Method and apparatus for performing communication in wireless communication system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. A method performed by a user equipment (UE) in a wireless communication system is provided. The method includes performing multicast reception in a radio resource control (RRC) inactive state on a first cell; performing cell selection on the second cell in a case where the cell selection criterion is satisfied; identifying whether the second cell supports multicast reception in the RRC inactive state; and continuing the multicast reception in the RRC inactive state on the second cell based on the second cell supporting the multicast reception in the RRC inactive state.

Description

Technical Field

[0001] The present disclosure relates to wireless communication systems, and more particularly, to methods and apparatus for handling mobility of multicast reception in wireless communication systems. Background Art

[0002] 5G mobile communication technology defines a wide frequency band, making high transmission rates and new services possible, and can be implemented not only in "below 6 GHz" frequency bands such as 3.5 GHz, but also in "above 6 GHz" frequency bands called millimeter waves including 28 GHz and 39 GHz. In addition, it has been considered to implement 6G mobile communication technology (called super 5G system) in terahertz frequency bands (e.g., 95 GHz to 3 THz frequency bands) to achieve a transmission rate fifty times faster than 5G mobile communication technology and an ultra-low latency one-tenth of 5G mobile communication technology.

[0003] At the beginning of the development of 5G mobile communication technology, in order to support services and meet performance requirements related to enhanced mobile broadband (eMBB), ultra-reliable low-latency communication (URLLC) and massive machine type communication (mMTC), standardization has been underway on the following items: beamforming and massive MIMO for mitigating radio wave path loss in millimeter waves and increasing radio wave transmission distance; parameter sets supporting efficient utilization of millimeter wave resources and dynamic operation of time slot formats (e.g., operating multiple subcarrier spacings); initial access technology for supporting multi-beam transmission and broadband; definition and operation of BWP (bandwidth part); new channel coding methods such as LDPC (low-density parity check) codes for large-scale data transmission and polarization codes for highly reliable transmission of control information; L2 preprocessing; and network slicing for providing dedicated networks dedicated to specific services.

[0004] Currently, discussions are underway on improvements and performance enhancements of initial 5G mobile communication technologies in consideration of the services they are to support, and there has been physical layer standardization on items such as: technologies for assisting driving determination of autonomous vehicles based on information sent by the vehicle about the location and status of the vehicle and for enhancing user convenience using V2X (Vehicle to Everything); NR-U (Unlicensed New Radio) for system operations that are intended to comply with various regulatory requirements in unlicensed bands; NR UE power saving; non-terrestrial network (NTN) as UE-satellite direct communication for providing coverage in areas where communication with terrestrial networks is unavailable; and positioning.

[0005] In addition, standardization is also being conducted on air interface architecture / protocols for technologies such as the Industrial Internet of Things (IIoT) for supporting new services by interworking and converging with other industries; IAB (Integrated Access and Backhaul) for providing nodes for network service area expansion by supporting wireless backhaul links and access links in an integrated manner; mobility enhancements including conditional handover and DAPS (Dual Active Protocol Stack) handover; and two-step random access for simplifying the random access procedure (2-step RACH for NR). Standardization is also being conducted on system architecture / services for the following items: 5G baseline architecture (e.g., service-based architecture or service-based interface) for combining network function virtualization (NFV) and software defined network (SDN) technologies; and mobile edge computing (MEC) for receiving services based on UE location.

[0006] As 5G mobile communication systems are commercialized, the number of connected devices, which has been increasing exponentially, will be connected to the communication network, and therefore, it is expected that enhanced functions and performance of the 5G mobile communication systems and integrated operations of the connected devices will be necessary. To this end, new research is planned in the following areas: extended reality (XR) for efficiently supporting augmented reality (AR), virtual reality (VR), mixed reality (MR), etc.; 5G performance improvement and complexity reduction by utilizing artificial intelligence (AI) and machine learning (ML); AI service support; metaverse service support; and drone communication.

[0007] In addition, this development of 5G mobile communication systems will serve as the basis for developing not only new waveforms for providing coverage in the terahertz band of 6G mobile communication technology, multi-antenna transmission technologies such as full-dimensional MIMO (FD-MIMO), array antennas and massive antennas, metamaterial-based lenses and antennas for improving the coverage of terahertz band signals, and high-dimensional spatial multiplexing technology using OAM (orbital angular momentum) and RIS (reconfigurable smart surface), but also full-duplex technology for improving the frequency efficiency of 6G mobile communication technology and improving system networks, AI-based communication technology for achieving system optimization from the design stage by utilizing satellites and AI (artificial intelligence) and internalizing end-to-end AI support functions, and next-generation distributed computing technology for implementing services at a complexity level that exceeds the limits of UE operating capabilities by utilizing ultra-high performance communication and computing resources. Summary of the invention

[0008] Technical Solution

[0009] The present disclosure relates to methods and apparatus for handling mobility of multicast reception in a wireless communication system.

[0010] According to aspects of the present disclosure, a method performed by a user equipment (UE) in a wireless communication system is provided. The method may include performing multicast reception in a radio resource control (RRC) inactive state on a first cell. The method may include: performing cell selection on a second cell when a cell selection criterion is met. The method may include identifying whether the second cell supports multicast reception in an RRC inactive state. The method may include: continuing multicast reception in an RRC inactive state on the second cell based on the second cell supporting multicast reception in an RRC inactive state.

[0011] According to aspects of the present disclosure, a user equipment (UE) in a wireless communication system is provided. The UE may include a transceiver and at least one processor coupled to the transceiver. The at least one processor may be configured to perform multicast reception in a radio resource control (RRC) inactive state on a first cell. The at least one processor may be configured to: perform cell selection on a second cell when a cell selection criterion is met. The at least one processor may be configured to identify whether the second cell supports multicast reception in an RRC inactive state. The at least one processor may be configured to continue multicast reception in an RRC inactive state on the second cell based on the second cell supporting multicast reception in an RRC inactive state. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A flow chart describing the operation of a UE according to an embodiment of the present disclosure is shown.

[0013] Figure 2 A flow chart describing the operation of a UE according to an embodiment of the present disclosure is shown.

[0014] Figure 3 A flow chart describing the operation of a UE according to an embodiment of the present disclosure is shown.

[0015] Figure 4 A flow chart describing the operation of a UE according to an embodiment of the present disclosure is shown.

[0016] Figure 5 A flow chart describing the operation of a UE according to an embodiment of the present disclosure is shown.

[0017] Figure 6 A flow chart describing the operation of a UE according to an embodiment of the present disclosure is shown.

[0018] Figure 7 A flow chart describing the operation of a UE according to an embodiment of the present disclosure is shown.

[0019] Figure 8 The structure of a UE according to an embodiment of the present disclosure is shown.

[0020] Fig. 9 The structure of a BS according to an embodiment of the present disclosure is shown.

[0021] Fig.10 A method performed by a UE according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0022] Throughout the present disclosure, the expression "at least one of a, b or c" refers to only a, only b, only c, both a and b, both a and c, both b and c, all of a, b and c, or variations thereof. Throughout the specification, a layer (or layer arrangement) may also be referred to as an entity. Hereinafter, the working principle of the present disclosure will be described in detail in conjunction with the accompanying drawings. In the following description, well-known functions or configurations are not described in detail because they would obscure the present disclosure with unnecessary details. The terms used in the specification are defined in consideration of the functions used in the present disclosure and may change according to the intention or common methods of the user or operator. Therefore, the definition of the terms is understood based on the complete description of the present specification.

[0023] For the same reason, in the accompanying drawings, some elements may be exaggerated, omitted or roughly shown. Moreover, the size of each element does not completely correspond to the actual size of each element. In each figure, the same or corresponding elements are presented with the same reference numerals.

[0024] With reference to the following detailed description of the embodiments and the accompanying drawings of the present disclosure, the advantages and features of the present disclosure and its implementation method can be more easily understood. However, the present disclosure can be embodied in many different forms and should not be interpreted as being limited to the embodiments set forth herein; rather, these embodiments of the present disclosure are provided so that the present disclosure will be thorough and complete, and the concepts of the present disclosure will be fully conveyed to those of ordinary skill in the art. Therefore, the scope of the present disclosure is defined by the appended claims. Throughout the specification, the same reference numerals represent the same elements. It should be understood that the blocks in the flowchart or the combination of flowcharts can be executed by computer program instructions. Because these computer program instructions can be loaded into a processor of a general-purpose computer, a special-purpose computer, or another programmable data processing device, the instructions executed by the processor of the computer or another programmable data processing device create a unit for performing the functions described in the flowchart block.

[0025] The computer program instructions may be stored in a computer-usable or computer-readable memory capable of directing a computer or another programmable data processing device to implement functions in a specific manner, and thus the instructions stored in the computer-usable or computer-readable memory may also be capable of producing an article of manufacture containing instruction units for performing the functions described in the flowchart blocks. The computer program instructions may also be loaded into a computer or another programmable data processing device, and thus, when a series of operations are performed in the computer or another programmable data processing device, the instructions for operating the computer or another programmable data processing device by generating a computer-implemented process may provide operations for performing the functions described in the flowchart blocks.

[0026] In addition, each frame can represent a module, segment or a part of code including one or more executable instructions for performing a specified logical function. It should also be noted that in some alternative embodiments, the functions mentioned in the frame may not occur in order. For example, two continuous blocks may also be executed simultaneously or in reverse order according to the function corresponding thereto.

[0027] As used herein, the term "unit" represents a software element or a hardware element, such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC), and performs a specific function. However, the term "unit" is not limited to software or hardware. A "unit" can be formed in an addressable storage medium, or can be formed to operate one or more processors. Therefore, for example, the term "unit" can include elements (e.g., software elements, object-oriented software elements, class elements, and task elements), processes, functions, attributes, processes, subroutines, program code segments, drivers, firmware, microcodes, circuits, data, databases, data structures, tables, arrays, or variables.

[0028] The functions provided by the elements and "units" may be combined into a smaller number of elements and "units", or may be divided into additional elements and "units". In addition, the elements and "units" may be embodied as reproducing one or more central processing units (CPUs) in a device or a secure multimedia card. In addition, in an embodiment of the present disclosure, a "unit" may include at least one processor. In the following description of the present disclosure, well-known functions or configurations are not described in detail because they would obscure the present disclosure with unnecessary details.

[0029] Hereinafter, for convenience of explanation, the present disclosure uses terms and names defined in the 3rd Generation Partnership Project Long Term Evolution (3GPP LTE) standard. However, the present disclosure is not limited to the terms and names and may also be applied to systems complying with other standards.

[0030] In the present disclosure, for the convenience of explanation, the evolved Node B (eNB) may be used interchangeably with the next generation Node B (gNB). That is, the base station (BS) described by the eNB may represent the gNB. In the following description, the term "base station" refers to an entity for allocating resources to a user equipment (UE), and may be used interchangeably with at least one of a gNode B, an eNode B, a Node B, a base station (BS), a radio access unit, a base station controller (BSC), or a node through a network. The term "terminal" may be used interchangeably with 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. However, the present disclosure is not limited to the above examples. Specifically, the present disclosure is applicable to the 3GPP New Radio (NR) (or fifth generation (5G)) mobile communication standard. In the following description, for the convenience of explanation, the term eNB may be used interchangeably with the term gNB. That is, a base station interpreted as an eNB may also refer to a gNB. The term UE may also refer to a mobile phone, a NB-IoT device, a sensor, and other wireless communication devices.

[0031] In recent years, several broadband wireless technologies have been developed to meet the increasing number of broadband users and to provide more and better applications and services. The second generation of wireless communication systems has been developed to provide voice services while ensuring the mobility of users. The third generation of wireless communication systems supports not only voice services but also data services. In recent years, the fourth generation of wireless communication systems has been developed to provide high-speed data services. However, at present, the fourth generation of wireless communication systems lacks resources to meet the growing demand for high-speed data services. Therefore, the fifth generation of wireless communication systems (also called next generation wireless or NR) is being developed to meet the growing demand for high-speed data services, support ultra-reliability and low-latency applications.

[0032] The fifth generation wireless communication system supports not only lower frequency bands, but also higher frequency (millimeter wave) bands, such as 10 GHz to 100 GHz bands, in order to achieve higher data rates. In order to mitigate the propagation loss of radio waves and increase the transmission distance, beamforming, massive multiple input multiple output (MIMO), full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and massive antenna technology are being considered in the design of the fifth generation wireless communication system. In addition, the fifth generation wireless communication system is expected to cope with different use cases with quite different requirements in terms of data rate, delay, reliability, mobility, etc. However, it is expected that the air interface design of the fifth generation wireless communication system will be flexible enough to serve UEs with very different capabilities depending on the use case and market segment, and the UE provides services to the end customer. A small number of example use cases that the fifth generation wireless communication system wireless system is expected to address are enhanced mobile broadband (eMBB), massive machine type communication (m-MTC), ultra-reliable low latency communication (URLL), etc. The eMBB requirements, such as tens of Gbps data rates, low latency, high mobility, etc., are aimed at market segments representing traditional wireless broadband users who need Internet connectivity anytime, anywhere. m-MTC requirements, such as very high connection density, infrequent data transfers, very long battery life, low mobility addresses, etc., which are targeted at the market segment representing the Internet of Things (IoT) / Internet of Everything (IoE) where billions of devices are envisioned to be connected. URLL requirements, such as very low latency, very high reliability, and variable mobility, etc., are targeted at the market segment for vehicle-to-vehicle / vehicle-to-infrastructure communications, which represents industrial automation applications and is foreseen as one of the enablers of autonomous vehicles.

[0033] In the fifth generation wireless communication system operating in a higher frequency (millimeter wave) band, UE and gNB communicate with each other using beamforming. Beamforming technology is used to mitigate propagation path loss and increase the propagation distance for communication in a higher frequency band. Beamforming enhances transmission and reception performance using high-gain antennas. Beamforming can be classified into transmit (TX) beamforming performed at the transmitting end and receive (RX) beamforming performed at the receiving end. Generally, TX beamforming can increase directivity by allowing the area reached by propagation to be densely distributed in a specific direction using multiple antennas. In this case, the aggregation of multiple antennas can be referred to as an antenna array, and each antenna included in the array can be referred to as an array element. The antenna array can be configured in various forms, such as a linear array, a planar array, and the like. The use of TX beamforming causes the directivity of the signal to increase, thereby increasing the propagation distance. In addition, since the signal is hardly transmitted in a direction other than the directional direction, the signal interference acting on the other receiving end is significantly reduced. The receiving end can beamform the RX signal by using an RX antenna array. RX beamforming increases the RX signal strength sent in a specific direction by allowing propagation to be concentrated in a specific direction, and excludes signals sent in directions other than the specific direction from the RX signal, thereby providing the effect of blocking interference signals. By using beamforming technology, the transmitter can generate multiple transmit beam patterns in different directions. Each of these transmit beam patterns may also be referred to as a transmit (TX) beam. Wireless communication systems operating at high frequencies use multiple narrow TX beams to transmit signals in a cell, because each narrow TX beam provides coverage for a portion of the cell. The narrower the TX beam, the higher the antenna gain, and therefore the greater the propagation distance of the signal sent using beamforming. The receiver may also generate multiple receive (RX) beam patterns in different directions. Each of these receive patterns may also be referred to as a receive (RX) beam. PDCP may refer to Packet Data Convergence Protocol, and SDAP may refer to Service Data Adaptation Protocol.

[0034] The fifth generation wireless communication system supports standalone operation mode and dual connection (DC). In DC, a multi-Rx / Tx UE can be configured to utilize resources provided by two different nodes (or NBs) connected via a non-ideal backhaul. One node acts as a master node (MN) and the other node acts as a secondary node (SN). MN and SN are connected via a network interface, and at least MN is connected to the core network. NR also supports multi-RAT dual connection (MR-DC) operation, whereby the UE under RRC_CONNECTED is configured to utilize radio resources provided by two different schedulers located in two different nodes connected via a non-ideal backhaul and providing E-UTRA (ie, if the node is ng-eNB) or NR access (ie, if the node is gNB). In NR, for UEs under RRC_CONNECTED that are not configured with CA / DC, only one serving cell includes the primary cell. For UEs under RRC_CONNECTED configured with CA / DC, the term "serving cell" is used to refer to a cell set including a special cell and all secondary cells. In NR, the term Master Cell Group (MCG) refers to a set of serving cells associated with a master node, which includes a PCell and optionally one or more SCells. In NR, the term Secondary Cell Group (SCG) refers to a set of serving cells associated with a secondary node, which includes a PSCell and optionally one or more SCells. In NR, PCell (primary cell) refers to a serving cell in an MCG operating on the primary frequency, where the UE performs an initial connection establishment procedure or initiates a connection reestablishment procedure. In NR, for UEs configured with CA, an Scell ​​is a cell that provides additional radio resources on top of a special cell. Primary SCG cell (PSCell) refers to a serving cell in an SCG, where the UE performs random access when performing a reconfiguration with a synchronization procedure. For dual connectivity operation, the term SpCell (i.e., special cell) refers to the PCell of an MCG or the PSCell of an SCG, otherwise the term special cell refers to the PCell.

[0035] In the fifth generation wireless communication system, the cell broadcast synchronization signal and the Node B (gNB) or base station in the PBCH block (SSB) consists of the primary synchronization signal and the secondary synchronization signal (PSS, SSS) and the system information. The system information includes the common parameters required for communication in the cell. In the fifth generation wireless communication system (also known as the next generation wireless or NR), the system information (SI) is divided into the MIB and several SIBs, where:

[0036] - MIB is always sent on BCH with a period of 80ms and repeated within 80ms, and it includes the parameters required to obtain SIB1 from the cell.

[0037] -SIB1 is transmitted on DL-SCH with a period of 160ms and a variable number of transmission repetitions. The default transmission repetition period of SIB1 is 20ms, but the actual transmission repetition period depends on the network implementation. The scheduling information in SIB1 includes the mapping between SIBs and SI messages, the period of each SI message, and the SI window length. The scheduling information in SIB1 includes an indicator for each SI message, which indicates whether the associated SI message is being broadcast. If at least one SI message is not being broadcast, SIB1 may include random access resources (PRACH preamble and PRACH resources) for requesting the gNB to broadcast one or more SI messages.

[0038] -The system information (SI) message sent on the DL-SCH carries SIBs other than SIB1. Only SIBs with the same period can be mapped to the same SI message. Each SI message is sent within a periodically occurring time domain window (called an SI window, which has the same length for all SI messages). Each SI message is associated with an SI window, and the SI windows of different SI messages do not overlap. That is, only corresponding SI messages are sent within one SI window. Using the indication in SIB1, any SIB other than SIB1 can be configured as cell-specific or area-specific. Cell-specific SIBs are applicable only within the cell where the SIB is provided, while area-specific SIBs are applicable within an area called an SI area, which is composed of one or more cells and is identified by a system information area ID (systemInformationAreaID).

[0039] In the fifth generation wireless communication system, the physical downlink control channel (PDCCH) is used to schedule DL transmission on PDSCH and UL transmission on PUSCH, wherein the downlink control information (DCI) on PDCCH includes: downlink allocation including at least modulation and coding format, resource allocation and hybrid ARQ information related to DL-SCH; uplink scheduling authorization including at least modulation and coding format, resource allocation and hybrid ARQ information related to UL-SCH. In addition to scheduling, PDCCH can also be used to: activate and deactivate configured PUSCH transmission with configuration authorization; activate and deactivate PDSCH semi-persistent transmission; notify one or more UEs of the time slot format; notify one or more UEs of PRBs and OFDM symbols, where the UE can assume that no transmission is to be used for the UE; transmit TPC commands for PUCCH and PUSCH; transmit one or more TPC commands for SRS transmission of one or more UEs; switch the active bandwidth part of the UE; initiate a random access process. The UE monitors a set of PDCCH candidates in the configured monitoring opportunities in one or more configured control resource sets (COntrol REsource SET, CORESET) according to the corresponding search space configuration. CORESET consists of a group of PRBs with a duration of 1 to 3 OFDM symbols. Resource element groups (Resource Element Group, REG) and control channel elements (Control Channel Element, CCE) are defined in CORESET, where each CCE consists of a group of REGs. The control channel is formed by the aggregation of CCEs. Different code rates for the control channel are achieved by aggregating different numbers of CCEs. Interleaved and non-interleaved CCE to REG mapping are supported in CORESET. Polarization coding is used for PDCCH. Each resource element group carrying PDCCH carries its own DMRS. QPSK modulation is used for PDCCH.

[0040] In the fifth generation wireless communication system, a list of search space configurations is signaled by the GNB for each configured BWP, where each search configuration is uniquely identified by an identifier. The identifier of the search space configuration to be used for a specific purpose (such as paging reception, SI reception, random access response reception) is explicitly signaled by the gNB. In NR, the search space configuration includes parameters Monitoring-periodicity-PDCCH-slot, Monitoring-offset-PDCCH-slot, Monitoring-symbols-PDCCH-within-slot and duration. The UE uses the parameters PDCCH monitoring period (Monitoring-periodicity-PDCCH-slot), PDCCH monitoring offset (Monitoring-offset-PDCCH-slo t) and PDCCH monitoring mode (Monitoring-symbols-PDCCH-within-slot) to determine the PDCCH monitoring timing within the timeslot. The PDCCH monitoring occasion is at time slot 'x' to time slot x+duration, where the time slot numbered 'x' in the radio frame numbered 'y' satisfies the following equation:

[0041] (y*(number of slots in a radio frame)+x-Monitoring-offset-PDCCH-slot)mod(Monitoring-periodicity-PDCCH-slot)=0;

[0042] The starting symbol of the PDCCH monitoring opportunity in each time slot with a PDCCH monitoring opportunity is given by Monitoring-symbols-PDCCH-within-slot. The length of the PDCCH monitoring opportunity (in symbols) is given in the corset associated with the search space. The search space configuration includes an indicator of the corset configuration associated with it. The list of coreset configurations is signaled by the GNB for each configured BWP, where each coreset configuration is uniquely identified by an identifier. Note that each radio frame has a duration of 10ms. Radio frames are identified by radio frame numbers or system frame numbers. Each radio frame includes several time slots, where the number of time slots in a radio frame and the duration of the time slots depend on the subcarrier spacing. The number of time slots of a radio frame and the time slot duration of a radio frame are pre-defined in NR for each supported SCS. Each coreset configuration is associated with a list of TCI (Transmission configuration indicator) states. Each TCI state configures a DL RS ID (SSB or CSI RS). The list of TCI states corresponding to the coreset configuration is signaled by the gNB via RRC signaling. One of the TCI states in the TCI state list is activated by the gNB and indicated to the UE. The TCI state indicates the DL TX beam used by the GNB to transmit the PDCCH in the PDCCH monitoring opportunity of the search space (the DL TX beam is quasi-co-located with the SSB / CSI RS of the TCI state).

[0043] In the fifth generation wireless communication system, bandwidth adaptation (BA) is supported. With BA, the receiving and transmitting bandwidth of the UE does not need to be as large as the bandwidth of the cell and can be adjusted: the width can be commanded to change (for example, shrink during low activity periods to save power); the position can be moved in the frequency domain (for example, to increase scheduling flexibility); and the subcarrier spacing can be commanded to change (for example, to allow different services). A subset of the total cell bandwidth of a cell is called a bandwidth part (Bandwidth Part, BWP). BA is implemented by configuring BWP for RRC-connected UEs and informing the UE which BWP among the configured BWPs is currently the active BWP. When BA is configured, the UE only needs to monitor the PDCCH on one active BWP, that is, it does not have to monitor the PDCCH on the entire DL frequency of the serving cell. In the RRC connected state, for each configured serving cell (i.e. PCell or SCell), the UE is configured with one or more DL and UL BWPs. For an activated serving cell, there is always an active UL and DL BWP at any point in time. BWP switching for a serving cell is used to activate an inactive BWP and deactivate an active BWP at once. BWP switching is controlled by the PDCCH indicating downlink allocation or uplink grant, by the bwp-InactivityTimer, by RRC signaling, or by the MAC entity itself when initiating a random access procedure. When adding a SpCell or activating an SCell, the DL BWP and UL BWP indicated by firstActiveDownlinkBWP-Id and firstActiveUplinkBWP-Id, respectively, are active without receiving a PDCCH indicating a downlink allocation or uplink grant. The active BWP for the serving cell is indicated by RRC or PDCCH. For unpaired spectrum, the DL BWP is paired with the UL BWP, and BWP switching is common to both UL and DL. When the BWP inactivity timer expires, the UE switches the active DL BWP to the default DL BWP or the initial DL BWP (if the default DL BWP is not configured).

[0044] The 5G wireless communication system supports random access (RA). Random access (RA) is used to achieve uplink (UL) time synchronization. RA is used for initial access, handover, radio resource control (RRC) connection reestablishment process, scheduling request transmission, secondary cell group (SCG) addition / modification, beam failure recovery, and data or control information transmission of an unsynchronized UE in the RRC connected state in the UL.

[0045] In a fifth generation (also known as NR or New Radio) wireless communication system, a UE may be in one of the following RRC states: RRC IDLE, RRC INACTIVE, and RRC CONNECTED. The RRC state may also have the following characteristics:

[0046] - In RRC_IDLE state, UE-specific DRX can be configured by upper layers (i.e., NAS). The UE monitors short messages sent using the Paging Radio Network Temporary Identifier (P-RNTI) via DCI; monitors the paging channel for CN paging using 5G-S-TMSI; - Performs neighbor cell measurements and cell (re)selection; obtains system information and can send SI requests (if configured).

[0047] -In RRC_INACTIVE state, UE-specific DRX can be configured by upper layers or the RRC layer; in this state, the UE stores a UE inactive AS context. The radio access network (RAN) based notification area is configured by the RRC layer. The UE monitors short messages sent using P-RNTI via DCI; monitors the paging channel for CN paging using 5G-S-TMSI and RAN paging using fullI-RNTI; performs neighbor cell measurements and cell (re)selection; performs RAN-based notification area updates periodically and when moving outside the configured RAN-based notification area; obtains system information and can send SI requests (if configured).

[0048] - In RRC_CONNECTED, the UE stores the AS context. Unicast data is sent to / received from the UE. In lower layers, the UE may be configured with UE-specific DRX. The UE monitors short messages sent with the P-RNTI via DCI, if configured; monitors the control channel associated with the shared data channel to determine if data is scheduled for it; provides channel quality and feedback information; performs neighbor cell measurements and measurement reports; obtains system information.

[0049] The NR-based 5G or Next Generation Radio Access Network (NG-RAN) consists of NG-RAN nodes, where the NG-RAN nodes are gNBs, providing NR user plane and control plane protocol terminations to the UE. The gNB is also connected to the 5GC via the NG interface, more specifically, to the AMF (Access and Mobility Management Function) via the NG-C interface, and to the UPF (User Plane Function) via the NG-U interface. In the fifth generation (also known as NR or new radio) wireless communication system, the UE can use discontinuous reception (DRX) in the RRC_IDLE and RRC_INACTIVE states to reduce power consumption. In the RRC_IDLE / RRC_INACTIVE state, the UE wakes up for a short period of time at regular intervals (i.e., every DRX cycle) to receive paging, SI update notifications, and emergency notifications. Paging messages are sent using the physical downlink shared channel (PDSCH). If there is a paging message in the PDSCH, the physical downlink common control channel (PDCCH) is addressed to the P-RNTI. The P-RNTI is common to all UEs. The UE identity (i.e., S-TMSI for RRC_IDLE UE or I-RNTI for RRC_INACTIVE UE) is included in the paging message to indicate paging for a specific UE. The paging message may include multiple UE identities to page multiple UEs. The paging message is broadcast on the data channel (i.e., PDSCH) (i.e., PDCCH is masked with P-RNTI). SI updates and emergency notifications are included in the DCI, and the PDCCH carrying the DCI is addressed to the P-RNTI. In RRC idle / inactive mode, the UE monitors one paging occasion (PO) in each DRX cycle. In RRC idle / inactive mode, the UE monitors PO in the initial DL BWP. In the RRC connected state, the UE monitors one or more POs to receive SI update notifications and receive emergency notifications. In the RRC connected state, the UE may monitor any PO in the paging DRX cycle and monitor at least one PO in the SI modification period. In RRC idle / inactive mode, the UE monitors PO in each DRX cycle in its active DL BWP. PO is a set of "S" PDCCH monitoring opportunities for paging, where "S" is the number of SSBs transmitted in the cell (i.e., synchronization signal and PBCH blocks (SSBs) consist of primary and secondary synchronization signals (PSS, SSS) and PBCH). The UE first determines the paging frame (PF) and then determines the PO for the determined PF. One PF is a radio frame (10ms).

[0050] Multicast reception in fifth generation wireless communication systems: Multicast communication services are delivered to UEs using multicast sessions. UEs can receive multicast communication services in the RRC_CONNECTED state using mechanisms such as PTP and / or PTM delivery. HARQ feedback / retransmission can be applied to PTP and PTM transmissions. For a multicast session, the gNB provides the UE with multicast multicast / broadcast service (MBS) radio bearer (MRB) configuration via dedicated RRC signaling: If the UE joining the multicast session is in the RRC_CONNECTED state and when the multicast session is activated, the gNB sends the UE an RRCReconfiguration message with the relevant MBS configuration for the multicast session. The gNB can use the RRCReconfiguration message to configure or reconfigure the multicast MRB, for example, to add / release / modify the radio link control (RLC) entity of the MRB.

[0051] The gNB may move the UE to RRC idle / inactive state when there is (temporarily) no data to send to the UE for a multicast session. A gNB supporting MBS uses a group notification mechanism to notify UEs in RRC idle / inactive state when a multicast session has been activated by the CN or when the gNB has multicast session data to be delivered. Upon receiving the group notification, the UE reconnects to the network, i.e. it initiates a connection establishment / resumption and enters RRC_CONNECTED. The group notification is addressed using the P-RNTI on the PDCCH.

[0052] In order to minimize the connection establishment / recovery of UEs in the RRC_INACTIVE state, multicast reception (also referred to as MBS multicast reception) by UEs in the RRC_INACTIVE state may be considered in the fifth generation wireless communication system. The network may provide a multicast reception configuration for RRC_INACTIVE in the RRC_Release / RRC reconfiguration message. The UE enters RRC_INACTIVE based on the configuration and starts multicast reception. Due to mobility, cell reselection occurs when the UE is receiving multicast reception in RRC_INACTIVE. In this scenario, a method for handling ongoing multicast reception is needed.

[0053] Method 1

[0054] Figure 1 A flow chart describing the operation of a UE according to an embodiment of the present disclosure is shown.

[0055] In operation S101: the UE is in RRC_CONNECTED state. The UE may receive multicast communication services in the RRC_CONNECTED state using mechanisms such as point-to-point (PTP) and / or point-to-multipoint (PTM) delivery. For a multicast session, the gNB provides the multicast MRB configuration to the UE via dedicated RRC signaling (e.g., RRCReconfiguration). If the UE has joined a multicast session and when the multicast session is activated, the gNB sends an RRCReconfiguration message with the relevant MBS configuration for the multicast session to the UE. The gNB may use the RRCReconfiguration message to configure or reconfigure the multicast MRB, for example, to add / release / modify the RLC entity of the MRB.

[0056] In operation S102: When the UE is in the RRC_CONNECTED state, the UE receives an RRCRelease message with a suspended configuration from the gNB. The UE enters the RRC_INACTIVE state upon receiving the RRCRelease message with the suspended configuration.

[0057] In operation S103: when in the RRC_INACTIVE state, the UE receives multicast reception for a multicast session that the UE has joined. The configuration of the MRB for multicast reception under RRC_INACTIVE may be received by the UE from the gNB in ​​system information or in an RRCReconfiguration message and / or in an RRCRelease message. If the multicast session is active when entering the RRC_INACTIVE state, the UE continues multicast reception of the multicast session; and the UE does not need to suspend the MRB (or MRB with PTM) corresponding to the active multicast session when entering the RRC_INACTIVE state. If the multicast session is inactive when entering the RRC_INACTIVE state, the UE suspends the MRB corresponding to the multicast session when entering the RRC_INACTIVE state. When the UE receives a session activation notification in a paging message for the multicast session (i.e., a temporary mobile group identity (TMGI) is included in the paging message for the activated one or more multicast sessions), the UE resumes the MRB and starts multicast reception under RRC_INACTIVE. In an embodiment of the present disclosure, if the UE receives a paging message:

[0058] 1> If in RRC_INACTIVE and the UE has joined one or more MBS sessions indicated by the TMGI included in pagingGroupList;

[0059] 2> If multicast reception in RRC_INACTIVE state is supported (or if the UE has configuration for multicast reception in RRC_INACTIVE and / or if the gNB has indicated in system information or RRC signalling (RRC Release or RRCReconfiguration) that it supports multicast reception in RRC_INACTIVE):

[0060] 3>UE initiates the process of receiving multicast reception under RRC_INACTIVE (e.g., recovering one or more MRBs, establishing / rebuilding PDCP / RLC entities for the recovered MRBs, etc.)

[0061] 2> Otherwise, if none of the ue-Identities included in any PagingRecord (if included in the Paging message) matches the UE identity assigned by the upper layer

[0062] 3> Initiate the RRC connection recovery process, where resumeCause is set as follows:

[0063] 4> If the UE is configured by upper layers with access identity 1:

[0064] 5>resumeCause is set to mps-PriorityAccess;

[0065] 4> Otherwise, if the UE is configured by upper layers with access identity 2:

[0066] 5>resumeCause is set to mcs-PriorityAccess;

[0067] 4> Otherwise, if the UE is configured by upper layers with one or more access identifiers equal to 11-15:

[0068] resumeCause is set to highPriorityAccess;

[0069] 4> Otherwise:

[0070] 5>resumeCause is set to mt-Access.

[0071] In operation S104: when the UE is in the RRC_INACTIVE state and is performing multicast reception in a cell (eg, cell A), a cell reselection criterion is satisfied and the UE performs reselection to another cell (eg, cell B).

[0072] In operation S105: when a cell is reselected while receiving multicast reception in the RRC_INACTIVE state, the UE performs the following operations: > The UE may stop the multicast reception in the RRC_INACTIVE state.

[0073] >In an embodiment of the present disclosure, the UE releases the established multicast MRB; the UE releases the PDCP entity and the mrb-Identity of the established multicast MRB; the UE indicates to the upper layer the release of the user plane resources for the tmgi; the UE releases the SDAP entity.

[0074] >In an embodiment of the present disclosure, the UE suspends all established multicast MRBs. The UE indicates PDCP suspension for all established multicast MRBs.

[0075] >The UE may initiate an RRC recovery procedure to enter the RRC_CONNECTED state.

[0076] Method 2

[0077] Figure 2 A flow chart describing the operation of a UE according to an embodiment of the present disclosure is shown.

[0078] In operation S201: the UE is in RRC_CONNECTED state. The UE may utilize mechanisms such as PTP and / or PTM delivery to receive multicast communication services in the RRC_CONNECTED state. For a multicast session, the gNB provides the multicast MRB configuration to the UE via dedicated RRC signaling (e.g., RRCReconfiguration). If the UE has joined a multicast session and when the multicast session is activated, the gNB sends an RRCReconfiguration message with the relevant MBS configuration for the multicast session to the UE. The gNB may use the RRCReconfiguration message to configure or reconfigure the multicast MRB, for example, to add / release / modify the RLC entity of the MRB.

[0079] In operation S202: When the UE is in the RRC_CONNECTED state, the UE receives an RRCRelease message with a suspended configuration from the gNB. The UE enters the RRC_INACTIVE state upon receiving the RRCRelease message with the suspended configuration.

[0080] In operation S203: when in the RRC_INACTIVE state, the UE receives multicast reception for a multicast session that the UE has joined. The configuration of the MRB for multicast reception under RRC_INACTIVE may be received by the UE from the gNB in ​​system information or in an RRCReconfiguration message and / or in an RRCRelease message. If the multicast session is active when entering the RRC_INACTIVE state, the UE continues multicast reception of the multicast session; and the UE does not need to suspend the MRB (or MRB with PTM) corresponding to the active multicast session when entering the RRC_INACTIVE state. If the multicast session is inactive when entering the RRC_INACTIVE state, the UE suspends the MRB corresponding to the multicast session when entering the RRC_INACTIVE state. When the UE receives a session activation notification in a paging message for the multicast session (i.e., the TMGI is included in the paging message for the activated multicast session), the UE resumes the MRB and starts multicast reception under RRC_INACTIVE. In an embodiment of the present disclosure, if the UE receives a paging message:

[0081] 1> if in RRC_INACTIVE and the UE has joined one or more MBS sessions indicated by the TMGI included in pagingGroupList; and

[0082] 2> If multicast reception in RRC_INACTIVE state is supported (or if the UE has configuration for multicast reception in RRC_INACTIVE and / or if the gNB has indicated in system information or RRC signaling (RRC Release or RRCReconfiguration) that it supports multicast reception in RRC_INACTIVE):

[0083] 4>UE initiates the process of receiving multicast reception under RRC_INACTIVE (e.g., recovering one or more MRBs, establishing / rebuilding PDCP / RLC entities for the recovered MRBs, etc.)

[0084] 1>2> Otherwise, if none of the ue-Identities included in any PagingRecord (if included in the Paging message) matches the UE identity assigned by the upper layer, then:

[0085] 3> Initiate the RRC connection recovery process, where resumeCause is set as follows:

[0086] 4> If the UE is configured by upper layers with access identity 1:

[0087] 5>resumeCause is set to mps-PriorityAccess;

[0088] 4> Otherwise, if the UE is configured by upper layers with access identity 2:

[0089] 5>resumeCause is set to mcs-PriorityAccess;

[0090] 4> Otherwise, if the UE is configured by upper layers with one or more access identifiers equal to 11-15:

[0091] resumeCause is set to highPriorityAccess;

[0092] 4> Otherwise:

[0093] 5>resumeCause is set to mt-Access.

[0094] The configuration of MRBs for multicast reception in RRC_INACTIVE may be received by the UE from the gNB in ​​system information or in an RRCReconfiguration message and / or in an RRCRelease message.

[0095] In operation S204: when the UE is in the RRC_INACTIVE state and is performing multicast reception in a cell (eg, cell A), a cell reselection criterion is satisfied and the UE performs reselection to another cell (eg, cell B).

[0096] In operation S205: when performing cell reselection while receiving multicast reception in the RRC_INACTIVE state, the UE performs the following operations:

[0097] >UE checks whether the reselected cell supports multicast reception in RRC_INACTIVE state.

[0098] >> An indication of whether a cell supports or does not support multicast reception in the RRC_INACTIVE state may be included in system information sent by the reselected cell or by another cell (e.g., the cell the UE resides in) prior to reselection. If the reselected cell does not provide a configuration for multicast reception of a multicast session joined by a UE in RRC_INACTIVE, the UE may consider that the cell does not support multicast reception in RRC_INACTIVE.

[0099] >If the reselected cell supports multicast reception in RRC_INACTIVE state:

[0100] >>UE continues to receive multicast reception in RRC_INACTIVE state. If the MRB configuration for multicast reception in RRC_INACTIVE is different in the reselected cell, the UE applies the configuration of the reselected cell (in system information or in RRCReconfiguration message and / or in RRCRelease message).

[0101] Otherwise, if the reselected cell does not support multicast reception in RRC_INACTIVE state:

[0102] >>UE stops multicast reception in RRC_INACTIVE.

[0103] >>In an embodiment of the present disclosure, the UE releases the established multicast MRB; the UE releases the PDCP entity and the mrb-Identity of the established multicast MRB; the UE indicates to the upper layer the release of the user plane resources for the tmgi; the UE releases the SDAP entity.

[0104] >>In an embodiment of the present disclosure, the UE suspends all established multicast MRBs. The UE indicates PDCP suspension for all established multicast MRBs.

[0105] >>UE may initiate an RRC recovery procedure to enter the RRC_CONNECTED state.

[0106] In operation S205 (alternative scheme): when performing cell reselection while receiving multicast reception in the RRC_INACTIVE state, the UE performs the following operations:

[0107] >UE checks whether the reselected cell supports multicast reception in RRC_INACTIVE state.

[0108] >>An indication of whether a cell supports multicast reception in the RRC_INACTIVE state may be included in system information sent by the reselected cell or by another cell (e.g., the cell in which the UE is camped) prior to reselection. If the reselected cell does not provide a configuration for multicast reception of a multicast session joined by a UE in RRC_INACTIVE, the UE may consider that the cell does not support multicast reception in RRC_INACTIVE. >If the reselected cell supports multicast reception in the RRC_INACTIVE state:

[0109] >>For the multicast sessions that the UE is currently receiving and that are supported in the reselected cell, the UE continues to receive the multicast reception in the RRC_INACTIVE state.

[0110] >>For multicast sessions that the UE is currently receiving but are not supported in the reselected cell, the UE stops multicast reception under RRC_INACTIVE.

[0111] >>If the MRB configuration for multicast reception in RRC_INACTIVE is different in the reselected cell, the UE applies the configuration of the reselected cell (in system information or in RRCReconfiguration message and / or in RRCRelease message).

[0112] Otherwise, if the reselected cell does not support multicast reception in RRC_INACTIVE state:

[0113] >>UE stops multicast reception in RRC_INACTIVE.

[0114] >>In an embodiment of the present disclosure, the UE releases the established multicast MRB; the UE releases the PDCP entity and the mrb-Identity of the established multicast MRB; indicates to the upper layer the release of the user plane resources for the tmgi; and the UE releases the SDAP entity.

[0115] >>In an embodiment of the present disclosure, the UE suspends all established multicast MRBs. The UE indicates PDCP suspension for all established multicast MRBs.

[0116] >>UE may initiate an RRC recovery procedure to enter the RRC_CONNECTED state.

[0117] Method 3

[0118] Figure 3 A flow chart describing the operation of a UE according to an embodiment of the present disclosure is shown.

[0119] In operation S301: the UE is in RRC_CONNECTED state. The UE may utilize mechanisms such as PTP and / or PTM delivery to receive multicast communication services in the RRC_CONNECTED state. For a multicast session, the gNB provides the multicast MRB configuration to the UE via dedicated RRC signaling (e.g., RRCReconfiguration). If the UE has joined a multicast session and when the multicast session is activated, the gNB sends an RRCReconfiguration message with the relevant MBS configuration for the multicast session to the UE. The gNB may use the RRCReconfiguration message to configure or reconfigure the multicast MRB, for example, to add / release / modify the RLC entity of the MRB.

[0120] In operation S302: When the UE is in the RRC_CONNECTED state, the UE receives an RRCRelease message with a suspended configuration from the gNB. The UE enters the RRC_INACTIVE state upon receiving the RRCRelease message with the suspended configuration.

[0121] In operation S303: When in the RRC_INACTIVE state, the UE receives multicast reception for the multicast session that the UE has joined. If the multicast session is active when entering the RRC_INACTIVE state, the UE continues the multicast reception of the multicast session; and the UE does not need to suspend the MRB (or MRB with PTM) corresponding to the active multicast session when entering the RRC_INACTIVE state. If the multicast session is inactive when entering the RRC_INACTIVE state, the UE suspends the MRB corresponding to the multicast session when entering the RRC_INACTIVE state. When the UE receives a session activation notification in a paging message for the multicast session (i.e., the paging message for the activated multicast session includes TMGI), the UE resumes the MRB and starts multicast reception under RRC_INACTIVE. In an embodiment of the present disclosure, if the UE receives a paging message:

[0122] 1> if in RRC_INACTIVE and the UE has joined one or more MBS sessions indicated by the TMGI included in pagingGroupList; and

[0123] 2> If multicast reception in RRC_INACTIVE state is supported (or if the UE has configuration for multicast reception in RRC_INACTIVE and / or if the gNB has indicated in system information or RRC signaling (RRC Release or RRCReconfiguration) that it supports multicast reception in RRC_INACTIVE):

[0124] 3>UE initiates the process of receiving multicast reception under RRC_INACTIVE (e.g., recovering one or more MRBs, establishing / rebuilding PDCP / RLC entities for the recovered MRBs, etc.)

[0125] 2> Otherwise, if none of the ue-Identities included in any PagingRecord (if included in the Paging message) matches the UE identity assigned by the upper layer, then:

[0126] 3> Initiate the RRC connection recovery process, where resumeCause is set as follows:

[0127] 4> If the UE is configured by upper layers with access identity 1:

[0128] 5>resumeCause is set to mps-PriorityAccess;

[0129] 4> Otherwise, if the UE is configured by upper layers with access identity 2:

[0130] 5>resumeCause is set to mcs-PriorityAccess;

[0131] 4> Otherwise, if the UE is configured by upper layers with one or more access identifiers equal to 11-15:

[0132] resumeCause is set to highPriorityAccess;

[0133] 4> Otherwise:

[0134] 5>resumeCause is set to mt-Access.

[0135] The configuration of MRBs for multicast reception in RRC_INACTIVE may be received by the UE from the gNB in ​​system information or in an RRCReconfiguration message and / or in an RRCRelease message.

[0136] In operation S304: when the UE is in the RRC_INACTIVE state and is performing multicast reception in a cell (eg, cell A), a cell reselection criterion is satisfied and the UE performs reselection to another cell (eg, cell B).

[0137] In operation S305: when receiving multicast reception and cell reselection in the RRC_INACTIVE state, the UE performs the following operations:

[0138] >The UE checks whether the reselected cell belongs to the same RAN notification area as the cell where the UE last received RRCRelease or entered RRC_INACTIVE state (the RAN notification area is signaled in the system information or RRC signaling sent by the cell). The UE may additionally check whether the reselected cell supports multicast reception in RRC_INACTIVE state.

[0139] > if the reselected cell belongs to the same RAN notification area as the cell on which the UE last received RRCRelease or entered RRC_INACTIVE state, and if the reselected cell supports multicast reception in RRC_INACTIVE state; or

[0140] > If the reselected cell belongs to the same RAN notification area as the cell where the UE last received RRCRelease or entered RRC_INACTIVE state:

[0141] >>UE continues to receive multicast reception in RRC_INACTIVE state. If the MRB configuration for multicast reception in RRC_INACTIVE is different in the reselected cell, the UE applies the configuration of the reselected cell (in system information or in RRCReconfiguration message and / or in RRCRelease message).

[0142] Otherwise:

[0143] >>UE stops multicast reception in RRC_INACTIVE.

[0144] >>In an embodiment of the present disclosure, the UE releases the established multicast MRB; releases the PDCP entity and the mrb-Identity of the established multicast MRB; indicates to the upper layer the release of the user plane resources for tmgi; and releases the SDAP entity.

[0145] >>In an embodiment of the present disclosure, the UE suspends all established multicast MRBs. The UE indicates PDCP suspension for all established multicast MRBs.

[0146] >>The UE may initiate an RRC recovery procedure to enter the RRC_CONNECTED state. In operation S305 (alternative scheme): when receiving a multicast reception while reselecting a cell in the RRC_INACTIVE state, the UE performs the following operations:

[0147] >The UE checks whether the reselected cell belongs to the same RAN notification area as the cell where the UE last received RRCRelease or entered RRC_INACTIVE state (the RAN notification area is signaled in the system information or RRC signaling sent by the cell). The UE may additionally check whether the reselected cell supports multicast reception in RRC_INACTIVE state.

[0148] > if the reselected cell belongs to the same RAN notification area as the cell on which the UE last received RRCRelease or entered RRC_INACTIVE state, and if the reselected cell supports multicast reception in RRC_INACTIVE state; or

[0149] > If the reselected cell belongs to the same RAN notification area as the cell where the UE last received RRCRelease or entered RRC_INACTIVE state:

[0150] >>For the multicast sessions that the UE is currently receiving and that are supported in the reselected cell, the UE continues to receive the multicast reception in the RRC_INACTIVE state.

[0151] >>For multicast sessions that the UE is currently receiving but are not supported in the reselected cell, the UE stops multicast reception under RRC_INACTIVE.

[0152] >>If the MRB configuration for multicast reception in RRC_INACTIVE is different in the reselected cell, the UE applies the configuration of the reselected cell (in system information or in RRCReconfiguration message and / or in RRCRelease message).

[0153] Otherwise:

[0154] >>UE stops multicast reception in RRC_INACTIVE.

[0155] >>In an embodiment of the present disclosure, the UE releases the established multicast MRB; releases the PDCP entity and the mrb-Identity of the established multicast MRB; indicates to the upper layer the release of the user plane resources for tmgi; and releases the SDAP entity.

[0156] >>In an embodiment of the present disclosure, the UE suspends all established multicast MRBs. The UE indicates PDCP suspension for all established multicast MRBs.

[0157] >>UE may initiate an RRC recovery procedure to enter the RRC_CONNECTED state.

[0158] Method 4

[0159] Figure 4 A flow chart describing the operation of a UE according to an embodiment of the present disclosure is shown.

[0160] In operation S401: the UE is in RRC_CONNECTED state. The UE may utilize mechanisms such as PTP and / or PTM delivery to receive multicast communication services in the RRC_CONNECTED state. For a multicast session, the gNB provides the multicast MRB configuration to the UE via dedicated RRC signaling (e.g., RRCReconfiguration). If the UE has joined a multicast session and when the multicast session is activated, the gNB sends an RRCReconfiguration message with the relevant MBS configuration for the multicast session to the UE. The gNB may use the RRCReconfiguration message to configure or reconfigure the multicast MRB, for example, to add / release / modify the RLC entity of the MRB.

[0161] In operation S402: When the UE is in the RRC_CONNECTED state, the UE receives an RRCRelease message with a suspended configuration from the gNB. The UE enters the RRC_INACTIVE state upon receiving the RRCRelease message with the suspended configuration.

[0162] In operation S403: When in the RRC_INACTIVE state, the UE receives multicast reception for the multicast session that the UE has joined. If the multicast session is active when entering the RRC_INACTIVE state, the UE continues the multicast reception of the multicast session; and the UE does not need to suspend the MRB (or MRB with PTM) corresponding to the active multicast session when entering the RRC_INACTIVE state. If the multicast session is inactive when entering the RRC_INACTIVE state, the UE suspends the MRB corresponding to the multicast session when entering the RRC_INACTIVE state. When the UE receives a session activation notification in a paging message for the multicast session (i.e., the TMGI is included in the paging message for the activated multicast session), the UE resumes the MRB and starts multicast reception under RRC_INACTIVE. In an embodiment of the present disclosure, if the UE receives a paging message:

[0163] 1> if in RRC_INACTIVE and the UE has joined one or more MBS sessions indicated by the TMGI included in pagingGroupList; and

[0164] 2> If multicast reception in RRC_INACTIVE state is supported (or if the UE has configuration for multicast reception in RRC_INACTIVE and / or if the gNB has indicated in system information or RRC signaling (RRC Release or RRCReconfiguration) that it supports multicast reception in RRC_INACTIVE):

[0165] 3>UE initiates the process of receiving multicast reception under RRC_INACTIVE (e.g., recovering one or more MRBs, establishing / rebuilding PDCP / RLC entities for the recovered MRBs, etc.)

[0166] 2> Otherwise, if none of the ue-Identities included in any PagingRecord (if included in the Paging message) matches the UE identity assigned by the upper layer, then:

[0167] 3> Initiate the RRC connection recovery process, where resumeCause is set as follows:

[0168] 4> If the UE is configured by upper layers with access identity 1:

[0169] 5>resumeCause is set to mps-PriorityAccess;

[0170] 4> Otherwise, if the UE is configured by upper layers with access identity 2:

[0171] 5>resumeCause is set to mcs-PriorityAccess;

[0172] 4> Otherwise, if the UE is configured by upper layers with one or more access identifiers equal to 11-15:

[0173] resumeCause is set to highPriorityAccess;

[0174] 4> Otherwise:

[0175] 5>resumeCause is set to mt-Access.

[0176] The configuration of MRBs for multicast reception in RRC_INACTIVE may be received by the UE from the gNB in ​​system information or in an RRCReconfiguration message and / or in an RRCRelease message.

[0177] In operation S404: when the UE is in the RRC_INACTIVE state and is performing multicast reception in a cell (eg, cell A), a cell reselection criterion is satisfied and the UE performs reselection to another cell (eg, cell B).

[0178] In operation S405: when receiving multicast reception and cell reselection in the RRC_INACTIVE state, the UE performs the following operations:

[0179] >The UE checks whether the last received RRCRelease message (or system information or any other message received from the network) indicates that the UE may continue multicast reception in RRC_INACTIVE upon cell reselection if the UE is in the same RAN notification area and if the reselected cell belongs to the same RAN notification area as the cell in which the UE last received RRCRelease or entered RRC_INACTIVE state (the RAN notification area is signaled in system information or RRC signaling sent by the cell). The UE may additionally check whether the reselected cell supports multicast reception in RRC_INACTIVE state.

[0180] > if the last received RRCRelease message (or system information or any other message received from the network) indicates that the UE may continue multicast reception in RRC_INACTIVE upon cell reselection if it is within the same RAN notification area and the reselected cell belongs to the same RAN notification area as the cell on which the UE last received RRCRelease or entered RRC_INACTIVE state, and if the reselected cell supports multicast reception in RRC_INACTIVE state;

[0181] or

[0182] > The UE may continue multicast reception in RRC_INACTIVE upon cell reselection if the last received RRCRelease message (or system information or any other message received from the network) indicates that the UE is in the same RAN area and the reselected cell belongs to the same RAN notification area as the cell on which the UE last received RRCRelease or entered RRC_INACTIVE state:

[0183] >>UE continues to receive multicast reception in RRC_INACTIVE state. If the MRB configuration for multicast reception in RRC_INACTIVE is different in the reselected cell, the UE applies the configuration of the reselected cell (in system information or in RRCReconfiguration message and / or in RRCRelease message).

[0184] Otherwise:

[0185] >>UE stops multicast reception in RRC_INACTIVE.

[0186] >>In an embodiment of the present disclosure, the UE releases the established multicast MRB; releases the PDCP entity and the mrb-Identity of the established multicast MRB; indicates to the upper layer the release of the user plane resources for tmgi; and releases the SDAP entity.

[0187] >>In an embodiment of the present disclosure, the UE suspends all established multicast MRBs. The UE indicates PDCP suspension for all established multicast MRBs.

[0188] >>UE may initiate an RRC recovery procedure to enter the RRC_CONNECTED state.

[0189] In operation S405 (alternative scheme): when receiving a cell reselection while receiving multicast reception in the RRC_INACTIVE state, the UE performs the following operations:

[0190] >The UE checks whether the last received RRCRelease message (or system information or any other message received from the network) indicates that the UE may continue multicast reception in RRC_INACTIVE upon cell reselection if within the same RAN notification area and if the reselected cell belongs to the same RAN notification area as the cell where the UE last received RRCRelease or entered RRC_INACTIVE state (the RAN notification area is signaled in system information or RRC signaling sent by the cell). The UE may additionally check whether the reselected cell supports multicast reception in RRC_INACTIVE state.

[0191] > if the last received RRCRelease message (or system information or any other message received from the network) indicates that the UE may continue multicast reception in RRC_INACTIVE upon cell reselection if it is within the same RAN notification area and the reselected cell belongs to the same RAN notification area as the cell on which the UE last received RRCRelease or entered RRC_INACTIVE state, and if the reselected cell supports multicast reception in RRC_INACTIVE state;

[0192] or

[0193] > The UE may continue multicast reception in RRC_INACTIVE upon cell reselection if the last received RRCRelease message (or system information or any other message received from the network) indicates that the UE is in the same RAN notification area and the reselected cell belongs to the same RAN notification area as the cell on which the UE last received RRCRelease or entered RRC_INACTIVE state:

[0194] >>For the multicast sessions that the UE is currently receiving and that are supported in the reselected cell, the UE continues to receive the multicast reception in the RRC_INACTIVE state.

[0195] >>For multicast sessions that the UE is currently receiving but are not supported in the reselected cell, the UE stops multicast reception under RRC_INACTIVE.

[0196] >>If the MRB configuration for multicast reception in RRC_INACTIVE is different in the reselected cell, the UE applies the configuration of the reselected cell (in system information or in RRCReconfiguration message and / or in RRCRelease message).

[0197] Otherwise:

[0198] >>UE stops multicast reception in RRC_INACTIVE.

[0199] >>In an embodiment of the present disclosure, the UE releases the established multicast MRB; releases the PDCP entity and the mrb-Identity of the established multicast MRB; indicates to the upper layer the release of the user plane resources for tmgi; and releases the SDAP entity.

[0200] >>In an embodiment of the present disclosure, the UE suspends all established multicast MRBs. The UE indicates PDCP suspension for all established multicast MRBs.

[0201] >>UE may initiate an RRC recovery procedure to enter the RRC_CONNECTED state.

[0202] Method 5

[0203] Figure 5 A flow chart describing the operation of a UE according to an embodiment of the present disclosure is shown.

[0204] In operation S501: the UE is in RRC_CONNECTED state. The UE may utilize mechanisms such as PTP and / or PTM delivery to receive multicast communication services in the RRC_CONNECTED state. For a multicast session, the gNB provides the multicast MRB configuration to the UE via dedicated RRC signaling (e.g., RRCReconfiguration). If the UE has joined a multicast session and when the multicast session is activated, the gNB sends an RRCReconfiguration message with the relevant MBS configuration for the multicast session to the UE. The gNB may use the RRCReconfiguration message to configure or reconfigure the multicast MRB, for example, to add / release / modify the RLC entity of the MRB.

[0205] In operation S502: When the UE is in the RRC_CONNECTED state, the UE receives an RRCRelease message with a suspended configuration from the gNB. The UE enters the RRC_INACTIVE state upon receiving the RRCRelease message with the suspended configuration. The RRCRelease message may include a list of cells in which the UE may receive multicast reception in the RRC_INACTIVE state using the configuration received from the PCell or any cell belonging to the list.

[0206] In operation S503: When in the RRC_INACTIVE state, the UE receives multicast reception for the multicast session that the UE has joined. If the multicast session is active when entering the RRC_INACTIVE state, the UE continues the multicast reception of the multicast session; and the UE does not need to suspend the MRB (or MRB with PTM) corresponding to the active multicast session when entering the RRC_INACTIVE state. If the multicast session is inactive when entering the RRC_INACTIVE state, the UE suspends the MRB corresponding to the multicast session when entering the RRC_INACTIVE state. When the UE receives a session activation notification in a paging message for the multicast session (i.e., the TMGI is included in the paging message for the activated multicast session), the UE resumes the MRB and starts multicast reception under RRC_INACTIVE. In an embodiment of the present disclosure, if the UE receives a paging message:

[0207] 1> if in RRC_INACTIVE and the UE has joined one or more MBS sessions indicated by the TMGI included in pagingGroupList; and

[0208] 2> If multicast reception in RRC_INACTIVE state is supported (or if the UE has configuration for multicast reception in RRC_INACTIVE and / or if the gNB has indicated in system information or RRC signaling (RRC Release or RRCReconfiguration) that it supports multicast reception in RRC_INACTIVE):

[0209] 3>UE initiates the process of receiving multicast reception under RRC_INACTIVE (e.g., recovering one or more MRBs, establishing / rebuilding PDCP / RLC entities for the recovered MRBs, etc.)

[0210] 2> Otherwise, if none of the ue-Identities included in any PagingRecord (if included in the Paging message) matches the UE identity assigned by the upper layer, then:

[0211] 3> Initiate the RRC connection recovery process, where resumeCause is set as follows:

[0212] 4> If the UE is configured by upper layers with access identity 1:

[0213] 5>resumeCause is set to mps-PriorityAccess;

[0214] 4> Otherwise, if the UE is configured by upper layers with access identity 2:

[0215] 5>resumeCause is set to mcs-PriorityAccess;

[0216] 4> Otherwise, if the UE is configured by upper layers with one or more access identifiers equal to 11-15:

[0217] resumeCause is set to highPriorityAccess;

[0218] 4> Otherwise:

[0219] 5>resumeCause is set to mt-Access.

[0220] The configuration of MRBs for multicast reception in RRC_INACTIVE may be received by the UE from the gNB in ​​system information or in an RRCReconfiguration message and / or in an RRCRelease message.

[0221] In operation S504: when the UE is in the RRC_INACTIVE state and is performing multicast reception in a cell (eg, cell A), a cell reselection criterion is satisfied and the UE performs reselection to another cell (eg, cell B).

[0222] In operation S505: when receiving multicast reception and cell reselection in the RRC_INACTIVE state, the UE performs the following operations:

[0223] >The UE checks whether the reselected cell belongs to the list of cells indicated in the last received RRCRelease message. The UE may additionally check whether the reselected cell supports multicast reception in the RRC_INACTIVE state.

[0224] > if the reselected cell belongs to the list of cells indicated in the last received RRCRelease message and if the reselected cell supports multicast reception in RRC_INACTIVE state; or

[0225] >If the reselected cell belongs to the list of cells indicated in the last received RRCRelease message:

[0226] >>UE continues to receive multicast reception in RRC_INACTIVE state. If the MRB configuration for multicast reception in RRC_INACTIVE is different in the reselected cell, the UE applies the configuration of the reselected cell (in system information or in RRCReconfiguration message and / or in RRCRelease message).

[0227] Otherwise:

[0228] >>UE stops multicast reception in RRC_INACTIVE.

[0229] >>In an embodiment of the present disclosure, the UE releases the established multicast MRB; releases the PDCP entity and the mrb-Identity of the established multicast MRB; indicates to the upper layer the release of the user plane resources for tmgi; and releases the SDAP entity.

[0230] >>In an embodiment of the present disclosure, the UE suspends all established multicast MRBs. The UE indicates PDCP suspension for all established multicast MRBs.

[0231] >>UE may initiate an RRC recovery procedure to enter the RRC_CONNECTED state.

[0232] In operation S505 (alternative scheme): when performing cell reselection while receiving multicast reception in the RRC_INACTIVE state, the UE performs the following operations:

[0233] >The UE checks whether the reselected cell belongs to the list of cells indicated in the last received RRCRelease message. The UE may additionally check whether the reselected cell supports multicast reception in RRC_INACTIVE state.

[0234] > if the reselected cell belongs to the list of cells indicated in the last received RRCRelease message and if the reselected cell supports multicast reception in RRC_INACTIVE state; or

[0235] >If the reselected cell belongs to the list of cells indicated in the last received RRCRelease message:

[0236] >>For the multicast sessions that the UE is currently receiving and that are supported in the reselected cell, the UE continues to receive the multicast reception in the RRC_INACTIVE state.

[0237] >>For multicast sessions that the UE is currently receiving but are not supported in the reselected cell, the UE stops multicast reception under RRC_INACTIVE.

[0238] >>If the MRB configuration for multicast reception in RRC_INACTIVE is different in the reselected cell, the UE applies the configuration of the reselected cell (in system information or in RRCReconfiguration message and / or in RRCRelease message).

[0239] Otherwise:

[0240] >>UE stops multicast reception in RRC_INACTIVE.

[0241] >>In an embodiment of the present disclosure, the UE releases the established multicast MRB; releases the PDCP entity and the mrb-Identity of the established multicast MRB; indicates to the upper layer the release of the user plane resources for tmgi; and releases the SDAP entity.

[0242] >>In an embodiment of the present disclosure, the UE suspends all established multicast MRBs. The UE indicates PDCP suspension for all established multicast MRBs.

[0243] >>UE may initiate an RRC recovery procedure to enter the RRC_CONNECTED state.

[0244] Method 6

[0245] Figure 6 A flow chart describing the operation of a UE according to an embodiment of the present disclosure is shown.

[0246] In operation S601: the UE is in RRC_CONNECTED state. The UE may utilize mechanisms such as PTP and / or PTM delivery to receive multicast communication services in the RRC_CONNECTED state. For a multicast session, the gNB provides the multicast MRB configuration to the UE via dedicated RRC signaling (e.g., RRCReconfiguration). If the UE has joined a multicast session and when the multicast session is activated, the gNB sends an RRCReconfiguration message with the relevant MBS configuration for the multicast session to the UE. The gNB may use the RRCReconfiguration message to configure or reconfigure the multicast MRB, for example, to add / release / modify the RLC entity of the MRB.

[0247] In operation S602: When the UE is in the RRC_CONNECTED state, the UE receives an RRCRelease message with a suspended configuration from the gNB. The UE enters the RRC_INACTIVE state upon receiving the RRCRelease message with the suspended configuration. The RRCRelease message may indicate whether the UE may continue multicast reception under RRC_INACTIVE upon cell reselection.

[0248] In operation S603: When in the RRC_INACTIVE state, the UE receives multicast reception for the multicast session that the UE has joined. If the multicast session is active when entering the RRC_INACTIVE state, the UE continues the multicast reception of the multicast session; and the UE does not need to suspend the MRB (or MRB with PTM) corresponding to the active multicast session when entering the RRC_INACTIVE state. If the multicast session is inactive when entering the RRC_INACTIVE state, the UE suspends the MRB corresponding to the multicast session when entering the RRC_INACTIVE state. When the UE receives a session activation notification in a paging message for the multicast session (i.e., the TMGI is included in the paging message for the activated multicast session), the UE resumes the MRB and starts multicast reception under RRC_INACTIVE. In an embodiment of the present disclosure, if the UE receives a paging message:

[0249] 1> if in RRC_INACTIVE and the UE has joined one or more MBS sessions indicated by the TMGI included in pagingGroupList; and

[0250] 2> If multicast reception in RRC_INACTIVE state is supported (or if the UE has configuration for multicast reception in RRC_INACTIVE and / or if the gNB has indicated in system information or RRC signaling (RRC Release or RRCReconfiguration) that it supports multicast reception in RRC_INACTIVE):

[0251] 3>UE initiates the process of receiving multicast reception under RRC_INACTIVE (e.g., recovering one or more MRBs, establishing / rebuilding PDCP / RLC entities for the recovered MRBs, etc.)

[0252] 2> Otherwise, if none of the ue-Identities included in any PagingRecord (if included in the Paging message) matches the UE identity assigned by the upper layer, then:

[0253] 3> Initiate the RRC connection recovery process, where resumeCause is set as follows:

[0254] 4> If the UE is configured by upper layers with access identity 1:

[0255] 5>resumeCause is set to mps-PriorityAccess;

[0256] 4> Otherwise, if the UE is configured by upper layers with access identity 2:

[0257] 5>resumeCause is set to mcs-PriorityAccess;

[0258] 4> Otherwise, if the UE is configured by upper layers with one or more access identifiers equal to 11-15:

[0259] resumeCause is set to highPriorityAccess;

[0260] 4> Otherwise:

[0261] 5>resumeCause is set to mt-Access.

[0262] The configuration of MRBs for multicast reception in RRC_INACTIVE may be received by the UE from the gNB in ​​system information or in an RRCReconfiguration message and / or in an RRCRelease message.

[0263] In operation S604: when the UE is in the RRC_INACTIVE state and is performing multicast reception in a cell (eg, cell A), a cell reselection criterion is satisfied and the UE performs reselection to another cell (eg, cell B).

[0264] In operation S605: when receiving multicast reception and cell reselection in the RRC_INACTIVE state, the UE performs the following operations:

[0265] >The UE checks whether the last received RRCRelease message (or in the system information or RRC message sent by the cell) indicates that the UE can continue multicast reception in RRC_INACTIVE when the cell is reselected. The UE can additionally check whether the reselected cell supports multicast reception in RRC_INACTIVE state.

[0266] > if the last received RRCRelease (or in system information or RRC message sent by the cell) indicates that if the reselected cell supports multicast reception in RRC_INACTIVE state, the UE may continue multicast reception in RRC_INACTIVE upon cell reselection; or

[0267] If the last received RRCRelease (or in system information or in an RRC message sent by the cell) indicates that the UE can continue multicast reception in RRC_INACTIVE upon cell reselection:

[0268] >>UE continues to receive multicast reception in RRC_INACTIVE state. If the MRB configuration for multicast reception in RRC_INACTIVE is different in the reselected cell, the UE applies the configuration of the reselected cell (in system information or in RRCReconfiguration message and / or in RRCRelease message).

[0269] Otherwise:

[0270] >>UE stops multicast reception in RRC_INACTIVE.

[0271] >>In an embodiment of the present disclosure, the UE releases the established multicast MRB; releases the PDCP entity and the mrb-Identity of the established multicast MRB; indicates to the upper layer the release of the user plane resources for tmgi; and releases the SDAP entity.

[0272] >>In an embodiment of the present disclosure, the UE suspends all established multicast MRBs. The UE indicates PDCP suspension for all established multicast MRBs.

[0273] >>UE may initiate an RRC recovery procedure to enter the RRC_CONNECTED state.

[0274] In operation S605 (alternative scheme): when receiving a cell reselection while receiving multicast reception in the RRC_INACTIVE state, the UE performs the following operations:

[0275] >The UE checks whether the last received RRCRelease message (or in the system information or RRC message sent by the cell) indicates that the UE can continue multicast reception in RRC_INACTIVE when the cell is reselected. The UE can additionally check whether the reselected cell supports multicast reception in RRC_INACTIVE state.

[0276] > if the last received RRCRelease (or in system information or RRC message sent by the cell) indicates that if the reselected cell supports multicast reception in RRC_INACTIVE state, the UE may continue multicast reception in RRC_INACTIVE upon cell reselection; or

[0277] If the last received RRCRelease (or in system information or in an RRC message sent by the cell) indicates that the UE can continue multicast reception in RRC_INACTIVE upon cell reselection:

[0278] >>For the multicast sessions that the UE is currently receiving and that are supported in the reselected cell, the UE continues to receive the multicast reception in the RRC_INACTIVE state.

[0279] >>For multicast sessions that the UE is currently receiving but are not supported in the reselected cell, the UE stops multicast reception under RRC_INACTIVE.

[0280] >>If the MRB configuration for multicast reception in RRC_INACTIVE is different in the reselected cell, the UE applies the configuration of the reselected cell (in system information or in RRCReconfiguration message and / or in RRCRelease message).

[0281] Otherwise:

[0282] >>UE stops multicast reception in RRC_INACTIVE.

[0283] >>In an embodiment of the present disclosure, the UE releases the established multicast MRB; releases the PDCP entity and the mrb-Identity of the established multicast MRB; indicates to the upper layer the release of the user plane resources for tmgi; and releases the SDAP entity.

[0284] >>In an embodiment of the present disclosure, the UE suspends all established multicast MRBs. The UE indicates PDCP suspension for all established multicast MRBs.

[0285] >>UE may initiate an RRC recovery procedure to enter the RRC_CONNECTED state.

[0286] Method 7

[0287] Figure 7 A flow chart describing the operation of a UE according to an embodiment of the present disclosure is shown.

[0288] In operation S701: the UE is in RRC_CONNECTED state. The UE may utilize mechanisms such as PTP and / or PTM delivery to receive multicast communication services in the RRC_CONNECTED state. For a multicast session, the gNB provides the multicast MRB configuration to the UE via dedicated RRC signaling (e.g., RRCReconfiguration). If the UE has joined a multicast session and when the multicast session is activated, the gNB sends an RRCReconfiguration message with the relevant MBS configuration for the multicast session to the UE. The gNB may use the RRCReconfiguration message to configure or reconfigure the multicast MRB, for example, to add / release / modify the RLC entity of the MRB.

[0289] In operation S702: When the UE is in the RRC_CONNECTED state, the UE receives an RRCRelease message with a suspended configuration from the gNB. The UE enters the RRC_INACTIVE state upon receiving the RRCRelease message with the suspended configuration. The RRCRelease message may indicate whether the UE may continue multicast reception under RRC_INACTIVE upon cell reselection.

[0290] In operation S703: When in the RRC_INACTIVE state, the UE receives multicast reception for the multicast session that the UE has joined. If the multicast session is active when entering the RRC_INACTIVE state, the UE continues the multicast reception of the multicast session; and the UE does not need to suspend the MRB (or MRB with PTM) corresponding to the active multicast session when entering the RRC_INACTIVE state. If the multicast session is inactive when entering the RRC_INACTIVE state, the UE suspends the MRB corresponding to the multicast session when entering the RRC_INACTIVE state. When the UE receives a session activation notification in a paging message for the multicast session (i.e., the paging message for the activated multicast session includes TMGI), the UE restores the MRB and starts multicast reception under RRC_INACTIVE. In an embodiment of the present disclosure, if the UE receives a paging message:

[0291] 1> if in RRC_INACTIVE and the UE has joined one or more MBS sessions indicated by the TMGI included in pagingGroupList; and

[0292] 2> If multicast reception in RRC_INACTIVE state is supported (or if the UE has configuration for multicast reception in RRC_INACTIVE and / or if the gNB has indicated in system information or RRC signaling (RRC Release or RRCReconfiguration) that it supports multicast reception in RRC_INACTIVE):

[0293] 3>UE initiates the process of receiving multicast reception under RRC_INACTIVE (e.g., recovering one or more MRBs, establishing / rebuilding PDCP / RLC entities for the recovered MRBs, etc.)

[0294] 2>2> Otherwise, if none of the ue-Identities included in any PagingRecord (if included in the Paging message) matches the UE identity assigned by the upper layer, then:

[0296] 3> Initiate the RRC connection recovery process, where resumeCause is set as follows:

[0297] 4> If the UE is configured by upper layers with access identity 1:

[0298] 5>resumeCause is set to mps-PriorityAccess;

[0299] 4> Otherwise, if the UE is configured by upper layers with access identity 2:

[0300] 5>resumeCause is set to mcs-PriorityAccess;

[0301] 4> Otherwise, if the UE is configured by upper layers with one or more access identifiers equal to 11-15:

[0302] resumeCause is set to highPriorityAccess;

[0303] 4> Otherwise:

[0304] 4>resumeCause is set to mt-Access.

[0305] The configuration of MRBs for multicast reception in RRC_INACTIVE may be received by the UE from the gNB in ​​system information or in an RRCReconfiguration message and / or in an RRCRelease message.

[0306] In operation S704: when the UE is in the RRC_INACTIVE state and is performing multicast reception in a cell (eg, cell A), a cell reselection criterion is satisfied and the UE performs reselection to another cell (eg, cell B).

[0307] In operation S705: when a cell is reselected while receiving multicast reception in the RRC_INACTIVE state, the UE performs the following operations:

[0308] >The UE checks whether the reselected cell belongs to the same AREA (AREA ID) as the AREA (AREA ID) of the PCell in which the UE last received RRCRelease or entered RRC_INACTIVE state. The UE may additionally check whether the reselected cell supports multicast reception in RRC_INACTIVE state. The AREA ID of the cell may be sent / received by the gNB / UE in the system information. The AREA ID of the cell may be sent / received by the gNB / UE in an RRC message or a NAS message. In an embodiment, the AREA ID may be a tracking area ID or a RAN notification area ID or a system information area ID or a new ID.

[0309] > if the reselected cell belongs to the same AREA (AREA ID) as the PCell where the UE last received RRCRelease or entered RRC_INACTIVE state, and if the reselected cell supports multicast reception in RRC_INACTIVE state; or

[0310] >If the reselected cell belongs to the same AREA (AREA ID) as the PCell where the UE last received RRCRelease or entered RRC_INACTIVE state:

[0311] >>UE continues to receive multicast reception in RRC_INACTIVE state. If the MRB configuration for multicast reception in RRC_INACTIVE is different in the reselected cell, the UE applies the configuration of the reselected cell (in system information or in RRCReconfiguration message and / or in RRCRelease message).

[0312] Otherwise:

[0313] >>UE stops multicast reception in RRC_INACTIVE.

[0314] >>In an embodiment of the present disclosure, the UE releases the established multicast MRB; releases the PDCP entity and the mrb-Identity of the established multicast MRB; indicates to the upper layer the release of the user plane resources for tmgi; and releases the SDAP entity.

[0315] >>In an embodiment of the present disclosure, the UE suspends all established multicast MRBs. The UE indicates PDCP suspension for all established multicast MRBs.

[0316] >>UE may initiate an RRC recovery procedure to enter the RRC_CONNECTED state.

[0317] In operation S705 (alternative scheme): when receiving a cell reselection while receiving multicast reception in the RRC_INACTIVE state, the UE performs the following operations:

[0318] >The UE checks whether the reselected cell belongs to the same AREA (AREA ID) as the AREA (AREA ID) of the PCell in which the UE last received RRCRelease or entered RRC_INACTIVE state. The UE may additionally check whether the reselected cell supports multicast reception in RRC_INACTIVE state. The AREA ID of the cell may be sent / received by the gNB / UE in the system information. The AREA ID of the cell may be sent / received by the gNB / UE in an RRC message or a NAS message. In an embodiment, the AREA ID may be a tracking area ID or a RAN notification area ID or a system information area ID or a new ID.

[0319] > if the reselected cell belongs to the same AREA (AREA ID) as the AREA (AREA ID) of the PCell where the UE last received RRCRelease or entered the RRC_INACTIVE state, and if the reselected cell supports multicast reception in the RRC_INACTIVE state; or

[0320] >If the reselected cell belongs to the same AREA (AREA ID) as the PCell where the UE last received RRCRelease or entered RRC_INACTIVE state:

[0321] >>For the multicast sessions that the UE is currently receiving and that are supported in the reselected cell, the UE continues to receive the multicast reception in the RRC_INACTIVE state.

[0322] >>For multicast sessions that the UE is currently receiving but are not supported in the reselected cell, the UE stops multicast reception under RRC_INACTIVE.

[0323] >>If the MRB configuration for multicast reception in RRC_INACTIVE is different in the reselected cell, the UE applies the configuration of the reselected cell (in system information or in RRCReconfiguration message and / or in RRCRelease message).

[0324] Otherwise:

[0325] >>UE stops multicast reception in RRC_INACTIVE.

[0326] >>In an embodiment of the present disclosure, the UE releases the established multicast MRB; releases the PDCP entity and the mrb-Identity of the established multicast MRB; indicates to the upper layer the release of the user plane resources for tmgi; and releases the SDAP entity.

[0327] >>In an embodiment of the present disclosure, the UE suspends all established multicast MRBs. The UE indicates PDCP suspension for all established multicast MRBs.

[0328] >>UE may initiate an RRC recovery procedure to enter the RRC_CONNECTED state.

[0329] Figure 8 The structure of a UE according to an embodiment of the present disclosure is shown.

[0330] Reference Figure 8 , UE 800 may include a processor 820, a memory 830, and a transceiver 810. However, the elements of UE 800 are not limited thereto. For example, UE 800 may include more or fewer elements than the above elements. Processor 820, memory 830, and transceiver 810 may be implemented as a single chip.

[0331] The processor 820 may include one or more processors. In this case, the one or more processors may include a general-purpose processor such as a CPU, AP, or DSP, a graphics processor such as a GPU or VPU, or an AI processor such as an NPU. For example, when the one or more processors are AI processors, they may be designed as a hardware structure dedicated to processing a specific AI model.

[0332] The processor 820 may control a series of processes so that the UE 800 operates according to the embodiment. For example, the processor 820 may receive a control signal and a data signal through the transceiver 810, and process the received control signal and data signal. The processor 820 may send the processed control signal and data signal through the transceiver 810. In addition, the processor 820 may control the input data obtained from the received control signal and the data signal to be processed according to the predefined operating rules or AI models stored in the memory 830. The processor 820 may write data to the memory 830 and read data from the memory 830, may perform the functions of the protocol stack required by the communication standard, and may include at least one processor. A portion of the transceiver 810 or the processor 820 may be referred to as a CP.

[0333] The memory 830 may store programs and data required for operating the UE 800, may store control information or data included in a signal obtained by the UE 800, and may store control information or data included in a signal obtained by the UE 800. The memory 830 may include a storage medium such as a ROM, a RAM, a hard disk, a CD-ROM, a DVD, or a combination thereof. The memory 830 may not be provided separately, but may be included in the processor 820. The memory 830 may include a volatile memory, a nonvolatile memory, or a combination of a volatile memory and a nonvolatile memory, and may provide stored data according to a request of the processor 820.

[0334] The transceiver 810 may refer to a transmitter and a receiver, and the transceiver 810 of the UE 800 may send a signal to a BS or a network entity or receive a signal from a BS or a network. The signal sent or received may include control information and data. To this end, the transceiver 810 may include an RF transmitter for up-converting and amplifying the frequency of the transmitted signal, and an RF receiver for low-noise amplification and down-converting the frequency of the received signal. However, this is only an example of the transceiver 810, and the elements of the transceiver 810 are not limited to the RF transmitter and the RF receiver. The transceiver 810 may receive a signal through a wireless channel and output the signal to the processor 820, and may send a signal output from the processor 820 through a wireless channel.

[0335] The processor 820 may be configured to: perform multicast reception in a radio resource control (RRC) inactive state on a first cell; select a second cell for multicast reception if a cell selection criterion is met; identify whether the selected second cell supports multicast reception in an RRC inactive state; and continuously perform multicast reception in an RRC inactive state on the selected second cell based on the selected second cell supporting multicast reception in an RRC inactive state.

[0336] Fig. 9 The structure of a BS according to an embodiment of the present disclosure is shown.

[0337] Reference Fig. 9 , BS 900 may include a transceiver 910, a processor 920, and a memory 930, which may operate together according to a communication method of BS 900. However, the elements of BS 900 are not limited thereto. For example, BS 900 may include more or less elements than the above elements. Transceiver 910, processor 920, and memory 930 may be implemented as a single chip, and processor 920 may include one or more processors.

[0338] The receiver and transmitter of the BS 900 are collectively referred to as a transceiver 910, which can send or receive signals (i.e., control information and data) to or from a UE or a network entity. To this end, the transceiver 910 may include an RF transmitter for up-converting and amplifying the frequency of the transmitted signal, and an RF receiver for low-noise amplification and down-converting the frequency of the received signal. However, this is merely an example of the transceiver 910, and the elements of the transceiver 910 are not limited to the RF transmitter and the RF receiver.

[0339] The transceiver 910 may perform a function for transmitting and receiving signals via a wireless channel. For example, the transceiver 910 may receive a signal through a wireless channel and output the signal to the processor 920, and may transmit a signal output from the processor 920 through a wireless channel.

[0340] The memory 930 may store programs and data required for operating the BS 900, and may store control information or data included in a signal obtained by the BS. The memory 930 may include a storage medium such as a read-only memory (ROM), a random access memory (RAM), a hard disk, a compact disk (CD)-ROM, or a digital versatile disk (DVD), or a combination thereof. The memory 930 may not be provided separately, but may be included in the processor 920. The memory 930 may include a volatile memory, a nonvolatile memory, or a combination of a volatile memory and a nonvolatile memory, and may provide stored data according to a request of the processor 920.

[0341] The processor 920 may control a series of processes so that the BS 900 operates according to the embodiment. For example, the processor 920 may receive a control signal and a data signal through the transceiver 910, and process the received control signal and data signal. The processor 920 may send the processed control signal and data signal through the transceiver 910, may write data to the memory 930 and read data from the memory 930, and may perform the functions of the protocol stack required by the communication standard. To this end, the processor 920 may include at least one processor or microprocessor. A part of the transceiver 910 or the processor 920 may be referred to as a communication processor (CP).

[0342] The processor 920 may include one or more processors, such as a central processing unit (CPU), an application processor (AP), a digital signal processor (DSP), a graphics processor such as a graphics processing unit (GPU) or a visual processing unit (VPU), or an AI processor such as a neural processing unit (NPU). For example, when one or more processors are AI processors, they may be designed as a hardware structure dedicated to processing a specific AI model.

[0343] Fig.10 A flowchart of a method performed by a UE according to an embodiment of the present disclosure is shown.

[0344] In operation S1010 , the method 1000 includes performing multicast reception in a radio resource control (RRC) inactive state on a first cell.

[0345] In operation S1020 , the method 1000 includes: in a case where the cell selection criterion is satisfied, performing cell selection on the second cell.

[0346] In operation S1030 , the method 1000 includes identifying whether the second cell supports multicast reception in an RRC inactive state.

[0347] In operation S1040 , the method 1000 includes: based on the second cell supporting the multicast reception in the RRC inactive state, continuing the multicast reception in the RRC inactive state on the second cell.

[0348] The method 1000 may include receiving, on the second cell, system information including information indicating whether the second cell supports multicast reception in an RRC inactive state.

[0349] Method 1000 may include: when a multicast / broadcast service radio bearer (MRB) configuration for multicast reception in an RRC inactive state on a second cell is different from the MRB configuration for multicast reception in an RRC inactive state on a first cell, continuing multicast reception in an RRC inactive state based on the MRB configuration on the second cell.

[0350] The method 1000 may include, if the second cell supports multicast reception in the RRC inactive state, continuing the multicast reception in the RRC inactive state for a multicast session supported in the second cell.

[0351] The method 1000 may include, if the second cell supports multicast reception in the RRC inactive state, stopping multicast reception in the RRC inactive state for a multicast session not supported in the second cell.

[0352] The method 1000 may include: if the second cell does not support multicast reception in the RRC inactive state, stopping the multicast reception in the RRC inactive state.

[0353] The method 1000 may include releasing one or more established multicast / broadcast service radio bearers (MRBs) if the second cell does not support multicast reception in an RRC inactive state.

[0354] The method 1000 may include suspending one or more established multicast / broadcast service radio bearers (MRBs) if the second cell does not support multicast reception in an RRC inactive state.

[0355] According to aspects of the present disclosure, a method performed by a user equipment (UE) in a wireless communication system is provided. The method may include performing multicast reception in a radio resource control (RRC) inactive state on a first cell. The method may include: performing cell selection on a second cell when a cell selection criterion is met. The method may include identifying whether the second cell supports multicast reception in an RRC inactive state. The method may include: continuing multicast reception in an RRC inactive state on the second cell based on the second cell supporting multicast reception in an RRC inactive state.

[0356] According to an embodiment, the method may include receiving system information on the second cell, the system information including information indicating whether the second cell supports multicast reception in an RRC inactive state.

[0357] According to an embodiment, the method may include: when a multicast / broadcast service radio bearer (MRB) configuration for multicast reception in the RRC inactive state on the second cell is different from the MRB configuration for multicast reception in the RRC inactive state on the first cell, continuing the multicast reception in the RRC inactive state based on the MRB configuration on the second cell.

[0358] According to an embodiment, the method may include: if the second cell supports multicast reception in the RRC inactive state, continuing the multicast reception in the RRC inactive state for the multicast session supported in the second cell.

[0359] According to an embodiment, the method may include: if the second cell supports multicast reception in the RRC inactive state, stopping multicast reception in the RRC inactive state for a multicast session not supported in the second cell.

[0360] According to an embodiment, the method may include: if the second cell does not support multicast reception in the RRC inactive state, stopping the multicast reception in the RRC inactive state.

[0361] According to an embodiment, the method may include: if the second cell does not support multicast reception in the RRC inactive state, releasing one or more established multicast / broadcast service radio bearers (MRBs).

[0362] According to an embodiment, the method may include: if the second cell does not support multicast reception in the RRC inactive state, suspending one or more established multicast / broadcast service radio bearers (MRBs).

[0363] According to aspects of the present disclosure, a user equipment (UE) is provided, the UE comprising a transceiver and at least one processor. The at least one processor may be configured to perform multicast reception in a radio resource control (RRC) inactive state on a first cell. The at least one processor may be configured to perform cell selection on a second cell if a cell selection criterion is met. The at least one processor may be configured to identify whether the second cell supports multicast reception in an RRC inactive state. The at least one processor may be configured to continue multicast reception in an RRC inactive state on the second cell based on the second cell supporting multicast reception in an RRC inactive state.

[0364] According to an embodiment, at least one processor may be configured to, when a multicast / broadcast service radio bearer (MRB) configuration for multicast reception in the RRC inactive state on the second cell is different from the MRB configuration for multicast reception in the RRC inactive state on the first cell, continue multicast reception in the RRC inactive state based on the MRB configuration on the second cell.

[0365] According to an embodiment, at least one processor may be configured to, in a case where the second cell supports multicast reception in the RRC inactive state, continue multicast reception in the RRC inactive state for a multicast session supported in the second cell.

[0366] According to an embodiment, at least one processor may be configured to, if the selected second cell supports multicast reception in the RRC inactive state, stop multicast reception in the RRC inactive state for a multicast session not supported in the second cell.

[0367] According to an embodiment, at least one processor may be configured to: stop multicast reception in the RRC inactive state if the second cell does not support multicast reception in the RRC inactive state.

[0368] According to an embodiment, at least one processor may be configured to release one or more established multicast / broadcast service radio bearers (MRBs) if the second cell does not support multicast reception in an RRC inactive state.

[0369] According to an embodiment, the at least one processor may be configured to: suspend one or more established MRBs if the selected second cell does not support multicast reception in the RRC inactive state.

[0370] According to an embodiment, at least one processor may be configured to: receive system information on the selected second cell, the system information including information indicating whether the selected second cell supports multicast reception in an RRC inactive state.

[0371] In an embodiment of the present disclosure, the gNB may indicate in an RRC signaling (e.g., RRCRelease) message that the UE applies a method (in methods 1 to 7 or in a subset of methods 1 to 7) when receiving multicast reception under RRC_INACTIVE at the time of cell reselection.

[0372] In an embodiment of the present disclosure, the UE may prioritize cell reselection for a cell supporting multicast reception under RRC_INACTIVE among available suitable cells on a carrier frequency (or cells satisfying the reselection criteria as specified in TS38.304). In an embodiment of the present disclosure, the UE may prioritize cell reselection for a carrier frequency supporting multicast reception under RRC_INACTIVE among available suitable cells on a carrier frequency (or cells satisfying the reselection criteria as specified in TS 38.304). In an embodiment of the present disclosure, the UE may prioritize cell reselection for a cell supporting multicast reception under RRC_INACTIVE among available suitable cells on a carrier frequency (or cells satisfying the reselection criteria as specified in TS38.304). In an embodiment of the present disclosure, the UE may prioritize cell reselection for a cell supporting multicast reception under RRC_INACTIVE for a multicast session of interest to the UE among available suitable cells on a carrier frequency (or cells satisfying the reselection criteria as specified in TS 38.304).

[0373] It should be understood that the embodiments described herein should be considered only in a descriptive sense, and not for limiting purposes. The description of the features or aspects within each embodiment should be considered to be applicable to other similar features or aspects in other embodiments. The aforementioned embodiments may be combined when necessary. For example, a base station and a UE may operate according to a combination of parts of the embodiments.

Claims

1. A method performed by a user equipment UE in a wireless communication system, the method comprising: Performing multicast reception in a radio resource control (RRC) inactive state on the first cell; When the cell selection criterion is met, performing cell selection on the second cell; identifying whether the second cell supports multicast reception in the RRC inactive state; and Based on the second cell supporting the multicast reception in the RRC inactive state, the multicast reception in the RRC inactive state is continued on the second cell.

2. The method according to claim 1, further comprising: System information is received on the second cell, the system information including information indicating whether the second cell supports multicast reception in the RRC inactive state.

3. The method according to claim 1, wherein: Continuing the multicast reception in the RRC inactive state on the second cell includes: When the multicast / broadcast service radio bearer MRB configuration for multicast reception in the RRC inactive state on the second cell is different from the MRB configuration for multicast reception in the RRC inactive state on the first cell, multicast reception in the RRC inactive state is continued based on the MRB configuration on the second cell.

4. The method according to claim 1, wherein: Continuing the multicast reception in the RRC inactive state on the second cell includes: In a case where the second cell supports multicast reception in the RRC inactive state, the multicast reception in the RRC inactive state is continued for the multicast session supported in the second cell.

5. The method according to claim 1, further comprising: If the second cell supports multicast reception in the RRC inactive state, multicast reception in the RRC inactive state is stopped for a multicast session not supported in the second cell.

6. The method according to claim 1, further comprising: If the second cell does not support multicast reception in the RRC inactive state, stop multicast reception in the RRC inactive state.

7. The method according to claim 1, further comprising: In a case where the second cell does not support multicast reception in the RRC inactive state, one or more established multicast / broadcast service radio bearers (MRBs) are released.

8. The method according to claim 1, further comprising: In a case where the second cell does not support multicast reception in the RRC inactive state, one or more established multicast / broadcast service radio bearers (MRBs) are suspended.

9. A user equipment UE, the user equipment comprising: Transceiver; as well as at least one processor coupled to the transceiver and configured to: Performing multicast reception in a radio resource control (RRC) inactive state on the first cell; When the cell selection criterion is met, performing cell selection on the second cell; identifying whether the second cell supports multicast reception in the RRC inactive state; and Based on the second cell supporting the multicast reception in the RRC inactive state, the multicast reception in the RRC inactive state is continued on the second cell.

10. The UE according to claim 9, wherein: The at least one processor is configured to: When the multicast / broadcast service radio bearer MRB configuration for multicast reception in the RRC inactive state on the second cell is different from the MRB configuration for multicast reception in the RRC inactive state on the first cell, multicast reception in the RRC inactive state is continued based on the MRB configuration on the second cell.

11. The UE according to claim 9, wherein: The at least one processor is configured to: In a case where the second cell supports multicast reception in the RRC inactive state, the multicast reception in the RRC inactive state is continued for the multicast session supported in the second cell.

12. The UE according to claim 9, wherein: The at least one processor is further configured to: If the second cell supports multicast reception in the RRC inactive state, multicast reception in the RRC inactive state is stopped for a multicast session not supported in the second cell.

13. The UE according to claim 9, wherein: The at least one processor is further configured to: If the second cell does not support multicast reception in the RRC inactive state, stop multicast reception in the RRC inactive state.

14. The UE according to claim 9, wherein: The at least one processor is further configured to: In a case where the second cell does not support multicast reception in the RRC inactive state, one or more established multicast / broadcast service radio bearers (MRBs) are released.

15. The UE according to claim 9, wherein: The at least one processor is further configured to: In a case where the second cell does not support multicast reception in the RRC inactive state, one or more established multicast / broadcast service radio bearers (MRBs) are suspended.

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