Terminal device, base station device, method, and integrated circuit

Abstract

To provide techniques relating to a terminal device, a base station device, a method, and an integrated circuit that can reduce complexity of protocol processing and efficiently communicate.SOLUTION: A terminal device receives a message indicating movement from a first RAT to a second RAT from a base station device, and on the basis that, in handover processing according to the message, establishment of connection to the second RAT is failed and the message does not include a first parameter, returns to setting used in a primary cell in the first RAT, and performs connection reconnection processing.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a terminal device, a base station device, a method, and an integrated circuit. [Background technology]

[0002] A radio access method and radio network for cellular mobile communications (hereinafter referred to as "Long Term Evolution (LTE: registered trademark)" or "Evolved Universal Terrestrial Radio Access: EUTRA"), and a core network (hereinafter referred to as "Evolved Packet Core: EPC") are being considered in the 3rd Generation Partnership Project (3GPP).

[0003] In addition, 3GPP is currently studying and formulating standards for LTE-Advanced Pro, an extension of LTE, and NR (New Radio technology), a new radio access technology, as radio access methods and radio network technologies for the fifth generation cellular system (Non-Patent Document 1). Also, 5GC (5th Generation Core Network), a core network for the fifth generation cellular system, is being studied (Non-Patent Document 2). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] 3GPP RP-170855, “Work Item on New Radio (NR) Access Technology” [Non-Patent Document 2] 3GPP TS 23.501 v15.3.0, “System Architecture for the 5G System; Stage 2” [Non-Patent Document 3] 3GPP TS 36.300, v15.6.0, "Evolved Universal Terestrial Radio Access (E-UTRA) and Evolved Universal Terestrial Radio Access Network (E-UTRAN); Overall description; Stage 2"

Non-licensed Document 4

Non-licensed Document 5

Non-licensed Document 6

Non-licensed Document 7

Non-licensed literature 9

Non-licensed literature 10

Non-licensed Document 11

Non-licensed Document 12

Non-licensed Document 13

Non-licensed Document 14

Non-licensed Document 15

Non-licensed Document 16

Non-licensed Document 17

[0005] As part of the technical studies on NR, architectures under consideration include an architecture in which E-UTRA connects to 5GC, an architecture in which NR connects to 5GC, and an architecture related to a mechanism in which cells of both E-UTRA and NR RATs (Radio Access Technologies) are grouped by RAT and assigned to UEs, and communication is performed between a terminal device and one or more base station devices (MR-DC: Multi-RAT Dual Connectivity, Multi-Radio Dual Connectivity) (Non-Patent Document 17).

[0006] However, because the formats and functions of the communication protocols used in each architecture are different, and because different core networks are used, moving to a network with a different architecture while continuing communications (handover) requires more complex protocol processing than moving within conventional LTE, making it difficult to efficiently communicate between base station equipment and terminal devices.

[0007] One aspect of the present invention has been made in consideration of the above-mentioned circumstances, and has as its object to provide a terminal device, a base station device, a method used in the terminal device, and an integrated circuit implemented in the terminal device, which can efficiently communicate with a base station device. [Means for solving the problem]

[0008] In order to achieve the above object, one aspect of the present invention provides the following: A terminal device that communicates with a base station device, the terminal device including a receiving unit that receives a message indicating a movement from a first RAT to a second RAT from the base station device, and a receiving unit that receives a message indicating a movement from the first RAT to a second RAT from the base station device, the receiving unit receiving a message indicating a movement from the first RAT to a second RAT from the base station device, the receiving unit receiving a message indicating a movement from the first RAT to a second RAT from the base station device, the receiving unit receiving a message indicating a movement from the first RAT to a second RAT from the base station device, the receiving unit receiving a message indicating a movement from the first RAT to a second RAT from the base station device, and a processing unit that, in a handover process according to a message, when establishment of a connection to a second RAT fails and a first parameter is included in the message indicating a move from the first RAT to the second RAT, attempts to select a cell in the second RAT, and, based on successful selection of a cell in the second RAT, performs some or all of the following processes: resetting a MAC, stopping some or all of the running timers, discarding some or all of the AS security keys, releasing some or all of the radio resources, and notifying a higher layer of the release of the RRC connection.

[0009] Another aspect of the present invention is a base station device that communicates with a terminal device, the base station device including a transmitter that transmits a message indicating a movement from a first RAT to a second RAT to the terminal device, and a control unit that, in a handover process in accordance with the message indicating the movement from the first RAT to the second RAT, causes the terminal device to return to a setting used in a primary cell in the first RAT and perform a process of reconnecting the connection based on a case where a connection to the second RAT fails to be established in a handover process in accordance with the message indicating the movement from the first RAT to the second RAT and a first parameter is not included in the message indicating the movement from the first RAT to the second RAT, and causes the terminal device to perform a process of reconnecting the connection based on a case where a connection to the second RAT fails to be established in a handover process in accordance with the message indicating the movement from the first RAT to the second RAT, and a processing unit that, in a handover process in accordance with a message indicating a movement from the first RAT to the second RAT, attempts to select a cell in the second RAT when a connection to a second RAT has failed to be established and the message indicating a movement from the first RAT to the second RAT contains a first parameter, and, based on a successful selection of a cell in the second RAT, performs some or all of the following processes: resetting a MAC, stopping some or all of the running timers, discarding some or all of the AS security keys, releasing some or all of the radio resources, and notifying a higher layer of the release of the RRC connection.

[0010] Another aspect of the present invention is a method of a terminal device communicating with a base station device, comprising: receiving from the base station device a message indicating a movement from a first RAT to a second RAT; and, in a handover process in accordance with the message indicating the movement from the first RAT to the second RAT, if a connection to the second RAT fails to be established and a first parameter is not included in the message indicating the movement from the first RAT to the second RAT, returning to a setting used in a primary cell in the first RAT, performing a process of reconnecting the connection, and performing a handover process from the first RAT to the second RAT based on the fact that the message indicating the movement from the first RAT to the second RAT does not include a first parameter. In a handover process in accordance with a message indicating a movement, if establishment of a connection to a second RAT fails and the message indicating a movement from the first RAT to the second RAT contains a first parameter, an attempt is made to select a cell in the second RAT, and based on successful selection of a cell in the second RAT, some or all of the following processes are performed: resetting a MAC, stopping some or all of the running timers, discarding some or all of the AS security keys, releasing some or all of the radio resources, and notifying a higher layer of the release of the RRC connection.

[0011] Another aspect of the present invention is a method of a base station device communicating with a terminal device, the method comprising: transmitting a message indicating a movement from a first RAT to a second RAT to the terminal device; and, in a handover process in accordance with the message indicating the movement from the first RAT to the second RAT, if a connection to the second RAT fails to be established and a first parameter is included in the message indicating the movement from the first RAT to the second RAT, the method further comprises the steps of: and, based on the fact that the first parameter is not included in the message indicating the movement from the first RAT to the second RAT, the setting used in the primary cell in the first RAT is returned to and a process for reconnecting the connection is performed; and, based on the fact that the first parameter is included in the message indicating the movement from the first RAT to the second RAT, if the establishment of the connection to the second RAT has failed and the message indicating the movement from the first RAT to the second RAT includes a first parameter, the selection of a cell in the second RAT is attempted; and, based on the fact that the selection of a cell in the second RAT is successful, some or all of the following processes are performed: resetting a MAC, stopping some or all of the operating timers, discarding some or all of the AS security keys, releasing some or all of the radio resources, and notifying a higher layer of the release of the RRC connection.

[0012] These comprehensive or specific aspects may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium, or may be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium. Effect of the Invention

[0013] According to one aspect of the present invention, a terminal device can reduce the complexity of protocol processing and perform communication efficiently. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic diagram of a communication system according to each embodiment of the present invention. [Diagram 2] FIG. 2 is a protocol stack diagram of the UP and CP of a terminal device and a base station device in E-UTRA in each embodiment of the present invention. [Diagram 3] A protocol stack diagram of UP and CP of a terminal device and a base station device in NR in each embodiment of the present invention. [Figure 4] FIG. 13 is a diagram showing an example of a flow of a procedure for various settings in the RRC 208 and / or the RRC 308 in each embodiment of the present invention. [Diagram 5]FIG. 2 is a block diagram showing a configuration of a terminal device in each embodiment of the present invention. [Figure 6] FIG. 2 is a block diagram showing a configuration of a base station device in each embodiment of the present invention. [Figure 7] An example of an ASN.1 description included in a message regarding reconfiguration of an RRC connection in NR in an embodiment of the present invention. [Figure 8] 4 is an example of an ASN.1 description included in a message regarding re-establishment of an RRC connection in E-UTRA in an embodiment of the present invention. [Figure 9] 13 shows an example of a processing method of a UE 122 according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0016] LTE (and LTE-A Pro) and NR are different radio access technologies. Access Technology (RAT). NR may be defined as a technology included in LTE. LTE may be defined as a technology included in NR. LTE that can be connected to NR with Multi Radio Dual connectivity may be distinguished from conventional LTE. LTE whose core network is 5GC may be distinguished from conventional LTE whose core network is EPC. This embodiment may be applied to NR, LTE, and other RATs. In the following description, the description will be given using terms related to LTE and NR, but may be applied to other technologies using other terms. The term E-UTRA in this embodiment may be replaced with the term LTE, and the term LTE may be replaced with the term E-UTRA.

[0017] FIG. 1 is a schematic diagram of a communication system according to each embodiment of the present invention.

[0018] E-UTRA 100 is a radio access technology described in Non-Patent Document 3 and the like, and is composed of cell groups (CGs) each consisting of one or more frequency bands. eNB (E-UTRAN Node B) 102 is a base station device of E-UTRA 100. EPC (Evolved Packet Core) 104 is a core network described in Non-Patent Document 14 and the like, and was designed as a core network for E-UTRA 100. Interface 112 is an interface between eNB 102 and EPC 104, and includes a control plane (CP) through which control signals pass, and a user plane (UP) through which user data passes.

[0019] NR106 is a radio access technology described in Non-Patent Document 9 and the like, and is composed of cell groups (CGs) consisting of one or more frequency bands. gNB (g Node B) 108 is a base station device of NR106. 5GC110 is a core network described in Non-Patent Document 2 and the like, and is designed as a core network for NR106, but may also be used as a core network for E-UTRA100 that has a function of connecting to 5GC110. Hereinafter, E-UTRA100 may include E-UTRA100 that has a function of connecting to 5GC110.

[0020] The above-mentioned cell group may necessarily include one special cell (SpCell). The above-mentioned cell group may also include one or more secondary cells different from the special cell. The above-mentioned special cell may be called a primary cell (PCell). The above-mentioned special cell may be a cell in which some or all of the settings of the NAS-related settings, security-related settings, random access-related settings, radio link-related settings, and handover-related settings described below are performed. The above-mentioned secondary cell may be a cell in which some or all of the settings of the NAS-related settings, security-related settings, random access-related settings, radio link-related settings, and handover-related settings described below are not performed.

[0021] The interface 114 is an interface between the eNB 102 and the 5GC 110, the interface 116 is an interface between the gNB 108 and the 5GC 110, the interface 118 is an interface between the gNB 108 and the EPC 104, the interface 120 is an interface between the eNB 102 and the gNB 108, and the interface 124 is an interface between the EPC 104 and the 5GC 110. The interface 114, the interface 116, the interface 118, the interface 120, the interface 124, and the like may be interfaces that pass only the CP, only the UP, or both the CP and the UP. In addition, the interface 114, the interface 116, the interface 118, the interface 120, the interface 124, and the like may not exist depending on the communication system provided by the communication carrier.

[0022] The UE 122 is a terminal device compatible with any or all of the E-UTRA 100 and the NR 106. As described in Non-Patent Document 3 and any or all of Non-Patent Document 9, when the UE 122 connects to the core network via any or all of the E-UTRA 100 and the NR 106, a logical path called a radio bearer (RB) is established between the UE 122 and any or all of the E-UTRA 100 and the NR 106. The radio bearer used for CP is called a signaling radio bearer (SRB), and the radio bearer used for UP is called a data radio bearer (DRB Data Radio Bearer). Each RB is assigned an RB identity (RB Identity, or RB ID) and a unique The RB identifier for the SRB is called an SRB identity (or SRB ID), and the RB identifier for the DRB is called a DRB identity (or DRB ID).

[0023] As described in Non-Patent Document 3, when the core network to which the UE 122 is connected is the EPC 104, each DRB established between the UE 122 and any or all of the E-UTRA 100 and the NR 106 is further uniquely associated with each EPS (Evolved Packet System) bearer passing through the EPC 104. Each EPS bearer is assigned an EPS bearer identifier (Identity, or ID) and is uniquely identified. In addition, the same QoS is guaranteed for data passing through the same EPS bearer.

[0024] As described in Non-Patent Document 9, when the core network to which the UE 122 is connected is the 5GC 110, one or more DRBs established between the UE 122 and any or all of the E-UTRA 100 and the NR 106 further include a PDU (Packet Receiver) established in the 5GC 110. Each DRB is associated with one of the PDU (Personal Data Unit) sessions. Each PDU session has one or more QoS flows. Each DRB may be mapped to one or more QoS flows in the associated PDU session, or may not be mapped to any QoS flow. Each PDU session is identified by a PDU session identifier (Identity, or ID). Each QoS flow is identified by a QoS flow identifier. Data passing through the same QoS flow is guaranteed the same QoS.

[0025] Any or all of the PDU sessions and QoS flows do not exist in the EPC 104, and no EPS bearers exist in the 5GC 110. In other words, when the UE 122 is connected to the EPC 104, the UE 122 has information on the EPS bearers, and when the UE 122 is connected to the 5GC 110, the UE 122 has information on any or all of the PDU sessions and QoS flows.

[0026] In the following description, eNB102 and / or gNB108 will also be referred to simply as base station equipment, and UE122 will also be referred to simply as terminal equipment.

[0027] FIG. 2 is a diagram showing protocol stacks of UP and CP of a terminal device and a base station device in an E-UTRA radio access layer in each embodiment of the present invention.

[0028] FIG. 2A is a protocol stack diagram of the UP used when the UE 122 communicates with the eNB 102 in the E-UTRA 100.

[0029] The PHY (Physical layer) 200 is a wireless physical layer, and provides a transmission service to a higher layer by using a physical channel. The PHY 200 is a higher layer that is connected to a MAC (Medium Access Control) The UE 122 is connected to the MAC 202 via a transport channel. Data is transferred between the MAC 202 and the PHY 200 via the transport channel. Data is transmitted and received between the PHYs of the UE 122 and the eNB 102 via a wireless physical channel.

[0030] The MAC 202 is a medium access control layer that maps various logical channels to various transport channels. The MAC 202 is connected to a higher-level RLC (Radio Link Control layer) 204 (described later) via a logical channel. They are roughly divided according to the type of information, into control channels that transmit control information and traffic channels that transmit user information. MAC202 has functions such as controlling PHY200 to perform discontinuous transmission and reception (DRX / DTX), executing random access procedures, notifying information on transmission power, and performing HARQ control (Non-Patent Document 7).

[0031] The RLC 204 is a radio link control layer that segments data received from the higher-level PDCP (Packet Data Convergence Protocol Layer) 206 (described later) and adjusts the data size so that the lower layer can transmit the data appropriately. The RLC 200 also has a function to guarantee the Quality of Service (QoS) required by each data. In other words, the RLC 204 has a function such as data retransmission control (Non-Patent Document 6).

[0032] The PDCP 206 is a packet data convergence protocol layer for efficiently transmitting user data such as IP packets over wireless sections. The PDCP 206 may have a header compression function for compressing unnecessary control information. The PDCP 206 may also have a data encryption function (Non-Patent Document 5).

[0033] The data processed in the MAC 202, RLC 204, and PDCP 206 are called MAC PDU (Protocol Data Unit), RLC PDU, and PDCP PDU, respectively. Moreover, the data passed to the MAC 202, RLC 204, and PDCP 206 from a higher layer or passed to a higher layer are called MAC SDU (Service Data Unit), RLC SDU, and PDCP SDU, respectively.

[0034] In addition, to distinguish between data and control PDUs, the PDCP PDUs may be called PDCP DATA PDUs (PDCP Data PDUs) and PDCP CONTROL PDUs (PDCP Control PDUs), respectively.In addition, to distinguish between data and control PDUs, the RLC PDUs may be called RLC DATA PDUs (RLC Data PDUs) and RLC CONTROL PDUs (RLC Control PDUs), respectively.

[0035] FIG. 2B is a protocol stack diagram of a CP used when a UE 122 communicates with an eNB 102 and an MME (Mobility Management Entity) which is a logical node that provides functions such as authentication and mobility management in E-UTRA 100.

[0036] The protocol stack of the CP includes a PHY 200, a MAC 202, an RLC 204, a PDCP 206, an RRC (Radio Resource Control layer) 208, and a NAS (non-access strarum) 210. The RRC 208 is a radio link control layer that performs processes such as establishment, re-establishment, suspending, and resuming of an RRC connection, reconfiguring an RRC connection, for example, establishing, changing, and releasing a radio bearer (RB) and a cell group, controlling logical channels, transport channels, and physical channels, and also performs handover and measurement configuration. The RB may be divided into a signaling radio bearer (SRB) and a data radio bearer (DRB), and the SRB may be used as a path for transmitting an RRC message, which is control information. The DRB is a radio link control layer that carries user data. The RBs may be used as a path for transmitting data. The RBs may be set between the eNB 102 and the RRC 208 of the UE 122. The portion of the RB that is configured with the RLC 204 and the MAC 202 may be called an RLC bearer (Non-Patent Document 4). In addition, some or all of the layers (layers) of the PHY 200, MAC 202, RLC 204, PDCP 206, and RRC 208 that carry signals and data between the UE 122 and the eNB 102 may be referred to as an AS (Access Layer). This layer may be called the Strarum layer (AS layer).

[0037] The above-mentioned functional classification of the MAC 202, the RLC 204, the PDCP 206, and the RRC 208 is an example, and some or all of the functions may not be implemented. Also, some or all of the functions of each layer may be included in another layer.

[0038] In addition, the IP layer and TCP (Transmission Control Protocol) above the IP layer The TCP (Transmission Control Protocol) layer, UDP (User Datagram Protocol) layer, and application layer are upper layers of the PDCP layer (not shown). The RRC layer and NAS (non-access Strarum) layer are also upper layers of the PDCP layer (not shown). In other words, the PDCP layer is a lower layer of the RRC layer, NAS layer, IP layer, and the TCP (Transmission Control Protocol) layer, UDP (User Datagram Protocol) layer, and application layer above the IP layer.

[0039] FIG. 3 is a protocol stack diagram of the UP and CP of a terminal device and a base station device in the NR radio access layer in each embodiment of the present invention.

[0040] FIG. 3(A) is a protocol stack diagram of the UP used when a UE 122 communicates with a gNB 108 in an NR 106.

[0041] The PHY (Physical layer) 300 is a radio physical layer of NR and may provide a transmission service to a higher layer using a physical channel. The PHY 300 may be connected to a higher-level MAC (Medium Access Control layer) 302 (described later) via a transport channel. Data may be transferred between the MAC 302 and the PHY 300 via the transport channel. Data may be transmitted and received between the PHYs of the UE 122 and the gNB 108 via a radio physical channel.

[0042] Here, the physical channel will be described.

[0043] The following physical channels may be used in wireless communication between a terminal device and a base station device.

[0044] PBCH (Physical Broadcast CHannel) PDCCH (Physical Downlink Control CHannel) PDSCH (Physical Downlink Shared CHannel) PUCCH (Physical Uplink Control CHannel) PUSCH (Physical Uplink Shared CHannel) PRACH (Physical Random Access CHannel)

[0045] The PBCH is used to broadcast system information required by terminal devices.

[0046] In addition, in NR, the PBCH may be used to broadcast a time index (SSB-Index) within the period of a block of a synchronization signal (also referred to as an SS / PBCH block).

[0047] The PDCCH is used to transmit (or carry) downlink control information (DCI) in downlink wireless communication (wireless communication from the base station device 3 to the terminal device). Here, one or more DCIs (which may be referred to as DCI formats) are defined for the transmission of the downlink control information. That is, a field for the downlink control information is defined as DCI and mapped to information bits. The PDCCH is transmitted in PDCCH candidates. The terminal device monitors a set of PDCCH candidates in the serving cell. Monitoring means attempting to decode the PDCCH according to a certain DCI format. A certain DCI format may be used for scheduling the PUSCH in the serving cell. The PUSCH may be used for transmitting user data, transmitting an RRC message, and the like.

[0048] The PUCCH may be used to transmit uplink control information (UCI) in uplink wireless communication (wireless communication from a terminal device to a base station device). Here, the uplink control information may include channel state information (CSI) used to indicate the state of a downlink channel. The uplink control information may also include a scheduling request (SR) used to request UL-SCH resources. The uplink control information may also include a hybrid automatic repeat request ACKnowledgement (HARQ-ACK).

[0049] The PDSCH may be used to transmit downlink data (DL-SCH: Downlink Shared CHannel) from the MAC layer, and is also used to transmit system information (SI: System Information) and random access response (RAR: Random Access Response) in the downlink.

[0050] The PUSCH may be used to transmit uplink data (UL-SCH: Uplink Shared CHannel) from the MAC layer or HARQ-ACK and / or CSI together with uplink data. Also, the PUSCH may be used to transmit only CSI, or only HARQ-ACK and CSI. That is, the PUSCH may be used to transmit only UCI. Also, the PDSCH or PUSCH may be used to transmit RRC signaling (also referred to as an RRC message) and a MAC control element. Here, in the PDSCH, the RRC signaling transmitted from the base station device may be common signaling for a plurality of terminal devices in a cell. Also, the RRC signaling transmitted from the base station device may be dedicated signaling (also referred to as dedicated signaling) for a certain terminal device. That is, terminal device-specific (UE-specific) information may be transmitted using dedicated signaling for a certain terminal device. Also, the PUSCH may be used to transmit UE capabilities in the uplink.

[0051] The PRACH may be used to transmit a random access preamble and may be used for initial connection establishment procedures, handover procedures, connection re-establishment procedures, synchronization (timing adjustment) for uplink transmissions, and to indicate a request for PUSCH (UL-SCH) resources.

[0052] The MAC 302 is a medium access control layer that maps various logical channels to various transport channels. The MAC 302 may be connected to a higher-level RLC (Radio Link Control layer) 304 (described later) via a logical channel. The logical channels are broadly classified according to the type of information to be transmitted, and may be classified into a control channel that transmits control information and a traffic channel that transmits user information. The MAC 302 may have a function to control the PHY 300 in order to perform discontinuous transmission and reception (DRX / DTX), a function to execute a random access procedure, a function to notify information on transmission power, a function to perform HARQ control, and the like (Non-Patent Document 13).

[0053] The RLC 304 is a radio link control layer that segments data received from the higher-level PDCP (Packet Data Convergence Protocol Layer) 306 (described later) and adjusts the data size so that the lower layers can transmit the data appropriately. The RLC 304 may also have a function for guaranteeing the Quality of Service (QoS) required by each piece of data. In other words, the RLC 304 may have a function for controlling retransmission of data, etc. (Non-Patent Document 12).

[0054] The PDCP 306 is a packet data convergence protocol layer that efficiently transmits user data such as IP packets over wireless sections. The PDCP 306 may have a header compression function that compresses unnecessary control information. The PDCP 306 may also have a function of encrypting data and protecting the integrity of data (Non-Patent Document 11).

[0055] SDAP (Service Data Adaptation Protocol) 310 is a service data adaptation protocol layer that has the function of mapping the downlink QoS flow sent from 5GC110 to a terminal device via a base station device with a DRB, and mapping the uplink QoS flow sent from the terminal device to 5GC110 via a base station device with a DRB, and storing mapping rule information (Non-Patent Document 16).

[0056] The data processed in MAC 302, RLC 304, PDCP 306, and SDAP 310 are called MAC PDU (Protocol Data Unit), RLC PDU, PDCP PDU, and SDAP PDU, respectively. Also, data passed to MAC 302, RLC 304, PDCP 306, and SDAP 310 from higher layers or data passed to higher layers are called MAC SDU (Service Data Unit), RLC SDU, PDCP SDU, and SDAP SDU, respectively.

[0057] In addition, in order to distinguish between data and control, the SDAP PDU may be called the SDAP DATA PDU (SDAP Data PDU) and the SDAP CONTROL PDU (SDAP Control PDU). In addition, in order to distinguish between data and control, the PDCP PDU may be called the PDCP DATA PDU (PDCP Data PDU). The RLC PDU may be called the RLC DATA PDU (RLC Data PDU) and the RLC CONTROL PDU (RLC Control PDU) to distinguish between data and control PDUs.

[0058] FIG. 3B shows how the UE 122 communicates with the gNB 108 and the AMF (Access and Mobile Facility), a logical node that provides functions such as authentication and mobility management, in the NR 106. FIG. 1 is a protocol stack diagram of the CP used when communicating with the Mobility Management function.

[0059] The protocol stack of the CP includes a PHY 300, a MAC 302, an RLC 304, a PDCP 306, an RRC (Radio Resource Control layer) 308, and a NAS (non-access strarum) 312. The RRC 308 is a radio link control layer that performs processes such as establishment, re-establishment, suspension, and resumption of an RRC connection, re-setting of an RRC connection, for example, setting, changing, and releasing of a radio bearer (RB) and a cell group, and controls logical channels, transport channels, and physical channels, as well as setting handovers and measurements. The RB may be divided into a signaling radio bearer (SRB) and a data radio bearer (DRB), and the SRB may be used as a path for transmitting an RRC message, which is control information. The DRB may be used as a path for transmitting user data. Each RB may be configured between the gNB 108 and the RRC 308 of the UE 122. In addition, a portion of the RB consisting of the RLC 304 and the MAC 302 may be called an RLC bearer (Non-Patent Document 10). In addition, in contrast to the NAS layer that carries signals between the AMF and the UE 122, some or all of the layers of the PHY 300, MAC 302, RLC 304, PDCP 306, RRC 308, and SDAP 310 that carry signals and data between the UE 122 and the gNB 108 may be called an AS (Access Strarum) layer.

[0060] The following SRBs may be defined: SRB0 to SRB3. SRB0 may be an SRB for RRC messages using the logical channel CCCH (Common Control CHannel). SRB1 may be an SRB for RRC messages (which may include piggybacked NAS messages) and for NAS messages before the establishment of SRB2, and all may use the logical channel DCCH (Dedicated Control CHannel). SRB2 may be an SRB for NAS messages, and all may use the logical channel DCCH. SRB2 may have a lower priority than SRB1. SRB3 may be an SRB for a specific RRC message when UE 122 is configured with EN-DC, NGEN-DC, NR-DC, etc., and all may use the logical channel DCCH. Other SRBs may be provided for other uses.

[0061] The above-mentioned functional classification of MAC 302, RLC 304, PDCP 306, SDAP 310, and RRC 308 is an example, and some or all of the functions may not be implemented. Also, some or all of the functions of each layer may be included in another layer.

[0062] The layer above the AS layer (not shown) may be called a PDU layer as described in Non-Patent Document 2. The PDU layer may include any or all of the IP layer, the TCP (Transmission Control Protocol) layer above the IP layer, the UDP (User Datagram Protocol) layer, and other layers. The application layer may be an upper layer of the PDU layer or may be included in the PDU layer. The PDU layer may be an upper layer of the user plane of the AS layer. The RRC layer and the NAS (non-access strarum) layer may be upper layers of any or all of the SDAP layer and the PDCP layer (not shown). In other words, any or all of the SDAP layer and the PDCP layer are lower layers of any or all of the RRC layer, the NAS layer, the IP layer, and the TCP (Transmission Control Protocol) layer, the UDP (User Datagram Protocol) layer, and the application layer above the IP layer.

[0063] In each embodiment of the present invention, any or all of the Session Initiation Protocol (SIP) and Session Description Protocol (SDP) used in IMS, the Real-time Transport Protocol (RTP), Real-time Transport Control Protocol (RTCP), HyperText Transfer Protocol (HTTP), and the like used in media communication or media communication control, and the codecs of various media may belong to the application layer.

[0064] The physical layer, MAC layer, RLC layer, PDCP layer, and SDAP layer of the terminal device may be established, configured, and / or controlled by the RRC layer of the terminal device. The RRC layer of the terminal device may establish and / or configure the physical layer, MAC layer, RLC layer, PDCP layer, and SDAP layer according to an RRC message transmitted from the RRC layer of the base station device. The MAC layer, RLC layer, PDCP layer, and SDAP layer may be called the MAC sublayer, RLC sublayer, PDCP sublayer, and SDAP sublayer, respectively.

[0065] Each layer belonging to the AS layer set in any or all of the terminal device and the base station device, or the function of each layer, may be called an entity. That is, the MAC layer, the RLC layer, the PDCP layer, the SDAP layer, and the RRC layer set in any or all of the terminal device and the base station device, or the function of each layer, may be called a MAC entity, an RLC entity, a PDCP entity, an SDAP entity, and an RRC entity, respectively. Also, each layer may include one or more entities. Also, the PDCP entity and the RLC entity may be established, configured, and controlled for each radio bearer, or all of them may be established, configured, and controlled for each cell group. Also, the MAC entity may be established, configured, and controlled for each PDU session, or all of them may be established, configured, and controlled for each SDAP entity.

[0066] The PDCP layer or PDCP entity may use a COUNT value when performing encryption or integrity protection processing. The COUNT value may be composed of a Hyper Frame Number (HFN) and a sequence number (SN: Sequence Number) added to the header of a PDCP PDU. The sequence number may be incremented by 1 every time a PDCP DATA PDU is generated in the transmitting PDCP layer or PDCP entity. The HFN may be incremented by 1 every time the sequence number reaches its maximum value.

[0067] In each embodiment of the present invention, in order to distinguish between the E-UTRA protocol and the NR protocol, the MAC 202, the RLC 204, the PDCP 206, and the RRC 208 are referred to as the MAC for E-UTRA or the MAC for LTE, the RLC for E-UTRA or the RLC for LTE, respectively. RLC, PDCP for E-UTRA or PDCP for LTE, and RRC for E-UTRA or RRC for LTE. MAC302, RLC304, PDCP306, and RRC308 may be referred to as MAC for NR, RLC for NR, RLC for NR, and RRC for NR, respectively. Or, they may be written with spaces, such as E-UTRA PDCP or LTE PDCP, and NR PDCP.

[0068] Also, as shown in FIG. 1, the eNB 102, the gNB 108, the EPC 104, and the 5GC 110 may be connected via an interface 112, an interface 116, an interface 118, an interface 120, and an interface 114. Therefore, in order to support various communication systems, the RRC 208 in FIG. 2 may be replaced with the RRC 308 in FIG. 3. The PDCP 206 in FIG. 2 may be replaced with the PDCP 306 in FIG. 3. The RRC 308 in FIG. 3 may include the function of the RRC 208 in FIG. 2. The PDCP 306 in FIG. 3 may be the PDCP 206 in FIG. 2. In the E-UTRA 100, even when the UE 122 communicates with the eNB 102, the NR PDCP may be used as the PDCP.

[0069] Next, state transition of the UE 122 in LTE and NR will be described. The UE 122 connected to the EPC has an RRC connection established. The UE 122 may be in the RRC_CONNECTED state when the RRC connection has been established. The UE 122 may also be in the RRC_INACTIVE state when the RRC connection is paused (if the UE 122 is connected to a 5GC). If these are not the cases, the UE 122 may be in the RRC_IDLE state.

[0070] Note that the UE 122 connected to the EPC does not have an RRC_INACTIVE state, but the suspension of the RRC connection may be initiated by the E-UTRAN. In this case, when the RRC connection is suspended, the UE 122 transitions to the RRC_IDLE state while retaining the UE AS context and an identifier (resumeIdentity) used for restoration. When the UE 122 retains the UE AS context, the restoration of the RRC connection is permitted by the E-UTRAN, and the UE 122 needs to transition from the RRC_IDLE state to the RRC_CONNECTED state, the restoration of the suspended RRC connection may be initiated by a higher layer (e.g., the NAS layer).

[0071] That is, the definition of dormancy may be different between UE 122 connected to EPC and UE 122 connected to 5GC. In addition, all or part of the procedure for returning from dormancy may be different between when UE 122 is connected to EPC (when dormant in RRC_IDLE state) and when UE 122 is connected to 5GC (when dormant in RRC_INACTIVE state).

[0072] The RRC_CONNECTED state, the RRC_INACTIVE state, and the RRC_IDLE state may also be referred to as the connected mode, the inactive mode, and the idle mode, respectively.

[0073] The UE AS context held by UE 122 may be information including all or part of the following: a current RRC setting, a current security context, a PDCP state including a ROHC (RObust Header Compression) state, a C-RNTI (Cell Radio Network Temporary Identifier) ​​used in the source PCell, a cell identifier, and a physical cell identifier of the source PCell. Note that the UE AS context held by any or all of eNB 102 and gNB 108 may include the same information as the UE AS context held by UE 122, or may include the same information as the UE AS context held by UE 122. It may contain information different from the information contained in the AS context.

[0074] The security context is the encryption key at the AS level, the NH (Next Hop The information may include all or part of the following: a Next Hop Chaining Counter parameter (NCC) used to derive the next hop access key, an identifier for the selected AS-level encryption algorithm, and a counter used for replay protection.

[0075] Fig. 4 is a diagram showing an example of a procedure flow for various settings in the RRC 208 and / or the RRC 308 in each embodiment of the present invention. Fig. 4 shows an example of a flow when an RRC message is sent from a base station device (eNB 102 and / or gNB 108) to a terminal device (UE 122).

[0076] In FIG. 4, the base station device creates an RRC message (step S400). The base station device creates the RRC message by receiving system information (SI) from the base station device. An RRC message may be sent when delivering RRC Information or paging information, or when the base station device determines that a process needs to be performed on a specific terminal device, for example, when performing security settings, reconfiguring an RRC connection (processing a radio line bearer (establishment, change, release, etc.), processing a cell group (establishment, addition, change, release, etc.), measurement settings, handover settings, etc.), or releasing an RRC connection state. An RRC message may also be used as a handover command to a different RAT. An RRC message includes information (parameters) for various information notifications and settings. In specifications related to RRC, such as Non-Patent Document 4 or Non-Patent Document 10, these parameters are called fields and / or information elements, and are described using a description format called ASN.1 (Abstract Syntax Notation One).

[0077] 4, the base station device then transmits the created RRC message to the terminal device (step S402). Next, the terminal device performs processing such as setting according to the received RRC message if necessary (step S404).

[0078] The creation of the RRC message is not limited to the above example, and may be created for other purposes as described in Non-Patent Document 4, Non-Patent Document 10, and the like.

[0079] For example, the RRC message may be used for settings related to Dual Connectivity (DC) or Multi-Radio Dual Connectivity (MR-DC) described in Non-Patent Document 8.

[0080] Dual Connectivity (DC) may be a technology for performing data communication using radio resources of both cell groups formed by two base station devices (nodes), i.e., a master cell group (MCG) formed by a master node (MN) and a secondary cell group (SCG) formed by a secondary node (SN). The master node and the secondary node may be the same node (same base station device). MR-DC described in Non-Patent Document 8 may be a technology for performing data communication using radio resources of both MCG and SCG by grouping cells of both E-UTRA and NR RATs (Radio Access Technologies) for each RAT and assigning them to UEs. In MR-DC, the master node may be a base station having main RRC functions related to MR-DC, such as functions of adding a secondary node, establishing, changing, and releasing RBs, adding, changing, releasing MCGs, and handover, and the secondary node is a base station having some RRC functions, such as S The base station may be a base station having a CG change and release function, etc. Also, a special cell in a master cell group may be called a primary cell, and a special cell in a secondary cell group may be called a primary SCG cell (PSCell).

[0081] In the MR-DC described in Non-Patent Document 8, the RRC of the RAT on the master node side may be used to configure both the MCG and the SCG. For example, in EN-DC (E-UTRA-NR Dual Connectivity), which is an MR-DC in which the core network is EPC104 and the master node is eNB102 (also referred to as enhanced eNB102), and in NGEN-DC (NG-RAN E-UTRA-NR Dual Connectivity), which is an MR-DC in which the core network is 5GC110 and the master node is eNB102, the RRC message of E-UTRA described in Non-Patent Document 4 may be transmitted and received between eNB102 and UE122. In this case, the RRC message may include not only the configuration information of LTE (E-UTRA) but also the configuration information of NR described in Non-Patent Document 10. The RRC message transmitted from eNB102 to UE122 may be transmitted from eNB102 to UE122 via gNB108. In addition, this RRC message configuration may be used for E-UTRA / 5GC (option 5 described in non-patent document 17) in which the eNB 102 (enhanced eNB) is non-MR-DC and uses 5GC as a core network.

[0082] Conversely, in NE-DC (NR-E-UTRA Dual Connectivity), which is an MR-DC when the core network is 5GC110 and the master node is gNB108 in the MR-DC described in Non-Patent Document 8, an NR RRC message described in Non-Patent Document 10 may be transmitted and received between gNB108 and UE122. In this case, the RRC message may include not only NR setting information but also LTE (E-UTRA) setting information described in Non-Patent Document 4. Also, the RRC message transmitted from gNB108 to UE122 may be transmitted from gNB108 to UE122 via eNB102.

[0083] In addition, regardless of whether MR-DC is used, the RRC message for E-UTRA transmitted from eNB102 to UE122 may include an RRC message for NR, or the RRC message for NR transmitted from gNB108 to UE122 may include an RRC message for E-UTRA.

[0084] Also, a network configuration in which the master node is eNB102 and the EPC104 is the core network may be called E-UTRA / EPC. Also, a network configuration in which the master node is eNB102 and the 5GC110 is the core network may be called E-UTRA / 5GC. Also, a network configuration in which the master node is gNB108 and the 5GC110 is the core network may be called NR or NR / 5GC. Also, this name does not have to be limited to the case where DC is set. When DC is not set, the above-mentioned master node may refer to a base station device that communicates with a terminal device.

[0085] FIG. 7 is an example of an ASN.1 description indicating any or all of the fields and information elements relating to radio bearer setting included in the message relating to re-establishment of an RRC connection in NR in FIG. 4. FIG. 8 is an example of an ASN.1 description indicating any or all of the fields and information elements relating to radio bearer setting included in the message relating to re-establishment of an RRC connection in E-UTRA in FIG. 4. In the ASN.1 examples in the embodiments of the present invention, not limited to FIG. 7 and FIG. 8, <omitted> and <omitted> are not part of the ASN.1 notation, but indicate that other information has been omitted. Note that information elements may be omitted even in places where <omitted> or <omitted> is not written. Note that in the embodiments of the present invention, <omitted> and <omitted> are not written. The ASN.1 example in the above does not exactly follow the ASN.1 notation method, but describes an example of parameters of a message related to reconfiguration of an RRC connection in an embodiment of the present invention, and other names and notations may be used. In addition, the ASN.1 example in the embodiment of the present invention shows only an example of main information closely related to the present invention in order to avoid complication of explanation. In addition, in the embodiment of the present invention, parameters described in ASN.1 may not be distinguished as fields, information elements, etc., and may all be referred to as information elements. In addition, in the embodiment of the present invention, parameters such as fields and information elements described in ASN.1 included in an RRC message may be referred to as information. In addition, the message related to reconfiguration of an RRC connection may be an RRC reconfiguration message in NR or an RRC connection reconfiguration message in E-UTRA.

[0086] In FIG. 7, the information element represented by RadioBearerConfig is an information element for setting radio bearers such as SRB and DRB, and includes a PDCP setting information element and an SDAP setting information element, which will be described later. The information element represented by SRB-ToAddMod, which is included in the information element represented by RadioBearerConfig, may be information indicating SRB (signaling radio bearer) setting, and may also be referred to as an SRB setting information element or a signaling radio bearer setting information element. The information element represented by SRB-ToAddModList may be a list of information indicating SRB setting. The information element represented by DRB-ToAddMod, which is included in the information element represented by RadioBearerConfig, may be information indicating DRB (data radio bearer) setting, and may also be referred to as a DRB setting information element or a data radio bearer setting information element. The information element represented by DRB-ToAddModList may be a list of information indicating DRB setting. Note that any or all of the SRB setting and the DRB setting may also be referred to as a radio bearer setting.

[0087] The information element represented by SRB-Identity in the SRB setting information element is information on the SRB identifier (SRB Identity) of the SRB to be added or changed, and may be an identifier that uniquely identifies the SRB in each terminal device. It may also be called an SRB identifier information element, a radio bearer identifier information element, or a signaling radio bearer identifier information element.

[0088] The information element represented by DRB-Identity in the DRB setting information element is information on the DRB identifier (DRB Identity) of the DRB to be added or changed, and may be an identifier that uniquely identifies the DRB in each terminal device. It may also be called the DRB identifier information element, the radio bearer identifier information element, or the data radio bearer identifier information element. The value of the DRB identifier is an integer value from 1 to 32 in the example of FIG. 7, but may take another value. In the case of DC, the DRB identifier is unique within the scope of the UE 122.

[0089] The information element represented by cnAssociation in the DRB configuration information element may be an information element indicating whether EPC104 or 5GC110 is used as the core network, and may be referred to as a core network association information element. That is, when UE122 connects to EPC, the DRB may be associated with the EPS bearer identifier information element (eps-BearerIdentity) in cnAssociation, or the EPS bearer identifier (EPS bearer identity) which is the value of the EPS bearer identifier information element, and when UE122 connects to 5GC110, the DRB may be associated with an SDAP entity configured according to an SDAP configuration information element (sdap-Config) described below, or a PDU session information element described below that is included in the SDAP configuration information element, or a PDU session identifier which is the value of the PDU session information element, or a PDU session indicated by the PDU session information element. That is, the information represented by cnAssociation includes When EPC104 is used in the core network, such as when EN-DC is used, it may include an EPS bearer identifier information element (eps-BearerIdentity), and when core network 5GC110 is used, i.e., when EN-DC is not used, it may include an information element indicating SDAP setting (sdap-Config).

[0090] The information element represented by sdap-Config may be information regarding the configuration or reconfiguration of an SDAP entity that determines how QoS flows and DRBs are mapped when the core network is 5GC110, and may be referred to as an SDAP configuration information element.

[0091] The field or information element indicated by pdu-session or PDU-SessionID included in the SDAP configuration information element may be the PDU session identifier of the PDU session described in Non-Patent Document 2 to which the QoS flow that is associated (mapped) with the radio bearer corresponding to the value of the radio bearer identifier information element included in the DRB configuration information element including this SDAP configuration information element belongs, and may be referred to as the PDU session identifier information element. The value of the PDU session identifier information element may be a non-negative integer. In addition, in each terminal device, multiple DRB identifiers may correspond to one PDU session identifier.

[0092] The information element indicated by mappedQoS-FlowsToAdd included in the SDAP configuration information element may be information indicating a list of QoS flow identity (QFI) information elements (to be described later) of the QoS flows to be mapped to the radio bearer corresponding to the value of the radio bearer identifier information element included in the DRB configuration information element including this SDAP configuration information element, or may be referred to as the QoS flow information element to be added. The above-mentioned QoS flow may be the QoS flow of the PDU session indicated by the PDU session information element included in this SDAP configuration information element.

[0093] In addition, the information element indicated by mappedQoS-FlowsToRelease included in the SDAP configuration information element may be information indicating a list of QoS flow identity (QFI) information elements (to be described later) of the QoS flows to be released among the QoS flows that correspond (map) to the radio bearer corresponding to the value of the radio bearer identifier information element included in the DRB configuration information element including this SDAP configuration information element, or may be rephrased as the QoS flow information element to be released. The above-mentioned QoS flow may be the QoS flow of the PDU session indicated by the PDU session information element included in this SDAP configuration information element.

[0094] The information element indicated by QFI may be a QoS flow identifier that uniquely identifies a QoS flow, as described in Non-Patent Document 2, and may also be referred to as a QoS flow identifier information element. The value of the QoS flow identifier information element may be a non-negative integer. The value of the QoS flow identifier information element may also be unique for a PDU session.

[0095] In addition, the SDAP setting information element may also include an uplink header information element indicating whether or not an uplink SDAP header is present in the uplink data transmitted via the set DRB, a downlink header information element indicating whether or not a downlink SDAP header is present in the downlink data received via the set DRB, and a default bearer information element indicating whether or not the set DRB is a default radio bearer (default DRB).

[0096] In addition, the information elements represented as pdcp-Config or PDCP-Config in the SRB configuration information element and the DRB configuration information element are information on the configuration of the NR PDCP entity to establish or change the PDCP 306 for the SRB and / or the DRB. The information elements related to the configuration of the NR PDCP entity may include an information element indicating the size of the uplink sequence number, an information element indicating the size of the downlink sequence number, an information element indicating the profile of the header compression (RoHC: RObust Header Compression), a re-ordering timer information element, etc.

[0097] An information element represented by DRB-ToReleaseList included in an information element represented by RadioBearerConfig may include information indicating one or more DRB identifiers to be released.

[0098] In FIG. 8, the information element represented by RadioResourceConfigDedicated may be an information element used for setting, changing, releasing, etc., of a radio bearer. The information element represented by SRB-ToAddMod included in the information element represented by RadioResourceConfigDedicated may be information indicating SRB (signaling radio bearer) setting, and may be referred to as an SRB setting information element or a signaling radio bearer setting information element. The information element represented by SRB-ToAddModList may be a list of information indicating SRB setting. The information element represented by DRB-ToAddMod included in the information element represented by RadioResourceConfigDedicated may be information indicating DRB (data radio bearer) setting, and may be referred to as a DRB setting information element or a data radio bearer setting information element. The information element represented by DRB-ToAddModList may be a list of information indicating DRB setting. Note that any or all of the SRB setting and the DRB setting may be referred to as a radio bearer setting.

[0099] The information element represented by SRB-Identity in the SRB setting information element is information on the SRB identifier (SRB Identity) of the SRB to be added or changed, and may be an identifier that uniquely identifies the SRB in each terminal device. It may also be called an SRB identifier information element, a radio bearer identifier information element, or a signaling radio bearer identifier information element. The information element represented by SRB-Identity in Fig. 8 may be an information element having the same role as the information element represented by SRB-Identity in Fig. 7.

[0100] The information element represented by DRB-Identity in the DRB setting is information on the DRB identifier (DRB Identity) of the DRB to be added or changed, and may be a DRB identifier that uniquely identifies the DRB in each terminal device. It may also be called a DRB identifier information element, a radio bearer identifier information element, or a data radio bearer identifier information element. The value of the DRB identifier is an integer value from 1 to 32 in the example of Figure 8, but may take another value. The information element represented by DRB-Identity in Figure 8 may be an information element having the same role as the information element represented by DRB-Identity in Figure 7.

[0101] The information element represented by eps-BearerIdentity in the DRB setting information element may be an EPS bearer identifier that uniquely identifies an EPS bearer in each terminal device. The information element represented by eps-BearerIdentity may also be called an EPS bearer identifier information element. The value of the EPS bearer identifier is an integer value from 1 to 15 in the example of FIG. 8, but may take another value. The information element represented by eps-BearerIdentity in FIG. 8 may be an information element having the same role as the information element represented by eps-BearerIdentity in FIG. 7. Furthermore, the EPS bearer identifier and the DRB identifier may correspond one-to-one in each terminal device.

[0102] In addition, the pdcp-Config or pdcp-DIR information element in the SRB configuration information element and the DRB configuration information element The information element represented by PDCP-Config may be an information element for configuring the E-UTRA PDCP entity to establish or modify the PDCP 206 for the SRB and / or DRB, and may be referred to as the PDCP configuration information element. The information elements regarding the configuration of the PDCP entity may include an information element indicating the size of a sequence number, an information element indicating a profile of header compression (RoHC: RObust Header Compression), re-ordering timer information, and the like.

[0103] Also, some or all of the information elements shown in FIG. 7 or FIG. 8 may be optional. That is, the information elements shown in FIG. 7 or FIG. 8 may be included in a message related to reconfiguration of an RRC connection according to necessity or conditions. Also, the message related to reconfiguration of an RRC connection may include an information element indicating that full configuration is applied in addition to information elements related to radio bearer configuration. The information element indicating that full configuration is applied may be represented by an information element name such as fullConfig, and may indicate that full configuration is applied using true, enable, etc. Note that the above-mentioned full configuration may be applied only at the time of intra-RAT intra-system handover described later. In the case of some or all of handovers other than intra-RAT intra-system handover, an information element name such as fullConfig may be used for an information element indicating that delta configuration is not applied.

[0104] (Embodiment) An embodiment of the present invention will be described with reference to Figures 1 to 9. In the embodiment of the present invention, a process for switching a connection RAT of a UE 122 from a first RAT (e.g., NR) to a second RAT (e.g., E-UTRA) different from the above-mentioned first RAT due to handover or the like will be described. The core network to which the UE 122 is connected may be switched from EPC 104 to 5GC 110 when the UE 122 is connected to EPC 104 via eNB 102 to a state in which the UE 122 is connected to 5GC 110 via eNB 102. The core network to which the UE 122 is connected may be switched from EPC 104 to 5GC 110 when the UE 122 is connected to EPC 104 via eNB 102 to a state in which the UE 122 is connected to 5GC 110 via gNB 108. The core network to which the UE 122 is connected may be switched from 5GC 110 to EPC 104 when the UE 122 is connected to 5GC 110 via eNB 102 to a state in which the UE 122 is connected to EPC 104 via eNB 102. In addition, the core network to which UE 122 is connected may be switched from 5GC 110 to EPC 104 when UE 122 switches from a state in which UE 122 is connected to 5GC 110 via gNB 108 to a state in which UE 122 is connected to EPC 104 via eNB 102.

[0105] In the embodiment of the present invention, a handover involving a change in the core network to which a terminal device is connected may be called an inter-system handover, and a handover not involving a change in the core network to which a terminal device is connected may be called an intra-system handover. For example, a handover in which the core network to which UE122 is connected is changed from 5GC110 to EPC104 or from EPC104 to 5GC110 may be called an inter-system handover. Also, a handover performed while maintaining EPC104 or 5GC110 as the core network to which UE122 is connected may be called an intra-system handover.

[0106] In the embodiment of the present invention, a handover involving switching of the RAT to which the terminal device is connected is sometimes called an inter-RAT handover. A handover that does not involve switching of the core network to which the device is connected is sometimes called an intra-RAT handover. For example, a handover in which the RAT to which the UE 122 is connected is switched from NR 106 to E-UTRA 100, or from E-UTRA 100 to NR 106 is sometimes called an inter-RAT handover, and a handover in which the RAT to which the UE 122 is connected is switched from NR 106 to NR 106, or from E-UTRA 100 to E-UTRA 100 is sometimes called an intra-RAT handover.

[0107] In addition, in embodiments of the present invention, a handover that involves switching the RAT and core network to which a terminal device is connected is sometimes referred to as an inter-RAT inter-system handover, a handover in which the RAT to which a terminal device is connected is switched but the core network is not switched is sometimes referred to as an inter-RAT intra-system handover, a handover in which the RAT to which a terminal device is connected is not switched but involves switching the core network is sometimes referred to as an intra-RAT inter-system handover, and a handover that does not involve switching the RAT to which a terminal device is connected and the core network is sometimes referred to as an intra-RAT intra-system handover.

[0108] In the embodiment of the present invention, when a terminal device receives a message regarding reconfiguration of an RRC connection transmitted from a base station device, handover may be performed based on the fact that various parameters regarding handover are included in the message regarding reconfiguration of an RRC connection. Furthermore, the various parameters regarding handover may be an information element named Mobility Control Info described in Non-Patent Document 4, an information element named Reconfiguration With Sync described in Non-Patent Document 10, or an information element with another name.

[0109] In addition, in the embodiment of the present invention, the handover may be performed based on the terminal device receiving an RRC message (hereinafter, a message indicating a movement from the first RAT to the second RAT) indicating a movement from the currently connected first RAT (E-UTRA, or NR, etc.) to the second RAT (E-UTRA, or NR, or UTRA, or GERAN, etc.) from the base station device. The above-mentioned message indicating a movement from the first RAT to the second RAT may be named MobilityFromEUTRACommand described in Non-Patent Document 4, may be named MobilityFromNRCommand described in Non-Patent Document 10, or may be named otherwise. The above-mentioned message indicating a movement from the first RAT to the second RAT may include a message regarding re-setting of the RRC connection to the above-mentioned second RAT.

[0110] In the embodiment of the present invention, the source may indicate the handover source, and the target may indicate the handover destination. For example, the source cell may be the handover source cell, and the target cell may be the handover destination cell. For example, the source base station device may be the handover source base station device, and the target base station device may be the handover destination base station device.

[0111] Fig. 5 is a block diagram showing the configuration of a terminal device (UE 122) in each embodiment of the present invention. In order to avoid complicating the explanation, Fig. 5 shows only main components closely related to the present invention.

[0112] The UE 122 shown in FIG. 5 is composed of a receiver 500 that receives an RRC message and the like from a base station device, and a processor 502 that performs processing according to any or all of the setting information of various information elements (IEs), various fields, and various conditions, etc., included in the received message. The above-mentioned base station device is the eNB 102. Sometimes it is, and sometimes it is gNB108.

[0113] Fig. 6 is a block diagram showing the configuration of a base station device in each embodiment of the present invention. In order to avoid complicating the explanation, Fig. 6 shows only main components closely related to the present invention. The above-mentioned base station device may be eNB102 or gNB108.

[0114] The base station device shown in Figure 6 comprises a transmitting unit 600 that transmits an RRC message, etc. to UE 122, and a processing unit 602 that creates an RRC message including any or all of the setting information among various information elements (IEs: Information Elements), various fields, and various conditions, and transmits the message to UE 122, thereby causing processing unit 502 of UE 122 to perform processing.

[0115] An example of a processing method of the UE 122 in the embodiment of the present invention will be described with reference to FIG.

[0116] The receiver 500 of the UE 122 connected to the first core network via the first RAT receives a message indicating a movement from the first RAT to the second RAT transmitted from the transmitter 600 of the base station device. The above-mentioned first RAT may be the NR 106. The above-mentioned first core network may be the 5GC 110. The message indicating the movement from the first RAT to the second RAT may be transmitted by the gNB 108. The above-mentioned second RAT may be the E-UTRA 100 (step S900).

[0117] The processing unit 502 of the UE 122 performs the handover process to the second RAT in accordance with the message indicating the movement from the first RAT to the second RAT (step S902).

[0118] The processing unit 502 of the UE 122 may determine that the handover process to the second RAT according to the message indicating the movement from the first RAT to the second RAT has failed based on the fact that any or all of the following conditions (A) to (C) are met. Note that the conditions for determining that the handover process to the second RAT according to the message indicating the movement from the first RAT to the second RAT has failed may include conditions other than the following (A) to (C). Also, the connection establishment in the following (A) may be the establishment of an RRC connection (step S904). (A) Failure to establish a connection to the second RAT mentioned above. (B) The terminal device is unable to comply with any part of the settings included in the message indicating the transition from the first RAT to the second RAT. (C) A protocol error exists in the information of the second RAT contained in the message indicating the movement from the first RAT to the second RAT, and the terminal device fails to process in the second RAT.

[0119] Based on determining that the handover process to the second RAT in accordance with the message indicating the movement from the first RAT to the second RAT has failed, the processing unit 502 of the UE 122 may perform processing for the case where the handover process to the second RAT in accordance with the message indicating the movement from the first RAT to the second RAT has failed (step S906).

[0120] In the process of step S906 in which the handover process to the second RAT according to the message indicating the movement from the first RAT to the second RAT fails, the processing unit 502 of the UE 122 performs any or all of the following (D) to (F): Based on the fact that the conditions including the above are met, before performing the handover process to the second RAT according to the message indicating the movement from the first RAT to the second RAT, the setting used in the primary cell of the first RAT (source RAT) may be returned to and the connection reconnection process may be performed. Note that the conditions for determining to return to the setting used in the primary cell of the first RAT (source RAT) and perform the connection reconnection process before performing the handover process to the second RAT according to the message indicating the movement from the first RAT to the second RAT may include conditions other than the following (D) to (F). Also, the connection establishment in the following (D) may be the establishment of an RRC connection. Also, the connection reestablishment may be the reestablishment of an RRC connection. (D) The establishment of a connection to the second RAT fails, and the message indicating the movement from the first RAT to the second RAT does not include the first information. (E) The terminal device is unable to comply with any part of the settings included in the message indicating the transition from the first RAT to the second RAT. (F) A protocol error exists in the information of the second RAT contained in the message indicating the movement from the first RAT to the second RAT, and the terminal device fails to process in the second RAT.

[0121] In addition, in the process in step S906 in which the handover process to the second RAT according to the message indicating the movement from the first RAT to the second RAT fails, the processing unit 502 of the UE 122 may select a cell in the second RAT or attempt to select a cell in the second RAT based on the fact that the following conditions including (G) are met. Note that the conditions for determining whether to select a cell in the second RAT or attempt to select a cell in the second RAT may include conditions other than the following (G). Also, the connection establishment in the following (G) may refer to the establishment of an RRC connection. (G) The establishment of a connection to the second RAT fails, and the first information is included in the message indicating the movement from the first RAT to the second RAT.

[0122] In addition, in the process of step S906 in which the handover process to the second RAT according to the message indicating the movement from the first RAT to the second RAT fails, when selecting a cell in the second RAT or attempting to select a cell in the second RAT, the processing unit 502 of the UE 122 may further determine whether or not an appropriate cell has been selected in the second RAT. Based on the processing unit 502 of the UE 122 judging that an appropriate cell has been selected in the second RAT, the processing unit 502 of the UE 122 may perform a process including some or all of the following processes: resetting the MAC, stopping some or all of the running timers, discarding some or all of the AS security keys, releasing some or all of the radio resources, releasing the PDCP entity and / or the SDAP entity for all the established radio bearers, and notifying the upper layer of the release of the RRC connection. The process of releasing some or all of the radio resources may include releasing the RLC entity and / or releasing the MAC configuration. The process of releasing some or all of the radio resources may include releasing the PDCP entities and / or SDAP entities for all established radio bearers. When the PDCP entities and / or SDAP entities used in the source RAT are reconfigured and / or reused in the target RAT, the release of the PDCP entities and / or SDAP entities for all established radio bearers may not be performed. The case where the PDCP entities and / or SDAP entities used in the source RAT are reconfigured and / or reused in the target RAT may be a case where delta signaling is used. The case where delta signaling is used may be a case where the PDCP entities and / or SDAP entities used in the source RAT are reconfigured and / or reused in the target RAT. The full configuration field may not be present in the message regarding the re-establishment of the RRC connection for the second RAT, which is included in the message indicating the movement to the second RAT. In addition, when notifying the upper layer of the release of the RRC connection, the release cause may be set to "RRC connection failure" and notified to the upper layer, or the release cause may be set to "other" and notified to the upper layer. In addition, other causes, such as a cause indicating that a cell has been selected in the target RAT, may be set as the release cause and notified to the upper layer. In addition, the information indicating that a cell has been selected in the target RAT may be notified to the upper layer independently of the process of notifying the upper layer of the release of the RRC connection. The selection of a cell in the target RAT may be rephrased as a cell in the target RAT being prioritized, or may be another expression as long as it indicates that a cell in the target RAT has been selected with priority.

[0123] In addition, in the processing in step S906 in the case where the handover processing to the second RAT fails in accordance with the message indicating the movement from the first RAT to the second RAT, when selecting a cell in the second RAT or attempting to select a cell in the second RAT, the processing unit 502 of the UE 122 may return to the setting used in the primary cell in the first RAT and perform the processing of reconnecting the connection based on the determination that an appropriate cell was not selected in the second RAT.

[0124] In addition, "an appropriate cell was selected in the second RAT" may be rephrased as "cell selection in the second RAT was successful" or may be rephrased with another expression indicating that an appropriate cell was selected in the second RAT. In addition, "an appropriate cell was not selected in the second RAT" may be rephrased as "cell selection in the second RAT was not successful" or "cell selection in the second RAT failed", or may be rephrased with another expression indicating that an appropriate cell was not selected in the second RAT. In addition, "an appropriate cell was not selected in the second RAT" may be rephrased as "other" in contrast to "an appropriate cell was selected in the second RAT". In addition, "an appropriate cell was selected in the second RAT" may be rephrased as "other" in contrast to "an appropriate cell was not selected in the second RAT".

[0125] In the embodiment of the present invention, the above-mentioned "first information" may be a parameter (field and / or information element) that instructs the selection of a cell in the above-mentioned second RAT when the establishment of an RRC connection to the above-mentioned second RAT fails. The above-mentioned "first information" may be a parameter (field and / or information element) that instructs the selection of a cell in the above-mentioned second RAT with priority when the establishment of an RRC connection to the above-mentioned second RAT fails. The above-mentioned "first information" may be another expression as long as it means an expression that instructs the selection of a cell in the above-mentioned second RAT with priority when the establishment of an RRC connection to the above-mentioned second RAT fails. The above-mentioned "first information" may be a parameter (field and / or information element) that means EPS fallback. The above-mentioned EPS fallback may be, for example, the EPS fallback described in Non-Patent Document 2. In other words, the EPS fallback may be a voice service using IMS that is redirected to EPS or handed over to EPS.

[0126] The parameter that indicates the EPS fallback is the first information mentioned above. The second information may be included in the message indicating the movement from the first RAT to the second RAT as second information different from the first RAT information. In this embodiment, when the second information is included in the message indicating the movement from the first RAT to the second RAT, in the above-mentioned step S904, the processing unit 502 of the UE 122 may notify the above-mentioned higher layer that the EPS fallback has failed based on the fact that any or all of the above-mentioned conditions (A) to (C) are met. Also, when the second information is included in the message indicating the movement from the first RAT to the second RAT, in the above-mentioned step S906, the processing unit 502 of the UE 122 may notify the above-mentioned higher layer that the EPS fallback has failed based on the fact that any or all of the above-mentioned conditions (D) to (F) are met. Furthermore, if the message indicating the movement from the first RAT to the second RAT includes the second information, in step S906, the processing unit 502 of the UE 122 may select a cell in the second RAT based on the fact that the condition including (G) above is met, and may notify the higher layer that the EPS fallback has failed based on determining that an appropriate cell has not been selected in the second RAT.

[0127] In addition, the above-mentioned "first information" may be optionally present only when the above-mentioned second RAT is the first specific RAT, and may not be present when the above-mentioned second RAT is other than the above-mentioned first specific RAT. In addition, the above-mentioned first specific RAT may be only E-UTRA, or may be a RAT including E-UTRA, for example, E-UTRA and UTRA. In addition, the above-mentioned "second information" or "parameter indicating EPS fallback" may be optionally present only when the above-mentioned second RAT is the second specific RAT, and may not be present when the above-mentioned second RAT is the above-mentioned second specific RAT. In addition, the above-mentioned second specific RAT may be only E-UTRA, or may be a RAT including E-UTRA, for example, E-UTRA and UTRA.

[0128] In addition, in an embodiment of the present invention, when an RRC connection is established with a terminal device via a gNB to a 5GC 110, a user or a telecommunications carrier may be able to set whether or not the above-mentioned terminal device receives a voice service using IMS. When an RRC connection is established with a terminal device via a gNB to a 5GC 110, the setting of whether or not the above-mentioned terminal device receives a voice service using IMS may be a setting through the interface of the terminal device, or may be a setting on the telecommunications carrier side that does not pass through the interface of the terminal device. When an RRC connection is established with a terminal device via a gNB to a 5GC 110, in the setting of whether or not the above-mentioned terminal device receives a voice service using IMS, if the setting is set to not receive, and a voice service using IMS is originated to the above-mentioned terminal device, the originating terminal device may be notified that the destination terminal device cannot respond to the above-mentioned origination. When the above-mentioned terminal device has an RRC connection established with the 5GC 110 via the gNB, if the above-mentioned terminal device is set to not receive voice services using IMS in the setting for whether or not to receive voice services using IMS, and if a voice service using IMS is sent to the above-mentioned terminal device, the above-mentioned terminal device (terminal device set to not receive voice services) may be notified that a voice service using IMS has been sent. At this time, user information of the destination terminal device may also be notified.

[0129] In the embodiment of the present invention, the RRC message including a message regarding RRC connection re-establishment or the message indicating a movement from the first RAT to the second RAT may be a message indicating a movement from E-UTRA to the second RAT, or may be a message named MobilityFromEUTRACommand described in Non-Patent Document 4. The RRC message including a message regarding mobile node reconfiguration, or the message indicating a move from the first RAT to the second RAT may be a message indicating a move from NR to the second RAT, or may be a message named MobilityFromNRCommand described in non-patent document 10.

[0130] In addition, in the embodiment of the present invention, the DRB setting information element is an NR DRB setting information element, which may be included in an information element named radioBearerConfig described in non-patent document 10, or an E-UTRA DRB setting information element, which may be included in an information element named radioResourceConfigDedicated described in non-patent document 4.

[0131] In the above description, expressions such as "linked," "associated," and "associated" may be interchangeable.

[0132] In the above explanation, "A may be replaced with B" or "A may be B" may include the meaning of replacing A with B or A with B, as well as replacing B with A or B with A. In the above explanation, when it is written that "C may be D" and "C may be E", it may also include that "D may be E". In the above explanation, when it is written that "F may be G" and "G may be H", it may also include that "F may be H".

[0133] In the above explanation, if condition "A" and condition "B" are contradictory conditions, condition "B" may be expressed as the "other" condition of condition "A."

[0134] In this way, in the embodiment of the present invention, it is possible to perform processing according to the types of the source RAT, destination RAT, source core network, and destination core network of the UE 122. That is, the terminal device can reduce the complexity of protocol processing and perform communication efficiently.

[0135] The terminal device and method in each embodiment of the present invention can be described, for example, as follows.

[0136] In order to achieve the above object, one aspect of the present invention provides the following means: A terminal device communicating with a base station device includes a receiver for receiving a message indicating a movement from a first RAT to a second RAT from the base station device, and a receiver for returning to a setting used in a primary cell in the first RAT and performing a process of reconnecting the connection based on a fact that a first parameter is not included in the message indicating the movement from the first RAT to the second RAT in a handover process in accordance with the message indicating the movement from the first RAT to the second RAT when a connection to the second RAT fails to be established and a first parameter is not included in the message indicating the movement from the first RAT to the second RAT, and the receiver for receiving a message indicating a movement from the first RAT to the second RAT in accordance with the message indicating the movement from the first RAT to the second RAT, and a processing unit that, in a handover process in accordance with a message indicating a movement from the first RAT to the second RAT, attempts to select a cell in the second RAT when establishment of a connection to the second RAT fails and based on the message indicating a movement from the first RAT to the second RAT containing a first parameter, and, based on the success of the selection of a cell in the second RAT, performs some or all of the following processes: resetting a MAC, stopping some or all of the running timers, discarding some or all of the AS security keys, releasing some or all of the radio resources, and notifying a higher layer of the release of the RRC connection.

[0137] Another aspect of the present invention is a base station device that communicates with a terminal device, the base station device transmitting a first a transmission unit that transmits a message indicating a movement from a first RAT to a second RAT; and a control unit that causes the terminal device to return to a setting used in a primary cell in a first RAT and perform a process of reconnecting a connection when a connection establishment to a second RAT has failed and a first parameter has not been included in the message indicating the movement from the first RAT to the second RAT in a handover process in accordance with the message indicating the movement from the first RAT to the second RAT, and and a processing unit that, in an over-processing process, attempts to select a cell in the second RAT when establishment of a connection to a second RAT fails and a first parameter is included in a message indicating a move from the first RAT to the second RAT, and, based on successful selection of a cell in the second RAT, performs some or all of the following processes: resetting a MAC, stopping some or all of the running timers, discarding some or all of the AS security keys, releasing some or all of the radio resources, and notifying a higher layer of the release of the RRC connection.

[0138] Another aspect of the present invention is a method of a terminal device communicating with a base station device, comprising: receiving from the base station device a message indicating a movement from a first RAT to a second RAT; and, in a handover process in accordance with the message indicating the movement from the first RAT to the second RAT, if a connection to the second RAT fails to be established and a first parameter is not included in the message indicating the movement from the first RAT to the second RAT, returning to a setting used in a primary cell in the first RAT, performing a process of reconnecting the connection, and performing a handover process from the first RAT to the second RAT based on the fact that the message indicating the movement from the first RAT to the second RAT does not include a first parameter. In a handover process in accordance with a message indicating a movement, if establishment of a connection to a second RAT fails and the message indicating a movement from the first RAT to the second RAT contains a first parameter, an attempt is made to select a cell in the second RAT, and based on successful selection of a cell in the second RAT, some or all of the following processes are performed: resetting a MAC, stopping some or all of the running timers, discarding some or all of the AS security keys, releasing some or all of the radio resources, and notifying a higher layer of the release of the RRC connection.

[0139] Another aspect of the present invention is a method of a base station device communicating with a terminal device, the method comprising: transmitting a message indicating a movement from a first RAT to a second RAT to the terminal device; and, when a handover process in accordance with the message indicating the movement from the first RAT to the second RAT fails to establish a connection to the second RAT and a first parameter is not included in the message indicating the movement from the first RAT to the second RAT, causing the terminal device to return to a setting used in a primary cell in the first RAT and perform a process of reconnecting the connection; In a handover process in accordance with a message indicating a move from the first RAT to the second RAT, if establishment of a connection to a second RAT fails and the message indicating a move from the first RAT to the second RAT contains a first parameter, an attempt is made to select a cell in the second RAT, and if the selection of a cell in the second RAT is successful, some or all of the following processes are performed: resetting a MAC, stopping some or all of the running timers, discarding some or all of the AS security keys, releasing some or all of the radio resources, and notifying a higher layer of the release of the RRC connection.

[0140] In one embodiment of the present invention, the first parameter in the terminal device, base station device, terminal device method, and base station device method is a parameter that instructs selection of a cell in the second RAT when establishment of an RRC connection to the second RAT fails.

[0141] The program that operates on the device according to the present invention implements the functions of the above-described embodiments according to the present invention. It may also be a program that controls a Central Processing Unit (CPU) and the like to make a computer function so as to realize the above. The program or the information handled by the program is temporarily loaded into volatile memory such as Random Access Memory (RAM) during processing, or stored in non-volatile memory such as flash memory or a Hard Disk Drive (HDD), and is read, modified, and written by the CPU as necessary.

[0142] It should be noted that a part of the device in the above-mentioned embodiment may be realized by a computer. In that case, a program for realizing this control function may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read by a computer system and executed to realize the control function. The "computer system" here refers to a computer system built into the device, and includes hardware such as an operating system and peripheral devices. The "computer-readable recording medium" may be any of a semiconductor recording medium, an optical recording medium, a magnetic recording medium, and the like.

[0143] Furthermore, the term "computer-readable recording medium" may include a medium that dynamically stores a program for a short period of time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, and a medium that stores a program for a certain period of time, such as a volatile memory in a computer system that serves as a server or client in such a case. The above program may be one that realizes part of the above-mentioned functions, or one that can realize the above-mentioned functions in combination with a program already recorded in the computer system.

[0144] Also, each functional block or feature of the device used in the above-mentioned embodiment may be implemented or executed by an electric circuit, i.e., typically an integrated circuit or a plurality of integrated circuits. The electric circuit designed to execute the functions described herein may include a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or a combination thereof. The general-purpose processor may be a microprocessor, or alternatively, the processor may be a conventional processor, controller, microcontroller, or state machine. The general-purpose processor or each of the aforementioned circuits may be composed of digital circuits or analog circuits. Also, when an integrated circuit technology that replaces the current integrated circuits appears due to the progress of semiconductor technology, it is possible to use an integrated circuit based on that technology.

[0145] The present invention is not limited to the above-described embodiment. In the embodiment, an example of a device is described, but the present invention is not limited to this, and can be applied to stationary or non-movable electronic devices installed indoors or outdoors, such as terminal devices or communication devices of AV equipment, kitchen equipment, cleaning / washing equipment, air conditioners, office equipment, vending machines, and other household appliances.

[0146] Although the embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes within the scope of the gist of the present invention are also included. Furthermore, the present invention can be modified in various ways within the scope of the claims, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. Furthermore, configurations in which elements described in the above embodiment are replaced with elements that have the same effect are also included. [Explanation of symbols]

[0147] 100 E-UTRA 102 eNB 104 EPC 106 NR 108 gNB 110 5GC 112, 114, 116, 118, 120, 124 Interface 122UE 200, 300 PHY 202, 302 MAC 204, 304 RLC 206, 306 PDCP 208, 308 RRC 310SDAP 210, 312 NAS 500 Receiver 502, 602 Processing section 600 Transmitter

Claims

1. A terminal device that communicates with a base station device, A receiving unit that receives a message indicating a transition from a first RAT (Radio Access Technology) to a second RAT from the base station device; In a handover process according to a message indicating a movement from the first RAT to a second RAT, if a connection establishment to the second RAT fails and a first parameter is not included in the message indicating a movement from the first RAT to the second RAT, returning to a setting used in a primary cell in the first RAT and performing a process of reconnecting the connection; a processing unit that, in a handover process in accordance with a message indicating a movement from the first RAT to the second RAT, attempts to select a cell in the second RAT when a connection to the second RAT fails to be established and a first parameter is included in the message indicating a movement from the first RAT to the second RAT, and, based on a successful selection of a cell in the second RAT, performs some or all of the following processes: resetting a MAC, stopping some or all of the running timers, discarding some or all of the AS security keys, releasing some or all of the radio resources, and notifying an upper layer of the release of an RRC connection; The second RAT is a different RAT from the first RAT. Terminal device.

2. The first parameter is a parameter that instructs selection of a cell in the second RAT when establishment of an RRC connection to the second RAT fails. The terminal device according to claim 1 .

3. A base station device that communicates with a terminal device, A transmitter that transmits a message indicating a transition from a first RAT (Radio Access Technology) to a second RAT to the terminal device; The terminal device, In a handover process according to a message indicating a movement from the first RAT to a second RAT, when a connection establishment to the second RAT fails and a first parameter is not included in the message indicating a movement from the first RAT to the second RAT, returning to a setting used in a primary cell in the first RAT and performing a process of reconnecting the connection; a processing unit that, in a handover process in accordance with a message indicating a movement from the first RAT to the second RAT, attempts to select a cell in the second RAT when a connection to the second RAT fails to be established and a first parameter is included in the message indicating a movement from the first RAT to the second RAT, and, based on a successful selection of a cell in the second RAT, performs some or all of the following processes: resetting a MAC, stopping some or all of the running timers, discarding some or all of the AS security keys, releasing some or all of the radio resources, and notifying a higher layer of the release of the RRC connection; The second RAT is a different RAT from the first RAT. Base station equipment.

4. The first parameter is a parameter that instructs selection of a cell in the second RAT when establishment of an RRC connection to the second RAT fails. The base station device according to claim 3 .

5. A method for a terminal device communicating with a base station device, comprising: receiving a message indicating a transition from a first RAT (Radio Access Technology) to a second RAT from the base station device; In a handover process according to a message indicating a movement from the first RAT to a second RAT, if a connection establishment to the second RAT fails and a first parameter is not included in the message indicating a movement from the first RAT to the second RAT, returning to a setting used in a primary cell in the first RAT and performing a process of reconnecting the connection; In a handover process according to a message indicating a movement from the first RAT to a second RAT, when a connection to the second RAT fails to be established and a first parameter is included in the message indicating a movement from the first RAT to the second RAT, a selection of a cell in the second RAT is attempted, and when a cell in the second RAT is successfully selected, some or all of the following processes are performed: resetting a MAC, stopping some or all of the running timers, discarding some or all of the AS security keys, releasing some or all of the radio resources, and notifying a higher layer of the release of the RRC connection; The second RAT is a different RAT from the first RAT. method.

6. The first parameter is a parameter for instructing to select a cell in the second RAT when establishment of an RRC connection to the second RAT fails. The method according to claim 5.

7. A method for a base station device communicating with a terminal device, comprising: Transmitting a message to the terminal device indicating a transition from a first RAT (Radio Access Technology) to a second RAT; The terminal device, In a handover process according to a message indicating a movement from the first RAT to a second RAT, if a connection establishment to the second RAT fails and a first parameter is not included in the message indicating a movement from the first RAT to the second RAT, returning to a setting used in a primary cell in the first RAT and performing a process of reconnecting the connection; In a handover process according to a message indicating a movement from the first RAT to a second RAT, when a connection to the second RAT fails to be established and a first parameter is included in the message indicating a movement from the first RAT to the second RAT, the mobile station attempts to select a cell in the second RAT, and, when the selection of a cell in the second RAT is successful, performs some or all of the following processes: resetting a MAC, stopping some or all of the running timers, discarding some or all of the AS security keys, releasing some or all of the radio resources, and notifying a higher layer of the release of the RRC connection; The second RAT is a different RAT from the first RAT. method.

8. The first parameter is a parameter that instructs selection of a cell in the second RAT when establishment of an RRC connection to the second RAT fails. The method of claim 7.

Images