Method and apparatus for base station altitude dependent mobility of a wireless device

Abstract

This invention describes a method and apparatus for efficient mobility of a wireless device wherein the method comprises: sending, by the apparatus an initial message comprising the wireless device capabilities, receiving, by the apparatus, a first message from a first access device with a handover configuration, sending, by the apparatus, a second message to perform a handover to a target access device, wherein the handover configuration comprises configuration parameters for access devices at different altitudes.

Description

[0001] METHOD AND APPARATUS FOR BASE STATION ALTITUDE DEPENDENT MOBILITY OF A WIRELESS DEVICE

[0002] FIELD OF THE INVENTION

[0003] This invention relates to a method, apparatus, and system for efficient mobility of a wireless device as a user equipment in a wireless system such as a cellular system, a Wi-Fi network or the like. In particular, this invention relates to mobility between access devices at different altitudes including terrestrial and non-terrestrial access devices.

[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 signaling). 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.2025P00150WQ

[0008] Current cellular systems are also further evolving to enable access through multiple non-terrestrial access devices located in different orbits, e.g., Low Earth Orbit (LEO), Medium Earth Orbit (MEO) or Geosynchronous Equatorial Orbit (GEO) satellites. This situation leads to the question on how to enable suitable mobility between access devices. Similarly, cellular systems are evolving towards a cell-free architecture, in which mobility also needs to be handled in a smooth manner.

[0009] SUMMARY OF THE INVENTION

[0010] An aim of the invention is to address above problem.

[0011] Another aim of the invention is to propose a method enabling the wireless device to select an optimal access devices depending on e.g. its needs or capabilities.

[0012] To this end it is proposed a method, an apparatus and a system as defined in the appended set of claims.

[0013] In accordance with a first aspect of the invention, it is proposed a method for efficient mobility of a wireless device, the method comprising:

[0014] sending, by the wireless device, a capability indication message comprising an indication of wireless device capabilities,

[0015] receiving, by the wireless device, a first message from a first access device with a handover configuration and / or a handover command,

[0016] sending, by the wireless device, a second message to perform a handover to a target access device,

[0017] wherein the handover configuration and / or handover command comprises configuration parameters for access devices at different altitudes.

[0018] In accordance with a first variant of the first aspect, the handover configuration comprises one or more conditions and / or parameters to select and / or start and / or perform the handover to the target access device, and the one or more conditions comprise at least one of:

[0019] altitude of a candidate target access device,

[0020] (estimated / expected) coverage of candidate target access devices having an altitude within a range relative to the altitude of the first access device, said range being defined by at least one threshold,

[0021] (estimated / expected) coverage of target access devices at an altitude different to the altitude of the first access device,

[0022] uplink synchronization information such as TCI or beam index, (estimated) received signal strength,2025P00150WQ

[0023] received signal quality,

[0024] required transmission power,

[0025] distance between wireless device and access device,

[0026] minimum coverage time,

[0027] type of access device (e.g., GSO vs NGSO),

[0028] frequency band and bandwidth availability,

[0029] movement speed and trajectory of the wireless device, power availability and consumption requirements of the wireless device, latency requirements for a specific application or service,

[0030] connection setup delay and / or handover delay,

[0031] operation in regenerative or transparent architecture, operation in store and forward mode,

[0032] which services are available in store and forward mode and / or which services are available in real-time,

[0033] time information of when access device operates in store and forward mode and / or timing when it does not,

[0034] support of a full core network,

[0035] support for UE-satellite-UE communication,

[0036] communication parameters to perform the handover with the target access device,

[0037] communication parameters to perform the handover with the target access device dependent on the communication parameters used with the first access device and / or wireless device capabilities and / or the handover configuration.

[0038] In another variant, communication parameters used to send the second message may be determined based on parameters used to communicate with the first access device.

[0039] In another variant, the method comprises one or more of the following features: the handover is a RACH-less handover, wherein the second message is an RRCSetupComplete message;

[0040] the handover configuration contains a set of handover conditions to perform a conditional handover,

[0041] the handover configuration contains communication parameters for enhanced coverage towards the target access device,

[0042] the handover configuration contains a time offset between the reference time of the first access device and the reference time of the target device;the handover command contains a command to execute the handover to the target access device.

[0043] In another variant, the method further comprises

[0044] receiving, by the wireless device, a second signal from a second access device and / or a third signal from a third access device, and

[0045] the wireless device selecting the second access device or the third access device as the target access device and / or determining to perform the handover to the target access device based on the wireless device capabilities and the handover configuration, prior to sending, by the wireless device, the second message to perform the handover to the target access device.

[0046] In another variant, the handover configuration comprises a first sub-configuration and a second sub-configuration, wherein

[0047] the first sub-configuration comprises conditions to perform a handover from the first access device to the target access device, wherein the first access device and the target access device have different altitudes (e.g., different meaning more than a given threshold), and

[0048] the second sub-configuration comprises conditions to perform a handover from the first access device to the target access device, wherein the target access device has an altitude within a first range relative to the altitude of the first access device.

[0049] In another variant, the method further comprises

[0050] determining, by the wireless device, by means of the handover configuration whether the wireless device performs the handover to a target access device at similar (e.g., a second) altitude within a second range of the altitude of the first access device or to a target access device at analtitude within a third range of the altitude of the first access device.

[0051] In another variant, the determination step may depend on one or more of:

[0052] an expected coverage;

[0053] communication latency;

[0054] uplink transmission power.

[0055] Additionally, the expected coverage and / or required- communication latency and / or required uplink transmission power may be one of:

[0056] a coverage and / or communication latency and / or uplink transmission power provided by a target access device whose altitude is within a second range of the altitude of the first access device;

[0057] a coverage and / or communication latency and / or uplink transmission power provided by a target access devices whose altitude is similartowithin a second range of the altitude of the first access device;a coverage and / or communication latency and / or uplink transmission power provided by a target access device whose altitude is within a third range of the altitude of the first access device.

[0058] Optionally, the wireless device may estimate the expected coverage for a plurality of altitudes / access devices and compare the estimated expected coverages in order to e.g. select the target access device, or trigger the handover.

[0059] In a further variant, the method further comprises determining, by the wireless device, by means of the handover configuration whether the wireless device performs the handover to a target access device at similar altitude of the first access device or to a target access device at a different altitude of the first access device depending on a coverage provided by access devices at an altitude different than the altitude of the first access device.

[0060] In a further variant, the first message may comprise a second communication parameter, wherein the second communication parameter for the sending of the second message to target access device, and wherein the second communication parameter is encoded in a differential manner with respect to a first communication parameter used for the communication between the wireless device and the first access device.

[0061] In a further variant, the first access device may be at a first altitude, and - the target access device maybe at a second altitude, and

[0062] - the difference between first altitude and the second altitude maybe greater than a first threshold; and

[0063] - the wireless device may perform the control plane communication with the first access device, and

[0064] - the handover may refer to the wireless device user plane handover to the target access device.

[0065] In accordance with a second aspect of the invention, it is proposed a method for efficient mobility management of a wireless device performed by an access device at a first altitude, the method comprising one or more of:

[0066] - receiving, by the access device, a capability indication message comprising an indication of the wireless device capabilities of the wireless device,

[0067] - transmitting, by the access device, a first message to the wireless device, the message including a handover configuration and / or handover command,

[0068] - receiving, by the access device, a second message to perform a handover to a target access device at a second altitude,

[0069] wherein the handover configuration and / or handover command comprises configuration parameters for access devices at different altitudes.In accordance with a third aspect of the invention, it is proposed an apparatus for efficient mobility comprising:

[0070] a wireless transceiver,

[0071] A processor, and

[0072] A memory,

[0073] wherein the apparatus is adapted to perform the steps of the method of any of the first and second aspects of the invention, and their variants.

[0074] In accordance with a fourth aspect of the invention, it is proposed a computer program for efficient mobility, wherein the program comprises instructions to perform the steps in the method of the first or second aspects of the invention or any of their variants.

[0075] 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.

[0076] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

[0077] BRIEF DESCRIPTION OF THE DRAWINGS

[0078] In the following drawings:

[0079] Fig. 1 schematically represents the overall cellular system including UEs, RAN, and core network;

[0080] Fig. 2 provides a schematic representation of a UE and its components;

[0081] 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 signaling procedure by an access device;

[0082] Fig. 6 schematically represents a location procedure involving non-terrestrial access devices according to various embodiments;

[0083] Fig. 7 schematically represents the distribution of communication signals such as synchronization signals from non-terrestrial access devices at different altitudes according to various embodiments;

[0084] Fig. 8 schematically represents the synchronization signals broadcasted by nonterrestrial access devices according to various embodiments;

[0085] Fig. 9 schematically represents a protocol stack of a wireless device;Fig. 10 schematically represents a state machine of a wireless device according to an embodiment;

[0086] Fig. 11 schematically represents a set of resources communication resources and the signaling used to transmit a signal in a reliable manner while keeping into account energy consumption of wireless devices;

[0087] Fig. 12 schematically represents a procedure for the resilient and efficient delivery of emergency messages according to embodiments of the invention; and

[0088] Fig. 13 schematically represents a procedure for efficient mobility according to embodiments of this invention.

[0089] DETAILED DESCRIPTION OF EMBODIMENTS

[0090] 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.

[0091] 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.

[0092] 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.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.

[0093] 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.

[0094] 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 signaling). 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.

[0095] 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. 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. Thisrelay 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.

[0096] 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:

[0097] - A universal integrated circuit card (UICC), which stores the user's identification and authentication information, such as the subscription permanent identifier (SUPI) or credentials. - 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.

[0098] -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.- 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.

[0099] - 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.

[0100] - A keyboard and / or a touch screen, which allow the user to enter and select commands, text, numbers, etc.

[0101] - 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.

[0102] - 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.

[0103] - A battery, which provides the power supply for the UE.

[0104] 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.

[0105] 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.

[0106] A UE may receive a configuration by means of different procedures:

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] Non-access stratum (NAS) messages are used for signaling 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.

[0113] 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.

[0114] 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 " Operator Controlled 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.UE configuration update (UCU) is used to update configuration parameters as perTS 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.

[0115] 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. 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).

[0116] 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.

[0117] 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.

[0118] - 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.

[0119] - 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.

[0120] -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.

[0121] - 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. 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.

[0122] 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

[0123] 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. 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 signaling and control functions for the UEs, such as authentication, authorization, mobility management,2025P00150WQ

[0124] 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), the 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.

[0125] 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.

[0126] 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-SIMsubscription 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.

[0127] 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 providing connectivity 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.

[0128] 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.

[0129] 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.

[0130] The RAN 143 includes base station 104 that 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.

[0131] Furthermore, a satellite gateway 141 is shown that connects to satellite 140 and may provide connectivity services to remote UE 136 or UE 100.

[0132] 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.

[0133] 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 signaling 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 and2025P00150WQ

[0134] 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 AM F and K_ASME is managed by the MME. A UE may connect to a serving network or serving Public Land Mobile Network (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.

[0135] 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 3092025P00150WQ

[0136] 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.

[0137] Non-terrestrial devices such as satellites distribute system information in specific SIBs, in particular, SIB31 in 4G and SIB19 in 5G. SIB19 information element as defined in TS 38.331 18.2.0.

[0138] — ASN1START

[0139] — TAG-SIB19-START

[0140] SIB19-rl7:: = SEQUENCE {

[0141] ntn-Conf ig-rl7 NTN-Conf ig-r!7

[0142] OPTIONAL, — Need R

[0143] t-Service-r!7 INTEGER ( 0..549755813887 ) OPTIONAL, — Need R

[0144] ref erenceLocation-r!7 Ref erenceLocation-rl7 OPTIONAL, — Need R

[0145] distanceThresh-r!7 INTEGER ( 0.. 65525 ) OPTIONAL, — Need R

[0146] ntn-NeighCellConf igList-r!7 NTN-NeighCellConf igList-r!7 OPTIONAL, — Need R

[0147] lateNonCriticalExtension OCTET STRING

[0148] OPTIONAL,

[0149] [ [

[0150] ntn-NeighCellConf igListExt-vl720 NTN-NeighCellConf igList-r!7 OPTIONAL — Need R

[0151] ] ],

[0152] [ [

[0153] movingRef erenceLocation-r!8 Ref erenceLocation-rl7 OPTIONAL, — Need R

[0154] ntnCovEnh-r!8 NTN-CovEnh-rl8

[0155] OPTIONAL, — Need R

[0156] satSwitchWithReSync-rl8 SatSwitchWithReSync-rl8 OPTIONAL — Need R

[0157] ] ]

[0158] }

[0159] NTN-NeighCellConf igList-r!7:: = SEQUENCE ( SIZE ( 1.. maxCellNTN-rl7 ) ) OF NTN-NeighCellConf ig-r!7

[0160] NTN-NeighCellConf ig-r!7 SEQUENCE {ntn-Conf ig-r!7 NTN-Conf ig-r!7

[0161] OPTIONAL, — Need R

[0162] carrierFreq-r!7 ARFCN-ValueNR

[0163] OPTIONAL, — Need R

[0164] physCellId-rl7 PhysCellld

[0165] OPTIONAL — Need R

[0166] }

[0167] NTN-CovEnh-rl8:: = SEQUENCE {

[0168] numberOfMsg4HARQ-ACK-Repetitions-rl8 BIT STRING ( SIZE ( 4 ) ), rsrp-ThresholdMsg4HARQ-ACK-r!8 RS RP- Range

[0169] OPTIONAL — Need R

[0170] }

[0171] SatSwitchWithReSync-rl8:: = SEQUENCE {

[0172] ntn-Config-rl8 NTN-Conf ig-r!7,

[0173] t-ServiceStart-r!8 INTEGER ( 0.. 549755813887 ) OPTIONAL, — Need R

[0174] ssb-TimeOf f set-r!8 INTEGER ( 0.. 159 )

[0175] OPTIONAL — Need R

[0176] }

[0177] — TAG-SIB19-ST0P

[0178] — ASN1ST0P

[0179] SIB19 field descriptions

[0180] distanceThresh

[0181] Distance from the serving cell reference location and is used in location-based measurement initiation in RRCJDLE and RRCJNACTIVE, as defined in TS 38.304

[0020] , Each step represents 50m. This field is only present in an NTN cell.

[0182] movingReferenceLocation

[0183] Reference location of the serving cell of an NTN Earth-moving cell at a time reference. It is used in the evaluation of eventD2 and condEventD2 criteria for the serving cell in RRC_CONNECTED, and location-based measurement initiation in RRCJDLE and RRCJNACTIVE when distanceThresh is also configured, as defined in TS 38.304

[0020] , The time reference of this field is indicated by epochTime in ntn-Config of the serving cell. This field is excluded when determining changes in system information, i.e., changes to movingReferenceLocation should neither result in system information change notifications nor in a modification of valueTag in SIB1. This field is only present in an NTN cell.

[0184] ntn-Config

[0185] Provides parameters needed for the UE to access NR via NTN access such as Ephemeris data, common TA parameters, k_offset, validity duration for UL sync information and epoch. In a TN cell, this field is only present in ntn-NeighCellConfigList and ntn-NeighCellConfigListExt.

[0186]

[0187] 2025P00150WQ

[0188] ntn-NeighCellConfigList, ntn-NeighCellConfigListExt

[0189] Provides a list of NTN neighbour cells including their ntn-Config, carrier frequency and PhysCellld. This set includes all elements of ntn-NeighCellConfigList and all elements of ntn- NeighCellConfigListExt. If ntn-Config is absent for an entry in ntn-NeighCellConfigListExt, the ntn- Config provided in the entry at the same position in ntn-NeighCellConfigList applies. Network provides ntn-Config for the first entry of ntn-NeighCellConfigList. If the ntn-Config is absent for any other entry in ntn-NeighCellConfigList, the ntn-Config provided in the previous entry in ntn- NeighCellConfigList applies.

[0190] referenceLocation

[0191] Reference location of the serving cell provided via NTN (quasi)-Earth fixed cell and is used in location-based measurement initiation in RRCJDLE and RRCJNACTIVE, as defined in TS 38.304

[0020] , This field is only present in an NTN cell.

[0192] satSwitchWithReSync

[0193] Provides parameters for the target satellite required to perform satellite switch with resynchronization. This field is only present in an NTN cell and its presence indicates that satellite switch without PCI change is supported in the cell.

[0194] t-Service

[0195] Indicates the time information on when a cell provided via NTN is going to stop serving the area it is currently covering. This field applies for both service link switches in NTN quasi-Earth fixed cell and feeder link switches for both NTN quasi-Earth fixed and Earth-moving cell. The field indicates a time in multiples of 10 ms after 00:00:00 on Gregorian calendar date 1 January, 1900 (midnight between Sunday, December 31, 1899 and Monday, January 1, 1900). The exact stop time is between the time indicated by the value of this field minus 1 and the time indicated by the value of this field. The reference point for t-Service is the uplink time synchronization reference point of the cell. This field is only present in an NTN cell.

[0196]

[0197] NTN-CovEnh field descriptions

[0198] numberOfMsg4HARQ-ACK-Repetitions

[0199] The number of repetition slots for PUCCH transmission with HARQ-ACK information for Msg4, see clause 9.2.6 in TS 38.213

[0013] , The first / leftmost bit corresponds to the repetition factor 1, the second bit corresponds to repetition factor 2, the third bit corresponds to the repetition factor 4, and the last / rightmost bit corresponds to the repetition factor 8. The repetition factor 1 shall be indicated together with at least one other repetition factor.

[0200] rsrp-ThresholdMsg4HARQ-ACK

[0201] This threshold is used by the UE for determining the configuration of the MAC entity for PUCCH repetition for Msg4 HARQ-ACK, as specified in clause 6.2.1 in TS 38.321 [3],

[0202]

[0203] SatSwitchWithReSync field descriptions

[0204] ssb-TimeOffset

[0205] Indicates the time offset between the SSB from source and target satellite at the uplink time synchronization reference point. It is given in number of subframes.

[0206] t-ServiceStart

[0207]

[0208] Indicates the time information on when the target satellite is going to start serving the area currently covered by the serving satellite. The field indicates a time in multiples of 10 ms after 00:00:00 on Gregorian calendar date 1stJanuary 1900 (midnight between Sunday, December 31, 1899, and Monday, January 1, 1900). The exact start time is between the time indicated by the value of this field minus 1 and the time indicated by the value of this field. The reference point for t-ServiceStart is the uplink time synchronization reference point of the serving satellite.

[0209]

[0210] 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:

[0211] MIB:: = SEQUENCE {

[0212] systemFrameNumber BIT STRING ( SIZE ( 6) ), subCarrierSpacingCommon ENUMERATED { scs!5or60, scs30or!20 },

[0213] ssb-SubcarrierOf f set INTEGER ( 0.. 15 ), dmrs-TypeA-Position ENUMERATED {pos2, pos3 }, pdcch-Conf igSIBl INTEGER ( 0..255 ), cellBarred ENUMERATED {barred, notBarred},

[0214] intraFreqReselection ENUMERATED { allowed, notAllowed},

[0215] spare BIT STRING ( SIZE ( 1 ) ) }

[0216] 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 (SI Bl) 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 DCImessage assigning resources (a communication grant). This message may be addressed using the RA-RNTL 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.

[0217] MIBand 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.

[0218] 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.

[0219] 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.

[0220] 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 2musymbols per subframe. Each slot typically spans 14 OFDM symbols. Each resource element in the grid, defined by the intersection of a time symbol and a2025P00150WQ

[0221] 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.

[0222] 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. 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.

[0223] 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).

[0224] 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 is2025P00150WQ

[0225] 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 / ...) 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.

[0226] 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-InactivityTimer. 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.2025P00150WQ

[0227] 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 Control Information (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.

[0228] 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 bandpass 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 a weighted 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.

[0229] 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. Thereceiver 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.

[0230] 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 the 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.

[0231] 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.

[0232] 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 to2025P00150WQ

[0233] 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.

[0234] 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 WiFi enabled devices, such as laptops, smartphones, tablets, smart TVs, etc., to a wired network, such as a local area network (LAN) or the Internet.

[0235] 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, 802.11n, 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.

[0236] 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.

[0237] 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 anAP 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.

[0238] 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.

[0239] This invention is illustrated in the context of non-terrestrial networks comprising mobile access devices at different altitudes. Such mobile access devices may be GEO, MEO, LEO, etc satellites or other types of mobile access devices. The location of those mobile access devices, the distance to earth, etc pose multiple challenges for the deployment of a cellular system with ubiquitous coverage, in particular, regarding mobility procedures. Although this invention is illustrated in the context of non-terrestrial communication, some embodiments may find application in other areas of a cellular communication system.

[0240] Section: mobility between mobile access devices at different altitudes

[0241] Mobile access devices may operate at different altitudes, e.g., UAVs, LEO, MEO, GEO,... satellites. Some wireless devices may be capable of communicating with certain access devices and some devices may not be able to communicate with other access devices. This also means that a wireless device may not be able to perform all operations with all the access devices.

[0242] In an embodiment of the invention that may be combined with other embodiments or used independently, the wireless device may be configured with its capabilities, wherein the capabilities refer to the ability to communicate with or through mobile access devices at different altitudes. The wireless device may only consider cells (mobile access devices) that fit its capabilities. For instance, if a UE is a low power device, the UE may only be able to access / communicate with / through terrestrial access devices and access devices mounted on a UAV. For instance, if the UE is a high-end device, the UE may be capable as well of communication over a LEO satellite and receiving broadcast messages from GEO satellites. For instance, if the UE is a high-end device designed for emergency situations, the UE may be capable of communication over a GEO satellite.

[0243] In an embodiment of the invention that may be combined with other embodiments or used independently, the wireless device may receive a first message from an access device, andmay use an indication in the first message and its capabilities (e.g., as in previous embodiment) to determine which operations / communication procedures it can perform.

[0244] In an embodiment of the invention that may be combined with other embodiments or used independently, a first (e.g., source, at a first altitude) access device may consider the capabilities of the wireless device when triggering a handover procedure towards a second (e.g., target, e.g., at a second altitude) access device. The first access device may (e.g., first) check whether the second access device fulfils the capabilities of the wireless device.

[0245] In an embodiment of the invention that may be combined with other embodiments or used independently, a first (e.g., source, at a first altitude) access device may consider the capabilities of the wireless device when providing the wireless device with a (N)TN conditional handover configuration (NT-CHC). The NT-CHC comprises a set of conditions configured to determine a suitable target access device and / or trigger a conditional handover procedure. The first access device may first check what the capabilities of the wireless device are, before providing / configuring the NT-CHC.

[0246] Conditions in the configuration that may allow selecting and / or that may determine / influence the selection may include:

[0247] (target) altitude of a potential target access device, e.g., whether the altitude is supported by the wireless device, e.g., whether the altitude is lower than a threshold,

[0248] (estimated) received signal strength, e.g., whether the received signal strength is higher than a threshold, minimum received signal strength that is required;

[0249] elevation angle since it may affect the line-of-sight (LoS) probability and / or shadow fading, in particular, lower angles may prevent useful satellite communication,

[0250] uplink synchronization information such as TCI or beam index,

[0251] received signal quality, e.g., that the received signal quality is higher than a threshold, minimum required transmission power,

[0252] distance, e.g., that the distance is less / greater than a threshold,

[0253] minimum coverage time, e.g., that the access device provides coverage for at least t seconds, type of access device (e.g., GSO vs NGSO), e.g., whether the access device is GSO or not, frequency band and bandwidth availability,

[0254] movement speed and trajectory of the wireless device,

[0255] power availability and consumption requirements,

[0256] latency requirements for the specific application or service (e.g. measured latency is higher or lower than a maximum latency requirement for a service or application),2025P00150WQ

[0257] connection setup delay and / or handover delay (e.g. expected delay to establish a new connection may cause long interruption beyond a certain threshold)

[0258] operation in regenerative or transparent architecture, e.g., whether the satellite is working in generative manner or not,

[0259] operation in store and forward mode, e.g., e.g., whether the satellite has an available feeder link or not (and thus it is working in store and forward mode),

[0260] which services are available in store and forward mode and / or which services are available in realtime. This may be compared with list of services requested or (actively) used by the wireless device, time information of when access device operates in store and forward mode and / or timing when it does not, e.g. when feeder link of the satellite is expected to be available or not available. support of a full core network, e.g., whether a full core network is available,

[0261] support for UE-satellite-UE communication.

[0262] In general, one or more values related to one or more of above conditions may be made available. The one or more values may refer to thresholds (lowest value, highest value) that may be required to select an access device.

[0263] In an embodiment of the invention that may be combined with other embodiments or used independently, a handover configuration used to perform a handover (e.g., the configuration used by an access device and / or the NT-CHC provided by an access device to a wireless device) may comprise two or more (types of) sub-configurations. A first (type of) sub-configuration may be used when performing handovers between access devices at the same altitude (plus / minus a threshold), e.g., access devices of the same type, e.g., terrestrial access device. A second (type of) subconfiguration may be used when performing handovers between access devices at different altitudes (from TN to LEO, and / or from LEO to GEO), e.g., access devices of different type. In an example, a wireless device when performing a conditional handover may use the first (type of) sub-configuration and / or the second (type of) sub-configuration depending on the type of source access device and / or the type of target access device and / or communication status.

[0264] In an example, the fact that two access devices are at different altitudes means that they may be in different orbits and / or may differentiate more than K kilometers within the same orbit, and / or may differ more than m meters being terrestrial devices.

[0265] In an example, a wireless device may receive one or more sub-configurations depending on its capabilities.

[0266] For instance, wireless devices capable of terrestrial access devices may only receive the first type of sub-configuration.For instance, LEO capable wireless devices may receive the first type of subconfiguration for handover between terrestrial access devices and LEO and second type of subconfiguration for handover between terrestrial and LEO satellites.

[0267] For instance, MEO capable wireless devices may receive the first type of subconfiguration for handover between terrestrial access devices and between LEO satellites and between MEO satellites and second type of sub-configuration for handover between terrestrial and LEO satellites, and between LEO and MEO satellites, and between terrestrial and MEO satellites.

[0268] In an example, each of the configurations may be associated with different communication parameters, e.g., different conditions to perform the mobility procedure, different mobility events, different timers (e.g., for conditional handover) triggering the mobility events.

[0269] In an example, the wireless device may signal which of the configurations it requires. In an example, an access device may signal which of the configurations will be configured.

[0270] In an example, the communication parameters between configurations may be encoded in a differential manner (delta-signaling).

[0271] In an example, each configuration may be identified by an altitude identifier, and / or orbit identifier.

[0272] Further elaborating on this embodiment, the first (type of) sub-configuration used for handovers between access devices at the same altitude, such as between Low Earth Orbit (LEO) satellites, may include parameters like signal strength thresholds, timing advance adjustments, and frequency band transitions that are specific to maintaining seamless connectivity at similar altitudes. For instance, a signal strength threshold parameter may be set to ensure that a handover is initiated only when the received signal strength from the target LEO satellite exceeds a certain level, thereby guaranteeing a reliable connection. Timing advance adjustments in this sub-configuration may be minimal, as the propagation delay between two satellites at the same altitude is relatively consistent. Moreover, the frequency band transitions may be limited to adjacent or overlapping frequency bands, facilitating a smooth transition between the satellites without significant disruption in the communication link.

[0273] Further elaborating on this embodiment, the second (type of) sub-configuration used for handovers between access devices at different altitudes, such as from LEO to Geostationary Earth Orbit (GEO) satellites, incorporates more complex parameters due to the variations in altitude and corresponding propagation delays. The signal strength threshold in this context may be more lenient to accommodate the higher path loss associated with the greater distance to the GEO satellite. Timing advance adjustments as well as beaming related information, such as TCI and beam index becomecrucial in this sub-configuration to account for the increased propagation delay when transitioning from LEO to GEO. This may ensure that the handover process compensates for the latency differences and maintains synchronization with the target access device. Frequency band transitions in this scenario may involve a broader range of frequencies, potentially requiring the wireless device to switch between different frequency bands that are optimized for communications at different altitudes. Additionally, power control settings may differ between the two sub-configurations. For handovers between LEO satellites, power adjustments may be minor, focusing on fine-tuning the transmit power to counteract minor variations in signal strength. However, when transitioning from LEO to GEO, more significant power adjustments may be necessary to compensate for the increased distance and associated path loss, ensuring that the transmitted signal remains within acceptable levels at the target GEO satellite.

[0274] Overall, these sub-configurations are tailored to address the specific challenges and requirements of handovers between access devices at the same or different altitudes, ensuring efficient and seamless mobility for the wireless device.

[0275] In a related embodiment of the invention that may be combined with other embodiments or used independently, a handover configuration used to perform a handover (e.g., the configuration used by an access device and / or the NT-CHC provided by an access device to a wireless device) may comprise more or less values depending on the capabilities of the wireless device. For instance, a wireless device only capable of terrestrial communication may only receive a first configuration for handover between terrestrial access devices. For instance, a wireless device capable of LEO access devices may receive a first configuration that may allow handover between a first terrestrial access device a second terrestrial access device; or between a first LEO access device and a second LEO access device; additionally, the wireless device may receive a second configuration that may allow the handover between terrestrial access device and LEO access devices.

[0276] It is to be noted in this and other embodiments, handover is a type of mobility event when the wireless device is in CONNECTED state and it may also refer, in general, i.e., be generalized to a mobility event, e.g., in IDLE state, e.g., cell (re-)selection.

[0277] In an embodiment of the invention that may be combined with other embodiments or used independently, a procedure for performing a handover from a Low Earth Orbit (LEO) satellite to a Geostationary Earth Orbit (GEO) satellite involves the wireless device being informed about a significant difference in timing advance required due to the disparate propagation delays between the two types of satellites. Specifically, upon initiation of the handover process, the LEO satellite transmits2025P00150WQ

[0278] a handover command to the wireless device, which includes detailed information regarding the required timing advance adjustment. This information encompasses the expected increase in propagation delay and the corresponding timing advance value needed to maintain synchronization with the GEO satellite. The wireless device then utilizes this information to recalibrate its internal timing mechanisms, ensuring that the communication signals are correctly synchronized with the GEO satellite's transmission windows. Additionally, to facilitate a seamless transition, the handover command may also include frequency band adjustments and power control parameters tailored to the GEO satellite's operational characteristics. By incorporating these technical details, the embodiment ensures that the wireless device can adapt to the increased distance and maintain robust communication links, thereby achieving efficient and reliable mobility across different orbital altitudes.

[0279] Additionally or alternatively, the wireless device may receive (conditional) handover information (e.g. from an access device, e.g., a base station on and / or through the satellite) that includes information related to connection setup delay (e.g. expected / minimum / maximum delay to establish a new connection via another base station) and / or handover delay / interruption (e.g. expected / minimum / maximum delay to complete a handover procedure with another base station). This allows the wireless device to compensate for the delay and / or select or propose a different (access device) satellite for handover and / or stay connected a bit longer to the same satellite and / or reject a proposed handover. When the wireless device needs to perform a mobility procedure, e.g., handover, the wireless device may evaluate the connection setup delays of different access devices, to determine which access device it selects to perform the handover.

[0280] The connection setup delay may depend, e.g., on the round-trip time between the wireless device and the target access device. In the case of non-terrestrial networks, the round-trip time will depend on the altitude (orbit) of the satellite as well as on the position of the satellite respect to the wireless device. Thus, a wireless device may be able to connect to multiple access devices, but because of the round-trip time, the delay to establish the connection may differ greatly.

[0281] Such delay to establish a connection via another base station may lead to an interruption of a communication service (e.g. phone call), e.g. if the underlying connection (e.g. via terrestrial base station) of the communication service may have deteriorated and / or have broken before the connection via non-terrestrial base station was established. Therefore, the communication setup delay needs to be taken into account during handover decisions (e.g. initiate handover procedure (e.g. to a non-terrestrial base station) some time before the quality of the underlying connection (e.g. via terrestrial base station) has deteriorated too much, and / or to determine the best time to switch the transmission of packets / frames (and / or start buffering, emptying the buffer orflushing the buffer) related to the communication service from the connection via terrestrial base station to a connection via a non-terrestrial base station and vice versa.

[0282] In an example, the connection setup and / or handover delay information / interruption information as provided in the (conditional) handover information may be based on connection setup and / or handover delays / interruptions measured by one or more wireless devices. In order to facilitate this, a base station or Core Network (e.g. base station or CN on the satellite) may instruct wireless devices to measure connection setup delay and / or handover delay / interruption, and / or to provide information about a measured connection setup and / or handover delay / interruption to the base station / core network.

[0283] Additionally or alternatively, the change in communication parameters such as latency or data rate due to the handover to a target access device (satellite) at a different altitude (orbit) may be considered / evaluated (by the wireless device and / or network) when determining whether and / or when a wireless device needs to perform a handover to said target access device, or not. For instance, if the wireless device is performing a call (e.g., IMS call) over a LEO satellite, and it has to switch to a MEO satellite, the latency will increase and the data rate will decrease. This may impact the quality of the call, may require a change in the voice compression algorithms, etc. If the MEO satellite is the only option, the wireless device may accept the degradation in the quality of the communication parameters, but if next to the target MEO satellite, there is another potential target LEO satellite (that may be in range briefly afterwards), the wireless device may opt for waiting with the handover procedure until the new target LEO satellite is in range.

[0284] Additionally or alternatively, a function, e.g., an Al model (e.g. on the wireless device), is used to obtain a prediction and / or predict an expected connection setup or handover delay / interruption. The function may take as input the location of the wireless device, and the location of the access device (e.g., ephemeris information of the satellite) since with this information, it is possible to determine the round-trip time, and this gives an indication of the connection setup time based on the number of exchanged messages. In the particular case of an Al model, the Al model can be trained based on the measurements of connection setup or handover delays / interruptions experienced by one or more wireless devices (e.g. wireless devices in similar location / area, or wireless devices connecting to the same satellite). The Al model may be provided to the wireless device (e.g. after it was sufficiently trained) and / or the wireless device may be given access to the Al model (e.g. if it runs on a server in the network) to obtain the predicted connection setup or handover delay / interruption.

[0285] Additionally or alternatively, the connection setup delay information and / or handover delay / interruption information as received or determined by the wireless device may includeinformation about whether a re-authentication of the wireless device is expected to be performed or not.

[0286] In an embodiment of the invention that may be combined with other embodiments, a mobility event may depend on the end-to-end delay / latency / communication properties of the communication path. This does not only refers to the latency of the communication between the wireless device and the access device it is connected to, but the end-to-end communication latency from the wireless device to the destination / source of the communication. For instance, if a wireless device performs a handover from a LEO satellite to a MEO satellite, this may improve coverage / decrease the number of handovers per unit of time, but the wireless device may expect a weaker signal, higher transmission power needs, higher latency.

[0287] In an example, the wireless device may have a multi-objective optimization, e.g., configured by an access device, network function (e.g., equivalent to PCF) that may, e.g., indicate "prefer E2E latency<75 ms unless battery<10%".

[0288] In an embodiment of the invention that may be combined with other embodiments or used independently, a mobility procedure (e.g., handover) from a first (e.g., altitude, e.g., LEO) access device to a second (e.g., altitude, e.g., GEO) access device may rely on a RACH-less (Random Access Channel-less) handover to reduce signaling and improve performance. Several critical technical features may be considered:

[0289] Firstly, the wireless device must perform precise measurements, such as assessing the strength of the synchronization signals, in particular, from the first access device. These measurements are crucial for determining the optimal moment to initiate the handover. The LEO satellite may be aware of the timing characteristics of the GEO satellite and may play a pivotal role in facilitating this transition. It may provide the wireless device with parameters indicating the time difference between its own reference signals and the reference signals of the GEO satellite (target access device) from the point of view of the wireless device. In other words, because of the propagation path from the LEO satellite to the wireless device and from the GEO satellite to the wireless device, the synchronization signals transmitted in certain communication resources in the resource grid will arrive at different time. This means that the resource grids of LEO and GEO are shifted in time. The time difference is what is indicated by this time shift. This may remove the need of the GEO satellite to transmit synchronization signals and the wireless device measure the time difference.

[0290] Secondly, the LEO satellite may provide the wireless device with specific parameters required for extended coverage, e.g., including the number of repetitions, repetitions via different beams, repetition patterns necessary for maintaining robust connectivity during the handovertowards the GEO satellite (in general target access device). These parameters may be used by the wireless device when connecting to the GEO satellite. These parameters ensure that the wireless device can adapt to the varying signal propagation environments encountered during the transition from LEO to GEO.

[0291] Thirdly, when the LEO satellite determines that the handover conditions are met, it may trigger the handover by sending a command to the wireless device. This handover command may include detailed information on the timing advance adjustments, and other information such as beaming information (e.g., TCI, beam index,...) needed to synchronize with the target access device, e.g., GEO satellite's transmission windows. It also encompasses frequency band adjustments and power control settings tailored to the GEO satellite's operational characteristics, ensuring that the wireless device can seamlessly adapt to the new communication environment without experiencing significant latency or signal degradation. This command may also include other parameters as in other embodiments / examples.

[0292] In an embodiment of the invention that may be combined with other embodiments or used independently, the wireless device may transmit an initial message to perform a handover to a target access device. This initial message may need to be transmitted with a certain signal strength / certain communication parameters, e.g., MCS. In case of that the target access device does not transmit a reference signal such as synchronization signals, the wireless device may need to determine the required transmission power and / or other communication parameters (e.g., amount of signal repetitions). Since (part of) the communication path is shared, e.g., the target access device can be a GEO satellite, and the first access device can be a LEO satellite, the parameters to be used in the transmission of this initial message to the target access device may depend on the parameters used in the communication with the first access device. For instance, consider that the current conditions in the ionosphere degrade the communication and thus the communication parameters with the first access device require a higher number of repetitions than standard, then it is likely that the communication parameters with the target access device also require a higher number of repetitions. In general, communication parameters with the target access device may be provided as an offset or difference value with the parameters with the first access device. This also allows for reduced communication overhead.

[0293] In an example, communication parameters assigned for the communication between device A and C are provided as an offset / delta value of the communication parameters between device A and B. Device B may be the source access device and device C may be the target access device.

[0294] In an example, communication parameters assigned for the communication between device A and C at time tl (e.g., when device performs cell (re-)selection) are provided as an offset / 2025P00150WQ

[0295] delta value of the communication parameters between device A and C (or B) at time to. For instance, device A may have connected with device C at time to (e.g., when device C is a satellite operating in store and forward mode). At a later moment, when a new device (device B) appears at time tl, the communication parameters are provided as the difference in value.

[0296] For instance, if the MCS index is 5 bits long, and the MCS value is indicated in a differential manner, if at time to, the wireless device was using MCS = 3 (00011) and at time 1, the wireless device is assigned MCS=2, i.e., (00010), then indication may be 001 instead, where 0 indicates -1 (subtraction) and 01 indicates 1, i..e, it indicates -1, so that given the old MCS value 3 and the indication -1, it is possible to obtain the assigned MCS value = 2.

[0297] It is to be noted that this procedure may also be applicable, e.g., to terrestrial access devices wherein the delta encoding is between the source TN access device and the targer TN access device. This may also be applicable between a primary node and secondary node.

[0298] In an embodiment of the invention that may be combined with other embodiments or used independently, a handover configuration used to perform a handover (e.g., the configuration used by an access device and / or the configuration provided by an access device to a wireless device) may comprise conditions to determine the type of target access device considering the capabilities of the wireless device, and the type of source access device. For instance, if the wireless device is LEO capable, and the type of source access device is a TN access device, the wireless device may prefer doing a handover to a TN access device, unless it is not available, in which case handover to a LEO access device may be performed. For instance, if the wireless device is GEO capable, and the type of source access device is a LEO access device, the wireless device may prefer doing a handover to another LEO access device, unless it is not available, in which case handover to a GEO access device may be performed.

[0299] In an embodiment of the invention that may be combined with other embodiments or used independently, the wireless device may have received a handover configuration and this handover configuration may determine and / or allow determining whether the wireless device performs the handover to a target access device at the same altitude of the first access device (the device the wireless device is currently connected to; note that "same altitude" may mean the same altitude of the first access device plus / minus a second threshold, i.e., within a second range; for instance, if the altitude of the first access device is 580 km, the second range may be 10 km) or to a target access device at a different altitude (here, different altitude may refer to the altitude of the first access device plus / minus a third threshold and / or within a third range; for instance if the altitude of the first access device is 580 km, then the third threshold may be, e.g, 1000 km, so that the altitude ofthe target access device could be up to 1580 km) of the first access device depending, one or more parameters, e.g., on the coverage of the access devices whose altitude equals the altitude of the first access device, the latency requirements, the uplink transmission power needs, etc. In general, it would be access devices whose altitude is equal up to a threshold. For instance, LEO satellites at an altitude of 600 Km plus minus 20 Km, wherein the threshold would mean 20 Km. Other parameters that may influence the decision may include latency requirements, uplink transmission power, etc.

[0300] In an embodiment of the invention that may be combined with other embodiments or used independently, the wireless device may have received a handover configuration and this handover configuration may determine and / or allow determining whether the wireless device performs the handover to a target access device at the same altitude of the first access device or to a target access device at a different altitude of the first access device depending on the coverage of the access devices at an altitude different than the altitude of the first access device. This information is therefore complementary to the information in the previous embodiment.

[0301] In the context of these embodiments, when determining the appropriate target access device for a handover, the expected coverage of the current access device and target access devices plays a crucial role. For instance, if the wireless device is connected to an access device in a terrestrial network, and the expected coverage is predicted to be insufficient— due to poor signal strength or geographical obstacles— the handover process may prioritize a target access device at a different altitude, such as a Low Earth Orbit (LEO) satellite, to maintain seamless connectivity. Similarly, if the LEO satellite network is sparse, with many satellites operating in a store and forward mode which cannot support real-time communication efficiently, the handover might instead prefer to transition to a Geostationary Earth Orbit (GEO) satellite. This is especially relevant for applications requiring continuous and stable connections, like voice calls or live video streaming, where the advantages of GEO satellites, such as their fixed position and broad coverage area, become particularly beneficial. The coverage configuration used in the handover decision can assess the expected coverage situation within a specific time window or geographic area. By considering factors such as the density of the satellite constellation, the operational modes of the satellites, and the coverage maps, the wireless device and / or the source access device can intelligently decide whether to maintain its connection at the same altitude or switch to a different altitude to ensure optimal performance and reliability.

[0302] In an example, access devices at different altitudes may refer to access devices at different orbits, since the different altitudes / orbits determine the communication latency, required (uplink) transmission power, etc so that a wireless device may not choose / be eligible for a given (target) access device due to communication latency, transmission power, etc. That is the reason whya wireless device may need to exchange its device capabilities and / or receive information about the target access device.

[0303] In an example, next to latency, uplink transmission power, other communication features that may influence the communication / selection of a (target) access device may include supported data rates, coverage area, and mobility support, all of which can play a role in optimizing the handover procedure. For example, a wireless device may take into account the modulation and coding schemes available, the access device's ability to support handovers with minimal interruption, and the expected variation in signal quality as the device moves through different coverage areas. These considerations, together with altitude, latency, and transmission power constraints, enable the wireless device to make informed decisions about which access device to select during a handover, thereby ensuring robust connectivity and service continuity across diverse non-terrestrial and terrestrial network environments.

[0304] In an example, the (conditional) handover configuration may depend on one or more features such as the ones in previous example, e.g., the altitude of the target access device. For instance, a target access device may only be eligible if it is at an altitude lower than a first threshold altitude, e.g., 800 km.

[0305] In an example, an alternative meaning of altitude may be distance between wireless device and access device since an access device at altitude of, e.g., h Km may have very different distances to wireless devices in its coverage area depending on where the wireless device is located. Different distances may also lead to very different latency values and / or round-trip times, that may make the access device eligible or not.

[0306] In an example, whether an access device is eligible depends not only on a feature of the access device (e.g., altitude) but may also depend on the RRC state, e.g., IDLE vs CONNECTED. In IDLE state a high orbit satellite may be an option, e.g., to transmit / receive small data, while for a call, when the wireless device is in RRC state, only a lower altitude satellite (e.g., LEO satellite) may be an option.

[0307] In an embodiment of the invention that may be combined with other embodiments or used independently, a procedure for efficient mobility of a wireless device may comprise sending, by the wireless device, a capability indication message comprising an indication of wireless device capabilities,

[0308] receiving, by the wireless device, a first message from a first access device (e.g., a MEO or GEO satellite) with a handover configuration and / or a handover command,

[0309] sending, by the wireless device, a second message to perform a handover to a target access device (e.g., a LEO satellite)wherein the handover configuration and / or handover command comprises configuration parameters for access devices at different altitudes. In an example, the first access device acts as anchor of the communication and controls the communication with the wireless device. In an example, the second access device performs the user plane. In an example, since the MEO and / or GEO are relatively stable on a fixed point on earth, the control plane remains stable (does not change). In an example the altitude difference between the altitude of the first access device and second access device may be greater than a first threshold, e.g., 100 Km. In an example, the handover command is a handover to change the user plane that may be exchanged over a LEO satellite (in general, an access device at a lower altitude). In an example, the handover command is a command to perform a handover of the user plane from a third access device (e.g., LEO satellite) to a target access device (e.g., another LEO satellite). In an example, the third access device and target access device may be in the same orbit, e.g., have a similar altitude (up to a threshold).

[0310] In an example, the wireless device and first access device may be synchronized (e.g., know timing advance, know frequency correction, etc since the first access device controls the control plane. Since the first access device may control the user plane and may determine the second access device the user plane may need to be handover to (and the location, speed, ephemeris of the second access device may be known), the first access device may determine which communication parameters (timing advance, frequency correction) the wireless device may need to use to communicate with the second access device. Thus, the communication parameters (e.g., timing advance, frequency correction) between wireless device and second access device may be provided to the wireless device in the first message (e.g., received from the first access device), so that the wireless device may use them when transmitting the second message to the target access device.

[0311] Fig. 13 schematically illustrates such as procedure, wherein entity 1300 represents a wireless device, entity 1302-S represents a source access device (handling the UP), entity 1302-T represents a target access device (handling the UP), entity 1303 represents an access device (handling the CP), and entity 1304 represents a network function / entity consuming / producing the traffic. The subsequent arrows in Fig. 13 may indicate one or more message exchanges between the entities. One or more of the steps may be optional. One or more of the steps may be repeatead. Some steps may not be included for clarity reasons.

[0312] Step 1305 may refer to the initial registration procedure in which the wireless device 1300 establishes communication with the access device 1303 that handles the control plane. During this step, the wireless device may transmit an identification or registration request, including capability information that indicates the types of access devices it supports, such as terrestrial devices, UAV-mounted devices, LEO satellites, MEO satellites, or GEO satellites. The access device 1303 may2025P00150WQ

[0313] then authenticate the wireless device, verify its capabilities, and assign initial control-plane parameters such as timing advance, frequency correction, system information references, or security credentials. This registration may allow access device 1303 to act as a stable communication anchor for subsequent mobility events, especially in scenarios where 1303 is located at a high and relatively fixed altitude (e.g., GEO or MEO).

[0314] Following this registration, access device 1303 may maintain control-plane connectivity with the wireless device even when the user-plane connectivity is established through other access devices. The control-plane anchor may track the wireless device's approximate location, mobility pattern, and predicted coverage conditions so that it can later instruct the wireless device to initiate a handover of the user plane toward a more suitable access device.

[0315] Step 1306 may refer to a first message transmitted by the control-plane anchor 1303 instructing the wireless device to establish or move its user-plane connection to a source access device 1302-S. This message may include configuration parameters enabling the wireless device to reach 1302-S efficiently, such as timing-advance values, frequency-correction values, uplink modulation or repetition settings, beam or TCI information, and any additional auxiliary information that may be needed to support a RACH-less or RACH-based procedure. The message may also indicate why 1302-S has been selected, for example because 1302-S provides a suitable coverage window, lower latency, reduced power consumption, or improved link budget at the wireless device's current altitude or geographic location.

[0316] After receiving this first message, the wireless device may perform the required adjustments and initiate the establishment of the user-plane connection toward 1302-S. Depending on the configuration, this may occur directly or through an initial access message that is relayed or synchronized using the control-plane parameters provided by 1303. Once connected, the wireless device may begin exchanging user-plane data through 1302-S while control-plane operations remain anchored at 1303.

[0317] Steps 1307-1 and 1307-2 may represent the phase in which user-plane communication between the wireless device and the network function 1304 occurs through the source access device 1302-S. In step 1307-1, the wireless device may transmit user-plane data toward 1302-S using the communication parameters established in the previous steps. This data may include application-layer packets, sensor data, multimedia streams, emergency data, or any type of uplink information required by the service. Step 1307-2 may represent the traffic where 1302-S exchanges user-plane data originating from / towards network function 1304.During this phase, 1302-S may act as the primary user-plane serving node. It may forward uplink data toward 1304, retrieve downlink data, and manage (directly or through 1303) link-layer operations such as scheduling, HARQ, buffering, or link adaptation. The wireless device may maintain stable user-plane operation as long as 1302-S continues to satisfy coverage and quality requirements. Meanwhile, access device 1303 may continue to supervise control-plane aspects, tracking whether a handover toward 1302-T will soon be required based on coverage predictions, mobility conditions, or satellite trajectory information.

[0318] Step 1308 may refer to a second first message from access device 1303 instructing the wireless device to move its user-plane connection from 1302-S to a target access device 1302-T. This message may include detailed handover configuration parameters tailored to the characteristics of 1302-T, which may be, for example, another LEO satellite entering a favorable coverage window. The message may specify conditions that trigger the handover, the expected handover execution time, updated timing-advance and frequency-correction values, beam or TCI values, delta-encoded communication parameters relative to those used with 1302-S, and any optional offsets needed to synchronize transmissions with 1302-T without requiring a full random-access procedure.

[0319] The message may further indicate whether the handover is to be performed directly or conditionally, whether the device should prepare buffering, whether uplink repetition or downlink robustness must be increased temporarily, and whether the handover corresponds to a change in user-plane only or includes additional service-level considerations. Upon receiving this message, the wireless device may prepare to contact 1302-T according to the supplied configuration, optionally waiting for the appropriate time window to ensure link establishment with minimal interruption.

[0320] Steps 1309-1 and 1309-2 may represent the user-plane communication that takes place once the wireless device has successfully handed over to target access device 1302-T. In step 1309-1, the wireless device may transmit uplink user-plane data toward 1302-T using the parameters configured during step 1308. In step 1309-2, data may be exchanged with network function / entity 1304 may be routed through 1302-T and delivered to / from the wireless device.

[0321] During this stage, 1302-T may assume all user-plane responsibilities, including data forwarding, scheduling, link maintenance, and buffering. The wireless device may benefit from improved coverage, lower latency, better link margin, or extended service continuity depending on the capabilities and orbital position of 1302-T. The control plane may remain anchored at 1303 throughout this process, ensuring stable signaling independent of changes in the user-plane route. Once the transition is complete, 1302-S may release any temporary context associated with the wireless device, and the communication path between the wireless device and 1304 may continue exclusively through 1302-T until a subsequent mobility event occurs.2025P00150WQ

[0322] In a simplified embodiment and as indicated in other embodiments of the invention, the source access device 1302-S and the target access device 1302-T may each handle both the control plane and the user plane, thereby removing the need for splitting these functions between a high-altitude control-plane anchor and a lower-altitude user-plane node. In this case, the procedure illustrated in Fig. 13 may be interpreted such that 1302-S initially provides full service to the wireless device 1300, including the distribution of system information, control signaling, and user-plane data forwarding, while 1303 may act merely as an optional intermediary or may be omitted entirely for clarity. When mobility is required, 1302-S may directly determine that 1302-T is the appropriate next serving access device based on coverage, altitude, trajectory, or communication-parameter thresholds, and may provide the wireless device with all necessary handover configuration in a single message, including timing-advance information, frequency-correction values, beam or cell identifiers, and any service-continuity instructions. The wireless device may then transmit the corresponding handover execution message directly or indirectly to 1302-T using the parameters provided by 1302-S, without relying on a separate control-plane anchor. Once 1302-T receives the message, it may immediately assume both the control-plane and user-plane roles, completing authentication or context-transfer functions as needed and enabling uninterrupted continuation of the data session. This unified-plane approach may simplify signaling, reduce protocol overhead, and provide a more direct mobility path, particularly in constellations where individual satellites or airborne platforms are capable of independently managing full control-plane and user-plane operations.

[0323] It is to be noted that when performing a handover, e.g., conditional handover, the wireless device may rely on a configuration that is explicitly aware of access devices operating at different altitudes, such as terrestrial nodes, UAV-mounted access points, LEO satellites, MEO satellites, or GEO satellites. This configuration may contain a plurality of parameters and decision criteria, including altitude thresholds, coverage predictions, expected latency, required uplink transmission power, movement speed and trajectory of the wireless device, service-mode information such as store-and-forward availability, and communication-parameter offsets such as timing-advance and frequency-correction values. For instance, upon reception of message 1306 and / or 1308, which may instruct the wireless device to establish user-plane communication through access device 1302-S, the wireless device may evaluate these conditions to verify whether 1302-S is the most suitable source access device at that moment. This evaluation may consider, for example, whether the predicted coverage duration for 1302-S satisfies the configured minimum, whether the elevation angle meets the line-of-sight requirements, whether the control-plane anchor (1303) indicates that lower-altitude candidates are approaching or departing, or whether the energy budget of the device favors a particular orbit. Based on this evaluation, the wireless device may either comply with the instructionto connect to 1302-S, delay the execution until configured trigger thresholds are met, or internally prepare for a future user-plane move. Through this mechanism, the wireless device may autonomously perform optimized mobility decisions that account for the heterogeneous nature of access devices at different altitudes, while ensuring continuity, robustness, and efficiency of communication.

[0324] In general, these examples and embodiments represent the role of the usage of altitude constraints and / or type of (mobile) access device when performing a handover procedure. Such altitude constraints and / or type of (mobile) access device preference may be included in the device capabilities and / or handover conditions (e.g., NT-CHC).

[0325] In general, these examples and embodiments are illustrated in the context of a handover mobility procedure of a wireless device. However, these examples and embodiments may also be understood in the context of other mobility procedures, e.g., for cell selection and / or cell reselection.

[0326] In general, it is described a method for efficient mobility of a wireless device wherein the method comprises (1) sending, by the wireless device, an initial message comprising the wireless device capabilities, (2) receiving, by the wireless device, a first message from a first access device with a handover configuration comprising handover conditions, (3) receiving, by the wireless device, a second signal from a second access device and a third signal from a third access device, (4) selecting, by the wireless device, the second access device or the third access device as the target access device and / or determining to perform a handover to the target access device based on the wireless device capabilities and the handover configuration, wherein the wireless device capabilities and / or handover conditions comprise the altitude constraints.

[0327] Section: interaction between satellites at different altitudes

[0328] In an embodiment of the invention that can be combined with other embodiments or used independently, a wireless device can communicate with or through the cellular system by:

[0329] receiving a first message, e.g., system information from a first access device located at a first altitude,

[0330] processing the first message received from the first access device,

[0331] determining a second access device at a second altitude based on the processed system information, and

[0332] performing a data exchange through a second access device.

[0333] In a related embodiment that can be combined with other embodiments or used independently, a wireless device can communicate with or through the cellular system by:2025P00150WQ

[0334] receiving a first message from a first access device before establishing an RRC connection with the first access device,

[0335] processing the first message received from the first access device,

[0336] determining a selected access device to perform a data exchange based on an indication in the first message, wherein the selected access device is one of the first access device and a second access device, and

[0337] performing a data exchange through a selected access device.

[0338] The first access device may be a GEO satellite that is located in a specific position over the earth such that this position remains constant. Since GEO satellites follow a circular geosynchronous orbit in Earth's equatorial plane, they cannot cover areas at high latitudes, in particular, 81° latitudes and higher are unable to view geocentric satellites at all. For those higher latitudes, satellites following a highly elliptical geosynchronous orbit (HEO) such as the tundra orbit may be applicable that follow an orbit with (high) inclination from the equatorial plane and a high eccentricity. Note that in this case, a few (e.g., 2 or 3) satellites are required to provide continuous coverage in a given area. Additionally, or alternatively, the first access device may also be a UAV that may be hovering over a specific area. The first access device may also be a MEO satellite moving slower than a LEO satellite. The second access device may be a LEO satellite located at an altitude below 2000 Km. The first message may be a signal including information. Several of the embodiments of this invention may be illustrated, e.g., by means of Fig. 3.

[0339] In an embodiment of the invention that may be combined with other embodiments or used independently, the first device may be a satellite following a highly elliptical geosynchronous orbit or a MEO satellite. A satellite following a highly elliptical geosynchronous orbit may be useful, e.g., to provide continuous coverage to a north or south region of the earth, e.g., northern Europe or Canada. In this case, the first access device does not remain at a constant altitude / position, but altitude / position changes as it moves in its orbit and a few units (e.g., 2 or 3) are required to provide continuous coverage. In other words, the first access device may comprise multiple units / satellites. Thus, in this case, the first message may include information about:

[0340] The identity of the first access device (or unit of the first access device) sending the first message; the position / altitude of the (unit of the) first access device when the first message was sent or will be received so that the receiver (wireless device) can use that information for further computations (e.g., determine location);

[0341] Whether another (unit of the) first access is currently providing a similar / related first message and whether the wireless device may be able to combine / said first messages.In an embodiment that may be combined with other embodiments or used independently, the wireless device receives the system information from a first access device by monitoring frequency and time resources preconfigured on the wireless device, e.g., in the wireless device itself or in a secure element such as a UICC / USIM. The frequency and time resources may depend on the location of the wireless device. Additionally, or alternatively, the frequency and time resources may depend on the altitude of the first device. In this embodiment, different frequency bands may be allocated to mobile access devices at different altitudes to avoid interferences between mobile access devices at different altitudes. In particular, a first access device such as a GEO satellite or a HEO satellite may be deployed to provide connectivity over a given area, and this first access device may be allocated specific frequency / time resources to distribute signals / messages, e.g., a first message that may comprise synchronization signals, SIB1, a paging message, etc.

[0342] These embodiments are advantageous because a wireless device may only need to monitor messages from the first access device, and these messages provide the wireless device with information about the second access devices it may connect to. This is useful because the number of mobile access devices (second access devices) at lower earth orbits keeps increasing, and due to its number, it may be more difficult for a wireless device to know which area of the sky it should monitor when in which time / frequency resources. Furthermore, if all deployed mobile access devices, e.g., LEO satellites, advertise themselves, interferences may be caused.

[0343] In an embodiment that may be combined with other embodiments or used independently, the first message comprises one or more of (fields included in):

[0344] a synchronization signal block (SSB) including Primary Synchronization Signal (PSS), Secondary Synchronization Signal (PSS), PBCH, PBCH DMRS and PBCH (Data);

[0345] - SIB1,

[0346] an NTN specific SIB such as 5G SIB19,

[0347] an early paging indication message,

[0348] a (low power (PW)) wake up signal (WUS), and

[0349] a paging message.

[0350] In an embodiment that may be combined with other embodiments or used independently, a first access device (e.g., a GEO satellite) may transmit a first message, e.g., a wake up signal (WUS), e.g., at a first low frequency, aiming at waking up a given wireless device. Upon reception of the first message, e.g., wake up signal, the wireless device may change its operational status, e.g., wake up (if the wake up signal is intended for the device), and may monitor further signaling from either the first access device or a second access device, e.g., a LEO satellite. The first message, e.g., WUS, may contain certain parameters (e.g., a flag) to indicate that it is a non-terrestrial2025P00150WQ

[0351] network first message, e.g., WUS. The first message, e.g., WUS, may include parameters indicating a subsequent transmission, and how to obtain the transmission (e.g., timing / frequency, e.g., as an offset with respect to the communication resources used to transmit the first message, e.g., WUS. If the first message is transmitted by a GEO / GSO satellite, the frequency shift will be little or zero, and thus, it allows using a receiver for the first message, e.g., WUS radio, that has to monitor a small frequency spectrum, thus, reducing energy consumption.

[0352] In an embodiment that may be combined with other embodiments or used independently, the first message, e.g., WUS, may include a frequency correction factor that the wireless device needs to apply to receive subsequent communication, e.g., from a second access device, e.g., a LEO satellite. The subsequent communication may be a SIB containing the ephemeris data of the second access device. This frequency correction factor may be required because the wireless device may not know, e.g., the ephemeris data of the access devices and / or its own location. Additionally or alternatively, the first message, e.g., WUS, may include only the current location / speed of the access device (e.g., second access device) or a subset of the ephemeris data -- instead of the whole ephemeris data -- responsible for further communication with the wireless device, so that the wireless device can obtain a frequency shift correction factor given its own location. Additionally or alternatively, the first message (e.g., WUS) may include the identifier of a second access device (e.g., LEO satellite) so that the wireless device can retrieve locally stored ephemeris data to obtain a frequency correction factor. This embodiment is advantageous because it provides a subset of the ephemeris data / ora frequency correction factor to aid with the subsequent communication that may be used to acquire the actual ephemeris data.

[0353] In an embodiment that may be combined with other embodiments or used independently, the first message may be transmitted by a first access device that may be at low altitude, e.g., a LEO satellite or UAV, to wake up the devices. The first access device and second access device may then coordinate themselves to distribute and / or exchange a second message or data.

[0354] In an embodiment that may be combined with other embodiments or used independently, in response to a first message, a wireless device may connect and / or access and / or reconnect with a second access device in order to perform data exchange.

[0355] In an embodiment that may be combined with other embodiments or used independently, the reception of the first message is performed when carrying out cell selection or (re-)selection. The wireless device may be configured to obtain information for cell (re-)selection, e.g., when being in IDLE / INACTIVE state, by monitoring (broadcast) messages, such as synchronization signals / SIBs / paging messages of a first access device, and based on the information obtained when2025P00150WQ

[0356] monitoring the messages, perform cell selection of a second access device. This means that the cell (re-)selection decision may be a two-step decision.

[0357] In a first step, the UE obtains certain information about suitable second cells in its area (at the current time) from one or more given first cells (e.g., first access device, e.g., a GEO satellite). And once obtained, in a second step, the UE uses the obtained information to perform cell (re-)selection towards those suitable second cells (second access device, e.g., LEO satellite). This two-step procedure may mean that the wireless device may be configured with one or more given first cells and the wireless device is required to monitor them when the UE is not connected to the network, e.g., in idle / inactive state, if the information about the suitable second cells is, e.g., too old, or is not available (e.g., if the wireless device changed its location) and / or in general when some contextual conditions apply.

[0358] The wireless device may be configured with one or more given first cells to monitor, e.g., by the home network based on its subscriber information. This may be configured when the wireless device connects to the home network, or may be configured in a USIM, e.g., a USIM giving access to NTN services.

[0359] Furthermore, the wireless device may obtain parameters required to be able to monitor those first cells, e.g., frequency band / timing / location where messages from the first cells are available. This information may be valid within a given area.

[0360] Furthermore, the wireless device may obtain parameters to retrieve the information, e.g., credentials such as cryptographic keys required to verify / obtain the information distributed by the first cells. This information may be stored in the wireless device, e.g., in the USIM.

[0361] The wireless device may have a timer, e.g., pre-configured by a core network and / or configured by the first access device (e.g., associated to the information received in the first message), determining how long the information received in the first message may be valid or used.

[0362] In a related embodiment that may be combined with other embodiments or used independently, a wireless device is featured by a state machine having multiple states as illustrated by the state machine in Fig. 10 that involves at least three states 1000, 1001, and 1002. State 1000 represents an idle / inactive device that only monitors messages from a group of first cells. State 1001 represents an idle / inactive device that has already obtained messages from a group of first cells, but has not connected to a suitable second cell. State 1002 represents a connected device that has connected to a suitable second cell. The (wireless) device moves from state 1000 to 1001 after monitoring and receiving information about a suitable second cell from a first cell. The (wireless) device moves from state 1001 to 1000 when the monitored information is outdated. The wireless device moves between states 1001 and 1002 when the wireless device connects / releases theconnection with a suitable second cell. A wireless device may also be able to move from state 1000 to 1002 by monitoring all possible resources (time / frequencies) directly. This may allow the wireless device to speed up the cell (re-)selection process. This embodiment may be advantageous because a wireless device can remain in state 1000 for a longer period of time requiring limited effort to monitor / scan synchronization signals / SIBs of multiple cells. This is feasible due to the ubiquitous range of the group of first cells. At the same time, a UE may be able to move directly to state 1001 by scanning directly other times / cells. This may be feasible only in certain situations, e.g., upon configuration, e.g., depending on the context of the UE.

[0363] It is to be noted that the first access device may be much further than the second access device. Thus, the communication parameters for the transmission from the first access device maybe optimized for reliability, e.g., at the cost of transmission speed. Furthermore, the wireless device should be able to monitor received messages with a low signal strength. For the same reason, in an embodiment that may be combined with other embodiments or used independently, the monitoring of messages in a first state, e.g., 1000, of messages from a first access device and the monitoring of messages in a second state, e.g., 1001, of messages from the second access device is featured by distinct sets of reception parameters.

[0364] In an embodiment that may be combined with other embodiments or used independent, processing the first message comprises synchronizing to the first access device (cellular system) and obtaining part or all the data contained in the first message. In the case of a high altitude first access device such as a GEO satellite at an altitude of around h = 35786 km, a message transmitted by the first access device would take h / c ~ 120 ms where c is the speed of light to arrive to the earth. This delay increases for higher latitudes since the distance between mobile access device and ground increases. For instance, if the first access device transmits the synchronization signals so that they arrive aligned with the start of a frame in the equator, the same signal when received at a latitude of 45 degrees will be delayed ( 37923 - 35786 ) / c ~ 7,12 milliseconds. Thus, under the assumption that a wireless device is properly synchronized with the frame structure of the cellular system (e.g., 5G NR frame structure), the wireless device may determine its rough latitude by measuring the delay of the received synchronization signals from the first access device (in the case that the first access device is a GEO satellite). In particular, if the GEO satellite transmits the first message in a narrow beam covering a specific area, the first message may include the specific latitude / longitude covered by the center of the beam. The wireless device may know that the beam, and the first message transported in the beam, is transmitted is such a way that the synchronization signals arrive to the center of the beam synchronized with the frame structure of the cellular system. A wireless device located at the center of the beam would then obtain the synchronization signals fully aligned with the frame structure ofthe cellular system. Wireless devices located further apart will receive the synchronization signals with a certain delay dependent on the distance to the center of the beam. This delay information can then be used to determine the distance to the center of the beam.

[0365] In an embodiment that may be combined with other embodiments or used independently, a wireless device (or UE) may be pre-configured with frequency / time resources (e.g., UL resource schedule) and their validity time, enabling the wireless device / UE to transmit a request message, e.g., an inverse-paging message, to at least an access device, e.g., in particular, one GEO / HEO satellite, soliciting / requesting system information, e.g., SIB19, which upon reception, may enable the wireless device / UE to retrieve the parameters needed (e.g., Ephemeris data, cell configurations, TA parameters, etc) for NTN cell (re-)selection, where the candidate cells / payloads are on-board satellites in a different orbit (e.g.., LEO satellite). The request message may include one or more or a combination of the following:

[0366] • location information of the UE, which may be a rough / approximate location such as Tracking Area Identity (TAI), or more granular location information such as coordinates (e.g., latitude and longitude);

[0367] • a preamble as used in message 1 the random-access procedure wherein the preamble may be indicative of the need of certain type of system information;

[0368] • an indication (e.g., flag / bit-value) indicating a request for certain system information parameters, e.g., SIB19 parameters,

[0369] • an RRCSystemInfoRequest message (e.g., as described in 6.6.2, of TS 38.331) where the requested-SI-List includes at least SIB19;

[0370] • identity of a cell on-board the GEO satellite (e.g., the cell whose UL time / frequency resources the UE is configured with);

[0371] • identity of the requesting UE (e.g., randomly generated identifier or a radio network temporary identity);

[0372] • timing information (e.g., UTC-based timer); and

[0373] • a Message Integrity Code (MIC) information element.

[0374] This approach takes advantage of the stationary nature of GEO satellites which allows the GEO satellites to provide such information on-demand, especially given the large coverage area (e.g., roughly one third of the globe) of a GEO satellite, which entails that network entities (e.g., gNB and / or some core network functions) on-board a GEO / HEO satellite can provide System Information (e.g., SIB19) associated with access devices in lower orbits (e.g., access devices on-board LEO satellites) without location information of the requesting UE. Furthermore, the identity of the requesting UE may be replayed in the response message e.g., to indicate, in case of contention, which UE is concernedwith the response message. The UE identity may be rotated every time a request message is sent, or may only be used in request messages within a time window to prevent tracking. The MIC value may be computed based on pre-shared credentials between the UE and the cell on-board GEO satellites, or keys derived from them, ensuring that the inverse paging message is integrity protected and is coming from an authorized UE. For instance, it may be based on keys used when the wireless device was connected the last time. It is worth noting that the request message may not require establishing an RRC connection and may be sent as the first message (e.g., similar to Msgl in a 2-step RACH procedure), although the main purpose is not access, but rather retrieve system information.

[0375] Additionally, or alternatively, the UE may not have valid resources to perform an UL transmission, in which case, the UE may be configured only with location information (e.g., of GEO satellites) enabling it to adjust its antenna(s) to detect the beams from gNB(s) on-board a GEO-satellite. The GEO satellite may distribute information / signals indicating UL resources to send a request message. In such case, the UE may retrieve resource information (e.g., schedule for UL transmission) associated with its location, which it may then use to perform the request message procedure to retrieve system information, e.g., SIB19.

[0376] In the case that the request message is a preamble, the access device (GEO satellite) may monitor the UL resources and aim at detecting preambles as transmitted by one or more wireless devices. Since many devices may send potentially requests that may collide leading to wrong decoding, the access device may be adapted to transmit system information when energy / messages in the UL resources allocated to the transmission of request messages is detected even if the messages cannot be perfectly decoded because of multiple messages arriving simultaneously. Because of this reason, the preamble may consists of a single pulse or may be a simple signal easily detectable.

[0377] In a particular example illustrated by means of Fig. 6, two mobile access devices GEO 600 and LEO 601 are shown and the figure shows the orbit 602 of the GEO satellite, the orbit 603 of the LEO satellite, and the earth 604 on the plane of the orbits. The GEO satellite 600 transmits a beam covering an area of the earth and this beam may be used to transmit the first message in other embodiments, e.g., synchronization signals. This beam has an angle a with respect to the equatorial plane. This area is shown in the 2D representation in Fig. 6 by means of a line between points A and B. If the beam includes the location (latitude / longitude) of the center of the beam (e.g., point D between A and B), and if the first message in the beam is transmitted such that the first message arrives at point D in synch with the cellular frame system, a wireless device in the area can determine its distance to D based on the time difference between the reference frame system of the cellular system and the reception time of the first message. For instance, if the first message is received later than expected (e.g., later than the start of a frame in the frame system), the wireless device will becloser to A; while if the first message is received earlier than expected (e.g., after the frame start), the wireless device will be closer to B. Furthermore, in Fig. 6 C represents the center of the earth, r represents the radius of the earth (r = 6378 km), β is the angle between points A and B as view from C, h is the distance / altitude of GEO satellite 600 measured from point E; and finally, Ω refers to the angle between points E and B as view from C (additionally / alternatively, it can be considered as the latitude of B). In Fig. 6, it is possible to observe that the distance between the GEO satellite 600 and point A is dl and the distance between the GEO satellite 600 and point B is d2, and dl > d2. The difference between dl and d2 leads to a different reception time of the first message in points A and B. By using a simple model, dl and d2 can be obtained by means of the law of the cosines

[0378] r2= s2+ t2— 2stcos y.

[0379] In another example, the reception timing of the first messages of two or more first access devices with respect to the frame system of the cellular system may be used to determine the location of the wireless device. In particular, two first access devices may be located in different GEO locations and may transmit first messages. A wireless device will receive them at a specific time dependent on the distance to the location of the first access devices, and the reception timings (and how they compare with the frame system in the cellular system) can be used to determine / estimate the location of the wireless device, e.g., via trilateration.

[0380] In another example, the first message may include timing information (e.g., transmission) that may allow the wireless device to determine the distance to the first access device. If multiple first access devices are involved, then the location can be obtained via trilateration.

[0381] In an embodiment that may be combined with other embodiments or used independently, the first message of a first access device may be a synchronization signal block transmitted by a satellite that may include a (global) cell identifier and the transmission time of the first message. In an option, the first message includes the whole transmission time value. In another option, it includes the least significant bits of the transmission time value assuming that the receiving wireless device has a clock that can help to resolve the most significant bits. In another option, the first message is transmitted so that it arrives in sync with a frame boundary of the (terrestrial) cellular system.

[0382] It is to be noted that similar techniques may be applicable to other satellite types, e.g., satellites following MEO or HEO orbits.

[0383] In an embodiment that may be combined with other embodiments or used independently, the first message may include information about the second access devices that maybe available in the area where the first message was received. For instance, the first message may be received in an area of 2000 km of diameter, and this area may be covered by multiple LEO satellites using smaller beams, e.g., of a few tens or a few hundreds of km in diameter, pointing towards subareas. The first message may include information about the LEO satellites (second access devices) currently covering each of those sub-areas.

[0384] In an embodiment that may be combined with other embodiments or used independently, once the first message is received, the wireless device can determine its location, e.g., by extracting the rough location from the information contained in the first message, and / or using the reception timing and or timing delay to obtain a better estimate as described in other embodiments. Additionally or alternatively, the wireless device may determine or obtain the area where it is located as it may be encoded in the first message. This may refer to latitude / longitude information or a tracking area. Given this information, the wireless device may retrieve the information about the second access devices that may be available at that point of time in that area. For instance, the wireless device may store ephemeris information of second access devices and use the current time and the location information obtained via the first message, to determine which of the second access devices is most suitable to provide further communication services, e.g., conditions to select the second access device may include one or more or a combination of:

[0385] which second access device is closest so that the latency is reduced, e.g., a LEO satellite may be preferred compared with a MEO satellite;

[0386] which second access device will provide coverage long enough to perform a data exchange without requiring a handover or cell-reselection or cell switch, e.g., a MEO satellite may be preferred instead of a LEO satellite;

[0387] which second access device provides access with the lowest energy requirements (e.g., a second access device may be further away (e.g., at a higher altitude) but be more powerful (more transmission power or more sensitivity) so that the wireless device can communicate using less energy. Note that this may requiring signaling and / or storing information about the communication capabilities (transmission power, sensitivity) of the access device;

[0388] Which second access device provides a higher reliability to receive the data exchange, for instance, a first second access device may comprise a single unit (e.g., a single LEO satellite) while a second second access device may comprise a few f units (e.g., a few LEO satellites moving together in a cluster). The second second access device may provide a higher reliability because the f units may work together as a moving antenna array to receive a weak data exchange more accurately.In an embodiment that may be combined with other embodiments or used independently, a wireless device may be required to monitor certain frequency / frequencies at specific time intervals, e.g., to receive a first message, e.g., from a first access device at a first altitude. However, the specific time to monitor such a first message may depend on the location of the wireless device and / or first access device. A wireless device may have a configuration or may be instructed to monitor during a long period of time a reference signal from an access device that may give an indication about the timing of the overall system. For instance, the (first) access device may transmit a synchronization signal, e.g., a synchronization block, with a low frequency, e.g., once every 10,24 seconds. This synchronization signal may then be received with a different delay on the earth surface by a wireless device, but once it has been received it, it can determine its range to the (first) access device and obtains the time reference for the reception of other messages. In particular, if the wireless device has to receive a first message (e.g., a WUS or early paging indication and / or paging message) whose transmission may be scheduled at specific times, the wireless device may be able to wake up at the corresponding times. This synchronization signal may contain the cell ID of the access device, e.g., a first access device. Since this access device may be a satellite with global range, it may be an identifier that fully identifies the access device.

[0389] In an embodiment that may be combined with other embodiments or used independently, since subsequent first messages may be transmitted with a frequency lower than the frequency of the synchronization signal, the synchronization signal may include its position in a longer time schedule, e.g., in the form of a counter. For example, assume that the time in the cellular system is organized in T ms frames, and that there are 2^k1 * 2^k2 frames, e.g., T=10 ms, k1=k2=10 of those frames. The synchronization signal may be transmitted every 2^k1 frames, and may include a counter between 0 and 2^k2-1. This allows the wireless device to synchronize to the wireless device, and then monitor a first message, e.g., a WUS / paging message, etc, that is transmitted with a period greater than 2^k1 frames. In an example, a first access device at a first altitude may broadcast synchronization signals with a first frequency (e.g., with a period between 2^k1 and 2^k2), and thus, the counter is a value between 0 and 2^k2-1. In an example, a second access device at a second altitude may broadcast synchronization signals with a second frequency (e.g., with a period less than 2^k1), and thus, the counter is a value between 0 and 2^k1-1. In an example, a flag indicates whether the counter included in the synchronization signal is a value between 0 and 2^k1-1 or between 0 and 2^k2-1.

[0390] In an embodiment that may be combined with other embodiments or used independently, a wireless device may synchronize with a first access device at a first altitude and maybe aware of the reception time at its location, i.e., taking into account the time delay from the first access device to the wireless device. The wireless device may then get an indication to receive a second message from / through a second access device, e.g., at a second altitude, e.g., a LEO satellite. However, the wireless device may not be aware yet of the specific timing advance (TA) to apply to that second access device. The first access device may not be aware of the specific location of the wireless device. Thus, the first message includes a value indicative of an offset and / or difference between the TA of the first access device and the TA of the second access device. This may be advantageous to reduce the message size. The offset and / or difference may be for the current location of the wireless device, so that the wireless device can directly obtain the TA for the second wireless device. The offset and / or difference may be for a reference location, e.g., the point on the earth surface between the first access device and the earth centre, so that the wireless device can obtain the TA for the second wireless device based on the offset and / or difference, the reference location, and its own location.

[0391] In an embodiment that may be combined with other embodiments or used independently, the first access device and / or the second access device may comprise a single unit (e.g., a single satellite) or a few f units (e.g., f satellites) working together and / or moving together. For instance, when the second access device comprises f satellites moving one after another (e.g., illustrated as 304" in Fig. 3), the wireless device may transmit a message towards the first unit of the satellites (i.e., the first unit in the second access device), and this message will be received by all f satellites that can then combine the received signal to obtain a better estimation. Another advantage of having an access device that comprises f units is that the transmission power of the wireless devices may be reduced. Another advantage may be that reliability may be increased. Because of these reasons, it is important that the first access device includes information about the capabilities (transmission power, sensitivity of reception, number of units) of the second access device in the first message. This allows the wireless device to select a suitable second access device.

[0392] In an embodiment that may be combined with other embodiments or used independently, the first message distributed by the first access device may include information about the capabilities of the second access device in terms of its transmission power and reception sensitivity so that the wireless device can determine the expected energy requirements when performing the data exchange through the second access device.

[0393] In an embodiment that may be combined with other embodiments or used independently, the first message transmitted by the first access device at a first altitude may be a setof synchronization signals blocks SSBs transmitted in an SSB burst. For instance, k synchronization signals transmitted in a regular interval in the first half of a frame (e.g., a 5G NR 10 ms frame) at a first frequency fl through the same beam. Fig. 7 schematically shows a wireless device 700, a second access device (e.g., LEO) 701, and a first access device (e.g., GEO) 702. The first access device transmits the first message comprising k=3 synchronization signals at time to at the first frequency fl. The first message 703 arrives at the second access device as message 704 at time tl, and at the wireless device as message 705 at time t2. The time difference t2 - to depends on the distance between wireless device 700 and the first access device 702. Note that as in other embodiments, the first access device 702 may have transmitted the first message such that it arrives in sync with the frame structure of the cellular system that t2 - to may also refer to this time difference. The second access device 701 may transmit a second message that may consist of k' synchronization signals at a second frequency f2. fl may be reserved for the first access device at the first altitude to avoid interferences with second messages from other second access devices at a second altitude. The first message may comprise k synchronization signals, e.g., in the first half of a frame, similar to the synchronization signal block (SSB) burst received by a 5G UE wherein the SSB bust comprises multiple synchronization signal blocks, each of them transmitted through different beams. A rationale for this design is that a wireless device is adapted to receive a SSB burst comprising multiple SSB, and such a first message (e.g. as in Fig. 7 or Fig. 8) resembles an SSB burst but it is adapted to be transmitted by the access device through the same beam wherein the same synchronization signal burst is transmitted multiple times. This can be useful to deal with a weak reception (due to the long distance).

[0394] In 5G New Radio, when the SSB are transmitted at a frequency under 3 GHz, there can be up to four SSB in an SSB burst, when the frequency range is between 3 and 6 GHz, there can be up to eight SSB in an SSB burst, and when the frequency range is higher than 6 GHz there can be 64 SSB in an SSB burst. An access device at very high altitude may prefer a lower frequency band so that the range is long enough. However, the current 5G cellular standard does not allow having more than 4 SSB in an SSB burst when the frequency is less than 3 GHz. Furthermore, each SSB is transmitted through a different beam. Thus, in an embodiment that may be combined with other embodiments or used independently, the access device is adapted to:

[0395] Transmit multiple k>l SSB (in general first message) through the same beam in the same SSB bust,

[0396] Transmit more than 4 SSB (in general first message) in an SSB burst for a frequency lower than 3 GHz,Transmit more than 8 SSB (in general first message) in an SSB burst for a frequency between 3 and 6 GHz,

[0397] Transmit the SSB bursts (in general first message) with a different period (e.g., very 20 ms, or 40 ms, or 80 ms, or 160 ms, or 320 ms, etc).

[0398] Fig. 8. A) represents the periodic transmission of the first message (comprising an SSB burst including k = 4 synchronization signals blocks) through a first beam of the first access device. The first message is transmitted so that it is aligned with the start of a (10 ms) frame in the frame system of the cellular system. The first message is transmitted periodically, In an example every second frame, i.e., every 20 ms. Fig. 8. B) represents a similar periodic transmission of the first message (comprising an SSB burst including k = 4 synchronization signals blocks) wherein 2 SSBs are transmitted through a first beam of the first access device and those 2 SSBs are followed by another 2 SSBs transmitted from a second beam of another access device, e.g., the second access device. Fig. 8. B may represent the situation in which the first access device distributes the synchronization signals in a large area and orchestrates second access devices under it (e.g., LEO satellites under the GEO satellite) to distribute their SSBs within the same SSB burst. The SSBs from the second access devices may include a different cell / access device ID. A wireless device may be adapted to monitor the SSB bursts and select the beam / SSB with the highest signal strength. This approach described by means of Fig. 8 may allow wireless devices to monitor a single frequency band used to distribute the SSB bursts initiated by the first access device, and the first access device may determine which second access devices contribute / add to the SSB burst in different areas, i.e., the first access device may indicate this to the second access device, that may then transmit its own SSB in a synchronized manner.

[0399] In an embodiment that may be combined with other embodiments or used independently, the wireless device is adapted to receive all k synchronization signals received from the first access device transmitted through a single beam, and combine the k received synchronization signals to improve the measurement. The wireless device may determine that all synchronization signals are in the same beam because all of them may have the same beam / SSB index. Other parameters in SIB1 may have a different meaning, for instance, ssb-PositionsInBurst (included in SI Bl) indicates which beams / synchronization signals are transmitted. In this case, this field may not be required, and instead, only the number of repetitions k may be required. Additionally or alternatively, the field may be reused and it may include as many "1" as synchronization signals are transmitted. The number of repetitions may also be included in the synchronization signals themselves. The combination of the k received synchronization signals may be performed, e.g., by means of softdecision combination of the received symbols in the k copies of the same synchronization signal, by majority voting of each of the received symbols in the k copies of the same synchronization signal, etc.

[0400] In an embodiment that may be combined with other embodiments or used independently, upon synchronization with the first access device, the wireless device determines which second access device at a second altitude may be suitable for further communication. If it is available, it will remain awake. If the second access device is not available yet, the wireless device may go back into a low energy state (e.g., INNACTIVE / IDLE state) till the selected second access device is available, e.g., when it is expected to be closest to the location of the wireless device in order to reduce the energy consumption of the wireless device. At this stage, the wireless device may then use the information obtained in the first message to synchronize with the second access device wherein the synchronization signals may be standard synchronization signals or as depicted in Fig. 8 or as in other embodiments.

[0401] In an embodiment that may be combined with other embodiments or used independently, the first access device performs the broadcast control plane functionality of the communication with the wireless device and the second access device performs the control plane and user plane communication. For instance, the first access device may be in charge of broadcasting synchronization signals and / or system information and / or paging messages so that this information reaches a large area; and this synchronization signals and system information may be then used by the wireless device to perform further communication steps such as synchronization to the second access device, random access, etc. The first access device and second access device interact so that when a large scale paging message is required, the second access device (or the core network on the ground) requests the first access device to deliver the paging message.

[0402] In an embodiment that may be combined with other embodiments or used independently, the core network and / or RAN has a policy or configuration such that large scale messages are preferred to be routed / distributed / broadcasted through first access devices at a first altitude, e.g., higher altitude devices and / or at a stable position area over the earth.

[0403] In an embodiment that may be combined with other embodiments or used independently, the first access device may perform the control plane functionality of the communication with the wireless device and the second access device performs the user plane communication. The first access device may hold therefore control plane protocol stacks such as RRCprotocol and / or core network functionality while the second access device comprises user plane protocols and a NF to connect to the data network, e.g., the 5G UPF. Note that, in an implementation, the lower layers of the wireless device protocol stack may be shared in a normal wireless device, and thus, the lower layers may need to be duplicated in the wireless device having a copy for the communication with the first access device and a second copy for the communication with the second access device. In another implementation, lower layers may be shared.

[0404] Fig. 9 depicts a potential protocol stack for the wireless device based on the protocol stack of a 5G UE involving the physical layer, MAC layer, radio link control (RLC) layer, packet data convergence protocol (PDCP) layer, radio resource control (RRC) layer, Non-access stratum (NAS) layer, and service data adaptation protocol (SDAP) layer. In Fig. 9, the PDCP layer is shared, but the upper layers and lower layers are different or duplicated. The upper layers are different because the first access device handles the control plane and the second access device handles the user plane; the lower layers are duplicated because the communication links between the first and second access devices may be of very different nature. In other implementations, all layers may be shared, and the wireless device may just split the communication at the lowest layers when communicating with the first and / or second access devices.

[0405] In the example of Fig. 9, common functionalities in the shared PDCP layer may include header compression, security, routing or duplication, re-ordering and in-order delivery, etc.

[0406] In an example, the RLC layer may also be shared, if the different modes used in the RLC layer (e.g., transparent mode (TM), unacknowledged mode (UM), or acknowledged mode (AM)) are applicable to user plane / control plane, i.e., first access device and second access device individually. For instance, user plane communication by only require UM but control plane communication may require AM. Thus, an alternative protocol stack to the one in Fig. 9 would be one in which the RLC is common, but the transmission mode depends on the UP / CO, i.e., first access device or second access device.

[0407] In an example, a similar remark may also apply to the MAC layer, although in this case, some MAC procedures may need to be applied to both UP and CP, i.e., first access device and second access device, e.g., the random access procedure or the reception of synchronization signals in the physical broadcast channel. However, some functionality may be applicable to each stack separately, e.g., the usage of DRX schedules.

[0408] In an example, IDLE / INNACTIVE DRX may be applicable through the control plane / first access device. Note that this embodiment may also be applicable to other cellular deployments, e.g., communication over a terrestrial and a non-terrestrial access device or only in a terrestrial environment. This split may also be beneficial in cell-free cellular systems wherein a first transmissionand reception point (TRP) may handle the control plane and a second TRP may handle the user plane. This split protocol stack may also be useful in applications such as Augmented Reality (AR) / Virtual Reality (VR) because data transport in the UP may be optimized. This embodiment may require that the first access device provides the second access device with parameters suitable for the communication (e.g., user plane keys in the AS layer). Additionally or alternatively, the first access device may act as the primary cell, and the second access device may act as a secondary cell.

[0409] In an embodiment that may be combined with other embodiments or used independently, the first access device at a stable position over an area over the earth (GEO or HEO) and at a first altitude contains and / or runs a full core network. The advantage is that it allows distributing from there communication / computational tasks through second access devices at a second altitude (e.g., LEO satellites). This may reduce the overall latency compared with a situation in which the CN is on the ground, and the communication needs to be multihop through multiple LEO satellites that may not always be connected (e.g., due to store and forward operation mode).

[0410] In an embodiment that may be combined with other embodiments or used independently, the first message may include an integrity and / or authentication code such as a message authentication code or a digital signature so that a wireless device can verify the authenticity of the information received. The wireless device, upon reception of the first message, processes the first message by verifying the integrity and / or authentication code.

[0411] In an embodiment that may be combined with other embodiments or used independently, when the wireless device knows its location, the wireless device can also know the direction from which the first message is supposed to arrive taking into account that the first access device may be a GEO satellite or that the first access device may be a HEO / MEO / LEO satellite following a very specific path. The first message may also include a timestamp indicating when the message was transmitted and / or when the message is suppose to arrive. The wireless device may check the physical properties of the received signal carrying the first message, in particular, that the first message is arriving from the expected direction and / or that the first message includes a timestamp that fits the expected propagation delay and / or that the signal is received with the expected signal strength and / or a specific frequency shift (doppler effect). Performing these checks on these measurements can ensure and / or help to ensure that the received signal is coming from the "real" first access device. Similar checks are applicable to the second access device.In an embodiment that may be combined with other embodiments or used independently, upon receiving the first message, the wireless device may perform primary authentication with a core network through and / or in the first access device, and may determine a first set of communication parameters for the first access device and a second set of communication parameters for the second access device.

[0412] In an embodiment that may be combined with other embodiments or used independently, a first set of communication parameters used for the communication with the first access devices comprises one or more of (1) a first timing advance value, (2) a hierarchy of NAS and AS keys; a connected control-plane radio network temporary identifier (CC-RNTI) and the second set of communication parameters comprise one or more of a second timing advance value; (2) user plane keys; a connected user-plane RNTI (CU-RNTI). In particular, the usage of a CC-RNTI and a CU-RNTI may be useful in other cellular deployments when protocol starts for user plane and control plane are separated. TS 38.300, Clause 8.1, summarizes different RNTIs in a cellular system such as 5G when the UE is connected, for power and slot control or during random access. In general, control plane related RNTIs may apply to the control plane stack (e.g., as in Fig. 9) and user plane related RNTIs may apply to the user plane. For instance, CS-RNTI, Configured scheduled unicast transmission may be used in the user plane only. For instance, TPC-PUCCH-RNTI, for PUCCH power control, may apply to both user plane (second access device) and (first access device) since power control is required in both cases, unless the communication from the first access device is only broadcast from first access device to wireless devices, in which case, such RNTIs may not be needed.

[0413] In an embodiment that may be combined with other embodiments or used independently, the first access device may be in charge of paging a wireless device, and thus, it may hold the I-RNTI (inactive RNTI). The first access device may be in charge of transmitting a large scale paging message and this may be advantageous because the first access device may be at a higher altitude, and thus, it may easily reach a larger area. The wireless device may however not be able to communicate back with the first access device (e.g., due to the high altitude of the first access device the first access device works on broadcast mode only), however, the wireless device may determine based on the received paging message or know its own location, and determine in this way, a second second access device (e.g., a second LEO satellite) it needs to contact to reconnect (e.g., sending an RRCResumeRequest message). Similarly, the wireless device may have received previously the I-RNTI (or an identifier fulfilling a similar purpose) in an RRCRelease message from a first second access device (e.g., a first LEO satellite). The first second access device may communicate this I-RNTI off-band (e.g.,via link 313 as shown in Fig. 3) to the first access device. The RRCResumeRequest message may include a ResumeMAC-I or a shortResumeMAC-I that may be computed using an integrity algorithm, e.g., 5G NIA algorithm, using the following parameters:

[0414] - Key: K_RCC_INT,

[0415] Bearer: all bits set to 1,

[0416] Direction: all bits set to 1,

[0417] Count: all bits set to 1,

[0418] Message: it may be VarResumeMAC-Input including the identity of the first access device, the identity of the second access device, and the source C-RNTI.

[0419] The identity of the first access device may be a global cell identity as per other embodiments. The identity of the second access device may also be a global cell identity. And the source C-RNTI may be a connected user-plane RNTI or a connected control-plane RNTI. Furthermore, the message may also take as input the position where the second second access device is currently located (based on the estimation of the wireless device) at the point of time of transmitting the ResumeMAC-l / shortResumeMAC-l as well as other physical parameters such as timing advance or frequency shift. Including this location / physical layer information may help to prevent a replay attack.

[0420] Section: emergency messages

[0421] In an embodiment that may be combined with other embodiments or used independently, the first message from a first access device includes an indication of an emergency message available in a first area and / or for some type of devices. In some cases, the wireless device may then directly retrieve the emergency message from the first access device through the first message or by means of a subsequent message. For instance, the fact that the first message indicates the existence of an emergency situation and / or presence of the emergency message may require the wireless device to monitor certain frequency / timing resources to receive the emergency message from the first access device. The wireless device may only need to do this when a set of conditions apply, e.g., the emergency message may be transmitted to a specific area or country or group of devices, and the wireless device may check whether the required conditions apply (e.g., whether it is located in the indicated area, and / or country and / or belongs to a specific type of device), and in this case, it may retrieve the emergency message. For instance, in reference to Fig. 8, if the first message (represented as the 4 synchronization signals in frame s, s+2, s+4) includes a flag indicating an emergency message, the emergency message may be transmitted in frames s+1, s+3, s+5, etc.Additionally or alternatively, this emergency message may be obtained through the second access device, e.g., when performing by the wireless device the data exchange through the second device. For instance, the data exchange may comprise receiving the emergency message from the second access device. This may depend on certain conditions, e.g., time (only at certain time) or location, e.g., only if the wireless device is located in the first area. This embodiment may be beneficial because it allows alerting wireless devices in a large area about a given emergency message. Furthermore, a wireless device to obtain this message efficiently through the second access device. The emergency message may be a public warning system (PWS) message or an ETWS (Earthquake and Tsunami Warning System), or a CMAS (Commercial Mobile Alert System) message.

[0422] In an embodiment that may be combined with other embodiments or used independently, the first message transmitted by the first access device may comprise one or more of the following parameters:

[0423] the latitude towards which the beam used to transmit the first message (e.g., synchronization signals, system information, emergency message,...) is directed;

[0424] the longitude towards which the beam used to transmit the first message (e.g., synchronization signals, system information, emergency message,...) is directed;

[0425] the radio around the latitude / longitude for which the emergency message is valid;

[0426] the set of coordinates defining one or more area, e.g., a set of vertices of one or more areas, within which the first message / emergency message is valid(e.g., synchronization signals, system information, emergency message,...);

[0427] the identity of one or more second access devices;

[0428] the frequency band used by the one or more second access devices to transmit a subsequent message, e.g., synchronization signals;

[0429] the second altitude of the second access device;

[0430] an (indication of) an emergency message; the set of wireless devices to which the emergency message is addressed ((registration) area, country, type of device or service,...);

[0431] a global cell identifier such as the NR Cell Global Identifier (NCGI) or the global cell identifier (e.g., global gNB ID), or the tracking area identity, and

[0432] the ephemeris data of the first and / or second access device.

[0433] The wireless device(s) receiving the first message may use said parameters to determine whether the message is addressed to it / them or not.In an embodiment that may be combined with other embodiments or used independently, the first message transmitted by the first access device may contain one or more identifiers associated with the location of valid service areas of the subsequent message scheduled by the first message. The one or more identifier may be mapped to a table configured by the first access device through dedicated RRC signaling or common signaling through broadcasted system information, e.g. SIBs. If the wireless device detects that the one or more identifiers embedded in the first message matches the identifier(s) configured to the wireless device, the wireless device may further decode the subsequent message scheduled by the first message to receive the further data; otherwise, the wireless device may stop further receiving the subsequent message scheduled by the first message.

[0434] A wireless device may receive signaling, either device specific or distributed via broadcast (e.g., SI Bl) including one or more identifiers that may be used as a filter at a later stage. The one or more identifiers may determine, e.g., a location or area or volume or context (e.g., time, wind speed, rain strength,...). The identifiers may be implicit, e.g., an identifier that specifies a specific area, or explicit, e.g., the identifier defines the area itself. When specifying a volume, it may refer to an area that is subject to emergencies, e.g., a region in earth until an altitude of 1000 m is exposed to high winds / heavy rain. This may be useful, e.g., for UAVs to move to a safe location, e.g., at altitude higher than 1000 m. The identifiers may be context dependent, e.g., different identifiers may apply depending on the time, weather conditions, or severity level indicated in the message. For instance, a wireless device may check whether it is in location A or location B or location C or location D depending on the respective severity level indicated in a message (e.g., low, medium, high, very high). Different devices may act also differently on the same emergency message based on their capabilities. For instance, a first device (e.g., lightweight UAV / drone) may process an emergency message when the emergency message indicates a first severity level (e.g., medium) or higher for a given feature (e.g., wind speed) because the first device has been configured with a first policy / configuration with this purpose. A second device (e.g., heavy UAV / drone) may process an emergency message when the emergency message indicates a second severity level (e.g., high) or higher for a given feature (e.g., wind speed) because the second device has been configured with a second policy / configuration with this purpose (because the second device can endure a stronger severity level than the first device). Although this may be done at application layer, embedding such a filtering at an early stage allows for a better performance / avoids false alarms / reduces energy consumption.

[0435] In a specific example, consider that a paging message is scheduled on the Physical Downlink Control Channel (PDCCH) by means of a Download Control Information (DCI) message, e.g., DCI l_0. The wireless device may need to wake up at the configured Paging Occasion to monitor PDCCH using a paging RNTI, e.g., P-RNTI, to see if any paging message is scheduled by the access device,e.g., first access device. If the scheduling information of paging is detected, wireless device will further decode the physical downlink shared channel (PDSCH) for the actual paging message, and check if an identifier associated with the wireless device is found in the paging record. These examples are based on the recognition that embedding the information of location of the valid service area in the DCI message (in general, any other message), e.g., DCI l_0, used to schedule paging message as well as short message and PWS message, is beneficial for the system efficiency. The wireless device may need to be configured with a table of location of the valid service areas, so that the DCI only needs to contain an identifier to associate to the related actual location so that DCI can be made compact.

[0436] In other words, a message such as the DCI message may use an identifier such as the P-RNTI to address many UEs. Thus, many UEs may receive the message. The message, e.g., DCI, may also include a second identifier, e.g., related to the area of interest (area where the message or a subsequent message is / are intended), so that only devices in the area of interest proceed further.

[0437] It is to be noted that this embodiment may apply to other situations or types of signals, e.g., a wake up signal instead of a DCI message.

[0438] In an embodiment that may be combined with other embodiments or used independently, the wireless device may work in RRC_IDLE or RRC_INACTIVE or RRC_CONNECTED state.

[0439] In an embodiment that may be combined with other embodiments or used independently, the first message may be the paging message from the first access device to the wireless device.

[0440] In an embodiment that may be combined with other embodiments or used independently, the first message may be a scheduling message on PDCCH, and the subsequent message may be the PWS message scheduled by the first message.

[0441] In some cases, some wireless devices may be required to receive an emergency message and other wireless devices may not be required. Similarly, the actions to be performed may also be quite different. For instance, an Internet of Things device such as a smart light may not require an emergency message at all. For instance, an Internet of Things device such as a device controlling a windmill may require messages indicating an incoming tornado to stop operation. For instance, a UE owned by a human may provide the human with a visual message through the UE screen. As a consequence, in an embodiment that may be combined with other embodiments or used independently, a wireless device may register its preferences (regarding the type of emergency messages that are required to receive) when registering in the network. Additionally or alternatively,the network may determine the type of input required by the device based on the device type. Additionally alternatively, the network (e.g., access device) may be configured with the type of information / emergency message to deliver and may include the device type / type of information in the first / emergency message so that a device can determine whether the message is addressed to it or not. The network, e.g., access device, may distribute different types of emergency messages depending on the device type / preferences. Additionally or alternatively, the network may send a configuration determining the behavior of the wireless device upon reception of an emergency message. Although the behavior, in some cases, may be application dependent, the emergency type / level / severity may not, and it may need to be communicated in a standardized mode as well so that different types of wireless devices can take the corresponding actions.

[0442] In an embodiment that may be combined with other embodiments or used independently, the first access device and / or the second access device may work in store and forward mode, i.e., the access device may not have a communication link with either wireless device or a ground station. Such an access device working on store and forward mode may be provided with emergency messages to be delivered to the wireless device fulfilling certain criteria, e.g., devices in a certain area. The emergency messages may be enhanced with metadata including the criteria that allow determining when / where / how the emergency messages should be delivered. The access device may use that metadata to determine when / where / how to distribute the emergency messages. For instance:

[0443] given the area that needs to receive the emergency messages, the access device may determine the time to transmit emergency messages based on its ephemeris data / trajectory of the access device;

[0444] given the area that needs to receive the emergency messages, the access device may determine beamforming parameters;

[0445] given the area that needs to receive the emergency messages, and propagation features (e.g., ionosphere status), the access device determines transmission parameters.

[0446] Additionally or alternatively, a wireless device may be configured with a policy determining how to process an emergency message when delivered from an access device in store in forward mode. The policy may consider, e.g., how old the received emergency message is to accept or disregard emergency messages. The messages distributed from an access device in store and forward mode may be enhanced with metadata that may contain, e.g., the time during which they have been stored and / or the transmission time and / or the validity time. A wireless device may use its policy and / or the timing information in the metadata to accept or reject the received emergency messages.Additionally or alternatively, a wireless device may expect a certain behaviour upon reception of an emergency message. When the emergency message is received from an access device that is operating or is about to operate in store and forward mode, the user operating the wireless device may expect, e.g., to perform a call or retrieve data, and the fact that the access device is in store and forward mode may lead to confusion, in particular, if the user is not aware of the fact. Thus, emergency messages may be displayed indicating the network / access device (expected) status.

[0447] In some types of emergencies, e.g., tsunami, the tsunami alert may be valid or lose its validity depending on the elapsed time. For instance, if an earthquake happens in the ocean at location L, the time when a position P that may be affected by the tsunami (or not) depends on the distance between P and L. Similarly, if a fire starts at location L, the time when a position P that may be affected by the fire (or not) depends on the distance between P and L. Thus, information about the emergency triggering event may be used to determine (by the wireless device) whether an emergency message is addressed to the wireless device or not. This may be used by the wireless device to perform such a verification preventing situations in which an emergency message is distributed to many wireless devices that are not affected by the emergency, and / or whether to (re-)route the emergency messages using a different interface (e.g., PC5 sidelink communication) towards areas where wireless devices are more concerned with the emergency. This information may be used by the network to determine to which devices / areas a message should be distributed. This information may be used by a wireless device to determine when to react to a message, e.g., a wake up signal.

[0448] In an embodiment that may be combined with other embodiments or used independently, the first message and / or emergency message are distributed from a non-terrestrial device, different wireless devices may receive the messages. In this embodiment, the action to be performed, e.g., message to be displayed or how the wireless device operates, may depend on the context / type / role of the wireless device receiving the message. For instance, in the case of a fire, the emergency message indicating the "fire alarm" may be distributed. The message to be displayed on a UE may be, e.g., " Evaluate immediately" or " Potential evacuation", depending on the location of the wireless device. It may be zone dependent since the device may encode the total area that is affected and a subarea that is more heavily affected. For instance, in the case of a Tsunami, users may receive in their phones the message " Tsunami approaching, leave the area". The same message, if received by loT devices may cause a different behavior that may have been configured previously, e.g., traffic lights controlled over satellite may setup a traffic schedule depending on the traffic direction (e.g., red traffic lights towards the emergency area to prevent users from moving / driving in that direction and2025P00150WQ

[0449] green traffic lights towards areas further away than the emergency area to facilitate the evaluation of users). This embodiment is advantageous because it allows distributing a single first / emergency message and it allows controlling the actions caused on the devices depending on their status / context.

[0450] In an embodiment that may be combined with other embodiments or used independently, the first message may be (as in other embodiments) a signal used to wake up the device, e.g., a paging message, that may be used to wake up one or more wireless devices. This first message may be followed by the emergency message(s). In an option the first message may be unicast to each wireless device that is determined / known to be "sleeping", e.g., in IDLE and / or INNACTIVE mode in that area. However, this may require the distribution of a high number of messages. In another option, two or more wireless devices may be assigned an identifier, and the identifier may be carried in the first message and may be used to wake up and / or address the two or more wireless devices indicating the distribution of one or more emergency messages. Next to the identifier, a common wake up schedule (e.g., Extended Discontinuous Reception (eDXR)) may be distributed so that the two or more wireless devices can wake up / be addressed simultaneously at the same time / using same frequency resources. Furthermore, a common occasion, e.g., paging occasion, for receiving the first message may be determined.

[0451] Additionally or alternatively, a wake-up signal may be transmitted (e.g., similar but different than in Clause 10.1.4 in TS 36.300), e.g., prior to a paging occasion. A group identifier may be determined according to the location, e.g., area that needs to receive the wake-up signal. The identifier itself may relate to the geographic location that requires receiving the wake-up signal, e.g., it may be the center of a circle (determined by the latitude and longitude) and the radius of the circle. Any wireless device within the area may be required to wake up. This approach may allow for the specific distribution of emergency messages without requiring the pre-configuration of many groups and this may be more specific than using a common WUS group to wake up all UEs monitoring the same WUS resource. For instance, all UEs may be required to monitor a same WUS resource, and react when they determine that their location falls within the area determined by the group ID transmitted in the WUS resource, where the group ID would encode the area. Since this approach may allow waking up millions of devices simultaneously, devices may be configured to not accept certain group IDs, e.g., group IDs encoding an area larger than a threshold. Additionally or alternatively, UEs may be configured with WUS resources to monitor and identifiers that according to the area where they were located. UEs in that area may then wake up when such a WUS is received and may monitor the paging message. The paging message may indicate the type of emergency message and may includeinformation about the area that is affected. Wireless devices accepting the paging message may then receive the emergency message that may further specify which devices are affected.

[0452] Additionally or alternatively, a signal such as (legacy) wake-up signal may have limited capacity to encode large messages (e.g., an ID that determines an area as in the previous embodiment), and thus, two or more signals may be used to encode a large message. A wireless device may be required to monitor the two or more signals, e.g., wake up signal resources, and use the information retrieved in the two or more signals to obtain the required information. A wireless device may be required to receive all configured signals and retrieve the message, e.g., area that is being waken up, to act on the signals.

[0453] In an embodiment that may be combined with other embodiments or used independently, a (group) wake up signal ((G)WUS) may not only be used not only in the most recent cell where the wireless device went in inactive / idle, but also in other cells. For instance, if a wireless device goes in inactive state when boarding a boat and going towards the sea, and then an emergency happens, the wireless device may not be able to receive an emergency message. Thus, wake up signals may also need to be monitored from other cells, e.g., NTN cells, e.g., a mobile access device at a first altitude, e.g., a GEO satellite. For instance, it may receive a message, e.g., an RRCConnectionRelease, indicating the WUS parameters to monitor. This may be beneficial because a wireless device in inactive / idle mode may not be able to connect to a cell (e.g., a mobile access device at a second altitude, e.g., a LEO satellite) first to obtain SIB(l) including the wake up signal configuration. Thus, this ensures that devices can always be able to receive emergency messages. The network may only send this configuration, e.g,. when the network determines that the wireless device is moving towards an area (e.g., the sea) without coverage, e.g., without terrestrial coverage.

[0454] In an embodiment that may be combined with other embodiments or used independently, the first message may be a wake up signal and / or paging message and / or early paging indication that may be used to wake up the first device. The distribution of such a first message may make use of features of other embodiments. It may also be transmitted at any time.

[0455] In an embodiment that may be combined with other embodiments or used independently, the first message (e.g., wake up signal or paging message) and / or the second message and / or the emergency messages may be integrity protected to make sure that emergency messages cannot be manipulated. In an option, the wireless devices may store keys, e.g., a symmetric key, thatmaybe used to securely verify a token, e.g., a message authentication code, included in the first message and / or second message and / or emergency messages. The credentials may be updated regularly, e.g., when the wireless device connects to the network, once per day, etc. The credentials may be stored in secure storage. The messages (e.g., first message) may include the key identifier used to protect the message. The messages (e.g., first message) may use a time reference as freshness parameter, e.g., the time / frame in the frame system. Additionally or alternatively, the stored keys may be used to encrypt (e.g., XOR) the identifier used to address one, two or more devices in the paging message. Only if the decrypted identifier matches the identifier of the device(s), the device will act on the paging message. This embodiment is advantageous because it may be used to prevent an attacker from transmitting a fake first / emergency message.

[0456] In an embodiment that may be combined with other embodiments or used independently, the wireless device may store a list of trusted access devices (e.g., first access device / second access device) and may use information such as the trajectory and its own position to verify the origin of the first message and / or the second message and / or the emergency messages.

[0457] In an embodiment that may be combined with other embodiments or used independently, a received message, e.g., first message or an emergency message may be executed according to a pre-configured policy based on the estimated confidence level that may depend on how trusted / untrusted the first message and / or emergency message is considered. For instance, if a wireless device missed several updates of the stored keys and receives an emergency message protected with old keys (e.g., 2 weeks old keys), the wireless device may still indicate the emergency message but including, e.g., an alert message, e.g., based on a pre-configured policy. The wireless device may be configured with the policy when / after it connects to the network.

[0458] Reliability and resilience are important goals when distributing emergency messages, and thus, in an embodiment that may be combined with other embodiments or used independently, a wireless device may be configured with a plurality of occurrences when the different messages (e.g., first message and / or second message) may be distributed. For instance, the first message (and / or second message / emergency message) may be distributed k times in a given set of communication resources, e.g., a period of time T. For instance, k repetitions distributed in time, or k repetitions distributed in different frequencies, or k repetitions using different codes, or k repetitions in time / using different frequencies / using different codes. This can be advantageous since there are devices with different clock accuracies, devices with different radio capabilities, devices with different radiocommunication links (e.g., line of sight vs non-light of sight) that may not be able to receive a message properly if it is sent a single time. Wireless devices may be given a configuration to monitor certain resources, e.g., a time window TW within T, or a subset of frequencies, etc to monitor those messages. The configured resources, e.g., the time window TW, may also be different for different (types of) wireless devices, e.g., depending on how many times a message may need to be received to ensure a certain level of reliability and resilience for a specific device, depending on the type of device, location, energy budget, etc. For instance, the first message may be a configuration provided by the network when the wireless device connects to it, e.g., by means of an RRC message. For instance, the first message may carry the configuration for the reception of the second message / emergency message. A wireless device may then be required to monitor the configured communication resources knowing that they carry the relevant message. The wireless device may use multiple measurements of multiple message to aggregate the signal / message, and improve the reliability when retrieving the corresponding message, e.g., first message and / or emergency message.

[0459] In an embodiment that may be combined with other embodiments (e.g., previous one) or used independently, the resources used to transmit the messages may be limited by nontransmission periods, e.g., a non-transmission period before and after or in the surrounding frequencies. If a wireless device determines that the configured resources used to receive the first and / or emergency messages have a higher signal strength, in general, fulfil a given criteria, than the resources surrounding it, the wireless device may be configured (e.g., based on a policy / configuration) to monitor other configured resources. This additional monitoring may be done even if the wireless device is not capable of decoding the signal properly. In general, the criteria may be configurable and may determine the communication features to consider (e.g., signal strength or quality), signal strength difference between the configured resources used to receive a signal and surrounding resources triggering further monitoring, whether part or whole of the signal needs to be decodable to trigger further monitoring, etc. If further monitoring is performed or required in a second set of resources, the wireless device may combine the messages / signals obtained from the first set of resources and second set of resources to obtain a signal of better quality (e.g., better Signal to Noise ratio). This embodiment is advantageous because it allows a wireless device to monitor a first set of resources only, and only if a potential signal is suspected, one or more second set of resources needs to be monitored. This approach provides a good trade-off between energy requirements of the wireless device and reliability when receiving communication signals. This and other embodiments may be illustrated by means of Fig. 11 that schematically represents a set of resources (e.g., time / frequency) resources and the signaling used to transmit a signal (e.g., first and / or second and / oremergency message) in a reliable manner while keeping into account energy consumption of wireless devices. An access device may be configured to transmit a signal of interest, e.g., first message, e.g., paging message, in a set of resources (e.g., at times tl, t2, and t3 using frequencies fl and f2). Furthermore, the resources around some of the selected resources may be kept "empty", i.e., nonsignal, i.e., zero signal (ZS). This may allow a wireless device to better determine whether there is a signal being transmitted in the selected resources. A wireless device may be provided with a policy determining the set of resources to monitor, e.g., frequencies fl at times tl, t2, and t3, whereby some of the monitoring may only be performed if an event occurs, e.g., when there is an indication that, e.g., some of the resources (e.g., at a first frequency fl and a first time tl) may carry a signal, and this indication may be obtained by comparing one or more communication features, such as, e.g., the signal strength, of the signal in such a first / time resources with the one or more communication features of surrounding frequencies / times. For instance, a wireless device may monitor usually only resources tl / fl unless it is determined that the signal strength in tl / fl is higher than in the surrounding resources. In this case, the wireless device is required to further monitor fl at t2 and t3 and use that information to receive the messages, e.g., to improve the quality of the received signal. The procedure in Fig. 11 may be used, e.g., to make the reception of paging messages / early paging messages more efficient / reliable.

[0460] Fig. 12 illustrates a message flow according to some embodiments of the invention allowing for the efficient and reliable distribution of emergency messages. Entities 1200, 1201-1, 1201-2, 1202 and 1203 represent a wireless device, a first access device, a second access device, a third access device, and a core network. In step 1204, some or all of the access devices and / or core network may negotiate parameters that may be used for reaching one or more wireless devices when an emergency parameter needs to be delivered. For example, this may mean that the first and / or second access devices share with the third access device parameters of a signal used to alert (e.g., wake up or page or emergency message), e.g., (group) WUS parameters, one or multiple wireless devices 1200. In step 1205, the wireless device may be connected to one of the access devices, e.g., the third access device, e.g., a terrestrial access device. In step 1203, the first and / or second access devices may be informed by the core network about an emergency situation. For instance, the indication may be delivered to the first access device that may be a GEO satellite. For instance, one of the first and / or second access devices may not be present. In step 1207, a first message may be delivered from one of the access devices, e.g., 1201-1, to the wireless device. This first message may be, e.g., a wake-up signal. In step 1208, a first message prime may be delivered, e.g., a paging message. This first message and / or first message prime may include parameters determining the communication resources forobtaining the emergency message. In step 1209, a data exchange may be performed, e.g., the emergency message may be delivered from the first access device and / or second access device to the wireless device.

[0461] In some scenarios, a catastrophic situation may happen in a given area and infrastructure such as communication networks, electricity networks, etc may be out of order. In such cases, it may be required to distribute emergency information to different sets of wireless devices, e.g., by distributing a targeted emergency message. Addressing this need may require a system with several features:

[0462] 1) Deployment / commissioning / usage of non-terrestrial infrastructure on demand: for instance, satellites may be instructed to deliver communication services and / or non-terrestrial devices such as UAVs may be launched to provide communication services;

[0463] 2) Wireless devices may need to be informed about the situation, either directly by the (newly) deployed / commissioned infrastructure or through other non-terrestrial devices (e.g., GEO / LEO satellites);

[0464] 3) Wireless devices may need to be assigned to different groups depending on the access rights, e.g., general population may only be allowed to receive general information while public safety stuff may obtain enhanced information reports;

[0465] 4) Wireless device may need to be able to verify the source / integrity of the data because such emergency messages may easily disrupt the communication.

[0466] In an embodiment that may be combined with other embodiments or used independently, the first message received from the first access device may include parameters to transmit an emergency message originated in the wireless device, and performing the data exchange through a second access device comprises preparing the emergency message including the permanent device identifier, and transmitting the emergency message. The first message may indicate which second access devices are available for the efficient delivery of emergency messages (e.g., have enough storage to store emergency messages when working on store and forward mode). If the wireless device has a low energy level, it is also preferred to identify the best possible candidate (i.e., the best second access device) to perform the delivery of the emergency message and this identification step is based on the first message received through the first access device. Once the best candidate is identified, the wireless device can efficiently deliver the emergency message to that second access device. In case that no good second access device is identified, e.g., no second access device capable of delivering the2025P00150WQ

[0467] emergency message within a time threshold, the wireless device may use the first access device, even if it involves a higher energy cost or a higher communication latency.

[0468] Granular store and forward notifications

[0469] In an example network, a first access device such as a LEO satellite can send an indication indicating that it is working in store and forward mode (or that another device is working in store and forward mode). This indication may be sent, e.g., when the feeder link (link between satellite and ground station) is not available. However, this may be a too restrictive indication because the satellite may have some connectivity, e.g., weak / slow connectivity, but the satellite may not wish to allow all wireless devices to exchange data.

[0470] Thus, in an embodiment of this invention that may be combined with other embodiments or used independently, an access device, e.g., the first access device, sends a granular store and forward indication. This granular store and forward indication may indicate - explicilty or implicitly - for which wireless devices / services the satellite is operating in store and forward mode and for which wireless devices / services the satellite is operating in real-time mode. The indication may be one or more flags / code and / or bitmap that may indicate the services / wireless devices for which the device is operating in store and forward mode.

[0471] For instance, a code may refer to the amount of data. For instance, this code may be code AD. For instance, if a device may require a service requiring the exchange of X data, e.g., X < 1 KB (code AD = 01), X < 10 KB (code AD = 10), X >= 10 KB (code AD = 11), the access device may distribute code AD = 00 if no data may be exchanged in real-time mode, the access device may distribute 01, if only data exchanges of less than 1 KB may be exchanged in non-store & forward (real-time mode), the access device may distribute 11 if all data exchanges may be performed in non-store & forward mode.

[0472] For instance, another code (code device type (DT)) may refer to the types of devices that may be allowed to use real-time communication. For instance, no-device may be allowed (e.g., code DT = 00). For instance, only public safety devices may be allowed to use real-time communication (e.g., code DT = 01). For instance, all devices may be allowed to use real-time communication (e.g., code DT = 10).

[0473] When multiples codes are used, multiple codes may be transmitted next to each other. For instance, it may be possible to transmit a 4 bit field comprising the two exemplary codes above, e.g., code AD, code DT.

[0474] When multiple codes are used, the usage of a store and forward functionality may be based on a logical operation between two or more codes. For instance, using above exemplary definitions, the access device may distribute code AD = 01, code DT = 01. This may indicate that onlydevices fulfilling both codes (logical AND) may transmit in real-time mode (e.g., public safety devices AND requiring the transmission of less than 1 KB). This may indicate that only devices fulfilling any of the codes (logical OR) may transmit in real-time mode (e.g., public safety devices OR devices requiring the transmission of less than 1 KB). When N codes are available more complex logical functions may be defined and configured.

[0475] When multiple codes are used, redundant values of two or more codes may be used to reduce the overhead. For instance, using above exemplary definitions, codes code DT = 00 and code AD = 00 indicate the same. Thus, one of those codes may be removed so that the same may be indicated by means of a 3 bit field.

[0476] in an embodiment of this invention that may be combined with other embodiments or used independently, a wireless device such as a user equipment may receive this granular store and forward indication from an access device and use this granular store and forward indication to better select the satellite for communication.

[0477] For instance, if two LEO access devices send different granular store and forward indications, the wireless device may use the granular store and forward indications to perform the selection of the access device, e.g., it may select, (re-select), move the access device the provides the best service for its requirements.

[0478] For instance, if a LEO access device sends a granular store and forward indication indicating that it only works in real-time mode for public safety services, a wireless device may then determine to perform an IMS voice call over a different satellite, e.g., a GEO satellite.

[0479] Thus, in a variant of this embodiment, the wireless device may, upon reception of an indication that a first access device currently operates in real time for safety services, switch to a second access device for an IP Multimedia Service. Alternatively, the access device may signal that no other public safety operation mode than real time is supported.

[0480] In accordance with a general definition of this embodiment, it is proposed a method comprising a wireless device comprising receiving e.g. from an access device, e.g., the first access device or a different access device, a store and forward indication, wherein the store and forward indication providing additional information on a store and forward operation of the first access device; the wireless device adapting its operation based on the information.

[0481] In a first variant, the indication indicates explicitly or implicitly one or more of:

[0482] for which wireless devices (or which wireless device group, or wireless device class / type) the satellite operates in store and forward mode, and / or

[0483] for which services the satellite operates in store and forward mode and / orfor which wireless devices (or which wireless device group, or wireless device class / type) the satellite operates in real-time mode; and / or

[0484] for which services the satellite operates in real-time mode.

[0485] time information of when access device operates in store and forward mode and / or real-time mode, and / or timing when it does not operate in store and forward mode and / or real-time mode, e.g. when feeder link of the satellite is expected to be available or not available.

[0486] Section: distribution reference signals and gathering of measurements

[0487] In a cellular system such as 5G, the synchronization signals are transmitted together with the physical broadcast channel (PBCH) in the first 5 ms of a frame with a typical periodicity of 20 ms. The SS + PBCH are transmitted through different beams forming a SSB burst. SS and PBCH are transmitted in the same 4 symbol block and consist of 240 continuous carriers (20 resource blocks). The information that is present in PBCH and MIB can be used to determine the location of SIB1 where other parameters such as paging search space is present. The PBCH data and MIB is transmitted through the PBCH that involves adding a CRC and error correction capabilities by means of a Polar code. These message structure may make challenging the distribution information contained in the first message. Thus, a further aim of the invention is to improve the distribution of information.

[0488] In an embodiment, transmitting measurements of reference signals such as channel state information or received signal strength between wireless device and the first and / or second access device may be inefficient because of the high signaling cost of the wireless device to the first and / or access device and the latency. Thus, in an embodiment that may be combined with other embodiments or used independently, the first access device may include an indication to provide measurements according to a probability p. Since the number of wireless devices is large due to the large coverage, this may provide sufficient information to the first / second access device to estimate the channel in a large area, and adapt communication parameters accordingly. Measurements may include the location where the wireless device is and / or the first / second access device should be aware of the location of the wireless devices. This embodiment is also advantageous because it saves energy in the devices since they only need to transmit measurements with probability p.

[0489] In another embodiment that may be combined with other embodiments or used independently, the second access device may be in charge of aggregating and forwarding the measurements to the first access device. The first access may provide / broadcast reference signals, and the wireless devices may make measurements, and send them to the second access device. The second access device may also run the logic / algorithms to control the communication parameters used by the first access device. For instance, if the first access device transmits a first message thatincludes a reference signal and the reported measurements (as measured by the wireless devices) indicate that the received signal is too weak, e.g., due to the current state of ionosphere (between ~ 48 and 960 km), the second access device (e.g., a LEO satellite at 400 Km) may indicate / command the first access device (e.g., a LEO or MEO satellite) to increase transmission power or use a lower data rate.

[0490] In some cases, the first access device is an access device that is between the wireless device and the second access device, e.g., when the first access device is a LEO satellite and the second access device is a GEO satellite. We can write that the transfer function (or path loss) of the channel between the wireless device and the first access device is called H1. We can write that the transfer function (or path loss) of the channel between the first access device and the second access device is called H2. We can write that the transfer function (or path loss) of the channel between the wireless device and the second access device is called H3. In some circumstances, H3 is approximately equal to the product of H1 and H2, or H3 ~ H1H2. Thus, instead of exchanging reference signals between the second access device and the wireless device, and the wireless device communicating the measurements to the second access device, an additional approach may be feasible illustrated by means of an embodiment that may be combined with other embodiments or used independently in which, the first access device may transfer reference signals to the wireless device and the wireless device may perform and send measurements to the first access device so that the first device can estimate the current channel transfer function H1. The first access device and second access device may also estimate the channel transfer function H2, e.g., in a similar manner. In some cases, the wireless device may also send the measurements to the second access device so that the second access device estimates Hl. The first device may then obtain H3 and send the estimated H3 to the second access device. The first device may then send Hl to the second access device so that the second access device may obtain H3. The second access device may then determine communication parameters based on H3. In this approach, in general, it is thus defined a method for communication between a wireless device and a second access device, wherein the wireless device receives reference signals from a first access device, the wireless device obtains measurements of the reference signals, and the wireless device transmits the measurements to the first access device and / or second access device.

[0491] Improvement in the setup of a communication with a second access device (e.g., GEO) through a first access device (e.g., LEO)

[0492] In an embodiment that may be combined with other embodiments or used independently, it may be beneficial to use a first access device at a first altitude (e.g., UAV or LEO2025P00150WQ

[0493] satellite) to establish the communication with a second access device at a second altitude, e.g., a GEO satellite. In some cases, the first access device may be an access device having a first path loss with the wireless device and the second access device may be another access device having a second path loss with the wireless device. For instance, a wireless device may not be able to wake up or trigger the communication with the second access device directly, but the wireless device may be able to do that through the first access device. In particular, the first access device may receive wake up signals (e.g., a preamble) to wake up and / or trigger the communication with the second access device. The first access device upon receiving such a signal, e.g., may contact (and optionally provide information / configurations to) the second access device and / or the wireless device to setup / enable the communication between both of them. This may comprise the second access device transmitting certain signals to the wireless device (e.g., synchronization signals or a SIB (e.g., SIB1) and / or the wireless device transmitting certain signals (e.g., preamble) to the second access device.

[0494] In a related embodiment that may be combined with other embodiments or used independently, the first access device may be used to provide the wireless device with a configuration. The configuration may facilitate / enable the wireless device to connect and / or perform the data exchange with and / or through the second access device. The configuration may contain communication resources (e.g., time / frequency resources) and / or beam information and / or communication parameters (coding, modulation,...), etc.

[0495] In a related embodiment that may be combined with other embodiments or used independently, the second access device may start said connection and / or data exchange with the wireless device. The first access device may provide the second access device with information to facilitate the connection and / or data exchange. For instance, information detailing the estimated area of the wireless device. For instance, information related to the wake up period of the device. In some cases, this information may be extracted from the first message received from the wireless device.

[0496] In some cases, the wireless device may start the connection and / or data exchange with / through the second access device. In some cases, the second access device may start the connection and / or data exchange.

[0497] In some cases, the wireless device may know that the first access device serves as a bridge / relay and / or allows facilitating the connection with the second access device, e.g., the first access device may inform about this capability in a SIB, e.g., SIB1 or an NTN specific SIB. The wireless device may then use a first message, e.g., a specific uplink wake up signal, to signal this need allowing for the setup of the connection with the second access device and / or data exchange with or through the second access device without the need to connect to the first access device first.In some cases, the first signal may be a wake up signal, or a preamble, or a message of the random-access procedure.

[0498] In some cases setting up a connection with the first access device may be required, and then performing, e.g., a handover to the second access device.

[0499] In some cases, the first access device and / or the second access device may also be terrestrial access devices.

[0500] This embodiment may be beneficial because the first access device may receive more easily the first message, and based on it, enable the connection with / data exchange with / through the second access device.

[0501] In general, it is described method for non-terrestrial communication with a wireless device wherein the method comprises:

[0502] - transmitting, by the wireless device, a first message to a first access device, and

[0503] - performing, by the wireless device, a data exchange through a second access device.

[0504] Voice over GEO satellite

[0505] R19 has performed work to enable UE to UE IMS-based communication over satellite. This involves the architecture, procedures, etc defined in Annex AE in TS 23.228, e.g., mobility procedures for UE-Satellite-UE communication in IMS - continuation of optimized media routing as described in TS 23.228. Similar, the setup of the IMS communication relies on the initial setup of a user plane connection / PDU session as described in Clause 4.3.3.2 in TS 23.502.

[0506] IMS-based communication over satellite may be performed over lower altitude access devices, e.g., LEO satellites, e.g., because the latency may be lower due to the lower altitude. Furthermore, the available link capacity may be higher. When the low altitude access devices move, a change of access device may be required, and a mobility procedure for UE-Satellite-UE communication in IMS may be required. This may involve a handover of wireless device to a different access device (e.g., handover of the user / control plane). This may also involve reserving / configuring IMS AGW in the target satellite. R19 has described procedures for mobility between satellites, and procedures for fallback. Procedures for fallback to an access device at a higher altitude (e.g., GEO satellite) are required, e.g., when terrestrial access devices are not available at a certain location (e.g., sea, energy savings, catastrophe situation) and lower altitude access devices are not available. Furthermore, in some scenarios, it is desired to enable voice over a GEO satellite, in particular, IMS-based voice. This may be desirable because a GEO satellite remains at a fixed (or relatively fixed) position over an area on the earth. Thus, wireless devices do not require changing the satellite frequently. However, the setup of the connection and / or theexecution of the connection may require specific techniques to handle the relatively low bandwidth communication links and / or the high latency of the communication link. To address these challenges, several embodiments of this invention may be applied:

[0507] In an embodiment that may be combined with other embodiments or used independently, it is required to authorize the resources required for the wireless device(s) (UE(s)) for the communication over a GEO / GSO satellite (e.g., a first (e.g., higher) altitude access device) because these resources may be scarce. These resources would be required to carry the communication flow. The PCF may authorize the required resources via Npcf_PolicyAuthorization_Update service operation.

[0508] In an embodiment that may be combined with other embodiments or used independently, the wireless device(s) may be required to perform a handover from a second (e.g., lower) altitude access device to a first (e.g., higher) altitude access device. For instance, if two wireless devices are performing a UE-Satellite-UE communication over one or more second altitude (e.g., lower altitude) access devices, if a second altitude access device is not available for one of the wireless devices (UEs), both wireless devices (both UEs) may be required to move (perform handover) to the first (higher) altitude access device. This may be beneficial to optimize the communication between the wireless devices.

[0509] According to Annex AE.2.1.1, for the IMS PDU Session, the IP address allocated to a wireless device (UE) corresponds to a PSA UPF located on the ground, so that the IP address of the UE is not changed when the serving satellite changes. In an embodiment (in the context of previous embodiment, that may be combined with other embodiments or used independently, the allocation of such an IP address should be done when the wireless device is still connected to a second altitude access device (e.g., a terrestrial access device). In some cases, the usage of a fixed IP address may also allow using / applying header compression, e.g. based on RFC 2507 and / or RFC 6282 and / or RFC 3095 and / or an extension of them. In some cases, IP header compression may be applicable to the case in which a single satellite enables the UE-satellite-communication. In some cases, IP header may be removed. Removal may be dependent, e.g., on whether the wireless devices connect through a first (e.g., higher) altitude access device or a second (e.g., lower) altitude access device. Removal and / or compression and / or the corresponding routing may be activated on the wireless access devices / satellite when the bandwidth capabilities drop below a given threshold (e.g., when the wireless device connects through a first (e.g., higher) altitude access device. This may be feasible because the wireless devices have a fixed IP address and fixed radio access network identifier (e.g., handled by a same access device) and because functionalities such as retransmission, reassembling, etc may be taken care of by upper or lower layers. The wireless device may get a commandindicating that the IP header should be compressed and / or removed. The wireless device may use a header compression functionality in the PDCP layer (e.g., extension of ROHC) to fully remove the IP header and / or compress it as required. The wireless device may still keep its IP address so that it can be reinserted as required. In some cases, the IP address may be mapped to an identifier of the wireless device, e.g., a radio access identifier (RNTI) so that the usage of a specific RNTI by a wireless devices indicates a given IP address.

[0510] In a related embodiment that may be combined with other embodiments or used independently, routing in the access device (e.g., satellite) may be performed based on the radio network identifiers (RNTIs), instead of the IP addresses. This means that the PDCP layer of the access device may get an indication of the RNTI used to receive a certain message. The PDCP layer may then have a routing table based on the RNTI (and / or a mapping between RNTIs and IP addresses) so that the message may be rerouted to the peer wireless device, e.g., in a UE-satellite-UE communication link.

[0511] In an embodiment that may be combined with other embodiments or used independently, a wireless device may be required to connect to a second (e.g., higher) altitude access device after receiving a first message from a first (e.g., lower) altitude access device. For instance, the first (e.g., lower) altitude access device may have indicated that it is working on store and forward mode and / or in transparent mode and / or it is going to move out of the area where the wireless device is located so that it does / will not support IMS-based communication for UE-satellite-UE. The first message may indicate the identity of and / or other information / parameters about a second access device capable of providing this service, e.g., a higher altitude access device.

[0512] In an embodiment that may be combined with other embodiments or used independently, it may be required to reduce the number of round trips required to establish the communication over the second (e.g., higher) access device, e.g., compared with the procedure in S2-2501088 (IMS AGW relocation and media routing path change due to change of satellites). In an example, the 5GC may be executed in the second altitude satellite so that, e.g., some messages 2-6 in AEX.5.2.1 (S2-2501088) may run locally.

[0513] In an embodiment that may be combined with other embodiments or used independently, step 3 (determining whether UE-Satellite-UE communication continues to be possible) may require checking the capabilities of the wireless device and checking its capability to communicate with a second altitude access device. If it is not capable, the communication may be dropped, and / or rejected.2025P00150WQ

[0514] In an embodiment that may be combined with other embodiments or used independently, step 3 may require setting up a connection to the second altitude access device to determine whether UE-Satellite-UE communication is feasible. This may require performing a soft satellite switch and / or actual handover from the first (e.g., lower) altitude access device to the second (e.g., higher) altitude access device. Due to the high-altitude difference, the received SSBs from the second altitude access device may be received with a much weaker signal strength. Thus, the first altitude access device may indicate in a first message specific parameters for the switch to the second altitude access device, e.g., expected signal strength / transmitted signal strength, and / or specific parameters to access the second altitude access device, e.g., number of repetitions when transmitting an initial message (e.g., PRACH, or an random access message) as required to reach the second altitude access device. The cell switch and / or handover may be triggered / controlled by the first altitude access device and / or may be based on a conditional handover wherein the conditional handover may be triggered by conditions configured by the first altitude access device, e.g., conditions related to the execution of an IMS call over satellite, e.g., when the wireless device is performing a voice call and the first altitude access device loses its capability to provide the service, the wireless device may be required to move to the second altitude access device.

[0515] In an embodiment that may be combined with other embodiments or used independently, in step 8 in Annex X.5.2.1, P-CSCF (Tdoc S2-2501088) receives the late notification of the satellite user plane management events associated with UE-Satellite-UE communication media traffic from PCF as defined in TS 23.502

[0094] , This late notification contains an indication being set " LATE" that indicates that 5GC has established the user plane path for optimized media routing through the target satellite while implying the user plane path for optimized media routing through the source satellite is still maintained as long as active traffic exists. This late indication may include information about the actual capacity / achievable QoS (e.g., max data rate) that may be provided by the communication link because due to the wide area coverage of the second altitude access device, the distance / communication may be variable. This information about the actual capacity / achievable QoS (e.g., max data rate, latency, etc) may be used by the IMS system to select suitable parameters to encode the communication.

[0516] In an embodiment that may be combined with other embodiments or used independently, the second (e.g., higher) altitude access device may execute the entities in the originating and terminating networks as a means to optimize performance, e.g., P-CSCP, IMS-AS, IMS AGW, etc. Thus, messages 8, 9, 10, 11 as per Annex X.5.2.1, P-CSCF (Tdoc S2-2501088) may run locally reducing signaling overhead.In an embodiment that may be combined with other embodiments or used independently, the wireless devices (UEs) may be requested to move to the second altitude access device and / or the wireless devices (UEs) may be adapted to confirm / reject moving to the second altitude access device.

[0517] In Annex X.5.2.1, P-CSCF (Tdoc S2-2501088), in step 1, the traffic from the originating network to the terminating network runs via IMS AGW on source satellite (ULCL / L-PSA on source satellite) to IMS AGW on the satellite in the terminating network. The same happens for the traffic from the terminating network to the originating network. In step 12, the traffic from the terminating network to the originating network is updated to run from the IMS AGW on the satellite of the terminating network to the IMS AGW on the target satellite of the originating network. In step 18, the traffic from the originating network to the terminating network is updated to run from the IMS AGW on the satellite of the terminating network to the IMS AGW on the target satellite of the originating network. To optimize performance when communication over two satellites is moved to a single second altitude access device, then in an embodiment that may be combined with other embodiments or used independently, in step 12, the traffic from the terminating network to the originating network is updated to run through the IMS AGW(s) on the target (second altitude access device) satellite. If two IMS AGW (for terminating and originating networks) are available, both of them would be on the same target satellite. Additionally or alternatively, in step 18, the traffic from the originating network to the terminating network is updated to run through the IMS AGW(s) on the target (second altitude access device) satellite. If two IMS AGW (for terminating and originating networks) are available, both of them would be on the same target satellite. This adaptation may allow reducing signaling and speeding up the IMS AGW relocation / media routing path change procedure.

[0518] In an embodiment that may be combined with other embodiments or used independently, in steps 10, 13, 17 in Annex X.5.2.1, P-CSCF (Tdoc S2-2501088), the target satellite ID and / or SDP offer (IMS AGW on target satellite (that may contain the corresponding IP address) is provided. This message may be enhanced to include IP addresses of both IMS AGW of both originating and terminating networks so that signaling can be reduced. Furthermore, the SIP reInvite messages may be enhanced to include an indication of the usage of a second (e.g., higher, e.g., GEO) altitude access device and / or expected communication parameters / capabilities (e.g., data rate and / or latency).

[0519] Steps 12 in Annex X.5.2.1, P-CSCF (Tdoc S2-2501088) may have the traffic through two communication paths of very different latency when applied to a second (e.g., higher) altitude access device as described in other embodiments. Thus, in an embodiment that may be combinedwith other embodiments or used independently, latency of the communication flow, e.g., in Step 12, from the originating to the terminating network may be adapted, e.g., artificially increased, e.g., by buffering the traffic, to match the latency in the opposite direction. Latency compensation techniques may be applied as in other embodiments.

[0520] Steps 12 in Annex X.5.2.1, P-CSCF (Tdoc S2-2501088) triggers the change of the routing path that may require a different type of compression (e.g., encoder) algorithm (high compression (encoding) algorithm, e.g., speech to text) in the communication from the terminating to the originating network. Thus, in an embodiment that may be combined with other embodiments or used independently, this step triggers the usage of the high compression algorithm.

[0521] When a media function (MF) is used and the media function performs networkcentric rendering, the media function based rendering may be a feasible solution when the communication is performed through a first (e.g., lower) altitude access device, but network based rendering may not be feasible when the communication is performed through the second altitude access device. The reason is that this may require the distribution the rendered data from MF to the wireless devices, and this may require too much bandwidth. The usage of the second altitude access device may then trigger a change from network-centric to device centric rendering. In this case, device-centric rendering means that the (both) receiving wireless devices (UEs) may be performing the rendering / transcoding since this may allow for lower bandwidth consumption. This may require the configuration of the wireless devices with the corresponding / required information, e.g., encoders to perform the encoding of the information, e.g., speech. This may require the configuration of the wireless devices with decoders to perform the decoding of the information, e.g., text.

[0522] 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 ofthe 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.

[0523] 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.

[0524] 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 efficient mobility of a wireless device, the method comprising:sending, by the wireless device, a capability indication message comprising an indication of wireless device capabilities,receiving, by the wireless device, a first message from a first access device with a handover configuration and / or a handover command,sending, by the wireless device, a second message to perform a handover to a target access device,wherein the handover configuration and / or handover command comprises configuration parameters for access devices at different altitudes.

2. The method of claim 1, wherein the handover configuration comprises one or more conditions and / or parameters to select and / or start and / or perform the handover to the target access device, and the one or more conditions comprise at least one of:altitude of a candidate target access device,(estimated / expected) coverage of candidate target access devices having an altitude within a range relative to the altitude of the first access device, said range being defined by at least one threshold,(estimated / expected) coverage of target access devices at an altitude different to the altitude of the first access device,uplink synchronization information such as TCI or beam index,(estimated) received signal strength,received signal quality,required transmission power,maximum and / or minimum distance between wireless device and access device,minimum coverage time,type of access device (e.g., GSO vs NGSO),frequency band and bandwidth availability,movement speed and trajectory of the wireless device,power availability and consumption requirements of the wireless device,latency requirements for a specific application or service,connection setup delay and / or handover delay,operation in regenerative or transparent architecture,operation in store and forward mode,which services are available in store and forward mode and / or which services are available in realtime,time information of when access device operates in store and forward mode and / or timing when it does not,support of a full core network,support for UE-satellite-UE communication,communication parameters to perform the handover with the target access device, communication parameters to perform the handover with the target access device dependent on the communication parameters used with the first access device.

3. The methods of claims 1 to 2, wherein communication parameters used to send the second message are determined based on parameters used to communicate with the first access device and / or wireless device capabilities and / or the handover configuration.

4. The method of any previous claims, comprising one or more of the following features:the handover is a RACH-less handover, wherein the second message is an RRCSetupComplete message;the handover configuration contains a set of handover conditions to perform a conditional handover,the handover configuration contains communication parameters for enhanced coverage towards the target access device,the handover configuration contains a time offset between the reference time of the first access device and the reference time of the target device;the handover command contains a command to execute the handover to the target access device.

5. The method of any previous claims, further comprisingreceiving, by the wireless device, a second signal from a second access device and / or a third signal from a third access device, andthe wireless device selecting the second access device or the third access device as the target access device and / or determining to perform the handover to the target access device basedon the wireless device capabilities and the handover configuration, prior to sending, by the wireless device, the second message to perform the handover to the target access device.

6. The method of any previous claims, wherein the handover configuration comprises a first subconfiguration and a second sub-configuration, whereinthe first sub-configuration comprises conditions to perform a handover from the first access device to the target access device, wherein the first access device and the target access device have different altitudes, andthe second sub-configuration comprises conditions to perform a handover from the first access device to the target access device, wherein the target access device has an altitude within a first range relative to the altitude of the first access device.

7. The method of any previous claims, further comprisingdetermining, by the wireless device, by means of the handover configuration whether the wireless device performs the handover to a target access device at an second altitude within a second range of the altitude of the first access device or to a target access device at analtitude within a third range of the altitude of the first access device.

8. The method of claim 7, wherein the determination step depends on one or more of:- an expected coverage;- communication latency;- uplink transmission power;9. The method of claim 8, wherein the expected coverage and / or required communication latency and / or required uplink transmission power is one of:a coverage and / or communication latency and / or uplink transmission power provided by a target access device whose altitude is within a second range of the altitude of the first access device;a coverage and / or communication latency and / or uplink transmission power provided by a target access device whose altitude is within a third range of the altitude of the first access device.

10. The methods of any previous claims, further comprising determining, by the wireless device, by means of the handover configuration whether the wireless device performs the handover to a target access device at similar altitude of the first access device or to a target access device at a differentaltitude of the first access device depending on a coverage provided by access devices at an altitude different than the altitude of the first access device.

11. The method of any of the previous claims, wherein the first message comprises a second communication parameter, wherein the second communication parameter for the sending of the second message to target access device, and wherein the second communication parameter is encoded in a differential manner with respect to a first communication parameter used for the communication between the wireless device and the first access device.

12. The method of Claim 1,- wherein the first access device is at a first altitude, and- wherein the target access device is at a second altitude, and- wherein the difference between first altitude and the second altitude is greater than a first threshold; and- wherein the wireless device performs the control plane communication with the first access device, and- wherein the handover refers to the wireless device user plane handover to the target access device.

13. A method for efficient mobility management of a wireless device performed by an access device at a first altitude, the method comprising:- receiving, by the access device, a capability indication message comprising an indication of the wireless device capabilities of the wireless device,- transmitting, by the access device, a first message to the wireless device, the message including a handover configuration and / or handover command,- receiving, by the access device, a second message to perform a handover to a target access device at a second altitude,wherein the handover configuration and / or handover command comprises configuration parameters for access devices at different altitudes.

14. An apparatus for efficient mobility comprising:a wireless transceiver,A processor, andA memory,wherein the apparatus is adapted to perform the steps of the method of any of the claims 1 to 12.

15. A computer program for efficient mobility, wherein the program comprises instructions to perform the steps in the methods of Claims 1 to 13.

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