Method and apparatus for enhanced mobility

Abstract

This invention describes a method and apparatus for enhanced mobility comprising: determining, by the wireless device, an incoming change of its roaming or coverage status, and performing, by the wireless device, a mobility procedure to and / or roaming procedure over a second access device, wherein the second access device is managed by a second serving network and / or co-managed by the first and the second serving network while being connected to the first serving network.

Description

[0001] METHOD AND APPARATUS FOR ENHANCED MOBILITY

[0002] FIELD OF THE INVENTION

[0003] This invention relates to a method, apparatus, and system for operating a wireless device such as a user equipment enabling enhanced mobility in a wireless system such as a cellular system, a WiFi network or the like.

[0004] BACKGROUND OF THE INVENTION

[0005] In conventional cellular networks, a primary station serves a plurality of secondary stations located within a cell served by this primary station. Wireless communication from the primary station towards each secondary station is done on downlink channels. Conversely, wireless communication from each secondary towards the primary station is done on uplink channels. The wireless communication can include data traffic (sometimes referred to User Data), and control information (also referred sometimes as signalling). This control information typically comprises information to assist the primary station and / or the secondary station to exchange data traffic (e.g. resource allocation / requests, physical transmission parameters, information on the state of the respective stations).

[0006] In the context of cellular networks as standardized by 3GPP, the primary station is referred to a base station, or a gNodeB (or gNB) in 5G (NR) or an eNodeB (or eNB) in 4G (LTE). The eNB / gNB is part of the Radio Access Network RAN, which interfaces to functions in the Core Network (CN). In the same context, the secondary station corresponds to a mobile station, or a User Equipment (or a UE) in 4G / 5G, which is a wireless client device or a specific role played by such device. The term "node" is also used to denote either a UE or a gNB / eNB.

[0007] Additionally, for example, in the case of PC5 interface or Sidelink communication, it is possible to have Direct communication between secondary stations, here UEs. It is then also possible for UEs to operate as Relays to allow for example out of coverage UEs to get an inter-mediate (or indirect) connection to the eNB or gNB. To be able to work as a relay, a UE may use discovery messages to establish new connections with other UEs.

[0008] Current wireless systems should support seamless mobility at all times, but there are still situations where the wireless connection may drop, e.g., when crossing country borders. In somecases, existing procedures may also be too heavy in some of these situations so that even if executed properly, the overhead may still lead to unnecessary delays.

[0009] SUMMARY OF THE INVENTION

[0010] An aim of the invention is to address above problems by providing solutions for enhanced mobility, in particular, when the roaming status of a wireless device changes or is about to change.

[0011] To this end, it is proposed in accordance with a first aspect of the invention, a method for an enhanced mobility procedure of a wireless device, comprising:

[0012] - determining, by the wireless device, an incoming change of its roaming and / or coverage status when registered in a first serving network, and

[0013] - performing, by the wireless device, a mobility procedure to and / or roaming procedure over a second access device, wherein the second access device is managed by a second serving network and / or co-managed by the first and the second serving network while the wireless device is still registered in the first serving network.

[0014] In accordance with a second aspect of the invention, it is proposed an apparatus adapted to perform an enhanced mobility procedure, wherein the apparatus comprises:

[0015] a. a processor,

[0016] b. one or two transceivers,

[0017] c. one or two USIMs,

[0018] wherein the apparatus is adapted to:

[0019] d. determine an incoming change of its roaming status, and

[0020] e. perform a mobility procedure to and / or roaming procedure over a second access device, wherein the second access device is managed by a second serving network and / or comanaged by the first and the second serving network.

[0021] This is achieved by means of the methods in claims 1 to 15, the apparatus in claim 16 and the computer program in claim 17.

[0022] It shall be understood that a preferred embodiment of the invention can also be any combination of the dependent claims or above embodiments with the respective independent claim.

[0023] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

[0024] BRIEF DESCRIPTION OF THE DRAWINGSIn the following drawings:

[0025] Fig. 1 schematically represents the overall cellular system including UEs, RAN, and core network;

[0026] Fig. 2 provides a schematic representation of a UE and its components; and

[0027] Fig. 3 schematically represents different entities involved in a non-terrestrial network; Fig. 4 schematically represents a random-access procedure in a wireless network; Fig. 5 schematically represents a signalling procedure by an access device; and Fig. 6 schematically represents the periodic transmission of SSB bursts;

[0028] Fig. 7 schematically represents examples of wireless devices according to some embodiments;

[0029] Fig. 8a and Fig. 8b schematically illustrate a deployment scenario according to embodiments of the invention; and

[0030] Fig. 9 schematically illustrates a procedure according to embodiments of the invention.

[0031] DETAILED DESCRIPTION OF EMBODIMENTS

[0032] Embodiments of the present invention are now described based on a cellular communication network environment, such as 5G or 6G. However, the present invention may also be used in connection with other wireless technologies.

[0033] Throughout the present disclosure, the abbreviation "gNB" (5G terminology) or "BS" (base station) or the term "access device" is intended to mean a wireless access device such as a cellular base station or a WiFi access point or a ultrawide band (UWB) personal area network (PAN) coordinator. The gNB may consist of a centralized control plane unit (gNB-CU-CP), multiple centralized user plane units (gNB-CU-UPs) and / or multiple distributed units (gNB-DUs). The gNB is part of a radio access network (RAN), which provides an interface to functions in the core network (CN). The RAN is part of a wireless communication network. It implements a radio access technology (RAT). Conceptually, it resides between a communication device such as a mobile phone, a computer, or any remotely controlled machine and provides connection with its CN. The CN is the communication network's core part, which offers numerous services to customers who are interconnected via the RAN. More specifically, it directs communication streams over the communication network and possibly other networks.Furthermore, the terms "base station" (BS) and "network" may be used as synonyms in this disclosure. This means for example that when it is written that the "network" performs a certain operation it may be performed by a CN function of a wireless communication network, or by one or more base stations that are part of such a wireless communication network, and vice versa. It can also mean that part of the functionality is performed by a CN function of the wireless communication network and part of the functionality by the base station.

[0034] It is further noted that throughout the present disclosure only those blocks, components and / or devices that are relevant are shown in the accompanying drawings. Other blocks have been omitted for reasons of brevity. Furthermore, blocks designated by same reference numbers are intended to have the same or at least a similar function, so that their function is not described again later.

[0035] A cellular system is a wireless communication system that consists of three main components: user equipment (UE), radio access network (RAN), and core network (CN). These components work together to provide voice and data services to mobile users over a large geographic area.

[0036] In conventional cellular networks, a primary station serves a plurality of secondary stations located within a cell served by this primary station. Wireless communication from the primary station towards each secondary station is done on downlink channels. Conversely, wireless communication from each secondary towards the primary station is done on uplink channels. The wireless communication can include data traffic (sometimes referred to User Data), and control information (also referred sometimes as signalling). This control information typically comprises information to assist the primary station and / or the secondary station to exchange data traffic (e.g. resource allocation / requests, physical transmission parameters, information on the state of the respective stations). In the context of cellular networks as standardized by 3GPP, the primary station is referred to a base station, or a gNodeB (or gNB) in 5G (NR) or an eNodeB (or eNB) in 4G (LTE). The eNB / gNB is part of the Radio Access Network RAN, which interfaces to functions in the Core Network (CN). In the same context, the secondary station corresponds to a mobile station, or a User Equipment (or a UE) in 4G / 5G, which is a wireless client device or a specific role played by such device. The term "node" is also used to denote either a UE or a gNB / eNB.

[0037] Additionally, for example, in the case of PC5 interface or Sidelink communication, it is possible to have Direct communication between secondary stations, here UEs. It is then also possible for UEs to operate as Relays to allow for example out of coverage UEs to get an inter-mediate (orindirect) connection to the eNB or gNB. To be able to work as a relay, a UE may use discovery messages to establish new connections with other UEs. Certain UEs may communicate with each other by using device-to-device communication, also known as sidelink communication using the PC5 interface that may rely on physical sidelink (PS) broadcast channel, PS shared channel, PS control, etc. Furthermore, the role of a relay node has been introduced in 3GPP. This relay node is a wireless communication station that includes functionalities for relaying communication between a primary station, e.g. a gNB and a secondary station, e.g. a UE. This relay function for example allows to extend the coverage of a cell to an out-of-coverage (OoC) secondary station. This relay node may be a mobile station or could be a different type of device. In the specifications for 4G, the Proximity Services (ProSe) functions are defined inter alia in TS 23.303, and TS 24.334 to enable - amongst others -connectivity for the cellular User Equipment (UE) that is temporarily not in coverage of the cellular network base station (eNB) serving the cell. This particular function is called ProSe UE-to-network relay, or Relay UE for short. The Relay UE relays application and network traffic in two directions between the OoC UE and the eNB. The local communication between the Relay UE and the OoC UE is called device-to-device (D2D) communication or Sidelink (also known as PC5) communication in TS 23.303 and TS 24.334. Once the relaying relation is established, the OoC-UE is, e.g., IP-connected via the Relay UE and acts in a role of "Remote UE". This situation means the Remote UE has an indirect network connection to selected functions of the Core Network as opposed to a direct network connection to all Core Network functions that is the normal case. Furthermore, it has been introduced the role of a UE-to-UE relay node, i.e., a relay node re-laying the communication between two UE devices. The relay node relays the communications between UE devices. UEs may connect to the core network through a base station when in-coverage. In such relay scenarios, the relay devices may receive and store some information for some time before forwarding it towards the target device. This information that may be stored and forwarded may be discovery messages received from a source UE whereby the relay UE may release them at some point of time later. This information that may be stored and forwarded may be a SIB that may contain a timestamp.

[0038] User equipment (UE) is the device that a user uses to access the cellular system, such as a smartphone, a tablet, a laptop, loT device, or a wearable device. A UE typically may contain the following components:

[0039] - A universal integrated circuit card (UICC), which stores the user's identification and authentication information, such as the subscription permanent identifier (SUPI) or credentials.

[0040] - A transceiver, which converts the digital signals from the processor into analog signals for transmission and reception over the air interface. The transceiver also performs modulation, demodulation, coding, decoding, and other signal processing functions.- A processor, which controls the operation of the UE and executes the applications and services that the user requests. The processor also communicates with the RAN and the CN using various protocols.

[0041] - A display, which shows the user the information and feedback from the UE, such as the signal strength, the battery level, the call status, the messages, the contacts, the menu, etc.

[0042] - A microphone and a speaker, which enable the user to make and receive voice calls, as well as use other audio features, such as voice mail, voice recognition, etc.

[0043] - A keyboard and / or a touch screen, which allow the user to enter and select commands, text, numbers, etc.

[0044] - A camera and / or a video recorder, which enable the user to capture and send images and videos, as well as use other multimedia features, such as video calling, video streaming, etc.

[0045] - A memory, which stores the data and programs that the user needs, such as the phone book, the messages, the photos, the videos, the applications, etc as well as a computer program to perform the operations of the RAN and CN protocols.

[0046] - A battery, which provides the power supply for the UE.

[0047] Fig. 2 provides a schematic representation of a UE and its components, e.g., UICC (201), processor (202), transceiver (203), memory (204), input devices (205) such as camera, microphone, etc and output devices (206) such as display, speaker, etc. Fig. 7 schematically represents wireless devices that may include the capabilities of a UE and / or a STA. Fig. 7a) represents AR / VR glasses; Fig. 7b) represents a connected vehicle; and Fig. 7c) represents a mobile phone. In these devices, a reflective intelligent surface (RIS) may be embedded, e.g., by covering and / or under the whole a part of the UE surface. This may be used, e.g., to better deal with interferences or improve wireless sensing.

[0048] A UE access the cellular network via the radio access network, as described below. Certain UEs may communicate with each other by using device-to-device communication, also known as sidelink communication using the PC5 interface that may rely on physical sidelink (PS) broadcast channel, PS shared channel, PS control, etc.

[0049] A UE may receive a configuration by means of different procedures:

[0050] Downlink control information (DCI) is a type of control information that is sent from the BS to the UE on the physical downlink control channel (PDCCH). DCI contains various parameters that instruct the UE how / when to decode and transmit data on the physical downlink shared channel (PDSCH) and the physical uplink shared channel (PUSCH), such as the resource allocation, the modulation and coding scheme. The UE needs to monitor the PDCCH in each subframe to detect and decode the DCI that is addressed to it.Uplink control information (UCI) is a type of control information that is sent from the UE to the BS on the physical uplink control channel (PUCCH) or the physical uplink shared channel (PUSCH). UCI contains various feedback signals that inform the BS about the status and quality of the downlink transmission, such as the HARQ. acknowledgments (ACKs), the channel state information (CSI ), and the scheduling requests (SRs). The UE needs to encode and transmit the UCI according to the configuration and timing indicated by the BS.

[0051] Sidelink control information (SCI) is a type of control information that is sent from the UE to another UE on the physical sidelink control channel (PSCCH) in device-to-device (D2D) communication scenarios. The main functions of SCI include resource allocation, synchronization, channel quality reporting.

[0052] Medium access control (MAC) control element (MAC CE) is a type of control information that is sent from the BS to the UE or vice versa on the MAC layer. MAC CE contains various commands or indications that regulate the MAC layer functions, such as the buffer status report (BSR), the timing advance command (TAC), the discontinuous reception (DRX) command, etc. The UE needs to process the MAC CE according to the MAC protocol and the configuration provided by the BS.

[0053] Radio resource control (RRC) command is a type of control information that is exchanged between the BS and the UE on the RRC layer. RRC Command contains various messages that modify / configure RRC parameters and / or initiate, modify, or release the RRC connection or the radio bearers between the UE and the BS, such as the RRC connection setup, the RRC connection reconfiguration, the RRC connection release, the security mode command, the mobility from E-UTRA command, the handover from E-UTRA preparation request, etc. The UE needs to respond to the RRC Command according to the RRC protocol and the configuration provided by the BS.

[0054] Non-access stratum (NAS) messages are used for signalling between UE and core network (CN) on the non-access stratum (NAS) layer. NAS messages enable functionality such as registration, session establishment, security, and mobility management. The UE needs to respond to the NAS Command according to the NAS protocol and the configuration provided by the CN.

[0055] UE parameter update (UPU) is a procedure between the UE and the home network that enables the home network to update configuration parameters in mobile phones and / or USIM using tthe UDM control plane procedure (TS 23.502). The UE can receive Parameters Update Data from the UDM after the UE has registered in the 5G network.

[0056] Steering of Roaming (SoR) enables the home network to guide the user equipment (UE) when registering on a visited network. For detailed information about the interfaces and registration in the 5G System, refer to 3GPP TS.23.501 (Release 15)

[0017] and 3GPP TS 24.501 (Release 15)

[0018] , The 5G CP-SOR is activated during or after registration to update the UE's "OperatorControlled PLMN Selector with Access Technology" list via secure NAS messages, as directed by the home PLMN based on specific operator policies, such as preferred networks or UE location.

[0057] UE configuration update (UCU) is used to update configuration parameters as per TS 23.502 that may include Access and Mobility Management related parameters decided and provided by the AMF, UE Policy provided by the PCF. When AMF wants to change the UE configuration for access and mobility management related parameters the AMF initiates the procedure defined in clause 4.2.4.2. When the PCF wants to change or provide new UE Policies in the UE, the PCF initiates the procedure defined in clause 4.2.4.3. If the UE Configuration Update procedure requires the UE to initiate a Registration procedure, the AMF indicates this to the UE explicitly. The procedure in clause 4.2.4.2 may be triggered also when the AAA Server that performed Network Slice-Specific Authentication and Authorization for an S-NSSAI revokes the authorization.

[0058] Radio access network (RAN) is the part of the cellular system that connects the UEs to the CN via the air interface. The RAN consists of base stations (BSs). A base station (BS) is a fixed or mobile transceiver that covers a certain geographic area, called a cell. In 5G, a BS is also called a gNB (next generation node B). A BS can serve multiple UEs simultaneously within its cell, by using different frequencies, time slots, codes, or beams. A BS also performs functions such as power control, handover control, channel allocation, interference management, etc. A base station can be divided into two units: a central unit (CU) and a distributed unit (DU). The CU performs the higher layer functions, such as RLC, PDCP, RRC, etc. The DU performs the lower layer functions, such as PHY and MAC. The CU and the DU can be co-located or separated, depending on the network architecture and deployment. In cellular systems, a base station may be denoted, based on context, as a cell, or gNB.

[0059] The cell may also refer to the coverage area of a base station. A BS may have different coverage areas such as a macro cell (e.g. several kilometres wide), a pico cell (e.g., for a given location such as a stadium) or a femto cell for a small location (e.g., a home or part of it).

[0060] A base station may communicate with the core network. Since there can be base stations for different cellular systems, different interfaces are required. For instance, a base station, eNB, in a 4G Long Term Evolution (LTE) system (also known as Evolved Universal Mobile Telecommunications Systems (UMTS) Terrestrial Radio Access Network (E-UTRAN)) may interface with the 4G CN known as EPC through the corresponding interface. For instance, a base station, gNB, in a 5G system (i.e., 5G New Radio or Next Generation RAN) may communicate with the 5GC through a different interface. 4G and 5G base stations may communicate with each other directly or through their corresponding core networks.

[0061] The main protocols used between the UEs and the RAN are:- The physical layer (PHY), which defines the characteristics of the air interface, such as the frequency bands, the modulation schemes, the coding rates, the frame structure, the synchronization, etc.

[0062] - The medium access control (MAC) layer, which regulates the access of the UEs to the shared radio channel, by using techniques such as orthogonal frequency division multiple access (OFDMA), time division duplex (TDD), frequency division duplex (FDD), etc.

[0063] - The radio link control (RLC) layer, which provides reliable data transmission over the radio channel, by using techniques such as segmentation, reassembly, error detection, error correction, retransmission, etc.

[0064] - The packet data convergence protocol (PDCP) layer, which compresses and decompresses the headers of the data packets, encrypts and decrypts the data, and performs data integrity protection.

[0065] - The radio resource control (RRC) layer, which establishes, maintains, and releases the radio bearers between the UEs and the RAN, as well as exchanges the signaling messages for functions such as connection setup, handover, measurement reporting, security activation, etc.

[0066] A transmission / reception communication unit or transceiver may be used by BS and UE to transmit / receive data. Control data may be required for a physical broadcast channel, physical downlink control channel, etc. Data may be for the physical downlink shared channel.

[0067] Data may be encoded by the UE and / or BS to obtain data symbols and / or control symbols that may be exchanged over the wireless interface. The conversion from digital data into analog symbols may be done by the transmission / reception communication unit

[0068] A medium access control control-element (MAC-CE) is a MAC layer communication element that is used to control the communication between wireless devices. A MAC-CE may be exchanged in a shared channel, e.g., the physical downlink / uplink / sidelink shared channel.

[0069] The communication between a UE and a base station or the communication between UEs (when sidelink is used) may involve the exchange of reference signals. Reference signals may include primary synchronization signal (PSS), a secondary synchronization signal (SSS), a physical broadcast channel demodulation reference signal (DMRS), a channel state information reference signal (CSI-RS). Core network (CN) is the part of the cellular system that connects the RAN to other networks, such as the Internet, or other cellular systems. The CN consists of two main (control / user) domains. The control domain is responsible for providing signalling and control functions for the UEs, such as authentication, authorization, mobility management, session management, etc. The control plane consists of several network functions (NFs), such as the access and mobility management function (AMF), the session management function (SMF), the unified data management (UDM), the2025P00097WQ 10

[0070] policy control function (PCF), the network exposure function (NEF), and the authentication server function (AUSF). The access and mobility management function (AMF) is a NF that handles the registration, deregistration, connection management, and mobility management for the UEs. The session management function (SMF) is a NF that handles the establishment, modification, and release of the sessions for the UEs. The SMF also communicates with the user plane devices to perform functions such as IP address allocation, tunneling, QoS, etc. The unified data management (UDM) is a NF that stores and manages the user data, such as the SUPI, the service profile, the subscription status, etc. The policy control function (PCF) is a NF that provides the policy rules and charging information for the UEs, such as the access type, the service level, the data rate, the quota, etc. The network exposure function (NEF) is a NF that exposes the network capabilities and services to external applications and devices, such as the IMS, the Internet of Things (loT), etc. The authentication server function (AUSF) is a NF that performs the primary authentication with the by using credentials and the SUPI. The user domain is responsible for providing data and multimedia services to the UEs, by using packets and IP addresses. The user plane consists of two main functions: the user plane function (UPF) and the data network (DN). The user plane function (UPF) is a device that forwards the data packets between the UEs and the DNs, as well as performs functions such as tunneling, firewall, QoS, charging, etc. The data network (DN) is a network that provides access to the services and applications that the UEs request, such as the Internet, the IMS, etc.

[0071] A residential gateway (RG) is a device that connects a home network to an external network, such as the Internet or a cellular system. An RG typically provides functions such as routing, switching, firewall, NAT, DHCP, DNS, VPN, etc. An RG can also support various types of interfaces, such as Ethernet, Wi-Fi, Bluetooth, USB, etc. A cellular-capable RG is an RG that has a cellular interface, such as a UICC slot, a cellular modem, or an antenna, that enables it to access the cellular system as a backup or an alternative to the wired or wireless broadband connection. A cellular-capable RG can provide benefits such as: (1) Enhanced reliability, by switching to the cellular connection in case of a failure or a degradation of the broadband connection; (2) Increased bandwidth, by aggregating the cellular connection and the broadband connection to achieve higher data rates or QoS.

[0072] A multi-SIM subscription is a subscription that allows a user to have multiple SIMs (or eSIMs) that are linked to the same account and service profile. A user can use the multi-SIM subscription to access the cellular system from different devices, such as a smartphone, a tablet, a laptop, or a wearable device, without having to switch the SIM card or the device.

[0073] Overall system: Fig. 1 provides an overall description of a wireless system wherein devices 100, 102, and 128 can play the role of UEs. Device 102 is part of a cellular-capable RG providingconnectivity to a home network 129 e.g., by means of a local area network and / or wireless local area network. Device 102 is served by base station 104.

[0074] The RAN 127 comprises base station 103 and serves UE 128. UE 128 may also be a UE to Network relay given access to remote UE 136 that is out of coverage of base station 103. UEs 134 and 136 also communicate with each other via a UE-to-UE relay 135. UE to UE communication via relays is enabled by means of sidelink communication / PC5 interface.

[0075] Within the RAN, the range of base station 103 is extended via smart repeater 137 and reflective intelligent surface (RIS) 138. Smart repeater 137 and RIS 138 give access to UE 142.

[0076] The RAN 143 includes base station 104 tand serves as wireless access infrastructure for the home network. Base station 104 also serves a mobile access device and / or UE as a UAV 139. UAV 139 may provide connectivity to remote UE 136.

[0077] Furthermore, a satellite gateway 141 is shown that connects to satellite 140 and may provide connectivity services to remote UE 136 or UE 100.

[0078] In Fig. 1, the 5G core network 133 may include one or more an AMF 121, SMF 123, UPF 122, AUSF 124, UDM 125, PCF 131, NEF 132 and allows the connection to a data network 130.

[0079] In Fig. 1, a second core network 142, e.g., a legacy core network as a 4G core network, is also shown that may interface with the 5G core network 133, interface with base stations denoted eNB in 4G, and provide a connection to the data network 130. The legacy 4G core network is denoted EPC and may include one or more mobility management entities (MME), a serving gateway, a multimedia broadcast multicast service gateway, a broadcast multicast service center, a packet data network gateway, etc. The mobility management entity may handle the signalling between UE and the 4G CN and may interact with the home subscriber server (HSS) in charge of the storage and management of subscriber data and secrets. The MME may provide connection management, similar to the AMF in 5G. The serving gateway may be used to exchange user internet protocol messages whereby the serving gateway may interact with the packet data network gateway that is connected to IP services. Multiple protocols in 4G and 5G have similar features. For example, the 5G network registration and 4G attach registration message are initially sent by the UE to establish a connection between the UE and the CN, which involves sending an initial request from the UE with its identity and capabilities, receiving an authentication request from the CN with a challenge, sending an authentication response from the UE with a response, receiving an authentication result from the CN with an indication of success or failure, and sending a security mode command from the CN with the selected security algorithms. As a result of this connection establishment procedure, NAS and AS keys are derived from the K_AMF (5G) and K_ASME (4G) where K_AMF is managed by the AMF and K_ASME is managed by the MME. A UE may connect to a serving network or serving Public Land Mobile Network2025P00097WQ 12

[0080] (PLMN). A UE may have a subscription with a home PLMN, and during the registration procedure, the (AM F of the) serving PLMN may forward the registration request to the (AUSF of the) home PLMN that may perform an initial authentication procedure between home PLMN and UE. If the authentication procedure is successful, keys are derived and the home PLMN may share derived credentials with the serving PLMN, including K_SEAF, that may be used to derive K_AMF, from which NAS keys and AS keys are derived. The registration request sent by the UE includes an identifier that can be used by the home PLMN to identify the UE. To prevent privacy vulnerabilities, the long-term subscriber's identifier known as Subscriber Permanent Identifier (SUPI) may not be exchanged in the clear, but instead, either a Subscription Concealed Identifier (SUCI) or a pseudonym known as GUTI are exchanged with the AMF of the serving PLMN. The AMF of the PLMN may then forward the SUCI to the home PLMN so that the home PLMN decrypts / verifies it.

[0081] Satellite access: Fig. 1 depicts satellite 140 providing access to one or more UEs. Satellite access can be performed by means of non-terrestrial devices at different altitudes such as Low Earth Orbit (LEO), Medium Earth Orbit (MEO) or Geosynchronous Equatorial Orbit (GEO) satellites. Other types of non-terrestrial devices may include high-altitude platform station (HAPS) or unmanned aerial vehicle (UAVs) that may comprise a base station. Fig. 3 illustrates different elements including a GEO satellite 302, a MEO satellite 303, a LEO satellites 304 and 304', a UAV 305, all of them potential non-terrestrial mobile access devices giving coverage to wireless device (e.g., a UE) 301. GEO satellite 302 remains static over a given earth position while MEO and LEO satellites move. MEO satellites 303 have a slower moving vector 306 in relation to the earth compared with LEO satellites 304 / 304' that have a faster moving vector 307 / 307'. A non-terrestrial gateway 308 is included that provides connectivity to the mobile access device via a feeder link 310. A mobile access device provides service to the wireless device via a service link 311. Two mobile access devices in the same orbit may communicate with each other via an intra-orbit-satellite link 312 while two mobile access devices in different orbits may communicate with each other via an inter-orbit-satellite link 313. Fig. 3 finally also includes a terrestrial access device 309 that may also provide connectivity to wireless device 301. The terrestrial access device 309, the wireless device 301, and non-terrestrial gateway are on the earth surface 314.

[0082] Non-terrestrial devices such as satellites distribute system information in specific SIBs, in particular, SIB31 in 4G and SIB19 in 5G. S19 information element as defined in TS 38.331 18.2.0.

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[0096] A UE in a cellular system performs an initial random-access procedure to connect an access device. The 5G random access procedure is illustrated by means of Fig. 4 wherein 401 represents a user equipment and 402 represents an access device. The access device distributes signals 402. Signals 402 can be distributed periodically or on demand. Signals 402 may comprise the Master Information Block (MIB) transmitted together with / in the physical broadcast channel (PBCH) and the synchronization signals. The MIB comprises:

[0097] MIB ::= SEQUENCE {

[0098] systemFrameNumber BIT STRING (SIZE (6)),2025P00097WQ 15

[0099] subCarrierSpacingCommon ENUMERATED {scsl5or60, scs30orl20}, ssb-SubcarrierOffset INTEGER (0..15),

[0100] dmrs-TypeA-Position ENUMERATED {pos2, pos3},

[0101] pdcch-ConfigSIBl INTEGER (0..255),

[0102] cellBarred ENUMERATED {barred, notBarred}, IntraFreqReselection ENUMERATED {allowed, notAllowed}, spare BIT STRING (SIZE (1))

[0103] }

[0104] MIB and PBCH are transmitted as part of a Synchronization Signal Block, and the access device may transmit multiple SSBs through different beams, allowing the user equipment to determine the preferred beam, and once the preferred beam is obtained, retrieve the MIB, and use the information in the MIB to attempt to retrieve System Information Block 1 (SIB1) that may also be distributed periodically. The UE can the use the information in SIB1 to perform the random-access procedure selecting a preamble to indicate its intention to access the cell by means of message 404, e.g., preamble transmission. This message may use a random-access radio network temporary identifier (RA-RNTI). Upon reception of message 404, access device 402 replies with message 405, e.g., a random access response. This message may include a time advance field to adapt the transmission timing, a value matching the preamble used by wireless device 401, and a grant (communication resources) for the wireless device. The access device also assigns a temporary cell radio network temporary identifier (TC-RNTI). Prior to this message 405, the access device may send a PDCCH DCI message assigning resources (a communication grant). This message may be addressed using the RA-RNTI. Upon reception of message 405, wireless device uses the initial grant received in the previous message and the RA-RNTI to transmit a subsequent message 406, e.g, an RRCSetupRequest or PHY layer. This message may include a Contention Resolution Identifier (CRI). This message may be sent in the PUSCH. As a response, access device replies with message 407, e.g., RRCSetup, that includes / repeats the received CRI confirming that the access device has identified the access device. This message includes a Cell RNTI (C-RNTI). Next, wireless device replies with message 408, e.g., an RRCSetupComplete that includes the RegistrationRequest message, and UE capabilities.

[0105] MIB and PBCH are transmitted as part of a Synchronization Signal Block, and the access device may transmit multiple SSBs through different beams. Multiple SSBs transmitted through multiple beams form an SSB burst. The multiple SSBs in an SSB burst are transmitted sequentially in the first part of a frame. SSB bursts are transmitted periodically, typically every 20 ms, or more.Fig. 5 schematically illustrates an access device 500 transmitting four beams, each of them transmitting an SSB, namely 501, 502, 503, and 504. A wireless device 505 can measure the signal strength, i.e., RSRP (Reference Signal Received Power), of the beams. This is illustrated by means of the graph in Fig. 5 where 501', 502', 503', and 504' represent the RSRP of beams 501, 502, 503, and 504, respectively, as measured by wireless device 505. Wireless device 505 can use this information to determine which one of the beams is the preferred beam for further communication, e.g., to perform the random access procedure.

[0106] Fig. 6 further schematically illustrates SSB bursts transmitted periodically. In this case, each SSB burst comprises four SSBs transmitted in the first part / half of every second frame. In this figure, frames are denoted as f, f+1, f+2, f+3,...A frame has a typical duration of 10 ms.

[0107] Resource grid: in a cellular network, such as a 5G network, the resource grid is a structured framework used to allocate and manage communication resources efficiently. It is characterized by a time-frequency matrix where each element, known as a resource element, is defined by its position in both time and frequency domains. The vertical axis represents frequency, segmented into subcarriers, which are spaced at intervals. The subcarrier spacing can vary depending on the deployment scenario, with common spacings being 15 kHz, 30 kHz, 60 kHz, 120 kHz, 240 kHz, and 480 kHz (corresponding to mu equal to 0, 1, 2, 3, 4, and 5, respectively). The horizontal axis of the grid represents time and is divided into frames, subframes, and slots, each frame has a duration of 10 ms and each subframe has a duration of 1 millisecond. Within these subframes, the time is further divided into slots. For mu, there are 2Amu symbols per subframe. Each slot typically spans 14 OFDM symbols. Each resource element in the grid, defined by the intersection of a time symbol and a frequency subcarrier, can carry a small portion of data, control information, or reference signals. These resource elements are grouped into larger units called Resource Blocks (RBs), which span 12 subcarriers in frequency and one slot in time. The allocation of these RBs is dynamically managed.

[0108] Reflective intelligent surfaces (RIS): may be used as part of the wireless infrastructure or as part of the wireless devices. RIS, often referred to as metasurfaces, are advanced materials engineered with sub-wavelength structures that can manipulate electromagnetic waves in a controlled manner. These surfaces consist of an array of unit cells, each capable of adjusting its electromagnetic response through electronic control, thus enabling dynamic alteration of the wavefront of the incident signal. The wireless device can utilize the RIS to fine-tune the reflection properties of the wireless sensing signal, such as phase, amplitude, and polarization. By dynamically adjusting these parameters, the RIS can enhance signal strength, directivity, and overall signal quality.2025P00097WQ 17

[0109] For instance, the RIS can focus the reflected signal towards the transmitter, significantly improving signal reception. This capability is particularly advantageous in urban environments where obstacles and interference are prevalent. Technical details of the RIS involve the implementation of tunable elements, such as varactor diodes or microelectromechanical systems (MEMS), in each unit cell. These elements allow real-time reconfiguration of the surface's electromagnetic properties in response to control signals from the wireless device. The control signals can be generated based on real-time analysis of the received signal's quality and contextual parameters, ensuring optimal reflection under varying conditions. The RIS can operate in various frequency bands, including sub-6 GHz and millimeter-wave (mmWave) frequencies, making it versatile for different wireless applications. Additionally, the RIS can incorporate sensing capabilities to monitor the environment and further refine the reflection parameters. For example, integrated sensors can detect changes in temperature, humidity, or the presence of obstacles, and adjust the reflection properties accordingly to maintain high signal quality.

[0110] Quality of Service: a wireless system may be used to transport data belonging to different types of applications such as Machine Type Communication (MTC), Critical Machine Type Communication (CMTC), Enhanced Mobile Broadband (EMB), or Fixed Wireless Access (FWA). MTC (e.g., smart meters, tracking,...) requires low bandwidth and non-latency critical, CMTC (e.g., industrial applications) has strict throughput, latency, and availability needs, EMB (VR / AR, 4K UDH, ...) and FWA (e.g., in the home) require high data rate, with low latency, and low end-to-end response time. In wireless network such as 5G the Quality of Service has to accommodate different applications such as EMB, MTC, ultra-reliable low latency communications. QoS is influenced by the entities involved in the communication, UE, RAN, UPF, and DN. Data exchanges between UE and DN are mapped to QoS flows, and each QoS flow is mapped to a 5G QoS Identifier (5QI) in TS 23.501 (Table 5.7.4-1) that describes resource types, priority, packet delay budget, packet error rate, maximum data burst volume. Network is configured to configure RAN and core network interfaces to achieve the requirements of a 5QI. QoS is applied to a data stream from the wireless physical layer to the core network. Between RAN and UPF, QoS is applied in terms of a QoS flow. QoS in the RAN is managed by means of Data Radio Bearers (DRB). A QoS flow on core network side is created by means of a PDU session establishment accept. The mapping between a QoS flow and a DRM is done by means of SDAP configuration in an RRC message (RRCSetup or RRCReconfiguration) The indication or identifier that connects the whole QoS pipe is called QoS flow identifier. Downlink traffic requires mapping IP messages and the QoS pipe, and this is done by the UPF. For each IP message or packet, the UPF checks (by means of a packet QoS assignment / detection rule) the packet information (source / destination / protocol / type of service / ...)2025P00097WQ 18

[0111] and directs the IP packet to a QoS flow. The packet QoS assignment / detection rule is provided by SMF interacting with PCF. In the uplink, the UE performs a similar task by applying QoS rules provided in NAS messages (e.g., PDU session establishment) by the SMF or are pre-configured / derived by the UE.

[0112] Discontinuous reception (DRX) in cellular networks such as 5G is in two types, Idle mode DRX and Connected mode DRX. In Idle mode DRX, the UE wakes up to monitor for paging messages. If no paging message is detected, it sleeps further. In Connected DRX mode, the UE enters in sleep mode periodically and during the sleep period the UE is not required to monitor the Physical Download Control Channel. The access device configures the UE device with C-DRX parameters. Connected DRX approach reduces energy consumption of the device because it does not require monitoring the PDCCH periodically and it also reduces the transmissions of CSI or SRS signals, that also has a positive effect in the network / access devices load. There are two types of DRX cycles, long and short. A long DRX cycle consists of an on period and an off period. The on duration is in terms of milliseconds. The long DRC cycle may be configured or the long DRX cycle and short DRX cycles may be configured. The access device can configure the time (drx-onDurationTimer) during which the UE is awake and goes back to sleep if there is no PDCCH received. The access device can also configure a given drx-LongCycleStartOffiset to start to awake period at a subframe boundary and / or drx-SlotOffset relative to the subframe boundary. If there is activity in an awake period, the UE may remain awake some more time determined by the drx-lnactivityTimer. Furthermore, the access device can configure long DRX cycle together with additional DRX cycle which is shorter than long DRX cycle. Configurable parameters include the drx-ShortCycle (duration of the short cycle) and drx-ShortCycleTImer that determines how many short cycles before the device should apply.

[0113] Data scheduling in a cellular network such as a 5G cellular network may be performed by means of a scheduler wherein the scheduler takes as input information such as measurements of UE / network, buffer status report, QoS requirements, associated radio bearers, or a scheduling request. In the downlink, data scheduling may be performed by means of dynamic scheduling and semi persistent scheduling (SPS). In dynamic scheduling, every data exchange in the Physical Downlink Shared Channel (PDSCH) is scheduled by means of a downlink control information (DCI) message in the Physical Downlink Control Channel (PDCCH). In SPS, the scheduling is done by means of an RRC message. In the uplink, scheduling can be performed by means of dynamic scheduling and configured scheduling (CS). In dynamic scheduling each Physical Uplink Shared Channel (PUSCH) is scheduled over DCI. In CS, the PUSCH transmission is scheduled via RRC message. Furthermore, a Scheduling Request message may be sent over the PUCCH (Physical Uplink Control Channel) or in an Uplink ControlInformation (UCI) in the PUSCH (Physical Uplink Shared Channel). An SR may be sent by a UE device when it has data to transmit. Upon reception, the access device can allocate resources (Uplink Grant by means of the Physical Downlink Control Channel. Upon resource allocation, the UE device can transmit data in the Physical Uplink Shared Channel.

[0114] Wireless sensing and integrated wireless sensing and communication: wireless systems are evolving to include wireless sensing capabilities. These wireless sensing capabilities may be implemented e.g. by a radar functionality in wireless communication involving one or more access devices (e.g., base stations (BS)) and / or one or more terminal devices (e.g., UEs). As an example, Frequency Modulated Continuous Wave (FMCW) mmWave radar systems can measure range, velocity, and angle of arrival (if two receivers are available) of objects in the scene which reflect radio waves. Such radar systems emit a chirp signal, e.g., a sine wave that increases in frequency over time. The chirp signal (e.g., a continuous wave pulse) has a bandwidth and a frequency increase rate. Generally, a continuous series of such chirps are emitted. The transmitted and received analogue chirp signals are mixed to generate an intermediate frequency (IF) signal which corresponds to the difference in frequencies of the two signals (outbound and inbound) and whose output phase corresponds to the difference in the phases of the two signals. Each surface of a scene or environment will therefore produce a constant frequency IF signal whose frequency relates to the distance to the surface (i.e., a first distance from the transmitter of the chirp signal to the surface plus a second distance from the surface to the receiver of the chirp signal). To resolve two surfaces at different distances, the two IF signals can be frequency resolved. A longer time window of the IF signal results in greater resolution. As the chirp time is related to its bandwidth (with constant chirp frequency change) the resolution of the radar is related to the chirp bandwidth. The IF signal may then be band pass filtered (to remove signals below some minimal range and frequencies above the maximum frequency for a subsequent analogue-to-digital converter (ADC)) and digitized prior to further processing. The upper frequency sensing range of the bandpass filter and ADC sets the maximum range that can be detected (i.e., IF frequencies increase with range). To detect vibrations, the phase of the IF signal is important, since the phase (i.e., the difference in phases of the transmitted and received chirp signals) is a sensitive measure of small changes in the distance of a surface. Small distance changes can be detected in the phase signal but may be indiscernible in the frequency signal. Moreover, phase difference measures between two consecutive chirp signals can be used to determine the velocity of the surface. As an example, a fast Fourier transform (FFT) processing can be performed across multiple chirp signals to enable separation of objects with the same range but moving at different velocities. A Fourier transform converts a signal from a space or time domain into the frequency domain. In the frequency domain the signal is represented by aweighted sum of sine and cosine waves. A discrete digital signal with N samples can be represented exactly by a sum of N waves. FFT provides a faster way of computing a discrete Fourier transform by using the symmetry and repetition of waves to combine samples and reuse partial results. This method can save a huge amount of processing time, especially with real-world signals that can have many thousands or even millions of samples. As a further example, angle estimation can be performed by using the phase difference between the received chirp signal at two separated receivers.

[0115] As another option, a channel state information (CSI) can be used, which is a measure of the phases and amplitudes of many frequencies detected at a receiver, thereby forming a complex 'map' of the radio environment, including effects of objects within that environment. CSI characterizes how wireless signals propagate from the transmitter to the receiver at certain carrier frequencies. CSI amplitude and phase are impacted by multi-path effects including amplitude attenuation and phase shift, e.g., by the displacements and movements of the transmitter, receiver, and surrounding objects and humans. In other words, CSI captures the wireless characteristics of the nearby environment. These characteristics, assisted by mathematical modeling or machine learning algorithms, can be used for different sensing applications. A radio channel may be divided into multiple subcarriers, as is done e.g. in 5G communication systems (using e.g. orthogonal frequency division multiplexing (OFDM)). To measure CSI, the transmitter may send long training symbols (LTFs), which contain pre-defined symbols for each subcarrier, e.g., in a packet preamble. When those LTFs are received, the receiver can estimate a CSI matrix using the received signals and the original LTFs. For each subcarrier, the channel can be modeled by y = Hx + n, where y is the received signal, x is the transmitted signal, H is the CSI matrix, and n is the noise vector. The receiver estimates the CSI matrix H using a pre-defined signal x and the received signal y after signal processing such as removing cyclic prefix, de-mapping and demodulation. The estimated CSI is then a three-dimensional matrix of complex values and this matrix represents an 'image' of the radio environment at that time. By processing a time series of such 'images' information on movements, locations and vibrations of objects can be extracted. Such a processing of a CSI matrix can be used for vital signs monitoring, presence detection, and human movement recognition. As an example, neural network like recognition techniques can be used to process the CSI matrix to perform such kinds of recognition.

[0116] It is noted that systems using channel state information (CSI) are somehow related to systems with FMCW mmWave radar. In a CSI-based system, the input signal X may be defined and the receiver may use the received signal Y to obtain H, i.e., as H = (Y - N) / X . In a FMCW mmWave radar, the transmitted signal Chirp X may also be predefined, and the receiver may uses the received signal Y to obtain a transfer function as H = Y / X . This last step is in fact somehow related to multiplying the2025P00097WQ 21

[0117] locally computed chirp signal and the received chirp signal and applying a bandpass filter. According to various embodiments in this invention, the above-described wireless sensing techniques are implemented in a mobile communication system (e.g. 5G or 6G or other cellular or WiFi communication systems), while the functional coexistence of radar and communication operating in the same frequency bands is configured to avoid interference bandwidths. Thereby, radio sensing can be integrated into large-scale mobile networks to create perceptive mobile networks.

[0118] As another example, the sensing signal may consist of a number of pulses sent, e.g., at specific frequencies and timing (sensing signal parameter information) by a sensing transmitter. The sensing receiver may include a number of bandpass filters that allow identifying the sensing signal parameter information, e.g, timing and frequency of the received pulses. In particular, if the transmitter determines a given pseudo-random sequence of frequency / timing pulses and beams it, e.g., by means of beamforming, in a specific direction, and if the transmitter communicates to the receiver the timing / frequency, in general, the sensing signal parameter information, of the transmitted sensing signal, the receiver can use its bandpass filters to identify the reception of the same transmitted pulses, i.e., sensing signal, based on the received sensing signal parameter information.

[0119] The wireless sensing signal may be part of the synchronization signal block. For instance, the wireless sensing signal may be a reference signal included in the primary synchronization signal or in the secondary synchronization signal. It may consist of a number of reference signals and / or it may be a wide band signal. This wireless sensing signal can allow the access devices to determine the presence of a wireless device. The wireless device may also use this wireless sensing signal to determine the access device that is more suitable to (re-)select.

[0120] Wireless local area network technologies such as Wi-Fi allow devices to connect to the Internet or to each other without using cables. Wi-Fi is based on radio waves that are transmitted and received by a device called a wireless access point (AP). The AP acts as a hub that connects Wi-Fi enabled devices, such as laptops, smartphones, tablets, smart TVs, etc., to a wired network, such as a local area network (LAN) or the Internet.

[0121] The term Wi-Fi is a trademark of the Wi-Fi Alliance, an industry association that certifies products that comply with the IEEE 802.11 standards for wireless local area networks (WLANs). These standards define the physical and data link layers of the communication protocol, such as the frequency bands, modulation schemes, encryption methods, authentication mechanisms, and data rates used by Wi-Fi devices. The most common Wi-Fi standards are 802.11a, 802.11b, 802.11g, 802. lln, 802.11ac, and 802.11ax, which operate in different frequency bands (2.4 GHz, 5 GHz, or both) and offer different levels of performance and compatibility.2025P00097WQ 22

[0122] To use Wi-Fi, a device needs to have a wireless network interface card (NIC) that can send and receive radio signals. The NIC scans the available wireless channels and detects the presence of nearby APs. The device then selects an AP to connect to, based on factors such as signal strength, security settings, and network name (SSID). The device and the AP exchange information, such as the MAC address, IP address, encryption key, and password, to establish a connection. This process is called association. After the connection is established, the device can communicate with the AP and other devices on the same network, or access the Internet through the AP.

[0123] IEEE 802. lln (Wi-Fi 4) provided new features such as MIMO and frame aggregation to increase throughput. IEEE 802.11ac (Wi-Fi 5) introduced wider bandwidth and MU-MIMO. IEEE 802.11 ax (WIFI-6) included OFDMA and BSS color or spatial reuse to use spectrum resources more efficiently. IEEE 802.11 ah introduced target wake time (TWT) to support low power loT applications by allowing STAs to go into sleep when not in a wake period after negotiation with AP. IEEE 802.11be (Wi-Fi 7) aims at improving throughput and latency operating in unlicensed bands between 1GHz and 7.125 GHz. Wi-Fi 7. Increases bandwidths up to 320 MHz, 4096 QAM modulation, and supporting up to 16 spatial streams in MU-MIMO with an improved sounding procedure. Wi-FI 7 also enables multiple resource units to be assigned to a single device. Furthermore, it includes an enhanced preamble with a universal SIG filed indicating the PHY version. It also extends the negotiated ack buffer size to 1024 bits.lt also enables multilink operation (MLO) enabling multiple links between a station and an access point, for instance an AP can have two radios 2.4 and 5 GHz and use both of them for simultaneous transmission and / or reception with a multi-link capable device (MLD) capable station. Wi-Fi 7 also includes a restricted TWT providing predictable latency by assigning STAs to different rTWT types and making sure that other STAs do not transmit if they do not belong to a given rTWT type. Wi-Fi 7 also include multi-AP coordination performing, e.g., coordinated transmission, beamforming, or joint transmission.

[0124] For instance, in references to Fig. 1, devices 100, 101 and 102 can be Wi-FI access points and device 106 can be a wireless station. Station 106 and access point 101 are MLD and communicate with two links 126. Device 102 is a cellular capable residential gateway.

[0125] Embodiments of this invention are illustrated in the context of mobility procedures required when a wireless device changes the access device or moves to a different network. A particular scenario being addressed in a mobility scenario is when a wireless device crosses a country border, in general, changes its roaming status. This may happen when travelling by car from the Netherlands to Spain and crossing the borders to Belgium, France and Spain. In this case, the wireless device needs to change the access device but also needs to change the serving network, e.g., from a Home PLMN to a Visiting PLMN.In other words, when a wireless device approaches the boundary of its current network, it may need to transfer its connection to a network operated by a second operator. As an example, a UE crossing an international boundary may need to switch its connection to a network operating in a different country in a different legal environment. This may require registration with the second network and the establishment of a new security context as well as the usual movement of UE context within the network and the switch over of control and user plane paths.

[0126] Roaming is a method of ensuring that a user can obtain service in a country other than his or her home country in RRCJDLE or RRCJNACTIVE states. When in RRC_CONNECTED, the wireless device will need to perform a handover from one (serving) network to another network. This may include performing a PLMN selection procedure In the exemplary case of a border crossing, a further complication may be that the overlap of coverage between the two networks is insufficient to enable a moving UE to perform a cell reselection to discover the new network, synchronise to it, register and perform the inter-network handover.

[0127] Current procedures can lead to service interruptions because the wireless device needs to register in the new serving network, etc.

[0128] It is an object of this invention to enhance the mobility of a wireless device, e.g., in case of roaming, e.g., when roaming and handover happen also simultaneously, by performing an enhanced mobility procedure, wherein a wireless device is not required to perform a full registration to change its roaming status, or wherein the wireless can perform an optimized handover procedure between two access devices managed by two different networks.

[0129] It is an object of this invention to enhance the mobility of a UE, e.g., over a crosscountry boundary. A cross-country boundary may be an international boundary, an internal boundary, a topographical boundary, e.g., a stretch or body of water or a landscape feature, and so on. Such boundaries are characterised by regions of poor, intermittent or no coverage from one or both land-based networks on each side of the boundary. In particular, there is insufficient overlapping coverage to ensure a smooth transition from one network to the other. Such boundary regions may nevertheless afford good coverage to NTN nodes serving the area.In an embodiment that may be combined with other embodiments or used independently, a proposed solution is to use the services of an NTN network node to compensate for the lack of overlapping coverage area by allowing the UE to register with the second serving network in advance of entering the coverage zone of said network.

[0130] In an embodiment that may be combined with other embodiments or used independently, a wireless device may connect to a first access device, wherein the first access device is managed by a first serving network; the wireless device and / or access device and / or core network may determine an incoming change of its roaming status (in general, the roaming status of the wireless device), and the wireless device may start and / or perform a mobility procedure to and / or roaming procedure over a second access device, wherein the second access device may be managed by a second serving network and / or co-managed by the first and the second serving network. For instance, the mobility procedure / PLMN selection procedure may be triggered by the wireless device itself (like in a conditional handover) or by the access device or core network (e.g., managed / triggered by means of a Steering of Roaming procedure).

[0131] In an example, the first access device may be a terrestrial access device, and the second access device may be a non-terrestrial access device. In this case, when the wireless device connected to the terrestrial access device approaches the border, the wireless device may rely on a non-terrestrial access device, e.g., trigger and / or rely on a mobility procedure via the non-terrestrial access device.

[0132] In an example, the first access device may be a terrestrial access device served or managed by the first serving network and the second access device may be a terrestrial access device served by the first serving network and the second serving network. In this case, when a wireless device approaches a border and it is connected to the first access device, the wireless device may move to the second access device that facilitates the registration / roaming to the second serving network.

[0133] In an embodiment that may be combined with other embodiments or used independently, the wireless device may need to move to a different access device / network. The wireless device may be able to use a legacy procedure and or use the enhanced mobility procedure as per embodiments of this invention. The wireless device may send an indication requesting the execution of the enhanced mobility procedure. This indication may be sent to the access device it is currently connected to, e.g., the second access device to perform the enhanced mobility procedure if the device supports it. It may also be used by the access device, e.g., first access device, to identify asuitable second access device, e.g., a second access device that can coordinate two or more serving networks.

[0134] Additionally or alternatively, the wireless device may send an indication requesting the execution of the enhanced mobility procedure to the core network (e.g. of its Home PLMN). The core network may use this to identify and select a suitable serving network and / or a second access device in the vicinity of the wireless device and / or that serves the area that the wireless device resides in or is moving toward, and may use this to initiate a mobility procecdure with the wireless device (e.g. steering of roaming procedure) to trigger the wireless device to select and / or connect to a selected serving network and / or second access device.

[0135] In an embodiment that may be combined with other embodiments or used independently, the indication requesting the execution of the enhanced mobility procedure may include additional parameters, e.g., the name of the required serving network name, the type of access that is allowed (e.g., TN and / or NTN, etc), location / area / trajectory information related to the wireless device..

[0136] In an embodiment that may be combined with other embodiments or used independently, a wireless device may be preconfigured (e.g. in its USIM) with and / or may receive from the network (e.g. through policy configuration e.g. as response to receiving a request for handover from the wireless device, or e.g. based on measurements received or location / trajectory information received from or related to the wireless device that may indicate that the wireless device is near the border) a prioritized list of PLMN / access technology combinations to consider for determining a (different) serving network and / or determining which (different) access technology to use when performing a handover, and / or a set of conditions for the wireless device to consider for triggering / executing a handover from the serving network / access device to a target network / access device, and / or a set of (priority-related) PLMN / access technology selection rules to consider whilst executing a handover. In order to improve the handover (e.g. in cross country scenarios), one or more of the following additional conditions / rules / policies may be (pre-)configured in the wireless device and / or provided by the network:

[0137] A list of areas / locations (e.g. in the form of geographical area descriptions (e.g. for wireless devices that can determine their own location), tracking area codes (e.g. for wireless devices that cannot determine their own location), or e.g. in the form of distance or timing advance from a base station) near the border and / or with poor coverage in which the wireless device is allowed to initiate handover / PLMN selection procedure, and e.g. select NTN access and / or a different PLMN, and / ora list of signal quality thresholds specifically for near-border situations, whereby the wireless device is configured with an additional condition that determines when the wireless device is able / allowed to use these thresholds (e.g. when the wireless device is residing in a certain area, which speed / movement it has, which cell-IDs can be received) as condition to initiate handover / PLMN selection procedure, and e.g. select NTN access and / or a different PLMN when the signal quality thresholds are below the configured threshold. Such conditions may be limited to a set of frequencies and / or may be added to PLMN / RAT selection rules in addition and / or next to legacy PLMN / RAT selection rules; and / or

[0138] a list of cell-IDs of gNBs operating close to the border and / or a condition that if a certain IE is received from an access device near the border, the IE indicating that the gNB is operating close to the border, then the wireless device is allowed to initiate handover / PLMN selection procedure, and e.g. select NTN access and / or a different PLMN; and / or

[0139] a set of configurations that allow the wireless device to increase transmit power or perform certain coverage enhancements to initiate handover, e.g. to perform RACH procedure and / or to request SIB, whereby such set of configurations may comprise a set of conditions, (e.g. location / area or time / duration or signal quality thresholds, or receiving a cell ID or SIB with an IE indicating that the gNB is operating close to the border) that indicate when the wireless device is allowed to do so, possibly limited to a number of frequencies in which it is allowed to do so.

[0140] In an embodiment that may be combined with other embodiments or used independently, a wireless device, on determining that it is approaching a cross-country boundary, attempts to perform a cell selection targeting a second access device, e.g., an NTN node operating on behalf of at least the the first seriving network and / or second serving network. Once a suitable second access device has been found, the UE may register with the second serving network, establishes an RRC connection and performs a handover.

[0141] In an embodiment that may be combined with other embodiments or used independently, a wireless device may start the mobility procedure to and / or roaming procedure by:

[0142] connecting to the second access device while remaining connected to the first access device, this may require a dual-stack device including two radio stacks,

[0143] registering, by the wireless device, in the second serving network once it is connected to the second access device,

[0144] transferring, by the wireless device, at least one communication link from the first access device managed by the first serving network to the second access device managed by the second serving network, andclosing the connection, by the wireless device, with the first access device and first serving network.

[0145] Wireless devices may be equipped with either a single radio transceiver or a dual-stack system, each offering distinct capabilities for connectivity and mobility. A wireless device with a single radio, such as a 5G transceiver, may be designed to connect to one network at a time. It may switch between different networks, but it may need to drop its current connection before establishing a new one. This type of device may be simpler and more cost-effective but may experience service interruptions during network transitions, particularly when crossing country borders or moving between different types of access devices. In contrast, a wireless device with a dual-stack system, which includes two 5G transceivers, may maintain simultaneous connections to multiple networks. This means that while connected to one network, the device may establish a connection with a second network before disconnecting from the first. This capability may significantly enhance the device's ability to manage mobility and roaming procedures, reducing service interruptions and ensuring a smoother transition when moving between networks. For instance, as the device approaches a border, it may connect to a new network while still maintaining its original connection, enabling a seamless handover.

[0146] Furthermore, in this context, a communication link may refer to the connection established between the User Equipment (UE) and the network, which could be a voice call, a data connection, or any other form of communication. For example, during a voice call, the communication link ensures the continuous exchange of audio signals between the caller and the recipient. Similarly, for a data connection, the communication link may facilitate the transfer of data packets, enabling activities such as browsing the internet, streaming videos, or accessing cloud services.

[0147] In an embodiment that may be combined with other embodiments or used independently, a wireless device may start the mobility procedure to and / or roaming procedure by performing one or more of the following steps:

[0148] performing a handover from the first access device to the second access device while being served by the first serving network;

[0149] registering in the second serving network while being served by the first serving network, and

[0150] transferring at least one communication link from the first serving network to the second serving network.

[0151] The second access device may be managed by both the first serving network and second serving network, and thus, it may provide advantages regarding switch between networks. In an option, thetransfer of the at least one communication link from the first serving network to the second serving network may be carried out when the roaming status changes and / or is required to change, e.g., when crossing the country border.

[0152] In some advanced embodiments (such as the previous one), an access device (e.g., the second access device) co-managed / shared by two different serving networks may play a pivotal role. This access device may be specifically designed to facilitate uninterrupted connectivity as a wireless device moves or roams between the first and second serving networks. Such a device may harness dual-network capabilities, maintaining active connections with both networks simultaneously. This unique feature may ensure that the wireless device remains connected to the access device, even during transitions, enabling a seamless handover process. The wireless device that is connected to such an access device in the air interface may be connected at time to the access device and be served by the first serving network. The wireless device may then start a procedure to switch to the second serving network. Once the second serving network has accepted the wireless device, the second serving network may trigger a request to perform the handover of the connection. The handover in the access device may preserve the same radio bearers, etc, and only a switch of certain parameters, e.g., the security context may be required. By leveraging sophisticated algorithms, the access device may continuously monitor the wireless device's signal quality, location, and movement patterns. When it detects that the wireless device is nearing a handover threshold, it may smoothly transition the communication link to the second serving network. During this process, the wireless device's active sessions, whether voice calls, data transfers, or other communications, may be preserved without interruption. Moreover, the access device's capability to manage dual-network connections may offer significant advantages in scenarios where the wireless device frequently moves across network boundaries. For example, in a border region between two countries, the access device may ensure that the wireless device automatically switches networks without the user experiencing any service disruption.

[0153] Such an access device may be, e.g., an NTN node, that may be managed by the second network, the first network, by a third network or any combination. The NTN node may behave to the UE as an access device / base station node belonging to the second serving network, through which the UE may register and receive a first configuration. In this mode, the access device, e.g., NTN node, may operate as a transparent relay to the second network or as a gNB belonging to the network.

[0154] In a further embodiment, the NTN may also provide similar services in the reverse direction; that is, provide means for a wireless device coming from the second network to register with the first network.The first access device / network may receive information about the second access device, e.g., NTN node, from the node manager through a network link or, if the NTN node can transport inter-network traffic, e.g., it can provide network backhaul capability, through the NTN node itself.

[0155] In an embodiment that may be combined with other embodiments or used independently, an access device may inform the wireless device about its capabilities to handle two or more serving networks. This information may be announced via a message, e.g., a broadcast message, e.g., a SIB or an RRC message. In some cases, a wireless device may also request the first access device it is currently connected to for information about surrounding access devices capable of serving two or more serving networks. The wireless device may base its handover decision from the first access device to the second access device on the capability of the second access device to serve two or more serving networks.

[0156] In an embodiment that may be combined with other embodiments or used independently, the wireless device may start a mobility procedure and / or roaming procedure, wherein the second access device may be managed by a second serving network and / or co-managed by the first and the second serving network. The wireless device may be about starting a roaming procedure while remaining connected to the first access device. In this embodiment, one or more of the following steps may be executed:

[0157] (1) the wireless device may send a pre-registration request to the second serving network while remaining connected to the first access device / first serving network,

[0158] (2) the wireless device may register with the second serving network (this may involve performing some security procedures as in other embodiments),

[0159] (3) the wireless device may receive a token from the second serving network, (4) the wireless device may transfer at least one communication link from the first access device and / or first serving network to the second access device and / or second serving network, and

[0160] (5) the wireless device may be close with the first access device and / or first serving network.

[0161] In an embodiment that may be combined with other embodiments or used independently, a wireless device may pre-register with the second network through its active connection with the first network. Advantageously, this does not require the wireless device to be capable of operating dual protocol stacks. An exemplary procedure might comprise the one or more of the following steps:on determining that a handover, e.g., a network handover, is required to the second access device / serving network, the first access device / serving network sends a handover request message, e.g., network handover request message, to the second access device / second serving network, carrying information necessary for the second access device / second serving network to prepare for the handover. This may comprise, for example, the context information of the wireless device.

[0162] After preparation, the second access device / second serving network may respond with a handover request acknowledge message, e.g., a network handover request acknowledge message, with a status flag indicating 'pre-registration' and a container to be sent to the wireless device as part of the registration process.

[0163] While maintaining the existing connection, the first access device / first service network may send a message with the container to the wireless device requesting it to pre-register with the second access device / second serving network

[0164] The wireless device may respond to the pre-registration request with a container carrying its responses to the second serving network, the first serving network forwarding said container to the second serving network.

[0165] If necessary, further dialogue can be conducted between the wireless device and the second serving network in this manner until the registration process is complete and the second serving network has created a context for the wireless device and / or the wireless device has created a context for the second serving network. Additionally or alternatively, the first network may perform the registration procedures on behalf of the second network using information supplied by the second network.

[0166] The second serving network may send the wireless device via the first serving network a token that can be used to locate the context when the wireless device accesses the second serving network directly via an access network (e.g., second access device) belonging to and / or managed by the second serving network. In an example, the token may comprise an l-RNTI that is used in an RRCResumeRequest message when the wireless device synchronises to the second access device / network.

[0167] Once the pre-registration process is complete, the first access device / network may initiate the handover process / network handover process by, for example, sending an RRCCReconfiguration message to the wireless device containing the information necessary to access the second access device / second serving network, comprising, for example, the cell ID of the second access device / second access network, a C-RNTI, the l-RNTI and necessary security parameters. The wireless device may be instructed to perform the handover immediately or conditionally, where thecondition might comprise a relative measure of signal strengths between the first access device / network and the second access device / network, loss of signal from the first access network, determination of its location, change of a roaming status, and so on.

[0168] Optionally, if the wireless device is capable, the handover may be performed in a 'make-before-break' manner, meaning that a connection is established with the second serving network before the connection with the first serving network is dropped.

[0169] In an embodiment that may be combined with other embodiments or used independently, the wireless device may determine an incoming change of its roaming status by one or more of:

[0170] receiving an indication from the first access device indicating that the wireless device is about to cross a country border and / or be forced to change the serving network (this may be, e.g., determined based on for example, the UE's motion as determined by the first access network);

[0171] receiving an indication from the first access device indicating that the first access device is about to cross a country border and / or be forced to change the serving network; and determining based on its own location estimate and movement pattern that the wireless device is about to cross a country border.

[0172] The indication may be received by means of, e.g., an RRC message, SIB, NAS message, etc.

[0173] In an example, an access device near the border may indicate via an indication (e.g., in a special IE) that this base station operates close to the border. This IE may be a flag and / or may contain information indicative of operating close to the border, e.g. location information of the access device (gNB), one or more distances to the border (which may be in the form of a timing advance and / or may include direction information), distance to one or more cross-border access devices, identifiers of one or more cross-border gNBs, identifiers of NTN-based access devices covering the area, SSB related information of the gNBs cell that is closest to the border, frequency / SSB information of cross-border access devices, signal quality related threshold conditions (e.g. if quality of signal reaches below certain threshold than that is the best moment to perform handover).

[0174] This IE, when received by the wireless device, could be used as a trigger (e.g. in addition to signal strength or location based methods) for the wireless device to transition (e.g., break) the ongoing connection with the respective access device / serving network and / or initiate handover and / or PLMN selection procedure and / or start searching for a gNB in neighbor country.

[0175] In an embodiment of the invention that may be combined with other embodiments or used independently, an access device that is close to a border may transmit an indication indicativeof the fact that it is providing service close to a country border. This indication may be exchanged via SIB1 or via an RRC message, e.g., then the wireless device connects to said access device. The indication may indicate which beams of the access device are close(r) to the border. The wireless device may have a configuration that may be influenced by the indication.

[0176] In an example, the wireless device may measure / determine its location, and transmit another indication indicating that it close to cross a country border.

[0177] In an example, the indications may include information such as the timing to cross the country border,

[0178] For instance, if the wireless device is connected to an access device distributing this indication, the wireless device may adapt thresholds related to measurement events (e.g., A3 event) triggering mobility. For instance, the reception of the indication may trigger the usage of different thresholds, e.g., a threshold in which the wireless device may more easily trigger the switch of access device (e.g., then the RSRP of the source access device goes below a given threshold). This may trigger mobility events more easily, e.g., either during a conditional handover and / or with a network-based triggered handover.

[0179] In an embodiment that may be combined with other embodiments or used independently, on request from the first access device, the wireless device may make measurements to determine the availability of a suitable second access device, e.g., an NTN node. On receipt of the measurements, the first access device / network may send a message to the wireless device to instruct it to attempt to reach the second access device, e.g., NTN node and register with the second network. This message may additionally supply the wireless device with necessary configuration information to assist the cell search and registration processes. The first access device / network may additionally issue a handover request message to the second access device / network and receive a handover request acknowledge. Thus, the message to the wireless device may additionally comprise an instruction to the wireless device to initiate a network handover together with information supplied by the second access network in the handover request acknowledge message.

[0180] In an embodiment that may be combined with other embodiments or used independently, if the wireless device makes its own determination, it may perform a blind cell search, use a stored configuration or request a configuration from the first access device / network. On receiving the configuration request, the first access device / network may issue a handover request message to the second access device / network as just described and return a similar message to the device.Section: security aspects

[0181] In an embodiment that may be combined with other embodiments or used independently, a wireless device may start the mobility procedure to and / or roaming procedure by:

[0182] performing a new primary authentication procedure with the home network through the second serving network;

[0183] creating a new security context based on said new primary authentication procedure; and

[0184] using said new security context when performing a handover procedure:

[0185] from the first access device managed by the first serving network to the second access device managed by the second serving network or

[0186] from the second access device managed by the first serving network to the second access device managed by the second serving network.

[0187] In particular, the wireless device may be connected to a second access device capable of serving both the first serving network and the second serving network. The handover may consist of switching security context from the current security context derived from a previous primary authentication to a new security context derived from the new primary authentication procedure.

[0188] In an embodiment that may be combined with other embodiments or used independently, a wireless device may start the mobility procedure to and / or roaming procedure by performing one or more of the following steps:

[0189] (1) signaling the need to move to the second access device managed by the second serving network. Such a signaling may be done when the wireless device gets close to a country border and / or detects a situation that will require changing the network. Such signaling may be send to the currently serving network.

[0190] (2) deriving a security context for the second serving network based on a previously executed primary authentication. This means that given a root secret derived from the previously executed primary authentication (e.g., K_AUSF in 5G), a root key for the new (second) serving network is derived. This root key should be such that it is specific for this current transaction from the first serving network to the second serving network.

[0191] (3) the wireless device may use said new security context when performing a handover procedure, e.g., from the first access device managed by the first serving network to the second access device managed by the second serving network or from the second access device managed by the first serving network to the second access device managed by the second serving network.(4) the wireless device may verify that it is connected to the second serving network upon successful reception of a message indicating the completion of the handover to the second access device managed by the second serving network.

[0192] In a related embodiment that may be combined with other embodiments or used independently, the wireless device may derive a security context for the second serving network based on a previously executed primary authentication by deriving a root key for the second serving network given the root key of the previously executed primary authentication, the serving network name of the second serving network, and at least a freshness parameter. The freshness parameter(s) may be exchanged between the wireless device, first serving network, second serving network, and home network so that the freshness of the newly generated key can be verified. In an option, each party may derive a freshness parameter, e.g., a NONCE, that is sent to both wireless device and home network. The wireless device may derive the key locally. The second serving network may receive the root key for the second serving network from the home network.

[0193] Note that this may mean that the root key from a first primary authentication procedure is kept in the home network. It may also mean that if a key for a serving network is derived during / after the primary authentication, that key is derived, e.g., by means of a key derivation function using the root key and the name of the serving network. It may also mean that when a key for a serving network is derived at some point later (e.g., when a UE roams as in other scenarios), the key may be derived from the root key, the name of the new serving network, and freshness parameters. The key hierarchy, e.g., compared with 5G, may require to be extended.

[0194] Section: actions after registration in the second serving network

[0195] In an embodiment that may be combined with other embodiments or used independently, after the wireless device is connected to the second access device, wherein the second access device may be managed by a second serving network and / or managed by the first serving network, the second access device / network may initiate the roaming between the first (i.e. serving) network to the second (i.e. new serving) network.

[0196] This may be based on measurements and / or location determination of the wireless device to estimate if the wireless device has crossed the border or not.

[0197] Additionally or alternatively, the second access device / network (and / or first access device / network) may configure / provide the wireless device with conditions (e.g. measurement thresholds (e.g. minimal signal strength towards the second access device or signal dissipationthreshold towards the first access device), satellite constellation information, angle information (e.g. relative to horizon or to satellite), position information, timing information (e.g. time since signal being below a certain level or time since signal loss with first access time or expected time before reaching the border) related to at which moment or position (e.g. in its current trajectory) the wireless device reaches the border.

[0198] In an embodiment that may be combined with other embodiments or used independently, during or as a result of a roaming procedure (e.g. as described in earlier embodiments) whilst the wireless device is connected to the second access device / network, the wireless device may be triggered to perform authentication with the second serving network and / or receive updated policy information and / or connect to a different ePDG / N3IWF and / or change its roaming status, change PSAP to connect to during emergency call, establish a new set of PDU sessions. Triggering such actions may for example be done through receiving a PDU Session Modification or RRC Reconfiguration message from the second access device / network.

[0199] In an embodiment that may be combined with other embodiments or used independently, a wireless device, having been instructed to perform a handover to the second access device / network, attempts to connect to the network via the second access device, e.g., NTN node, and complete the handover including data path switching. Once the border has been crossed (in general, the roaming status of the wireless device has changed), the wireless device and / or the second access network may instigate a handover from the second access device (e.g., NTN node) to a third access device, e.g., TN node.

[0200] In an embodiment that may be combined with other embodiments or used independently, the second access device / network may suspend the RRC connection, e.g., at the NTN. The second access device may supply the UE with a token representing the UE's configuration with the second serving network, for example, an l-RNTL On completion of the border crossing / roaming status change, the wireless device may synchronize with a third access device, e.g., base station, of the second serving network. The wireless device may send an RRC resume request to the network to complete the handover. This may avoid overloading the second access device, e.g., NTN node, with multiple data streams and may be more cost effective for the user.

[0201] In some scenarios, cross border (or cross-country) handover may cause some problems not only for the customer but also for network operator (ping pong effects, charging issues, emergency call routing, etc.) There is no way to control inter-PLMN handover for single users acrossborders. For this reason, the Subscription Data may contain an indication that inter-PLMN handover shall be restricted. If the UE is restricted from inter-PLMN handover, the AMF shall not send EPLMN IDs in the Registration Accept sent to the UE or in the Mobility Restriction List sent to the RAN. In general, the Cross-Border HO-Restricted indicator may indicate whether the inter-PLM N handover for a wireless device is restricted or not. However, this restriction may not be sufficient in some cases. Thus:

[0202] In an embodiment of the invention that may be combined with other embodiments or used independently, a wireless device may be configured and / or be associated with a configuration for cross-border handover, this configuration may comprise the Cross-Border HO-Restricted indicator, that may be configured in the subscription data, and may be used (upon configuration) in the radio access network (e.g., access device may be configured by the network (e.g., PCF) with it) and / or wireless device (e.g., access device and / or network may configure the wireless device) and wherein the configuration may indicate and / or specify one or more of:

[0203] Whether the Cross-Border HO-Restricted indicator may be dependent on one or more values such as, e.g., the speed and / or trajectory of the wireless device such that if the wireless device is static and / or not moving towards the border, then the restriction does apply, but if the wireless device is moving at a speed higher than a threshold and / or closer to the border than a second threshold, then the restriction does not apply. For instance, if the user is at home next to the border, the restriction would apply. For instance, if the user is walking towards the border and it is 200 m, then the restriction applies, but if he is just 50 m away, the restriction does not apply. For instance, if the user is driving towards the border at 100 Km per hour and he is 5 km away, then the restriction applies, but if he is just 2 km away, the restriction does not apply.

[0204] Indicate whether a non-terrestrial access device may be used to facilitate cross-border handover. For instance, while a non-terrestrial access device may facilitate handover, its usage may incur additional charges, and thus, it may only be allowed to wireless devices with a higher subscription; Indicate the quality of service expected during a cross-border handover. For instance, different users may have different needs when performing a cross-border handover. While some users may need a very smooth handover (to ensure service continuity during calls), other users may not have this need.

[0205] Specify the types of authentication methods to be used when moving between networks. For example, certain authentication protocols may be required for cross-border handovers to ensure secure and seamless transitions between the serving networks.Set limitations on the frequency of cross-border handovers to prevent excessive signaling and potential service disruptions. The configuration may include a timer or counter that restricts how often a wireless device can perform such handovers within a specified period.

[0206] Define whether / how emergency services should be prioritized during cross-border handover scenarios. This could ensure that emergency call routing and access to public safety answering points (PSAP) are maintained or adapted as the device changes networks.

[0207] Indicate network selection preferences based on cost, coverage, historical information, or user subscription level. For instance, a device may be configured to prefer networks with lower roaming charges or better service quality, depending on user or operator policies.

[0208] In general, it is a proposed a method that may be implemented in a wireless device and / or access device, wherein the method comprises:

[0209] adapting the operation of a cross-border handover based on a Cross-Border HO-Restricted indicator and one or more conditions associated with the Cross-Border HO-Restricted indicator; and

[0210] receiving, by the wireless device and / or access device, the Cross-Border HO-Restricted indicator and one or more conditions associated with the Cross-Border HO-Restricted indicator;

[0211] determining, by the wireless device and / or access device, the eligibility to perform a cross-border handover based on the Cross-Border HO-Restricted indicator and the one or more conditions.

[0212] In an embodiment of the invention that may be combined with other embodiments or used independently, the signal strength of access devices next to a country border may be kept low, e.g., to ensure that a wireless device in country A does not connect to an access device in country B (transmitting signals with high power). However, this may also cause a long break in the communication. On the other hand, if the signal strength is higher, then a wireless device in country A may keep connecting to an access device in country B. To address this problem:

[0213] In an example, an access device located in country A next to a country border with country B may transmit with a high enough transmission power so that it reaches country B. The access device may need to provide information indicating it is next to a country border, it may provide information about the border (e.g., a set of coordinates defining the border), it may provide information about a target access device / target network when performing handover / roaming, it may provide information about the number of handover / roaming interactions that may be performed per unit of time (to avoid ping pong situations), it may indicate / provide cross-border specific conditionsfor the mobility events (e.g., RSRP thresholds triggering the handover / roaming / network change) and specific for a cross-border change, etc.

[0214] In an example, a wireless device may detect that it is a next to a country border, e.g., because the wireless device receives an indication from the access device itself indicating that it is an access device located next to a country border, the wireless device may obtain its specific location. Location may be obtained via GNSS, but also via the current network, either in connected or IDLE / INACTIVE mode (e.g., when synchronization signals or other reference signals of the cellular network may be used as reference time / location signals), etc.

[0215] In an example, the wireless device may also determine a potential location that acts as a trigger to perform handover / change the network based on one or more values such as measurements of the wireless signals, historical data. For instance, if the wireless device is moving along a given trajectory, e.g., a road between the Netherlands and Germany, the trigger may be based on the timing advance value with the access device. For instance, when the timing advance value is longer than a threshold and the wireless device determines that is on the road (because of historical data), the wireless device may consider this as a condition for handover / network change.

[0216] In an example, the wireless device may also need to retrieve / obtain specific information about the country border, e.g., a set of coordinates indicating the location of the border. This information may be made available from the cellular network it is connected, e.g., provided via an RRC message or a NAS message. It may also be stored locally on the wireless device (e.g., upon retrieval). It may be associated with one or more networks / PLMNs.

[0217] In an example, the wireless device may perform a mobility operation such as cell selection (or re-selection) or handover taking into account its own location and the location of the country it is located. This may mean that depending on its location and / or direction of movement and / or time of the day and / or RRC State certain networks may be preferred. For instance, when performing cell selection, only the strongest cell may be considered without considerations of the country, while when performing handover, the country where the wireless device is located may be considered in the selection, e.g., giving priority.

[0218] In an example, the wireless device may report its position and / or perform a positioning procedure with the source and / or target access device and / or with the current network (in the country it is currently located) and / or with the target network (i.e., the country it is moving towards) to verify the location of the wireless device, so that the handover and / or network change can be performed in an optimized manner.

[0219] In an example, a wireless device, e.g., when moving from country A to country B, may pre-register with a visiting network (e.g., in country B) setting up a timer to leave the current network(e.g., home PLMN in country A). This may allow to reduce the disruption time during the network change.

[0220] Fig. 8a schematically illustrates a scenario addressed by this invention wherein a wireless device 800 is moving from Country A to Country B along a given trajectory 804. Fig. 8 schematically illustrates an access device 801 in country A, access device 802 in country B, and mobile access device 803 covering both countries.

[0221] Related Fig. 8b includes the coverage areas 801-1, 802-1, and 803-1 provided by access device 801, 802, and 803, respectively. Coverage area provided by access device 803 is wider, so that it can facilitate the cross-border handover / network change.

[0222] In this setting described by means of Fig. 8a and 8b, the wireless device 800 may determine an incoming change of its roaming and / or coverage status when registered in a first serving network, e.g., the serving network of country A since the wireless device is moving along trajectory 804. The wireless device may then perform a mobility procedure to and / or roaming procedure over a second access device, wherein the second access device may be managed by a second serving network (e.g., network of country B) and / or co-managed by the first and the second serving network while the wireless device is still registered in the first serving network. For instance, wireless device may be move from access device 801 to access device 803 since it gives coverage over both countries and it is co-managed by the networks of both countries. Based on the specific location and trajectory of the wireless device, access device 803 may request the change of the network, e.g., change of an access and mobility function (e.g., 5G AMF) from the access and mobility function of the first network to the access and mobility function of the second network. Once the network has been changed, the wireless device may move from access device 803 to access device 802.

[0223] Fig. 9 further describes this procedure for the enhanced mobility procedure of the wireless device, wherein, in step 900, the wireless device may determine an incoming change of its roaming and / or coverage status when registered in a first serving network, and wherein in step 901, the wireless device, may perform a mobility procedure to and / or roaming procedure over a second access device, wherein the second access device is managed by a second serving network and / or comanaged by the first and the second serving network while the wireless device is still registered in the first serving network.

[0224] Furthermore, this invention can be applied to various types of UEs or terminal devices, such as mobile phone, vital signs monitoring / telemetry devices, smartwatches, detectors, vehicles (for vehicle-to-vehicle (V2V) communication or more general vehicle-to-everything (V2X) communication), V2X devices, Internet of Things (loT) hubs, loT devices, including low-power medical sensors for healthmonitoring, medical (emergency) diagnosis and treatment devices, for hospital use or first-responder use, virtual reality (VR) headsets, etc.

[0225] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. The foregoing de-scription details certain embodiments of the invention. It will be appreciated, however, that no matter how detailed the foregoing appears in the text, the invention may be practiced in many ways, and is therefore not limited to the embodiments disclosed. It should be noted that the use of particular terminology when describing certain features or aspects of the invention should not be taken to imply that the terminology is being re-defined herein to be restricted to include any specific characteristics of the features or aspects of the invention with which that terminology is associated. Additionally, the expression "at least one of A, B, and C" is to be understood as disjunctive, i.e., as "A and / or B and / or C". The same applies to the expressions "A or B" and "at least one of A or B", i.e., they may indicate all possible combinations of the listed items.

[0226] A single unit or device may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0227] The described operations like those indicated in the above embodiments may be implemented as program code means of a computer program and / or as dedicated hardware of the related network device or function, respectively. The computer program may be stored and / or distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

Claims

Claims1. A method for an enhanced mobility procedure of a wireless device, comprising:- determining, by the wireless device, an incoming change of its roaming and / or coverage status when registered in a first serving network, and- performing, by the wireless device, a mobility procedure to and / or roaming procedure over a second access device, wherein the second access device is managed by a second serving network and / or co-managed by the first and the second serving network while the wireless device is still registered in the first serving network.

2. The method of claim 1, further comprisingconnecting, by the wireless device, to a first access device, wherein the first access device is managed by the first serving network prior to determining, by the wireless device, an incoming change of its roaming and / or coverage status.

3. The method of claim 2, wherein:- the first access device is a terrestrial access device, and the second access device is a non-terrestrial access device; or- the first access device is a terrestrial access device served or managed by the first serving network and the second access device is a terrestrial access device served by the first serving network and the second serving network.

4. The method of any previous claims, comprising:determining, by the wireless device, whether the second access device supports the enhanced mobility procedure based on a capability indication.

5. The method of any previous claims, comprising:sending, by the wireless device, an indication requesting the execution of the enhanced mobility procedure.

6. The method of any previous claims, wherein the step of performing, by the wireless device, the mobility procedure and / or roaming procedure comprises:- sending, by the wireless device, a pre-registration request to the second serving network while remaining connected to the first serving network,- registering, by the wireless device, in the second serving network,- receiving, by the wireless device, a token from the second serving network, - transferring, by the wireless device, at least one communication link from the first serving network to the second serving network,- performing the handover to the second access device, and- closing the connection, by the wireless device, with the first access device and / or first serving network.

7. The method of any of claims 1 to 5, wherein the step of performing, by the wireless device, the mobility procedure and / or roaming procedure comprises:- connecting, by the wireless device, to the second access device while remaining connected to the first access device,- registering, by the wireless device, in the second serving network,- transferring, by the wireless device, at least one communication link from the first access device managed by the first serving network to the second access device managed by the second serving network, and-closing the connection, by the wireless device, with the first access device and first serving network.

8. The method of any of claims 1 to 5, wherein the step of performing, by the wireless device, the mobility procedure and / or roaming procedure comprises:- performing, by the wireless device, a handover from the first access device to the second access device while being served by the first serving network;- registering, by the wireless device, in the second serving network while being served by the first serving network, and- transferring, by the wireless device, at least one communication link from the first serving network to the second serving network.

9. The method of any previous claims, wherein the step of determining, by the wireless device, an incoming change of its roaming status comprises:- receiving, by the wireless device, an indication from the first access device indicating that the first access device is about to cross a country border and / or be forced to change the serving network; and- determining, by the wireless device, based on its own location estimate and movement pattern that the wireless device is about to cross a country border.

10. The method of any of the previous claims, wherein the step of performing, by the wireless device, a mobility procedure and / or roaming procedure comprises:- performing, by the wireless device, primary authentication to register in the second serving network with a home network;- creating, by the wireless device, a new security context based on said primary authentication; and- using, by the wireless device, said new security context when performing a handover procedure:* from the first access device managed by the first serving network to the second access device managed by the second serving network or * from the second access device managed by the first serving network to the second access device managed by the second serving network.

11. The method of any of the previous claims, wherein the step of performing, by the wireless device, a mobility procedure and / or roaming procedure comprises:- deriving, by the wireless device, a security context for the second serving network based on a previously executed primary authentication;- using, by the wireless device, said new security context when performing a handover procedure:* from the first access device managed by the first serving network to the second access device managed by the second serving network or * from the second access device managed by the first serving network to the second access device managed by the second serving network. - verifying, by the wireless device, to be connected to the second serving network upon successful reception of a message indicating the completion of the handover to the second access device managed by the second serving network.

12. The method of claim 11, wherein deriving, by the wireless device, a security context for the second serving network based on a previously executed primary authentication comprises deriving a root key for the second serving network given the root key of the previously executed primary authentication, the serving network name, and at least a freshness parameter.

13. The method of any of the previous claims, comprising receiving, by the wireless device, one or more of:- an indication from an access device, the indication indicative of the access device providing coverage in the surroundings of a border between countries;- an indication of the location of a border between countries;- a request to determine the location of the wireless device; and- one or more values to determine a condition to trigger the mobility procedure and / or roaming procedure.

14. The method of any of the previous claims, comprising transmitting, by the wireless device, one or more of:- an indication requesting an enhanced mobility procedure;- an indication indicative of the wireless device approaching a border between countries; - an indication indicative of time when the wireless device will arrive at the border between countries;- the location of the wireless device; and- one or more values to determine a condition to trigger the mobility procedure and / or roaming procedure.

15. A method for an enhanced mobility procedure performed by a first access device, the method comprising:- detecting, by the access device, a wireless device registered with a first serving network and approaching a country border or coverage boundary;- transmitting, by the access device, information to the wireless device comprising one or more of (1) an indication to the wireless device of the access device's proximity to the country border, (2) the presence of cross-border coverage the coordinates and / or location of the country border, and / or (3) conditions for cross-border handover, including network selection preferences and thresholds; and- coordinating with a second access device managed by a second serving network and / or comanaged by the first and second serving networks to support the mobility procedure while the wireless device remains registered in the first serving network, optionally, requesting or verifying the enhanced mobility capability of the second access device prior to executing the handover or roaming procedure.

16. An apparatus adapted to perform an enhanced mobility procedure, wherein the apparatus comprises:a. a processor,b. one or two transceivers,c. one or two USI Ms,wherein the apparatus is adapted to perform the steps of the method of any of the claims 1 to 15.

17. A computer program for enhanced mobility wherein the program comprises instructions implementing the steps of the method of any of the claims 1 to 15.

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