KR20230031768A - Method and apparatus of beam management in wireless communication system - Google Patents

Abstract

According to various embodiments of the present invention, a method of a base station supporting beam forming in a wireless communication system comprises the following processes of: mapping reconfiguration intelligent surface (RIS) pattern information and a synchronization signal block (SSB); transmitting the mapped SSB to a RIS controller; and receiving a random access preamble for a terminal from the RIS controller.

Description

Beam operation method and apparatus in wireless communication system {METHOD AND APPARATUS OF BEAM MANAGEMENT IN WIRELESS COMMUNICATION SYSTEM}

The present invention relates to a method and apparatus for operating a beam in a wireless communication system.

Efforts are being made to develop an improved 5G (5th-Generation) communication system or pre-5G communication system in order to meet the growing demand for wireless data traffic after the commercialization of the 4G (4th-Generation) communication system. For this reason, the 5G communication system or the pre-5G communication system is called a system beyond the 4G network (beyond 4G network) or a system after the LTE system (post LTE).

In order to achieve a high data rate, the 5G communication system is being considered for implementation in an ultra-high frequency (mmWave) band (eg, a 60 gigabyte (60 GHz) band). In order to mitigate the path loss of radio waves and increase the propagation distance of radio waves in the ultra-high frequency band, beamforming, massive MIMO, and full dimensional MIMO (FD-MIMO) are used in 5G communication systems. , array antenna, analog beam-forming, and large scale antenna technologies are being discussed.

In addition, to improve the network of the system, in the 5G communication system, an evolved small cell, an advanced small cell, a cloud radio access network (cloud RAN), and an ultra-dense network , device to device communication (D2D), wireless backhaul, moving network, cooperative communication, coordinated multi-points (CoMP), and interference cancellation etc. are being developed.

In addition, in the 5G system, FQAM (hybrid FSK and QAM modulation) and SWSC (sliding window superposition coding), which are advanced coding modulation (ACM) methods, and advanced access technologies such as FBMC (filter bank multi carrier) and NOMA (non-orthogonal multiple access) and SCMA (sparse code multiple access) are being developed.

On the other hand, the Internet is evolving from a human-centered connection network in which humans create and consume information to an Internet of Things (IoT) network in which information is exchanged and processed between distributed components such as things. IoE (Internet of Everything) technology, which combines IoT technology with big data processing technology through connection with cloud servers, etc., is also emerging. In order to implement IoT, technical elements such as sensing technology, wired/wireless communication and network infrastructure, service interface technology, and security technology are required, and recently, sensor networks for connection between objects and machine to machine , M2M), and MTC (Machine Type Communication) technologies are being studied. In the IoT environment, intelligent IT (Internet Technology) services that create new values in human life by collecting and analyzing data generated from connected objects can be provided. IoT is a field of smart home, smart building, smart city, smart car or connected car, smart grid, health care, smart home appliances, advanced medical service, etc. can be applied to

Accordingly, various attempts are being made to apply the 5G communication system to the IoT network. For example, 5G communication such as sensor network, machine to machine (M2M), and machine type communication (MTC) is implemented by techniques such as beamforming, MIMO, and array antenna. The application of the cloud radio access network (cloud RAN) as the big data processing technology described above can be said to be an example of convergence of 5G technology and IoT technology.

On the other hand, in accordance with the recent development of communication systems, research on reconfiguration intelligent surface (RIS) is being conducted in 5G-based wireless communication systems.

The RIS may form a reflection pattern with a combination of phases and/or amplitudes of each reflecting element (RE) included in the RIS, and may reflect a beam incident to the RIS in a desired direction according to the reflection pattern.

In an environment where a base station supports a plurality of beams and a RIS supports a plurality of reflection patterns, it is necessary to select an appropriate beam and reflection pattern among a plurality of beams and a plurality of reflection patterns in order to eliminate a shadow area.

One aspect of the present disclosure is to provide a method and apparatus for operating a beam in a wireless communication system.

One aspect of the present disclosure is to provide a method and apparatus through which a base station can efficiently transmit/receive a signal to a terminal in a shadow area using beamforming to a terminal in a wireless communication system.

One aspect of the present disclosure is to provide a method and apparatus capable of performing efficient communication between a base station and a terminal using a reconfiguration intelligent surface (RIS) in a wireless communication system.

A method of a base station supporting beam forming in a wireless communication system according to various embodiments of the present disclosure includes a process of mapping a reconfiguration intelligent surface (RIS) pattern value and a synchronization signal block (SSB) It may include transmitting the mapped SSB to the RIS controller and receiving a random access preamble for the terminal from the RIS controller.

A method of a reconfiguration intelligent surface (RIS) controller supporting beamforming in a wireless communication system according to various embodiments of the present disclosure is a process of receiving a first synchronization signal block (SSB) mapped to a RIS pattern value from a base station And the process of setting the phase value of the RIS element of the RIS based on the RIS pattern value based on the received first SSB and the phase value of the RIS element Based on and transmitting the first SSB to the terminal.

According to various embodiments of the present disclosure, a base station can efficiently communicate with terminals using RIS.

According to various embodiments of the present disclosure, a terminal located in a shadow area and a base station can communicate efficiently.

Effects obtainable in the present disclosure are not limited to the effects mentioned above, and other effects not mentioned may be clearly understood by those skilled in the art from the description below. will be.

1 is a diagram illustrating a time-frequency domain structure in LTE according to various embodiments of the present disclosure.
2 is a diagram illustrating a downlink control channel of LTE according to various embodiments of the present disclosure.
3 is a diagram illustrating transmission resources of a downlink control channel in 5G according to various embodiments of the present disclosure.
4 is a diagram illustrating an example of setting a control region in 5G according to various embodiments of the present disclosure.
5 is a diagram illustrating an example of configuration for a downlink RB structure in 5G according to various embodiments of the present disclosure.
6 is a diagram schematically illustrating the structure of a wireless communication system including a RIS according to various embodiments of the present disclosure.
7 is a diagram illustrating an SSB used by terminals located in various locations in a wireless communication system to perform a beam establishment procedure with a base station according to various embodiments of the present disclosure.
8 is a diagram illustrating an SSB used by terminals located in various locations in a wireless communication system to perform a beam establishment procedure with a base station according to various embodiments of the present disclosure.
9 is a diagram illustrating an SSB used by terminals located in various locations in a wireless communication system to perform a beam establishment procedure with a base station according to various embodiments of the present disclosure.
10 is a diagram illustrating an SSB used by terminals located in various locations in a wireless communication system to perform a RACH procedure with a base station according to various embodiments of the present disclosure.
11A and 11B are flowcharts illustrating a method for a base station and a terminal to perform a beam establishment procedure through RIS according to various embodiments of the present disclosure.
12 is a flowchart illustrating a process in which a base station and a terminal perform a beam establishment procedure through SSB according to various embodiments of the present disclosure.
13 is a flowchart illustrating a sequence of an operation of beam sweeping in downlink after a base station and a terminal are connected according to various embodiments of the present disclosure.
14 is a diagram illustrating an example of a method in which a base station sets a reference signal to a terminal through downlink according to various embodiments of the present disclosure.
15 is a diagram illustrating an example of a method in which a base station sets a reference signal to a terminal through downlink according to various embodiments of the present disclosure.
16 is a diagram illustrating an example of a method in which a base station sets a reference signal to a terminal through downlink according to various embodiments of the present disclosure.
17 is a diagram illustrating an operation of a terminal reporting a reference signal through an uplink according to various embodiments of the present disclosure.
18 is a flowchart illustrating a sequence of a process in which a base station informs a terminal of base station beam and RIS RP information to a terminal through a downlink.
19 is a diagram schematically illustrating a structure of a terminal according to various embodiments of the present disclosure.
20 is a diagram schematically illustrating a structure of a base station according to various embodiments of the present disclosure.
21 is a diagram schematically illustrating a structure of RIS according to various embodiments of the present disclosure.
22 is a diagram illustrating a channel model between a base station, a RIS, and a terminal according to various embodiments of the present disclosure.
23 is a diagram illustrating an example of SINR CDF performance according to various embodiments of the present disclosure.
24a and 24b are diagrams illustrating another example of SINR CDF performance according to various embodiments of the present disclosure.
25 is a diagram illustrating another example of SINR CDF performance according to various embodiments of the present disclosure.

Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. At this time, it should be noted that the same components in the accompanying drawings are indicated by the same reference numerals as much as possible. In addition, detailed descriptions of well-known functions and configurations that may obscure the subject matter of the present disclosure will be omitted.

In describing the embodiments in this specification, descriptions of technical contents that are well known in the art to which the present disclosure pertains and are not directly related to the present disclosure will be omitted. This is to more clearly convey the gist of the present disclosure without obscuring it by omitting unnecessary description.

For the same reason, in the accompanying drawings, some components are exaggerated, omitted, or schematically illustrated. Also, the size of each component does not entirely reflect the actual size. In each figure, the same reference number is assigned to the same or corresponding component.

Advantages and features of the present disclosure, and methods for achieving them, will become clear with reference to embodiments described below in detail in conjunction with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below and may be implemented in various different forms, only the present embodiments make the disclosure of the present disclosure complete, and the common knowledge in the art to which the present disclosure belongs It is provided to fully inform the possessor of the scope of the disclosure, and the disclosure is only defined by the scope of the claims. Like reference numbers designate like elements throughout the specification.

At this time, it will be understood that each block of the process flow chart diagrams and combinations of the flow chart diagrams can be performed by computer program instructions. These computer program instructions may be embodied in a processor of a general purpose computer, special purpose computer, or other programmable data processing equipment, so that the instructions executed by the processor of the computer or other programmable data processing equipment are described in the flowchart block(s). It creates means to perform functions. These computer program instructions may also be stored in a computer usable or computer readable memory that can be directed to a computer or other programmable data processing equipment to implement functionality in a particular way, such that the computer usable or computer readable memory The instructions stored in are also capable of producing an article of manufacture containing instruction means that perform the functions described in the flowchart block(s). The computer program instructions can also be loaded on a computer or other programmable data processing equipment, so that a series of operational steps are performed on the computer or other programmable data processing equipment to create a computer-executed process to generate computer or other programmable data processing equipment. Instructions for performing processing equipment may also provide steps for performing the functions described in the flowchart block(s).

Additionally, each block may represent a module, segment, or portion of code that includes one or more executable instructions for executing specified logical function(s). It should also be noted that in some alternative implementations it is possible for the functions mentioned in the blocks to occur out of order. For example, two blocks shown in succession may in fact be executed substantially concurrently, or the blocks may sometimes be executed in reverse order depending on their function.

At this time, the term '~unit' used in this embodiment means software or a hardware component such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC), and '~unit' refers to certain roles. carry out However, '~ part' is not limited to software or hardware. '~bu' may be configured to be in an addressable storage medium and may be configured to reproduce one or more processors. Therefore, as an example, '~unit' refers to components such as software components, object-oriented software components, class components, and task components, processes, functions, properties, and procedures. , subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. Functions provided within components and '~units' may be combined into smaller numbers of components and '~units' or further separated into additional components and '~units'. In addition, components and '~units' may be implemented to play one or more CPUs in a device or a secure multimedia card.

In embodiments of the present disclosure, a base station is a subject that allocates resources of a terminal, and at least one of gNode B, gNB, eNode B, eNB, Node B, BS, radio access unit, base station controller, or node on the network can be one In addition, the base station includes an Integrated Access and Backhaul-donor (IAB-donor), which is a gNB that provides network access to the terminal (s) through a network of backhaul and access links in the NR system, and the terminal (s) ) and an IAB-node, which is a radio access network (RAN) node supporting NR backhaul links to the IAB-donor or other IAB-nodes. . The terminal is wirelessly connected through the IAB-node and can transmit and receive data with an IAB-donor connected to at least one IAB-node through a backhaul link.

In addition, the terminal may include a user equipment (UE), a mobile station (MS), a cellular phone, a smart phone, a computer, or various devices capable of performing communication functions. In the present disclosure, downlink (DL) is a radio transmission path of a signal transmitted from a base station to a terminal, and uplink (UL) refers to a radio transmission path of a signal transmitted from a terminal to a base station. In addition, although an LTE or LTE-A system may be described as an example in the following, embodiments of the present disclosure may be applied to other communication systems having a similar technical background or channel type. For example, the 5th generation mobile communication technology (5G, new radio, NR) developed after LTE-A may be included in this, and the following 5G may be a concept including existing LTE, LTE-A and other similar services there is. In addition, the present disclosure can be applied to other communication systems through some modifications within a range that does not greatly deviate from the scope of the present disclosure as determined by those skilled in the art.

In the following description, terms referring to signals, terms referring to channels, terms referring to control information, terms referring to network entities, terms referring to components of a device, etc. are used for convenience of description. it is exemplified In addition, terms for identifying nodes, terms for messages, terms for interfaces between network entities, terms for various information, and the like used in the following description are illustrated for convenience of description. Accordingly, the present disclosure is not limited to the terms described below, and other terms having equivalent technical meanings may be used.

In addition, although the present disclosure describes various embodiments using terms used in some communication standards (eg, 3rd Generation Partnership Project (3GPP)), this is only an example for explanation. Various embodiments of the present disclosure may be easily modified and applied to other communication systems.

1 is a diagram illustrating a time-frequency domain structure in a system in LTE according to various embodiments of the present disclosure.

Referring to FIG. 1, the horizontal axis represents the time domain and the vertical axis represents the frequency domain. The minimum transmission unit in the time domain is an OFDM symbol. Nsymb (101) OFDM symbols are gathered to form one slot (102), and two slots are gathered to form one subframe (103). The length of the slot is 0.5 ms, and the length of the subframe is 1.0 ms. And, the radio frame 104 is a time domain unit consisting of 10 subframes. The minimum transmission unit in the frequency domain is a subcarrier, and the bandwidth of the entire system transmission bandwidth consists of a total of NBW (105) subcarriers. A basic unit of resources in the time-frequency domain is a Resource Element (RE) 106, which can be represented by an OFDM symbol index and a subcarrier index. A Resource Block (RB; or Physical Resource Block, PRB) 107 is defined by Nsymb (101) consecutive OFDM symbols in the time domain and NRB (108) consecutive subcarriers in the frequency domain. Accordingly, one RB 108 is composed of Nsymb x NRB number of REs 106 . In general, the minimum transmission unit of data is the RB unit. In an LTE system, Nsymb = 7 and NRB = 12, and NBW and NRB are proportional to the bandwidth of the system transmission band.

Next, downlink control information (DCI) in LTE and LTE-Advanced (LTE-A) systems will be described in detail.

In the LTE system, scheduling information for downlink data or uplink data is transmitted from a base station to a terminal through DCI. DCI defines various formats, whether it is scheduling information for uplink data or scheduling information for downlink data, whether it is a compact DCI with a small size of control information, and applying spatial multiplexing using multiple antennas. DCI format is applied and operated depending on whether DCI is used for power control or not. For example, DCI format 1, which is scheduling control information for downlink data, is configured to include at least the following control information.

- Resource allocation type 0/1 flag: Notifies whether the resource allocation method is type 0 or type 1. Type 0 allocates resources in units of resource block groups (RBGs) by applying a bitmap method. In the LTE system, a basic unit of scheduling is a resource block (RB) represented by time and frequency domain resources, and an RBG is composed of a plurality of RBs to become a basic unit of scheduling in the type 0 scheme. Type 1 allows a specific RB to be allocated within an RBG.

- Resource block assignment: RBs allocated for data transmission are notified. The resource to be expressed is determined according to the system bandwidth and resource allocation method.

- Modulation and Coding Scheme (MCS): Notifies the modulation scheme used for data transmission and the size of the transport block, the data to be transmitted.

- HARQ process number: Notifies the process number of HARQ.

- New data indicator: Notifies whether it is HARQ initial transmission or retransmission.

- Redundancy version: Notifies the redundancy version of HARQ.

- Transmit Power Control (TPC) command for Physical Uplink Control CHannel (PUCCH): Notifies a transmit power control command for PUCCH, which is an uplink control channel.

The DCI is transmitted through a physical downlink control channel (PDCCH) that is a downlink physical control channel through channel coding and modulation processes.

A Cyclic Redundancy Check (CRC) is attached to the DCI message payload, and the CRC is scrambled with a Radio Network Temporary Identifier (RNTI) corresponding to the identity of the terminal. Different RNTIs are used according to the purpose of the DCI message, eg, UE-specific data transmission, power control command, or random access response. Soon, the RNTI is not transmitted explicitly but is included in the CRC calculation process and transmitted. Upon receiving the DCI message transmitted on the PDCCH, the terminal checks the CRC using the allocated RNTI, and if the CRC check result is correct, it can be known that the corresponding message has been transmitted to the terminal.

2 is a diagram illustrating a downlink control channel of LTE according to various embodiments of the present disclosure. The downlink control channel of LTE may be, for example, PDCCH 201.

Referring to FIG. 2, a PDCCH 201 is time multiplexed with a physical downlink shared CHannel (PDSCH) 202, which is a data transmission channel, and is transmitted over the entire system bandwidth. The area of the PDCCH 201 is represented by the number of OFDM symbols, which is indicated to the terminal by a Control Format Indicator (CFI) transmitted through a Physical Control Format Indicator CHannel (PCFICH). By allocating the PDCCH 201 to the OFDM symbol coming at the beginning of the subframe, the UE can decode the downlink scheduling assignment as quickly as possible, and through this, the decoding delay for the DownLink Shared CHannel (DL-SCH), that is, the overall downlink There is an advantage of reducing link transmission delay. Since one PDCCH carries one DCI message and multiple UEs can be simultaneously scheduled for downlink and uplink, multiple PDCCHs are simultaneously transmitted in each cell. A cell-specific reference signal (CRS) 203 is used as a reference signal for decoding the PDCCH 201. The CRS 203 is transmitted every subframe over the entire band, and scrambling and resource mapping vary according to a cell ID (IDentity). Since the CRS 203 is a reference signal commonly used by all terminals, terminal-specific beamforming cannot be used. Therefore, the multi-antenna transmission method for the PDCCH of LTE is limited to open-loop transmission diversity. The number of ports of the CRS 203 is implicitly known to the UE from decoding of the PBCH (Physical Broadcast CHannel).

Resource allocation of the PDCCH 201 is based on a Control-Channel Element (CCE), and one CCE is composed of 9 Resource Element Groups (REGs), that is, a total of 36 Resource Elements (REs). The number of CCEs required for a specific PDCCH 201 may be 1, 2, 4, or 8, which varies depending on the channel coding rate of the DCI message payload. As such, different numbers of CCEs are used to implement link adaptation of the PDCCH 201. The terminal needs to detect a signal without knowing information about the PDCCH 201. In LTE, a search space representing a set of CCEs is defined for blind decoding. The search space is composed of a plurality of sets at the aggregation level (AL) of each CCE, which is not explicitly signaled but implicitly defined through a function and subframe number according to the UE identity. Within each subframe, the UE decodes the PDCCH 201 for all possible resource candidates that can be created from CCEs within the set search space, and information declared valid for the corresponding UE through CRC check. to process

The search space is classified into a terminal-specific search space and a common search space. A certain group of terminals or all terminals can search the common search space of the PDCCH 201 in order to receive cell-common control information such as dynamic scheduling for system information or paging messages. For example, scheduling allocation information of a DL-SCH for transmission of System Information Block (SIB)-1 including cell operator information may be received by examining the common search space of the PDCCH 201.

In LTE, the entire PDCCH region is composed of a set of CCEs in a logical region, and a search space consisting of a set of CCEs exists. The search space is divided into a common search space and a UE-specific search space, and the search space for the LTE PDCCH is defined as follows in TS 36.213 of the 3GPP communication standard document.

According to the definition of the search space for the PDCCH described above, the UE-specific search space is not explicitly signaled, but is implicitly defined through a function and a subframe number according to the UE identity. In other words, since the terminal-specific search space can change according to the subframe number, this means that it can change over time, and through this, the problem that a specific terminal cannot use the search space by other terminals among terminals ( blocking problem). If a UE cannot be scheduled in a corresponding subframe because all CCEs it examines are already being used by other UEs scheduled in the same subframe, since this search space changes over time, in the next subframe Such a problem may not occur. For example, even if parts of the UE-specific search spaces of UE #1 and UE #2 overlap in a specific subframe, since the UE-specific search spaces change for each subframe, the overlap in the next subframe is expected to be different from this. can be expected

According to the definition of the search space for the PDCCH described above, in the case of a common search space, since a certain group of terminals or all terminals must receive the PDCCH, it is defined as a set of pre-promised CCEs. In other words, the common search space does not change according to the identity of the terminal or the subframe number. Although a common search space exists for transmission of various system messages, it can also be used to transmit control information of individual terminals. Through this, the common search space can also be used as a solution to a phenomenon in which a terminal is not scheduled due to insufficient resources available in the terminal-specific search space.

The search space is a set of candidate control channels consisting of CCEs that the UE should attempt to decode on a given aggregation level. have a search space. The number of PDCCH candidates to be monitored by the terminal in the search space defined according to the aggregation level in the LTE PDCCH is defined as the following table in TS 36.213 of the 3GPP communication standard document.

<Table 1>

According to <Table 1>, in the case of a UE-specific search space, aggregation levels {1, 2, 4, 8} are supported, and at this time, {6, 6, 2, 2} PDCCH candidate groups are respectively provided. In the case of the common search space 302, aggregation levels {4, 8} are supported, and at this time, {4, 2} PDCCH candidate groups are respectively provided. The reason why the common search space supports only {4, 8} aggregation level is to improve coverage characteristics because system messages generally have to reach cell edges.

DCI transmitted in the common search space is defined only for a specific DCI format such as 0/1A/3/3A/1C corresponding to a purpose such as system message or power control for a terminal group. Within the common search space, DCI formats with spatial multiplexing are not supported. The downlink DCI format to be decoded in the UE-specific search space depends on the transmission mode set for the corresponding UE. Since the setting of the transmission mode is performed through RRC (Radio Resource Control) signaling, an exact subframe number for whether the corresponding setting is effective for the corresponding terminal is not specified. Therefore, the terminal can be operated not to lose communication by always performing decoding for DCI format 1A regardless of the transmission mode.

3 is a diagram illustrating transmission resources of a downlink control channel in 5G according to various embodiments of the present disclosure. 3 is a diagram showing an example of a basic unit of time and frequency resources constituting a downlink control channel that can be specifically used in 5G. Referring to FIG. 3, a resource element group (REG) of time and frequency resources constituting a control channel is composed of 1 OFDM symbol 301 on the time axis and 12 subcarriers on the frequency axis ( 302), that is, it is composed of 1 RB. In configuring the basic unit of the control channel, by assuming that the time axis basic unit is 1 OFDM symbol 301, the data channel and the control channel can be time-multiplexed within one subframe. By locating the control channel before the data channel, the user's processing time can be reduced, making it easy to satisfy the latency requirement. By setting the basic unit of the frequency axis of the control channel to 1 RB 302, frequency multiplexing between the control channel and the data channel can be performed more efficiently.

Referring to FIG. 3, control channel regions of various sizes can be set by concatenating REGs 303. For example, when a basic unit to which a downlink control channel is allocated in 5G is a CCE 304, 1 CCE 304 may include a plurality of REGs 303. Referring to FIG. 3, for example, REG 303 may consist of 12 REs, and if 1 CCE 304 consists of 6 REGs 303, 1 CCE 304 may consist of 72 REs. means there is When a downlink control region is set, the corresponding region can be composed of a plurality of CCEs 304, and a specific downlink control channel is mapped to one or more CCEs 304 according to the aggregation level (AL) in the control region and transmitted. It can be. The CCEs 304 in the control area are identified by numbers, and at this time, the numbers may be assigned according to a logical mapping method.

Referring to FIG. 3, the REG 303 may include both REs to which DCI is mapped and a region to which a Demodulation Reference Signal (DMRS) 305, which is a reference signal for decoding them, is mapped. For example, DMRS 305 may be transmitted in 6 REs within 1 REG 303. For reference, since the DMRS 303 is transmitted using the same precoding as the control signal mapped in the REG 303, the terminal can decode the control information even if there is no information about which precoding is applied by the base station.

4 is a diagram illustrating an example of setting a control region in a 5G wireless communication system according to various embodiments of the present disclosure. 4 is a diagram showing an example of a control resource set (CORESET) in which a downlink control channel is transmitted. Referring to FIG. 4, two control areas (control area #1 (401) and control area #2 (402)) may be set within a system bandwidth 410 on the frequency axis and one slot 420 on the time axis. . Referring to FIG. 4, it is assumed that one slot is composed of 7 OFDM symbols. The control regions 401 and 402 may be set to specific subbands 403 within the entire system bandwidth 410 on the frequency axis. The time axis can be set to one or a plurality of OFDM symbols, and this can be defined as a control region length (Control Resource Set Duration, 404). Referring to FIG. 4, control region #1 (401) is set to a control region length of 2 symbols, and control region #2 (402) is set to a control region length of 1 symbol.

Referring to FIG. 4, a control region in 5G may be set by a base station to a terminal through higher layer signaling (eg, system information, master information block (MIB), RRC signaling). Setting the control region to the terminal means providing information such as the location of the control region, subbands, resource allocation of the control region, and the length of the control region. For example, the information disclosed in Table 2 may be included.

<Table 2>

In addition to the above setting information, various pieces of information necessary for transmitting a downlink control channel may be set in the terminal.

5 is a diagram illustrating an example of a description of a downlink RB structure in 5G according to various embodiments of the present disclosure. Referring to FIG. 5, in a 5G system, scheduling information for a Physical Uplink Shared CHannel (PUSCH) or a Physical Downlink Shared CHannel (PDSCH) is transmitted from a base station to a terminal through DCI. The UE may monitor the DCI format for fallback and the DCI format for non-fallback with respect to PUSCH or PDSCH. The contingency DCI format may be composed of a fixed field between the base station and the terminal, and the DCI format for non-preparation may include a configurable field.

The DCI for a countermeasure for scheduling the PUSCH may include, for example, information disclosed in Table 3.

<Table 3>

The DCI for non-preparation scheduling for PUSCH may include, for example, the information disclosed in Table 4.

<Table 4>

The DCI for a backup plan for scheduling the PDSCH may include, for example, the information disclosed in Table 5.

<Table 5>

The non-preparation DCI for scheduling the PDSCH may include, for example, information disclosed in Table 6.

<Table 6>

The DCI may be transmitted through a downlink physical control channel (PDCCH) through channel coding and modulation processes. A Cyclic Redundancy Check (CRC) is attached to the DCI message payload, and the CRC is scrambled with a Radio Network Temporary Identifier (RNTI) corresponding to the identity of the terminal. Different RNTIs are used according to the purpose of the DCI message, eg, UE-specific data transmission, power control command, or random access response. Soon, the RNTI is not transmitted explicitly but is included in the CRC calculation process and transmitted. Upon receiving the DCI message transmitted on the PDCCH, the terminal checks the CRC using the allocated RNTI, and if the CRC check result is correct, it can be known that the corresponding message has been transmitted to the terminal.

According to an embodiment of the present disclosure, a DCI scheduling a PDSCH for System Information (SI) may be scrambled with an SI-RNTI. For example, a DCI for scheduling a PDSCH for a Random Access Response (RAR) message may be scrambled with a RA-RNTI. For example, a DCI for scheduling a PDSCH for a paging message may be scrambled with a P-RNTI. For example, DCI notifying SFI (Slot Format Indicator) may be scrambled with SFI-RNTI. For example, DCI notifying TPC (Transmit Power Control) may be scrambled with TPC-RNTI. For example, a DCI for scheduling a UE-specific PDSCH or PUSCH may be scrambled with C-RNTI (Cell RNTI).

Referring to FIG. 5, when a specific terminal receives a schedule for a data channel, for example, a PUSCH or a PDSCH, through the PDCCH, data is transmitted and received along with the DMRS within the scheduled resource region.

는 LTE/LTE-A 시스템의 경우에 15kHz이고 5G 시스템의 경우 {15, 30, 60, 120, 240, 480}kHz 중 하나가 사용된다. Referring to FIG. 5, a specific terminal uses 14 OFDM symbols as one slot (or subframe) in downlink, the PDCCH is transmitted in the initial two OFDM symbols 501, and the DMRS in the third symbol 502 Indicates a case where it is set to be transmitted. Within a specific RB in which the PDSCH is scheduled, data may be mapped and transmitted to REs in which the DMRS is not transmitted in the third symbol and REs from the fourth to the last symbol 503 thereafter. According to an embodiment of the Japanese disclosure, the subcarrier spacing

is 15 kHz in case of LTE/LTE-A system and one of {15, 30, 60, 120, 240, 480} kHz is used in case of 5G system.

According to various embodiments of the present disclosure, in order to measure a downlink channel state in a wireless communication system, a base station needs to transmit a reference signal. In the case of a Long Term Evolution Advanced (LTE-A) system of 3GPP, a terminal can measure a channel state between a base station and a terminal using a CRS or CSI-RS transmitted by a base station. The channel state should be measured in consideration of various factors, which may include the amount of interference in downlink. The amount of interference in the downlink includes an interference signal and thermal noise generated by an antenna belonging to a neighboring base station, and the amount of interference in the downlink is important for a terminal to determine a downlink channel condition. For example, when a base station with one transmit antenna transmits a signal to a terminal with one receive antenna, the terminal simultaneously receives energy per symbol from a reference signal received from the base station in downlink and a corresponding symbol in a receiving period. Es/Io must be determined by determining the amount of interference to be received. The determined Es/Io is converted into a data transmission rate or a value corresponding thereto and transmitted to the base station in the form of a channel quality indicator (CQI), and is used by the base station to determine at what data transmission rate to transmit to the terminal. can be used

According to various embodiments of the present disclosure, in the case of an LTE-A system, a terminal feeds back information about a downlink channel state to a base station so that the base station can utilize it for downlink scheduling. For example, the terminal measures the reference signal transmitted by the base station in the downlink and feeds back information extracted thereto to the base station in a form defined in the LTE/LTE-A standard. As described above, information fed back by the terminal in LTE/LTE-A may be referred to as channel state information, and the channel state information may include the following three pieces of information.

Rank Indicator (RI): The number of spatial layers that the UE can receive in the current channel state

Precoding Matrix Indicator (PMI): An indicator for a precoding matrix preferred by the terminal in the current channel state.

Channel Quality Indicator (CQI): Maximum data rate that a terminal can receive in the current channel state

CQI may be replaced with a signal to interference plus noise ratio (SINR) that can be used similarly to the maximum data rate, maximum error correction code rate and modulation scheme, and data efficiency per frequency. there is.

According to various embodiments of the present disclosure, RI, PMI, and CQI included in channel state information are associated with each other and have meaning. For example, since the precoding matrix supported by LTE/LTE-A is defined differently for each rank, the PMI value X when RI has a value of 1 and the PMI value X when RI has a value of 2 are may be interpreted differently.

According to various embodiments of the present disclosure, even when the UE determines the CQI, it is assumed that the PMI and X notified to the eNB are applied by the eNB. For example, when the UE reports RI_X, PMI_Y, and CQI_Z to the base station, it is equivalent to reporting that the corresponding UE can receive the data rate corresponding to CQI_Z when the rank is RI_X and the PMI is PMI_Y. In this way, when the UE calculates the CQI, it is assumed which transmission method will be performed by the base station so that optimized performance can be obtained when actual transmission is performed using the corresponding transmission method.

According to various embodiments of the present disclosure, RI, PMI, and CQI, which are channel state information fed back by a terminal in LTE/LTE-A, may be fed back in a periodic or aperiodic form. When the base station wants to acquire channel state information of a specific terminal aperiodically, the base station transmits an aperiodic feedback indicator (or channel state information request field, channel state) included in downlink control information (DCI) for the terminal. It can be configured to perform aperiodic feedback (or aperiodic channel state information reporting) using information request information). In addition, when the terminal receives an indicator set to perform aperiodic feedback in the nth subframe, the terminal includes aperiodic feedback information (or channel state information) in data transmission in the n+kth subframe to perform uplink transmission. can do. Here, k is a parameter defined in the 3GPP LTE Release 11 standard, which is 4 in frequency division duplexing (FDD) and may be defined as shown in [Table 7] in time division duplexing (TDD).

<Table 7> k value for each subframe number n in TDD UL/DL configuration

When aperiodic feedback is set, feedback information (or channel state information) includes RI, PMI, and CQI, and RI and PMI may not be fed back according to feedback settings (or channel state report settings).

6 is a diagram schematically illustrating the structure of a wireless communication system including a Reconfigurable Intelligent Surface (RIS) according to various embodiments of the present disclosure. Referring to FIG. 6, a wireless communication system may include a base station 600, terminals 603, 604, and 605, a RIS 607, and a RIS controller 608. The present invention proposes a technique for operating a base station beam and a RIS pattern (RP) in a RIS-based wireless communication system. According to various embodiments of the present disclosure, the RP may be operated by setting a phase value or reflection pattern of a RIS element, which is a basic unit of the RIS (607). Referring to FIG. 6 , a RIS (607) may be controlled by a RIS controller (608).

According to various embodiments of the present disclosure, in a beam establishment step before the base station 600 and the terminals 603, 604, and 605 are connected, in order for the base station 600 to perform beam sweeping, The beam of the base station 600 and the RP of the RIS 607 are specified, and the base station 600 maps the beam of the base station 600 and the RP value of the RIS 607 with a synchronization signal block (SSB). A method in which the base station 600 transmits the SSB to the terminals 603, 604, and 605 through downlink after proceeding, and when the base station 600 transmits the SSB to the terminals 603, 604, and 605 through downlink, RIS A method of applying the RP value of 607, when the terminals 603, 604, and 605 measure the signal strength (RSRP) of the SSB received from the base station 600 and transmit PRACH (Physical Random Access CHannel) through uplink After the RP value application method of the RIS 607 and the base station 600 and the terminals 603, 604, and 605 are connected, the base station 600 beam and RIS 607 using CSI-RS (Channel State Information-Reference Signal) ), including how to operate the RP.

개의 빔을 운용하는 기지국 및 음영 지역에 위치한 단말(603)을 지원하기 위해

개의 RP 값이 가능한 RIS(607)가 존재하는 셀을 나타낸다. 기지국(600)의

개의 빔들 중

개의 빔을 통해 송신되는 신호(601)들은 RIS(607)를 향하여 신호가 송신되고, RIS(607)에 의해 반사될 수 있으며, 나머지

개의 빔을 통해 송신되는 신호들(602)은 RIS(607)를 향하지 않아 신호가 RIS(607)를 이용하여 반사되지 않을 수 있다. 본 개시의 다양한 실시예에 따르면, 음영 지역에 위치하는 단말(603), 기지국(600)과 RIS(607) 사이에 위치하는 단말 (604) 및 통신 장애를 일으킬 수 있는 물체가 기지국(600)과 단말(605) 사이에 존재하지 않는 위치에 위치하는 단말(605)이 존재하는 상황에서 기지국(600) 빔 및 RIS(607)의 RP 값을 운용하는 방식을 포함한다. Referring to Figure 6,

To support a base station operating two beams and a terminal 603 located in a shadow area

RP values indicate a cell in which a possible RIS 607 exists. base station 600

of the beams

Signals 601 transmitted through the number of beams are transmitted toward the RIS 607, may be reflected by the RIS 607, and the remaining

Signals 602 transmitted through the N beams may not be directed to the RIS 607 so that the signal may not be reflected using the RIS 607. According to various embodiments of the present disclosure, a terminal 603 located in a shadow area, a terminal 604 located between the base station 600 and the RIS 607, and an object that may cause communication failure are connected to the base station 600. This includes a method of operating the beam of the base station 600 and the RP value of the RIS 607 in a situation where the terminal 605 located at a location that does not exist between the terminals 605 exists.

7 is a diagram illustrating an SSB used by terminals located in various locations in a wireless communication system to perform a beam establishment procedure with a base station according to various embodiments of the present disclosure. 7 illustrates a method in which the RIS controller 608 directly applies the RP value of the RIS 607 set by the base station 600 according to various embodiments of the present disclosure.

), RIS(607)가 적용할 수 있는 RP 값

인 상황을 가정하고 있다.Referring to FIG. 7, in the RIS-based wireless communication system shown in FIG. 6, terminals 603, 604, and 605 located in various locations perform an initial beam establishment procedure with a base station, The base station 600 illustrates a method of mapping and transmitting an SSB to a combination of a beam of the base station 600 and an RP of the RIS 607. Referring to FIG. 7, the number of beams of the base station 600 toward the RIS 607 is set to 2 (

), RP value that RIS (607) can apply

We are assuming a situation where

번 만큼 반복하여 각각 RIS(607)의 RP를 SSB에 매핑되어 있다. (일 예로, SSB 0~SSB 5) 각각의 SSB(일 예로, SSB 0~SSB 5)는 각 Beam에 해당되는 각도로 빔포밍(beamforming) 되어 송신 될 수 있다. 일 예로, 기지국의 Beam 0에 RIS(607) RP의 값 "OFF", RIS(607) RP의 값 "1" 및 RIS(607) RP의 값 "2"이 SSB 0, SSB 1 및 SSB 2가 매핑될 수 있다. 또한, 기지국의 Beam 1에 RIS(607) RP의 값 "OFF", RIS(607) RP의 값 "1" 및 RIS(607) RP의 값 "2"이 SSB 3, SSB 4 및 SSB 5가 매핑될 수 있다. 기지국의 Beam 2에도 Beam 0 및 Beam 1과 마찬가지로 RIS RP와 조합하여 SSB에 매핑될 수 있다.Referring to FIG. 7, Beam 0 and Beam 1 of the base station 600 toward the RIS 607 are

Each RP of the RIS 607 is mapped to the SSB repeatedly. (For example, SSB 0 to SSB 5) Each SSB (for example, SSB 0 to SSB 5) may be beamformed at an angle corresponding to each beam and transmitted. For example, in Beam 0 of the base station, the RIS (607) RP value "OFF", the RIS (607) RP value "1" and the RIS (607) RP value "2" are SSB 0, SSB 1, and SSB 2 can be mapped. In addition, the RIS (607) RP value "OFF", the RIS (607) RP value "1", and the RIS (607) RP value "2" are SSB 3, SSB 4, and SSB 5 mapped to Beam 1 of the base station It can be. Like Beam 0 and Beam 1, Beam 2 of the base station may be mapped to the SSB in combination with the RIS RP.

들은 RIS(607)를 향하지 않은 기지국(600)의 빔들에 매핑되어 각 빔에 해당되는 각도로 빔포밍(beamforming)되어 전송될 수 있으며, 이때 RIS(607)의 RP 값은 "OFF" 모드로 매핑 될 수 있다. 일 예로, SSB 신호를 반사시키지 않고 흡수하는 모드는 기지국(600)과 RIS(607)사이에 위치하는 단말(605)를 위해 이용될 수 있다.According to various embodiments of the present disclosure, the RP value of the RIS 607 may be mapped to each SSB, and the RP value of the RIS 607 may include a “RIS OFF” mode that absorbs the SSB signal without reflecting it. there is. For example, SSB 6 ~ SSB

may be mapped to beams of the base station 600 that are not directed to the RIS 607, beamformed at an angle corresponding to each beam, and transmitted. At this time, the RP value of the RIS 607 is mapped to "OFF" mode It can be. For example, a mode of absorbing SSB signals without reflecting them may be used for a terminal 605 located between the base station 600 and the RIS 607.

8 is a diagram illustrating an SSB used by terminals located in various locations in a wireless communication system to perform a beam establishment procedure with a base station according to various embodiments of the present disclosure. Referring to FIG. 8 , a method in which the RIS controller 608 applies the RP value of the RIS 607 set by the base station 600 according to various embodiments of the present disclosure will be described.

), RIS(607)가 적용할 수 있는 RP 값

인 상황을 가정하고 있다.Referring to FIG. 8, the number of beams of the base station 600 toward the RIS 607 is set to 2 (

), RP value that RIS (607) can apply

We are assuming a situation where

은 기지국(600)이 운용하는 beam 0 ~ beam

과 매핑되어 각 기지국(600)의 빔에 해당 되는 각도로 빔포밍(beamforming) 되어 순차적으로 송신 될 수 있으며, 이때 RIS(607)의 RP 값은 "OFF" 모드로 매핑될 수 있다. 일 예로, SSB 0 ~ SSB

은 기지국(600)이 운용하는 beam 0~ beam

과 매핑되어, 빔 스위핑 절차를 수행할 수 있다. 빔 스위핑 절차는 RIS(607)의 RP를 이용하지 않을 수 있으므로, RIS(607)의 RP 값이 "OFF"모드로 각각의 SSB에 매핑될 수 있다.Referring to FIG. 8, SSB0 to SSB

beam 0 ~ beam operated by the base station 600

It can be mapped to and beamformed at an angle corresponding to the beam of each base station 600 and transmitted sequentially. At this time, the RP value of the RIS 607 can be mapped to the “OFF” mode. For example, SSB 0 to SSB

Beam 0 ~ beam operated by the base station 600

It is mapped with , and a beam sweeping procedure can be performed. Since the beam sweeping procedure may not use the RP of the RIS 607, the RP value of the RIS 607 may be mapped to each SSB in “OFF” mode.

을 제외한 나머지 SSB

~ SSB

의 SSB 들은 RIS(607)를 향하는 기지국(600)의 beam 0 및 beam 1 에

번 (일 예로, 3) 만큼 반복하여 서로 다른 RIS(607)의 RP 값 (일 예로, {(beam 0, RP 1), (beam 0, RP 2), (beam 1, RP 1), (beam 1, RP 2)})과 매핑되어 기지국(600)의 빔에 해당하는 각도로 빔포밍되어 송신 될 수 있다.본 개시의 일 실시예에 따르면, 기지국 빔을 고정된 빔으로 사용하는 경우, SSB들에 RIS(607) RP 값을 매핑하여, 기지국과의 빔 수립 절차를 수행하는 것도 가능하다.Referring to FIG. 8, SSB0 to SSB used in the beam sweeping procedure

Except SSB

~SSB

The SSBs of beam 0 and beam 1 of the base station 600 toward the RIS 607

RP values of different RIS 607 (for example, {(beam 0, RP 1), (beam 0, RP 2), (beam 1, RP 1), (beam 1, RP 2)}) and may be beamformed at an angle corresponding to the beam of the base station 600 and transmitted. According to an embodiment of the present disclosure, when a base station beam is used as a fixed beam, SSB It is also possible to perform a beam establishment procedure with the base station by mapping the RIS 607 RP value to .

9 is a diagram illustrating an SSB used by terminals located in various locations in a wireless communication system to perform a beam establishment procedure with a base station according to various embodiments of the present disclosure.

, RIS(607)가 적용할 수 있는 RP 값

인 상황을 가정하고 있다. Referring to FIG. 9, it is a diagram illustrating an SSB used by terminals located in various locations in a wireless communication system to perform a beam establishment procedure with a base station according to various embodiments of the present disclosure. Referring to FIG. 9, the number of beams of the base station 600 toward the RIS 607 is set to 2 (

, RP value that RIS (607) can apply

We are assuming a situation where

에

개의 서로 다른 RIS(607)의 RP 값이 조합으로 각 SSB에 매핑되어 기지국(600)의 beam에 해당하는 각도로 빔포밍되어 송신될 수 있다.Referring to FIG. 9, all beams 0 to beams operated by the base station 600

to

RP values of different RIS 607 may be mapped to each SSB in combination, beamformed at an angle corresponding to the beam of the base station 600, and transmitted.

10 is a diagram illustrating an SSB used by terminals located in various locations in a wireless communication system to perform a RACH procedure with a base station according to various embodiments of the present disclosure.

As described in FIGS. 7 to 9 , the base station 600 may transmit SSBs to terminals 603, 604, and 605 located in various locations by mapping beams of the base station 600 to SSBs, respectively.

According to various embodiments of the present disclosure, the terminals 603, 604, and 605 located in various locations select an SSB having the strongest RSRP among the received SSBs, and perform a random access procedure with the base station 600 can be performed.

개의 SSB 들의 수신 신호 세기(e.g. L1-RSRP)를 측정 후, 측정한 수신 신호세기가 가장 큰 SSB와 관련된 RACH occasion (RO)에서 Random access Preamble을 상향 링크를 통해 송신하기 위해, 기지국(600)이 특정 RO일 경우 RIS(607) 제어부(controller)로 전송해야 할 RIS(607) RP 값을 도시한다.Referring to FIG. 10, terminals 603, 604, and 605 located in various locations

After measuring the received signal strength (eg L1-RSRP) of SSBs, the base station 600 transmits a random access preamble through uplink on a RACH occasion (RO) related to the SSB having the largest measured received signal strength. In the case of a specific RO, the RIS 607 RP value to be transmitted to the controller of the RIS 607 is shown.

Since the beam of the base station 600 and the beam of the terminal 604 are determined, the optimal RIS 607 RP value set for the base station to transmit in the downlink is the signal transmitted by the terminal 604 in the uplink It can be seen that it is equal to the optimal RIS (607) RP value to be set for reception. For example, when the base station 600 of the terminal 604 is a specific RO, the RIS 607 RP value mapped to the SSB received from the base station 600 is used for the SSB transmitted to the base station. can be set

11A and 11B are flowcharts illustrating a method for a base station and a terminal to perform a beam establishment procedure through RIS according to various embodiments of the present disclosure.

11a and 11b, in a situation in which the base station 600 and the RIS controller 608 transmit the RIS 607 RP value in real time without time synchronization (eg, wireless or wired communication (eg, , Wi-Fi, Bluetooth, wired, etc.) method can be used to communicate between the base station and the RIS controller 608), and represents a process in which the base station 600 and the terminal 1100 perform initial beam establishment through SSB .

Prior to step 1101, at least one of the base station 600, the RIS controller 608, and the terminal 1110 may perform an algorithm for determining an optimal RIS location.

The location of the optimal RIS for the terminal 1110 may be determined based on at least one of an optimal distance between the terminal and the RIS, a bearing angle of the RIS, and maximum reception power of the terminal. Here, the maximum received power of the terminal may be signal power received by the terminal after the signal transmitted by the base station is reflected by the RIS.

Depending on the embodiment, the optimal distance between the terminal and the RIS may be determined based on RIS height (RSI height) information and UE height information.

Depending on the embodiment, a bearing angle of the RIS may be calculated for each of the candidate positions of the RIS separated from the terminal by an optimal distance.

Depending on the embodiment, the reception power of the terminal may be calculated for each of the candidate locations of the RIS separated by an optimal distance from the terminal. Depending on the embodiment, the maximum received power of the UE may be the one having the maximum value among the received powers of the UE calculated for each of the candidate locations of the RIS.

According to the embodiment, a RIS candidate position having an optimal RIS bearing angle and maximum US reception power among candidate positions of the RIS separated by an optimal distance from the terminal may be determined as the position of the RIS.

The base station 600 transmits configuration information including the RP value of the RIS 607 mapped to SSB 0 to the RIS controller 608 (step 1101). For example, the RIS 607 RP value is set as described in FIGS. 7 to 9 . The RIS controller 608 receives the setting information including the RIS 607 RP value, and then sets the phase value of each RIS element corresponding to the RIS 607 RP value in the received setting information (1102 step). The base station 600 may transmit the SSB in the base station beam direction mapped to SSB 0 through the RIS 6107 (step 1103).

개의 SSB 들에 순차적으로 동작을 수행할 수 있다. According to various embodiments of the present disclosure, in relation to the steps 1101 to 1103, the base station 600 and the RIS 607

Operations may be sequentially performed on SSBs.

각각의 수신 전력 세기(e.g. RSRP)값을 측정할 수 있다(1104 단계). The terminal 1100 may receive SSBs from the base station 600 and synchronize time, frequency, and cell information with the base station 600 through the received SSBs. SSB 0 to SSB received after synchronizing time, frequency, and cell information with the base station 600 through the received SSBs

Each received power level (eg RSRP) value may be measured (step 1104).

The base station may transmit configuration information including a RIS 607 RP value mapped to an SSB associated with RACH occasion 0 to the RIS controller 608 (step 1105). For example, the base station may set the RIS 607 RP value as described in FIG. 10 . The RIS controller 608 receives the setting information including the RIS 607 RP value from the base station 600, and then, based on the RIS 607 RP in the received setting information, each corresponding to the RIS 607 RP It can be set to the phase value of the RIS element (step 1106).

개의 RO 에 대하여 순차적으로 동작을 수행 할 수 있다.According to various embodiments of the present disclosure, in relation to steps 1105 to 1106, the base station 600 and the RIS 607

Operations can be performed sequentially on the ROs.

The terminal 1100 may transmit a preamble to the base station 600 on a RACH occasion corresponding to the SSB having the maximum value among the RSRSP values of the SSBs measured in step 1104. If there are a number of RSRPs similar to the maximum RSRP value of each SSB measured by the terminal 1100 in step 1104, the terminal 604 located between the base station 600 and the RIS 607 determines that RIS OFF A preamble may be transmitted to an RO corresponding to the mapped SSB (e.g., terminal 604 in FIG. 6).

12 is a flowchart illustrating a process in which a base station 600 and a terminal perform a beam establishment procedure through SSB according to various embodiments of the present disclosure. Referring to FIG. 12 , the RIS controller 608 may perform time synchronization with the base station 600 (step 1201).

Referring to FIG. 12, after time synchronization with the RIS controller 608 is performed, the base station 600 transmits the RP value of the RIS 607 to the RIS through a new physical channel or interface (e.g. L1 signal, RRC, MAC signal). When a scheduling signal can be transmitted to the controller 608, a process in which the base station 600 and the terminal 1110 initially establish a beam through SSB is shown.

As described in FIGS. 7 to 9, the base station 600 may transmit a scheduling signal including the RP value of the RIS 607 mapped to each SSB to the RIS controller 608 (step 1202). According to various embodiments, the RIS controller 608 may set a phase value of each RIS element corresponding to the RP value of the RIS 607 included in the received scheduling signal at a specific scheduled time point.

개의 SSB 들을 순차적으로 매핑된 기지국(600) 빔 방향으로 송신할 수 있다(1203 단계).After the base station 600 sets the RP value of the RIS 607 of the RIS element,

SSBs may be transmitted in the sequentially mapped beam direction of the base station 600 (step 1203).

각각의 RSRP 값을 측정할 수 있다(1204 단계).The terminal 1110 may synchronize time, frequency, and cell information with the base station 600 based on the received SSBs. After the terminal 1110 performs synchronization with the base station 600, SSB 0 to SSB

Each RSRP value can be measured (step 1204).

The base station 600 may transmit a scheduling signal including an RP value of the RIS 607 mapped to an SSB associated with RACH occasion 0 to the RIS controller 608 (step 1205). For example, the base station 600 may set the RIS 607 RP value as described in FIG. 10

The terminal 1100 may transmit a preamble to the base station 600 on a RACH occasion corresponding to the SSB having the maximum value among the RSRSP values of the SSBs measured in step 1204. If there are a number of RSRPs similar to the maximum RSRP value of each SSB measured by the terminal 1100 in step 1204, the terminal 604 located between the base station 600 and the RIS 607 determines that RIS OFF A preamble may be transmitted in an RO corresponding to the mapped SSB (e.g., terminal 604 in FIG. 6).

13 is a flowchart illustrating a sequence of an operation of beam sweeping in downlink after a base station and a terminal are connected according to various embodiments of the present disclosure. Referring to FIG. 13, after the base station 600 and the terminal 1100 are connected, the base station 600 beam and the RIS 607 RP are transmitted using a reference signal (RS) (e.g. CSI-RS or SSB). In the process of operation, it represents an operation of beam sweeping in the downlink.

The base station 600 determines the best SSB index of each terminal 1100 through a random access procedure in the initial access step (eg, the index of the SSBs having the highest RSRP among the received SSBs). ), it is possible to determine whether each terminal 1100 has a RIS association (step 1301).

After the base station 600 determines whether each terminal 1100 has a RIS association, based on this, the number of beams of the base station 600 and RIS 607 RPs to perform beam sweeping RS (e.g. CSI-RS) resources can be set (step 1302).

Depending on the embodiment, between steps 1301 and 1302, at least one of the base station 600, the RIS controller 608, and the terminal 1110 may perform an algorithm for determining an optimal RIS position.

The location of the optimal RIS for the terminal 1110 may be determined based on at least one of an optimal distance between the terminal and the RIS, a bearing angle of the RIS, and maximum reception power of the terminal. Here, the maximum received power of the terminal may be signal power received by the terminal after the signal transmitted by the base station is reflected by the RIS.

Depending on the embodiment, the optimal distance between the terminal and the RIS may be determined based on RIS height (RSI height) information and UE height information.

Depending on the embodiment, a bearing angle of the RIS may be calculated for each of the candidate positions of the RIS separated from the terminal by an optimal distance.

Depending on the embodiment, the reception power of the terminal may be calculated for each of the candidate locations of the RIS separated by an optimal distance from the terminal. Depending on the embodiment, the maximum received power of the UE may be the one having the maximum value among the received powers of the UE calculated for each of the candidate locations of the RIS.

According to the embodiment, a RIS candidate position having an optimal RIS bearing angle and maximum US reception power among candidate positions of the RIS separated by an optimal distance from the terminal may be determined as the position of the RIS.

The base station 600 may transmit a preset RS resource configuration and report configuration to the terminal 1100 through RRC signaling (step 1303). According to various embodiments of the present disclosure, the RIS 607 RP value may be maintained at a value set in the initial access step.

If RIS RP sweeping exists among the preset RS resources, a mapped RIS RP value may be set or transmitted to the RIS controller (step 1304).

The base station 600 may transmit the RS in the beam direction of the base station 600 corresponding to the preset RS resource configuration (step 1306).

The RIS controller 608 may apply the phase value of each RIS element corresponding to the RP of the RIS 607 set or transmitted by the base station 600 to the RS resource set by the base station 600 (step 1305 ). The terminal 1100 may measure received signal strength (L1-RSRP) of all configured RSs (step 1307).

14 is a diagram illustrating an example of a method in which a base station sets a reference signal (RS) to a terminal through downlink according to various embodiments of the present disclosure.

Referring to FIG. 14, in step 1302 of FIG. 13, an example of a method in which the base station 600 configures the RS to the terminal 100 through downlink is shown. In the initial access step, the base station 600 checks the best SSB index of each terminal 1110 through a random access procedure, and then uses the SSB corresponding to the best SSB index to determine that the terminal is connected to the RIS 607 603 may be set as a first group, and terminals 605 determined not to be connected to the RIS 607 may be set as a second group.

개 일 수 있다.The base station may configure RSs so that the beam sweeping operation using the RIS 607 RP can be performed on the terminal 604 belonging to the first group. For example, the maximum number of RSs that the base station 600 can set is:

can be a dog

개 일 수 있다. The base station 600 may configure an RS for the terminal 605 belonging to the second group to perform a beam sweeping operation using a base station beam set. For example, the maximum number of RSs that can be set by the base station 600 is

can be a dog

15 is a diagram illustrating an example of a method in which a base station sets a reference signal to a terminal through downlink according to various embodiments of the present disclosure. Referring to FIG. 15 , in the same manner as described in FIG. 14 , the base station 600 may divide the terminals 1100 into a first group and a second group.

일 수 있다.The base station 600 may set an RS for the terminal 603 belonging to the first group to perform a beam sweeping operation using both the RIS 607 RP and the base station 600 beam set. For example, the maximum number of RSs that can be set by the base station 600 is

can be

일 수 있다. The base station 600 may set RS so that the terminal 603 belonging to the second group can perform a beam sweeping operation using the beam set of the base station 600 . For example, the maximum number of RSs that can be set by the base station 600 is

can be

16 is a diagram illustrating an example of a method in which a base station sets a reference signal to a terminal through downlink according to various embodiments of the present disclosure. Referring to FIG. 16 , in the same manner as described in FIG. 14 , the base station 600 may divide the terminals 1100 into a first group and a second group.

일 수 있다.Referring to FIG. 16, a base station 600 provides a RIS 607 RP and a set of beams that can be swept by the base station 600 to a terminal 603 belonging to the first group and a terminal 605 belonging to the second group. ) can be used to set RS so that beam sweeping can be performed. For example, the maximum number of RSs that can be set by the base station 600 is

can be

17 is a diagram illustrating an operation of reporting a reference signal through an uplink by the terminal 1100 according to various embodiments of the present disclosure. Referring to FIG. 17, after the base station 600 and the terminal 1100 are connected, the base station 600 beam and the RIS 607 RP are operated using a reference signal (RS) (e.g. CSI-RS or SSB) It is a diagram showing an operation in which the terminal 1100 reports an RS through uplink in the process.

When the base station 600 transmits the RS configuration to the terminal 1110, it may set or transmit a preset RP value of the RIS 607 to the RIS controller 608 (step 1701). Based on the received RIS (607) RP value, the RIS controller (608) applies the phase value of each RIS element corresponding to the RIS (607) RP value to the reference signal reporting resource set by the base station (600) Yes (step 1702).

The terminal 600 transmits RS-report quantities (eg, best 4 RS index, best RSRP value or The difference between the remaining three RSRP values, etc.) can be fed back (step 1703).

18 is a flowchart illustrating a sequence of a process in which the base station 600 informs the terminal 1100 of the base station 600 beam and RIS 607 RP information to the terminal 1100 through downlink.

Referring to FIG. 18, based on the reference signal report t information fed back from the terminal 1100 to the base station 600 in step 1702 of FIG. ) represents a process of informing the terminal 1100 of beam and RIS 607 RP information.

개의 TCI state 에 매핑을 수행한 후 단말(1100)에게 RRC 신호를 통해 송신 할 수 있다(1801 단계). Referring to FIG. 18, the base station 600 uses a base station beam mapped to a reference signal (RS) and a RIS (607) RP combination.

After mapping to the number of TCI states, it can be transmitted to the terminal 1100 through an RRC signal (step 1801).

Based on the reference signal report information fed back from the terminal 1100, the base station 600 uses a MAC control element (MAC CE) for the TCI state index to which the base station 600 beam and the RIS 607 RP are mapped to be used for PDCCH transmission. It can be transmitted to the terminal 1100 through. According to an embodiment of the present disclosure, PDSCH transmission may be transmitted to the UE through MAC CE or DCI of PDCCH (step 1802).

The base station 600 may set or transmit, to the RIS controller 608, the RP value of the RIS 607 mapped to the TCI state indicated to the terminal 1100. According to an embodiment of the present disclosure, the RIS controller 608 may apply the phase value of each RIS element corresponding to the RP value of the RIS 607 when the base station 600 transmits data in downlink there is.

19 is a diagram schematically illustrating an internal structure of a terminal 1100 according to an embodiment of the present disclosure.

Referring to FIG. 19 , a terminal 1100 includes a controller 1910, a receiver 1920, and a transmitter 1930.

The controller 1910 controls overall operations of the terminal 1100, and in particular, controls operations related to beamforming control to be performed. Since the operation of the controller 1910 to control the terminal 1100 is the same as that described in FIGS. 6 to 18 , a detailed description thereof will be omitted here.

The receiver 1920 receives various messages and information under the control of the controller 1910.

The transmitter 1930 transmits various messages and information under the control of the controller 1910.

In FIG. 19, the terminal 1100 has a controller 1910, a receiver 1920, and a transmitter 1930 implemented as separate units, but at least two of the controller 1910, the receiver 1920, and the transmitter 1930 Dogs can be integrated into one. Also, the controller 1910, the receiver 1920, and the transmitter 1930 may be implemented with at least one processor.

20 is a diagram schematically illustrating an internal structure of a base station 600 according to an embodiment of the present disclosure.

Referring to FIG. 20 , a base station 600 includes a controller 2010, a receiver 2020, and a transmitter 2030. In addition, it may be implemented by including a processor for controlling setting information related to beamforming and RIS RP of the base station 600 . In addition, the base station 600 may be implemented by including the functions of the terminal 1100 in a server.

The controller 2010 controls the overall operation of the terminal 1100, and in particular, controls setting information related to beamforming and RIS RP to perform operations related to control. Since the operation of the controller 2010 to control the base station 600 is the same as that described in FIGS. 6 to 19 , a detailed description thereof will be omitted here.

The receiver 2020 receives various messages and information under the control of the controller 2010.

The transmitter 2030 transmits various messages and information under the control of the controller 2010.

In FIG. 20, the base station 600 has a controller 2010, a receiver 2020, and a transmitter 2030 implemented as separate units, but at least two of the controller 2010, receiver 2020, and transmitter 2030. Dogs can be integrated into one. Also, the controller 2010, the receiver 2020, and the transmitter 2030 may be implemented with at least one processor.

21 is a diagram schematically illustrating an internal structure of a RIS controller 608 according to an embodiment of the present disclosure.

Referring to FIG. 21 , the RIS controller 608 includes a controller 2110, a receiver 2120, and a transmitter 2130. In addition, the RIS controller 608 may be implemented by including a processor for controlling configuration information related to beamforming and RIS RP.

The controller 2110 controls the overall operation of the RIS controller 608, and in particular, controls setting information related to beamforming and RIS RP to perform operations related to control. Since the operation of the controller 2110 to control the RIS controller 608 is the same as that described in FIGS. 6 to 19 , a detailed description thereof will be omitted here.

The receiver 2120 receives various messages and information under the control of the controller 2110.

The transmitter 2130 transmits various messages and information under the control of the controller 2110.

In FIG. 21, the RIS controller 608 has a controller 2110, a receiver 2120, and a transmitter 2130 implemented as separate units, but at least one of the controller 2110, the receiver 2120, and the transmitter 2130 The two can be integrated into one. Also, the controller 2110, the receiver 2120, and the transmitter 2130 may be implemented with at least one processor.

In the above-described embodiments, a technique in which at least one of the base station and the RIS indicates (or provides) pattern information of the RIS and information on a mapped SSB (or mapped beam) is proposed, and FIGS. In the embodiments related to 25, a technique (or algorithm) for determining the optimal location of the RIS is proposed.

Specifically, the embodiments related to FIGS. 22 to 25 may be performed prior to step 1101 of FIG. 11A or may be performed between steps 1301 and 1302 of FIG. 13 .

22 is a diagram illustrating a channel model between a base station, a RIS, and a terminal according to various embodiments of the present disclosure.

이고, k번째 RIS 와 수신 측(Rx)인 k번째 단말(UE) 간 거리는

이고, i번째 기지국과 k번째 단말(UE) 간 거리는

일 수 있다. 여기서, (a)는 기지국과 RIS 간 채널을 의미하고, (b)는 RIS와 단말 간 채널을 의미할 수 있다.Referring to FIG. 22, the distance between the i-th base station, which is the transmitting side (Tx), and the k-th RIS is

, and the distance between the k-th RIS and the k-th terminal (UE) of the receiving side (Rx) is

And, the distance between the i-th base station and the k-th terminal (UE) is

can be Here, (a) may mean a channel between the base station and the RIS, and (b) may mean a channel between the RIS and the terminal.

For convenience of description, it is assumed that signals are transmitted and received between the k-th base station, the k-th RIS, and the k-th terminal.

An optimum location of the k-th RIS for the k-th terminal may be determined based on at least one of an optimal distance between the terminal and the RIS, a bearing angle of the RIS, and maximum reception power of the terminal. Here, the maximum received power of the terminal may be signal power received by the terminal after the signal transmitted by the base station is reflected by the RIS.

Depending on the embodiment, the optimal distance between the terminal and the RIS may be determined based on RIS height (RSI height) information and UE height information.

Depending on the embodiment, a bearing angle of the RIS may be calculated for each of the candidate positions of the RIS separated from the terminal by an optimal distance. Depending on the embodiment, the bearing angle of the RIS may be determined based on an azimuth angle for a signal received by the RIS from the base station on the basis of global coordinate systems (GCS) and an azimuth angle for a signal transmitted by the RIS to the terminal on the basis of the GCS. .

Depending on the embodiment, the reception power of the terminal may be calculated for each of the candidate locations of the RIS separated by an optimal distance from the terminal. Depending on the embodiment, the maximum received power of the UE may be the one having the maximum value among the received powers of the UE calculated for each of the candidate locations of the RIS.

Depending on the embodiment, the reception power of the terminal is the transmission power of the transmission signal of the base station, the channel coefficient between the IS and the terminal, the channel coefficient between the base station and the terminal, the number of antennas of the base station, the number of antennas of the terminal, the number of elements of RIS, the base station and RIS distance, distance between RIS and UE, height of base station, height of RIS, azimuth angle for signals transmitted from base station to RIS based on RIS location, azimuth angle for signals received by RIS from base station based on RIS location It may be determined based on at least one of , and an azimuth angle for a signal transmitted by the RIS to the terminal based on the RIS location.

According to the embodiment, a RIS candidate position having an optimal RIS bearing angle and maximum US reception power among candidate positions of the RIS separated by an optimal distance from the terminal may be determined as the position of the RIS.

For example, the RIS deployment algorithm proposed in the present disclosure may be implemented as follows.

<RIS Deployment Algorithm>

를 획득할 수 있다. In the RIS deployment algorithm, for the k-th user (or terminal), based on Equation 11, the optimal distance between the k-th RIS and the k-th terminal

can be obtained.

<Equation 11>

를 획득하기 위해 수학식 11을 만족하는

를 찾을 수 있다. 여기서,

는 k번째 RIS 와 k번째 단말 간 거리이고, h_RIS는 RIS의 높이이고, h_UE는 단말의 높이이다. The optimal distance between the kth RIS and the kth terminal

Satisfying Equation 11 to obtain

can be found. here,

is the distance between the k-th RIS and the k-th terminal, h _RIS is the height of the RIS, and h _UE is the height of the terminal.

에서 k번째 단말로부터 반경

m(meter)에 위치하는 RIS 의 후보 위치 중에서 RIS에 대한 최적의 베어링 각도(bearing angle)를 계산할 수 있다. In the RIS deployment algorithm, the interval

Radius from the kth terminal in

An optimal bearing angle for the RIS can be calculated among candidate positions of the RIS located at m (meter).

<Equation 15>

는 RIS에 대한 최적의 베어링 각도이고,

는 GCS(global coordinate systems) 기준으로 RIS가 기지국으로부터 수신하는 신호에 대한 azimuth angle이고,

는 GCS 기준으로 RIS가 단말로 송신하는 신호에 대한 azimuth angle이다. in Equation 15

is the optimal bearing angle for RIS,

Is the azimuth angle for the signal received by the RIS from the base station on the basis of global coordinate systems (GCS),

is an azimuth angle for a signal transmitted by RIS to a terminal based on GCS.

In the RIS deployment algorithm, the reception power of the k-th terminal can be calculated based on Equation 10.

<Equation 10>

는 RIS와 단말 간의 채널 계수의 절대값이고,

는 기지국과 단말 간의 채널 계수의 절대값일 수 있다.In Equation 10, P _r,k is the terminal reception power when the signal transmitted from the base station is reflected by the RIS and then received by the terminal, P _t is the transmission power of the transmission signal of the base station,

Is the absolute value of the channel coefficient between RIS and the terminal,

May be the absolute value of the channel coefficient between the base station and the terminal.

및

는 수학식 9에 기반하여 결정될 수 있다.Also, in Equation 10

and

Can be determined based on Equation 9.

<Equation 9>

는 k번째 기지국과 k번째 RIS 간 거리이고,

는 k번째 RIS 와 k번째 단말 간 거리이고, f()는 zenith angle을 계산하기 위한 함수이고, A()는 angle을 처리하기 위한 함수이고, h_BS는 기지국의 높이이고, h_RIS는 RIS의 높이이고,

는 RIS 위치를 기준으로 기지국에서 RIS로 송신하는 신호에 대한 azimuth angle이고,

는 RIS 위치를 기준으로 RIS가 기지국으로부터 수신하는 신호에 대한 azimuth angle이고,

는 RIS 위치를 기준으로 RIS가 단말로 송신하는 신호에 대한 azimuth angle일 수 있다.In Equations 9 and 10, S is the number of antennas of the base station, U is the number of antennas of the terminal, N is the number of elements of RIS, PL () is a function related to path loss,

Is the distance between the k-th base station and the k-th RIS,

is the distance between the kth RIS and the kth terminal, f() is a function for calculating the zenith angle, A() is a function for processing the angle, h _BS is the height of the base station, and h _RIS is the RIS of is high,

Is an azimuth angle for a signal transmitted from the base station to the RIS based on the RIS location,

Is the azimuth angle for the signal received by the RIS from the base station based on the RIS location,

May be an azimuth angle for a signal transmitted by the RIS to the terminal based on the location of the RIS.

m(meter)에 위치하는 RIS 의 후보 위치 중에서 최적의 RIS의 위치가 결정될 수 있다. Afterwards, in the RIS Deployment Algorithm. Based on the optimal bearing angle of the RIS and the maximum receiving power of the terminal. radius

An optimal RIS position may be determined among candidate positions of RIS located at m (meter).

23 is a diagram illustrating an example of SINR CDF performance according to various embodiments of the present disclosure.

값들에 대한 SINR (signal-to-interference-plus-noise ratio) CDF (cumulative distribution function) 성능을 나타낸 도면이다. 여기서,

는 k번째 RIS 와 k번째 단말 간 거리이다. 23, different

It is a diagram showing signal-to-interference-plus-noise ratio (SINR) cumulative distribution function (CDF) performance for values. here,

Is the distance between the k-th RIS and the k-th terminal.

가 3m, 7m, 11m, 15m, 19m 인 경우 SINR CDF 성능을 도시한다. Referring to Figure 23,

When is 3m, 7m, 11m, 15m, 19m, the SINR CDF performance is shown.

24a and 24b are diagrams illustrating another example of SINR CDF performance according to various embodiments of the present disclosure.

)에 따른 SINR CDF 성능을 나타낸 도면이다. 도 24a에서는

인 경우의 SINR CDF 성능을 나타내고, 도 24b에서는

인 경우의 SINR CDF 성능을 나타낸다. 24a and 24b, the base station downtilt angle (BS downtilt angle,

) It is a diagram showing the SINR CDF performance according to. In Figure 24a

SINR CDF performance in the case of

Represents the SINR CDF performance in the case of

25 is a diagram illustrating another example of SINR CDF performance according to various embodiments of the present disclosure.

25 is a diagram showing SINR CDF performance for different RIS height values. Referring to FIG. 25, SINR CDF performance when RIS heights are 2.5m, 5m, 7.5m, 10m, 12.5m, and 15m is shown.

Claims (20)

In a method of a base station supporting beamforming in a wireless communication system,
mapping pattern information of a reconfiguration intelligent surface (RIS) to reflect a beam of the base station and a synchronization signal block (SSB);
transmitting setting information including the RIS pattern information to a RIS controller that controls the RIS;
Transmitting the mapped SSB to a terminal through the RIS based on the setting information; and
and receiving a random access preamble from the terminal through the RIS.
According to claim 1,
The process of mapping the RIS pattern information and the SSB
The method of the base station further comprising the step of mapping a combination of the beam of the base station and the RIS pattern information to the SSB.
According to claim 1,
When the terminal is located between the RIS and the base station, the RIS pattern information is set to 'OFF'.
According to claim 1,
The process of mapping the RIS pattern information and the SSB is:
performing a synchronization operation with the RIS controller based on the SSB; and
Method of the base station further comprising mapping the combination of the beam and the RIS pattern information of the base station to the SSB
According to claim 4,
The method of the base station, characterized in that the mapped SSB is transmitted through a scheduling signal.
In a base station supporting beamforming in a wireless communication system,
transceiver; and
Mapping pattern information of a reconfiguration intelligent surface (RIS) for reflecting the beam of the base station and a synchronization signal block, and setting information including the RIS pattern information to a RIS controller for controlling the RIS Control the transceiver to transmit, control the transceiver to transmit the mapped SSB to the terminal through the RIS based on the configuration information, and random access from the terminal through the RIS controller Preamble ) Base station including a control unit for controlling the transceiver to receive.
According to claim 6,
The base station, characterized in that the control unit maps a combination of the beam and the RIS pattern information of the base station to the SSB.
According to claim 6,
When the terminal is located between the RIS and the base station, the RIS pattern information is set to 'OFF'.
According to claim 6,
The base station, characterized in that the control unit performs a synchronization operation with the RIS controller based on the SSB, and maps a combination of the beam and the RIS pattern information of the base station to the SSB.
According to claim 9,
The base station, characterized in that the mapped SSB is transmitted through a scheduling signal.
In a method of a reconfiguration intelligent surface (RIS) controller for reflecting a beam supporting beamforming in a wireless communication system,
Receiving a synchronization signal block (SSB) mapped with pattern information of the RIS from a base station;
setting a phase value of a RIS element of the RIS based on the received SSB; and
and transmitting the SSB to a terminal based on a phase value of the RIS element.
According to claim 11,
Receiving configuration information including an SSB index from the terminal; and
The method of the RIS controller further comprising the step of transmitting the configuration information to the base station.
According to claim 11,
The method of the RIS controller, characterized in that the first SSB is mapped with a combination of the number of beams of the base station and the RIS pattern information.
According to claim 11,
The method of the RIS controller, characterized in that the first SSB is received through a scheduling signal.
According to claim 14,
The first SSB is a method of a RIS controller, characterized in that mapped with a random access channel (RACH) occasion.
In a reconfiguration intelligent surface (RIS) controller for reflecting a beam supporting beamforming in a wireless communication system,
transceiver; and
Controls the transceiver to receive a synchronization signal block (SSB) mapped with RIS pattern information from a base station, and sets a phase value of a RIS element of the RIS based on the received SSB, , RIS controller comprising a control unit for controlling the transceiver to transmit the SSB to the terminal based on the phase value of the RIS element.
According to claim 16,
The RIS controller, characterized in that the control unit controls the transceiver to receive configuration information including an SSB index from the terminal, and controls the transceiver to transmit the configuration information to the base station.
According to claim 16,
RIS controller, characterized in that the SSB is mapped with a combination of the number of beams of the base station and the RIS pattern information.
According to claim 16,
The SSB is received through a scheduling signal RIS controller.
According to claim 19,
The SSB is a RIS controller, characterized in that mapped with a random access channel (RACH) occasion.

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