CN118160339A

CN118160339A - Cell coverage extension method and device for same

Info

Publication number: CN118160339A
Application number: CN202280071950.6A
Authority: CN
Inventors: 文盛铉; 金哲淳; 李正薰
Original assignee: Electronics and Telecommunications Research Institute ETRI
Current assignee: Electronics and Telecommunications Research Institute ETRI
Priority date: 2021-08-26
Filing date: 2022-08-26
Publication date: 2024-06-07

Abstract

A method of operating a repeater in a mobile communication system may include the steps of: receiving information about a backhaul receive beam and/or a backhaul transmit beam from a base station; receiving information on an access link transmit beam and/or an access link receive beam from a base station or obtaining information on an access link transmit beam and/or an access link receive beam from information on a backhaul receive beam and/or a backhaul transmit beam; communicating with the base station by using a backhaul receive beam and/or a backhaul transmit beam, the backhaul receive beam and/or the backhaul transmit beam being formed using information about the backhaul receive beam and/or the backhaul transmit beam; and communicating with the terminal by using an access link transmit beam and/or an access link receive beam formed using information about the access link transmit beam and/or the access link receive beam.

Description

Cell coverage extension method and device for same

Technical Field

The present disclosure relates to a cell coverage extension method in a mobile communication system, and more particularly, to a method of extending cell coverage by using a relay node or an Intelligent Reflection Surface (IRS) in a mobile communication system and an apparatus therefor.

Background

Communication systems are continually evolving to extend the communication infrastructure to realize a super-interconnect society. For example, new Radio (NR) communication systems may support frequency bands up to 100GHz and frequency bands of 6GHz or less. In addition, NR communication systems may support more diversified services and scenarios compared to conventional communication systems, such as Long Term Evolution (LTE) communication systems. For example, the usage scenarios of NR communication systems may include enhanced mobile broadband (eMBB), ultra-reliable low-delay communication (URLLC), large-scale machine type communication (mMTC), and so on. Further, the sixth generation (6G) communication system, which is recently being discussed, is expected to realize more diversified services and user experiences by utilizing terahertz (THz) frequency bands, artificial intelligence, satellite communication, quantum technology, and the like. Such communication systems must meet various requirements of the industry and require high levels of communication technology to fulfill these requirements.

Disclosure of Invention

[ Problem ]

The present disclosure relates to providing a cell coverage extension method using a relay node or an intelligent reflection plane.

The present disclosure also relates to providing a configuration of an apparatus for performing a cell coverage extension method.

[ Technical solution ]

The operation method of a repeater in a mobile communication system for achieving the above object according to an exemplary embodiment of the present disclosure may include: receiving information about a backhaul receive beam and/or a backhaul transmit beam from a base station; receiving information on an access link transmit beam and/or an access link receive beam from a base station or obtaining information on an access link transmit beam and/or an access link receive beam from information on a backhaul receive beam and/or a backhaul transmit beam; performing communication with the base station by using a backhaul reception beam and/or a backhaul transmission beam formed using information about the backhaul reception beam and/or the backhaul transmission beam; and performing communication with the terminal by using an access link transmit beam and/or an access link receive beam, the access link transmit beam and/or the access link receive beam being formed using information about the access link transmit beam and/or the access link receive beam, wherein the backhaul receive beam is a beam for the repeater to receive signals from the base station, the backhaul transmit beam is a beam for the repeater to transmit signals to the base station, the access link transmit beam is a beam for the repeater to transmit signals to the terminal, and the access link receive beam is a beam for the terminal to receive signals from the repeater.

Information about the backhaul receive beam may be indicated based on a quasi co-located (QCL) source signal having a QCL relationship with a downlink signal transmitted from the base station to the relay and QCL parameters for which the QCL relationship is established.

The information about the backhaul transmit beam may be indicated based on a source signal having a QCL relationship or spatial relationship with an uplink signal transmitted from the relay to the base station or a downlink signal transmitted from the base station to the relay and QCL parameters for which the QCL relationship or spatial relationship is established.

The information about the access link transmit beam may be based on a codebook indication, the codebook including entries each corresponding to a precoder applied to signals transmitted to the terminal over the access link with the terminal.

At least a portion of the codebook may be preconfigured in the repeater or received from the base station, and the information about the access link transmit beam may be indicated by an index indicating at least one entry belonging to the codebook.

The information about the access link receive beam may be indicated based on a codebook, the codebook including entries each corresponding to a receive filter applied to signals received from the terminal over the access link with the terminal.

At least a portion of the codebook may be preconfigured in the repeater or received from the base station, and the information about the access link reception beam may be indicated by an index indicating at least one entry belonging to the codebook.

When the repeater is configured as an Intelligent Reflective Surface (IRS), the information about the backhaul transmit beam and/or the information about the access link transmit beam may include phase shift values for a plurality of phase control elements that make up the IRS.

Backhaul transmit beams and/or access link transmit beams may be formed by phase control elements based on beamforming.

The operation method of a base station in a mobile communication system for achieving the above object according to another exemplary embodiment of the present disclosure may include: transmitting information about the backhaul receive beam and/or the backhaul transmit beam to the relay; transmitting information about the access link transmit beam and/or the access link receive beam to the repeater; performing communication with the relay by using a backhaul receive beam and/or a backhaul transmit beam that are formed using information about the backhaul receive beam and/or the backhaul transmit beam; and allowing the repeater to communicate with the terminal by using an access link transmit beam and/or an access link receive beam formed using information about the access link transmit beam and/or the access link receive beam, wherein the backhaul receive beam is a beam for the repeater to receive signals from the base station, the backhaul transmit beam is a beam for the repeater to transmit signals to the base station, the access link transmit beam is a beam for the repeater to transmit signals to the terminal, and the access link receive beam is a beam for the terminal to receive signals from the repeater.

A repeater for achieving the above another object according to an exemplary embodiment of the present disclosure may include: a processor; at least one transceiver coupled to the processor; and a memory storing at least one instruction executable by the processor, wherein the at least one instruction, when executed by the processor, causes the repeater to: receiving information about a backhaul receive beam and/or a backhaul transmit beam from a base station and through at least one transceiver; receiving information on an access link transmit beam and/or an access link receive beam from a base station and through at least one transceiver, or obtaining information on an access link transmit beam and/or an access link receive beam from information on a backhaul receive beam and/or a backhaul transmit beam; performing communication with the base station by using a backhaul receive beam and/or a backhaul transmit beam, which are formed using information about the backhaul receive beam and/or the backhaul transmit beam, and by at least one transceiver; and performing communication with the terminal by using an access link transmit beam and/or an access link receive beam, which are formed using information about the access link transmit beam and/or the access link receive beam, wherein the backhaul receive beam is a beam for the repeater to receive signals from the base station, the backhaul transmit beam is a beam for the repeater to transmit signals to the base station, the access link transmit beam is a beam for the repeater to transmit signals to the terminal, and the access link receive beam is a beam for the terminal to receive signals from the repeater.

[ Beneficial effects ]

According to an exemplary embodiment of the present disclosure, a cell coverage extension method using a relay or Intelligent Reflection Surface (IRS) may be provided. Thus, the performance of the communication system can be improved.

Drawings

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

Fig. 2 is a block diagram showing a first exemplary embodiment of a communication node constituting a communication system.

Fig. 3 is a conceptual diagram illustrating a first exemplary embodiment of a beamforming operation method using a repeater.

Fig. 4A is a conceptual diagram illustrating a first exemplary embodiment of a beamforming operation method using an IRS.

Fig. 4B is a conceptual diagram illustrating a second exemplary embodiment of a beamforming operation method using an IRS.

Fig. 5 is a conceptual diagram illustrating a first exemplary embodiment of a beamforming operation method of a relay node for beam management of a terminal.

Fig. 6 is a conceptual diagram illustrating a second exemplary embodiment of a beamforming operation method of a relay node for beam management of a terminal.

Fig. 7A and 7B are conceptual diagrams illustrating a first exemplary embodiment of SSB transmission and SSB resource allocation based on multiple beams.

Fig. 8A is a conceptual diagram illustrating a first exemplary embodiment of a method of indicating an access link beam of a relay node.

Fig. 8B is a conceptual diagram illustrating a second exemplary embodiment of a method of indicating an access link beam of a relay node.

Fig. 9 is a conceptual diagram illustrating a first exemplary embodiment of a method for determining a transmission timing of a relay node.

Detailed Description

Embodiments of the present disclosure are disclosed herein. However, specific structural and functional details disclosed herein are merely representative for purposes of describing embodiments of the present disclosure. Thus, embodiments of the present disclosure may be embodied in many alternate forms and should not be construed as limited to the embodiments of the present disclosure set forth herein.

Thus, while the disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure. In the description of the drawings, like reference numerals refer to like elements.

It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present disclosure. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

In exemplary embodiments of the present disclosure, "at least one of a and B" may refer to "at least one of a or B" or "at least one of a combination of one or more of a and B". In addition, "one or more of a and B" may refer to "one or more of a or B" or "one or more of a and B in combination.

It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a similar fashion (i.e., "between" and "directly between", "adjacent" and "directly adjacent", etc.).

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes," and/or "including" when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Unless defined otherwise, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

Hereinafter, exemplary embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. In describing the present disclosure, for the convenience of overall understanding, like parts in the drawings are denoted by like reference numerals, and repetitive description thereof will be omitted.

A communication system to which the exemplary embodiments according to the present disclosure are applied will be described. The communication system may be a 4G communication system (e.g., a Long Term Evolution (LTE) communication system or an LTE-a communication system), a 5G communication system (e.g., a New Radio (NR) communication system), a sixth generation (6G) communication system, etc. The 4G communication system may support communication in a frequency band of 6GHz or less, and the 5G communication system may support communication in a frequency band of 6GHz or more and a frequency band of 6GHz or less. The communication system to which the exemplary embodiments according to the present disclosure are applied is not limited to what is described below, and the exemplary embodiments according to the present disclosure may be applied to a variety of communication systems. Here, the communication system may be used in the same sense as the communication network, "LTE" may refer to "4G communication system", "LTE communication system" or "LTE-a communication system", "NR" may refer to "5G communication system" or "NR communication system".

In an exemplary embodiment, "configuration of an operation (e.g., a transmit operation)" may mean "signaling of configuration information (e.g., information elements, parameters) for the operation" and/or "signaling of information indicating that the operation is performed. The "configuration of information elements (e.g., parameters)" may mean that the corresponding information elements are signaled. "configuration of resources (e.g., resource areas)" may mean that configuration information of the corresponding resources is signaled. The signaling may be performed based on at least one of System Information (SI) signaling (e.g., transmission of System Information Blocks (SIBs) and/or Master Information Blocks (MIB)), RRC signaling (e.g., transmission of RRC parameters and/or higher layer parameters), MAC Control Element (CE) signaling, PHY signaling (e.g., transmission of Downlink Control Information (DCI), uplink Control Information (UCI), and/or side-link control information (SCI)), or a combination thereof.

Referring to fig. 1, a communication system 100 may include a plurality of communication nodes 110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6. Furthermore, the communication system 100 may also include a core network (e.g., a serving gateway (S-GW), a Packet Data Network (PDN) gateway (P-GW), and a Mobility Management Entity (MME)). When the communication system 100 is a 5G communication system (e.g., a New Radio (NR) system), the core network may include an access and mobility management function (AMF), a User Plane Function (UPF), a Session Management Function (SMF), and the like.

The plurality of communication nodes 110 to 130 may support communication protocols (e.g., LTE communication protocol, LTE-a communication protocol, NR communication protocol, etc.) defined in third generation partnership project (3 GPP) technical specifications. The plurality of communication nodes 110 through 130 may support Code Division Multiple Access (CDMA) -based communication protocols, wideband CDMA (WCDMA) -based communication protocols, time Division Multiple Access (TDMA) -based communication protocols, frequency Division Multiple Access (FDMA) -based communication protocols, orthogonal Frequency Division Multiplexing (OFDM) -based communication protocols, filtered OFDM-based communication protocols, cyclic prefix OFDM (CP-OFDM) -based communication protocols, discrete fourier transform-spread OFDM (DFT-s-OFDM) -based communication protocols, orthogonal Frequency Division Multiple Access (OFDMA) -based communication protocols, single carrier FDMA (SC-FDMA) -based communication protocols, non-orthogonal multiple access (NOMA) -based communication protocols, generalized Frequency Division Multiplexing (GFDM) -based communication protocols, filter band multi-carrier (FBMC) -based communication protocols, universal filtered multi-carrier (UFMC) -based communication protocols, spatial Division Multiple Access (SDMA) -based communication protocols, and the like. Each of the plurality of communication nodes may mean a device or apparatus. The exemplary embodiments may be performed by a device or apparatus. The structure of the apparatus (or device) may be as follows.

Referring to fig. 2, a communication node 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 communication node 200 may further include an input interface device 240, an output interface device 250, a storage device 260, and the like. The various components included in the communication node 200 may communicate with each other through a bus 270 connection.

The processor 210 may execute programs stored in at least one of the memory 220 and the storage 260. Processor 210 may refer to a Central Processing Unit (CPU), a Graphics Processing Unit (GPU), or a special-purpose processor on which methods according to embodiments of the present disclosure are performed. Each of the memory 220 and the storage 260 may be composed of at least one of a volatile storage medium and a nonvolatile storage medium. For example, the memory 220 may include at least one of Read Only Memory (ROM) and Random Access Memory (RAM).

Referring again to fig. 1, the communication system 100 may include a plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2, and a plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6. Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 may constitute a macrocell, and each of the fourth base station 120-1 and the fifth base station 120-2 may constitute 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. In addition, 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. In addition, 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. In addition, the first terminal 130-1 may belong to the cell coverage of the fourth base station 120-1, and 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 may refer to a NodeB (NB), an evolved NodeB (eNB), a gNB, an Advanced Base Station (ABS), a high reliability base station (HR-BS), a Base Transceiver Station (BTS), a wireless base station, a radio transceiver, an Access Point (AP), an access node, a Radio Access Station (RAS), a mobile multi-hop relay base station (MMR-BS), a Relay Station (RS), an Advanced Relay Station (ARS), a high reliability relay station (HR-RS), a Home NodeB (HNB), a home eNodeB (HeNB), a roadside 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 may be referred to as a User Equipment (UE), a Terminal Equipment (TE), an Advanced Mobile Station (AMS), a high reliability mobile station (HR-MS), a terminal, an access terminal, a mobile terminal, a station, a subscriber station, a mobile station, a portable subscriber station, a node, an apparatus, an on-board unit (OBU), etc.

Furthermore, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may operate in the same frequency band or different frequency bands. 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 exchange information with each other through an ideal backhaul or a non-ideal backhaul. In addition, 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 may transmit a signal received from the core network to a corresponding terminal 130-1, 130-2, 130-3, 130-4, 130-5, or 130-6 and transmit a signal received from a corresponding terminal 130-1, 130-2, 130-3, 130-4, 130-5, or 130-6 to the core network.

Further, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may support multiple-input multiple-output (MIMO) transmission (e.g., single-user MIMO (SU-MIMO), multi-user MIMO (MU-MIMO), massive MIMO, etc.), coordinated multi-point (CoMP) transmission, carrier Aggregation (CA) transmission, transmission in an unlicensed band, device-to-device (D2D) communication (or proximity services (ProSe)), internet of things (IoT) communication, dual Connectivity (DC), etc. Here, each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 may perform operations corresponding to the operations of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 (i.e., operations supported by the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2). For example, the second base station 110-2 may transmit signals to the fourth terminal 130-4 in SU-MIMO mode, and the fourth terminal 130-4 may receive signals from the second base station 110-2 in SU-MIMO mode. Or the second base station 110-2 may transmit signals to the fourth and fifth terminals 130-4 and 130-5 in MU-MIMO, and the fourth and fifth terminals 130-4 and 130-5 may receive the signals from the second base station 110-2 in MU-MIMO.

Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 may transmit signals to the fourth terminal 130-4 in CoMP transmission, and the fourth 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 in CoMP transmission. Furthermore, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may exchange signals with a corresponding terminal 130-1, 130-2, 130-3, 130-4, 130-5, or 130-6 belonging to its cell coverage in a CA manner. Each of the base stations 110-1, 110-2, and 110-3 may control D2D communication between the fourth terminal 130-4 and the fifth terminal 130-5, and thus the fourth terminal 130-4 and the fifth terminal 130-5 may perform D2D communication under the control of the second base station 110-2 and the third base station 110-3.

The present disclosure relates to a cell coverage extension method using a relay node in a communication system, and more particularly, may include a method of a base station controlling the relay node and an operation method of the relay node according thereto. The following exemplary embodiments may be applied to NR communication systems, and may be applied to other communication systems (e.g., LTE communication systems, fifth generation (5G) communication systems, sixth generation (6G) communication systems, etc.) in addition to NR communication systems.

The set of parameters applied to the physical signals and channels in a communication system (e.g., an NR communication system or a 6G communication system) may be variable. The parameter set may be varied to meet various specifications of the communication system. In a communication system to which a Cyclic Prefix (CP) based OFDM waveform technique is applied, a parameter set may include a subcarrier spacing and a CP length (or CP type). Table 1 below may be a first exemplary embodiment of a parameter set configuration for CP-based OFDM. The subcarrier spacing may have an exponential multiplication relation of 2 and the CP length may be scaled by the same ratio as the OFDM symbol length. Depending on the frequency band in which the communication system operates, at least some of the parameter sets of table 1 may be supported. In addition, in a communication system, parameter sets not listed in table 1 may also be supported. For a specific subcarrier spacing (e.g., 60 kHz), CP types (e.g., extended CPs) not listed in table 1 may be additionally supported.

Table 1 relates to a first exemplary embodiment of a method for configuring a parameter set for a CP-OFDM based communication system.

TABLE 1

In the following description, a frame structure in a communication system will be described. In the time domain, elements constituting the frame structure may include subframes, slots, mini-slots, symbols, and the like. The subframe may be used as a unit for transmission, measurement, and the like, and the length of the subframe may have a fixed value (e.g., 1 ms) regardless of the subcarrier spacing. A slot may include consecutive symbols (e.g., 14 OFDM symbols). The length of the slot may vary differently from the length of the subframe. For example, the length of a slot may be inversely proportional to the subcarrier spacing.

The time slots may be used as units of transmission, measurement, scheduling, resource configuration, timing (e.g., scheduling timing, hybrid automatic repeat request (HARQ) timing, channel State Information (CSI) measurement and reporting timing, etc.), etc. The length of the actual time resources for transmission, measurement, scheduling, resource allocation, etc. may not match the length of the time slots. The mini-slot may include consecutive symbols and the length of the mini-slot may be shorter than the length of the slot. Mini-slots may be used as units for transmission, measurement, scheduling, resource allocation, timing, etc. Mini-slots (e.g., length of mini-slots, mini-slot boundaries, etc.) may be predefined in the technical specification. Or mini-slots (e.g., length of mini-slots, mini-slot boundaries, etc.) may be configured (or indicated) to the terminal. The use of mini-slots may be configured (or indicated) to the terminal when certain conditions are met.

The base station may schedule data channels (e.g., physical Downlink Shared Channel (PDSCH), physical Uplink Shared Channel (PUSCH), physical side link shared channel (PSSCH)) using some or all of the symbols comprising the time slot. In particular, for URLLC transmissions, unlicensed band transmissions, transmissions where an NR communication system and an LTE communication system coexist, and multi-user scheduling based on analog beamforming, a portion of a slot may be used to transmit a data channel. In addition, the base station may schedule the data channel using a plurality of time slots. In addition, the base station may schedule the data channel using at least one mini-slot.

In the frequency domain, elements constituting the frame structure may include Resource Blocks (RBs), subcarriers, and the like. One RB may include consecutive subcarriers (e.g., 12 subcarriers). The number of subcarriers constituting one RB may be constant regardless of the parameter set. In this case, the bandwidth occupied by one RB may be proportional to the subcarrier spacing of the parameter set. The RB may serve as a transmission and resource allocation unit for a data channel, a control channel, and the like. The resource allocation of the data channel may be performed in units of RBs or RB groups (e.g., resource Block Groups (RBGs)). An RBG may include one or more consecutive RBs. The resource allocation of the control channel may be performed in units of Control Channel Elements (CCEs). One CCE in the frequency domain may include one or more RBs.

In a communication system, a time slot (e.g., a time slot format) may be comprised of a combination of one or more of a downlink period, a flexible period (or an unknown period), and an uplink period. Each of the downlink period, the flexible period, and the uplink period may be composed 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, or between a first uplink period and a second uplink period. The flexible period may be used as a guard period when the flexible period is interposed between the downlink period and the uplink period.

One slot may include one or more flexible periods. Or the time slot may not include a flexible period. The terminal may perform predefined operations within a flexible period of time. Or the terminal may perform the operation configured by the base station semi-statically or periodically. For example, the periodic operation configured by the base station may include a PDCCH monitoring operation, a synchronization signal/physical broadcast channel (SS/PBCH) block receiving and measuring operation, a channel state information-reference signal (CSI-RS) receiving and measuring operation, a downlink semi-persistent scheduling (SPS) PDSCH receiving operation, a Sounding Reference Signal (SRS) transmission operation, a Physical Random Access Channel (PRACH) transmission operation, a periodically configured PUCCH transmission operation, a PUSCH transmission operation according to a configured grant, and the like. Flexible symbols may be covered by downlink symbols or uplink symbols. When a flexible symbol is covered by a downlink symbol or an uplink symbol, the terminal may perform a new operation in place of the existing operation in the corresponding flexible symbol (e.g., the covered flexible symbol).

The slot format may be semi-statically configured by higher layer signaling (e.g., radio Resource Control (RRC) signaling). Information indicating a semi-static slot format may be included in the system information, and the semi-static slot format may be configured in a cell-specific manner. In addition, a semi-static slot format may be additionally configured for each terminal through terminal-specific higher layer signaling (e.g., RRC signaling). Flexible symbols of a cell-specific configured slot format may be covered by downlink symbols or uplink symbols through terminal-specific higher layer signaling. In addition, the slot format may be dynamically indicated by physical layer signaling, e.g., a Slot Format Indicator (SFI) included in Downlink Control Information (DCI). The semi-statically configured slot formats may be covered by dynamically indicated slot formats. For example, semi-static flexible symbols may be covered by downlink symbols or uplink symbols through the SFI.

The base station and the terminal may perform downlink operation, uplink operation, and side link operation in the portion of bandwidth. A bandwidth portion may be defined as a set of consecutive RBs (e.g., physical Resource Blocks (PRBs)) having a particular set of parameters in the frequency domain. RBs constituting one bandwidth part may be contiguous in the frequency domain. A set of parameters may be used to transmit signals (e.g., transmission of control channels or data channels) in one portion of bandwidth. In an exemplary embodiment, a "signal" when used in a broad sense may refer to any physical signal and channel. The terminal performing the initial access procedure may acquire configuration information of the initial bandwidth part from the base station through system information. A terminal operating in the RRC connected state may obtain configuration information of the bandwidth part from the base station through terminal-specific higher layer signaling.

The configuration information of the bandwidth part may include a parameter set (e.g., subcarrier spacing and CP length) applied to the bandwidth part. Further, the configuration information of the bandwidth part may further include information indicating a position of a starting RB (e.g., starting PRB) of the bandwidth part and information indicating the number of RBs (e.g., PRBs) constituting the bandwidth part. At least one of the bandwidth parts configured in the terminal may be activated. For example, within one carrier, one uplink bandwidth portion and one downlink bandwidth portion may be activated, respectively. In a Time Division Duplex (TDD) based communication system, a pair of uplink and downlink bandwidth portions may be activated. The base station may configure a plurality of bandwidth parts to the terminal within one carrier and may switch active bandwidth parts of the terminal.

In an exemplary embodiment, the RB may mean a Common RB (CRB). Or RB may mean PRB or Virtual RB (VRB). In an NR communication system, CRB may refer to RBs that constitute a set of consecutive RBs (e.g., a common RB grid) based on a reference frequency (e.g., point a). Carriers, bandwidth parts, etc. may be arranged on a common RB grid. That is, the carrier, bandwidth part, etc. may be composed of CRBs. RBs or CRBs constituting the bandwidth part may be referred to as PRBs, and CRB indexes within the bandwidth part may be appropriately converted into PRB indexes. In an exemplary embodiment, the RB may refer to an Interleaved RB (IRB).

The minimum resource unit constituting the PDCCH may be a Resource Element Group (REG). The REG may consist of 1 PRB (e.g., 12 subcarriers) in the frequency domain and 1 OFDM symbol in the time domain. Thus, one REG may include 12 Resource Elements (REs). A demodulation reference signal (DMRS) for demodulating the PDCCH may be mapped to 3 REs among the 12 REs constituting the REG, and control information (e.g., modulated DCI) may be mapped to the remaining 9 REs.

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

The control resource set (CORESET) may be a resource region in which the terminal performs blind decoding on the PDCCH. CORESET may be composed of multiple REGs. CORESET may consist of one or more PRBs in the frequency domain and one or more symbols (e.g., OFDM symbols) in the time domain. The symbols constituting one CORESET may be contiguous in the time domain. The PRBs constituting 1 CORESET may be contiguous or non-contiguous in the frequency domain. A DCI (e.g., a DCI format or a PDCCH) may be transmitted within one CORESET. Multiple CORESET may be configured for cells and terminals and multiple CORESET may overlap on time-frequency resources.

CORESET may be configured in the terminal through a PBCH, e.g., system information or a Master Information Block (MIB) transmitted on the PBCH. The Identifier (ID) of CORESET configured by the PBCH may be 0. That is, CORESET configured by PBCH may be referred to as CORESET #0. A terminal operating in the RRC idle state may perform a monitoring operation in CORESET #0 in order to receive the first PDCCH during initial access. Not only the terminal operating in the RRC idle state but also the terminal operating in the RRC connected state may perform the monitoring operation in CORESET #0. CORESET may be configured in the terminal by other system information (e.g., system information block type 1 (SIB 1)) in addition to the system information transmitted via the PBCH. For example, to receive a random access response (or Msg 2) in a random access procedure, the terminal may receive SIB1 including CORESET configuration information. Further, CORESET may be configured in the terminal through terminal-specific higher layer signaling (e.g., RRC signaling).

In each downlink bandwidth portion, one or more CORESET may be configured for the terminal. The terminal may monitor CORESET PDCCH candidates configured in the downlink active bandwidth portion. Or the terminal may monitor PDCCH candidates of CORESET (e.g., CORESET # 0) configured in a downlink bandwidth portion other than the downlink active bandwidth portion. The initial downlink active bandwidth portion may include CORESET #0 and may be associated with CORESET #0. CORESET #0 having a quasi co-location (QCL) relationship with SS/PBCH blocks may be configured for terminals in a primary cell (PCell), a secondary cell (SCell), and a primary secondary cell (PSCell). In a secondary cell (SCell), CORESET #0 may not be configured for the terminal.

In the present disclosure, a set of signals including a synchronization signal may be transmitted to a terminal, which may be referred to as a Synchronization Signal Block (SSB). The signals constituting the SSB may be predefined in the technical specification. The synchronization signals included in the SSB may be a Primary Synchronization Signal (PSS), a Secondary Synchronization Signal (SSS), etc. The SSB may include the above-described signals (e.g., PBCH, DM-RS for decoding PBCH, CSI-RS, etc.) in addition to the synchronization signal, and may repeat transmission through a beam scanning operation. In an NR communication system, SSB may refer to a Synchronization Signal (SS)/PBCH block, and SSB resources may refer to SS/PBCH block resources.

The search space may be a set of candidate resource regions through which the PDCCH may be transmitted. The terminal may perform blind decoding for each PDCCH candidate within the predefined search space. A terminal may determine whether to transmit a PDCCH to itself by performing a Cyclic Redundancy Check (CRC) on the result of blind decoding. When it is determined that the PDCCH is a PDCCH for the terminal itself, the terminal may receive the PDCCH. The terminal may periodically monitor the search space and may monitor the search space at one or more time locations (e.g., PDCCH monitoring occasions, CORESET) within a period.

The PDCCH candidates may be configured with CCEs selected by a predefined hash function within CORESET or the occasion of the search space. The search space may be defined and configured for each CCE aggregation level. In this case, the set of search spaces for all CCE aggregation levels may be referred to as a "search space set". In an exemplary embodiment, "search space" may mean "set of search spaces" and "set of search spaces" may mean "search space".

The set of search spaces may be logically associated with one CORESET. One CORESET may be logically associated with one or more sets of search spaces. The set of search spaces for transmitting the common DCI or the group common DCI may be referred to as a common set of search spaces (hereinafter, referred to as "CSS set"). The common DCI or group common DCI may include at least one of resource allocation information, paging, power control commands, SFI, or a preemption indicator of PDSCH for system information transmission. In the case of an NR communication system, the common DCI may correspond to DCI formats 0_0, 1_0, etc., and a Cyclic Redundancy Check (CRC) of the common DCI may be scrambled by a system information-radio network temporary identifier (SI-RNTI), a paging-RNTI (P-RNTI), a random access-RNTI (RA-RNTI), a temporary cell-RNTI (TC-RNTI), etc. The group common DCI may correspond to DCI formats 2_X (x=0, 1,2,) and the like, and the CRC of the group common DCI may be scrambled by a slot format indicator-RNTI (SFI-RNTI) or the like. The CSS sets may include type 0, type 0A, type 1, type 2, and type 3CSS sets.

The set of search spaces for transmitting UE-specific DCI may be referred to as a UE-specific set of search spaces (hereinafter, referred to as a "USS set"). The UE-specific DCI may include scheduling and resource allocation information for PDSCH, PUSCH, PSSCH and the like. 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., and the CRC of the UE-specific DCI may be scrambled by a C-RNTI, a configured scheduling-RNTI (CS-RNTI), a modulation and coding scheme-C-RNTI (MCS-C-RNTI), etc. UE-specific DCI may be transmitted even in CSS sets in view of scheduling free or fallback transmission. In this case, the UE-specific DCI may be transmitted according to a DCI format corresponding to the common DCI. For example, the terminal may monitor PDCCHs (e.g., DCI formats 0_0, 0_1) in the CSS set whose CRC is scrambled with a C-RNTI, CS-RNTI, MCS-C-RNTI, etc.

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

The terminal may assume that the PDCCH DM-RS has a QCL relationship with a specific signal (e.g., SS/PBCH block, CSI-RS, PDSCH DM-RS, PDCCH DM-RS, etc.). In addition, since the PDCCH has the same antenna port as the corresponding PDCCH DM-RS, the PDCCH and the PDCCH DM-RS may have a QCL relationship with each other. Accordingly, the terminal may acquire information on the large-scale propagation characteristics of the radio channels experienced by the PDCCH and the PDCCH DM-RS through the QCL hypothesis, and may perform channel estimation, reception beamforming, etc. using the information on the large-scale propagation characteristics. The QCL parameters may include at least one of delay spread, doppler shift, average gain, average delay, or spatial Rx parameters. The spatial Rx parameter may correspond to at least one characteristic of a receive beam, a receive channel spatial correlation, or a transmit/receive beam pair. For convenience, the spatial Rx parameter may be referred to as "spatial QCL". The PDCCH may be used in a sense of including the PDCCH DM-RS, and the expression that the PDCCH has a QCL relationship with a certain signal may include a sense that the PDCCH DM-RS of the PDCCH has a QCL relationship with a certain signal. The signal having a QCL relation with the PDCCH or its resources may be referred to as a QCL source, a QCL source signal, a QCL source resource, etc.

The PDCCHs transmitted in the same CORESET (and the search space set corresponding thereto, PDCCH monitoring opportunities, etc.) may have the same QCL relationship. That is, the terminal may assume that the unit of the set of the same QCL may be CORESET and the QCL assumption for each CORESET may be independent. In an exemplary embodiment, the QCL, QCL source, etc. of a certain CORESET may mean the QCL, QCL source, etc. of the PDCCH received through the corresponding CORESET, respectively. As an exception, different QCL hypotheses may be applied to the set of search spaces corresponding to one CORESET. For example, the set of search spaces (e.g., type 1CSS set) and other sets of search spaces used to monitor RA-RNTIs may have different QCL relationships.

CORESET QCL relationships or QCL assumptions (e.g., QCL sources, QCL types, etc.) can be determined by predefined methods. For example, the terminal may assume that PDCCH DM-RS received through a specific CORESET or a specific search space set has a QCL relationship with respect to a predefined QCL type with SS/PBCH blocks and/or CSI-RS selected in an initial access or random access procedure. Here, QCL type may mean a set of one or more QCL parameters. Or CORESET (e.g., QCL source, QCL type, etc.) may be signaled from the base station to the terminal (e.g., by RRC signaling, medium Access Control (MAC) Control Element (CE) signaling, DCI signaling, or a combination thereof). That is, the base station may configure a Transmission Configuration Information (TCI) state of CORESET to the terminal. In general, the TCI state may include an ID of a signal (e.g., a QCL source or QCL source resource of a PDCCH DM-RS) having a QCL relationship with a DM-RS (e.g., a PDCCH DM-RS) of a physical channel to which the TCI is applied, and/or at least one QCL type thereof. For example, the base station may configure one or more TCI state candidates of each CORESET to the terminal through RRC signaling, and may indicate or configure one of the one or more TCI state candidates for CORESET monitoring of the terminal to the terminal through MAC signaling (or DCI signaling). When 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 receiving operations for the corresponding CORESET based on TCI state configuration information received from the base station.

The above-described transmission/reception operation between the base station and the terminal may be equally or similarly applied between the base station and the relay node and between the relay node and the terminal, which will be described below. That is, in the above operation, the terminal may be replaced by a relay node. Or in the above operation, the base station may be replaced with a relay node.

In a communication system, beam operations of a high frequency band and a low frequency band may be different from each other. Since signal path loss caused by a channel is relatively small in a low frequency band (e.g., a frequency band of 6GHz or less), a beam having a wide beamwidth can be used to transmit/receive signals. In particular, in the case of control channels, even a single beam may be utilized to cover the entire coverage of a cell (or sector). However, in a high frequency band (e.g., a frequency band of 6GHz or more) having a large signal path loss, beamforming of a large antenna may be used to extend coverage. In addition, beamforming may be applied not only to the data channel but also to the common signal and control channels. A communication node (e.g., a base station) may form a beam having a small beam width through a plurality of antennas and transmit and receive signals a plurality of times by using a plurality of beams having different directivities to cover an entire spatial area of a cell (or sector). The operation of repeatedly transmitting a signal in a plurality of time resources by using a plurality of beams may be referred to as a beam scanning operation. A system for transmitting signals using a plurality of beams having such a narrow beam width may be referred to as a multi-beam system.

For multi-beam system operation, the base station may manage the transmit and receive beams of the terminal. In addition, the terminal may manage its own transmit and receive beams. The terminal may measure beam quality with respect to signals (e.g., SSB, CSI-RS, etc.) transmitted from a base station or Transmission and Reception Points (TRP), and may report the measurement result of the beam quality to the base station. For example, the terminal may calculate a beam quality measurement value, such as Reference Signal Received Power (RSRP) and signal to interference plus noise ratio (SINR), for each beam (e.g., for each signal or resource) and report the optimal beam and its corresponding measurement value to the base station. The base station may determine a transmit beam for the terminal based on the beam quality measurements received from the terminal. In addition, based on the beam quality measurements received from the terminals, the base station may configure the terminals with information (e.g., QCL information, TCI status information, etc.) needed for the terminals to receive the physical signals and channels (e.g., PDCCH, PDSCH, CSI-RS, PUCCH, PUSCH, SRS, PRACH, etc.). In exemplary embodiments, unless otherwise indicated, "beam" may refer to "transmit beam", "receive beam" and/or "transmit/receive beam pair". In addition, the terms "beam", "transmit beam", "receive beam" and "transmit/receive beam pair" may be used in the same sense. Hereinafter, the "transmission beam" may correspond to "precoder", "beam former", "transmission spatial filter", etc., and the information about the transmission beam may include information about the precoder, beam former, transmission spatial filter, transmission spatial relationship information, spatial transmission parameters, etc., corresponding thereto. In addition, the "reception beam" may correspond to "reception filter", "reception spatial filter", "reception beamformer", and the like, and the information on the reception beam may include information on the reception filter, the reception spatial filter, the reception beamformer, and the like, information on the spatial QCL, information on the QCL type D, reception spatial relationship information, spatial reception parameters, and the like. In addition, hereinafter, "multi-beam" may mean at least one beam.

Meanwhile, the path loss of the signal is positively correlated with the frequency band (i.e., frequency value). In very high frequency band (e.g., millimeter-wave band, terahertz-band) communications, it may be desirable to use ultra-fine beams with very small beamwidths to provide target coverage due to the very large path loss of the signals. However, although the beam arrival distance increases as the beam width decreases, the beam quality rapidly deteriorates even if the terminal moves little or the channel changes little, and frequent beam changes may be required. Thus, the beam management load may increase.

As another method of coverage enhancement, a relay node may be used. The relay node may be used to receive signals from a base station or TRP and forward them to a terminal, or vice versa. The signal received at the relay node may be amplified or beamforming may be applied thereto such that the signal is transmitted back to the peer node and the coverage of the signal may be extended. Relay nodes may be classified into various types according to their functions. For example, an amplify-and-forward (AF) relay may simply amplify a received signal and retransmit the amplified signal. The AF relay may be referred to as a layer 1 (L1) relay, a repeater, or the like. A decode-and-forward (DF) relay may decode a received signal to obtain data, re-encode the data, and transmit the re-encoded data. DF relay may be referred to as layer 2 (L2) relay, layer 3 (L3) relay, etc. An Integrated Access and Backhaul (IAB) node may be functionally classified as an L3 relay.

In the above-described relay node type, the relay has a simple structure and operation, so it can be manufactured at low cost and can provide a high effect compared with the input cost. The basic repeater generally does not distinguish between uplink and downlink, and may not perform beamforming operations. However, to maximize the effect of coverage extension, a repeater may be preferred to support beamforming operations.

On the other hand, as a relay node that performs a function similar to a repeater, an Intelligent Reflection Surface (IRS) is attracting attention. The IRS is a planar surface having a plurality of passive elements (hereinafter referred to as "IRS elements" or "phase control elements") made of a metamaterial, and the IRS elements (or phase control elements) can form a light beam having a desired shape by applying a phase shift to a received signal, and can reflect or transmit the received signal to which the formed beam is applied. The phase shift of each IRS element (or phase control element) may be independently controlled by the base station or TRP. In this disclosure, the aforementioned beamforming operation may be referred to as "reflection beamforming". In addition, the formed beam may be referred to as a "reflected beam". Some IRS allows signals to pass through the IRS rather than reflecting them. In this case, the signal may pass through each IRS element of the IRS and form a beam when subjected to a phase shift, which may be referred to as "transmission beamforming. In addition, the formed beam may be referred to as a "transmitted beam". Hereinafter, the reflection beam forming and the transmission beam forming are collectively referred to as reflection beam forming, and the reflection beam and the transmission beam are collectively referred to as reflection beam. The IRS is similar to a repeater in that it provides a repeater function capable of beam forming only by a simple structure and operation, and thus it can be used for a similar purpose to a repeater. IRS may also be referred to as a "Reflective Intelligent Surface (RIS)" or the like.

The present disclosure proposes a cell coverage extension method using relay nodes, in particular relays and IRSs. The proposed method can be applied to communications using repeaters and IRSs, and can be easily applied to communications using other types of relay nodes. In addition, the proposed method can be applied to TDD systems and Frequency Division Duplex (FDD) systems. Hereinafter, a relay may refer to an IRS or another type of relay node, and an IRS may refer to a relay or another type of relay node. In addition, the relay node may be an implementation form of a terminal, and may be regarded as a terminal. Or a relay node may be an implementation of a base station and may be considered a base station. In the present disclosure, a link between a base station and a relay (or IRS, relay node, etc.) may be referred to as a backhaul link, a forward link, a control link, etc., a link between a base station and a terminal may be referred to as a Uu link, a Uu interface, etc., and a link between a relay (or IRS, relay node, etc.) and a terminal may be referred to as an access link. Or the link between the relay (or IRS, relay node, etc.) and the terminal may be referred to as a Uu link or Uu interface, without distinguishing from the link between the base station and the terminal. Hereinafter, links between the base station and the relay (or IRS, relay node, etc.) will be collectively referred to as backhaul links or control links, and links between the relay (or IRS, relay node, etc.) and the terminal will be collectively referred to as access links, as the case may be. The physical signals and channels used in the Uu link or Uu interface (e.g., the signals and channels described above) may be equally used in the access link, backhaul link, and/or control link.

Meanwhile, the relay node may be composed of a plurality of entities. Each entity may perform its own relay communication function. For example, the repeater may include a first entity and a second entity. The first entity may perform a function of exchanging control information (e.g., side control information) with the base station. The first entity may be referred to as a "Mobile Terminal (MT)" or a "repeater MT". The first entity may perform communication for exchanging the control information with the base station via the control link. In addition, the first entity may control an operation (e.g., a signal relay operation) of the second entity based on the control information. The control link may be a Uu link or a Uu interface.

The second entity may perform the function of relaying signals from the base station to the terminal or from the terminal to the base station. The second entity may be referred to as "forwarding (Fwd)" or "repeater Fwd". The signal relay operation may be performed through the above-described backhaul link and access link. The operation of the second entity (e.g., signal relay operation) may be controlled by control information (e.g., side control information) received from the base station. For example, the operation of the second entity may be controlled by the first entity constituting the same repeater based on control information received from the base station.

The control link (or Uu link) and the backhaul link may use the same frequency band (e.g., the same carrier, the same bandwidth portion, the same frequency region, etc.). In this case, the control link transmission beam and the control link reception beam of the relay node may coincide with the backhaul link transmission beam and the backhaul link reception beam of the relay node, respectively, or they may have QCL relations, respectively. For example, the QCL source or QCL reference signal that determines the backhaul link receive beam (or spatial QCL or TCI) may be a downlink signal or channel (e.g., SSB, TRS, CSI-RS, CORESET, etc.) of the control link. In contrast, the QCL source or QCL reference signal that determines the control link receive beam (or spatial QCL or TCI) may be the downlink signal or channel of the backhaul link. In addition, the reference signal or QCL source that determines the backhaul link transmit beam (or spatial relationship or TCI) may be a downlink signal or channel of the control link (e.g., SSB, TRS, CSI-RS, CORESET, etc.) or an uplink signal or channel of the control link (e.g., PRACH, SRS, PUCCH, etc.). Conversely, the reference signal or QCL source that determines the control link transmit beam (or spatial relationship or TCI) may be a downlink signal or channel of the backhaul link or an uplink signal or channel of the backhaul link. Or the control link (or Uu link) and the backhaul link may be formed in different frequency bands (e.g., different carriers, different bandwidth portions, different frequency regions, etc.). In this case, the QCL relationship may not be established between the control link transmit/receive beam of the relay node and the backhaul link transmit/receive beam of the relay node. The relay node may receive information from the base station indicating a beam of the backhaul link and may determine a transmit beam and/or a receive beam of the backhaul link based on the information.

Based on the above-described relationship, the backhaul link transmission beam mentioned in the following exemplary embodiments may be regarded as a control link (or Uu link) transmission beam even if not separately described, and the backhaul link reception beam mentioned in the following exemplary embodiments may be regarded as a control link (or Uu link) reception beam even if not separately described.

The above-described configuration of a repeater composed of a plurality of entities can be applied to all of the following exemplary embodiments. In an exemplary embodiment, even though not otherwise described, the operation of the repeater to transmit and receive control signals to and from the base station may be considered to be performed by a specific entity (e.g., a first entity) of the repeater, and the operation of the repeater to relay signals between the base station and the terminal may be considered to be performed by another specific entity (e.g., a second entity) of the repeater.

[ Beamforming operation ]

Referring to fig. 3, a base station (or TRP) and a terminal may transmit/receive signals using a plurality of beams. In addition, a repeater may be disposed between the base station and the terminal, and the repeater may repeat signals between the base station and the terminal using a plurality of beams. In the case of downlink transmission, the repeater may receive a downlink signal from the base station by applying reception beamforming to a backhaul link (or control link) which is a link between the base station and the repeater, and transmit the downlink signal to the base station through an access link by applying transmission beamforming to the downlink signal. In the case of uplink transmission, the repeater may receive an uplink signal from the terminal by applying reception beamforming to the access link, and may transmit the uplink signal to the base station through the backhaul link (or control link) by applying transmission beamforming to the uplink signal.

A terminal (e.g., a first terminal (1 ^st UE)) may be connected to the repeater via an access link and may communicate with the base station via a relay of the repeater. Or another terminal, such as a second terminal (2 ^nd UE), may be directly connected to the base station through an access link to perform communication with the base station. Or a terminal may communicate with a base station using both a relay link via a relay and a direct link with the base station. In the present disclosure, unless otherwise indicated, a terminal may mean a terminal having the above-described link. Meanwhile, although it is assumed in the exemplary embodiment of fig. 3 that only one relay performs a relay operation between a base station and a terminal, the exemplary embodiment of the present disclosure may also be applied to a case where a plurality of relays perform a relay operation between a base station and a terminal (i.e., a multi-hop scenario). In a multi-hop scenario, the radio interface between relay nodes (e.g., relays, IRSs, etc.) may be referred to as a backhaul link, a backhaul interface, a control link, etc. For example, the transmission operation between the base station and the relay node of the exemplary embodiment may be regarded as the transmission operation between the first relay node and the second relay node. In addition, the transmission operation between the relay node and the terminal according to the exemplary embodiment may be regarded as the transmission operation between the first relay node and the second relay node.

The transmit and receive beams of the repeater may be controlled by the base station. For downlink transmissions, the base station may transmit information about the backhaul receive beam and/or the access link transmit beam and information indicating its application to the relay. In addition, for uplink transmissions, the base station may transmit information about the access link receive beam and/or the backhaul transmit beam and information indicating its application to the relay. The information may be transmitted to the repeater through a signaling process. In the present disclosure, the signaling procedure may include physical layer signaling (e.g., DCI, PDCCH, etc.), RRC signaling (or its equivalent semi-static signaling), MAC signaling (e.g., MAC CE or its equivalent signaling), a combination of the above, etc.

The backhaul receive beam of the repeater may be determined based on quasi co-sited (QCL) information or TCI state information transmitted from the base station to the repeater. For example, the relay may receive downlink signals, such as control channels (e.g., PDCCH), data channels (e.g., PDSCH), DM-RS, CSI-RS, tracking Reference Signals (TRS), SSB, phase tracking reference signals (PT-RS), or Positioning Reference Signals (PRS), from the base station. In this case, the repeater may receive information on a QCL source having a QCL relationship with a downlink signal (or DM-RS corresponding thereto) and information on QCL parameters (e.g., QCL type, spatial QCL, spatial reception parameters, QCL type D, etc.) of the QCL relationship from the base station, and may receive the downlink signal based thereon. For example, the QCL source may be SSB, CSI-RS, TRS, etc., received by the relay from the base station. As described above, the downlink signal or QCL source may be transmitted over the control link.

In addition, the backhaul transmit beam of the relay may be determined based on spatial relationship information, uplink QCL information, uplink TCI status information, etc., transmitted from the base station to the relay. For example, the repeater may transmit an uplink signal such as PUCCH, PUSCH, DM-RS, PRACH, SRS or PT-RS to the base station. In this case, the repeater may receive information about a signal source (e.g., QCL source) having a QCL relationship or spatial relationship with an uplink signal (or DM-RS corresponding thereto) and/or information about QCL parameters (e.g., QCL type, spatial QCL, spatial relationship information, spatial transmission parameters, QCL type D, etc.) of the QCL relationship or spatial relationship from the base station, and may transmit the uplink signal based thereon. The signal source (e.g., QCL source) may be SSB, CSI-RS, TRS, SRS, PRACH, etc. As described above, an uplink signal or signal source (e.g., QCL source) may be transmitted over the control link.

The above method may be referred to as "method 100". The "method 100" may also be used to determine an access link transmit beam or an access link receive beam of a repeater. According to the "method 100", the relay may itself determine the beam (e.g., beam, precoder, receive filter coefficients, etc.) based on reference signals (e.g., SSB, CSI-RS, TRS, etc.) received by the relay from the base station. That is, the repeater may determine the access link transmit beam or the access link receive beam by using information about QCL source/QCL parameters on the backhaul receive beam and information about QCL source/QCL parameters on the backhaul transmit beam. However, the access link beam of the repeater may preferably be determined by the base station. In addition, there may not be a QCL source having a QCL relationship with the access link beam of the repeater or the reference beam used to determine the access link beam of the repeater.

To solve the above problem, the access link transmit beam and the access link receive beam of the repeater may be controlled using a codebook. The codebook may be composed of one or more entries or codewords, and each codeword (or entry) may correspond to a candidate beam or a candidate precoder (or a candidate receive filter) applied to a signal transmitted by the repeater to the terminal (or a signal received by the repeater from the terminal) through the access link. When the transmission (or reception) signal s of the repeater is represented as an mx 1 vector and the transmission (or reception) signal x to which beamforming or precoding (or reception filtering) is applied is represented as an nx1 vector in the spatial domain, each codeword may be represented as an nxm matrix (or mxn matrix). M may correspond to the number of layers or data streams of the transmit (or receive) signal of the access link, and N may correspond to the number of transmit (or receive) antenna ports of the access link. In general, each element of the nxm matrix may be a complex number. In an exemplary embodiment, m=1. That is, a single stream signal may be transmitted (or received), and in this case, each codeword of the codebook may be represented as an n×1 vector. In the case of receiving a codebook, the dimensions of the vector and matrix may be appropriately changed. For example, each codeword of the received codebook may be represented as an mxn matrix or a 1 xn vector.

The codebook may be predefined in the technical specification. Multiple codebooks may be defined and a codebook may be defined for each dimension (e.g., M, N, etc.) of an access link transmit/receive signal of a repeater. Or the size or dimension of the codebook may be determined by the dimension (e.g., M, N, etc.) of the access link transmit/receive signal. Information about the codebook, e.g., the size or dimension of the codeword, the number of codewords (or over-sampling coefficients), the codebook type, the transmission direction (e.g., downlink or uplink), etc., may be predefined in the technical specification. In addition, the codewords may be predefined in the technical specification. For example, a codeword may be defined as an (oversampled) Discrete Fourier Transform (DFT) vector (i.e., a column of an (oversampled) DFT matrix). Or at least a portion of the information about the codebook may be transmitted from the base station to the relay through a signaling procedure (e.g., DCI, PDCCH, MAC CE or its equivalent signaling, RRC message or its equivalent signaling, etc.).

Or at least a portion of the information about the codeword or codebook may be preconfigured in the repeater. That is, at least a portion of the information about the candidate beam applied to the repeater may be preconfigured to the repeater. As an example of the pre-configuration, some information (or parameters) for performing the communication may be stored in the communication node (e.g., repeater, IRS, terminal) in advance. In this disclosure, "configuring" may mean configuring by a signaling procedure between communication nodes, pre-configuring without a signaling procedure, or both in some cases, unless otherwise specified.

The base station may select or determine a codebook considering the dimension of the access link transmit/receive signals of the repeater, the number of transmit layers, the number of antennas or antenna ports, the transmit direction, etc. The base station may select a codeword (or codewords) from the determined codebook and may signal information about the selected codeword to the repeater. For example, the base station may inform the relay of the index (or beam index) of the selected codeword. For example, the signaling may be dynamic signaling (e.g., DCI, PDCCH, physical layer signaling, MAC CE transmitted from a base station to a relay, etc.). The repeater may determine an access link transmit beam or an access link receive beam based on information received from the base station about the codeword (e.g., codeword index, beam index). The beam indicating method using the codebook described above may correspond to a method of explicitly signaling beam information. The above method may be referred to as "method 110". The "method 110" may also be used to determine a backhaul transmit beam or a backhaul receive beam of a repeater.

Fig. 4A is a conceptual diagram illustrating a first exemplary embodiment of a beamforming operation method using an IRS, and fig. 4B is a conceptual diagram illustrating a second exemplary embodiment of a beamforming operation method using an IRS.

Referring to fig. 4A and 4B, a base station (or TRP) and a terminal may transmit/receive signals using a plurality of beams. In addition, the IRS (or RIS) may be disposed between the base station and the terminal, and the IRS (or RIS) may relay signals between the base station and the terminal using a plurality of beams. In the case of downlink transmissions, the reflected beam forming by the IRS may be applied to the downlink signal transmitted by the base station to be received by the terminal. When the IRS is regarded as an operation subject, the IRS may receive a downlink signal from the base station and may transmit the downlink signal to which the reflected beam forming is applied to the terminal by applying the reflected beam forming to the received downlink signal. In the case of uplink transmission, the reflected beam forming by the IRS may be applied to the uplink signal transmitted by the terminal to be received by the base station. That is, the IRS may receive an uplink signal from the terminal and may transmit the uplink signal to which the reflected beam forming is applied to the base station by applying the reflected beam forming to the received uplink signal.

The reflected beam of the IRS may be controlled by the base station. Since the reflected beam of the IRS is formed by the phase shift of the IRS element, controlling the reflected beam of the IRS may mean controlling the phase shift value (or phase value, phase control value) of the IRS element. The base station may transmit information about the reflected beam and information indicating its application to the IRS. This information may be transmitted to the IRS through a signaling procedure.

As described above, the information used to control the reflected beam of the IRS may include the phase shift value of the IRS element. When the number of IRS elements is L, the base station may notify the IRS of information of L phase shift values { Φ ₁,Φ₂,...,Φ_L } (L is a natural number). Or the same phase shift value may be applied to multiple IRS elements and in this case the base station may inform the IRS about less than L phase shift values. For example, each phase shift value may be a real number greater than or equal to 0 and less than 2π. The signal received at the IRS element may be represented as a vector y= [ y ₁y₂...y_L ] of size 1 xl, in which case the 1 xl signal vector reflected (or passed) by the IRS may be represented as s＝[s₁s₂...s_L]＝[e^jφ1e^jφ2...e^jφL]*о*[y₁y₂...y_L]. where "o" may refer to the hadamard product or the element product. That is, the signal received by the ith IRS element may be transmitted (e.g., reflected or passed) with a phase offset of Φ _i of the signal. To reduce the overhead of control information, quantized phase shift values may be transmitted to the IRS. For example, the range of each phase shift value may be uniformly or non-uniformly quantized such that each phase shift value may be represented as one of the B values. Each quantized phase shift value may be indicated to the IRS by, for example, ceil (log ₂ (B)) bits.

Alternatively, the codebook may be used to control the reflected beam of the IRS. As in the case of the repeater described above, the codebook may be made up of one or more entries or codewords, and each codeword may correspond to a candidate reflected beam for the IRS. When the number of IRS elements is L, each codeword may be represented as an l×1 vector, a1×l vector, an l×l diagonal matrix, or the like, and may be referred to as a phase control vector, a phase control matrix, or the like. Or the same phase shift value may be applied to multiple IRS elements and in this case the size or dimension of each codeword may be smaller than the above-mentioned size or dimension of the codeword. For example, when the phase shift value of the IRS element is { Φ ₁,Φ₂,...,Φ_L }, each codeword may be defined as R*[e^jΦ1e^jΦ2...e^jΦL],R*[e^jΦ1e^jΦ2...e^j ^φL]^T,R*diag(e^jφ1,e^jφ2,...,e^jφL). where R may be a constant for power saving, e.g., r=1 or r=1/sqrt (L). In addition, sqrt (a) may represent the square root of a, B ^T may represent the transpose of matrix B, diag (a, B) may represent a diagonal matrix with a and B as diagonal elements.

As described above, the codebook may be predefined in the technical specification. Multiple codebooks may be defined and the codebook may be defined according to the number of IRS elements. Information about the codebook, e.g., the size or dimension of the codewords, the number of codewords, the codebook type, the transmission direction (e.g., downlink or uplink), etc., may be predefined in the technical specification. In addition, the codewords may be predefined in the technical specification. Or at least a portion of the information about the codebook may be transmitted from the base station to the IRS through a signaling procedure (e.g., DCI, PDCCH, MAC CE or equivalent signaling thereto, RRC message or equivalent signaling thereto, etc.). Or at least a portion of the information about the codeword or codebook may be preconfigured in the IRS. That is, at least a portion of the information about the candidate phase shift value or candidate beam applied to the IRS may be transmitted from the base station to the IRS or may be preconfigured in the IRS.

The base station may select or determine a codebook considering the number of IRS elements of the IRS, the transmission direction, etc. The base station may select a codeword (or codewords) from the determined codebook and may transmit information about the selected codeword to the IRS. For example, the base station may inform the IRS of the index (e.g., beam index) of the selected codeword. For example, the signaling may be dynamic signaling (e.g., DCI, PDCCH, physical layer signaling, MAC CE transmitted from a base station to an IRS). The IRS may determine the reflected beam (e.g., uplink reflected beam, downlink reflected beam) based on information received from the base station about the codeword (e.g., codeword index, beam index).

The codebook may be used by relay nodes to determine access link transmit beams, receive beams, reflected beams, etc. In the case of a repeater, a codebook for downlink transmission of an access link (e.g., a downlink codebook, a set of candidate transmit beams, etc.) and a codebook for uplink transmission of an access link (e.g., an uplink codebook, a set of candidate receive beams, etc.) may be defined or configured separately in the repeater. The access link transmit beam of the repeater may be determined by one codeword (or beam) of the downlink codebook (or set of candidate transmit beams) and the access link receive beam of the repeater may be determined by one codeword (or beam) of the uplink codebook (or set of candidate receive beams). Or the same (or a common) codebook (or set of candidate beams) may be applied for downlink and uplink transmissions for the access link. Each of the access link transmit beam and the access link receive beam of the repeater may be determined by one codeword (or beam) of the same (or common) codebook. In addition, when the access link transmit beam and the access link receive beam correspond to each other, they may correspond to the same codeword (or the same beam) or the same codeword index (or the same beam index).

The beam (or precoder, receive filter, etc.) of the relay node may be equally applied to the entire operating frequency range of the relay node. That is, the beam of the relay node may be a broadband beam. In this case, the above-described beam-related information (e.g., codeword index, beam coefficient or phase shift value, etc.) may be single information applied to the entire frequency range (e.g., the entire frequency range in which the relay node operates). In this case, the relay node may perform a beamforming operation regardless of the frequency domain resource allocation. Or the beam (or precoder, receive filter, etc.) of the relay node may be applied to each subband. That is, the beam of the relay node may be a narrowband beam. In this case, the above beam-related information (e.g., codeword index, beam coefficient, phase shift value, etc.) may be indicated to the relay node for each sub-band. Each subband may be a set of RBs. For example, a subband may be a set of RBGs, a set of Precoding Resource Groups (PRGs), a carrier, a bandwidth portion, a set of RBs separated by an intra-carrier guard band, etc. Each subband may be composed of consecutive RBs. Further, the wideband beam related information and the narrowband beam related information may be transmitted together to the relay node. The narrowband beam-related information may be determined based on the wideband beam-related information.

In this disclosure, for convenience, a physical signal or channel may be referred to as a signal. Further, signals may be classified into a plurality of categories. Hereinafter, unless otherwise indicated, "signal" may refer to a signal according to one of the categories to be described later.

The first type of signal may be a signal transmitted for a relay node (e.g., a repeater or IRS). The first type of signal may be transmitted over a control link between the base station and a relay node (e.g., a relay or MT entity of a relay). Or the first type of signal may be transmitted over a backhaul link between the base station and a relay node (e.g., a relay or MT entity of a relay). For example, the first type of signals may include PDCCH, PUCCH, etc., which includes control information for indicating the operation of the relay node. The first type of signal may not need to be transmitted to a terminal (e.g., a terminal connected to a relay node). Thus, signals of the first type may not be transmitted over the access link. That is, the relay node may not relay the first type signal to the terminal. Or the relay node may relay the first type of signal to the terminal. For example, the relay node may relay all received signals to a terminal or to a base station without distinguishing the category of the signals. The terminal may not receive the first type signal even when the relay node transmits the first type signal to the terminal.

Or the relay node may not relay the first type signal to the terminal when the predetermined condition is satisfied, otherwise relay the first type signal to the terminal. The predetermined condition may include a condition that the first type of signal does not overlap in time with another signal (e.g., a signal to be relayed to the terminal, a second type of signal, etc.). That is, when the first type signal is not overlapped with another signal (e.g., a signal other than the first type signal) in the same symbol, the relay node may not perform an operation of transmitting the first type signal to the terminal. Or conversely, the relay node may relay the first type signal to the terminal when the predetermined condition is satisfied, otherwise, the relay node may not relay the first type signal to the terminal.

The second type of signal may be a signal transmitted for a terminal (e.g., a terminal connected to a relay node) or a terminal-specific signal. The second type of signal may be transmitted over a backhaul link between the base station and a relay node (e.g., a relay or a forwarding entity of the relay) or a control link between the base station and a relay node (e.g., a relay, MT entity of the relay), and may be transmitted over an access link between the relay node and the terminal. That is, the relay node may relay the second type signal from the base station to the terminal or from the terminal to the base station. The relay node may be a relay, a forwarding entity of a relay, etc. The second type of signal may include physical signals and channels on the access link described above. In addition, the second type of signals may include signals for beam management of the terminal. The access link beams applied to the second type of signals may be terminal specific beams (or precoders, receive filters, etc.).

The third type of signal may be a signal transmitted to provide a coverage area of the relay node. The third type of signal may be transmitted through a backhaul link or a control link between the base station and the relay node, and may be transmitted through an access link between the relay node and the terminal. The relay node may be a relay, a forwarding entity of a relay, etc. The third type of signal may be a signal transmitted (e.g., broadcast) for a plurality of terminals or unspecified terminals within the coverage area. For example, the third type of signal may be repeatedly transmitted based on beam scanning. For example, a third type of signal may be transmitted for beam management by the terminal and may include SSB, CSI-RS, PRS, SRS, etc. The access link beams applied to the third type of signals may be cell specific beams (or precoders, receive filters, etc.), common beams, beams predetermined by cell planning, etc.

The relay node may relay all signals mapped to the symbols to which the second type of signals and/or the third type of signals received from the terminal are mapped to the base station. In addition, the relay node may relay all signals mapped to symbols to which the second type signal and/or the third type signal received from the base station are mapped to the terminal. The transmission/reception operation of the relay node for the second type of signals and the transmission/reception operation of the relay node for the third type of signals may not be distinguished.

The fourth type of signal may be a signal that does not involve a relay node. The operation of the relay node to transmit or receive the fourth type of signal may not be defined in the technical specification. The fourth type of signal may be transmitted over the Uu interface or a direct link between the base station and the terminal. The fourth type of signals may include the physical signals and channels on the Uu interface described above.

A relay node (e.g., a repeater or IRS) may receive signals (e.g., signals of a third type) from a base station for beam management of a terminal and relay them to the terminal, or receive signals from a terminal and relay them to the base station. For this reason, some beamforming operations required for the relay node will be described below with reference to exemplary embodiments.

Fig. 5 is a conceptual diagram illustrating a first exemplary embodiment of a beam forming operation method of a relay node for beam management of a terminal, and fig. 6 is a conceptual diagram illustrating a second exemplary embodiment of a beam forming operation method of a relay node for beam management of a terminal.

Referring to fig. 5 and 6, a base station, a relay node, and a terminal (UE) may transmit signals using a plurality of beams. The relay node may use four beams, i.e., beam #0, beam #1, beam #2, and beam #3, for backhaul transmission with the base station, and may use four beams, i.e., beam #4, beam #5, beam #6, and beam #7, for access link transmission with the terminal.

Referring to fig. 5, a specific signal (e.g., a third type of signal) may be repeatedly transmitted over the entire coverage area of the relay node through a plurality of beams. In this case, signals may be repeatedly transmitted over the backhaul link over the same beam (or the same spatial QCL hypothesis, the same TCI, the same spatial relationship), and may be repeatedly transmitted (i.e., may be scanned by the beam) over the access link over multiple beams (or the multiple spatial QCL hypotheses, the multiple TCIs, the multiple spatial relationships). For example, the downlink signal Kd (among Kd resources) may be repeatedly transmitted from the base station to the relay node using the same beam (e.g., beam # 2), and the downlink signal Kd (among Kd resources) may be repeatedly transmitted (i.e., relayed) from the relay node to the terminals within the coverage area using multiple beams (e.g., beams #4 to # 7). For example, the above operations may be used to transmit SSBs or CSI-RSs within the coverage of a relay node. The resources (e.g., kd resources) for repeated transmissions may be SSB resources or CSI-RS resources. In an exemplary embodiment, kd may be 4. For another example, the relay node may repeatedly receive or monitor uplink signals in Ku resources from the terminal using a plurality of beams (e.g., beams #4 to # 7), and may repeatedly transmit uplink signals Ku to the base station using the same beam (e.g., beam # 2). For example, the above operation may be used to receive PRACH or SRS from a terminal within the coverage of the relay node. The resources (e.g., ku resources) for repeated transmissions may be PRACH resources or SRS resources. In an exemplary embodiment, ku may be 4. The Kd resources or Ku resources may be arranged in different symbol sets (or time slot sets). That is, kd resources or Ku resources may not overlap in time. Or at least a portion of Kd resources or Ku resources may be mapped to the same symbol. The beamforming operation may be indicated to the relay node by the base station. For example, an access link transmit beam applied to each time period (e.g., symbol) of transmitting multiple SSBs and/or multiple CSI-RSs over an access link may be indicated by the base station to the relay node.

Referring to fig. 6, a specific signal (e.g., a second type signal) may be repeatedly transmitted from a relay node to a terminal through the same beam. In this case, the signals may be repeatedly transmitted through the backhaul link and the access link, through the same beam (or the same spatial QCL hypothesis, the same TCI, or the same spatial relationship), respectively. For example, the downlink signal may be repeatedly transmitted Kd times (among Kd resources) from the base station to the relay node using the same beam (e.g., beam # 2), and the downlink signal may be repeatedly transmitted Kd times (among Kd resources) from the relay node to the terminal via the same beam (e.g., beam # 5). For example, the above operation may be used for the purpose of repeatedly transmitting SSB or CSI-RS when updating the reception beam of the terminal. In an exemplary embodiment, kd may be 4. As another example, the uplink signal may be repeatedly transmitted Ku times (in Ku resources) from the terminal to the relay node by using the same beam (e.g., beam # 5), and the uplink signal may be repeatedly transmitted Ku times (in Ku resources) from the relay node to the base station by using the same beam (e.g., beam # 2). For example, the above operation may be used for the purpose of repeatedly receiving SRS when updating the transmission beam of the terminal. In an exemplary embodiment, ku may be 4. The beamforming operation may be indicated to the relay node by the base station. For example, an access link reception beam applied to each time period (e.g., symbol) in which a plurality of SRSs are transmitted over an access link may be indicated by a base station to a relay node.

In the above exemplary embodiments, the beam of the relay node may be indicated by the above method. For example, the backhaul beam of the relay node may be indicated to the relay node by the base station through "method 100," based on QCL information, TCI status information, and the like. In addition, the access link beam of the relay node may be indicated to the relay node by the base station via the "method 110" based on a codebook, coefficients or phase values for beamforming, or the like.

[ Backhaul beam management ]

To determine the best backhaul beam (e.g., receive beam, transmit beam, beam pair), a relay node (e.g., repeater or IRS) may receive a signal (e.g., SSB or CSI-RS) from a base station, may measure the strength of the received signal (e.g., RSRP, L1-RSRP), and report the measurement to the base station. The signal receiving operation and the reporting of the measured value to the base station may be performed by a control link, and the signal strength measuring operation may be performed by a specific entity constituting the relay node (e.g., MT entity of the relay).

For example, the relay node may measure the received signal strength of SSBs in the plurality of SSB resources, determine an SSB (or SSBs) based thereon, and receive the determined SSB (or SSBs). Additionally, an initial backhaul beam of the relay node may be determined based on the determined SSB. That is, the determined SSB may be used as a QCL source (or reference beam, default beam) for the relay node to receive downlink signals or transmit uplink signals in the backhaul. SSBs may be transmitted from a base station to a relay node over a control link (or Uu link). The relay node may receive or transmit signals other than the SSB by using a reception beam for receiving the determined SSB as an initial beam or a service beam. In addition, the determined SSB (or SSB resource, beam to which SSB corresponds) may be reported from the relay node to the base station based on the association between SSB and PRACH resource. The relay node may transmit the PRACH in PRACH resources (or PRACH occasions) associated with the determined SSB resources. The base station may identify the SSB (or SSB resources, beams corresponding to SSBs) determined by the relay node by successfully receiving PRACH from at least some of the PRACH resources, and then perform subsequent signaling operations with the relay node based thereon. The PRACH may be transmitted from the relay node to the base station over a control link (or Uu link).

Or a downlink signal other than SSB may be used to determine the initial backhaul beam of the relay node. For example, the relay node may perform the initial beam determination operations described above based on PSS, SSS, CSI-RS, PRS, PDCCH or the like transmitted from the base station. In addition, uplink signals other than PRACH may be used to determine the initial backhaul beam of the relay node. For example, the relay node may perform the above implicit beam reporting operation based on SRS, PUCCH, and the like. Since signals can be transmitted by occupying less physical resources than SSB or PRACH, overhead according to beam management can be reduced. The downlink signal (or the downlink resource corresponding thereto) other than SSB and the uplink signal (or the uplink resource corresponding thereto) other than PRACH may be respectively associated with each other, and the terminal may report the initial beam to the base station by transmitting the uplink signal in the uplink resource associated with the downlink resource determined as the initial beam. Downlink signals other than SSB (or downlink resources corresponding thereto) and uplink signals other than PRACH (or uplink resources corresponding thereto) may be transmitted through a control link (or Uu link) and, as described above, may be transmitted in a frequency band other than a frequency band in which a backhaul link or an access link operates (e.g., a carrier bandwidth or a bandwidth portion configured in a terminal).

Configuration information of downlink resources, configuration information of uplink resources, and information on association between the downlink resources and the uplink resources may be transmitted from the base station to the relay node. This information may be indicated to the relay node through a signaling procedure (e.g., physical layer signaling (e.g., PDCCH, DCI), RRC signaling or equivalent thereto, MAC CE or equivalent thereto, etc.). The relay node may generate an uplink signal such as PRACH, SRS, or PUCCH, and the uplink signal may be generated based on configuration information received from the base station. In addition, the relay node may map the generated uplink signals such as PRACH, SRS, and PUCCH to uplink resources, and may transmit the uplink signals in the uplink resources. The operation of generating the uplink signal may include operations such as channel coding, interleaving, modulation, and DM-RS generation. In addition, an operation of measuring the received signal strength of the downlink signal may be performed based on configuration information received from the base station.

As described above, the backhaul beam of the relay node may be determined by the control link beam of the relay node. When downlink reception of the backhaul link and downlink reception of the control link are performed simultaneously (e.g., in the same symbol), the reception beam of the backhaul link may be the same as the reception beam of the control link (i.e., QCL relationship may be established therebetween), and the transmission beam of the backhaul link may be the same as the transmission beam of the control link (i.e., QCL relationship may be established therebetween). Otherwise, the receive beam of the backhaul link may be determined to be one of the receive beams of the control link (e.g., the default receive beam) and the transmit beam of the backhaul link may be determined to be one of the transmit beams of the control link (e.g., the default transmit beam). The default receive beam of the control link may refer to the PDCCH receive beam of the control link (e.g., the receive beam of CORESET, QCL, TCI, etc.). Specifically, the PDCCH reception beam of the control link may refer to a reception beam (e.g., QCL or TCI) of a specific CORESET (e.g., CORESET having the lowest ID) among specific slots (e.g., the latest slot in which the PDSCH has been received). Or the default receive beam of the control link may refer to the PDSCH receive beam of the control link (e.g., QCL or TCI). In particular, the PDSCH reception beam of the control link may refer to one of the TCIs of the TCI pool (or TCI state pool) of the PDSCH constituting the control link or one of the active TCIs. The default transmit beam of the control link may refer to a PUCCH transmit beam (e.g., spatial relationship, TCI) or PUSCH transmit beam (e.g., spatial relationship, TCI) of the control link.

Or the backhaul beam of the relay node may be independent of or have low correlation with the control link beam of the relay node and may be indicated or configured to the relay node by separate signaling from the base station. For example, the receive beam of the backhaul link may be indicated or configured to the relay node with one or more TCIs belonging to a control link or a pool of TCIs of the backhaul link (e.g., a downlink TCI pool or a joint uplink/uplink TCI pool). Similarly, the transmit beam of the backhaul link may be indicated or configured to the relay node with one or more TCIs belonging to a control link or a pool of TCIs of the backhaul link (e.g., an uplink TCI pool or a joint uplink/downlink TCI pool). According to the above method, the receive beam of the backhaul link may be different from the receive beam of the control link, and the transmit beam of the backhaul link may be different from the transmit beam of the control link. When different beams of the backhaul link and the control link collide at the same time (e.g., the same symbol), the relay node may select one of the different beams and may perform a transmission/reception operation of the control link and/or the backhaul link based on the selected beam.

The relay node may not perform transmission/reception for the access link when the relay node determines or changes the backhaul beam. For example, the relay node may not perform access link transmission with the terminal when performing an operation of acquiring an initial beam (or SSB, SSB resources) of the backhaul. The relay node may perform access link transmission with the terminal after acquiring the backhaul initial beam or when receiving a response signal (or message) from the base station after reporting the backhaul initial beam to the base station. For example, the relay node may perform an access link transmission operation after a predetermined time (e.g., symbol or slot) from a point in time (e.g., symbol or slot) at which a response signal from the base station is received. For example, the response signal may be Msg2, msg4, msgB or a message equivalent thereto. The response signal may be transmitted from the base station to the relay node on a control channel (e.g., PDCCH) or a data channel (e.g., PDSCH).

For another example, the relay node may not perform or stop access link transmission with the terminal when it is determined that the backhaul beam has failed. For example, the relay node may identify a new valid beam and perform a beam failure recovery procedure based thereon, and may resume access link transmission with the terminal after the beam recovery procedure is completed. When the relay node receives a response signal (or message) to the beam restoration request or the beam change request from the base station, the relay node may consider that the beam restoration process has been successfully completed, and may perform an access link transmission operation after a predetermined time (e.g., symbol or slot) from a point of time (e.g., symbol or slot) at which the response signal is received. More specific operations of beam failure and beam restoration of the relay node will be described later.

As described above, the relay node may not perform a signal transmission operation with the terminal. That is, the relay node may not perform a signal relay operation from the base station to the terminal or a signal relay operation from the terminal to the base station (hereinafter, this is referred to as a "non-relay operation"). The above-described non-relay operation may be performed for a predetermined period of time. The period in which the relay node performs the non-relay operation may be referred to as a "non-relay period". Further, this operation may be regarded as a partial switching operation (or a partial turning-off operation) of the relay node. The power consumption of the relay node may be reduced in the non-relay period. As described above, the relay node may perform a signal transmission operation, a signal monitoring operation, etc. with the base station in the non-relay period. For example, the relay node may receive a corresponding signal or channel from the base station or transmit it to the base station in the non-relay period in order to perform operations such as backhaul beam measurement, change, management, etc. of the backhaul beam. In addition, a relay node (e.g., a relay, MT entity of the relay) may monitor CORESET, a search space set, PDCCH monitoring occasions, etc. to receive a PDCCH (or relay (R) -PDCCH, etc.) transmitted from a base station. In addition, the base station may transmit indication information for controlling an operation of the relay node in the non-relay period to the relay node (e.g., the relay or MT entity of the relay), and the relay node (e.g., the relay or MT entity of the relay) may transmit HARQ-ACK to the base station in response to a signal received from the base station or transmit other control information to the base station in the non-relay period.

The relay node may determine the non-relay period, an operation of the relay node in the non-relay period, whether the relay node performs an operation in the non-relay period, and the like through an implicit scheme or an explicit scheme.

As an example of the implicit scheme, as described above, the relay node may stop (or suspend) or restart (or resume) the signal transmission operation with the terminal through the access link based on the operation of transmitting or receiving a specific signal to or from the base station. Or the relay node may stop (i.e., not perform) the signal transmission operation with the terminal through the access link for a predetermined period of time based on the operation of transmitting or receiving a specific signal to or from the base station. The operation of transmitting or receiving a specific signal to or from the base station may include an operation of receiving a signal (e.g., SSB, CSI-RS) for beam quality measurement and/or reporting from the base station, an operation of receiving a signal (e.g., physical layer control information, DCI, higher layer message, RRC signaling or semi-static signaling equivalent thereto, MAC CE or dynamic higher layer signaling equivalent thereto, etc.) indicating that a beam failure has been recovered from the base station, an operation of transmitting a response signal to the received signal to the base station, etc.

In addition, the operation of the relay node transmitting or receiving the specific signal to or from the base station may include an operation of the relay node receiving information indicating or configuring a slot format from the base station. The relay node may determine the transmission direction of the symbol as downlink, uplink or flexible according to the slot format configuration or the indication information. The relay node may perform a non-relay operation in the symbol determined to be a flexible symbol. That is, the relay node may omit or not perform a transmission/reception operation of the access link in a period configured or indicated as a flexible period by the base station. According to the above method, the non-relay operation of the relay node may be performed in units of symbols or symbol groups. That is, the relay node may switch from a relay operation to a non-relay operation or from a non-relay operation to a relay operation according to the boundary of a symbol or a symbol group.

The base station may designate any symbol as a flexible symbol. Or only symbols satisfying a predetermined condition may be allowed to be designated as flexible symbols and other symbols may be designated as downlink symbols or uplink symbols. For example, symbols comprising a particular downlink signal (e.g., SSB) or a particular uplink signal (e.g., PRACH) may be configured or indicated as flexible symbols. For another example, symbols comprising signals of the first type may be configured or indicated as flexible symbols.

The flexible symbols may be used for downlink or uplink transmissions by dynamic indication (e.g., DCI, SCI for backhaul or control link) from the base station. That is, flexible symbols may be overwritten or converted to downlink symbols or uplink symbols. The flexible symbols may be symbols determined as flexible symbols by RRC configuration from the base station or static/semi-static configuration equivalent thereto. The relay node may perform a non-relay operation in the remaining symbols not dynamically indicated as downlink symbols or uplink symbols among the symbols configured as flexible symbols.

As an example of the explicit scheme, the base station may transmit information to the relay node instructing the relay node not to perform or stop a signal transmission operation with the terminal. In addition, the base station may transmit information to the relay node instructing the relay node to perform or resume a signal transmission operation with the terminal. Or the base station may transmit information to the relay node instructing the relay node not to perform a signal transmission operation with the terminal for a predetermined period of time (e.g., a non-relay period). The relay node may receive the indication information from the base station and may or may not perform a signal relay operation based on the indication information. The indication information may be transmitted from the base station to the relay node through a signaling procedure (e.g., physical layer control information, DCI, higher layer message, RRC signaling or semi-static signaling equivalent thereto, MAC CE or higher layer dynamic signaling equivalent thereto, etc.). For example, the indication information may be transmitted from the base station to the relay node over a control link (or Uu link).

Specifically, the indication information may include at least one of information about a start time (e.g., a start slot, a start symbol, etc.) of the non-relay period, information about an end time (e.g., an end slot, an end symbol, etc.) of the non-relay period, information about a position (e.g., a slot index and/or a symbol index, etc.) of the non-relay period, information about a duration (e.g., a number of slots and/or a number of symbols, or an absolute time value (e.g., a ms or B us)) of the non-relay period, or a combination thereof. For example, the indication information may include only information (e.g., a start slot, a start symbol, etc.) on a start time of the non-relay period, and the relay node may not perform the signal relay operation for a predefined period of time from the indicated start time or a period of time preconfigured by the base station.

The point in time at which the relay node performs an operation of stopping or resuming the access link signal transmission operation may be a point in time after a predetermined time (e.g., a predetermined number of slots or symbols, or a number of slots or symbols set by the base station) from a point in time (e.g., a reception slot, a reception symbol, a transmission slot, or one symbol of a transmission symbol) at which a signal is received by the base station or transmitted to the base station, or may be a point in time thereafter. The predetermined time may include a time required for the relay node to process a signal received from the base station or a time required for the base station to process a signal received from the relay node.

On the other hand, the relay node may not perform both the signal transmission operation of the backhaul link and the signal transmission operation of the access link. The above operation may be referred to as a shutdown operation (or a deactivation operation or a shutdown operation). The closing operation may be performed for a predetermined period of time. Or the shutdown operation may be performed continuously (e.g., as a default operation for the relay node) until a separate indication is received from the base station. The shutdown operation of the relay node may be distinguished from the non-relay operation (i.e., the partial shutdown operation) described above. The relay node may instruct by the base station to perform the shutdown operation for a predetermined period of time. Or may selectively instruct the relay node to perform one of a shutdown operation and a non-relay operation (i.e., a partial shutdown operation). Its indication information may be transmitted from the base station to the relay node through the above-described signaling scheme. Similar to the non-relay operation described above, the shutdown operation may also be indicated to the relay node by an explicit scheme or an implicit scheme. The period of performing the shutdown operation may be configured as a set of slots and/or a set of symbols, and its configuration information may be signaled from the base station to the relay node. For example, the shutdown operation may be performed in symbols and/or slots configured as flexible symbols by slot format configuration. The relay node can transmit and receive signals to and from the base station even when performing a shutdown operation of the relay node. For example, when the forwarding entity of the repeater performs a shutdown operation, the MT entity of the repeater may perform a transmit/receive operation with the base station through the control link. The base station may transmit information instructing the relay node (e.g., MT of the relay) to stop (or start or resume) the shutdown operation or the non-relay operation. For example, the MT entity of the relay node may instruct the forwarding entity of the relay to stop the shutdown operation or the non-relay operation according to the indication information, and the forwarding entity may initiate or resume the relay operation according to the indication.

Referring to fig. 7A and 7B, a base station may repeatedly transmit SSB using a plurality of beams. For example, the base station may repeatedly transmit SSB 8 times using 8 (=n1) beams (e.g., beams #0 to # 7) for a direct link. The direct link may be formed between the base station and a terminal, e.g., a second terminal (2 ^nd UE), or between the base station and a relay node. In this case, a relay node (e.g., a repeater or IRS) may be arranged. The relay node may receive SSBs based on a particular beam (e.g., beam # 6) from the base station and relay the received SSBs to terminals (e.g., first terminal (1 ^st UE)) within its coverage area. For example, the relay node may repeatedly receive SSB 4 (=n2) times based on a specific beam (e.g., beam # 6), and may relay 4 SSBs received through four beams (e.g., beams #6, #8, #9, and # 10) to the access link.

According to the above-described exemplary embodiments, the number of repeated transmissions of SSBs may be increased to support beamforming or beam scanning operations of the relay node. For example, if there is no relay node, the base station may transmit SSB 8 (=n1) times, and if there is a relay node, the base station may transmit SSB 11 (=n1+n2) times. Accordingly, the number of SSB resources required may also increase from 8 to 11.

As a method for increasing the number of SSB resources, a method of increasing the length of an SSB transmission frame (or SSB burst period, SSB burst setup period, SSB resource group) may be considered. SSB transmission frames may refer to a period of time within one resource period in which SSB resources are mapped, and may also be referred to as an SSB transmission window. For example, the SSB transmission frame may be 5ms, and SSB resources may be arranged within 5 ms. As another example, SSB transmission frames may be defined or configured as A1 consecutive slots, A2 consecutive subframes, A3 consecutive radio frames, and so on. In the above-described exemplary embodiments, the SSB transmission frame including 11 (=n1+n2) SSB resources may be longer than the SSB transmission frame including 8 (=n1) SSB resources. SSB transmission frames of different lengths may be defined or configured and may be extended to have longer lengths or reduced to have shorter lengths. The expansion or reduction of SSB transmission frames may be indicated from the base station to the relay node or terminal by a signaling procedure.

Or multiple SSB transmission frames (or multiple SSB bursts or corresponding periods, multiple SSB burst groups or corresponding periods, and multiple SSB resource groups) may be arranged. For example, 8 (=n1) SSB resources may be arranged in the first SSB transmission frame, and 3 (=n2) SSB resources may be arranged in the second SSB transmission frame. The lengths of the first SSB transmission frame and the second SSB transmission frame may be different from each other. The first SSB transmission frame and the second SSB transmission frame may be arranged in different time resources. That is, SSB resources included in the first SSB transmission frame may not overlap in time with SSB resources included in the second SSB transmission frame. N1 and/or N2 may be predefined in the technical specification or may be set from the base station to the relay node or terminal. The periods (or periodicity) of the first SSB transmission frame and the second SSB transmission frame may be the same, and the first SSB transmission frame and the second SSB transmission frame may occur in each period. Or the periods (or periodicity) of the first SSB transmission frame and the second SSB transmission frame may generally be different from each other.

Additionally or alternatively to the above method, SSB resources may be arranged in a plurality of frequency locations (or frequency regions). For example, multiple SSB transmission frames may be arranged in different frequency regions. The plurality of SSB transmission frames (or SSBs belonging thereto) may not overlap each other in the frequency domain. For example, a plurality of SSB transmission frames may overlap in time within a certain period of time, and may be arranged in different frequency regions within the overlapping period of time. Multiple SSB transmission frames (or SSBs belonging thereto) may be mapped to the same symbol and transmitted simultaneously.

Information about the above described SSB resource placement may be transmitted from the base station to the relay node and/or terminal through a signaling procedure. For example, the information may be transmitted through an RRC signaling procedure (or higher layer semi-static signaling equivalent thereto). For example, the information may be included in a SIB, and the SIB may be transmitted to the relay node or terminal in a message including in a cell specific message.

Referring again to fig. 7A and 7B, the relay node may consider the transmission direction of the symbol to which the SSB is mapped as a downlink, and may relay a signal received in the symbol to which the SSB is mapped to the terminal. In this case, the relay node may relay all SSBs to the terminal. Or the relay node may relay some SSBs to the terminal and may not relay some other SSBs to the terminal. The relay node may consider the transmission direction of the symbols to which SSBs relayed to the terminal are mapped as downlink. On the other hand, the relay node may consider a transmission direction of a symbol to which SSBs not relayed to the terminal are mapped as a transmission direction other than the downlink (e.g., uplink, flexible, side link, etc.), and may perform transmission corresponding to the considered transmission direction. The relay node may determine SSB (or SSB resources) to be relayed to the terminal or SSB (or SSB resources) not to be relayed to the terminal based on configuration information received from the base station (e.g., DCI or SCI received through a control link or Uu link). In addition, the relay node may determine a transmission direction of a symbol to which the SSB, which is not relayed to the terminal, is mapped based on configuration information received from the base station (e.g., DCI or SCI received through a control link or Uu link).

In the first exemplary embodiment of fig. 7A and 7B, the relay node may relay all SSBs (e.g., SSBs #0 to # 10) to a terminal (e.g., first terminal (1 ^st UE)). Or the relay node may relay some SSBs (e.g., ssb#6, ssb#8, ssb#9, and ssb#10) to the terminal (e.g., first terminal (1 ^st UE)), and may not relay other SSBs (e.g., ssbs#0 to #5, and ssb#7) to the terminal. The relay node and terminal (e.g., first terminal (1 ^st UE)) may perform other transmissions (e.g., uplink transmissions, sidelink transmissions) than downlink transmissions in the symbols to which the unrepeated SSBs are mapped. Meanwhile, another terminal (e.g., a second terminal (2 ^nd UE)) may receive the downlink transmission from the base station in the symbol. That is, a full duplex communication scheme may be used in the symbol. Or when a predetermined condition is satisfied, the relay node relays some SSBs (e.g., ssb#6, ssb#8, ssb#9, and ssb#10) to the terminal (e.g., the first terminal). For example, the relay node may relay some SSBs to the terminal when another signal (e.g., downlink signal) is mapped to symbols to which some SSBs are mapped, and may not relay these SSBs to the terminal when another signal (e.g., downlink signal) is not mapped to symbols to which some SSBs are mapped. The relay node may transmit information (e.g., SSB resource index) about SSBs to be relayed to the terminal or information (e.g., SSB resource index) about SSBs not to be relayed to the terminal from the base station.

The relay node may assume that a QCL relationship is established between some SSBs. For example, the relay node may consider ssb#6, ssb#8, ssb#9, and ssb#10 to have a QCL relationship with each other and receive SSB or measure the received signal strength of SSB based on QCL assumption. SSBs that establish QCL relationships with each other may be associated with each other. In addition, the same transmission beam (or spatial relationship information, etc.) may be applied to the transmission of PRACH resources (or PRACH occasions) associated with SSBs having a mutual QCL relationship or SSBs associated with each other, and the PRACH resources may be associated with each other. For example, the relay node may be configured with a first PRACH resource (or first PRACH occasion) and the first PRACH resource (or first PRACH occasion) may be configured to be associated with a plurality of SSBs (e.g., SSBs #6, #8, #9, and # 10). When one of the SSBs (e.g., SSBs #6, #8, #9, and # 10) is determined to be the best SSB, the terminal may transmit PRACH in a first PRACH resource (or a first PRACH occasion). The QCL relationship may include a spatial QCL (or spatial reception parameter, QCL type D, etc.). Moreover, QCL relationships may be established for other QCL parameters (e.g., delay spread, doppler shift, average gain, average delay, etc.). The relay node may determine the above QCL relationship or association relationship between SSBs based on configuration information received from the base station. SSBs quasi co-located or associated with each other may be SSBs that relay nodes relay from a base station to a terminal. SSBs quasi-co-located or associated with each other may belong to the same SSB transmission frame. Or SSBs quasi-co-located or associated with each other may belong to multiple SSB transmission frames. Information about SSBs (or sets thereof) quasi-co-located or associated with each other may be explicitly configured from the base station to the relay node.

In another exemplary embodiment, SSBs quasi-co-located with each other (e.g., ssb#6, ssb#8, ssb#9, and ssb#10) may be associated with multiple PRACH resources (or multiple PRACH opportunities). The relay node may repeatedly transmit PRACH to the base station in a plurality of PRACH resources. As described above, the same transmit beam (or transmit spatial relationship, QCL assumption, or TCI) may be applied to the repeatedly transmitted PRACH, and the same transmit beam may be formed based on the receive beam (or QCL assumption, or TCI) of the SSB associated with the PRACH resource. Uplink coverage of the backhaul link may be extended by the repeated PRACH transmission described above. Or the relay node may select one PRACH resource from among a plurality of PRACH resources and transmit PRACH to the base station in the selected PRACH resource.

[ Access Link Beam management ]

The access link beams (e.g., transmit and receive beams) of a relay node (e.g., a repeater or IRS) may be controlled by a base station. The base station may transmit information indicating an access link transmission beam of the relay node, information indicating an access link reception beam, and the like to the relay node, and the relay node may determine the access link transmission beam, the access link reception beam, and the like based on the information, and may perform a signal transmission/reception operation of the access link by applying the determined beam.

Fig. 8A is a conceptual diagram illustrating a first exemplary embodiment of a method of indicating an access link beam of a relay node, and fig. 8B is a conceptual diagram illustrating a second exemplary embodiment of a method of indicating an access link beam of a relay node.

Referring to fig. 8A and 8B, a plurality of signals (or a plurality of signal resources, a plurality of resources) may be allocated to physical resources (i.e., time-frequency resources). In this disclosure, "signal," "resource to which a signal is mapped," and "resource" may be used interchangeably. The first signal may be assigned to symbol # (n+1) and symbol # (n+2), and the second signal may be assigned to symbol # (n+1), symbol # (n+2) and symbol # (n+3). For example, the signal may be a downlink signal. Symbol # (n+1), symbol # (n+2), and symbol # (n+3) may be downlink symbols or flexible symbols. The relay node may receive the first signal and the second signal from the base station and may relay them to the terminal. In this case, the base station may control the access link of the first signal and the second signal of the relay node to transmit the beam.

Referring to fig. 8A, an access link transmit beam of a relay node may be controlled for each signal or for each resource to which each signal is mapped. For example, the relay node may be instructed to apply a first beam to a first signal and may be instructed to apply a second beam to a second signal. When the first signal and the second signal are mapped to the same symbol, the relay node may select one of the first beam and the second beam and transmit both the first signal and the second signal using the selected beam. When summarizing this, the relay node may select one beam (or multiple beams) from among the multiple beams indicated for the same symbol, and transmit all signals of the corresponding symbol by equally applying the selected beam to all signals of the corresponding symbol. Or the relay node may select one beam (or a plurality of beams) from among a plurality of beams indicated for a plurality of resources overlapping in time and transmit signals corresponding to the plurality of resources by equally applying the selected beam to the plurality of resources. The selection of beams may be determined by priorities between signals or between beams. For example, a beam corresponding to a signal having a higher priority may be selected. On the other hand, when the relay node may transmit the first beam and the second beam simultaneously, the first signal and the second signal may be transmitted based on the first beam and the second beam, respectively. The above method may be referred to as "method 200".

In communications using a direct link between a base station and a terminal, the terminal may assume that the base station determines a transmit beam of the Uu link for each signal. According to the method 200, since the relay node can also determine the access link transmit beam of each signal, the terminal can apply the same reception operation to the reception of the signal (or beam) from the base station and the reception of the signal (or beam) from the relay node. However, in order for the relay node to apply a transmit beam to each signal, it may be necessary to know the location of the resource region (or at least the time region (e.g., symbol)) to which each signal is mapped, and information about each transmit beam, and thus it may be necessary to receive resource allocation information for each signal from the base station. Or the relay node may have difficulty in knowing the resource region to which the signal transmitted to the terminal is mapped, and in this case, the relay node may receive information on the beam and information on the resource region to which the beam is mapped from the base station without resource allocation information (e.g., time resource and frequency resource) of each signal. The resource allocation information of each signal may be included in control information for the relay node (e.g., DCI for the relay node) and transmitted to the relay node. In this case, the overhead of the control information may be greatly increased.

Or the resource allocation information of each signal may be included in control information (e.g., DCI, RRC signaling, and/or MAC CE for the terminal) transmitted to the terminal and transmitted through downlink signals (e.g., PDCCH, PDSCH, etc.). In this case, a method in which the relay node receives (i.e., demodulates and/or decodes) a downlink signal (e.g., PDCCH, PDSCH, etc.) for the terminal and obtains control information may be considered. However, in order to receive the downlink signal, since the relay node needs to know additional information such as carrier or bandwidth part configuration, CORESET resource allocation, ID of the terminal (e.g., C-RNTI), etc., in advance, additional signaling from the base station may be required for this purpose, and there is a problem in that it may be difficult to maintain security of the terminal.

Referring to fig. 8B, an access link transmit beam of a relay node may be controlled and applied for each unit time resource. The unit time resources may be K1 symbols, K2 slots, etc. (K1 and K2 are natural numbers). For example, the access link transmit beam of the relay node may be controlled for each symbol. In addition, when a relay node may transmit multiple beams in the same symbol, the relay node may be instructed to transmit a signal by applying multiple access link beams to a particular symbol. In this case, information about a frequency region to which each of a plurality of access link beams is applied may be indicated to the relay node. Referring to fig. 8B, the relay node may be instructed to apply the first, second and third beams to symbol # (n+1), symbol # (n+2) and symbol # (n+3), respectively. The beam indicated for each symbol may be applied in common to all signals transmitted in the corresponding symbol. Thus, the first signal may be transmitted over a first beam and a second beam of two symbols, respectively, and the second signal may be transmitted over a first beam, a second beam, and a third beam of three symbols, respectively. The first beam, the second beam, and the third beam may be the same or different from each other. The above method may be referred to as "method 210".

When using the "method 210", the relay node may apply the same access link transmit beam to multiple time-overlapping resources to transmit signals corresponding thereto, or apply the same access link receive beam to multiple time-overlapping resources to receive signals corresponding thereto. Accordingly, a terminal (e.g., a first terminal) may transmit or receive a corresponding signal by applying the same beam (e.g., the same spatial QCL, the same receive beam, the same transmit/receive beam pair), and the base station may be expected to configure the terminal to apply the same beam as described above. That is, a terminal may not be desirably configured to transmit and receive signals by applying different beams (e.g., different spatial QCL, different receive beams, different transmit/receive beam pairs, etc.) to multiple, time-overlapping resources. The terminal may be instructed from the base station or configured to perform the above operations. Or as described above, when a relay node has the capability to transmit or receive multiple access link beams in the same time resource, the terminal may transmit or receive multiple beams (e.g., multiple spatial QCLs, multiple receive beams, multiple transmit/receive beam pairs, multiple TCIs, etc.) to multiple time overlapping resources. For example, if the relay node has the capability to transmit and receive a maximum of two access link beams in the same time resource, the terminal may also transmit and receive signals using a maximum of two beams in the same time resource (e.g., the same symbol). That is, the number of beams that the terminal can simultaneously transmit or receive in the same time resource may be determined by the number of beams that the relay node can simultaneously transmit or receive in the same time resource. The terminal may receive from the base station the number (or maximum) of beams that the relay node can simultaneously transmit or receive in the same time resource. Or the number of beams that the relay node can simultaneously transmit or receive in the same time resource may be determined by the number of beams that the terminal can simultaneously transmit or receive in the same time resource. The relay node may receive from the base station the number (or maximum) of beams that the terminal can simultaneously transmit or receive in the same time resource.

Beam indication information (e.g., access link beam indication information) may be transmitted from the base station to the relay node through a signaling procedure. For example, the beam indication information may be configured to the relay node through semi-static signaling (e.g., RRC signaling or its equivalent higher layer semi-static signaling) or dynamic signaling (e.g., MAC CE or its equivalent higher layer dynamic signaling), and may be transmitted on a control channel (e.g., PDCCH, R-PDCCH, etc.) or a data channel (e.g., PDSCH, relay (R) -PDSCH, etc.) for the relay node. As another example, the beam indication information may be included in control information (e.g., DCI, relay (R) -DCI, side Control Information (SCI), etc.) for the relay node, and may be transmitted on a control channel (e.g., PDCCH, R-PDCCH, etc.) or a data channel (e.g., PDSCH, R-PDSCH, etc.) for the relay node. For example, beam indication information may be included in the payloads of DCI format 2_X (where X is 0,1, 2,) and SCI format and transmitted to the relay node. The relay node may monitor CORESET, PDCCH the search space, PDCCH monitoring occasions, etc. (or PDCCH candidates belonging thereto) in order to receive DCI or DCI formats including the beam indication information. The search space, PDCCH monitoring occasion, etc. may be configured CORESET, PDCCH from the base station to the relay node by the above method. The beam indication information described above may be transmitted from the base station to a relay node (e.g., a relay or MT of a relay, etc.) over a control link or Uu link. For example, the MT entity of the relay may instruct the forwarding entity to perform an access link transmit/receive beamforming operation based on the beam indication information.

The beam indication information (e.g., access link beam indication information) may include information about a time period for which the beam indication information is applied, beam information for the time period, and the like. The time period may be a time slot. For example, the beam indication information may include beam information corresponding to each symbol (or each symbol group) belonging to the period, and the information about each beam may include a codeword index of a codebook, information about coefficients or phase values of the beam, and the like, as described above. In this case, the number of beam information may coincide with the number of symbols (or the number of symbol groups) belonging to the period. The relay node may receive information on the granularity of time to which the beam indication information is applied, i.e., a time unit (e.g., a symbol or a symbol group) to which each beam indication information is applied, from the base station. In addition, the beam indication information may further include information about a frequency region (e.g., RB, subband, RB set, bandwidth part, carrier, etc.) to which the beam indication information is applied. At least a portion of the above information may be transmitted from the base station to the relay node through semi-static signaling (e.g., RRC signaling or equivalent). For example, the number of slots K3 included in the period to which the beam indication information is applied may be semi-statically set. The relay node may consider the beam indication information included in the DCI to be for a K3 slot. In addition, the relay node may determine a size of a field of DCI (or R-DCI, SCI, etc.) including the beam indication information based on a length of the time period and monitor the DCI (or R-DCI, SCI, etc.) accordingly.

In addition, the duration of the above-described time periods, symbols, etc. may be determined by a particular parameter set (e.g., a reference parameter set). Here, the parameter set may refer to a subcarrier spacing. Or the parameter set may represent a subcarrier spacing and a CP length. The specific parameter set (e.g., reference parameter set) may be configured to the relay node through semi-static signaling or may be indicated to the relay node to be included in the DCI. The information about the reference parameter set may be included in or transmitted together with the slot format information (e.g., included in the same DCI (format) as the slot format information). In addition, the above beam indication information may be included in or transmitted together with slot format information (e.g., included in the same DCI (format) as slot format information). Or the relay node may be configured with a carrier and/or bandwidth portion from the base station and may determine one of the parameter sets (or subcarrier spacing) used in the carrier or bandwidth portion as a reference parameter set (or reference subcarrier spacing). For example, the duration of the time period, symbol, or the like may be determined based on the smallest subcarrier spacing among subcarrier spacing configured in a carrier or bandwidth portion configured in the relay node. Or the duration of the time period, symbol, etc. may be determined based on the subcarrier spacing of the carrier or bandwidth portion that is activated (or indicated to be activated) in the relay node.

The relay node may transmit or receive multiple signals belonging to multiple carriers or multiple bandwidth portions simultaneously (e.g., within the same time period). Multiple carriers or multiple bandwidth parts may have the same parameter set (or subcarrier spacing and/or CP length). That is, the relay node may not be expected to be configured with or instructed to activate multiple carriers or multiple bandwidth portions with different parameter sets (or different subcarrier spacing and/or CP lengths). The operation of the relay node may be limited to the same frequency band. That is, the relay node may desire a configuration based on different parameter sets (or different subcarrier spacing and/or CP length) for multiple carriers or multiple bandwidth parts belonging to different frequency bands. Or, regardless of the frequency band, the multiple carriers or multiple bandwidth portions may have different parameter sets (or subcarrier spacing and/or CP length) and the symbol durations corresponding thereto may also be different from each other. The relay node may transmit or receive symbols having different durations (in different frequency regions) simultaneously and transmit or receive signals by applying the same or different beams to signals mapped to symbols having different durations.

Although the access link transmit beam for downlink transmission is considered in the above-described exemplary embodiment, the above-described methods (e.g., "method 200" and "method 210") are not limited thereto, and may also be applied to control of the access link receive beam for uplink transmission. In addition, the above-described methods (e.g., "method 200" and "method 210") may also be applied to control of backhaul beams (e.g., transmit beams and receive beams) of the relay node. In this case, the access link beam, the access link transmission beam, and the access link reception beam in the above-described exemplary embodiments may be interpreted as a backhaul beam, a backhaul transmission beam, and a backhaul reception beam, respectively. The base station may transmit backhaul beam indication information to the relay node according to the above method. Different beam pointing methods may be applied for backhaul beam control and access link beam control. For example, backhaul beam control may be performed by "method 200" and access link beam control may be performed by "method 210".

[ Beam failure recovery ]

When the quality of a beam for CORESET or PDCCH reception deteriorates, the terminal may determine a beam failure. When a beam failure occurs, it may be difficult for a terminal connected to the relay node to know which link among the backhaul link and the access link the beam failure occurs. Accordingly, the terminal can perform the beam fault determination process and the beam restoration process according to the same method without distinguishing between the case where the terminal is directly connected to the base station and the case where the terminal is connected to the relay node. The beam-fault-recovery request signal (e.g., PRACH or PUCCH) of the terminal and the response signal (e.g., PDCCH) of the base station thereto may be relayed between the terminal and the base station by the relay node.

Meanwhile, when the quality of a beam of a backhaul link (or a control link or Uu link) is degraded, the relay node may determine a beam failure. When the relay node has a higher layer protocol layer (e.g., MAC layer, RRC layer, etc.), a beam fault determination procedure and/or a beam recovery procedure of the relay node may be performed in a physical layer and higher layers of the relay node. On the other hand, when the relay node does not have a higher layer protocol layer (e.g., MAC layer, RRC layer, etc.), a beam failure determination process and/or a beam recovery process may be performed in the physical layer of the relay node.

Similar to the terminal, the relay node may monitor CORESET (or PDCCH search space set, PDCCH monitoring occasion), CORESET of the relay node (e.g., relay (R) -core (s)), or control channel transmission resources equivalent thereto. In this case, a signal quasi co-located with the DM-RS of CORESET (e.g., SSB or CSI-RS) or a control channel transmission resource equivalent thereto (or DM-RS for demodulating the PDCCH candidate included in CORESET) or a signal explicitly configured by the base station equivalent thereto may be referred to as a first signal set. The relay node may determine a beam fault when beam quality (e.g., RSRP, L1-RSRP, hypothesized PDCCH BLER, etc.) of all signals belonging to the first signal set (or the first signal set corresponding to a particular TRP) is less than or equal to a first reference value. When a beam failure occurs, the relay node may measure beam quality (e.g., RSRP, L1-RSRP, hypothetical PDCCH BLER, etc.) of signals (e.g., SSBs or CSI-RSs) belonging to the second signal set (or the second signal set corresponding to a specific TRP) and determine signals having beam quality equal to or greater than a second reference value as new beam candidates. The signals of the second set of signals may be configured from the base station to the relay node.

The relay node may report information about the new candidate beam (e.g., a resource index, SSB index, or CSI-RS resource index corresponding thereto) to the base station explicitly or implicitly, thereby requesting beam fault recovery. The information may be transmitted on a PRACH (e.g., relay (R) -PRACH)), PUCCH (e.g., relay (R) -PUCCH)), or the like. For example, the relay node may transmit an uplink signal (e.g., PRACH) in uplink resources (e.g., PRACH resources, PRACH occasions) associated with the new candidate beam, and the base station may identify the new candidate beam determined by the relay node by successfully receiving the uplink signal in the uplink resources. Or the information may be included in the MAC CE or an equivalent higher layer message. For example, information may be transmitted to the base station on PUSCH. Information about the new candidate beam may be transmitted to the base station over the control link or Uu link. In this case, the entity transmitting the information may be a repeater (e.g., MT entity of the repeater). Or information about the new candidate beam may be transmitted to the base station over the backhaul link. In this case, the entity transmitting the information may be a repeater (e.g., a forwarding entity of the repeater).

The relay node may monitor a response signal to the beam fault recovery request. For example, the response signal may be a PDCCH (e.g., R-PDCCH) and may be transmitted through CORESET (e.g., CORESET or R-CORESET configured for a beam fault recovery procedure). When the relay node performs CORESET monitoring operations, it may be assumed that the DM-RS of the PDCCH is quasi co-located with signals corresponding to the new candidate beam (e.g., corresponding signals belonging to the second signal set). The response signal may be transmitted to the relay node over a control link or Uu link. In this case, the entity receiving the response signal may be a repeater (e.g., MT entity of the repeater). Or may transmit the response signal to the relay node through the backhaul link. In this case, the entity receiving the response signal may be a repeater (e.g., a forwarding entity of the repeater).

The above backhaul beam fault detection and beam recovery procedure of the relay node may take a predetermined time. When the above procedure is performed, the terminal may transmit a beam fault recovery request signal and may not receive a response message from the base station (or relay node) due to deterioration of the backhaul link quality. In this case, the terminal may determine a Radio Link Failure (RLF) of the corresponding serving cell, and may initiate a cell re-search, a handover procedure, etc. As a result, the terminal may not be able to communicate with the serving cell for a predetermined time.

As a method of solving the above-described problem, a base station (or relay node) may notify information about backhaul beam failure to a terminal. The information about the backhaul beam failure may include information indicating that the backhaul beam failure has occurred and information about a time (e.g., slot, subframe) required to recover from the backhaul beam failure. In addition, the information on the backhaul beam failure may include information instructing the terminal not to perform a beam failure recovery procedure, a PDCCH monitoring operation, and other transmission or reception operations for a predetermined time, or information instructing the terminal to suspend or delay the procedure and operation. In this case, the information may be implicit information instead of information explicitly informing of the backhaul beam failure. Or as described above, the base station (or relay node) may notify the terminal of information indicating that the relay node does not perform the signal relay operation (i.e., information indicating that the relay node does not perform the non-relay operation), information about the non-relay period, or the like, and the terminal may not perform the transmission operation or the reception operation for a predetermined period of time based on the information. Or the base station (or relay node) may explicitly instruct the terminal not to perform a transmitting operation or a receiving operation for a predetermined period of time. The terminal may not perform a measurement operation for determining beam faults, RLFs, etc. or may ignore the performed measurement operation for a predetermined period of time.

[ Timing alignment and control Signaling ]

A relay node (e.g., a repeater or IRS) may receive information about a slot format from a base station through the above-described method, and may determine a transmission direction of each symbol belonging to a slot based on the information. The information about the slot format may be configured or indicated to the relay node by semi-static signaling, dynamic signaling, etc. In this case, the backhaul beam and the access link beam of the relay node may be switched from the transmit beam to the receive beam or from the receive beam to the transmit beam according to the transmission direction of the symbol. As described above, the beam may refer to a precoder, a receive filter, a spatial QCL, or an assumption of spatial transmit/receive parameters, etc. In this case, the beam switching operation may need to be performed in alignment with the symbol boundary. To this end, the relay node may determine a downlink reception timing and an uplink transmission timing, and may perform a signal transmission operation and a beam switching operation based thereon. The relay node may determine downlink timing (e.g., symbol timing, slot timing, radio frame timing, etc.) based on receipt of downlink signals (e.g., SSB, CSI-RS, TRS, etc.). The downlink signal may be a downlink signal of a backhaul link (or a control link or Uu link). The relay node may perform a handover operation between the transmit beam and the receive beam for each of the backhaul link (or the control link or Uu link) and the access link according to the determined symbol timing (i.e., symbol boundary). In addition, the relay node may determine uplink timing based on a Timing Advance (TA) received from the base station. The relay node may determine a point of time of a TA earlier than the downlink timing as an uplink signal transmission timing, and may transmit an uplink signal according to the determined timing. The downlink timing and uplink timing may be used for transmission/reception of the backhaul link (or control link or Uu link).

Referring to fig. 9, a relay node may receive a downlink signal from a base station through a backhaul link (or a control link) and determine downlink timing of the backhaul link (or the control link). The relay node may determine an access link downlink timing based on the downlink timing of the backhaul link (or control link) and transmit a signal over the access link based on the determined access link downlink timing. For example, the access link downlink timing may be T2 later than the downlink timing of the backhaul link (or control link). T2 may include a time delay (e.g., a time delay of a signal receiving unit, a signal transmitting unit, etc.) required for the relay node to relay the downlink signal. T2 may generally have a value greater than or equal to 0. In some cases, T2 may be a negative number, and thus the access link downlink timing of the relay node may precede the downlink timing of the backhaul link (or control link).

T2 may be arbitrarily determined by the relay node. Or T2 may be determined by the base station and may be transmitted from the base station to the relay node. A time delay from a point of time when the relay node receives the downlink signal to a point of time when the relay node transmits the received downlink signal or a time value (e.g., t 2) corresponding thereto may be defined as a capability of the relay node. The relay node may report this capability to the base station. The base station may determine T2 based on the capabilities received from the relay node. For example, T2 may be determined to be greater than or equal to T2.

In addition, the relay node may determine a backhaul link (or control link) uplink timing (a preamble UL timing) based on a downlink timing of the backhaul link (or control link), and may transmit a backhaul link (or control link) uplink signal based on the determined backhaul link (or control link) uplink timing. For example, backhaul link (or control link) uplink timing may be advanced by T1 from backhaul link (or control link) downlink timing. Or the backhaul link (or control link) uplink timing may be advanced by T1 from the access link downlink timing. T1 may include a propagation delay time between the base station and the relay node. T1 may generally have a value greater than or equal to 0. In some cases, T1 may be negative, and thus, the backhaul link (or control link) uplink timing of the relay node may be later than the backhaul link (or control link) downlink timing. Or T1 may be negative and the backhaul link (or control link) uplink timing of the relay node may be later than the access link downlink timing. T1 may correspond to the TA of the relay node. T1 may be determined by the base station and may be transmitted from the base station to the relay node. The base station may determine T1 based on a reception timing of a signal (e.g., SRS) received from the relay node.

Since the relay node receives an uplink signal from the terminal and relays it to the base station, the access link uplink timing of the relay node may precede the backhaul link (or control link) uplink timing. For example, the access link uplink timing of the relay node may be advanced by T3 from the backhaul link (or control link) uplink timing. Or the access link uplink timing of the relay node may be advanced by T3 from the backhaul link (or control link) downlink timing or the access link downlink timing. T3 may include a time delay (e.g., a time delay of a signal receiving unit, a signal transmitting unit, etc.) required for the relay node to relay the uplink signal. T3 may generally have a value greater than or equal to 0. In some cases, T3 may be negative, and thus, the access link uplink timing of the relay node may be later than the backhaul link (or control link) uplink timing.

T3 may be arbitrarily determined by the relay node. Or T3 may be determined by the base station and may be transmitted from the base station to the relay node. A time delay from a point of time when the relay node receives the uplink signal to a point of time when the relay node transmits the received uplink signal or a time value (e.g., t 3) corresponding thereto may be defined as a capability of the relay node. The relay node may report this capability to the base station. The base station may determine T3 based on the capabilities received from the relay node. For example, T3 may be determined to be greater than or equal to T3. In an exemplary embodiment, t3=t2. In addition, t3=t2. In this case, the capability related to uplink timing and the capability related to downlink timing may be defined as one capability.

The base station may determine a TA of a terminal (e.g., a first terminal) in consideration of timing differences (e.g., T1, T2, T3, etc.), and may indicate the TA to the terminal. For example, the TA of the terminal may be determined to be greater than or equal to t1+t2+t3. Therefore, as described above, it is important for the base station to know the transmission timing (e.g., T2, T3, etc.) of the relay node.

As described above, the base station may transmit control information for controlling the operation of the relay node to the relay node. The control information may be transmitted to the relay node through a semi-static signaling procedure (e.g., an RRC signaling procedure or a higher layer semi-static signaling procedure equivalent thereto). Or the control information may be transmitted to the relay node through a dynamic signaling procedure (e.g., a dynamic signaling procedure through a MAC CE or a higher-layer dynamic signaling procedure equivalent thereto). Additionally or alternatively, the control information may be referred to as DCI (e.g., R-DCI), SCI, downlink Side Control Information (DSCI), forward Control Information (FCI), etc., and may be transmitted on a control channel (e.g., PDCCH or R-PDCCH), a data channel (e.g., PDSCH or R-PDSCH), a reference signal (e.g., CSI-RS), etc., in a DCI format (e.g., R-DCI format), SCI format, DSCI format, etc. In case that the relay node performs the random access operation, the relay node may receive the DCI format before performing the random access operation. For example, the DCI format may be transmitted through a type 3PDCCH CSS set (or a search space set equivalent thereto), CORESET #0 (or CORESET equivalent thereto), or the like. When the RRC state and RRC state transition for the relay node are defined, the relay node may perform a PDCCH monitoring operation for receiving the DCI format in the RRC idle state and may receive the DCI format.

The DCI (e.g., R-DCI) may include the above-described slot format information, the above-described beam information or beam indication information, information indicating an on/off operation of a relay node, information indicating the above-described non-relay operation (or information indicating a partial switching operation), and the like. The relay node may perform a corresponding operation based on the information. In order for the base station to recognize whether the DCI has been successfully transmitted, the relay node may transmit HARQ-ACK to the base station in response to the DCI (or PDCCH or PDSCH). The HARQ-ACK reported by the relay node to the base station may include only ACK information. Or the HARQ-ACK reported by the relay node to the base station may include ACK/NACK information. The link adaptation technique may be applied to transmission of physical channels or physical signals including DCI. To this end, the relay node may calculate CSI of the backhaul link and may report the calculated CSI to the base station. CSI may be calculated based on receipt of backhaul downlink signals (e.g., CSI-RS, SSB, etc.). The CSI may include a Channel Quality Indicator (CQI), a Precoding Matrix Indicator (PMI), a Rank Indicator (RI), a Layer Indicator (LI), a CSI-RS resource indicator (CRI), a Beam Indicator (BI), and the like.

In addition, the relay node may transmit control information to the base station that helps the base station control its operation. The control information may be referred to as UCI, SCI, uplink Side Control Information (USCI), FCI, etc., and may be transmitted on a control channel (e.g., PUCCH, R-PUCCH), a data channel (e.g., PUSCH, R-PUSCH), a reference signal (e.g., SRS), etc. Or the control information may be included in a MAC CE, an RRC message, or a message equivalent thereto, and may be transmitted to the base station on a control channel (e.g., PUCCH or R-PUCCH), a data channel (e.g., PUSCH or R-PUSCH), a reference signal (e.g., SRS), or the like. The control information may include the above HARQ-ACK, a Scheduling Request (SR), CSI, the above beam fault recovery request message, an uplink beam quality measurement result of the access link, and the like. The link adaptation technique may be applied to the transmission of physical channels or physical signals including control information. To this end, the relay node may transmit an SRS to the base station, and the base station may receive the SRS and estimate the quality of the uplink channel.

The control information may be transmitted to the relay node or to the base station over a control link or Uu link. In this case, the entity transmitting or receiving the control information may be a repeater (e.g., MT entity of the repeater). Or the control information may be transmitted to the relay node or to the base station through the backhaul link. In this case, the entity transmitting or receiving the control information may be a repeater (e.g., a forwarding entity of the repeater).

The relay node may relay signals transmitted for itself (e.g., PDCCH including DCI, PDSCH, signals transmitted for beam management of the relay node, etc.) to the terminal. Or the relay node may not relay the signal transmitted for itself to the terminal. Or whether to transmit a signal may be determined by the relay node. For example, when a relay node receives a signal for itself in a certain downlink symbol and does not receive a signal for a terminal, the relay node may not relay the corresponding downlink symbol (or its signal) to the terminal.

As described above, the relay node may relay a signal (e.g., an uplink signal) received from the terminal to the base station through a backhaul link (or control link). This signal may be referred to as a relay signal (e.g., an uplink relay signal). Further, the relay node may transmit a signal (e.g., an uplink signal) generated by the relay node to the base station through a backhaul link (or control link). This signal may be referred to as a non-relayed signal (e.g., an uplink non-relayed signal). The uplink relay signal and the uplink non-relay signal may be transmitted to the base station in a manner multiplexed in the time domain, the frequency domain, and/or the spatial domain. The uplink relay signal and the uplink non-relay signal may include PUCCH, PUSCH, DM-RS, PT-RS, SRS, PRACH, and the like.

For example, uplink relay signals and uplink non-relay signals may be transmitted from the relay node to the base station in the same time period (e.g., the same symbol and the same time slot). In this case, the relay node may perform an operation of summing the uplink relay signal and the uplink non-relay signal, and the summed signal may be transmitted to the base station. The uplink relay signal may refer to an uplink signal received from the terminal or an uplink signal received from the terminal and passing through a predetermined Radio Frequency (RF) processing unit (e.g., filtering, power amplifier, etc.). The uplink unrepeatered signal may refer to a signal generated in baseband and operated through an RF processing unit or passband. The operation of summing the uplink relayed signal and the uplink non-relayed signal may be performed in the RF band or passband. Further, the operation of summing the uplink relay signal and the uplink non-relay signal may be performed in the time domain. The relay node may transmit the summed (or multiplexed) signal according to the above-described transmission timing (e.g., backhaul link (or control link) uplink timing).

When a terminal connected to a relay node through an access link does not transmit an uplink signal for a corresponding period of time, the uplink relay signal may not include a meaningful signal (e.g., an uplink signal of the terminal). That is, the relay node may not recognize whether the uplink non-relay signals are actually multiplexed with the uplink signals received from the terminal through the above-described operation, and may perform the operation of summing the signals, regardless of whether they are multiplexed. The base station may allocate the uplink non-relay signal and the uplink relay signal such that the uplink non-relay signal and the uplink relay signal do not overlap in the same resource. Thus, the relay node may assume that the uplink non-relay signal and the uplink relay signal do not overlap in the same resource (e.g., the same symbol and the same frequency region), and perform an operation based on the assumption.

As another example, the uplink relay signal and the uplink non-relay signal may be arranged in different time periods (e.g., different symbols and different time slots). In this case, the above multiplexing operation of the relay node may not be performed. The relay node may perform an operation of relaying an uplink signal received from the terminal to the base station in a first period of time, and may perform an operation of transmitting a signal generated by itself to the base station in a second period of time. The first time period and the second time period may not overlap. The signal transmitted in the first period and the signal transmitted in the second period may be transmitted according to the same transmission timing (e.g., the above-described backhaul link (or control link) uplink timing). Or the signal transmitted in the first period and the signal transmitted in the second period may be transmitted based on different transmission timings.

Operations of the method according to the exemplary embodiments of the present disclosure may be implemented as computer-readable programs or codes in a computer-readable recording medium. The computer readable recording medium may include all kinds of recording apparatuses for storing data that can be read by a computer system. Furthermore, the computer-readable recording medium may store and execute a program or code that can be distributed in computer systems connected through a network and read by a computer in a distributed manner.

The computer readable recording medium may include a hardware device such as a ROM, a RAM, or a flash memory that is specially configured to store and execute program commands. The program commands may include not only machine language code created by a compiler but also high-level language code that may be executed by a computer using an interpreter.

Although some aspects of the present disclosure have been described in the context of apparatus, these aspects may indicate corresponding descriptions in terms of methods, and blocks or apparatus may correspond to steps or features of steps of the methods. Similarly, aspects described in the context of the present method may be represented as features of a respective block or item or a respective apparatus. Some or all of the steps of the method may be performed by (or using) a hardware device, such as a microprocessor, a programmable computer, or electronic circuitry. In some embodiments, one or more of the most important steps of the method may be performed by such an apparatus.

In some exemplary embodiments, programmable logic devices such as field programmable gate arrays may be used to perform some or all of the functions of the methods described herein. In some exemplary embodiments, a field programmable gate array may be operated with a microprocessor to perform one of the methods described herein. In general, it is preferred that the methods be performed by some hardware means.

The description of the disclosure is merely exemplary in nature and, thus, variations that do not depart from the gist of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.

Claims

1. A method of operation of a repeater in a mobile communication system, the method of operation comprising:

receiving information about a backhaul receive beam and/or a backhaul transmit beam from a base station;

Receiving information on an access link transmit beam and/or an access link receive beam from the base station or obtaining information on the access link transmit beam and/or the access link receive beam from the information on the backhaul receive beam and/or the backhaul transmit beam;

performing communication with the base station by using the backhaul reception beam and/or the backhaul transmission beam, which are formed using the information about the backhaul reception beam and/or the backhaul transmission beam; and

Performing communication with a terminal by using the access link transmit beam and/or the access link receive beam, which are formed using the information about the access link transmit beam and/or the access link receive beam,

Wherein the backhaul reception beam is a beam for the relay to receive a signal from the base station, the backhaul transmission beam is a beam for the relay to transmit a signal to the base station, the access link transmission beam is a beam for the relay to transmit a signal to the terminal, and the access link reception beam is a beam for the terminal to receive a signal from the relay.

2. The method of operation of claim 1, wherein the information about the backhaul receive beam is indicated based on a quasi co-located (QCL) source signal having a QCL relationship with a downlink signal transmitted from the base station to the relay and QCL parameters for which the QCL relationship is established.

3. The method of operation of claim 1, wherein the information about the backhaul transmit beam is indicated based on a source signal having a QCL relationship or a spatial relationship with an uplink signal transmitted from the relay to the base station or a downlink signal transmitted from the base station to the relay and QCL parameters for which the QCL relationship or the spatial relationship is established.

4. The method of operation of claim 1, wherein the information about the access link transmit beam is indicated based on a codebook including entries each corresponding to a precoder applied to a signal transmitted to the terminal over an access link with the terminal.

5. The method of operation of claim 4, wherein at least a portion of the codebook is preconfigured in the repeater or received from the base station, and the information about the access link transmit beam is indicated by an index indicating at least one entry belonging to the codebook.

6. The method of operation of claim 1, wherein the information about the access link receive beam is indicated based on a codebook including entries each corresponding to a receive filter applied to signals received from the terminal over an access link with the terminal.

7. The method of operation of claim 6, wherein at least a portion of the codebook is preconfigured in the repeater or received from the base station, and the information about the access link receive beam is indicated by an index indicating at least one entry belonging to the codebook.

8. The method of operation of claim 1, wherein the information about the backhaul transmit beam and/or the information about the access link transmit beam comprises phase shift values for a plurality of phase control elements constituting an Intelligent Reflection Surface (IRS) when the repeater is configured as the IRS.

9. The method of operation of claim 8, wherein the backhaul transmit beam and/or the access link transmit beam are formed by the phase control element based on beamforming.

10. A method of operating a base station in a mobile communication system, the method comprising:

transmitting information about the backhaul receive beam and/or the backhaul transmit beam to the relay;

transmitting information about an access link transmit beam and/or an access link receive beam to the repeater;

Performing communication with the relay by using the backhaul reception beam and/or the backhaul transmission beam formed using the information about the backhaul reception beam and/or the backhaul transmission beam; and

Allowing the repeater to communicate with a terminal by using the access link transmit beam and/or the access link receive beam, which are formed using the information about the access link transmit beam and/or the access link receive beam,

11. The method of operation of claim 10, wherein the information about the backhaul receive beam is indicated based on a quasi co-located (QCL) source signal having a QCL relationship with a downlink signal transmitted from the base station to the relay and QCL parameters for which the QCL relationship is established.

12. The method of operation of claim 10, wherein the information about the backhaul transmit beam is indicated based on a source signal having a QCL relationship or a spatial relationship with an uplink signal transmitted from the relay to the base station or a downlink signal transmitted from the base station to the relay and QCL parameters for which the QCL relationship or spatial relationship is established.

13. The method of operation of claim 10, wherein the information about the access link transmit beam is indicated based on a codebook including entries each corresponding to a precoder applied to a signal transmitted to the terminal over an access link with the terminal.

14. The method of operation of claim 10, wherein the information about the access link receive beam is indicated based on a codebook including entries each corresponding to a receive filter applied to signals received from the terminal over an access link with the terminal.

15. The method of operation of claim 10, wherein the information about the backhaul transmit beam and/or the information about the access link transmit beam comprises phase shift values for a plurality of phase control elements constituting an Intelligent Reflection Surface (IRS) when the repeater is configured as the IRS.

16. A repeater in a mobile communication system, the repeater comprising:

A processor;

At least one transceiver connected to the processor; and

A memory storing at least one instruction executable by the processor,

Wherein the at least one instruction, when executed by the processor, causes the repeater to:

Receiving information about a backhaul receive beam and/or a backhaul transmit beam from a base station and through the at least one transceiver;

receiving information on an access link transmit beam and/or an access link receive beam from the base station and through the at least one transceiver, or obtaining information on the access link transmit beam and/or the access link receive beam from the information on the backhaul receive beam and/or the backhaul transmit beam;

performing communication with the base station by using the backhaul receive beam and/or the backhaul transmit beam, which are formed using the information about the backhaul receive beam and/or the backhaul transmit beam, and by the at least one transceiver; and

17. The terminal of claim 16, wherein the information about the backhaul receive beam is indicated based on a quasi co-located (QCL) source signal having a QCL relationship with a downlink signal transmitted from the base station to the relay and QCL parameters for which the QCL relationship is established.

18. The terminal of claim 16, wherein the information about the backhaul transmit beam is indicated based on a source signal having a QCL relationship or a spatial relationship with an uplink signal transmitted from the relay to the base station or a downlink signal transmitted from the base station to the relay and QCL parameters for which the QCL relationship or spatial relationship is established.

19. The terminal of claim 16, wherein the information about the access link transmit beam is indicated based on a codebook comprising entries each corresponding to a precoder applied to a signal transmitted to the terminal over an access link with the terminal.

20. The terminal of claim 16, wherein the information about the access link receive beam is indicated based on a codebook comprising entries each corresponding to a receive filter applied to signals received from the terminal over an access link with the terminal.