Managing layer-1 / layer-2 triggered mobility cell switch in a wireless communication network system

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. Embodiments of the present invention provide a method for managing Layer-2 Triggered Mobility (LTM) cell switch in a wireless communication network system. The method includes receiving by a User Equipment (UE) (101) a LTM configuration including Radio Resource Control (RRC) reconfiguration message to be applied during the LTM cell switch to a candidate cell from a network apparatus (106). Further, the method includes triggering by the UE (101) a LTM cell switch procedure based on the LTM configuration. Further, the method includes applying by the UE (101) a default Medium Access Control (MAC) Cell Group configuration to each cell group for which the RRC reconfiguration message is applied due to the triggered LTM cell switch.

Description

MANAGING LAYER-1 / LAYER-2 TRIGGERED MOBILITY CELL SWITCH IN A WIRELESS COMMUNICATION NETWORK SYSTEM

[0001] The present invention relates generally to wireless communication systems, and more particularly, to a method and system for managing Layer-1 / Layer-2 Triggered Mobility (LTM) cell switching within a wireless communication 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] The 3rd Generation Partnership Project (3GPP) Release 18 introduces Lower Layer (L1 / L2) Triggered Mobility to address issues related to latency, signaling overhead, and similar limitations associated with Layer 3 (L3) mobility procedures. The primary objective of LTM is to enable a serving cell change using L1 / L2 signaling to reduce latency and interruption time. This is achieved by allowing a network node (gNB) to configure a User Equipment (UE) with multiple candidate cells and allowing early uplink (UL) and downlink (DL) synchronisation before the LTM cell switch, facilitating the rapid application of configurations corresponding to these candidate cells. The UE may be provisioned with a complete configuration for certain LTM candidate cells or with an LTM reference configuration in conjunction with an LTM candidate cell configuration.

[0009] Despite the advancements introduced by LTM, several challenges and limitations persist in existing systems. One of the primary issues is that the LTM cell switch does not allow the Inter-CU mobility. In dual connectivity, for both the Master Cell Group (MCG) and Secondary Cell Group (SCG), Inter-CU mobility is not possible. Another issue is that the LTM in dual connectivity does not allow the change or modification or addition of SCG during MCG LTM cell switch.

[0010] Furthermore, the LTM procedure includes the gNB receiving L1 measurement reports from the UE and initiating a serving cell change by transmitting a cell switch command via a MAC CE. This command identifies an LTM candidate cell configuration that the gNB previously prepared and delivered to the UE through Radio Resource Control (RRC) signaling. The UE then performs a switch to the target cell based on the received cell switch command. UE also may perform switch to a LTM candidate cell after MCG Radio Link Failure. Even for this case, the existing LTM mechanisms do not support Inter-CU mobility or the MCG with addition / modification / change of SCG configuration.

[0011] Moreover, the existing LTM mechanisms do not address the application of MAC cell group configuration and the configuration of Layer 1 parameters during an LTM cell switch, where an applied MCG RRC Reconfiguration message configures the UE with an SCG configuration, for example for the PSCell change or PSCell addition. Additionally, the LTM cell switch triggered on a Secondary Cell Group (SCG) where the LTM configuration is associated with the MCG, including Inter-Centralised Unit (CU) Secondary Node (SN) LTM or Intra-CU SN LTM, is not adequately addressed by current mechanisms. This includes scenarios where the LTM configuration is provided via an (Master Node) MN RRC Reconfiguration message.

[0012] The existing systems also face challenges in supporting multiple consecutive LTM operations, ensuring seamless mobility within and across different network architectures, and managing inter-frequency mobility, including mobility toward a non-serving inter-frequency cell. These challenges are further compounded in scenarios involving a Primary Cell (PCell) change in both non-Carrier Aggregation (CA) and CA scenarios, as well as mobility in dual-connectivity scenarios.

[0013] Thus, it is desired to address the above-mentioned disadvantages, issues, or other shortcomings or at least provide a useful alternative.

[0014] The principal object of the invention herein is to manage LTM cell switch in a wireless communication network system.

[0015] Yet another object of the invention is to manage LTM cell switch in a wireless communication network system by applying default Medium Access Control (MAC) Cell Group configuration for cell groups affected by the LTM cell switch.

[0016] Yet another object of the invention is to enable efficient handling of MAC Cell Group configuration during LTM cell switch by selectively applying default MAC Cell Group configuration based on whether the MCG RRC configuration includes Primary Secondary Cell (PSCell) addition or PSCell change.

[0017] Yet another object of the invention is to facilitate inter-SN SCG LTM and MCG LTM configuration by generating and transmitting RRC Reconfiguration messages including LTM candidate configurations and inter-SN SCG LTM configurations from a network apparatus to a UE.

[0018] In an aspect, the objectives are achieved by providing a method for managing LTM cell switch in a wireless communication network system. Further, the method includes receiving by a UE, a LTM configuration including a Radio Resource Control (RRC) reconfiguration message to be applied during LTM cell switch to a candidate cell from a network apparatus. Further, the method includes triggering by the UE a LTM cell switch procedure based on theLTM configuration. Further, the method includes applying by the UE a default Medium Access Control (MAC) Cell Group configuration to each cell group for which the RRC reconfiguration message is applied due to the triggered LTM cell switch.

[0019] In another aspect, the objectives are achieved by providing the method for managing LTM cell switch in a wireless communication network system. Further, the method includes generating by a network apparatus a RRC Reconfiguration message by adding at least one of an inter-SN SCG LTM configuration and a list of LTM candidate configurations. Further, the method includes transmitting by a network apparatus a RRC Reconfiguration message to a UE. The inter-SN SCG LTM configuration includes a list of RRC Reconfiguration messages. Each RRC Reconfiguration message of the list of RRC Reconfiguration messages includes an SCG configuration included in an RRC Reconfiguration message received from a candidate SN and a source SN. Further, each LTM candidate configuration of the list of LTM candidate configurations includes a plurality of RRC Reconfiguration messages. Each RRC Reconfiguration message plurality of RRC Reconfiguration messages includes a MCG configuration and optionally a SCG configuration.

[0020] In yet another aspect, the objectives are achieved by providing User Equipment for managing LTM cell switch in a wireless communication network system. The UE includes a memory. Further, the memory includes information about a network apparatus. Further, the UE includes a processor and an LTM-MAC configuration controller. The LTM-MAC configuration controller is coupled to the memory and the processor. The LTM-MAC configuration controller receives a LTM configuration including a Radio Resource Control (RRC) reconfiguration message to be applied during LTM cell switch to a candidate cell from a network apparatus. Further, the LTM-MAC configuration controller triggers a LTM cell switch procedure based on the LTM configuration. Further, the LTM-MAC configuration controller applies a default Medium Access Control (MAC) Cell Group configuration to each cell group for which the RRC reconfiguration message is applied due to the triggered LTM cell switch.

[0021] another aspect, the objectives are achieved by providing network apparatus for managing LTM cell switch in a wireless communication network system. The network apparatus includes a memory. The memory includes information about a UE. The network apparatus includes a processor and an LTM-MAC configuration controller. The LTM-MAC configuration controller is coupled to the memory and the processor. The LTM-MAC configuration controller generates a RRC Reconfiguration message by adding at least one of an inter-SN SCG LTM configuration and a list of LTM candidate configurations. Further, the LTM-MAC configuration controller transmits a RRC Reconfiguration message to a UE. The inter-SN SCG LTM configuration includes a list of RRC Reconfiguration messages. Each RRC Reconfiguration message of the list of RRC Reconfiguration messages includes an SCG configuration included in an RRC Reconfiguration message received from a candidate SN and a source SN. Further, each LTM candidate configuration of the list of LTM candidate configurations includes a plurality of RRC Reconfiguration messages. Each RRC Reconfiguration message plurality of RRC Reconfiguration messages includes a MCG configuration and optionally a SCG configuration.

[0022] 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 may be made within the scope of the embodiments herein, and the embodiments herein include all such modifications.

[0023] According to an embodiment of the disclosure, a system and method for performing a LTM cell switch effectively in a communication network system are provided.

[0024] These and other features, aspects, and advantages of the present invention 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:

[0025] FIG. 1A is a block diagram that illustrates a User Equipment for managing LTM cell switch in a wireless communication network system according to embodiments as disclosed herein.

[0026] FIG. 1B is a block diagram that illustrates the network apparatus for managing LTM cell switch in a wireless communication network system according to embodiments as disclosed herein.

[0027] FIG. 2A is a flowchart that illustrates a method for managing LTM cell switch in the wireless communication network system by the UE according to embodiments as disclosed herein.

[0028] FIG. 2B is a flowchart that illustrates a method for managing LTM cell switch in the wireless communication network system by the network apparatus according to embodiments as disclosed herein.

[0029] FIG. 3 is a flow diagram that illustrates a Medium Access Control (MAC) cell group configuration handling during MCG cell switch execution according to embodiments as disclosed herein.

[0030] FIG. 4 is a flow diagram that illustrates the MAC cell group configuration handling during SCG cell switch execution according to embodiments as disclosed herein.

[0031] FIG. 5 is a flowchart that illustrates the MAC cell group configuration handling during cell switch execution according to embodiments as disclosed herein.

[0032] FIG. 6 is a flowchart that illustrates a Layer-1 L1 parameter handling during the MCG cell switch execution according to embodiments as disclosed herein.

[0033] FIG. 7 is a flow diagram that illustrates the L1 parameter handling during the SCG cell switch execution according to embodiments as disclosed herein.

[0034] FIG. 8 is a flowchart that illustrates the L1 parameter handling during the LTM cell switch execution according to embodiments as disclosed herein.

[0035] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. Also, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments. The term "or" as used herein, refers to a non-exclusive or, unless otherwise indicated. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein can be practiced and to further enable those skilled in the art to practice the embodiments herein. Accordingly, the examples are not be construed as limiting the scope of the embodiments herein.

[0036] 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 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 optionally be driven by firmware and software. The circuits, for example, 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 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 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 be physically combined into more complex blocks without departing from the scope of the proposed method.

[0037] The accompanying drawings facilitate understanding of various technical features. The embodiments are not limited by these drawings and extend to any alterations, equivalents, and substitutes. Terms like first, second, etc., are used for distinction and may not limit the elements.

[0038] In an existing LTM cell switch execution, upon the indication by lower layers that a LTM cell switch procedure is triggered, or upon performing LTM cell switch following cell selection performed while timer T311 is running, as specified in 5.3.7.3, the UE shall perform various steps for LTM cell switch as in TS 38.331 section 5.3.5.18.6.

[0039] 1> if the LTM cell switch is triggered by an indication from lower layers:

[0040] 2> apply the RRC Reconfiguration message in ltm-CandidateConfig within LTM-Candidate IE in ltm-Config identified by the LTM candidate configuration identity received from lower layers according to clause 5.3.5.3;

[0041] 1> else (LTM cell switch triggered upon cell selection performed while timer T311 was running):

[0042] 2> apply the RRC Reconfiguration message in ltm-CandidateConfig within LTM-Candidate IE in ltm-Config related to the LTM candidate configuration identity for the selected cell (i.e., in accordance with 5.3.7.3) according to clause 5.3.5.3;

[0043] 1> release the radio bearer(s) and the logical channel(s) that were part of the UE configuration before of this LTM cell switch procedure but not part of the LTM candidate configuration either indicated by lower layers or for the selected cell in accordance with 5.3.7.3, or the LTM reference configuration (in case the LTM candidate configuration does not include ltm-ConfigComplete).om

[0044] NOTE 2: When ltm-ConfigComplete is not included for an LTM candidate configuration, before an LTM cell switch is triggered a UE implementation may generate and store an RRC Reconfiguration message by applying the received LTM candidate configuration on top of the LTM reference configuration, and the stored RRC Reconfiguration message is applied when the LTM cell switch is triggered. It is up to the UE to ensure that the RRC reconfiguration applied at the time of LTM cell switch is in accordance with the latest LTM reference configuration and LTM candidate configuration.

[0045] Further, during a Release 18 LTM cell switch, the UE applies a default Medium Access Control (MAC) cell group configuration only on the cell group for which the LTM cell switch is triggered. If the LTM cell switch is triggered on MCG, while performing LTM cell switch, the UE applies the default MAC cell group configuration on MCG alone. If the LTM cell switch is triggered on SCG, while performing LTM cell switch, the UE applies the default MAC cell group configuration on SCG. This ensures that the UE operates using a configuration known to the network during the LTM cell switch for that cell group. This also allows the network to configure the UE without MAC cell group configuration in the LTM configuration. Network apparatus can omit including the MAC cell group configuration in the reference configuration or the candidate configuration, there by saving the precious signalling resources over the air interface. Since the MAC cell group configuration is typically generated by the distributed units (DU) and transferred to the Centralised Unit (CU), UE applying default configuration saves signalling on the network interface (F1) also. With this approach, if the network configures the UE with MAC cell group configuration, it can be as a delta configuration to the default configuration.

[0046] In addition, while Release 18 supports LTM within the same gNB CU, Release 19 plans to introduce Inter-CU LTM. For SN LTM, both intra-SN LTM and inter-SN LTM may be configured simultaneously. For Inter-CU SCG LTM configuration, the SN generates the SCG portion of the configuration, and the Master Node (MN) includes this SCG configuration within the MN RRC Reconfiguration message. For Inter-CU SCG LTM, the LTM cell switch command MAC CE is transmitted by the source SN. Upon execution of inter-SN SCG LTM, the UE sends an MN RRC Reconfiguration Complete message to the MN, which includes an SN RRC Reconfiguration Complete message.

[0047] Further, network implementations avoid simultaneous execution of both MCG and SCG LTM procedures. In Release 19, an Inter-CU MCG LTM with intra-SN PSCell change is supported.

[0048] Further, with respect to dual connectivity, multiple LTM scenarios may coexist within the existing system, including Inter-MN LTM operating concurrently with intra-SN LTM, as well as Inter-SN LTM operating concurrently with intra-MN LTM.

[0049] Furthermore, Version 18.4.0 of TS 38.331, TS 38.321, TS 38.306, TS 37.340, and TS 38.300 are regarded as the existing mechanisms applicable to the present invention.

[0050] V18.4.0 of TS 38.331 specifies the mechanism for including SCG configuration using mrdc-SecondaryCellGroup in the RRCReconfiguration message. If the network wants to setup SCG, it includes mrdc-SecondaryCellGroup in the RRCReconfiguration message.

[0051] RRCReconfiguration-v1560-IEs ::= SEQUENCE { mrdc-SecondaryCellGroupConfig SetupRelease { MRDC-SecondaryCellGroupConfig } OPTIONAL, -- Need M

[0052] }

[0053] MRDC-SecondaryCellGroupConfig ::= SEQUENCE {

[0054] mrdc-ReleaseAndAdd ENUMERATED {true} OPTIONAL, -- Need N

[0055] mrdc-SecondaryCellGroup CHOICE { nr-SCG OCTET STRING (CONTAINING RRCReconfiguration),

[0056] eutra-SCG OCTET STRING

[0057] }

[0058] V18.4.0 of TS 38.331 specifies the details for configuring LTM and the LTM candidates. According to this specification, LTM configuration can include LTM reference configuration, LTM candidate configuration, Configuration of the LTM CSI resources etc. LTM candidate configuration may include the configuration of the reference signals to be measured, configuration related to early uplink and early downlink synchronization, ltm-CandidateConfig which contain the RRCReconfiguration message used to configure an LTM candidate configuration either as a complete configuration or in conjunction with a reference configuration etc.

[0059] To overcome the disadvantages of existing technology, the present invention addresses the application of MAC cell group configuration and the configuration of Layer 1 parameters during an LTM cell switch triggered on the MCG where the applied MCGRRC Reconfigurationconfigures the UE for SCG setup. The present invention further addresses the LTM cell switch triggered on the SCG in which the LTM configuration is associated with the MCG. LTM configuration is considered associated with the MCG for a LTM cell switch triggered on SCG when the LTM candidate configuration (such as ltm-CandidateConfig) contains MCG configuration also. This includes Inter-CU SN LTM and Intra-CU SN LTM conditions, and the LTM configuration is provided in an MNRRC Reconfigurationmessage.

[0060] In an embodiment, the present invention discloses various steps for applying a default MAC cell group configuration during the LTM cell switch as specified in section 5.3.5.18.6 of TS 38.331. The LTM cell switch may be performed based on an indication from lower layers that the LTM cell switch procedure has been triggered, or it may be performed following cell selection executed while timer T311 may be running, as specified in section 5.3.7.3 of TS 38.331. Other scenarios such as executing LTM cell switch based on the execution of conditions are not precluded.

[0061] FIG. 1A is a block diagram illustrating the UE (101) for managing LTM cell switch in a wireless communication network system according to embodiments disclosed herein. Examples of the UE (101) include, but are not limited to, terminals, Consumer Electronics (such as Mobile Phones and Smartphones), Tablets, Wearable Devices, Television, Computing Devices (such as Laptops, Notebooks, Desktops, Workstations, etc.), IoT Devices, Automotive Systems (such as connected cars, Autonomous Vehicles, Vehicle-to-Everything (V2X) communication devices, etc.), Enterprise Devices such as robotics, Specialized Equipment (such as Medical Devices, Public Safety Devices, etc.), and Media Devices (such as Gaming Consoles, Streaming Devices, etc.).

[0062] Examples of the wireless communication network system include, but are not limited to, Cellular Networks (such as 2G, 3G, 4G, 5G, Beyond 5G (B5G) / 6G or advanced cellular networks), Local Area Networks (LANs) (such as Wi-Fi, Li-Fi, etc.), Personal Area Networks (PANs) (such as Bluetooth, Zigbee, Z-Wave, etc.), Wide Area Networks (WANs) (such as Satellite Communication Networks, Long Range Wide Area Network, Narrowband IoT, Low-bandwidth communication for IoT, etc.), Metropolitan Area Networks (MANs), Machine-to-Machine (M2M), Ad Hoc and Mesh Networks, and Emerging and Advanced Networks.

[0063] The UE (101) includes a processor (102), memory (104), an I / O interface (103), and an LTM-MAC configuration controller (105). The processor (102) of the UE (101) communicates with the memory (104), the I / O interface (103), and the LTM-MAC configuration controller (105). Configured to execute instructions stored in the memory (104), the processor (102) performs various processes. The processor (102) can include one or a plurality of processors and 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).

[0064] The memory (104) of the UE (101) includes storage locations addressable through the processor (102). Not limited to volatile memory and / or non-volatile memory, the memory (104) can include one or more computer-readable storage media. Non-volatile storage elements in the memory (104) can include magnetic hard disks, optical disks, floppy disks, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable (EEPROM) memories. The memory (104) stores configuration information and parameters associated with LTM cell switch operations, including storage for RRC reconfiguration messages, LTM candidate configurations, ltm-Config information elements, MCG and SCG configuration parameters, default Medium Access Control (MAC) Cell Group configuration values, Primary Secondary Cell (PSCell) addition and change parameters, mrdc-SecondaryCellGroup configuration, and cell group timing information.

[0065] The I / O interface (103) transmits information between the memory (104) and external peripheral devices, which are the input-output devices associated with the UE (101). The I / O interface (103) receives several pieces of information from the UE (101).

[0066] Coupled to the memory (104) and the processor (102), the LTM-MAC configuration controller (105) allows for efficient data transfer and communication between the components, ensuring that the LTM-MAC configuration controller (105) can access and process LTM cell switch data in real-time. The LTM-MAC configuration controller (105) is an innovative integrated circuit implemented in the UE (101). In an embodiment, the structure of such an innovative integrated circuit includes a multi-core architecture that enables dynamic management of default MAC Cell Group configuration application during LTM cell switch operations in a wireless communication system. Each core is optimized for specific tasks such as determining cell group configuration based on RRC reconfiguration messages, identifying whether the LTM cell switch is triggered on MCG or SCG, checking for mrdc-SecondaryCellGroup presence in the RRC configuration, and managing selective application of default MAC Cell Group configuration for MCG and SCG based on PSCell addition or change parameters. The innovative integrated circuit for managing LTM-MAC configuration is composed of a combination of analog and digital components designed to optimize configuration application accuracy and timing precision of the LTM cell switch mechanism. The analog components include a high-precision clock and timing reference circuit to ensure accurate configuration application timing, while the digital components include a microcontroller unit (MCU) and a digital signal processor (DSP) that work in tandem to dynamically manage default MAC Cell Group configuration application based on RRC reconfiguration parameters and cell group identification during LTM cell switch execution.

[0067] The LTM-MAC configuration controller (105) receives the RRC reconfiguration message from a network apparatus (106). Upon receiving the RRC reconfiguration message, the LTM-MAC configuration controller (105) triggers an LTM cell switch procedure. The LTM-MAC configuration controller (105) applies a default MAC configuration to each cell group for which the RRC reconfiguration message is applied due to the triggered LTM cell switch. The default MAC Cell Group configuration is applied to both an MCG and an SCG when an RRC configuration for the MCG applied during the LTM cell switch includes a configuration for Primary Secondary Cell (PSCell). The default MAC Cell Group configuration is applied for the SCG (along with MCG) when the RRC configuration for the MCG applied during the LTM cell switch includes a configuration for PSCell addition. The default MAC Cell Group configuration is applied for the MCG alone when the RRC configuration for the MCG applied during the LTM cell switch does not include a configuration for either PSCell addition or PSCell change or modification, i.e. when the SCG is maintained without any change, default MAC cell group configuration is applied for MCG alone. The LTM-MAC configuration controller (105) applies the default MAC Cell Group configuration for both an MCG and an SCG when the LTM cell switch triggered on MCG adds or changes the PSCell.

[0068] In an embodiment, applying the default MAC Cell Group configuration to each cell group includes performing one of the following operations. In a first operation, the UE (101) applies the default MAC Cell Group configuration for both an MCG and an SCG when the LTM cell switch is triggered on the MCG and the RRC Reconfiguration message applied during the LTM cell switch execution procedure includes mrdc-SecondaryCellGroup. This embodiment is based on the RRC signalling structure from the background TS 38.331. gNB includes mrdc-SecondaryCellGroup to setup NR SCG in NR-DC or E-UTRA SCG in NE-DC. In a second operation, the UE (101) applies the default MAC Cell Group configuration for the MCG only when the LTM cell switch is triggered on the MCG and the RRC Reconfiguration message applied during the LTM cell switch execution procedure does not include mrdc-SecondaryCellGroup.

[0069] If the RRC Reconfiguration applied during LTM cell switch execution triggered on MCG sets up SCG, UE applies the default MAC cell group configuration for both MCG and SCG.

[0070] The LTM-MAC configuration controller (105) triggers the LTM cell switch procedure upon receiving an indication from lower layers that the LTM cell switch procedure is triggered, upon performing the LTM cell switch following cell selection performed while a timer T311 is running or upon the fulfillment of LTM cell switch execution conditions. The LTM-MAC configuration controller (105) identifies the RRC Reconfiguration message applied during the LTM cell switch as the RRC Reconfiguration message in ltm-CandidateConfig within the LTM-Candidate Information Element (IE) in ltm-Config for the LTM candidate to which the UE (101) is performing the LTM cell switch.

[0071] The LTM-MAC configuration controller (105) applies the default MAC configuration by setting the value of at least one of periodicBSR-Timer, retxBSR-Timer, phr-PeriodicTimer, phr-ProhibitTimer, and phr-Tx-PowerFactorChange. A typical set of values that the the LTM-MAC configuration controller (105) applies the default MAC configuration can be by setting the value of at least one of periodicBSR-Timer to 10 subframes, retxBSR-Timer to 80 subframes, phr-PeriodicTimer to 10 subframes, phr-ProhibitTimer to 10 subframes, and phr-Tx-PowerFactorChange to 1dB.

[0072] FIG. 1B is a block diagram illustrating the network apparatus (106) for managing LTM cell switch in a wireless communication network system according to embodiments disclosed herein. The network apparatus (106) includes various hardware and software components that facilitate communication between user equipment and network infrastructure. Examples of the network apparatus (106) include, but are not limited to, Base Stations (such as macro cells, small cells, femtocells, Pico cells) for wireless communication, Antennas and RF Units (e.g., MIMO beam forming) to enhance signal coverage and data throughput, Core Network Equipment (e.g., MMEs, S-GWs, P-GWs in 4G, AMFs, UPFs in 5G) for data routing, mobility, and session control, Network Function Virtualization (NFV) and Software-Defined Networking (SDN) for dynamic resource allocation and scalability, Edge Computing Nodes (e.g., MEC servers) for low-latency processing, Backhaul and Transport Equipment (e.g., fiber-optic links, microwave relays, Ethernet switches) to connect base stations to the core network, Network Management Systems (NMS) and Operation Support Systems (OSS) for network configuration, fault management, and optimization, Radio Network Controllers (RNCs) in 3G, Distributed Units (DUs) and Centralized Units (CUs) in 5G, Network Slicing Components for virtualized resource allocation, and Security elements (e.g., Firewalls, IDS, AAA Servers) for secure communication.

[0073] The network apparatus (106) includes a processor (107), memory (109), an I / O interface (108), and an LTM-MAC configuration controller (110). The processor (107) of the network apparatus (106) communicates with the memory (109), the I / O interface (108), and the LTM-MAC configuration controller (110). Configured to execute instructions stored in the memory (109), the processor (107) performs various processes. The processor (107) can include one or a plurality of processors and 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).

[0074] The memory (109) of the network apparatus (106) includes storage locations addressable through the processor (107). Not limited to volatile memory and / or non-volatile memory, the memory (109) can include one or more computer-readable storage media. Non-volatile storage elements, such as magnetic hard disks, optical disks, floppy disks, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable (EEPROM) memories, are included in the memory (109). Configuration information and parameters associated with LTM cell switch operations are stored in the memory (109). Storage for RRC reconfiguration messages, LTM candidate configurations, ltm-Config information elements, MCG and SCG configuration parameters, default Medium Access Control (MAC) Cell Group configuration values, Primary Secondary Cell (PSCell) addition and change parameters, mrdc-SecondaryCellGroup configuration, and cell group timing information are included in the memory (109).

[0075] The I / O interface (108) transmits information between the memory (109) and external peripheral devices. Peripheral devices are the input-output devices associated with the network apparatus (106). The I / O interface (108) receives several pieces of information from the network apparatus (106).

[0076] Coupled to the memory (109) and the processor (107), the LTM-MAC configuration controller (110) allows for efficient data transfer and communication between the components, ensuring that the LTM-MAC configuration controller (110) can access and process LTM configuration data in real-time. Implemented as an innovative integrated circuit in the network apparatus (106), the LTM-MAC configuration controller (110) includes a multi-core architecture that enables dynamic generation and management of RRC Reconfiguration messages for LTM cell switch operations in a wireless communication system. Each core is optimized for specific tasks such as generating RRC Reconfiguration messages with inter-SN SCG LTM configurations, creating LTM candidate configurations with MCG and SCG parameters, determining PSCell addition or change requirements, configuring mrdc-SecondaryCellGroup information elements, and coordinating inter-CU and intra-CU LTM configurations for transmission to the UE (101). The innovative integrated circuit for managing LTM-MAC configuration is composed of a combination of analog and digital components designed to optimize configuration generation accuracy and transmission timing precision of the LTM configuration mechanism. Analog components include a high-precision clock and timing reference circuit to ensure accurate configuration message generation and transmission timing, while digital components include a microcontroller unit (MCU) and a digital signal processor (DSP) that work in tandem to dynamically generate and manage RRC Reconfiguration messages with appropriate LTM candidate configurations and inter-SN SCG LTM parameters based on network conditions and UE (101) capabilities during LTM configuration procedures.

[0077] The LTM-MAC configuration controller (110) generates the RRC Reconfiguration message by adding at least one of an inter-SN SCG LTM configuration and a list of LTM candidate configurations. The LTM-MAC configuration controller (110) transmits the RRC Reconfiguration message to a UE (101). The inter-SN SCG LTM configuration includes a list of RRC Reconfiguration messages. Each RRC Reconfiguration message of the list includes an SCG configuration received from a candidate SN and a source SN. Each LTM candidate configuration of the list includes a plurality of RRC Reconfiguration messages. Each RRC Reconfiguration message includes the MCG configuration and optionally a SCG configuration.

[0078] The LTM-MAC configuration controller (110) generates each RRC Reconfiguration message to include the MCG configuration.

[0079] FIG 2A is a flowchart that illustrates a method for managing LTM cell switch in the wireless communication network system by the UE (101) according to embodiments as disclosed herein. The method ensures seamless transition and connectivity for the UE as it moves between different cells within the network. This process is used for maintaining the quality of service and minimizing disruptions during mobility events. The method leverages advanced signaling and configuration protocols to achieve efficient cell switching.

[0080] At step 201, the method includes the LTM configuration. The a LTM configuration further includes the RRC reconfiguration message applied during LTM cell switch to a candidate cell from a network apparatus (106). This message includes information regarding the new cell configuration, including parameters such as frequency bandwidth and cell ID. The RRC reconfiguration message may also include instructions for the UE to adjust its transmission power and timing advance to align with the new cell's requirements. The UE processes this message to prepare for the upcoming cell switch.

[0081] At step 202, the method includes triggering the LTM cell switch procedure based on the LTM configuration by the UE (101). This includes the UE initiating a series of actions to disconnect from the current cell and establish a connection with the target cell. The UE may perform measurements to ensure the target cell meets the necessary signal quality criteria before proceeding with the switch. The LTM cell switch procedure is designed to be fast and efficient to minimize any potential service interruption.

[0082] At step 203, the method includes applying the default MAC configuration to each cell group for which the RRC reconfiguration message is applied due to the triggered LTM cell switch by the UE (101). The default MAC configuration includes parameters such as scheduling information, HARQ processes, and buffer status reports. This ensures that the UE can immediately start communicating with the new cell without waiting for additional configuration messages. The application of the default MAC configuration is used for smooth transition and maintaining the UE's ongoing data sessions.

[0083] FIG 2B is a flowchart that illustrates a method for managing LTM cell switch in the wireless communication network system by the network apparatus (106) according to embodiments as disclosed herein. The network apparatus is used in orchestrating the cell switch by coordinating the necessary signaling and configuration updates. This method ensures that the network can dynamically adapt to the UE's mobility patterns and maintain optimal connectivity.

[0084] At step 204, the method includes generating the RRC Reconfiguration message by adding at least one of the inter-secondary nodes (SN) SCG LTM configuration and a list of LTM candidate configurations by the network apparatus (106). The RRC Reconfiguration message is crafted to include detailed configuration parameters for the target cell, such as physical layer settings, security keys, and quality of service (QoS) parameters. The inclusion of LTM candidate configurations allows the UE to have multiple options for potential target cells, enhancing the robustness of the mobility procedure.

[0085] At step 205, the method includes transmitting by the network apparatus (106) the RRC Reconfiguration message to the UE (101) by the network apparatus (106). Further, the inter-SN SCG LTM configuration includes the list of RRC Reconfiguration messages. This transmission is performed using reliable signaling channels to ensure the message is received correctly by the UE. The network apparatus may also include additional information such as timing synchronization and handover commands to facilitate the cell switch. Further, each RRC Reconfiguration message of the list of RRC Reconfiguration messages includes the SCG configuration included in the RRC Reconfiguration message received from the candidate SN and the source SN. This ensures that the UE has all the necessary information to connect to the new cell seamlessly. Further, each LTM candidate configuration of the list of LTM candidate configurations includes the plurality of RRC Reconfiguration messages. Each RRC Reconfiguration message plurality of RRC Reconfiguration messages includes an MCG configuration and optionally an SCG configuration. This comprehensive approach allows the UE to select the best possible target cell based on current network conditions and its own capabilities.

[0086] FIG. 3 is a flow diagram that illustrates the MAC cell group configuration handling during MCG cell switch execution according to embodiments as disclosed herein. At step 301, triggering execution of the LTM cell switch on the MCG. At step 302, determining whether the RRC Reconfiguration message to be applied during the LTM cell switch includes the mrdc-SecondaryCellGroup configuration. If the RRC Reconfiguration message does not include the mrdc-SecondaryCellGroup configuration, control proceeds to step 303; otherwise, control proceeds to step 304. This determination dictates the subsequent configuration steps and ensures that the UE (101) applies the correct MAC Cell Group settings.

[0087] At step 303, applying a default MAC Cell Group configuration for the MCG as specified in Section 9.2.2. The default configuration includes parameters such as parameters required for scheduling, power control, buffer status reporting that are essential for maintaining efficient communication. These parameters are predefined in the standard to ensure interoperability and consistent performance across different network deployments. At step 304, applying a default MAC Cell Group configuration for both the MCG and an SCG as specified in Section 9.2.2. This step ensures that both the primary and secondary cell groups are configured with compatible settings, facilitating seamless dual connectivity and improved data throughput. This also ensures that both MCG and SCG can configure the UE without providing the relevant parameters in the MAC cellgroup configuration, as the UE can apply standardized parameters.

[0088] In an embodiment, when the UE (101) performs an LTM cell switch triggered on the MCG, the UE (101) applies the default MAC Cell Group configuration for the MCG and the SCG, such as the configuration specified in section 9.2.2 of TS 38.331 for NR. This ensures that the UE (101) can maintain optimal performance and connectivity during the cell switch. In an embodiment, when the RRC Reconfiguration message applied during the LTM cell switch includes configuration for PSCellChange, the UE (101) applies the default MAC Cell Group configuration for both the MCG and the SCG (such as specified in 9.2.2 of TS 38.331 in NR). When the RRC Reconfiguration message applied during the LTM cell switch does not include configuration for PSCellChange, the UE (101) applies the default MAC Cell Group configuration for the MCG alone. This differentiation allows the UE (101) to adapt its configuration based on the specific instructions received from the network.

[0089] In an embodiment, the flow may include at step 1, the UE (101) is configured for dual connectivity and has a PSCell. This initial configuration enables the UE (101) to simultaneously connect to multiple cell groups, enhancing data rates and reliability. At step 2, the UE (101) receives the LTM configuration for MCG (step 1 and step 2 are interchangeable). This configuration may include parameters such as cell identifiers, frequency information, and timing advance values. At step 3, the UE (101) performs the LTM cell switch triggered on the MCG. The RRC Reconfiguration message applied due to the LTM cell switch execution procedure (such as according to clause 5.3.5.18.6 in TS 38.331) changes the PSCell. This change may include updating the UE's (101) connection parameters to align with the new primary SCG cell. At step 4, the UE (101) applies the default MAC Cell Group Configuration for both MCG and SCG while performing the LTM cell switch. This ensures that the UE (101) maintains consistent performance and connectivity during the transition.

[0090] In an additional embodiment, when the RRC Reconfiguration message applied during the LTM cell switch includes configuration for PSCellAddition, the UE (101) applies the default MAC Cell Group configuration for the SCG (such as specified in 9.2.2 of TS 38.331 in NR) along with that of MCG which is always applied during MCG LTM cell switch. When the RRC Reconfiguration message applied during the LTM cell switch does not include configuration for PSCellAddition or PSCellChange, the UE (101) applies the default MAC Cell Group configuration for the MCG alone. This ensures that the UE (101) only updates the necessary configurations, minimizing unnecessary changes and potential disruptions.

[0091] In an embodiment, the flow may include at step 1, the UE (101) receives the LTM configuration for MCG. This configuration may be received via a dedicated control channel or as part of a broader RRC signaling message. At step 2, the UE (101) performs the LTM cell switch triggered on the MCG. This includes the UE (101) updating its connection parameters to align with the new primary cell. The RRC Reconfiguration message applied due to the LTM cell switch execution procedure (such as according to clause 5.3.5.18.6 in TS 38.331) adds the PSCell. This addition may include configuring new secondary cells to enhance the UE's (101) overall data throughput. At step 3, the UE applies the default MAC Cell Group Configuration for the MCG and SCG while performing the LTM cell switch. This ensures that the UE (101) maintains consistent performance and connectivity during the transition.

[0092] In an embodiment in NR, when the RRC Reconfiguration message applied during the LTM cell switch includes mrdc-SecondaryCellGroup (with mrdc-SecondaryCellGroupConfig set to setup), the UE (101) applies the default MAC Cell Group configuration for the MCG and the SCG. mrdc-SecondaryCellGroupConfig is used in NR to setup SCG (add / modify / change SCG). This ensures that both the primary and secondary cell groups are configured with compatible settings, facilitating seamless dual connectivity and improved data throughput. When the RRC Reconfiguration message applied during the LTM cell switch does not include mrdc-SecondaryCellGroup, the UE (101) applies the default MAC Cell Group configuration for the MCG alone. This differentiation allows the UE (101) to adapt its configuration based on the specific instructions received from the network.

[0093] In an embodiment, when the RRC Reconfiguration message applied during the LTM cell switch includes an SCG RRC Reconfiguration message, the UE (101) applies the default MAC Cell Group configuration for the MCG and the SCG. This ensures that both the primary and secondary cell groups are configured with compatible settings, facilitating seamless dual connectivity and improved data throughput. When the RRC Reconfiguration message applied during the LTM cell switch does not include an SCG RRC Reconfiguration message, the UE (101) applies the default MAC Cell Group configuration for the MCG alone. This differentiation allows the UE (101) to adapt its configuration based on the specific instructions received from the network.

[0094] In an embodiment, when the MCG RRC Configuration applied during the LTM cell switch does not include mrdc-SecondaryCellGroup, the UE (101) applies the default MAC Cell Group configuration for MCG alone. This ensures that the UE (101) only updates the necessary configurations, minimizing unnecessary changes and potential disruptions. In an embodiment, the UE (101) performing LTM cell switch triggered on MCG applies the default MAC Cell Group Configuration for MCG and SCG when the MCG RRC Reconfiguration message to be applied due to the LTM cell switch execution procedure includes SCG RRC Reconfiguration message (such as nr-SCG in NR). This ensures that both the primary and secondary cell groups are configured with compatible settings, facilitating seamless dual connectivity and improved data throughput.

[0095] In an embodiment, when the MCG RRC Configuration applied during the LTM cell switch does not include SCG RRC Reconfiguration message, the UE (101) applies the default MAC Cell Group configuration for MCG alone. This ensures that the UE (101) only updates the necessary configurations, minimizing unnecessary changes and potential disruptions. FIG 4 is a flow diagram that illustrates the MAC cell group configuration handling during SCG cell switch execution according to embodiments as disclosed herein.

[0096] In an embodiment, during performance of the LTM cell switch, when the LTM cell switch is triggered on the SCG, the UE (101) applies the default MAC Cell Group configuration for the MCG and SCG as specified in clause 9.2.2 of TS 38.331 in NR when the LTM cell switch is for the Inter-CU SCG LTM. This ensures that the UE (101) maintains optimal performance and connectivity during the cell switch, even when switching between different CUs. In an embodiment, during performance of the LTM cell switch, when the LTM cell switch is triggered on the SCG, the UE (101) applies the default MAC Cell Group configuration for the MCG and SCG as specified in clause 9.2.2 of TS 38.331 in NR when the LTM cell switch is for the Intra-CU SCG LTM where the LTM configuration is associated with the MCG. LTM configuration is considered to be associated with the MCG if the configuration such as ltm-CandideConfig modifies MCG also. This ensures that the UE (101) maintains consistent performance and connectivity during the transition within the same central unit.

[0097] In an embodiment, during performance of the LTM cell switch, when the LTM cell switch is triggered on the SCG, the UE (101) applies the default MAC Cell Group configuration for the MCG and SCG as specified in clause 9.2.2 of TS 38.331 in NR when the LTM configuration is associated with the MCG. This ensures that the UE (101) maintains optimal performance and connectivity during the cell switch. In an embodiment in NR, when the ltm-Config related to the LTM cell switch is included within the RRC Reconfiguration message received via SRB1 during performance of the LTM cell switch and when the LTM cell switch is triggered on the SCG, the UE (101) applies the default MAC Cell Group configuration for the MCG and SCG as specified in clause 9.2.2 of TS 38.331 in NR. This ensures that the UE (101) applies the correct configuration settings based on the received signaling message.

[0098] In an embodiment, the flow may include the UE (101) is configured for dual connectivity and has a PSCell at the initial step. This initial configuration enables the UE (101) to simultaneously connect to multiple cell groups, enhancing data rates and reliability. Further, at step 401 and 402, triggering execution of the Layer1 / Layer 2 Triggered Mobility cell switch on the SCG and the LTM configuration being received in MN format (i.e., the LTM configuration is associated with the MCG or is received in the RRC Reconfiguration message via SRB1 in NR). This step includes the UE (101) receiving the necessary configuration parameters to perform the cell switch. At step 403, the UE (101) performs the LTM cell switch triggered on the SCG. This includes the UE (101) updating its connection parameters to align with the new SCG cell. At step 404, the UE (101) applies the default MAC Cell Group configuration for the MCG and SCG during performance of the LTM cell switch. This ensures that the UE (101) maintains consistent performance and connectivity during the transition.

[0099] In an embodiment, according to TS 38.331, upon the indication by lower layers that the LTM cell switch procedure is triggered, or upon performing the LTM cell switch following cell selection performed while timer T311 may be running, as specified in 5.3.7.3, the UE (101) shall:

[0100] 1> if the LTM cell switch is triggered on the MCG:

[0101] 2> release / clear all current dedicated and common radio configurations which have neither been received via SRB1 within mrdc-SecondaryCellGroup, nor via SRB3 except for the following:

[0102] - the radio bearer configuration (configured via RadioBearerConfig)

[0103] - the logicalChannelIdentity and logicalChannelIdentityExt of RLC bearers configured in RLC-BearerConfig and the associated RLC entities, their state variables, buffers, and timers, except for triggering the associated RLC entities to reset the variable RETX_COUNT its initial value, as specified in TS 38.322 [4];

[0104] - the bh-LogicalChannelIdentity of BH RLC channels configured in BH-RLC-ChannelConfig and the associated RLC entities, their state variables, buffers, and timers, except for triggering the associated RLC entities to reset the variable RETX_COUNT its initial value, as specified in TS 38.322 [4];

[0105] - the UE (101) variables VarLTM-ServingCellNoResetID and VarLTM-ServingCellUE-MeasuredTA-ID;

[0106] - the ltm-Config;

[0107] - the MCG C-RNTI;

[0108] - the AS security configurations associated with the master key;

[0109] - the logged measurement configuration;

[0110] 2> apply the default MAC Cell Group configuration as specified in 9.2.2 for MCG.

[0111] 2> if the RRC Reconfiguration to be applied during the LTM cell switch includes mrdc-SecondaryCellGroup:

[0112] 3> apply the default MAC Cell Group configuration as specified in 9.2.2 for SCG.

[0113] 1> else, if the LTM cell switch is triggered on the SCG:

[0114] 2> release / clear all current dedicated and common radio configurations which have been received either via SRB1 within mrdc-SecondaryCellGroup, or via SRB3 except for the following:

[0115] - the radio bearer configuration (configured via RadioBearerConfig IE)

[0116] - the logicalChannelIdentity and logicalChannelIdentityExt of RLC bearers configured in RLC-BearerConfig and the associated RLC entities, their state variables, buffers, and timers, except for triggering the associated RLC entities to reset the variable RETX_COUNT its initial value, as specified in TS 38.322 [4];

[0117] - the bh-LogicalChannelIdentity of BH RLC channels configured in BH-RLC-ChannelConfig and the associated RLC entities, their state variables, buffers, and timers, except for triggering the associated RLC entities to reset the variable RETX_COUNT its initial value, as specified in TS 38.322 [4];

[0118] - the UE (101) variables VarLTM-ServingCellNoResetID and VarLTM-ServingCellUE-MeasuredTA-ID;

[0119] - the ltm-Config;

[0120] - the AS security configurations associated with the secondary key;

[0121] 2> apply the default MAC Cell Group configuration as specified in 9.2.2 for SCG.

[0122] 2> if the ltm-Config is associated with the MCG

[0123] 3>apply the default MAC Cell Group configuration as specified in 9.2.2 for MCG.

[0124] In an embodiment, the UE (101) performing LTM cell switch applies the default MAC Cell Group configuration as specified in 9.2.2 for the cell group(s) for which the RRC Reconfiguration may be applied due to the triggered LTM cell switch.

[0125] FIG. 5 is a flow chart that illustrates the MAC cell group configuration handling during cell switch execution, according to embodiments as disclosed herein. At step 501, performing the LTM cell switch.

[0126] At step 502, applying the default MAC Cell Group configuration for the cell group(s) for which the RRC Reconfiguration message may be applied due to the triggered LTM cell switch.

[0127] In another embodiment, according to TS 38.331, upon the indication by lower layers that the LTM cell switch procedure is triggered, or upon performing LTM cell switch following cell selection performed while timer T311 was running, as specified in 5.3.7.3, the UE (101) shall:

[0128] 1> apply the default MAC Cell Group configuration as specified in 9.2.2 for the cell group(s) for which the RRC Reconfiguration may be applied due to the triggered LTM cell switch (step 502).

[0129] In an embodiment, the UE (101) applies the default MAC Cell group configuration for both MCG and SCG when the LTM cell switch is for Inter-Central Unit (Inter-CU) SCG LTM or for the Intra-CU SCG LTM where the LTM configuration is associated with the MCG and the RRC Reconfiguration to be applied includes both MCG and SCG RRC Reconfiguration. The embodiment allows to configure Inter-CU SCG LTM and Intra-CU SCG LTM more efficiently, for example by avoiding the MCG related parts.

[0130] In an embodiment, the UE (101) applies the default MAC Cell group configuration for both MCG and SCG when the LTM cell switch is for Inter-CU SCG LTM or for the Intra-CU SCG LTM where the LTM configuration is associated with the MCG and the MCG RRC Reconfiguration to be applied during LTM cell switch includes CellGroupConfig for MCG (In NR), CellGroupConfig for MCG is received in RRC Reconfiguration message received via a Signaling Radio Bearer 1 (SRB1) and not embedded in SCG RRC Reconfiguration message received via SRB1). This embodiment allows to minimize the impact on the MCG due to Inter-CU SCG LTM or Intra-CU SCG LTM when the MAC of MCG does not change.

[0131] In an embodiment, according to TS 38.331,

[0132] 1> if the LTM cell switch is triggered on the SCG:

[0133] 2> apply the default MAC Cell Group configuration as specified in 9.2.2 for SCG.

[0134] 2> if the ltm-Config is associated with the MCG and the MCG RRC Reconfiguration includes Cellgroupconfig.

[0135] 3> apply the default MAC Cell Group configuration as specified in 9.2.2 for MCG.

[0136] FIG. 6 is a flow chart that illustrates the L1 parameter handling during the MCG cell switch execution, according to embodiments as disclosed herein.

[0137] At step 601, triggering execution of the Layer 2 Triggered Mobility cell switch on the MCG.

[0138] At step 602, determining whether the RRC reconfiguration message, to be applied during the LTM cell switch, includes the mrdc-SecondaryCellGroup configuration. When the RRC Reconfiguration message may not include the mrdc-SecondaryCellGroup configuration, control proceeds to step 603, otherwise, control proceeds to step 604.

[0139] At step 603, applying the default L1 parameter values as specified in corresponding physical layer specifications except for the parameters for which values are provided in System Information Block 1 (SIB1) for the MCG.

[0140] At step 604, applying the default L1 parameter values as specified in corresponding physical layer specifications except for the parameters for which values are provided in the SIB1 for both the MCG and SCG.

[0141] In an embodiment, while performing LTM cell switch by the UE (101), and the LTM cell switch is triggered on the MCG, the UE (101) applies the default L1 parameter values as specified in corresponding physical layer specifications except for the parameters for which values are provided in the SIB1 for the SCG and MCG (such as specified in 9.2.2 of TS 38.331 in NR) when the MCG RRCConfiguration applied during the LTM cell switch includes configuration for PSCellChange.

[0142] In an embodiment, the flow may include, at step 1, the UE (101) is configured for dual connectivity and has a PSCell. At step 2, the UE (101) receives LTM configuration for MCG (order of step 1 and step2 are interchangeable). At step 3, the UE (101) performs LTM cell switch, triggered on MCG. The RRC Reconfiguration message applied due to the LTM cell switch execution procedure (such as according to clause 5.3.5.18.6 in TS 38.331) changes the PSCell also. At step 4, the UE (101) applies default L1 parameter values as specified in corresponding physical layer specifications except for the parameters for which values are provided in SIB1, for SCG and MCG while performing LTM cell switch.

[0143] In an embodiment, while performing the LTM cell switch by the UE(101), where the LTM cell switch is triggered on the MCG, the UE (101) applies default Layer 1 L1 parameter values as specified in the corresponding physical layer specifications, except for those parameters for which values are provided in the SIB1 for the SCG and the MCG (for example, as specified in Section 9.2.2 of TS 38.331 for NR), when the MCG RRC configuration applied during the LTM cell switch includes configuration for the PSCellAddition procedure.

[0144] In an embodiment, the flow may include, at step 1, the UE (101) receives LTM configuration for MCG (order of step 1 and step2 are interchangeable). At step 2, the UE (101) performs LTM cell switch, triggered on MCG. The RRC Reconfiguration message applied due to the LTM cell switch execution procedure (such as according to clause 5.3.5.18.6 in TS 38.331) adds the PSCell. At step 3, the UE (101) applies default L1 parameter values as specified in corresponding physical layer specifications except for the parameters for which values are provided in the SIB1 for SCG and MCG while performing the LTM cell switch.

[0145] In an embodiment, in NR, when the UE (101) performs the LTM cell switch triggered on the MCG, the UE (101) applies default L1 parameter values as specified in the corresponding physical layer specifications, except for those parameters for which values are provided in the SIB1 for the SCG and the MCG, when the RRC Reconfiguration message to be applied due to execution of the LTM cell switch procedure includes themrdc-SecondaryCellGroupconfiguration ( i.e. includesmrdc-SecondaryCellGroupConfigset tosetup).

[0146] In an embodiment, when the UE (101) performs the LTM cell switch triggered on the MCG, the UE (101) applies default L1 parameter values as specified in the corresponding physical layer specifications, except for those parameters for which values are provided in SIB1 for the SCG and the MCG, when the MCG RRC Reconfiguration message to be applied due to execution of the LTM cell switch procedure includes an SCG RRC Reconfiguration message.

[0147] FIG.7 is a flow diagram that illustrates the L1 parameter handling during the SCG cell switch execution, according to embodiments as disclosed herein.

[0148] At step 701, triggering execution of the LTM cell switch on the SCG.

[0149] At step 702, determining whether the ltm-Config is associated with the MCG. When the ltm-Config is not associated with the MCG, control proceeds to step 703, otherwise, control proceeds to step 704.

[0150] At step 703, applying the default L1 parameter values as specified in corresponding physical layer specifications except for the parameters for which values are provided in the SIB1 for the SCG.

[0151] At step 704, applying the default L1 parameter values as specified in corresponding physical layer specifications except for the parameters for which values are provided in the SIB1 for both the MCG and SCG.

[0152] In an embodiment, while performing the LTM cell switch, and the LTM cell switch is triggered on the SCG, the UE (101) applies the default L1 parameter values as specified in corresponding physical layer specifications except for the parameters for which values are provided in the SIB1 for the MCG and SCG (such as specified in clause 9.2.2 of TS 38.331 in NR), when the LTM cell switch is for the Inter-CU SCG LTM.

[0153] In an embodiment, while performing the LTM cell switch, and the LTM cell switch is triggered on the SCG, the UE (101) applies the default L1 parameter values as specified in corresponding physical layer specifications except for the parameters for which values are provided in the SIB1 for the MCG and SCG (such as specified in clause 9.2.2 of TS 38.331 in NR), when the LTM cell switch is for the Intra-CU SCG LTM where the LTM configuration is associated with the MCG.

[0154] In an embodiment, while performing the LTM cell switch, and the LTM cell switch is triggered on the SCG, the UE (101) applies the default L1 parameter values as specified in corresponding physical layer specifications except for the parameters for which values are provided in the SIB1 for the MCG and SCG (such as specified in 9.2.2 of TS 38.331 in NR), when the LTM configuration is associated with the MCG.

[0155] In an embodiment, in NR, when the ltm-Config related to the LTM cell switch is included within the RRC Reconfiguration message received via SRB1, while performing the LTM cell switch, and the LTM cell switch is triggered on the SCG, the UE (101) applies the default L1 parameter values as specified in corresponding physical layer specifications except for the parameters for which values are provided in the SIB1 for the MCG and SCG (such as specified in clause 9.2.2 of TS 38.331 in NR).

[0156] In an embodiment, the flow may include, at step 1, the UE (101) is configured for dual connectivity and has the PSCell. At step 2, the UE (101) receives LTM configuration for SCG LTM and the LTM configuration is received in MN format (i.e., LTM configuration is associated to MCG or is received in RRC Reconfiguration message received via SRB1 in NR) (order of step 1 and step 2 are interchangeable). At step 3, the UE (101) performs LTM cell switch, triggered on SCG. At step 4, the UE (101) applies the default default L1 parameter values as specified in corresponding physical layer specifications except for the parameters for which values are provided in SIB1 for MCG and SCG while performing LTM cell switch.

[0157] In an embodiment, the UE (101) performing LTM cell switch applies the default L1 parameter values as specified in corresponding physical layer specifications except for the parameters for which values are provided in the SIB1 for the cell group(s) for which the RRC Reconfiguration will be applied due to the triggered LTM cell switch.

[0158] FIG. 8 is a flow chart that illustrates the L1 parameter handling during the LTM cell switch execution, according to embodiments as disclosed herein. At step 801, performing LTM cell switch. At step 802, applying the default L1 parameter values except for the parameters for which values are provided in SIB1 for the cell group(s) for which the RRC Reconfiguration message may be applied due to the triggered LTM cell switch.

[0159] In an embodiment, according to TS 38.331, upon the indication by lower layers that the LTM cell switch procedure is triggered, or upon performing LTM cell switch following cell selection performed while timer T311 was running, as specified in 5.3.7.3, the UE (101) shall:

[0160] 1> apply the default L1 parameter values as specified in corresponding physical layer specifications except for the parameters for which values are provided in the SIB1 for the cell group(s) for which the RRC Reconfiguration will be applied due to the triggered LTM cell switch (step 802).

[0161] In an embodiment, according to TS 38.331, upon the indication by lower layers that the LTM cell switch procedure is triggered, or upon performing LTM cell switch following cell selection performed while timer T311 was running, as specified in 5.3.7.3, the UE (101) shall:

[0162] 1> if the LTM cell switch is triggered on the MCG:

[0163] 2> release / clear all current dedicated and common radio configurations which have neither been received via SRB1 within mrdc-SecondaryCellGroup, nor via SRB3 except for the following:

[0164] - the radio bearer configuration (configured via RadioBearerConfig)

[0165] - the logicalChannelIdentity and logicalChannelIdentityExt of RLC bearers configured in RLC-BearerConfig and the associated RLC entities, their state variables, buffers, and timers, except for triggering the associated RLC entities to reset the variable RETX_COUNT its initial value, as specified in TS 38.322 [4];

[0166] - the bh-LogicalChannelIdentity of BH RLC channels configured in BH-RLC-ChannelConfig and the associated RLC entities, their state variables, buffers, and timers, except for triggering the associated RLC entities to reset the variable RETX_COUNT its initial value, as specified in TS 38.322 [4];

[0167] - the UE (101) variables VarLTM-ServingCellNoResetID and VarLTM-ServingCellUE-MeasuredTA-ID;

[0168] - the ltm-Config;

[0169] - the MCG C-RNTI;

[0170] - the AS security configurations associated with the master key;

[0171] - the logged measurement configuration;

[0172] 2> apply the default MAC Cell Group configuration as specified in 9.2.2 for MCG.

[0173] 2>apply the default L1 parameter values as specified in corresponding physical layer specifications except for the parameters for which values are provided in SIB1 for the MCG.

[0174] 2> if the RRC Reconfiguration to be applied during the LTM cell switch includes mrdc-SecondaryCellGroup:

[0175] 3> release / clear all current dedicated and common radio configurations which have either been received via SRB1 within mrdc-SecondaryCellGroup, or via SRB3 except for the following:

[0176] - the radio bearer configuration (configured via RadioBearerConfig IE)

[0177] - the logicalChannelIdentity and logicalChannelIdentityExt of RLC bearers configured in RLC-BearerConfig and the associated RLC entities, their state variables, buffers, and timers, except for triggering the associated RLC entities to reset the variable RETX_COUNT its initial value, as specified in TS 38.322 [4];

[0178] - the bh-LogicalChannelIdentity of BH RLC channels configured in BH-RLC-ChannelConfig and the associated RLC entities, their state variables, buffers, and timers, except for triggering the associated RLC entities to reset the variable RETX_COUNT its initial value, as specified in TS 38.322 [4];

[0179] - the UE variables VarLTM-ServingCellNoResetID and VarLTM-ServingCellUE-MeasuredTA-ID;

[0180] - the ltm-Config;

[0181] - the AS security configurations associated with the secondary key;

[0182] 3> apply the default MAC Cell Group configuration as specified in 9.2.2 for SCG.

[0183] 3>apply the default L1 parameter values as specified in corresponding physical layer specifications except for the parameters for which values are provided in SIB1 for the SCG.

[0184] 1> else, if the LTM cell switch is triggered on the SCG:

[0185] 2> release / clear all current dedicated and common radio configurations which have been received either via SRB1 within mrdc-SecondaryCellGroup, or via SRB3 except for the following:

[0186] - the radio bearer configuration (configured via RadioBearerConfig IE)

[0187] - the logicalChannelIdentity and logicalChannelIdentityExt of RLC bearers configured in RLC-BearerConfig and the associated RLC entities, their state variables, buffers, and timers, except for triggering the associated RLC entities to reset the variable RETX_COUNT its initial value, as specified in TS 38.322 [4];

[0188] - the bh-LogicalChannelIdentity of BH RLC channels configured in BH-RLC-ChannelConfig and the associated RLC entities, their state variables, buffers, and timers, except for triggering the associated RLC entities to reset the variable RETX_COUNT its initial value, as specified in TS 38.322 [4];

[0189] - the UE variables VarLTM-ServingCellNoResetID and VarLTM-ServingCellUE-MeasuredTA-ID;

[0190] - the ltm-Config;

[0191] - the AS security configurations associated with the secondary key;

[0192] 2> apply the default MAC Cell Group configuration as specified in 9.2.2 for SCG.

[0193] 2>apply the default L1 parameter values as specified in corresponding physical layer specifications except for the parameters for which values are provided in SIB1 for the SCG.

[0194] 2> if the ltm-Config is associated with the MCG

[0195] 3>apply the default MAC Cell Group configuration as specified in 9.2.2 for MCG.

[0196] 3>apply the default L1 parameter values as specified in corresponding physical layer specifications except for the parameters for which values are provided in SIB1 for the MCG.

[0197] The present invention enables efficient handling of the MAC Cell Group configuration during the LTM cell switch by selectively applying default MAC Cell Group configuration based on whether the MCG RRC configuration includes PSCell addition or PSCell change. The selective application minimizes unnecessary configuration overhead and reduces interruption time during mobility procedures.

[0198] Further, the present invention facilitates inter-SN SCG LTM and the MCG LTM configuration by generating and transmitting RRC Reconfiguration messages including the LTM candidate configurations and inter-SN SCG LTM configurations from the network apparatus (106) to the UE (101), thereby enabling seamless mobility across different network architectures including intra-gNB-DU mobility, intra-gNB-CU mobility, and inter-gNB-DU mobility.

[0199] Further, the method ensures proper synchronization between the MCG and SCG configurations during the LTM cell switch execution, preventing data loss and minimizing additional delay associated with data recovery. Additionally, the invention provides clear guidelines for applying default Layer-1 parameter values during LTM cell switch, ensuring that the UE (101) operates using a configuration known to the network during the mobility procedure. The advantages collectively improve the efficiency, reliability, and performance of Layer-2 Triggered Mobility in wireless communication networks.

[0200] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and / or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and 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. Therefore, 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 modification 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:receiving, from a base station, a layer 1 / layer 2 triggered mobility (LTM) configuration;triggering, a LTM cell switch procedure based on the LTM configuration; andapplying a default medium access control (MAC) configuration for at least one cell group for which a radio resource control (RRC) reconfiguration message is applied due to the triggered LTM cell switch.2.The method of claim 1, further comprising:receiving, from a master node (MN) associated with a master cell group (MCG), a RRC reconfiguration message including an LTM configuration for a secondary cell group (SCG) LTM,wherein an LTM cell switch triggered on the SCG is performed, and the default MAC configuration is applied for the MCG and the SCG.3.The method of claim 2, wherein the RRC reconfiguration message further includes an LTM configuration for the MCG LTM.4.The method of claim 1, further comprising:receiving, from a MN associated with an MCG, a RRC reconfiguration message including an LTM configuration for a MCG LTM,wherein an LTM cell switch triggered on the MCG is performed, and the default MAC configuration is applied for the MCG and the SCG, in case that a PSCellChange is included in the RRC reconfiguration message including the LTM configuration for the MCG LTM.5.The method of claim 1, further comprising:receiving, from a MN associated with an MCG, a RRC reconfiguration message including an LTM configuration for a MCG LTM,wherein an LTM cell switch triggered on the MCG is performed, and the default MAC configuration is applied for the SCG, in case that a PSCellAddition is included in the RRC reconfiguration message including the LTM configuration for the MCG LTM.6.The method of claim 1, further comprising:receiving, from a MN associated with an MCG, a RRC reconfiguration message including an LTM configuration for a MCG LTM,wherein an LTM cell switch triggered on the MCG is performed, and the default MAC configuration is applied for the MCG, in case that a PSCellChange and a PSCellAddition are not included in the RRC reconfiguration message including the LTM configuration for the MCG LTM.7.The method of claim 1, wherein the LTM cell switch procedure is triggered in case that at least one of: an indication by at least one lower layer that the LTM cell switch procedure is triggered, or the LTM cell switch procedure is performed following a cell selection performed while a timer T311 is running, or at least one LTM cell switch execution condition is fulfilled.8.A terminal in a wireless communication system, the terminal comprising:a transceiver; andat least one processor configured to:receive, from a base station via the transceiver, a layer 1 / layer 2 triggered mobility (LTM) configuration,trigger, a LTM cell switch procedure based on the LTM configuration, andapply a default medium access control (MAC) configuration for at least one cell group for which a radio resource control (RRC) reconfiguration message is applied due to the triggered LTM cell switch.9.The terminal of claim 8, wherein the at least one processor is further configured to:receive, from a master node (MN) associated with a master cell group (MCG), a RRC reconfiguration message including an LTM configuration for a secondary cell group (SCG) LTM,wherein an LTM cell switch triggered on the SCG is performed, and the default MAC configuration is applied for the MCG and the SCG.10.The terminal of claim 9, wherein the RRC reconfiguration message further includes an LTM configuration for the MCG LTM.11.The terminal of claim 8, wherein the at least one processor is further configured to:receive, from a MN associated with an MCG via the transceiver, a RRC reconfiguration message including an LTM configuration for a MCG LTM,wherein an LTM cell switch triggered on the MCG is performed, and the default MAC configuration is applied for the MCG and the SCG, in case that a PSCellChange is included in the RRC reconfiguration message including the LTM configuration for the MCG LTM.12.The terminal of claim 8, wherein the at least one processor is further configured to:receive, from a MN associated with an MCG via the transceiver, a RRC reconfiguration message including an LTM configuration for a MCG LTM,wherein an LTM cell switch triggered on the MCG is performed, and the default MAC configuration is applied for the SCG, in case that a PSCellAddition is included in the RRC reconfiguration message including the LTM configuration for the MCG LTM.13.The terminal of claim 8, wherein the at least one processor is further configured to:receive, from a MN associated with an MCG via the transceiver, a RRC reconfiguration message including an LTM configuration for a MCG LTM,wherein an LTM cell switch triggered on the MCG is performed, and the default MAC configuration is applied for the MCG, in case that a PSCellChange and a PSCellAddition are not included in the RRC reconfiguration message including the LTM configuration for the MCG LTM.14.The terminal of claim 8, wherein the LTM cell switch procedure is triggered in case that at least one of: an indication by at least one lower layer that the LTM cell switch procedure is triggered, or the LTM cell switch procedure is performed following a cell selection performed while a timer T311 is running, or at least one LTM cell switch execution condition is fulfilled.

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