Patent ID: 12200801

DETAILED DESCRIPTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, in the description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, the terms to be described later are terms defined in consideration of functions in the present invention, which may vary according to intentions or customs of users and operators. Therefore, the definition should be made based on the content throughout this specification.

The terms used, in the following description, for indicating access nodes, network entities, messages, interfaces between network entities, and diverse identity information is provided for convenience of explanation. Accordingly, the terms used in the following description are not limited to specific meanings but may be replaced by other terms equivalent in technical meanings.

In the following descriptions, the terms and definitions given in the latest 3GPP standards are used for convenience of explanation. However, the present disclosure is not limited by use of these terms and definitions and other arbitrary terms and definitions May be employed instead.

Table 1 lists the acronyms used throughout the present disclosure.

TABLE 1AcronymFull nameAcronymFull name5GC5G Core NetworkRACHRandom Access ChannelACKAcknowledgementRANRadio Access NetworkAMAcknowledged ModeRARRandom Access ResponseAMFAccess and MobilityRA-RNTIRandom Access RNTIManagement FunctionARQAutomatic Repeat RequestRATRadio Access TechnologyASAccess StratumRBRadio BearerASN.1Abstract Syntax NotationRLCRadio Link ControlOneBSRBuffer Status ReportRNARAN-based Notification AreaBWPBandwidth PartRNAURAN-based Notification AreaUpdateCACarrier AggregationRNTIRadio Network TemporaryIdentifierCAGClosed Access GroupRRCRadio Resource ControlCGCell GroupRRMRadio Resource ManagementC-RNTICell RNTIRSRPReference Signal ReceivedPowerCSIChannel State InformationRSRQReference Signal ReceivedQualityDCIDownlink ControlRSSIReceived Signal StrengthInformationIndicatorDRB(user) Data Radio BearerSCellSecondary CellDRXDiscontinuous ReceptionSCSSubcarrier SpacingHARQHybrid Automatic RepeatSDAPService Data AdaptationRequestProtocolIEInformation elementSDUService Data UnitLCGLogical Channel GroupSFNSystem Frame NumberMACMedium Access ControlS-GWServing GatewayMIBMaster Information BlockSISystem InformationNASNon-Access StratumSIBSystem Information BlockNG-RANNG Radio Access NetworkSpCellSpecial CellNRNR Radio AccessSRBSignalling Radio BearerPBRPrioritised Bit RateSRSSounding Reference SignalPCellPrimary CellSSSearch SpacePCIPhysical Cell IdentifierSSBSS/PBCH blockPDCCHPhysical Downlink ControlSSSSecondary SynchronisationChannelSignalPDCPPacket Data ConvergenceSULSupplementary UplinkProtocolPDSCHPhysical Downlink SharedTMTransparent ModeChannelPDUProtocol Data UnitUCIUplink Control InformationPHRPower Headroom ReportUEUser EquipmentPLMNPublic Land Mobile NetworkUMUnacknowledged ModePRACHPhysical Random AccessCS-RNTIConfigured Scheduling-RNTIChannelPRBPhysical Resource BlockTAGTiming Advance GroupPSSPrimary SynchronisationSDTSmall Data TransmissionSignalPUCCHPhysical Uplink ControlRA-SDTRandom Access -SDTChannelPUSCHPhysical Uplink SharedCG-SDTConfigured Grant-SDTChannelPTAGPrimary TAGSTAGSecondary TAG

Table 2 lists the terminologies and their definition used throughout the present disclosure.

TABLE 2TerminologyDefinitionCarrier frequencycenter frequency of the cell.Cellcombination of downlink and optionally uplink resources. Thelinking between the carrier frequency of the downlink resourcesand the carrier frequency of the uplink resources is indicated in thesystem information transmitted on the downlink resources.Cell Groupin dual connectivity, a group of serving cells associated with eitherthe MeNB or the SeNB.Cell reselectionA process to find a better suitable cell than the current serving cellbased on the system information received in the current serving cellCell selectionA process to find a suitable cell either blindly or based on thestored informationCell ReselectionPriority of a carrier frequency regarding cell reselection. SystemPriorityInformation Block 2 and System Information Block 3 provide theCRP of the serving frequency and CRPs of inter-frequenciesrespectively. UE consider higher priority frequency for cellreselection if channel condition of the frequency is better than aspecific threshold even if channel condition of a lower priorityfrequency is better than that of the higher priority frequency.DedicatedSignalling sent on DCCH logical channel between the network andsignallinga single UE.FieldThe individual contents of an information element are referred to asfields.Frequency layerset of cells with the same carrier frequency.Global cellAn identity to uniquely identifying an NR cell. It is consisted ofidentitycellIdentity and plmn-Identity of the first PLMN-Identity in plmn-IdentityList in SIB1.gNBnode providing NR user plane and control plane protocolterminations towards the UE, and connected via the NG interface tothe 5GC.Handoverprocedure that changes the serving cell of a UE inRRC_CONNECTED.InformationA structural element containing single or multiple fields is referredelementas information element.LThe Length field in MAC subheader indicates the length of thecorresponding MAC SDU or of the corresponding MAC CELCID6 bit logical channel identity in MAC subheader to denote whichlogical channel traffic or which MAC CE is included in the MACsubPDULogical channela logical path between a RLC entity and a MAC entity. There aremultiple logical channel types depending on what type ofinformation is transferred e.g. CCCH (Common Control Channel),DCCH (Dedicate Control Channel), DTCH (Dedicate TrafficChannel), PCCH (Paging Control Channel)NRNR radio accessPCellSpCell of a master cell group.registered PLMNPLMN which UE has registered toselected PLMNPLMN which UE has selected to perform registration procedureequivalent PLMNPLMN which is equivalent to registered PLMN. UE is informed oflist of EPLMNs by AMF during registration procedurePLMN ID Checkthe process that checks whether a PLMN ID is the RPLMN identityor an EPLMN identity of the UE.Primary CellThe MCG cell, operating on the primary frequency, in which theUE either performs the initial connection establishment procedureor initiates the connection re-establishment procedure.Radio BearerLogical path between a PDCP entity and upper layer (i.e. SDAPentity or RRC)RLC bearerRLC and MAC logical channel configuration of a radio bearer inone cell group.RLC bearerThe lower layer part of the radio bearer configuration comprisingconfigurationthe RLC and logical channel configurations.Serving CellFor a UE in RRC_CONNECTED not configured with CA/DCthere is only one serving cell comprising of the primary cell. For aUE in RRC_CONNECTED configured with CA/DC the term‘serving cells’ is used to denote the set of cells comprising of theSpecial Cell(s) and all secondary cells.SpCellprimary cell of a master or secondary cell group.Special CellFor Dual Connectivity operation the term Special Cell refers to thePCell of the MCG or the PSCell of the SCG, otherwise the termSpecial Cell refers to the PCell.SRBSignalling Radio Bearers” (SRBs) are defined as Radio Bearers(RBs) that are used only for the transmission of RRC and NASmessages.SRB0SRB0 is for RRC messages using the CCCH logical channelSRB1SRB1 is for RRC messages (which may include a piggybackedNAS message) as well as for NAS messages prior to theestablishment of SRB2, all using DCCH logical channel;SRB2SRB2 is for NAS messages and for RRC messages which includelogged measurement information, all using DCCH logical channel.SRB2 has a lower priority than SRB1 and may be configured bythe network after AS security activation;SRB3SRB3 is for specific RRC messages when UE is in (NG)EN-DC orNR-DC, all using DCCH logical channelSRB4SRB4 is for RRC messages which include application layermeasurement reporting information, all using DCCH logicalchannel.DCCHDCCH is a logical channel to transfer RRC messages after RRCconnection establishmentSuitable cellA cell on which a UE may camp. Following criteria applyThe cell is part of either the selected PLMN or the registeredPLMN or PLMN of the Equivalent PLMN listThe cell is not barredThe cell is part of at least one TA that is not part of the list of“Forbidden Tracking Areas for Roaming” (TS 22.011 [18]), whichbelongs to a PLMN that fulfils the first bullet above.The cell selection criterion S is fulfilled (i.e. RSRP and RSRQ arebetter than specific values

In the present invention, “trigger” or “triggered” and “initiate” or “initiated” may be used in the same meaning. In the present invention, “radio bearer second resume procedure is allowed”, “radio bearer second resume procedure is configured” and “radio bearer second resume procedure is enabled” may be used in the same meaning. In the present invention, second resume procedure and Small Data Transfer (SDT) may be used in the same meaning. In the present invention, UE and terminal may be used in the same meaning. In the present invention, base station and NG-RAN node may be used in the same meaning.

FIG.1Ais a diagram illustrating the architecture of an 5G system and a NG-RAN to which the disclosure may be applied.

5G system consists of NG-RAN1A-01and 5GC1A-02. An NG-RAN node is either:a gNB, providing NR user plane and control plane protocol terminations towards the UE; oran ng-eNB, providing E-UTRA user plane and control plane protocol terminations towards the UE.

The gNBs1A-05or1A-06and ng-eNBs1A-03or1A-04are interconnected with each other by means of the Xn interface. The gNBs and ng-eNBs are also connected by means of the NG interfaces to the 5GC, more specifically to the AMF (Access and Mobility Management Function) and to the UPF (User Plane Function). AMF1A-07and UPF1A-08may be realized as a physical node or as separate physical nodes.

A gNB1A-05or1A-06or an ng-eNBs1A-03or1A-04hosts the functions listed below.

Functions for Radio Resource Management such as Radio Bearer Control, Radio Admission Control, Connection Mobility Control, Dynamic allocation of resources to UEs in uplink, downlink and sidelink(scheduling); andIP and Ethernet header compression, uplink data decompression and encryption of user data stream; andSelection of an AMF at UE attachment when no routing to an MME can be determined from the information provided by the UE; andRouting of User Plane data towards UPF; andScheduling and transmission of paging messages; andScheduling and transmission of broadcast information (originated from the AMF or O&M); andMeasurement and measurement reporting configuration for mobility and scheduling; andSession Management; andQoS Flow management and mapping to data radio bearers; andSupport of UEs in RRC_INACTIVE state; andRadio access network sharing; andTight interworking between NR and E-UTRA; andSupport of Network Slicing.

The AMF1A-07hosts the functions such as NAS signaling, NAS signaling security, AS security control, SMF selection, Authentication, Mobility management and positioning management.

The UPF1A-08hosts the functions such as packet routing and forwarding, transport level packet marking in the uplink, QoS handling and the downlink, mobility anchoring for mobility etc.

FIG.1Bis a diagram illustrating a wireless protocol architecture in an 5G system to which the disclosure may be applied.

User plane protocol stack consists of SDAP1B-01or1B-02, PDCP1B-03or1B-04, RLC1B-05or1B-06, MAC1B-07or1B-08and PHY1B-09or1B-10. Control plane protocol stack consists of NAS1B-11or1B-12, RRC1B-13or1B-14, PDCP, RLC, MAC and PHY.

Each protocol sublayer performs functions related to the operations listed in the table 3.

TABLE 3SublayerFunctionsNASauthentication, mobility management, security control etcRRCSystem Information, Paging, Establishment, maintenance and releaseof an RRC connection, Security functions, Establishment,configuration, maintenance and release of Signalling Radio Bearers(SRBs) and Data Radio Bearers (DRBs), Mobility, QoS management,Detection of and recovery from radio link failure, NAS messagetransfer etc.SDAPMapping between a QoS flow and a data radio bearer, Marking QoSflow ID (QFI) in both DL and UL packets.PDCPTransfer of data, Header compression and decompression, Cipheringand deciphering, Integrity protection and integrity verification,Duplication, Reordering and in-order delivery, Out-of-order deliveryetc.RLCTransfer of upper layer PDUs, Error Correction through ARQ,Segmentation and re-segmentation of RLC SDUs, Reassembly ofSDU, RLC re-establishment etc.MACMapping between logical channels and transport channels,Multiplexing/demultiplexing of MAC SDUs belonging to one ordifferent logical channels into/from transport blocks (TB) deliveredto/from the physical layer on transport channels, Schedulinginformation reporting, Priority handling between UEs, Priorityhandling between logical channels of one UE etc.PHYChannel coding, Physical-layer hybrid-ARQ processing, Ratematching, Scrambling, Modulation, Layer mapping, DownlinkControl Information, Uplink Control Information etc.
The terminal supports three RRC states. Table 4 lists the characteristics of each state.

TABLE 4RRC stateCharacteristicRRC_IDLEPLMN selection; Broadcast of system information;Cell re-selection mobility;Paging for mobile terminated data is initiated by 5GC;DRX for CN paging configured by NAS.RRC_INACTIVEPLMN selection; Broadcast of system information; Cell re-selectionmobility;Paging is initiated by NG-RAN (RAN paging);RAN-based notification area (RNA) is managed by NG- RAN;DRX for RAN paging configured by NG-RAN;5GC - NG-RAN connection (both C/U-planes) is established forUE;The UE AS context is stored in NG-RAN and the UE;NG-RAN knows the RNA which the UE belongs to.RRC_CONNECTED5GC - NG-RAN connection (both C/U-planes) is established forUE; The UE AS context is stored in NG-RAN and the UE; NG-RANknows the cell which the UE belongs to;Transfer of unicast data to/from the UE;Network controlled mobility including measurements.

FIG.1Cis a diagram illustrating an RRC state transition.

Between RRC_CONNECTED1C-11and RRC_INACTIVE1C-13, a state transition occurs due to the exchange of the Resume message and the Release message containing the Suspend IE.

A state transition occurs between RRC_CONNECTED1C-11and RRC_IDLE1C-through RRC connection establishment and RRC connection release.

<SuspendConfig>

1. The first terminal identifier: an identifier of a terminal that may be included in the ResumeRequest when a state transition to RRC_CONNECTED is made. It has a 40-bit length.2. The second terminal identifier: an identifier of a terminal that may be included in the Resume Request when a state transition to RRC_CONNECTED is made. It has a 24-bit length.3. ran-Paging Cycle: Paging cycle to be applied in RRC_INACTIVE state.4. ran-Notification AreaInfo: Configuration information of a ran-Notification Area consisting of a list of cells and the like. The terminal initiates a resume procedure when the ran_Notification Area is changed.5. t380: Timer related to the periodic resumption procedure.6. NextHopChangingCount (NCC): Counter used to derive new security keys after performing the resume procedure.7. Extended-ran-Paging-Cycle: Paging cycle to be applied when extended DRX is configured. It indicates one of predefined values. rf256, rf512, rf1024 and reserved value.

UE's that are registered to more than one network need to be able to receive pages from more than one network. Dependent on UE capabilities (e.g., Rx and Tx capabilities) this can create situations in which a UE is occupied listening to pages from one network while pages from other networks also may be sent. Further UE's may be actively communicating with one network while another network pages the UE. If a user switch between communications towards different networks, situations may occur when a UE/user can no longer receive data from a network it was recently communicating in. Such situations can have a negative impact on performance, e.g., if pages are sent and not properly received, or if users are scheduled while not being able to receive communication.

In the disclosure, a method is provided for UE to request UE state transition for the purpose of UE power saving or to handle the aforementioned problems from MUSIM.

FIG.2Ais a diagram illustrating operation of UE and base station In2A-11, UE (2A-01) transmits to GNB (2A-03) UECapabilityInformation.

UECapabilityInformation message is used to transfer UE radio access capabilities requested by the network.

UE may include in the message releasePreference capability IE and releaseRequest capability IE. releasePreference IE indicates whether the UE supports providing its preference assistance information to transition out of RRC_CONNECTED for power saving. releaseRequest IE indicates whether the UE supports providing its assistance information to request transition out of RRC_CONNECTED for MUSIM.

UECapabilityInformation message includes a UE-NR-Capability IE. A UE-NR-Capability IE includes plurality of non-critical extensions. Non-critical extensions are characterised by the addition of new information to the original specification of the PDU type. If not comprehended, a non-critical extension may be skipped by the decoder, whilst the decoder is still able to complete the decoding of the comprehended parts of the PDU contents.

Non-critical extensions for UE-NR-Capability are defined release basis. A NCE for later release is placed later than a NCE for earlier release.

releasePreference capability IE and releaseReqeust capability IE are placed under different non-critical extensions.

releaseRequest capability IE is enumerated with a single value of “supported”. If UE includes releaseRequest capability IE in a NCE of UE-NR-Capability, UE supports the functionality of releaseRequest IE for both FDD and TDD and for both FR1 and FR2.

GNB determines the configuration to be applied to the UE based on the capability information received in2A-11.

GNB generates RRCReconfiguration message based on the determined configuration.

In2A-13, GNB transmits to UE RRCReconfiguration. The RRCReconfiguration message is the command to modify an RRC connection. It may convey information for measurement configuration, mobility control, radio resource configuration (including RBs, MAC main configuration and physical channel configuration) and AS security configuration.

GNB may include the UE assistance information configuration such as releasePreferenceConfig IE or musim-AssistanceConfig IE in the message. releasePreferenceConfig IE is configuration for the UE to report assistance information to inform the gNB about the UE's preference to leave RRC_CONNECTED state. releasePreferenceConfig IE includes releasePreferenceProhibitTimer which is a prohibit timer for release preference assistance information reporting. musim-AssistanceConfig IE is configuration for the UE to report assistance information for MUSIM. musim-AssistanceConfig IE includes musim-LeaveWithoutResponseTimer, which indicates the timer for UE to leave RRC_CONNECTED without network response.

UE consider itself to be configured to provide assistance information to transition out of RRC_CONNECTED if the received otherConfig of RRCReconfiguration message includes the releasePreferenceConfig and if releasePreferenceConfig is set to setup.

UE consider itself to be configured to provide MUSIM assistance information if the received otherConfig of RRCReconfiguration includes the musim-AssistanceConfig and if musim-AssistanceConfig is set to setup.

In2A-15, UE initiates UE Assistance Information procedure to inform the network of its preference on the RRC state or its MUSIM assistance information.

A UE capable of providing assistance information to transition out of RRC_CONNECTED state may initiate the procedure if it was configured to do so, upon determining that it prefers to transition out of RRC_CONNECTED state, or upon change of its preferred RRC state.

A UE capable of providing MUSIM assistance information may initiate the procedure if it was configured to do so, upon determining that it needs to leave RRC_CONNECTED state, or upon determining it needs the gaps, or upon change of the gap information.

If UE is configured to provide its release preference and timer T1is not running and if the UE determines that it would prefer to transition out of RRC_CONNECTED state, UE start timer T1with the timer value set to the releasePreferenceProhibitTimer and UE initiates transmission of the UEAssistanceInformation message to provide the release preference.

If UE is configured to provide MUSIM assistance information and if the UE needs to leave RRC_CONNECTED state, UE initiate transmission of the UEAssistanceInformation message to provide MUSIM assistance information and UE start the timer T2with the timer value set to the MUSIM-Leave WithoutResponseTimer.

If transmission of the UEAssistanceInformation message is initiated to provide a release preference, UE include releasePreference in the UEAssistanceInformation message. UE sets preferredRRC-State in releasePreference to the desired RRC state on transmission of the UEAssistanceInformation message.

If transmission of the UEAssistanceInformation message is initiated to provide MUSIM assistance information, UE includes musim-PreferredRRC-State in the UEAssistanceInformation. UE sets musim-PreferredRRC-State to the desired RRC state.

preferredRRC-State is enumerated with IDLE and INACTIVE and CONNECTED and OUTOFCONNECTED. musim-PreferredRRC-State is enumerated with IDLE and INACTIVE.

GNB receives the UEAssistanceInformation message. GNB recognize that UE prefer RRC state transition for power saving purpose if UEAssistanceInformation includes releasePreference IE. GNB recognize that UE requests RRC state transition for MUSIM purpose if UEAssistanceInformation includes musim-PreferredRRC-State IE.

If GNB successfully receives the UEAssistanceInformation message, GNB would take proper measure such as commanding UE state transition.

If GNB fails to receive the UEAssistanceInformation message, GNB does not take proper measure. In such case, T2may expire. GNB can also send mobility related RRC message if GNB deemed required.2A-17or2A-19take place in such case.

In2A-17, T2expires. UE performs the first action set, which are listed below.

UE resets MAC. UE stops all timers that are running except T302(related to RRCRelease with waitTime), T320(related to validity time configured for dedicated6priorities), T325(related to RRCRelease message with deprioritisationTimer), T330(related to LoggedMeasurementConfiguration), T331(related to RRCRelease message with measIdleDuration) and T400(related to RRCReconfigurationSidelink). UE stops T1if running. UE releases all radio resources, including release of the RLC entity, the MAC configuration and the associated PDCP entity and SDAP for all established RBs. UE enter RRC_IDLE and perform cell selection.

In2A-19, GNB may generates mobility related RRC message if UEAssistanceInformation is not received. Mobility related RRC message could be RRCReconfiguration message for handover or RRC reconfiguration message for conditional handover or MobilityFromNRCommand message.

RRCReconfiguration message for handover includes masterCellGroup IE which includes reconfigurationWithSync:

RRCReconfiguration message for conditional handover includes conditionalReconfiguration IE which includes another RRCReconfiguration message for handover.

MobilityFromNRCommand message is used to command handover from NR to E-UTRA/EPC, E-UTRA/5GC or UTRA-FDD. MobilityFromNRCommand message includes targetRAT-MessageContainer IE which carries information about the target cell identifier(s) and radio parameters relevant for the target radio access technology.

Upon receiving RRCReconfiguration message for handover, UE executes handover toward the cell indicated in RRCReconfiguration message and starts T304. UE initiates random access procedure in the target cell. If the random access procedure is successfully completed before T304expires, UE consider the handover is successful.

After handover is successfully completed, UE checks whether the first condition set are met. If first condition set are met, UE performs the second action set. As consequence of second actions set UE transmits UEAssistanceInformation in the target cell and starts T2to perform local release, if UE has transmitted UEAssistanceInformation in the source cell during the near fast.

First condition set includes following conditions.If reconfiguration WithSync was included in masterCellGroup;If the UE initiated transmission of a UEAssistanceInformation message during the last 1 second; andIf the UE is still configured to provide the concerned UE assistance information

The second action set includes followings.

UE stops T2if running. UE initiates transmission of a UEAssistanceInformation message to provide the concerned UE assistance information. UE starts or restart T1with the timer value set to the value of releasePreferenceProhibitTimer. UE starts T2with the timer value set to the value of musim-Leave WithoutResponseTimer.

The reason UE stops T2upon receiving RRCReconfiguration message for handover is to prevent local RRC connection release while handover is ongoing.

Upon receiving RRCReconfiguration message for conditional handover, UE evaluates execution condition based on the information in received RRCReconfiguration. If execution condition is fulfilled, UE executes handover toward the cell indicated in RRCReconfiguration message and starts T304. UE initiates random access procedure in the target cell. If the random access procedure is successfully completed before T304expires, UE consider the handover is successful.

After conditional handover (or conditional reconfiguration) is successfully completed, UE checks whether the second condition set are met. If the second condition set are met, UE performs the second action set.

Second condition set includes following conditions.If reconfiguration WithSync was included in masterCellGroup; andIf the RRCReconfiguration message is applied due to a conditional reconfiguration execution; andIf the UE is configured to provide UE assistance information; andIf the UE has initiated transmission of a UEAssistanceInformation message since it was configured to do so.

As consequence of second actions set UE transmits UEAssistanceInformation in the target cell and starts T2to perform local release, if UE has transmitted UEAssistanceInformation in any cell.

The different handling as above is to mitigate the difference between the handover and the conditional handover. GNB knows the exact time when handover is executed. GNB does not know exact time when conditional handover is executed.

Upon receiving MobilityFromNRCommand message, UE checks whether T2is running. If T2is running, UE delays performing the action set until T2expires. Upon expiry2of T2, UE applies the first action set.

Alternatively, UE stops T2and performs the first action set.

If T2is not running, UE applies third action set. The third action set includes followings.

UE access the target cell indicated in the inter-RAT message in accordance with the specifications of the target RAT. UE resets MAC. UE stops all timers (including T1) that are running except T325, T330and T400. UE releases all radio resources, including release of the RLC entity and the MAC configuration. UE releases the associated PDCP entity and SDAP entity for all established RBs.

If handover or mobility from NR fails, UE may initiate RRC connection re-establishment procedure.

In2A-21, UE initiates RRC re-establishment procedure. UE performs fourth action set upon initiation of the procedure. The fourth action set includes followings.

UE stops T310(related to physical layer problem detection) and T304(related to handover) and T1. UE starts T311. UE resets MAC. UE suspend all RBs except SRB0. UE performs cell selection.

Upon selecting a suitable NR cell, UE stops T311and transmits RRCReestablishmentRequest message. If RRCReestablishment is received in response to RRCReestablishmentRequest, UE re-establishes the RRC connection based on the received RRC message.

If a suitable cell is not found until T311expires, UE stops T2and performs the first action set.

If GNB has received UEAssistanceInformation transmitted in2A-15, GNB can transmits RRCRelease message for state transition instead of transmitting mobility related RRC message.

In2A-23, GNB transmits RRCRelease message to UE. The RRCRelease message includes SuspendConfig.

Upon reception of RRCRelease, UE stops T2and UE delays the fifth action set 60 ms from the moment the RRCRelease message was received or optionally when lower layers indicate that the receipt of the RRCRelease message has been successfully acknowledged, whichever is earlier.

Upon reception of RRCRelease, UE stops T2before applying 60 ms delay and performs fifth action set after 60 ms delay.

UE stops timer T380and T320and T316and T350. UE applies the received suspendConfig. UE resets MAC and releases the default MAC Cell Group configuration. UE re-establishes RLC entities for SRB1. UE stores in the UE Inactive AS Context the current KgNB and KRRCint keys, the ROHC state, the stored QoS flow to DRB mapping rules, the C-RNTI used in the source PCell, the cellIdentity and the physical cell identity of the source PCell.

By applying 60 ms delay, UE can transmit RLC acknowledgement for RRCRelease message. However, if 60 ms delay is applied to T2stopage, T2may expire to cause state transition to IDLE state before RLC acknowledgement is transmitted.

FIG.3Aillustrates the operation of the terminal.

In step3A-11, the terminal receives an RRC reconfiguration message including a MUSIM-AssistanceConfig IE from the base station.

In step3A-13, the terminal starts the terminal assistance information procedure based on the fact that the Musim-AssistanceConfig is set up as a set up.

In step3A-15, when the UEAssistanceInformation includes a Musim-Preferredrc-State IE, the terminal starts the first timer after the start of the UEAssistanceInformation transmission.

In step3A-17, the terminal receives a second RRC reconfiguration message including a reconfigurationwithsync IE.

In step3A-19, the terminal starts a second timer set by the second timer value included in the reconfigurationwithsync IE.

In step3A-21, the terminal operates the first timer according to the state of the second timer and operates the second timer according to the state of the first timer.

Terminal consider the first timer to be expired when the second timer expires and stops the second timer when the first timer expires.

Alternatively, terminal stops the first timer when the second timer expires and stops the second timer when the first timer expires.

Terminal initiates RRC connection reestablishment procedure if the second timer expires while the first timer is not running. Terminal does not initiates RRC connection reestablishment procedure if the second timer expires while the first timer is running.

Alternatively, terminal initiates RRC connection reestablishment procedure if the second timer expires while the first timer is not running. Terminal stops the first timer and initiates RRC connection reestablishment procedure if the second timer expires while the first timer is running.

Terminal stops the second timer and enters RRC_IDLE if the first timer expires while the second timer is running. Terminal enters into RRC_IDLE if the first timer expires while the second timer is not running.

Terminal transmits, before the first RRC reconfiguration message is received, UECapabilityInformation including a terminal capability IE related to the first time, the functionality related to the first timer is supported by the terminal in FDD and in TDD and in FR1 and in FR2 if terminal capability IE related to the first timer is included in the UECapabilityInformation.

FIG.4Ais a block diagram illustrating the internal structure of a UE to which the disclosure is applied.

Referring to the diagram, the UE includes a controller4A-01, a storage unit4A-02, a transceiver4A-03, a main processor4A-04and I/O unit4A-05.

The controller4A-01controls the overall operations of the UE in terms of mobile communication. For example, the controller4A-01receives/transmits signals through the transceiver4A-03. In addition, the controller4A-01records and reads data in the storage unit4A-02. To this end, the controller4A-01includes at least one processor. For example, the controller4A-01may include a communication processor (CP) that performs control for communication and an application processor (AP) that controls the upper layer, such as an application program. The controller controls storage unit and transceiver such that UE operations illustrated inFIG.2AandFIG.3Aare performed.

The storage unit4A-02stores data for operation of the UE, such as a basic program, an application program, and configuration information. The storage unit4A-02provides stored data at a request of the controller4A-01.

The transceiver4A-03consists of a RF processor, a baseband processor and one or more antennas. The RF processor performs functions for transmitting/receiving signals through a wireless channel, such as signal band conversion, amplification, and the like. Specifically, the RF processor up-converts a baseband signal provided from the baseband processor into an RF band signal, transmits the same through an antenna, and down-converts an RF band signal received through the antenna into a baseband signal. The RF processor may include a transmission filter, a reception filter, an amplifier, a mi10r, an oscillator, a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), and the like. The RF processor may perform MIMO and may receive multiple layers when performing the MIMO operation. The baseband processor performs a function of conversion between a baseband signal and a bit string according to the physical layer specification of the system. For example, during data transmission, the baseband processor encodes and modulates a transmission bit string, thereby generating complex symbols. In addition, during data reception, the baseband processor demodulates and decodes a baseband signal provided from the RF processor, thereby restoring a reception bit string.

The main processor4A-04controls the overall operations other than mobile operation. The main processor4A-04process user input received from I/O unit4A-05, stores8data in the storage unit4A-02, controls the controller4A-01for required mobile communication operations and forward user data to I/O unit4A-05.

I/O unit4A-05consists of equipment for inputting user data and for outputting user data such as a microphone and a screen. I/O unit4A-05performs inputting and outputting user data based on the main processor's instruction.

FIG.4Bis a block diagram illustrating the configuration of a base station according to the disclosure.

As illustrated in the diagram, the base station includes a controller4B-01, a storage unit4B-02, a transceiver4B-03and a backhaul interface unit4B-04.

The controller4B-01controls the overall operations of the main base station. For example, the controller4B-01receives/transmits signals through the transceiver4B-03, or through the backhaul interface unit4B-04. In addition, the controller4B-01records and reads data in the storage unit4B-02. To this end, the controller4B-01may include at least one processor. The controller controls transceiver, storage unit and backhaul interface such that base station operation illustrated inFIG.2Aare performed.

The storage unit4B-02stores data for operation of the main base station, such as a basic program, an application program, and configuration information. Particularly, the storage unit4B-02may store information regarding a bearer allocated to an accessed UE, a measurement result reported from the accessed UE, and the like. In addition, the storage unit4B-02may store information serving as a criterion to determine whether to provide the UE with multi-connection or to discontinue the same. In addition, the storage unit4B-02provides stored data at a request of the controller4B-01.

The transceiver4B-03consists of a RF processor, a baseband processor and one or more antennas. The RF processor performs functions for transmitting/receiving signals through a wireless channel, such as signal band conversion, amplification, and the like. Specifically, the RF processor up-converts a baseband signal provided from the baseband processor into an RF band signal, transmits the same through an antenna, and down-converts an RF band signal received through the antenna into a baseband signal. The RF processor may include a transmission filter, a reception filter, an amplifier, a mi10r, an oscillator, a DAC, an ADC, and the like. The RF processor may perform a down link MIMO operation by transmitting at least one layer. The baseband processor performs a function of conversion between a baseband signal and a bit string according to the physical layer specification of the first radio access technology. For example, during data transmission, the baseband processor encodes and modulates a transmission bit string, thereby generating complex symbols. In addition, during data reception, the baseband processor demodulates and decodes a baseband signal provided from the RF processor, thereby restoring a reception bit string.

The backhaul interface unit4B-04provides an interface for communicating with other nodes inside the network. The backhaul interface unit4B-04converts a bit string transmitted from the base station to another node, for example, another base station or a core network, into a physical signal, and converts a physical signal received from the other node into a bit string.