Method by user equipment, user equipment, and storage medium, and method by base station, base station, and storage medium

Abstract

This UE may determine, as valid RACH occasions, RACH occasions satisfying a predetermined condition among RACH occasions of a cell, map SSBs of the cell to the valid RACH occasions, and transmit a RACH preamble in a valid RACH occasion to which at least one SSB of the cell is mapped. The predetermined condition includes the following: A corresponding RACH occasion is within a stay interval.

Description

A method by means of a user device, a user device, and a storage medium, and a method by means of a base station, a base station, and a storage medium

[0001] This specification relates to a wireless communication system.

[0002] Various devices and technologies, such as machine-to-machine (M2M) communication, machine type communication (MTC), and devices requiring high data transmission rates like smartphones and tablet PCs (Personal Computers), are emerging and becoming widespread. Consequently, the amount of data required to be processed in cellular networks is increasing very rapidly. To satisfy this rapidly increasing demand for data processing, technologies such as carrier aggregation and cognitive radio are being developed to efficiently utilize more frequency bands, while technologies such as multi-antenna technology and multi-base station (BS) cooperation are being developed to increase the data capacity transmitted within a limited frequency range.

[0003] Recently, support for wireless communication services via non-terrestrial networks (NTNs) is being considered to provide wireless communication services in locations where providing wireless communication services via terrestrial networks is technically very difficult or costly.

[0004] A method is required to provide wireless communication signals to the UE accurately and efficiently via airborne platforms or space.

[0005] The technical problems that this specification aims to solve are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art related to this specification from the detailed description below.

[0006] In one aspect of the present specification, a method performed by a user device is provided. In another aspect of the present specification, a device is provided comprising: at least one processor; and at least one computer memory operably connectable to the at least one processor and, when executed, storing instructions that cause the at least one processor to perform operations. In yet another aspect of the present specification, a computer-readable storage medium is provided that stores at least one program code including instructions that cause the at least one processor to perform operations when executed. The method or operations may include: setting a random access channel (RACH) for a cell, setting an SSB-related setting for SSBs of different synchronization signal block (SSB) indices transmitted from the cell, and determining a dwell period of the cell; determining RACH times based on the RACH setting; determining RACH times among the RACH times that satisfy a predetermined condition as valid RACH times; and mapping the SSBs to the valid RACH times. The above cell includes transmitting a RACH preamble at a valid RACH time mapped to at least one SSB of the above cell, and the predetermined condition may include: the RACH time is within the stay interval.

[0007] In each aspect of the present specification, the method or operation may include obtaining the number of said SSBs based on the said SSB-related settings. The user device may expect that the number of valid RACH times existing within said dwell time is greater than or equal to the number of said SSBs.

[0008] In each aspect of the present specification, transmitting the RACH preamble may include: transmitting the RACH preamble at a RACH time associated with an SSB whose received reference signal power (RSRP) is greater than a threshold among the SSBs mapped to RACH times within the stay interval, based on the fact that the time length of the stay interval is less than the time length by a minimum number of RACH setting cycles such that the SSBs of the cell are mapped to RACH times at least once.

[0009] In each aspect of the present specification, the method or operation may include obtaining the revisit period of the cell.

[0010] In each aspect of the present specification, the method or operation may include: mapping the SSBs to the valid RACH times, which is based on the fact that the time length of the dwell time interval is smaller than the time length of the minimum number of RACH setting cycles such that the SSBs of the cell are mapped to the RACH times at least once, and which includes mapping the SSBs to the RACH times within a plurality of dwell times each (respectively) belonging to a plurality of consecutive revisit cycles.

[0011] In another aspect of the present specification, a method performed by a base station is provided. In another aspect of the present specification, a base station is provided comprising: at least one processor; and at least one computer memory operablely connectable to the at least one processor and storing instructions that, when executed, cause the at least one processor to perform operations. In another aspect of the present specification, a computer-readable storage medium is provided for storing at least one program code that, when executed, causes the at least one processor to perform operations. The method or operations include: setting a random access channel (RACH) for a cell; setting an SSB-related configuration regarding SSBs of different synchronization signal block (SSB) indices transmitted from the cell; and transmitting information regarding a dwell period of the cell; determining RACH times satisfying a predetermined condition among the RACH times according to the RACH setting as valid RACH times; and mapping the SSBs to the valid RACH times. and may include attempting to receive a RACH preamble at a valid RACH time mapped to at least one SSB of the cell. The predetermined condition may include: the corresponding RACH time is within the dwell period.

[0012] In each aspect of this specification, the above method or operation may: generate the SSB-related setting such that the number of valid RACH times existing within the stay interval is greater than or equal to the number of SSBs.

[0013] In each aspect of the present specification, the method or operation may include: transmitting information regarding the revisit period of the cell.

[0014] In each aspect of the present specification, mapping the SSBs to the valid RACH periods may include mapping the SSBs to RACH periods within a plurality of consecutive revisit periods, respectively, based on the fact that the time length of the dwell period is smaller than the time length by a minimum number of RACH setting periods such that the SSBs of the cell are mapped to the RACH periods at least once.

[0015] According to some implementations of this specification, wireless communication signals can be efficiently transmitted and received over airborne platforms or space. Accordingly, the overall throughput of the wireless communication system can be increased.

[0016] According to some implementations of this specification, the continuity of wireless communication services can be guaranteed, the reliability of wireless communication services can be enhanced through connectivity between various access technologies, and network resilience and reliability against disasters can be improved.

[0017] According to some implementations of this specification, random access processes in beam-hopping-based NTN communication can be efficiently performed.

[0018] The effects of this specification are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art related to this specification from the detailed description below.

[0019] The attached drawings, included as part of the detailed description to aid in understanding the implementations of this specification, provide examples of the implementations of this specification and describe the implementations of this specification together with the detailed description:

[0020] FIG. 1 is a block diagram illustrating examples of communication devices capable of performing the method according to the present specification;

[0021] FIG. 2 illustrates an example of a frame structure available in a 3GPP-based wireless communication system;

[0022] FIG. 3 illustrates a resource grid of slots;

[0023] FIG. 4 illustrates multi-beam operation in a 3GPP-based system;

[0024] FIG. 5 illustrates an example of SS / PBCH blocks (SS / PBCH block, SSB) being transmitted on a cell;

[0025] FIG. 6 illustrates examples of random access (RA) processes;

[0026] FIG. 7 illustrates the initial connection process;

[0027] FIG. 8 illustrates the RACH timing according to arbitrary access channel settings;

[0028] FIGS. 9 through 11 illustrate examples of mapping between a synchronization signal block and an arbitrary access channel timing related to some implementations of the present specification;

[0029] FIG. 12 illustrates a non-terrestrial network (NTN) structure;

[0030] FIG. 13 illustrates an NTN deployment scenario;

[0031] Figure 14 is illustrated to explain the concept of a beam-hopping-based NTN;

[0032] FIG. 15 is illustrated to explain the concepts of dwell time and revisit time based on beam hopping;

[0033] FIG. 16 illustrates the process of a UE setting up a radio resource control (RRC) connection with a BS through a cell;

[0034] FIG. 17 illustrates an example of mapping a synchronization signal block (SSB) to a random access channel occasion (RO) in a general environment;

[0035] FIG. 18 illustrates an example of mapping SSBs to ROs according to some implementations of the present specification in an NTN environment with beam hopping;

[0036] FIG. 19 illustrates another example of mapping SSBs to ROs according to some implementations of the present specification in an NTN environment with beam hopping;

[0037] FIG. 20 illustrates another example of mapping SSBs to ROs according to some implementations of the present specification in an NTN environment with beam hopping;

[0038] FIG. 21 illustrates the flow of an arbitrary connection process in a UE according to some implementations of the present specification;

[0039] FIG. 22 illustrates the flow of an arbitrary connection process in BS according to some implementations of the present specification.

[0040] Implementations according to this specification are described below with reference to the accompanying drawings. The detailed description disclosed below, together with the accompanying drawings, is intended to describe exemplary implementations of this specification and is not intended to represent the only form in which this specification may be practiced. The detailed description below includes specific details to provide a complete understanding of this specification. However, a person skilled in the art will know that this specification may be practiced without such specific details.

[0041] In some cases, to avoid ambiguity regarding the concepts of this specification, known structures and devices may be omitted or illustrated in the form of block diagrams focusing on the core functions of each structure and device. Additionally, throughout this specification, the same reference numerals are used to describe identical components.

[0042] The techniques, devices, and systems described below can be applied to various wireless multiple access systems.

[0043] For the sake of convenience of explanation, the following description of this specification is based on 3GPP (3rd Generation Partnership Project) based communication systems. However, the technical features of this specification are not limited thereto. For example, even though the following detailed description is based on 3GPP (3rd Generation Partnership Project) LTE or 5G technology, some implementations of this specification are applicable to any other mobile communication systems and future systems (e.g., 6G), except for those specific to 3GPP LTE / 5G.

[0044] For terms and technologies used in this specification that are not specifically described, refer to 3GPP-based standard documents, e.g., 3GPP TS 23.304, 3GPP TS 23.285, 3GPP TS 23.287, 3GPP TS 24.587, 3GPP TS 36.211, 3GPP TS 36.212, 3GPP TS 36.213, 3GPP TS 36.300, 3GPP TS 36.321, 3GPP 36.322, 3GPP TS 36.323, 3GPP TS and 3GPP TS 36.331, 3GPP TS 37.213, 3GPP TS 38.211, 3GPP TS 38.212, You may refer to 3GPP TS 38.213, 3GPP TS 38.214, 3GPP TS 38.300, 3GPP TS 38.321, 3GPP TS 38.322, 3GPP TS 38.323, and 3GPP TS 38.331, etc.

[0045] In the examples of this specification described below, the expression that the device "assumes" may mean that the entity transmitting the channel transmits the channel in accordance with said "assume." It may mean that the entity receiving the channel receives or decodes the channel in a form that conforms to said "assume," under the premise that the channel was transmitted in accordance with said "assume."

[0046] In this specification, UEs may be fixed or mobile and include various devices that communicate with a BS (base station) to transmit and / or receive user data and / or various control information. A UE may be referred to as Terminal Equipment, Mobile Station (MS), Mobile Terminal (MT), User Terminal (UT), etc. Furthermore, in this specification, a BS generally refers to a fixed station that communicates with a UE and / or other BSs, and exchanges various data and control information by communicating with a UE and other BSs. A BS may be referred to by other terms such as Advanced Base Station (ABS), Node-B (NB), eNB (evolved-NodeB), gNB, Base Transceiver System (BTS), Access Point, and Processing Server (PS). For convenience of explanation, base stations are collectively referred to as BSs below, regardless of the type or version of the communication technology.

[0047] In this specification, the term "node" refers to a fixed point capable of transmitting or receiving wireless signals by communicating with a UE. Various types of BSs may be used as nodes regardless of their designation. At least one antenna is installed at a node. The antenna may refer to a physical antenna, an antenna port, a virtual antenna, or an antenna group. A node is also referred to as a point or a transmission and reception point (TRP).

[0048] Meanwhile, 3GPP-based communication systems use the concept of a cell to manage wireless resources, and a cell associated with wireless resources is distinguished from a cell in a geographical area. A "cell" in a geographical area can be understood as the coverage where a node can provide services using a carrier wave, while a "cell" in wireless resources is associated with the bandwidth (BW), which is the frequency range configured by the said carrier wave. Since downlink coverage, which is the range where a node can transmit a valid signal, and uplink coverage, which is the range where a valid signal can be received from a UE, depend on the carrier wave carrying the corresponding signal, the node's coverage is also associated with the coverage of the "cell" of the wireless resources used by the node. Therefore, the term "cell" can be used to refer sometimes to the coverage of a service provided by a node, sometimes to wireless resources, and sometimes to the range where a signal using said wireless resources can reach with effective strength.

[0049] The term "cell" associated with wireless resources may be defined as a combination of downlink resources (DL resources) and uplink resources (UL resources), that is, a combination of a DL component carrier (CC) and a UL CC. A cell may be configured as a DL resource alone or as a combination of a DL resource and a UL resource. Where carrier aggregation is supported, the linkage between the carrier frequency of a DL resource (or DL ​​CC) and the carrier frequency of a UL resource (or UL CC) may be indicated by system information. Here, the carrier frequency may be equal to or different from the center frequency of each cell or CC.

[0050] In a wireless communication system, the UE receives information from the BS via the downlink (DL) and transmits information to the BS via the uplink (UL). The information transmitted and / or received by the BS and the UE includes data and various control information, and various physical channels exist depending on the type and purpose of the information they transmit and / or receive.

[0051] 3GPP-based communication standards define downlink physical channels corresponding to resource elements that carry information originating from upper layers, and downlink physical signals corresponding to resource elements used by the physical layer but not carrying information originating from upper layers. For example, the physical downlink shared channel (PDSCH), physical broadcast channel (PBCH), and physical downlink control channel (PDCCH) are defined as downlink physical channels, and the reference signal and synchronization signal are defined as downlink physical signals.

[0052] In this specification, PDCCH refers to a set of time-frequency resources (e.g., resource elements (REs)) carrying downlink control information (DCI), and PDSCH refers to a set of time-frequency resources carrying downlink data. Additionally, PUCCH, PUSCH, and PRACH each refer to a set of time-frequency resources carrying uplink control information (UCI), uplink data, and random access preamble, respectively. Hereinafter, the expression that a UE / BS transmits / receives PUCCH / PUSCH / PRACH is used to mean that a UCI / uplink data / random access preamble is transmitted / received on or through PUCCH / PUSCH / PRACH, respectively. In addition, the expression that BS / UE transmits / receives PBCH / PDCCH / PDSCH is used with the same meaning as transmitting / receiving broadcast information / DCI / downlink data on or through PBCH / PDCCH / PDSCH, respectively.

[0053] In this specification, radio resources (e.g., time-frequency resources) scheduled or set for a UE by a BS for the transmission or reception of PUCCH / PUSCH / PDSCH are also referred to as PUCCH / PUSCH / PDSCH resources.

[0054] Since the communication device receives physical channels and / or physical signals in the form of radio signals on a cell, it is not possible to selectively receive only radio signals containing only specific physical channels or specific physical signals through a radio frequency (RF) receiver, or to selectively receive only radio signals excluding only specific physical channels or physical signals through an RF receiver. In actual operation, the communication device receives radio signals on a cell through an RF receiver, converts the radio signals, which are RF band signals, into baseband signals, and decodes the physical signals and / or physical channels within the baseband signals using one or more processors. Therefore, in some implementations of this specification, not receiving physical signals and / or physical channels may not actually mean that the communication device does not receive radio signals containing such physical signals and / or physical channels at all, but rather that it does not attempt to recover said physical signals and / or physical channels from said radio signals, for example, that it does not attempt to decode said physical signals and / or physical channels.

[0055] The communication systems to which this specification applies include wireless devices, BSs, and networks. Here, a wireless device may refer to a device that performs communication using wireless access technology (e.g., 5G NR (New RAT), LTE (e.g., E-UTRA), WiFi, and 6G to be introduced later).

[0056] Wireless devices may include, but are not limited to, robots, transportation vehicles, XR (eXtended Reality) devices, hand-held devices, home appliances, IoT (Internet of Thing) devices, and AI devices / servers. For example, a BS or network may be implemented as a wireless device, and a specific wireless device may act as a BS / network node to other wireless devices.

[0057] Wireless devices can be connected to a network via a BS. Artificial Intelligence (AI) technology can be applied to wireless devices, and wireless devices can be connected to an AI server via a network. Wireless devices can communicate with each other via a BS / network, but they can also communicate directly (e.g., sidelink communication) without using a BS / network.

[0058] Wireless communication / connection may be established between a wireless device and a BS, between BSs and BSs, and / or between wireless devices. Here, wireless communication / connection may be established through uplink / downlink communication (UL / DL) and sidelink communication (SL) (or D2D communication) via various wireless access technologies (e.g., 5G NR). Through wireless communication / connection (UL / DL, SL), wireless devices and BSs / wireless devices may transmit / receive wireless signals to / from each other. To this end, based on various proposals of this specification, at least some of the following may be performed: a process for setting various configuration information for the transmission / reception of wireless signals, various signal processing processes (e.g., channel encoding / decoding, modulation / demodulation, resource mapping / demapping, etc.), resource allocation processes, etc.

[0059] FIG. 1 is a block diagram illustrating examples of communication devices capable of performing a method according to the present specification. Referring to FIG. 1, a first wireless device (100) and a second wireless device (200) can transmit and / or receive wireless signals through various wireless access technologies. Here, {the first wireless device (100), the second wireless device (200)} may be wireless devices included in a communication system.

[0060] Each of the first wireless device (100) and the second wireless device (200) includes one or more processors (102, 202) and one or more memories (104, 204), and may additionally include one or more transceivers (106, 206) and / or one or more antennas (108). The processor (102, 202) controls the memory (104, 204) and / or transceivers (106, 206) and may be configured to implement the functions, procedures and / or methods described / suggested below. For example, the processor (102, 202) may process information within the memory (104, 204) to generate a first information / signal and then transmit a wireless signal containing the first information / signal through the transceiver (106, 206). Additionally, the processor (102, 202) may receive a wireless signal containing a second information / signal through a transceiver (106, 206) and then store information obtained from signal processing of the second information / signal in a memory (104, 204). The memory (104, 204) may be connected to the processor (102, 202) and may store various information related to the operation of the processor (102, 202). For example, the memory (104, 204) may store software code containing instructions for performing some or all of the processes controlled by the processor (102, 202) or for performing the procedures and / or methods described / suggested below. Here, the processor (102, 202) and the memory (104, 204) may be part of a communication modem / circuit / chip designed to implement wireless communication technology. The transceiver (106, 206) may be connected to a processor (102, 202) and may transmit and / or receive wireless signals through one or more antennas (108, 208). The transceiver (106, 206) may include a transmitter and / or receiver.

[0061] One or more protocol layers may be implemented by one or more processors (102, 202), though not limited thereto. For example, one or more processors (102, 202) may implement one or more layers (e.g., functional layers such as a physical (PHY) layer, a medium access control (MAC) layer, a radio link control (RLC) layer, a packet data convergence protocol (PDCP) layer, a radio resource control (RRC) layer, and a service data adaptation protocol (SDAP). One or more processors (102, 202) may generate one or more protocol data units (PDUs) and / or one or more service data units (SDUs) according to the functions, procedures, proposals and / or methods disclosed in this specification. One or more processors (102, 202) may generate messages, control information, data, or information according to the functions, procedures, proposals, and / or methods disclosed in this specification. One or more processors (102, 202) may generate a signal (e.g., baseband signal) containing a PDU, SDU, message, control information, data, or information according to the functions, procedures, proposals, and / or methods disclosed in this specification and provide it to one or more transceivers (106, 206). One or more processors (102, 202) may receive a signal (e.g., baseband signal) from one or more transceivers (106, 206) and may obtain a PDU, SDU, message, control information, data, or information according to the functions, procedures, proposals, and / or methods disclosed in this specification.

[0062] One or more processors (102, 202) may be referred to as a controller, microcontroller, microprocessor, or microcomputer. One or more processors (102, 202) may be implemented by hardware, firmware, software, or a combination thereof, and the firmware or software may be implemented to include modules, procedures, functions, etc. Firmware or software configured to perform the functions, procedures, proposals and / or methods disclosed in this specification may be included in one or more processors (102, 202) or stored in one or more memories (104, 204) and driven by one or more processors (102, 202). The functions, procedures, proposals and / or methods disclosed in this specification may be implemented using firmware or software in the form of code, instructions and / or sets of instructions.

[0063] One or more memories (104, 204) may be connected to one or more processors (102, 202) and may store various forms of data, signals, messages, information, programs, codes, instructions, and / or commands. One or more memories (104, 204) may be located inside and / or outside of one or more processors (102, 202). Additionally, one or more memories (104, 204) may be connected to one or more processors (102, 202) through various technologies such as wired or wireless connections.

[0064] One or more transceivers (106, 206) may transmit to / receive user data, control information, wireless signals / channels, etc., as mentioned in the methods and / or operation flowcharts, etc. of this specification to / from one or more other devices. Additionally, one or more processors (102, 202) may control one or more transceivers (106, 206) to transmit to / receive user data, control information, or wireless signals to / from one or more other devices. Additionally, one or more transceivers (106, 206) may be connected to one or more antennas (108, 208), and one or more transceivers (106, 206) may be configured to transmit and / or receive user data, control information, wireless signals / channels, etc., as mentioned in the functions, procedures, proposals, methods and / or operation flowcharts, etc. disclosed in this specification through one or more antennas (108, 208). In this specification, one or more antennas may be multiple physical antennas or multiple logical antennas (e.g., antenna ports). One or more transceivers (106, 206) may convert received wireless signals / channels, etc. from RF band signals to baseband signals in order to process received user data, control information, wireless signals / channels, etc. using one or more processors (102, 202). One or more transceivers (106, 206) may convert processed user data, control information, wireless signals / channels, etc. from baseband signals to RF band signals using one or more processors (102, 202). To this end, one or more transceivers (106, 206) may include (analog) oscillators and / or filters.

[0065] In this specification, at least one memory (104, 204) may store instructions or programs, and said instructions or programs may, when executed, cause at least one processor (102, 202) operabably connected to said at least one memory to perform operations according to some embodiments or implementations of this specification.

[0066] In this specification, a computer-readable (non-transitory) storage medium may store at least one instruction or computer program, and when executed by at least one processor, said at least one instruction or computer program may cause said at least one processor to perform operations according to some embodiments or implementations of this specification.

[0067] Figure 2 illustrates an example of a frame structure available in a 3GPP-based wireless communication system.

[0068] The structure of the frame in FIG. 2 is merely an example, and the number of subframes, slots, and symbols in the frame can be varied. In some wireless communication systems, OFDM numerology (e.g., subcarrier spacing (SCS)) may be set differently among multiple cells aggregated to a single UE. Accordingly, the (absolute time) duration of time resources (e.g., subframes, slots, or transmission time interval (TTI)) consisting of the same number of symbols may be set differently among the aggregated cells. Here, the symbol may include an OFDM symbol (or, cyclic prefix - orthogonal frequency division multiplexing (CP-OFDM) symbol) or an SC-FDMA symbol (or, discrete Fourier transform-spread-OFDM (DFT-s-OFDM) symbol). In this specification, the symbols, OFDM-based symbols, OFDM symbols, CP-OFDM symbols, and DFT-s-OFDM symbols may be interchangeable.

[0069] Referring to Fig. 2, uplink and downlink transmissions are organized into frames. Each frame is T f = (△f max *N f / 100)*T c = has a duration of 10 ms, where T is the basic time unit. c = 1 / (△f max *N f ) and, △f max = 480*10 3 It is Hz, and N f = 4096. For reference, the sampling time T s = 1 / (△f ref *Nf,ref ) and, △f ref = 15*10 3 It is Hz, and N f,ref =2048. T s Wow T c is a constant κ = T s / T c It has a relationship of = 64. A frame consists of 10 subframes, and the period T of a single subframe. sf is 1ms. Subframes are further divided into slots, and the number of slots within a subframe depends on the subcarrier interval. Each slot is based on a cyclic prefix (CP) N slot symb It can be composed of symbols. For example, in some scenarios, for a normal CP, each slot consists of 14 OFDM symbols, and for an extended CP, each slot consists of 12 OFDM symbols. The above numerology is an exponentially scalable subcarrier spacing △f = 2 u It depends on 15 kHz. The following table shows the subcarrier spacing △f = 2 for normalized CP. u *Number of OFDM symbols per slot according to 15 kHz (N slot symb ), number of slots per frame (N frame,u slot ) and the number of slots per subframe (N subframe,u slot It represents ).

[0070]

[0071] In the following description, implementations of this specification are described by referring to the minimum unit of time for scheduling uplink, downlink, and sidelink transmissions as a slot; however, depending on the wireless communication system, the minimum unit of time for scheduling may be referred to by other terms. For example, in LTE-based systems, the minimum unit of time for scheduling transmissions is referred to as a subframe or transmission time interval (TTI), whereas in NR-based systems, the minimum unit of time for scheduling is referred to as a slot.

[0072] Figure 3 illustrates a resource grid of slots. Slots are multiple (e.g., N) in the time domain. slot symb Includes the symbols of ). For each numeral (e.g., subcarrier interval) and carrier, the common resource block (CRB)N indicated by upper-layer signaling (e.g., radio resource control (RRC) signaling). start,u grid Starting from,N size,u grid,x *N RB sc individual subcarriers and N subframe,u symb A resource grid of N OFDM symbols is defined. Here, N size,u grid,x is the number of resource blocks (RB) in the resource grid, and the subscript x is DL for downlinks and UL for uplinks. RB sc is the number of subcarriers per RB, and in 3GPP-based wireless communication systems, N RB scis typically 12. There is one resource grid for a given antenna port p, subcarrier spacing configuration u, and transmission direction (DL or UL). Carrier bandwidth N for subcarrier spacing configuration u. size,u grid This is provided to the UE by upper-layer parameters (e.g., RRC parameters) from the network. Each element within the resource grid for antenna port p and subcarrier spacing u is referred to as a resource element (RE), and a single complex-valued symbol can be mapped to each resource element. Each resource element within the resource grid is uniquely identified by an index k in the frequency domain and an index l in the time domain indicating the symbol position relative to a reference point. RBs can be classified into Common Resource Blocks (CRBs) and Physical Resource Blocks (PRBs). CRBs are numbered upwards from 0 in the frequency domain for subcarrier spacing u. The center of the subcarrier 0 of CRB 0 for subcarrier spacing u coincides with 'Point A', which is the common reference point for the resource block grids. PRBs for subcarrier spacing u are defined within the bandwidth part (BWP) and number from 0 to N size,u BWP,i Numbered up to -1, where i is the number of the above bandwidth part. Common resource block n u CRB and physical resource block n within bandwidth part i PRB The relationships between them are as follows: n u PRB = n u CRB +N start,u BWP,i , here N start,u BWP,iis a common resource block where the above bandwidth part starts relative to CRB 0. A BWP contains multiple contiguous RBs in the frequency domain. For example, a BWP is a given numerator u within a BWP i on a given carrier. i It is a subset of contiguous CRBs defined for. A carrier can contain up to N (e.g., 5) BWPs. A UE can be configured to have one or more BWPs on a given component carrier. Data communication is performed through the enabled BWPs, and only a predetermined number (e.g., 1) of the BWPs configured for the UE can be enabled on the carrier.

[0073] Figure 4 illustrates multi-beam operation in a 3GPP-based system.

[0074] 5G and subsequent 3GPP-based systems may utilize high ultra-high frequency bands, such as millimeter frequency bands above 6 GHz, to transmit data to multiple users while maintaining high transmission rates using wide frequency bands. However, due to the use of such high frequencies, millimeter frequency bands exhibit frequency characteristics where signal attenuation with distance occurs very rapidly. Therefore, when using a band of at least 6 GHz or higher, 3GPP-based systems employ a narrow beam transmission technique to compensate for the rapid propagation attenuation characteristics. This technique resolves the problem of reduced coverage caused by rapid propagation attenuation by collecting and transmitting energy in a specific direction rather than omni-direction. However, if service is provided using only a single narrow beam, the service range of a single BS becomes limited; thus, the BS combines multiple narrow beams to provide service as a wide beam.

[0075] Figure 5 illustrates an example of SS / PBCH blocks (SS / PBCH block, SSB) being transmitted on a cell.

[0076] In a 3GPP-based system, each synchronization signal (SS) / physical broadcast channel (PBCH) block (SS / PBCH block, i.e., SSB) is associated with each beam. For example, during a half-frame, different SSBs can be transmitted in different spatial directions (using different beams that span the cell's coverage area). The possible time positions of SSBs within a half-frame are determined by the subcarrier interval, and the periododicity of the half-frames in which SSBs are transmitted is set by the network. Multiple SSBs can be transmitted within the carrier frequency span. Different indices of SSBs transmitted / detected on a single cell can correspond to different BS (wide) Tx beams.

[0077] In 3GPP-based systems, multi-beam operation is based on beam switching / beam scanning, which transmits / receives signals by changing beam directions over time. For example, assuming that a BS supports up to N transmission beams, beam sweeping can be performed to transmit a synchronous signal block (SSB) consisting of a PSS, SSS, and PBCH to each of the up to N beam directions (see SSB beam sweeping in Fig. 4).

[0078] Referring again to FIG. 4, the UE can use a wide reception (Rx) beam to measure the power of the received SSB(s) from the BS transmission (Tx) beams and select a preferred beam. For example, the UE can select one SSB from among the detected / received SSBs. 3GPP-based systems define a specific mapping between the SSB and the random access channel (RACH) occasion to enable the network to know which beam the UE has selected. The RACH occasion is the time and frequency resource available for the transmission of the RACH preamble (also called the PRACH preamble). In this specification, the RACH occasion is also referred to as the PRACH occasion.

[0079] Information regarding how many SSBs can be mapped to a single RACH time and how many preamble indices can be mapped to a single SSB may be provided to the UE by the network. For example, if the network configures the number of SSBs per RACH time to 1 / N, one SSB is associated with N RACH times (where N is a positive integer), and if the network configures the number of SSBs per RACH time to N, N preamble indices are mapped to a single SSB. The UE selects an SSB from among the SSBs detected / received by the UE on the cell, and selects and transmits a RACH time based on the selected SSB. The BS can determine which SSB among the SSBs transmitted on the cell the UE has selected by detecting a RACH time including a PRACH from the UE through BS Rx beam sweeping. The BS can determine the BS Tx beam for communication with the UE based on the SSB selected by the UE.

[0080] For finer beam tuning, CSI-RS can be transmitted. The BS can perform beam refinement using CSI-RS transmissions in narrower beams around the BS Tx beam determined based on the RACH time at which PRACH from the UE is detected (see CSI-RS beam sweeping in Fig. 4). The UE can measure the power of the CSI-RS received from these BS Tx narrow beams and report to the BS which beam among the BS Tx narrow beams it prefers. For example, the UE can measure the CSI-RS on the CSI-RS resources to select at least one CSI-RS resource and report to the BS the CSI-RS resource indicator (CRI) and the corresponding reference signal received power (RSRP) of the selected CSI-RS resource. The BS can determine a BS Tx narrow beam based on the CRI and / or the corresponding RSRP reported by the UE, and repeatedly transmit CSI-RS to the BS Tx narrow beam (see P3 CSI-RS beam sweeping in Fig. 4) to allow the UE to perform Rx beam sweeping to find an appropriate UE Rx beam. The UE can find an appropriate UE Rx beam by measuring the power of the CSI-RS received in each UE Rx beam.

[0081] The UE can detect beam failures using CSI-RS / SSB. For example, if the L1-RSRP for a beam to be connected falls below a certain threshold, the UE determines that it is a beam failure and searches for another candidate beam of good quality. Upon a predetermined number of beam failure detections, a beam failure recovery (BFR) procedure can be triggered using the candidate beam. The network may provide the UE with an identifier (ID) of the SSB transmitted by the cell, which is used to determine the candidate beam for BFR, and a preamble index used to perform BFR when selecting the candidate beam identified by this SSB. Upon a predetermined number of beam failure detections, the UE sends a BFR request to the network by transmitting a PRACH associated with the SSB ID, and the network provides a random access response (RAR) to the UE in response to the BFR request.

[0082] When receiving a PDSCH, with respect to the Doppler shift, Doppler spread average delay, delay spread, and spatial Rx parameters, the UE can assume that the demodulation reference signal (DM-RS) port of the PDSCH is quasi-co-located (QCL) with the associated SSB.

[0083] Figure 6 illustrates examples of random access (RA) processes. Figure 6(a) illustrates a 4-step random access process, and Figure 6(b) illustrates a 2-step random access process.

[0084] In some scenarios, the following two random access processes may be used: 4-stage random access and 2-stage random access. For both the 4-stage random access and the 2-stage random access, contention-based random access (CBRA) and contention-free random access (CFRA) may be supported.

[0085] FIG. 7 illustrates an initial connection process. FIG. 7 illustrates a case where a 4-stage random connection is performed during the random connection process, but a 2-stage random connection is also possible. The 4-stage random connection process and the 2-stage random connection process are respectively referred to as the Type-1 random connection process and the Type-2 random connection process.

[0086] The initial connection process may refer to a series of processes performed between the UE and the BS to obtain a specific identifier (ID) for uplink synchronization and wireless communication. The initial connection process may include downlink synchronization, SIB1 acquisition, and random connection processes.

[0087] A UE that has lost connection with a wireless communication system can first search for a suitable cell to camp on and perform an initial cell search process, such as synchronizing with said cell or its BS. During the initial cell search process, the UE can receive a synchronization signal (SS) and a PBCH on the cell. In some scenarios, a block consisting of a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a physical broadcast channel (PBCH) is referred to as a synchronization signal block (SSB) or an SS / PBCH block. Based on the PSS / SSS, the UE synchronizes with the BS and obtains information such as the cell identity (ID). Additionally, the UE can obtain in-cell broadcast information based on the PBCH.

[0088] The above UE can obtain PDCCH configuration information regarding a control resource set (CORESET) #0 and a search space #0 for receiving a PDCCH scheduling SIB1 from a master information block (MIB) carried by a PBCH. The above UE can i) determine frequency time domain resources and time domain resource durations for PDCCH monitoring based on information related to CORESET #0 within the PDCCH configuration information, and ii) determine timing for PDCCH monitoring based on information related to search space #0 within the PDCCH configuration information. The above UE can perform PDCCH monitoring within search space #0 on CORESET #0 and detect a PDCCH related to system information scheduling. The above UE can receive and decode a PDSCH carrying a system information block (SIB1) based on downlink control information (DCI) carried by the PDCCH.

[0089] The SIB1 of a cell can define the scheduling of other system information and may include random access channel (RACH) settings regarding cell-specific random access parameters.

[0090] A UE that has acquired the cell's SIB1 can perform a random access process based on the RACH settings within the said SIB1. The random access process can be used for various purposes, such as initial access, uplink adjustment, resource allocation, handover, reconfiguration of the wireless link after a wireless link failure, and localization. In the case of CBRA, since the UE randomly selects a random access (RA) preamble, it is possible for multiple UEs to transmit the same RA preamble simultaneously, which necessitates a contention resolution process. On the other hand, in the case of CFRA, the UE uses the RA preamble uniquely assigned to it by the BS. Therefore, the UE can perform the random access process without conflict with other UEs.

[0091] Referring to FIG. 6(a) and FIG. 7, the 4-step random access process may include steps 1 through 4, and the messages transmitted in steps 1 through 4 may be referred to as Msg1 through Msg4, respectively.

[0092] - Step 1: The UE transmits an RA preamble via PRACH. The UE may select an SSB from among those received on the cell for which the reference signal received power (RSRP) measured based on the SSB exceeds a threshold, and transmit an RA preamble via the PRACH associated with the selected SSB. For example, if random access is required, the UE transmits Msg1 (e.g., preamble) to the BS via PRACH. The BS can distinguish each random access preamble through the time / frequency resource (RA Occasion, RO) and the random access preamble index (Preamble Index, PI) at which the random access preamble was transmitted. When the BS receives a random access preamble from the UE, the BS transmits a RAR message to the UE via PDSCH. Random Access-RNTI (RA-RNTI) can be determined based on the time-frequency resources used for the transmission of PRACH.

[0093] - Step 2: The UE receives a random access response (RAR) from the BS via the PDSCH. In relation to the reception of the RAR, the UE may assume the same numerology (e.g., subcarrier interval) as SIB1. Subcarrier intervals for SIB1, Msg2, Msg4, and MsgB for initial access, paging, and broadcast system information messages may be provided via the MIB. To receive the RAR message, the UE monitors the L1 / L2 control channel (PDCCH), which is masked with a cyclic redundancy check (CRC) containing scheduling information for the RAR message, within a preset time window called the RAR window (e.g., ra-ResponseWindow). The length of the RAR window may be set by upper-layer signaling (e.g., SIB1), and the RAR window may start at a specific timing after a PRACH transmission (e.g., the first symbol of the fastest control resource set (CORESET) of the Type-1 PDCCH common seek space starting at least one symbol after the PRACH time corresponding to the PRACH transmission). When scheduling information is received via a PDCCH masked with RA-RNTI, the UE may receive a RAR message from the PDSCH indicated by the scheduling information. Subsequently, the UE determines whether there is a RAR for itself in the RAR message. Whether a RAR for itself exists can be determined by whether a RAPID (Random Access preamble ID) exists for the preamble transmitted by the UE. The index of the preamble transmitted by the UE and the RAPID may be the same.RAR includes a corresponding random access preamble index, timing offset information for UL synchronization (e.g., timing advance command (TAC)), UL scheduling information for Msg3 transmission (e.g., UL grant) and UE temporary identification information (e.g., Temporary-C-RNTI, TC-RNTI).

[0094] - Step 3: Upon receiving the RAR, the UE transmits Msg3 via PUSCH on the same cell from which the UE transmitted PRACH, according to the UL scheduling information and timing offset value within the RAR. The PUSCH carrying Msg3 may be scrambled by the TC-RNTI within Msg2 and transmitted. Msg3 may include the UE's ID (or the UE's global ID). Additionally, Msg3 may include information related to an RRC connection request for initial access to the network (e.g., an RRCSetupRequest message). Msg3 may include the 5G-S temporary mobile subscriber identity (5G-S-TMSI), etc. In some scenarios, when a UE receives a PDSCH with Msg2 ending in slot #n, the UE transmits a PUSCH carrying the corresponding Msg3 in slot #(n+K2+△), where K2 can be obtained from a UL grant within the RAR and △ can be determined according to the table below.

[0095]

[0096] Here, the subcarrier spacing u used for the PUSCH transmission carrying Msg3 is PUSCHmay be the same as the subcarrier interval provided through the MIB. If a contention resolution timer (e.g., ra-ContentionResolutionTimer) is set through RRC signaling (e.g., SIB1), when the UE transmits Msg3, the contention resolution timer is started or restarted at the first symbol after the end of the Msg3 transmission, or at the first symbol after the end of all iterations of the Msg3 transmission if the Msg3 transmission is scheduled as a PUSCH iteration.

[0097] - Step 4: The UE can perform PDCCH monitoring based on TC-RNTI. If a contention resolution timer (e.g., ra-ContentionResolutionTimer) is set via RRC signaling (e.g., SIB1), the UE can attempt to receive a PDCCH within the PDCCH common seek space while the contention resolution timer is running. When a PDCCH with a scrambled CRC is detected by TC-RNTI, the UE can receive a contention resolution message from the BS via the PDSCH corresponding to the PDCCH. Msg4 may include the UE's ID and / or information related to the RRC connection (e.g., an RRCSetup message). If a C-RNTI MAC control element (CE) was included in Msg3 and a PDCCH received by the UE while the competition resolution timer is running is addressed in the C-RNTI, the UE may consider the competition resolution successful, stop the competition resolution timer, discard the TC-RNTI, and consider the random access process to have been successfully completed. If a common control channel (CCCH) SDU was included in Msg3 and a PDCCH received by the UE while the competition resolution timer is running is addressed in its TC-RNTI, and a MAC PDU carried by a PDSCH scheduled by the PDCCH is successfully decoded, the UE may stop the competition resolution timer.If the above MAC PDU includes a UE Contention Resolution Identity MAC CE and the UE Contention Resolution Identity within the above UE Contention Resolution Identity MAC CE matches the CCCH SDU transmitted to Msg3, the UE may consider the competition resolution to be successful, discard the TC-RNTI, and consider this random access process to be successfully completed. If, while the above-mentioned competition resolution timer is running (i.e., before the above-mentioned competition resolution timer expires), the UE does not receive the PDCCH addressed in the C-RNTI within the C-RNTI MAC CE transmitted via Msg3, or does not receive the PDCCH addressed in its TC-RNTI, or fails to successfully decode the MAC PDU within the PDSCH corresponding to the PDCCH addressed in its TC-RNTI, or even if the MAC PDU is successfully decoded, the UE competition resolution identifier within the MAC PDU does not match the CCCH SDU transmitted via Msg3, the UE may consider the competition resolution to be unsuccessful. If the competition resolution is unsuccessful and the random access process is not completed, the UE may perform a random access resource selection process for transmitting Msg1 (if the above-mentioned random access process is a 4-stage random access process) or a random access resource selection process for transmitting MsgA (if the above-mentioned random access process is a 2-stage random access process).

[0098] Referring to FIG. 6(b), the two-stage random access process may consist of two stages: the transmission of MsgA from the UE to the BS and the transmission of MsgB from the BS to the UE. The transmission of MsgA may include the transmission of an RA preamble via PRACH and the transmission of a UL payload via PUSCH. In the transmission of MsgA, PRACH and PUSCH may be transmitted using time division multiplexing (TDM). Alternatively, in the transmission of MsgA, PRACH and PUSCH may be transmitted using frequency division multiplexing (FDM).

[0099] A BS that receives MsgA may transmit MsgB to a UE. MsgB may include a RAR for said UE. After MsgA transmission, said UE monitors for a response from the network within a time window to monitor for a RAR for a two-stage random access process. The length of said time window may be set by upper-layer signaling, and said time window may start at a specific timing after MsgA transmission (e.g., the first symbol of the fastest CORESET of the Type-1 PDCCH common seek space starting at least one symbol after the last symbol of the PUCCH time corresponding to the PRACH transmission of said MsgA transmission).

[0100] A message related to an RRC connection request (e.g., RRCSetupRequest message) requesting to establish a connection between the RRC layer of the BS and the RRC layer of the UE may be transmitted by being included in the payload of MsgA. In this case, MsgB may be used to transmit RRC connection-related information (e.g., RRCSetup message). Alternatively, the RRC connection request message (e.g., RRCSetupRequest message) may be transmitted via PUSCH transmitted based on a UL grant within MsgB. In this case, the RRC connection-related information (e.g., RRCSetup message) related to the RRC connection request may be transmitted via PDSCH associated with said PUSCH transmission after the PUSCH transmission based on MsgB.

[0101] In some scenarios, regarding the PRACH preamble, the total number of available preambles within each time-frequency PRACH occasion is 64. A total of 64 preambles can be generated depending on the cycle transition value and the root sequence value.

[0102] FIG. 8 illustrates the RACH timing according to arbitrary access channel settings. In particular, FIG. 8 illustrates the RACH timing according to RACH settings used in 5G-based systems, but some implementations of this specification are not limited to 5G-based systems.

[0103] The RACH configuration within SIB1 may include an information element (IE) RACH-ConfigCommon used to specify cell-specific random access parameters that the UE can use for CBRA and CFRA. IERACH-ConfigCommon may include information regarding the subcarrier spacing of PRACH, ra-ContentionResolutionTimer, and information regarding the total number of preambles used for contention-based and contention-free 4-stage or 2-stage random access within the RACH resources defined in IERACH-ConfigCommon. IERACH-ConfigCommon may include IERACH-ConfigGeneric used to specify random access parameters for regular random access as well as beam failure recovery (BFR), and IERACH-ConfigGeneric may include the following information.

[0104] PRACH configuration index: Indicates PRACH configurations regarding format and time resources for PRACH transmission. Based on the PRACH configuration index, the preamble format, system frame number (SFN), subframe number, start symbol, number of PRACH slots within the subframe, number of PRACH times within the PRACH slots, and PRACH duration can be specified.

[0105] Msg1-FDM: Indicates the number of PRACH times that are frequency division multiplexed (FDM) in a single time instance.

[0106] Msg1-FrequencyStart: Indicates the offset of the lowest PRACH time in the frequency domain for PRB #0.

[0107] The physical random access process can be triggered by a higher layer (e.g., the medium access control (MAC) layer) or by a request for a PRACH transmission by a PDCCH order.

[0108] The UE may be provided with RRC parameters regarding the number of SS / PBCH block indices N associated with a single PRACH period and the number of contention-based preambles R per SS / PBCH block index per valid PRACH period. If N < 1, a single SS / PBCH block index is mapped to 1 / N consecutive valid PRACH periods, and R contention-based preambles with consecutive indices associated with the said SS / PBCH block index per valid PRACH period start from preamble index 0. If N ≥ 1, R contention-based preambles with consecutive indices associated with SS / PBCH block index n (where 0 ≤ n ≤ N-1) per valid PRACH period start from preamble index n. In the case of a paired spectrum or supplementary uplink band, which is a frequency arrangement using two distinct frequency bands for communication—one for the uplink and one for the downlink—all PRACH times may be considered valid. In the case of an unpaired spectrum, which is a frequency band using TDD for transmission and reception on the same frequency band, the PRACH times deemed valid may vary depending on whether a time division duplex (TDD) uplink-downlink UL-DL configuration for the cell is provided to the UE(s) via RRC signaling. For example, if a TDD UL-DL configuration is provided for the cell, the PRACH time within the PRACH slot does not precede the SSB within said PRACH slot and is at least N after the last SSB symbol. gapIt may be determined to be valid if it starts after 2 symbols. If no TDD UL-DL setting is provided for the cell, the PRACH timing within the PRACH slot is if it is within UL symbols, or if it does not precede the SSB within the said PRACH slot and is at least N after the last SSB symbol. gap If it starts after the dog symbols, it can be determined to be valid.

[0109] Here, N gap It can be given according to the following table based on the subcarrier interval used for preamble transmission.

[0110]

[0111] The UE may not expect to detect a DCI format (e.g., DCI format 2_0) having a slot format instruction indicating a downlink for a PRACH occasion (also called a RACH occasion). If a valid RACH occasion (RACH occasion, RO) overlaps with a DL reception, the UE may not perform the DL reception. For example, a set of slot symbols corresponding to the valid RO and N prior to the valid RO. gap For each symbol, the UE may not receive PDCCH, PDSCH, or CSI-RS in the slot if the reception of PDCCH, PDSCH, or CSI-RS overlaps with the symbols.

[0112] The ordering of the PRACH periods can be as follows.

[0113] First, in order of increasing frequency resource indices for frequency-multiplexed PRACH periods,

[0114] Second, in increasing order of time resource indices for time-multiplexed PRACH periods within the PRACH slot,

[0115] Third, in increasing order of the indices for the PRACH slots.

[0116] FIGS. 9 through 11 illustrate examples of mapping between a synchronization signal block and an arbitrary connection channel time related to some implementations of the present specification.

[0117] The mapping between SSB and RACH timing can be defined by the following two RRC parameters:

[0118] Msg1-FDM: Indicates the number of PRACH times that are frequency division multiplexed (FDM) in a single time instance.

[0119] ssb-perRACH-OccasionAndCB-PreamblesPerSSB: ssb-perRACH-OccasionAndCB-PreamblesPerSSB carries information about the number of SSBs per RACH period and includes one value selected from the values ​​oneEighth, oneFourth, oneHalf, one, two, four, eight, and sixteen, and includes an enumerated value or an integer value for the selected value. The value oneEighth indicates that one SSB is associated with 8 RACH periods, the value oneFourth indicates that one SSB is associated with 4 RACH periods, oneHalf indicates that one SSB is associated with 2 RACH periods, and one, two, four, eight, and sixteen indicate, respectively, that one SSB is associated with 1, 2, 4, 8, and 16 RACH periods. The enumerated part represents the number of competition-based preambles per SSB, such that the value n4 corresponds to 4 competition-based preambles per SSB and the value n8 corresponds to 8 competition-based preambles per SSB. The total number of competition-based preambles within a RACH period can be given, for example, by CB-preamble-per-SSB*max(1, SSB-per-rach-occasion), where CB-preamble-per-SSB is the number of competition-based preambles per SSB and SSB-per-rach-occasion is the number of SSBs per RACH period.

[0120] The SS / PBCH indexes provided by IEServingCellConfigCommon, used to set cell-specific parameters of the serving cell of SIB1 or UE, can be mapped to valid ROs in the following order.

[0121] First, in the order of increasing preamble indices within a single PRACH period,

[0122] Second, in the order of increasing frequency resource indices for frequency-multiplexed PRACH periods,

[0123] Third, in increasing order of time resource indices for multiplexed PRACH periods within the PRACH slot,

[0124] Fourth, in increasing order of indices for the PRACH slots.

[0125] Accordingly, when “msg1-FDM = two” and “ssb-perRACH-OccasionAndCB-PreamblesPerSSB = one”, the SSBs can be mapped to the ROs as exemplified in FIG. 9; when “msg1-FDM = two” and “ssb-perRACH-OccasionAndCB-PreamblesPerSSB = eight”, the SSBs can be mapped to the ROs as exemplified in FIG. 10; and when “msg1-FDM = two” and “ssb-perRACH-OccasionAndCB-PreamblesPerSSB = oneHalf”, the SSBs can be mapped to the ROs as exemplified in FIG. 11.

[0126] Figure 12 illustrates a non-terrestrial network (NTN) structure.

[0127] Recently, discussions have been underway to enable 3GPP-based systems to support non-terrestrial networks (NTNs). An NTN is any network that includes non-terrestrial flying objects. If wireless communication via NTN becomes possible in 3GPP-based systems, the continuity of wireless communication services can be guaranteed, the reliability of wireless communication services can be enhanced through connectivity between various access technologies, and network resilience and reliability against disasters can be improved. For the sake of convenience of explanation, the following terms are used below.

[0128] - NTN: A radio access network composed of BSs that provides non-terrestrial radio access to UEs using NTN payloads and NTN gateways mounted on airborne or space-borne NTN vehicles.

[0129] - NTN Gateway: An earth station located on the surface that provides connectivity to NTN payloads using feeder links. The NTN Gateway is a transport network layer (TNL) node.

[0130] - NTN Payload: A network node mounted on a satellite or high altitude platform station that provides connectivity functions between a service link and a feeder link, or a satellite or high altitude platform station that provides high altitude platform connectivity.

[0131] - Service Link: Wireless link between the NTN payload and the UE.

[0132] - Feeder Link: A wireless link between the NTN gateway and the NTN payload.

[0133] - Satellite: A space-borne vehicle orbiting the Earth while carrying an NTN payload.

[0134] - NTN Cell: A cell that provides a service link between the UE and the NTN payload.

[0135] Referring to FIG. 12, an NTN gateway is connected to an NTN payload mounted on a satellite or a high altitude platform system (HAPS), etc., via a feeder link. The NTN payload is connected to a UE via a service link. The NTN gateway can be connected to the core network of a 3GPP-based system.

[0136] The NTN payload transmits radio protocols received from the UE (via a service link) to the NTN gateway (via a feeder link) and transmits radio protocols received from the NTN gateway (via a feeder link) to the UE (via a feeder link). The NTN gateway can service multiple NTN payloads, and NTN payloads can be serviced by multiple NTN gateways. For NTN, the tracking area may correspond to a fixed geographical area, and each mapping can be established in the radio access network.

[0137] The following three types of service links are supported:

[0138] - Earth-fixed service link: A service link provisioned by beam(s) that continuously cover the same geographic areas (e.g., in the case of GSO satellites).

[0139] - Quasi-Earth-fixed service link: A service link supplied by beam(s) that cover one geographic area for a limited period and another geographic area for another period (e.g., in the case of NGSO generating steerable beams).

[0140] - Earth-moving service link: A service link supplied by beam(s) whose coverage area slides over the Earth's surface (e.g., in the case of NGSO satellites generating fixed or non-steerable beams).

[0141] NTN can include satellite communication networks, air-to-ground networks, UAV networks, etc. One of the key concepts in NTN is that NTN cells are provided by non-geostationary orbit (NGSO) satellites that periodically orbit the Earth. Each satellite has its own orbit, which is included in satellite position estimation information. Based on satellite position estimation information, the network can predict feeder link switchovers and manage UE mobility and radio resource control. A BS providing NTN access can broadcast orbital trajectory information or ephemeris information regarding coordinates for NTN payloads. EphemerisInfo can provide satellite position estimation in the format of position and velocity state vectors or in the format of orbital parameters. The following tables provide examples of descriptions of the EphemerisInfo information elements broadcast by BS and the fields of EphemerisInfo IE.

[0142]

[0143]

[0144] Satellite communication networks may include LEO (low Earth orbit) satellites, MEO (medium Earth orbit) satellites, and GEO (geosynchronous Earth orbit) satellites as follows.

[0145]

[0146] The following are examples of NTN deployment scenarios.

[0147]

[0148] Referring to the NTN Batch-D3 and NTN Batch-D4 scenarios, the S-band of 2 to 4 GHz and the Ka-band of 26 to 40 GHz are considered as satellite frequency bands for LEO.

[0149] Figure 13 illustrates an NTN deployment scenario. In particular, Figure 13 illustrates a case where multi-beam operation is applied to the NTN deployment-D4 scenario among the NTN deployment scenarios illustrated in Table 7.

[0150] Since LEO satellites operating in the Ka-band suffer from severe path loss, multi-beam operation can be considered for LEO satellites in the Ka-band, as exemplified in Fig. 13.

[0151] According to the NTN Batch-D4 scenario, the beam footprint formed on the ground by beams steered from the satellite toward the ground area is fixed to the Earth. However, from the perspective of the UE on the ground, the beam direction that the UE must see changes over time. The following describes implementations of this specification for cases where multi-beam operation is applied in the NTN Batch-D4 scenario.

[0152] Figure 14 is illustrated to explain the concept of a beam-hopping-based NTN.

[0153] A satellite may have a large satellite footprint and limited feeder link bandwidth. Consequently, if a served beam footprint is defined as a beam footprint to which a common message (e.g., SSB, SIB1, and / or SIB19 containing satellite assistance information for NTN access) is provided, only about 1.5% to 10% of the beam footprints within the satellite footprint may be served at a time. If the percentage of served beam footprints is too low, UEs may not be able to access satellite communication within the areas of unserved beam footprints. To provide satellite communication services evenly across the beam footprints within the satellite footprint, beam-hopping transmission of a common control channel / signal may be considered.

[0154] From the perspective of a beam footprint, beam hopping may mean that the beam illuminating the beam footprint is turned on and off with respect to the beam footprint. From the perspective of a satellite, beam hopping may mean that the beam footprint illuminated by the satellite's active beam changes over time. Since the active beam illuminating the beam footprint is periodically turned on and off, from the perspective of a UE within the beam footprint, beam hopping may mean that the cell is activated toward a specific Earth.

[0155] In the following explanation, T dwell represents the time a specific cell is active and is also referred to as dwell time. rev It represents the period during which a specific cell is activated, and is also referred to as revisit time or revisit periodicity.

[0156] FIG. 15 is illustrated to explain the concepts of dwell time and revisit time based on beam hopping. In the example of FIG. 15, it is assumed that the revisit time is 320 ms and the dwell time for one cell is 20 ms. The satellite can change the beam footprint(s) illuminated by the active beam over time. For example, it can transmit SSB(s) with a period of 320 ms for one cell and perform communication through the active beam for 20 ms for said cell.

[0157] FIG. 16 illustrates the process of a UE setting up an RRC connection with a BS via a cell. In FIG. 16, Msg5 can carry an RRC Setup Complete message transmitted by the UE to the BS. In FIG. 16, K offset is a cell-specific scheduling offset used for timing relationships modified for NTN, and can be provided through NTN-configuration within SIB19 containing phase auxiliary information for NTN access. K offset The unit of may be the number of slots for a specific subcarrier interval (e.g., 15 kHz SCS). K offset If the value of is not provided, it may be assumed to be 0. K2 is a slot offset value between the PDCCH or RAR carrying the UL grant and the actual PUSCH transmission, and may be provided by the UL grant. K1 is a slot offset value between the slot containing the DL reception and the UL slot for HARQ-ACK feedback for the DL reception.

[0158] The UE performs SSB monitoring on the cell, and upon detecting an SSB, performs a random access process based on the SSB. The UE can notify the BS that an RRC connection has been established between the BS and the UE by sending an RRC setup completion message to the BS. However, if the dwell time on the cell is short or the time required for the random access process is long, the random access process may not be completed within the dwell time. If the random access process is not successfully completed, the UE cannot establish an RRC connection with the BS and thus cannot perform data transmission / reception; therefore, redefinitions regarding RO validation, RAR reception windows, etc., are required. Several implementations of this specification regarding the random access process for beam-hopping-based NTNs are described below. In particular, several implementations of this specification regarding determining RACH occasions (ROs) by considering the beam-hopping cycle are described below.

[0159] The association period, starting from frame 0, for mapping SS / PBCH block indexes to PRACH periods is N SSB Tx The smallest integer in the set determined by the PRACH configuration period according to the following table, which ensures that the SS / PBCH block indices are mapped at least once to PRACH periods within the aforementioned association period, where UE is N from the value of the parameter ssb-PositionInBurst in SIB1 or the RRC setting ServingCellConfigCommon. SSB Tx...can be obtained. In the case of operation within the spectrum, the parameter ssb-PositionsInBurst indicates the time domain positions of the SS / PBCH blocks transmitted within the half-frame containing the SS / PBCH blocks. The PRACH configuration period refers to the periododicity of the PRACH configuration indicated by the PRACH configuration index. The bits of the bitmap provided by the parameter ssb-PositionsInBurst correspond one-to-one with the SS / PBCH block indices, such that the first / leftmost bit in the bitmap corresponds to SS / PBCH block index 0 and the second bit corresponds to SS / PBCH block index 1, and a value of 0 in the bitmap indicates that the corresponding SS / PBCH block is not transmitted and a value of 1 indicates that the corresponding SS / PBCH block is not transmitted. After an integer number of mapping cycles of SS / PBCH block indexes to PRACH occasions within an associated period, N SSB Tx If there is a set of PRACH periods or PRACH preambles that are not mapped to any SS / PBCH block indices, no SS / PBCH block indices are mapped to the said set of PRACH periods or PRACH preambles. The associated pattern interval includes one or more associated cycles, and the pattern between PRACH periods and SS / PBCH block indices is determined to repeat at most every 160 msec. After an integer number of associated cycles, PRACH periods not associated with SS / PBCH block indices are not used for PRACH transmissions.

[0160]

[0161] FIG. 17 illustrates an example of mapping a synchronization signal block (SSB) to a random access channel occasion (RO) in a general environment, and FIG. 18 illustrates an example of mapping SSBs to ROs according to some implementations of this specification in an NTN environment with beam hopping. In the examples of FIG. 17 and FIG. 18, N is known by the parameter ssb-PositionsInBurst. SSB Tx It is assumed that = 8, one PRACH setting cycle is 10 ms, and there are a total of 5 ROs within the PRACH setting cycle.

[0162] Referring to Fig. 17, if the PRACH setting period is 10 ms, the set corresponding to the PRACH setting period of 10 ms in Table 8 is {1, 2, 4, 8, 16}, and the minimum number of PRACH setting periods that map a total of 8 SSB indices at least once is 2.

[0163] Referring to Fig. 18, T dwell If = 10 ms, the minimum association period(s) required to map SSBs to ROs within the residence interval may not be guaranteed. Therefore, when BS performs beam hopping, ROs need to be determined considering the residence time.

[0164] <Implementation #1. Only ROs existing within the dwell time are valid>

[0165] In some implementations of this specification, the UE may determine that only ROs existing within the dwell time are valid. In this regard, the following may be considered.

[0166] * Alt #1-1.UE is always T dwell It is expected that this will be set larger than the association time, which is the time length of the association cycle. For example, the UE expects that the number of ROs existing within the dwell interval is N SSBTx One can expect that BS will provide the UE with residence time settings and / or PRACH settings to be greater than N. As another example, the UE may expect that the number of ROs within the residence interval is N SSB Tx You may not expect residence time settings and / or PRACH settings that do not exceed a certain size.

[0167] * Alt #1-2.T dwell If this can be smaller than the association time, for example, T dwell If the system does not mandate that the association time be greater than this, the UE may consider or determine that only the ROs within the dwell period are valid ROs available for the random access process. Referring to FIG. 18, the UE may consider only the ROs existing within the dwell period to be valid, and may consider that only SSB#0, SSB#1, SSB#2, and SSB#3 are mapped to valid ROs. The UE may perform a PRACH transmission on an RO associated with one of the SSB indices having an SSB-RSRP exceeding the SSB-RSRP threshold among the SSBs existing within the dwell period (e.g., SSBs of different SSB indices transmitted within the dwell period). The SSB-RSRP is the cell RSRP measured based on the SSB, and the SSB-RSRP threshold may be set for the UE by the BS or be a value predefined by the system.

[0168] <Implementation #2. Determining association cycle based on revisit time>

[0169] FIG. 19 illustrates another example of the mapping of SSBs to ROs according to some implementations of the present specification in an NTN environment with beam hopping. In the example of FIG. 19, N is known by the parameter ssb-PositionsInBurst. SSB TxIt is assumed that = 8, the PRACH setting cycle is 10 ms, and there are a total of 5 ROs within one PRACH setting cycle.

[0170] N within the stay area SSB Tx If the SSBs cannot be mapped to the ROs at least once, then in the next cycle (e.g., at the start of the current stay interval T revisit SSB-RO mapping can be performed up to ROs existing in the (later starting stay interval). In this case, as exemplified in FIG. 19, the association cycle can be defined over multiple revisit intervals.

[0171] In order for BS and UE to know whether the SSB is a mapped frame, N SSB Tx It is necessary to define an SFN that maps the SSB with the lowest SSB index among the SSBs (e.g., SSB#0).

[0172] In some implementations of this specification, the mapping of SSB#0 can always start from a frame where SFN#0 is the mapping.

[0173] In some embodiments of this specification, the starting SFN value mapped to SSB#0 (e.g., SFN offset value) may be set to the UE by the BS. For example, SFN offset value SFN offset If provided to this UE, the BS and the UE are SFN = SFN offset It can be assumed that SSB#0 is mapped from the effective RO of the in-frame.

[0174] <Implementation #3. Determining association cycle based on revisit time>

[0175] FIG. 20 illustrates another example of the mapping of SSBs to ROs according to some implementations of the present specification in an NTN environment with beam hopping. In the example of FIG. 20, N is known by the parameter ssb-PositionsInBurst. SSB TxIt is assumed that = 8, the PRACH setting cycle is 10 ms, and there are a total of 5 ROs within one PRACH setting cycle.

[0176] In some implementations of this specification, the UE has a dwell time T based on the association period dwell It can be extended. In this regard, the following may be considered.

[0177] * Alt #3-1.UE can extend the dwell period only for PRACH transmission. Referring to FIG. 20, N SSB Tx If it is difficult for the individual SSB indexes to be mapped to the ROs within the dwell period at least once, the UE and BS are the above N SSB Tx It can be assumed / considered that the dwell period is extended only for PRACH transmissions, for example, so that the dwell period after extension is at least equal to the extended period, such that the individual SSB indices can be mapped to ROs at least once. In this case, as exemplified in FIG. 20, the dwell period may be extended such that the time length of the dwell period is an integer multiple of the time length of the PRACH setting period.

[0178] * Alt #3-2. In Alt #3-1, whether the dwell period is extended may be provided to the UE by the BS. In some implementations of this specification, since the dwell period extension is for the random access process, whether the dwell period extension is extended may be provided to the UE through the RACH setting. For example, if there is no field in the RACH setting set to support or true that the dwell period extension is supported, the UE may consider or assume that the dwell period set for said UE cannot be extended, otherwise the UE may consider or assume that the dwell period can be extended for random access. In some implementations, if the dwell period extension is allowed, the UE and the BS may operate according to Alt #3-1 on the cell that said UE is monitoring or attempting to access. Where extension of the dwell period is not permitted, in some implementations, the BS and the UE assume that SSB-to-RO mapping is performed only within the originally set dwell period for the cell that the UE is monitoring or attempting to connect to, and the UE may perform PRACH transmission only on ROs within the originally set dwell period, and the BS may attempt to receive PRACH on the cell only within the originally set dwell period. Alternatively, where extension of the dwell period is not permitted, in some implementations, the BS and the UE may operate according to the aforementioned implementation #2.

[0179] FIGS. 17 to 20 illustrate a case where one SSB is mapped per RACH period, but according to ssb-perRACH-OccasionAndCB-PreamblesPerSSB, multiple SSBs may be mapped to RACH periods or one SSB may be mapped to multiple RACH periods.

[0180] According to some implementations of this specification, the probability that a UE can successfully perform a random connection process can be increased even on beam-hopping-based cells. According to some implementations of this specification, NTN services can be reliably provided even on cells where beam-hopping is applied.

[0181] FIG. 21 illustrates the flow of an arbitrary connection process in a UE according to some implementations of the present specification.

[0182] A UE may perform operations according to some implementations of this specification in relation to performing random access. A UE may include at least one transceiver; at least one processor; and at least one computer memory operably connected to said at least one processor and storing instructions that, when executed, cause said at least one processor to perform operations according to some implementations of this specification. A processing device for a UE may include at least one processor; and at least one computer memory operably connected to said at least one processor and storing instructions that, when executed, cause said at least one processor to perform operations according to some implementations of this specification. A computer-readable (non-transient) storage medium may store at least one computer program including instructions that, when executed by said at least one processor, cause said at least one processor to perform operations according to some implementations of this specification. A computer program or computer program product is written on at least one computer-readable (non-transient) storage medium and may include instructions that, when executed, cause (at least one processor) to perform operations according to some implementations of this specification.In the UE, the processing device, the computer-readable (non-transient) storage medium, and / or the computer program product, the operations include: setting a random access channel (RACH) for a cell, setting an SSB-related configuration regarding SSBs of different synchronization signal block (SSB) indices transmitted from the cell, and determining a dwell period of the cell; determining RACH times based on the RACH setting; determining RACH times satisfying a predetermined condition among the RACH times as valid RACH times (S2101); mapping the SSBs to the valid RACH times, and may include transmitting a RACH preamble at a valid RACH time where at least one SSB of the cell is mapped (S2103). The predetermined condition may include: the corresponding RACH time is within the dwell period.

[0183] In some implementations, the operations may include obtaining the number of the SSBs based on the SSB-related settings. In some implementations, the UE may expect that the number of valid RACH times existing within the stay interval is greater than or equal to the number of the SSBs.

[0184] In some implementations, transmitting the RACH preamble may include transmitting the RACH preamble at a RACH time associated with an SSB whose received reference signal power (RSRP) is greater than a threshold among the SSBs mapped to RACH times within the stay interval, based on the fact that the time length of the stay interval is less than the time length by a minimum number of RACH setting cycles such that the SSBs of the cell are mapped to RACH times at least once.

[0185] In some implementations, the operations may include obtaining the revisit period of the cell. In some implementations, mapping the SSBs to the valid RACH periods may include mapping the SSBs to RACH periods within multiple revisit periods, respectively, which belong to multiple consecutive revisit periods, based on the fact that the time length of the dwell period is smaller than the time length by a minimum number of RACH setting periods such that the SSBs of the cell are mapped to the RACH periods at least once.

[0186] FIG. 22 illustrates the flow of an arbitrary connection process in BS according to some implementations of the present specification.

[0187] A BS may perform operations according to some implementations of this specification in relation to performing random access. A BS may include at least one transceiver; at least one processor; and at least one computer memory operably connectable to said at least one processor and, when executed, stores instructions that cause said at least one processor to perform operations according to some implementations of this specification. A processing device for a BS may include at least one processor; and at least one computer memory operably connectable to said at least one processor and, when executed, stores instructions that cause said at least one processor to perform operations according to some implementations of this specification. A computer-readable (non-transient) storage medium may store at least one computer program including instructions that cause said at least one processor to perform operations according to some implementations of this specification when executed by said at least one processor. A computer program or computer program product is written on at least one computer-readable (non-transient) storage medium and may include instructions that, when executed, cause (at least one processor) to perform operations according to some implementations of this specification.In the above BS, the above processing device, the above computer-readable (non-transient) storage medium, and / or the above computer program product, the operations may include: setting a random access channel (RACH) for a cell, setting an SSB-related configuration regarding SSBs of different synchronization signal block (SSB) indices transmitted from the cell, and transmitting information regarding a dwell period of the cell; determining RACH periods satisfying a predetermined condition among the RACH periods according to the RACH setting as valid RACH periods (S2201); mapping the SSBs to the valid RACH periods; and attempting to receive a RACH preamble in a valid RACH period to which at least one SSB of the cell is mapped (S2203). The predetermined condition may include: the corresponding RACH period is within the dwell period.

[0188] In some implementations, the BS may generate the SSB-related settings such that the number of valid RACH periods existing within the stay interval is greater than or equal to the number of SSBs.

[0189] In some implementations, the operations may include: transmitting information regarding the revisit period of the cell. In some implementations, mapping the SSBs to the valid RACH periods may include: mapping the SSBs to RACH periods within multiple revisit periods, respectively belonging to multiple consecutive revisit periods, based on the fact that the time length of the dwell period is smaller than the time length by a minimum number of RACH setting periods such that the SSBs of the cell are mapped to the RACH periods at least once.

[0190] As described above, the examples of this specification disclosed are provided to enable a person skilled in the art related to this specification to implement and practice this specification. Although the foregoing has been described by reference to the examples of this specification, a person skilled in the art may modify and change the examples of this specification in various ways. Accordingly, this specification is not intended to be limited to the examples described herein, but to be given the broadest possible scope consistent with the principles and novel features disclosed herein.

[0191] Implementations of this specification may be used in wireless communication systems, BS or UE, or other equipment.

Claims

1. In a method performed by user equipment, Establishing a random access channel (RACH) for a cell, SSB-related settings regarding SSBs of different synchronization signal block (SSB) indices transmitted from the cell, and determining the dwell period of the cell; Determine RACH timings based on the above RACH settings; Among the above RACH periods, RACH periods satisfying predetermined conditions are determined as valid RACH periods; It includes mapping the SSBs to the valid RACH periods, and The above cell includes transmitting a RACH preamble at a valid RACH time in which at least one SSB is mapped, and The above predetermined conditions include the following: the relevant RACH period is within the above stay period, method.

2. In Paragraph 1, Based on the above SSB-related settings, the method includes obtaining the number of the above SSBs, and The user device expects that the number of valid RACH periods existing within the stay interval is greater than or equal to the number of SSBs, method.

3. In Paragraph 1, Transmitting the above RACH preamble is: Based on the fact that the time length of the above-mentioned dwell period is smaller than the time length by a minimum number of RACH setting periods such that the SSBs of the cell are mapped to RACH periods at least once, the method comprises transmitting the RACH preamble in the RACH period associated with an SSB whose received reference signal power (RSRP) is greater than a threshold among the SSBs mapped to RACH periods within the dwell period. method.

4. In Paragraph 1, It includes obtaining the revisit period of the above cell, and Mapping the SSBs to the above valid RACH periods is: Based on the fact that the time length of the above-mentioned dwell period is smaller than the time length by a minimum number of RACH setting cycles such that the above-mentioned SSBs of the cell are mapped to RACH times at least once, the method comprises mapping the SSBs to RACH times within multiple dwell periods, each (respectively) belonging to a plurality of consecutive revisit cycles. method.

5. At least one processor; and It includes at least one computer memory operablely connectable to the at least one processor and, when executed, stores instructions that cause the at least one processor to perform operations, wherein the operations are: Establishing a random access channel (RACH) for a cell, SSB-related settings regarding SSBs of different synchronization signal block (SSB) indices transmitted from the cell, and determining the dwell period of the cell; Determine RACH timings based on the above RACH settings; Among the above RACH periods, RACH periods satisfying predetermined conditions are determined as valid RACH periods; It includes mapping the SSBs to the valid RACH periods, and The above cell includes transmitting a RACH preamble at a valid RACH time in which at least one SSB is mapped, and The above predetermined conditions include the following: the relevant RACH period is within the above stay period, User device.

6. In a computer-readable storage medium, the storage medium stores at least one program code comprising instructions that cause at least one processor to perform operations when executed, and said operations are: Establishing a random access channel (RACH) for a cell, SSB-related settings regarding SSBs of different synchronization signal block (SSB) indices transmitted from the cell, and determining the dwell period of the cell; Determine RACH timings based on the above RACH settings; Among the above RACH periods, RACH periods satisfying predetermined conditions are determined as valid RACH periods; It includes mapping the SSBs to the valid RACH periods, and The above cell includes transmitting a RACH preamble at a valid RACH time in which at least one SSB is mapped, and The above predetermined conditions include the following: the relevant RACH period is within the above stay period, Storage medium.

7. In a method performed by a base station, Transmitting information regarding a random access channel (RACH) setting for a cell, SSB-related settings regarding SSBs of different synchronization signal block (SSB) indices transmitted from the cell, and a dwell period of the cell; Among the RACH periods according to the above RACH setting, RACH periods satisfying predetermined conditions are determined as valid RACH periods; Mapping the SSBs to the valid RACH periods; and At least one SSB of the cell attempts to receive a RACH preamble during a valid RACH time in which it is mapped, and The above predetermined conditions include the following: the relevant RACH period is within the above stay period, method.

8. In Paragraph 7, The base station generates the SSB-related settings such that the number of valid RACH periods existing within the dwell period is greater than or equal to the number of SSBs. method.

9. In Paragraph 7, It includes transmitting information regarding the revisit period of the above cell, and Mapping the SSBs to the above valid RACH periods is: Based on the fact that the time length of the above-mentioned dwell period is smaller than the time length by a minimum number of RACH setting cycles such that the above-mentioned SSBs of the cell are mapped to RACH times at least once, the method comprises mapping the SSBs to RACH times within multiple dwell periods, each (respectively) belonging to a plurality of consecutive revisit cycles. method.

10. At least one processor; and It includes at least one computer memory operablely connectable to the at least one processor and, when executed, stores instructions that cause the at least one processor to perform operations, wherein the operations are: Transmitting information regarding a random access channel (RACH) setting for a cell, SSB-related settings regarding SSBs of different synchronization signal block (SSB) indices transmitted from the cell, and a dwell period of the cell; Among the RACH periods according to the above RACH setting, RACH periods satisfying predetermined conditions are determined as valid RACH periods; Mapping the SSBs to the valid RACH periods; and At least one SSB of the cell attempts to receive a RACH preamble during a valid RACH time in which it is mapped, and The above predetermined conditions include the following: the relevant RACH period is within the above stay period, Base station.

11. A computer-readable storage medium, wherein the storage medium stores at least one program code comprising instructions that cause at least one processor to perform operations when executed, and said operations are: Transmitting information regarding a random access channel (RACH) setting for a cell, SSB-related settings regarding SSBs of different synchronization signal block (SSB) indices transmitted from the cell, and a dwell period of the cell; Among the RACH periods according to the above RACH setting, RACH periods satisfying predetermined conditions are determined as valid RACH periods; Mapping the SSBs to the valid RACH periods; and At least one SSB of the cell attempts to receive a RACH preamble during a valid RACH time in which it is mapped, and The above predetermined conditions include the following: the relevant RACH period is within the above stay period, Storage medium.

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