KR20210137880A - Method and appratus for bwp configuration for mbs service continuity in wireless communication system - Google Patents

Abstract

Disclosed are a method for setting a bandwidth part (BWP) for service continuity of a multicast and broadcast service (MBS) in a wireless communication system, which effectively support the MBS in a mobile communication system, and an apparatus thereof. According to one embodiment of the present invention, an operation method of a base station for transmitting a MBS comprises the following steps: determining, by a terminal, a BWP to receive the MBS service; transmitting determined setting information for the BWP to the terminal including at least one of a system information block, a radio resource control (RRC) release message, and an RRC reset message; and using the determined BWP to transmit the MBS to the terminal.

Description

BWP setting method and apparatus for MBS service continuity in wireless communication system

The present disclosure relates to a wireless communication system, and more particularly, to a method and apparatus for setting a Bandwidth Part (BWP) for Multicast and Broadcast Service (MBS) service continuity in a wireless communication system.

Efforts are being made to develop an improved 5G communication system or pre-5G communication system in order to meet the increasing demand for wireless data traffic after the commercialization of the 4G communication system. For this reason, the 5G communication system or the pre-5G communication system is called a system after the 4G network (Beyond 4G Network) communication system or after the LTE system (Post LTE). In order to achieve a high data rate, the 5G communication system is being considered for implementation in a very high frequency (mmWave) band (eg, such as a 60 gigabyte (80 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, in the 5G communication system, beamforming, massive MIMO, and Full Dimensional MIMO (FD-MIMO) are used. ), array antenna, analog beam-forming, and large scale antenna technologies are being discussed. In addition, for network improvement 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 (ultra-dense network) , Device to Device communication (D2D), wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), and interference cancellation Technology development is underway. 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 FBMC (Filter Bank Multi Carrier), which are advanced access technologies, NOMA (non-orthogonal multiple access), and sparse code multiple access (SCMA) are being developed.

On the other hand, the Internet is evolving from a human-centered connection network where humans create and consume information to an Internet of Things (IoT) network that exchanges and processes information between distributed components such as objects. Internet of Everything (IoE) technology, which combines big data processing technology through connection with cloud servers, etc. with IoT technology, is also emerging. In order to implement IoT, technology elements such as sensing technology, wired and wireless communication and network infrastructure, service interface technology, and security technology are required. , M2M), and MTC (Machine Type Communication) are being studied. In the IoT environment, an intelligent IT (Internet Technology) service that collects and analyzes data generated from connected objects and creates new values in human life can be provided. IoT is the field of smart home, smart building, smart city, smart car or connected car, smart grid, health care, smart home appliance, 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, technologies such as sensor network, machine to machine (M2M), and MTC (Machine Type Communication) are being implemented by 5G communication technologies such as beamforming, MIMO, and array antenna. . The application of a cloud radio access network (cloud RAN) as the big data processing technology described above is an example of the convergence of 5G technology and IoT technology.

As various services can be provided according to the above-mentioned and the development of wireless communication systems, there is a need for a method for smoothly providing services related to multicast and broadcast in particular.

The disclosed embodiments are intended to provide an apparatus and method capable of effectively supporting Multicast and Broadcast Service (MBS) in a mobile communication system.

An operating method of a base station for transmitting a Multicast and Broadcast Service (MBS) service in a wireless communication system according to an embodiment of the present disclosure includes the steps of: determining, by a terminal, a Bandwidth Part (BWP) to be provided with the MBS service; transmitting the determined configuration information for the BWP to the terminal including at least one of a system information block, an RRC release message, and an RRC reset message; and transmitting the MBS service to the terminal by using the determined BWP.

In a method of operating a terminal for receiving a Multicast and Broadcast Service (MBS) service in a wireless communication system according to an embodiment of the present disclosure, a terminal in an idle mode or an inactive mode is provided with an MBS service from a base station. Setting information for BWP receiving; and receiving an MBS service from the base station based on the configuration information for the BWP, wherein the configuration information for the BWP to be provided with the MBS service includes a system information block (System Information Block), an RRC release message, and It may be received by being included in at least one of the RRC reconfiguration messages.

1 is a diagram illustrating an operation method of MBS communication according to an embodiment of the present disclosure.
2 is a diagram illustrating a configuration procedure for performing MBS communication according to an embodiment of the present disclosure.
3 is a diagram illustrating a method of setting an Initial BWP for reception of an MBS service according to an embodiment of the present disclosure.
4 is a diagram illustrating a method of setting a downlink BWP for reception of an MBS service according to an embodiment of the present disclosure.
5 is a diagram illustrating an operation for receiving an MBS service when a connected mode transitions according to an embodiment of the present disclosure.
6 is a diagram illustrating a method of configuring a dedicated carrier for an MBS service according to an embodiment of the present disclosure.
7 is a diagram illustrating an operation for MBS service reception when an idle mode or an inactive mode transitions according to an embodiment of the present disclosure.
8 is a diagram illustrating a BWP setting method for an MBS service according to an embodiment of the present disclosure.
9 is a diagram illustrating a BWP setting method for an MBS service according to an embodiment of the present disclosure.
10 is a diagram illustrating a structure of a base station according to an embodiment of the present disclosure.
11 is a diagram illustrating a structure of a terminal according to an embodiment of the present disclosure.
12 is a diagram illustrating an MBS split bearer and path switching according to an embodiment of the present disclosure.
13 is a diagram illustrating an MBS split bearer and a path switching process according to an embodiment of the present disclosure.
14 is a diagram illustrating an MBS split bearer and a path switching process according to an embodiment of the present disclosure.
15 is a diagram illustrating a first packet reception operation after path switching of an MBS split bearer according to an embodiment of the present disclosure.
16 is a diagram illustrating a first packet reception operation after path switching of an MBS split bearer according to an embodiment of the present disclosure.
17 is a diagram illustrating a first packet reception operation after path switching of an MBS split bearer according to an embodiment of the present disclosure.
18 is a diagram illustrating a path switching operation of an MBS split bearer according to an embodiment of the present disclosure.
19 is a diagram illustrating an operation of an MBS radio bearer during handover according to an embodiment of the present disclosure.
20 is a diagram illustrating a bearer format conversion including an MBS split bearer according to an embodiment of the present disclosure.

Hereinafter, the operating principle of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description of the present disclosure, if it is determined that a detailed description of a related well-known function or configuration may unnecessarily obscure the subject matter of the present disclosure, the detailed description thereof will be omitted. In addition, the terms described below are terms defined in consideration of functions in the present disclosure, which may vary according to intentions or customs of users and operators. Therefore, the definition should be made based on the content throughout this specification.

For the same reason, some components are exaggerated, omitted, or schematically illustrated in the accompanying drawings. In addition, the size of each component does not fully reflect the actual size. The same reference numerals are assigned to the same or corresponding elements in each figure.

Advantages and features of the present disclosure, and methods for achieving them, will become apparent with reference to the 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, and only the embodiments allow the present disclosure to be complete, and those of ordinary skill in the art to which the present disclosure pertains. It is provided to fully understand the scope of the disclosure, and the present disclosure is only defined by the scope of the claims. Like reference numerals refer to like elements throughout.

At this time, it will be understood that each block of the flowchart diagrams and combinations of the flowchart diagrams may 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, such that the instructions performed by the processor of the computer or other programmable data processing equipment are not described in the flowchart block(s). It creates a means to perform functions. These computer program instructions may also be stored in a computer-usable or computer-readable memory that may direct a computer or other programmable data processing equipment to implement a function in a particular manner, and thus the computer-usable or computer-readable memory. It is also possible that the instructions stored in the flow chart block(s) produce an article of manufacture containing instruction means for performing the function described in the flowchart block(s). The computer program instructions may also be mounted on a computer or other programmable data processing equipment, such that a series of operational steps are performed on the computer or other programmable data processing equipment to create a computer-executed process to create a computer or other programmable data processing equipment. It is also possible that instructions for performing the processing equipment 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 also possible for the functions recited in blocks to occur out of order. For example, two blocks shown one after another may in fact be performed substantially simultaneously, or it is possible that the blocks are sometimes performed in the reverse order according to the corresponding function.

In this case, the term '~ unit' used in this embodiment means software or hardware components such as FPGA (Field Programmable Gate Array) or ASIC (Application Specific Integrated Circuit), and '~ unit' performs certain roles do. However, '-part' is not limited to software or hardware. The '~ unit' may be configured to reside on an addressable storage medium or may be configured to refresh one or more processors. Thus, as an example, '~' denotes components such as software components, object-oriented software components, class components, and task components, and processes, functions, properties, and procedures. , subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. The functions provided in the components and '~ units' may be combined into a smaller number 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 secure multimedia card. Also, in an embodiment, '~ part' may include one or more processors.

In the following description of the present disclosure, if it is determined that a detailed description of a related well-known function or configuration may unnecessarily obscure the subject matter of the present disclosure, the detailed description thereof will be omitted. Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

A term for identifying an access node used in the following description, a term referring to network entities, a term referring to messages, a term referring to an interface between network objects, and a term referring to various identification information and the like are exemplified for convenience of description. Accordingly, the present disclosure is not limited to the terms described below, and other terms referring to objects having equivalent technical meanings may be used.

Hereinafter, the base station is a subject that performs resource allocation of the terminal, and may be at least one of gNode B, eNode B, Node B, a base station (BS), a radio access unit, a base station controller, or a node on a network. The terminal may include a user equipment (UE), a mobile station (MS), a cellular phone, a smart phone, a computer, or a multimedia system capable of performing a communication function. Also, the term terminal may refer to mobile phones, NB-IoT devices, sensors, as well as other wireless communication devices. Of course, the base station and the terminal are not limited to the above example.

For convenience of description, the present disclosure uses terms and names defined in 3GPP LTE (3rd Generation Partnership Project Long Term Evolution) and/or 3GPP NR (3rd Generation Partnership Project New Radio) standards. However, the present disclosure is not limited by the above terms and names, and may be equally applied to systems conforming to other standards. In the present disclosure, eNB may be used interchangeably with gNB for convenience of description. That is, a base station described as an eNB may represent a gNB.

In particular, the present disclosure is applicable to 3GPP NR (5th generation mobile communication standard). In addition, the present disclosure provides intelligent services (eg, smart home, smart building, smart city, smart car or connected car, healthcare, digital education, retail business, security and safety-related services based on 5G communication technology and IoT-related technology) etc.) can be applied. In the present disclosure, eNB may be used interchangeably with gNB for convenience of description. That is, a base station described as an eNB may represent a gNB. Also, the term terminal may refer to mobile phones, NB-IoT devices, sensors, as well as other wireless communication devices.

A wireless communication system, for example, 3GPP's HSPA (High Speed Packet Access), LTE (Long Term Evolution or E-UTRA (Evolved Universal Terrestrial Radio Access)), LTE-Advanced (LTE-A), LTE-Pro, 3GPP2's High Rate Packet Data (HRPD), UMB (Ultra Mobile Broadband), and IEEE's 802.16e, such as communication standards such as communication standards such as broadband wireless that provides high-speed, high-quality packet data service It is evolving into a communication system.

As a representative example of a broadband wireless communication system, in an LTE system, an Orthogonal Frequency Division Multiplexing (OFDM) scheme is employed in a downlink (DL; DownLink), and Single Carrier Frequency Division Multiple Access (SC-FDMA) in an uplink (UL). ) method is used. Uplink refers to a radio link in which a UE (User Equipment or MS; Mobile Station) transmits data or control signals to a base station (eNode B or BS; Base Station), and downlink refers to a radio link in which the base station transmits data or control to the UE A radio link that transmits signals. The multiple access method as described above divides the data or control information of each user by allocating and operating the time-frequency resources to which data or control information is to be transmitted for each user so that they do not overlap each other, that is, orthogonality is established. .

As a future communication system after LTE, that is, the 5G communication system must be able to freely reflect various requirements such as users and service providers, so services that simultaneously satisfy various requirements must be supported. Services considered for the 5G communication system include Enhanced Mobile BroadBand (eMBB), massive Machine Type Communication (mMTC), and Ultra Reliability Low Latency Communication (URLLC). There is this.

According to an embodiment, the eMBB may aim to provide a data transmission rate that is more improved than the data transmission rate supported by the existing LTE, LTE-A, or LTE-Pro. For example, in the 5G communication system, the eMBB should be able to provide a maximum data rate of 20 Gbps in the downlink and a maximum data rate of 10 Gbps in the uplink from the viewpoint of one base station. In addition, the 5G communication system may have to provide the maximum transmission speed and at the same time provide the increased user perceived data rate of the terminal. In order to satisfy such a requirement, in the 5G communication system, it may be required to improve various transmission/reception technologies, including a more advanced multi-antenna (MIMO) transmission technology. In addition, while transmitting signals using a transmission bandwidth of up to 20 MHz in the 2 GHz band currently used by LTE, the 5G communication system uses a frequency bandwidth wider than 20 MHz in the frequency band of 3 to 6 GHz or 6 GHz or more Data transfer speed can be satisfied.

At the same time, mMTC is being considered to support application services such as the Internet of Things (IoT) in the 5G communication system. In order to efficiently provide the Internet of Things, mMTC may require large-scale terminal access support, improved terminal coverage, improved battery life, and reduced terminal cost within a cell. Since the Internet of Things is attached to various sensors and various devices to provide communication functions, it must be able to support a large number of terminals (eg, 1,000,000 terminals/km2) within a cell. In addition, since the terminal supporting mMTC is highly likely to be located in a shaded area that the cell does not cover, such as the basement of a building, due to the nature of the service, wider coverage may be required compared to other services provided by the 5G communication system. A terminal supporting mMTC should be composed of a low-cost terminal, and since it is difficult to frequently exchange the battery of the terminal, a very long battery life time such as 10 to 15 years may be required.

Finally, in the case of URLLC, as a cellular-based wireless communication service used for a specific purpose (mission-critical), remote control for a robot or a machine, industrial automation, It may be used for a service used in an unmanned aerial vehicle, remote health care, emergency alert, and the like. Therefore, the communication provided by URLLC may have to provide very low latency (ultra-low latency) and very high reliability (ultra-reliability). For example, a service supporting URLLC must satisfy an air interface latency of less than 0.5 milliseconds, and at the same time may have a requirement of a packet error rate of 10-5 or less. Therefore, for a service supporting URLLC, the 5G system must provide a smaller Transmit Time Interval (TTI) than other services, and at the same time, it is a design that requires a wide resource allocation in the frequency band to secure the reliability of the communication link. items may be required.

The three services considered in the above-described 5G communication system, ie, eMBB, URLLC, and mMTC, may be multiplexed and transmitted in one system. In this case, different transmission/reception techniques and transmission/reception parameters may be used between services to satisfy different requirements of each service. However, the aforementioned mMTC, URLLC, and eMBB are only examples of different service types, and the service types to which the present disclosure is applied are not limited to the above-described examples.

In addition, the embodiments of the present disclosure will be described below using LTE, LTE-A, LTE Pro, or 5G (or NR, next-generation mobile communication) systems as an example, but the present disclosure also applies to other communication systems having a similar technical background or channel type. An embodiment of can be applied. In addition, the embodiments of the present disclosure may be applied to other communication systems through some modifications within a range that does not significantly depart from the scope of the present disclosure as judged by a person having skilled technical knowledge.

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

1 is a diagram illustrating an operation method of MBS communication according to an embodiment of the present disclosure. MBS (Multicast and Broadcast Service) communication refers to a method in which one transmitting device communicates with several receiving devices in a wireless communication system. Here, the transmitting apparatus may be a base station, and each receiving apparatus may be a terminal. However, the present invention is not limited thereto, and the transmitting apparatus may be a terminal.

Referring to FIG. 1 , a process of performing MBS communication when a base station 110 is a transmitting device and terminals 120 , 130 , 140 , 150 is a receiving device is illustrated. Such MBS communication may be broadcast for an unspecified number of people, or may be multicast for a plurality of specific reception devices. If communication is performed in a multicast method, the base station may set a specific terminal to receive a corresponding multicast packet. To this end, a set of terminals to perform a specific multicast communication may be set, and this is referred to as a multicast group 160 in FIG. 1 .

The terminals 120 , 130 , and 140 in the multicast group 160 are allocated the same Group-Radio Network Temporary Identity (G-RNTI) from the base station 110 to receive data allocated for the corresponding G-RNTI. can do. In the embodiment of FIG. 1 , terminal 1 120 , terminal 2 130 , and terminal 3 140 are configured as one multicast group 160 , and receive data from the base station 110 by receiving a G-RNTI assignment. It is assumed that reception is performed in a multicast manner. Since the terminal 4 150 is not included in the multicast group, it is not assigned a G-RNTI, and accordingly, the terminal 1 120 , the terminal 2 130 , and the terminal 3 140 receive data from the base station 110 . Terminal 4 (150) cannot receive.

One or more multicast groups may be set in the coverage of the base station 110 , and each multicast group may be divided into a G-RNTI. One terminal may be allocated one or more G-RNTIs from the base station 110 . The terminal can receive multicast data using the G-RNTI value allocated in the connected mode not only in the connected mode (RRC CONNECTED MODE) but also in the idle mode (RRC IDLE MODE) or inactive mode (RRC INACTIVE MODE). The G-RNTI may be configured for the UE by being included in at least one of RRC reconfiguration, RRC establishment, and RRC reestablishment messages that the UE can receive in the connected mode. However, the present invention is not limited thereto, and the base station may transmit to the terminal including a G-RNTI value that the terminal can receive in a system information block (SIB). The terminal having the G-RNTI value set according to one or more of the above-described various methods may apply the G-RNTI value after receiving the G-RNTI value.

2 is a diagram illustrating a configuration procedure for performing MBS communication according to an embodiment of the present disclosure.

Referring to FIG. 2 , in the case of the terminal 220 that is not connected to the base station 210 and the RRC (Radio Resource Control) setting, in order to perform MBS communication, a base station to request the MBS service may be selected. In this case, in step 230 , the terminal 220 may receive a synchronization signal transmitted from the base station and perform a cell selection or cell reselection procedure for selecting a base station having a strong received signal. In the embodiment of FIG. 2 , it is assumed that the UE transitions to the idle mode or the inactive mode after the initial connection state performs a cell reselection operation for selecting a cell.

In step 235, the terminal 220 may receive a system information block (System Information Block, SIB) from the selected cell. At this time, if the terminal 220 wants to receive the MBS service, it may receive a system information block including MBS information among the system information blocks. The system information block including MBS information may include a list of MBS services that are already provided or may be provided by each serving cell. A list of MBS services that are already provided or can be provided in each of these serving cells may be referred to as AvailableMBSList. AvailableMBSList may include MBS session information. The MBS session information may include a Temporary Mobile Group Identity (tmgi) value capable of identifying a group and an MBS session ID (sessionID). The tmgi value may include a Public Land Mobile Network (PLMN) ID (plmn-id) that identifies whether a service is provided by a telecommunication service provider and a service ID (serviceID) that identifies the service provided by the carrier. have. When such information is combined, AvailableMBSList can have a structure like the following example.

- AvailableMBSList = MBSSessionInfoList

■ MBSSessionInfoList = Sequence of (tmgi, sessionID)

◆ tmgi = (plmn-id, serviceID)

When all terminals request RRC configuration to receive all MBS services, the base station may be overloaded by instantaneous access to many terminals. Therefore, an access control method for the MBS service may be required. For this purpose, an access category value and uac-BarringForAccessIdentity for access control may be set in each tmgi. Using the set access category and uac-BarringForAccessIdentity, the frequency of requesting access to the base station for each tmgi can be controlled. In the embodiment of FIG. 2 , it is assumed that the terminal receives the system information block including the MBS information, but the present invention is not limited thereto, and the MBS information may be transmitted by a DL Information Transfer message.

Upon receiving the system information block including the MBS information, the terminal 220 may identify an MBS service of interest from a list of MBS services that are already provided or may be provided in each serving cell in step 240 . The terminal 220 may determine which MBS service the terminal 220 is interested in according to whether it is an MBS service required by the application of the terminal 220 or other conditions. The criterion by which the terminal 220 identifies the MBS service may be a tmgi unit. That is, the terminal 220 may check whether the tmgi of the MBS service that the terminal 220 wants to receive (or the terminal 220 is interested in) is included in the system information block including the MBS information. Specifically, the terminal 220 may check whether the tmgi of the MBS service to be received by the terminal 220 is included in the AvailableMBSList of the system information block including the MBS information. If the tmgi of the MBS service that the terminal 220 wants to receive is included in the system information block including the MBS information, the terminal 220 may perform the step of establishing an RRC connection to receive the corresponding MBS service. . In step 245, the terminal 220 may perform an access control operation to determine whether to start RRC connection establishment. The terminal 220 may perform access control using UAC-Barring information for the corresponding PLMN ID based on the PLMN ID (plmn-ID) included in the tmgi of the MBS service to be received. It may be determined whether access is permitted for the uac-BarringForAccessIdentity and the access category of the MBS service that the terminal 220 intends to receive the service from. If access to this MBS service is permitted, the terminal 220 may start a procedure for requesting an RRC connection.

In step 250 , if the terminal 220 is allowed access to receive the MBS service, the terminal 220 may transmit an RRC Setup Request message to the base station 210 . However, the present invention is not limited thereto, and an RRC Reestablishment Request message may also be used for the same purpose as the RRC establishment request message. Since this RRC establishment request message or RRC re-establishment request message is a general message that can be used for the UE to transition to the connected mode (RRC CONNECTED MODE), for what purpose the UE intends to transition to the connected mode. It can contain values. In this case, the terminal 220 may transmit an RRC establishment request or RRC re-establishment request message to the base station 210 including a Cause value indicating that MBS configuration is desired to receive the MBS service. However, if the RRC establishment request or RRC re-establishment request is not for the terminal 220 to receive the MBS service, the terminal 220 may transmit an RRC establishment request or RRC re-establishment request message using the Cause value transmitted from the upper layer. .

In step 260 , the base station 210 may transmit an RRC Setup message to the terminal 220 in order to transition the terminal 220 to the connected mode. However, the present invention is not limited thereto, and the RRC Reestablishment message may also be used for the same purpose as the RRC establishment message. When the terminal 220 receives the RRC establishment message or the RRC re-establishment message, SRB1 may be configured by the configuration information of Signaling Radio Bearer 1 (SRB1) included in the received message. SRB1 may be a radio bearer for exchanging RRC (Radio Resource Control) messages between the base station 210 and the terminal 220 .

In step 265, the terminal 220 applies the configuration information included in the RRC establishment message or the RRC re-establishment message, and transmits the RRC establishment complete or RRC re-establishment complete message to the base station 210 to receive from the base station 210 It can inform you that the settings have been applied successfully. In addition, the RRC establishment complete or RRC re-establishment complete message transmitted in step 265 may include a list of MBS services to be received by the terminal 220 . This MBS service list may be a list including a tmgi value corresponding to an MBS service that the terminal wants to receive. At this time, the tmgi including the MBS service list is a list of MBS services that are already provided or can be provided in each serving cell, included in the system information block or downlink information transfer message transmitted in step 235 by the base station 210. It can be all or part of the tmgi included in .

Since SRB1 is set in step 265 and the list of MBS services that the terminal 220 wants to receive is delivered to the base station 210 , the base station 210 may configure reception of the MBS service based on this in step 270 . This MBS service may be configured using an RRC reconfiguration message (RRC Reconfiguration) transmitted from the base station 210 to the terminal 220 . This RRC reset message includes a Signaling Radio Bearer 2 (SRB2) used for transmitting and receiving NAS (Non-Access Stratum) messages, a Data Radio Bearer (DRB) used for transmitting and receiving data, and a Point To Multipoint (PTM) used for multicast transmission. DRB configuration information and the like may be included. Here, the PTM DRB may be configured without distinction from the normal DRB, or may be configured by the received G-RNTI. In addition, an RLC (Radio Link Control) bearer to which the configured radio bearer is transmitted may be configured, and a radio bearer to which this RLC bearer is connected may be configured. Herein, a G-RNTI through which terminals belonging to a multicast group can receive multicast data may be configured. This G-RNTI is an RNTI configured for reception of a transport block (TB) and may be used to indicate scheduling information for the PDSCH. This G-RNTI may be configured in units of MAC devices, or may be configured in units of BandWidth Part (BWP). If the G-RNTI is configured in units of BWP, the configured G-RNTI may be used only when receiving the PDSCH resource of the BWP. That is, the corresponding G-RNTI may not be used in other BWPs. To this end, the G-RNTI may be configured by being included in the downlink BWP configuration (BWP-Downink configuration) field of the RRC message. A BWP ID to be used when G-RNTI is set may be set. In another embodiment, the G-RNTI may be configured in units of cells. If the G-RNTI is configured for each cell, the configured G-RNTI may be used only when receiving the PDSCH resource of the cell. That is, the corresponding G-RNTI may not be used in another cell. To this end, the G-RNTI may be configured by being included in the cell configuration field of the RRC message. A cell ID to be used when G-RNTI is configured may be configured.

In order to receive the MBS service, the BWP and the search space may be separately set. Information on the BWP and search space for receiving a specific MBS service may be configured from the base station to the terminal, and the MBS BWP and MBS search space may be included in the configuration information on the BWP and search space for receiving a specific MBS service. . Here, the MBS BWP may mean a BWP to which the assigned G-RNTI is applied. According to an embodiment, the BWP including the G-RNTI in the BWP-Downlink configuration field may be the MBS BWP. The MBS search space may be a search space in which a Downlink Control Information (DCI) format for MBS reception is set in the search space configuration information, or a search space including an indicator indicating that it is a search space for MBS reception in the search space configuration information. For example, the search space setting information may include a 1-bit indicator indicating whether the corresponding search space is an MBS search space. If this indicator indicates whether it is an MBS search space, the corresponding search space may be an MBS search space and may be used as a search space monitoring G-RNTI for MBS reception.

If the terminal applied the contents included in the RRC configuration message of step 270, in step 275, the terminal 220 transmits an RRC reconfiguration complete message (RRC Reconfiguration Complete) to the base station 210 to apply the information of the RRC configuration message. can inform Accordingly, in step 280, the terminal 220 may receive a broadcast or multicast packet by performing MBS communication. That is, the MBS service can be received from the base station.

3 is a diagram illustrating a method of setting an Initial BWP for reception of an MBS service according to an embodiment of the present disclosure.

If the idle mode or inactive mode terminal is to receive the MBS service, it is necessary to set a BWP capable of receiving the MBS service. Since multiple BWPs can be configured in one cell and the UE can only activate one BWP, the UE needs to receive the MBS service from the UE's Active BWP. To this end, the base station may set the BWP for the terminal to receive the MBS service in the idle mode or the inactive mode of the terminal. Referring to FIG. 3 , the terminal 320 in the idle mode or the inactive mode may receive the MBS service in the Initial BWP set by the base station 310 . Initial BWP indicates a BWP to be used when the terminal makes an initial connection, but in the embodiment of FIG. 3 , the Initial BWP may be used for receiving the MBS service. The setting of the Initial BWP may be accomplished by the base station 310 transmitting a message 330 for setting the Initial BWP to the terminal 320 . The message for setting the Initial BWP may be periodically transmitted as a system information block or may be transmitted when the UE transitions to an idle mode or an inactive mode by an RRC release message or the like. In another embodiment, Initial BWP information may be transmitted and set by an RRC reconfiguration message. The message for setting the Initial BWP may include at least one or more of the BWP ID of the Initial BWP, the tmgi of the MBS service that can be serviced in the BWP, and the G-RNTI value that can receive the data of the MBS service. By applying the information included in the message for setting the Initial BWP, the terminal can receive the MBS service in the idle mode or the inactive mode. According to an embodiment, the terminal may detect whether there is data for MBS service reception using the G-RNTI in the initial BWP set in the idle mode or the inactive mode, and the downlink radio resource using the G-RNTI is detected. In this case, the MBS service may be received in the downlink radio resource using the G-RNTI.

A search space and CORESET (Control Resource Set) for a PDCCH (Physical Downlink Control Channel) that the UE needs to monitor in order to receive the MBS service in the Initial BWP are included in the message 330 for setting the Initial BWP. can Although the embodiment of FIG. 3 has been mainly described when the terminal is in an idle mode or an inactive mode, it is not limited thereto, and the MBS service may be received in the Initial BWP even when the terminal is in the connected mode.

4 is a diagram illustrating a method of setting a downlink BWP for reception of an MBS service according to an embodiment of the present disclosure.

If the idle mode or inactive mode terminal is to receive the MBS service, it is necessary to set a BWP capable of receiving the MBS service. Since multiple BWPs can be configured in one cell and the UE can only activate one BWP, the UE needs to be provided with the MBS service in the UE's Active BWP. To this end, the base station may set a downlink BWP for the terminal to receive the MBS service in an idle mode or an inactive mode. Referring to FIG. 4 , the terminal 420 in the idle mode or the inactive mode may receive the MBS service in the downlink BWP set by the base station 410 . The downlink BWP set by the base station 410 is a BWP set by the base station 410 in order for the terminal 420 to receive the MBS service. The downlink BWP setting for the MBS may be configured by a message 430 for setting the downlink BWP for the MBS that the base station 410 transmits to the terminal 420 . The message for setting the downlink BWP for MBS may be periodically transmitted to a system information block or transmitted when the UE transitions to an idle mode or an inactive mode by an RRC release message or the like. In another embodiment, the downlink BWP configuration may be configured by transmitting downlink BWP information for MBS by an RRC reconfiguration message. The message for setting the downlink BWP for the MBS purpose may include at least one or more of the BWP ID of the corresponding BWP, the tmgi of the MBS service that can be serviced in the BWP, and the G-RNTI value that can receive the data of the MBS service. . By applying these information, the terminal can receive the MBS service in the idle mode or the inactive mode. The downlink BWP for MBS set in the embodiment of FIG. 4 may be a BWP different from the Initial BWP. According to an embodiment, the UE may detect whether there is data for MBS service reception using the G-RNTI in the downlink BWP for MBS set in the idle mode or the inactive mode, and downlink radio resources using the G-RNTI. When this is detected, the MBS service may be received in the corresponding downlink radio resource. However, in another embodiment, the UE detects a downlink radio resource from the Initial BWP to the G-RNTI, and reception of the corresponding downlink radio resource may be performed in the downlink BWP for MBS configured. The search space and CORESET (Control Resource Set) for the PDCCH (Physical Downlink Control Channel) that the UE needs to monitor in order to receive the MBS service in the Active BWP are in the message 430 for setting the downlink BWP for the MBS. It can be included and set.

5 is a diagram illustrating an operation for receiving an MBS service when a connected mode transitions according to an embodiment of the present disclosure.

3 or 4, the terminal may receive the MBS service in an idle mode or an inactive mode. While the terminal is receiving the MBS service, a transition to the connected mode may be required according to a preset condition. Referring to FIG. 5 , in step 530 , the terminal 520 in the idle mode or the inactive mode may perform a procedure for transitioning to the connected mode. In order for the terminal to transition to the connected mode, the terminal 520 may transmit a message such as an RRC Connection Request or an RRC Resume Request to the base station 510 . Accordingly, the terminal 520 may request the transition to the connected mode by transmitting a message such as an RRC Connection Request or an RRC Resume Request to the base station 510 . If the terminal was receiving the MBS service in the idle mode or the inactive mode and wants to receive the received MBS service also in the connected mode, in step 540, the terminal 510 tells the base station 520 that the terminal 510 is idle. A list of MBS services received in the mode or inactive mode may be transmitted to the base station 520 . The list of MBS services that the terminal 510 has been receiving may be the tmgi of the MBS services that the terminal 510 has received. In addition, the terminal 510 may transmit to the base station 520 including an indicator indicating that it wants to continuously receive the service even in the connected mode in the list of MBS services it is receiving. In another embodiment, the terminal 510 is a list of MBS services that it wants to continuously receive service in the connected mode among the list of MBS services that have been received from the base station 520, and a list of MBS services that do not need to receive any more services. may be transmitted separately. In another embodiment, the terminal 510 may transmit to the base station 520 only a list of MBS services that it wants to continuously receive service in the connected mode from among the list of MBS services that have been received when the connected mode transitions. In step 550 , the base station 520 may set the MBS service that can be received in the connected mode to the terminal 510 based on the information received from the terminal 510 . The MBS service configuration information that can be received in the connected mode may include a tmgi list that can be received by the terminal, configuration of a radio bearer for MBS, G-RNTI information, and the like. In addition, the base station 520 may set the active BWP for receiving the terminal MBS service. Based on these configuration information, the terminal can continuously receive the MBS service in the connected mode.

6 is a diagram illustrating a method of configuring a dedicated carrier for an MBS service according to an embodiment of the present disclosure.

A base station providing the MBS service may provide the MBS service in a specific carrier or a specific cell. In the mobile communication network, a terminal receiving a unicast communication service other than the MBS service and a terminal receiving the MBS service may exist at the same time. In addition, a certain terminal 610 may receive both unicast communication and MBS service. A mobile communication operator or a mobile communication base station may provide each service in a different carrier or in a different cell by distinguishing between unicast data and data for the MBS service. Referring to FIG. 6 , normal unicast data may be transmitted on a downlink carrier 620 , and data for an MBS service may be transmitted on a Supplementary Downlink (SDL) carrier, which is a separate dedicated carrier. However, this is only one embodiment and is not limited thereto, and unicast data may be transmitted in a certain cell and data for an MBS service may be transmitted in another cell. In order to classify traffic, the base station may configure an SDL carrier or an MBS dedicated cell for the MBS service to the terminal. Configuration information for traffic classification may be transmitted using a system information block as shown in FIG. 3 or FIG. 4 or using at least one of an RRC release message and an RRC reset message. In addition, the configuration information may include a PCI (Physical-layer Cell ID) or SDL configuration indicator for the SDL carrier or cell for the MBS service. In addition, the configuration information may include an SDL carrier for the MBS service or a list of MBS services provided by the cell. tmgi may be used as a list of these MBS services.

7 is a diagram illustrating an operation for MBS service reception when an idle mode or an inactive mode transitions according to an embodiment of the present disclosure.

Referring to FIG. 7 , in step 730 , the terminal 720 may receive the MBS service from the connection board by receiving the MBS setting from the base station 710 . However, when the base station 710 determines that connected mode communication is no longer required for the corresponding terminal 720 , in step 740 , the base station 710 transmits an RRC Release message to the terminal 720 . Thus, the terminal 720 may instruct to transition to the idle mode or the inactive mode. However, when the terminal 720 has been receiving the MBS service in the existing connected mode and it is necessary to continue to receive the MBS service that is being provided, the terminal 720 continues the MBS service in the idle mode or the inactive mode. It is necessary to set up the MBS service to receive it. The setting of the MBS service for continuing to receive the MBS service may include a setting for the BWP through which the terminal 720 will receive the MBS service in an idle mode or an inactive mode. For the setting of the BWP for the terminal 720 to receive the MBS service, the base station 710 includes the BWP ID for the BWP to be received by the terminal 720 in the idle mode or the inactive mode in the RRC release message. Including information on whether to receive the MBS service can be transmitted. However, the present invention is not limited thereto, and in one embodiment, the BWP ID is not included in the RRC release message, and the base station 710 may instruct the terminal 720 to continue to use the currently used Active BWP. In another embodiment, the BWP ID is not included in the RRC release message, and the base station 710 may instruct the terminal 720 to switch to the Initial BWP to receive the MBS service. In another embodiment, the BWP ID is not included in the RRC release message, and the base station 710 may instruct the terminal 720 to switch to the Default BWP to receive the MBS service. In another embodiment, if the RRC release message includes a BWP ID indicating in which BWP to receive the MBS service, the terminal can receive the MBS service using the corresponding BWP in the idle mode or inactive mode, but RRC release If the message does not include the BWP ID, the terminal may receive the MBS service in the Initial BWP. In another embodiment, if the RRC release message includes a BWP ID indicating in which BWP to receive the MBS service, the terminal can receive the MBS service using the corresponding BWP in the idle mode or inactive mode, but RRC release If the message does not include the BWP ID, the terminal can receive the MBS service from the last active BWP used in the connected mode. In another embodiment, if the RRC release message includes a BWP ID indicating in which BWP to receive the MBS service, the terminal can receive the MBS service using the corresponding BWP in the idle mode or inactive mode, but RRC release If the message does not include the BWP ID, the terminal may receive the MBS service in the Default BWP. In addition, the MBS configuration information that can be transmitted by being included in the RRC connection release message may include a list of MBS services that the terminal can use in the BWP. The list of these MBS services may include a list of tmgi. In step 750, the terminal 720 may continue to receive the MBS service in the idle mode or the inactive mode. If the terminal is currently being provided and the MBS service to be continuously received is not included in the MBS service list included in the RRC connection release message, after RRC release, the terminal 720 requests RRC setup to transition to the connected mode again A message or an RRC connection resumption request message may be transmitted to the base station 710 .

In one embodiment, an indicator indicating that the base station does not stop the MBS service being received by the terminal when the base station releases the RRC is included in the RRC connection release message (when the indicator indicating that the MBS service is not included is not included), RRC If the terminal is currently being provided in the connection release message and the MBS service to be continuously received is not included in the list, after RRC release, the terminal sends an RRC establishment request message or RRC connection resumption request message to the base station to transition to the connected mode again can be transmitted On the other hand, the indicator indicating that the base station does not stop the MBS service being received by the terminal when the base station releases the RRC is not included in the RRC connection release message (when an indicator indicating that the MBS service is stopped) is included, and the RRC connection is released If the message indicates that the terminal is currently being provided and the MBS service to be continuously received is not included in the list, the terminal may transition to an idle mode or an inactive mode and may no longer receive the MBS service it has been receiving.

8 is a diagram illustrating a BWP setting method for an MBS service according to an embodiment of the present disclosure. The base station may operate several BWPs in one cell, and may configure one active BWP for one terminal at a single time. The MBS service may be provided in all or some of these multiple BWPs.

Referring to FIG. 8 , it is assumed that a total of four BWPs 800 , 810 , 820 , and 830 are configured in one cell. Of the four BWPs (800, 810, 820, 830), data for MBS service is transmitted only in BWP0 (800) and BWP1 (810), and data for MBS service is transmitted in other BWPs, BWP2 (820) and BWP3 (830). may not be transmitted.

In the embodiment of FIG. 8 , it is assumed that the same MBS service is provided in the two BWPs 800 and 810 for transmitting data for the MBS service. Therefore, if the terminal can receive data in at least one of the BWP0 800 and the BWP1 810, the terminal can receive the same MBS service. In this case, the terminal needs to know which BWP transmits data for the MBS service. To this end, the base station transmits data for the MBS service using at least one of RRC reconfiguration, RRC setup, RRC re-establishment, RRC release, or system information block message. may inform the terminal which BWP is. In an embodiment, the base station may inform the terminal of the list of BWPs for transmitting data for the MBS service in each cell. In another embodiment, the base station may transmit to the terminal including an indicator indicating whether the BWP transmits data for the MBS service in each BWP configuration information.

9 is a diagram illustrating a BWP setting method for an MBS service according to an embodiment of the present disclosure. The base station may operate several BWPs in one cell, and may configure one active BWP for one terminal at a single time. The MBS service may be provided in all or some of these multiple BWPs.

Referring to FIG. 9 , it is assumed that a total of four BWPs 900 , 910 , 920 , and 930 are configured in one cell. Of the four BWPs (900, 910, 920, 930), data for MBS service is transmitted only in BWP0 (900) and BWP1 (910), and data for MBS service is transmitted in other BWPs, BWP2 (920) and BWP3 (930). may not be transmitted.

In the embodiment of FIG. 9 , it is assumed that different MBS services are provided in two BWPs for transmitting data for the MBS service. Therefore, in order for the terminal to receive any MBS service, it must receive data from the BWP in which the MBS service is provided. In this case, the terminal needs to know in which BWP data for which MBS service is transmitted. Accordingly, the base station uses at least one of RRC reconfiguration, RRC setup, RRC re-establishment, RRC release, or system information block message MBS service provided by each BWP. may inform the terminal of the list of In an embodiment, a list of tmgi may be used and transmitted as a list of MBS services provided by the BWP.

10 is a diagram illustrating a structure of a base station according to an embodiment of the present disclosure.

Referring to FIG. 10 , the base station may include a transceiver 1010 , a controller 1020 , and a storage 1030 . In the present disclosure, the controller 1020 may be defined as a circuit or an application-specific integrated circuit or at least one processor. According to the above-described communication method of the base station, the transceiver 1010 , the control unit 1020 , and the storage unit 1030 of the base station may operate. However, the components of the base station are not limited to the above-described example. For example, the base station may include more or fewer components than the above-described components. In addition, the transceiver 1010 , the control unit 1020 , and the storage unit 1030 may be implemented in the form of a single chip.

The transceiver 1010 may transmit/receive a signal to/from another network entity. The transceiver 1010 may transmit, for example, system information to the terminal, and may transmit a synchronization signal or a reference signal. The transceiver 1010 collectively refers to a receiver of a base station and a transmitter of the base station, and may transmit/receive a signal to and from a terminal or a network entity. A signal transmitted and received with a terminal or a network entity may include control information and data. To this end, the transceiver 1010 may include an RF transmitter for up-converting and amplifying the frequency of a transmitted signal, and an RF receiver for low-noise amplifying a received signal and down-converting the frequency. However, this is only an embodiment of the transceiver 1010 , and components of the transceiver 1010 are not limited to the RF transmitter and the RF receiver. In addition, the transceiver 1010 may receive a signal through a wireless channel and output it to the control unit 1020 , and transmit the signal output from the control unit 1020 through the wireless channel.

The controller 1020 may control the overall operation of the base station according to the embodiment proposed in the present disclosure. For example, the controller 1020 may control a signal flow between blocks to perform an operation according to the above-described flowchart. The controller 1020 may receive a control signal and a data signal through the transceiver 1010 and process the received control signal and data signal. Also, the controller 1020 may transmit the processed control signal and data signal through the transceiver 010 . Also, the controller 1020 may configure downlink control information (DCI) including allocation information for a physical downlink shared channel (PDSCH) and control each component of the base station to transmit it. The control unit 1020 may be one, but may be plural, and may consist of one or a plurality of processors. The control unit 1020 may execute a program stored in the storage unit 1030 to control the components of the base station.

The storage unit 1030 may store at least one of information transmitted and received through the transceiver 1010 and information generated through the control unit 1020 . The storage unit 1030 may be defined as a 'memory'. The storage unit 1030 may store programs and data necessary for the operation of the base station. Also, the storage unit 1030 may store control information or data included in a signal obtained from the base station. The storage unit 1030 may be configured of a storage medium such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD, or a combination of storage media. Also, the storage unit 1030 may not exist separately and may be included in the control unit 1020 .

11 is a diagram illustrating a structure of a terminal according to an embodiment of the present disclosure.

Referring to FIG. 11 , the terminal may include a transceiver 1110 , a control unit 1120 , and a storage unit 1130 . In the present disclosure, the controller may be defined as a circuit or an application specific integrated circuit or at least one processor. According to the communication method of the terminal described above, the transceiver 1110 , the control unit 1120 , and the storage unit 1130 of the terminal may operate. However, the components of the terminal are not limited to the above-described examples. For example, the terminal may include more or fewer components than the aforementioned components. In addition, the transceiver 1110 , the control unit 1120 , and the storage unit 1130 may be implemented in the form of a single chip.

The transceiver 1110 may transmit/receive signals to and from other network entities. The transceiver 1110 may receive, for example, system information from a base station, and may receive a synchronization signal or a reference signal. The transceiver 1110 collectively refers to a receiver of a terminal and a transmitter of the terminal, and may transmit/receive a signal to and from a network entity, a base station, or another terminal. A signal transmitted and received with a network entity, a base station, or another terminal may include control information and data. To this end, the transceiver 1110 may include an RF transmitter that up-converts and amplifies the frequency of a transmitted signal, and an RF receiver that low-noise amplifies and down-converts a received signal. However, this is only an embodiment of the transceiver 1110 , and components of the transceiver 1110 are not limited to the RF transmitter and the RF receiver. In addition, the transceiver 1110 may receive a signal through a wireless channel and output it to the control unit 1120 , and transmit a signal output from the control unit 1120 through a wireless channel.

The controller 1120 may control the overall operation of the terminal according to the embodiment proposed in the present disclosure. For example, the controller 1120 may control a signal flow between blocks to perform an operation according to the above-described flowchart. The controller 1120 may receive a control signal and a data signal through the transceiver 1110 and process the received control signal and data signal. Also, the controller 1120 may transmit the processed control signal and data signal through the transceiver 1110 . In addition, the controller 1120 may receive DCI composed of two layers and control the components of the terminal to receive a plurality of PDSCHs at the same time. The control unit 1120 may be one or plural, and may be composed of one or a plurality of processors. The control unit 1120 may execute a program stored in the storage unit 1130 to perform a component control operation of the terminal.

The storage unit 1130 may store at least one of information transmitted/received through the transceiver 1110 and information generated through the control unit 1120 . The storage unit 1130 may be defined as a 'memory'. The storage unit 1130 may store programs and data necessary for the operation of the terminal. Also, the storage unit 1130 may store control information or data included in a signal obtained from the terminal. The storage unit 1130 may be configured of a storage medium such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD, or a combination of storage media. Also, the storage unit 1130 may not exist separately and may be included in the control unit 1120 .

12 is a diagram illustrating an MBS split bearer and path switching according to an embodiment of the present disclosure.

In MBS, since a plurality of terminals receive data, transmission to one specific terminal cannot be guaranteed. If the provided MBS service requires high stability for data, it is difficult to satisfy this requirement with a broadcast or multicast transmission method. For this reason, although it is data for the MBS service, some packets need to be transmitted in a unicast manner. To this end, an MBS Radio Bearer (MRB) that mixes transmission of a PTM method and a PTP method rather than a specific PTM or PTP (Point to Point) method may be defined. Because this MBS radio bearer handles the same MBS service, there is only one SDAP (Service Data Adaptation Protocol) and PDCP (Packet Data Convergence Protocol) layer connected to the upper layer, and there are two RLC devices for the RLC (Radio Link Control) layer. Since there are more than one, some RLCs can be used in the PTM method (RLC-PTM, PTM RLC), and other RLCs can be used in the PTP method (RLC-PTP, PTP RLC). Each RLC device may correspond to a logical channel, and the PTM RLC may be transmitted through a radio resource allocated as a G-RNTI, and the PTP RLC may be transmitted through a radio resource allocated as a C-RNTI. In this way, a radio bearer having both PTP RLC and PTM RLC in one radio bearer may be referred to as an MBS split radio bearer.

12 shows an operation method of determining whether data for the MBS service is transmitted through PTM or PTP according to selection of a base station. The base station may determine whether to transmit using the PTM RLC or the PTP RLC in consideration of various factors, such as the location of the terminal, the signal strength, and the number of terminals receiving the MBS service. If the BS transmits data using the PTM RLC, the PTM RLC may be activated and the PTP RLC may be deactivated. (1210) At this time, the UE may receive data through the activated PTM RLC. Conversely, when the base station transmits data using the PTP RLC, the PTP RLC may be activated and the PTM RLC may be deactivated. (1220) At this time, the terminal may receive data through the activated PTP RLC. PTM RLC may use uni-directional RLC UM (Unacknowledged Mode), and PTP RLC may use unidirectional or bi-directional RLC UM or RLC AM (Acknowledged Mode).

Whether to use the activated PTM RLC or to activate and use the PTP RLC, the base station may instruct the UE. In addition, the terminal may receive data using the RLC to be activated and used as instructed by the base station. In another embodiment, the terminal may determine the RLC device activated by itself by detecting data received from the base station. A detailed operation of whether to activate and use the PTM RLC or to activate and use the PTP RLC will be described later with reference to FIGS. 12 and 13 . Based on such a scheme, the base station and the terminal may perform an operation of switching the activated RLC. (1230) After the operation of switching the activated RLC, the terminal transmits a PDCP status report message to inform the base station of the information of the packet successfully received by the terminal and enables the base station to perform retransmission.

13 is a diagram illustrating an MBS split bearer and a path switching process according to an embodiment of the present disclosure.

The base station 1310 may provide an MBS service to a plurality of terminals through an MBS radio bearer. In this case, the base station may select one of PTM RLC or PTP RLC for each terminal 1320 to perform data transmission. To this end, the base station may transmit a message (or may be referred to as a path change instruction message, a path change instruction message, etc.) to the terminal instructing which path to transmit data through among the PTM RLC and the PTP RLC. (1330) The terminal receives this path change indication message and activates it based on this information to apply an RLC device (data path) used for data transmission. In the embodiment of FIG. 13 , it is assumed that the terminal receives data through a first path (PTM or PTP) but receives data through a second path (indicated PTM or PTP) after receiving the path change indication message 1330 .

The path change indication message may be indicated by a medium access control-control element (MAC CE) or downlink control information (DCI) transmitted through a physical downlink control channel (PDCCH). Information included at this time may indicate which MBS radio bearer the path is for switching and which RLC device the changed path is. As the identifier of the RLC device, at least one of whether it is a PTM RLC/PTP RLC and a logical channel ID may be used. In another embodiment, the path switch indication message may be indicated by a PDCP Control PDU (Protocol Data Unit) and may mean a path switch for the MBS radio bearer through which the PDCP Control PDU is transmitted. The information included at this time may indicate which RLC device the switched path is. As the identifier of the RLC device, at least one of whether it is a PTM RLC/PTP RLC and a logical channel ID may be used.

14 is a diagram illustrating an MBS split bearer and a path switching process according to an embodiment of the present disclosure.

In the embodiment of FIG. 14 , it is assumed that the UE monitors both the PTM RLC and the PTP RLC configured in the MBS radio bearer, but activates only one RLC. To this end, when the reception of a packet is detected by the PTP RLC device or the PTM RLC device, the method of switching and applying the activated RLC device (active data path) is shown. In the embodiment of FIG. 14 , it is assumed that the base station 1410 is transmitting data to the terminal 1420 using PTM RLC. (1430, 1440, 1450) At this time, the activated path of the UE in the MBS radio bearer becomes the PTM RLC. Thereafter, when data to the PTP RLC is detected ( 1460 ), the terminal switches the activated RLC device to the PTP RLC. After that, data transmission to the PTP RLC is continued (1470), and when data arrives to the PTM RLC again (1480), the RLC device activated as the PTM RLC is switched and applied. Thereafter, when data additionally arrives to the PTM RLC ( 1490 ), data reception may continue with the activated PTM RLC device.

In an embodiment, once the RLC device is deactivated or newly activated, the RLC device may be initialized. That is, an operation of initializing the state variable of the RLC and emptying the reception RLC buffer may be performed. In another embodiment, a re-establishment operation of the RLC device may be performed. In addition, active path information may be known to the upper layer PDCP device.

15 is a diagram illustrating a first packet reception operation after path switching of an MBS split bearer according to an embodiment of the present disclosure.

After the UE is instructed to switch a path from the PTM RLC or PTM RLC to another RLC of the MBS split bearer by the method of FIG. 13 or 14 or other methods, the UE switches to the PTM RLC or PTP RLC ( If the RLC device is configured), it can receive the first packet. In order for the UE to receive data of the MBS radio bearer including the first received packet (1510), re-establishment of a corresponding RLC device may be performed. (1520) The operation of re-establishing the RLC device may include an operation of initializing a state variable of the RLC and emptying a receive RLC buffer.

16 is a diagram illustrating a first packet reception operation after path switching of an MBS split bearer according to an embodiment of the present disclosure.

After the UE is instructed to change a path from the PTM RLC or PTM RLC of the MBS split bearer to another RLC in the method of FIG. 13 or 14 or other methods of FIG. 13 or 14, the UE switches to the PTM RLC or PTP RLC After the RLC device is configured), the first packet may be received. In order to receive the data of the MBS radio bearer including the first received packet (1610), the UE may perform an operation of initializing a state variable of a corresponding RLC device and emptying the reception RLC buffer. The UE may check whether the switched RLC device is an RLC UM device or an RLC AM device (in the case of initial configuration, after the RLC device is configured). (1620) If it is an RLC UM device, the UE may set RX_Next_Reassembly and RX_Next_Highest among RLC state variables of the corresponding RLC device to the SN value of the packet having the first received SN. (1630) Otherwise, if it is an RLC AM device, the UE may set RX_Next and RX_Next_Highest among RLC state variables of the corresponding RLC device to the SN value of the packet having the first received SN. The operation after 1640 may follow the previously defined RLC reception operation.

17 is a diagram illustrating a first packet reception operation after path switching of an MBS split bearer according to an embodiment of the present disclosure.

After the UE is instructed to switch a path from the PTM RLC or PTM RLC to another RLC of the MBS split bearer by the method of FIG. 13 or 14 or other methods, the UE switches to the PTM RLC or PTP RLC ( If the RLC device is configured), it can receive the first packet. In order to receive data of the MBS radio bearer including the first received packet (1710), the UE may perform an operation of initializing a state variable of a corresponding RLC device and emptying the reception RLC buffer. The UE may check whether the switched RLC device is an RLC UM device or an RLC AM device (in the case of initial configuration, after the RLC device is configured). (1720) If it is an RLC UM device, the UE may set the SN value of the packet in which SI=01 while having the SN that first received RX_Next_Reassembly and RX_Next_Highest among the RLC state variables of the corresponding RLC device. (1730) The SI (Segment Info) field is a field indicating the segmentation type of the corresponding packet. The first bit of the SI field is a field indicating whether the front part of the received SDU is divided. . The second bit of the SI field has a value of 1 when divided into a field indicating whether the rear part of the received SDU is divided. If the value of the SI field is 01, it indicates that it is the first segment of the RLC service data unit (SDU), and when this first segmented packet is received, it may mean that there is a high probability of receiving all the corresponding packets. In step 1720, if it is an RLC AM device, the UE may set the SN value of the packet in which SI=00 or 01 while having the SN that first received RX_Next and RX_Next_Highest among the RLC state variables of the corresponding RLC device. (1740) If the value of the SI field is 00, it indicates that it is a complete RLC SDU that is not divided. Subsequent operations may follow the previously defined RLC reception operation.

18 is a diagram illustrating a path switching operation of an MBS split bearer according to an embodiment of the present disclosure.

When the UE is instructed to switch a path from the PTM RLC or PTM RLC to another RLC of the MBS split bearer by the method of FIG. 13 or 14 or other methods (1810), in the existing RLC bearer, HARQ (Hybrid Automatic Repeat reQuest) retransmission, etc. There may be data that can be received by the existing RLC. In order to complete the reception of the residual data and to complete the indicated RLC conversion, the RLC path conversion may be delayed by a predetermined time set in advance. (1820) The length of the delay time may be set by being transmitted by the RRC reconfiguration message from the base station. In addition, unnecessary path switching due to retransmission packets can be prevented by not performing additional path switching during this predetermined time period. In the embodiment of FIG. 18 , it is shown that the PTM RLC is activated and used, and then the path conversion to the PTP RLC is indicated, but the reverse case is also applicable. After a predetermined delay time, the path may be switched to the PTP RLC and the PTP RLC may be activated and used. Also, even if data is received through the PTM RLC during this delay time, a method of switching to the PTP RLC after the delay time without switching to the PTM RLC is shown.

19 is a diagram illustrating an operation of an MBS radio bearer during handover according to an embodiment of the present disclosure.

When the terminal is receiving the MBS service from the serving base station 1910 and moves to the area of the target base station 1920, the terminal may receive data from the target base station by performing a handover procedure to the target base station. However, since each base station operates independently, the same packet (PDCP PDU or PDCP SDU unit) may not have the same PDCP SN (sequence number). In the embodiment of FIG. 19 , packets assigned with sequence numbers of 0, 1, 2, 3, and 4, respectively, may be assigned and used with sequence numbers of 7, 8, 9, 10, and 11 by the target base station. In this case, the terminal may have to modify the sequence number used by the terminal during handover. In the embodiment of FIG. 19, the serving base station and the target base station have a difference of 7 sequence numbers for PDCP packets of a specific MBS radio bearer. Therefore, the RRC reconfiguration message transmitted by the serving base station during handover informs that there is a difference of 7 in the PDCP sequence number of the target base station, and using this value, the terminal changes the PDCP sequence number after handover, so that the same You can continue to use the MBS radio bearer for the service. The UE may perform the PDCP reception operation by correcting the difference by the difference in the sequence number for the PDCP state variable as much as the difference in the PDCP sequence number. If a PDCP status report message is transmitted to the target base station after handover, the COUNT value used for the PDCP status report message may be a COUNT value derived by being converted into a sequence number used by the target base station.

20 is a diagram illustrating a bearer format conversion including an MBS split bearer according to an embodiment of the present disclosure.

In MBS, since a plurality of terminals receive data, transmission to one specific terminal cannot be guaranteed. If the provided MBS service requires high stability for data, it is difficult to satisfy this requirement with a broadcast or multicast transmission method. For this reason, although it is data for the MBS service, some packets need to be transmitted in a unicast manner. To this end, an MBS radio bearer (MRB) that mixes transmission of a PTM scheme and a PTP scheme rather than a specific PTM or PTP scheme may be defined. Because this MBS radio bearer handles the same MBS service, there is only one SDAP (Service Data Adaptation Protocol) and PDCP (Packet Data Convergence Protocol) layer connected to the upper layer, and there are two RLC devices for the RLC (Radio Link Control) layer. Since there are more than one, some RLCs can be used in the PTM method (RLC-PTM, PTM RLC), and other RLCs can be used in the PTP method (RLC-PTP, PTP RLC). Each RLC device may correspond to a logical channel, and the PTM RLC may be transmitted through a radio resource allocated as a G-RNTI, and the PTP RLC may be transmitted through a radio resource allocated as a C-RNTI. In this way, a radio bearer having both PTP RLC and PTM RLC in one radio bearer may be referred to as an MBS split radio bearer. (2010) In this MBS split radio bearer, which RLC device is used to transmit data, the base station may arbitrarily determine without a separate indication. In addition, the path through which the base station transmits data may be switched (Switching). The UE may receive packets in order without overlapping by using reordering and duplicate detection techniques in the PDCP device. In the MBS split radio bearer shown in step 2010, it is assumed that the UE always receives data in the PTM RLC and the PTP RLC.

However, the MBS radio bearer does not necessarily have a PTP RLC. That is, there is no need to have a separate PTP RLC if the multicast or broadcast method transmitted by the base station through the PTM RLC is sufficient. A radio bearer having one PTM RLC in this way may be referred to as a PTM MBS radio bearer (PTM MRB). (2020) and there may also be a radio bearer with only PTP RLC in which resources are allocated to C-RNTI without PTM RLC. This radio bearer may be referred to as a DRB because it has the same structure as the existing Data Radio Bearer (DRB), but may also be referred to as a PTP MBS radio bearer (PTP MRB) for a radio bearer through which MBS data is transmitted. (2030) A bearer format change operation may be performed between the MBS split radio bearer, the PTM MBS radio bearer, and the PTP MBS radio bearer.

When the bearer format is changed, if the PDCP sequence number is maintained as it is or the difference in the status number is corrected as shown in FIG. 19 , the UE may transmit a PDCP status report message to the base station to request retransmission. To this end, when establishing the MBS radio bearer (MBS split radio bearer, PTM MBS radio bearer, PTP MBS radio bearer), whether to maintain the PDCP sequence number (in some embodiments, re-establishment of the MBS radio bearer is performed) separately to the UE. can tell you In another embodiment, the base station may inform the terminal of the difference in the PDCP sequence number (or COUNT) when the MBS radio bearer is established. The PDCP status report message may be transmitted only when the PTP RLC is RLC AM, and may not be transmitted when the PTP RLC is RLC UM. In some embodiments, when at least one of an operation of releasing a preset RLC device, a MAC reset, and an operation of re-establishing a preset RLC device is involved when the bearer format is changed, PDCP status report The message may be transmitted to the base station.

On the other hand, the embodiments disclosed in the present specification and drawings are only presented as specific examples to easily explain the technical content of the present disclosure and help the understanding of the present disclosure, and are not intended to limit the scope of the present disclosure. That is, it is apparent to those of ordinary skill in the art to which the present disclosure pertains that other modifications can be implemented based on the technical spirit of the present disclosure. In addition, each of the above embodiments may be operated in combination with each other as needed. For example, the base station and the terminal may be operated by combining parts of one embodiment and another embodiment of the present disclosure with each other. In addition, the embodiments of the present disclosure are applicable to other communication systems, and other modifications based on the technical spirit of the embodiments may also be implemented.

Claims (2)

A method of operating a base station for transmitting a Multicast and Broadcast Service (MBS) service in a wireless communication system, the method comprising:
Determining a BWP (Bandwidth Part) for the terminal to receive the MBS service;
transmitting the determined configuration information for the BWP to the terminal including at least one of a system information block, an RRC release message, and an RRC reset message; and
Using the determined BWP, comprising the step of transmitting the MBS service to the terminal. A method of operating a terminal for receiving a Multicast and Broadcast Service (MBS) service in a wireless communication system, the method comprising:
Receiving, by a terminal in an idle mode or an inactive mode, configuration information for a BWP to be provided with an MBS service from a base station; and
Based on the configuration information for the BWP, comprising the step of receiving the MBS service from the base station,
The configuration information for the BWP to be provided with the MBS service is received by being included in at least one of a system information block (System Information Block), an RRC release message, and an RRC reset message.

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