beam width), and based on this, a random access procedure, initial beam determination, and beam management It may be advantageous to perform an action or the like. However, if the UE simply selects the SSB having the largest received signal strength (eg, RSRP, L1-RSRP, etc.) as the optimal SSB, the probability that the UE selects an SSB belonging to the first SSB layer may be low. In order to solve the above problem, a conventional random access operation may need to be improved. The proposed methods are described below.

First, the terminal may determine SSB(s) satisfying a certain condition as valid SSB(s). In addition, the terminal may determine SSB(s) that do not satisfy the predetermined condition as invalid SSB(s). The terminal may measure received signal strength of SSBs (or initial access signals in general) and compare the measured value with a threshold value (or reference value). SSB(s) having a received signal strength that satisfies the threshold (eg greater than or equal to the threshold) may be regarded as valid SSB(s), and the beam(s) corresponding to the SSB(s) are valid can be regarded as beam(s). Conversely, SSB(s) having a received signal strength that does not satisfy the threshold (eg, less than the threshold) may be regarded as invalid SSB(s), and the beam corresponding to the SSB(s) is may be regarded as non-effective beam(s). For this purpose, the measurement threshold may be defined. The measurement threshold may be predefined in technical standards or may be set in a terminal from a base station. The UE may select or determine at least one SSB(s) among valid SSBs, and report the determined SSB(s) to the BS or perform a random access procedure based thereon. If there is no valid SSB(s), the UE can determine one SSB among the non-valid SSBs. The one SSB may be the SSB having the largest received signal strength. In this specification, determining or reporting SSB(s) by the UE means that the UE determines or reports SSB resource(s) corresponding to the SSB(s) or beam(s) corresponding to the SSB(s). can

The UE may determine one SSB among valid SSBs. When the UE determines valid SSBs in a plurality of SSB layers (eg, the first SSB layer and the second SSB layer), the UE first determines one SSB layer (eg, the first SSB layer) among the plurality of SSB layers. and one SSB among valid SSBs belonging to the next determined SSB layer (eg, the first SSB layer) may be determined. For the determination of the SSB layer, priorities between SSB layers may be defined or set in the UE. For example, the terminal may obtain configuration information for determining priorities between SSB layers through a signaling procedure from the base station. Simultaneously or separately, the priority between SSB layers may be determined based on other information about the SSB layer. For example, the priority between SSB layers may be determined based on the number of SSBs included in SSB layers, SSB beam width, SSB resource location, or a combination of the above factors. According to an embodiment, an SSB layer having a smaller number of SSBs may be considered to have a higher priority than an SSB layer having a larger number of SSBs. In addition, an SSB layer with a smaller number of SSBs may correspond to a relatively wider beam width than an SSB layer with a larger number of SSBs.

The UE may determine an SSB layer having a higher priority (or the highest) among SSB layers in which a valid SSB exists. A criterion for determining one SSB among valid SSBs in the determined SSB layer may be a received signal strength measurement value. Alternatively, the above criteria may not be defined in technical specifications. As described above, when a valid SSB does not exist, the UE may determine one SSB among ineffective SSBs.

The determined one SSB (or beam corresponding thereto) may be reported to the base station. For example, based on the coupling relationship between the SSB resource and the PRACH resource described with reference to FIG. 3, the UE can identify the PRACH resource mutually combined with the determined SSB, and the UE transmits the PRACH in the identified PRACH resource. can do. The base station can know which SSB (or beam corresponding thereto) has been determined or selected by the terminal by successfully receiving the PRACH in the PRACH resource. The method described above may be referred to as (method 200).

10 is a conceptual diagram for explaining a first embodiment of a method for determining and reporting an initial beam according to (method 200).

Referring to FIG. 10, 5 SSB resources may be divided into 2 SSB layers. SSB resource #0 (or SSB #0) may belong to the first SSB layer, and SSB resources #1 to #4 (or SSB #1 to #4) may belong to the second SSB layer. SSB resource #0 may be combined with SSB resources #1 to #4, respectively. In addition, the 5 SSB resources may be mutually combined with 5 PRACH resources, respectively.

The UE may determine SSB resource #0 belonging to the first SSB layer and SSB resource #1 belonging to the second SSB layer as valid SSBs. At this time, the UE can determine one SSB by (method 200). For example, the first SSB layer may have a higher priority than the second SSB layer, and the UE may determine SSB resource #0 belonging to the first SSB layer as the optimal SSB. In addition, the terminal may determine a beam corresponding to SSB resource #0 as a serving beam. The UE can transmit a PRACH on PRACH resource #0 combined with SSB resource #0, and the base station can confirm that the UE has selected SSB resource #0 by receiving the PRACH.

According to (Method 200), the UE preferentially selects an SSB belonging to a specific SSB layer (eg, the first SSB layer) or having a specific beam width (eg, a wide beam width) and uses a beam corresponding thereto as a serving beam. . Therefore, the problem of frequent serving beam change described above with reference to FIG. 2 can be solved. However, the use of an SSB (or a beam corresponding thereto) belonging to another SSB layer (eg, the second SSB layer) or having a different beam width (eg, narrow beam width) may be useful for the cell center terminal. For example, when transmitting a data channel, a transmission rate may be more important than reliability, and beamforming using a fine beam rather than a wide beam may be advantageous. Therefore, a method of using a beam having a wide beamwidth for transmission of the control channel and using a beam having a narrow beamwidth for transmission of the data channel may be considered. However, according to (method 200), the UE does not determine an SSB (or a beam corresponding thereto) belonging to another SSB layer (eg, the second SSB layer) or having a different beamwidth (eg, narrow beamwidth). or may not be reported to the base station, and the SSB (or a beam corresponding thereto) is difficult to utilize for transmission of a later procedure.

Alternatively, the UE may determine one or a plurality of SSB(s) among valid SSBs. According to the first embodiment, the UE can determine at most one SSB for each of K SSB layers, and can determine a total of up to L SSBs (K and L are natural numbers). For example, L=K. When two SSB layers are used, L=K=2. According to the first embodiment, the UE can select an SSB with a maximum of one wide beamwidth in the first SSB layer and select an SSB with a maximum of one narrow beamwidth in the second SSB layer. According to the second embodiment, the terminal can determine up to L SSBs among valid SSBs belonging to K SSB layers. For example, L=K. When two SSB layers are used, L=K=2. According to the second embodiment, more diverse combinations of SSBs can be determined. For example, the UE may select SSB(s) having up to two wide beamwidths in the first SSB layer. Alternatively, the UE may select SSB(s) having up to two narrow beamwidths in the second SSB layer. Similarly, when there are no valid SSBs, the UE can determine one SSB or a plurality of SSBs (eg, up to L SSBs) from among the non-valid SSBs.

The determined one or more SSB(s) (or beam(s) corresponding thereto) may be reported to the base station. When the UE determines one SSB, the UE may implicitly report the SSB to the base station by transmitting a PRACH in a PRACH resource combined with the one SSB. Meanwhile, when the UE determines a plurality of SSBs, the UE may transmit a PRACH in a plurality of PRACH resources combined with the plurality of SSBs. If the plurality of SSBs are combined with the same PRACH resource, the UE can transmit the PRACH on the PRACH resource. For example, by the above-described method, the UE may determine two mutually coupled SSBs as initial SSBs. The determined SSBs may belong to different SSB layers. The UE may transmit a PRACH in two PRACH resources mutually coupled with the two SSBs. In this case, the UE may repeatedly transmit the same PRACH (eg, the same preamble, the same sequence) in the two PRACH resources. The two PRACH resources may belong to the same PRACH resource period, and repeated PRACH transmissions may be performed within the same PRACH resource period. A transmission beam applied to each PRACH resource by the UE may be formed based on a reception beam of an SSB resource combined with the corresponding PRACH resource. Due to mutual coupling between the SSBs, the PRACH resources may also have a mutual coupling relationship. That is, mutually coupled SSBs and mutually coupled PRACHs may be mutually coupled. The method described above may be referred to as (method 210).

11 is a conceptual diagram for explaining a first embodiment of a method for determining and reporting an initial beam by (method 210).

Referring to FIG. 11, 5 SSB resources may be divided into 2 SSB layers. SSB resource #0 (or SSB #0) may belong to the first SSB layer, and SSB resources #1 to #4 (or SSB #1 to #4) may belong to the second SSB layer. SSB resource #0 may be combined with SSB resources #1 to #4, respectively. In addition, the 5 SSB resources may be mutually combined with 5 PRACH resources, respectively.

The UE may determine SSB resource #0 belonging to the first SSB layer and SSB resource #1 belonging to the second SSB layer as valid SSBs. At this time, the UE can determine a plurality of SSBs by (method 210). For example, the UE may determine SSB resource #0 in the first SSB layer and SSB resource #1 in the second SSB layer. Also, the terminal may determine beams corresponding to SSB resource #0 and SSB resource #1 as serving beams. The UE can transmit PRACH on PRACH resources combined with SSB resource #0 and SSB resource #1, that is, PRACH resource #0 and PRACH resource #1. And it can be confirmed that SSB resource #1 is selected.

That is, the terminal may perform an initial access procedure with the base station using a beam corresponding to SSB resource #0 (hereinafter, first initial beam) and a beam corresponding to SSB resource #1 (hereinafter, second initial beam). there is. Alternatively, the terminal initially accesses the base station using at least one beam of a beam corresponding to SSB resource #0 (hereinafter, first initial beam) and a beam corresponding to SSB resource #1 (hereinafter, second initial beam). procedure can be performed. Here, at least one beam used in the initial access procedure among the first initial beam and the second initial beam may be determined based on rules predefined in technical specifications or configuration information received from the base station.

Meanwhile, the use of initial beams may be defined. For example, among a plurality of initial beams determined by the terminal, one beam (hereinafter referred to as “primary beam”) may be used for transmission and reception of a control channel (eg, PDCCH, PUCCH), and another beam (hereinafter referred to as “primary beam”) may be used. Referred to as “secondary beam”) may be used for transmission and reception operations of data channels (eg, PDSCH and PUSCH). The control channel and the data channel may be channels transmitted during a random access procedure. For example, the PDSCH may be a PDSCH including Msg2 or a random access response message, and the PDCCH may be a PDCCH scheduling the Msg2 PDSCH (eg, a PDCCH in which a CRC is scrambled with RA-RNTI). Also, the PUSCH may be a PUSCH including Msg3, and the PUCCH may be a PUCCH including HARQ-ACK of Msg2 PDSCH or Msg4 PDSCH. The uses of the aforementioned initial beams may be predefined in technical specifications. For example, the primary beam may correspond to a beam having a wide beam width, and the secondary beam may correspond to a beam having a narrow beam width.

When the base station successfully receives the PRACH from a plurality of PRACH resources, the base station can find out the plurality of SSBs determined by the terminal or beams corresponding thereto. For example, the base station may receive the PRACH in the first PRACH resource and the second PRACH resource to find out the first SSB and the second SSB determined by the terminal, respectively. The base station can determine for what purpose the first initial beam corresponding to the first SSB and the second initial beam corresponding to the second SSB are to be used, and can perform transmission with the terminal accordingly. For example, the first initial beam may be a beam with a wide beam width and the second initial beam may be a beam with a narrow beam width. In this case, the base station may determine the first initial beam as the primary beam and the second initial beam as the secondary beam.

Alternatively, uses of the first initial beam and the second initial beam may be determined by the terminal. For example, the terminal may determine one of the first initial beam and the second initial beam corresponding to the plurality of SSBs determined by the terminal as the primary beam and the other as the secondary beam. The terminal may report information about which beam is determined as the primary beam to the base station. For example, the information may be reported based on a plurality of PRACH sequences. When the first initial beam is determined as the primary beam, the UE can transmit the first PRACH sequence to the base station, and when the second initial beam is determined as the primary beam, the UE can transmit the second PRACH sequence to the base station. For example, a first PRACH sequence may be transmitted in a first PRACH resource corresponding to a first initial beam, and a second PRACH sequence may be transmitted in a second PRACH resource corresponding to a second initial beam. For another example, either of the first PRACH sequence and the second PRACH sequence may be transmitted in the same PRACH resource. For another example, the information may be included in the payload of the MsgA PUSCH and transmitted to the base station. Alternatively, the information may be reported to the base station after the terminal receives Msg2 or MsgB. For example, the information may be reported to the base station as an RRC message or MAC CE.

When (method 210) is used, the UE can transmit PRACH in a plurality of PRACH resources. In this case, when a plurality of PRACH resources are mapped to the same symbol (s), the UE can transmit the PRACH in any one of the plurality of PRACH resources. Any one of the above PRACH resources may be arbitrarily determined by the UE. Alternatively, any one of the PRACH resources may be a resource corresponding to a specific SSB, a specific SSB layer, or a specific beam. For example, any one of the PRACH resources may be a PRACH resource combined with an SSB belonging to the first SSB layer. For another example, any one PRACH resource may be a PRACH resource combined with an SSB corresponding to a primary beam. Alternatively, when a plurality of PRACH resources are mapped to the same symbol (s), the UE can transmit PRACH on all of the plurality of PRACH resources. Alternatively, the UE may not expect the plurality of PRACH resources to be mapped to the same symbol(s). The base station can eliminate the number of cases in which the terminal selects the PRACH resources arranged on the same symbol by appropriately arranging SSB resources and PRACH resources.

When (method 210) is used, the terminal may determine a plurality of SSBs, and CORESET may correspond to each of the plurality of SSBs. For example, a first CORESET and a second CORESET may correspond to the first SSB and the second SSB, respectively. The first CORESET and the second CORESET may be CORESET #0 disposed in different resources. That is, the first CORESET and the second CORESET may have the same CORESET ID. The terminal may monitor both the first CORESET and the second CORESET. Alternatively, the terminal may monitor any one CORESET among the plurality of CORESETs. For example, any one CORESET may be arbitrarily determined by the terminal. For another example, any one CORESET may be a CORESET corresponding to a specific SSB, a specific SSB layer, or a specific beam. For example, any one CORESET may be a CORESET indicated from an SSB belonging to the first SSB layer (or a PBCH or MIB included in the SSB). For another example, any one CORESET may be a CORESET indicated from the SSB corresponding to the primary beam. Due to the above-described QCL relationship, a QCL relationship may be established between the first CORESET and the second CORESET. The UE can monitor both PDCCH candidates belonging to the first CORESET and PDCCH candidates belonging to the second CORESET in the same symbol (or simultaneously), and receive all (or simultaneously) PDCCHs transmitted from the PDCCH candidates. In the above embodiments, the terminal may perform operations such as initial access, random access, transmission and reception of control and data channels, beam management, and CSI acquisition and reporting using only some of the plurality of SSB layers. For example, the terminal may select one or a plurality of SSB layer (s) based on information about its location in the serving cell, and perform an initial access operation or a random access operation based on the selected SSB layer (s). can do. For example, a cell edge terminal can selectively use only an SSB layer corresponding to a narrow beamwidth, and a cell center terminal can utilize both an SSB layer corresponding to a wide beamwidth and an SSB layer corresponding to a narrow beamwidth for the above operation. .

The methods according to the present invention may be implemented in the form of program instructions that can be executed by various computer means and recorded on a computer readable medium. Computer readable media may include program instructions, data files, data structures, etc. alone or in combination. Program instructions recorded on a computer readable medium may be specially designed and configured for the present invention or may be known and usable to those skilled in computer software.

Examples of computer readable media include hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include high-level language codes that can be executed by a computer using an interpreter or the like as well as machine language codes generated by a compiler. The hardware device described above may be configured to operate with at least one software module to perform the operations of the present invention, and vice versa.

Although described with reference to the above embodiments, those skilled in the art will understand that the present invention can be variously modified and changed without departing from the spirit and scope of the present invention described in the claims below. You will be able to.

Claims (20)

As a beam management method performed in a terminal,
Receiving at least one synchronization signal block (SSB) belonging to a first layer from a base station;
Receiving at least one SSB belonging to a second layer from the base station;
determining valid SSBs from among at least one SSB belonging to the first layer and at least one SSB belonging to the second layer;
selecting at least one first SSB belonging to a layer having a higher priority among the first layer and the second layer from among the valid SSBs; and
Reporting the selected first SSB to the base station and using a beam used to receive the first SSB in an initial access procedure for communication with the base station;
Each SSB includes at least one of a synchronization signal and a broadcast channel,
Beam management method. The method of claim 1,
The valid SSBs are SSBs received by the terminal with a received signal strength greater than or equal to a predetermined threshold,
Beam management method. The method of claim 1,
The priority between the first layer and the second layer is determined by configuration information received from the base station.
Beam management method. The method of claim 1,
When the first layer has a higher priority than the second layer, the number of SSBs belonging to the first layer is smaller than the number of SSBs belonging to the second layer, and the second layer is higher than the first layer. When having a high priority, the number of SSBs belonging to the second layer is smaller than the number of SSBs belonging to the first layer,
Beam management method. The method of claim 1,
The first SSB is an SSB having the highest received signal strength among the valid SSBs,
Beam management method. The method of claim 1,
The terminal transmits a random access preamble to the base station in the uplink resource (s) coupled to the selected first SSB to report the selected first SSB to the base station.
Beam management method. The method of claim 1,
The step of using the beam used to receive the first SSB in the initial access procedure for communication with the base station includes receiving a downlink signal for initial access based on the beam and initial access based on the beam. Including at least one of the operations of transmitting an uplink signal for
Beam management method. As a beam management method performed in a terminal,
Receiving at least one SSB belonging to a first layer from a base station;
Receiving at least one SSB belonging to a second layer from the base station;
determining valid SSBs from among at least one SSB belonging to the first layer and at least one SSB belonging to the second layer;
selecting a first SSB belonging to the first layer and a second SSB belonging to the second layer from among the available SSBs; and
Reports the selected first SSB and the selected second SSB to the base station, and at least one beam among a first beam used to receive the first SSB and a second beam used to receive the second SSB Using for an initial access procedure for communication with the base station,
Each SSB includes at least one of a synchronization signal and a broadcast channel,
Beam management method. The method of claim 8,
The valid SSBs are SSBs received by the terminal with a received signal strength greater than or equal to a predetermined threshold,
Beam management method. The method of claim 8,
The first SSB is an SSB having the highest received signal strength among valid SSBs belonging to the first layer, and the second SSB is an SSB having the highest received signal strength among valid SSBs belonging to the second layer,
Beam management method. The method of claim 8,
The terminal transmits a random access preamble to the base station on the uplink resource(s) associated with the selected first SSB to report the selected first SSB to the base station, and the uplink resource associated with the selected second SSB. In (s), transmitting a random access preamble to the base station to report the selected second SSB to the base station,
Beam management method. The method of claim 10,
At least one beam used in the initial access procedure among the first beam and the second beam is determined based on a predefined rule in the technical standard or configuration information received from the base station,
Beam management method. The method of claim 12,
One of the first beam and the second beam is selected as a primary beam used for transmitting a control channel to the base station, and the other beam is selected as a secondary beam used for transmitting a data channel to the base station. And, the beam width of the primary beam is wider than that of the secondary beam,
Beam management method. As a beam management method performed in a base station,
Transmitting at least one SSB belonging to a first layer;
Transmitting at least one SSB belonging to a second layer; and
Receiving a report from a terminal of a first SSB selected by the terminal, and using a beam used to transmit the first SSB in an initial access procedure for communication with the terminal,
The first SSB is a layer having a higher priority among the first layer and the second layer among valid SSBs among at least one SSB belonging to the first layer and at least one SSB belonging to the second layer. SSB belonging to
Each SSB includes at least one of a synchronization signal and a broadcast channel,
Beam management method. The method of claim 14,
The valid SSBs are SSBs received by the terminal with a received signal strength greater than or equal to a predetermined threshold,
Beam management method. The method of claim 14,
Further comprising the step of transmitting setting information used to determine the priority between the first layer and the second layer to the terminal,
Beam management method. The method of claim 14,
When the first layer has a higher priority than the second layer, the number of SSBs belonging to the first layer is smaller than the number of SSBs belonging to the second layer, and the second layer is higher than the first layer. When having a high priority, the number of SSBs belonging to the second layer is smaller than the number of SSBs belonging to the first layer,
Beam management method. The method of claim 14,
The first SSB is an SSB having the highest received signal strength among the valid SSBs,
Beam management method. The method of claim 14,
The selected first SSB is reported from the terminal by receiving a random access preamble from the terminal on the uplink resource (s) combined with the first SSB,
Beam management method. The method of claim 14,
Within an SSB transmission period, SSBs belonging to the first layer are disposed before SSBs belonging to the second layer, or SSBs belonging to the first layer and SSBs belonging to the second layer intersect within the SSB transmission period. arranged in an interlaced manner,
Beam management method.

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