Radio terminal, radio access network node, core network node, and methods thereof

Abstract

This radio terminal receives first information in a first cell in a first radio access network (RAN) according to a first radio access technology (RAT). In response to the reception of the first information, the radio terminal establishes, in addition to first Radio Resource Control (RRC) connection already established between the radio terminal and the first RAN, second RRC connection between the radio terminal and a second RAN according to a second RAT different from the first RAT in a second cell in the second RAN. For example, this can provide an improvement that may be beneficial for implementing a scenario in which the radio terminals communicate with each other via the different radio accesses according to the different RATs in one network or two different networks (e.g., 5G network and 6G network).

Description

Wireless terminals, wireless access network nodes, core network nodes, and methods thereof

[0001] This disclosure relates to wireless communication systems, and more particularly to scenarios in which wireless terminals communicate via different wireless access points in one network or two different networks.

[0002] There are various technologies for implementing scenarios in which wireless terminals (or user devices) communicate via different wireless access points on one or two different networks. These technologies include Dual Subscriber Identity Module (SIM) Dual Active (DSDA), Dual SIM Dual Standby (DSDS), Multiple Universal SIMs (MUSIM), dual steering (DualSteer), and dual connectivity (DC).

[0003] One network may mean a cellular network provided by one operator, specifically a Public Land Mobile Network (PLMN). Two different networks may mean two cellular networks provided by the same or different operators, specifically two PLMNs, or a PLMN and a Non-Public Network (NPN). There may be only one (PLMN) subscription to communicate with the two networks via different cellular access. Alternatively, two (PLMN) subscriptions may be used for the two networks.

[0004] Different radio accesses refer to multiple radio access networks (RANs) using different radio access technologies (RATs). RATs refer to various methods and protocols used to establish wireless communication between wireless terminals (e.g., User Equipments (UEs)) and (cellular) networks. Different radio accesses may be multiple cellular accesses using different RATs. Multiple cellular accesses include, for example, Evolved Universal Terrestrial Radio Access (EUTRA) (i.e., Long Term Evolution (LTE) or 4G access) and NR access (i.e., 5G access). Different radio accesses may be cellular access (i.e., Terrestrial Network (TN) access) and satellite access (i.e., Non-Terrestrial Network (NTN) access).

[0005] A wireless terminal (DSDA device) supporting DSDA can use two SIMs in both idle mode and connected mode. Since each SIM has a dedicated transceiver, there are no interdependencies in the operation of idle mode and connected mode at the modem level.

[0006] A wireless terminal that supports DSDS (DSDS device) can use two SIMs for network connectivity in idle mode, but when one wireless connection is active, the second wireless connection is disabled. Similar to the passive case, where the wireless terminal contains two SIMs but only one is available at any given time, the SIMs in a DSDS device share one transceiver. Time division multiplexing maintains two wireless connections in idle mode. If a call is in progress on the network for one SIM, it is no longer possible to maintain wireless connectivity to the network for the second SIM, and therefore that connection is unavailable for the duration of the call. Registration to the second network is maintained.

[0007] MUSIM is a term used by the 3rd Generation Partnership Project (3GPP®) (see, for example, Non-Patent Documents 1-5). A MUSIM device or UE refers to Mobile Equipment (ME) with multiple USIMs operating simultaneously. A MUSIM device or UE can be single-Rx or dual-Rx, and single-Tx or dual-Tx. Single-Rx allows a MUSIM UE to receive traffic from only one network at a time, while dual-Rx allows a MUSIM UE to receive traffic from two networks simultaneously. Single-Tx allows a MUSIM UE to transmit traffic to one network at a time, while dual-Tx allows a MUSIM UE to transmit traffic to two networks simultaneously. The terms single-Rx / Tx and dual-Rx / Tx do not imply a type of device. For example, a single UE may use dual-Tx in some cases and single-Tx in others.

[0008] Non-patent document 2 discloses solutions for single Rx and single Tx MUSIM UEs. One of these solutions relates to avoiding paging occasion collisions. The UE can change the timing of paging occasions by triggering the reallocation of a new 5G Global Unique Temporary Identifier (GUTI) in a 5G system (5GS) or the reallocation of an International Mobile Subscriber Identity (IMSI) offset in an Evolved Packet System (EPS).

[0009] Another MUSIM-related solution disclosed in Non-Patent Document 2 is a solution for a MUSIM UE to notify a network of its switching away for MUSIM purposes. It introduces Access Stratum (AS)-based network switching for leaving Radio Resource Control (RRC)_CONNECTED, and network switching that does not leave RRC_CONNECTED (i.e., requesting / setting a MUSIM gap). Both methods can be configured individually by the network. When the UE determines it needs to leave RRC_CONNECTED, it sends a UE Assistance Information message. This UE Assistance Information message indicates the UE's preferred RRC state when leaving RRC_CONNECTED for MUSIM purposes. The UE is allowed to enter the RRC_IDLE state if it does not receive a response message from the network within a set time. On the other hand, when the UE determines a MUSIM gap is needed, it sends a UE Assistance Information message. This UE Assistance Information message indicates the UE's preference regarding the MUSIM gap. A UE can request a maximum of one aperiodic MUSIM gap and two periodic MUSIM gaps. The MUSIM gaps are configured per UE.

[0010] Non-patent document 4 discloses solutions for dual Rx and dual Tx MUSIM UEs. One of these solutions concerns temporary capability restrictions. When USIM B is in the RRC_IDLE or RRC_INACTIVE state on network B, and USIM A is in the RRC_CONNECTED state on network A, all capabilities are occupied by USIM A for communication. When USIM B enters the RRC_CONNECTED state, some of the capabilities need to be switched to USIM B. In this case, the UE of USIM A needs to indicate temporary capability restrictions to the network. Furthermore, band contention may occur when both USIMs are in the RRC_CONNECTED state, and this problem can also be solved by a solution that addresses the temporary capability restriction issue. If permitted by the network, reporting of temporary capability restriction information is done via the UE Assistant Information (UAI) procedure. In UAI, the UE can display temporary capability limitation information for the following types of UE capabilities: Carrier Aggregation (CA) / DC capabilities; maximum multiple-input and multiple-output (MIMO) layers; maximum channel bandwidth; measurement gap requirement; and maximum number of component carriers.

[0011] Another MUSIM-related solution disclosed in Non-Patent Document 4 concerns MUSIM gap enhancements. This includes MUSIM gap priority and keep solutions, as well as coordination between the Master Node (MN) and Secondary Node (SN) of a DC. To address collisions between MUSIM gaps and legacy measurement gaps (3GPP Releases 15-17 measurement gaps), as well as collisions between MUSIM gaps, gap priority is introduced for periodic MUSIM gaps. Furthermore, for collisions between MUSIM gaps, the UE is permitted to hold all colliding MUSIM gaps (referred to as "keep solutions"). For non-periodic MUSIM gaps, they are always held by the UE in case of collisions with other gaps (i.e., all gaps, including MUSIM gaps). Where permitted by the network, the UE can indicate preferences for MUSIM gap priority(s) and "keep solutions". The network can set priorities for MUSIM gaps and grant "keep solutions" based on UE preferences. If a "keep solution" is not designated or granted, the UE uses a priority-based solution to resolve periodic collisions between MUSIM gaps. When a collision occurs, the lower-priority gap is removed.

[0012] In the MN-SN coordination disclosed in Non-Patent Document 4, if the UE is configured with NR-DC, the MN can transmit to the SN via inter-node messages a network indication that includes the configured MUSIM gap pattern(s), configured MUSIM gap priority(s), and all conflicted MUSIM gaps.

[0013] Non-patent document 5 discloses solutions for MUSIM UEs. One of these solutions concerns a case where a single MUSIM device uses multiple USIMs from the same mobile network operator (MNO). It is beneficial for the network to know that these two UEs reside within the same MUSIM device. This allows for many network-side optimizations through implementation, such as common radio resource management (RRM) or mobility (e.g., handover to the same gNB or cell simultaneously) or network-based UE capability sharing between the two USIMs. Specifically, the UE of one USIM notifies the gNB of the UE ID (e.g., Cell Radio Network Temporary Identifier (C-RNTI)) of the other USIM in the same cell. Alternatively, the UE of one USIM indicates to the gNB that it wishes to connect to a specific cell (e.g., cell ID) so that the two USIMs belong to the same cell.

[0014] Non-patent documents 6 and 7 disclose DualSteer. DualSteer functionality is an enhancement of the Access Traffic Steering, Switching, Splitting (ATSSS) feature. The ATSSS feature is described, for example, in non-patent document 8. The ATSSS feature supports dual user plane connectivity between the UE and the data network using one 3GPP access network and one non-3GPP access network. In contrast, DualSteer supports traffic steering and switching of user data (for different services) across two 3GPP access networks. A DualSteer device is a device that supports such DualSteer functionality. A DualSteer device is a single UE for non-synchronous data transmission across two networks, and two separate UEs for synchronous data transmission across two networks.

[0015] The ATSSS and DualSteer functions utilize the Multipath Transmission Control Protocol (MPTCP). The ATSSS and DualSteer functions, using MPTCP, can be described as techniques that provide redundancy for the user plane path for packet forwarding between the UE and a single endpoint (i.e., a PDU Session Anchor (PSA) User Plane Function (UPF)).

[0016] DC is defined, for example, in Non-Patent Document 9. In Multi-Radio DC (MR-DC), the UE has a single RRC state based on MN RRC and a single control plane connection to the core network.

[0017] vivo, China Telecom, China Unicom, "Revised WID: Core part: Support for Multi-SIM devices for LTE / NR", RP-212610, 3GPP TSG RAN Meeting #93e, Electronic Meeting, September 13-17, 2021vivo, "Summary for WI: Support for Multi-SIM devices for LTE / NR", RP-220604, 3GPP TSG RAN Meeting #95, Electronic Meeting, March 17-23, 2022Qualcomm Incorporated, "Revised WID: Dual Transmission / Reception (Tx / Rx) Multi-SIM for NR", RP-231461, 3GPP TSG RAN Meeting #100, Taipei, June 12-14, 2023vivo, "WI summary: Dual Transmission Reception (TxRx) Multi-SIM for NR", RP-233072, 3GPP TSG RAN Meeting #102, Edinburgh, Scotland, December 11-15, 2023vivo, China Broadnet, NTT DOCOMO, INC., China Telecom, China Unicom, CMCC, Vodafone, Charter, TCL, Spreadtrum, Lenovo, CATT, NEC, Motorola Mobility, CableLabs, "Rel-19 MUSIM enhancements work item", RP-241049, 3GPP TSG RAN Meeting #104, Shanghai, China, June 17-20, 20243GPP TR 22.841 V19.0.0 (2023-12) "3rd Generation Partnership Project; Technical Specification Group TSG SA; Study on Upper layer traffic steer, switch and split over dual 3GPP access (Release 19)", December 20233GPP TR 23.700-54 V1.0.0 (2024-06) "3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Study on Multi-Access (DualSteer and ATSSS_Ph4) (Release 19)", June 20243GPP TR 23.700-93 V17.0.0 (2021-03) "3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Study on access traffic steering, switch and splitting support in the 5G System (5GS) architecture; Phase 2 (Release 17)", March 20213GPP TS 37.340 V18.2.0 (2024-06) "3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and NR; Multi-connectivity; Overall Description; Stage 2 (Release 18)", June 2024.

[0018] 6G demands higher performance than 5G in terms of data rates, mobility speeds, and device density. Achieving these higher levels of performance will likely require a new system rather than a simple upgrade of 5G. 5G introduced dual connectivity (DC), leveraging existing 4G LTE coverage for a smoother 5G deployment in the market. This has been successful in initial deployments. However, DC is highly complex. Therefore, introducing a DC similar to the one used in 5G between 5G and 6G might be best avoided due to its complexity.

[0019] As mentioned above, technologies are known for implementing scenarios in which wireless terminals (e.g., UEs) communicate via different radio access points in one or two different networks. These technologies include DSDA, DSDS, MUSIM, DualSteer, and DC. Some or all of these technologies may be at least partially applicable in scenarios in which wireless terminals use 6G systems in addition to 5G systems. However, it is not entirely clear how these technologies should be used or extended.

[0020] One objective of the embodiments disclosed herein is to provide apparatus, methods, and programs that offer improvements that may be useful for implementing scenarios in which wireless terminals communicate via different radio access following different RATs in one network or two different networks (e.g., a 5G network and a 6G network). It should be noted that this objective is only one of several objectives that the embodiments disclosed herein aim to achieve. Other objectives or problems and novel features will be revealed by the description herein or by the accompanying drawings.

[0021] In a first embodiment, a wireless terminal is configured to receive first information in a first cell of a first RAN that conforms to a first RAT. In response to receiving the first information, the wireless terminal is configured to establish a second RRC connection between the wireless terminal and the second RAN in a second cell of a second RAN that conforms to a second RAT different from the first RAT, in addition to a first RRC connection already established between the wireless terminal and the first RAN.

[0022] In a second embodiment, the method performed by the wireless terminal includes: a) receiving first information in a first cell of a first RAN that conforms to a first RAT; and b) in response to the reception of the first information, establishing a second RRC connection between the wireless terminal and the second RAN in a second cell of a second RAN that conforms to a second RAT different from the first RAT, in addition to a first RRC connection already established between the wireless terminal and the first RAN.

[0023] In a third embodiment, a RAN node is configured to transmit first information to a wireless terminal in a first cell of a first RAN that conforms to a first RAT. The first information causes the wireless terminal to establish a second RRC connection in a second cell of a second RAN that conforms to a second RAT different from the first RAT, in addition to a first RRC connection already established between the wireless terminal and the first RAN.

[0024] In a fourth aspect, the method performed by the RAN node includes transmitting first information to a wireless terminal in a first cell of a first RAN that conforms to a first RAT. The first information causes the wireless terminal to establish a second RRC connection in a second cell of a second RAN that conforms to a second RAT different from the first RAT, in addition to a first RRC connection already established between the wireless terminal and the first RAN.

[0025] In a fifth embodiment, a first RAN node belonging to a first RAN of a first network is configured to communicate with a wireless terminal via a first cell of the first RAN. The first RAN node is configured to receive a first message from a second RAN node of a second RAN of a second network that triggers the establishment or activation of a control plane connection specific to the wireless terminal between the wireless terminal or the second RAN node and the second core network of the second network. In response to receiving the first message, the first RAN node is configured to send a second message that triggers the establishment or activation of the control plane connection to a first core network node of the first core network of the first network.

[0026] In a sixth aspect, a method performed by a first RAN node belonging to a first RAN of a first network includes: a) communicating with a wireless terminal via a first cell of the first RAN; b) receiving a first message from a second RAN node of a second RAN of a second network that triggers the establishment or activation of a control plane connection specific to the wireless terminal between the wireless terminal or the second RAN node and the second core network of the second network; and c) sending a second message to a first core network node of the first core network of the first network that triggers the establishment or activation of the control plane connection in response to the receipt of the first message.

[0027] In a seventh embodiment, a first core network node belonging to a first core network of a first network is configured to communicate with a wireless terminal via a first RAN node and a first cell of the first network. The first core network node is configured to receive a first message from the first RAN node that triggers the establishment or activation of a control plane connection specific to the wireless terminal between the wireless terminal or the second RAN of the second network and the second core network of the second network. In response to receiving the first message, the first core network node is configured to send a second message to the second core network node of the second core network that triggers the establishment or activation of the control plane connection.

[0028] In the eighth aspect, a method performed by a first core network node belonging to the first core network of the first network includes: a) communicating with a wireless terminal via the first RAN node and the first cell of the first network; b) receiving from the first RAN node a first message that triggers the establishment or activation of a control plane connection specific to the wireless terminal between the wireless terminal or the second RAN of the second network and the second core network of the second network; and c) sending a second message that triggers the establishment or activation of the control plane connection to the second core network node of the second core network in response to the receipt of the first message.

[0029] In the ninth aspect, a second RAN node belonging to a second RAN of a second network is configured to communicate with a wireless terminal via a second cell of the second RAN. The second RAN node is configured to send a first message to a first RAN node of a first RAN of a first network that triggers the establishment or activation of a control plane connection specific to the wireless terminal between the wireless terminal or the second RAN node and the second core network of the second network. The second RAN node is configured to receive a second message relating to the establishment or activation of the control plane connection from the first RAN node or from a second core network node of the second core network of the second network.

[0030] In a tenth aspect, a method performed by a second RAN node belonging to a second RAN of a second network includes: a) communicating with a wireless terminal via a second cell of the second RAN; b) sending a first message to a first RAN node of a first RAN of a first network to trigger the establishment or activation of a control plane connection specific to the wireless terminal between the wireless terminal or the second RAN node and the second core network of the second network; and c) receiving a second message relating to the establishment or activation of the control plane connection from the first RAN node or from a second core network node of the second core network of the second network.

[0031] In the eleventh embodiment, a second core network node belonging to the second core network of the second network is configured to receive a first message from the first core network node of the first core network of the first network that triggers the establishment or activation of a control plane connection specific to the wireless terminal between the wireless terminal or a second RAN node belonging to the second RAN of the second network and the second core network. The second core network node is configured to send a second message relating to the establishment or activation of the control plane connection to the first core network node or the second RAN node in response to receiving the first message.

[0032] In a twelfth aspect, a method performed by a second core network node belonging to a second core network of a second network includes: a) receiving a first message from a first core network node of a first core network of a first network that triggers the establishment or activation of a control plane connection specific to a wireless terminal between the wireless terminal or a second RAN node belonging to a second RAN of the second network and the second core network; and b) sending a second message relating to the establishment or activation of the control plane connection to the first core network node or the second RAN node in response to the receipt of the first message.

[0033] In the 13th aspect, the program includes a set of instructions (software code) that, when loaded into a computer, cause the computer to perform the method according to any of the above aspects.

[0034] According to the above-described embodiments, it is possible to provide apparatus, methods, and programs that offer improvements that may be useful for implementing scenarios in which wireless terminals communicate via different radio access following different RATs in one network or two different networks (e.g., a 5G network and a 6G network).

[0035] This is a diagram showing an example configuration of a wireless communication system related to one or more embodiments. This is a diagram showing an example configuration of a wireless communication system related to one or more embodiments. This is a diagram showing an example configuration of a wireless communication system related to one or more embodiments. This is a flowchart showing an example of the operation of a wireless terminal related to one or more embodiments. This is a diagram showing an example of signaling related to one or more embodiments. This is a diagram showing an example of signaling related to one or more embodiments. This is a diagram showing an example of signaling related to one or more embodiments. This is a flowchart showing an example of the operation of a wireless terminal related to one or more embodiments. This is a diagram showing an example of the operation of a wireless terminal and a RAN node related to one or more embodiments. This is a flowchart showing an example of the operation of a wireless terminal and a RAN node related to one or more embodiments. This is a diagram showing an example of the operation of a wireless terminal and a RAN node related to one or more embodiments. This is a diagram showing an example of signaling related to one or more embodiments. This is a block diagram showing an example configuration of a wireless terminal related to one or more embodiments. This is a block diagram showing an example configuration of a RAN node related to one or more embodiments. This is a block diagram showing an example configuration of a core network node related to one or more embodiments.

[0036] The following describes specific embodiments in detail with reference to the drawings. In each drawing, the same or corresponding elements are denoted by the same reference numerals, and redundant explanations are omitted where necessary for clarity.

[0037] The multiple embodiments described below may be used individually or two or more embodiments may be combined as appropriate. These multiple embodiments may have novel features that differ from each other. Therefore, these multiple embodiments may contribute to achieving different objectives or solving different problems, and may contribute to producing different effects.

[0038] Each drawing is merely illustrative to illustrate one or more embodiments. Each drawing may be associated with one or more other embodiments, rather than being associated with only one specific embodiment. As those skilled in the art will understand, various features or steps described with reference to any one drawing can be combined with features or steps shown in one or more other drawings, for example, to create embodiments not explicitly shown or described. Not all features or steps shown in any one drawing to illustrate an exemplary embodiment are necessarily required, and some features or steps may be omitted. The order of steps described in any of the drawings may be changed as appropriate.

[0039] The following embodiments are described primarily with reference to 3GPP mobile communication systems, such as future 3GPP Beyond 5G or 6G systems. However, these embodiments may also be applicable to other wireless communication systems.

[0040] As used herein, depending on the context, “if” may be interpreted as meaning “when,” “while,” “at or around the time,” “after,” “upon,” “in response to determining,” “in accordance with a determination,” or “in response to detecting.” These expressions may be interpreted as having the same meaning depending on the context. As used herein, depending on the context, “in response to” may be rephrased as “based on.”

[0041] First, the configuration and operation of several network elements common to multiple embodiments will be described. Figures 1 to 3 show examples of the configuration of wireless communication systems according to multiple embodiments. Each of the elements shown in Figures 1 to 3 is a network function, providing, for example, an interface defined by 3GPP. Each element (network function) shown in Figures 1 to 3 can be implemented, for example, as a network element on dedicated hardware, as a running software instance on dedicated hardware, or as an instantiated virtualization function on an application platform.

[0042] Figure 1 shows an example where the 6G Core Network (6GC) 5 exists independently of the 5G Core Network (5GC) 3. UE 1 communicates wirelessly with the 5G RAN 2 and communicates with 5GC 3 via the 5G RAN 2. UE 1 may also be referred to by other terms such as wireless terminal, mobile terminal, mobile station, wireless device, user terminal, user device, or wireless transmit-receive unit (WTRU). Communication between UE 1 and 5GC 3 includes at least control plane communication and may further include user plane communication. UE 1 communicates wirelessly with the 6G RAN 4 and communicates with 6GC 5 via the 6G RAN 4. Communication between UE 1 and 6GC 5 includes user plane communication and may further include control plane communication.

[0043] In the architecture shown in FIG. 1, the combination of 5G RAN 2 and 5GC 3 is called a 5G network, and the combination of 6G RAN 4 and 6GC 5 is called a 6G network. The 5G network and the 6G network can be provided by the same mobile network operator or different mobile network operators. The 5G network and the 6G network may be two PLMNs. In this case, either the 5G network or the 6G network may be the Home PLMN (HPLMN) of UE 1, and the other may be the Visitor PLMN (VPLMN). Instead, either the 5G network or the 6G network may be a PLMN, and the other may be an NPN.

[0044] Only one (PLMN) subscription may be used for UE 1 to communicate with the 5G network and the 6G network. Instead, two (PLMN) subscriptions may be used for UE 1 to communicate with the 5G network and the 6G network. For example, when two (PLMN) subscriptions are used, the two (PLMN) subscriptions may be associated with the same network administrator (e.g., operator, carrier), or may be associated with different network administrators. When the two (PLMN) subscriptions are associated with the same network administrator, the network administrator may hold two different PLMNs, where one PLMN is the 5G network and the other PLMN is the 6G network.

[0045] UE1 may support dual registration to 5GC3 and 6GC5. That is, UE1 may process independent registrations for both 5GC3 and 6GC5. This enables UE1 to be registered with both 5GC3 and 6GC5. UE1 can simultaneously manage two mobility management states in 5GC3 and 6GC5. UE1 may manage these two registrations or two mobility management states using two independent RRC connections. Here, the RRC connection mentioned does not only include the state where the RRC connection of UE1 is established (e.g., RRC_CONNECTED), but may also include the state where the RRC connection of UE1 is released (e.g., RRC_IDLE, RRC_INACTIVE).

[0046] UE1 may perform single Rx and single Tx operations, single Rx and dual Tx operations, dual Rx and single Tx operations, or dual Rx and dual Tx operations. UE1 may switch between two or more of these four operations according to the situation.

[0047] UE1 may use at least one of DSDS, DSDA, MUSIM, and DualSteer or a technology similar thereto to communicate with the 5G network and the 6G network. The outlines of DSDS, DSDA, MUSIM, and DualSteer are described in the Background Art section of this specification.

[0048] 5G RAN2 includes one or more 5G RAN nodes 21. The 5G RAN node 21 complies with or uses 5G RAT. The 5G RAN node 21 may also be called by other terms such as gNB, 5G base station, 5G radio station, or 5G access point.

[0049] 5GC3 includes one or more control plane nodes or functions, and one or more user plane nodes or functions. In the example in Figure 1, one or more 5G control plane nodes or functions include a 5G Access and Mobility Management Function (AMF) 31, a 5G Session Management Function (SMF) 32, and a 5G Unified Data Management (UDM) 34. One or more 5G user plane nodes or functions include a 5G User Plane Function (UPF) 33.

[0050] 5G AMF 31 is one of the network function nodes in the control plane of 5GC 3. 5G AMF 31 provides the termination of the RAN Control Plane (CP) interface (i.e., N2 interface) with 5G RAN node 21. 5G AMF 31 terminates a single Non-Access Stratum (NAS) signaling connection with UE 1 and provides functionalities including registration management, connection management, and mobility management.

[0051] Registration management includes transitioning the registration status of UE1 between the Registration Management (RM)-DEREGISTERED state and the RM-REGISTERED state, and assigning a registration area to UE1. A registration area is a set of one or more Tracking Areas (TAs), represented by a list of one or more TA Identifiers (TAIs) (i.e., a TAI list). Each TA consists of one or more cells covering a geographical area.

[0052] Connection management includes establishing a NAS signaling connection with UE1 and transitioning the connection management state of UE1 between the Connection Management (CM)-IDLE state and the CM-CONNECTED state.

[0053] Mobility management provides UE identification, NAS security, mobility, and general NAS message forwarding. NAS message forwarding is used for message exchange with UE1 for registration management and connection management, and for message exchange with UE1 for session management, as described later.

[0054] 5G SMF32 is one of the network function nodes in the control plane of 5GC3. 5G SMF32 provides session management, including the establishment, modification, and release of 5G Protocol Data Unit (PDU) sessions. 5G SMF32 sends and receives SM signaling messages to and from the NAS Session Management (SM) layer of UE1 via communication services provided by 5G AMF31. 5G PDU sessions are used to provide PDU connectivity services (i.e., the exchange of PDUs between UE1 and the Data Network (DN)). From a data transfer perspective, a 5G PDU session consists of a tunnel within 5GC3 (e.g., the N9 tunnel), a tunnel between 5GC3 and 5G RAN2 (e.g., the N3 tunnel), and one or more radio bearers.

[0055] 5G UDM34 is one of the network function nodes in the control plane of 5GC3. 5G UDM34 provides subscription management for UE1 on the 5G network and offers various functions based on this. These functions include: - Generation of Authentication and Key Agreement (AKA) authentication credentials; - User identification handling (e.g., storage and management of each subscriber's Subscription Permanent Identifier (SUPI)); - Support for de-concealment of Subscription Concealed Identifier (SUCI); - Access authentication based on subscription data (e.g., roaming restrictions); - Serving Network Function (NF) registration management for UE1 (e.g., store of UE1's Serving AMF and store of UE1's Serving SMF for UE1's 5G PDU sessions); - Support for service or session continuity (e.g., maintaining SMF and Data Network Name (DNN) assignments for ongoing sessions).

[0056] 5G UPF 33 is one of the network function nodes in the user plane of 5GC 3. The functionality of 5G UPF 43 is controlled by 5G SMF 32. 5G UPF 33 handles the user plane path of UE 1's 5G PDU session. 5G UPF 33 processes and forwards user data from UE 1. 5G UPF 33 may include multiple interconnected 5G UPFs. In other words, a single 5G UPF or an arrangement using multiple 5G UPFs can be used for one 5G PDU session of UE 1. More specifically, 5G UPF 33 may include a PDU Session Anchor (PSA) UPF and one or more intermediate UPFs. Intermediate UPFs may provide Uplink Classifier (UL CL) or Branching Point (BP) functionality.

[0057] A 6G RAN 4 includes one or more 6G RAN nodes 41. Each 6G RAN node 41 follows or uses a 6G RAT that is different from the 5G RAT. Each 6G RAN node 41 may also be referred to by other terms such as a 6G base station, 6G radio station, or 6G access point.

[0058] 6GC5 includes one or more control plane nodes or functions, and one or more user plane nodes or functions. In the example of Figure 1, the one or more 6G control plane nodes or functions include 6G AMF51, 6G SMF52, and 6G UDM54. The one or more 6G user plane nodes or functions include 6G UPF53. 6G AMF51, 6G SMF52, 6G UPF54, and 6G UDM54 may have functions similar to those of 5G AMF31, 5G SMF32, 5G UPF34, and 5G UDM34 as described above.

[0059] The 6G AMF 51 provides termination of the RAN CP interface with the 6G RAN node 41. The 6G AMF 51 terminates a single NAS signaling connection with UE 1 and provides functionalities including registration management, connection management, and mobility management. The 6G AMF 51 may assign a 6G registration area to UE 1. The 6G registration area may be a set of one or more 6G TAs. The 6G registration area assigned to UE 1 by the 6G AMF 51 may be different from, the same as, or common to the 5G registration area assigned to UE 1 by the 5G AMF 31.

[0060] The 6G SMF 52 provides session management, including the establishment, modification, and release of 6G PDU sessions. The 6G PDU session is used to provide PDU connectivity services (i.e., the exchange of PDUs between UE 1 and DN). From a data transfer perspective, the 6G PDU session may consist of a tunnel within 6GC 5, a tunnel between 6GC 5 and 6G RAN 4, and one or more radio bearers.

[0061] The 6G UDM 54 provides subscription management for the UE1's 6G network and offers various functions based on this. The functions provided by the 6G UDM 54 may be the same as those provided by the 5G UDM 34.

[0062] The 6G UPF 53 handles the user plane path of the UE1's 6G PDU session. The 6G UPF 53 processes and forwards the UE1's user data. The 5G UPF 53 may include multiple interconnected UPFs.

[0063] As described above, in some implementations, only one (PLMN) subscription may be used for UE1 to communicate with the 5G network and the 6G network. In this case, one of the 5G UDM34 and 6G UDM54 may be omitted. If 5G UDM34 is omitted, the 5G network may be UE1's VPLMN and the 6G network may be UE1's HPLMN. If 6G UDM54 is omitted, the 5G network may be UE1's HPLMN and the 6G network may be UE1's VPLMN.

[0064] The 5G AMF 31 may have an interface with the 6G AMF 51. The 5G AMF 31 may have an interface with the 6G SMF 52. The 6G AMF 51 may have an interface with the 5G SMF 32. The 5G SMF 32 may have an interface with the 6G SMF 52. The 5G SMF 32 may have an interface with the 6G UPF 53. The 6G SMF 52 may have an interface with the 5G UPF 33. The 5G UPF 33 may have an interface with the 6G UPF 53.

[0065] Figure 2 shows an architecture in which 5G RAN2 and 6G RAN4 are connected to the same 5GC3. UE1 communicates wirelessly with 5G RAN2 and communicates with 5GC3 via 5G RAN2. Communication between UE1 and 5GC3 via 5G RAN2 includes at least control plane communication and may further include user plane communication. UE1 communicates wirelessly with 6G RAN4 and communicates with 5GC3 via 6G RAN4. Communication between UE1 and 5GC3 via 6G RAN4 includes user plane communication and may further include control plane communication.

[0066] In the architecture shown in Figure 2, 5G RAN2, or a combination of 5G RAN2 and 5GC3, is called the 5G network, and 6G RAN4, or a combination of 6G RAN4 and 5GC3, is called the 6G network. In the architecture of Figure 2, generally, the 5G network and the 6G network are provided by the same mobile network operator. UE1 may use only one (PLMN) subscription to communicate with the 5G network and the 6G network. Alternatively, UE1 may use two (PLMN) subscriptions to communicate with the 5G network and the 6G network.

[0067] Figure 3 shows an architecture in which 5G RAN2 and 6G RAN4 are connected to the same 6GC5. UE1 communicates wirelessly with 5G RAN2 and communicates with 6GC5 via 5G RAN2. Communication between UE1 and 6GC5 via 5G RAN2 includes at least control plane communication and may further include user plane communication. UE1 communicates wirelessly with 6G RAN4 and communicates with 6GC5 via 6G RAN4. Communication between UE1 and 6GC5 via 6G RAN4 includes user plane communication and may further include control plane communication.

[0068] In the architecture shown in Figure 3, 5G RAN2, or a combination of 5G RAN2 and 6GC5, is called the 5G network, and 6G RAN4, or a combination of 6G RAN4 and 6GC5, is called the 6G network. In the architecture of Figure 3, generally, the 5G network and the 6G network are provided by the same mobile network operator. UE1 may use only one (PLMN) subscription to communicate with the 5G network and the 6G network. Alternatively, UE1 may use two (PLMN) subscriptions to communicate with the 5G network and the 6G network.

[0069] Each of the 5G RAN2 and 5GC3 shown in Figures 1 to 3 is extended to support connectivity and coordination with 6G RAN4 or 6GC5 or both. Therefore, 5G RAN2 may be called evolved or enhanced 5G RAN (or NG-RAN). Similarly, 5GC3 may be called evolved or enhanced 5GC.

[0070] The network architectures, network elements, and technical terms described with reference to Figures 1-3 may be modified as appropriate. These examples are written following those of 5G systems. However, for example, in the case of a 6G system, those described with reference to Figures 1-3 may be modified to suit a 6G system that may be defined in the future. For example, the terms "6G PDU session," "6G RAN node," "6G AMF," "6G SMF," "6G UPF," and "6G UDM" may be replaced with corresponding terms in a 6G system. Also, those described with reference to Figures 1-3 may be cellular networks (ie.e., TN) and satellite networks (ie.e., NTN access).

[0071] <First Embodiment> The configuration example of the wireless communication system according to this embodiment is the same as any of the configuration examples described with reference to Figures 1 to 3. This embodiment provides an example of a method by which UE1 establishes a second RRC connection in a 6G cell in addition to a first RRC connection already established in a 5G cell while UE1 is continuing communication in a 5G cell.

[0072] Figure 4 shows an example of the operation of UE1. UE1 performs the operation shown in Figure 4 when it is in a connected state (i.e., RRC_CONNECTED state, or RRC_CONNECTED and CM-CONNECTED state) in a 5G cell. For example, but not limited to this, UE1 may perform the operation shown in Figure 4 after notifying 5G RAN2 of the detection of a 6G cell in accordance with the operation described in the sixth embodiment below, while UE1 is in a connected state.

[0073] In step 401, UE1 receives specific, certain, given, or predetermined information in the 5G cell. The specific information may include a request, permission or allowance, or indication of establishing a second RRC connection in the 6G cell. Furthermore or alternatively, the specific information may include an indication that interaction or coordination between the 5G network (or 5G RAN2) and the 6G network (or 6G RAN4) is supported. The indication may, for example, indicate that functionality is supported to enable UE1, which is communicating in the 5G cell, to communicate in the 6G cell. Alternatively, the indication may indicate to a UE that has already established a first RRC connection in the 5G cell, that functionality is supported to enable the establishment of a second RRC connection in the 6G cell.

[0074] UE1 may receive the specific information via UE common signaling (e.g., system information broadcast) in the 5G cell. Alternatively, UE1 may receive the specific information using dedicated signaling, such as RRC messages.

[0075] The specific information may be the system information of the 6G cell (e.g., either or both of the Master Information Block (MIB) and / or System Information Block type 1 (SIB1)). In this case, the 5G RAN node 21 may transmit the 6G cell's system information in the 5G cell. The UE 1 may transmit an inter-RAT on-demand system information request via the 5G cell. Specifically, the 5G RAN node 21 may transmit information indicating that the 5G cell supports inter-RAT on-demand system information requests. After receiving this information, the UE 1 may request the transmission of the 6G cell's system information (in the 5G cell) in the 5G cell. In response to this request, the 5G RAN node 21 may transmit the 6G cell's system information in the 5G cell.

[0076] In step 402, in response to receiving the specific information in step 401, UE1 establishes a second RRC connection between UE1 and 6G RAN4 in the 6G cell, in addition to the first RRC connection already established between UE1 and 5G RAN2.

[0077] During the procedure for establishing a second RRC connection, UE1 may send one or more RRC messages in the 6G cell of 6G RAN4. At least one of these RRC messages may include notification information indicating that the second RRC connection relates to interaction or coordination between 5G RAN2 (or the 5G network) and 6G RAN4 (or the 6G network). This RRC message may be an RRC setup request message, and the notification information may be contained in the cause field or information element of the RRC setup request message. Alternatively, the RRC message may be an RRC setup completion message.

[0078] The notification information may indicate a request for dual registration to both 5G and 6G networks (e.g., dualRegistrationRequest).

[0079] Alternatively, the notification information may indicate terminal identification information assigned to UE1 by 5G RAN2, for example, C-RNTI in a serving 5G cell. Alternatively, the notification information may indicate terminal identification information assigned to UE1 by 5GC3, for example, 5G Serving Temporary Mobile Subscriber Identity (5G-S-TMSI). Alternatively, the notification information may indicate identification information of a serving 5G RAN node 21, for example, gNB ID. Alternatively, the notification information may indicate identification information of a serving 5G cell, for example, Physical Cell ID (PCI) or Cell Global Identity (CGI). Alternatively, the notification information may indicate identification information of a serving core network node (e.g., 5G AMF 31) belonging to 5GC3, for example, registeredAMF.

[0080] Furthermore or alternatively, the notification information may indicate identification information relating to the 6G core network, e.g., registered6GC-Identity, provided to UE1 via 5G RAN2. Furthermore or alternatively, the notification information may indicate terminal identification information assigned to UE1 by 6G RAN4, e.g., temporary UE ID in the 6G cell, provided to UE1 via 5G RAN2. Furthermore or alternatively, the notification information may indicate terminal identification information assigned to UE1 by 6GC5 (e.g., 6G AMF51), e.g., 6G-S-TMSI, provided to UE1 via 5G RAN2. Either or both of the temporary UE ID in the 6G cell and the 6G-S-TMSI may be ID(s) assigned to UE1 for use in coordination between the 5G network and the 6G network.

[0081] Figure 5 shows an example of signaling according to this embodiment. UE1 in Figure 5 may be a DSDA device or a MUSIM device. UE1 in Figure 5 has a 5G radio stack and a 6G radio stack. Alternatively, UE1 has a 5G UE portion and a 6G UE portion. The 5G UE portion of UE1 corresponds to a combination of Mobile Equipment (ME) and a 5G USIM for 5G network subscriptions (e.g., SUPI). The 6G UE portion of UE1 corresponds to a combination of ME and a 6G USIM for 6G network subscriptions.

[0082] In step 501, the 5G UE portion of UE1 is in a connected state in the 5G network, including 5G RAN2, and communicates with the 5G network for data or services (user plane communication). The connected state means the RRC_CONNECTED state, the RRC_CONNECTED and CM-CONNECTED state, or the RRC_CONNECTED and CM-CONNECTED and PDU SESSION ACTIVE state. The PDU SESSION ACTIVE state is one of the 5G Session Management (5GSM) states. In the PDU SESSION ACTIVE state, the PDU session of UE1 is active and data transmission is feasible.

[0083] In step 502, 5G RAN2 (e.g., 5G RAN node 21) sets up an inter-RAT direct connection between 5G RAN2 and 6G RAN4 (e.g., 6G RAN node 41). The setup of this inter-RAT direct connection may occur when 5G RAN2 sends a setup request to 6G RAN4, and 6G RAN4 responds to the request. Alternatively, 6G RAN4 may send a setup request to 5G RAN2, and 5G RAN2 responds to the request. This direct connection is used for sending and receiving one or both of the control information and / or user data. This inter-RAT direct connection may be a non-UE associated connection, or it may be a UE associated connection specific to UE1 or a UE group.

[0084] Furthermore, 6G RAN 4 may transmit to 5G RAN 2 one or any combination of the following: information about 6G cells (e.g., identification information (e.g., PCI, CGI), frequency information), the identifier of 6G RAN node 41, and information indicating support for interaction or coordination between 5G and 6G. For example, information indicating support for interaction or coordination between 5G and 6G may indicate to a UE 1 communicating on a 5G cell that communication on a 6G cell will be enabled. Alternatively, the information may indicate that the 6G cell supports the establishment of a second RRC connection in the 6G cell to a UE that has already established a first RRC connection on a 5G cell. Furthermore or alternatively, the information may indicate information about a Use Case supported by the 6G cell.

[0085] Similarly, 5G RAN 2 may transmit to 6G RAN 4 one or any combination of the following: information about 5G cells (e.g., identification information (e.g., PCI, CGI), frequency information), the identifier of 5G RAN node 21, and information indicating support for interaction or coordination between 5G and 6G. For example, the information indicating support for interaction or coordination between 5G and 6G may indicate that a function is supported to enable communication in a 6G cell by UE 1 that is communicating in a 5G cell. Alternatively, the information may indicate to a UE that has already established a first RRC connection in a 5G cell that a function is supported to enable the establishment of a second RRC connection in a 6G cell.

[0086] Instead of step 502, the connection between 5G RAN2 and 6G RAN4 (e.g., 6G RAN node 41) may be established via the core network, i.e., 5GC3 and 6GC5 (Figure 1), 5GC3 (Figure 2), or 6GC5 (Figure 3). In other words, 5G RAN2 may communicate with 6G RAN4 via the core network. In this case, information indicating support for interaction or coordination between 5G and 6G may be transmitted between 5G RAN2 and 5G RAN4 via the core network.

[0087] The order of steps 501 and 502 is not limited to that shown in Figure 5. Step 502 may be performed before step 501.

[0088] In step 503, 5G RAN2 (e.g., 5G RAN node 21) transmits a 6G connection setup indication to UE1 in the 5G cell. The 6G connection setup indication corresponds to the specific information transmitted in step 401 in Figure 4. The 6G connection setup indication may include a request, permission or allowance, or indication of establishing a second RRC connection in the 6G cell. Furthermore or alternatively, the 6G connection setup indication may include an indication that interaction or coordination between the 5G network (or 5G RAN2) and the 6G network (or 6G RAN4) is supported. Such indication may, for example, show that functionality is supported to enable UE1, which is communicating in the 5G cell, to communicate in the 6G cell. Alternatively, such indication may show to a UE that has already established a first RRC connection in the 5G cell, that functionality is supported to enable the establishment of a second RRC connection in the 6G cell. Furthermore, the 6G connection setup display, or the message that transmits it (e.g., RRC message), may include information about the 6G cell (e.g., identification information (e.g., PCI, CGI), frequency information).

[0089] In steps 504-506, in response to receiving the 6G connection setup indicator (step 503), UE1 sets up a second RRC connection with 6G RAN4. Steps 504-506 correspond to step 402 in Figure 4. Specifically, in steps 504 and 505, the 5G UE portion of UE1 triggers the 6G UE portion of UE1 to set up the 6G connection.

[0090] In step 506, the 6G UE portion of UE1 performs a procedure to establish or set up an RRC connection in a 6G cell. UE1 may perform this procedure if certain, certain, given, or predetermined conditions are met. The certain conditions may be at least one of the following: the radio quality of the 6G cell (e.g., RSRP, RSRQ, Signal-to-Interference-plus-Noise Ratio (SINR)) is greater than (or greater than) a certain, certain, given, or predetermined threshold; specific or certain system information (e.g., MIB, SIB1) is detected in the 6G cell; or a 6G cell designated by the network (e.g., 5G RAN2, 6G RAN4) is detected. Information related to the specific conditions may be transmitted from 6G RAN4 to UE1 via 5G RAN2.

[0091] In step 507, the 6G UE portion of UE1 may notify the 5G UE portion of UE1 that the setup of the 6G connection (or the second RRC connection) is complete. In step 508, the 5G UE portion of UE1 may send information about the completion of the setup of the 6G connection (or the second RRC connection) to 5G RAN2. Steps 507 and 508 are optional. For example, 6G RAN4 may send information about the completion of the setup of the 6G connection (or the second RRC connection) to 5G RAN2 via an inter-RAT (direct) connection.

[0092] In step 502, or in another message transmitted between 5G RAN2 and 6G RAN4, 6G RAN4 may transmit to 5G RAN2 at least one of the following: terminal identification information assigned to UE1 by 6G RAN4, terminal identification information assigned to UE1 by 6GC5, or information regarding radio resources used by UE1 to access 6G cells.

[0093] According to the operation of UE1 and 5G RAN node 21 described in this embodiment, UE1 can, in response to receiving specific information from 5G RAN node 21, additionally establish a second RRC connection in a 6G cell, in addition to the first RRC connection already established in the 5G cell. This allows the 5G network to control, for example, the establishment of the second RRC connection in the 6G cell.

[0094] <Second Embodiment> The configuration example of the wireless communication system according to this embodiment is the same as any of the configuration examples described with reference to Figures 1 to 3. This embodiment provides an example of a method for establishing or activating a control plane connection specific to UE1 between UE1 and 6GC5 or between 6G RAN4 and 6GC5 while UE1 is continuing communication in a 5G cell. Establishing or activating this control plane connection may include at least one of the following: a) updating the registration status of UE1 with 6GC5, b) updating the connection management status of UE1 in 6GC5, and c) establishing a NAS signaling connection between UE1 and 6GC5. This control plane connection will be referred to below as a "6G end-to-end (E2E) connection".

[0095] Figure 6 shows an example of signaling according to this embodiment. The procedure shown in Figure 6 is performed after UE1 establishes a second RRC connection in the 6G cell. For example, but not limited to, the establishment of the second RRC connection in the 6G cell may be performed according to the operation described in the first embodiment.

[0096] The procedure shown in Figure 6 is performed after a direct RAT connection is set up between 5G RAN2 and 6G RAN4 (e.g., 6G RAN node 41). This direct connection is used for sending and receiving control information and user data. This direct connection may be a non-UE associated connection, or it may be a UE associated connection specific to UE1 or a UE group.

[0097] The UE1 in Figure 6 may be a DSDA device or a MUSIM device. The UE1 in Figure 6 has a 5G radio stack and a 6G radio stack. Alternatively, the UE1 has a 5G UE portion and a 6G UE portion. For example, the 5G UE portion of the UE1 may correspond to a combination of the ME and a 5G USIM for a 5G network subscription (e.g., SUPI). The 6G UE portion of the UE1 may correspond to a combination of the ME and a 6G USIM for a 6G network subscription.

[0098] UE1 may perform dual registration with 5GC3 and 6GC5. Dual registration may be performed before the procedure shown in Figure 6.

[0099] When the network architecture described with reference to Figure 2 is used, 6GC5 in Figure 6 may be omitted or integrated with 5GC3. In this case, 5GC3 may associate or manage together two subscriptions, two registrations, two authentications, or two E2E connections for UE1 in the 5G and 6G networks.

[0100] When the network architecture described with reference to Figure 3 is used, 5GC3 in Figure 6 may be omitted or integrated with 6GC5. In this case, 6GC5 may associate or manage two subscriptions, two registrations, two authentications, or two E2E connections for UE1 in the 5G and 6G networks.

[0101] In step 601, 6G RAN4 (e.g., 6G RAN node 41) sends a message to 5G RAN2 (e.g., 5G RAN node 21) indicating a request for a 6G E2E connection. This message triggers the establishment or activation of the 6G E2E connection. 6G RAN4 may send this message using an RRC container (e.g., an inter-RAN node RRC message) or an inter-RAN node message. Alternatively, 6G RAN4 may send part of the message in step 601 using an RRC container and the other part using an inter-RAN node message.

[0102] The message in step 601 may include information about a second RRC connection established between UE1 and 6G RAN4. This information may include the cause of establishment that was included in an RRC message (e.g., RRC Setup Request) received by 6G RAN4 from UE1. Alternatively, this information may include notification information that was included in another RRC message (e.g., RRC Setup Complete) received by 6G RAN4 from UE1.

[0103] Alternatively, the message in step 601 may indicate terminal identification information assigned to UE1 by 5G RAN2, for example, C-RNTI in the serving 5G cell. Alternatively, the message in step 601 may indicate terminal identification information assigned to UE1 by 5GC3, for example, 5G-S-TMSI. Alternatively, the message in step 601 may indicate identification information of the serving 5G RAN node 21, for example, gNB ID. Alternatively, the message in step 601 may indicate identification information of the serving 5G cell, for example, PCI or CGI. Alternatively, the message in step 601 may indicate identification information of 6G RAN4, for example, 6G RAN Node ID. Alternatively, the message in step 601 may indicate identification information of a serving core network node (e.g., 5G AMF 31) belonging to 5GC3, for example, registeredAMF. This information may be provided from UE1 to 6G RAN4 (e.g., 6G RAN node 41). This information may be provided from UE1 to 6G RAN4 (e.g., 6G RAN node 41) in the procedure for establishing a second RRC connection between UE1 and 6G RAN4.

[0104] Furthermore or alternatively, the message in step 601 may indicate information about 6G RAN 4 (e.g., 6G RAN node 41) (e.g., 6G RAN node ID, Transport Layer Information (e.g., Transport Layer Address, Tunnel Endpoint Identifier (TEID))). Furthermore or alternatively, the message in step 601 may indicate identification information about the 6G core network provided to UE 1 via 5G RAN 2, e.g., registered6GC-Identity. Furthermore or alternatively, the message in step 601 may indicate terminal identification information assigned to UE 1 by 6GC 5 (e.g., 6G AMF 51) provided to UE 1 via 5G RAN 2, e.g., 6G-S-TMSI. 6G-S-TMSI may be ID(s) assigned to UE 1 for use in coordination between the 5G network and the 6G network. This information may be provided from UE 1 to 6G RAN 4 (e.g., 6G RAN node 41). This information may be provided from UE1 to 6G RAN4 (e.g., 6G RAN node 41) in the procedure for establishing a second RRC connection between UE1 and 6G RAN4.

[0105] In step 602, in response to receiving the message in step 601, 5G RAN2 (e.g., 5G RAN node 21) sends a message to 5GC3 (e.g., 5G AMF 31) indicating a request for a 6G E2E connection. This message triggers the establishment or activation of the 6G E2E connection. 5G RAN2 may transparently forward the request or information received from 6G RAN4 in step 601 to 5GC3. Alternatively, 5G RAN2 may forward to 5GC3 a portion of the information elements or items contained in the request or information received from 6G RAN4 in step 601. The message in step 602 may indicate identification information relating to the 6G core network, such as registered6GC-Identity. Furthermore or alternatively, the message in step 602 may indicate identification information of 6G RAN4, such as the 6G RAN Node ID. Alternatively, the message in step 602 may indicate terminal identification information, such as 6G-S-TMSI, that has been assigned to UE1 by 6GC5 (e.g., 6G AMF51).

[0106] In step 603, in response to receiving the message in step 602, 5GC3 (e.g., 5G AMF 31) sends a message to 6GC5 (e.g., 6G AMF 61) indicating a request for a 6G E2E connection. This message triggers the establishment or activation of a 6G E2E connection. 5GC3 may transparently forward the request or information received from 5G RAN2 in step 602 to 6GC5. Alternatively, 5GC3 may forward to 6GC5 a portion of the information elements or items contained in the request or information received from 5G RAN2 in step 602. The message in step 603 may indicate identification information relating to the 6G core network, e.g., registered6GC-Identity. Furthermore or alternatively, the message in step 603 may indicate terminal identification information assigned to UE1 by 6GC5 (e.g., 6G AMF 51), e.g., 6G-S-TMSI. Alternatively, the message in step 603 may indicate identification information for 6G RAN 4, such as the 6G RAN Node ID.

[0107] In response to receiving the message in step 603, 6GC5 (e.g., 6G AMF51) completes the establishment or activation of the 6G E2E connection, or any necessary 6GC-side processing for that purpose. In step 604, 6GC5 (e.g., 6G AMF51) sends a response message to 5GC3 (e.g., 5G AMF31) regarding the establishment or activation of the 6G E2E connection. This response message includes information regarding the establishment or activation of the 6G E2E connection. Alternatively, the message in step 604 may also indicate identification information for 6G RAN4, such as the 6G RAN Node ID.

[0108] When the network architecture described with reference to Figure 2 is used, steps 603 and 604 may be signaling within one control plane node (e.g., 5G AMF 31) in 5GC3. Alternatively, steps 603 and 604 may be signaling between two control plane nodes located within 5GC3, for example, a control plane node associated with 5G RAN2 (e.g., 5G AMF 31) and a control plane node associated with 6G RAN4 (e.g., evolved or enhanced 5G AMF 31).

[0109] When the network architecture described with reference to Figure 3 is used, steps 603 and 604 may be signaling within one control plane node (e.g., 6G AMF 51) in 6GC 5. Alternatively, steps 603 and 604 may be signaling between two control plane nodes located within 6GC 5, for example, a control plane node associated with 5G RAN 2 (e.g., 6G AMF 51) and a control plane node associated with 6G RAN 4 (e.g., another 6G AMF 51).

[0110] In step 605, in response to receiving the message in step 604, 5GC3 (e.g., 5G AMF 31) sends a response message regarding the establishment or activation of the 6G E2E connection to 5G RAN2 (e.g., 5G RAN node 21). 5GC3 may transparently forward the information regarding the establishment or activation of the 6G E2E connection contained in the message in step 604 to 5G RAN2. Alternatively, 5GC3 may forward some of the information elements or items regarding the establishment or activation of the 6G E2E connection contained in the message in step 604 to 5G RAN2. The message in step 605 may indicate identification information of 6G RAN4, such as the 6G RAN Node ID.

[0111] In step 606, in response to receiving the message in step 605, 5G RAN2 (e.g., 5G RAN node 21) sends a response message regarding the establishment or activation of a 6G E2E connection to 6G RAN4 (e.g., 6G RAN node 41). 5G RAN2 may transparently forward the information regarding the establishment or activation of a 6G E2E connection contained in the message in step 605 to 6G RAN4. Alternatively, 5G RAN2 may forward some of the information elements or items regarding the establishment or activation of a 6G E2E connection contained in the message in step 605 to 6G RAN4.

[0112] In step 607, 6G RAN 4 (e.g., 6G RAN node 41) may send an RRC message to the 6G UE portion of UE 1 indicating the completion of the establishment or activation of the 6G E2E connection. This RRC message may be an RRC Reconfiguration message.

[0113] Figure 7 shows another example of signaling according to this embodiment. Comparing Figure 6 and Figure 7, in Figure 6, information regarding the establishment or activation of a 6G E2E connection is sent from 6GC5 to 6G RAN4 via 5GC3 and 5G RAN2 (steps 604-606), whereas in Figure 7, information regarding the establishment or activation of a 6G E2E connection is sent directly from 6GC5 to 6G RAN4 (step 704). Steps 701-702 in Figure 7 are the same as steps 601-603 in Figure 6. Step 705 in Figure 7 is the same as step 607 in Figure 6.

[0114] The message in step 701 may contain an identifier, such as a 6G RAN Association ID, for association with the message in step 704, which is later received by 6G RAN 4. Similarly, the messages in steps 702, 703, and 704 may contain identifiers, such as a 6G RAN Association ID, for association with the message in step 701 and the message in step 704.

[0115] The message in step 703 may indicate identification information for 6G RAN 4, for example, a 6G RAN Node ID. Alternatively, the message in step 703 may indicate identification information for a 6G cell of 6G RAN 4, for example, a 6G-CGI. The message in step 704 may indicate identification information for a 6G cell of 6G RAN 4, for example, a 6G-CGI.

[0116] Some of the operations of 5G RAN2, 5GC3, 6G RAN4, and 6GC5 described in this embodiment may be replaced with different operations. For example, in addition to or instead of step 601 in Figure 6 or step 701 in Figure 7, the following operations may be performed: 6G RAN4 transmits to 5G RAN2 information indicating that UE1 has established an RRC connection in a 6G cell (or information regarding UE1's RRC connection in a 6G cell). 5G RAN2 transmits to 6G RAN4 a request to move at least some of the User Plane (UP) connections set up for UE1 from 5G RAN2 (or 5G cell) to 6G RAN4 (or 6G cell), or to hand over UE1 to 6G RAN4 (or 6G cell). The UP connections may correspond to, for example, a PDU session, a QoS flow, a DRB, or a network slice. 5G RAN2 may request steering or switching of UP connections on a per-PDU session, per-QoS flow, per-DRB, or per-network slice basis. A request to move an UP connection to 6G RAN or a request for a handover to 6G RAN may require that it be performed at this time, or it may mean that it will be performed later (i.e., prior confirmation).

[0117] 6G RAN 4 sends a response to the request to 5G RAN 2. Upon receiving a response from 6G RAN 4 indicating acceptance of the request, 5G RAN 2 sends a message to 5GC 3 indicating a request for a 6G E2E connection, as in step 602 or step 702. At this time, 5G RAN 2 may also send information to 5GC 3 indicating whether it intends to transfer at least a portion of UE 1's UP connection to 6G RAN 4 or to hand over UE 1 to 6G RAN 4. Furthermore, 5G RAN 2 may send information to 5GC 3 regarding the intended operation (e.g., details of the target UP connection).

[0118] According to the operation of 5G RAN2, 5GC3, 6G RAN4, and 6GC5 described in this embodiment, the establishment or activation of a 6G E2E connection can be performed via 5G RAN2 and 5GC3.

[0119] <Third Embodiment> The configuration example of the wireless communication system according to this embodiment is the same as any of the configuration examples described with reference to Figures 1 to 3. This embodiment provides another example of a method for establishing or activating a 6G E2E connection while UE1 is continuing communication in a 5G cell. As described in the second embodiment, the 6G E2E connection is a control plane connection specific to UE1 established between UE1 and 6GC5 or between 6G RAN4 and 6GC5. Establishing or activating the 6G E2E connection may include at least one of the following: a) updating the registration status of UE1 with 6GC5, b) updating the connection management status of UE1 in 6GC5, and c) establishing a NAS signaling connection between UE1 and 5GC5.

[0120] Figure 8 shows an example of signaling according to this embodiment. The procedure shown in Figure 8 is performed after UE1 establishes a second RRC connection in the 6G cell. For example, but not limited to this, the establishment of the second RRC connection in the 6G cell may be performed according to the operation described in the first embodiment.

[0121] The procedure shown in Figure 8 may be performed after a direct RAT connection has been set up between 5G RAN2 and 6G RAN4 (e.g., 6G RAN node 41). This direct connection is used to send and receive control information and user data. This direct connection may be a non-UE associated connection, or it may be a UE associated connection specific to UE1 or a UE group.

[0122] UE1 in Figure 8 may be a DSDA device or a MUSIM device. UE1 in Figure 8 has a 5G radio stack and a 6G radio stack. Alternatively, UE1 has a 5G UE portion and a 6G UE portion. For example, the 5G UE portion of UE1 may correspond to a combination of ME and a 5G USIM for a 5G network subscription (e.g., SUPI). The 6G UE portion of UE1 may correspond to a combination of ME and a 6G USIM for a 6G network subscription.

[0123] UE1 may perform dual registration with 5GC3 and 6GC5. Dual registration may be performed before the procedure shown in Figure 8.

[0124] When the network architecture described with reference to Figure 2 is used, 6GC5 in Figure 8 may be omitted or integrated with 5GC3. In this case, 5GC3 may associate or manage two subscriptions, two registrations, two authentications, or two E2E connections for UE1 in the 5G and 6G networks.

[0125] When the network architecture described with reference to Figure 3 is used, 5GC3 in Figure 8 may be omitted or integrated with 6GC5. In this case, 6GC5 may associate or manage two subscriptions, two registrations, two authentications, or two E2E connections for UE1 in the 5G and 6G networks.

[0126] In step 801, 6G RAN 4 (e.g., 6G RAN node 41) sends a message to 6GC 5 (e.g., 6G AMF 51) indicating a request for a 6G E2E connection. This message triggers the establishment or activation of the 6G E2E connection. This message may be, for example, an Initial UE message. The Initial UE message forwards the NAS message received by 6G RAN 4 from UE 1, such as a Registration Request message or a Service Request message, to 6GC 5.

[0127] The message in step 801 may include information about a second RRC connection established between UE1 and 6G RAN4. This information may include the cause of establishment that was included in an RRC message received from UE1 (e.g., RRC Setup Request). Alternatively, this information may include notification information that was included in another RRC message received from UE1 (e.g., RRC Setup Complete).

[0128] Alternatively, the message in step 801 may indicate terminal identification information assigned to UE1 by 5G RAN2, for example, C-RNTI in the serving 5G cell. Alternatively, the message in step 801 may indicate terminal identification information assigned to UE1 by 5GC3, for example, 5G-S-TMSI. Alternatively, the message in step 801 may indicate identification information of the serving 5G RAN node 21, for example, gNB ID. Alternatively, the message in step 801 may indicate identification information of the serving 5G cell, for example, PCI or CGI. Alternatively, the message in step 801 may indicate identification information of a serving core network node (e.g., 5G AMF 31) belonging to 5GC3, for example, registeredAMF. This information may be provided from UE1 to 6G RAN4 (e.g., 6G RAN node 41). This information may be provided from UE1 to 6G RAN4 (e.g., 6G RAN node 41) in the procedure for establishing a second RRC connection between UE1 and 6G RAN4.

[0129] Furthermore or alternatively, the message in step 801 may indicate identification information relating to the 6G core network, e.g., registered6GC-Identity, provided to UE1 via 5G RAN2. Furthermore or alternatively, the message in step 801 may indicate terminal identification information, e.g., 6G-S-TMSI, assigned to UE1 by 6GC5 (e.g., 6G AMF51), provided to UE1 via 5G RAN2. 6G-S-TMSI may be ID(s) assigned to UE1 for use in coordination between the 5G network and the 6G network. This information may be provided from UE1 to 6G RAN4 (e.g., 6G RAN node 41). This information may be provided from UE1 to 6G RAN4 (e.g., 6G RAN node 41), for example, in the procedure for establishing a second RRC connection between UE1 and 6G RAN4.

[0130] In response to receiving the message in step 801, 6GC5 (e.g., 6G AMF51) establishes or activates the 6G E2E connection, or completes the necessary 6GC-side processing. In step 802, 6GC5 (e.g., 6G AMF51) sends a response message regarding the establishment or activation of the 6G E2E connection to 6G RAN4 (e.g., 6G RAN node 41). This response message contains information regarding the establishment or activation of the 6G E2E connection. This response message may also be an Initial context setup request message. The Initial context setup request message is sent to establish the entire initial UE context required by 6G RAN node 41. The UE context includes, for example, a PDU session context, security keys, mobility restriction lists, UE Radio Capability, UE Security Capabilities, etc.

[0131] In step 803, 6G RAN 4 (e.g., 6G RAN node 41) may send an RRC message to the 6G UE portion of UE 1 indicating the completion of the establishment or activation of the 6G E2E connection. This RRC message may be an RRC Reconfiguration message.

[0132] In step 804, 6G RAN 4 (e.g., 6G RAN node 41) may send a message to 6GC 5 (e.g., 6G AMF 51) indicating the completion of the establishment or activation of the 6G E2E connection. The message in step 804 may be an Initial context setup response message. The Initial context setup response message indicates the result of the establishment of the initial UE context requested in the Initial context setup request message, for example, the result of the PDU session resource.

[0133] In step 805, 6GC5 (e.g., 6G AMF51) may send a notification to 5GC3 (e.g., 5G AMF31) indicating the establishment or activation of a 6G E2E connection. This notification may indicate terminal identification information assigned to UE1 by 5GC3, for example, 5G-S-TMSI. Alternatively, the notification may indicate terminal identification information assigned to UE1 by 5G RAN2, for example, C-RNTI in the serving 5G cell. This allows 5GC3 (e.g., 5G AMF31) to identify or distinguish UE1 (i.e., the 5G UE portion of UE1) for which a 6G E2E connection has been established or activated. Depending on the establishment or activation of the 6G E2E connection of UE1, 5GC3 (e.g., 5G AMF31, 5G SMF32) may control the UE1's 5G NAS connection or 5G PDU session or both.

[0134] According to the operation of 6G RAN4 and 6GC5 described in this embodiment, the establishment or activation of a 6G E2E connection can be performed using direct signaling between 6G RAN4 and 6GC5.

[0135] <Fourth Embodiment> The configuration example of the wireless communication system according to this embodiment is the same as any of the configuration examples described with reference to Figures 1 to 3. This embodiment provides an example of a method in which UE1 performs user plane communication in a 6G cell while maintaining a logical connection in a 5G cell.

[0136] UE1 establishes an RRC connection in a 6G cell, establishes a 6G E2E connection via the 6G cell, and establishes a user plane path (e.g., a 6G PDU session) via the 6G cell. For example, but not limited to, the establishment of an RRC connection in a 6G cell may be performed according to the operation described in the first embodiment. For example, but not limited to, the establishment of a 6G E2E connection may be performed according to the operation described in the second or third embodiment. As described in the second and third embodiments, the 6G E2E connection is a control plane connection specific to UE1 established between UE1 and 6GC5 or between 6G RAN4 and 6GC5. Establishing or activating a 6G E2E connection may include at least one of the following: a) updating the registration status of UE1 with 6GC5, b) updating the connection management status of UE1 in 6GC5, and c) establishing a NAS signaling connection between UE1 and 5GC5.

[0137] While maintaining a control plane connection via a 6G cell, or while performing user plane communication via a 6G cell, UE1 maintains an RRC connection in the 5G cell. Furthermore, UE1 may maintain a 5G E2E connection, i.e., a NAS signaling connection with the 5G AMF31. In other words, UE1 may maintain a CM-CONNECTED state. Furthermore, UE1 may maintain a user plane path (e.g., a 5G PDU session) via the 5G cell.

[0138] In one implementation, while maintaining a control plane connection via a 6G cell, or while performing user plane communication via a 6G cell, UE1 may be in the RRC_CONNECTED or RRC_INACTIVE state in 5G RAN2, and may maintain the CM-CONNECTED state. In this case, 5G RAN2 and 5GC3 maintain a signaling connection (i.e., N2 connection) for UE1 between 5G RAN2 (e.g., 5G RAN node 21) and 5GC3 (e.g., 5G AMF 31). 5G AMF 31 maintains the CM-CONNECTED state with respect to UE1. UE1 and 5GC3 (e.g., 5G SMF 32) may maintain the 5GSM state of UE1's 5G PDU session in the PDU SESSION ACTIVE state, or move it to the PDU SESSION INACTIVE state.

[0139] Alternatively, in other implementations, while maintaining a control plane connection via a 6G cell, or while performing user plane communication via a 6G cell, UE1 may enter a new CM state (e.g., CM-SUSPEND or CM-INACTIVE state) in 5G RAN2 that is either RRC_CONNECTED or RRC_INACTIVE, and is different from both CM-CONNECTED and CM-IDLE states. In this case, 5G RAN2 and 5GC3 release the signaling connection (e.g., N2 connection) for UE1 between 5G RAN2 and 5GC3. 5G AMF31 maintains the UE context of UE1. 5G AMF31 enters a new CM state (e.g., CM-SUSPEND or CM-INACTIVE state) with respect to UE1 that is different from both CM-CONNECTED and CM-IDLE states. UE1 and 5GC3 (e.g., 5G SMF32) may change the 5GSM state of UE1's 5G PDU session to the PDU SESSION INACTIVE state.

[0140] UE1, the 5G network, and the 6G network may perform Voice over NR (VoNR) communication on the 5G network and other data communications on the 6G network.

[0141] 5G RAN2 and 6G RAN4 may provide UE1 in the 5G RRC_CONNECTED state and 6G RRC_CONNECTED state with a common Discontinuous Reception (DRX) pattern for 5G and 6G cells. Alternatively, the DRX pattern for 5G cells may differ from the DRX pattern for 6G cells. 5G RAN2 and 6G RAN4 may provide UE1 with separate DRX patterns that differ for 5G and 6G cells. The separate DRX patterns may be configured so that the Active period (e.g., On-Duration) or Sleep period in 6G cells does not overlap with those in 5G cells. Furthermore, or alternatively, UE1 and 5G RAN2 may apply microsleep or deep sleep to 5G cells independently of 6G cells.

[0142] <Fifth Embodiment> The configuration example of the wireless communication system according to this embodiment is the same as any of the configuration examples described with reference to Figures 1 to 3. This embodiment provides an example of how UE1 uses the 6G wireless stack.

[0143] Figure 9 shows an example of the operation of UE1. In step 901, UE1 communicates with 5G RAN2 using the 5G radio stack. The 5G radio stack includes the 5G radio protocol stack. The 5G radio protocol stack includes the 5G control plane protocol stack and may further include the 5G user plane protocol stack. The 5G control plane protocol stack includes the physical layer, the Medium Access Control (MAC) sublayer, the Radio Link Control (RLC) sublayer, the Packet Data Convergence Protocol (PDCP) sublayer, and the RLC layer. The 5G user plane protocol stack includes the physical layer, the MAC sublayer, the RLC sublayer, the PDCP sublayer, and the Service Data Adaptation Protocol (SDAP) sublayer.

[0144] In step 902, UE1 turns on the 6G radio stack, provided that a specific, certain, given, defined, or predetermined event occurs while UE1 is staying in the 5G cell. UE1 staying in the 5G cell may mean that UE1 is camped on to the 5G cell. Camping on a cell means that UE1 has completed the cell selection or re-selection process and has selected the cell. The term "camped on" means that UE1 is staying in a cell and is ready to initiate a potential dedicated service in that cell. To this end, UE1 must acquire or possess essential system information (e.g., MIB and SIB1, either or both) in that cell. In particular, when UE1 is in the RRC_IDLE or RRC_INACTIVE state, UE1's serving cell can be said to be a cell that UE1 is camped on. A serving cell is sometimes called a camped cell.

[0145] The 6G radio stack includes a 6G radio protocol stack. The 6G radio protocol stack includes a 6G control plane protocol stack and may further include a 6G user plane protocol stack. The 6G control plane protocol stack includes a physical layer, a data link layer, and an RRC layer. The 6G user plane protocol stack includes a physical layer and a data link layer. The data link layer of the 6G control plane may include a MAC sublayer, an RLC sublayer, and a PDCP sublayer, similar to that of 5G. The data link layer of the 6G user plane may include a MAC sublayer, an RLC sublayer, a PDCP sublayer, and an SDAP sublayer, similar to that of 5G.

[0146] In some implementations, the above event may relate to the proximity of UE1 to the radio coverage of 6G RAN4. This event may include the broadcasting of neighbor cell information containing one or more 6G cells of 6G RAN4 in a 5G cell of 5G RAN2. When UE1 is in the RRC_IDLE or RRC_INACTIVE state in a 5G cell, UE1 may autonomously turn on the 6G radio stack, provided that neighbor cell information containing one or more 6G cells of 6G RAN4 is broadcast in the 5G cell. When UE1 is in the RRC_CONNECTED state in a 5G cell, UE1 may autonomously turn on the 6G radio stack, provided that neighbor cell information containing one or more 6G cells of 6G RAN4 is broadcast.

[0147] The above-described event may include the UE 1 receiving some indication or instruction 1001 from 5G RAN 2, as shown in Figure 10. The indication or instruction 1001 may be called a 6G radio stack activation trigger. The indication or instruction 1001 may indicate, for example, that 5G RAN 2 supports a function to enable a UE communicating in a 6G cell (e.g., 6G cell 42) while the UE is communicating in a 5G cell (e.g., 5G cell 22). Alternatively, the indication or instruction 1001 may indicate that 5G RAN 2 supports a function to enable a UE communicating in a 6G cell (e.g., 6G cell 42) while the UE is communicating in a 5G cell (e.g., 5G cell 22). The indication or instruction 1001 may indicate that a UE that has already established a first RRC connection in a 5G cell is supported with the ability to establish a second RRC connection in a 6G cell. The indication or instruction 1001 may also indicate that a UE that has already established a first RRC connection in a 5G cell is permitted to either or both detect and report proximity to a 6G cell.

[0148] 5G RAN2 (e.g., 5G RAN node 21) may transmit a display or instruction 1001 via a UE common signaling (e.g., system information broadcast) that can be received by multiple UEs in the RRC_IDLE, RRC_INACTIVE, and RRC_CONNECTED states. When UE1 is in the RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED state in a 5G cell, UE1 may turn on the 6G radio stack, provided that UE1 has received a display or instruction 1001 via the UE common signaling of the 5G cell.

[0149] 5G RAN2 (e.g., 5G RAN node 21) may send a display or instruction 1001 to UE1, which is in the RRC_CONNECTED state, using dedicated signaling, such as an RRC message. When UE1 is in the RRC_CONNECTED state in 5G cell 22, UE1 may turn on the 6G radio stack, provided that it has received a display or instruction 1001 in 5G cell 22. Alternatively, when UE1 is in the RRC_CONNECTED state in a 5G cell, UE1 may turn on the 6G radio stack, provided that neighboring cell information including one or more 6G cells (e.g., 6G cell 42) of 6G RAN4 has been broadcast and it has received a display or instruction 1001 in 5G cell 22.

[0150] The events described above may include the fact that UE1 has determined its proximity to the 6G RAN4's wireless coverage based on historical information about locations where communication with 6G RAN4 has occurred in the past. For example, UE1 may maintain information associating information about cells it has stayed in in the past with its own location at that time, and determine its proximity to the 6G RAN4's wireless coverage based on its current location and the information it has maintained.

[0151] The events described above may include the result of inference by UE1 using an artificial intelligence or machine learning model indicating the proximity of UE1 to 6G RAN4 radio coverage or the need to turn on the 6G radio stack. For example, UE1 may perform inference based on one or any combination of information from previously occupied cells and its own location at that time, radio quality information of the serving cell (or occupied cell), and mobility information. UE1 may perform such inference only if it is permitted (by 5G RAN2) to do so in the serving cell (or occupied cell).

[0152] Turning on the 6G radio stack may include UE1 initiating operation or processing using the 6G radio stack. In other words, turning on the 6G radio stack may cause UE1 to initiate operation or processing using the 6G radio stack. Furthermore or alternatively, turning on the 6G radio stack may include UE1 activating the 6G radio stack. Furthermore or alternatively, turning on the 6G radio stack may include UE1 initiating communication using the 6G radio stack.

[0153] Furthermore, or alternatively, turning on the 6G radio stack may include UE1 performing a measurement of one or more 6G cells in the 6G RAN4. In other words, turning on the 6G radio stack may cause UE1 to perform a measurement of one or more 6G cells in the 6G RAN4.

[0154] Furthermore, or alternatively, turning on the 6G radio stack may include UE1 performing a search for one or more 6G cells in the 6G RAN4. In other words, turning on the 6G radio stack may cause UE1 to perform a search for one or more 6G cells in the 6G RAN4.

[0155] Furthermore, or alternatively, turning on the 6G radio stack may include UE1 considering one or more 6G cells of 6G RAN4 in cell selection or reselection. In other words, turning on the 6G radio stack may cause UE1 to consider one or more 6G cells of 6G RAN4 in cell selection or reselection. For example, UE1 may treat a 6G cell as one of the candidate (target) cells in the cell selection or reselection process or procedure.

[0156] If DC is not performed in the communication between UE1 and 5G RAN2 (e.g., 5G RAN node 21), UE1 may use one of the two transmit / receive functions available for communication with 5G RAN2 for the 6G radio stack. On the other hand, if DC is performed in the communication between UE1 and 5G RAN2 (e.g., 5G RAN node 21), UE1 may use one of the two transmit / receive functions used for communication with 5G RAN2 for the 6G radio stack in a time-division multiplexer.

[0157] After UE1 has turned on the 6G radio stack and remained in a 6G cell, UE1 may keep the 5G radio stack on or turn it off. After UE1 has moved from a 6G cell to a 5G cell, if the specific, certain, given, or predetermined conditions described above are not met, UE1 may turn off the 6G radio stack. Turning off the 5G radio stack may include deactivating the 5G radio stack. Furthermore or alternatively, turning off the 5G radio stack may include not performing any operations that may occur when the 5G radio stack is on. Furthermore or alternatively, turning off the 5G radio stack may mean not performing any communication using the 5G radio stack.

[0158] According to the operation of UE1 described in this embodiment, UE1 turns on the 6G radio stack if a specific, certain, given, or predetermined event occurs while UE1 is staying in a 5G cell. This can reduce the power consumption of UE1 compared to if UE1 always turns on the 6G radio stack, for example, in situations where 6G coverage is geographically localized, particularly during the initial deployment of 6G.

[0159] <Sixth Embodiment> The configuration example of the wireless communication system according to this embodiment is the same as any of the configuration examples described with reference to Figures 1 to 3. This embodiment provides an example of a method by which UE1 prepares for communication on a 6G cell while UE1 is communicating on a 5G cell.

[0160] Figures 11 and 12 show an example of the operation of UE1. UE1 performs the operations shown in Figures 11 and 12 when it is in a connected state (i.e., RRC_CONNECTED state, or RRC_CONNECTED and CM-CONNECTED state) in a 5G cell. For example, UE1 may perform the operations shown in Figures 11 and 12 after turning on the 6G radio stack according to the operation described in the first embodiment, while in a connected state.

[0161] In steps 1101 and 1201, UE1 detects the 6G cell 42 using the 6G radio stack. In steps 1102 and 1202, UE1 transmits reporting information in the 5G cell 22 based on the detection of the 6G cell 42.

[0162] In steps 1101 and 1201, the 6G cell 42 (i.e., the 6G network managing it) may transmit information in the 6G cell 42 indicating that the 6G cell 42 supports interaction or coordination between 5G and 6G. This information may indicate that the 6G cell 42 supports interaction or coordination between 5G and 6G. This information may indicate to the UE 1 communicating in the 5G cell 22 that communication in the 6G cell 42 is permitted. Alternatively, this information may indicate to the UE 1 communicating in the 5G cell 22 that communication in the 6G cell 42 is possible. Alternatively, the information may indicate that the 6G cell 42 (i.e., the 6G network managing the 6G cell) supports the establishment of a second RRC connection in the 6G cell 42 to a UE that has already established a first RRC connection in the 5G cell 22. Alternatively, this information may indicate information about the Use Cases supported in the 6G cell 42. A use case may be at least one of the following: normal service (e.g., handled), Ultra Low Latency Communications (URLLC), immersive (e.g., extended reality (XR), Augmented Reality (AR) / Virtual Reality (VR)), massive communication (e.g., Internet of Things (IoT), Reduced Capability devices (RedCap)), Non-Terrestrial Network (NTN), and Uncrewed Aerial Vehicle (UAV).

[0163] UE1 may send the reporting information from steps 1102 and 1202 using RRC messages. These RRC messages may also be UE assistance information messages. In other words, UE1 may send the reporting information using the UE assistance information (UAI) procedure.

[0164] The reporting information in steps 1102 and 1202 may include information indicating that a 6G cell 42 has been detected. Furthermore or alternatively, the reporting information may include information indicating that the cell detected by UE1 is a 6G cell.

[0165] Furthermore, or alternatively, the reporting information in steps 1102 and 1202 may include information indicating that UE1 wishes to communicate on the 6G cell 42.

[0166] Furthermore, or alternatively, the reporting information in steps 1102 and 1202 may include information regarding the establishment of an RRC connection in 6G cell 42. This information may indicate that there will be an interruption in communication in 5G cell 22. This information may indicate a request for a gap (i.e., a period during which one or both of the downlink and uplink transmissions for UE1 in 5G cell are not performed). This information may indicate that a gap is not required.

[0167] Furthermore, or alternatively, the reporting information in steps 1102 and 1202 may include information indicating that UE1 is or has initiated the procedure for establishing an RRC connection in 6G cell 42.

[0168] Furthermore or alternatively, the reporting information in steps 1102 and 1202 may include information indicating that UE 1 has received specific, certain, given, or predetermined information in 6G cell 42. The specific information may indicate that 6G cell 42 supports interaction or coordination between 5G and 6G. For example, such information may indicate to UE 1, which is communicating in 5G cell 22, that communication in 6G cell 42 is enabled. Alternatively, such information may indicate that 6G cell 42 (i.e., the 6G network managing the 6G cell) supports the establishment of a second RRC connection in 6G cell 42 for a UE that has already established a first RRC connection in 5G cell 22. Furthermore or alternatively, such information may indicate information regarding a Use Case supported in 6G cell 42.

[0169] Furthermore, or alternatively, the reporting information in steps 1102 and 1202 may include identification information (e.g., PCI or CGI) of the detected 6G cell 42.

[0170] Furthermore, or alternatively, the reporting information in steps 1102 and 1202 may include at least one of the following information regarding the detected 6G cell 42: cell radio quality, identifier of RAN node 41, and area identifier (e.g., RAN area ID, TAI, Tracking Area Code (TAC)). Cell radio quality may be Reference Signal Received Power (RSRP) or Reference Signal Received Quality (RSRQ) or both.

[0171] Furthermore, or alternatively, the reporting information in steps 1102 and 1202 may include information about the 6G network to which the detected 6G cell 42 belongs (e.g., PLMN identity, 6G NAS information). Additionally, if UE 1 has already registered with the 6G network, the reporting information may include 6GC identification information (e.g., registered 6GC-Identity).

[0172] Furthermore, or alternatively, the reporting information in steps 1102 and 1202 may include information about communications that UE1 wishes to conduct in 6G cell 42. For example, this information may include information indicating at least one of the following regarding communications that UE1 wishes to conduct in 6G cell 42: use case, type, network slice, and quality of service (QoS) level. The network slice may be identified by Single Network Slice Selection Assistance Information (S-NSSAI) or Network Slice Access Stratum Group (NSAG) ID.

[0173] Furthermore, or alternatively, the reporting information in steps 1102 and 1202 may include information regarding switching to 6G cell 42. This information may relate to a handover from 5G cell 22 to 6G cell 42, or to the switching or steering of data or services from 5G cell 22 to 6G cell 42. The switching or steering of data or services may be performed on a PDU session basis, a QoS flow basis, a radio bearer (e.g., Data Radio Bearer (DRB)) basis, or a network slice basis.

[0174] The 5G RAN node 21 receives the reporting information from UE1 in the 5G cell 22 in steps 1102 and 1202. In response to receiving the reporting information, the 5G RAN node 21 may transmit the corresponding information to UE1 in the 5G cell 22. For example, the 5G RAN node 21 may transmit permission or indication to UE1 in the 5G cell 22 to establish a second RRC connection between UE1 and 6G RAN4, in addition to the first RRC connection already established between UE1 and 5G RAN2.

[0175] Figure 13 shows an example of signaling when UE1 has a 5G radio stack and a 6G radio stack. UE1 in Figure 13 may be a DSDA device. Alternatively, UE1 may have a 5G UE portion and a 6G UE portion. For example, the 5G UE portion of UE1 may correspond to a combination of ME and a 5G USIM for a 5G network 25 subscription (e.g., SUPI). The 6G UE portion of UE1 may correspond to a combination of ME and a 6G USIM for a 6G network 45 subscription. The 5G network 25 in Figure 13 corresponds to 5G RAN2, or 5G RAN2 and 5GC3 (Figure 1 or 2), or 5G RAN2 and 6GC5 (Figure 3). The 6G network 45 in Figure 13 corresponds to 6G RAN4, or 6G RAN4 and 6GC5 (Figure 1 or 3), or 6G RAN4 and 5GC3 (Figure 2).

[0176] In step 1301, the 5G UE portion of UE1 is in a connected state in the 5G network 25 and performs data or service communication (user plane communication) with the 5G network 25. The connected state means the RRC_CONNECTED state, the RRC_CONNECTED and CM-CONNECTED state, or the RRC_CONNECTED, CM-CONNECTED and PDU SESSION ACTIVE state.

[0177] In step 1302, the 6G UE portion of UE1 detects a 6G cell of the 6G network 45. At this time, the 6G network 45 may transmit information similar to the information transmitted by the 6G network 45 as described with reference to Figures 11 and 12 (steps 1101 and 1201).

[0178] In step 1303, the 6G UE portion of UE1 notifies the 5G UE portion of UE1 of the detection of a 6G cell. For example, the RRC layer of the 6G UE portion of UE1 may make this notification to the RRC layer of the 5G UE portion of UE1.

[0179] In step 1304, the 5G UE portion of UE1 transmits 6G cell-related assistance information to the 5G network 25 (e.g., 5G RAN node 21). The 6G cell-related assistance information corresponds to the reporting information (steps 1102 and 1202) described with reference to Figures 11 and 12.

[0180] In step 1305, the 5G network 25 (e.g., one or both of the 5G RAN node 21 and the 5G AMF 31) initiates 6G cell-aware control. For example, this control may include mobility control for the movement of the UE 1 from the 5G network 25 to the 6G network 45, steering of data or service communications (user plane communications) from the 5G network 25 to the 6G network 45, or control for establishing a NAS connection between the UE 1 and the 6G network 45, or any combination thereof.

[0181] Figure 14 shows an example of signaling when UE1 is a MUSIM device. UE1 in Figure 14 has a 5G radio stack and a 6G radio stack. Alternatively, UE1 has a 5G UE portion and a 6G UE portion. The 5G UE portion of UE1 corresponds to a combination of ME and a 5G USIM for a subscription (e.g., SUPI) to the 5G network 25. The 6G UE portion of UE1 corresponds to a combination of ME and a 6G USIM for a subscription to the 6G network 45. The 5G network 25 in Figure 14 corresponds to 5G RAN2, or 5G RAN2 and 5GC3 (Figure 1 or Figure 2), or 5G RAN2 and 6GC5 (Figure 3). The 6G network 45 in Figure 13 corresponds to 6G RAN4, or 6G RAN4 and 6GC5 (Figure 1 or Figure 3), or 6G RAN4 and 5GC3 (Figure 2).

[0182] Here, UE1's subscription to the 5G network 25 may be the same subscription to the same operator (e.g., a mobile network operator (MNO), carrier, or network operator) as UE1's subscription to the 6G network 45. For example, an operator may own multiple PLMNs, and the 5G network 25 and the 6G network 45 may each be assigned a different PLMN. Alternatively, the 5G network 25 and the 6G network 45 may be assigned the same PLMN. In other words, UE1 has the ability to simultaneously connect to different types of networks (e.g., Radio Access Technology (RAT), 5G, or 6G) managed by a single operator. This function or such form can also be called an Intra-PLMN (or Intra-MNO, Intra-Operator) MUSIM.

[0183] In step 1401, the 5G UE portion of UE1 completes registration with the 5G network 25 and is in a connected state on the 5G network 25. The connected state means the RRC_CONNECTED state, the RRC_CONNECTED and CM-CONNECTED state, or the RRC_CONNECTED, CM-CONNECTED and PDU SESSION ACTIVE state.

[0184] In step 1402, the 6G UE portion of UE1 completes registration with the 6G network 45 and is in an idle or inactive state on the 6G network 45. The idle or inactive state means the RRC_IDLE state, the RRC_INACTIVE state, the RRC_IDLE and RM-REGISTERED state, or the RRC_INACTIVE and RM-REGISTERED state.

[0185] In step 1403, the 5G UE portion of UE1 is connected to the 5G network 25 and performs data or service communication (user plane communication) with the 5G network 25.

[0186] In step 1404, the 6G UE portion of UE1 detects a 6G cell of the 6G network 45. Alternatively, the 6G UE portion of UE1 receives paging from the 6G network 45. In step 1405, the 6G UE portion of UE1 notifies the 5G UE portion of UE1 of the detection of a 6G cell or the reception of 6G paging.

[0187] In step 1406, the 5G UE portion of UE1 transmits 6G cell-related assistance information to the 5G network 25 (e.g., 5G RAN node 21). The 6G cell-related assistance information corresponds to the reporting information (steps 1102 and 1202) described with reference to Figures 11 and 12. Furthermore, UE1 may include in the reporting information information indicating that the intent (or purpose, subject) of the reporting information is Intra-PLMN MUSIM.

[0188] In step 1407, the 5G network 25 (e.g., one or both of the 5G RAN node 21 and the 5G AMF 31) initiates 6G cell-aware control. For example, this control may include mobility control for the movement of the UE 1 from the 5G network 25 to the 6G network 45, steering of data or service communications (user plane communications) from the 5G network 25 to the 6G network 45, or control for establishing a NAS connection between the UE 1 and the 6G network 45, or any combination thereof.

[0189] According to the operation of UE1 and 5G RAN node 21 described in this embodiment, UE1 transmits reporting information in the 5G cell based on the detection of a 6G cell. This enables UE1 to trigger the 5G network to begin preparing for communication in the 6G cell, for example.

[0190] <Other Embodiments> The embodiments described above have focused on the case where UE1 uses a 5G network and a 6G network. However, these embodiments can also be applied to the case where UE1 uses any two networks with different RATs, for example, a 4G network and a 6G network.

[0191] The embodiments described above may be modified in part as appropriate. For example, at least part of the information transmitted via the inter-RAT direct connection between 5G RAN2 and 6G RAN4 may be transmitted via 5GC3 or via 5GC3 and 6GC5. Also, the operation by UE1 to establish an RRC connection in a 6G cell while communicating in a 5G cell of 5G RAN2 may be performed as part of a series of procedures for handover between different RATs or as preparation. For example, between the start and completion of a series of procedures for inter-RAT handover, UE1 may operate to use the 6G radio stack in addition to the 5G radio stack.

[0192] Next, the configuration examples of UE1, 5G RAN node 21, 6G RAN node 41, and core network nodes (e.g., 5G AMF31, 5G SMF32, 6G AMF51, 6G SMF52) related to the above-described embodiments will be explained. Figure 15 is a block diagram showing a configuration example of UE1. The RF transceiver 1501 performs analog RF signal processing to communicate with the 5G RAN node 21 and the 6G RAN node 41. The RF transceiver 1501 may include multiple transceivers. The analog RF signal processing performed by the RF transceiver 1501 includes frequency upconversion, frequency downconversion, and amplification. The RF transceiver 1501 is coupled with the antenna array 1502 and the baseband processor 1503. The RF transceiver 1501 receives modulation symbol data (or orthogonal frequency-division multiplexing (OFDM) symbol data) from the baseband processor 1503, generates a transmit RF signal, and supplies the transmit RF signal to the antenna array 1502. The RF transceiver 1501 also generates a baseband receive signal based on the received RF signal received by the antenna array 1502 and supplies this to the baseband processor 1503. The RF transceiver 1501 may include an analog beamformer circuit for beamforming. The analog beamformer circuit may include, for example, multiple phase shifters and multiple power amplifiers.

[0193] The baseband processor 1503 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. Digital baseband signal processing may include (a) data compression / decompression, (b) data segmentation / concatenation, (c) generation / decomposition of transmission format (transmission frame), (d) transmission path coding / decoding, (e) modulation (symbol mapping) / demodulation, and (f) generation of OFDM symbol data (baseband OFDM signal) by Inverse Fast Fourier Transform (IFFT). On the other hand, control plane processing may include communication management at Layer 1 (e.g., transmit power control), Layer 2 (e.g., radio resource management and hybrid automatic repeat request (HARQ) processing), and Layer 3 (e.g., signaling related to attach, mobility, and call management).

[0194] For example, the digital baseband signal processing by the baseband processor 1503 may include signal processing for the PDCP layer, RLC layer, MAC layer, and PHY layer. Furthermore, the control plane processing by the baseband processor 1503 may include processing for the Non-Access Stratum (NAS) protocol, RRC protocol, MAC Control Elements (CEs), and Downlink Control Information (DCIs).

[0195] The baseband processor 1503 may perform MIMO encoding and precoding for beamforming.

[0196] The baseband processor 1503 may include a modem processor (e.g., Digital Signal Processor (DSP)) for performing digital baseband signal processing and a protocol stack processor (e.g., Central Processing Unit (CPU) or Micro Processing Unit (MPU)) for performing control plane processing. In this case, the protocol stack processor for performing control plane processing may be shared with the application processor 1504 described later.

[0197] The application processor 1504 is also called a CPU, MPU, microprocessor, or processor core. The application processor 1504 may include multiple processors (multiple processor cores). The application processor 1504 implements various functions of the UE 1 by executing system software programs (Operating System (OS)) and various application programs (e.g., calling applications, web browsers, mail clients, camera operation applications, music playback applications) read from memory 1506 or other memory.

[0198] In some implementations, the baseband processor 1503 and the application processor 1504 may be integrated on a single chip, as shown by the dashed line (1505) in Figure 15. In other words, the baseband processor 1503 and the application processor 1504 may be implemented as a single System on Chip (SoC) device 1505. An SoC device is sometimes called a System Large Scale Integration (LSI) or chipset.

[0199] Memory 1506 is volatile memory, non-volatile memory, or a combination thereof. Memory 1506 may include multiple physically independent memory devices. Volatile memory is, for example, Static Random Access Memory (SRAM) or Dynamic RAM (DRAM), or a combination thereof. Non-volatile memory is Mask Read Only Memory (MROM), Electrically Erasable Programmable ROM (EEPROM), flash memory, or hard disk drive, or any combination thereof. For example, memory 1506 may include an external memory device accessible from the baseband processor 1503, the application processor 1504, and the SoC 1505. Memory 1506 may also include an internal memory device integrated within the baseband processor 1503, the application processor 1504, or the SoC 1505. Furthermore, memory 1506 may include memory within a Universal Integrated Circuit Card (UICC).

[0200] The memory 1506 may store one or more software modules (computer programs) 1507 containing instruction sets and data for processing by the UE 1. In some implementations, the baseband processor 1503 or the application processor 1504 may be configured to read and execute the software modules 1507 from the memory 1506 to perform the processing of the UE 1 as described in one or more of the multiple embodiments.

[0201] Furthermore, the control plane processing and operations performed by the UE 1 described in the above embodiment can be realized by other elements other than the RF transceiver 1501 and antenna array 1502, namely at least one of the baseband processor 1503 and application processor 1504 and the memory 1506 storing the software module 1507.

[0202] Figure 16 is a block diagram showing an example configuration of a 5G RAN node 21. The configuration of a 6G RAN node 41 may be similar to that of Figure 16. Referring to Figure 16, the 5G RAN node 21 includes an RF transceiver 1601, a network interface 1603, a processor 1604, and a memory 1605. The RF transceiver 1601 performs analog RF signal processing to communicate with UEs 1. The RF transceiver 1601 may include multiple transceivers. The RF transceiver 1601 is coupled with an antenna array 1602 and a processor 1604. The RF transceiver 1601 receives modulation symbol data from the processor 1604, generates a transmit RF signal, and supplies the transmit RF signal to the antenna array 1602. The RF transceiver 1601 also generates a baseband receive signal based on the received RF signal received by the antenna array 1602 and supplies this to the processor 1604. The RF transceiver 1601 may include an analog beamformer circuit for beamforming. The analog beamformer circuit may include, for example, multiple phase shifters and multiple power amplifiers.

[0203] The network interface 1603 is used to communicate with network nodes (e.g., other RAN nodes, as well as control and forwarding nodes of the core network). The network interface 1603 may include, for example, a network interface card (NIC) compliant with the IEEE 802.3 series.

[0204] Processor 1604 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. Processor 1604 may include multiple processors. For example, processor 1604 may include a modem processor (e.g., Digital Signal Processor (DSP)) for digital baseband signal processing and a protocol stack processor (e.g., CPU or MPU) for control plane processing. Processor 1604 may also include a digital beamformer module for beamforming. The digital beamformer module may include a MIMO encoder and a precoder.

[0205] Memory 1605 is composed of a combination of volatile memory and non-volatile memory. The volatile memory is, for example, SRAM or DRAM or a combination thereof. The non-volatile memory is MROM, EEPROM, flash memory, or a hard disk drive or any combination thereof. Memory 1605 may include storage located away from the processor 1604. In this case, the processor 1604 may access memory 1605 via the network interface 1603 or other I / O interfaces.

[0206] The memory 1605 may store one or more software modules (computer programs) 1606 containing instruction sets and data for processing by the 5G RAN node 21. In some implementations, the processor 1604 may be configured to read the software modules 1606 from the memory 1605 and execute them to perform the processing of the 5G RAN node 21 as described in one or more of the multiple embodiments.

[0207] Furthermore, the control plane processing and operation performed by the 5G RAN node 21 described in the above embodiment can be realized by elements other than the RF transceiver 1601 and antenna array 1602, namely the processor 1604 and the memory 1605 storing the software module 1606.

[0208] Figure 17 shows an example configuration of 5G AMF 31. The configurations of other 5G core network nodes and 6G core network nodes such as 5G SMF 32, 5G UPF 33, 5G UDM 34, 6G AMF 51, 6G SMF 52, 6G UPF 53, and 6G UDM 54 may be similar to those shown in Figure 17. Referring to Figure 17, 5G AMF 31 includes a network interface 1701, a processor 1702, and memory 1703.

[0209] The network interface 1701 is used, for example, to communicate with other network functions (NFs) or nodes. The network interface 1701 may include, for example, a network interface card (NIC) compliant with the IEEE 802.3 series.

[0210] The processor 1702 may be, for example, a microprocessor, an MPU, or a CPU. The processor 1702 may include multiple processors.

[0211] Memory 1703 is composed of volatile memory and non-volatile memory. Memory 1703 may include a plurality of physically independent memory devices. The volatile memory is, for example, SRAM or DRAM or a combination thereof. The non-volatile memory is MROM, EEPROM, flash memory, or a hard disk drive or any combination thereof. Memory 1703 may include storage located away from the processor 1702. In this case, the processor 1702 may access memory 1703 via a network interface 1701 or an I / O interface.

[0212] The memory 1703 may store one or more software modules (computer programs) 1704 containing instruction sets and data for performing processing by the 5G AMF 31 as described in the above embodiments. In some implementations, the processor 1702 may be configured to perform the 5G AMF 31 processing as described in the above embodiments by reading and executing the software modules 1704 from the memory 1703.

[0213] As illustrated with reference to Figures 15 to 17, each processor in the UE1, 5G RAN node 21, 6G RAN node 41, and core network nodes (e.g., 5G AMF31, 5G SMF32, 6G AMF51, 6G SMF52) according to the above embodiment can execute one or more programs containing a set of instructions for causing a computer to perform the algorithms described with reference to the drawings. The program, when loaded into a computer, contains a set of instructions (or software code) for causing the computer to perform one or more functions described in the embodiment. The program may be stored in a non-temporary computer-readable medium or a physical storage medium. Examples, but not limited to, include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD), or other memory technologies, CD-ROM, digital versatile disk (DVD), Blu-ray® disc, or other optical disc storage, magnetic cassette, magnetic tape, magnetic disk storage, or other magnetic storage devices. The program may be transmitted over a temporary computer-readable medium or communication medium. For example, but not limited to, a temporary computer-readable medium or communication medium may include electrical, optical, acoustic, or other forms of propagating signals.

[0214] The embodiments described above are merely examples of how the technical concept obtained by the present inventor can be applied. In other words, the technical concept is not limited to the embodiments described above, and various modifications are certainly possible.

[0215] For example, some or all of the embodiments described above may also be described as follows, but are not limited to: Some or all of the elements (e.g., configuration and function) described in the notes directed to devices (e.g., wireless terminals, RAN nodes, core network nodes) may also be described as notes directed to methods and programs. For example, some or all of the elements described in notes 2-9, which are dependent on note 1, may also be described as notes dependent on notes 10 and 11, in a similar dependency relationship to notes 2-9. Similarly, some or all of the elements described in notes 13-15, which are dependent on note 12, may also be described as notes dependent on notes 16 and 17, in a similar dependency relationship to notes 13-15. Some or all of the elements described in any note may be applied to various hardware, software, recording means for recording software, systems, and methods.

[0216] (Note 1) A wireless terminal comprising: means for receiving first information in a first cell of a first radio access network (RAN) conforming to a first radio access technology (RAT); and means for establishing a second RRC connection between the wireless terminal and the second RAN in a second cell of a second RAN conforming to a second RAT different from the first RAT, in response to the reception of the first information, in addition to a first Radio Resource Control (RRC) connection already established between the wireless terminal and the first RAN. (Note 2) The wireless terminal according to Note 1, wherein the first information includes a request, permission, or indication for establishing the second RRC connection. (Note 3) The wireless terminal according to Note 1 or 2, wherein the first information includes an indication that interaction or coordination between the first RAN and the second RAN is supported. (Note 4) The wireless terminal according to any one of Notes 1 to 3, wherein the establishing means is configured to transmit an RRC message in a second cell of the second RAN during the procedure for establishing the second RRC connection, and the RRC message includes second information indicating that the second RRC connection relates to interaction or coordination between the first RAN and the second RAN. (Note 5) The wireless terminal according to Note 4, wherein the RRC message is an RRC setup request message, and the second information is contained in an establishment factor field or information element in the RRC setup request message. (Note 6) The wireless terminal according to Note 4 or 5, wherein the second information includes at least one of the following: a) terminal identification information assigned to the wireless terminal by the first RAN, b) terminal identification information assigned to the wireless terminal by a first core network associated with the first RAN, c) identification information of a RAN node belonging to the first RAN, d) identification information of a first cell, and e) identification information of a core network node belonging to the first core network.(Note 7) The wireless terminal according to any one of Notes 4 to 6, wherein the second information includes identification information relating to a second core network associated with the second RAN, provided to the wireless terminal via the first RAN. (Note 8) The wireless terminal according to any one of Notes 4 to 7, wherein the second information includes terminal identification information assigned to the wireless terminal by the second RAN or by a second core network associated with the second RAN, provided to the wireless terminal via the first RAN. (Note 9) The wireless terminal according to any one of Notes 1 to 8, further comprising means for transmitting a notification indicating the completion of the establishment of the second RRC connection to the first RAN via the first cell. (Note 10) A method performed by a wireless terminal, comprising: receiving first information in a first cell of a first radio access network (RAN) that conforms to a first radio access technology (RAT); and, in response to the reception of the first information, establishing a second RRC connection between the wireless terminal and the second RAN in a second cell of a second RAN that conforms to a second RAT different from the first RAT, in addition to a first Radio Resource Control (RRC) connection already established between the wireless terminal and the first RAN. (Note 11) A program causing a computer to perform a method for a wireless terminal, the method comprising: receiving first information in a first cell of a first radio access network (RAN) that conforms to a first radio access technology (RAT); and, in response to the reception of the first information, establishing a second RRC connection between the wireless terminal and the second RAN in a second cell of a second RAN that conforms to a second RAT different from the first RAT, in addition to a first Radio Resource Control (RRC) connection already established between the wireless terminal and the first RAN.(Note 12) A radio access network (RAN) node comprising means for transmitting first information to a radio terminal in a first cell of a first radio access network (RAN) conforming to a first radio access technology (RAT), wherein the first information causes the radio terminal to establish a second RRC connection in a second cell of the second RAN between the radio terminal and a second RAN conforming to a second RAT different from the first RAT, in addition to a first Radio Resource Control (RRC) connection already established between the radio terminal and the first RAN. (Note 13) The RAN node according to Note 12, wherein the first information includes a request, permission, or indication for establishing the second RRC connection. (Note 14) The RAN node according to Note 12 or 13, wherein the first information includes an indication that interaction or coordination between the first RAN and the second RAN is supported. (Note 15) A RAN node according to any one of Notes 12 to 14, further comprising means for receiving a notification from the wireless terminal via the first cell indicating the completion of the establishment of the second RRC connection. (Note 16) A method performed by a radio access network (RAN) node, comprising transmitting first information to a wireless terminal in a first cell of a first radio access network (RAN) conforming to a first radio access technology (RAT), the first information causing the wireless terminal to establish a second RRC connection in a second cell of the second RAN between the wireless terminal and a second RAN conforming to a second RAT different from the first RAT, in addition to a first Radio Resource Control (RRC) connection already established between the wireless terminal and the first RAN.(Note 17) A program that causes a computer to perform a method for a line access network (RAN) node, comprising transmitting first information to a wireless terminal in a first cell of a first radio access network (RAN) conforming to a first radio access technology (RAT), wherein the first information causes the wireless terminal to establish a second RRC connection in a second cell of the second RAN, between the wireless terminal and a second RAN conforming to a second RAT different from the first RAT, in addition to a first Radio Resource Control (RRC) connection already established between the wireless terminal and the first RAN. (Note 18) A first RAN node belonging to a first radio access network (RAN) of a first network, comprising: means for communicating with a radio terminal via a first cell of the first RAN; means for receiving a first message from a second RAN node of a second RAN of a second network that triggers the establishment or activation of a control plane connection specific to the radio terminal between the radio terminal or the second RAN node and the second core network of the second network; and means for sending a second message to a first core network node of the first core network of the first network that triggers the establishment or activation of the control plane connection in response to the reception of the first message. (Note 19) The first RAN node according to Note 18, further comprising: means for receiving a third message relating to the establishment or activation of the control plane connection from a first core network node; and means for sending a fourth message relating to the establishment or activation of the control plane connection to the second RAN node in response to the reception of the third message. (Note 20) The means for communicating is configured to communicate with the wireless terminal using a first Radio Resource Control (RRC) connection between the wireless terminal and the first RAN, and the first message includes information about a second RRC connection established between the wireless terminal and the second RAN, the first RAN node as described in Note 18 or 19.(Note 21) The first RAN node according to any one of Notes 18 to 20, wherein the first message includes at least one of a) terminal identification information assigned to the wireless terminal by the first RAN, b) terminal identification information assigned to the wireless terminal by the first core network, c) identification information of the first RAN node, d) identification information of the first cell, and e) identification information of a core network node belonging to the first core network. (Note 22) The first RAN node according to any one of Notes 18 to 21, wherein the first message includes identification information relating to the second core network provided to the wireless terminal via the first RAN. (Note 23) The first RAN node according to any one of Notes 18 to 22, wherein the first message includes terminal identification information assigned to the wireless terminal by the second core network provided to the wireless terminal via the first RAN. (Note 24) The establishment or activation of the control plane connection includes at least one of the following: a) updating the registration status of the wireless terminal to the second core network; b) updating the connection management status of the wireless terminal in the second core network; and c) establishing a Non-Access Stratum (NAS) signaling connection between the wireless terminal and the second core network, as described in any one of Notes 18 to 23.(Note 25) A method performed by a first RAN node belonging to a first radio access network (RAN) of a first network, comprising: communicating with a wireless terminal via a first cell of the first radio access network (RAN) of the first network; receiving a first message from a second RAN node of a second RAN of a second network that triggers the establishment or activation of a control plane connection specific to the wireless terminal between the wireless terminal or the second RAN node and the second core network of the second network; and sending a second message to a first core network node of the first core network of the first network that triggers the establishment or activation of the control plane connection in response to the receipt of the first message. (Note 26) A program for causing a computer to perform a method for a first RAN node belonging to a first radio access network (RAN) of a first network, the method comprising: communicating with a wireless terminal via a first cell of the first radio access network (RAN) of the first network; receiving a first message from a second RAN node of a second RAN of a second network that triggers the establishment or activation of a control plane connection specific to the wireless terminal between the wireless terminal or the second RAN node and the second core network of the second network; and sending a second message to a first core network node of the first core network of the first network that triggers the establishment or activation of the control plane connection in response to the receipt of the first message.(Note 27) A first core network node belonging to the first core network of a first network, comprising: means for communicating with a wireless terminal via a first radio access network (RAN) node and a first cell of the first network; means for receiving a first message from the first RAN node that triggers the establishment or activation of a control plane connection specific to the wireless terminal between the wireless terminal or the second RAN of the second network and the second core network of the second network; and means for sending a second message to the second core network node of the second core network that triggers the establishment or activation of the control plane connection in response to the reception of the first message. (Note 28) The first core network node according to Note 27, further comprising: means for receiving a third message relating to the establishment or activation of the control plane connection from the second core network node; and means for sending a fourth message relating to the establishment or activation of the control plane connection to the first RAN node in response to the reception of the third message. (Note 29) The first core network node according to Note 27 or 28, wherein the first message includes identification information relating to the second core network provided to the wireless terminal via the first RAN. (Note 30) The first core network node according to any one of Notes 27 to 29, wherein the first message includes terminal identification information assigned to the wireless terminal by the second core network provided to the wireless terminal via the first RAN. (Note 31) The establishment or activation of the control plane connection includes at least one of the following: a) updating the registration status of the wireless terminal to the second core network; b) updating the connection management status of the wireless terminal in the second core network; and c) establishing a Non-Access Stratum (NAS) signaling connection between the wireless terminal and the second core network, as described in any one of Notes 27 to 30.(Note 32) A method performed by a first core network node belonging to a first core network of a first network, comprising: communicating with a wireless terminal via a first radio access network (RAN) node and a first cell of the first network; receiving a first message from the first RAN node that triggers the establishment or activation of a control plane connection specific to the wireless terminal between the wireless terminal or a second RAN of a second network and a second core network of the second network; and sending a second message to a second core network node of the second core network that triggers the establishment or activation of the control plane connection in response to the receipt of the first message. (Note 33) A program for causing a computer to perform a method for a first core network node belonging to a first core network of a first network, the method comprising: communicating with a wireless terminal via a first radio access network (RAN) node and a first cell of the first network; receiving a first message from the first RAN node to trigger the establishment or activation of a control plane connection specific to the wireless terminal between the wireless terminal or a second RAN of a second network and a second core network of the second network; and sending a second message to a second core network node of the second core network to trigger the establishment or activation of the control plane connection in response to the receipt of the first message.(Note 34) A second RAN node belonging to a second radio access network (RAN) of a second network, comprising: means for communicating with a radio terminal via a second cell of the second RAN; means for sending a first message to a first RAN node of a first RAN of a first network to trigger the establishment or activation of a control plane connection specific to the radio terminal between the radio terminal or the second RAN node and the second core network of the second network; and means for receiving a second message relating to the establishment or activation of the control plane connection from the first RAN node or from a second core network node of the second core network of the second network. (Note 35) The second RAN node according to Note 34, wherein the first message includes information relating to a second RRC connection established between the radio terminal and the second RAN. (Note 36) The second RAN node according to Note 34 or 35, wherein the first message includes at least one of the following: a) terminal identification information assigned to the wireless terminal by the first RAN, b) terminal identification information assigned to the wireless terminal by the first core network of the first network, c) identification information of the first RAN node, d) identification information of the first cell of the first RAN node where the wireless terminal resides, and e) identification information of a core network node belonging to the first core network. (Note 37) The second RAN node according to any one of Notes 34 to 36, wherein the first message includes identification information relating to the second core network provided to the wireless terminal via the first RAN. (Note 38) The second RAN node according to any one of Notes 34 to 37, wherein the first message includes terminal identification information assigned to the wireless terminal by the second core network provided to the wireless terminal via the first RAN.(Note 39) The establishment or activation of the control plane connection includes at least one of the following: a) updating the registration status of the wireless terminal to the second core network; b) updating the connection management status of the wireless terminal in the second core network; and c) establishing a Non-Access Stratum (NAS) signaling connection between the wireless terminal and the second core network, as described in any one of Notes 34 to 38. (Note 40) A method performed by a second RAN node belonging to a second radio access network (RAN) of a second network, comprising: communicating with a radio terminal via a second cell of the second RAN; sending a first message to a first RAN node of a first RAN of a first network to trigger the establishment or activation of a control plane connection specific to the radio terminal between the radio terminal or the second RAN node and the second core network of the second network; and receiving a second message relating to the establishment or activation of the control plane connection from the first RAN node or from a second core network node of the second core network of the second network. (Note 41) A program for causing a computer to perform a method for a second RAN node belonging to a second radio access network (RAN) of a second network, the method comprising: communicating with a radio terminal via a second cell of the second RAN; sending a first message to a first RAN node of the first RAN of the first network to trigger the establishment or activation of a control plane connection specific to the radio terminal between the radio terminal or the second RAN node and the second core network of the second network; and receiving a second message from the first RAN node or from a second core network node of the second core network of the second network regarding the establishment or activation of the control plane connection.(Note 42) A second core network node belonging to a second core network of a second network, comprising: means for receiving a first message from a first core network node of a first core network of a first network that triggers the establishment or activation of a control plane connection specific to a wireless terminal between the wireless terminal or a second RAN node belonging to a second radio access network (RAN) of the second network and the second core network; and means for sending a second message relating to the establishment or activation of the control plane connection to the first core network node or the second RAN node in response to the reception of the first message. (Note 43) The second core network node according to Note 42, wherein the first message includes identification information relating to the second core network provided to the wireless terminal via the first RAN of the first network. (Note 44) The second core network node according to Note 42 or 43, wherein the first message includes terminal identification information assigned to the wireless terminal by the second core network, provided to the wireless terminal via the first RAN of the first network. (Note 45) The second core network node according to any one of Notes 42 to 44, wherein the establishment or activation of the control plane connection includes at least one of a) updating the registration status of the wireless terminal to the second core network, b) updating the connection management status of the wireless terminal in the second core network, and c) establishing a Non-Access Stratum (NAS) signaling connection between the wireless terminal and the second core network.(Note 46) A method performed by a second core network node belonging to a second core network of a second network, comprising: receiving a first message from a first core network node of a first core network of a first network that triggers the establishment or activation of a control plane connection specific to a wireless terminal between the wireless terminal or a second RAN node belonging to a second radio access network (RAN) of the second network and the second core network; and sending a second message relating to the establishment or activation of the control plane connection to the first core network node or the second RAN node in response to the receipt of the first message. (Note 47) A program for causing a computer to perform a method for a second core network node belonging to a second core network of a second network, the method comprising: receiving a first message from a first core network node of a first core network of a first network that triggers the establishment or activation of a control plane connection specific to a wireless terminal between the wireless terminal or a second RAN node belonging to a second radio access network (RAN) of the second network and the second core network; and sending a second message relating to the establishment or activation of the control plane connection to the first core network node or the second RAN node in response to the receipt of the first message.

[0217] This application claims priority based on Japanese Patent Application No. 2024-167381, filed on 26 September 2024, and incorporates all of its disclosures herein.

[0218] 1 UE 2 5G RAN 3 5GC 4 6G RAN 5 6GC 21 5G RAN node 22 5G cell 31 5G AMF 32 5G AMF 33 5G UPF 34 5G UDM 41 6G RAN node 42 6G cell 51 6G UPF 52 6G SMF 53 6G UPF 54 6G UDM

Claims

1. A wireless terminal comprising: means for receiving first information in a first cell of a first radio access network (RAN) conforming to a first radio access technology (RAT); and means for establishing a second RRC connection between the wireless terminal and the second RAN in a second cell of a second RAN conforming to a second RAT different from the first RAT, in addition to a first Radio Resource Control (RRC) connection already established between the wireless terminal and the first RAN, in response to the reception of the first information.

2. The wireless terminal according to claim 1, wherein the first information includes a request, permission, or indication to establish the second RRC connection.

3. The wireless terminal according to claim 1 or 2, wherein the first information includes an indication that interaction or coordination between the first RAN and the second RAN is supported.

4. The wireless terminal according to any one of claims 1 to 3, wherein the establishing means is configured to transmit an RRC message in a second cell of the second RAN during the procedure for establishing the second RRC connection, the RRC message includes second information indicating that the second RRC connection relates to interaction or coordination between the first RAN and the second RAN.

5. The wireless terminal according to claim 4, wherein the RRC message is an RRC setup request message, and the second information is contained in an establishment factor field or information element in the RRC setup request message.

6. The wireless terminal according to claim 4 or 5, wherein the second information includes at least one of the following: a) terminal identification information assigned to the wireless terminal by the first RAN; b) terminal identification information assigned to the wireless terminal by a first core network associated with the first RAN; c) identification information of a RAN node belonging to the first RAN; d) identification information of a first cell; and e) identification information of a core network node belonging to the first core network.

7. The wireless terminal according to any one of claims 4 to 6, wherein the second information includes identification information relating to a second core network associated with the second RAN, provided to the wireless terminal via the first RAN.

8. The wireless terminal according to any one of claims 4 to 7, wherein the second information includes terminal identification information provided to the wireless terminal via the first RAN and assigned to the wireless terminal by the second RAN or by a second core network associated with the second RAN.

9. The wireless terminal according to any one of claims 1 to 8, further comprising means for transmitting a notification to the first RAN via the first cell indicating the completion of the establishment of the second RRC connection.

10. A method performed by a wireless terminal, comprising: receiving first information in a first cell of a first radio access network (RAN) conforming to a first radio access technology (RAT); and, in response to the reception of the first information, establishing a second RRC connection between the wireless terminal and the second RAN in a second cell of a second RAN conforming to a second RAT different from the first RAT, in addition to a first Radio Resource Control (RRC) connection already established between the wireless terminal and the first RAN.

11. A program causing a computer to perform a method for a wireless terminal, the method comprising: receiving first information in a first cell of a first radio access network (RAN) conforming to a first radio access technology (RAT); and, in response to the reception of the first information, establishing a second RRC connection between the wireless terminal and the second RAN in a second cell of a second RAN conforming to a second RAT different from the first RAT, in addition to a first Radio Resource Control (RRC) connection already established between the wireless terminal and the first RAN.

12. A radio access network (RAN) node comprising means for transmitting first information to a radio terminal in a first cell of a first radio access network (RAN) conforming to a first radio access technology (RAT), wherein the first information causes the radio terminal to establish a second RRC connection in a second cell of the second RAN, which conforms to a second RAT different from the first RAT, in addition to a first Radio Resource Control (RRC) connection already established between the radio terminal and the first RAN.

13. The RAN node according to claim 12, wherein the first information includes a request, permission, or indication to establish the second RRC connection.

14. The RAN node according to claim 12 or 13, wherein the first information includes an indication that interaction or coordination between the first RAN and the second RAN is supported.

15. The RAN node according to any one of claims 12 to 14, further comprising means for receiving a notification from the wireless terminal via the first cell indicating the completion of the establishment of the second RRC connection.

16. A method performed by a radio access network (RAN) node, comprising transmitting first information to a radio terminal in a first cell of a first radio access network (RAN) conforming to a first radio access technology (RAT), wherein the first information causes the radio terminal to establish a second RRC connection in a second cell of the second RAN, which conforms to a second RAT different from the first RAT, in addition to a first Radio Resource Control (RRC) connection already established between the radio terminal and the first RAN.

17. A program causing a computer to perform a method for a line access network (RAN) node, comprising transmitting first information to a wireless terminal in a first cell of a first radio access network (RAN) conforming to a first radio access technology (RAT), wherein the first information causes the wireless terminal to establish a second RRC connection in a second cell of a second RAN conforming to a second RAT different from the first RAT, in addition to a first Radio Resource Control (RRC) connection already established between the wireless terminal and the first RAN.

18. A first RAN node belonging to a first radio access network (RAN) of a first network, comprising: means for communicating with a radio terminal via a first cell of the first RAN; means for receiving a first message from a second RAN node of a second RAN of a second network that triggers the establishment or activation of a control plane connection specific to the radio terminal between the radio terminal or the second RAN node and the second core network of the second network; and means for sending a second message to a first core network node of the first core network of the first network that triggers the establishment or activation of the control plane connection in response to the reception of the first message.

19. The first RAN node according to claim 18, further comprising: means for receiving a third message relating to the establishment or activation of the control plane connection from the first core network node; and means for sending a fourth message relating to the establishment or activation of the control plane connection to the second RAN node in response to the receipt of the third message.

20. The first RAN node according to claim 18 or 19, wherein the means for communicating is configured to communicate with the wireless terminal using a first Radio Resource Control (RRC) connection between the wireless terminal and the first RAN, and the first message includes information relating to a second RRC connection established between the wireless terminal and the second RAN.

21. The first RAN node according to any one of claims 18 to 20, wherein the first message includes at least one of the following: a) terminal identification information assigned to the wireless terminal by the first RAN, b) terminal identification information assigned to the wireless terminal by the first core network, c) identification information of the first RAN node, d) identification information of the first cell, and e) identification information of a core network node belonging to the first core network.

22. The first RAN node according to any one of claims 18 to 21, wherein the first message includes identification information relating to the second core network, provided to the wireless terminal via the first RAN.

23. The first RAN node according to any one of claims 18 to 22, wherein the first message includes terminal identification information assigned to the wireless terminal by the second core network, provided to the wireless terminal via the first RAN.

24. The establishment or activation of the control plane connection comprises at least one of the following: a) updating the registration status of the wireless terminal to the second core network; b) updating the connection management status of the wireless terminal in the second core network; and c) establishing a Non-Access Stratum (NAS) signaling connection between the wireless terminal and the second core network, as described in any one of claims 18 to 23.

25. A method performed by a first RAN node belonging to a first radio access network (RAN) of a first network, comprising: communicating with a radio terminal via a first cell of the first radio access network (RAN) of the first network; receiving a first message from a second RAN node of a second RAN of a second network that triggers the establishment or activation of a control plane connection specific to the radio terminal between the radio terminal or the second RAN node and the second core network of the second network; and sending a second message to a first core network node of the first core network of the first network that triggers the establishment or activation of the control plane connection in response to the receipt of the first message.

26. A program for causing a computer to perform a method for a first RAN node belonging to a first radio access network (RAN) of a first network, the method comprising: communicating with a radio terminal via a first cell of the first radio access network (RAN) of the first network; receiving a first message from a second RAN node of a second RAN of a second network that triggers the establishment or activation of a control plane connection specific to the radio terminal between the radio terminal or the second RAN node and the second core network of the second network; and sending a second message to a first core network node of the first core network of the first network that triggers the establishment or activation of the control plane connection in response to the receipt of the first message.

27. A first core network node belonging to a first core network of a first network, comprising: means for communicating with a wireless terminal via a first radio access network (RAN) node and a first cell of the first network; means for receiving a first message from the first RAN node that triggers the establishment or activation of a control plane connection specific to the wireless terminal between the wireless terminal or the second RAN of the second network and the second core network of the second network; and means for sending a second message to the second core network node of the second core network that triggers the establishment or activation of the control plane connection in response to the reception of the first message.

28. The first core network node according to claim 27, further comprising: means for receiving a third message relating to the establishment or activation of the control plane connection from the second core network node; and means for sending a fourth message relating to the establishment or activation of the control plane connection to the first RAN node in response to the receipt of the third message.

29. The first core network node according to claim 27 or 28, wherein the first message includes identification information relating to the second core network, provided to the wireless terminal via the first RAN.

30. The first core network node according to any one of claims 27 to 29, wherein the first message includes terminal identification information assigned to the wireless terminal by the second core network, provided to the wireless terminal via the first RAN.

31. The establishment or activation of the control plane connection comprises at least one of the following: a) updating the registration status of the wireless terminal to the second core network; b) updating the connection management status of the wireless terminal in the second core network; and c) establishing a Non-Access Stratum (NAS) signaling connection between the wireless terminal and the second core network, as described in any one of claims 27 to 30.

32. A method performed by a first core network node belonging to a first core network of a first network, comprising: communicating with a wireless terminal via a first radio access network (RAN) node and a first cell of the first network; receiving a first message from the first RAN node that triggers the establishment or activation of a control plane connection specific to the wireless terminal between the wireless terminal or a second RAN of a second network and a second core network of the second network; and sending a second message to a second core network node of the second core network that triggers the establishment or activation of the control plane connection in response to the receipt of the first message.

33. A program for causing a computer to perform a method for a first core network node belonging to a first core network of a first network, the method comprising: communicating with a wireless terminal via a first radio access network (RAN) node and a first cell of the first network; receiving a first message from the first RAN node to trigger the establishment or activation of a control plane connection specific to the wireless terminal between the wireless terminal or a second RAN of a second network and a second core network of the second network; and sending a second message to a second core network node of the second core network to trigger the establishment or activation of the control plane connection in response to the receipt of the first message.

34. A second RAN node belonging to a second radio access network (RAN) of a second network, comprising: means for communicating with a radio terminal via a second cell of the second RAN; means for sending a first message to a first RAN node of a first RAN of a first network to trigger the establishment or activation of a control plane connection specific to the radio terminal between the radio terminal or the second RAN node and the second core network of the second network; and means for receiving a second message relating to the establishment or activation of the control plane connection from the first RAN node or from a second core network node of the second core network of the second network.

35. The second RAN node according to claim 34, wherein the first message includes information relating to a second RRC connection established between the wireless terminal and the second RAN.

36. The second RAN node according to claim 34 or 35, wherein the first message includes at least one of the following: a) terminal identification information assigned to the wireless terminal by the first RAN; b) terminal identification information assigned to the wireless terminal by the first core network of the first network; c) identification information of the first RAN node; d) identification information of the first cell of the first RAN node where the wireless terminal resides; and e) identification information of a core network node belonging to the first core network.

37. The second RAN node according to any one of claims 34 to 36, wherein the first message includes identification information relating to the second core network, provided to the wireless terminal via the first RAN.

38. The second RAN node according to any one of claims 34 to 37, wherein the first message includes terminal identification information assigned to the wireless terminal by the second core network, provided to the wireless terminal via the first RAN.

39. The establishment or activation of the control plane connection comprises at least one of the following: a) updating the registration status of the wireless terminal to the second core network; b) updating the connection management status of the wireless terminal in the second core network; and c) establishing a Non-Access Stratum (NAS) signaling connection between the wireless terminal and the second core network, as described in any one of claims 34 to 38.

40. A method performed by a second RAN node belonging to a second radio access network (RAN) of a second network, comprising: communicating with a radio terminal via a second cell of the second RAN; sending a first message to a first RAN node of a first RAN of a first network to trigger the establishment or activation of a control plane connection specific to the radio terminal between the radio terminal or the second RAN node and the second core network of the second network; and receiving a second message relating to the establishment or activation of the control plane connection from the first RAN node or from a second core network node of the second core network of the second network.

41. A program for causing a computer to perform a method for a second RAN node belonging to a second radio access network (RAN) of a second network, the method comprising: communicating with a radio terminal via a second cell of the second RAN; sending a first message to a first RAN node of the first RAN of the first network to trigger the establishment or activation of a control plane connection specific to the radio terminal between the radio terminal or the second RAN node and the second core network of the second network; and receiving a second message from the first RAN node or from a second core network node of the second core network of the second network relating to the establishment or activation of the control plane connection.

42. A second core network node belonging to a second core network of a second network, comprising: means for receiving a first message from a first core network node of a first core network of a first network that triggers the establishment or activation of a control plane connection specific to a wireless terminal between the wireless terminal or a second RAN node belonging to a second radio access network (RAN) of the second network and the second core network; and means for sending a second message relating to the establishment or activation of the control plane connection to the first core network node or the second RAN node in response to the reception of the first message.

43. The second core network node according to claim 42, wherein the first message includes identification information relating to the second core network, provided to the wireless terminal via the first RAN of the first network.

44. The second core network node according to claim 42 or 43, wherein the first message includes terminal identification information assigned to the wireless terminal by the second core network, provided to the wireless terminal via the first RAN of the first network.

45. The establishment or activation of the control plane connection comprises at least one of the following: a) updating the registration status of the wireless terminal to the second core network; b) updating the connection management status of the wireless terminal in the second core network; and c) establishing a Non-Access Stratum (NAS) signaling connection between the wireless terminal and the second core network, as described in any one of claims 42 to 44.

46. ​​A method performed by a second core network node belonging to a second core network of a second network, comprising: receiving a first message from a first core network node of a first core network of a first network that triggers the establishment or activation of a control plane connection specific to a wireless terminal between the wireless terminal or a second RAN node belonging to a second radio access network (RAN) of the second network and the second core network; and sending a second message relating to the establishment or activation of the control plane connection to the first core network node or the second RAN node in response to the receipt of the first message.

47. A program for causing a computer to perform a method for a second core network node belonging to a second core network of a second network, the method comprising: receiving a first message from a first core network node of a first core network of a first network that triggers the establishment or activation of a control plane connection specific to a wireless terminal between the wireless terminal or a second RAN node belonging to a second radio access network (RAN) of the second network and the second core network; and sending a second message relating to the establishment or activation of the control plane connection to the first core network node or the second RAN node in response to the receipt of the first message.

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