Method and apparatus for resuming radio resource control connection during multicast broadcast service in a wireless communication system

Abstract

The disclosure relates to a method for resuming RRC connection during MBS multicast service. The method includes, transmitting, by UE (101), transition request message to network apparatus for state change from RRC-inactive state to RRC-connected state. Further, method includes, receiving signaling message from network apparatus in response to transition request message indicating to transit. Further, method includes, invoking protocol layer reset operation at MAC layer when UE (101) is configured to receive MBS multicast in the RRC-inactive state. Further, method includes, determining whether RRC setup message and RRC resume message is received and protocol layer reset operation at MAC layer is invoked. Further, method includes, performing protocol layer reset operation at MAC layer during transition from RRC-inactive state to RRC-connected state, when RRC setup message and RRC resume message is received and protocol layer reset operation at MAC layer is invoked thereby enhancing the reliability and continuity for MBS reception.

Description

METHOD AND APPARATUS FOR RESUMING RADIO RESOURCE CONTROL CONNECTION DURING MULTICAST BROADCAST SERVICE IN A WIRELESS COMMUNICATION SYSTEM

[0001] The proposed embodiments relate to a telecommunication network system. More particularly, the present disclosure relates to handling RRC connection during Multicast Broadcast Service (MBS) multicast service in telecommunication network.

[0002] 5G mobile communication technologies define broad frequency bands such that high transmission rates and new services are possible, and can be implemented not only in "Sub 6GHz" bands such as 3.5GHz, but also in "Above 6GHz" bands referred to as mmWave including 28GHz and 39GHz. In addition, it has been considered to implement 6G mobile communication technologies (referred to as Beyond 5G systems) in terahertz bands (for example, 95GHz to 3THz bands) in order to accomplish transmission rates fifty times faster than 5G mobile communication technologies and ultra-low latencies one-tenth of 5G mobile communication technologies.

[0003] At the beginning of the development of 5G mobile communication technologies, in order to support services and to satisfy performance requirements in connection with enhanced Mobile BroadBand (eMBB), Ultra Reliable Low Latency Communications (URLLC), and massive Machine-Type Communications (mMTC), there has been ongoing standardization regarding beamforming and massive MIMO for mitigating radio-wave path loss and increasing radio-wave transmission distances in mmWave, supporting numerologies (for example, operating multiple subcarrier spacings) for efficiently utilizing mmWave resources and dynamic operation of slot formats, initial access technologies for supporting multi-beam transmission and broadbands, definition and operation of BWP (BandWidth Part), new channel coding methods such as a LDPC (Low Density Parity Check) code for large amount of data transmission and a polar code for highly reliable transmission of control information, L2 pre-processing, and network slicing for providing a dedicated network specialized to a specific service.

[0004] Currently, there are ongoing discussions regarding improvement and performance enhancement of initial 5G mobile communication technologies in view of services to be supported by 5G mobile communication technologies, and there has been physical layer standardization regarding technologies such as V2X (Vehicle-to-everything) for aiding driving determination by autonomous vehicles based on information regarding positions and states of vehicles transmitted by the vehicles and for enhancing user convenience, NR-U (New Radio Unlicensed) aimed at system operations conforming to various regulation-related requirements in unlicensed bands, NR UE Power Saving, Non-Terrestrial Network (NTN) which is UE-satellite direct communication for providing coverage in an area in which communication with terrestrial networks is unavailable, and positioning.

[0005] Moreover, there has been ongoing standardization in air interface architecture / protocol regarding 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 a node for network service area expansion by supporting a wireless backhaul link and an access link in an integrated manner, mobility enhancement including conditional handover and DAPS (Dual Active Protocol Stack) handover, and two-step random access for simplifying random access procedures (2-step RACH for NR). There also has been ongoing standardization in system architecture / service regarding a 5G baseline architecture (for example, service based architecture or service based interface) for combining Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, and Mobile Edge Computing (MEC) for receiving services based on UE positions.

[0006] As 5G mobile communication systems are commercialized, connected devices that have been exponentially increasing will be connected to communication networks, and it is accordingly expected that enhanced functions and performances of 5G mobile communication systems and integrated operations of connected devices will be necessary. To this end, new research is scheduled in connection with eXtended Reality (XR) for efficiently supporting AR (Augmented Reality), VR (Virtual Reality), MR (Mixed Reality) and the like, 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] Furthermore, such development of 5G mobile communication systems will serve as a basis for developing not only new waveforms for providing coverage in terahertz bands of 6G mobile communication technologies, multi-antenna transmission technologies such as Full Dimensional MIMO (FD-MIMO), array antennas and large-scale antennas, metamaterial-based lenses and antennas for improving coverage of terahertz band signals, high-dimensional space multiplexing technology using OAM (Orbital Angular Momentum), and RIS (Reconfigurable Intelligent Surface), but also full-duplex technology for increasing frequency efficiency of 6G mobile communication technologies and improving system networks, AI-based communication technology for implementing system optimization by utilizing 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 levels of complexity exceeding the limit of UE operation capability by utilizing ultra-high-performance communication and computing resources.

[0008] 5th generation (5G) or new radio (NR) mobile communications is recently gathering increased momentum with all the worldwide technical activities on the various candidate technologies from industry and academia. The candidate enablers for the 5G / NR mobile communications include massive antenna technologies, from legacy cellular frequency bands up to high frequencies, to provide beamforming gain and support increased capacity, new waveform (e.g., a new radio access technology (RAT)) to flexibly accommodate various services / applications with different requirements, new multiple access schemes to support massive connections, and so on.

[0009] In line with development of the communication systems, there is a need for method for performing MAC reset operation associated with MBS multicast.

[0010] The principal object of the embodiments herein is to handle RRC state transition during MBS multicast service in the telecommunication network.

[0011] Another object of the invention is to resume RRC connection for the UEs receiving NR MBS multicast service when the UE is capable of receiving the multicast service in the RRC-INACTIVE state.

[0012] Yet another object of the invention is to perform MAC reset operation for MBS multicast only for the UE engaged in receiving multicast in RRC-INACTIVE during state transitions and also to avoid impact to other services.

[0013] Yet another object of the invention is to invoke MAC reset and perform MAC reset for multicast when UE receives RRC Resume or RRC Setup message in response to an RRC Resume Request or RRC Resume Request1 and to continue multicast service reliably across RRC state transition.

[0014] Yet another object of the invention is to ensure reliable reception of multicast across RRC state transitions.

[0015] The technical subjects pursued in the disclosure may not be limited to the above mentioned technical subjects, and other technical subjects which are not mentioned may be clearly understood, through the following descriptions, by those skilled in the art to which the disclosure pertains.

[0016] Embodiments herein provide method and UE for resuming RRC connection during MBS multicast service. The method includes, transmitting, by UE (101), transition request message to network apparatus for state change from RRC-inactive state to RRC-connected state. Further, method includes, receiving signaling message from network apparatus in response to transition request message indicating to transit. Further, method includes, invoking protocol layer reset operation at MAC layer when UE (101) is configured to receive MBS multicast in the RRC-inactive state. Further, method includes, determining whether RRC setup message and RRC resume message is received and protocol layer reset operation at MAC layer is invoked. Further, method includes, performing protocol layer reset operation at MAC layer during transition from RRC-inactive state to RRC-connected state, when RRC setup message and RRC resume message is received and protocol layer reset operation at MAC layer is invoked thereby enhancing the reliability and continuity for MBS reception.

[0017] In an embodiment, the method performed by a terminal in a wireless communication system is provided, the method comprising:

[0018] transmitting, to a base station, radio resource control (RRC) resume request message; receiving, from the base station, one of an RRC resume message, or an RRC setup message; identifying whether the terminal is configured to receive a multicast broadcast service (MBS) multicast in an RRC inactive state; and in case that the terminal is configured to receive the MBS multicast in the RRC inactive state, resetting a medium access control (MAC), wherein the resetting the MAC comprises at least one of: stopping at least one MBS multicast discontinuous reception (DRX) timer; or flushing at least one soft buffer for all downlink (DL) hybrid automatic repeat and request (HARQ) processes used for the MBS multicast.

[0019] In an embodiment, wherein the RRC resume request message comprises at least one of an RRCResumeRequest, or an RRCResumeRequest1, wherein the resetting the MAC is performed by an MAC entity of the terminal.

[0020] In an embodiment, the method further comprising: considering a next received transmission for a transport block (TB) as a very first transmission for each DL HARQ process used for the MBS multicast.

[0021] In an embodiment, the method further comprising: resuming at least one multicast MBS radio bearer (MRB).

[0022] In an embodiment, a method performed by a base station in a wireless communication system is provided, the method comprising: receiving, from a terminal, radio resource control (RRC) resume request message; and transmitting, to the terminal, one of an RRC resume message, or an RRC setup message, wherein, in case that receiving a multicast broadcast service (MBS) multicast in an RRC inactive state is configured to the terminal, a medium access control (MAC) of the terminal is reset, wherein the MAC of the terminal is reset comprises at least one of: at least one MBS multicast discontinuous reception (DRX) timer is stopped, or at least one soft buffer for all downlink (DL) hybrid automatic repeat and request (HARQ) processes used for the MBS multicast is flushed.

[0023] In an embodiment, a terminal in a wireless communication system is provided, the terminal comprising: a transceiver; and at least one processor coupled with the transceiver and configured to: ransmit, to a base station, radio resource control (RRC) resume request message, receive, from the base station, one of an RRC resume message, or an RRC setup message, identify whether the terminal is configured to receive a multicast broadcast service (MBS) multicast in an RRC inactive state, and in case that the terminal is configured to receive the MBS multicast in the RRC inactive state, reset a medium access control (MAC),

[0024] wherein, in resetting the MAC, the at least one processor is configured to at least one of: stop at least one MBS multicast discontinuous reception (DRX) timer, or flush at least one soft buffer for all downlink (DL) hybrid automatic repeat and request (HARQ) processes used for the MBS multicast.

[0025] In an embodiment, a base station in a wireless communication system is provided, the base station comprising: a transceiver; and at least one processor coupled with the transceiver and configured to: receive, from a terminal, radio resource control (RRC) resume request message, and transmit, to the terminal, one of an RRC resume message, or an RRC setup message, wherein, in case that receiving a multicast broadcast service (MBS) multicast in an RRC inactive state is configured to the terminal, a medium access control (MAC) of the terminal is reset, wherein the MAC of the terminal is reset comprises at least one of: at least one MBS multicast discontinuous reception (DRX) timer is stopped, or at least one soft buffer for all downlink (DL) hybrid automatic repeat and request (HARQ) processes used for the MBS multicast is flushed.

[0026] In one aspect, the objectives are achieved by providing a method for resuming radio resource control (RRC) connection during MBS multicast service in a telecommunication network system. The method includes transmitting by a user equipment (UE) a transition request message to a network apparatus for a state change from an RRC-inactive state to an RRC-connected state. Further, the method includes receiving by the UE a signaling message from the network apparatus in response to the transition request message indicating to transit from the RRC-inactive state to the RRC-connected state. The signaling message is an RRC setup message and RRC resume message that indicates the UE to transit. Further, the method includes invoking by the UE a protocol layer reset operation at the MAC layer if the UE is configured to receive MBS multicast in the RRC-inactive state. Further, the method includes determining by the UE whether the RRC setup message and RRC resume message are received and protocol layer reset operation at the MAC layer is invoked. Further, the method includes performing by the UE the protocol layer reset operation at the MAC layer during the transition from the RRC-inactive state to the RRC-connected state when the RRC setup message and RRC resume message are received and protocol layer reset operation at the MAC layer is invoked, thereby enhancing the reliability and continuity for multicast and broadcast service (MBS) reception.

[0027] In an embodiment, the method of performing the protocol layer reset operation at the MAC layer includes flushing soft buffers for all downlink (DL) Hybrid Automatic Repeat Request (HARQ) processes used for MBS multicast. Further, the method includes considering the next received transmission for a transport block as first transmission for each of the DL HARQ processes used for MBS multicast. Further, the method includes stopping Discontinuous Reception (DRX) timers configured for multicast MRBs that are configured to receive multicast in the RRC-inactive state.

[0028] In an embodiment, the transition request message is one of a RRC resume request or a RRC resume request1 message, and wherein the signaling message comprises one of a RRC resume message or a RRC setup message.

[0029] Accordingly, the embodiment herein is to provide a UE for handling RRC connection during MBS multicast service in a telecommunication network system. The UE includes a processor and an MBS controller communicatively coupled to the processor. The MBS controller transmits a transition request message to a network apparatus for a state change from an RRC-inactive state to an RRC-connected state. Further, the MBS controller receives a signaling message from the network apparatus in response to the transition request message indicating to transit from the RRC-inactive state to the RRC-connected state. The signaling message is an RRC setup message and RRC resume message that indicates the UE to transit. Further, the MBS controller invokes a protocol layer reset operation at the MAC layer if the UE is configured to receive MBS multicast in the RRC-inactive state. Further, the MBS controller determines whether the RRC setup message and RRC resume message are received and protocol layer reset operation at the MAC layer is invoked. Further, the MBS controller performs the protocol layer reset operation at the MAC layer during the transition from the RRC-inactive state to the RRC-connected state when the RRC setup message and RRC resume message are received and protocol layer reset operation at the MAC layer is invoked, thereby enhancing the reliability and continuity for multicast and broadcast service (MBS) reception.

[0030] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications be made within the scope of the embodiments herein.

[0031] The present disclosure provides an effective and efficient method for performing MAC reset operation associated with MBS multicast. Advantageous effects obtainable from the disclosure may not be limited to the above mentioned effects, and other effects which are not mentioned may be clearly understood, through the following descriptions, by those skilled in the art to which the disclosure pertains

[0032] These and other features, aspects, and advantages of the present embodiments are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:

[0033] Fig. 1 is a block diagram of a UE that handles RRC state transition during MBS multicast service in a telecommunication network system according to embodiments disclosed herein.

[0034] Fig. 2 is a flow diagram that illustrates a method for handling RRC state transition during MBS multicast service in a telecommunication network system according to embodiments disclosed herein.

[0035] Fig. 3 is a flow diagram that illustrates a method of an operational flow of UE receiving an RRC Resume message and resuming multicast MBS radio bearers (MRBs) except the multicast MRBs that are configured to receive multicast in the RRC-INACTIVE state according to embodiments disclosed herein.

[0036] Fig. 4 is a flow diagram that illustrates a method of an operational flow of the UE receiving the RRC resume message and performing a Medium Access Control (MAC) reset procedure according to the embodiments disclosed herein.

[0037] Fig. 5 is a flow diagram that illustrates a method of an operational flow of the UE receiving the RRC setup message in response to a RRC resume request or a RRC resume request1 message and performing a Medium Access Control (MAC) reset procedure according to the embodiments disclosed herein.

[0038] Fig. 6 is a flow diagram that illustrates a method of UE receiving an RRC resume message or RRC release with suspend Config message while the Small Data Transmission (SDT) procedure is ongoing and performing the MAC reset procedure according to embodiments disclosed herein.

[0039] It may be noted that, to the extent possible, like reference numerals have been used to represent like elements in the drawing. Furthermore, those of ordinary skill in the art will appreciate that elements in the drawing are illustrated for simplicity and may not necessarily have been drawn to scale. For example, the dimensions of some of the elements in the drawing may be exaggerated relative to other elements to improve the understanding of aspects of the invention. Further, the elements may have been represented in the drawing by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the invention so as not to obscure the drawing with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

[0040] It may be noted that, to the extent possible, like reference numerals have been used to represent like elements in the drawing. Furthermore, those of ordinary skill in the art will appreciate that elements in the drawing are illustrated for simplicity and may not necessarily have been drawn to scale. For example, the dimensions of some of the elements in the drawing may be exaggerated relative to other elements to improve the understanding of aspects of the invention. Further, the elements may have been represented in the drawing by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the invention so as not to obscure the drawing with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

[0041] As is traditional in the field, embodiments are described and illustrated in terms of blocks that carry out a described function or functions. These blocks, which are referred to herein as managers, units, modules, hardware components, or the like, are physically implemented by analog and / or digital circuits such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive electronic components, active electronic components, optical components, hardwired circuits, and the like, and may optionally be driven by firmware and software. The circuits, for example, may be embodied in one or more semiconductor chips or on substrate supports such as printed circuit boards and the like. The circuits constituting a block may be implemented by dedicated hardware or by a processor (e.g., one or more programmed microprocessors and associated circuitry) or by a combination of dedicated hardware to perform some functions of the block and a processor to perform other functions of the block. Each block of the embodiments may be physically separated into two or more interacting and discrete blocks without departing from the scope of the proposed method. Likewise, the blocks of the embodiments may be physically combined into more complex blocks without departing from the scope of the proposed method.

[0042] The accompanying drawings are used to help easily understand various technical features, and it is understood that the embodiments presented herein are not limited by the accompanying drawings. As such, the proposed method is construed to extend to any alterations, equivalents, and substitutes in addition to those which are particularly set out in the accompanying drawings. Although the terms "first," "second," etc. are used herein to describe various elements, these elements are not limited by these terms. These terms are generally used to distinguish one element from another.

[0043] The evolution of NR MBS (Multimedia Broadcast and Multicast Services) is a significant step forward in enhancing the efficiency and reach of multicast and broadcast services in mobile networks. These services are designed to deliver common content to multiple user equipment (UEs) simultaneously, thereby optimizing network resources and improving user experience. In multicast services, content is specifically targeted to a group of UEs that have opted into a multicast group within a designated coverage area. The broadcast services aim to deliver content to UEs within a broader coverage area, which can range from a single radio cell to a much larger region. This dual approach allows network operators to tailor content delivery strategies based on the specific needs and characteristics of their user base.

[0044] In the context of legacy systems, such as those defined in 3GPP Release 17, the process of informing UEs about the activation of a multicast session involves a group notification or paging mechanism. This mechanism is used by the UEs in the RRC-IDLE or RRC-INACTIVE states, as it prompts them to transition to the RRC-CONNECTED state to receive the multicast session. This transition is necessary because, traditionally, multicast services could be received when UEs were in the RRC-CONNECTED state. However, with advancements anticipated in 3GPP Release 18, there is potential for UEs to receive multicast sessions even while in the RRC-INACTIVE state. This development could significantly enhance the flexibility and efficiency of multicast service delivery, allowing UEs to conserve battery life and reduce signaling overhead while still accessing multicast content.

[0045] Despite these advancements, challenges remain in ensuring seamless service continuity for UEs capable of receiving MBS multicast services in the RRC-INACTIVE state. An issue arises when these UEs need to resume their RRC connection, as there is a need of a robust mechanism to manage the transition without disrupting the ongoing multicast session. This involves specifying how the Medium Access Control (MAC) entity handles Hybrid Automatic Repeat reQuest (HARQ) buffers, timers, and MBS radio bearers during RRC connection resumption. Addressing these technical challenges is essential to maintain service quality and reliability, ensuring that users experience uninterrupted access to multicast content. Therefore, it is needed to develop a solution that either resolve these issues or provide viable alternatives, thereby enhancing the overall robustness and adaptability of NR MBS services.

[0046] The problem at hand addresses the challenge of supporting a large number of multicast UEs within a network, specifically when these UEs are in the RRC INACTIVE state. This state is used for managing network resources efficiently, allowing more UEs to be supported than would be possible if all were in an active connection state. However, enabling multicast reception in this state introduces certain complications. Primarily, when a UE transitions from RRC INACTIVE to RRC CONNECTED, the continuity of multicast reception is jeopardized. This disruption occurs because the Medium Access Control (MAC) layer timers and buffers are not cleared during such transitions, leading to potential data loss or service interruption.

[0047] Moreover, performing a MAC reset during these transitions to clear the buffers and timers can have unintended consequences on other services, such as those related to Non-Terrestrial Networks (NTNs). NTNs are important as they provide connectivity in remote areas and enhance network robustness. Therefore, a solution that isolates the MAC reset to affect only the multicast services without impacting other services is essential. The invention in question proposes a standardized solution that specifically targets the MAC reset operation for MBS multicast. This solution is designed to be invoked when a UE engaged in multicast reception receives an RRC Resume or RRC Setup message in response to an RRC Resume Request or RRCResumeRequest1. By doing so, it ensures that multicast services can continue reliably across RRC state transitions without adversely affecting other network services.

[0048] The technical advantage of this invention lies in its ability to provide an efficient and effective MAC reset operation tailored for UEs receiving multicast in the RRC INACTIVE state. This proposed solution ensures the reliable reception of multicast data across RRC state transitions and enhances the performance of both the UE and the network in handling multicast data reception. By addressing the shortcomings of prior art, which lacked a mechanism to handle these specific cases, the invention offers a robust solution that enhances the overall network efficiency and user experience. Consequently, network operators can support a larger number of multicast UEs without compromising the quality of service, paving the way for more scalable and resilient network architectures.

[0049] Referring now to the drawings and more particularly to Figs. 1 through 5, where similar reference characters denote corresponding features consistently throughout the figure, these are shown preferred embodiments.

[0050] Fig 1 is the block diagram of the UE that handles RRC connection during MBS multicast service in telecommunication network system, according to embodiments disclosed herein. The UE (101) includes a processor (103), a memory (105), an I / O interface (107), and an MBS controller (109). Furthermore, the processor (103) of the UE (101) communicates with the memory (105), the I / O interface (107), and the MBS controller (109). The processor (103) is configured to execute instructions stored in the memory (105) and to perform various processes. The processor (103) can include one or a plurality of processors, can be a general-purpose processor such as a central processing unit (CPU), an application processor (AP), or the like, a graphics-only processing unit such as a graphics processing unit (GPU), a visual processing unit (VPU), and / or an Artificial Intelligence (AI) dedicated processor such as a neural processing unit (NPU).

[0051] Furthermore, the memory (105) of the UE (101) includes storage locations that can be addressed through the processor (103). The memory (105) is not limited to volatile or non-volatile memory and can include one or more computer-readable storage media. Non-volatile storage elements such as magnetic hard disks, optical discs, floppy discs, flash memories, EPROM, or EEPROM memories can also be included in the memory (105). Further, the memory (105) of the UE (101) can store various information received from the network. The various information includes an indication for transiting from the RRC-inactive state to RRC-connected state in the signaling messages such as the RRC setup message and RRC resume message.

[0052] The I / O interface (107) transmits information between the memory (105) and external peripheral devices, which are input-output devices associated with the UE (101). The I / O interface (107) receives various information from the network. This information can include, an indication for transiting from the RRC-inactive state to RRC-connected state in the signaling messages such as the RRC setup message and RRC resume message.

[0053] The MBS controller (109) communicates with the I / O interface (107) and memory (105) for handling RRC connection during MBS multicast service in the telecommunication network system. The MBS controller (109) is an innovative hardware that is realized through the physical implementation of both analog and digital circuits, including logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive and active electronic components, as well as optical components.

[0054] The MBS controller (109) of the UE (101) transmits the transition request message to the network apparatus for the state change from an RRC-inactive state to the RRC-connected state. For example, the transition request message can include, but is not limited to, the RRC resume request or the RRC resume request1 message. In an embodiment, the message is encoded with specific identifiers that allow the network apparatus to recognize the UE's request and prioritize it based on network conditions and UE capabilities. Further, the MBS controller (109) receives the signaling message from the network apparatus in response to the transition request message indicating to transit from the RRC-inactive state to the RRC-connected state. For example, the signaling message can include, but is not limited to, the RRC setup message and RRC resume message that indicates the UE to transit from the RRC-inactive state to the RRC-connected state.

[0055] Further, the MBS controller (109) invokes the protocol layer reset operation at the MAC layer when the UE (101) is configured to receive MBS multicast in the RRC-inactive state. This operation ensures that any residual data or errors from previous transmissions do not affect the new session. Further, the MBS controller (109) determines whether the RRC setup message and / or the RRC resume message is received and protocol layer reset operation at the MAC layer is invoked. This determination involves checking the integrity and authenticity of the received messages to prevent unauthorized access or erroneous transitions. Further, the MBS controller (109) performs the protocol layer reset operation at the MAC layer during the transition from the RRC-inactive state to the RRC-connected state when the RRC setup message and RRC resume message is received and protocol layer reset operation at the MAC layer is invoked. Thus, the MBS controller (109) enhances the reliability and continuity for the MBS reception by ensuring that the UE (101) is in the state for receiving multicast data without interruptions.

[0056] The protocol layer reset operation is performed by flushing the soft buffers for all the downlink HARQ processes used for MBS multicast. This involves clearing any partially received data packets and resetting the HARQ process counters to their initial state. Upon flushing, the next received transmission for the transport block is considered as the first transmission for each of the the DL HARQ processes used for MBS multicast. This ensures that the UE (101) can correctly decode the incoming data without relying on potentially corrupted previous transmissions. Further, the DRX timers configured for multicast MRB are stopped that are configured to receive the multicast in the RRC-inactive state. These timers are for managing power consumption and ensuring that the UE (101) wakes up at the correct intervals to receive multicast data, thereby balancing energy efficiency with data reception reliability.

[0057] In an embodiment, the MBS controller (109) receives the signaling message from the network apparatus to resume the UE (101) from the RRC-inactive state to the RRC-connected state. This signaling message may include specific instructions or parameters that dictate how the UE (101) should handle ongoing or pending multicast sessions. Further, the MBS controller (109) determines whether the multicast MRB were configured to receive multicast service in the RRC-inactive state. This determination involves checking the configuration settings stored in the UE's (101) memory to ensure that the correct multicast resources are activated. Further, the MBS controller (109) skips the resumption of multicast MRB that is configured to receive multicast in the RRC-inactive state upon receiving the signaling message from the network apparatus when the multicast MRB were configured to receive multicast service in the RRC-inactive state. This selective resumption helps in conserving resources and avoiding unnecessary data processing. Also, the MBS controller (109) resumes other multicast MRBs that are not configured to receive multicast in the RRC-inactive state upon receiving the signaling message from the network apparatus when the multicast MRB were configured to receive multicast service in the RRC-inactive state. This ensures that all necessary multicast services are available to the UE (101) without delay, enhancing the user experience.

[0058] In an embodiment, the MBS controller (109) receives the signaling message from the network apparatus to resume the UE (101) from the RRC-inactive state to the RRC-connected state. This message may include a list of multicast MRBs, allowing the MBS controller to make informed decisions about which resources to activate. Further, the MBS controller (109) determines whether the multicast MRB are suspended and not suspended when the UE was transitioned from the RRC-connected state to the RRC-inactive state upon receiving RRC release message. This involves checking the status of each MRB in the UE's configuration to ensure that only necessary resources are resumed. Further, the MBS controller (109) skips the resumption of the multicast MRB that are not suspended when transiting from the RRC-inactive state to the RRC-connected state. This helps in maintaining efficient use of network resources and reducing unnecessary signaling overhead. Further, the MBS controller (109) resumes the multicast MRB that are suspended when transiting from the RRC-inactive state to the RRC-connected state. This ensures that all required multicast services are promptly available to the UE, maintaining service continuity and user satisfaction.

[0059] Fig. 2 is the flow diagram that illustrates the method for handling RRC state transition during MBS multicast service in telecommunication network by UE, according to embodiments disclosed herein.

[0060] At block 201, the method includes transmitting the transition request message to the network apparatus for the state change from the RRC-inactive state to the RRC-connected state. This transition request message is used for initiating the state change process, allowing the UE (101) to prepare for data transmission and reception. The message may include parameters such as the UE's (101) current state, state, and any relevant context information to facilitate the transition. Further, the transition request message can be optimized to reduce signaling overhead, thereby improving network efficiency and reducing the time required for state transitions.

[0061] At block 203, the method includes receiving the signaling message from the network apparatus in response to the transition request message indicating to transit from the RRC-inactive state to the RRC-connected state. The signaling message can be the RRC setup message and / or RRC resume message that indicates the UE (101) to transit.

[0062] At block 205, the method includes invoking the protocol layer reset operation at the MAC layer when the UE (101) is configured to receive MBS multicast in the RRC-inactive state. This reset operation is necessary to clear any residual data or configuration settings that may interfere with the new connection setup. By resetting the MAC layer, the UE (101) ensures that it starts with a clean slate, minimizing the risk of data corruption or transmission errors. The reset operation may also involve reinitializing protocol parameters, such as timers and counters, to align with the requirements of the new connection state. This proactive approach helps maintain the integrity and performance of the multicast service.

[0063] At block 207, the method includes determining whether the at least one of RRC setup message and RRC resume message is received and protocol layer reset operation at the MAC layer is invoked. This determination step is used for ensuring that the UE (101) only proceeds with the transition if all necessary conditions are met. The UE may employ a decision-making logic to evaluate the received messages and the status of the MAC layer reset operation. If any discrepancies are detected, the UE (101) can initiate corrective actions, such as retransmitting the transition request or re-invoking the reset operation, to ensure a successful transition. This step enhances the robustness of the method by providing a mechanism for error detection and recovery.

[0064] At block 209, the method includes performing the protocol layer reset operation at the MAC layer during the transition from the RRC-inactive state to the RRC-connected state, when the at least one of RRC setup message and RRC resume message is received and protocol layer reset operation at the MAC layer is invoked thereby enhancing the reliability and continuity for MBS reception. This operation ensures that the UE (101) is fully prepared to handle the demands of the RRC-connected state, particularly in terms of data throughput and latency requirements. By performing the reset operation in conjunction with the state transition, the UE can seamlessly switch between states without interrupting the multicast service. This capability is important for applications that rely on real-time data delivery, such as live video streaming or emergency broadcast services, where any disruption could have significant consequences.

[0065] Fig. 3 is a flow diagram that illustrates the method of the operational flow of the UE receiving the RRC Resume message and resuming multicast MBS radio bearers (MRBs), except the multicast MRBs that are configured to receive multicast in the RRC INACTIVE state, according to embodiments disclosed herein.

[0066] At block 301, the method includes the UE (101) being capable of receiving multicast in the RRC INACTIVE state, and the UE (101) is configured in the RRC release message with suspend configuration with multicast MRBs to receive multicast in the RRC INACTIVE state.

[0067] At block 303, the method includes, upon receiving the RRC release message, the UE (101) transiting from the RRC-CONNECTED state to the RRC-INACTIVE state.

[0068] At block 305, the method includes determining whether the UE (101) receives the RRC resume message from the network.

[0069] At block 307, the method includes resuming by the UE (101) SRB2 (if suspended), SRB3 (if configured), all DRBs (that are suspended), and multicast MRBs, and skipping resuming the multicast MRBs that are configured to receive multicast in the RRC-INACTIVE state.

[0070] Embodiments herein provide methods and systems for resuming RRC connection for UEs (101) receiving NR MBS multicast service reception. Particularly, the UEs (101) which are supporting 3GPP Release 18 MBS may be capable and / or configured to receive multicast in RRC INACTIVE state whereas the UEs (101) pertaining to previous release (i.e., 3GPP Release 17 MBS) may not be capable and / or not configured to receive multicast in the RRC INACTIVE state. Co-existence of these two sets of UEs (101) in the same cell / network is feasible and needs to be supported.

[0071] When the UE (101) receives RRC Resume message from the network (201), the UE (101) does not resume the multicast MRBs that are configured to receive multicast in the RRC INACTIVE state and the UE (101) resumes other multicast MRBs that are not configured to receive multicast in the RRC INACTIVE state.

[0072] In an embodiment, a few examples for specification are provided as follows:

[0073] Example A:

[0074] 5.x.y.z Reception of the RRC Resume by the UE (101)

[0075] The UE shall

[0076] ...

[0077] 1> resume SRB2 (if suspended), SRB3 (if configured), all DRBs (that are suspended) and multicast MRBs, except multicast MRBs that are configured to receive multicast in RRC INACTIVE.

[0078] Example B:

[0079] 5.x.y.z Reception of the RRC Resume by the UE (101)

[0080] The UE shall

[0081] ...

[0082] 1> resume SRB2 (if suspended), SRB3 (if configured), all DRBs (that are suspended) and multicast MRBs not configured to receive multicast in RRC INACTIVE.

[0083] In an embodiment, when the UE (101) receives RRC Resume message from the network (210), the UE (101) skips to resume the multicast MRBs that are not suspended (e.g. when transiting from RRC-CONNECTED state to RRC-INACTIVE state) and UE (101) resumes other multicast MRBs that are suspended (e.g. when transiting from RRC-CONNECTED state to RRC-INACTIVE state).

[0084] In an embodiment, an example specification is provided as follows:

[0085] Example C:

[0086] 5.x.y.z Reception of the RRC Resume by the UE (101)

[0087] The UE shall

[0088] ...

[0089] 1> resume SRB2 (if suspended), SRB3 (if configured), all DRBs (that are suspended) and multicast MRBs (that are suspended);

[0090] In an embodiment, when the UE (101) that is capable of receiving multicast service in the RRC-INACTIVE state and has at least one multicast MRB configured to receive multicast service in the RRC-INACTIVE state (e.g. UE has at least one activated multicast session in RRC-INACTIVE state), receives RRC Resume message from the network (201) in response to an RRC Resume Request or RRC Resume Request1 message sent from the UE (101), the UE (101) does not resume the multicast MRBs that are configured to receive multicast in the RRC-INACTIVE state and UE (101) resumes other multicast MRBs that are not configured to receive multicast in the RRC-INACTIVE state.

[0091] In an embodiment, when the UE (101) that is capable of receiving multicast service in the RRC-INACTIVE state and has at least one multicast MRB configured to receive multicast service in the RRC-INACTIVE state (e.g. UE has at least one activated multicast session in RRC-INACTIVE state), receives RRC Resume message from the network (201) in response to an RRC Resume Request or RRC Resume Request1 message sent from the UE (101), the UE (101) skips to resume the multicast MRBs that are not suspended (e.g. when transiting from RRC-CONNECTED state to RRC-INACTIVE state) and UE (101) resumes other multicast MRBs that are suspended (e.g. when transiting from RRC-CONNECTED state to RRC-INACTIVE state).

[0092] In an embodiment, when the UE (101) that is capable of receiving multicast service in the RRC-INACTIVE state and has at least one multicast MRB configured to receive multicast service in the RRC-INACTIVE state, receives RRC Resume message or RRC Setup message from the network (201) in response to an RRC Resume Request or RRCResumeRequest1 message sent from the UE (101), the UE (101) skips to release the multicast MRBs that are configured as part of suspend Configuration (e.g. when transiting from RRC-CONNECTED state to RRC-INACTIVE state).

[0093] In an embodiment, when the UE (101) receives RRC Resume message or UE (101) receives RRC Setup message from the network (201) in response to an RRC Resume Request or RRCResumeRequest1 message sent from the UE (101), the UE (101) releases the suspend Configuration except the multicast-Inactive Configuration (i.e. multicast MRB configurations that were configured for multicast reception in RRC-INACTIVE).

[0094] In an embodiment, when the UE (101) receives RRC Resume message or UE (101) receives RRC Setup message from the network (201) in response to an RRC Resume Request or RRCResumeRequest1 message sent from the UE (101), the UE (101) releases the multicast MRBs that were configured as part of suspend Configuration (e.g. multicast MRBs that were configured when transiting from RRC-CONNECTED state to RRC-INACTIVE state).

[0095] In an embodiment, when the UE (101) that is capable of receiving multicast service in the RRC-INACTIVE state and has at least one multicast MRB configured to receive multicast service in the RRC-INACTIVE state, receives RRC Resume message or RRC Setup message from the network (201) in response to an RRC Resume Request or RRC Resume Request1 message sent from the UE (101), the UE (101) releases the suspend Configuration except the multicast-Inactive Configuration (i.e. multicast MRB configurations that were configured for multicast reception in RRC-INACTIVE).

[0096] In an embodiment, when the UE (101) that is capable of receiving multicast service in the RRC-INACTIVE state and has at least one multicast MRB configured to receive multicast service in the RRC-INACTIVE state, receives RRC Resume message or RRC Setup message from the network (201) in response to an RRC Resume Request or RRC Resume Request1 message sent from the UE (101), the UE (101) releases the multicast MRBs that were configured as part of suspend Configuration (e.g. multicast MRBs that were configured when transiting from RRC-CONNECTED state to RRC-INACTIVE state).

[0097] Fig 4 is the flow diagram that illustrates the method of the operational flow of the UE (101) receiving the RRC resume message and performing the Medium Access Control (MAC) reset procedure according to the embodiments disclosed herein.

[0098] At block 401, the method includes the UE (101) being capable of receiving multicast in the RRC-INACTIVE state, and the UE (101) is configured in the RRC release message with a suspend configuration message with multicast MRBs to receive multicast in the RRC INACTIVE state.

[0099] At block 403, the method includes the UE (101) transitioning from the RRC-CONNECTED state to the RRC-INACTIVE state.

[0100] At block 405, the method includes determining by the UE (101) whether it receives the RRC resume message from the network.

[0101] At block 407, the method includes the RRC layer of the UE (101) invoking the MAC reset procedure, and the MAC layer in the UE (101) performs the MAC reset when the UE (101) receives the RRC resume message from the network. However, the method continues to determine whether the UE (101) receives the RRC resume message when the RRC resume message is not received.

[0102] At block 409, the method includes flushing, by the UE (101), the soft buffers for all DL HARQ processes used for MBS multicast.

[0103] At block 411, the method includes considering, by the UE (101), the next received transmission for a transport block as first transmission for each of the DL HARQ processes used for MBS multicast.

[0104] At block 413, the method includes stopping, by the UE (101), DRX timers configured for multicast MRBs that are configured to receive multicast in the RRC-inactive state.

[0105] When the UE (101) receives an RRC Resume message or RRC Setup message from the network (201) in response to an RRC Resume Request or RRC Resume Request1 message sent from the UE (101). The upper layer (e.g., RRC layer) in the UE (101) invokes the MAC reset, and the lower layer (e.g., MAC layer) in the UE (101) performs the MAC reset operation. Wherein the MAC reset operation includes at least one of the flushing of the soft buffers for downlink Hybrid Automatic Repeat Request (HARQ) processes and clearing (stopping) of the Discontinuous Reception (DRX) timers configured / used for the multicast MRBs that are configured to receive multicast in the RRC-INACTIVE state. Further, UE considers the next received transmission for a transport block (TB) as the very first transmission for each of the HARQ processes used for MBS multicast.

[0106] In an embodiment, when the UE (101) that is capable of receiving multicast service in the RRC-INACTIVE state and has at least one multicast MRB configured to receive multicast service in the RRC-INACTIVE state (e.g., UE has at least one activated multicast session in RRC-INACTIVE state) receives an RRC Resume message or RRC Setup message from the network (201) in response to an RRC Resume Request or RRC Resume Request1 message sent from the UE (101), the upper layer (e.g., RRC layer) in the UE (101) invokes the MAC reset, and the lower layer (e.g., MAC layer) in the UE (101) performs the MAC reset operation. Wherein the MAC reset operation includes at least one of the flushing of the soft buffers for downlink HARQ processes and clearing (stopping) of the DRX timers configured / used for the multicast MRBs that are configured to receive multicast in the RRC INACTIVE state. Further, UE considers the next received transmission for a transport block (TB) as the very first transmission for each of the HARQ processes used for MBS multicast.

[0107] Fig. 5 is the flow diagram that illustrates the method of the operational flow of the UE receiving the RRC setup message in response to the RRC resume request or the RRC resume request1 message and performing a Medium Access Control (MAC) reset procedure according to the embodiments disclosed herein.

[0108] At block 501, the method includes the UE (101) being capable of receiving multicast in the RRC-INACTIVE state, and the UE (101) is configured in the RRC release message with a suspend configuration message with multicast MRBs to receive multicast in the RRC INACTIVE state.

[0109] At block 503, the method includes the UE (101) transitioning from the RRC-CONNECTED state to the RRC-INACTIVE state.

[0110] At block 505, the method includes transmitting, by the UE (101) a RRC resume request message or RRC resume request 1 message to network for transitioning from RRC-Inactive state to the RRC-connected state.

[0111] At block 507, the method includes determining by the UE (101) whether it receives the RRC Setup message from the network in response to the RRC resume request message or RRC resume request 1 message.

[0112] At block 509, the method includes the RRC layer of the UE (101) invoking the MAC reset procedure, and the MAC layer in the UE (101) performs the MAC reset when the UE (101) receives the RRC resume message from the network. However, the method continues to determine whether the UE (101) receives the RRC resume message when the RRC resume message is not received.

[0113] At block 511, the method includes flushing, by the UE (101), the soft buffers for all DL HARQ processes used for MBS multicast.

[0114] At block 513, the method includes considering, by the UE (101), the next received transmission for a transport block as first transmission for each of the DL HARQ processes used for MBS multicast.

[0115] At block 515, the method includes stopping, by the UE (101), DRX timers configured for multicast MRBs that are configured to receive multicast in the RRC-inactive state.

[0116] Fig. 6 is the flow diagram that illustrates the method of UE (101) receiving RRC resume message or RRC release with suspend Configuration message while Small Data Transmission (SDT) procedure is ongoing and performing the MAC reset procedure, according to embodiments disclosed herein.

[0117] While the SDT procedure is ongoing and the UE (101) receives RRC Release with suspend Configuration message with multicast MRB config from the network in response to an RRC Resume Request or RRC Resume Request1 message sent from the UE (101), the upper layer (e.g. RRC layer) in the UE (101) skips to invoke the MAC reset and the lower layer (e.g. MAC layer) in the UE (101) skips to perform the MAC reset operation.

[0118] In an embodiment, when the UE (101) is capable of receiving multicast service in the RRC-INACTIVE state and has at least one multicast MRB configured to receive multicast service in the RRC-INACTIVE state (e.g., UE has at least one activated multicast session in the RRC-INACTIVE state) and the SDT procedure is initiated, the upper layer (e.g., RRC layer) in the UE (101) invokes the MAC reset, and the lower layer (e.g., MAC layer) in the UE (101) performs the MAC reset operation. Wherein the MAC reset operation includes at least one of the flushing of the downlink HARQ soft buffers and clearing (stopping) of the DRX timers configured / used for the multicast MRBs that are configured to receive multicast in the RRC-INACTIVE state. Further, UE considers the next received transmission for a transport block (TB) as the very first transmission for each of the HARQ processes used for MBS multicast. This enables the UE (101) to not misinterpret the unicast data addressed by C-RNTI as the Point-To-Point (PTP) retransmission and not mistakenly soft combine with the multicast data already present in the soft buffers.

[0119] In an embodiment, while the SDT procedure is ongoing and the UE (101) receives an RRC Release with suspend Configuration message with multicast Configuration Inactive configured to indicate activation of at least one multicast session, the upper layer (e.g., RRC layer) in the UE (101) skips invoking the MAC reset, and the lower layer (e.g., MAC layer) in the UE (101) skips performing the MAC reset operation. Further, UE (101) applies the multicast PTM configuration received for the active session(s) pertaining to the multicast MRBs. UE (101) may perform reconfiguration, including the MAC reconfiguration for the multicast MRBs. If multicast Configuration Inactive does not include the PTM configuration for the already activated session(s) during the SDT procedure, the UE (101) releases the pertinent multicast MRBs and stops monitoring the relevant G-RNTI(s). If multicast Configuration Inactive includes a deactivation indication or stop monitoring G-RNTI(s)' indication for the already activated session(s) during the SDT procedure, the UE (101) stops receiving the pertinent multicast MRBs and stops monitoring the relevant G-RNTI(s). If multicast Configuration Inactive includes the PTM configuration for the deactivated session(s) during the SDT procedure, the UE (101) starts monitoring G-RNTI(s) corresponding to the multicast services. UE (101) starts monitoring multicast MCCH-RNTI if not already monitoring (i.e., if UE had no earlier activated session during the SDT procedure).

[0120] In an embodiment, while the SDT procedure is ongoing and the UE (101) receives an RRC Release with Suspend Configuration message with Multicast Configuration Inactive configured to indicate activation of at least one multicast session, the UE (101) skips cell selection as the UE (101) is already in the RRC-INACTIVE state.

[0121] In an embodiment, while the SDT procedure is ongoing and the UE (101) receives an RRC Release with Suspend Configuration message with Multicast Configuration Inactive configured to indicate activation of at least one multicast session, the UE (101) selects the same cell on which it received the RRC Release with Suspend Configuration message.

[0122] In an embodiment, while the SDT procedure is ongoing and the UE (101) receives an RRC Release with Suspend Configuration message with Multicast Configuration Inactive configured to indicate activation of at least one multicast session, the UE (101) prioritizes the same cell for cell selection on which it received the RRC Release with Suspend Configuration message.

[0123] In an embodiment, while the SDT procedure is ongoing and the UE (101) receives an RRC Release with Suspend Configuration message with Multicast Configuration Inactive configured to indicate activation of at least one multicast session, and if the UE (101) selects the same cell on which it received the RRC Release with Suspend Configuration message, the UE (101) applies the multicast PTM configuration received. Otherwise, the UE (101) does not apply the multicast PTM configuration received.

[0124] In an embodiment, the UE (101) is capable of receiving multicast service while in the RRC-INACTIVE state. This UE (101) has at least one multicast MRB configured to receive multicast service in this state, such as when the UE (101) has at least one activated multicast session in the RRC-INACTIVE state. Upon receiving an RRC Resume message from the network, which is in response to an RRC Resume Request or RRC Resume Request1 message sent from the UE (101), the UE (101) performs at least one of the following actions:

[0125] If the RRC Resume message includes the radio Bearer Configuration with the mrb-To Add Mod List, the UE (101) executes the addition or reconfiguration of the multicast MRB. If the RRC Resume message contains the radio Bearer Configuration with the mrb-To Release List, the UE (101) carries out the release of the multicast MRB.

[0126] In an embodiment, when the UE (101) that is capable of receiving multicast service in the RRC-INACTIVE state and is configured with frequency prioritization for the multicast services (e.g., frequency priority for cell reselection for multicast service) receives an RRC Resume message or RRC Setup message from the network in response to an RRC Resume Request or RRC Resume Request1 message sent from the UE (101), the UE (101) discards the stored frequency prioritization information for the multicast services.

[0127] In an embodiment, when the UE (101) that is capable and / or configured to receive multicast in RRC INACTIVE receives an RRC Setup in response to an RRC Reestablishment Request or receives RRC Setup in response to an RRC Resume Request or RRC Resume Request1, the UE (101) releases the radio resources for established radio bearers except signaling Radio Bearer 0 (SRB0), broadcast MRBs, and multicast MBS radio bearers (MRBs) that are configured for multicast reception in the RRC-INACTIVE state, including the release of the RLC entities of the associated PDCP entities and of SDAP. Further, the UE (101) releases the RRC configuration except for the default L1 parameter values, default MAC cell group configuration, and CCCH configuration, broadcast MRBs, and multicast MBS Radio Bearers (MRBs) that are configured for multicast reception in the RRC-INACTIVE state. Further, the UE (101) performs the radio bearer configuration procedure, including multicast MRBs addition / modification or release in accordance with the received radio Bearer Configuration in RRC Setup. An example specification for the above scenario is as follows.

[0128]

[0129]

[0130] In an embodiment, when the UE (101) that is capable and / or configured to receive multicast in RRC INACTIVE receives an RRC Setup in response to an RRC Reestablishment Request or receives RRC Setup in response to an RRC Resume Request or RRCResumeRequest1, the UE (101) skips releasing the radio resources for established MBS radio bearers (MRBs) for MBS multicast services that are configured to receive multicast in the RRC-INACTIVE state, including the release of the PDCP entities and of SDAP entities. Further, UE (101) may release or re-establish the RLC entities for the multicast MRBs that are configured to receive multicast in the RRC-INACTIVE state.

[0131] The various actions, acts, blocks, steps, or the like in the Figs. 2-5 are performed in the order presented, in a different order, or simultaneously. Furthermore, in some embodiments, some of the actions, acts, blocks, steps, or the like are omitted, added, modified, skipped, or the like without departing from the scope of the proposed method.

[0132] Unlike the existing system, the invention presents a new mechanism for handling MAC reset operations specifically for the UE (101) receiving multicast services while in the RRC INACTIVE state. This is crucial for seamless state transitions, ensuring multicast services continue without disrupting other services like those in the NTN. Current standards do not adequately address these challenges, often resulting in service interruptions. By focusing on multicast-only MAC reset operations, this invention enhances user experience and network reliability.

[0133] A key advantage is its ability to efficiently manage MAC reset operations for UEs (101) in the RRC INACTIVE state receiving multicast services. This approach maintains multicast data integrity and minimizes negative impacts on other services. Traditional systems could inadvertently affect other services, leading to suboptimal experiences. By isolating the multicast MAC reset process, the invention ensures that other services, especially NTNs, remain unaffected, preserving network performance and service quality.

[0134] Further, the proposed invention improves multicast service reception during RRC state transitions. Maintaining uninterrupted multicast reception is critical for applications like live broadcasts or emergency alerts. The invention ensures these transitions do not compromise multicast service quality or reliability, improving UE (101) and network performance. This advancement elevates multicast service delivery standards and sets a new benchmark for future innovations.

[0135] The foregoing description of the specific embodiments will fully reveal the general nature of the embodiments herein such that others can readily modify and / or adapt such specific embodiments for various applications without departing from the generic concept. Therefore, such adaptations and modifications are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Thus, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modifications within the scope of the embodiments as described herein.

Claims

1.A method performed by a terminal in a wireless communication system, the method comprising:transmitting, to a base station, radio resource control (RRC) resume request message;receiving, from the base station, one of an RRC resume message, or an RRC setup message;identifying whether the terminal is configured to receive a multicast broadcast service (MBS) multicast in an RRC inactive state; andin case that the terminal is configured to receive the MBS multicast in the RRC inactive state, resetting a medium access control (MAC),wherein the resetting the MAC comprises at least one of:stopping at least one MBS multicast discontinuous reception (DRX) timer; orflushing at least one soft buffer for all downlink (DL) hybrid automatic repeat and request (HARQ) processes used for the MBS multicast.2.The method of claim 1,wherein the RRC resume request message comprises at least one of an RRCResumeRequest, or an RRCResumeRequest1,wherein the resetting the MAC is performed by an MAC entity of the terminal.3.The method of claim 1, further comprising:considering a next received transmission for a transport block (TB) as a very first transmission for each DL HARQ process used for the MBS multicast.4.The method of claim 1, further comprising:resuming at least one multicast MBS radio bearer (MRB).5.A method performed by a base station in a wireless communication system, the method comprising:receiving, from a terminal, radio resource control (RRC) resume request message; andtransmitting, to the terminal, one of an RRC resume message, or an RRC setup message,wherein, in case that receiving a multicast broadcast service (MBS) multicast in an RRC inactive state is configured to the terminal, a medium access control (MAC) of the terminal is reset,wherein the MAC of the terminal is reset comprises at least one of:at least one MBS multicast discontinuous reception (DRX) timer is stopped, orat least one soft buffer for all downlink (DL) hybrid automatic repeat and request (HARQ) processes used for the MBS multicast is flushed.6.The method of claim 5,wherein the RRC resume request message comprises at least one of an RRCResumeRequest, or an RRCResumeRequest1,wherein the MAC reset procedure is performed by an MAC entity of the terminal.7.The method of claim 5,wherein a next received transmission for a transport block (TB) is considered as a very first transmission for each DL HARQ process used for the MBS multicast, andwherein at least one multicast MBS radio bearer (MRB) is resumed.8.A terminal in a wireless communication system, the terminal comprising:a transceiver; andat least one processor coupled with the transceiver and configured to:transmit, to a base station, radio resource control (RRC) resume request message,receive, from the base station, one of an RRC resume message, or an RRC setup message,identify whether the terminal is configured to receive a multicast broadcast service (MBS) multicast in an RRC inactive state, andin case that the terminal is configured to receive the MBS multicast in the RRC inactive state, reset a medium access control (MAC),wherein, in resetting the MAC, the at least one processor is configured to at least one of:stop at least one MBS multicast discontinuous reception (DRX) timer, orflush at least one soft buffer for all downlink (DL) hybrid automatic repeat and request (HARQ) processes used for the MBS multicast.9.The terminal of claim 8,wherein the RRC resume request message comprises at least one of an RRCResumeRequest, or an RRCResumeRequest1,wherein the resetting the MAC is performed by an MAC entity of the terminal.10.The terminal of claim 8, wherein the at least one processor is further configured to:consider a next received transmission for a transport block (TB) as a very first transmission for each DL HARQ process used for the MBS multicast.11.The terminal of claim 8, wherein the at least one processor is further configured to:resume at least one multicast MBS radio bearer (MRB).12.A base station in a wireless communication system, the base station comprising:a transceiver; andat least one processor coupled with the transceiver and configured to:receive, from a terminal, radio resource control (RRC) resume request message, andtransmit, to the terminal, one of an RRC resume message, or an RRC setup message,wherein, in case that receiving a multicast broadcast service (MBS) multicast in an RRC inactive state is configured to the terminal, a medium access control (MAC) of the terminal is reset,wherein the MAC of the terminal is reset comprises at least one of:at least one MBS multicast discontinuous reception (DRX) timer is stopped, orat least one soft buffer for all downlink (DL) hybrid automatic repeat and request (HARQ) processes used for the MBS multicast is flushed.13.The base station of claim 12,wherein the RRC resume request message comprises at least one of an RRCResumeRequest, or an RRCResumeRequest1,wherein the MAC reset procedure is performed by an MAC entity of the terminal.14.The base station of claim 12,wherein a next received transmission for a transport block (TB) is considered as a very first transmission for each DL HARQ process used for the MBS multicast.15.The base station of claim 12,wherein at least one multicast MBS radio bearer (MRB) is resumed.

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