Method and apparatus for transmitting synchronization signal in wireless communication system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. The present disclosure proposes a method and an apparatus for defining efficient frequency use and transmission / reception operations of a terminal.

Description

Method and device for transmitting synchronous signals in a wireless communication system

[0001] The present disclosure relates to a communication method of a wireless communication system, and more specifically to a method and apparatus for defining efficient frequency usage and transmission and reception operations of a terminal.

[0002] 5G mobile communication technology defines a wide frequency band to enable fast transmission speeds and new services, and can be implemented not only in frequency bands below 6 GHz ('Sub 6 GHz'), such as 3.5 gigahertz (3.5 GHz), but also in ultra-high frequency bands called millimeter waves (mmWave), such as 28 GHz and 39 GHz ('Above 6 GHz'). In addition, for 6G mobile communication technology, which is referred to as a system beyond 5G, implementation in the terahertz band (e.g., the 3 terahertz (3 THz) band at 95 GHz) is being considered to achieve even faster transmission speeds and even lower ultra-low latency compared to 5G mobile communication technology.

[0003] In the early stages of 5G mobile communication technology, aiming to satisfy service support and performance requirements for enhanced Mobile BroadBand (eMBB), Ultra-Reliable Low-Latency Communications (URLLC), and massive Machine-Type Communications (mMTC), technologies such as beamforming and Massive MIMO to mitigate path loss and increase transmission distance in ultra-high frequency bands, support for various numerologies (such as operating multiple subcarrier spacings) and dynamic operation of slot formats for the efficient utilization of ultra-high frequency resources, initial access techniques to support multi-beam transmission and broadband, definition and operation of Band-Width Parts (BWP), Low Density Parity Check (LDPC) codes for high-volume data transmission, new channel coding methods such as Polar Codes for reliable transmission of control information, and L2 pre-processing (L2 Standardization has been carried out for pre-processing, network slicing which provides a dedicated network specialized for specific services, and other methods.

[0004] In addition, discussions are underway to improve and enhance the performance of the initial 5G mobile communication technology in consideration of the services that the 5G mobile communication technology was intended to support. Standardization has been carried out for technologies such as V2X (Vehicle-to-Everything), which helps autonomous vehicles make driving decisions and enhance user convenience based on their own location and status information transmitted by the vehicle; NR-U (New Radio Unlicensed), which aims for system operation in unlicensed bands to comply with various regulatory requirements; NR terminal low power consumption technology (UE Power Saving); Non-Terrestrial Network (NTN), which is direct terminal-satellite communication for securing coverage in areas where communication with the terrestrial network is impossible; and positioning.

[0005] In addition, standardization was also carried out for technologies such as the Industrial Internet of Things (IIoT) to support new services through linkage and convergence with other industries, Integrated Access and Backhaul (IAB) which provides nodes to expand network service areas by integrating wireless backhaul links and access links, Mobility Enhancement including Conditional Handover and Dual Active Protocol Stack (DAPS) Handover, and 2-step RACH for NR which simplifies random access procedures.

[0006] In addition, standardization is underway for 5G baseline architectures (e.g., Service based Architecture, Service based Interface) for the integration of Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, as well as for Mobile Edge Computing (MEC), which provides services based on the location of the terminal.

[0007] With the commercialization of such 5G mobile communication systems, connected devices, which are increasing explosively, will be connected to communication networks. Accordingly, it is expected that there will be a need to enhance the functionality and performance of 5G mobile communication systems and to integrate the operation of connected devices. To this end, new research is planned to be conducted on 5G performance improvement and complexity reduction, support for AI services, support for metaverse services, and drone communication using eXtended Reality (XR), Artificial Intelligence (AI), and Machine Learning (ML) to efficiently support Augmented Reality (AR), Virtual Reality (VR), and Mixed Reality (MR).

[0008] In addition, the advancement of these 5G mobile communication systems can serve as a foundation for the development of new waveforms for ensuring coverage of 6G mobile communication technology, multi-antenna transmission technologies such as Full Dimensional MIMO (FD-MIMO), array antennas, and large-scale antennas, metamaterial-based lenses and antennas, high-dimensional spatial multiplexing technology using Orbital Angular Momentum (OAM), and Reconfigurable Intelligent Surface (RIS) technology, as well as Full Duplex technology for improving frequency efficiency and system networks of 6G mobile communication technology, AI-based communication technology that realizes system optimization by utilizing satellites and AI from the design stage and internalizing end-to-end AI support functions, and next-generation distributed computing technology that realizes services of complexity exceeding the limits of terminal computing capabilities by utilizing ultra-high-performance communication and computing resources.

[0009] One embodiment of the present invention aims to provide a device and a method capable of effectively providing mobile communication services. Specifically, one embodiment of the present invention aims to provide a procedure for energy saving between a base station and a terminal.

[0010] The technical problems to be solved by the present invention are not limited to those mentioned above, and other unmentioned technical problems may be considered by those skilled in the art from the various embodiments of the present disclosure described below.

[0011] A method performed by a terminal of a wireless communication system according to an embodiment of the present invention for solving the above-mentioned problems may include: receiving a discovery signal from a base station; transmitting a request message to the base station requesting the transmission of a synchronization signal; receiving an on-demand SSB (SS / PBCH block, synchronization signal / physical broadcast channel block) that is transmitted repeatedly at least once from the base station; and transmitting a random access preamble to the base station based on a RACH (random access channel) occasion associated with the on-demand SSB that is transmitted repeatedly at least once or a RACH occasion associated with the SSB that is transmitted periodically.

[0012] According to an embodiment, the on-demand SSB that is transmitted at least once may be transmitted in half-frame units, frame units, or quarter-frame units, according to at least one of the above.

[0013] According to an embodiment, the RACH occasion associated with the at least one on-demand SSB that is transmitted repeatedly may be associated with at least one of the first on-demand SSB received among the at least one on-demand SSB that is transmitted repeatedly or the last on-demand SSB received among the at least one on-demand SSB that is transmitted repeatedly.

[0014] According to an embodiment, each of the on-demand SSBs that are transmitted at least once repeatedly may include a plurality of SSBs corresponding to a plurality of different beams.

[0015] In addition, a method performed by a base station of a wireless communication system according to an embodiment of the present invention for solving the above-mentioned problems may include: a step of broadcasting a discovery signal; a step of receiving a request message from a terminal requesting the transmission of a synchronization signal based on the discovery signal; a step of transmitting an on-demand SSB (SS / PBCH block, synchronization signal / physical broadcast channel block) that is transmitted repeatedly at least once to the terminal; and a step of receiving a random access preamble from the terminal based on a RACH (random access channel) occasion associated with the on-demand SSB that is transmitted repeatedly at least once or a RACH occasion associated with the SSB that is transmitted periodically.

[0016] In addition, a terminal of a wireless communication system according to an embodiment of the present invention for solving the above-mentioned problems comprises: a transceiver; and a control unit connected to the transceiver; wherein the control unit receives a discovery signal from a base station, transmits a request message requesting the transmission of a synchronization signal to the base station, receives an on-demand SSB (SS / PBCH block, synchronization signal / physical broadcast channel block) that is transmitted repeatedly at least once from the base station, and controls the transmission of a random access preamble to the base station based on a RACH (random access channel) occasion associated with the on-demand SSB that is transmitted repeatedly at least once or a RACH occasion associated with the SSB that is transmitted periodically.

[0017] In addition, a base station of a wireless communication system according to an embodiment of the present invention for solving the above-mentioned problems comprises: a transceiver; and a control unit connected to the transceiver; wherein the control unit broadcasts a discovery signal, receives a request message from a terminal requesting the transmission of a synchronization signal based on the discovery signal, transmits an on-demand SSB (SS / PBCH block, synchronization signal / physical broadcast channel block) that is transmitted at least once repeatedly to the terminal, and controls the terminal to receive a random access preamble based on a RACH (random access channel) occasion associated with the on-demand SSB that is transmitted at least once repeatedly or a RACH occasion associated with the SSB that is transmitted periodically.

[0018] One embodiment of the present invention may provide a transceiver device and method for a terminal and a base station that increases frequency usage efficiency in a mobile communication system. Specifically, according to at least one embodiment of the present disclosure, the base station and the terminal can effectively perform an initial connection procedure for energy saving between the base station and the terminal.

[0019] The effects obtainable from the present invention are not limited to those mentioned above, and other unmentioned effects can be clearly derived and understood by those skilled in the art based on the following detailed description.

[0020] FIG. 1 is a diagram showing the basic structure of the time-frequency resource domain of a 5G system according to one embodiment of the present disclosure.

[0021] FIG. 2 is a diagram illustrating a random access procedure according to one embodiment of the present disclosure.

[0022] FIG. 3 is a diagram illustrating a procedure in which a terminal reports terminal capability (UE capability) information to a base station according to one embodiment of the present disclosure.

[0023] FIG. 4 is a drawing showing an example of a bandwidth portion setting according to an embodiment of the present disclosure.

[0024] FIG. 5 is a diagram showing the interrelationship between frequency bands and coverage according to one embodiment of the present disclosure.

[0025] FIG. 6 is a diagram showing an example of a base station energy saving method according to one embodiment of the present disclosure.

[0026] FIG. 7 is a drawing showing an example of a base station energy saving method according to one embodiment of the present disclosure.

[0027] FIG. 8 is a drawing showing an example of a base station energy saving method according to one embodiment of the present disclosure.

[0028] FIG. 9 is a drawing showing an example of a base station energy saving method according to one embodiment of the present disclosure.

[0029] FIG. 10 is a diagram illustrating a method for repetitive transmission of an on-demand SSB according to one embodiment of the present disclosure.

[0030] FIG. 11 is a diagram illustrating a method for repetitive transmission of an on-demand SSB according to one embodiment of the present disclosure.

[0031] FIG. 12 is a diagram illustrating a method for repetitive transmission of an on-demand SSB according to one embodiment of the present disclosure.

[0032] FIG. 13 is a diagram showing the initial connection procedure of a terminal according to one embodiment of the present disclosure.

[0033] FIG. 14 is a diagram showing an example of an initial connection procedure of a terminal according to one embodiment of the present disclosure.

[0034] FIG. 15 is a diagram showing an example of a base station procedure for supporting a terminal initial connection procedure according to one embodiment of the present disclosure.

[0035] FIG. 16 is a drawing showing a terminal transceiver device according to one embodiment of the present disclosure.

[0036] FIG. 17 is a block diagram illustrating the structure of a terminal according to one embodiment of the present disclosure.

[0037] FIG. 18 is a block diagram illustrating the structure of a base station according to one embodiment of the present disclosure.

[0038] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Furthermore, in describing the present disclosure, if it is determined that a detailed description of related known functions or configurations might unnecessarily obscure the essence of the present disclosure, such detailed description will be omitted. Additionally, the terms described below are defined considering their functions in the present disclosure, and these may vary depending on the intentions or practices of the user or operator. Therefore, their definitions should be based on the content throughout this specification.

[0039] The advantages and features of the present disclosure and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below but may be implemented in various different forms. The embodiments provided are merely to make the present disclosure complete and to fully inform those skilled in the art of the scope of the disclosure, and the present disclosure is defined only by the scope of the claims. Throughout the specification, the same reference numerals refer to the same components.

[0040] At this point, it will be understood that each block of the process flow diagrams and combinations of the flow diagrams can be executed by computer program instructions. Since these computer program instructions can be loaded into the processor of a general-purpose computer, a special-purpose computer, or other programmable data processing equipment, the instructions executed through the processor of the computer or other programmable data processing equipment create means to perform the functions described in the flow diagram block(s). Since these computer program instructions can also be stored in computer-available or computer-readable memory that can be directed toward the computer or other programmable data processing equipment to implement the function in a specific way, the instructions stored in computer-available or computer-readable memory can also produce a manufactured item containing instruction means to perform the function described in the flow diagram block(s). Since computer program instructions can be loaded onto a computer or other programmable data processing equipment, instructions that perform a series of operation steps on the computer or other programmable data processing equipment to create a process executed by the computer can also provide steps for executing the functions described in the flowchart block(s).

[0041] Additionally, each block may represent a module, segment, or part of code containing one or more executable instructions for executing a specific logical function(s). It should also be noted that in some alternative execution examples, the functions mentioned in the blocks may occur out of order. For example, two blocks described in succession may actually be executed substantially simultaneously, or the blocks may sometimes be executed in reverse order according to their corresponding functions.

[0042] In this embodiment, the term "part" refers to a software or hardware component such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit), and the "part" performs certain roles. However, the meaning of "part" is not limited to software or hardware. The "part" may be configured to reside in an addressable storage medium or may be configured to run one or more processors. Accordingly, as an example, the "part" includes components such as software components, object-oriented software components, class components, and task components, as well as processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functions provided within the components and "parts" may be combined into a smaller number of components and "parts" or further separated into additional components and "parts." In addition, the components and '~parts' may be implemented to utilize one or more CPUs within the device or secure multimedia card. Also, in the embodiment, the '~part' may include one or more processors.

[0043] In the present disclosure, each of the phrases such as “A or B,” “at least one of A and B,” “at least one of A or B,” “A, B or C,” “at least one of A, B and C,” and “at least one of A, B, or C” may include any one of the items listed together in the corresponding phrase, or all possible combinations thereof. Terms such as “first,” “second,” or “first” or “second” may be used simply to distinguish a corresponding component from another corresponding component and do not limit the components in any other aspect (e.g., importance or order).

[0044] In describing the present disclosure below, specific descriptions of related known functions or configurations will be omitted if it is determined that such detailed descriptions would unnecessarily obscure the essence of the present disclosure. Embodiments of the present disclosure will be described below with reference to the attached drawings.

[0045] Terms used in the following description to identify connection nodes, terms referring to network entities, terms referring to messages, terms referring to interfaces between network entities, terms referring to various identification information, etc., are examples provided for the convenience of explanation. Accordingly, the present disclosure is not limited to the terms described below, and other terms referring to objects having equivalent technical meanings may be used.

[0046] In the following description, the terms "physical channel" and "physical signal" may be used interchangeably with "data" or "control signal." For example, PDSCH (physical downlink shared channel) is a term referring to a physical channel through which data is transmitted, but PDSCH may also be used to refer to data. That is, in this disclosure, the expression "transmits a physical channel" may be interpreted as equivalent to the expression "transmits data or a signal through a physical channel."

[0047] In the present disclosure, upper layer signaling refers to a signal transmission method transmitted from a base station to a terminal using a physical layer downlink data channel, or from a terminal to a base station using a physical layer uplink data channel. Upper layer signaling can be understood as a Master Information Block (MIB), System Information Block (SIB), Radio Resource Control (RRC) signaling, or Media Access Control (MAC) control element (CE).

[0048] For the convenience of the following description, the present disclosure uses terms and names defined in the 3GPP NR (New Radio: 5th generation mobile communication standard) specifications. However, the present disclosure is not limited to the above terms and names and may be applied equally to systems conforming to other standards. For example, regarding 6G systems, which are still in the early stages of standardization discussion, terms and names defined in 5G systems may be generalized and used to describe the operation of 6G systems unless otherwise specifically noted.

[0049] Hereinafter, the base station is an entity that performs resource allocation for terminals and may be at least one of a gNodeB, gNB, eNodeB, eNB, NodeB, BS (Base Station), wireless access unit, base station controller, or a node on a network. The terminal may include a UE (User Equipment), MS (Mobile Station), cellular phone, smartphone, computer, IoT device, sensor, or multimedia system capable of performing communication functions. Of course, it is not limited to the examples described.

[0050] While existing mobile communication systems focused on conventional voice / data communication, 5G systems aim to satisfy various services and requirements, such as enhanced mobile broadband (eMBB) services to improve existing voice / data communication, ultra-reliable and low latency communication (URLLC) services, and massive machine type communication (MTC) services to support mass communication of the machine.

[0051] While the transmission bandwidth per carrier of existing mobile communication systems, such as LTE (Long Term Evolution or E-UTRA (Evolved Universal Terrestrial Radio Access)) and LTE-A (LTE-Advanced or E-UTRA Evolution), is limited to a maximum of 20 MHz, 5G systems aim to provide ultra-high-speed data services reaching several Gbps by utilizing significantly wider ultra-wide bandwidths. Accordingly, 5G systems are considering ultra-high frequency bands ranging from several GHz to up to 100 GHz as operating frequencies, where securing ultra-wide bandwidth frequencies is relatively easy. Additionally, it is possible to secure wide bandwidth frequencies for 5G systems through frequency reallocation or allocation from frequency bands ranging from hundreds of MHz to several GHz used by existing mobile communication systems.

[0052] Radio waves in the ultra-high frequency band have wavelengths of several millimeters and are also called millimeter waves (mmWave). However, in the ultra-high frequency band, path loss of radio waves increases in proportion to the frequency band, so the coverage of mobile communication systems can be reduced.

[0053] To overcome the disadvantage of reduced coverage in the ultra-high frequency band, beamforming technology can be applied. This technology uses multiple antennas to concentrate radio wave radiated energy toward a specific target point, thereby increasing the reach of the radio waves. In other words, a signal to which beamforming technology is applied has a relatively narrower beam width, and as radiated energy is concentrated within this narrowed beam width, the reach of the radio waves increases. Beamforming technology can be applied to both the transmitting and receiving ends. In addition to the effect of increasing coverage, beamforming technology also has the effect of reducing interference in areas outside the beamforming direction. For beamforming technology to operate properly, accurate measurement and feedback methods for the transmit and receive beams are required. Beamforming technology can be applied to control channels or data channels that correspond one-to-one between a specific terminal and a base station. Furthermore, beamforming technology can be applied to control channels and data channels used to transmit common signals—such as synchronization signals, physical broadcast channels (PBCH), and system information—that a base station transmits to multiple terminals within the system, in order to increase coverage. When applying beamforming technology to a common signal, beam sweeping technology, which changes the beam direction to transmit the signal, is additionally applied to ensure that the common signal reaches terminals located at any position within the cell.

[0054] Another requirement for 5G systems is ultra-low latency services, where the transmission delay between the transmitter and receiver is approximately 1ms. As a measure to reduce transmission delay, it is necessary to design a frame structure based on a short TTI (transmission time interval) that is shorter than that of LTE and LTE-A. TTI is the basic time unit for performing scheduling, and the TTI of existing LTE and LTE-A systems is 1ms, which corresponds to the length of one subframe. For example, in 5G systems, short TTIs such as 0.5ms, 0.25ms, and 0.125ms are possible, which are shorter than those of existing LTE and LTE-A systems, to satisfy the requirements for ultra-low latency services.

[0055] FIG. 1 is a diagram showing the basic structure of a time-frequency resource domain of a 5G system according to one embodiment of the present disclosure. That is, FIG. 1 is a diagram showing the basic structure of a time-frequency resource domain, which is a wireless resource domain where data or control channels of a 5G system are transmitted.

[0056] Referring to FIG. 1, the horizontal axis represents the time domain, and the vertical axis represents the frequency domain. The minimum transmission unit in the time domain of a 5G system is an OFDM (orthogonal frequency division multiplexing) symbol, wherein A number of symbols (102) are combined to form a slot (106), and A number of slots can be combined to form a single subframe (105). The length of a single subframe (105) is 1.0 ms, and 10 subframes can be combined to form a single frame (114), and the length of the frame (114) is 10 ms. The minimum transmission unit in the frequency domain is a subcarrier, and the bandwidth of the entire system transmission bandwidth is a total of N BW It can be composed of several subcarriers (104).

[0057] In the time-frequency domain, the basic unit of a resource is a resource element (RE) (112), which can be represented by an OFDM symbol index and a subcarrier index. A resource block (RB or Physical Resource Block, PRB) is in the frequency domain. It can be defined as a series of consecutive subcarriers (110). In a 5G system = 12, and the data rate can increase in proportion to the number of RBs scheduled to the terminal.

[0058] In a 5G system, base stations map data in RB units and can generally perform scheduling on RBs that constitute a slot for a given terminal. That is, in a 5G system, the basic time unit for which scheduling is performed is a slot, and the basic frequency unit for which scheduling is performed may be an RB.

[0059] OFDM symbol count It is determined by the length of the cyclic prefix (CP) added to each symbol to prevent interference between symbols; for example, if a normal CP is applied = 14, if Extended CP is applied = 12. Extended CP is applied to systems with relatively longer transmission distances than standard CP, enabling the maintenance of orthogonality between symbols. In the case of standard CP, the ratio of CP length to symbol length is maintained at a constant value, allowing the overhead caused by CP to remain constant regardless of subcarrier spacing (SCS). That is, if the subcarrier spacing is small, the symbol length increases, and consequently, the CP length can also increase. Conversely, if the subcarrier spacing is large, the symbol length decreases, and consequently, the CP length can be reduced. The symbol length and CP length can be inversely proportional to the subcarrier spacing.

[0060] In 5G systems, various frame structures can be supported by adjusting the subcarrier spacing to satisfy various services and requirements. For example, the characteristics according to the subcarrier spacing are as follows.

[0061] From the perspective of the operating frequency band, a larger subcarrier spacing is advantageous for recovering phase noise in the high-frequency band.

[0062] - From the perspective of transmission time, a large subcarrier spacing shortens the symbol length in the time domain, and consequently shortens the slot length, which is advantageous for supporting ultra-low latency services such as URLLC.

[0063] - From the perspective of cell size, a longer CP length allows for the support of larger cells, so a smaller subcarrier spacing allows for the support of relatively larger cells. A cell is a concept in mobile communication that refers to the area covered by a single base station.

[0064] Subcarrier spacing and CP length are essential information for OFDM transmission and reception; therefore, smooth transmission and reception are possible only when the base station and the terminal recognize these values ​​as common. [Table 1] shows the subcarrier spacing configuration (μ) and subcarrier spacing ( It shows an example of the relationship between ), CP lengths.

[0065]

[0066] [Table 2] shows the number of symbols per slot for each subcarrier spacing setting (μ) in the case of general type CP ( ), number of slots per frame( ), and number of slots per subframe( Represents an example of ).

[0067]

[0068] [Table 3] shows the number of symbols per slot for each subcarrier spacing setting (μ) in the case of extended CP ( ), number of slots per frame( ), number of slots per subframe( Represents an example of ).

[0069]

[0070] A 5G system can satisfy various user requirements through coexistence or dual-mode operation with existing LTE or / and LTE-A (hereinafter LTE / LTE-A) systems. For example, existing LTE / LTE-A systems can provide stable system operation to terminals, while 5G systems can perform the role of providing enhanced services to terminals. Therefore, the frame structure of a 5G system needs to include at least the frame structure of LTE / LTE-A or a set of essential parameters (subcarrier spacing = 15 kHz).

[0071] For example, when comparing a frame structure with a subcarrier spacing setting μ=0 (hereinafter frame structure A) and a frame structure with a subcarrier spacing setting μ=1 (hereinafter frame structure B), compared to frame structure A, frame structure B shows that the subcarrier spacing and RB size are doubled, while the slot length and symbol length are doubled. In the case of frame structure B, 2 slots can form one subframe, and 20 subframes can form one frame.

[0072] By generalizing the frame structure of a 5G system, high scalability can be provided by ensuring that the essential parameter sets, such as subcarrier spacing, CP length, and slot length, have an integer multiple relationship with each other for each frame structure. Additionally, a subframe of a fixed length of 1ms can be defined to represent a reference time unit independent of the frame structure.

[0073] The frame structure of a 5G system can be applied to various scenarios. From the perspective of cell size, since a longer CP length enables support for larger cells, Frame Structure A can support relatively larger cells compared to Frame Structure B. From the perspective of operating frequency band, since a larger subcarrier spacing is advantageous for recovering phase noise in the high-frequency band, Frame Structure B can support relatively higher operating frequencies compared to Frame Structure A. From the perspective of service, since a shorter slot length—the basic time unit of scheduling—is advantageous for supporting ultra-low latency services such as URLLC, Frame Structure B may be relatively more suitable for URLLC services compared to Frame Structure A.

[0074] In a manner similar to the coexistence of 5G and LTE / LTE-A mentioned above, it may be necessary to design a system for the coexistence of 6G, which will arrive with the evolution of future communication systems, and existing systems such as 5G or LTE / LTE-A.

[0075] In the following description of the present disclosure, an uplink (UL) refers to a wireless link through which a terminal transmits data or control signals to a base station, and a downlink (DL) may refer to a wireless link through which a base station transmits data or control signals to a terminal.

[0076] In the initial access phase, when the terminal first connects to the system, the terminal can synchronize downlink time and frequency from the synchronization signal transmitted by the base station through cell search and obtain a cell ID. Then, the terminal can receive a physical broadcast channel (PBCH) using the obtained cell ID and obtain a master information block (MIB), which is essential system information, from the PBCH. The MIB may include at least one of the following information.

[0077]

[0078] For example, the above essential system information may include at least one of the following: information regarding the location of a synchronization signal received by the terminal in the time domain and / or frequency domain; control information for the terminal to receive at least one of system information (or system information block, SIB) transmitted by the base station (which may be information for scheduling a data channel for receiving system information); information regarding whether the cell is connectable; and information regarding the SCS of the cell. The above essential system information may be referred to as system information.

[0079] Additionally, the terminal can receive system information transmitted by the base station to obtain cell-common transmission and reception control information. Cell-common transmission and reception control information may include random access control information, paging control information, and at least one of various physical channels and signals (at least one of channels and signals, such as an uplink control channel, an uplink data channel, a downlink control channel and a downlink data channel, a physical signal for obtaining uplink channel status information, a physical signal for obtaining downlink channel status information, and a physical signal for demodulating a physical channel). The control information may be configuration information for each channel or signal. The system information may be referred to, for example, as SIB1 or RMSI (remaining minimum system information).

[0080] The synchronization signal is a signal that serves as a reference for cell search, and a subcarrier spacing may be applied for each frequency band to suit channel environments such as phase noise. In the case of data channels or control channels, as described above, the subcarrier spacing may be applied differently depending on the service type to support various services. In a 5G system, a combination consisting of PSS (primary synchronization signal), SSS (secondary synchronization signal), and PBCH (Physical broadcast channel) may be referred to as an SS / PBCH block or SSB. For example, an SSB may consist of N1 PSS symbols, N2 SSS symbols, and N3 PBCH symbols.

[0081] In addition to the initial connection procedure described above, the terminal may also receive the SSB to determine whether the radio link quality of the current cell is maintained at a certain level or higher. Furthermore, during the procedure for the terminal to perform a handover from the current cell to an adjacent cell, the terminal may receive the SSB of the adjacent cell to determine the radio link quality of the adjacent cell and to obtain time / frequency synchronization with the adjacent cell.

[0082] After the terminal obtains MIB and system information from the base station through the initial access procedure, the terminal may perform a random access procedure to transition the link with the base station to a connected state (connected state or RRC_CONNECTED state). Upon completion of the random access procedure, the terminal transitions to a connected state, enabling one-to-one communication between the base station and the terminal. The random access procedure will be described in detail below with reference to FIG. 2.

[0083] FIG. 2 is a diagram illustrating a random access procedure according to one embodiment of the present disclosure.

[0084] Referring to FIG. 2, as a first step (210) of the random access procedure, the terminal may transmit a random access preamble to the base station. The random access preamble, which is the initial transmission message of the terminal in the random access procedure, may be referred to as message 1 (Msg 1). The base station may measure the transmission delay value between the terminal and the base station from the random access preamble and synchronize the uplink. At this time, the terminal may arbitrarily select which random access preamble to use from a set of random access preambles given in advance by system information. The initial transmission power of the random access preamble may be determined according to the path loss between the base station and the terminal measured by the terminal. Additionally, the terminal may transmit the random access preamble by determining the transmission beam direction of the random access preamble from the synchronization signal received from the base station.

[0085] In the second step (220), the base station may transmit a message to the terminal containing an uplink transmission timing control command based on the transmission delay value measured from the random access preamble received in the first step (210). The terminal may receive control information for scheduling the message over the downlink control channel and receive the message over the downlink data channel based on the control information. The message transmitted in the second step may be referred to as message 2 (Msg 2), a response to the random access preamble, or a random access response. Additionally, the base station may transmit the message by including, as scheduling information, uplink resources to be used by the terminal to transmit a response message (message 3, Msg 3) to message 2 and power control commands to be applied to the response message. The scheduling information may include control information regarding the terminal's uplink transmission beam. Additionally, the message may further include a temporary identifier of the terminal to be used during the random access procedure. The information included in the message is merely an example, and one or more of the information described above may be included in message 2.

[0086] If the terminal does not receive message 2, which is scheduling information for message 3, from the base station within a predetermined time in the second step (220), the terminal may perform the first step (210) again. If the first step (210) is performed again, the terminal may increase the probability of receiving the random access preamble at the base station by increasing the transmission power of the random access preamble by a predetermined step (power ramping).

[0087] In the third step (230), the terminal can transmit uplink data (message 3) including its terminal ID to the base station via the uplink data channel (physical uplink shared channel, PUSCH) based on the uplink resources allocated in the second step (220) (scheduled transmission). The transmission timing of the uplink data channel for transmitting Message 3 may follow the uplink transmission timing control command received from the base station in the second step (220). The transmission power of the uplink data channel for transmitting Message 3 may be determined by considering the power control command received from the base station in the second step (220) and the power ramping value of the random access preamble. The uplink data channel for transmitting Message 3 may refer to the first uplink data signal transmitted by the terminal to the base station after the transmission of the random access preamble. For example, the message 3 may include an upper layer message for the terminal to connect to the network.

[0088] In step 4 (240), if the base station determines that the terminal has performed random access without collision with other terminals, it may transmit data (message 4, Msg 4) containing the ID of the terminal that transmitted uplink data in step 3 (230) to the terminal (contention resolution). If the terminal receives the signal transmitted by the base station in step 4 (240), it may determine that the random access was successful. Then, the terminal may transmit HARQ-ACK information indicating successful reception of message 4 to the base station through the Physical Uplink Control Channel (PUCCH).

[0089] If the data transmitted by the terminal in the third step (230) collides with the data of another terminal and the base station fails to receive the data signal from the terminal, the base station may not transmit any further data to the terminal. Accordingly, if the terminal fails to receive the data transmitted from the base station in the fourth step (240) within a certain period of time, it is determined that the random access procedure has failed, and the process may be restarted from the first step (210).

[0090] The four-step random access procedure described above is merely an example, and the information between the terminal and the base station described above may be transmitted through messages other than the four-step message described above. For example, the random access procedure may be performed in two steps, and the terminal may perform the random access procedure by transmitting message A (Msg A) and receiving message B (Msg B). For example, the terminal may transmit one or more messages containing at least one of the information of message 1 and message 3 to the base station simultaneously or sequentially, and the base station may transmit one or more messages containing at least one of the information of message 2 and message 4 to the terminal simultaneously or sequentially.

[0091] Upon successful completion of the random access procedure, the terminal transitions to a connected state, enabling one-to-one communication between the base station and the terminal. The base station can receive Terminal Equivalent (UE) capability information from the connected terminal. The base station can adjust scheduling by referring to the terminal's UE capability information. Through the UE capability information, the terminal can inform the base station whether it supports certain functions and / or the maximum allowable value of the functions supported by the terminal. Therefore, the UE capability information reported by each terminal to the base station may vary depending on the terminal.

[0092] For example, the terminal may report UE capability information to the base station as UE capability information, including at least a portion of the following control information.

[0093] - Control information related to frequency bands supported by the terminal

[0094] - Control information related to channel bandwidth supported by the terminal

[0095] - Control information regarding the maximum modulation scheme supported by the terminal

[0096] - Control information regarding the maximum number of beams supported by the terminal

[0097] - Control information regarding the maximum number of layers supported by the terminal

[0098] - Control information related to CSI reporting supported by the terminal

[0099] - Control information on whether the terminal supports frequency hopping

[0100] - Bandwidth-related control information when Carrier Aggregation (CA) is supported

[0101] - Control information on whether cross-carrier scheduling is supported when carrier bundling is supported

[0102] FIG. 3 is a diagram illustrating a procedure in which a terminal reports terminal capability (UE capability) information to a base station according to one embodiment of the present disclosure.

[0103] Referring to FIG. 3, at step 310, the base station (302) can send a UE capability information request message to the terminal (301). In response to the UE capability information request from the base station (302), the terminal (301) can send UE capability information to the base station (302) at step 320.

[0104] Next, the Bandwidth Part (BWP) setting in the 5G communication system will be explained in detail with reference to the drawing.

[0105] FIG. 4 is a drawing illustrating an example of a bandwidth portion setting according to an embodiment of the present disclosure of 5G.

[0106] FIG. 4 shows an example in which the terminal bandwidth (UE bandwidth) (400) is configured into two bandwidth portions, namely bandwidth portion #1 (BWP#1) (401) and bandwidth portion #2 (BWP#2) (402). The base station may configure one or more bandwidth portions for the terminal and may configure the information in [Table 4] below for each bandwidth portion.

[0107]

[0108] Of course, the configuration of the bandwidth portion is not limited to the above examples, and various parameters related to the bandwidth portion may be configured for the terminal in addition to the above configuration information. The above information may be transmitted by the base station to the terminal via upper-layer signaling, for example, Radio Resource Control (RRC) signaling. Among the one or more configured bandwidth portions, at least one bandwidth portion may be activated. Whether a configured bandwidth portion is activated may be transmitted semi-statically from the base station to the terminal via RRC signaling or dynamically via Downlink Control Information (DCI).

[0109] According to one embodiment, prior to the RRC connection, the terminal may receive an Initial Bandwidth Part (Initial BWP) for initial connection from the base station via a Master Information Block (MIB). More specifically, during the initial connection phase, the terminal may receive configuration information regarding a Control Resource Set (CORESET) and a Search Space via the MIB, through which a Physical Downlink Control Channel (PDCCH) can be transmitted to receive System Information Blocks (System Information Block) required for initial connection. The Control Resource Set and Search Space configured via the MIB may each be considered as Identity (ID) 0 (CORESET 0, Search Space 0). The base station may notify the terminal via the MIB of configuration information, such as frequency allocation information, time allocation information, and subcarrier interval settings, for Control Resource Set #0. Additionally, the base station may notify the terminal via the MIB of configuration information regarding the monitoring period and monitoring occasion for Control Resource Set #0, i.e., configuration information for Search Space #0. The terminal may consider the frequency region set as control region #0 obtained from the MIB as the initial bandwidth portion for initial access. In this case, the identifier (ID) of the initial bandwidth portion may be considered as 0.

[0110] The settings for the bandwidth portion supported by the above 5G can be used for various purposes.

[0111] According to one embodiment, if the bandwidth supported by the terminal is smaller than the system bandwidth, this can be supported through the bandwidth portion setting. For example, by setting the frequency position of the bandwidth portion (setting information 2) to the terminal, the terminal can transmit and receive data at a specific frequency position within the system bandwidth.

[0112] In addition, according to one embodiment, a base station may set multiple bandwidth portions for a terminal for the purpose of supporting different subcarrier spacing settings. For example, to support data transmission and reception using both a 15 kHz subcarrier spacing and a 30 kHz subcarrier spacing for a terminal, two bandwidth portions may be set to subcarrier spacings of 15 kHz and 30 kHz, respectively. Different bandwidth portions may be frequency division multiplexed (FDM), and when data is to be transmitted and received at a specific subcarrier spacing, the bandwidth portion set to that subcarrier spacing may be activated.

[0113] In addition, according to some embodiments, a base station may set bandwidth portions with different bandwidth sizes for the purpose of reducing the power consumption of the terminal. For example, if the terminal supports a very large bandwidth, such as 100 MHz, and always transmits and receives data using that bandwidth, very large power consumption may occur. In particular, in a situation where there is no traffic, performing monitoring of unnecessary downlink control channels using a large bandwidth of 100 MHz may be very inefficient in terms of power consumption. To reduce the power consumption of the terminal, the base station may set a bandwidth portion with a relatively small bandwidth, such as 20 MHz, for the terminal. In a situation where there is no traffic, the terminal can perform monitoring operations in the 20 MHz bandwidth portion, and when data is generated, it can transmit and receive data using the 100 MHz bandwidth portion according to the instructions of the base station.

[0114] In the method for configuring the above bandwidth portion, terminals prior to RRC connection (Connected) can receive configuration information for the Initial Bandwidth Part (Initial BWP) through the MIB during the initial connection phase. More specifically, the terminal can receive a configuration of a control area (i.e., CORESET) for a downlink control channel through which a DCI scheduling a System Information Block (SIB) can be transmitted from the MIB of the Physical Broadcast Channel (PBCH). The bandwidth of the control area configured based on the MIB can be considered as the Initial Bandwidth Part, and through the configured Initial Bandwidth Part, the terminal can receive the Physical Downlink Shared Channel (PDSCH) through which the SIB is transmitted. In addition to the purpose of receiving the SIB, the Initial Bandwidth Part may also be utilized for paging or random access.

[0115] Next, downlink control information (DCI) in 5G systems will be explained in detail.

[0116] In a 5G system, scheduling information for uplink data (or physical uplink shared channel (PUSCH)) or scheduling information for downlink data (or physical downlink shared channel (PDSCH)) can be transmitted from a base station to a terminal via DCI. The terminal can monitor the fallback DCI format and the non-fallback DCI format for PUSCH or PDSCH. The fallback DCI format may consist of fixed fields predefined between the base station and the terminal, and the non-fallback DCI format may include configurable fields.

[0117] DCI can be transmitted through the physical downlink control channel (PDCCH) after undergoing channel coding and modulation processes. A cyclic redundancy check (CRC) is attached to the DCI message payload, and the CRC can be scrambled with the terminal's identity identifier (e.g., radio network temporary identifier, RNTI). Different RNTIs may be used depending on the purpose of the DCI message, such as UE-specific data transmission, power control commands, or random access responses. In other words, the RNTI may not be transmitted explicitly but may be included in the CRC calculation process. Upon receiving a DCI message transmitted via the PDCCH, the terminal checks the CRC using the assigned RNTI; if the CRC check result is correct, the terminal knows that the message has been transmitted to it.

[0118] For example, a DCI scheduling a PDSCH for system information can be scrambled to SI-RNTI. For example, a DCI scheduling a PDSCH for a RAR message can be scrambled to RA-RNTI. For example, a DCI scheduling a PDSCH for a paging message can be scrambled to P-RNTI. A DCI notifying a SFI (slot format indicator) can be scrambled to SFI-RNTI. A DCI notifying a TPC (transmit power control) can be scrambled to TPC-RNTI. For example, a DCI scheduling a terminal-specific PDSCH or PUSCH can be scrambled to C-RNTI (cell RNTI).

[0119] A base station may operate by applying a predetermined DCI format to a terminal to be scheduled, depending on whether the DCI is for scheduling information for downlink data (downlink assignment), scheduling information for uplink data (uplink grant), and / or for DCI used for purposes other than data scheduling, such as power control.

[0120] The base station can transmit downlink data to the terminal via the Physical Downlink Shared Channel (PDSCH), which is a physical channel for downlink data transmission. Scheduling information, such as specific mapping locations in the time and frequency domains of the PDSCH, modulation schemes, HARQ-related control information, and power control information, can be provided by the base station to the terminal through the DCI related to downlink data scheduling information among the DCIs transmitted via the PDSCH.

[0121] The terminal can transmit uplink data to the base station via the physical uplink shared channel (PUSCH), which is a physical channel for uplink data transmission. Scheduling information, such as specific mapping locations in the time and frequency domains of the PUSCH, modulation schemes, HARQ-related control information, and power control information, can be provided by the base station to the terminal through the DCI related to uplink data scheduling information among the DCIs transmitted via the PDCCH.

[0122] The time-frequency resource to which the PDCCH is mapped is called the control resource set (CORESET). In the frequency domain, the CORESET can be set to all or part of the frequency resources within the bandwidth supported by the terminal. In the time domain, it can be set to one or more OFDM symbols, which can be defined as the CORESET duration. The base station can set one or more CORESETs to the terminal through higher-layer signaling (e.g., System Information, Master Information Block (MIB), Radio Resource Control (RRC) signaling). Setting the CORESET to the terminal may mean providing information such as the CORESET identifier, the frequency location of the CORESET, and the symbol length of the CORESET. The information provided by the base station to the terminal to set the CORESET may include at least some of the information included in [Table 5].

[0123]

[0124]

[0125]

[0126] CORESET in the frequency domain It can be composed of RBs, and in the time domain ∈ It can be composed of {1,2,3} symbols. A PDCCH can be composed of one or more Control Channel Elements (CCEs). One CCE can be composed of six Resource Element Groups (REGs), and a REG can be defined as one RB during one OFDM symbol. Within a CORESET, REGs can be indexed in Time-First order starting with REG index 0, beginning with the first OFDM symbol of the CORESET, the lowest RB.

[0127] Interleaved and non-interleaved methods may be supported as transmission methods for PDCCH. The base station may configure the terminal to perform interleaved or non-interleaved transmission for each CORESET through upper-layer signaling. Interleaving may be performed on a REG bundle basis. A REG bundle may be defined as a set of one or more REGs. Based on the interleaved or non-interleaved transmission configuration received from the base station, the terminal may determine the CCE-to-REG mapping method in the corresponding CORESET in the manner shown in [Table 6] below.

[0128]

[0129] The base station can inform the terminal of configuration information, such as which symbol the PDCCH is mapped to within the slot and the transmission period, through signaling.

[0130] The search space of a PDCCH is described as follows. The number of CCEs required to transmit a PDCCH can be 1, 2, 4, 8, or 16 depending on the Aggregation Level (AL), and different numbers of CCEs can be used for link adaptation of the downlink control channel. For example, when AL=L, one downlink control channel can be transmitted through L CCEs. The terminal performs blind decoding to detect signals without knowing information about the downlink control channel; to this end, a search space representing a set of CCEs can be defined. The search space is a set of downlink control channel candidates consisting of CCEs that the terminal must attempt to decode at a given aggregation level. Since there are various aggregation levels that form a group of 1, 2, 4, 8, or 16 CCEs, the terminal may have multiple search spaces. A Search Space Set can be defined as a set of search spaces at all established aggregation levels.

[0131] Search spaces can be classified into Common Search Spaces (CSS) and UE-specific Search Spaces (USS). A certain group of terminals or all terminals may monitor the Common Search Space of the PDCCH to receive cell-common control information, such as dynamic scheduling or paging messages for System Information Blocks (SIBs). For example, a terminal may receive scheduling allocation information for the PDSCH for receiving System Information by monitoring the Common Search Space of the PDCCH. In the case of the Common Search Space, since a certain group of terminals or all terminals must receive the PDCCH, it may be defined as a pre-agreed set of CCEs. Scheduling allocation information for the UE-specific PDSCH or PUSCH may be received by the terminal by examining the UE-specific Search Space of the PDCCH. The UE-specific Search Space may be defined specifically as a function of the terminal's ID (Identity) and various system parameters.

[0132] The base station may configure configuration information for the search space of the PDCCH to the terminal through upper-layer signaling (e.g., SIB, MIB, RRC signaling). For example, the base station may configure the number of PDCCH candidates at each aggregation level L, the monitoring period for the search space, the occasion for monitoring in slot-symbol units for the search space, the search space type (common search space or terminal-specific search space), the combination of DCI format and RNTI to be monitored in the search space, the CORESET index to be monitored in the search space, etc., to the terminal. For example, parameters for the search space for the PDCCH may include at least one of the information shown in [Table 7] below.

[0133]

[0134]

[0135]

[0136]

[0137]

[0138]

[0139] According to the configuration information, the base station may set one or more sets of search spaces for the terminal. According to one embodiment, the base station may set search space set 1 and search space set 2 for the terminal. In search space set 1, the terminal may be configured to monitor DCI format A scrambled with X-RNTI in a common search space, and in search space set 2, the terminal may be configured to monitor DCI format B scrambled with Y-RNTI in a terminal-specific search space.

[0140] According to the configuration information, one or more sets of search spaces may exist in a common search space or a terminal-specific search space. For example, Search Space Set #1 and Search Space Set #2 may be configured as a common search space, and Search Space Set #3 and Search Space Set #4 may be configured as a terminal-specific search space.

[0141] In a common search space, the terminal may monitor at least one of the following combinations of DCI format and RNTI. However, the scope of the present invention is not limited to the following examples.

[0142] - DCI format 0_0 / 1_0 with CRC scrambled by C-RNTI, CS-RNTI, SP-CSI-RNTI, RA-RNTI, TC-RNTI, P-RNTI, SI-RNTI

[0143] - DCI format 2_0 with CRC scrambled by SFI-RNTI

[0144] - DCI format 2_1 with CRC scrambled by INT-RNTI

[0145] - DCI format 2_2 with CRC scrambled by TPC-PUSCH-RNTI, TPC-PUCCH-RNTI

[0146] - DCI format 2_3 with CRC scrambled by TPC-SRS-RNTI

[0147] In a terminal-specific search space, the terminal may monitor at least one of the following combinations of DCI format and RNTI. However, the scope of the present invention is not limited to the following examples.

[0148] - DCI format 0_0 / 1_0 with CRC scrambled by C-RNTI, CS-RNTI, TC-RNTI

[0149] - DCI format 1_0 / 1_1 with CRC scrambled by C-RNTI, CS-RNTI, TC-RNTI

[0150] RNTIs may follow at least one of the following definitions and uses.

[0151] C-RNTI (Cell RNTI): Used for terminal-specific PDSCH or PUSCH scheduling

[0152] TC-RNTI (Temporary Cell RNTI): Used for terminal-specific PDSCH scheduling

[0153] CS-RNTI (Configured Scheduling RNTI): Used for semi-static terminal-specific PDSCH scheduling.

[0154] RA-RNTI (Random Access RNTI): Used for PDSCH scheduling during the random access phase.

[0155] P-RNTI (Paging RNTI): Used for PDSCH scheduling where paging is transmitted.

[0156] SI-RNTI (System Information RNTI): Used for PDSCH scheduling where system information is transmitted.

[0157] INT-RNTI (Interruption RNTI): Used to indicate whether PDSCH has been punctured.

[0158] TPC-PUSCH-RNTI (Transmit Power Control for PUSCH RNTI): Used to instruct power control commands to the PUSCH

[0159] TPC-PUCCH-RNTI (Transmit Power Control for PUCCH RNTI): Used to instruct power control commands to the PUCCH

[0160] TPC-SRS-RNTI (Transmit Power Control for SRS RNTI): Used to instruct power regulation commands to the SRS

[0161] The DCI formats described above may follow the definitions in [Table 8] below.

[0162]

[0163] The search space of aggregation level L in CORESET p and search space set s can be expressed as [Equation 1] below.

[0164]

[0165] - L: Lamination Level

[0166] - n CI : Carrier Index

[0167] - N CCE,p : Total number of CCEs existing in control resource set p

[0168] - n μ s,f : Slot Index

[0169] - M (L) p,s,max : Number of PDCCH candidates at assembly level L

[0170] - m snCI = 0, ..., M (L) p,s,max -1: PDCCH candidate index of aggregation level L

[0171] - i = 0, ..., L-1

[0172] -

[0173] - n RNTI : Terminal identifier

[0174] The value may be 0 for the common search space.

[0175] In the case of a terminal-specific search space, the value may correspond to a value that changes according to the terminal's ID (C-RNTI or the ID set by the base station for the terminal) and the time index.

[0176] The following describes in detail how a terminal measures channel conditions in a 5G communication system and reports them to a base station.

[0177] Channel state information (CSI) may include at least one of the following information.

[0178] - Channel Quality Indicator (CQI): CQI index indication information consisting of a modulation scheme and coding rate that satisfy the predefined minimum receive error rate of PDSCH.

[0179] - Precoding Matrix Indicator (PMI): Precoding matrix indicator information selected by the terminal

[0180] - CRI (CSI-RS resource indicator): CSI-RS information measured by the terminal

[0181] - RI (Rank Indicator): Rank indicator information selected by the terminal

[0182] - LI (Layer indicator): Indicator information for the best layer among the precoding matrices reported by the terminal

[0183] - SSBRI (SS / PBCH block resource indicator): SSB information measured by the terminal

[0184] - L1-RSRP (Reference Signal Received Power): L1 RSRP information measured by the terminal

[0185] The base station can control at least one of the time and frequency resources for the aforementioned CSI measurement and reporting of the terminal.

[0186] For CSI measurement and reporting operations, 'Aperiodic', 'Semi-Persistent', and 'Periodic' methods are supported, and the base station can configure which method to use for the terminal via signaling. Semi-persistent CSI reporting methods may support 'Semi-PersistentOnPUCCH' and 'Semi-PersistentOnPUSCH'. In the case of periodic or semi-persistent CSI reporting methods, the terminal can receive the PUCCH or PUSCH resources to transmit the CSI from the base station via upper-layer signaling. The period and slot offset of the PUCCH or PUSCH resources to transmit the CSI can be provided by the subcarrier interval setting of the uplink (UL) bandwidth part configured for CSI reporting transmission. In the case of a non-periodic CSI reporting method, the terminal can receive a PUSCH resource to transmit the CSI from the base station via L1 signaling (the aforementioned DCI format 0_1) through scheduling.

[0187] Non-periodic CSI reporting by the terminal can utilize PUSCH, and periodic CSI reporting can utilize PUCCH. Additionally, semi-permanent CSI reporting can be performed using PUSCH when triggered or activated by DCI, and using PUCCH after being activated by the MAC control element (MAC CE).

[0188] Non-periodic CSI reporting can be triggered by the "CSI request" field of the aforementioned DCI format 0_1, which corresponds to the scheduling DCI for PUSCH.

[0189] As a measure to support ultra-high-speed data services, 5G systems can support signal transmission and reception with ultra-wide bandwidths of tens to hundreds of MHz or several GHz. The above ultra-wide bandwidth signal transmission and reception can be supported through a single component carrier (CC) or through Carrier Aggregation (CA) technology that combines multiple component carriers. Carrier aggregation technology enables ultra-high-speed data services by combining individual component carriers with relatively small bandwidths to increase the total frequency bandwidth when a mobile operator has not secured a frequency bandwidth sufficient for providing ultra-high-speed data services through a single component carrier.

[0190] As mentioned above, the frequency bands utilized by 5G systems range from hundreds of MHz to tens of GHz.

[0191] FIG. 5 is a diagram showing the interrelationship between frequency bands and coverage according to one embodiment of the present disclosure.

[0192] Referring to FIG. 5, the interrelationships of frequency, coverage, and bandwidth are illustrated. FIG. 5 illustrates an example of frequency bands including a low band (501), a mid band (502), a high band (503), and an ultra-high band (504). Generally, the lower the frequency band, the greater the coverage due to relatively lower path loss, while the higher the frequency band, the smaller the coverage due to relatively higher path loss. In low frequency bands, frequencies available for mobile communication are fragmented, resulting in small bandwidth, whereas high frequency bands are relatively easy to secure wide bandwidth frequencies, making them suitable for ultra-high-speed data services. As mobile communication systems evolve, efforts are being made to discover and utilize new frequency bands. For example, the next-generation mobile communication system, 6G (6 th In generation mobile communication systems, the 7 to 15 GHz band, called the upper midband, is being considered as one of the candidate frequencies.

[0193] Generally, mobile carriers can secure multiple frequency bands to provide mobile communication services to users. For example, a mobile carrier can operate a combined LTE and 5G system by combining existing frequency bands for LTE systems with newly secured frequency bands for 5G systems. As another example, a mobile carrier can secure frequency bands for 5G systems across multiple bands and then combine the frequencies from those bands to provide mobile communication services through 5G CA. Similarly, a 6G mobile communication system can provide mobile communication services through 6G CA by combining 6G frequencies with existing 4G or 5G frequencies, or by combining 6G frequencies with each other.

[0194] As mentioned above, since characteristics such as coverage and bandwidth vary depending on the frequency band, there is a growing trend toward mobile communication services that combine multiple frequency bands rather than those relying on a single frequency band.

[0195] As another measure to support ultra-high-speed data services, data rates can be increased through spatial multiplexing using multiple transmitting and receiving antennas. Generally, the number of required power amplifiers (PAs) increases in proportion to the number of transmitting antennas equipped in a base station or terminal. The maximum output of base stations and terminals depends on the characteristics of the power amplifiers, and generally, the maximum output of a base station varies depending on the cell size it covers. Maximum output is usually expressed in dBm units. The maximum output of a terminal is typically 23 dBm or 26 dBm.

[0196] As an example of a commercial 5G base station, it is equipped with 64 transmitting antennas and a corresponding 64 power amplifiers in the 3.5GHz frequency band and can operate at a bandwidth of 100MHz. Consequently, the energy consumption of the base station increases in proportion to the output of the power amplifiers and their operating time. Compared to LTE base stations, 5G base stations are characterized by a relatively higher operating frequency band, requiring a wider bandwidth and a larger number of transmitting antennas. While this characteristic effectively increases data rates, it incurs the cost of higher base station energy consumption. Therefore, the more base stations that constitute a mobile communication network, the greater the energy consumption of the entire network becomes in proportion to them.

[0197] As mentioned above, the energy consumption of a base station is largely determined by the operation of the power amplifier. Since the power amplifier is involved in the base station's transmission operation, the base station's downlink (DL) transmission operation is highly correlated with the base station's energy consumption. Relatively speaking, the base station's uplink (UL) reception operation accounts for a small portion of the base station's energy consumption. The physical channel and physical signal transmitted by the base station via the downlink are as follows.

[0198] - PDSCH (Physical Downlink Shared Channel): A downlink data channel containing data to be transmitted to one or more terminals.

[0199] - PDCCH (Physical Downlink Control Channel): A downlink control channel containing scheduling information for PDSCH and PUSCH (Physical Uplink Control Channel). Alternatively, PDCCH alone can transmit control information such as slot formats and power control commands without the PDSCH or PUSCH to be scheduled. The scheduling information includes resource information mapped to the PDSCH or PUSCH, HARQ-related information, power control information, etc.

[0200] - PBCH (Physical Broadcast Channel): A downlink broadcast channel that provides the MIB (Master Information Block), which is essential system information required for the transmission and reception of the terminal's data and control channels.

[0201] - PSS (Primary Synchronization Signal): A signal that serves as the reference for DL ​​time / frequency synchronization and provides some cell ID information.

[0202] - SSS (Secondary Synchronization Signal): A signal that serves as the reference for DL ​​time and / or frequency (hereinafter time / frequency) synchronization and provides the cell ID and some other information.

[0203] - DM-RS (Demodulation Reference Signal): A reference signal for terminal channel estimation for each of PDSCH, PDCCH, and PBCH.

[0204] - CSI-RS (Channel-state Information Reference Signal): A downlink signal that serves as a reference for measuring the downlink channel state of a terminal.

[0205] - PT-RS (Phase-tracking Reference Signal): Downlink signal for phase tracking

[0206] From the perspective of base station energy conservation, stopping downlink transmission operations can enhance energy savings by halting power amplifier operation. Additional energy savings are possible as the operation of other base station devices, such as baseband units, is also reduced, in addition to the power amplifiers. Similarly, even though uplink reception operations account for a relatively small portion of the base station's total energy consumption, suspending uplink reception can yield additional energy savings.

[0207] Various methods for saving base station energy will be explained below with reference to FIGS. 6, 7, 8, and 9.

[0208] FIG. 6 is a diagram showing an example of a base station energy saving method according to one embodiment of the present disclosure.

[0209] FIG. 7 is a drawing showing an example of a base station energy saving method according to one embodiment of the present disclosure.

[0210] FIG. 8 is a drawing showing an example of a base station energy saving method according to one embodiment of the present disclosure.

[0211] FIG. 9 is a drawing showing an example of a base station energy saving method according to one embodiment of the present disclosure.

[0212] - Base Station Energy Saving Method 1: The downlink transmission operation of a base station depends on the amount of downlink traffic. For example, if there is no data to be transmitted to a terminal via the downlink, the base station does not need to transmit PDSCH and PDCCH for scheduling PDSCH. Alternatively, if transmission can be temporarily deferred for reasons such as the data not being sensitive to transmission delay, the base station may not transmit PDSCH or / and PDCCH. This is illustrated with reference to FIG. 6. FIG. 6 is a diagram illustrating an example of a base station energy saving method according to an embodiment of the present disclosure. Referring to FIG. 6, the amount of traffic that the base station intends to transmit is maintained at a high level above a threshold value during the T1 period (610) and the T3 period (630), and the amount of traffic that the base station intends to transmit is maintained at a low level below a threshold value during the T2 period (620). At this time, the base station can save energy by stopping or minimizing the operation of the base station power amplifier, base station RF device, baseband device, etc., by not transmitting the PDSCH (602) for data transmission and the PDCCH (601) for scheduling the PDSCH during the T2 period (620). In addition, if the traffic intended to be processed during the T2 period (620) is not sensitive to transmission delay, the base station can defer transmission during the T2 period (620) and perform delayed transmission during the T3 period (630). On the other hand, during the T1 period (610) and the T3 period (630), the PDSCH (602) for data transmission and the PDCCH (601) for scheduling the PDSCH are transmitted without restriction so that there is no hindrance to the provision of communication services by the base station.The base station state in the above T1 section (610) and T3 section (630) may be referred to as the base station normal state, and the base station state in the above T2 section (620) may be referred to as the base station energy saving state (ES state). The threshold value for the amount of traffic may be communicated to the base station by a higher entity governing the base station operation through signaling, or the base station may determine it on its own.

[0213] - Base Station Energy Saving Method 2: Physical channels and physical signals such as PSS, SSS, PBCH, and CSI-RS are characterized by being transmitted repeatedly at a predetermined period, regardless of data transmission to the terminal. Therefore, even if the terminal does not receive data, it can continuously update downlink time / frequency synchronization, downlink channel status, radio link quality, etc. That is, PSS, SSS, PBCH, and CSI-RS are necessarily transmitted through the downlink regardless of downlink data traffic, thereby causing base station energy consumption. Therefore, base station energy can be saved by controlling the transmission of signals unrelated to (or with low relevance to) data traffic to occur less frequently. This is explained through an example with reference to FIG. 7. FIG. 7 is a diagram illustrating an example of a base station energy saving method according to an embodiment of the present disclosure. Referring to FIG. 7, in the T1 (710) and T3 (730) sections, which are the base station normal state, the base station can transmit periodic signals (703), such as PSS, SSS, PBCH, or CSI-RS, with a predefined transmission period 1 (701). On the other hand, in the T2 (720) section, which is the base station power saving state, the base station can save base station energy by transmitting periodic signals (704) with a transmission period 2 (702), which is relatively longer than the transmission period 1 (701), thereby intermittently performing or minimizing the operation of base station power amplifiers, base station RF devices, baseband devices, etc.

[0214] - Base Station Energy Saving Method 3: A base station can reduce energy consumption by switching off at least a portion of the base station's antennas or power amplifiers. For example, this is illustrated with reference to FIG. 8. FIG. 8 is a diagram illustrating an example of a base station energy saving method according to an embodiment of the present disclosure. Referring to FIG. 8, in the base station normal state T1 interval (810) and T3 interval (830), the base station transmits a downlink signal based on a predefined transmit power 1 or M1 transmit antennas (801). On the other hand, in the base station power saving state T2 interval (820), the base station can reduce energy consumption by transmitting a downlink signal based on a transmit power 2 (802) that is smaller than the transmit power 1 (801) or M2 transmit antennas (802) that are relatively smaller than the M1 transmit antennas (801), thereby stopping or minimizing the operation of the base station power amplifier, base station RF device, baseband device, etc.

[0215] - Base station energy saving method 4: In an environment where carrier bundles are applied, when the amount of traffic that the base station intends to transmit is kept below a threshold value, the base station transmits the traffic through a predetermined configuration carrier and switches off the remaining configuration carriers, thereby stopping or minimizing the operation of the power amplifier, RF device, baseband device, etc. of the switched-off configuration carriers, and saving base station energy. For example, this is explained through FIG. 9. FIG. 9 is a diagram illustrating an example of a base station energy saving method according to an embodiment of the present disclosure. Referring to FIG. 9, configuration carrier 1 (carrier 1) (901) and configuration carrier 2 (carrier 2) (902) are operated as a carrier bundle. In the example of FIG. 9, the amount of traffic that the base station intends to transmit during the T1 period (910) and the T3 period (930) may be maintained at a level higher than a threshold value, and the amount of traffic that the base station intends to transmit during the T2 period (920) may be maintained at a level lower than a threshold value. In this case, to save energy, the base station may operate the base station in a power saving state during the T2 period (920), switch off configuration carrier 2 (902), and have configuration carrier 1 (901) handle the traffic processing during the T2 period (920). On the other hand, during the base station normal state in the T1 period (910) and the T3 period (930), both configuration carrier 1 (901) and configuration carrier 2 (902) are activated to quickly process a relatively large amount of traffic.

[0216] The above-described base station energy saving methods 1, 2, 3, and 4 can be applied and operated individually, or combined and operated together.

[0217] In the above description, the base station state is described in two stages: the base station general state and the base station power saving state; however, the base station power saving state can be distinguished and described in more detail. For example, the base station power saving state can be linked with the base station energy saving method, so that base station power saving state 1 represents the base station power saving state according to the base station energy saving method 1, base station power saving state 2 represents the base station power saving state according to the base station energy saving method 2, base station power saving state 3 represents the base station power saving state according to the base station energy saving method 3, and base station power saving state 4 represents the base station power saving state according to the base station energy saving method 4.

[0218] The operation of the system proposed in the present disclosure is explained below through specific embodiments.

[0219] The main gist of the present invention is that the base station transmits a discovery signal to facilitate base station identification by the terminal, even when the base station is in a base station power saving state. The discovery signal can be transmitted by the base station to the terminal to inform it of the presence of the base station or cell. Similar to a synchronization signal, the discovery signal can be a sequence-based signal and can be composed of a combination of one or more sequences. The discovery signal can be transmitted periodically, and by transmitting it with a relatively long transmission periodicity, a base station power saving effect can be expected during the period when the discovery signal is not transmitted. Upon detecting the discovery signal, the terminal can recognize that a cell transmitting the discovery signal exists in the vicinity of the terminal. Accordingly, the terminal can transmit a terminal request signal requesting the base station to transmit a synchronization signal, and the base station can transmit a synchronization signal to the terminal in response to the terminal request. The present invention refers to the synchronization signal responding to such a terminal request as an on-demand SSB. Through the on-demand SSB, the terminal can rapidly acquire time and frequency synchronization. By repeatedly transmitting the on-demand SSB, the base station can improve the synchronization accuracy of the terminal, shorten the synchronization completion time of the terminal, or improve the coverage of the on-demand SSB. The repeated transmission of the on-demand SSB may be repeated a predetermined number of times (N) or repeated transmission for a predetermined time interval (W). The values ​​N and W may be pre-agreed values ​​or may be set by the base station for the terminal. The on-demand SSB may be composed of a combination of at least some of the PSS, SSS, and PBCH.The base station can provide seamless communication services to terminals within the cell by switching its state from a power-saving state to a normal state before and after the transmission of an on-demand SSB. In the normal state, the base station can transmit an SSB according to a predefined transmission cycle, independently of the transmission of the on-demand SSB. That is, since a separate terminal request for SSB transmission is not required, it can be free from errors in the transmission and reception of terminal request signals. A terminal that has successfully received the SSB can obtain cell-common transmission and reception control information from the base station's SIB. The terminal can transmit a random access preamble to initiate a random access procedure by referring to the control information in the SIB.

[0220] The following initial access procedure may be understood to include at least one of the discovery signal between the terminal and the base station, the terminal request signal, the on-demand SSB, the transmission and reception of SSB and system information, and the random access procedure between the terminal and the base station. Subsequently, the terminal may request an attach to the network, and after the attach procedure is completed, may transmit and receive packets (or data) through the network.

[0221] The following is a description of each specific embodiment. The present invention may include a plurality of embodiments, each of which is distinguished for convenience to explain the implementation according to the present disclosure and may be implemented independently; however, as long as they are not mutually exclusive, all or part of the plurality of embodiments may be selectively combined and implemented. Such combinations include various variations and modifications of the present invention and may be made in various ways depending on technical needs or application environments. Even if the plurality of embodiments use different approaches to achieve the purpose of the invention, they may be used simultaneously or complementarily as long as the embodiments of the present invention are not technically mutually exclusive. Such combinations may be varied depending on technical requirements or specific application cases, and the present invention may encompass various embodiments including such variations and combinations. Although the name of a 5G system is used to describe the embodiments of the present disclosure, this is merely an example and can be understood as a message that includes information or performs the same role as described below.

[0222] FIG. 10 is a diagram illustrating a method for repetitive transmission of an on-demand SSB according to one embodiment of the present disclosure.

[0223] The embodiment illustrated in FIG. 10 explains a method for the repeated transmission of an on-demand SSB in the initial connection procedure of the terminal described above. The embodiment illustrated in FIG. 10 explains that the basic unit in which the on-demand SSB is repeatedly transmitted is a half frame.

[0224] Referring to FIG. 10, for example, one frame (1010, 1011) may each be composed of two half frames (1040), and each half frame (1040) may be composed of 10 slots (1090).

[0225] To ensure sufficient coverage with limited base station transmission power, beamforming technology can be applied to increase the propagation range by concentrating the radiated energy of the on-demand SSB in a specific direction. A signal to which beamforming technology is applied has a relatively narrower beam width, and since the radiated energy is concentrated within the narrowed beam width, the propagation range can be increased. Therefore, to transmit the on-demand SSB in all directions centered on the base station, a beam sweeping operation may be required to transmit the on-demand SSB by changing the beam direction multiple times. In the case of FIG. 10, a total of L = 8 on-demand SSBs (1020) are mapped within a half-frame (1040) and transmitted via beam sweeping. The on-demand SSBs (1020) are mapped to a designated slot and symbol position within the half-frame. In the example of FIG. 10, on-demand SSB#1 and on-demand SSB#2, to which beam sweeping is applied, are mapped to the first slot within the half-frame (1040); on-demand SSB#3 and on-demand SSB#4, to which beam sweeping is applied, are mapped to the second slot within the half-frame (1040); on-demand SSB#5 and on-demand SSB#6, to which beam sweeping is applied, are mapped to the third slot within the half-frame (1040); and on-demand SSB#7 and on-demand SSB#8, to which beam sweeping is applied, are mapped to the fourth slot within the half-frame (1040). In the notation of the above On-demand SSB#k, the index k represents the beam direction, k ∈ {1, ..., L}, and it is assumed that if the index is different, the beam direction is different. Below, a method for the repeated transmission of an on-demand SSB is described to further expand the coverage of the on-demand SSB mapped within a half-frame as described above.

[0226] - Case 1 (1050): This is the case where L on-demand SSBs mapped within the above half-frame are transmitted once (N = 1). That is, this is the case where repeated transmission of on-demand SSBs is not applied. In the example of FIG. 10, it shows that L on-demand SSBs (1051) are mapped and transmitted during the time interval T1 (1001).

[0227] - Case 2 (1060): This is a case where L on-demand SSBs mapped within the above half-frame are transmitted repeatedly twice (N = 2). In the example of FIG. 10, the first L on-demand SSBs (1061) are mapped to the time interval T1 (1001) and transmitted, and the second L on-demand SSBs (1062) are mapped to the time interval T2 (1002) and transmitted repeatedly. The terminal can improve reception performance for on-demand SSBs by combining the L on-demand SSBs repeatedly received. At this time, the terminal can perform combining processing for on-demand SSBs of the same beam index. For example, reception performance can be improved by combining on-demand SSB#1 from the first L on-demand SSBs (1061) and on-demand SSB#1 from the second L on-demand SSBs (1062).

[0228] - Case 3 (1070): This is a case where L on-demand SSBs mapped within the above half-frame are transmitted repeatedly three times (N = 3). In the example of FIG. 10, the first L on-demand SSBs (1071) are mapped to the time interval T1 (1001) and transmitted, the second L on-demand SSBs (1072) are mapped to the time interval T2 (1002) and transmitted, and the third L on-demand SSBs (1073) are mapped to the time interval T3 (1003) and transmitted repeatedly. The terminal can combine the L on-demand SSBs repeatedly received to improve the reception performance for the on-demand SSBs. At this time, the terminal can perform combination processing for on-demand SSBs of the same beam index.

[0229] - Case 4 (1080): This is a case where L on-demand SSBs mapped within the above half-frame are transmitted repeatedly 4 times (N = 4). In the example of FIG. 10, the first L on-demand SSBs (1081) are mapped and transmitted during the time interval T1 (1001), the second L on-demand SSBs (1082) are mapped and transmitted during the time interval T2 (1002), the third L on-demand SSBs (1083) are mapped and transmitted during the time interval T3 (1003), and the fourth L on-demand SSBs (1084) are mapped and transmitted during the time interval T4 (1004). The terminal can combine the L on-demand SSBs repeatedly received to improve the reception performance for the on-demand SSBs. At this time, the terminal can perform combination processing for on-demand SSBs of the same beam index.

[0230] The number of transmissions N of the above-mentioned on-demand SSB can be determined by at least one of the following methods.

[0231] - Method 1: A value agreed upon in advance between the terminal and the base station can be applied.

[0232] - Method 2: The base station can notify the terminal through signaling. For example, the signaling can be included as control information in the discovery signal and transmitted by the base station to the terminal.

[0233] - Method 3: The terminal can notify the base station through signaling. For example, the signaling can be included as control information in the terminal request signal and transmitted by the terminal to the base station.

[0234] - Method 4: Both Method 2 and Method 3 above may be applied. For example, if a terminal informs the base station of a preferred N value through signaling, the base station may refer to this to make a final decision on the N value and inform the terminal through signaling.

[0235] - Method 5: The base station determines the value of N but does not notify the terminal via separate signaling. Therefore, the terminal can process the repeatedly transmitted on-demand SSBs through blind detection. Thus, the terminal may require processing capability for up to N hypotheses for the number of transmissions of on-demand SSBs.

[0236] FIG. 11 is a diagram illustrating a method for repetitive transmission of an on-demand SSB according to one embodiment of the present disclosure.

[0237] The embodiment illustrated in FIG. 11 describes another iterative transmission method of an on-demand SSB in the initial connection procedure of the terminal described above.

[0238] The embodiment illustrated in FIG. 11 explains that the basic unit of repeated transmission of an on-demand SSB is a frame.

[0239] Referring to FIG. 11, for example, one frame (1110, 1111, 1112, 1113) is each composed of two half frames (1140), and each half frame (1140) can be composed of 10 slots (1190).

[0240] In the case of FIG. 11, a total of L = 8 on-demand SSBs (1120) are mapped within a half-frame (1140) and transmitted via beam sweeping. The on-demand SSBs (1120) can be mapped to designated slots and symbol positions within the half-frame (1140). Below, a method for the repeated transmission of on-demand SSBs is described to further expand the coverage of the on-demand SSBs mapped within the half-frame (1140) as described above.

[0241] - Case 1 (1150): This is the case where L on-demand SSBs mapped within the above half-frame are transmitted once (N = 1). That is, this is the case where repeated transmission of on-demand SSBs is not applied. In the example of FIG. 11, it shows that L on-demand SSBs (1151) are mapped to and transmitted in the time interval T1 (1101). The time interval T1 (1101) may be the time interval corresponding to the first half-frame constituting the k-th frame (1110).

[0242] - Case 2 (1160): This is a case where L on-demand SSBs mapped within the above half-frame are transmitted repeatedly twice (N = 2). In the example of FIG. 11, it indicates that the first L on-demand SSBs (1161) are mapped to the time interval T1 (1101) and transmitted, and the second L on-demand SSBs (1162) are mapped to the time interval T3 (1103) and transmitted repeatedly. The time interval T1 (1101) may be the time interval corresponding to the first half-frame constituting the k-th frame (1110), and the time interval T3 (1103) may be the time interval corresponding to the first half-frame constituting the k+1-th frame (1111). That is, it indicates that the L on-demand SSBs are transmitted repeatedly on a frame-by-frame basis. The terminal can combine the L on-demand SSBs received repeatedly to improve the reception performance for the on-demand SSBs. At this time, the terminal can perform combined processing for on-demand SSBs of the same beam index. For example, reception performance can be improved by combining on-demand SSB#1 among the first L on-demand SSBs (1161) and on-demand SSB#1 among the second L on-demand SSBs (1162).

[0243] - Case 3 (1170): This is a case where L on-demand SSBs mapped within the above half-frame are transmitted repeatedly three times (N = 3). In the example of FIG. 11, it shows that the first L on-demand SSBs (1171) are mapped and transmitted during the time interval T1 (1101), the second L on-demand SSBs (1172) are mapped and transmitted during the time interval T3 (1103), and the third L on-demand SSBs (1173) are mapped and transmitted during the time interval T5 (1105). The above T1 (1101) time interval may be a time interval corresponding to the first half-frame constituting the k-th frame (1110), the above T3 (1103) time interval may be a time interval corresponding to the first half-frame constituting the k+1-th frame (1111), and the above T5 (1105) time interval may be a time interval corresponding to the first half-frame constituting the k+2-th frame (1112). The terminal can improve reception performance for on-demand SSBs by combining the L on-demand SSBs repeatedly received. At this time, the terminal can perform combination processing for on-demand SSBs of the same beam index.

[0244] - Case 4 (1180): This is a case where L on-demand SSBs mapped within the above half-frame are transmitted repeatedly 4 times (N = 4). In the example of FIG. 11, the first L on-demand SSBs (1181) are mapped and transmitted during the time interval T1 (1101), the second L on-demand SSBs (1182) are mapped and transmitted during the time interval T3 (1103), the third L on-demand SSBs (1183) are mapped and transmitted during the time interval T5 (1105), and the fourth L on-demand SSBs (1184) are mapped and transmitted during the time interval T7 (1107). The above T1 (1101) time interval may be a time interval corresponding to the first half-frame constituting the k-th frame (1110), the above T3 (1103) time interval may be a time interval corresponding to the first half-frame constituting the k+1-th frame (1111), the above T5 (1105) time interval may be a time interval corresponding to the first half-frame constituting the k+2-th frame (1112), and the above T7 (1107) time interval may be a time interval corresponding to the first half-frame constituting the k+3-th frame (1113). The terminal can improve reception performance for on-demand SSBs by combining the L on-demand SSBs repeatedly received. At this time, the terminal can perform combination processing for on-demand SSBs of the same beam index.

[0245] In the example of Figure 11 above, it was shown that an on-demand SSB that is repeatedly transmitted frame by frame is mapped to the first half-frame of each frame, but this is only one possible example. For instance, an on-demand SSB that is repeatedly transmitted frame by frame can be mapped to the second half-frame of each frame.

[0246] The number of transmissions N of the above-mentioned on-demand SSB can be determined by at least one of methods 1 to 6, as described in the embodiment associated with FIG. 10.

[0247] FIG. 12 is a diagram illustrating a method for repetitive transmission of an on-demand SSB according to one embodiment of the present disclosure.

[0248] The embodiment illustrated in FIG. 12 describes another iterative transmission method of an on-demand SSB in the initial connection procedure of the terminal described above.

[0249] The embodiment illustrated in FIG. 12 explains that the basic unit in which the On-demand SSB is repeatedly transmitted is a quarter frame.

[0250] Referring to FIG. 12, for example, one frame (1210, 1211) may each be composed of four quarter frames (1240), and each quarter frame (1240) may be composed of five slots (1290). The quarter frames (1240) correspond to one-quarter of the frame length and one-half of the half-frame length.

[0251] In the case of FIG. 12, a total of L = 8 on-demand SSBs (1220) are mapped within a 1 / 4 frame (1240) and transmitted via beam sweeping. The on-demand SSBs (1220) can be mapped to designated slots and symbol positions within the 1 / 4 frame (1240). Below, a method for the repeated transmission of on-demand SSBs is described to further extend the coverage of the on-demand SSBs mapped within the 1 / 4 frame (1240) as described above.

[0252] - Case 1 (1250): This is the case where L on-demand SSBs mapped within the above 1 / 4 frame are transmitted once (N = 1). That is, this is the case where repeated transmission of on-demand SSBs is not applied. In the example of FIG. 12, it indicates that L on-demand SSBs (1251) are mapped and transmitted during the time interval T1 (1201). The time interval T1 (1201) may be the time interval corresponding to the first 1 / 4 frame constituting the k-th frame (1110).

[0253] - Case 2 (1260): This is a case where L on-demand SSBs mapped within the above half-frame are transmitted repeatedly twice (N = 2). In the example of FIG. 12, it indicates that the first L on-demand SSBs (1261) are mapped to the time interval T1 (1201) and transmitted, and the second L on-demand SSBs (1262) are mapped to the time interval T2 (1202) and transmitted repeatedly. The time interval T1 (1201) may be the time interval corresponding to the first 1 / 4 frame constituting the k-th frame (1210), and the time interval T2 (1202) may be the time interval corresponding to the second 1 / 4 frame constituting the k-th frame (1210). That is, it indicates that the L on-demand SSBs are transmitted repeatedly in 1 / 4 frame units. The terminal can improve reception performance for on-demand SSBs by combining the L on-demand SSBs repeatedly received above. At this time, the terminal can perform combination processing for on-demand SSBs of the same beam index. For example, reception performance can be improved by combining on-demand SSB#1 among the first L on-demand SSBs (1261) and on-demand SSB#1 among the second L on-demand SSBs (1262).

[0254] - Case 3 (1270): This is a case where L on-demand SSBs mapped within the above half-frame are transmitted repeatedly three times (N = 3). In the example of FIG. 12, the first L on-demand SSBs (1271) are mapped and transmitted during the time interval T1 (1201), the second L on-demand SSBs (1272) are mapped and transmitted during the time interval T2 (1202), and the third L on-demand SSBs (1273) are mapped and transmitted during the time interval T3 (1203). The above T1 (1201) time interval may be a time interval corresponding to the first 1 / 4 frame constituting the k-th frame (1210), the above T2 (1202) time interval may be a time interval corresponding to the second half frame constituting the k-th frame (1210), and the above T3 (1203) time interval may be a time interval corresponding to the third half frame constituting the k-th frame (1210). The terminal can improve reception performance for on-demand SSBs by combining the L on-demand SSBs repeatedly received. At this time, the terminal can perform combination processing for on-demand SSBs of the same beam index.

[0255] - Case 4 (1280): This is a case where L on-demand SSBs mapped within the above half-frame are transmitted repeatedly 4 times (N = 4). In the example of FIG. 12, the first L on-demand SSBs (1281) are mapped and transmitted during the T1 (1201) time interval, the second L on-demand SSBs (1282) are mapped and transmitted during the T2 (1202) time interval, the third L on-demand SSBs (1283) are mapped and transmitted during the T3 (1203) time interval, and the fourth L on-demand SSBs (1284) are mapped and transmitted during the T4 (1204) time interval. The above T1 (1201) time interval may be a time interval corresponding to the first quarter frame constituting the k-th frame (1210), the above T2 (1202) time interval may be a time interval corresponding to the second quarter frame constituting the k-th frame (1210), the above T3 (1203) time interval may be a time interval corresponding to the third half frame constituting the k-th frame (1210), and the above T4 (1104) time interval may be a time interval corresponding to the fourth quarter frame constituting the k-th frame (1210). The terminal may combine the L on-demand SSBs repeatedly received to improve reception performance for on-demand SSBs. At this time, the terminal may perform combination processing for on-demand SSBs of the same beam index.

[0256] The number of transmissions N of the above-mentioned on-demand SSB can be determined by at least one of methods 1 to 6, as described in the embodiment associated with FIG. 10.

[0257] One embodiment of the present disclosure may include the interrelationship between an on-demand SSB and a random access preamble that are repeatedly transmitted during the initial connection procedure of the terminal described above, and the terminal and base station-related operations accordingly.

[0258] Referring to the example of N=2 in FIG. 10 above, the interrelationship between the on-demand SSB and the random access preamble that are repeatedly transmitted during the initial access procedure, and the operations related to the terminal and the base station accordingly, will be explained below. The terminal needs a method to determine a random access transmission occasion (random access transmission occasion, or RACH occasion, or PRACH occasion; RO) for executing a random access procedure by referring to the received on-demand SSB. The RO refers to radio resources, such as time and frequency, for the terminal to transmit the random access preamble. For example, the transmission reliability of the random access preamble can be increased by transmitting the random access preamble through an RO associated with the on-demand SSB that exhibits the best received signal quality among the on-demand SSBs received by the terminal. However, when the on-demand SSB is repeatedly transmitted N times, uncertainty may arise regarding which on-demand SSB the terminal should use as the basis for determining the RO. The fourth embodiment describes the following method regarding the interrelationship between an on-demand SSB and a random access preamble that are repeatedly transmitted.

[0259] - Method 1: A terminal receives an on-demand SSB that has been transmitted N times and, through combination processing, can obtain an on-demand SSB#k whose reception quality is higher than a predetermined threshold. Method 1 allows the terminal to determine, for the L on-demand SSBs that have been transmitted N times, that the RO associated with the first L on-demand SSBs received is a valid RO, and to transmit a random access preamble through the RO. For example, in the case where N = 2 in FIG. 10, the terminal determines that the RO associated with the L on-demand SSBs (1061) received during the time interval T1 (1001) is a valid RO, and among them, can transmit a random access preamble through the RO associated with the on-demand SSB#k determined by the terminal.

[0260] - Method 2: A terminal receives an on-demand SSB that has been transmitted N times and, through combination processing, can obtain an on-demand SSB#k whose reception quality is higher than a predetermined threshold. Method 2 allows the terminal to determine, for the L on-demand SSBs that have been transmitted N times, that the RO associated with the last received L on-demand SSBs is a valid RO, and to transmit a random access preamble through the RO. For example, in the case where N = 2 in FIG. 10, the terminal determines that the RO associated with the L on-demand SSBs (1062) received during the time interval T2 (1002) is a valid RO, and among them, can transmit a random access preamble through the RO associated with the on-demand SSB#k determined by the terminal.

[0261] - Method 3: A terminal can receive an on-demand SSB that has been transmitted N times and, through combined processing, obtain an on-demand SSB#k whose reception quality is higher than a predetermined threshold. Method 3 allows the terminal to determine that, for the L on-demand SSBs that have been transmitted N times, the ROs associated with the first and second received L on-demand SSBs are all valid ROs, and among them, transmit a random access preamble through one RO according to the terminal's selection. For example, in the case where N = 2 in FIG. 10, the terminal determines that the ROs associated with the L on-demand SSBs (1061) received in the time interval T1 (1001) and the ROs associated with the L on-demand SSBs (1062) received in the time interval T2 (1002) are all valid ROs, and among them, transmit a random access preamble through the RO associated with the on-demand SSB#k determined by the terminal. That is, the terminal can select either the RO associated with L on-demand SSBs (1061) received during the T1 (1001) time interval or the RO associated with L on-demand SSBs (1062) received during the T2 (1002) time interval according to a predetermined condition, and select a random access preamble based thereon. In this case, the base station can monitor both the RO associated with L on-demand SSBs (1061) transmitted during the T1 (1001) time interval and the RO associated with L on-demand SSBs (1062) transmitted during the T2 (1002) time interval to check whether a random access preamble is transmitted from the terminal.

[0262] - Method 4: The terminal may not use the on-demand SSB transmitted N times repeatedly to determine a valid RO, but may determine the RO associated with the periodically transmitted SSB, which is not based on the terminal request, as a valid RO and apply it to the transmission of a random access preamble. For example, after receiving the on-demand SSB transmitted N times repeatedly, the terminal may receive a periodically transmitted SSB (normal SSB), determine the RO associated with it based on the periodically transmitted SSB, and transmit a random access preamble.

[0263] Which of the above methods 1, 2, 3, and 4 to apply may be agreed upon in advance by the base station and the terminal, or the base station may inform the terminal through signaling.

[0264] FIG. 13 is a diagram showing the initial connection procedure of a terminal according to one embodiment of the present disclosure.

[0265] The embodiment illustrated in FIG. 13 explains the terminal and base station procedures when the on-demand SSB repetitive transmission method is applied in the initial connection procedure of the terminal described above.

[0266] Referring to FIG. 13, as described above, the discovery signal is transmitted with a relatively long transmission period, the SSB is transmitted with a relatively short transmission period, and the on-demand SSB is transmitted in response to a terminal request signal. In the example of FIG. 13, the transmission period of the discovery signal is P1 (1330), and the transmission period of the SSB is P2 (1340) (P1 > P2). For convenience of explanation, the candidate time interval in which the discovery signal can be transmitted is referred to as the discovery signal transmission occasion (1310), and the candidate time interval in which the SSB can be transmitted is referred to as the SSB transmission occasion (1320). In the example of FIG. 13, it is assumed that the base station is in a base station power saving state during phase 1 (1350), and subsequently, during phase 2 (1360), the base station is in a base station normal state. In the base station power saving state, the base station can achieve a base station power saving effect by omitting the periodically transmitted SSB transmission and transmitting discovery signals (1301, 1302) with a relatively long transmission period. Additionally, to respond quickly to a request from a terminal, an on-demand SSB (1304) can be transmitted according to a terminal request signal (UE request) (1303). Therefore, during phase 1 (1350), when the base station is in a power saving state, the terminal may attempt to detect the discovery signal at the discovery signal transmission occasion (1310) and not attempt to detect the SSB at the SSB transmission occasion (1320). Afterwards, the terminal can attempt to detect the SSB at the SSB transmission occasion (1320) during phase 2 (1360), which is the base station's normal state.

[0267] If the terminal succeeds in detecting a discovery signal (1302) transmitted within the discovery signal transmission occasion (1310) at time T1 (1390), the terminal can transmit a terminal request signal (1303) to the base station requesting the transmission of an on-demand SSB. The base station can then transmit an on-demand SSB (1304) to the terminal in accordance with the terminal request signal. The terminal can obtain a certain level of time and frequency synchronization from the received on-demand SSB (1304). The base station can repeatedly transmit the on-demand SSB to ensure sufficient coverage. In accordance with the terminal request signal, the base station can switch the base station state from the base station power saving state to the base station normal state to perform normal transmission and reception operations. The terminal can attempt to detect an SSB at every SSB transmission occasion (1320) during phase 2 (1360) when the base station has switched to the base station normal state. In the base station's normal state, the terminal can synchronize time and frequency with the SSB (1306, 1307, 1308, 1309) transmitted by the base station and obtain a cell identifier. Then, from the MIB obtained through the SSB, the terminal can obtain control information (e.g., time and frequency resource information of the PDCCH) related to the PDCCH that schedules the SIB to be received in the next step (hereinafter referred to as SIB PDCCH). Subsequently, the terminal can obtain the SIB by receiving the SIB PDCCH and the PDSCH scheduled by the SIB PDCCH (hereinafter referred to as SIB PDSCH). The SIB contains cell-common control information related to transmission and reception. The terminal can transmit a random access preamble by referring to the control information of the SIB. In some cases, the terminal can perform a random access procedure by transmitting a random access preamble for the reception of the on-demand SSB.

[0268] The example in FIG. 13 above illustrates a case where beam sweeping operation of the SSB in a multi-beam environment is not considered, but it can be generalized to operate even when beam sweeping is applied. For example, the SSB transmitted at each SSB transmission occasion (1320) can be replaced with L SSBs corresponding to L different beams. Similarly, the discovery signal transmitted at each discovery signal transmission occasion (1310) can be replaced with K discovery signals corresponding to K different beams (K ≤ L). And the on-demand SSB can also be replaced with M on-demand SSBs corresponding to M different beams (M ≤ L).

[0269] Although the names of 5G systems have been used to describe the embodiments of the present disclosure, the names described above, such as discovery signal, on-demand SSB, SSB, PDCCH, PDSCH, SIB, etc., are merely examples and can be understood as messages that include information or perform the same role as described above.

[0270] FIG. 14 is a diagram showing an example of an initial connection procedure of a terminal according to one embodiment of the present disclosure.

[0271] Referring to Fig. 14, in step 1401, the terminal may attempt to detect a discovery signal transmitted by the base station.

[0272] When the terminal successfully detects a discovery signal, the terminal recognizes that there is a cell around the terminal, and in step 1402, the terminal can transmit a terminal request signal to the base station to request the transmission of an on-demand SSB.

[0273] The terminal that transmitted the terminal request signal may attempt to receive the on-demand SSB in step 1403. As described above, the on-demand SSB may be transmitted repeatedly.

[0274] A terminal that has received an on-demand SSB may attempt to receive the SSB in step 1404. The terminal may perform downlink time and frequency synchronization from the SSB received from the base station and obtain a cell identifier (cell ID). In one embodiment, the SSB may include at least one of a synchronization signal and a PBCH. In one embodiment, the terminal may obtain an MIB, which is essential system information, in step 1404. In one embodiment, the terminal may receive a PBCH using the cell ID obtained from the synchronization signal and obtain an MIB, which is essential system information, from the PBCH. In one embodiment, the MIB may include at least one of CORESET information or PDCCH configuration information, which are time-frequency resources to which the PDCCH is mapped.

[0275] In step 1405, the terminal can monitor the SIB PDCCH by referring to the acquired PDCCH configuration information. The terminal can obtain system information (e.g., SIB) by receiving the SIB PDCCH from the scheduling information of the SIB PDCCH. The SIB includes cell-common transmission and reception control information, which may include, for example, random access control information, paging control information, and common control information for various physical channels.

[0276] In step 1406, the terminal may perform a random access procedure. Depending on the case, the terminal may perform the random access procedure by transmitting a random access preamble associated with the on-demand SSB received in step 1403.

[0277] The steps described above may be modified, omitted, changed in order, or undesired steps may be added to carry out the present invention.

[0278] FIG. 15 is a diagram showing an example of a base station procedure for supporting a terminal initial connection procedure according to one embodiment of the present disclosure.

[0279] Referring to Fig. 15, in step 1501, the base station can transmit a discovery signal to inform terminals within the cell coverage of the presence of the base station.

[0280] In step 1502, the base station may attempt to receive a terminal request signal transmitted by the terminal.

[0281] In step 1503, the base station that receives the terminal request signal may transmit an on-demand SSB to the terminal in response to the terminal request signal. As described above, the on-demand SSB may be transmitted repeatedly.

[0282] A base station that has transmitted an on-demand SSB can transmit an SSB in step 1504. In one embodiment, the SSB may include at least one of a synchronization signal and a PBCH.

[0283] In step 1505, the base station may transmit a SIB PDCCH and a SIB PDSCH to the terminal for transmitting the SIB. The SIB contains cell-common transmission and reception control information, which may include, for example, random access control information, paging control information, and common control information for various physical channels.

[0284] In step 1506, the base station may perform a random access procedure based on a terminal request. In some cases, the base station may perform the random access procedure by receiving a random access preamble associated with the on-demand SSB transmission of step 1503.

[0285] The steps described above may be modified, omitted, changed in order, or undesired steps may be added to carry out the present invention.

[0286] FIG. 16 is a drawing showing an example of a terminal transceiver in a wireless communication system according to an embodiment of the present disclosure. For convenience of explanation, devices not directly related to the present disclosure may be omitted from illustration and description.

[0287] Referring to FIG. 16, the terminal may be configured to include at least one of a transmitter (1604) composed of an uplink transmission processing block (1601), a multiplexer (1602), and a transmission RF block (1603), a receiver (1608) composed of a downlink reception processing block (1605), a demultiplexer (1606), and a reception RF block (1607), and a control unit (1609). The control unit (1609) can control each of the configuration blocks of the receiver (1608) for receiving a data channel or control channel transmitted by the base station as described above, and each of the configuration blocks of the transmitter (1604) for transmitting an uplink signal.

[0288] In the transmission unit (1604) of the terminal, the uplink transmission processing block (1601) can generate a signal to be transmitted by performing processes such as channel coding and modulation. The signal generated in the uplink transmission processing block (1601) can be multiplexed with other uplink signals by a multiplexer (1602), then processed by a transmission RF block (1603), and then transmitted to a base station.

[0289] The receiving unit (1608) of the terminal can demultiplex a signal received from a base station and distribute it to each downlink receiving processing block. The downlink receiving processing block (1605) can obtain control information or data transmitted by the base station by performing processes such as demodulation and channel decoding on the downlink signal of the base station. The receiving unit (1608) of the terminal can apply the output result of the downlink receiving processing block to the control unit (1609) to support the operation of the control unit (1609).

[0290] FIG. 17 is a block diagram showing an example of the configuration of a terminal according to one embodiment of the present disclosure.

[0291] As illustrated in FIG. 17, the terminal of the present disclosure may include at least one of a processor (control unit) (1730), a transceiver (communication unit) (1710), or a memory (1720). However, the components of the terminal are not limited to the examples described above. For example, the terminal may include more components or fewer components than the components described above. Furthermore, the processor (1730), the transceiver (1710), and the memory (1720) may be implemented in the form of a single chip. According to one embodiment, the transceiver (1710) of FIG. 17 may include the transceiver (1604) and the receiver (1608) of FIG. 16. Additionally, the processor (1730) of FIG. 17 may include the control unit (1609) of FIG. 16.

[0292] According to one embodiment, the processor (1730) can control a series of processes that allow the terminal to operate according to the embodiments of the present disclosure described above. For example, according to the embodiments of the present disclosure, the components of the terminal can be controlled to perform a transmission and reception method of the terminal according to the repeated transmission of the on-demand SSB of the base station. The processor (1730) may include at least one processor, and the processor (1730) can perform a transmission and reception operation of the terminal in a wireless communication system applying the operation of the aforementioned present disclosure by executing a program stored in memory (1720).

[0293] The transceiver (1710) can transmit and receive signals with a base station. The signals transmitted and received with the base station may include control information and data. The transceiver (1710) may be composed of an RF transmitter that up-converts and amplifies the frequency of a transmitted signal, and an RF receiver that low-noise amplifies a received signal and down-converts the frequency. However, this is merely an example of the transceiver (1710), and the components of the transceiver (1710) are not limited to an RF transmitter and an RF receiver. Additionally, the transceiver (1710) can receive a signal through a wireless channel and output it to a processor (1730), and transmit the signal output from the processor (1730) through a wireless channel.

[0294] According to one embodiment, the memory (1720) may store programs and data necessary for the operation of the terminal. Additionally, the memory (1720) may store control information or data included in signals transmitted and received by the terminal. The memory (1720) may be composed of a storage medium or a combination of storage media such as ROM, RAM, hard disk, CD-ROM, and DVD. Additionally, there may be multiple memory (1720). According to one embodiment, the memory (1720) may store a program for performing the transmission and reception operation of the terminal in the repeated transmission of the on-demand SSB of the base station, which is one of the embodiments of the present disclosure described above.

[0295] FIG. 18 is a block diagram showing an example of the configuration of a base station according to one embodiment of the present disclosure.

[0296] As illustrated in FIG. 18, the base station of the present disclosure may include at least one of a processor (control unit) (1830), a transceiver (communication unit) (1810), or a memory (1820). However, the components of the base station are not limited to the examples described above. For example, the base station may include more components or fewer components than the components described above. In addition, the processor (1830), the transceiver (1810), and the memory (1820) may be implemented in the form of a single chip.

[0297] The processor (1830) can control a series of processes to enable the base station to operate according to the embodiments of the present disclosure described above. For example, the components of the base station can be controlled to perform a method of scheduling a terminal for the repeated transmission of the base station's on-demand SSB according to the embodiments of the present disclosure. The processor (1830) may include at least one processor, and the processor (1830) can perform a method of scheduling a terminal by the frequency instruction of the base station of the present disclosure described above by executing a program stored in memory (1820).

[0298] The transceiver (1810) can transmit and receive signals with a terminal. The signals transmitted and received with the terminal may include control information and data. The transceiver (1810) may be composed of an RF transmitter that up-converts and amplifies the frequency of a transmitted signal, and an RF receiver that low-noise amplifies a received signal and down-converts the frequency. However, this is merely an example of the transceiver (1810), and the components of the transceiver (1810) are not limited to an RF transmitter and an RF receiver. Additionally, the transceiver (1810) can receive a signal through a wireless channel and output it to a processor (1830), and transmit the signal output from the processor (1830) through a wireless channel.

[0299] According to one embodiment, the memory (1820) may store programs and data necessary for the operation of the base station. Additionally, the memory (1820) may store control information or data included in signals transmitted and received by the base station. The memory (1820) may be composed of a storage medium or a combination of storage media such as ROM, RAM, hard disk, CD-ROM, and DVD. Additionally, there may be multiple memory (1820). According to one embodiment, the memory (1820) may store a program for performing a method of scheduling a terminal for the repeated transmission of the on-demand SSB of the base station, which is one of the embodiments of the present disclosure described above.

[0300] In the specific embodiments of the present disclosure described above, the components included in the present disclosure are expressed in a singular or plural form according to the specific embodiments presented. However, the singular or plural expression is selected to suit the situation presented for convenience of explanation, and the present disclosure is not limited to singular or plural components; even if a component is expressed in the plural, it may be composed of a singular form, and even if a component is expressed in the singular form, it may be composed of a plural form.

[0301] Meanwhile, the present specification and drawings disclose preferred embodiments of the present disclosure. Although specific terms have been used, they are used merely in a general sense to facilitate the explanation of the technical content of the present disclosure and to aid in understanding the invention, and are not intended to limit the scope of the present disclosure. It is obvious to those skilled in the art that, in addition to the embodiments disclosed herein, other variations based on the technical concept of the present disclosure are possible. Furthermore, each of the above embodiments may be combined and operated together as needed. For example, the first, second, third, fourth, and fifth embodiments may be implemented independently, or at least one of the embodiments may be combined and implemented together.

[0302] Meanwhile, although specific embodiments have been described in the detailed description of the present disclosure, it is understood that various modifications are possible within the scope of the present disclosure. Therefore, the scope of the present disclosure should not be limited to the described embodiments, but should be defined by the claims set forth below as well as equivalents thereof.

Claims

In a method performed by a terminal of a wireless communication system, A step of receiving a discovery signal from a base station; A step of transmitting a request message to the base station requesting the transmission of a synchronization signal; A step of receiving an on-demand SSB (SS / PBCH block, synchronization signal / physical broadcast channel block) that is transmitted repeatedly at least once from the base station; and A method comprising the step of transmitting a random access preamble to the base station based on a random access channel (RACH) occasion associated with an on-demand SSB that is transmitted at least once repeatedly, or a RACH occasion associated with an SSB that is transmitted periodically. In Article 1, A method characterized in that the on-demand SSB transmitted repeatedly at least once is transmitted according to at least one of half-frame units, frame units, or quarter-frame units. In Article 1, A method characterized in that the RACH occasion associated with the at least one on-demand SSB that is repeatedly transmitted at least once is associated with at least one of the first on-demand SSB received among the at least one on-demand SSB that is repeatedly transmitted at least once, or the last on-demand SSB received among the at least one on-demand SSB that is repeatedly transmitted at least once. In Article 1, A method characterized in that each of the above-mentioned on-demand SSBs that are transmitted at least once includes a plurality of SSBs corresponding to a plurality of different beams. In a method performed by a base station of a wireless communication system, Step of broadcasting a discovery signal; A step of receiving a request message from a terminal requesting the transmission of a synchronization signal based on the above discovery signal; A step of transmitting an on-demand SSB (SS / PBCH block, synchronization signal / physical broadcast channel block) that is transmitted repeatedly at least once to the terminal; and A method comprising the step of receiving a random access preamble from the terminal based on a random access channel (RACH) occasion associated with an on-demand SSB that is transmitted at least once repeatedly or a RACH occasion associated with an SSB that is transmitted periodically. In Article 5, A method characterized in that the on-demand SSB transmitted repeatedly at least once is transmitted according to at least one of half-frame units, frame units, or quarter-frame units. In Article 5, A method characterized in that the RACH occasion associated with the at least one on-demand SSB that is repeatedly transmitted at least once is associated with at least one of the first on-demand SSB received among the at least one on-demand SSB that is repeatedly transmitted at least once, or the last on-demand SSB received among the at least one on-demand SSB that is repeatedly transmitted at least once. In Article 5, A method characterized in that each of the above-mentioned on-demand SSBs that are transmitted at least once includes a plurality of SSBs corresponding to a plurality of different beams. In a terminal of a wireless communication system, Transmitter / receiver; and It includes a control unit connected to the above-mentioned transmitting and receiving unit, and The above control unit is, Receives a discovery signal from the base station, A request message requesting the transmission of a synchronization signal is transmitted to the base station, and Receive an on-demand SSB (SS / PBCH block, synchronization signal / physical broadcast channel block) that is transmitted repeatedly at least once from the base station, and A terminal that controls the transmission of a random access preamble to the base station based on a RACH (random access channel) occasion associated with an on-demand SSB that is transmitted at least once repeatedly, or a RACH occasion associated with an SSB that is transmitted periodically. In Article 9, A terminal characterized in that the on-demand SSB transmitted repeatedly at least once is transmitted according to at least one of half-frame units, frame units, or quarter-frame units. In Article 9, A terminal characterized in that the RACH occasion associated with the on-demand SSB that is transmitted at least once is associated with at least one of the on-demand SSB received first among the on-demand SSBs transmitted at least once or the on-demand SSB received last among the on-demand SSBs transmitted at least once. In Article 9, A terminal characterized in that each of the above-mentioned on-demand SSBs that are transmitted repeatedly at least once includes a plurality of SSBs corresponding to a plurality of different beams. In a base station of a wireless communication system, Transmitter / receiver; and It includes a control unit connected to the above-mentioned transmitting and receiving unit, and The above control unit is, Broadcasting the Discovery signal, Receive a request message from a terminal requesting the transmission of a synchronization signal based on the above discovery signal, and Transmit an on-demand SSB (SS / PBCH block, synchronization signal / physical broadcast channel block) that is transmitted repeatedly at least once to the terminal, and A base station that controls the reception of a random access preamble from the terminal based on a random access channel (RACH) occasion associated with an on-demand SSB that is transmitted at least once repeatedly, or a random access channel (RACH) occasion associated with an SSB that is transmitted periodically. In Article 13, A base station characterized by the above-mentioned on-demand SSB, which is transmitted repeatedly at least once, being transmitted according to at least one of half-frame units, frame units, or quarter-frame units. In Article 13, The RACH occasion associated with the on-demand SSB that is transmitted at least once is associated with at least one of the first on-demand SSB received among the on-demand SSBs that are transmitted at least once, or the last on-demand SSB received among the on-demand SSBs that are transmitted at least once, and A method characterized in that each of the above-mentioned on-demand SSBs that are transmitted at least once includes a plurality of SSBs corresponding to a plurality of different beams.

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