Method and apparatus for supporting continuity of broadcast service in a wireless communication system

Abstract

An operation method of a user equipment (UE) in a wireless communication system according to an embodiment of the disclosure can include receiving, from a first base station (BS), a radio resource control (RRC) message including multicast and broadcast service (MBS) configuration information, receiving, from the first BS, an MBS based on the MBS configuration information, receiving, from the first BS, a handover command received from a second BS based on information on the MBS, performing a handover to the second BS based on the handover command, and receiving the MBS from the second BS, wherein the MBS is transmitted from the first BS until the handover is successful.

Description

Technical Field

[0001] This disclosure relates to a method and apparatus for supporting the continuity of broadcast services in a wireless communication system. Background Technology

[0002] To meet the growing demand for wireless data services following the commercialization of fourth-generation (4G) communication systems, efforts are underway to develop fifth-generation (5G) or pre-5G communication systems. For this purpose, 5G or pre-5G communication systems are referred to as "beyond 4G network" communication systems or "post-LTE (post-Long Term Evolution)" systems. The 5G communication system defined in the 3rd Generation Partnership Project (3GPP) is called a New Radio (NR) system. To achieve high data rates, the implementation of 5G communication systems in ultra-high frequency millimeter-wave (mmWave) bands (e.g., the 60 GHz band) is being considered. To reduce path loss of radio waves in the ultra-high frequency bands of 5G communication systems and increase transmission distance, various technologies such as beamforming, massive MIMO, full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and massive MIMO are being researched and applied to NR systems. To improve the system network for 5G communication systems, various technologies have been developed, such as evolved small cells, advanced small cells, cloud radio access networks (Cloud-RAN), ultra-dense networks, device-to-device communication (D2D), wireless backhaul, mobile networks, cooperative communication, cooperative multipoint (CoMP), and receive interference cancellation. Furthermore, for 5G communication systems, advanced coding and modulation (ACM) technologies such as hybrid frequency shift keying (FSK), quadrature amplitude modulation (QAM) (FQAM), and sliding window superposition coding (SWSC) have been developed, as well as advanced access technologies such as filter bank multicarrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA).

[0003] The internet has evolved from a human-based network of connections where humans create and consume information to the Internet of Things (IoT), in which distributed elements such as objects exchange and process information. The Internet of Everything (IoE) technology has emerged, where IoT technologies, for example, combine with technologies for processing big data by connecting to cloud servers. To realize IoT, various technological elements are needed, such as sensing technology, wired / wireless communication and network infrastructure, service interface technology, and security technology. Therefore, in recent years, technologies related to sensor networks, machine-to-machine (M2M) communication, and machine-type communication (MTC) for connecting objects have been researched. In the IoT environment, intelligent internet technology (IT) services can be provided to collect and analyze data obtained from connected objects to create new value in human life. With the convergence and integration of existing information technology (IT) and various industries, IoT can be applied to various fields such as smart homes, smart buildings, smart cities, smart cars or connected cars, smart grids, healthcare, smart appliances, and advanced medical services.

[0004] Various attempts are underway to apply 5G communication systems to IoT networks. For example, technologies related to sensor networks, M2M communication, and MTC are being implemented using 5G communication technologies such as beamforming, MIMO, and array antennas. Cloud Radio Access Network (Cloud-RAN), as an application of the aforementioned big data processing technologies, can be seen as an example of the convergence of 5G communication and IoT technologies.

[0005] Due to the development of the aforementioned mobile communication systems, various services can be provided, thus requiring an effective method for providing services, especially a method that seamlessly supports broadcast or multicast services. Summary of the Invention

[0006] Technical issues

[0007] The disclosed embodiments provide methods and apparatus for supporting the continuity of broadcast services in wireless communication systems.

[0008] Solution to the problem

[0009] According to embodiments of this disclosure, an operation method for a user equipment (UE) in a wireless communication system may include: receiving a radio resource control (RRC) message including multicast and broadcast service (MBS) configuration information from a first base station (BS); receiving an MBS from the first BS based on the MBS configuration information; receiving a handover command from a second BS from the first BS based on information about the MBS; performing a handover to the second BS based on the handover command; and receiving the MBS from the second BS, wherein the MBS was sent from the first BS until the handover was successful.

[0010] Information about MBS may include information about the list of Temporary Mobile Group Identifiers (TMGIs) corresponding to MBS.

[0011] The handover command may include at least one of the following: the MBS data radio bearer (DRB) information of the second BS, the MBS radio link control (RLC) bearer configuration information, and the group radio network temporary identifier (G-RNTI) corresponding to the TMGI included in the TMGI list.

[0012] The operation method may also include monitoring the G-RNTI from the first BS until the handover is completed based on the handover command, and monitoring the cell RNTI (C-RNTI) from the second BS.

[0013] According to embodiments of this disclosure, an operation method of a first base station (BS) in a wireless communication system may include: sending a radio resource control (RRC) message including multicast and broadcast service (MBS) configuration information to a user equipment (UE); sending an MBS to the UE based on the MBS configuration information; sending information about the MBS to a second BS based on measurement information of the channel on which the MBS is sent; and sending a handover command received from the second BS to the UE based on the information about the MBS, wherein the UE performs a handover to the second BS based on the handover command, and wherein the MBS is sent from the first BS until the handover is successful.

[0014] Information about MBS may include information about the list of Temporary Mobile Group Identifiers (TMGIs) corresponding to MBS.

[0015] The handover command may include at least one of the following: an indicator corresponding to the MBS Data Radio Bearer (DRB) of the second BS, MBS Radio Link Control (RLC) bearer configuration information, and a Group Radio Network Temporary Identifier (G-RNTI) corresponding to a TMGI included in the TMGI list.

[0016] The operation method may also include transmitting data stored in a point-to-point (PTP) bearer configured with an indicator to a higher layer.

[0017] According to embodiments of this disclosure, a user equipment (UE) in a wireless communication system may include: a transceiver; and

[0018] At least one processor coupled to the transceiver, wherein the at least one processor is configured to receive a radio resource control (RRC) message including multicast and broadcast service (MBS) configuration information from a first base station (BS), receive an MBS from the first BS based on the MBS configuration information, receive a handover command received from a second BS from the first BS based on information about the MBS, and perform a handover to the second BS based on the handover command, wherein the MBS is transmitted from the first BS until the handover is successful.

[0019] According to embodiments of this disclosure, a first base station (BS) in a wireless communication system may include: a transceiver; and at least one processor coupled to the transceiver, wherein the at least one processor is configured to send a radio resource control (RRC) message including multicast and broadcast service (MBS) configuration information to a user equipment (UE), send an MBS to the UE based on the MBS configuration information, send information about the MBS to a second BS based on measurement information of the channel on which the MBS is sent, and send a handover command received from the second BS to the UE based on the information about the MBS, wherein the UE performs a handover to the second BS based on the handover command, and wherein the MBS is sent from the first BS until the handover is successful.

[0020] The beneficial effects of openness

[0021] According to the disclosed embodiments, services can be effectively provided in a mobile communication system. Attached Figure Description

[0022] Figure 1a This is a diagram illustrating the architecture of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0023] Figure 1b This is a flowchart of a process for providing Multimedia Broadcast Multicast Service (MBMS) in a Long Term Evolution (LTE) system according to embodiments of the present disclosure.

[0024] Figure 1c This is a flowchart of a process for providing single-cell point-to-multipoint (SC-PTM) service in an LTE system according to embodiments of the present disclosure.

[0025] Figure 1d This is a flowchart of a process for providing broadcast services according to embodiments of the present disclosure.

[0026] Figure 1e This is a flowchart of a process for supporting the continuity of broadcast services in a connected mode, according to embodiments of the present disclosure.

[0027] Figure 1fThis is a flowchart illustrating user equipment (UE) operation in connection mode that supports the continuity of broadcast services according to embodiments of the present disclosure.

[0028] Figure 1g This is a flowchart of base station (BS) operation supporting the continuity of broadcast services in connected mode according to embodiments of the present disclosure.

[0029] Figure 1h This is a flowchart of a process for supporting the continuity of broadcast services in idle or inactive modes, according to embodiments of the present disclosure.

[0030] Figure 1i This is a flowchart illustrating UE operation that supports the continuity of broadcast services in idle or inactive modes according to embodiments of the present disclosure.

[0031] Figure 1j This is a block diagram illustrating the internal structure of a UE according to an embodiment of the present disclosure.

[0032] Figure 1k This is a block diagram illustrating the configuration of a BS according to an embodiment of the present disclosure. Detailed Implementation

[0033] In the following description of this disclosure, well-known functions or configurations are not described in detail, as they would obscure this disclosure with unnecessary detail. Embodiments of this disclosure will be described in detail below with reference to the accompanying drawings.

[0034] The advantages and features of this disclosure, as well as methods of implementing it, can be more readily understood through the following detailed description of embodiments and accompanying drawings. However, this disclosure may be implemented in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to make this disclosure thorough and complete, and to fully convey the concept of this disclosure to those skilled in the art, and this disclosure is defined only by the appended claims. Throughout this specification, the same reference numerals denote the same elements.

[0035] It will be understood that each box in a flowchart illustration, and combinations of boxes in a flowchart illustration, can be implemented by computer program instructions. Computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create a means module for performing the functions specified in the flowchart box(s). Computer program instructions can also be stored in a computer-executable or computer-readable storage medium, which can direct the computer or other programmable data processing apparatus to operate in a particular manner, such that the instructions stored in the computer-executable or computer-readable storage medium can create an article of art comprising instruction means for performing the functions specified in the flowchart box(s). Computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus, thereby producing a computer-implemented process, such that the instructions, which execute on the computer or other programmable apparatus, provide operations for implementing the functions specified in the flowchart box(s).

[0036] Furthermore, each box in the flowchart can represent a module, code segment, or code section, which includes one or more executable instructions for performing a specified logical function(s). It should also be noted that in some alternative implementations, the functions mentioned in the boxes may not appear in a specific order. For example, two boxes shown consecutively may actually be executed substantially simultaneously, or these boxes may sometimes be executed in reverse order, depending on the functions involved.

[0037] The term "...unit" as used in this embodiment refers to a software or hardware component that performs certain tasks, such as a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC). However, the term "...unit" is not intended to be limited to software or hardware. "...unit" can be configured to reside in addressable storage media or to operate one or more processors. Thus, according to one embodiment, as an example, "...unit" can include components such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, program code segments, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functionality provided in elements and "...units" can be combined into fewer elements and "...units," or further divided into additional elements and "...units." Furthermore, elements and "...units" can be implemented as one or more central processing units (CPUs) in an operating device or secure multimedia card. Additionally, in embodiments, "...unit" can include one or more processors.

[0038] In the description of this disclosure, detailed descriptions of related technologies have been omitted where it is believed that such descriptions might unnecessarily obscure the essence of this disclosure. Hereinafter, embodiments of this disclosure will be described in detail with reference to the accompanying drawings.

[0039] In the following description, for ease of explanation, examples are given of terms used to identify access nodes, network entities, messages, interfaces between network entities, and various types of identification information. Therefore, this disclosure is not limited to the terms described below, and other terms indicating objects with the same technical meaning may be used.

[0040] For ease of description, this disclosure uses the terms and names defined in the 3GPP Long Term Evolution (LTE) standard. However, this disclosure is not limited to these terms and names and can be applied equivalently to communication systems conforming to other standards. In this disclosure, for ease of description, the evolved Node B (eNB) can be used interchangeably with the next-generation Node B (gNB). That is, a base station described by an eNB can represent a gNB. Furthermore, the term "terminal (user equipment)" can refer not only to mobile phones, NB-IoT devices, and sensors, but also to other wireless communication devices.

[0041] This disclosure is based on an LTE system, but can be applied to other mobile communication systems that are next-generation mobile communication systems, such as NR. For example, in this disclosure, the eNB in ​​LTE can correspond to the gNB in ​​NR, and the Mobility Management Entity (MME) in LTE can correspond to the Access and Mobility Management Function (AMF) in NR.

[0042] In the following description, a base station is an entity that allocates resources to a terminal and can be at least one of a next-generation node B (gNode B), an evolved Node B (eNode B), a node B, a base station (BS), a radio access unit, a BS controller, and a node on a network. A terminal may include a user equipment (UE), a mobile station (MS), a cellular phone, a smartphone, a computer, or a multimedia system capable of performing communication functions. However, this disclosure is not limited to the examples described above.

[0043] Specifically, this disclosure can be applied to 3GPP NR (5th generation mobile communication standard). This disclosure applies to smart services based on 5G communication technology and Internet of Things (IoT) technology (e.g., smart homes, smart buildings, smart cities, smart cars or connected cars, healthcare, digital education, retail, security and safety services). In this disclosure, for ease of description, eNB and gNB can be used interchangeably. That is, a BS described by an eNB can represent a gNB. Furthermore, the term "terminal (UE)" can refer not only to mobile phones, NB-IoT devices, and sensors, but also to other wireless communication devices.

[0044] Wireless communication systems have evolved from early voice-centric systems to broadband systems that provide high-speed, high-quality packet data services, such as High Speed ​​Packet Access (HSPA), Long Term Evolution (LTE or Evolved Universal Terrestrial Radio Access (E-UTRA)), 3GPP's LTE-Advanced (LTE-A) and LTE-Pro, 3GPP2's High Speed ​​Packet Data (HRPD) and Ultra Mobile Broadband (UMB), and the Institute of Electrical and Electronics Engineers (IEEE) 802.16e communication standards.

[0045] As a representative example of a broadband wireless communication system, the LTE system employs Orthogonal Frequency Division Multiplexing (OFDM) in the downlink (DL) and Single-Carrier Frequency Division Multiple Access (SC-FDMA) in the uplink (UL). UL refers to the radio link used to transmit data or control signals from the UE or MS to the eNode B or BS, and DL refers to the radio link used to transmit data or control signals from the BS to the UE. Multiple access schemes identify the data or control information of different users by allocating and managing time-frequency resources used to carry user data or control information in a way that prevents them from overlapping, i.e., achieving orthogonality between them.

[0046] As a post-LTE communication system, 5G communication systems are required to freely reflect the diverse needs of users and service providers, and therefore must support services that simultaneously meet various demands. Services being considered for 5G communication systems include enhanced mobile broadband (eMBB), massive machine-type communications (mMTC), and ultra-reliable low-latency communications (URLLC) services.

[0047] eMBB can be designed to provide improved data rates than those supported by traditional LTE, LTE-A, or LTE-Pro. For example, in a 5G communication system, eMBB should be able to provide a peak data rate of 20Gbps in the DL of a BS and 10Gbps in the UL. Furthermore, 5G communication systems will simultaneously provide the UE's peak data rate and increased user-aware data rate. To meet these requirements, 5G communication systems need improvements in transmit / receive technologies, including improved multiple-input multiple-output (MIMO) transmission techniques. Additionally, the required data rates in 5G communication systems can be met by using a wider frequency bandwidth than 20MHz in the 3GHz to 6GHz or 6GHz or higher frequency bands, instead of the current LTE's maximum of 20MHz used in the 2GHz band.

[0048] Furthermore, mMTC is being considered to support applications such as IoT in 5G communication systems. To effectively deliver IoT, mMTC may need to support a large number of terminals in a cell, improve terminal coverage, improve battery life, and reduce terminal costs. Because IoT is attached to various sensors and devices to provide communication capabilities, mMTC should be able to support a large number of terminals in a cell (e.g., 1,000,000 terminals / km). 2 Furthermore, due to the nature of the service, mMTC-enabled terminals may be located in shadow areas not covered by cell coverage, such as building basements, and therefore may require wider coverage than other services offered by 5G communication systems. mMTC-enabled terminals should be configured as low-cost devices and may require a very long battery life of 10 to 15 years, as frequent battery replacements are difficult.

[0049] Finally, URLLC refers to cellular-based wireless communication services for mission-critical purposes, such as remote control of robots or machines, industrial automation, unmanned aerial vehicles, remote healthcare, and emergency alerts. Therefore, URLLC should provide communication with extremely low latency (ultra-low latency) and extremely high reliability (ultra-high reliability). For example, services supporting URLLC should meet an air interface latency of less than 0.5 milliseconds and can simultaneously require 10... -5 Or a lower packet error rate. Therefore, for services that support URLLC, 5G systems should provide shorter transmission time intervals (TTIs) than other services, and can also have the design requirement to allocate wide resources in the frequency band to ensure the reliability of the communication link.

[0050] The three services considered for 5G communication systems—eMBB, URLLC, and mMTC—can be multiplexed and transmitted within a single system. Here, to meet the different needs of each service, different transmit / receive schemes and parameters can be used. While mMTC, URLLC, and eMBB can be examples of different service types, the types of services to which this disclosure applies are not limited to these examples.

[0051] Although LTE, LTE-A, LTE Pro, or 5G (or NR, next-generation mobile communications) systems are mentioned by way of example in the following description, embodiments of this disclosure can also be applied to other communication systems with similar technical backgrounds or channel types. Furthermore, embodiments of this disclosure can be applied to other communication systems with modifications determined by those skilled in the art themselves, without significantly departing from the scope of this disclosure.

[0052] This disclosure relates to mobile communication systems, and more specifically, provides a UE, a BS, and a method of operating thereof to support the continuity of broadcast services in a mobile communication system.

[0053] Figure 1a This is a diagram illustrating the architecture of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0054] refer to Figure 1a The radio access network for next-generation mobile communication systems (e.g., new radio (NR) systems) includes next-generation BS (e.g., new radio node B, hereinafter referred to as gNB) 1a-10 and new radio core network (AMF) 1a-05. New radio user equipment (hereinafter referred to as NR UE or terminal) 1a-15 can access external networks via gNB 1a-10 and AMF 1a-05.

[0055] exist Figure 1aIn this context, gNB 1a-10 corresponds to the evolved Node B (eNB) 1a-30 of a traditional LTE system. gNB 1a-10 can connect to NR UE 1a-15 via radio channel 1a-20 and can provide better service compared to the traditional Node B 1a-30. In next-generation mobile communication systems, all user service data can be served via a shared channel; therefore, an entity may be needed to perform scheduling by organizing, for example, the buffer state information, available transmit power state information, and channel state information of UE 1a-15, and gNB 1a-10 can operate as such an entity. Typically, one gNB 1a-10 can control multiple cells. Next-generation mobile communication systems can have a larger bandwidth than the maximum bandwidth of traditional LTE systems to achieve ultra-high data rates, and beamforming technology can be additionally associated with orthogonal frequency division multiplexing (OFDM) as a radio access technology. Furthermore, next-generation mobile communication systems can use adaptive modulation and coding (AMC) schemes to determine the modulation scheme and channel coding rate based on the UE's channel state. The AMF 1a-05 performs functions such as mobility support, bearer establishment, and Quality of Service (QoS) configuration. The AMF 1a-05 is the entity used to perform mobility management functions and various control functions on the UE 1a-15 and can connect to multiple BSs. Furthermore, next-generation mobile communication systems can cooperate with legacy LTE systems, and the AMF 1a-05 can connect to the Mobility Management Entity (MME) 1a-25 via a network interface. The MME 1a-25 connects to the eNB 1a-30, which acts as a legacy BS. The UE 1a-15, supporting LTE-NR Dual Connectivity (EN-DC), can send and receive data while maintaining connectivity not only to the gNB 1a-10 but also to the eNB 1a-30.

[0056] Figure 1b This is a flowchart of a process for providing Multimedia Broadcast Multicast Service (MBMS) in an LTE system according to embodiments of the present disclosure.

[0057] LTE MBMS refers to the technology used to provide broadcast services to UEs in standby mode (Radio Resource Control (RRC)_IDLE) or connected mode (RRC_CONNECTED). An MBMS service area indicates a network area comprising multiple BSs capable of performing Multimedia Broadcast Multicast Service Single Frequency Network (MBSFN) transmissions. An MBSFN area refers to a network area comprising multiple cells integrated for MBSFN transmissions, and cells within an MBSFN area can be simultaneously used for MBSFN transmissions. All cells except reserved cells in the MBSFN area can be used for MBSFN transmissions. Reserved cells in the MBSFN area are cells not used for MBSFN transmissions and can be used for transmissions for other purposes, but are allowed limited transmission power relative to the radio resources allocated for MBSFN transmissions.

[0058] In Operation 1b-15, UE 1b-05 receives System Information Block (SIB) 1 from eNB 1b-10. SIB1 may include scheduling information for other SIBs. Therefore, SIB1 can be received first in order to receive other SIBs.

[0059] In Operation 1b-20, UE 1b-05 can receive SIB2 from eNB 1b-1. The MBSFN-SubframeConfigList IE of SIB2 can indicate the subframes available for MBSFN transmission. The MBSFN-SubframeConfigList IE can include the MBSFN-SubframeConfig IE and can indicate which subframe of which radio frame can be an MBSFN subframe. The configuration of the MBSFN-SubframeConfig IE is shown in Table 1 below.

[0060] [Table 1]

[0061] MBSFN-SubframeConfig Information Element

[0062]

[0063] Here, radioFrameAllocationPeriod and radioFrameAllocationOffset can be used to indicate radio frames with MBSFN subframes, and radio frames that satisfy the equation SFN mod radioFrameAllocationPeriod = radioFrameAllocationOffset can have MBSFN subframes.

[0064] SFN stands for System Frame Number and indicates the radio frame number. SFNs can repeat in the range of 0 to 1023. Subframe Allocation indicates which subframe is an MBSFN subframe among the radio subframes indicated by the equation above. MBSFN subframes can be indicated in units of one radio frame or four radio frames. When using a unit of one radio frame, MBSFN subframes can be indicated by a oneFrame IE. For example, MBSFN subframes can exist in subframes 1, 2, 3, 6, 7, and 8 out of a total of 10 subframes in a radio frame. Therefore, a oneFrame IE can indicate MBSFN subframes among the subframes listed above using 6 bits. When using a unit of four radio frames, a fourFrames IE can indicate it. A fourFrames IE indicates MBSFN subframes among the aforementioned subframes in each radio frame by using a total of 24 bits to cover four radio frames. Therefore, by using the MBSFN-SubframeConfigList IE, the UE can correctly identify the subframes available for MBSFN subframes.

[0065] In Operation 1b-25, if UE 1b-05 attempts to receive an MBSFN, UE 1b-05 can receive SIB13 from eNB 1b-10. The MBSFN-AreaInfoList IE of SIB13 can include location information where the multicast control channel (MCCH) provided by the cell for each MBSFN area is transmitted.

[0066] In Operation 1b-30, UE 1b-05 can receive the MCCH using location information. [Table 2] is associated with the MBSFN-AreaInfoList IE. There exists an MCCH corresponding to each MBSFN area, and the MBSFN-AreaInfoList IE can include MCCH scheduling information for all MBSFN areas. The MBSFN-AreaInfo IE can include MCCH scheduling and other information. Mbsfn-AreaId represents the MBSFN area ID. Non-MBSFNregionLength indicates the number of symbols in the MBSFN subframe corresponding to non-MBSFN areas. This symbol can be located at the beginning of the subframe. The notificationIndicator can be used to indicate the Physical Downlink Control Channel (PDCCH) bit that notifies UE 1b-05 of changes in MCCH information. The Mcch-Config IE can include MCCH scheduling information. Mcch-RepetitionPeriod and mcch-Offset can be used to indicate the location of the frame containing the MCCH. Mcch-ModificationPeriod indicates the transmission period of the MCCH, and sf-AllocInfo indicates the location of the subframe containing the MCCH within a frame that includes the MCCH. signallingMCS indicates the modulation and coding scheme (MCS) applied to the subframe indicated by sf-AllocInfo and (P)MCH.

[0067] [Table 2]

[0068] MBSFN-AreaInfoList Information Element

[0069]

[0070] The MCCH's MBSFNAreaConfiguration IE can indicate the location of resources used for MBSFN transmission. In Operation 1b-35, UE 1b-05 can receive MBSFN subframes by using the MBSFNAreaConfiguration IE. commonSF-Alloc can indicate the subframes allocated to the MBSFN area. commonSF-AllocPeriod refers to the period during which the subframe indicated by commonSF-Alloc repeats. The Pmch-InfoList IE can include all PMCH configuration information for an MBSFN area.

[0071] [Table 3]

[0072] MBSFNAreaConfiguration message

[0073]

[0074] In Operation 1b-40, UE 1b-05 obtains the location of the MBSFN subframe on which the desired multicast traffic channel (MTCH) is transmitted from the Multicast Channel (MCH) scheduling information Media Access Control (MAC) control element (CE), where the MCH scheduling information MAC CE is one of the MAC CEs of the received MAC Protocol Data Unit (PDU). In Operation 1b-45, UE 1b-05 can decode the desired MTCH by using the MCH scheduling information.

[0075] Figure 1c This is a flowchart of a process for providing single-cell point-to-multipoint (SC-PTM) service in an LTE system according to embodiments of the present disclosure.

[0076] LTE MBMS aims to provide broadcast services to multiple users within an MBSFN area comprising multiple cells. Broadcast services can be provided to multiple users within a cell using MBSFN subframes allocated in a static or semi-static manner. A key feature of LTE MBMS is its ability to provide the same content to multiple users. Additionally, the SC-PTM technology was developed in the Rel-13 LTE standard. SC-PTM is designed to facilitate group calls for commercial or disaster relief purposes within the service area of ​​a single cell. Furthermore, group calls can be facilitated within a cell even without a connection to an external backhaul network. Scheduling information is provided to multiple UEs participating in the group call, and applying scheduling information to group calls where data transmission and reception are irregular is highly efficient.

[0077] In Operation 1c-15, eNB 1c-10 can provide UE 1c-05 with Temporary Mobility Group Identifier (TMGI) information. TMGI information may include the Public Land Mobile Network (PLMN) ID and service ID, and may indicate the MBMS service ID.

[0078] UE 1c-05 may have a TMGI of interest. For example, a police officer may have a TMGI for security purposes. In Operation 1c-20, when UE 1c-05 attempts to perform a group call associated with a TMGI, UE 1c-05 may receive SIB20 broadcast by eNB1c-10. SIB20 may include scheduling information required to receive SC-MCCH as a control channel and a single-cell radio network temporary identifier (SC-RNTI).

[0079] In Operation 1c-25, UE 1c-05 can receive an SC-MCCH indicated by an SC-RNTI on a PDCCH indicated by the obtained scheduling information. The SC-MCCH may include mapping information about the TMGI and the Group Radio Network Temporary Identifier (G-RNTI). In Operation 1c-30, UE 1c-05 can receive an SC-MTCH indicated by a G-RNTI corresponding to the TMGI of interest.

[0080] Figure 1d This is a flowchart of a process for providing broadcast services according to embodiments of the present disclosure.

[0081] LTE MBMS is suitable for providing broadcast services to multiple users within a cell using MBSFN subframes allocated in a static or semi-static manner. Therefore, this scheduling scheme has limitations in dynamically allocating radio resources. On the other hand, SC-PTM uses an efficient scheduling scheme similar to connectivity mode, but it is optimized for group calls in limited areas, thus being inefficient in supporting group calls between dispersed users in a wide area.

[0082] According to embodiments of this disclosure, the provision of multicast and broadcast services (MBS) can be configured in the UE's connected mode. Furthermore, to support the continuity of MBS, a serving cell handover scheme is proposed. Additionally, a scheme is provided to continue ongoing MBS when the UE switches from connected mode to idle mode or inactive mode.

[0083] The flowchart for the operation of the UE that will be provided with MBS is as follows.

[0084] In Operation 1d-05, a UE in idle or inactive mode can switch to connected mode via an establishment or recovery process to receive a preset MBS.

[0085] In Operation 1d-10, MBS configuration information can be provided from the BS to a UE that has switched to connected mode to receive MBS. Additionally, the UE can receive cell measurement configuration information from the BS. MBS configuration information can be received along with RRC reconfiguration information.

[0086] In Operation 1d-15, based on the provided MBS configuration information, the UE can be provided with MBS information about the TMGI of interest.

[0087] In Operation 1d-20, based on the provided cell measurement configuration information, the UE can report the collected measurements to the BS.

[0088] In Operation 1d-25, the UE can receive a handover command regarding the MBS from the BS.

[0089] In Operation 1d-30, the UE can perform a handover and can maintain MBS reception from the source cell until a preset time point. For example, the preset time point could be the time when the handover to the target cell is considered successful.

[0090] In Operation 1d-35, a UE receiving MBS from a target cell can receive an RRRCRelease message containing MBS configuration information from the target cell.

[0091] In Operation 1d-40, based on the RRRCRelease message being received, the UE can switch to idle mode or inactive mode.

[0092] In Operation 1d-45, based on the MBS configuration information, the UE can maintain MBS reception even in idle or inactive modes.

[0093] Figure 1e This is a flowchart of a process for supporting the continuity of broadcast services in a connected mode, according to embodiments of the present disclosure.

[0094] In Operation 1e-20, a UE 1e-05 in idle or inactive mode can switch to connected mode via an establishment or recovery procedure to receive a preset MBS. During this procedure, the UE 1e-05 can report an indicator to the source BS 1e-10 indicating the MBS information the UE is attempting to receive. If the source BS 1e-10 does not support it, the source BS 1e-10 can terminate the establishment or recovery procedure via an RRCReject message.

[0095] In Operation 1e-25, UE 1e-05, which has switched to connected mode to receive MBS, can receive an RRCReconfiguration message from source BS 1e-10, including MBS configuration information. The RRCReconfiguration message may include configuration information about Signaling Radio Bearer 2 (SRB2), Data Radio Bearer (DRB), and MBS DRB. Here, MBSDRB indicates the data radio bearer delivering MBS data. UE 1e-05 may require not only MBS but also unicast service, and DRB configuration information may also be provided here. After receiving the MBS DRB configuration information, UE 1e-05 can initiate the Packet Data Convergence Protocol (PDCP) state variables of the SRB and the normal DRB as follows.

[0096] -RX_NEXT=0

[0097] -RX_DELIV=0

[0098] Considering the scenario of participating in an ongoing MBS session, the state variables of the MBS DRB's PDCP can be started as follows.

[0099] - The UE sets the initial RCVD_HFN to a fixed value (e.g., fixed value = 1).

[0100] - The UE sets the initial RX_NEXT (RX_NEXT = RCVDHFN + rcvd PDCP SN + 1) based on the first received PDCP SN and the initial RCVD HFN.

[0101] - The UE sets the initial RX_DELIV (RX_DELIV = RCVD_HFN + rcvd PDCP SN) based on the first received PDCP SN and the initial RCVD_HFN.

[0102] The state variables for radio link control (RLC) serving SRB, normal DRB, and PTM DRB can begin as follows.

[0103] -RX_NEXT=0

[0104] -RX_NEXT_Highest=0

[0105] In addition, cell measurement configuration information can be provided from source BS 1e-10 to UE 1e-05 via RRCReconfiguration messages.

[0106] In Operation 1e-30, based on the provided MBS configuration information, the UE 1e-05 can be provided with the MBS for the TMGI of interest. The UE 1e-05 can monitor the configured G-RNTI and C-RNTI (cell-RNTI) on the scheduled PDCCH. If the UE 1e-05 receives a Transport Block (TB) indicated by the G-RNTI, taking into account the Logical Channel ID (LCID) of the MAC SDU included in the MAC PDU and the G-RNTI of the MAC PDU, the UE 1e-05 can determine the MBS RLC bearer to deliver the MAC Service Data Unit (SDU). If the UE 1e-05 receives a TB indicated by the C-RNTI, taking into account the LCID of the MAC SDU, the UE 1e-05 can determine the Point-to-Point (PTP) (unicast) RLC bearer to deliver the MAC SDU.

[0107] In Operation 1e-35, UE 1e-05 can perform measurements based on the provided cell measurement configuration information. In Operation 1e-40, UE 1e-05 can report measurement results to the source BS 1e-10.

[0108] In Operation 1e-45, the source BS 1e-10, which has received a report of the measurement results, can determine the handover based on that report.

[0109] In Operation 1e-50, the source BS 1e-10 can send a HandoverPreparationInformation message to the target BS 1e-15. The HandoverPreparationInformation message can include a list of TMGIs and a list of TMGI indices for the MBSs that UE 1e-05 is receiving. A TMGI index is an index value corresponding to the TMGI of the MBS served by the source BS 1e-10. Because a TMGI value consists of several bits, sending or receiving a TMGI value is inefficient. Therefore, using the index value corresponding to a TMGI is efficient. For example, the source BS 1e-10 can provide UE 1e-05 with a list of TMGIs served by the source BS 1e-10 and a list of TMGI indices corresponding to each TMGI. UE 1e-05 can report the TMGI index value, instead of the TMGI, to the source BS 1e-10 to inform the source BS 1e-10 of the preferred TMGI.

[0110] In Operation 1e-55, when the target BS 1e-15 receives the HandoverPreparationInformation message, the target BS 1e-15 can send a handover command to the source BS 1e-10.

[0111] The handover command may include MBS RLC bearer configuration information and MBS DRB configuration information for the target BS 1e-15. The MBS DRB or MBS RLC bearer may include information indicating which MBS service is associated with the corresponding bearer (e.g., a TMGI index).

[0112] The target BS 1e-15 may not determine the TMGI index by using its SIB, but may determine the TMGI index mapped to the bearer based on the TMGI list and TMGI index list sent by the source BS 1e-10.

[0113] In Operation 1e-60, UE 1e-05 can receive an RRCReconfiguration message from source BS 1e-10, which includes a handover command regarding the MBS. The RRCReconfiguration message may include the following information.

[0114] - The target BS's MBS DRB configuration information and MBS RLC bearer configuration information, as well as the first indicator corresponding to the MBS DRB.

[0115] - The target BS's (PTP) DRB configuration information and (PTP) RLC bearer configuration information, and the first indicator corresponding to the PTP DRB respectively.

[0116] In Operation 1e-65, UE 1e-05 can perform a handover and can perform the following operations according to the first instruction.

[0117] When the first indicator is configured, for MBS bearers, UE 1e-05 can process data stored in the reordering buffer and deliver the data to higher layers. This operation can be performed upon handover completion or after receiving the first PDCP PDU from the target BS 1e-10. Similarly, state variables can be initialized as follows.

[0118] - The UE sets the initial RCVD_HFN to a fixed value (e.g., fixed value = 1).

[0119] - The UE sets the initial RX_NEXT (RX_NEXT = RCVD_HFN + rcvd PDCP SN + 1) based on the first PDCP SN received from the target node and the initial RCVD HFN.

[0120] - The UE sets the initial RX_DELIV (RX_DELIV = RCVD_HFN + rcvd PDCP SN) based on the first PDCP SN received from the target node.

[0121] Even after UE 1e-05 receives the handover command, UE 1e-05 can still receive PDCPPDUs from source BS 1e-10, but these have no effect on RX_NEXT and RX_DELIV. Alternatively, the initialization of RX_NEXT and RX_DELIV can be performed upon completion of the handover or after receiving the first PDCP PDU from target BS 1e-15.

[0122] When the first indicator is configured, for PTP bearers, UE 1e-05 can process data stored in the reordering buffer and deliver that data to higher layers. Furthermore, the state variables and RX_NEXT can each be initialized to 0, and RX_DELIV can also be initialized to 0. This operation can be performed immediately upon receiving a handover command.

[0123] When no first indicator is configured, MBS DRB and PTP DRB can retain the stored PDCP PDU and can retain state variables.

[0124] In Operation 1e-70, UE 1e-05 can maintain MBS reception from source cell 1e-10 until a preset time point. For example, the preset time point could correspond to the time when handover to target cell 1e-15 is considered successful (in other words, the time when the RRCReconfigurationComplete message is considered successfully sent to the target cell). That is, until handover is complete, UE 1e-05 can monitor G-RNTI from source BS 1e-10 and C-RNTI from the target BS.

[0125] In Operation 1e-75, a UE 1e-05 that has received a handover order can perform a random access procedure on the target BS 1e-15.

[0126] In Operation 1e-80, UE 1e-05 can send an RRCReconfigurationComplete message to target cell 1e-15. When the RRCReconfigurationComplete message is successfully sent, the handover process is considered successfully completed. At this point, UE 1e-05 can monitor the G-RNTI and C-RNTI from target BS 1e-15.

[0127] Figure 1f This is a flowchart illustrating UE operation in connection mode that supports the continuity of broadcast services according to embodiments of the present disclosure.

[0128] In Operation 1f-05, a UE in idle or inactive mode can switch to connected mode via an establishment or recovery process to receive a preset MBS.

[0129] In Operation 1f-10, the UE can receive RRCReconfiguration messages from the BS that include MBS configuration information and cell measurement configuration information.

[0130] In Operation 1f-15, the UE can receive MBS and perform cell measurement operations.

[0131] In Operation 1f-20, the UE can report the results of the measured cell measurements to the BS.

[0132] In Operation 1f-25, the UE can receive an RRCReconfiguration message, which includes a handover command, from the BS.

[0133] In Operation 1f-30, the UE can initialize preset state variables for the MBS bearer, for which a first indicator is configured in RRCReconfiguration.

[0134] In Operation 1f-35, the UE can perform a random access procedure with respect to the target BS. The UE can continue receiving MBS from the source BS until the handover to the target BS is successfully completed.

[0135] In Operation 1f-40, after the handover is completed, the UE can receive the MBS from the target BS.

[0136] Figure 1g This is a flowchart of a BS operation that supports the continuity of broadcast services in connection mode according to an embodiment of the present disclosure.

[0137] In Operation 1g-05, the source BS can send an RRCReconfiguration message, which includes MBS configuration information and cell measurement configuration information, to the UE that has switched to connected mode to receive MBS.

[0138] In Operation 1g-10, the source BS can receive a measurement report of the cell measurement results from the UE.

[0139] In Operation 1g-15, the source BS can trigger handover based on cell measurement results.

[0140] In Operation 1g-20, the source BS can send a HandoverPreparationInformation message to the target BS, which includes a list of TMGIs and a list of TMGI indices.

[0141] In Operation 1g-25, the source BS can receive an RRCReconfiguration message, including a handover command, from the target BS.

[0142] In Operation 1g-30, the source BS can send RRCReconfiguration to the UE.

[0143] In Operation 1g-35, if it is determined that no UE is receiving MBS in the service area of ​​the source BS, the source BS can stop MBS transmission.

[0144] Figure 1h This is a flowchart of a process for supporting the continuity of broadcast services in idle or inactive modes, according to embodiments of the present disclosure.

[0145] In operation 1h-15, UE 1h-05 can receive an RRCRelease message from eNB 1h-10 indicating a switch to idle or inactive mode. When the RRCRelease message includes a pause configuration, UE 1h-05 can switch to inactive mode; when it does not include a pause configuration, UE 1h-05 can switch to idle mode. The RRCRelease message may include a second indicator. A second indicator can be configured for all MBS DRBs or for each MBS DRB.

[0146] In Operation 1h-20, when the second indicator is configured, UE 1h-05 can maintain MBS DRBs and receive MBS information about all MBS DRBs or their corresponding MBS DRBs, even after the RRC connection is released. Furthermore, the RRC Release message can include a list of cells or Tracking Areas (TAs) that UE 1h-05 can maintain MBS reception for. For example, in the case of a cell list, NR Cell Global Identifier (NCGI) or cell identification information, or Tracking Area Code (TAC) information, can be used as information about the MBS reception area. If the MBS reception area is not explicitly configured, only the serving cell receiving the RRC Release message can belong to the MBS reception area.

[0147] When the RRCRelease message includes Suspend Config, the normal PTP DRB is suspended and the MBS DRB configured with the second indicator is retained; otherwise, the MBS DRB is released.

[0148] If the RRCRelease message does not include Suspend Config, then release the MBS DRB and DRB that are not configured with a second indicator, and retain the MBS DRB that are configured with a second indicator.

[0149] UE 1h-05 configured with a second indicator can maintain MBS reception in idle or inactive mode. When the current serving cell is in the MBS reception area, UE 1h-05 can monitor the MBS DRB configured with the second indicator and its corresponding G-RNTI on the BWP corresponding to the G-RNTI.

[0150] UE 1h-05 can receive the TB indicated by G-RNTI and can determine the MBS RLC bearer to which the MAC SDU will be delivered by taking into account the LCID of the MAC SDU included in the MAC PDU and the G-RNTI of the MAC PDU.

[0151] If the serving cell is not within the MBS receiving area, the MBS DRB can be released.

[0152] Figure 1i This is a flowchart illustrating UE operation that supports the continuity of broadcast services in idle or inactive modes according to embodiments of the present disclosure.

[0153] In Operation 1i-05, the UE can receive the RRRCRelease message from the BS.

[0154] In Operation 1i-10, a UE that has switched to idle mode or inactive mode according to the configuration information included in the release message can maintain a specific MBS DRB and maintain MBS reception according to the configuration.

[0155] In Operation 1i-15, when a serving cell that does not belong to the MBS reception area indicated by the configuration is reselected, the UE can stop MBS reception and release the corresponding MBS DRB.

[0156] Figure 1j This is a block diagram illustrating the internal structure of a UE according to an embodiment of the present disclosure.

[0157] refer to Figure 1j The UE may include a radio frequency (RF) processor 1j-10, a baseband processor 1j-20, a memory 1j-30, and a controller 1j-40.

[0158] RF processor 1j-10 performs functions such as transmitting and receiving signals through a radio channel, including signal band conversion and amplification. Specifically, RF processor 1j-10 can up-convert a baseband signal provided by baseband processor 1j-20 into an RF band signal, which can then be transmitted via an antenna. It can also down-convert an RF band signal received via an antenna back to a baseband signal. For example, RF processor 1j-10 may include transmit filters, receive filters, amplifiers, mixers, oscillators, digital-to-analog converters (DACs), analog-to-digital converters (ADCs), etc. Although only one antenna is shown in the figures, the UE may include multiple antennas. Furthermore, RF processor 1j-10 may include multiple RF chains. Additionally, RF processor 1j-10 can perform beamforming. For beamforming, RF processor 1j-10 can adjust the phase and intensity of signals to be transmitted or received through multiple antennas or antenna elements. Furthermore, the RF processor can perform multiple-input multiple-output (MIMO) operation and can receive multiple layers in MIMO operation.

[0159] The baseband processor 1j-20 performs conversions between baseband signals and bit strings according to the system's physical layer specifications. For example, for data transmission, the baseband processor 1j-20 can generate complex symbols by encoding and modulating the transmitted bit string. For data reception, the baseband processor 1j-20 can reconstruct the received bit string by demodulating and decoding the baseband signal provided from the RF processor 1j-10. For example, according to the OFDM scheme, for data transmission, the baseband processor 1j-20 can generate complex symbols by encoding and modulating the transmitted bit string, map the complex symbols to subcarriers, and then configure the OFDM symbols by performing an inverse fast Fourier transform (IFFT) operation and cyclic prefix (CP) insertion. For data reception, the baseband processor 1j-20 can segment the baseband signal provided from the RF processor 1j-10 into OFDM symbol units, reconstruct the signal mapped to the subcarriers by performing a fast Fourier transform (FFT) operation, and then reconstruct the received bit string by demodulating and decoding the signal.

[0160] The baseband processor 1j-20 and RF processor 1j-10 transmit and receive signals as described above. Therefore, the baseband processor 1j-20 and RF processor 1j-10 can also be referred to as transmitters, receivers, transceivers, or communicators. Furthermore, at least one of the baseband processor 1j-20 and RF processor 1j-10 may include multiple communication modules to support various different radio access technologies. At least one of the baseband processor 1j-20 and RF processor 1j-10 may include different communication modules to process signals in different frequency bands. For example, different radio access technologies may include wireless LAN (e.g., IEEE 802.11), cellular networks (e.g., LTE), etc. Different frequency bands may include ultra-high frequency (SHF) (e.g., 2.0 NRHz, NRhz) bands and millimeter wave (mmWave) (e.g., 60 GHz) bands.

[0161] Memory 1j-30 stores basic programs, application programs, and data for UE operation, such as configuration information. Specifically, memory 1j-30 may store information about a second access node performing wireless communication using a second radio access technology. Memory 1j-30 provides the stored data based on requests from controller 1j-40.

[0162] Controller 1j-40 controls the overall operation of the UE. For example, controller 1j-40 transmits and receives signals via baseband processor 1j-20 and RF processor 1j-10. Furthermore, controller 1j-40 records data on or reads data from memory 1j-40. For this purpose, controller 1j-40 may include at least one processor. For example, controller 1j-40 may include a communication processor (CP) for controlling communications and an application processor (AP) for controlling higher-level components such as applications.

[0163] Figure 1k This is a block diagram illustrating the configuration of a BS according to an embodiment of the present disclosure.

[0164] like Figure 1k As shown, the BS includes an RF processor 1k-10, a baseband processor 1k-20, a backhaul communicator 1k-30, a memory 1k-40, and a controller 1k-50.

[0165] RF processor 1k-10 performs functions such as transmitting and receiving signals via a radio channel, including signal band conversion and amplification. Specifically, RF processor 1k-10 can up-convert a baseband signal provided by baseband processor 1k-20 to an RF band signal, which can then be transmitted via an antenna. It can also down-convert an RF band signal received via an antenna back to a baseband signal. For example, RF processor 1k-10 may include transmit filters, receive filters, amplifiers, mixers, oscillators, DACs, ADCs, etc. Although only one antenna is shown in the figures, the first access node may include multiple antennas. Furthermore, RF processor 1k-10 may include multiple RF chains. Additionally, RF processor 1k-10 can perform beamforming. For beamforming, RF processor 1k-10 can adjust the phase and intensity of individual signals to be transmitted or received via multiple antennas or antenna elements. The RF processor can perform DL MIMO operation by transmitting one or more layers.

[0166] The baseband processor 1k-20 performs conversions between baseband signals and bit strings according to the physical layer specifications of the first radio access technology. For example, for data transmission, the baseband processor 1k-20 generates complex symbols by encoding and modulating the transmitted bit string. For data reception, the baseband processor 1k-20 reconstructs the received bit string by demodulating and decoding the baseband signal provided from the RF processor 1k-10. For example, according to the OFDM scheme, for data transmission, the baseband processor 1k-20 generates complex symbols by encoding and modulating the transmitted bit string, maps the complex symbols to subcarriers, and then configures the OFDM symbols by performing IFFT operations and CP insertion. For data reception, the baseband processor 1k-20 segments the baseband signal provided from the RF processor 1k-10 into OFDM symbol units, reconstructs the signal mapped to the subcarriers by performing FFT operations, and then reconstructs the received bit string by demodulating and decoding the signal. The baseband processor 1k-20 and the RF processor 1k-10 transmit and receive signals as described above. Therefore, the baseband processor 1k-20 and the RF processor 1k-10 can also be referred to as transmitters, receivers, transceivers, communicators, or wireless communicators.

[0167] The backhaul communicator 1k-30 provides an interface for performing communication with other nodes in the network. That is, the backhaul communicator 1k-30 converts bit strings sent from the primary BS to another node, such as an auxiliary BS, core network, etc., into physical signals, and converts physical signals received from another node into bit strings.

[0168] Memory 1k-40 stores basic programs, application programs, and data used for the operation of the primary BS, such as configuration information. Specifically, memory 1k-40 may store information about bearers assigned to access UEs, measurement results reported from access UEs, etc. Furthermore, memory 1k-40 may store information as a reference for whether to provide or terminate multiple connections to the UE. Memory 1k-40 provides the stored data based on requests from controller 1k-50.

[0169] The controller 1k-50 controls the overall operation of the main base station. For example, the controller 1k-50 transmits and receives signals via the baseband processor 1k-20 and the RF processor 1k-10 or the backhaul communicator 1k-30. Furthermore, the controller 1k-50 records data on or reads data from the memory 1k-40. For this purpose, the controller 1k-50 may include at least one processor.

[0170] The methods described in the claims or specification according to embodiments of this disclosure can be implemented in hardware, software, or a combination of hardware and software.

[0171] When implemented as software, a computer-readable storage medium may be provided to store one or more programs (e.g., software modules). The one or more programs stored in the computer-readable storage medium are configured to be executed by one or more processors in an electronic device. The one or more programs include instructions that direct the electronic device to perform methods according to embodiments of this disclosure as described in the claims or specification.

[0172] The program (e.g., a software module or software) can be stored in non-volatile memory, including random access memory (RAM) or flash memory, read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), disk storage devices, optical disc (CD)-ROM, digital versatile disc (DVD), another optical storage device, or magnetic tape. Alternatively, the program can be stored in a memory that includes a combination of some or all of the above storage media. Multiple such memories may be included.

[0173] Furthermore, the program can be stored on an attachable storage device accessible via any one or a combination of communication networks such as the Internet, intranet, local area network (LAN), wide area network (WLAN), and storage area network (SAN). Such a storage device can access a device executing embodiments of this disclosure via an external port. Additionally, a separate storage device on the communication network can access an electronic device executing embodiments of this disclosure.

[0174] In the foregoing embodiments of this disclosure, the configuration elements included in this disclosure are represented in singular or plural form. However, for ease of description, singular or plural forms are suitably chosen, and this disclosure is not limited thereto. Thus, configuration elements expressed in plural form can also be configured as a single element, and configuration elements expressed in singular form can also be configured as multiple elements.

[0175] Specific embodiments are described in the description of this disclosure; however, it should be understood that various modifications can be made without departing from the scope of this disclosure. Therefore, the scope of this disclosure is not limited to the embodiments described herein, but should be defined by the appended claims and their equivalents. In other words, other modifications based on the technical concept of this disclosure are feasible to those skilled in the art. Furthermore, embodiments of this disclosure can be implemented in combination when needed. For example, portions of the methods provided by this disclosure can be combined with each other to enable operation of the BS and UE. Moreover, although embodiments are described based on 5G and NR systems, modifications based on the technical scope of the embodiments can be applied to other communication systems, such as LTE, LTE-A, LTE-A-Pro systems, etc.

Claims

1. A method performed by a source base station in a wireless communication system, the method comprising: A handover preparation information message is sent to the target base station. This handover preparation information message includes a list of Temporary Mobile Group Identifiers (TMGIs) corresponding to the multicast broadcast service (MBS) being received by the user equipment (UE) and a list of TMGI indices. in, The TMGI index is the index value corresponding to the TMGI of the MBS being received by the UE; as well as A handover command message is received from the target base station. The handover command message includes MBS Data Radio Bearer (DRB) configuration information and MBS Radio Link Control (RLC) bearer configuration information. The MBS DRB configuration information includes a list based on TMGI and a list of TMGI indices indicating which MBS is associated with the DRB, and The MBS RLC bearer configuration information includes a list based on TMGI and a list of TMGI indexes indicating which MBS is associated with the RLC bearer; as well as Send a Radio Resource Control (RRC) reconfiguration message, including the handover command message, to the UE. The RRC reconfiguration message includes configuration information that enables the UE to set the Packet Data Convergence Protocol (PDCP) state variables for the MBS DRB based on the first PDCP sequence number received from the target base station and the predefined header field number (HFN).

2. The method according to claim 1, wherein the information associated with the TMGI includes a Public Land Mobile Network (PLMN) ID and a Service ID.

3. A source base station operating in a wireless communication system, the source base station comprising: transceiver; Memory, which stores one or more instructions; and At least one processor, coupled to the transceiver, and configured to execute one or more instructions to cause the source base station to: A handover preparation information message is sent to the target base station. This handover preparation information message includes a list of Temporary Mobile Group Identifiers (TMGIs) corresponding to the multicast broadcast service (MBS) being received by the user equipment (UE) and a list of TMGI indices. Wherein, the TMGI index is the index value corresponding to the TMGI of the MBS being received by the UE, and A handover command message is received from the target base station. The handover command message includes MBS Data Radio Bearer (DRB) configuration information and MBS Radio Link Control (RLC) bearer configuration information. The MBS DRB configuration information includes a list based on TMGI and a list of TMGI indices indicating which MBS is associated with the DRB, and The MBS RLC bearer configuration information includes a list based on TMGI and a list of TMGI indexes indicating which MBS is associated with the RLC bearer; as well as Send a Radio Resource Control (RRC) reconfiguration message, including the handover command message, to the UE. The RRC reconfiguration message includes configuration information that enables the UE to set the Packet Data Convergence Protocol (PDCP) state variables for the MBS DRB based on the first PDCP sequence number received from the target base station and the predefined header field number (HFN).

4. The source base station according to claim 3, wherein the information associated with the TMGI includes a Public Land Mobile Network (PLMN) ID and a Service ID.

5. A method performed by a target base station in a wireless communication system, the method comprising: The system receives a handover preparation information message from the source base station. This message includes a list of Temporary Mobility Group Identifiers (TMGIs) corresponding to the multicast broadcast service (MBS) being received by the user equipment (UE) and a list of TMGI indices. in, The TMGI index is the index value corresponding to the TMGI of the MBS being received by the UE; as well as A handover command message is sent to the target base station. The handover command message includes MBS Data Radio Bearer (DRB) configuration information and MBS Radio Link Control (RLC) bearer configuration information. The MBS DRB configuration information includes a list based on TMGI and a list of TMGI indexes indicating which MBS is associated with the DRB. The MBS RLC bearer configuration information includes a list based on TMGI and a list of TMGI indexes indicating which MBS is associated with the RLC bearer, and The handover command message also includes configuration information that enables the UE to set the Packet Data Convergence Protocol (PDCP) status variables for the MBS DRB based on the first PDCP sequence number received from the target base station and the predefined header field number (HFN).

6. The method of claim 5, wherein the information associated with the TMGI includes a Public Land Mobile Network (PLMN) ID and a Service ID.

7. A target base station executed in a wireless communication system, the target base station comprising: transceiver; Memory, which stores one or more instructions; and At least one processor, coupled to the transceiver, and configured to execute one or more instructions to cause the target base station to: The system receives a handover preparation information message from the source base station. This message includes a list of Temporary Mobility Group Identifiers (TMGIs) corresponding to the multicast broadcast service (MBS) being received by the user equipment (UE) and a list of TMGI indices. Wherein, the TMGI index is the index value corresponding to the TMGI of the MBS being received by the UE, and A handover command message is sent to the target base station. The handover command message includes MBS Data Radio Bearer (DRB) configuration information and MBS Radio Link Control (RLC) bearer configuration information. The MBS DRB configuration information includes a list based on TMGI and a list of TMGI indexes indicating which MBS is associated with the DRB. The MBS RLC bearer configuration information includes a list based on TMGI and a list of TMGI indexes indicating which MBS is associated with the RLC bearer, and The handover command message also includes configuration information that enables the UE to set the Packet Data Convergence Protocol (PDCP) status variables for the MBS DRB based on the first PDCP sequence number received from the target base station and the predefined header field number (HFN).

8. The target base station according to claim 7, wherein the information associated with the TMGI includes a Public Land Mobile Network (PLMN) ID and a Service ID.

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