WO2024070447A1 - Terminal device, method, and integrated circuit - Google Patents

Abstract

This terminal device determines whether or not the two following conditions (1) and (2) are satisfied on the basis of the reception of a MAC signaling: (1) A candidate target cell indicated by the MAC signaling belongs to one or a plurality of TA groups of the cell groups that have received the MAC signaling, and a TA timer corresponding to the TA group is running; and (2) The MAC signaling does not include information instructing the execution of a random access procedure, and when it is determined that any of the above conditions is not satisfied, the terminal device notifies an RRC layer that the random access procedure needs to be executed.

Description

Terminal device, method, and integrated circuit

The present invention relates to a terminal device, a method, and an integrated circuit.
This application claims priority to Japanese Patent Application No. 2022-153655, filed in Japan on September 27, 2022, the contents of which are incorporated herein by reference.

The 3rd Generation Partnership Project (3GPP, registered trademark), a standardization project for cellular mobile communication systems, is conducting technical studies and formulating standards for cellular mobile communication systems, including wireless access, core networks, and services.

For example, 3GPP has begun technical discussions and standardization of E-UTRA (Evolved Universal Terrestrial Radio Access) as a radio access technology (Radio Access Technology: RAT) for 3.9G and 4G cellular mobile communication systems. 3GPP is currently conducting technical discussions and standardization of E-UTRA extension technologies. E-UTRA is also known as Long Term Evolution (LTE: registered trademark), and the extension technology is sometimes referred to as LTE-Advanced (LTE-A) and LTE-Advanced Pro (LTE-A Pro).

In addition, 3GPP has begun technical studies and standardization of NR (New Radio, or NR Radio access) as a radio access technology (Radio Access Technology: RAT) for cellular mobile communication systems for the 5th generation (5G). 3GPP is currently conducting technical studies and standardization of NR extension technologies.

3GPP TS 38.331 v17.1.0, "Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specifications" pp70-116, pp218-223, pp316-1107 3GPP TS 38.321 v17.1.0, "NR; Medium Access Control (MAC) protocol specification" pp17-104 3GPP TS 38.213 v17.2.0, "NR; Physical layer procedures for control" pp14-20

As an extension technology of 3GPP NR, research has begun on Layer 1/Layer 2 mobility, which allows terminal devices to move between cells not only by the conventional RRC layer signaling (handover) when connected to RRC, but also by signaling in the MAC layer and PHY layer, which are layers below the RRC layer; however, efficient operation to reduce processing delays has not yet been considered.

One aspect of the present invention was made in consideration of the above circumstances, and one of its objectives is to provide a terminal device, a communication method, and an integrated circuit that can efficiently control communications.

In order to achieve the above object, one aspect of the present invention takes the following measures. That is, one aspect of the present invention is a terminal device that communicates with a base station device, and includes a receiver that receives MAC signaling from the base station device to change a source SpCell to a target SpCell, a MAC processor, and an RRC processor. Based on receiving the MAC signaling from the base station device, the MAC processor determines whether or not the following two conditions are met: (1) a candidate target cell indicated by the MAC signaling belongs to one or more TA groups of the cell group that received the MAC signaling, and a TA timer corresponding to the TA group is running, and (2) the MAC signaling does not include information instructing the execution of a random access procedure. Based on determining that either of the above conditions is not met, the MAC processor notifies the RRC processor that a random access procedure needs to be executed.

Another aspect of the present invention is a method for a terminal device communicating with a base station device, comprising the steps of: receiving MAC signaling from the base station device to change a source SpCell to a target SpCell; and, based on receiving the MAC signaling from the base station device, determining whether the following two conditions are met as MAC layer processing: (1) a candidate target cell indicated by the MAC signaling belongs to one or more TA groups of the cell group that received the MAC signaling, and a TA timer corresponding to the TA group is running; and (2) the MAC signaling does not include information instructing the execution of a random access procedure; and, based on determining that either of the above conditions is not met, notifying the RRC layer of the terminal device that a random access procedure needs to be executed.

Another aspect of the present invention is an integrated circuit implemented in a terminal device that communicates with a base station device, which has the following functions: receiving MAC signaling from the base station device to change a source SpCell to a target SpCell; and, based on receiving the MAC signaling from the base station device, determining whether or not the following two conditions are met as MAC layer processing: (1) a candidate target cell indicated by the MAC signaling belongs to one or more TA groups of the cell group that received the MAC signaling, and a TA timer corresponding to the TA group is running; and (2) the MAC signaling does not include information that instructs the execution of a random access procedure; and, based on determining that either of the above conditions is not met, notifying the RRC layer of the terminal device that a random access procedure needs to be executed.

These comprehensive or specific aspects may be realized as a system, device, method, integrated circuit, computer program, or recording medium, or as any combination of a system, device, method, integrated circuit, computer program, and recording medium.

According to one aspect of the present invention, a terminal device, method, and integrated circuit can realize efficient communication control processing.

1 is a schematic diagram of a communication system according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of an E-UTRA protocol configuration according to the present embodiment. FIG. 1 is a diagram showing an example of an NR protocol configuration according to the present embodiment. FIG. 2 is a diagram showing an example of a procedure flow for various settings in the RRC according to the present embodiment. FIG. 2 is a block diagram showing the configuration of a terminal device according to the embodiment. FIG. 2 is a block diagram showing the configuration of a base station device according to the present embodiment. An example of an ASN.1 description of a message regarding reconfiguration of an RRC connection in NR in this embodiment. 13 is an example of an ASN.1 description representing a field and/or an information element related to a ServingCellConfigCommon information element in this embodiment. 5 is an example of processing of a terminal device in the present embodiment.

This embodiment will be described in detail below with reference to the drawings.

LTE (and LTE-A, LTE-A Pro) and NR may be defined as different radio access technologies (Radio Access Technologies: RATs). NR and LTE that can be connected via Multi-Radio Dual Connectivity (MR-DC) may be distinguished from conventional LTE. LTE that uses 5GC in the core network (Core Network: CN) may be distinguished from conventional LTE that uses EPC in the core network. Conventional LTE may refer to LTE that does not implement technologies standardized after Release 15 in 3GPP. This embodiment may be applied to NR, LTE, and other RATs. In the following description, terms related to LTE and NR are used, but this embodiment may be applied to technologies that use other terms and/or other radio access technologies. In this embodiment, the term E-UTRA and the term LTE may be interchangeable.

In this embodiment, the names of each node and entity and the processing in each node and entity when the radio access technology is E-UTRA or NR are described, but this embodiment may be applied to other radio access technologies. The names of each node and entity in this embodiment may be different names.

FIG. 1 is a schematic diagram of a communication system according to this embodiment. Note that the functions of each node, radio access technology, core network, interface, etc. described using FIG. 1 are only some of the functions closely related to this embodiment, and the system may have other functions.

E-UTRA100 may be a radio access technology. E-UTRA100 may also be an air interface between UE122 and eNB102. The air interface between UE122 and eNB102 may be referred to as a Uu interface. eNB (E-UTRAN Node B) 102 may be a base station device of E-UTRA100. eNB102 may have the E-UTRA protocol described below. The E-UTRA protocol may be composed of the E-UTRA User Plane (UP) protocol described below and the E-UTRA Control Plane (CP) protocol described below. eNB102 may terminate the E-UTRA User Plane (UP) protocol and the E-UTRA Control Plane (CP) protocol for UE122. The radio access network composed of eNBs may be referred to as E-UTRAN.

EPC (Evolved Packet Core) 104 may be a core network. Interface 112 is an interface between eNB 102 and EPC 104, and may be referred to as an S1 interface. Interface 112 may include a control plane interface through which control signals pass, and/or a user plane interface through which user data passes. The control plane interface of interface 112 may terminate at a Mobility Management Entity (MME: not shown) in EPC 104. The user plane interface of interface 112 may terminate at a Serving Gateway (S-GW: not shown) in EPC 104. The control plane interface of interface 112 may be referred to as an S1-MME interface. The user plane interface of interface 112 may be referred to as an S1-U interface.

Note that one or more eNBs 102 may be connected to the EPC 104 via an interface 112. An interface may exist between the multiple eNBs 102 connected to the EPC 104 (not shown). The interface between the multiple eNBs 102 connected to the EPC 104 may be referred to as an X2 interface.

NR106 may be a radio access technology. NR106 may also be an air interface between UE122 and gNB108. The air interface between UE122 and gNB108 may be referred to as a Uu interface. gNB (g Node B) 108 may be a base station device for NR106. gNB108 may have the NR protocol described below. The NR protocol may be composed of the NR user plane (User Plane: UP) protocol described below and the NR control plane (Control Plane: CP) protocol described below. gNB108 may terminate the NR user plane (User Plane: UP) protocol and the NR control plane (Control Plane: CP) protocol for UE122.

5GC110 may be a core network. Interface 116 is an interface between gNB108 and 5GC110, and may be referred to as an NG interface. Interface 116 may have a control plane interface through which control signals pass, and/or a user plane interface through which user data passes. The control plane interface of interface 116 may terminate at an Access and Mobility Management Function (AMF: not shown) in 5GC110. The user plane interface of interface 116 may terminate at a User Plane Function (UPF: not shown) in 5GC110. The control plane interface of interface 116 may be referred to as an NG-C interface. The user plane interface of interface 116 may be referred to as an NG-U interface.

Note that one or more gNBs 108 may be connected to the 5GC 110 via an interface 116. An interface may exist between multiple gNBs 108 connected to the 5GC 110 (not shown). The interface between multiple gNBs 108 connected to the 5GC 110 may be referred to as an Xn interface.

　eNB102 may have a function to connect to 5GC110. eNB102 with a function to connect to 5GC110 may be called ng-eNB. Interface 114 is an interface between eNB102 and 5GC110, and may be called an NG interface. Interface 114 may have a control plane interface through which control signals pass, and/or a user plane interface through which user data passes. The control plane interface of interface 114 may terminate at an AMF in 5GC110. The user plane interface of interface 114 may terminate at a UPF in 5GC110. The control plane interface of interface 114 may be called an NG-C interface. The user plane interface of interface 114 may be called an NG-U interface. A radio access network composed of ng-eNB or gNB may be called NG-RAN. NG-RAN, E-UTRAN, etc. may simply be called a network. In addition, the network may include eNB, ng-eNB, gNB, etc.

Note that one or more eNB102 may be connected to 5GC110 via interface 114. An interface may exist between multiple eNB102 connected to 5GC110 (not shown). The interface between multiple eNB102 connected to 5GC110 may be called an Xn interface. Furthermore, an eNB102 connected to 5GC110 and a gNB108 connected to 5GC110 may be connected by interface 120. The interface 120 between an eNB102 connected to 5GC110 and a gNB108 connected to 5GC110 may be called an Xn interface.

The gNB108 may have the function of connecting to the EPC104. The gNB108 with the function of connecting to the EPC104 may be called an en-gNB. The interface 118 is an interface between the gNB108 and the EPC104, and may be called an S1 interface. The interface 118 may have a user plane interface through which user data passes. The user plane interface of the interface 118 may terminate at an S-GW (not shown) in the EPC104. The user plane interface of the interface 118 may be called an S1-U interface. Furthermore, the eNB102 connecting to the EPC104 and the gNB108 connecting to the EPC104 may be connected by an interface 120. The interface 120 between the eNB102 connecting to the EPC104 and the gNB108 connecting to the EPC104 may be called an X2 interface.

Interface 124 is an interface between EPC 104 and 5GC 110, and may be an interface that passes only CP, only UP, or both CP and UP. In addition, some or all of interfaces such as interface 114, interface 116, interface 118, interface 120, and interface 124 may not exist depending on the communication system provided by the communication carrier, etc.

UE122 may be a terminal device capable of receiving system information and paging messages transmitted from eNB102 and/or gNB108. UE122 may also be a terminal device capable of wireless connection with eNB102 and/or gNB108. UE122 may also be a terminal device capable of wireless connection with eNB102 and wireless connection with gNB108 simultaneously. UE122 may have an E-UTRA protocol and/or an NR protocol. The wireless connection may be a Radio Resource Control (RRC) connection.

UE122 may also be a terminal device capable of connecting to EPC104 and/or 5GC110 via eNB102 and/or gNB108. When the core network to which eNB102 and/or gNB108, with which UE122 communicates, is connected is EPC104, each Data Radio Bearer (DRB: Data Radio Bearer) described below established between UE122 and eNB102 and/or gNB108 may further be uniquely linked to each EPS (Evolved Packet System) bearer passing through EPC104. Each EPS bearer may be identified by an EPS bearer identifier (Identity, or ID). Furthermore, the same QoS may be guaranteed for data such as IP packets and Ethernet (registered trademark) frames passing through the same EPS bearer.

Furthermore, if the core network to which eNB102 and/or gNB108, with which UE122 communicates, is connected is 5GC110, each DRB established between UE122 and eNB102 and/or gNB108 may be further linked to one of the PDU (Packet Data Unit) sessions established within 5GC110. One or more QoS flows may exist in each PDU session. Each DRB may be mapped to one or more QoS flows, or may not be mapped to any QoS flow. Each PDU session may be identified by a PDU session identifier (Identity, or ID). Furthermore, each QoS flow may be identified by a QoS flow identifier (Identity, or ID). Furthermore, the same QoS may be guaranteed to data such as IP packets and Ethernet frames passing through the same QoS flow.

　PDU sessions and/or QoS flows may not exist in EPC104. Also, EPS bearers may not exist in 5GC110. When UE122 is connected to EPC104, UE122 has information on EPS bearers, but may not have information on PDU sessions and/or QoS flows. Also, when UE122 is connected to 5GC110, UE122 has information on PDU sessions and/or QoS flows, but may not have information on EPS bearers.

In the following description, eNB102 and/or gNB108 will also be referred to simply as base station devices, and UE122 will also be referred to simply as terminal device or UE.

FIG. 2 is a diagram showing an example of an E-UTRA protocol architecture according to this embodiment. FIG. 3 is a diagram showing an example of an NR protocol architecture according to this embodiment. Note that the functions of each protocol described using FIG. 2 and/or FIG. 3 are only some of the functions closely related to this embodiment, and other functions may be included. Note that in this embodiment, the uplink (UL) may be a link from a terminal device to a base station device. Also, in this embodiment, the downlink (DL) may be a link from a base station device to a terminal device.

Figure 2(A) is a diagram of the E-UTRA user plane (UP) protocol stack. As shown in Figure 2(A), the E-UTRA UP protocol may be a protocol between the UE 122 and the eNB 102. That is, the E-UTRA UP protocol may be a protocol that terminates at the eNB 102 on the network side. As shown in Figure 2(A), the E-UTRA user plane protocol stack may be composed of PHY (Physical layer) 200, which is the radio physical layer, MAC (Medium Access Control) 202, which is the medium access control layer, RLC (Radio Link Control) 204, which is the radio link control layer, and PDCP (Packet Data Convergence Protocol) 206, which is the packet data convergence protocol layer.

Figure 3(A) is a diagram of the NR user plane (UP) protocol stack. As shown in Figure 3(A), the NRUP protocol may be a protocol between the UE 122 and the gNB 108. That is, the NR UP protocol may be a protocol that terminates at the gNB 108 on the network side. As shown in Figure 3(A), the NR user plane protocol stack may be composed of a radio physical layer, PHY 300, a medium access control layer, MAC 302, a radio link control layer, RLC 304, a packet data convergence protocol layer, PDCP 306, and a service data adaptation protocol layer, SDAP (Service Data Adaptation Protocol) 310.

Figure 2(B) is a diagram of the E-UTRA control plane (CP) protocol configuration. As shown in Figure 2(B), in the E-UTRA CP protocol, RRC (Radio Resource Control) 208, which is the radio resource control layer, may be a protocol between UE 122 and eNB 102. In other words, RRC 208 may be a protocol that terminates at eNB 102 on the network side. Also, in the E-UTRA CP protocol, NAS (Non Access Stratum) 210, which is the non-AS (Access Stratum) layer, may be a protocol between UE 122 and MME. In other words, NAS 210 may be a protocol that terminates at MME on the network side.

Figure 3(B) is a diagram of the NR control plane (CP) protocol configuration. As shown in Figure 3(B), in the NR CP protocol, RRC308, which is a radio resource control layer, may be a protocol between UE122 and gNB108. In other words, RRC308 may be a protocol that terminates at gNB108 on the network side. Also, in the NR CP protocol, NAS312, which is a non-AS layer, may be a protocol between UE122 and AMF. In other words, NAS312 may be a protocol that terminates at AMF on the network side.

The AS (Access Stratum) layer may be a layer that terminates between the UE 122 and the eNB 102 and/or the gNB 108. In other words, the AS layer may be a layer that includes some or all of the PHY 200, the MAC 202, the RLC 204, the PDCP 206, and the RRC 208, and/or a layer that includes some or all of the PHY 300, the MAC 302, the RLC 304, the PDCP 306, the SDAP 310, and the RRC 308.

In this embodiment, the terms PHY (PHY layer), MAC (MAC layer), RLC (RLC layer), PDCP (PDCP layer), RRC (RRC layer), and NAS (NAS layer) may be used without distinguishing between the E-UTRA protocol and the NR protocol. In this case, PHY (PHY layer), MAC (MAC layer), RLC (RLC layer), PDCP (PDCP layer), RRC (RRC layer), and NAS (NAS layer) may respectively refer to the PHY (PHY layer), MAC (MAC layer), RLC (RLC layer), PDCP (PDCP layer), RRC (RRC layer), and NAS (NAS layer) of the E-UTRA protocol, or the PHY (PHY layer), MAC (MAC layer), RLC (RLC layer), PDCP (PDCP layer), RRC (RRC layer), and NAS (NAS layer) of the NR protocol. The SDAP (SDAP layer) may also be the SDAP (SDAP layer) of the NR protocol.

In this embodiment, when distinguishing the E-UTRA protocol from the NR protocol, PHY200, MAC202, RLC204, PDCP206, and RRC208 may be referred to as E-UTRA PHY or LTE PHY, E-UTRA MAC or LTE MAC, E-UTRA RLC or LTE RLC, E-UTRA PDCP or LTE PDCP, and E-UTRA RRC or LTE RRC, respectively. PHY200, MAC202, RLC204, PDCP206, and RRC208 may be referred to as E-UTRA PHY or LTE PHY, E-UTRA MAC or LTE MAC, E-UTRA RLC or LTE RLC, E-UTRA PDCP or LTE PDCP, and E-UTRA RRC or LTE RRC, respectively. Also, when distinguishing NR protocols from E-UTRA protocols, PHY300, MAC302, RLC304, PDCP306, and RRC308 are sometimes referred to as NR PHY, NR MAC, NR RLC, NR RLC, and NR RRC, respectively. Also, PHY300, MAC302, RLC304, PDCP306, and RRC308 are sometimes referred to as NR PHY, NR MAC, NR RLC, NR PDCP, and NR RRC, respectively.

　Describes entities in the AS layer of E-UTRA and/or NR. An entity having some or all of the functions of the MAC layer may be called a MAC entity. An entity having some or all of the functions of the RLC layer may be called an RLC entity. An entity having some or all of the functions of the PDCP layer may be called a PDCP entity. An entity having some or all of the functions of the SDAP layer may be called an SDAP entity. An entity having some or all of the functions of the RRC layer may be called an RRC entity. The MAC entity, RLC entity, PDCP entity, SDAP entity, and RRC entity may be referred to as MAC, RLC, PDCP, SDAP, and RRC, respectively.

In addition, data provided from MAC, RLC, PDCP, and SDAP to lower layers, and/or data provided from lower layers to MAC, RLC, PDCP, and SDAP may be referred to as MAC PDU (Protocol Data Unit), RLC PDU, PDCP PDU, and SDAP PDU, respectively. Data provided from higher layers to MAC, RLC, PDCP, and SDAP, and/or data provided from MAC, RLC, PDCP, and SDAP to higher layers may be referred to as MAC SDU (Service Data Unit), RLC SDU, PDCP SDU, and SDAP SDU, respectively. In addition, a segmented RLC SDU may be referred to as an RLC SDU segment.

Here, the base station device and the terminal device exchange (send and receive) signals at a higher layer. The higher layer may be referred to as the upper layer, and the terms may be interchangeable. For example, the base station device and the terminal device may send and receive RRC messages (also referred to as RRC signaling) at the Radio Resource Control (RRC) layer. The base station device and the terminal device may also send and receive MAC control elements at the Medium Access Control (MAC) layer. The RRC layer of the terminal device acquires system information reported from the base station device. Here, the RRC message, system information, and/or MAC control elements are also referred to as higher layer signals (higher layer signaling) or higher layer parameters (higher layer parameters). Each of the parameters included in the higher layer signals received by the terminal device may be referred to as a higher layer parameter. For example, in PHY layer processing, a higher layer means a higher layer as seen from the PHY layer, and may mean one or more of the MAC layer, RRC layer, RLC layer, PDCP layer, NAS (Non Access Stratum) layer, etc. For example, in MAC layer processing, a higher layer may mean one or more of the RRC layer, RLC layer, PDCP layer, NAS layer, etc.

Hereinafter, the meaning of "A is given (provided) by the upper layer" or "A is given (provided) by the upper layer" may mean that the upper layer (mainly the RRC layer or MAC layer, etc.) of the terminal device receives A from the base station device, and the received A is given (provided) from the upper layer of the terminal device to the physical layer of the terminal device. For example, in a terminal device, "upper layer parameters are provided" may mean that an upper layer signal is received from the base station device, and the upper layer parameters included in the received upper layer signal are provided from the upper layer of the terminal device to the physical layer of the terminal device. Setting upper layer parameters in a terminal device may mean that the upper layer parameters are given (provided) to the terminal device. For example, setting upper layer parameters in a terminal device may mean that the terminal device receives an upper layer signal from the base station device, and sets the received upper layer parameters in the upper layer. However, setting upper layer parameters in a terminal device may include setting default parameters that are given in advance to the upper layer of the terminal device. When explaining the transmission of an RRC message from a terminal device to a base station device, the expression "submitting a message from the RRC entity of the terminal device to the lower layer (lower layer)" may be used. In a terminal device, "submitting a message to a lower layer" from an RRC entity may mean submitting a message to the PDCP layer. In a terminal device, "submitting a message to a lower layer" from the RRC layer may mean submitting the message to the PDCP entity corresponding to each SRB, since RRC messages are transmitted using SRBs (SRB0, SRB1, SRB2, SRB3, etc.). When the RRC entity of the terminal device receives an indication from a lower layer, the lower layer may mean one or more of the PHY layer, MAC layer, RLC layer, PDCP layer, etc.

An example of the functions of the PHY will be described. The PHY of the terminal device may have a function of receiving data transmitted from the PHY of the base station device via a downlink (DL) physical channel. The PHY of the terminal device may have a function of transmitting data to the PHY of the base station device via an uplink (UL) physical channel. The PHY may be connected to an upper MAC via a transport channel. The PHY may pass data to the MAC via the transport channel. The PHY may also be provided with data from the MAC via the transport channel. In the PHY, a Radio Network Temporary Identifier (RNTI) may be used to identify various control information.

Here, we will explain physical channels. The physical channels used for wireless communication between a terminal device and a base station device may include the following physical channels:

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)

The PBCH may be used to notify the terminal device of system information required.

In addition, in NR, the PBCH may be used to report the time index (SSB-Index) within the period of a synchronization signal block (SSB).

The PDCCH may be used to transmit (or carry) downlink control information (DCI) in downlink wireless communication (wireless communication from a base station device to a terminal device). Here, one or more DCIs (which may also be referred to as DCI formats) may be defined for the transmission of the downlink control information. That is, a field for the downlink control information may be defined as a DCI and mapped to information bits. The PDCCH may be transmitted in PDCCH candidates. The terminal device may monitor a set of PDCCH candidates in a serving cell. Monitoring a set of PDCCH candidates may mean attempting to decode the PDCCH according to a certain DCI format. In addition, the terminal device may monitor the PDCCH candidates in configured monitoring occasions in one or more configured control resource sets (CORESET: Control Resource Set) configured by search space configuration. The DCI format may be used for scheduling the PUSCH in the serving cell. The PUSCH may be used to transmit user data and RRC messages, which are described below.

PDCCH repetition may be operated by using two search space sets that are explicitly linked by a configuration provided by a higher layer (RRC layer), and the two linked search space sets may be associated with a corresponding CORESET. For PDCCH repetition, the two linked search space sets may be configured in the terminal device with the same number of PDCCH candidates. The two PDCCH candidates present in the two linked search space sets may be linked by the same candidate index. When PDCCH repetition is scheduled in the terminal device, inter-slot repetition may be allowed, and each repetition may have the same number of Control Channel Elements (CCEs) and coded bits, and the same DCI payload.

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: Channel State Information) used to indicate the state of the downlink channel. The uplink control information may also include a scheduling request (SR: Scheduling Request) used to request UL-SCH (UL-SCH: Uplink Shared CHannel) resources. The uplink control information may also include a hybrid automatic repeat reQuest ACKnowledgement (HARQ-ACK).

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

PUSCH may be used to transmit uplink data from the MAC layer (UL-SCH: Uplink Shared CHannel) or HARQ-ACK and/or CSI together with uplink data. PUSCH may also be used to transmit only CSI, or only HARQ-ACK and CSI. That is, PUSCH may be used to transmit only UCI. PDSCH or PUSCH may also be used to transmit RRC messages and MAC CE, which will be described later. Here, in the PDSCH, the RRC message transmitted from the base station device may be common signaling for multiple terminal devices in the cell. The RRC message transmitted from the base station device may also be 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. PUSCH may also be used to transmit UE capabilities in the uplink.

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

An example of the functions of the MAC is described below. The MAC may be called a MAC sublayer. The MAC may have the function of mapping various logical channels to corresponding transport channels. The logical channels may be identified by a logical channel identifier (Logical Channel Identity, or Logical Channel ID). The MAC may be connected to the higher-level RLC via a logical channel. Depending on the type of information being transmitted, the logical channels may be divided into a control channel that transmits control information and a traffic channel that transmits user information. The logical channels may also be divided into an uplink logical channel and a downlink logical channel. The MAC may have the function of multiplexing MAC SDUs belonging to one or more different logical channels and providing them to the PHY. The MAC may also have the function of demultiplexing the MAC PDUs provided by the PHY and providing them to the higher layer via the logical channel to which each MAC SDU belongs. The MAC may also have the function of performing error correction through HARQ (Hybrid Automatic Repeat reQuest). The MAC may also have a Scheduling Report (SR) function to report scheduling information. The MAC may have the function of performing priority processing between terminal devices using dynamic scheduling. The MAC may also have the function of performing priority processing between logical channels within one terminal device. The MAC may have the function of performing priority processing of overlapping resources within one terminal device. The E-UTRA MAC may have the function of identifying Multimedia Broadcast Multicast Services (MBMS). The NR MAC may have the function of identifying Multicast/broadcast services (MBS). The MAC may have the function of selecting a transport format. The MAC may have functions such as discontinuous reception (DRX) and/or discontinuous transmission (DTX), a function to execute random access (RA) procedures, a power headroom report (PHR) function to notify information on the transmit power available, and a buffer status report (BSR) function to notify information on the amount of data in the transmit buffer. The NR MAC may have a bandwidth adaptation (BA) function. The MAC PDU format used in the E-UTRA MAC may differ from the MAC PDU format used in the NR MAC. The MAC PDU may also include a MAC control element (MAC CE), which is an element for performing control in the MAC.

This article explains the logical channels for the uplink (UL) and/or downlink (DL) used in E-UTRA and/or NR.

The BCCH (Broadcast Control Channel) may be a downlink logical channel for broadcasting control information such as system information (SI).

PCCH (Paging Control Channel) may be a downlink logical channel for carrying paging messages.

The Common Control Channel (CCCH) may be a logical channel for transmitting control information between a terminal device and a base station device. The CCCH may be used when the terminal device does not have an RRC connection. The CCCH may also be used between a base station device and multiple terminal devices.

　DCCH (Dedicated Control Channel) may be a logical channel for transmitting dedicated control information in a point-to-point bidirectional manner between a terminal device and a base station device. The dedicated control information may be control information dedicated to each terminal device. DCCH may be used when the terminal device has an RRC connection.

DTCH (Dedicated Traffic Channel) may be a logical channel for transmitting user data point-to-point between a terminal device and a base station device. DTCH may be a logical channel for transmitting dedicated user data. Dedicated user data may be user data dedicated to each terminal device. DTCH may exist in both the uplink and downlink.

　Describes the mapping of logical channels and transport channels for the uplink in E-UTRA and/or NR.

The CCCH may be mapped to the uplink transport channel, UL-SCH (Uplink Shared Channel).

The DCCH may be mapped to the uplink transport channel, UL-SCH (Uplink Shared Channel).

The DTCH may be mapped to the uplink transport channel, UL-SCH (Uplink Shared Channel).

Describes the mapping of logical channels and transport channels for the downlink in E-UTRA and/or NR.

The BCCH may be mapped to the downlink transport channels BCH (Broadcast Channel) and/or DL-SCH (Downlink Shared Channel).

The PCCH may be mapped to the PCH (Paging Channel), which is a downlink transport channel.

The CCCH may be mapped to the downlink transport channel, DL-SCH (Downlink Shared Channel).

The DCCH may be mapped to the downlink transport channel, DL-SCH (Downlink Shared Channel).

DTCH may be mapped to the downlink transport channel, DL-SCH (Downlink Shared Channel).

An example of the RLC function is described below. RLC may be called an RLC sublayer. E-UTRA RLC may have the function of segmenting and/or concatenating data provided from the upper layer PDCP and providing it to the lower layer. E-UTRA RLC may have the function of reassembling and reordering data provided from the lower layer and providing it to the upper layer. NR RLC may have the function of adding a sequence number independent of the sequence number added by PDCP to data provided from the upper layer PDCP. NR RLC may also have the function of segmenting data provided from PDCP and providing it to the lower layer. NR RLC may also have the function of reassembling data provided from the lower layer and providing it to the upper layer. RLC may also have the function of retransmitting data and/or requesting retransmission (Automatic Repeat reQuest: ARQ). RLC may also have the function of performing error correction through ARQ. The control information sent from the receiving side of RLC to the transmitting side to perform ARQ, indicating the data that needs to be retransmitted, may be called a status report. The instruction to send a status report sent from the transmitting side of RLC to the receiving side may be called a poll. RLC may also have the function of detecting data duplication. RLC may also have the function of discarding data. RLC may have three modes: Transparent Mode (TM), Unacknowledged Mode (UM), and Acknowledged Mode (AM). In TM, data received from the upper layer is not divided, and an RLC header does not need to be added. The TM RLC entity is a uni-directional entity and may be configured as a transmitting TM RLC entity or a receiving TM RLC entity. In UM, the data received from the upper layer may be divided and/or combined, an RLC header may be added, etc., but data retransmission control is not required. The UM RLC entity may be a unidirectional entity or a bi-directional entity. If the UM RLC entity is a unidirectional entity, it may be configured as a transmitting UM RLC entity or a receiving UM RLC entity. If the UM RLC entity is a bi-directional entity, the UM RRC entity may be configured as a UM RLC entity consisting of a transmitting side and a receiving side. In AM, the data received from the upper layer may be divided and/or combined, an RLC header may be added, data retransmission control is required, etc. The AM RLC entity is a bi-directional entity and may be configured as an AM RLC consisting of a transmitting side and a receiving side. Note that data provided to the lower layer in TM and/or data provided from the lower layer may be called TMD PDU. Furthermore, data provided to a lower layer in UM and/or data provided by a lower layer may be referred to as a UMD PDU. Data provided to a lower layer in AM and/or data provided by a lower layer may be referred to as an AMD PDU. The RLC PDU format used in E-UTRA RLC may be different from the RLC PDU format used in NR RLC. Furthermore, RLC PDUs may include RLC PDUs for data and RLC PDUs for control. The RLC PDUs for data may be referred to as RLC DATA PDU (RLC Data PDU, RLC Data PDU). The RLC PDUs for control may be referred to as RLC CONTROL PDU (RLC Control PDU, RLC Control PDU, RLC Control PDU).

An example of the functions of PDCP is described below. PDCP may be called a PDCP sublayer. PDCP may have a function for maintaining sequence numbers. PDCP may also have a header compression/decompression function for efficiently transmitting user data such as IP packets and Ethernet frames over wireless sections. The protocol used for IP packet header compression/decompression may be called the ROHC (Robust Header Compression) protocol. The protocol used for Ethernet frame header compression/decompression may be called the EHC (Ethernet (registered trademark) Header Compression) protocol. PDCP may also have a data encryption/decryption function. PDCP may also have a data integrity protection/integrity verification function. PDCP may also have a re-ordering function. PDCP may also have a PDCP SDU retransmission function. PDCP may also have a data discard function using a discard timer. PDCP may also have a duplication function. PDCP may also have the function of discarding duplicated data received. The PDCP entity is a bidirectional entity and may consist of a transmitting PDCP entity and a receiving PDCP entity. The PDCP PDU format used in E-UTRA PDCP may differ from the PDCP PDU format used in NR PDCP. PDCP PDUs may include data PDCP PDUs and control PDCP PDUs. The data PDCP PDU may be called PDCP DATA PDU (PDCP Data PDU, PDCP Data PDU). The control PDCP PDU may be called PDCP CONTROL PDU (PDCP Control PDU, PDCP Control PDU, PDCP Control PDU).

An example of the SDAP function is described below. SDAP is a service data adaptation protocol layer. SDAP may have a function of mapping the downlink QoS flow sent from 5GC110 to the terminal device via the base station device with a data radio bearer (DRB), and/or mapping the uplink QoS flow sent from the terminal device to 5GC110 via the base station device with a DRB. SDAP may also have a function of storing mapping rule information. SDAP may also have a function of marking the QoS flow identifier (QoS Flow ID: QFI). Note that there may be an SDAP PDU for data and an SDAP PDU for control. The SDAP PDU for data may be called the SDAP DATA PDU (SDAP Data PDU, SDAP Data PDU). The SDAP PDU for control may be called the SDAP CONTROL PDU (SDAP Control PDU, SDAP Control PDU, SDAP Control PDU). There may be one SDAP entity in a terminal device for each PDU session.

An example of the functions of RRC will be described. RRC may have a broadcast function. RRC may have a paging function from EPC104 and/or 5GC110. RRC may have a paging function from eNB102 connected to gNB108 or 5GC110. RRC may also have an RRC connection management function. RRC may also have a radio bearer control function. RRC may also have a cell group control function. RRC may also have a mobility control function. RRC may also have terminal device measurement reporting and terminal device measurement reporting control functions. RRC may also have a QoS management function. RRC may also have a radio link failure detection and recovery function. RRC may use RRC messages to perform notification, paging, RRC connection management, radio bearer control, cell group control, mobility control, terminal device measurement reporting and terminal device measurement reporting control, QoS management, detection and recovery of radio link failures, etc. Note that the RRC messages and parameters used in E-UTRA RRC may differ from the RRC messages and parameters used in NR RRC.

The RRC message may be sent using the logical channel BCCH, the logical channel PCCH, the logical channel CCCH, or the logical channel DCCH. RRC messages sent using the DCCH are called Dedicated RRC signaling, or RRC signaling.

RRC messages sent using the BCCH may include, for example, a Master Information Block (MIB), various types of System Information Blocks (SIBs), and other RRC messages. RRC messages sent using the PCCH may include, for example, paging messages, and other RRC messages.

RRC messages sent in the uplink (UL) direction using the CCCH may include, for example, an RRC setup request message (RRC Setup Request), an RRC resume request message (RRC Resume Request), an RRC reestablishment request message (RRC Reestablishment Request), an RRC system information request message (RRC System Info Request), etc. They may also include, for example, an RRC connection request message (RRC Connection Request), an RRC connection resume request message (RRC Connection Resume Request), an RRC connection reestablishment request message (RRC Connection Reestablishment Request), etc. They may also include other RRC messages.

RRC messages sent in the downlink (DL) direction using the CCCH may include, for example, an RRC connection reject message (RRC Connection Reject), an RRC connection setup message (RRC Connection Setup), an RRC connection reestablishment message (RRC Connection Reestablishment Reject), an RRC connection reestablishment reject message (RRC Connection Reestablishment Reject), etc. They may also include, for example, an RRC reject message (RRC Reject), an RRC setup message (RRC Setup), etc. They may also include other RRC messages.

RRC signalling sent in the uplink (UL) direction using the DCCH may include, for example, a measurement report message (Measurement Report), an RRC connection reconfiguration complete message (RRC Connection Reconfiguration Complete), an RRC connection setup complete message (RRC Connection Setup Complete), an RRC connection reestablishment complete message (RRC Connection Reestablishment Complete), a security mode complete message (Security Mode Complete), and a UE capability information message (UE Capability Information). It may also include, for example, a measurement report message (Measurement Report), an RRC reconfiguration complete message (RRC Reconfiguration Complete), an RRC setup complete message (RRC Setup Complete), an RRC reestablishment complete message (RRC Resumé Complete), a security mode complete message (Security Mode Complete), a UE capability information message (UE Capability Information), etc. It may also include other RRC signaling.

The RRC signaling sent in the downlink (DL) direction using the DCCH may include, for example, an RRC connection reconfiguration message (RRC Connection Reconfiguration), an RRC connection release message (RRC Connection Release), a security mode command message (Security Mode Command), a UE capability enquiry message (UE Capability Enquiry), etc. It may also include, for example, an RRC reconfiguration message (RRC Reconfiguration), an RRC resume message (RRC Resume), an RRC release message (RRC Release), an RRC reestablishment message (RRC Reestablishment), a security mode command message (Security Mode Command), a UE capability enquiry message (UE Capability Enquiry), etc. It may also include other RRC signaling.

An example of NAS functions is described below. The NAS may have an authentication function. The NAS may also have a mobility management function. The NAS may also have a security control function.

The above-mentioned PHY, MAC, RLC, PDCP, SDAP, RRC, and NAS functions are just examples, and some or all of the functions may not be implemented. In addition, some or all of the functions of each layer may be included in other layers.

Next, state transitions of UE122 in LTE and NR will be described. When UE122 connected to EPC or 5GC has an RRC connection established, UE122 may be in the RRC_CONNECTED state. The state in which the RRC connection is established may include a state in which UE122 holds some or all of the UE context described below. The state in which the RRC connection is established may also include a state in which UE122 can transmit and/or receive unicast data. When the RRC connection is suspended, UE122 may be in the RRC_INACTIVE state. UE122 may be in the RRC_INACTIVE state when UE122 is connected to 5GC and the RRC connection is suspended. When UE122 is neither in the RRC_CONNECTED state nor in the RRC_INACTIVE state, UE122 may be in the RRC_IDLE state.

Note that when UE 122 is connected to the EPC, it does not have the RRC_INACTIVE state, but E-UTRAN may initiate suspension of the RRC connection. When UE 122 is connected to the EPC, UE 122 may transition to the RRC_IDLE state while retaining the UE AS context and an identifier (resumeIdentity) used for resumption (resume) when the RRC connection is suspended. A layer above the RRC layer of UE 122 (e.g., the NAS layer) may initiate restoration of the suspended RRC connection when UE 122 retains the UE AS context, E-UTRAN has permitted restoration of the RRC connection, and UE 122 needs to transition from the RRC_IDLE state to the RRC_CONNECTED state.

The definition of dormancy may be different for UE 122 connected to EPC 104 and UE 122 connected to 5GC 110. In addition, some or all of the procedures for UE 122 to return from dormancy may be different when UE 122 is connected to EPC (when UE 122 is dormant in RRC_IDLE state) and when UE 122 is connected to 5GC (when UE 122 is dormant in RRC_INACTIVE state).

The RRC_CONNECTED state, RRC_INACTIVE state, and RRC_IDLE state may be referred to as the connected state (connected mode), the inactive state (inactive mode), and the idle state (idle mode), respectively, or as the RRC connected state (RRC connected mode), the RRC inactive state (RRC inactive mode), and the RRC idle state (RRC idle mode).

The UE AS context held by UE122 may be information including all or part of the following: the current RRC settings, the current security context, the PDCP state including the ROHC (RObust Header Compression) state, the C-RNTI (Cell Radio Network Temporary Identifier) used in the source PCell, the cell identifier, and the physical cell identifier of the source PCell. Note that the UE AS context held by any or all of eNB102 and gNB108 may include the same information as the UE AS context held by UE122, or may include information different from the information included in the UE AS context held by UE122.

The security context may be information that includes all or part of the encryption key at the AS level, the Next Hop parameter (NH), the 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.

Next, the serving cell will be described. In a terminal device in an RRC connected state where CA and/or DC, which will be described later, are not configured, the serving cell may be composed of one primary cell (PCell). In addition, in a terminal device in an RRC connected state where CA and/or DC, which will be described later, are configured, the multiple serving cells may refer to a set of multiple cells (set of cell(s)) composed of one or more special cells (SpCells) and one or more all secondary cells (SCells). The SpCell may support PUCCH transmission and contention-based random access (CBRA), and the SpCell may be always activated. The PCell may be a cell used in the RRC connection establishment procedure when a terminal device in an RRC idle state transitions to an RRC connected state. The PCell may also be a cell used in the RRC connection re-establishment procedure in which the terminal device re-establishes the RRC connection. The PCell may be a cell used in a random access procedure during handover. The PSCell may be a cell used in a random access procedure when adding a secondary node, which will be described later. The SpCell may be a cell used for purposes other than those mentioned above.

When a group of serving cells configured for a terminal device is composed of an SpCell and one or more SCells, it may be considered that carrier aggregation (CA) is configured for the terminal device. Furthermore, for a terminal device in which CA is configured, a cell providing additional radio resources to the SpCell may refer to an SCell.

This section describes cell groups, which are set by a base station device for a terminal device. A cell group may be composed of one SpCell. A cell group may also be composed of one SpCell and one or more SCells. In other words, a cell group may be composed of one SpCell and, optionally, one or more SCells. A cell group may also be expressed as a set of cells (set of cell(s)).

Dual Connectivity (DC) may be a technology for performing data communication using radio resources of cell groups respectively configured by a first base station device (first node) and a second base station device (second node). When DC or MR-DC, which will be described later, is performed, a cell group may be added from the base station device to the terminal device. To perform DC, the first base station device may add a second base station device. The first base station device may be called a master node (MN). Furthermore, the cell group configured by the master node may be called a master cell group (MCG). The second base station device may be called a secondary node (SN). Furthermore, the cell group configured by the secondary node may be called a secondary cell group (SCG). The master node and the secondary node may be configured within the same base station device.

In addition, when DC is not configured, the cell group configured in the terminal device may be called MCG. In addition, when DC is not configured, the SpCell configured in the terminal device may be a PCell. In addition, NR in which DC is not configured may be called NR standalone (NR SA).

Multi-Radio Dual Connectivity (MR-DC) may be a technology that performs DC using E-UTRA for MCG and NR for SCG. MR-DC may be a technology that performs DC using NR for MCG and E-UTRA for SCG. MR-DC may be a technology that performs DC using NR for both MCG and SCG. MR-DC may be a technology included in DC. An example of MR-DC that uses E-UTRA for MCG and NR for SCG may be EN-DC (E-UTRA-NR Dual Connectivity) that uses EPC in the core network, or NGEN-DC (NG-RAN E-UTRA-NR Dual Connectivity) that uses 5GC in the core network. An example of MR-DC that uses NR for MCG and E-UTRA for SCG may be NE-DC (NR-E-UTRA Dual Connectivity) that uses 5GC in the core network. Another example of MR-DC that uses NR for both MCG and SCG is NR-DC (NR-NR Dual Connectivity), which uses 5GC for the core network.

In addition, in the terminal device, one MAC entity may exist for each cell group. For example, when DC or MR-DC is configured in the terminal device, there may be one MAC entity for the MCG and one MAC entity for the SCG. The MAC entity for the MCG in the terminal device may always be established in the terminal device in all states (RRC idle state, RRC connected state, RRC inactive state, etc.). The MAC entity for the SCG in the terminal device may be created by the terminal device when the SCG is configured in the terminal device. The MAC entity for each cell group in the terminal device may be configured by the terminal device receiving RRC signaling from the base station device. When the MAC entity is associated with the MCG, the SpCell may mean the PCell. When the MAC entity is associated with the SCG, the SpCell may mean the primary SCG cell (PSCell). When the MAC entity is not associated with a cell group, the SpCell may mean the PCell. The PCell, PSCell, and SCell are serving cells. In EN-DC and NGEN-DC, the MAC entity for the MCG may be an E-UTRA MAC entity, and the MAC entity for the SCG may be an NR MAC entity. Also, in NE-DC, the MAC entity for the MCG may be an NR MAC entity, and the MAC entity for the SCG may be an E-UTRA MAC entity. Also, in NR-DC, the MAC entities for both the MCG and SCG may be NR MAC entities. Note that the existence of one MAC entity for each cell group may be rephrased as the existence of one MAC entity for each SpCell. Also, one MAC entity for each cell group may be rephrased as one MAC entity for each SpCell.

　Explains radio bearers. When a terminal device communicates with a base station device, a wireless connection may be established by establishing a radio bearer (RB: Radio Bearer) between the terminal device and the base station device. The radio bearer used for CP may be called a signaling radio bearer (SRB: Signaling Radio Bearer). The radio bearer used for UP may be called a data radio bearer (DRB: Data Radio Bearer). Each radio bearer may be assigned a radio bearer identity (ID). The radio bearer identifier for an SRB may be called an SRB identifier (SRB Identity, or SRB ID). The radio bearer identifier for a DRB may be called a DRB identifier (DRB Identity, or DRB ID). SRB0 to SRB2 may be defined as SRBs for E-UTRA, and other SRBs may also be defined. NR SRBs may be defined as SRB0 to SRB3, or other SRBs may be defined. SRB0 may be an SRB for RRC messages, which are transmitted and/or received using the logical channel CCCH. SRB1 may be an SRB for RRC signaling and for NAS signaling before the establishment of SRB2. The RRC signaling transmitted and/or received using SRB1 may include piggybacked NAS signaling. The logical channel DCCH may be used for all RRC and NAS signaling transmitted and/or received using SRB1. SRB2 may be an SRB for NAS signaling and for RRC signaling including logged measurement information. The logical channel DCCH may be used for all RRC and NAS signaling transmitted and/or received using SRB2. SRB2 may also have a lower priority than SRB1. SRB3 may be an SRB for transmitting and/or receiving specific RRC signaling when EN-DC, NGEN-DC, NR-DC, etc. are configured in the terminal device. The logical channel DCCH may be used for all RRC signaling and NAS signaling transmitted and/or received using SRB3. Other SRBs may also be provided for other uses. DRB may be a radio bearer for user data. The logical channel DTCH may be used for RRC signaling transmitted and/or received using the DRB.

The following describes the radio bearer in the terminal device. The radio bearer may include an RLC bearer. The RLC bearer may be composed of one or two RLC entities and logical channels. When there are two RLC entities in an RLC bearer, the RLC entities may be a TM RLC entity, and/or a transmitting RLC entity and a receiving RLC entity in a unidirectional UM mode RLC entity. SRB0 may be composed of one RLC bearer. The RLC bearer of SRB0 may be composed of a TM RLC entity and a logical channel. SRB0 may always be established in the terminal device in all states (RRC idle state, RRC connected state, RRC inactive state, etc.). SRB1 may be established and/or configured in the terminal device by RRC signaling received from the base station device when the terminal device transitions from the RRC idle state to the RRC connected state. SRB1 may be composed of one PDCP entity and one or more RLC bearers. The RLC bearer of SRB1 may be composed of an AM RLC entity and a logical channel. SRB2 may be established and/or configured in the terminal device by RRC signaling received from the base station device by the terminal device in the RRC connected state with AS security activated. SRB2 may be composed of one PDCP entity and one or more RLC bearers. The RLC bearer of SRB2 may be composed of an RLC entity of AM and a logical channel. The PDCP of SRB1 and SRB2 on the base station device side may be placed in the master node. SRB3 may be established and/or configured in the terminal device by RRC signaling received from the base station device by the terminal device in the RRC connected state with AS security activated when a secondary node is added in EN-DC, NGEN-DC, or NR-DC, or when the secondary node is changed. SRB3 may be a direct SRB between the terminal device and the secondary node. SRB3 may be composed of one PDCP entity and one or more RLC bearers. The RLC bearer of SRB3 may be composed of an RLC entity of AM and a logical channel. The PDCP of SRB3 on the base station device side may be placed in the secondary node. One or more DRBs may be established and/or configured in a terminal device by RRC signaling received from a base station device by a terminal device in an RRC connected state with AS security activated. A DRB may consist of one PDCP entity and one or more RLC bearers. The RLC bearer of a DRB may consist of an AM or UM RLC entity and a logical channel.

In addition, in MR-DC, a radio bearer in which a PDCP is placed in the master node may be called an MN terminated bearer. Also, in MR-DC, a radio bearer in which a PDCP is placed in a secondary node may be called an SN terminated bearer. Also, in MR-DC, a radio bearer in which an RLC bearer exists only in an MCG may be called an MCG bearer. Also, in MR-DC, a radio bearer in which an RLC bearer exists only in an SCG may be called an SCG bearer. Also, in DC, a radio bearer in which an RLC bearer exists in both an MCG and an SCG may be called a split bearer.

When MR-DC is configured in a terminal device, the bearer type of SRB1 and SRB2 established and/or configured in the terminal device may be MN terminated MCG bearer and/or MN terminated split bearer. Also, when MR-DC is configured in a terminal device, the bearer type of SRB3 established and/or configured in the terminal device may be SN terminated SCG bearer. Also, when MR-DC is configured in a terminal device, the bearer type of DRB established and/or configured in the terminal device may be any of all bearer types.

For an RLC bearer established and/or configured in a cell group consisting of E-UTRA, the RLC entity established and/or configured may be an E-UTRA RLC. For an RLC bearer established and/or configured in a cell group consisting of NR, the RLC entity established and/or configured may be an NR RLC. When an EN-DC is configured in the terminal device, the PDCP entity established and/or configured for an MN terminated MCG bearer may be either an E-UTRA PDCP or an NR PDCP. When an EN-DC is configured in the terminal device, the PDCP entity established and/or configured for radio bearers of other bearer types, i.e., MN terminated split bearers, MN terminated SCG bearers, SN terminated MCG bearers, SN terminated split bearers, and SN terminated SCG bearers, may be an NR PDCP. When an NGEN-DC, NE-DC, or NR-DC is configured in the terminal device, the PDCP entity established and/or configured for radio bearers of all bearer types may be an NR PDCP.

In addition, in NR, a DRB established and/or configured in a terminal device may be linked to one PDU session. One SDAP entity may be established and/or configured for one PDU session in the terminal device. The SDAP entity, PDCP entity, RLC entity, and logical channels established and/or configured in the terminal device may be established and/or configured by RRC signaling received by the terminal device from the base station device.

Note that regardless of whether MR-DC is configured, a network configuration in which the master node is eNB102 and EPC104 is the core network may be called E-UTRA/EPC. A network configuration in which the master node is eNB102 and 5GC110 is the core network may be called E-UTRA/5GC. A network configuration in which the master node is gNB108 and 5GC110 is the core network may be called NR or NR/5GC. When MR-DC is not configured, the above-mentioned master node may refer to a base station device that communicates with a terminal device.

The following describes the flow of RRC signaling transmitted and received between a terminal device and a base station device. Figure 4 is a diagram showing an example of the flow of procedures for various settings in the RRC according to this embodiment. Figure 4 shows an example of the flow when RRC signaling is sent from a base station device (eNB102 and/or gNB108) to a terminal device (UE122).

In FIG. 4, the base station device creates an RRC message (step S400). The base station device may create an RRC message in order to deliver system information (SI) or a paging message. The base station device may also create an RRC message in order to transmit RRC signaling for a specific terminal device to perform a process. The process to be performed by a specific terminal device may include, for example, security settings, RRC connection reconfiguration, handover to a different RAT, RRC connection suspension, and RRC connection release. The RRC connection reconfiguration process may include, for example, radio bearer control (establishment, modification, release, etc.), cell group control (establishment, addition, modification, release, etc.), measurement settings, handover, security key update, and other processes. The base station device may also create an RRC message in order to respond to RRC signaling transmitted from a terminal device. Responses to RRC signaling sent from a terminal device may include, for example, a response to an RRC setup request, a response to an RRC reconnection request, a response to an RRC resume request, etc. RRC messages include information (parameters) for various information notifications and settings. These parameters may be fields of RRC messages and/or information elements, or field values (including information elements). The structure of an RRC message may be described using a description method called ASN.1 (Abstract Syntax Notation One).

In FIG. 4, the base station device then transmits the created RRC signaling to the terminal device (step S402). The terminal device then performs processing such as setting according to the received RRC signaling described above if necessary (step S404). After performing the processing, the terminal device may transmit RRC signaling in response to the base station device (not shown).

RRC signaling may be used for other purposes, not limited to the above examples.

In addition, in MR-DC, the RRC on the master node side may be used to transfer RRC signaling for SCG side configuration (cell group configuration, radio bearer configuration, measurement configuration, etc.) between the terminal device. For example, in EN-DC or NGEN-DC, NR RRC signaling may be included in the form of a container in E-UTRA RRC signaling transmitted and received between eNB102 and UE122. Also, in NE-DC, E-UTRA RRC signaling may be included in the form of a container in NR RRC signaling transmitted and received between gNB108 and UE122. RRC signaling for SCG side configuration may be transmitted and received between the master node and secondary node.

Note that, regardless of whether MR-DC is used, the RRC signaling for E-UTRA transmitted from the eNB102 to the UE122 may include the RRC signaling for NR, and the RRC signaling for NR transmitted from the gNB108 to the UE122 may include the RRC signaling for E-UTRA.

Here, we explain the bandwidth part (BWP).

A BWP may be a part or the entire bandwidth of the serving cell. A BWP may also be referred to as a carrier BWP. One or more BWPs may be configured in a terminal device. A BWP may be configured by information included in system information associated with a synchronization signal detected in an initial cell search. A BWP may also be a frequency bandwidth (initial downlink BWP: initial DL BWP) associated with a frequency at which an initial cell search is performed. A BWP may also be configured by RRC signaling (e.g., Dedicated RRC signaling). A downlink BWP (DL BWP) and an uplink BWP (UL BWP) may also be configured separately. One or more uplink BWPs may be associated with one or more downlink BWPs. Furthermore, the correspondence between the uplink BWP and the downlink BWP may be a default correspondence, or it may be correspondence based on RRC signaling (e.g., Dedicated RRC signaling), or it may be correspondence based on physical layer signaling (e.g., Downlink Control Information (DCI) notified on the downlink control channel), or it may be a combination of these. Furthermore, a CORESET may be set in the DL BWP.

A BWP may consist of a group of consecutive physical radio blocks (PRBs: Physical Resource Blocks). Furthermore, parameters of the BWP of each component carrier (one or multiple BWPs) may be set for a connected terminal device. The parameters of the BWP of each component carrier may include some or all of the following: (A) cyclic prefix type, (B) subcarrier spacing, (C) frequency location of the BWP (e.g., the start location or center frequency location of the BWP on the low frequency side) (for example, the ARFCN may be used for the frequency location, or an offset from a specific subcarrier of the serving cell may be used. The offset unit may be a subcarrier unit or a resource block unit. Both the ARFCN and the offset may be set.), (D) bandwidth of the BWP (e.g., the number of PRBs), (E) resource configuration information of the control signal, (F) center frequency location of the SS block (for example, the ARFCN may be used for the frequency location, or an offset from a specific subcarrier of the serving cell may be used. The offset unit may be a subcarrier unit or a resource block unit. Both the ARFCN and the offset may be set.). The resource configuration information of the control signal may be included in the configuration of the BWP of at least some or all of the PCell and/or PSCell.

A terminal device may transmit and receive in an Active BWP among one or more configured BWPs. One or more BWPs may be configured in a serving cell associated with the terminal device. Among one or more BWPs configured for a serving cell associated with the terminal device, at a given time, up to one uplink BWP and/or up to one downlink BWP may be configured to be the Active BWP. An Active BWP in the downlink is also referred to as an Active DL BWP. An Active BWP in the uplink is also referred to as an Active UL BWP. Furthermore, among one or more BWPs configured in a terminal device, a BWP that is not an Active BWP may be referred to as an Inactive BWP.

Next, we will explain the activation/inactivation of BWPs. Activation of BWPs may mean activating a BWP or activating an inactive BWP. Inactivation of BWPs may mean inactivating a BWP or inactivating an active BWP. BWP switching in a serving cell may be used to activate an inactive BWP and inactivate an active BWP.

BWP switching may be controlled by the PDCCH indicating a downlink allocation or uplink grant, the BWP inactivity timer, RRC signaling, or the MAC entity itself for initiation of a random access procedure. Active BWP in the serving cell may be indicated by RRC or PDCCH.

For a serving cell in which the first active downlink BWP identifier (firstActiveDownlinkBWP-Id) and/or the first active uplink BWP identifier (firstActiveUplinkBWP-Id) have been (re)configured by RRC signaling (RRC reconfiguration message, RRC connection reconfiguration message, etc.), the MAC entity may perform the following (A) and/or (B).
(A) When the serving cell is not a PSCell of a cell group in which the SCG described below is inactivated, the downlink BWP and/or uplink BWP indicated by the first active downlink BWP identifier (firstActiveDownlinkBWP-Id) and/or the first active uplink BWP identifier (firstActiveUplinkBWP-Id), respectively, are regarded as the Active BWP.
(B) When the serving cell is a PSCell of a cell group in which the SCG described below is inactivated, the downlink BWP is switched to the BWP indicated by the first active downlink BWP identifier (firstActiveDownlinkBWP-Id).

Next, the BWP inactivity timer will be described. For each activated serving cell for which the BWP inactivity timer is set, the MAC entity performs the following (A). The BWP inactivity timer may be a timer named bwp-InactivityTimer.
(A) If the default downlink BWP identifier (defaultDownlinkBWP-Id) is configured and the Active DL BWP is not the BWP indicated by the identifier (dormantDownlinkBWP-Id), or if the default downlink BWP identifier (defaultDownlinkBWP-Id) is not configured, the Active DL BWP is not the initialDownlinkBWP, and the Active DL BWP is not the BWP indicated by the identifier (dormantDownlinkBWP-Id), the MAC entity performs the following (B) and (D).
(B) If a PDCCH addressed to the C-RNTI or CS-RNTI is received indicating a downlink assignment or uplink grant for an Active DL BWP, or if a PDCCH addressed to the C-RNTI or CS-RNTI is received indicating a downlink assignment or uplink grant for an Active DL BWP, or if a MAC PDU is sent with a configured uplink grant or a MAC PDU is received with a configured downlink assignment, the MAC entity performs the following (C).
(C) If no random access procedure associated with this serving cell is ongoing or an ongoing random access procedure associated with this serving cell is successfully completed by reception of a PDCCH addressed to the C-RNTI, start or restart the BWP inactivity timer associated with the Active DL BWP.
(D) If the BWP inactivity timer associated with an Active DL BWP expires, the MAC entity performs (E) below.
(E) If defaultDownlinkBWP-Id is set, perform BWP switching to the BWP indicated by this defaultDownlinkBWP-Id; if not, perform BWP switching to the initialDownlinkBWP.

Furthermore, if the MAC entity receives a PDCCH for BWP switching and switches the Active DL BWP, it performs the following (A).
(A) If a default downlink BWP identifier (defaultDownlinkBWP-Id) is set and the switched-to Active DL BWP is not the BWP indicated by its identifier (dormantDownlinkBWP-Id), and if the switched-to Active DL BWP is not the BWP indicated by dormantDownlinkBWP-Id, start or restart the BWP inactivity timer associated with the Active DL BWP.

In each active serving cell in which a BWP is configured, the MAC entity performs some or all of steps (A) to (H) of the following procedure BA if the BWP is active (Active BWP) and the Active DL BWP in that serving cell is not a dormant BWP.

(Processing BA)
(A) Transmit UL-SCH with that BWP.
(B) If a PRACH occasion is configured, send a RACH in that BWP.
(C) Monitor the PDCCH in that BWP.
(D) If PUCCH is configured, transmit PUCCH in that BWP.
(E) Report the CSI in that BWP.
(F) If SRS is configured, send SRS in that BWP.
(G) Receive DL-SCH on that BWP.
(H) (re)initialize all suspended configured uplink grants of grant type 1 in that Active BWP according to the stored configuration, if any.

A MAC entity shall, if a BWP is deactivated, do some or all of the following:
(A) Do not transmit UL-SCH in that BWP.
(B) Do not send a RACH in that BWP.
(C) Do not monitor the PDCCH in that BWP.
(D) Do not transmit PUCCH in that BWP.
(E) Failing to report a CSI in that BWP.
(F) Do not send SRS in that BWP.
(G) DL-SCH is not received on that BWP.
(H) Clear all configured downlink assignments and/or all configured uplink grants of grant type 2 configured in that BWP.
(I) Suspend all configured uplink grants of grant type 1 for that Inactive BWP.

Next, handover in LTE and NR will be described. Handover may be a process in which a terminal device in an RRC connected state changes the serving cell from a source SpCell to a target SpCell. Handover may be part of mobility control performed by RRC. In the terminal device, handover may be performed based on RRC signaling instructing a handover received from a base station device. The RRC signaling instructing a handover may be a message regarding reconfiguration of an RRC connection including an information element (e.g., a MobilityControlInfo information element, or a ReconfigurationWithSync information element) including a parameter instructing a handover. The MobilityControlInfo information element may be referred to as a mobility control setting information element, mobility control setting, or mobility control information. The ReconfigurationWithSync information element may be referred to as a reconfiguration with synchronization information element. Additionally or alternatively, the RRC signaling indicating the handover may be a message indicating a movement to a cell of another RAT (e.g., MobilityFromEUTRACommand or MobilityFromNRCommand). The handover may be triggered by the RRC. Additionally or alternatively, the handover may be triggered by a DCI or a MAC Control Element (MAC CE). The conditions under which the terminal device can perform a handover may include some or all of the following conditions: AS security is activated, an SRB2 is established, and at least one DRB is established.

An example of parameters included in a message regarding reconfiguration of an RRC connection is described below. Figure 7 shows an example of an ASN.1 description representing fields and/or information elements included in a message regarding reconfiguration of an RRC connection in NR in Figure 4.

Not only in FIG. 7, but also in the ASN.1 examples in this embodiment, <omitted> indicates that other information is omitted, not that it is part of the ASN.1 notation. Note that even in places where <omitted> is not written, information elements may be omitted. In this embodiment, the ASN.1 example represents an example of a parameter of the RRC signaling in this embodiment, and other names and notations may be used. In addition, in order to avoid complicating the explanation, the ASN.1 example shows only an example of main information closely related to this embodiment. Note that in each embodiment, parameters described in ASN.1 may not be distinguished into fields, information elements, etc., and may all be expressed as information elements. In each embodiment, fields and/or information elements described in ASN.1 included in RRC signaling may be referred to as information, and may be referred to as parameters in addition to or instead of information.

Note that the message regarding reconfiguration of the RRC connection may be an RRC reconfiguration message in NR. Also, the message regarding reconfiguration of the RRC connection may be an RRC connection reconfiguration message in E-UTRA.

In FIG. 7, a message regarding reconfiguration of an RRC connection may include an information element (CellGroupConfig information element) used for setting, changing, releasing, etc., a cell group of an NR MCG or SCG. A message regarding reconfiguration of an RRC connection may independently include a CellGroupConfig information element for setting an MCG and a CellGroupConfig information element for setting an SCG. The CellGroupConfig information element may be referred to as a cell group setting information element or a cell group setting.

The CellGroupConfig information element may include a cellGroupId information element as identifier information for identifying this cell group.

The CellGroupConfig information element may include an RLC-BearerConfig information element as information used to configure the RLC entity.

The CellGroupConfig information element may include a MAC-CellGroupConfig information element as information used to configure MAC parameters in that cell group.

The CellGroupConfig information element may include a PhysicalCellGroupConfig information element as information used to configure PHY (L1) parameters specific to that cell group.

The CellGroupConfig information element may include an SpCellConfig information element as information used to set parameters for the SpCell of the cell group. The SpCellConfig information element may be referred to as an SpCell configuration information element or an SpCell configuration.

The CellGroupConfig information element may include a SCellConfig information element for each SCell as information used to configure parameters for one or more SCells in the cell group. The SCellConfig information element may be referred to as a SCell configuration information element or a SCell configuration.

The MAC-CellGroupConfig information element may include a TAG-Config information element as information used to configure parameters related to the TAG. The TAG-Config information element may include one or more TAG identifiers (TAG-Id) configured in the terminal device and the value of the time adjustment timer corresponding to the TAG identifiers.

The SpCellConfig information element may include a ServingCellConfig information element as information used to configure terminal device specific (UE specific) parameters related to the SpCell. The SCellConfig information element may include this ServingCellConfig information element as information used to configure terminal device specific (UE specific) parameters related to the SCell. The CellGroupConfig information element may include a ServingCellConfig information element for each serving cell to configure terminal device specific parameters related to the SpCell and each SCell. Each ServingCellConfig information element may include a TAG identifier (TAG-Id) indicating which TAG in the cell group the serving cell belongs to. The ServingCellConfig information element may include not only terminal device specific parameters but also cell specific parameters.

The SpCellConfig information element may include a ReconfigurationWithSync information element as information including parameters necessary for processing synchronous reconfiguration from the source SpCell to the target SpCell. The ReconfigurationWithSync information element may be the synchronous reconfiguration information element described above. If the SpCellConfig information element of the MCG includes a ReconfigurationWithSync information element, the synchronous reconfiguration processing to the target SpCell may be a handover. If the SpCellConfig information element of the SCG includes a ReconfigurationWithSync information element, the synchronous reconfiguration processing to the target SpCell may be a PSCell addition or a PSCell change.

The ReconfigurationWithSync information element and the SCellConfig information element may include a ServingCellConfigCommon information element as information used to configure cell-specific parameters of the serving cell. The ServingCellConfigCommon information element may include parameters that are typically obtained from the SSB, MIB, or one or more SIBs of the cell when the terminal device accesses the cell from the idle state.

The ReconfigurationWithSync information element may include, for example, information on the value of the C-RNTI used in the cell group of the target SpCell. The ReconfigurationWithSync information element may include, for example, information required to execute a non-contention random access procedure in the target SpCell.

Figure 8 shows an example of an ASN.1 description representing fields and/or information elements related to the ServingCellConfigCommon information element contained in the SCellConfig information element and the ReconfigurationWithSync information element in the SpCellConfig information element in Figure 7.

The ServingCellConfigCommon information element may include the physical cell identifier (physCellId) of the cell.

The ServingCellConfigCommon information element may include a DownlinkConfigCommon information element as information that provides cell-specific (cell-common) downlink parameters. The DownlinkConfigCommon information element is also referred to as downlink common configuration.

The ServingCellConfigCommon information element may include an UplinkConfigCommon information element as information that provides cell-specific (cell-common) uplink parameters. The UplinkConfigCommon information element is also referred to as uplink common configuration.

The ServingCellConfigCommon information element may contain the value of N_{TA,offset} that applies to all uplink transmissions in that cell.

The DownlinkConfigCommon information element may include a FrequencyInfoDL information element as basic information regarding the downlink carrier and transmission on the downlink carrier. For example, the FrequencyInfoDL information element may include frequency information of the SSB.

The DownlinkConfigCommon information element may include a BWP-DownlinkCommon information element as the initial downlink BWP configuration for that cell. The BWP-DownlinkCommon information element is also referred to as the downlink BWP common configuration.

The BWP-DownlinkCommon information element may include a BWP information element as information for setting generic parameters of the BWP.

The BWP-DownlinkCommon information element may include a PDCCH-ConfigCommon information element as information for setting cell-specific parameters for the PDCCH of this BWP. The PDCCH-ConfigCommon information element is also referred to as a PDCCH common configuration.

The BWP-DownlinkCommon information element may include a PDSCH-ConfigCommon information element as information for setting cell-specific parameters for the PDSCH of this BWP. The PDSCH-ConfigCommon information element is also referred to as the PDSCH common configuration.

The PDCCH-ConfigCommon information element may include a SearchSpaceZero information element as information for setting parameters of the common search space (CSS) #0. This SearchSpaceZero information element may be included in the PDCCH-ConfigCommon information element only if the BWP is an initial downlink BWP.

The PDCCH-ConfigCommon information element may include a ControlResourceSetZero information element as information for setting parameters of the common CORESET#0 used in one or more common search spaces and one or more UE-specific search spaces. This ControlResourceSetZero information element may be included in the PDCCH-ConfigCommon information element only if the BWP is an initial downlink BWP.

The PDCCH-ConfigCommon information element may include a ControlResourceSet information element as information for setting additional common CORESET parameters.

The PDCCH-ConfigCommon information element may include a list (commonSearchSpaceList) of information elements (SearchSpace information elements) that indicate the configuration of one or more additional CSSs.

The PDCCH-ConfigCommon information element may include information (searchSpaceSIB1) indicating which CSS in the commonSearchSpaceList the search space setting for the system information (SIB1) is.

The PDCCH-ConfigCommon information element may include information (searchSpaceOtherSystemInformation) indicating which CSS in the commonSearchSpaceList the search space setting for system information (SIB2 and later) is.

The PDCCH-ConfigCommon information element may include information (pagingSearchSpace) indicating which CSS in the commonSearchSpaceList is used to set the search space for paging messages.

Note that each of the above information elements may include other information in addition to the information described above.

The RRC reconfiguration procedure will be described. The RRC reconfiguration procedure may be a procedure for a terminal device to modify an RRC connection based on a message related to reconfiguration of the RRC connection. The purpose of the RRC reconfiguration procedure may be some or all of the following (A) to (F).
(A) Establishing, modifying and/or releasing radio bearers; (B) Performing synchronized reconfiguration; (C) Setting up, modifying and/or releasing measurements; (D) Adding, modifying and/or releasing SCells and cell groups; (E) Adding, modifying and/or releasing conditional handover (CHO) configurations; (F) Adding, modifying and/or releasing conditional PSCell change (CPC) or conditional PSCell addition (CPA) configurations.

The base station device (network) may initiate an RRC reconfiguration procedure for a terminal device in the RRC_CONNECTED state. Note that "the base station device initiates an RRC reconfiguration procedure for a terminal device" may be rephrased as "the base station device sends a message regarding the reconfiguration of the RRC connection to the terminal device."

When the terminal device receives a message regarding reconfiguration of an RRC connection or when performing a conditional reconfiguration (CHO, CPA, or CPC), it may perform some or all of the following processes RRP (A) to (E).
(Processing RRP)
(A) If the message regarding the RRC connection reconfiguration includes a cell group configuration of the MCG, perform cell group configuration using the cell group configuration. In addition, if the cell group configuration includes an SpCell configuration including a synchronized reconfiguration information element, perform synchronized reconfiguration.
(B) If the message regarding the RRC connection reconfiguration includes a cell group configuration of the SCG, perform cell group configuration using the cell group configuration, and if the cell group configuration includes an SpCell configuration with a synchronized reconfiguration information element, perform synchronized reconfiguration.
(D) If the message regarding the reconfiguration of the RRC connection includes information regarding conditional reconfiguration, the information regarding the conditional reconfiguration is used to perform a configuration process for the conditional reconfiguration.
(E) Submit an RRC reconfiguration complete message to the lower layers (PHY, MAC, etc.) of the terminal device for transmission using the new settings.

In order to execute synchronous reconfiguration, the terminal device may perform some or all of the following processes RWS (A) to (E). "Executing synchronous reconfiguration" may be rephrased as "implementing synchronous reconfiguration" or "triggering synchronous reconfiguration."
(Processing RWS)
(A) If the frequencyInfoDL information element is included in the synchronization-assisted reconfiguration information element, it is determined that the target SpCell is a cell that is located at the SSB frequency indicated in the frequencyInfoDL information element and is indicated by the physical cell identifier included in the synchronization-assisted reconfiguration information element. If the frequencyInfoDL information element is not included in the synchronization-assisted reconfiguration information element, it is determined that the target SpCell is a cell that is located at the same SSB frequency as the source SpCell and is indicated by the physical cell identifier included in the synchronization-assisted reconfiguration information element.
(B) Initiate downlink synchronization to the target SpCell.
(C) If the timing information required for the random access procedure is not held, the MIB of the target SpCell is obtained.
(C) Reset the MAC entity of the cell group that is the target of synchronized reconfiguration.
(D) The value of the new UE identifier (newUE-Identity) included in the synchronized reconfiguration information element is applied as the C-RNTI for the cell group that is the target of the synchronized reconfiguration.
(E) Configure the RRC lower layers (PHY, etc.) according to the SpCell common settings.

Conditional reconfiguration will now be described. The network configures one or more conditional reconfiguration information elements for the terminal device, which causes the network to configure, for the terminal device, candidate target SpCells that correspond to the conditional reconfiguration information elements, respectively. The terminal device evaluates the state of the configured candidate target SpCells. The terminal device performs the evaluation and applies one of the conditional RRC reconfiguration information elements included in the conditional reconfiguration information elements associated with one or more candidate target SpCells that satisfy the execution conditions. The terminal device may also hold a list of entries (VarConditionalReconfig), described later, for conditional reconfiguration.

The conditional reconfiguration may be referred to as a conditional handover if the candidate target SpCell is an SpCell (i.e., a PCell) of an MCG. The conditional reconfiguration may also be referred to as a conditional PSCell addition and/or conditional PSCell change if the candidate target SpCell is an SpCell (i.e., a PSCell) of an SCG.

When the terminal device receives information about conditional reconfiguration (e.g., a conditional reconfiguration information element) as a setting process for conditional reconfiguration, and the information about the conditional reconfiguration includes an entry deletion list (condReconfigToRemoveList), the terminal device may delete (remove) the conditional reconfiguration settings specified in the entry deletion list from the settings held by the terminal device. Specifically, when an entry identifier (condReconfigId) included in the entry deletion list is included in the list of entries held by the terminal device, the terminal device may delete the entry corresponding to the entry identifier from the list of entries held by the terminal device.

In the following description, the list of conditional reset entries held by the terminal device is also simply referred to as the entry list. In other words, in the following description, "entry list" refers to the list of conditional reset entries held by the terminal device unless otherwise specified. The conditional reset entry list may also be a variable named VarConditionalReconfig. The entry identifier is also simply referred to as the entry identifier.

If the information regarding conditional reconfiguration includes an entry add/modify list (condReconfigToAddModList), the terminal device may add or modify the conditional reconfiguration settings included in the entry add/modify list to the settings held by the terminal device as a conditional reconfiguration configuration process. The entry add/modify list may be a list of one or more conditional reconfiguration information elements. Each entry may be configured by a conditional reconfiguration information element. The conditional reconfiguration information element may include an entry identifier, an execution condition, and a conditional RRC reconfiguration information element.

Specifically, when each entry identifier included in the entry addition/modification list exists in an entry of the entry list, the terminal device may perform the following processing (A) and/or (B).
(A) If an entry included in the addition/modification list of an entry includes an execution condition (condExecutionCond), the execution condition of an entry in the entry list that matches the entry identifier of this entry is replaced with the execution condition included in the addition/modification list of that entry.
(B) If an entry included in the additional modification list of an entry includes a conditional RRC reconfiguration information element (condRRCReconfig), the conditional RRC reconfiguration information element in the entry list that matches the entry identifier of this entry is replaced with the conditional RRC reconfiguration information element included in the additional modification list of that entry.

In addition, if an entry identifier included in the entry addition/modification list is not included in the entry list, the terminal device may add to the entry list a new entry corresponding to the entry identifier not included in the entry list.

Note that the entry deletion list may be a list of one or more entry identifiers to be deleted. Each entry included in the entry addition modification list includes an entry identifier and may additionally include an execution condition and/or a conditional RRC reconfiguration information element. Each entry may be associated with one of one or more candidate target SpCells. The entry identifier may be an identifier used to identify each entry of the CHO, CPA, and CPC. The entry list may include one or more entries. Each entry may include one entry identifier, one or more execution conditions, and one conditional RRC reconfiguration information element. If the entry list held by the terminal device does not include an entry, the terminal device may hold an empty list. The execution condition may be a condition that needs to be satisfied to trigger the execution of the conditional reconfiguration. The conditional RRC reconfiguration information element may be a message regarding the reconfiguration of the RRC connection that is applied when the execution condition is satisfied. The message regarding the reconfiguration of the RRC connection may be a message used to connect to the candidate target SpCell.

The terminal device may evaluate the execution conditions of the entries included in the entry list held by the terminal device. If the entry list held by the terminal device is empty or if the terminal device does not hold an entry list, it is not necessary to evaluate the execution conditions.

Executing a conditional reconfiguration may mean that the terminal device evaluates the execution conditions of entries included in an entry list held by the terminal device, and if one or more execution conditions are satisfied, applies a conditional RRC reconfiguration information element included in the entry that includes the execution condition. Applying a conditional RRC reconfiguration information element may mean executing an RRC reconfiguration procedure using the conditional RRC reconfiguration information element.

If there are multiple entries that satisfy the execution condition, the terminal device may select one entry from the multiple entries that satisfy the execution condition and apply the conditional RRC reconfiguration information element of the selected entry.

When a reset of the MAC entity is requested from an upper layer (e.g., RRC), the MAC entity of the terminal device may perform part or all of (A) to (O) of the following process MR. The reset of the MAC entity may be simply referred to as a MAC reset. When a partial reset of the MAC entity is requested from an upper layer (e.g., RRC), the MAC entity of the terminal device may perform part or all of (A) to (O) of the following process MR. The partial reset of the MAC entity may be simply referred to as a partial MAC reset. The process performed in the partial MAC reset may be a process in which only a part of the process performed in the MAC reset is performed. The process performed in the partial MAC reset may be a process in which some of the process performed in the MAC reset is not performed. The MAC entity of the terminal device may perform a MAC reset based on an instruction from the RRC entity of the terminal device to the MAC entity of the terminal device to perform an MAAC reset. Additionally or alternatively, the MAC entity of the terminal device may perform a partial MAC reset based on an instruction from the RRC entity of the terminal device to the MAC entity of the terminal device to perform a partial MAAC reset.

(Processing MR)
(A) The parameter Bj set for each logical channel is initialized to 0.
(B) Stop all running timers, except for some timers.
(C) If one or more time adjustment timers are set, all of those time adjustment timers are considered to have expired, and processing for the expiration of a time adjustment timer is carried out.
(D) Set the New Data Indicator (NDI) value of all uplink HARQ processes to 0.
(E) If there is a random access procedure in progress, stop the random access procedure.
(F) If there are explicitly signalled contention-free random access (CFRA) resources for 4-step and 2-step RA types, discard those resources.
(G) Flush the Msg3 buffer.
(H) Flush the MSGA buffer.
(I) If any Scheduling Request (SR) procedure has been triggered, cancel the SR procedure.
(J) If a Buffer Status Reporting (BSR) procedure has been triggered, cancel the BSR procedure.
(K) If a Power Headroom Reporting (PHR) procedure has been triggered, cancel the PHR procedure.
(L) Flush the soft buffers of all downlink HARQ processes.
(M) If any Beam Failure Reporting (BFR) has been triggered, cancel the BFR.
(N) If there is a Temporary C-RNTI, release the temporary C-RNTI.
(O) Reset all BFI_COUNTERs.

The terminal device may adjust the uplink transmission timing. For example, the terminal device may adjust the uplink transmission timing based on receiving a Timing Advance Command (TAC) MAC CE. A group of serving cells configured by RRC that uses the same timing reference cell and the same timing advance value for the cells in which the uplink is configured may be referred to as a Timing Advance Group (TAG). A TAG including the SpCell of a MAC entity may be referred to as a Primary Timing Advance Group (PTAG). TAGs other than the above PTAGs may be referred to as Secondary Timing Advance Groups (STAG). One or more of the TAGs may be independently configured for each cell group described below. In addition, an additional TAG (Secondary PTAG: SPTAG) other than the PTAG may be set in the terminal device as a TAG including an SpCell. The SPTAG may be set in association with a physical cell identifier different from the serving cell. The SPTAG may also be set in association with one of multiple TRPs set in the terminal device, which will be described later.

For example, upon receiving a TAC MAC CE for a certain TAG, the terminal device may adjust the uplink transmission timing for transmitting PUSCH, SRS, and/or PUCCH in some or all serving cells in that TAG. The uplink transmission timing may be adjusted to be earlier by T_TA based on the timing of the beginning of the downlink frame with the same frame number. T_TA may be calculated based on N_TA and the TA offset (N_{TA,offset}). N_TA may be set based on information contained in the TAC MAC CE. The TA offset (N_{TA,offset}) may be set based on an RRC parameter (n-TimingAdvanceOffset) set in the terminal device for each serving cell. N_{TA,offset} is set for each serving cell, but N_{TA,offset} may have the same value for serving cells of the same TAG. Also, for example, in the mTRP operation described below, an independent N_{TA,offset} value may be set for each TRP in a certain TAG. In this case, the uplink transmission timing may be different for each TRP in one TAG. Alternatively, in mTRP operation, each TRP may belong to a different TAG. In this case, for example, one TRP of an SpCell may belong to a PTAG, and another TRP may belong to an SPTAG. Additionally or alternatively, for example, one TRP of an SCell may belong to a STAG, and another TRP may belong to another STAG. This STAG may also be referred to as a Secondary STAG (SSTAG).

Furthermore, in Dual Connectivity, the cells in each cell group may belong to different TAGs. That is, the PTAG of the MCG and the PTAG of the SCG may be independent and different TAGs.

The RRC entity of the terminal device may set the value of a time alignment timer (timeAlignmentTimer) in the MAC to maintain uplink time alignment. The time alignment timer may be used to control the time at which the MAC entity considers the uplink time of a serving cell belonging to the TAG associated with the time alignment timer to be aligned. The value of the time alignment timer may be set from the base station device to the terminal device by RRC signaling.

The MAC entity of the terminal device may apply a TAC to the TAG indicated in the TAC MAC CE based on receipt of a Timing Advance Command (TAC) MAC CE and based on the N_TA of the TAG indicated in the TAC MAC CE being maintained. The MAC of the terminal device may also start, or restart if already running, the timeAlignmentTimer associated with the TAG indicated in the TAC MAC CE based on receipt of a Timing Advance Command (TAC) MAC CE and based on the N_TA of the TAG indicated in the TAC MAC CE being maintained.

When the time adjustment timer associated with the PTAG expires, the MAC entity of the terminal device may perform some or all of the following processes (A) to (G).
(A) Flush all HARQ buffers for all serving cells (in the cell group).
(B) If PUCCH is configured, notify RRC that PUCCH for all serving cells has been released.
(C) If SRS is configured, notify RRC that SRS for all serving cells has been released.
(D) Clear all configured downlink assignments and configured uplink grants.
(E) Clear all PUSCHs for semi-persistent CSI reporting.
(F) All timing timers, including STAG, are considered to have expired.
(G) Maintain the N_TA for all TAGs.

When a time adjustment timer associated with a STAG expires, the MAC entity of the terminal device may perform some or all of the following processes (A) to (F) for all serving cells belonging to this STAG.
(A) Flush all HARQ buffers.
(B) If PUCCH is configured, notify RRC that the PUCCH has been released.
(C) If SRS is configured, notify RRC that SRS has been released.
(D) Clear all configured downlink assignments and configured uplink grants.
(E) Clear all PUSCHs for semi-persistent CSI reporting.
(F) Maintain the N_TA for this TAG.

　The MAC entity of the terminal device may, when the time adjustment timer associated with the SPTAG expires, perform the processing for when the time adjustment timer associated with the PTAG expires, or alternatively, may perform the processing for when the time adjustment timer associated with the STAG expires. Additionally or alternatively, the MAC of the terminal device may perform other processing when the time adjustment timer associated with the SPTAG expires.

The terminal device may determine not to perform uplink transmissions in any serving cell other than transmission of a random access preamble in the SpCell and transmission of an MSGA (in the 2-step RACH) based on the fact that one or more time adjustment timers associated with the PTAG are not running.

This section explains multiple transmit/receive point (also called multi-TRP or mTRP) operation.

In mTRP operation, the serving cell may be able to schedule terminal devices from multiple TRPs (Transmit/Receive Points) to provide better coverage, reliability, and/or data rates for PDSCH, PDCCH, PUSCH, and PUCCH.

There may be two different operation modes for scheduling PDSCH transmissions of mTRP. The two operation modes may be single-DCI and multi-DCI. The control of uplink and downlink operation for both modes may be performed at the PHY and MAC layers with configuration provided by the RRC layer. In single-DCI mode, the terminal device may be scheduled for both TRPs by the same DCI. In multi-DCI mode, the terminal device may be scheduled for each TRP by an independent DCI.

Each TRP of the mTRP may be identified by TRP information. For example, the TRP information may be information for identifying one TRP among one or more TRPs. For example, the TRP information may be an index for identifying one TRP. For example, one TRP may be determined based on the TRP information. For example, the TRP information may be information for identifying one or more TRPs. The TRP information may be used to select one TRP. The TRP information may be a CORESET pool index. One CORESET may be associated with one CORESET pool index and one CORESET resource set identifier. The terminal device may transmit a PUSCH with a corresponding TRP based on the CORESET resource set identifier. The TRP information may be associated with an index of the CORESET resource pool. For example, a first CORESET pool index may be associated with a first TRP, and a second CORESET pool index may be associated with a second TRP. The TRP information may be associated with a pool (or a pool index) of a TCI state. For example, a first TCI state pool (or pool index) may be associated with a first TRP, and a second TCI state pool (or pool index) may be associated with a second TRP.

There may be two different operation modes for scheduling PDCCH transmissions of an mTRP. The two operation modes may be PDCCH repetition and single frequency network (SFN) based PDCCH transmission. In both modes, the terminal device can receive each of the PDCCH transmissions carrying the same DCI from each TRP. In the PDCCH repetition mode, the terminal device can receive two PDCCH transmissions carrying the same DCI from two linked search spaces, each associated with a different CORESET. In the SFN based PDCCH transmission mode, the terminal device can receive two PDCCH transmissions carrying the same DCI from a single search space/CORESET using different TCI states.

In mTRP PUSCH repetition, upon indication by a single DCI or a configured uplink grant provided by RRC signaling, the terminal device may perform PUSCH transmission of the same content in beam directions associated with different spatial relations corresponding to two TRPs.

In mTRP PUCCH repetition, the terminal device may perform PUCCH transmission of the same content in beam directions associated with different spatial relationships corresponding to two TRPs.

In inter-cell mTRP operation, one or more TCI states in a multi-DCI PDSCH transmission may be associated with an SSB of a Physical Cell Identity (PCI) different from the PCI of the serving cell. Also, at most one TCI state associated with a PCI different from the serving cell may be active at a time.

In mTRP operation, uplink timing adjustments may be made for each TRP. The terminal device may determine the uplink transmission timing based at least on some or all of the TAC MAC CE, TA offset (Timing advance offset), and TRP information.

The timing advance (TA) may be determined based at least on a TA offset. The value of the TA offset may be provided by higher layer parameters (e.g., RRC layer or MAC layer parameters). One TA offset may be provided in one serving cell. Two TA offsets may be provided in one serving cell. If higher layer parameters are not provided, the terminal device may determine the value of the TA offset based on a default rule. The terminal device may determine two TA offset values in one serving cell. Determining the TA may be synonymous with adjusting the uplink transmission timing.

When two TRPs are configured in one serving cell, one TA offset value may be applied to the uplink carrier of each TRP. When two TRPs are configured in one serving cell, two independent TA offset values may be applied to each TRP.

Next, we will explain the central unit (CU) and distributed unit (DU). The central unit may be a logical node that hosts the RRC layer, SDAP layer, and PDCP layer of the base station device. The distributed unit may be a logical node that hosts the RLC layer, MAC layer, and PHY layer of the base station device. The central unit may control the operation of one or more distributed units. One distributed unit may support one or more cells. One cell may be supported by only one distributed unit. Some of the functions of the central unit may be implemented in the distributed unit. Some of the functions of the distributed unit may be implemented in the central unit.

Next, we will explain Layer 1/Layer 2 mobility (L1/L2 mobility) in this embodiment.

Layer 1/Layer 2 mobility may be a procedure in which a base station device transmits a DCI or MAC CE that causes a terminal device to identify one or more cells that are targets for the serving cell, and instructs the terminal device to change the serving cell or cells through the DCI or MAC CE. In addition or instead, Layer 1/Layer 2 mobility may be a procedure in which a terminal device receives a DCI or MAC CE from a base station device that identifies one or more cells that are targets for the serving cell, and changes the serving cell to one or more cells indicated by the DCI or MAC CE.

For example, the DCI that allows the terminal device to identify one or more cells that are targets of the serving cell may be a DCI that includes one or more identifiers indicating one or more cells that are targets of the serving cell. Also, for example, the MAC CE that allows the terminal device to identify one or more cells that are targets of the serving cell may be a MAC CE that includes one or more identifiers indicating one or more cells that are targets of the serving cell. The identifiers may be identifiers that correspond to each of the information regarding one or more serving cell targets that is set in advance in the terminal device by, for example, RRC signaling.

In Layer 1/Layer 2 mobility, the base station device may determine the serving cell target based on a measurement report provided from the terminal device. The measurement report may be a CSI report transmitted from the terminal device on a PUSCH. Additionally or alternatively, the measurement report may be a measurement report message transmitted from the terminal device as RRC signaling. Additionally or alternatively, the measurement report may be measurement report information transmitted from the terminal device as a MAC CE. The measurement report may also be other information.

Note that "Layer 1/Layer 2 mobility" may be rephrased as "Layer 1/Layer 2 based inter-cell mobility," "Layer 1/Layer 2 inter-cell mobility," "Layer 1/Layer 2 serving cell change processing," "Layer 1/Layer 2 serving cell change," or "Layer 1/Layer 2 handover," etc.

"DCI that causes the terminal device to identify one or more cells that are targets of the serving cell" may be rephrased as "DCI that instructs the terminal device to change the serving cell to one or more target cells" or "DCI that changes one or more serving cells of the terminal device", etc.

"A MAC CE that causes a terminal device to identify one or more cells that are targets of a serving cell" may be rephrased as "a MAC CE that instructs a change of the serving cell to one or more target cells" or "a MAC CE that changes one or more serving cells of a terminal device", etc.

DCI may also be referred to as Layer 1 signaling. MAC CE may also be referred to as Layer 2 signaling. The above-mentioned measurements may be performed by Layer 1 (PHY layer) and/or Layer 3 (RRC layer). The above-mentioned measurements may also be reported by Layer 1 (PHY layer), Layer 2 (MAC layer), and/or Layer 3 (RRC layer).

In Layer 1/Layer 2 mobility, the base station device may notify the terminal device of information regarding the serving cell target. The information regarding the serving cell target may be notified to the terminal device by RRC signaling. In addition or instead, the information regarding the serving cell target may be notified to the terminal device by MAC CE and/or DCI. For example, part of the information regarding the serving cell target may be notified to the terminal device in advance by RRC signaling, and when changing the serving cell to a target, another part of the information regarding the target may be notified to the terminal device by MAC CE and/or DCI. The information regarding the serving cell target is also referred to as Layer 1/Layer 2 inter-cell mobility candidate target setting, L1/L2 candidate target setting, or simply candidate target setting. In the following description, to avoid confusion with the candidate target SpCell for conditional reconfiguration, the information regarding the serving cell target is referred to as L1/L2 candidate target setting. In addition, one or more L1/L2 candidate target settings corresponding to one or more targets of the serving cell may be notified to the terminal device. The terminal device may store one or more L1/L2 candidate target settings notified by the base station device.

In order to identify each of the one or more L1/L2 candidate target settings, for example, an L1/L2 candidate target identifier associated with each L1/L2 candidate target setting may be notified to the terminal device. The terminal device may store one or more L1/L2 candidate target settings notified from the base station device and the L1/L2 candidate target identifier associated with the L1/L2 candidate target setting.

In Layer 1/Layer 2 mobility, some or all of the mobility scenarios (A) to (C) below may be supported, or other mobility scenarios may be supported. In addition, in a terminal device in which CA is not configured, the mobility scenario (A) below may be a scenario in which only the PCell is changed, and in a terminal device in which CA is configured, the mobility scenario (A) below may be a scenario in which the PCell and one or more SCells are changed.
(A) PCell change (B) Intra-DU mobility and intra-CU-inter-DU mobility (C) Inter-cell beam management

In Layer 1/Layer 2 mobility, the following principles (A) and/or (B) may be applied.
(A) A base station device provides L1/L2 candidate target configuration so that dynamic switching can be performed without requiring full configuration.
(B) The user plane communicates continuously, preferably without resets, to avoid data loss and additional delays for data recovery.

In Layer 1/Layer 2 mobility, some or all of the following (A) to (F) may be used for L1/L2 candidate targeting.
(A) Messages related to RRC connection reconfiguration (B) Cell group configuration (C) SpCell configuration and/or SCell configuration (D) Measurement configuration (E) Radio bearer configuration (F) Other information elements

The terminal device may be notified of one or more L1/L2 candidate target settings by RRC signaling or other signaling (MAC CE, DCI, etc.). The terminal device may store the L1/L2 candidate target settings until it receives a DCI or MAC CE instructing a change of the serving cell to one or more cells that are targets of the serving cell. The L1/L2 candidate target settings may be common between intra-distributed unit mobility and inter-distributed unit mobility within an aggregation unit, or some of the L1/L2 candidate target settings may be different. The L1/L2 candidate target settings may include some or all of the system information (searchSpaceSIB1, searchSpaceOtherSystemInformation, etc.), paging messages (pagingSearchSpace, etc.), and common search spaces (commonSearchSpaceList, etc.). In addition, security key updates may not be performed in Layer 1/Layer 2 mobility.

Each of the one or more cells configured in a given L1/L2 candidate target configuration is called a candidate cell or a candidate target cell.

The above cell group configuration, SpCell configuration, SCell configuration, measurement configuration, and bearer configuration may use the same information elements as those included in the message regarding the reconfiguration of the RRC connection, or may use information elements in which new parameters have been added and/or some or all of the parameters have been deleted from those included in the message regarding the reconfiguration of the RRC connection.

Each L1/L2 candidate target configuration may be a message regarding reconfiguration of an RRC connection. In this case, the L1/L2 candidate target configuration may include at least a cell group configuration related to the MCG. The cell group configuration may include at least an SpCell configuration. The cell group configuration may also include an SCell configuration. In addition, the L1/L2 candidate target configuration may include other information. For example, a cell group configuration related to the SCG may be included in the L1/L2 candidate target configuration. For example, a measurement configuration may be included in the L1/L2 candidate target configuration. For example, a radio bearer configuration may be included in the L1/L2 candidate target configuration. In addition to one or more L1/L2 candidate target configurations, an L1/L2 candidate target identifier for identifying each L1/L2 candidate target configuration may be notified from the base station device to the terminal device.

For example, the terminal device may receive DCI or MAC CE from the base station device that identifies one or more cells that are targets of the serving cell, and based on the L1/L2 candidate target identifier indicated by the DCI or MAC CE, apply a message regarding reconfiguration of the RRC connection, which is the L1/L2 candidate target setting corresponding to the L1/L2 candidate target identifier, to the RRC settings of the terminal device.

Each L1/L2 candidate target configuration may be a cell group configuration. In this case, the L1/L2 candidate target configuration may be a cell group configuration of an MCG. The cell group configuration may include at least an SpCell configuration. The cell group configuration may also include an SCell configuration. In addition, other information may be associated with the L1/L2 candidate target configuration. For example, a cell group configuration related to an SCG that is separately notified to a terminal device may be associated with the L1/L2 candidate target configuration. For example, a measurement configuration that is separately notified to a terminal device may be associated with the L1/L2 candidate target configuration. For example, a radio bearer configuration that is separately notified to a terminal device may be associated with the L1/L2 candidate target configuration. In addition to one or more L1/L2 candidate target configurations, an L1/L2 candidate target identifier for identifying each L1/L2 candidate target configuration may be notified from the base station device to the terminal device. In addition, when the L1/L2 candidate target setting is a cell group setting, the cell group of this L1/L2 candidate target setting may be referred to as a candidate cell group (CCG).

For example, the terminal device may receive DCI or MAC CE from the base station device, which identifies one or more cells that are targets of the serving cell, and apply a cell group setting, which is an L1/L2 candidate target setting corresponding to the L1/L2 candidate target identifier, to the MCG setting of the RRC of the terminal device based on the L1/L2 candidate target identifier indicated by the DCI or MAC CE. In addition, if there is information associated with the applied L1/L2 candidate target setting, the terminal device may apply the associated information to the RRC setting of the terminal device. Note that, for example, if the L1/L2 candidate target setting is set by a secondary node, this L1/L2 candidate target setting may be a cell group setting of the SCG. The terminal device may determine which cell group setting, MCG or SCG, to apply to the RRC setting of the terminal device based on which cell group the DCI or MAC CE identifying one or more cells that are targets of the serving cell is received from.

Each L1/L2 candidate target configuration may be an SpCell configuration and/or an SCell configuration. In this case, each L1/L2 candidate target configuration may be considered as a candidate target cell configuration. At least one of the one or more L1/L2 candidate target configurations notified to the terminal device may include an SpCell configuration. In addition, among the one or more L1/L2 candidate target configurations, one or more L1/L2 candidate target configurations for targets that are not set to an SpCell may include only an SCell configuration. In addition or instead, each L1/L2 candidate target configuration may include both an SpCell configuration and an SCell configuration. The terminal device may not expect a candidate target cell that does not include an SpCell configuration in the L1/L2 candidate target configuration to be set to an SpCell. In addition or instead, the terminal device may determine that the configuration has failed based on a candidate target cell that does not include an SpCell configuration in the L1/L2 candidate target configuration being set to an SpCell. Furthermore, the L1/L2 candidate target configuration may have a structure that includes parameter settings that are common (overlapping) between the SpCell configuration and the SCell configuration as common settings, and parameter settings that are not common as settings for the SpCell configuration and the SCell configuration, respectively. In addition to one or more L1/L2 candidate target settings, an L1/L2 candidate target identifier for identifying each L1/L2 candidate target setting may be notified from the base station device to the terminal device.

For example, the terminal device may receive DCI or MAC CE from the base station device, which identifies one or more cells that are targets of the serving cell, and apply the L1/L2 candidate target configuration corresponding to the L1/L2 candidate target identifier to the current RRC configuration of the terminal device based on one or more L1/L2 candidate target identifiers indicated by the DCI or MAC CE. For example, when multiple L1/L2 candidate target identifiers are indicated by the DCI or MAC CE, the terminal device may determine which candidate target cell is to be an SpCell and which candidate target cell is to be an SCell based on the order in which the L1/L2 candidate target identifiers are indicated. In addition or instead, when one or more L1/L2 candidate target identifiers are indicated by the DCI or MAC CE, an identifier identifying the serving cell associated with each L1/L2 candidate target identifier (serving cell identifier) and/or an identifier identifying the SCell associated with each L1/L2 candidate target identifier (SCell identifier) may also be indicated. This allows the terminal device to determine which candidate target cell will be which serving cell and/or which candidate target cell will be which SCell.

Additionally or alternatively, for example, a list of one or more L1/L2 candidate target identifiers may be provided from the base station device to the terminal device by a certain signaling (MAC CE or RRC signaling). This list may include information indicating which candidate target cell is to be an SpCell and/or which candidate target cell is to be an SCell. Furthermore, multiple lists may be notified to the terminal device. Furthermore, the terminal device may be notified of a list identifier for identifying each list. The terminal device may receive DCI or MAC CE from the base station device and, based on the list identifier indicated by the DCI or MAC CE, apply one or more L1/L2 candidate target configurations corresponding to the list identifier to the RRC configuration of the terminal device. Furthermore, for example, a measurement configuration notified separately to the terminal device may be associated with the L1/L2 candidate target configuration. For example, a radio bearer configuration notified separately to the terminal device may be associated with the L1/L2 candidate target configuration. If there is information associated with the applied L1/L2 candidate target configuration, the terminal device may apply the associated information to the current terminal device RRC configuration. The list may also be referred to as a Candidate Cell Group (CCG). One or more candidate target cells may also be collectively referred to as a candidate target cell set.

Furthermore, each of the L1/L2 candidate target settings notified to the terminal device may be a setting of a different structure. For example, one L1/L2 candidate target setting may be a cell group setting, and another L1/L2 candidate target setting may be an SpCell setting. In other words, the L1/L2 candidate target settings may have different structures depending on the choice (CHOICE) in the ASN.1 notation.

Furthermore, each of the L1/L2 candidate target settings notified to the terminal device may be referred to as a candidate target entry, and a list of one or more candidate target entries (candidate target entry list) may be notified to the terminal device.

An example of the processing of the terminal device (UE 122) in this embodiment will be described with reference to FIG. 9. Note that in this embodiment, the processing unit 502 of the UE 122 may include an RRC processing unit that performs RRC processing and a MAC processing unit that performs MAC processing.

FIG. 9 is a diagram showing an example of processing by the UE 122 in this embodiment. The processing unit 502 of the UE 122 judges the conditions (step S1000) and operates based on the judgment (step S1002).

UE122 receives RRC signaling from a base station device (gNB108 and/or eNB102). The RRC signaling may include one or more L1/L2 candidate target configurations. The RRC processing unit of UE122 may hold one or more L1/L2 candidate target configurations included in the RRC signaling. The RRC signaling may include an identifier (L1/L2 candidate target identifier) that identifies each of the one or more L1/L2 candidate target configurations.

Furthermore, the SpCell configuration and/or SCell configuration included in the L1/L2 candidate target configuration may include an identifier related to the TAG (first identifier). Furthermore, the configuration of each serving cell (SpCell configuration and/or SCell configuration) may also include the first identifier. That is, the first identifier may be associated with each of the candidate target cells and the serving cell. Furthermore, the first identifiers associated with each of the candidate target cells and the serving cell may be the same value or different values.

The first identifier may be a TAG identifier (TAG-Id).

UE122 may receive a MAC CE from a base station device (gNB108 and/or eNB10XXXX) that identifies one or more cells that are targets of a serving cell in a serving cell of a cell group. In the following description, the MAC processing unit of UE122 may be the MAC processing unit of this cell group unless otherwise specified.

In step S1000, the MAC processing unit of the UE 122 that has received the MAC CE determines whether the following conditions (a) and (b) are satisfied.
(a) The first identifier of the cell that is the target of the SpCell identified by the MAC CE is the same value as any one of the identifiers of one or more TAGs maintained in the cell group that received the MAC CE, and a time adjustment timer for that TAG is running.
(b) The MAC CE does not include information that suggests to the UE 122 to initiate a random access procedure.

In step S1002, the MAC processing unit of UE122 notifies the RRC processing unit of information indicating the target of the serving cell identified by the MAC CE (e.g., L1/L2 candidate target identifier).

In addition or instead, the MAC processing unit of UE122, based on the determination in step S1000 that the conditions (a) and (b) are satisfied, does not notify the RRC processing unit that a random access procedure is necessary in step S1002. Or, instead, the MAC processing unit of UE122, based on the determination in step S1000 that the conditions (a) and (b) are satisfied, notifies the RRC processing unit that a random access procedure is unnecessary in step S1002.

In addition or instead, the MAC processing unit of UE122 notifies the RRC processing unit that a random access procedure is necessary in step S1002 based on the determination in step S1000 that either condition (a) or (b) is not satisfied. Or, instead, the MAC processing unit of UE122 does not notify the RRC processing unit that a random access procedure is unnecessary in step S1002 based on the determination in step S1000 that either condition (a) or (b) is not satisfied.

The RRC processing unit of UE122 performs a process (L1/L2 candidate target setting application process) of applying the L1/L2 candidate target setting selected based on the information indicating the serving cell target identified by the MAC CE to the RRC setting of the terminal device.

The RRC processing unit of UE122 may instruct the MAC processing unit of UE122 to start a random access procedure based on the fact that the MAC processing unit of UE122 has notified the user that a random access procedure is necessary during the L1/L2 candidate target setting application process, and/or based on the fact that the MAC processing unit of UE122 has not notified the user that a random access procedure is unnecessary.

In addition or instead, the RRC processing unit of UE122 may not instruct the MAC processing unit of UE122 to start a random access procedure based on the fact that the MAC processing unit of UE122 has notified the L1/L2 candidate target setting application process that a random access procedure is not required and/or that a random access procedure is not required.

In the L1/L2 candidate target setting application process, the MAC processing unit of UE 122 may decide not to stop the time adjustment timers of one or more TAGs that are being maintained.

Note that the random access procedure being necessary and the random access procedure not being necessary may mean that a MAC reset is necessary and that a MAC reset is not necessary, respectively. In this case, the RRC processing unit of UE 122 may instruct the MAC processing unit to perform a MAC reset based on the fact that the MAC processing unit has notified the UE 122 in the L1/L2 candidate target setting application process that a MAC reset is necessary and/or that the MAC processing unit has not notified the UE 122 that a MAC reset is not necessary. The MAC reset may also be a partial MAC reset.

In this embodiment, the first identifier may be an identifier different from the TAG identifier (TAG-Id).

In this case, the condition (a) in step S1000 may be the following condition.
(a) The first identifier of the cell that is the target of the SpCell identified by the MAC CE has the same value as the first identifier associated with any of the serving cells of the cell group that received the MAC CE, the TAG to which the serving cell belongs is maintained, and the time adjustment timer of the TAG is running.

Next, an example of another process of the terminal device (UE122) in this embodiment will be described with reference to FIG. 9. Note that the processes described in this embodiment may be used in combination with each other.

In FIG. 9, the processing unit 502 of the UE 122 judges the conditions (step S1000) and operates based on the judgment (step S1002).

UE122 receives RRC signaling from a base station device (gNB108 and/or eNB102). The RRC signaling may include one or more L1/L2 candidate target configurations. The RRC processing unit of UE122 may hold one or more L1/L2 candidate target configurations included in the RRC signaling. The RRC signaling may include an identifier (L1/L2 candidate target identifier) that identifies each of the one or more L1/L2 candidate target configurations.

Furthermore, the SpCell configuration and/or SCell configuration included in the L1/L2 candidate target configuration may include an identifier related to the TAG (first identifier). Furthermore, the configuration of each serving cell (SpCell configuration and/or SCell configuration) may also include the first identifier. That is, the first identifier may be associated with each of the candidate target cells and the serving cell. Furthermore, the first identifiers associated with each of the candidate target cells and the serving cell may be the same value or different values.

The first identifier may be a TAG identifier (TAG-Id).

UE122 may receive a MAC CE from a base station device (gNB108 and/or eNB10XXXX) that identifies one or more cells that are targets of a serving cell in a serving cell of a cell group. In the following description, the MAC processing unit of UE122 may be the MAC processing unit of this cell group unless otherwise specified.

The RRC processing unit of UE122 performs a process (L1/L2 candidate target setting application process) of applying the L1/L2 candidate target setting selected based on the information indicating the serving cell target identified by the MAC CE to the RRC setting of the terminal device.

In the L1/L2 candidate target setting application process, the MAC processing unit of UE 122 determines whether the first identifier of the cell that is the target of the SpCell is the same as the first identifier of the source SpCell (i.e., the TAG-Id of the PTAG). (Step S1000)

　The MAC processing unit of UE122 may replace the TAG-Id of the TAG indicated by the first identifier with the TAG-Id of the PTAG based on the determination in step S1000 that the first identifier of the cell that is the target of the SpCell is not the same as the first identifier of the source SpCell. (Step S1002)

For example, in step S1002, if the first identifier of the cell that is the target of the SpCell is 3 and the TAG-Id of the PTAG is 0, the MAC processing unit of UE 122 may swap the value and state (whether the time adjustment timer is running or stopped, etc.) of the time adjustment timer of the TAG whose TAG-Id is 3 set in the TAG-Config information element with the value and state (whether the time adjustment timer is running or stopped, etc.) of the time adjustment timer of the TAG whose TAG-Id is 0. Or, instead, it may swap the TAG-Id of 0 and 3 set in the TAG-Config information element.

Furthermore, in the L1/L2 candidate target setting application process, the RRC processing unit of UE 122 may determine whether the first identifier of the cell that is the target of the SpCell is the same as the first identifier of the source SpCell (i.e., the TAG-Id of the PTAG), and based on determining that the first identifier of the cell that is the target of the SpCell is not the same as the first identifier of the source SpCell, may replace the value of the first identifier that has the same value as the first identifier of the cell that is the target of the SpCell with the value of the first identifier that has the same value as the first identifier of the source SpCell, among the first identifiers that are associated with and held for each of the candidate target cells and the serving cell.

As a result, for example, in a system where the PTAG identifier is always set to 0, even if the TAG-Id of the cell that is the target of the SpCell is other than 0, it is possible to set the PTAG identifier to 0 while retaining the value and state of the time adjustment timer in Layer 1/Layer 2 mobility.

Alternatively, the MAC processing unit of UE122 and/or the RRC processing unit of UE122 may consider the TAG-Id of the TAG indicated by the first identifier to be the TAG-Id of the PTAG based on the determination in step S1000 that the first identifier of the cell that is the target of the SpCell is not the same as the first identifier of the source SpCell. (Step S1002)

For example, in step S1002, if the first identifier of the cell that is the target of the SpCell is 3 and the TAG-Id of the PTAG is 0, the MAC processing unit of UE122 and/or the RRC processing unit of UE122 may determine that the TAG-Id of the PTAG has become 3.

This makes it possible to set the PTAG appropriately, for example in systems where the PTAG identifier is not fixed to 0.

In the above description, once a timer is started, it runs until it is stopped or expires. Once a timer expires, it may be considered to be not running (stopped). A timer is always started (if the timer is stopped) or restarted (if the timer is running) from its initial value. The period from when the timer is started or restarted to when it expires is not updated until the timer is stopped or expired. The MAC entity of the terminal device may set the period from when the timer is started or restarted to when it expires as a value notified by a higher layer (e.g., the RRC layer). In addition to or instead of this, the MAC entity of the terminal device may set the period from when the timer is started or restarted to when it expires as a pre-configured default value. If the MAC entity of the terminal device sets the period from when the timer is started or restarted to when it expires to 0, the timer may expire immediately after it is started, unless other conditions are specified.

Furthermore, unless otherwise specified, the radio bearer in the above description may be a DRB, an SRB, or a DRB and an SRB. In addition or instead, the radio bearer in the above description may be an MRB.

In addition, in the above description, expressions such as "link to," "corresponding to," and "associate with" may be used interchangeably.

In addition, in the above explanation, expressions such as "determined to be A," "A is set," and "A is included" may be used interchangeably.

In the above explanation, "transition from X to Y" may be rephrased as "X becomes Y." Also, in the above explanation, "cause a transition" may be rephrased as "determine a transition."

Furthermore, in each of the process examples or process flow examples in the above description, some or all of the steps may not be executed. Furthermore, in each of the process examples or process flow examples in the above description, the order of the steps may be different. Furthermore, in each of the process examples or process flow examples in the above description, some or all of the processing within each step may not be executed.

In the above explanation, "A may be replaced with B" may mean replacing A with B, as well as replacing B with A. Also, in the above explanation, when it is written that "C may be D" and "C may be E", it may also mean that "D may be E". Also, in the above explanation, when it is written that "F may be G" and "G may be H", it may also mean that "F may be H".

The program that runs on the device related to this embodiment may be a program that controls a Central Processing Unit (CPU) or the like to cause a computer to function so as to realize the functions of this embodiment. 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.

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 this recording medium may be read into a computer system and executed to realize the control function. The "computer system" referred to here is a computer system built into the device, and includes hardware such as an operating system and peripheral devices. Furthermore, the "computer-readable recording medium" may be any of semiconductor recording media, optical recording media, magnetic recording media, etc.

Furthermore, "computer-readable recording medium" may include something that dynamically holds 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, or something that holds a program for a fixed period of time, such as volatile memory within a computer system that serves as a server or client in such cases. The above program may also be one that realizes part of the functions described above, or one that can realize the functions described above in combination with a program already recorded in the computer system.

Furthermore, each functional block or feature of the device used in the above-mentioned embodiment may be implemented or executed by an electric circuit, typically an integrated circuit or a number 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. Furthermore, if an integrated circuit technology that replaces current integrated circuits emerges due to advances in semiconductor technology, it is also possible to use an integrated circuit based on that technology.

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

Although this embodiment has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like that do not depart from the gist of this embodiment are also included. Furthermore, this embodiment 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 this embodiment. Also included are configurations in which elements described in the above embodiments are substituted for elements that have the same effect.

One aspect of the present invention can be used, for example, in a communication system, a communication device (e.g., a mobile phone device, a base station device, a wireless LAN device, or a sensor device), an integrated circuit (e.g., a communication chip), or a program, etc.

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, 604 Receiver
502, 602 Processing section
504, 600 Transmitter

Claims (3)

A terminal device that communicates with a base station device,
A receiver that receives MAC signaling from the base station device to change the source SpCell to a target SpCell;
A MAC processing unit and an RRC processing unit are provided,
Based on receiving the MAC signaling from the base station device,
The MAC processing unit determines whether or not: (1) a candidate target cell indicated by the MAC signaling belongs to one or more TA groups of the cell group that received the MAC signaling, and a TA timer corresponding to the TA group is running; and
(2) the MAC signaling does not include information indicating execution of a random access procedure;
Determine whether the above two conditions are met,
The terminal device notifies the RRC processing unit that a random access procedure needs to be executed based on the determination that any of the conditions is not satisfied. A method applied to a terminal device communicating with a base station device, comprising:
receiving MAC signaling from the base station device to change the source SpCell to a target SpCell;
Based on receiving the MAC signaling from the base station device,
As a MAC layer process, (1) a candidate target cell indicated by the MAC signaling belongs to one or more TA groups of the cell group that received the MAC signaling, and a TA timer corresponding to the TA group is running; and
(2) the MAC signaling does not include information indicating execution of a random access procedure;
Determine whether the above two conditions are met,
and based on determining that any of the conditions is not satisfied, notifying an RRC layer of the terminal device that a random access procedure needs to be performed. An integrated circuit implemented in a terminal device that communicates with a base station device,
receiving MAC signaling from the base station device to change the source SpCell to a target SpCell;
Based on receiving the MAC signaling from the base station device,
As a MAC layer process, (1) a candidate target cell indicated by the MAC signaling belongs to one or more TA groups of the cell group that received the MAC signaling, and a TA timer corresponding to the TA group is running; and
(2) the MAC signaling does not include information indicating execution of a random access procedure;
Determine whether the above two conditions are met,
and a function of notifying an RRC layer of the terminal device that a random access procedure needs to be executed based on a determination that any of the conditions is not satisfied.

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