System and method for multicast reception and small data transmission

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. The invention provides equipment, a method and a system for MBS multicast reception and small data transmission. A method performed by a terminal includes: receiving an RRC release message from a BS, the RRC release message including information indicating a pause configuration for an RRC inactive state; identifying, in the presence of a configuration for MBS multicast reception by an upper layer, whether the SDT process is being performed in an RRC inactive state; and monitoring a paging channel for paging using the TMGI associated with the MBS session based on the SDT procedure being not in progress. The MBS session is associated with a bearer for MBS multicast reception.

Description

Technical Field

[0001] The present disclosure relates generally to a wireless communication system, and more particularly, to an apparatus, method, and system for multicast and broadcast service (MBS) multicast reception and small data transmission (SDT). Background Art

[0002] The fifth generation (5G) mobile communication technology defines a wide frequency band, making high transmission rates and new services possible, which can be implemented in "sub-6 GHz" frequency bands such as 3.5 GHz, and also in "6 GHz and above frequency bands" (including 28 GHz and 39 GHz) which can be called millimeter waves. In addition, the implementation of the sixth generation (6G) mobile communication technology (also called super 5G system) in the terahertz frequency band (e.g., 95 GHz to 3 THz frequency band) has been considered to achieve a transmission rate fifty times faster than that of the 5G mobile communication technology and an ultra-low latency that is one-tenth of that of the 5G mobile communication technology.

[0003] Since the initial development of 5G mobile communication technology, in order to support services and meet performance requirements related to enhanced mobile broadband (eMBB), ultra-reliable and low-latency communications (URLLC), and massive machine type communications (mMTC), standardization has been ongoing on the following technologies: beamforming and massive multiple-input multiple-output (MIMO) for mitigating radio wave path loss in millimeter waves and increasing radio wave transmission distance, parameter sets supporting dynamic operations for efficient utilization of millimeter wave resources and time slot formats (e.g., operating multiple subcarrier spacings (SCSs)), initial access technology for supporting multi-beam transmission and broadband, definition and operation of bandwidth parts (BWPs), new channel coding methods such as low-density parity-check (LDPC) codes for large-scale data transmission and polarization codes for highly reliable transmission of control information, layer 2 (L2) preprocessing, and network slicing for providing dedicated networks dedicated to specific services.

[0004] Currently, in view of the services supported by 5G mobile communication technology, discussions on the improvement and performance enhancement of initial 5G mobile communication technology are underway, and there is already physical layer standardization on the following technologies, for example, V2X (Vehicle-to-Everything) for assisting driving decisions by autonomous vehicles based on information about the location and status of the vehicle transmitted by the vehicle and for improving user convenience, NR-U (New Radio Unlicensed) for system operation designed to comply with various regulatory requirements in unlicensed bands, NR UE energy saving, and non-terrestrial network (NTN) for UE-satellite direct communication for providing coverage and positioning in areas where terrestrial network communications are not available.

[0005] Air interface architecture / protocols are being standardized for technologies such as Industrial Internet of Things (IIoT) for supporting new services through interworking and convergence with other industries, IAB (Integrated Access and Backhaul) for providing nodes for network service area extension 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 (2-step RACH for NR) for simplifying the random access process. System architecture / services for technologies such as 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 are also being standardized.

[0006] With the commercialization of 5G mobile communication systems, the number of connected devices, which has been growing exponentially, will be connected to the communication network, and it is therefore expected that there will be a need to enhance the functions and performance of the 5G mobile communication systems and the integrated operations of the connected devices. To this end, new research is planned related to the following technologies: Extended Reality (XR) for effectively supporting AR (Augmented Reality), VR (Virtual Reality), MR (Mixed Reality), etc., as well as 5G performance improvement and complexity reduction by utilizing artificial intelligence (AI) and machine learning (ML), AI service support, virtual world service support, and drone communication.

[0007] This development of 5G mobile communication systems will serve as a foundation for developing new waveforms for providing coverage in the terahertz band for 6G mobile communication technology, multi-antenna transmission technologies such as full-dimensional MIMO (FD-MIMO), array antennas, and large antennas, metamaterial-based lenses and antennas for improving the coverage of terahertz band signals, high-dimensional spatial multiplexing technology using OAM (orbital angular momentum), RIS (Reconfigurable Smart Surface), full-duplex technology for increasing the frequency efficiency of 6G mobile communication technology and improving system networks, AI-based communication technology for achieving system optimization by leveraging satellites and AI (artificial intelligence) from the design stage 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 issues

[0009] The SDT procedure may be initiated in the RRC_INACTIVE state. According to current operation, a UE in the RRC_INACTIVE state monitors the paging channel for MBS multicast reception using TMGI regardless of whether an SDT procedure is ongoing. As a result, a recovery procedure may be triggered in the middle of an ongoing SDT procedure if a paging for MBS is received. If the network never sends a paging for MBS during SDT, paging monitoring is unnecessary and results in increased power consumption.

[0010] Solution to the problem

[0011] The present disclosure is to address at least the above-mentioned problems and / or disadvantages and to provide at least the advantages described below.

[0012] One aspect of the present disclosure provides a communication method and system for aggregating a 5G communication system, wherein the 5G communication system is used to support a higher data rate than a 4G communication system.

[0013] According to one aspect of the present disclosure, a method performed by a terminal is provided. The method includes receiving a radio resource control (RRC) release message from a base station (BS), the RRC release message including information indicating a suspension configuration for an RRC inactive state; in the presence of a configuration for MBS multicast reception by an upper layer, identifying whether an SDT process is being performed in the RRC inactive state; and based on the SDT process not being performed, monitoring a paging channel for paging using a temporary mobile group identity (TMGI) associated with an MBS session, wherein the MBS session is associated with a bearer for MBS multicast reception.

[0014] According to another aspect of the present disclosure, a terminal is provided. The terminal includes a transceiver and a controller, the controller being configured to: control the transceiver to receive an RRC release message from a BS, the RRC release message including information indicating a suspension configuration for an RRC inactive state; in the presence of a configuration for MBS multicast reception by an upper layer, identify whether an SDT process is being performed in the RRC inactive state; and based on the SDT process not being performed, monitor a paging channel for paging using a TMGI associated with an MBS session, wherein the MBS session is associated with a bearer for MBS multicast reception.

[0015] Advantageous Effects of the Invention

[0016] According to an embodiment of the present disclosure, a paging method for MBS multicast reception during an ongoing SDT process is defined, and a UE in an RRC_inactive state can effectively perform a paging operation for MBS multicast reception. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and other aspects, features and advantages of certain embodiments of the present disclosure will become more apparent through the following description in conjunction with the accompanying drawings, in which:

[0018] Figure 1 is a flow chart illustrating the operation of a UE according to an embodiment;

[0019] Figure 2 is a flow chart illustrating the operation of a UE according to an embodiment;

[0020] Figure 3 is a flow chart illustrating the operation of a UE according to an embodiment;

[0021] Figure 4 is a flow chart illustrating the operation of a UE according to an embodiment;

[0022] Figure 5 shows a terminal according to an embodiment; and

[0023] Figure 6 A BS according to an embodiment is shown. DETAILED DESCRIPTION

[0024] The following description is provided with reference to the accompanying drawings to assist in a comprehensive understanding of the various embodiments of the present disclosure as defined by the claims and their equivalents. The following description includes various specific details that are helpful for understanding, but these should be considered as exemplary only. Therefore, it will be appreciated by those of ordinary skill in the art that various changes and modifications may be made to the various embodiments described herein without departing from the scope and spirit of the present disclosure. In addition, for the sake of clarity and conciseness, descriptions of well-known functions and structures may be omitted.

[0025] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but are used to provide a clear and consistent understanding of the present disclosure. Therefore, it will be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration purposes only and not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents.

[0026] Unless the context clearly dictates otherwise, singular forms such as "a," "an," and "the" include plural referents. Thus, for example, reference to "a component surface" includes reference to one or more of such surfaces.

[0027] The term "substantially" is intended to convey that the recited characteristics, parameters or values ​​need not be achieved precisely, but deviations or variations may occur within an amount that does not impair the effect that the characteristic is intended to provide, including, for example, tolerances, measurement errors, measurement accuracy limitations and other factors known to those skilled in the art.

[0028] The combination of the blocks and flow charts of a flow chart (or sequence diagram) can be represented and executed by computer program instructions. These computer program instructions can be loaded on a processor of a general-purpose computer, a special-purpose computer, or a programmable data processing device. When the loaded program instructions are executed by the processor, they create a device for performing the functions described in the flow chart. Since the computer program instructions can be stored in a computer-readable memory that can be used in a special-purpose computer or a programmable data processing device, it is also possible to create an article that performs the functions described in the flow chart. Since the computer program instructions can be loaded on a computer or a programmable data processing device, when executed as a process, it can perform the operations of the functions described in the flow chart.

[0029] The blocks of the flow chart may correspond to a module, segment or code containing one or more executable instructions that implement one or more logical functions, or may correspond to a portion thereof. In some cases, the functions described by the blocks may be performed in an order different from the order listed. For example, two blocks listed in sequence may be performed simultaneously or in reverse order.

[0030] The words "unit", "module", etc. may refer to software components or hardware components that can perform functions or operations, such as field programmable gate arrays (FPGAs) or application specific integrated circuits (ASICs). However, "units", etc. are not limited to hardware or software. Units, etc. may be configured to reside in an addressable storage medium or drive one or more processors. Units, etc. may refer to software components, object-oriented software components, category components, task components, processes, functions, attributes, programs, subroutines, program code fragments, drivers, firmware, microcodes, circuits, data, databases, data structures, tables, arrays, or variables. The functions provided by components and units may be a combination of smaller components and units, and may be combined with others to form larger components and units. Components and units may be configured to drive devices or one or more processors in a secure multimedia card.

[0031] Herein, the BS is an entity that communicates with the UE and may be referred to as a base transceiver station (BTS), a Node B (NB), an evolved NB (eNB), an access point (AP), a 5G NB (5GNB), or a next generation NB (gNB).

[0032] The UE is an entity communicating with the BS and may be referred to as a device, a mobile station (MS), a mobile equipment (ME), or a terminal.

[0033] As mentioned above, several broadband wireless technologies have been developed to meet the growing number of broadband subscribers and provide more and better applications and services. The second generation (2G) wireless communication system was developed to provide voice services while ensuring user mobility. The third generation (3G) wireless communication system supports voice services and data services. The 4G wireless communication system provides high-speed data services. However, the resources of the 4G wireless communication system are insufficient to meet the growing demand for high-speed data services. Therefore, the 5G wireless communication system (i.e., next generation radio or NR) is being developed to meet the growing demand for high-speed data services and support ultra-reliability and low-latency applications.

[0034] 5G wireless communication systems support lower frequency bands, as well as higher frequency (millimeter wave) bands such as 10GHz to 100GHz bands to provide higher data rates. In order to reduce the propagation loss of radio waves and increase the transmission distance, beamforming, massive MIMO, FD-MIMO, array antennas, analog beamforming, and large antenna technology are considered in the design of 5G wireless communication systems. In addition, it is expected that 5G wireless communication systems will solve different use cases with quite different requirements in terms of data rate, waiting time, reliability, mobility, etc. However, it is expected that the design of the air interface of the 5G wireless communication system will be flexible enough to serve UEs with different capabilities depending on the use case and the market segmentation that the UE will cater to the service to the end customer. 5G wireless communication system wireless systems are expected to solve eMBB, mMTC, URLLC, etc.

[0035] eMBB requirements (such as tens of Gbps data rates, low latency, high mobility, etc.) address the market segment representing conventional wireless broadband subscribers who actively provide Internet connectivity anytime and anywhere.

[0036] mMTC requirements (such as high connection density, infrequent data transmission, long battery life, low mobility address, etc.) address the market segment representing the connectivity of billions of devices envisioned by the Internet of Things (IoT) / Internet of Everything (IoE).

[0037] URLLC requirements such as low latency, high reliability, and variable mobility address market segments representing industrial automation applications such as vehicle-to-vehicle / vehicle-to-infrastructure communications for autonomous vehicles.

[0038] In a 5G wireless communication system operating at a higher frequency (millimeter wave) band, UE and gNB communicate with each other using beamforming. More specifically, beamforming technology is used to mitigate propagation path loss and increase the propagation distance of communications at a higher frequency band. Beamforming enhances the transmission and reception performance using high-gain antennas. Generally, beamforming can be classified into transmit (TX) beamforming performed at the transmitting end and receive (RX) beamforming performed at the receiving end. TX beamforming generally increases directivity by allowing the area reached by propagation to be densely located 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 results in an increase in the directivity of the signal, thereby increasing the propagation distance. In addition, since the signal is basically not transmitted in a direction other than the directivity direction, the signal interference acting on the other receiving end is significantly reduced.

[0039] The receiving end can perform beamforming on the RX signal by using an RX antenna array. RX beamforming increases the strength of the RX signal transmitted in a specific direction by allowing propagation to be concentrated in a specific direction, and excludes signals transmitted in directions other than the specific direction from the RX signal, thereby blocking interference signals.

[0040] By using beamforming technology, the transmitter can generate multiple transmit beam patterns in different directions. Each of these transmit beam patterns can also be called a TX beam.

[0041] A wireless communication system operating at a high frequency can use multiple narrow TX beams to transmit signals in a cell, because each narrow TX beam provides coverage to 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 transmitted using beamforming. The receiver can also generate multiple RX beam patterns in different directions. Each of these receive patterns can also be called an RX beam.

[0042] Carrier Aggregation (CA) / Multiple Connections in 5G Wireless Communication Systems

[0043] The 5G wireless communication system supports independent operation mode as well as dual connectivity (DC). In DC, multiple Rx / Tx UEs can be configured to utilize resources provided by two different nodes (or NBs) connected via a non-ideal backhaul. One node serves as a master node (MN) and the other serves as a secondary node (SN). The MN and SN are connected via a network interface, and at least the MN is connected to a core network (CN).

[0044] NR also supports multi-radio access technology (RAT) DC (MR-DC) operation, whereby a UE in RRC_CONNECTED state is configured to utilize radio resources provided by two different schedulers located in two different nodes connected via a non-ideal backhaul and providing Evolved Universal Terrestrial Mobile Telecommunications System (UMTS) Radio Access (E-UTRA) (i.e., if the node is an ng-eNB) or NR access (i.e., if the node is a gNB). In NR for a UE in RRC_CONNECTED state without CA / DC configured, there is only one serving cell, the primary cell (PCell). For a UE in RRC_CONNECTED state configured with CA / DC, the term "serving cell" is used to refer to a set of cells including a special cell (SpCell) and a secondary cell (SCell). In NR, the term master cell group (MCG) refers to a serving cell group associated with a MN, which includes a PCell and optionally one or more SCells. In NR, the term SCell group (SCG) refers to a serving cell group associated with a SN, which includes a primary SCell (PSCell) and optionally one or more SCells.

[0045] In NR, PCell refers to the serving cell operating at the primary frequency in the MCG, where the UE performs the initial connection establishment procedure, or initiates the connection re-establishment procedure.

[0046] In NR, for UEs configured with CA, SCell provides additional radio resources on top of SpCell. PSCell refers to the serving cell in SCG where the UE performs random access (RA) when performing reconfiguration with synchronization procedure. For DC operation, SpCell refers to PCell of MCG or PSCell of SCG. Otherwise, SpCell refers to PCell.

[0047] System Information (SI) Acquisition in 5G Wireless Communication Systems

[0048] In a 5G wireless communication system, a NB (gNB) or BS in a cell broadcasts a synchronization signal (SS) and a physical broadcast channel (PBCH) block (SSB), which includes a primary SS (PSS), a secondary SS (SSS), and SI. SI includes common parameters for communication in a cell.

[0049] In the 5G wireless communication system, SI can be divided into a master information block (MIB) and multiple SI blocks (SIBs).

[0050] The MIB is always transmitted on the broadcast channel (BCH) with a period of 80 ms, and the MIB is repeated within 80 ms. The MIB includes parameters for obtaining SIB1 from the cell.

[0051] SIB1 is transmitted on the downlink (DL) shared channel (SCH) with a period of 160ms and a variable transmission repetition. The default transmission repetition period of SIB1 is 20ms, but the actual transmission repetition period can be determined based on the network implementation. The scheduling information in SIB 1 includes the mapping between SIBs and SI messages, the periodicity 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 relevant SI message is being broadcast. If at least one SI message is not broadcast, SIB1 may include RA resources (e.g., physical RA channel (PRACH) preamble and PRACH resources) for requesting the gNB to broadcast one or more SI messages.

[0052] SIBs other than SIB1 are carried in SI messages, which are transmitted on DL-SCH. Only SIBs with the same periodicity can be mapped to the same SI message. Each SI message is transmitted within a regularly occurring time domain window (called an SI window) that 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, within an SI window, only the corresponding SI message is transmitted. Except for SIB 1, any SIB can be configured as cell-specific or area-specific by using the indication in SIB 1. Cell-specific SIBs are only applicable to the cell where the SIB is provided, while area-specific SIBs are applicable to an area called an SI area, which includes one or several cells and is identified by systemInformationAreaID.

[0053] Physical DL Control Channel (PDCCH) in 5G Wireless Communication Systems

[0054] In 5G wireless communication systems, PDCCH is used to schedule DL transmissions on the physical DL shared channel (PDSCH) and UL transmissions on the physical uplink (UL) shared channel (PUSCH).

[0055] The DL control information (DCI) on the PDCCH includes DL allocations, which contain at least the modulation and coding format, resource allocation and hybrid automatic repeat request (HARQ) information related to the DL-SCH, and the UL scheduling grant contains at least the modulation and coding format, resource allocation and HARQ information related to the UL-SCH.

[0056] In addition to scheduling, PDCCH can be used for: activation and deactivation of configured PUSCH transmissions with configured grants (CG); activation and deactivation of PDSCH semi-persistent transmissions; notifying one or more UEs of the time slot format; notifying one or more UEs of physical resource blocks (PRBs) and orthogonal frequency division multiplexing (OFDM) symbols, where the UE can assume that there are no transmissions intended for the UE, transmission of transmit power control (TPC) commands for the physical UL control channel (PUCCH) and PUSCH, transmission of one or more TPC commands for sounding reference signal (SRS) transmissions by one or more UEs; switching the active BWP of the UE; and initiating the RA procedure.

[0057] According to the corresponding search space configuration, the UE monitors the PDCCH candidate set in the configured monitoring opportunities in one or more configured control resource sets (CORESETs). A CORESET includes a set of PRBs with a duration of 1 to 3 OFDM symbols. Resource element groups (REGs) and control channel elements (CCEs) are defined within a CORESET, where each CCE includes a set of REGs.

[0058] 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 is supported in CORESET. Polarity coding is used for PDCCH. Each REG carrying PDCCH carries its own demodulation reference signal (DMRS). Quadrature phase shift keying (QPSK) modulation is used for PDCCH.

[0059] In a 5G wireless communication system, for each configured BWP, the gNB signals a list of search space configurations, where each search configuration is uniquely identified by an identifier (ID). The gNB explicitly signals an IF of the search space configuration, which will be used for a specific purpose, such as paging reception, SI reception, or RA response (RAR) reception.

[0060] In NR, the search space configuration includes the parameters monitoring-periodicity-PDCCH-timeslot, monitoring-offset-PDCCH-timeslot, intra-timeslot-monitoring-symbol-PDCCH and duration. The UE uses the parameters of PDCCH monitoring periodicity (monitoring-periodicity-PDCCH-timeslot), PDCCH monitoring offset (monitoring-offset-PDCCH-timeslot) and PDCCH monitoring mode (intra-timeslot-monitoring-symbol-PDCCH) to determine the PDCCH monitoring opportunity within the time slot. The PDCCH monitoring opportunity exists in time slots x to x+duration, where the number of time slots x in the radio frame with number y satisfies the following equation (1).

[0061] (y*(number of slots in a radio frame)+x-monitoring-offset-PDCCH-slot)mod(monitoring-periodicity-PDCCH-slot)=0...(1)

[0062] The starting symbol of a PDCCH monitoring opportunity in each slot with a PDCCH monitoring opportunity is given by Intra-Slot-Monitoring-Symbol-PDCCH. The length of the PDCCH monitoring opportunity (in symbols) is given in the CORESET associated with the search space. The search space configuration includes the ID of the CORESET configuration associated with it. For each configured BWP, the gNB signals a list of CORESET configurations, where each CORESET configuration is uniquely identified by an ID. Each radio frame has a duration of 10 ms. A radio frame is identified by a radio frame number or a system frame number.

[0063] Each radio frame includes a plurality of time slots, wherein the number of time slots in a radio frame and the duration of the time slots depend on the SCS. More specifically, the number of time slots in a radio frame and the duration of the time slots depend on the radio frame of each SCS, which is predefined. For example, for an SCS of 15KHz, there are 10 time slots in a radio frame, and the duration of each time slot is 1ms. For an SCS of 30KHz, there are 20 time slots in a radio frame, and the duration of each time slot is 0.5ms. For an SCS of 60KHz, there are 40 time slots in a radio frame, and the duration of each time slot is 0.25ms. For an SCS of 120KHz, there are 80 time slots in a radio frame, and the duration of each time slot is 0.125ms. For an SCS of 240KHz, there are 160 time slots in a radio frame, and the duration of each time slot is 0.0625ms.

[0064] Each CORESET configuration is associated with a list of Transmit Configuration Indicator (TCI) states. Each TCI state configures a DL Reference Signal (RS) ID (e.g., SSB or Channel State Information (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 (e.g., the DL TX beam is quasi-co-located (QCLed) with the SSB / CSI-RS of the TCI state) used by the gNB to transmit PDCCH in the PDCCH monitoring occasion of the search space.

[0065] BWP Operation in 5G Wireless Communication Systems

[0066] In 5G wireless communication systems, bandwidth adaptation (BA) is supported. With BA, the UE's receive and transmit bandwidth should be less than the cell's bandwidth and can be adjusted. The width can be commanded to change (for example, to reduce during low activity periods to save power). The position can be moved in the frequency domain (for example, to increase scheduling flexibility). In addition, the SCS can be commanded to change (for example, to allow different services).

[0067] A subset of the total cell bandwidth of a cell is called a BWP. BA is achieved by configuring a BWP for an RRC connected UE and informing the UE which configured BWP is currently active. When BA is configured, the UE only needs to monitor the PDCCH on the active BWP, i.e. it does not have to monitor the PDCCH on the entire DL frequency of the serving cell.

[0068] In the RRC connected state, one or more DL and UL BWPs are configured for the UE for each configured serving cell (i.e., PCell or SCell). For an activated serving cell, there is always one active UL and DL BWP at any point in time. BWP switching of a serving cell is used to simultaneously activate an inactive BWP and deactivate an active BWP. BWP switching is controlled by the PDCCH indicating a DL allocation or UL grant, by a bwp-Inactivity Timer, by RRC signaling, or by the Medium Access Control (MAC) entity itself after the RA procedure is initiated.

[0069] After 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 DL allocation or UL grant. The active BWP of 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 for UL and DL.

[0070] After the BWP inactivity timer expires, the UE switches from the currently active DL BWP to the default DL BWP or the initial DL BWP (eg, if no default DL BWP is configured).

[0071] RA in 5G wireless communication systems

[0072] In the 5G wireless communication system, RA is supported. RA is used to achieve UL time synchronization. RA is used during initial access, handover, RRC connection reestablishment process, scheduling request (SR) transmission, SCG addition / modification, beam failure recovery, and data or control information transmission in the UL by an unsynchronized UE in the RRC connected state.

[0073] Contention-Based RA (CBRA) (or 4-step CBRA)

[0074] In CBRA, the UE first transmits a RA preamble (called Msg1) and then waits for the RAR in the RAR window. The RAR is also called Msg2.

[0075] The gNB transmits the RAR on the PDSCH. The PDCCH that schedules the PDSCH carrying the RAR is addressed to the RA-Radio Network Temporary Identifier (RA-RNTI). The RA-RNTI identifies the time-frequency resource (also called PRACH opportunity, PRACH transmission opportunity, or RA channel (RACH) opportunity) where the gNB detects the RA preamble.

[0076] RA-RNTI is calculated using equation (2).

[0077] RA-RNTI=1+s_id+14*t_id+14*80*f_id+14*80*8*ul_carrier_id...(2)

[0078] In equation (2), s_id is the index of the first OFDM symbol of the PRACH opportunity in which the UE has Msg1 transmitted, i.e., the RA preamble (0≤s_id<14); t_id is the index of the first time slot of the PRACH opportunity (0≤t_id<80); f_id is the index of the PRACH opportunity within the time slot in the frequency domain (0≤f_id<8); and ul_carrier_id is the UL carrier used for Msg1 transmission (0 for the normal UL (NUL) carrier and 1 for the supplementary UL (SUL) carrier).

[0079] The gNB may multiplex several RARs for various RA preambles detected by the gNB in ​​the same RAR MAC Protocol Data Unit (PDU). If the RAR includes the RA preamble ID (RAPID) of the RA preamble transmitted by the UE, the RAR in the MAC PDU corresponds to the RA preamble transmission of the UE. If no RAR corresponding to its RA preamble transmission is received during the RAR window, and the UE has not transmitted a configurable (configured by the gNB in ​​the RACH configuration) number of RA preambles, the UE returns to the first step, i.e., selecting a RA resource (preamble / RACH opportunity) and transmitting the RA preamble. A backoff may be applied before returning to the first step.

[0080] If a RAR corresponding to its RA preamble transmission is received, the UE transmits a message 3 (Msg3) in the UL grant received in the RAR. Msg3 includes an RRC connection request, an RRC connection reestablishment request, an RRC handover confirmation, an SR, an SI request, etc. Msg3 may include a UE identity (i.e., a cell-RNTI (C-RNTI) or a system architecture evolution (SAE)-temporary mobile subscriber identity (S-TMSI) or a random number).

[0081] After transmitting Msg3, the UE starts the contention resolution timer.

[0082] When the contention resolution timer is running, if the UE receives a PDCCH addressed to the C-RNTI included in Msg3, the contention resolution timer is stopped and the RA procedure is successfully completed. When the contention resolution timer is running, if the UE receives a contention resolution MAC control element (CE) including the UE's contention resolution identifier (the first X bits of the common control channel (CCCH) service data unit (SDU) transmitted in Msg3), the contention resolution is considered successful, the contention resolution timer is stopped and the RA procedure is successfully completed.

[0083] If the contention resolution timer expires and the UE has not transmitted a configurable number of RA preambles, the UE returns to the first step, i.e., selecting RA resources (preambles / RACH opportunities) and transmitting RA preambles.Before returning to the first step, a backoff may be applied.

[0084] Contention-free RA (CFRA) (traditional CFRA or 4-step CFRA)

[0085] The CFRA procedure is used for scenarios such as handover requiring low latency, timing advance establishment of SCell, etc. The eNB allocates a dedicated RA preamble to the UE. The UE transmits a dedicated RA preamble. The eNB transmits a RAR on the PDSCH addressed to the RA-RNTI. The RAR conveys the RAPID and timing alignment information. The RAR may also include a UL grant. The RAR is transmitted in a RAR window similar to the CBRA procedure. After receiving the RAR including the RAPID of the RA preamble transmitted by the UE, the CFRA is considered to have been successfully completed. In the case of initiating RA for beam failure recovery, if a PDCCH addressed to the C-RNTI is received in the search space for beam failure recovery, the CFRA is considered to have been successfully completed. If the RAR window expires, the RA is not successfully completed, and the UE has not transmitted the RA preamble a configurable number of times (configured by the gNB in ​​the RACH configuration), the UE retransmits the RA preamble.

[0086] For certain events, such as handover and beam failure recovery, if a dedicated preamble is assigned to the UE, the UE determines whether to transmit a dedicated preamble or a non-dedicated preamble during the first step of RA, i.e., during RA resource selection for Msg1 transmission. Dedicated preambles are usually provided for a subset of SSB / CSI-RS. If no SSB / CSI RS has a DL RS received power (RSRP) above a threshold among the SSB / CSI RS for which the gNB provides CFRA resources (i.e., dedicated preamble / RACH opportunity (RO)), the UE selects a non-dedicated preamble. Otherwise, the UE selects a dedicated preamble. Therefore, during the RA procedure, one RA attempt can be CFRA and the other RA attempt can be CBRA.

[0087] 2-step CBRA

[0088] In the first step, the UE transmits a RA preamble on the PRACH and transmits a payload (ie, MAC PDU) on the PUSCH. The RA preamble and payload transmission is also referred to as MsgA.

[0089] In the second step, after the MsgA is transmitted, the UE monitors the response from the network (i.e., gNB) within the configured window. The response is also called MsgB. The gNB transmits MsgB on the PDSCH. The PDCCH scheduling the PDSCH carrying MsgB is addressed to the MSGB-RNTI. The MSGB-RNTI identifies the time-frequency resource (also called PRACH opportunity, PRACH transmission opportunity, or RACH opportunity) where the gNB detects the RA preamble.

[0090] MSGB-RNTI is calculated using equation (3).

[0091] MSGB-RNTI=1+s_id+14*t_id+14*80*f_id+14*80*8*ul_carrier_id+14Х80Х8Х2...(3)

[0092] In equation (3), s_id is the index of the first OFDM symbol of the PRACH opportunity, where the UE has Msg1 transmitted, i.e., the RA preamble code (0≤s_id<14); t_id is the index of the first time slot of the PRACH opportunity (0≤t_id<80); f_id is the index of the PRACH opportunity within the time slot in the frequency domain (0≤f_id<8); and ul_carrier_id is the UL carrier used for Msg1 transmission (NUL carrier is 0 and SUL carrier is 1).

[0093] If a CCCH SDU is transmitted in the MsgA payload, the UE performs contention resolution using the contention resolution information in MsgB. If the contention resolution ID received in MsgB matches the first 48 bits of the CCCH SDU transmitted in MsgA, contention resolution is successful. If C-RNTI is transmitted in the MsgA payload, contention resolution is successful if the UE receives a PDCCH addressed to C-RNTI. If contention resolution is successful, the RA process is deemed to have been successfully completed. Instead of the contention resolution information corresponding to the transmitted MsgA, MsgB may include backoff information corresponding to the RA preamble transmitted in MsgA. If backoff information is received, the UE transmits Msg3 and performs contention resolution using Msg4 as in the CBRA process. If contention resolution is successful, the RA process is deemed to have been successfully completed. If contention resolution fails at backoff (i.e., when Msg3 is transmitted), the UE retransmits MsgA. If the configured window for the UE to monitor the network response expires after transmitting MsgA and the UE does not receive MsgB including contention resolution information or backoff information as described above, the UE retransmits MsgA. If the RA procedure is not successfully completed even after transmitting a configurable number of MsgA, the UE falls back to the 4-step RACH procedure, i.e., the UE transmits only the PRACH preamble.

[0094] The MsgA payload may include one or more of the following: CCCH SDU, dedicated control channel (DCCH) SDU, dedicated traffic channel (DTCH) SDU, buffer status report (BSR) MAC CE, power headroom report (PHR) MAC CE, SSB information, C-RNTI MAC CE or padding. MsgA may include UE ID (e.g., random ID, S-TMSI, C-RNTI, recovery ID, etc.) and the preamble in the first step. The UE ID may be included in the MAC PDU of MsgA. The UE ID (such as C-RNTI) may be carried in the MAC CE, which is included in the MAC PDU. Other UE IDs (such as random ID, S-TMSI, C-RNTI, recovery ID, etc.) may be carried in the CCCH SDU. The UE ID may be one of a random ID, S-TMSI, C-RNTI, recovery ID, international mobile subscriber ID (IMSI), idle mode ID, inactive mode ID, etc. The UE ID may be different in different situations where the RA process is performed. When the UE performs RA after power-on (before it is attached to the network), the UE ID is a random ID. When the UE performs RA in the idle state after it is attached to the network, the UE ID is the S-TMSI. If the UE has an assigned C-RNTI (e.g., in the connected state), the UE ID is the C-RNTI. In the case where the UE is in the RRC_Inactive state, the UE ID is the recovery ID.

[0095] In addition to the UE ID, some additional control information may be sent in MsgA. The control information may be included in the MAC PDU of MsgA. The control information may include one or more of the following: connection request indication, connection recovery request indication, SI request indication, buffer status indication, beam information (e.g., one or more DL TX beam IDs or SSB IDs), beam failure recovery indication / information, data indicator, cell / BS / transmit and receive point (TRP) switching indication, connection reestablishment indication, reconfiguration complete or switching complete message, etc.

[0096] 2-step CFRA

[0097] In 2-step CFRA, the gNB allocates dedicated RA preamble and PUSCH resources for MsgA transmission to the UE. It may also indicate the RO to be used for preamble transmission.

[0098] In the first step, the UE transmits a RA preamble on the PRACH and a payload on the PUSCH using CFRA resources (ie, dedicated preamble / PUSCH resources / RO).

[0099] In the second step, after MsgA is transmitted, the UE monitors the response from the network (i.e., gNB) within the configured window. The response is also called MsgB.

[0100] The gNB transmits MsgB on the PDSCH. The PDCCH that schedules the PDSCH carrying MsgB is addressed to the MSGB-RNTI. The MSGB-RNTI identifies the time-frequency resource (also called PRACH opportunity, PRACH transmission opportunity, or RACH opportunity) where the gNB detects the RA preamble. As shown above, the MSGB-RNTI is calculated using equation (3).

[0101] The RA procedure is considered to be successfully completed if the UE receives a PDCCH addressed to the C-RNTI.The RA procedure is considered to be successfully completed if the UE receives backoff information corresponding to the preamble it transmitted.

[0102] For certain events, such as handover and beam failure recovery, if dedicated preamble and PUSCH resources are allocated to the UE, the UE determines whether to transmit a dedicated preamble or a non-dedicated preamble during the first step of RA, i.e., during RA resource selection for MsgA transmission. Dedicated preambles are usually provided for a subset of SSB / CSI RSs. If no SSB / CSI RS has a DL RSRP above a threshold among the SSB / CSI RSs for which the gNB provides CFRA resources (i.e., dedicated preamble / RO / PUSCH resources), the UE selects a non-dedicated preamble. Otherwise, the UE selects a dedicated preamble. Therefore, during the RA procedure, one RA attempt can be a 2-step CFRA, while another RA attempt can be a 2-step CBRA.

[0103] When starting the RA procedure, the UE first selects a carrier (SUL or NUL). If the gNB explicitly signals the carrier for the RA procedure, the UE selects the signaled carrier to perform the RA procedure. If the gNB does not explicitly signal the carrier for the RA procedure; and if the serving cell of the RA procedure is configured with supplementary UL, and if the RSRP of the DL pathloss reference is less than rsrp-ThresholdSSB-SUL: then the UE selects the SUL carrier to perform the RA procedure. Otherwise, the UE selects the NUL carrier to perform the RA procedure.

[0104] After selecting the UL carrier, the UE determines the UL BWP and DL BWP for the RA procedure as specified in Section 5.15 of TS 38.321. The UE then determines whether to perform a 2-step RACH or a 4-step RACH for this RA procedure.

[0105] If the RA procedure is initiated by a PDCCH order and if the ra-PreambleIndex explicitly provided by the PDCCH is not 0b000000, the UE selects 4-step RACH.

[0106] If the gNB signals 2-step CFRA resources for the RA procedure, the UE selects 2-step RACH.

[0107] If the gNB signals 4-step CFRA resources for the RA procedure, the UE selects 4-step RACH.

[0108] If the UL BWP selected for the RA procedure is configured with only 2-step RACH resources, the UE selects 2-step RACH.

[0109] If the UL BWP selected for this RA procedure is configured with only 4-step RACH resources, the UE selects 4-step RACH.

[0110] If the UL BWP selected for this RA procedure is configured with both 2-step and 4-step RACH resources, and the DL pathloss-referenced RSRP is below the configured threshold, the UE selects 4-step RACH. Otherwise, the UE selects 2-step RACH.

[0111] In a 5G wireless communication system, the UE may be in an RRC idle state, an RRC inactive state, or an RRC connected state.

[0112] In the RRC_IDLE state, UE-specific discontinuous reception (DRX) can be configured by upper layers (i.e., non-access stratum (NAS)). A UE in the RRC_IDLE state monitors short messages transmitted via DCI using the paging RNTI (P-RNTI), monitors the paging channel for CN paging using the 5G-S-TMSI, performs neighbor cell measurements and cell selection (or reselection), acquires SI, and can send SI requests (if configured).

[0113] In the RRC_INACTIVE state, UE-specific DRX can be configured by upper layers or by the RRC layer. In this state, the UE stores the UE inactive access layer (AS) context. The Notification Area (RNA) based on the Radio Access Network (RAN) is configured by the RRC layer. In the RRC_INACTIVE state, the UE monitors short messages transmitted with the P-RNTI via DCI, monitors the paging channel for CN paging using 5G-S-TMSI and RAN paging using a fully inactive RNTI (fullI-RNTI), performs neighbor cell measurements and cell (re)selection, periodically performs RAN-based notification area updates, and when moving outside the configured RAN-based notification area, acquires SI and can send SI requests (if configured).

[0114] In the RRC_CONNECTED state, the UE stores the AS context. Unicast data is transmitted to / received from the UE. At lower layers, the UE may be configured with UE-specific DRX. In the RRC_CONNECTED state, the UE monitors short messages transmitted with the P-RNTI via the DCI, and if configured, monitors the control channel associated with the shared data channel to determine whether to schedule data for it, provides channel quality and feedback information, performs neighbor cell measurements and measurement reports, and obtains SI.

[0115] NR-based 5G or Next Generation RAN (NG-RAN) includes NG-RAN nodes, where the NG-RAN node is the gNB, providing NR user plane and control plane protocol termination to the UE. The gNB is also connected to the 5GC through the NG interface, that is, to the Access and Mobility Management Function (AMF) through the NG-C interface, and to the User Plane Function (UPF) through the NG-U interface.

[0116] In the 5G wireless communication system, in order to reduce power consumption, the UE can use DRX in the RRC_idle state and the RRC_inactive state. In the RRC_idle / RRC_inactive state, the UE wakes up briefly at regular intervals (i.e., every DRX cycle) to receive paging, SI update notifications, and emergency notifications.

[0117] Paging messages are transmitted using the PDSCH. If there is a paging message in the PDSCH, the PDCCH will be addressed to the P-RNTI. The P-RNTI is common to all UEs. The UE ID (i.e., S-TMSI for RRC_idle UEs or I-RNTI for RRC_inactive UEs) is included in the paging message to indicate that paging is performed 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., the PDCCH is masked with the P-RNTI). SI updates and emergency notifications are included in the DCI, and the PDCCH carrying the DCI is addressed to the P-RNTI.

[0118] In RRC idle / inactive mode, the UE monitors one paging occasion (PO) in each DRX cycle. In RRC idle / inactive mode, the UE monitors the 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 can monitor any PO in the paging DRX cycle and monitor at least one PO in the SI modification cycle. In RRC idle / inactive mode, the UE monitors the PO in every DRX cycle in its active DL BWP. PO is a set of "S" PDCCH monitoring occasions for paging, where "S" is the number of SSBs transmitted in the cell (i.e., SSBs include (PSS, SSS, and PBCH). The UE first determines the paging frame (PF) and then determines the PO relative to the determined PF. One PF is a radio frame (10ms).

[0119] SDT in 5G Wireless Communication Systems

[0120] SDT is a process that allows data and / or signaling transmission while remaining in the RRC_INACTIVE state (i.e., without transitioning to the RRC_CONNECTED state). SDT is enabled on a radio bearer basis, and the UE will only start SDT when the UL data available for transmission on all radio bearers with SDT enabled is less than the configured UL data amount, the DL RSRP is above the configured threshold, and valid SDT resources are available.

[0121] The SDT procedure is initiated by transmission on RACH (configured via SI) or by type 1 CG resources (configured via dedicated signaling of RRCRelease message). SDT resources can be configured on the initial BWP of both RACH and CG. RACH and CG resources for SDT can be configured on one or both of NUL and SUL carriers. CG resources for SDT are only valid in the cell where the UE receives the RRCRelease message and transitions to the RRC_inactive state. For RACH, the network can configure 2-step and / or 4-step RA resources for SDT. When both 2-step and 4-step RA resources are configured for SDT, the UE selects the RA type. CFRA does not support SDT on RACH.

[0122] Once started, the SDT procedure is successfully completed after the UE is directed to RRC_IDLE (via RRCRelease) or RRC_INACTIVE (via RRCRelease or RRCReject) or RRC_CONNECTED (via RRCResume or RRCSetup), or is unsuccessfully completed upon cell reselection, expiration of the SDT failure detection timer (also known as T319a), expiration of the MAC entity reaching the configured maximum PRACH preamble transmission threshold, expiration of the RLC entity reaching the configured maximum retransmission threshold, or expiration of the SDT specific timing alignment timer (when the SDT procedure is in progress on the CG) and the UE does not receive a response from the network after the initial PUSCH transmission.

[0123] When the SDT procedure is not successfully completed, the UE transitions to RRC_IDLE.

[0124] The initial PUSCH transmission during the SDT procedure includes at least a CCCH message. After initiating the SDT procedure, when the UE transmits a MAC PDU containing a CCCH message for the first time, the UE starts the SDT failure detection timer. When using CG resources for the initial SDT transmission, if the UE does not receive an acknowledgement (dynamic UL grant or DL ​​allocation) from the network before the configured timer expires, the UE may perform an autonomous retransmission of the initial transmission. After the initial PUSCH transmission, subsequent transmissions are handled differently depending on the type of resources used to initiate the SDT procedure.

[0125] When using CG resources, the network may use dynamic grants to schedule subsequent UL transmissions, or subsequent UL transmissions may be performed on the following CG resource opportunities. DL transmissions are scheduled using dynamic allocations. The UE may initiate subsequent UL transmissions only after receiving confirmation (dynamic UL grant or DL ​​allocation) from the network for the initial PUSCH transmission. For subsequent UL transmissions, the UE cannot initiate retransmissions through CG resources.

[0126] When using RACH resources, the network may schedule subsequent UL and DL transmissions using dynamic UL grants and DL allocations, respectively, after the RA procedure is completed.

[0127] While the SDT procedure is ongoing, if data appears in the buffer of any radio bearer not enabled for SDT, the UE initiates transmission of a non-SDT data arrival indication to the network using a UEAssistanceInformation message and includes the resumption cause if available.

[0128] The SDT process over CG resources can be initiated only in case of valid UL timing alignment. UL timing alignment is maintained by the UE based on the SDT-specific timing alignment timer configured by the network via dedicated signaling, and a configured number of DL RSRPs of the highest ranking SSBs (above the configured RSRP threshold) are also configured for the initial CG-SDT transmission. After the SDT-specific timing alignment timer (cg-SDT-TimeAlignmentTimer) expires, the CG resources are released while maintaining the CG resource configuration.

[0129] During the SDT procedure, the logical channel restrictions (if any) configured by the network in the RRC_CONNECTED state and / or RRCRelease message for the SDT enabled radio bearers are applied by the UE.

[0130] When the UE starts SDT in a cell where the UE receives an RRCRelease message and transitions to the RRC_Inactive state, or when the UE starts SDT in a cell of its RAN Notification Area (RNA), the network may configure the UE to apply Robust Header Compression (ROHC) continuity for SDT.

[0131] Multicast Reception in 5G Wireless Communication Systems

[0132] Multicast communication services are delivered to UEs using multicast sessions. UEs can receive multicast communication services using mechanisms such as point-to-point (PTP) and / or point-to-multipoint (PTM) delivery in the RRC_CONNECTED state. HARQ feedback / retransmission can be applied to both PTP transmissions and PTM transmissions. For a multicast session, the gNB provides the multicast MBS radio bearer (MRB) configuration to the UE via dedicated RRC signaling. If a UE joining a multicast session is in the RRC_CONNECTED state and when the multicast session is activated, the gNB sends an RRCReconfiguration message to the UE with the relevant MBS configuration for the multicast session. The gNB can use the RRCReconfiguration message to configure or reconfigure a multicast MRB, for example, to add / release / modify the RLC entity of the MRB.

[0133] When there is (temporarily) no data to send to the UE for a multicast session, the gNB may move the UE to RRC_IDLE / RRC_INACTIVE state. When the CN has activated a multicast session or the gNB has multicast session data to deliver, the gNB supporting MBS uses the group notification mechanism to notify the UE in RRC_IDLE / RRC_INACTIVE state. After receiving the group notification, the UE reconnects to the network, i.e. the UE initiates connection establishment / resumption and enters RRC_CONNECTED. The group notification is addressed by the P-RNTI on the PDCCH.

[0134] According to the current operation for MBS multicast reception, the UE monitors the paging channel for paging using the TMGI. If the UE receives a paging message while monitoring the paging channel, it may initiate the RRC connection recovery procedure as follows:

[0135] 1> if the UE is in RRC_INACTIVE state and the UE has joined one or more MBS sessions indicated by the TMGI included in the pagingGroupList; and

[0136] 1> If any ue-Identity contained in any PagingRecord (if included in a Paging message) does not match the UE identity assigned by upper layers:

[0137] 2>Start the RRC connection recovery process

[0138] The SDT procedure may be initiated in the RRC_INACTIVE state. According to current operation, a UE in the RRC_INACTIVE state monitors the paging channel for paging using the TMGI regardless of whether an SDT procedure is ongoing. As a result, a recovery procedure may be triggered in the middle of an ongoing SDT procedure if paging for MBS is received. If the network never sends paging for MBS during SDT, paging monitoring is unnecessary and results in increased power consumption.

[0139] In the present disclosure, various embodiments are provided to solve the above-mentioned problems.

[0140] Figure 1 is a flow chart illustrating the operation of a UE according to an embodiment.

[0141] refer to Figure 1 In step S110, the UE (RRC_CONNECTED state) receives multicast communication services through mechanisms such as PTP and / or PTM delivery.

[0142] 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 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 RLC entity of the MRB.

[0143] In step S120, when the UE is in the RRC_CONNECTED state, the UE receives an RRCRelease message with a suspension configuration from the gNB and then enters the RRC_INACTIVE state.

[0144] When the UE is in the RRC_INACTIVE state, the SDT process may be initiated as described above. In step S130, if the UE is in the RRC_INACTIVE state and if configured by an upper layer (e.g., NAS or application layer) for MBS multicast reception (or for MBS multicast reception in RRC_CONNECTED), the UE checks whether the SDT process is in progress.

[0145] If the SDT procedure is in progress in step S130, then in step S140, the UE does not monitor the paging channel for paging using the TMGI and will not receive the PDSCH for paging.

[0146] However, if the SDT procedure is not performed in step S130, the UE monitors a paging channel for paging using the TMGI in step S150.

[0147] If the UE is in the RRC_INACTIVE state, and if configured by an upper layer (eg, NAS or application layer) for MBS multicast reception in the RRC_INACTIVE state, the UE monitors a paging channel for paging using a TMGI.

[0148] Alternatively, if the UE is in RRC_INACTIVE state and if configured by upper layers (e.g. NAS or application layer) for MBS multicast reception (or for MBS multicast reception in RRC_CONNECTED), it checks whether a timer (e.g. T319a timer) is running. If the timer is running, the UE does not monitor the paging channel for paging using the TMGI and the UE will not receive PDSCH for paging. If the timer is not running, the UE monitors the paging channel for paging using the TMGI. The timer may be started when the UE initiates the SDT procedure, or it may also be started when the first UL transmission containing a CCCH message is transmitted during the SDT procedure, or it may be started when the RA procedure initiated for the SDT procedure is successfully completed, or when a network response (i.e. PDCCH addressed to the C-RNTI) is received from the network (i.e. gNB) for the first UL transmission containing a CCCH message.

[0149] Alternatively, the SDT process can be started as described above when the UE is in the RRC_INACTIVE state. If the UE is in the RRC_INACTIVE state, and if configured by an upper layer (e.g., NAS or application layer) for MBS multicast reception (or for MBS multicast reception in RRC_CONNECTED), it checks whether the timer is running. If the timer is running, the UE can determine whether SDT or multicast reception has a higher priority. The priority may be indicated or predefined by the network in SI, RRC signaling. If the priority of MBS multicast reception is higher than the priority of SDT, the UE monitors the paging channel for paging using TMGI. If the priority of MBS multicast reception is lower than the priority of SDT, the UE does not monitor the paging channel for paging using TMGI. If the timer is not running, the UE monitors the paging channel for paging using TMGI.

[0150] Alternatively, the SDT process can be started as described above when the UE is in the RRC_INACTIVE state. If the UE is in the RRC_INACTIVE state, and if configured by an upper layer (e.g., NAS or application layer) for MBS multicast reception (or for MBS multicast reception in RRC_CONNECTED), it checks whether the SDT process is in progress. If the SDT process is in progress, the UE can determine whether SDT or multicast reception has a higher priority. The priority may be indicated or predefined by the network in SI, RRC signaling. If the priority of MBS multicast reception is higher than the priority of SDT, the UE monitors the paging channel for paging using TMGI. If the priority of MBS multicast reception is lower than the priority of SDT, the UE does not monitor the paging channel for paging using TMGI. If the SDT process is not in progress, the UE monitors the paging channel for paging using TMGI.

[0151] If the UE receives a paging message while monitoring the paging channel, it may initiate the RRC connection recovery procedure as follows:

[0152] 1> if the UE is in RRC_INACTIVE and the UE has joined one or more MBS sessions indicated by the TMGI included in pagingGroupList; and

[0153] 1> If any ue-Identity contained in any PagingRecord (if included in a Paging message) does not match the UE identity assigned by upper layers:

[0154] 2>Start the RRC connection recovery process

[0155] Alternatively,

[0156] 1> if in RRC_INACTIVE and the UE has joined one or more MBS sessions indicated by the TMGI included in pagingGroupList; and

[0157] 1> If any ue-Identity contained in any PagingRecord (if included in a Paging message) does not match the UE identity assigned by upper layers

[0158] 2> If multicast reception is supported in RRC_INACTIVE state (or if the UE has a configuration for multicast reception in RRC_INACTIVE state and / or if the gNB has indicated through SI or RRC signaling (RRC Release or RRCReconfiguration) that it supports multicast reception in RRC_INACTIVE state):

[0159] 3>UE starts the process of receiving multicast reception under RRC_inactive (e.g., recovering one or more MRBs, establishing / re-establishing PDCP / RLC entities for the recovered MRBs, etc.)

[0160] 2> Otherwise:

[0161] 3> Start the RRC connection recovery process, where resumeCause is set as follows:

[0162] 4> If the UE is configured with access identification 1 by the upper layer:

[0163] 5>resumeCause is set to mps-PriorityAccess;

[0164] 4> Otherwise, if the UE is configured with access identifier 2 by upper layers:

[0165] 5>resumeCause is set to mcs-PriorityAccess;

[0166] 4> Otherwise, if the UE is configured by upper layers with one or more access identifiers equal to 11 to 15:

[0167] resumeCause is set to highPriorityAccess;

[0168] 4> Otherwise:

[0169] 5>resumeCause is set to mt-Access.

[0170] Figure 2 is a flow chart illustrating the operation of a UE according to an embodiment.

[0171] refer to Figure 2 In step S210, the UE in the RRC_connected state receives the multicast communication service through a mechanism such as PTP and / or PTM delivery.

[0172] 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 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 RLC entity of the MRB.

[0173] When the UE is in the RRC_CONNECTED state, in step S220, the UE receives an RRCRelease message from the gNB with the suspension configuration and enters the RRC_INACTIVE state.

[0174] When the UE is in RRC_Inactive state, the SDT process may be initiated as described above. In step S230, if configured by an upper layer (eg, NAS or application layer) for MBS multicast reception (or for MBS multicast reception under RRC_Connected), the UE monitors a paging channel for paging using TMGI.

[0175] If a paging message including the TMGI of one or more MBS sessions to which the UE has joined is received in step S240, then in step S250, the UE checks whether an SDT procedure is in progress.

[0176] If the SDT process is in progress in step S250, the UE does not start the recovery process in step S260, and the UE starts the recovery process after completing the SDT process.

[0177] If the SDT process is not in progress in step S250 , then in step 270 , the UE initiates a recovery process.

[0178] Alternatively, if a paging message is received containing the TMGI of one or more MBS sessions to which the UE has joined, it checks whether a timer (e.g., T319a timer) is running. If the timer is running, the UE does not initiate the recovery procedure, and the UE initiates the recovery procedure after completing the SDT procedure. If the timer is not running, the UE initiates the recovery procedure. The timer may be started when the UE initiates the SDT procedure, it may be started when the first UL transmission containing a CCCH message is transmitted during the SDT procedure, it may be started when the RA procedure initiated for the SDT procedure is successfully completed, or it may be started when a network response (i.e., a PDCCH addressed to the C-RNTI) is received from the network (i.e., the gNB) for the first UL transmission containing a CCCH message.

[0179] Alternatively, the SDT process can be started as described above when the UE is in the RRC_inactive state. If configured by an upper layer (e.g., NAS or application layer) for MBS multicast reception (or for MBS multicast reception under RRC_connection), the UE monitors a paging channel for paging using TMGI. If a paging message containing the TMGI of one or more MBS sessions to which the UE has joined is received, the UE checks whether the SDT process is in progress. If the SDT process is in progress, the UE can determine whether SDT or multicast reception has a higher priority. The priority may be indicated or predefined by the network in SI, RRC signaling. If the priority of MBS multicast reception is lower than the priority of SDT, the UE does not start the recovery process, and the UE starts the recovery process after completing the SDT process. If the SDT process is not in progress, the UE starts the recovery process.

[0180] Alternatively, the SDT process can be started as described above when the UE is in the RRC_INACTIVE state. If configured by an upper layer (e.g., NAS or application layer) for MBS multicast reception (or for MBS multicast reception under RRC_CONNECTED), the UE monitors a paging channel for paging using TMGI. If a paging message containing the TMGI of one or more MBS sessions to which the UE has joined is received, the UE checks whether the timer is running. If the timer is running, the UE can determine whether SDT or multicast reception has a higher priority. The priority may be indicated or predefined by the network in SI, RRC signaling. If the priority of MBS multicast reception is lower than that of SDT, the UE does not start the recovery process, and the UE starts the recovery process after completing the SDT process. If the timer is not running, the UE starts the recovery process.

[0181] If the UE receives a paging message while monitoring the paging channel:

[0182] 1> if in RRC_INACTIVE and the UE has joined one or more MBS sessions indicated by the TMGI included in pagingGroupList; and

[0183] 1> if any ue-Identity contained in any PagingRecord (if included in a Paging message) does not match the UE identity assigned by upper layers; and

[0184] If the T319a is not running:

[0185] 2> Start the RRC connection recovery process according to 5.3.13, where resumeCause is set as follows:

[0186] 3> If the UE is configured with access identification 1 by the upper layer:

[0187] 4>resumeCause is set to mps-PriorityAccess;

[0188] 3> Otherwise, if the UE is configured with access identifier 2 by upper layers:

[0189] 4>resumeCause is set to mcs-PriorityAccess;

[0190] 3> Otherwise, if the UE is configured by upper layers with one or more access identifiers equal to 11 to 15:

[0191] resumeCause is set to highPriorityAccess;

[0192] 3> Otherwise:

[0193] 4>resumeCause is set to mt-Access.

[0194] If the UE is in the RRC_INACTIVE state and the UE has joined one or more MBS sessions indicated by the TMGI contained in the pagingGroupList, and if any ue-Identity contained in any PagingRecord (if contained in the Paging message) does not match the UE identity assigned by upper layers, and if T319a is running, the UE initiates the RRC Connection Recovery procedure after completing the SDT procedure (i.e., T319a stops when the UE is in the RRC_INACTIVE state).

[0195] Alternatively, if the UE receives a paging message while monitoring a paging channel:

[0196] 1> if in RRC_INACTIVE and the UE has joined one or more MBS sessions indicated by the TMGI included in pagingGroupList; and

[0197] 1> If any ue-Identity contained in any PagingRecord (if included in a Paging message) does not match the UE identity assigned by upper layers

[0198] 2> When the UE is in RRC_INACTIVE state, after T319a stops, start the RRC connection recovery procedure according to 5.3.13 and set resumeCause as follows:

[0199] 3> If the UE is configured with access identification 1 by the upper layer:

[0200] 4>resumeCause is set to mps-PriorityAccess;

[0201] 3> Otherwise, if the UE is configured with access identifier 2 by upper layers:

[0202] 4>resumeCause is set to mcs-PriorityAccess;

[0203] 3> Otherwise, if the UE is configured by upper layers with one or more access identifiers equal to 11 to 15:

[0204] resumeCause is set to highPriorityAccess;

[0205] 3> Otherwise:

[0206] 4>resumeCause is set to mt-Access.

[0207] Figure 3 is a flow chart illustrating the operation of a UE according to an embodiment.

[0208] refer to Figure 3 In step S310, the UE in the RRC_connected state receives multicast communication services through mechanisms such as PTP and / or PTM delivery.

[0209] 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 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 RLC entity of the MRB.

[0210] When the UE is in the RRC_CONNECTED state, the UE receives an RRCRelease message from the gNB with the suspend configuration. In step S320, the UE enters the RRC_INACTIVE state after receiving the RRCRelease message with the suspend configuration.

[0211] When the UE is in the RRC_INACTIVE state, the SDT process may be initiated as described above. In step S330, if the UE is in the RRC_INACTIVE state and if configured by an upper layer (e.g., NAS or application layer) for MBS multicast reception (or for MBS multicast reception in RRC_CONNECTED), the UE checks whether the SDT process is in progress.

[0212] If the SDT process is in progress in step S330, then in step S340, the UE terminates the ongoing SDT process, continues to be in the RRC_inactive state, and then initiates the RRC connection recovery process.

[0213] If the SDT process is not in progress in step S330, then in step S350, the UE initiates the RRC connection recovery process.

[0214] Alternatively, if the UE is in the RRC_INACTIVE state and is configured by an upper layer (e.g., NAS or application layer) for MBS multicast reception, the UE checks whether the timer is running. If the timer is running, the UE terminates the ongoing SDT procedure, continues to be in the RRC_INACTIVE state, and then initiates the RRC connection recovery procedure. If the timer is not running, the UE initiates the RRC connection recovery procedure.

[0215] Figure 4is a flow chart illustrating the operation of a UE according to an embodiment.

[0216] refer to Figure 4 In step S410, the UE in the RRC_CONNECTED state receives the multicast communication service in the RRC_CONNECTED state through a mechanism such as PTP and / or PTM delivery.

[0217] 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 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 RLC entity of the MRB.

[0218] In step S420, when the UE is in the RRC_CONNECTED state, the UE receives an RRCRelease message from the gNB with the suspension configuration and enters the RRC_INACTIVE state.

[0219] When the UE is in the RRC_INACTIVE state, the SDT process may be initiated as described above. In step S430, if the UE is in the RRC_INACTIVE state and if configured by an upper layer (e.g., NAS or application layer) for MBS multicast reception (or for MBS multicast reception in RRC_CONNECTED), it is checked whether the SDT process is in progress.

[0220] If the SDT process is in progress in step S430, the UE determines whether SDT or multicast reception has a higher priority in step S440.

[0221] The priority may be indicated by the network in SI or RRC signaling. If the priority of MBS multicast reception is higher than the priority of SDT, then in step S450, the UE terminates the ongoing SDT process, continues in the RRC_inactive state, and then initiates the RRC connection recovery process.

[0222] If the priority of MBS multicast reception is lower than the priority of SDT in step S440, or if the SDT process is not in progress in step S430, then in step S460, the UE initiates an RRC connection recovery process.

[0223] Alternatively, if the UE is in the RRC_INACTIVE state and if configured by an upper layer (e.g., NAS or application layer) for MBS multicast reception (or for MBS multicast reception in RRC_CONNECTED), the UE checks whether the timer is running. If the timer is running, the UE can determine whether SDT or multicast reception has a higher priority. The priority may be indicated by the network in the SI or RRC signaling. If the priority of MBS multicast reception is higher than the priority of SDT, the UE terminates the ongoing SDT process, continues to be in the RRC_INACTIVE state, and then initiates the RRC connection recovery process. If the priority of MBS multicast reception is lower than the priority of SDT or the timer is not running, the UE initiates the RRC connection recovery process.

[0224] Figure 5 A terminal according to an embodiment is shown.

[0225] refer to Figure 5 The terminal includes a transceiver 510, a controller 520, and a memory 530. The controller 520 may refer to a circuit, an ASIC, or at least one processor. The transceiver 510, the controller 520, and the memory 530 are configured to execute Figures 1 to 4 The operation of the terminal shown or described above.

[0226] Although the transceiver 510, the controller 520, and the memory 530 are shown as separate entities, they may be implemented as a single entity like a single chip. The transceiver 510, the controller 520, and the memory 530 may be electrically connected or coupled to each other.

[0227] The transceiver 510 may transmit and receive signals to and from other entities (ie, a BS).

[0228] The controller 520 may control the terminal to perform various functions according to at least one of the embodiments described above. For example, the controller 520 controls the transceiver 510 to perform transmission of the SDT process and perform paging monitoring for MBS multicast reception. The controller 520 controls the transceiver 510 and / or the memory 530 to perform paging monitoring operations or SDT process operations according to various embodiments of the present disclosure.

[0229] In an embodiment of the present disclosure, the operation of the terminal can be implemented using a memory 530 storing a corresponding program code. Specifically, the terminal can be equipped with a memory 530 to store a program code for implementing the desired operation. In order to perform the desired operation, the controller 520 can read and execute the program code stored in the memory 530 by using at least one processor or a central processing unit (CPU).

[0230] Figure 6 A BS according to an embodiment is shown.

[0231] refer to Figure 6 , the BS includes a transceiver 610, a controller 620, and a memory 630. The controller 620 may refer to a circuit, an ASIC, or at least one processor. The transceiver 610, the controller 620, and the memory 630 are configured to execute Figures 1 to 4 The operation of the terminal shown or described above.

[0232] Although the transceiver 610, the controller 620, and the memory 630 are shown as separate entities, they may be implemented as a single entity like a single chip. The transceiver 610, the controller 620, and the memory 630 may be electrically connected or coupled to each other.

[0233] The transceiver 610 may transmit and receive signals to and from other network entities (ie, terminals).

[0234] The controller 620 may control the BS to perform various functions according to at least one of the embodiments described above. For example, in response to transmission of an SDT from a terminal, the controller 620 controls the transceiver 610 to transmit configuration information or confirmation associated with an MRB for a multicast session to the terminal.

[0235] In one embodiment, the operation of the BS may be implemented using a memory 630 storing corresponding program codes. Specifically, according to various embodiments of the present disclosure, the BS may be equipped with a memory 630 to store program codes for implementing desired operations. In order to perform the desired operations, the controller 620 may read and execute the program codes stored in the memory 630 by using at least one processor or CPU.

[0236] As described above, the embodiments disclosed in the specification and the drawings are only used to present specific examples to easily explain the content of the present disclosure and help understanding, but are not intended to limit the scope of the present disclosure. Therefore, in addition to the embodiments disclosed herein, the scope of the present disclosure should be analyzed to include all changes or modifications based on the technical concept of the present disclosure.

[0237] While the disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims and their equivalents.

Claims

1. A method performed by a terminal in a wireless communication system, the method comprising: receiving a radio resource control RRC release message from a base station BS, the RRC release message including information indicating a suspension configuration for an RRC inactive state; In the presence of a configuration of multicast and broadcast service MBS multicast reception by an upper layer, identifying whether a small data transmission SDT process is being performed in the RRC inactive state; as well as Based on the SDT process not being performed, monitoring a paging channel for paging using a temporary mobile group identity TMGI associated with the MBS session, The MBS session is associated with a bearer used for the MBS multicast reception.

2. The method of claim 1, further comprising: Based on the SDT process being ongoing, the paging channel for paging using the TMGI associated with the MBS session is not monitored.

3. The method of claim 1, wherein: Monitoring the paging channel for paging using the TMGI comprises: receiving a paging message from the BS; and It is identified whether the paging message includes information about the TMGI.

4. The method according to claim 3, in, In case that the paging message includes information about the TMGI and a user equipment UE identifier ID contained in the paging message matches an ID allocated to the terminal, an RRC connection recovery procedure is initiated.

5. The method according to claim 1, in, Based on the SDT error detection timer being running, the SDT process is recognized as being in progress.

6. The method according to claim 1, in, Configuration information about the bearer associated with the MBS session is received from the BS via dedicated RRC signaling when the terminal is in an RRC connected state.

7. The method according to claim 1, in, The RRC release message also includes information about SDT configuration.

8. A terminal in a wireless communication system, the terminal comprising: Transceiver; as well as The controller is configured as: controlling the transceiver to receive a radio resource control RRC release message from a base station BS, the RRC release message including information indicating a suspension configuration for an RRC inactive state, In the presence of a configuration of multicast and broadcast service MBS multicast reception by an upper layer, identifying whether a small data transmission SDT process is being performed in the RRC inactive state, and Based on the SDT process not being performed, monitoring a paging channel for paging using a temporary mobile group identity TMGI associated with the MBS session, The MBS session is associated with a bearer used for the MBS multicast reception.

9. The terminal according to claim 8, in, The controller is further configured to: based on the SDT process being ongoing, not monitor the paging channel for paging using the TMGI associated with the MBS session.

10. The terminal according to claim 8, in, The controller is further configured to monitor the paging channel for paging using the TMGI by: receiving a paging message from the BS, and It is identified whether the paging message includes information about the TMGI.

11. The terminal according to claim 10, in, The controller is further configured to: initiate an RRC connection recovery procedure if the paging message includes information about the TMGI and a user equipment (UE) identifier (ID) contained in the paging message matches an ID allocated to the terminal.

12. The terminal according to claim 8, in, Based on the SDT error detection timer being running, the SDT process is recognized as being in progress.

13. The terminal according to claim 8, in, Configuration information about the bearer associated with the MBS session is received from the BS via dedicated RRC signaling when the terminal is in an RRC connected state.

14. The terminal according to claim 8, in, The RRC release message also includes information about SDT configuration.

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