Patent Description:
A radio access method and a radio network for cellular mobile communications (which will hereinafter be referred to as "Long Term Evolution (LTE; trade name)" or "Evolved Universal Terrestrial Radio Access (E-UTRA)") and a core network (which will be referred to as "Evolved Packet Core or EPC") have been studied by the 3rd Generation Partnership Project (3GPP).

Furthermore, as a radio access method and a radio network technology for a 5th generation cellular system, technical studies and standardization of LTE-Advanced Pro which is an enhanced technology of LTE and New Radio technology (NR) which is a new radio access technology have been conducted by the 3GPP (Non Patent Literature (NPL) <NUM>). Furthermore, <NUM> Generation Core Network (5GC), which is a core network for the 5th generation cellular system, has also been studied (NPL <NUM>).

<NPL>, describes reception of the RRCConnectionRelease by the UE, wherein if the RRCConnectionRelease message includes idleModeMobilityControllnfo including freqPriorityListGERAN, if AS security has not been activated; and if upper layers indicate that redirect to GERAN without AS security is not allowed: ignore the content of the RRCConnectionRelease. The document also describes UE actions upon leaving RRC CONNECTED or RRC INACTIVE.

<NPL>, describes UE actions upon leaving RRC CONNECTED or RRC INACTIVE. <CIT> describes a base station controlling the state transition of a wireless terminal among a first RRC state, a second RRC state, and a third RRC state. Further, the base station explicitly or implicitly notifies, to the wireless terminal, whether or not a network slice that has been set to the wireless terminal for data communication in at least the first RRC state is available in each cell included in a RAN notification area that has been set by a RAN. Thus, for example, a wireless terminal in a first state (e.g., a RRC_INACTIVE state) can easily know the availability of a network slice in a cell to be reselected or a cell that has been reselected.

<CIT>describes a radio terminal is used in a mobile communication system. The radio terminal is provided with: a receiving unit which, from a base station, receives a unicast signal for transitioning the radio terminal to a specific state; and a control unit which, in response to receiving the unicast signal, transitions the radio terminal into the specific state. The aforementioned specific state is a state in which paging area information is set in the radio terminal which indicates a paging area used in a paging method driven by the base station. The receiving unit further receives an area identifier broadcast by the base station. In response to satisfaction of a prescribed condition, the control unit holds the area identifier as the paging area information. The aforementioned prescribed condition includes the condition of the area identifier being designated by the base station as paging area information.

As one of the NR technologies, an inactive state (also referred to as RRC_INACTIVE, an RRC_INACTIVE state) has been introduced. The inactive state is a state in which a particular area configured to the RAN (RAN nortification area (RNA)) can be moved without notification to the RAN while maintaining connection with a core network. The terminal apparatus transitions among this inactive state, an idle state (also referred to as RRC_IDLE, an RRC_IDLE state) which is a waiting state, and a connected state (also referred to as RRC_CONNECTED, an RRC_CONNECTED state) based on a determined condition. Furthermore, in this state transition, the terminal apparatus stores and discards various parameters based on the determined condition (NPL <NUM>).

However, in the state transition, management of the parameter is not correctly performed (the desired result cannot be obtained) in some cases, and there is thus a problem that the terminal apparatus cannot efficiently perform selection and/or re-selection of the cell.

One aspect of the present invention is realized with the situations described above taken into account, and one object thereof is to provide a terminal apparatus capable of efficiently performing cell selection and/or re-selection of the terminal apparatus, a method used for the terminal apparatus, and an integrated circuit mounted in the terminal apparatus.

The above object is achieved by a terminal apparatus, a method applied to a terminal apparatus, and an integrated circuit implemented in a terminal apparatus, as defined in the claims, respectively.

According to an aspect of the present invention, the terminal apparatus can efficiently perform cell selection and/or re-selection based on an optimum parameter configuration.

LTE (and LTE-A Pro) and NR may be defined as different RATs. The NR may be defined as a technology included in the LTE. The LTE may be defined as a technology included in the NR. In addition, the LTE that is connectable to the NR using Multi RAT Dual connectivity may be distinguished from the existing LTE. Furthermore, LTE with a core network of 5GC may be distinguished from the existing LTE with a core network of EPC. The present embodiment may be applied to the NR, the LTE and other RATs. Terms associated with the LTE and the NR are used in the following description. However, the present invention may be applied to other technologies using other terms. In the present embodiment, the term "E-UTRA" may be replaced with "LTE," and the term "LTE" may be replaced with "E-UTRA".

<FIG> is a schematic diagram of a communication system according to each embodiment of the present invention.

An E-UTRA <NUM> is a radio access technology described in NPL <NUM> or the like, and includes a cell group (CG) configured in one or multiple frequency bands. An E-UTRAN Node B (eNB) <NUM> is a base station apparatus of the E-UTRA <NUM>. An Evolved Packet Core (EPC) <NUM> is a core network described in NPL <NUM> or the like and is designed as a core network for the E-UTRA <NUM>. An interface <NUM> is an interface between the eNB <NUM> and the EPC <NUM>, where there is a control plane (CP) through which control signals are transferred and a user plane (UP) through which user data is transferred.

An NR <NUM> is a radio access technology described in NPL <NUM> or the like, and includes a cell group (CG) configured in one or multiple frequency bands. A g Node B (gNB) <NUM> is a base station apparatus of the NR <NUM>. A 5GC <NUM> is a core network described in NPL <NUM> or the like, and is designed as a core network for the NR <NUM>, but may also be used as a core network for the E-UTRA <NUM> having a function of connecting to the 5GC <NUM>. Hereinafter, the E-UTRA <NUM> may include the E-UTRA <NUM> having a function of connecting to the 5GC <NUM>.

An interface <NUM> is an interface between the eNB <NUM> and the 5GC <NUM>, an interface <NUM> is an interface between the gNB <NUM> and the 5GC <NUM>, an interface <NUM> is an interface between the gNB <NUM> and the EPC <NUM>, an interface <NUM> is an interface between the eNB <NUM> and the gNB <NUM>, and an interface <NUM> is an interface between the EPC <NUM> and the 5GC <NUM>. The interface <NUM>, the interface <NUM>, the interface <NUM>, the interface <NUM>, the interface <NUM>, and the like may be interfaces that transfer CP only, UP only, or both the CP and the UP. Furthermore, the interface <NUM>, the interface <NUM>, the interface <NUM>, the interface <NUM>, the interface <NUM>, and the like may not exist depending on communication systems provided by network operators in some cases.

A UE <NUM> is a terminal apparatus supporting the NR <NUM> or both the E-UTRA <NUM> and the NR <NUM>. As described in NPL <NUM> and/or NPL <NUM>, in a case that the UE <NUM> connects to the core network via the E-UTRA <NUM> and/or the NR <NUM>, a logical path called a Radio Bearer (RB) is established between the UE <NUM> and the E-UTRA <NUM> and/or the NR <NUM>. The radio bearer used for the CP is referred to as a Signaling Radio Bearer (SRB), and the radio bearer used for the UP is referred to as a Data Radio Bearer (DRB). An RB Identity (or RB ID) is assigned to each RB and the RB is uniquely identified. The RB identity for SRB is referred to as an SRB Identity (or SRB ID), and the RB identity for DRB is referred to as a DRB Identity (or DRB ID).

As described in NPL <NUM>, in a case that a connection destination core network of the UE <NUM> is the EPC <NUM>, each DRB established between the UE <NUM> and the E-UTRA <NUM> and/or the NR <NUM> is further uniquely linked to each Evolved Packet System (EPS) bearer passing through the inside the EPC <NUM>. An EPS bearer Identity (or ID) is assigned to each EPS bearer and the bearer is uniquely identified. Furthermore, for data passing through the same EPS bearer, the same QoS is ensured.

As described in NPL <NUM>, in a case that a connection destination core network of the UE <NUM> is the 5GC <NUM>, one or multiple DRBs established between the UE <NUM> and the E-UTRA <NUM> and/or the NR <NUM> are further linked to one of Packet Data Unit (PDU) sessions established in the 5GC <NUM>. One or multiple QoS flows are present in each PDU session. Each DRB may be mapped with one or multiple QoS flows present in the PDU session to which the DRB is linked, or may not be mapped to any QoS flows. Each PDU session is identified by a PDU session Identity (or ID). Furthermore, each QoS flow is identified by a QoS flow identity. Furthermore, for data passing through the same QoS flow, the same QoS is ensured.

There is no PDU session and/or QoS flow in the EPC <NUM> and there is no EPS bearer in the 5GC <NUM>. In other words, in a case that the UE <NUM> is connected to the EPC <NUM>, the UE <NUM> has information of the EPS bearer, and in a case that the UE <NUM> is connected to the 5GC <NUM>, the UE <NUM> has information of the PDU session and/or the QoS flow.

<FIG> is a diagram of protocol stacks of UP and CP of a terminal apparatus and a base station apparatus in an E-UTRA radio access layer according to each embodiment of the present invention.

<FIG> is a diagram of the protocol stack of the UP used in a case that the UE <NUM> communicates with the eNB <NUM> in the E-UTRA <NUM>.

A physical layer (PHY) <NUM> is a radio physical layer for providing a transmission service to an upper layer by using a physical channel. The PHY <NUM> is connected with a Medium Access Control layer (MAC) <NUM> of an upper layer to be described below via transport channels. Data is exchanged between the MAC <NUM> and the PHY <NUM> via the transport channels. The data is transmitted and/or received via radio physical channels between the PHYs of the UE <NUM> and the eNB <NUM>.

The MAC <NUM> is a medium access control layer that maps various logical channels to various transport channels. The MAC <NUM> is connected with a radio link control layer (RLC) <NUM> of an upper layer to be described below via logical channels. The major classifications of the logical channel depend on the type of information to be transmitted, specifically, the logical channels are classified into control channels for transmitting control information and traffic channels for transmitting user information. The MAC <NUM> has a function of controlling the PHY <NUM> in order to perform the Discontinuous Reception and Transmission (DRX and DTX), a function of performing a random access procedure, a function of reporting transmit power information, a function of performing HARQ control, and the like (NPL <NUM>).

The RLC <NUM> is a radio link control layer that divides (Segmentation) the data received from a Packet Data Convergence Protocol Layer (PDCP) <NUM> of an upper layer to be described below, and adjusts the data size such that a lower layer can properly perform data transmission. Furthermore, the RLC <NUM> also has a function of ensuring Quality of Service (QoS) required for each piece of data. In other words, the RLC <NUM> has a function of data retransmission control or the like (NPL <NUM>).

The PDCP <NUM> is a packet data convergence protocol layer for efficiently transmitting an IP Packet, which is user data, in a radio section. The PDCP <NUM> may have a header compression function of compressing unnecessary control information. Furthermore, the PDCP <NUM> may also have a data encryption function (NPL <NUM>).

Note that data processed in the MAC <NUM>, the RLC <NUM>, and the PDCP <NUM> are referred to as a MAC Protocol Data Unit (PDU), an RLC PDU, and a PDCP PDU, respectively. In addition, data delivered from an upper layer to the MAC <NUM>, the RLC <NUM>, and the PDCP <NUM> or data delivered therefrom to an upper layer are respectively referred to as a MAC Service Data Unit (SDU), an RLC SDU, and a PDCP SDU.

<FIG> is a diagram of the protocol stack of the CP used in a case that the UE <NUM> communicates with the eNB <NUM> and a Mobility Management Entity (MME), which is a logical node for providing functions such as authentication and mobility management, in the E-UTRA <NUM>.

In addition to the PHY <NUM>, the MAC <NUM>, the RLC <NUM>, and the PDCP <NUM>, there are a Radio Resource Control layer (RRC) <NUM> and a non Access Strarum (NAS) <NUM> in the protocol stack of the CP. The RRC <NUM> is a radio link control layer that performs processing such as establishment, re-establishment, suspending, and resuming of suspending of RRC connection, a reconfiguration of RRC connection, for example, configurations of establishment, change, release, and the like of a Radio Bearer (RB) and a Cell Group, and performs, in addition to performing control and the like of a logical channel, a transport channel, and a physical channel, configurations and the like of a handover and Measurement. The RBs may be classified 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 the user data. Each RB may be configured between the RRCs <NUM> of the eNB <NUM> and the UE <NUM>. In addition, a portion of the RB including the RLC <NUM> and the MAC <NUM> may be referred to as an RLC bearer (NPL <NUM>). In addition, for the NAS layer for carrying a signal between the MME and the UE <NUM>, some layers or all layers of the PHY <NUM>, the MAC <NUM>, the RLC <NUM>, the PDCP <NUM>, and the RRC <NUM> for carrying signals between the UE <NUM> and the eNB <NUM> may be referred to as Access Strarum (AS) layers.

The functional classification of the MAC <NUM>, the RLC <NUM>, the PDCP <NUM>, and the RRC <NUM> described above is an example, and some or all of the respective functions may not be implemented. Some or all of the functions of each layer may be included in another layer.

In addition, an IP layer and a Transmission Control Protocol (TCP) layer, a User Datagram Protocol (UDP) layer, an application layer, and the like that are upper layers than the IP layer are upper layers than the PDCP layer (not illustrated). In addition, the RRC layer and a non Access Strarum (NAS) layer are also upper layers of the SDAP layer (not illustrated). In other words, the PDCP layer is a lower layer of the RRC layer, the NAS layer, the IP layer, and the Transmission Control Protocol (TCP) layer, the User Datagram Protocol (UDP) layer, and the application layer that are upper layers than the IP layer.

<FIG> is a diagram of protocol stacks of UP and CP of a terminal apparatus and a base station apparatus in an NR radio access layer according to each embodiment of the present invention.

<FIG> is a diagram of the protocol stack of the UP used in a case that the UE <NUM> communicates with the gNB <NUM> in the NR <NUM>.

A physical layer (PHY) <NUM> is a radio physical layer of the NR and may provide a transmission service to an upper layer by using the physical channel. The PHY <NUM> may be connected with the Medium Access Control layer (MAC) <NUM> of an upper layer to be described below via the transport channels. Data may be exchanged between the MAC <NUM> and the PHY <NUM> via the transport channels. The data may be transmitted and/or received between the PHYs of the UE <NUM> and the gNB <NUM> via the radio physical channel.

The MAC <NUM> is a medium access control layer that maps various logical channels to various transport channels. The MAC <NUM> may be connected with a Radio Link Control layer (RLC) <NUM> of an upper layer to be described below via the logical channels. The classification of the logical channel depends on the type of information to be transmitted, and the logical channels may be classified into the control channels for transmitting the control information and the traffic channels for transmitting the user information. The MAC <NUM> has a function of controlling the PHY <NUM> in order to perform the Discontinuous Reception and Transmission (DRX and DTX), a function of performing the random access procedure, a function of reporting the transmit power information, a function of performing the HARQ control, and the like (NPL <NUM>).

The RLC <NUM> is a radio link control layer that divides (Segmentation) the data received from the Packet Data Convergence Protocol Layer (PDCP) <NUM> of an upper layer to be described below, and adjusts the data size such that a lower layer can properly perform data transmission. Furthermore, the RLC <NUM> may also have a function of ensuring Quality of Service (QoS) required for each piece of data. In other words, the RLC <NUM> may have a function of data retransmission control or the like (NPL <NUM>).

A PDCP <NUM> is a packet data convergence protocol layer that efficiently transmits an IP Packet, which is user data, in a radio section. The PDCP <NUM> may have a header compression function of compressing unnecessary control information. Furthermore, the PDCP <NUM> may also have a data encryption function (NPL <NUM>).

A Service Data Adaptation Protocol (SDAP) <NUM> is a service data adaptation protocol layer that has a function of mapping a QoS flow of a downlink transmitted from the 5GC <NUM> to a terminal apparatus through a base station apparatus and a DRB, mapping a QoS flow of an uplink transmitted from the terminal apparatus to the 5GC <NUM> through the base station apparatus and the DRB, and storing mapping rule information (NPL <NUM>).

<FIG> is a diagram of the protocol stack of the CP used in a case that the UE <NUM> communicates with the gNB <NUM> and an Access and Mobility Management function (AMF), which is a logical node for providing functions such as authentication and mobility management, in the NR <NUM>.

In addition to the PHY <NUM>, the MAC <NUM>, the RLC <NUM>, and the PDCP <NUM>, there are a Radio Resource Control layer (RRC) <NUM> and a non Access Strarum (NAS) <NUM> in the protocol stack of the CP. The RRC <NUM> is a radio link control layer that performs processing such as establishment, re-establishment, suspending, and resuming of suspending of RRC connection, a reconfiguration of RRC connection, for example, configurations of establishment, change, release, and the like of a Radio Bearer (RB) and a Cell Group, and performs, in addition to performing control and the like of a logical channel, a transport channel, and a physical channel, configurations and the like of handover and Measurement. The RBs may be classified 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 the user data. Each RB may be configured between the RRCs <NUM> of the gNB <NUM> and the UE <NUM>. In addition, a portion of the RB including the RLC <NUM> and the MAC <NUM> may be referred to as an RLC bearer (NPL <NUM>). In addition, for the NAS layer for carrying a signal between the AMF and the UE <NUM>, some layers or all layers of the PHY <NUM>, the MAC <NUM>, the RLC <NUM>, the PDCP <NUM>, and the RRC <NUM> for carrying signals between the UE <NUM> and the gNB <NUM> may be referred to as Access Strarum (AS) layers.

The functional classification of the MAC <NUM>, the RLC <NUM>, the PDCP <NUM>, the SDAP <NUM>, and the RRC <NUM> described above is an example, and some or all of the functions may not be implemented. Furthermore, some or all of the functions of each layer may be included in another layer.

Note that each layer configured to the terminal apparatus and/or the base station apparatus may be referred to as an entity. That is, the MAC layer, the RLC layer, the PDCP layer, the SDAP layer, and the RRC layer configured to the terminal apparatus and/or the base station apparatus may be referred to as an MAC entity, an RLC entity, a PDCP entity, an SDAP entity, and an RRC entity, respectively.

Hereinafter, in each embodiment of the present invention, in order to distinguish an E-UTRA protocol and an NR protocol from each other, the MAC <NUM>, the RLC <NUM>, the PDCP <NUM>, and the RRC <NUM> may be respectively referred to as a MAC for E-UTRA or a MAC for LTE, an RLC for E-UTRA or an RLC for LTE, a PDCP for E-UTRA or a PDCP for LTE, and an RRC for E-UTRA or an RRC for LTE. Furthermore, the MAC <NUM>, the RLC <NUM>, the PDCP <NUM>, and the RRC <NUM> may also be referred to as MAC for NR, RLC for NR, RLC for NR, and RRC for NR, respectively. Alternatively, there may be descriptions using a space such as an E-UTRA PDCP or an LTE PDCP, an NR PDCP, and the like.

As also illustrated in <FIG>, the eNB <NUM>, the gNB <NUM>, the EPC <NUM>, and the 5GC <NUM> may be connected to one another via the interface <NUM>, the interface <NUM>, the interface <NUM>, the interface <NUM>, and the interface <NUM>. Thus, the RRC <NUM> in <FIG> may be replaced with the RRC <NUM> in <FIG> to support various communication systems. Furthermore, the PDCP <NUM> in <FIG> may also be replaced with the PDCP <NUM> in <FIG>. Furthermore, the RRC <NUM> in <FIG> may include the function of the RRC <NUM> in <FIG>. Furthermore, the PDCP <NUM> in <FIG> may be the PDCP <NUM> in <FIG>. In addition, in the E-UTRA <NUM>, even in a case that the UE <NUM> communicates with the eNB <NUM>, the NR PDCP may be used as a PDCP.

Next, a state transition of the UE <NUM> in LTE will be described. The UE <NUM> may be in an RRC_CONNECTED state in a case that an RRC connection has been established. Additionally, in a case that the RRC connection is suspended, (in a case that the UE <NUM> is connected to the 5GC), the UE <NUM> may be in an RRC_INACTIVE state. In a case that these cases are not established, the UE <NUM> may be in the RRC_IDLE state.

Note that the UE <NUM> connected to the EPC does not have the RRC_INACTIVE state, but suspension of the RRC connection may be started by the E-UTRAN. In this case, in a case that the RRC connection is suspended, the UE <NUM> stores an AS context of the UE and an identity (resumeIdentity) used for the resume, and transitions to the RRC_IDLE state. In a case that the UE <NUM> stores the AS context of the UE, the resume of the RRC connection is permitted by the E-UTRAN, and the UE <NUM> is required to transition from the RRC_IDLE state to the RRC_CONNECTED state, the resume of the suspended RRC connection may be started by the upper layer (e.g., the NAS layer).

That is, the definition of suspension may differ between the UE <NUM> connected to the EPC and the UE <NUM> connected to the 5GC. Furthermore, between a case that the UE <NUM> is connected to the EPC (a case of suspending in the RRC_IDLE state) and a case that the UE is connected to the 5GC (a case of suspending in the RRC_INACTIVE state), all or part of a procedure of resuming from the suspension may be different.

The AS context of the UE stored by the UE <NUM> may be information that includes all or some of a current RRC configuration, a current security context, a PDCP state including a RObust Header Compression (ROHC) state, a C-RNTI used in a connection source PCell, a cell identity (cellIdentity), and a physical cell identity of the connection source PCell. Note that the AS context of the UE stored by the eNB <NUM> and/or the gNB <NUM> may include the same information as the AS context of the UE stored by the UE <NUM>, or may include information different from the information included in the AS context of the UE stored by the UE <NUM>.

The security context may be information that includes all or part of a cipher key at the AS level, a Next Hop parameter (NH), a Next Hop Chaining Counter parameter (NCC) used for access key derivation of the next hop, an identity of an encryption algorithm of the selected AS level, a counter used for replay protection.

An embodiment of the present invention will be described with reference to <FIG>. Note that, in each of the procedures described below, processing other than processing to be described may be included in the implementation procedure, and part of processing to be described may not be included in the implementation procedure.

An example of a radio resource control (RRC) connection resume procedure according to an embodiment of the present invention will be described with reference to <FIG>.

This procedure may be used to transfer the UE <NUM> from RRC_INACTIVE to RRC_CONNECTED. This procedure may be initiated in a case that there is a request for resume of the RRC connection from the upper layer of the RRC, or in a case that the RRC requests the resume of the RRC connection (e.g., for notifying the network that the RNA is changed due to cell re-selection (RNA update), or due to reception of paging of the RAN by the UE <NUM> in RRC_INACTIVE).

The UE <NUM> stops a timer T380 used to trigger processing of the RNA update, and starts transmission processing of an RRC connection resume request (RRCConnectionResumeRequest) message described below.

First, the UE <NUM> performs setting as described below, as a content to be included in the RRC connection resume request message (step S401).

In a case that system information to be broadcast includes information indicating that full ResumeID is used, the value of a full I-RNTI (fullI-RNTI) that is provided at Suspending and Stored is set to fullI-RNTI. Otherwise, the value of a short I-RNTI (shortI-RNTI) that is provided at suspending and stored is set to shortI-RNTI. Here, the full I-RNTI is an identity used to identify the suspended UE context of the UE <NUM> in RRC_INACTIVE, and may be information of <NUM> bits, for example. Furthermore, the short I-RNTI is also an identity used to identify the suspended UE context of the UE <NUM> in RRC _INACTIVE, but a smaller number of bits than that of the full I-RNTI is used therefor. For example, the short I-RNTI may be information of <NUM> bits. The UE context here is information related to the UE <NUM> stored by the network, and may include information of capability related to security and information of capability related to the radio of the UE <NUM>.

In accordance with information received from the upper layer or the AS layer (e.g., RRC), resumeCause is set. Here, resumeCause is information indicating a cause for the resume to be included in the RRC connection resume request message. For example, resumeCause includes emergency indicating being an emergency call, rna-Update indicating being resume for update of the RNA, and the like.

The lower <NUM> bits of Message Authentication Code-Integrity (MAC-I) are set to shortResumeMAC-I. Here, shortResumeMAC-I is information used as an authentication token to facilitate authentication of the UE <NUM> at the eNB <NUM> and/or the gNB <NUM>.

Next, except for the configuration of the PHY and the MAC, the RRC configuration and the security context are restored from the stored AS context of the UE (step S402).

A key used for Integrity protection is updated, and the lower layer is configured such that the integrity protection is resumed for all SRBs other than SRB0 (step S403).

The lower layer is configured such that encryption is resumed for all radio bearers other than the SRB0 (step S404).

A default configuration is applied to SRB <NUM> (step S405).

A default NR PDCP configuration is applied (step S406).

The UE <NUM> submits the RRC connection resume request message to the lower layer for transmission (step S408).

As a reply to the RRC connection resume request message described above, an RRC connection resume message, an RRC connection setup message, an RRC connection rejection message, an RRC connection release message, and the like may be transmitted from the eNB <NUM> or the gNB <NUM> to the UE <NUM>.

For example, the eNB <NUM> or the gNB <NUM> may transmit the RRC connection resume message to the UE <NUM> in order to resume the connected state of the UE <NUM>. Furthermore, the eNB <NUM> or the gNB <NUM> may transmit the RRC connection setup message to the UE <NUM> in order to cause the UE <NUM> to establish the connected state instead of resume. Furthermore, the eNB <NUM> or the gNB <NUM> may transmit the RRC connection rejection message to the UE <NUM> in order to return the UE <NUM> to the inactive state. Furthermore, the eNB <NUM> or the gNB <NUM> may transmit the RRC connection release message to the UE <NUM> in order to shift the UE <NUM> to the idle state.

The operations of the UE <NUM> in a case that the RRC connection release message is received will be described below with reference to <FIG>.

The UE <NUM> may delay the following operations up to earlier of a predetermined time (e.g., <NUM>) from receiving the RRC connection release message and a time at which the UE is notified that an affirmative response with respect to this RRC connection release message has been successfully completed from the lower layer (step S701).

In a case that the RRC connection release message includes redirectedCarrierInfo indicating redirection to the GERAN or includes IdleModeMobilityControlInfo including freqPriorityListGERAN, processing 1A described below is performed, and otherwise the process transitions to step S704 without performing the processing 1A (step S702). Here, redirectedCarrierInfo may be information indicating, for example, a carrier frequency (of downlink in the FDD) and a type of a target RAT (e.g., EUTRA, GERAN, UTRA-FDD, UTRA-TDD, NR release <NUM>, and the like). freqPriorityListGERAN may be information indicating, for example, information of cell re-selection priority of each frequency in the GERAN. idleModeMobilityControlInfo may be information, for example, for providing information of cell re-selection priority individually for the UE <NUM> and may be used for cell re-selection of the UE <NUM>.

Processing 1A: In a case that AS security is not activated and in a case that the upper layer indicates not permitting redirection to the GERAN without the AS security or the UE <NUM> is connected to the 5GC, the content of the RRC connection release message is ignored, the release cause is configured to "other", an operation (first operation) in a case of leaving RRC_CONNECTED or RRC_INACTIVE described later is performed, and this procedure is terminated (step S703).

In a case that the AS security is not activated, processing 1B as described below is performed, and otherwise the process transitions to step S706 without performing the processing 1B (step S704).

Processing 1B: In a case that redirection to the NR is indicated, the content of redirectedCarrierInfo is ignored. In a case that freqPriorityListNR is included in idleModeMobilityControlInfo, the content of idleModeMobilityControlInfo is ignored. In a case that the UE <NUM> ignores the content of redirectedCarrierInfo or idleModeMobilityControlInfo, the release cause is configured to "other", the first operation described later is performed, and this procedure is terminated (step S705). Here, freqPriorityListNR may be information indicating, for example, information of the cell re-selection priority of each frequency in the NR.

In a case that the RRC connection release message includes redirectedCarrierInfo indicating redirection to the EUTRA and the UE <NUM> is connected to the 5GC, processing 1C described below is performed, and otherwise the process transitions to step S708 without performing the processing 1C (step S706).

Processing 1C: In a case that the RRC connection release message includes cn-Type, this received cn-Type is provided to the upper layer (step S707).

In a case that the RRC connection release message includes idleModeMobilityControlInfo, processing 1D described below is performed, and otherwise processing 1E is performed (step S708).

Processing 1D: Cell re-selection priority information provided by idleModeMobilityControlInfo included in the RRC connection release message is stored. In a case that t320 is included in the RRC connection release message, a timer T320 is started with a timer value set in accordance with the value of this t320 (step S709). Here, the timer T320 may be a timer used to manage a period during which the cell re-selection priority information of which the UE <NUM> is individually notified is applied, and may be started at the time of receiving t320. Furthermore, the timer T320 may be started under another condition. The timer T320 may be stopped at the time of entering RRC_CONNECTED. Furthermore, the timer T320 may be stopped under another condition. In a case that the timer T320 expires, that is, in a case that a predetermined time has elapsed after the timer T320 is started (e.g., t320), the cell re-selection priority information of which the UE <NUM> is individually notified may be discarded.

Processing 1E: The cell re-selection priority information broadcast with system information is applied (step S710).

In a case that the release cause included in the RRC connection release message indicates loadBalancingTAURequired (step S711), the release cause is configured to "load Balancing TAU Required", and the first operation described later is performed (step S712). Here, loadBalancingTAURequired may be information indicating that a load distribution of TAU is required, for example.

Otherwise, in a case that the release cause included in the RRC connection release message indicates cs-FallbackHighPriority (step S713), the release cause is configured to "cs-Fallback High Priority", and the first operation described later is performed (step S714). Here, cs-FallbackHighPriority may be information indicating being Circuit Switched FallBack having a high priority, for example.

Otherwise, processing 1F described below is performed (step S715).

Processing 1F: In a case that there is extendedWaitTime and in a case that the UE <NUM> supports delay allowable access or the UE <NUM> is an Nb-IoT UE, extendedWaitTime is transferred to the upper layer (step S716). In a case that the release cause included in the RRC connection release message indicates rrc-Suspend, processing <NUM> described below is performed, and otherwise processing <NUM> is performed (step S717). Here, for example, rrc-Suspend may be information indicating that the RRC connection is suspended.

Processing <NUM>: In a case that rrc-InactiveConfig is included, processing for entering RRC_INACTIVE is performed, otherwise the release cause is configured to "RRC suspension", and the first operation described later is performed (step S718). Here, rrc-InactiveConfig may be a configuration that the UE <NUM> entering RRC_INACTIVE applies, for example.

Processing <NUM>: The release cause is configured to "other", and the first operation described later is performed (step S719).

An example of the operation (first operation) of the UE <NUM> in a case that the UE <NUM> leaves, not according to the claimed invention, RRC_CONNECTED or leaves RRC_INACTIVE and transitions to RRC_IDLE, according to the embodiment of the present invention, will be described below with reference to <FIG>.

The UE <NUM> performs the following processing.

In a case that the UE <NUM> satisfies a condition A (step S802), (A) in a case the timer T320 is running, the timer is stopped, and (B) in a case that the cell re-selection priority information provided by idleModeMobilityControlInfo is stored, the information is discarded (step S803).

The condition A described above includes, according to the claimed invention, a case of leaving RRC_INACTIVE and transitioning to RRC_IDLE, and leaving RRC _INACTIVE and transitioning to RRC_IDLE is not triggered by the RRC connection release message. The following examples for the condition A are not or not completely encompassed by the wording of the claims, but are considered as useful for understanding the invention.

The condition A described above may include, for example, a case of leaving RRC_INACTIVE, and a case that leaving RRC_INACTIVE is not triggered by the RRC connection release message.

The condition A described above may include, for example, a case of leaving RRC_INACTIVE, and a case that leaving RRC_INACTIVE is not triggered by the RRC connection release message received as a reply to the RRC connection resume request message.

Furthermore, the condition A described above may include, for example, a case of leaving RRC_INACTIVE, and a case that (<NUM>) leaving RRC_INACTIVE is not triggered by the RRC connection release, or (<NUM>) leaving RRC_INACTIVE is triggered by the RRC connection release message and idleModeMobilityControlInfo included in the RRC connection release message is ignored.

Furthermore, the condition A described above may include, for example, a case of leaving RRC_INACTIVE, and a case that (<NUM>) leaving RRC_INACTIVE is not triggered by the RRC connection release, or (<NUM>) leaving RRC_INACTIVE is triggered by the RRC connection release and is triggered by the RRC connection release message not including idleModeMobilityControlInfo.

Furthermore, the condition A described above may include, for example, a case of leaving RRC_INACTIVE, and a case that (<NUM>) leaving RRC_INACTIVE is not triggered by the RRC connection release, or (<NUM>) leaving RRC_INACTIVE is triggered by the RRC connection release message, and the UE <NUM> ignores the content of redirectedCarrierInfo included in the RRC connection release message, or ignores the content of idleModeMobilityControlInfo included in the RRC connection release message.

Furthermore, the condition A described above may include, for example, a case of leaving RRC_INACTIVE, and a case that (<NUM>) leaving RRC_INACTIVE is not triggered by the RRC connection release, or (<NUM>) leaving RRC_INACTIVE is triggered by the RRC connection release message and the UE <NUM> does not store the cell re-selection priority information provided by the RRC connection release message.

Furthermore, the condition A described above may include a combination of the multiple conditions described above.

In a case that the condition A is not satisfied, the U <NUM> may not perform processing included in step S803. For example, in a case of leaving RRC_INACTIVE, and in a case that leaving RRC_INACTIVE is triggered by the RRC connection release, step S803 may not be performed. Furthermore, for example, in a case of leaving RRC _INACTIVE, and in a case that leaving RRC_INACTIVE is triggered by the RRC connection release and is triggered by the RRC connection release including idleModeMobilityControlInfo, processing included in step S803 may not be performed.

Here, the expression "triggered by the RRC connection release" may include the meaning of either or both (<NUM>) triggered by receiving the RRC connection release message and (<NUM>) triggered by the RRC connection being released regardless of whether or not the RRC connection release message has been received.

Timer other than timers T320, T322, T325, and T330 is stopped (step S804). Here, the timer T322 may be a timer used to control a period during which part of offset information of which the UE <NUM> is individually notified is applied. Furthermore, the timer T325 may be a timer used to control a period of a carrier frequency (e.g., a carrier frequency with which an RRC connection refusal message is received) or during which the priority of the RAT is lowered (de-prioritised). Furthermore, the timer T330 may be a timer used to control measurement performed by the UE <NUM> in the RRC_IDLE.

In a case that leaving RRC_CONNECTED is triggered by suspension of the RRC (step S805), the following processing 2A is performed (step S806), and otherwise processing 2B is performed (step S807).

Processing 2A: RLC entities of all SRBs and DRBs including a radio bearer configured with the NR PDCP are re-established (also referred to as re-founded). A UE AS Context is stored which includes all or some of a current RRC configuration, a current security context, a PDCP state including an ROHC state, a C-RNTI used in a connection source PCell, a cell identity (cellIdentity), and a physical cell identity of the connection source PCell. All or some of resumeIdentity, nextHopChainingCount in a case of being present, and drb-ContinueROHC in a case of being present, provided by E-UTRAN are stored. All SRBs and DRBs including a radio bearer configured with the NR PDCP, excluding the SRB0, are suspended. The upper layer is notified of suspension of the RRC connection. A lower layer is configured such that integrity protection and encryption are suspended. Here, nextHopChainingCount may be information associated with the parameter NCC and used to update the key. Furthermore, drb-ContinueROHC may be information indicating whether to continue using or reset information (context) of the header compression protocol for the DRB configured in the header compression protocol.

Processing 2B: All radio resources including release of the PDCP entity associated with the RLC entity and an MAC configuration for all established radio bearers are released. The upper layer is notified of release of the RRC connection with the release cause.

An example of various procedures related to the operation at the time of leaving RRC_INACTIVE will be described below.

Operations related to reception of a paging message by the UE <NUM> will be described.

In a case of the idle state, the following processing 3A is performed on each PagingRecord included in the paging message. Here, PagingRecord may include information for identifying the UE <NUM> to be a target.

Processing 3A: In a case that ue-Identity included in PagingRecord matches one of UE identities assigned by the upper layer, ue-Identity, accessType, and the like are transferred to the upper layer. Here, accessType may be information indicating an access type, and for example, may include circuit switched (CS), packet switched (PS), and the like.

In a case of the inactive state, the following processing 3B is performed on each PagingRecord included in the paging message.

Processing 3B: In a case that ue-Identity included in PagingRecord matches the stored I-RNTI, a Cause Value based on an access identity with which the UE <NUM> is configured is configured, and the RRC connection resume procedure is initiated. Otherwise, in a case that ue-Identity included in PagingRecord matches one of UE identities assigned by the upper layer, ue-Identity, accessType, and the like are transferred to the upper layer, the release cause is configured to "other", and the first operation is performed.

Operations related to cell re-selection while timer T300 or T302 is running by the UE <NUM> in the inactive state will be described.

In a case that the cell re-selection occurs while the timer T300 or T302 is running, processing 4A described below is performed.

Processing 4A: In a case that a variable pendingRnaUpdate is set to TRUE, the variable is set to FALSE. The release cause is configured to "RRC resume failure", and the first operation is performed.

Operations related to the timer T300 expiration by the UE <NUM> in the inactive state will be described.

In a case that the timer T300 expires, the following process is performed.

In a case that the UE <NUM> has transmitted the RRC connection resume request message and has not received the RRC connection resume message, the MAC is reset, the RLC for all established radio bearers is re-established, and the SRB1 is suspended. Otherwise, the MAC is reset, the configuration of the MAC is released, and the RLC for all established radio bearers is re-established.

In a case of the inactive state, the release cause is configured to "RRC connection failure", and the first operation is performed.

An example of part of operations related to reception of the RRC connection resume message by the UE <NUM> in the inactive state will be described.

The UE <NUM> stops various timers including the timer T320, in a case that the timers are running.

In a case that the RRC connection resume message is received as a reply to the RRC connection resume request for Early Data Transmission (EDT), a value of part of parameters (e.g., nextHopChyainingCounter) included in the RRC connection resume message is ignored.

In a case that the RRC connection resume message is not a message received as a reply to the RRC connection resume request for the Early Data Transmission (EDT), in a case that check for integrity protection of the RRC connection resume message is failed, (A) in a case of resume from the suspended RRC connection (resume from the RRC_IDLE state), the release cause is configured to "other" and the first operation is performed, (B) in a case of resume from RRC_INACTIVE, the release cause is configured to "RRC resume failure", and the first operation is performed, and this procedure is terminated.

The UE <NUM> enters RRC_CONNECTED and notifies the upper layer that the RRC connection is resumed.

The description of the subsequent processing is omitted.

An example of part of operations in a case that the UE <NUM> enters the inactive state will be described.

In a case of entering RRC_INACTIVE, the UE <NUM> performs the following operations.

The UE <NUM> resets the MAC and stops all timers except some timers. Some timers described above may include T320.

The UE <NUM> re-establishes RLC entities for all SRBs and DRBs.

The UE <NUM> applies the received configuration (e.g., rrc-InactiveConfig).

In a case of receiving the RRC connection release message as a reply to the RRC connection resume request, the UE <NUM> replaces stored security contexts with newly received security contexts (e.g., included in rrc-InactiveConfig), replaces the stored C-RNTI with a temporary C-RNTI used in a case that the UE <NUM> receives the RRC connection release message, and replaces the stored cell identity (cellIdentity) and Physical cell identity with cellIdentity and the physical cell identity of the PCell in a case that the UE <NUM> receives the RRC connection release message.

In a case that the RRC connection release message is not a message received as a reply to the RRC connection resume request, the AS context of the UE is stored.

The UE <NUM> starts the timer T380 used for update of the RNA and suspends all SRBs and DRBs except SRB0.

The RRC layer of the UE <NUM> notifies the upper layer of suspension of the RRC connection and enters RRC _INACTIVE.

In a case of selecting a cell of a different RAT or selecting a different core network (CN) type in cell re-selection in RRC_INACTIVE, the UE <NUM> configures the release cause to "other", and performs the first operation.

In operations other than those described above as well, there may be a case that the operation (first operation) is performed in a case of leaving RRC_CONNECTED or RRC _INACTIVE.

<FIG> is a block diagram illustrating a configuration of the terminal apparatus (UE <NUM>) according to an embodiment of the present invention. Note that <FIG> illustrates only the main components closely related to the present invention in order to avoid complexity of description.

The UE <NUM> illustrated in <FIG> includes a receiver <NUM> configured to receive, from the eNB <NUM>, an RRC connection reconfiguration message, an RRC connection resume message, an RRC connection setup message, an RRC connection rejection message, an RRC connection release message, and the like, a processing unit <NUM> configured to perform processing in accordance with various types of Information Elements (IEs), various types of conditions, and the like included in the received messages, and a transmitter <NUM> configured to transmit an RRC connection resume request message and the like to the eNB <NUM>. Furthermore, a controller configured to control operation of each unit based on various conditions may be separately provided.

<FIG> is a block diagram illustrating a configuration of a base station apparatus (eNB <NUM>) according to an embodiment of the present invention, which is not covered by the claims. Note that <FIG> illustrates only the main components closely related to the present invention in order to avoid complexity of description.

The eNB <NUM> illustrated in <FIG> includes a transmitter <NUM> configured to transmit, to the UE <NUM>, an RRC connection reconfiguration message, an RRC connection resume message, an RRC connection setup message, an RRC connection rejection message, an RRC connection release message, and the like, a processing unit <NUM> configured to cause the processing unit <NUM> of the UE <NUM> to perform processing by creating a message including various types of Information Elements (IEs) and transmitting the message to the UE <NUM>, and a receiver <NUM> configured to receive an RRC connection resume request message and the like from the UE <NUM>. Note that the configuration illustrated in <FIG> may be applied to the gNB <NUM>. In a case that the configuration is applied to the gNB <NUM>, a message transmitted to the UE <NUM> from the transmitter <NUM> may be an RRC reconfiguration message, an RRC resume message, an RRC setup message, an RRC rejection message, an RRC release message, or the like. Furthermore, the eNB <NUM> and/or the gNB <NUM> may separately include a controller configured to control operation of each unit based on various conditions.

As described above, according to the embodiment of the present invention, the UE <NUM> stores or discards the configuration based on the condition of the state transition, whereby appropriate mobility can be achieved.

To describe in detail, the UE <NUM> can prevent unnecessary cell re-selection priority information discard, by discarding cell re-selection priority information based on a condition in which the state transition is triggered.

The following aspects (<NUM>) to (<NUM>) of the terminal apparatus (UE <NUM>) and the base station apparatus (eNB <NUM> and/or gNB <NUM>), not encompassed by the claimed invention, will be described.

As a result, the UE <NUM> can store or discard the configuration based on the condition of the state transition, and thus appropriate mobility can be achieved.

A program operating on an apparatus according to the present invention may serve as a program that controls a Central Processing Unit (CPU) and the like to cause a computer to operate in such a manner as to realize the functions of the above-described embodiment according to the present invention. Programs or the information handled by the programs are temporarily loaded into a volatile memory such as a Random Access Memory (RAM) while being processed, or stored in a non-volatile memory such as a flash memory, or a Hard Disk Drive (HDD), and then read, modified, and written by the CPU, as necessary.

Note that the apparatuses in the above-described embodiment may be partially enabled by a computer. In such a case, a program for realizing such control functions may be recorded on a computer-readable recording medium to cause a computer system to read the program recorded on the recording medium to perform the program. It is assumed that the "computer system" mentioned here refers to a computer system built into the apparatuses, and the computer system includes an operating system and hardware components such as a peripheral device. Furthermore, the "computer-readable recording medium" may be any of a semiconductor recording medium, an optical recording medium, a magnetic recording medium, and the like.

Moreover, the "computer-readable recording medium" may include a medium that dynamically retains a program for a short period of time, such as a communication line that is used to transmit the program over a network such as the Internet or over a communication line such as a telephone line, and may also include a medium that retains a program for a fixed period of time, such as a volatile memory within the computer system for functioning as a server or a client in such a case. Furthermore, the above-described program may be configured to realize some of the functions described above, and additionally may be configured to realize the functions described above, in combination with a program already recorded in the computer system.

Furthermore, each functional block or various characteristics of the apparatuses used in the above-described embodiment may be implemented or performed with an electric circuit, that is, typically an integrated circuit or multiple integrated circuits. An electric circuit designed to perform the functions described in the present specification 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 devices, discrete gates or transistor logic, discrete hardware components, or a combination thereof. The general-purpose processor may be a microprocessor, or the processor may be a processor of known type, a controller, a microcontroller, or a state machine instead. The general-purpose processor or the above-mentioned circuits may include a digital circuit, or may include an analog circuit. Furthermore, in a case that with advances in semiconductor technology, a circuit integration technology appears that replaces the present integrated circuits, it is also possible to use an integrated circuit based on the technology.

Claim 1:
A terminal apparatus (<NUM>) comprising:
a transmission unit (<NUM>) configured to transmit a first message for requesting resume from an inactive state to a connected state;
a receiving unit (<NUM>) configured to receive an RRC connection release message that indicates a transition to an idle state; and
a controlling unit (<NUM>) configured to store priority information in a case that the RRC connection release message includes idleModeMobilityControlinfo, the idleModeMobilityControllnfo includes the priority information for cell selection,
characterised in that
the controlling unit (<NUM>) is further configured to determine, based on a transition from an inactive state to an idle state is not triggered by reception of the RRC connection release message, in a case the priority information is stored, discard the priority information.