Paging of communication device of non-terrestrial communication network

Abstract

Methods, communication devices, network infrastructure equipment, core network section and circuitry for paging communication devices that may be outside of coverage of a non-terrestrial network are disclosed. The communication device registered with the non-terrestrial network also registers with the terrestrial network and pages from the non-terrestrial network over the terrestrial network.

Description

Paging of communication devices in non-terrestrial communication networks

[0001] This application claims priority under the Paris Convention to European patent application EP23203045.2, filed on 11 October 2023, the contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure generally relates to methods, circuit systems, communication devices, network portions of terrestrial networks and network portions of non-terrestrial networks, and specifically to communication devices for paging when a connection to a non-terrestrial network has been lost. Background Technology

[0003] The “Background Art” description provided herein is for the purpose of presenting the general context of this disclosure. The work of the currently named inventors, within the scope described in this Background Art section and in aspects that may not be described as prior art at the time of application, is neither explicitly nor implicitly acknowledged as prior art to this invention.

[0004] Third- and fourth-generation mobile telecommunications systems (such as those based on the UMTS and LTE architectures defined by 3GPP) are capable of supporting more complex services than the simple voice and messaging services provided by previous generations of mobile telecommunications systems. For example, leveraging the improved radio interfaces and enhanced data rates offered by LTE systems, users can enjoy high-data-rate applications previously only possible through fixed-line data connections, such as mobile video streaming and mobile video conferencing. Therefore, there is a strong demand for deploying such networks, and the coverage areas (i.e., geographical locations where network access is possible) of these and future networks are expected to increase rapidly.

[0005] Current and future wireless communication networks are expected to routinely and efficiently support communication with a wider range of devices, associated with a broader range of data traffic profiles and types than previously developed systems were optimized to support. For example, future wireless communication networks are expected to efficiently support communication with devices including reduced-complexity devices, machine-type communication (MTC) devices, high-resolution video displays, virtual reality headsets, and more. Some of these different types of devices can be deployed in very large numbers, such as low-complexity devices supporting the “Internet of Things”, and can typically be associated with the transmission of relatively small amounts of data with relatively high latency tolerance.

[0006] In light of this, it is expected that more advanced wireless communication networks (such as those that may be referred to as 5G or New Radio (NR) systems / New Radio Access Technology (RAT) systems) and future iterations / versions of existing systems will be needed to efficiently support connectivity for a wide range of devices associated with different applications and data traffic profiles with different characteristics.

[0007] One example area of ​​current focus in this regard includes so-called “non-terrestrial networks”, or NTN for short. 3GPP proposed in 3GPP specification version 15: develop technologies that provide coverage by one or more antennas mounted on air or space vehicles[1].

[0008] Non-terrestrial networks can provide service in areas not covered by terrestrial cellular networks (i.e., areas that provide coverage via ground-based antennas), such as isolated or remote areas, on aircraft or ships, or in other areas, providing enhanced service. The extended coverage that can be achieved through non-terrestrial networks can provide service continuity for passengers on machine-to-machine (M2M) or “Internet of Things” (IoT) devices, or mobile platforms such as passenger vehicles like airplanes, ships, high-speed trains, or buses. Using non-terrestrial networks to provide multicast / broadcast resources for data transmission can also offer other benefits.

[0009] The use of network infrastructure equipment and the demand for enhanced coverage have brought new challenges to the efficient processing of communications in wireless communication systems. Summary of the Invention

[0010] The aspects of the invention are defined in the appended claims.

[0011] The relevant aspects and features of this disclosure are defined in the appended claims.

[0012] It should be understood that the foregoing general description and the following detailed description are exemplary and not intended to limit the technology. The described embodiments and additional advantages will be best understood with reference to the following detailed description taken in conjunction with the accompanying drawings. Attached Figure Description

[0013] Because a more comprehensive understanding of the present disclosure and its many additional advantages becomes better understood when considered in conjunction with the accompanying drawings and with reference to the following detailed description, and thus they will be readily available, wherein the same reference numerals refer to the same or corresponding parts in several figures, and in the figures: Figure 1 schematically illustrates some aspects of an LTE-type wireless telecommunication system that can be configured to operate according to some embodiments of the present disclosure; Figure 2 schematically illustrates some aspects of a novel radio access technology (RAT) wireless telecommunication system that can be configured to operate according to some embodiments of the present disclosure; Figure 3 is a schematic block diagram of an example infrastructure equipment and communication apparatus configured according to an example embodiment; Figure 4A is quoted from [1] and illustrates a non-terrestrial network (NTN) The first example is an NTN characterized as an access network based on a satellite / airborne platform with a bend-tube payload; Figure 4B is cited from [1] and shows a second example of an NTN characterized as an access network based on a satellite / airborne platform including a gNodeB; Figure 5 is cited from [1] and shows a third example of an NTN characterized as an access network including a serving relay node and based on a satellite / airborne platform with a bend-tube payload; Figure 6 schematically shows an example of a wireless communication system including an NTN portion and a terrestrial network (TN) portion, which can be configured to operate according to embodiments of the present disclosure; Figures 7A and 7B respectively show NTN coverage of UEs that are not blocked by obstacles and are blocked by obstacles.

[0014] Figure 8 shows an example arrangement of the UE, NTN network portion, and TN network portion according to the example implementation.

[0015] Figure 9A illustrates a first example method for paging NTN UEs outside of coverage via a terrestrial network, where the NTN and the terrestrial network share the same core network.

[0016] Figure 9B illustrates a second example method for paging NTN UEs outside of coverage via a terrestrial network, where the NTN and the terrestrial network do not share the same core network.

[0017] Figure 9C illustrates a third example method for paging NTN UEs outside of coverage via a terrestrial network, where the NTN and the terrestrial network share the same core network.

[0018] Figure 9D illustrates a fourth example method for paging NTN UEs outside of coverage via a terrestrial network, where the NTN and the terrestrial network do not share the same core network.

[0019] Figure 10A illustrates a first example method for a communication device.

[0020] Figure 10B illustrates a second example method for a communication device.

[0021] Figure 11 illustrates an example method for infrastructure equipment used in terrestrial networks.

[0022] Figure 12A illustrates a first example method for the core network section of a non-terrestrial network.

[0023] Figure 12B illustrates a first example method for the core network section of non-terrestrial networks and terrestrial networks.

[0024] Figure 12C illustrates a second example method for the core network section of a non-terrestrial network.

[0025] Figure 12D illustrates a first example method for the core network section of a terrestrial network.

[0026] Figure 12E illustrates a second example method for the core network section of both non-terrestrial and terrestrial networks.

[0027] Figure 12F illustrates a third example method for the core network section of a non-terrestrial network.

[0028] Figure 12G illustrates a second example method for the core network section of a terrestrial network.

[0029] Figure 13 illustrates an example method for paging NTN UEs outside of paging coverage.

[0030] Figure 14 illustrates an example method for a communication device.

[0031] Figure 15 illustrates an example method for non-terrestrial infrastructure equipment used in non-terrestrial networks. Detailed Implementation

[0032] 4G (Long Term Evolution) Advanced Radio Access Technology

[0033] Figure 1 provides a schematic diagram illustrating some basic functions of a mobile telecommunications network / system 100 that typically operates according to LTE principles, but may also support other radio access technologies and may be adapted to implement the embodiments of this disclosure as described herein. Some aspects of the various elements of Figure 1 and their corresponding operating modes are well known and defined in relevant standards managed by the 3GPP (RTM) organization, and described in numerous books on the subject (e.g., Holma H. ​​and Toskala A [2]). It should be understood that operational aspects of the telecommunications network discussed herein that are not specifically described (e.g., regarding specific communication protocols and physical channels for communication between different elements) can be implemented according to any known technology (e.g., according to relevant standards and modifications and additions to known recommendations of relevant standards).

[0034] Network 100 includes multiple base stations 101 connected to core network unit 102. Each base station provides a coverage area 103 (e.g., a communication cell) within which data can be transmitted to and from communication device 104. Data is transmitted from base station 101 to communication device 104 within its respective coverage area 103 via a radio downlink. Data is transmitted from communication device 104 to base station 101 via a radio uplink. Core network unit 102 routes data to and from communication device 104 via the respective base station 101 and provides functions such as authentication, mobility management, and billing. Communication device may also be referred to as mobile station, user equipment (UE), user terminal, mobile radio, terminal device, etc. Base stations, as examples of network infrastructure equipment / network access nodes, may also be referred to as transceiver station / nodeB / e-nodeB (eNB) / g-nodeB (gNB), etc. In this respect, different terms are generally associated with different generations of wireless telecommunication systems that provide elements for providing a wide range of comparable functions. However, the exemplary implementations of this disclosure can be equivalently implemented in different generations of wireless telecommunication systems (such as 5G or newer types of radio as explained below), and for simplicity, some terminology may be used regardless of the underlying network architecture. That is, the use of specific terminology with respect to some exemplary implementations is not intended to indicate that these implementations are limited to a particular generation of networks that may be most associated with that particular term.

[0035] New radio access technology (5G NR)

[0036] Figure 2 is a schematic diagram illustrating the network architecture of a novel RAT wireless communication network / system 200 based on previously proposed methods, which can also be adapted to provide the functionality of embodiments of the present disclosure described herein. The novel RAT network 200 shown in Figure 2 includes a first communication cell 201 and a second communication cell 202. Each communication cell 201, 202 includes control nodes (centralized units) 221, 222 that communicate with the core network component 210 via corresponding wired or wireless links 251, 252. The corresponding control nodes 221, 222 also communicate with multiple distributed units (radio access nodes / remote transmit and receive points (TRPs)) 211, 212 in their respective cells. Again, these communications can be conducted via corresponding wired or wireless links. Distributed units (DUs) 211, 212 are responsible for providing radio access interfaces for communication devices connected to the network. Each distributed unit 211, 212 has a coverage area (radio access range) 241, 242, wherein the sum of the coverage areas of the distributed units under the control of the control node collectively defines the coverage range of the corresponding communication cell 201, 202. Each distributed unit 211, 212 includes transceiver circuitry for transmitting and receiving radio signals and processor circuitry configured to control the corresponding distributed unit 211, 212.

[0037] In terms of overall top-level functionality, the core network component 210 of the novel RAT communication network shown in Figure 2 can be broadly considered to correspond to the core network 102 shown in Figure 1, and the corresponding control nodes 221, 222 and their associated distributed units / TRPs 211, 212 can be broadly considered to provide functions corresponding to the base station 101 in Figure 1. The term "network infrastructure equipment / access node" can be used to include these elements as well as more conventional base station-type elements of the wireless communication system. Depending on the application, the responsibility for scheduling transmissions on the radio interface between the corresponding distributed unit and the communication device can be undertaken by the control node / central unit and / or the distributed unit / TRP.

[0038] The communication device or UE 260 is shown in Figure 2 within the coverage area of ​​the first communication cell 201. Therefore, the communication device 260 can exchange signaling with the first control node 221 in the first communication cell through a distributed unit 211 associated with the first communication cell 201. In some cases, communication for a given communication device is routed through only one distributed unit; however, it should be understood that in some other implementations, communication associated with a given communication device can be routed through more than one distributed unit (e.g., in soft handover scenarios and other scenarios).

[0039] In the example in Figure 2, for simplicity, two communication cells 201 and 202 and one communication device 260 are shown, but it should be understood that in implementation, the system may include a larger number of communication cells (each with its own control node and multiple distributed units supporting it) serving a larger number of communication devices.

[0040] It should be further understood that Figure 2 presents only one example of the architecture of the proposed novel RAT communication system, in which the methods based on the principles described herein can be employed, and the functions disclosed herein can also be applied to wireless communication systems with different architectures.

[0041] Therefore, the exemplary embodiments of this disclosure discussed herein can be implemented in wireless telecommunication systems / networks according to various different architectures (such as the example architectures shown in Figures 1 and 2). Thus, it should be understood that the specific wireless telecommunication architecture in any given implementation is not particularly important to the principles described herein. In this regard, the exemplary embodiments of this disclosure are generally described in the context of communication between network infrastructure devices / access nodes and communication devices, wherein the specific nature of the network infrastructure devices / access nodes and communication devices will depend on the network infrastructure used for the implementation in question. For example, in some scenarios, the network infrastructure devices / access nodes may include base stations (such as the LTE-type base station 101 shown in Figure 1) adapted to provide the functions according to the principles described herein, and in other examples, the network infrastructure devices / access nodes may include control units / control nodes 221, 222 and / or TRPs 211, 212 of the type shown in Figure 2, adapted to provide the functions according to the principles described herein.

[0042] Figure 3 shows a more detailed illustration of communication device 270 and example network infrastructure device 272, which can be considered as an eNB or gNB 101 or a combination of control node 221 and TRP 211. As shown in Figure 3, communication device 270 is shown sending uplink data to infrastructure device 272 via radio access interface, approximately indicated by arrow 274. UE 270 is shown receiving downlink data sent by infrastructure device 272 via resources of radio access interface, approximately indicated by arrow 288. Similar to Figures 1 and 2, infrastructure device 272 is connected to core network 276 (which may correspond to core network 102 of Figure 1 or core network 210 of Figure 2) via interface 278 to connect to controller 280 of infrastructure device 272. Infrastructure device 272 can also connect to other similar infrastructure devices via inter-radio access network node interface (not shown in Figure 3).

[0043] Infrastructure device 272 includes a receiver 282 connected to antenna 284 and a transmitter 286 connected to antenna 284. Correspondingly, communication device 270 includes a controller 290 connected to receiver 292 (which receives signals from antenna 294) and a transmitter 296 also connected to antenna 294.

[0044] Controller 280 is configured to control infrastructure device 272 and may include processor circuitry, which in turn may include various sub-units / sub-circuits for providing the functions as further explained herein. These sub-units may be implemented as independent hardware elements or as appropriately configured functions of processor circuitry. Therefore, controller 280 may include circuitry systems appropriately configured / programmed to provide the desired functions using conventional programming / configuration techniques for devices in wireless telecommunications systems. Transmitter 286 and receiver 282 may include signal processing and RF filters, amplifiers, and circuitry arranged according to conventional methods. For ease of illustration, transmitter 286, receiver 282, and controller 280 are schematically shown as independent elements in FIG. 3. However, it should be understood that the functionality of these elements may be provided in various different ways, such as using one or more appropriately programmed programmable computers, or one or more appropriately configured application-specific integrated circuits / circuitry systems / chips / chipsets. As should be understood, infrastructure device 272 will generally include various other elements associated with its operational functions.

[0045] Correspondingly, the controller 290 of the communication device 270 is configured to control the transmitter 296 and the receiver 292, and may include processor circuitry, which may further include various sub-units / sub-circuits for providing the functions as further explained herein. These sub-units may be implemented as independent hardware elements or as appropriately configured functions of the processor circuitry. Thus, the controller 290 may include a circuitry system appropriately configured / programmed to provide the desired functions using conventional programming / configuration techniques for devices in a wireless telecommunications system. Similarly, the transmitter 296 and the receiver 292 may include signal processing and RF filters, amplifiers, and circuitry systems arranged according to conventional methods. For ease of illustration, the transmitter 296, receiver 292, and controller 290 are schematically shown as independent elements in FIG3. However, it should be understood that the functions of these elements may be provided in various different ways, such as using one or more appropriately programmed programmable computers, or one or more appropriately configured application-specific integrated circuits / circuitry systems / chips / chipsets. It should be understood that the communication device 270 will typically include various other components associated with its operational functions, such as power supply, user interface, etc., but for simplicity, these are not shown in Figure 3.

[0046] Controllers 280 and 290 can be configured to execute instructions stored on a computer-readable medium, such as non-volatile memory. The processing steps described herein can be implemented, for example, by a microprocessor in conjunction with random access memory (which may be non-volatile memory), which operates according to instructions stored on the computer-readable medium.

[0047] Non-terrestrial networks (NTN)

[0048] An overview of NR-NTN can be found in [1], and most of the following content, as well as Figures 4A, 4B and 5, are cited from that document as background information.

[0049] Due to the wide service coverage and the reduced vulnerability of space / airborne vehicles to physical attacks and natural disasters, non-terrestrial networks are expected to: Promote the rollout of 5G services in unserved areas (isolated / remote areas, on airplanes or ships) where terrestrial 5G networks cannot cover, and in underserved areas (such as suburban / rural areas) to upgrade the performance of limited terrestrial networks in a cost-effective manner; Enhancing the reliability of 5G services by providing service continuity to passengers on M2M / IoT devices or mobile platforms (e.g., passenger vehicles—airplanes, ships, high-speed trains, buses) or ensuring service availability anywhere (especially for critical communications, future rail / maritime / aviation communications); and 5G networks achieve scalability by providing efficient multicast / broadcast resources to deliver data to the network edge and even user terminals.

[0050] These benefits relate to standalone non-terrestrial networks (NTNs) or integrated terrestrial and non-terrestrial networks. They will impact at least coverage, user bandwidth, system capacity, service reliability or availability, energy consumption, and connection density. The anticipated role of non-terrestrial network components in 5G systems is expected to extend to at least the following verticals: transportation, public safety, media and entertainment, eHealth, energy, agriculture, finance, and the automotive industry. It should also be noted that the same NTN benefits apply to 4G and / or LTE technologies, and although NR is sometimes mentioned in this disclosure, the teachings and techniques presented herein are equally applicable to 4G and / or LTE.

[0051] Figure 4A illustrates a first example of an NTN architecture based on a satellite / airborne platform (which can be referred to as a non-terrestrial infrastructure device) with a U-shaped payload. This means that data received by the satellite / airborne platform is transmitted back to the ground as is, with only the frequency or amplification factor changed; that is, it works like a pipe with a U-shaped bend. In this example NTN, the satellite or airborne platform will transparently relay NR (or LTE) signals between the gNodeB (or eNodeB) and the UE. In such examples, the UE can be considered as receiving signals from the satellite, even though the signal originates from the gNodeB (or eNodeB) and the satellite transparently relays the signal to the UE.

[0052] Figure 4B illustrates a second example of an NTN architecture based on a satellite / airborne platform (which may also be referred to as non-terrestrial infrastructure equipment), which includes a gNodeB (or an eNodeB in this example disclosure). In this example NTN, the satellite or airborne platform carries a complete or partial gNodeB to generate NR signals to or receive NR signals from the UE. For example, in addition to frequency conversion and amplification, the satellite / airborne platform can also decode the received signals. This requires the satellite or airborne platform to have sufficient onboard processing capabilities to include gNodeB or eNodeB functionality.

[0053] Figure 5 illustrates a first example of an NTN architecture based on a satellite / airborne platform (which may be referred to as a non-terrestrial infrastructure device) with a bendable payload and including relay nodes. In this example NTN, the satellite or airborne platform will transparently relay NR (or LTE) signals between the gNodeB (or eNodeB) and the (terrestrial) relay nodes. In such examples, the relay can be considered as receiving signals from the satellite, even though the signal originates from the gNodeB (or eNodeB) and the satellite transparently relays the signal to the UE. The UE can then communicate with the NTN through the relay nodes. It should also be understood that examples of NTNs can be implemented based on a satellite / airborne platform including a gNodeB (or an eNodeB in this disclosure example), wherein the NTN includes relay nodes, as shown in Figure 5.

[0054] Figure 6 schematically illustrates an example of a wireless communication system 300 that can be configured to operate according to embodiments of this disclosure. The wireless communication system 300 in this example is generally based on an LTE-type or 5G-type architecture. Many aspects of the operation of the wireless communication system / network 300 are well known and will not be described in detail here for the sake of brevity. Operational aspects of the wireless communication system 300 not specifically described herein can be implemented according to any known technology, such as current LTE or 5G standards.

[0055] The wireless communication system 300 includes a core network unit 302 (which may be a 4G core network or a 5G core network) communicatively connected to a radio network unit. The radio network unit may include a ground station 301 connected to a non-terrestrial network unit 310. The non-terrestrial network unit 310 may be an example of infrastructure equipment. Alternatively or additionally, the non-terrestrial network unit 310 may be mounted on a satellite launch vehicle or an airborne vehicle. In some cases, base stations (e.g., g-nodeB / e-nodeB) may be implemented entirely in the ground station 301 or in the non-terrestrial network unit 310, or may be partially implemented in one or both of the ground station 301 and / or the non-terrestrial network unit 310.

[0056] The non-terrestrial network portion 310 can communicate with the communication device 306 located within cell 308 via a wireless access interface provided by wireless communication link 314. For example, cell 308 may correspond to the coverage area of ​​a spot beam generated by the non-terrestrial network portion 310. The boundary of cell 308 may depend on the height of the non-terrestrial network portion 310 and the configuration of one or more antennas of the non-terrestrial network portion 310, through which the non-terrestrial network portion 310 transmits and receives signals on the wireless access interface.

[0057] The non-terrestrial network segment 310 can be a satellite in orbit relative to the Earth, or can be mounted on such a satellite. For example, the satellite can be in geostationary orbit (GEO), such that the non-terrestrial network segment 310 does not move relative to a fixed point on the Earth's surface. The geostationary orbit can be located approximately 36,786 km above the Earth's equator. The satellite can also be in low Earth orbit (LEO), where the non-terrestrial network segment 310 can complete its orbital journey around the Earth relatively quickly, thereby providing moving cell coverage. Alternatively, the satellite can be in any other non-geostationary orbit (NGSO), such that the non-terrestrial network segment 310 moves relative to a fixed point on the Earth's surface. The non-terrestrial network segment 310 can be an airborne vehicle such as an aircraft, or can be mounted on such a vehicle. The airborne vehicle (and therefore the non-terrestrial network segment 310) can remain stationary relative to the Earth's surface or can move relative to the Earth's surface.

[0058] In Figure 6, ground station 301 is shown as ground-based and connected to non-terrestrial network portion 310 via wireless communication link 312. Non-terrestrial network portion 310 receives signals representing downlink data transmitted by base station 301 on wireless communication link 312, and based on the received signals, transmits signals representing downlink data via wireless communication link 314, which provides a wireless access interface for communication device 306. Similarly, non-terrestrial network portion 310 receives signals representing uplink data transmitted by communication device 306 via a wireless access interface including wireless communication link 314, and transmits signals representing uplink data to ground station 301 on wireless communication link 312. Wireless communication links 312 and 314 may operate at the same frequency or at different frequencies.

[0059] The extent to which the non-terrestrial network portion 310 processes the received signal may depend on its processing capabilities. For example, the non-terrestrial network portion 310 may receive signals representing downlink data on the wireless communication link 312, amplify these signals, and (if necessary) remodulate them to an appropriate carrier frequency for forwarding through the wireless access interface provided by the wireless communication link 314. Alternatively, the non-terrestrial network portion 310 may be configured to decode the signals representing downlink data received on the wireless communication link 312 into uncoded downlink data, recode the downlink data, and modulate the encoded downlink data to an appropriate carrier frequency for forwarding through the wireless access interface provided by the wireless communication link 314.

[0060] The non-terrestrial network portion 310 can be configured to perform some functions traditionally performed by a base station (e.g., a gNodeB or eNodeB) (such as base station 101 in Figure 1). Specifically, delay-sensitive functions (such as acknowledging the receipt of uplink data or responding to RACH requests) can be performed by the non-terrestrial network portion 310, which partially implements some of the functions of the base station.

[0061] As described above, the base station can be co-located with the non-terrestrial network portion 310; for example, both can be installed on the same satellite launch vehicle or airborne vehicle, and a physical (e.g., wired or fiber optic) connection can exist on the satellite launch vehicle or airborne vehicle, thereby providing connectivity between the base station and the non-terrestrial network portion 310. In such a co-located arrangement, a wireless communication feeder link between the base station and the ground station 301 can provide connectivity between the base station (co-located with the non-terrestrial network portion 310) and the core network portion 302.

[0062] Ground station 301 may be an NTN gateway, configured to transmit signals to the non-terrestrial network portion 310 and communicate with the core network portion 302 via wireless communication link 312. That is, in some examples, ground station 301 may not include base station functionality. For example, as described above, if the base station is co-located with the non-terrestrial network portion 310, ground station 301 does not implement base station functionality. In other examples, the base station may be co-located with the NTN gateway located in ground station 301, enabling ground station 301 to perform base station (e.g., gNodeB or eNodeB) functionality.

[0063] In some examples, even if the base station is not co-located with the non-terrestrial network portion 310 (so that the base station function is implemented by the terrestrial component), the ground station 301 does not necessarily implement the base station function. In other words, the base station (e.g., a gNodeB or eNodeB) may not be co-located with the ground station 301 (NTN gateway). In this way, the ground station 301 (NTN gateway) transmits signals received from the non-terrestrial network portion 310 to the base station (not shown in Figure 6). In this example, the base station (e.g., a gNodeB or eNodeB) may be considered part of the core network portion 302, or it may be separate from the core network portion 302 (not shown in Figure 6) and logically located between the ground station 301 (NTN gateway) and the core network portion 302.

[0064] In some cases, the communication device 306 shown in FIG. 6 can be a terminal device. However, in other cases, the communication device 306 shown in FIG. 6 can be configured as a relay node. That is, the communication device 306 can provide a connection to one or more terminal devices (such as terminal device 304). When acting as a relay node, the communication device 306 sends data to and receives data from the terminal device 304, and relays data to the ground station 301 via the non-terrestrial network section 310. As a relay node, the communication device 306 can provide a connection to the core network section 302 for terminal devices within the transmission range of the communication device 306.

[0065] In some cases, the non-terrestrial network portion 310 is also connected to the ground station 320 via a wireless link 322. The ground station may be operated by a satellite operator (which may be the same as or a different operator from the mobile operator of the core and / or radio network), and link 322 may be used as a management link and / or for exchanging control information. In some cases, once the non-terrestrial network portion 310 identifies its current location and speed, it may send location and speed information to the ground station 320. The location and speed information may be shared appropriately, for example, with one or more of the UE 306, ground station 301, and base station, to configure wireless communications accordingly (e.g., via links 312 and / or 314).

[0066] Temporarily lost NTN connection

[0067] As discussed above, NTN cell 308 may correspond to the coverage area of ​​the spot beam generated by non-terrestrial network portion 310. Therefore, the non-terrestrial network coverage of communication device 306 located within cell 308 may depend on whether communication device 306 has a good line of sight (LOS) with non-terrestrial network portion 310. For example, the LOS between communication device 306 and non-terrestrial network portion 310 may be interrupted or obstructed by, for example, buildings, foliage, tunnels, or other obstacles, or communication device 306 may be indoors.

[0068] Figure 7A illustrates an example arrangement of a cell 708 provided by a non-terrestrial network portion 710, where a UE (or any other communication device) 706 located within cell 708 can access the network via a connection to the non-terrestrial network portion 710. In the example of Figure 7A, an obstacle 720 is present, but this obstacle does not obstruct the LOS between the UE 706 and the non-terrestrial network portion 710, allowing the UE 706 to still reliably receive transmissions from and / or send transmissions to the non-terrestrial network portion 710. However, as shown in Figure 7B, in some cases, the UE 706 may move relative to the obstacle 702, potentially obstructing the LOS between the UE 706 and the non-terrestrial network portion 710. In the example shown in Figure 7B, the UE 706 has moved indoors; however, even if the UE 706 is not indoors, the obstacle may still obstruct the LOS between the UE 706 and the non-terrestrial network portion 710. If the LOS between UE 706 and the non-terrestrial network portion 710 is blocked, UE 706 may be unable to reliably receive transmissions from and / or send transmissions to the non-terrestrial network portion 710. In other words, UE 706 may move out of the coverage area of ​​the non-terrestrial network portion 710 (and the entire NTN), even though it is within the geographical area of ​​cell 708 (i.e., the coverage area) provided by the non-terrestrial network portion 710.

[0069] When UE 706 temporarily moves out of NTN's coverage area in this manner, NTN can still identify downlink transmissions to be sent to UE 706. Therefore, NTN can determine that UE 706 should be paged by NTN to wake it up. That is, when UE 706 is within NTN's coverage area, NTN can page UE 706 using known paging procedures of 4G or 5G networks, as described in [3] and [4]. When connected to NTN, UE 706 can enter a relatively low-power state (such as RRC idle or RRC inactive state), in which UE 706 can periodically monitor paging messages from NTN that indicate that UE 706 should wake up (i.e., switch to a relatively high-power state, such as RRC connected state) to receive downlink transmissions. However, when UE 706 loses its connection with NTN, NTN cannot page UE 706 because UE 706 will not receive paging messages. Therefore, UE 706 will not wake up to receive downlink transmissions for UE 706.

[0070] This invention identifies a method for reliably paging a communication device that has moved out of the coverage area of ​​a non-terrestrial network. Figure 8 illustrates an example of a UE 820 registering with both a non-terrestrial network (NTN) 801 and a terrestrial network (TN) 802. Terrestrial network 802 includes a core network 835, and NTN 801 also includes a core network 815. NTN 801 and terrestrial network 802 may have independent core networks 815 and 835, or they may share the same core network 825. In this case, there is no signaling between the core network of NTN 801 and the core network of terrestrial network 802 because they are the same logical entity. Additionally, NTN 801 and terrestrial network 802 can communicate via their respective core networks (NTN core network 815 and terrestrial core network 835, and / or shared core network 825), or via a wireless access interface (e.g., the Xn interface) between the terrestrial infrastructure equipment 830 of terrestrial network 802 and the infrastructure equipment (IE) 810 (terrestrial or non-terrestrial) of NTN 801. Furthermore, the steps performed by NTN 801 as discussed later herein can be performed by non-terrestrial infrastructure equipment 810, or NTN core network 815, or both. Similarly, the steps performed by terrestrial network 802 as discussed later herein can be performed by terrestrial infrastructure equipment 830, or terrestrial core network 835, or both. Furthermore, although the process discussed herein describes UE 820 as communicating with NTN IE 810, it should be understood that due to the movement of NTN IE 810, UE 820 may actually communicate with different NTN IE 810 for parts or each step of the process described herein.

[0071] Figure 9A illustrates a first example arrangement of paging UE 820, where NTN 801 and TN 802 share the same core network 825 (i.e., operated by the same provider or the core network is shared by multiple operators). In step 941, UE 820 registers with core network 825. This can occur at any time, such as immediately before or significantly earlier than subsequent steps in Figure 9A (e.g., when UE 820 is powered on). UE 820 can register with the core network via NTN IE 810, or TN base station 830, or both. In step 942, NTN IE 810 sends (e.g., broadcasts) one or more reference signals 942 for UE 820 to receive (e.g., periodically). Reference signals 942 can be any form of reference signal whose strength UE 820 can measure. For example, reference signal 942 can be a synchronization signal block (SSB), or it can be a different form of downlink reference signal. UE 820 measures the received strength of reference signal 942 (e.g., periodically). That is, UE 820 may measure the strength of each reference signal 942, or only a subset of reference signals 942 transmitted by NTN IE 810. UE 820 measures the strength of reference signal 942 to determine whether UE 820 has sufficient link budget (i.e., whether the connection between NTN IE 810 and UE 820 is strong enough) to receive downlink transmissions from NTN IE 810. When measuring the strength of reference signal 942, UE 820 may measure one or more different signal strength metrics. For example, UE 820 may measure Reference Signal Received Power (RSRP), Received Signal Strength Indication (RSSI), Received Signal-to-Noise Ratio (RSNR), or any other metric of signal strength or quality. UE 820 may measure the strength of reference signal 942 in low-power modes (e.g., RRC idle or RRC inactive modes) or high-power modes (e.g., RRC connected modes).

[0072] UE 820 compares the measured signal strength of reference signal 942 with a predetermined (network configuration) threshold to determine whether UE 820 has sufficient link budget. In an arrangement such as that shown in Figure 7A, the UE and NTN IE 810 have a clear LOS, and the measured signal strength of reference signal 942 is above the predetermined threshold, causing UE 820 to determine that it has sufficient link budget to reliably receive downlink transmissions from NTN IE 810. Conversely, in an arrangement such as that shown in Figure 7B, UE 820 and NTN IE 810 do not have a clear LOS, and the measured signal strength of reference signal 942 is below the predetermined threshold, causing UE 820 to determine that it does not have sufficient link budget to reliably receive downlink transmissions from NTN IE 810. In the example of Figure 9A, when measurement 943 is received from reference signal 942 of NTN IE 810, UE 820 determines that the received strength of reference signal 942 is below a predetermined threshold, causing UE 820 to lack sufficient link budget to reliably receive downlink transmissions from NTN IE 810. When UE 820 determines that there is insufficient link budget, UE 820 can determine that it has lost connection with NTN IE 810 (and therefore lose connection with the entire NTN 801). Furthermore, UE 820 can determine that it has lost connection with NTN IE 810 based on the received strength of reference signal 942 being below a predetermined threshold for a set number of paging occasions, paging cycles, or measurement cycles. For example, UE 820 can determine that it has lost connection with UE 810 based on the received strength of reference signal 942 being below a predetermined threshold for a set number of consecutive measurement / paging occasions / cycles, or based on the received strength of reference signal 942 being below a predetermined threshold for a specific threshold percentage of measurement / paging occasions / cycles. When UE 820 fails to find its NTN Public Land Mobile Network (PLMN), UE 820 can cooperate with the Non-Access Stratum (NAS) layer to perform out-of-coverage detection (for NTN 801).

[0073] Based on the determination that UE 820 has lost its connection with NTN IE 810, UE 820 sends an indication 944A to TN base station 830 of TN 802 indicating that the NTN connection has been lost. In other words, UE 820 notifies TN base station 830 of 944A that the UE is (temporarily) outside the coverage area of ​​NTN 801. In some cases, this can be performed when establishing a connection with terrestrial network 802. For example, the indication 944A that UE 820 is not within the coverage area of ​​NTN 801 can be included in an RRC establishment completion message (for indicating relatively early that UE 820 is outside the coverage area of ​​NTN 801), or in UE assistance information and / or RRC reconfiguration completion messages sent to TN IE 810 (for indicating secure transmission). Indication 944A can also / alternatively be sent in the RRC Establishment Request message (i.e., message 3 of the RACH procedure) to provide the terrestrial network 802 with indication 944A that UE 820 is outside the coverage area of ​​NTN 801 as early as possible; however, this message has a limited size. Besides being sent during the connection establishment process, or alternatively, indication 944A that UE 820 is outside the coverage area of ​​NTN 801 can be sent to the terrestrial network after UE 820 establishes a connection with TN IE 810. After receiving indication 944A from UE 820, TN base station 830 can forward the indication to core network 825, or it can generate its own indication 944B that UE 820 is outside the coverage area of ​​NTN 810 and send this indication 944B to core network 825.

[0074] Based on UE 820 notifying TN base station 830 that UE 820 has lost NTN 801 coverage, TN base station 830 configures paging resources for UE 820. UE 820 can receive paging configuration information from TN base station 830 (details of paging resources). In some examples, paging resources can be shared by multiple (or all) NTN UEs (such as UE 820) that have lost NTN coverage and UEs not registered to the terrestrial network 802. That is, the same paging resources can be used to paging both types of UEs. In some cases, in response to receiving indication 944A from UE 820, TN base station 830 configures paging resources for UE 820 and may instruct UE 820 to enter a low-power mode (such as RRC idle or RRC inactive mode). This configuration can be similar to that of a normal UE registered to terrestrial network 802, but in other examples, all NTN UEs (i.e., UEs such as UE 820 that have lost NTN coverage) can be assigned to the same paging group. As discussed above, the paging resources configured for NTN UE 820 can be the same as those used for paging terrestrial UEs (not registered to NTN), but the paging message content sent to NTN UE 820 can indicate that the paging is for NTN 801 service. This approach will result in the wake-up of all NTN and TN UEs (including UEs not interested in NTN services) because the paging resources may be monitored by a specific group of UEs. Sharing paging resources as described above can be beneficial when the total number of NTN UEs to be paged is relatively small, in order to avoid over-allocation of paging resources.

[0075] Unlike sharing paging resources between NTN UEs that have lost NTN coverage and terrestrial UEs not registered with NTN, in some examples, TN base station 830 can configure separate paging resources for UE 820 that has lost NTN 801 coverage and other UEs not registered with NTN 801. In other words, TN base station 830 configures paging resources only for UE 820 that has lost connection with NTN 801. These paging resources can be pre-configured (i.e., pre-allocated) to UEs that have lost connection with NTN (i.e., NTN UEs). Configuring separate paging resources in this way can be beneficial when paging a large number of NTN UEs is required, in order to avoid network congestion in specific resource clusters. Furthermore, when configuring separate paging resources in this way, TN base station 810 can configure separate paging discontinuous reception (DRX) cycles for NTN UE 820 in the TN cell and TN UEs in the same TN cell. In some cases, the TN base station 810 may determine whether to configure separate paging resources or share paging resources based on whether the total number of NTN UEs or the total number of general UEs (NTN UEs and non-NTN UEs) in a specific cell, tracking area, or other areas of the terrestrial network 802 exceeds a predetermined threshold.

[0076] In one example, these paging resources may be indicated in paging configuration information in the form of a Paging Configuration Channel (PCCH) configuration (which may also include RAN paging configuration). The PCCH configuration may be included in an information block (such as a System Information Block (SIB)) broadcast by the TN base station 830. Therefore, the UE may obtain paging configuration information during the registration process with the TN (e.g., if UE 820 registers via the TN base station 830). In addition to receiving the PCCH in the SIB or MIB, or as an alternative, UE 820 may request the PCCH configuration from the TN base station 810. Specifically, a periodic information block (such as an SIB or MIB) broadcast by the TN base station 810 may include an indication (e.g., a bit) indicating whether the TN base station 810 has a available PCCH configuration for the NTN UE 820 that has lost NTN 801 coverage. Based on this indication, UE 820 may send a request to the TN base station 810 for the PCCH configuration, which may be provided on demand by the TN base station 810 (e.g., in a System Information Block). UE 820, which loses coverage from NTN 801, can then camp on a TN cell that provides PCCH configuration (e.g., a cell provided by TN base station 810).

[0077] As discussed above, UE 820 can enter a low-power mode (and can be instructed to do so by NTN IE 810 or TN base station 830). For example, UE 820 can enter an idle mode (e.g., RRC idle mode), in which UE 820 maintains registration with core network 825, but in which, in low-power mode, UE 820 turns off its receivers and periodically wakes them up (as part of the DRX cycle) to check paging messages (e.g., paging messages from TN base station 830), which can instruct UE 820 to enter a high-power mode (i.e., a connected mode), such as RRC connected mode, by activating one or more of UE 820's receivers. Alternatively, UE 820 may enter an inactive mode (e.g., RRC inactive mode), in which the connection of UE 820 to NTN IE 810 or TN base station 810 is released and UE 820 turns off its receiver, but UE 820 periodically wakes up its receiver (as part of the DRX cycle) to check paging messages (e.g., paging messages from TN base station 810), which may instruct UE 820 to activate one or more of its receivers. UE 820 may be instructed to enter a low-power mode, or may enter a low-power mode without being instructed. In low-power mode, UE 820 may, in some cases, camp on a specific cell provided by TN base station 810 and therefore will not attempt to acquire or establish connections with other cells of the terrestrial network 802.

[0078] In low-power mode, UE 820 may continue to measure the signal strength of reference signal 942 transmitted by NTN 801 in some cases, or may not monitor reference signal 942 in others. Furthermore, UE 820 may allocate a higher measurement priority to the frequency / resources expected to carry NTN 801 reference signal 942 than to the frequency / resources of TN 802. Therefore, if a time conflict is expected between the transmission of NTN 801 reference signal 942 and TN 802, UE 820 will monitor NTN 801 reference signal 942. If UE 820 detects that the signal strength of reference signal 942 is higher than the aforementioned predetermined threshold, UE 820 may re-establish the connection with NTN 801. In this case, NTN 801 may indicate to TN base station 830 that UE 820 has re-established the connection with NTN 801. TN base station 830 may, in some cases, notify core network 825 that UE 820 has re-established the connection with NTN 801.

[0079] The core network 825 can identify at a specific time 945 that it has data to send to UE 820. In other words, the core network 825 can determine that it intends to send a downlink transmission to UE 820. Therefore, since the core network 825 learns that UE 820 has lost connection with NTN IE 810, the core network 825 sends an indication 946A to the TN base station 830 that UE 820 should be paged. Indication 946A can be sent to multiple TN base stations 830 (such as TN base stations 830 that provide a specific notification area (e.g., tracking area (TA)) or cell group in TN 802 where UE 820 is located), or indication 946A can be sent to only a single TN base station 830. Indication 946A can indicate the identifier and / or TA identifier of UE 820. Therefore, in some examples, the TN base station 830 may have already notified the core network 825 of UE 820's paging information.

[0080] Based on the received indication 946A that UE 820 will be paged, TN base station 830 sends a paging message 946B (or other notification message) to UE 820. In response to receiving (and successfully decoding) the paging message 946B, UE 820 may send an acknowledgment (not shown) to TN base station 830. The paging message 946B may include an identifier specifically for UE 820, or may refer to all UEs in the notification area, or all NTN UEs in the notification area. As discussed above, UE 820 may periodically monitor paging messages and may detect the paging message 946B from TN base station 830 at specific monitoring times. The paging message 946B may notify UE 820 that the core network 825 intends to send a downlink transmission to UE 820 via NTN IE 810. Therefore, when UE 820 is outside the coverage area of ​​NTN 801, UE 820 may generate an alarm for its user. The alarm can request or instruct the user to move UE 820 to an area covered by the improved NTN 801 (such as outdoors or away from obstacles). The core network 825 can also instruct the NTN IE 810 (948A) that UE 820 should be paged (i.e., instruct the NTN IE providing the tracking area for the cell where UE 820 is located). This may occur based on receiving an indication that the UE has been successfully paged by TN 802, or automatically after a predetermined amount of time has elapsed following an instruction to the TN base station 830 (946A) that UE 820 should be paged.

[0081] Alternatively, paging message 946B can notify UE 820 that core network 825 intends to send a downlink transmission to UE 820 via TN base station 830 and that UE 820 should wake up (i.e., re-establish connection with the TN base station) to receive the downlink transmission from TN base station 830. Core network 825 can then send data from UE 820 to TN base station 830, which can then send data to UE 820 in a downlink transmission.

[0082] Returning to the example where paging message 946B notifies UE 820 that the core network 825 intends to send a downlink transmission to UE 820 via NTN IE 810, after receiving paging message 946B, UE 820 begins monitoring 947 for paging message 948B from NTN IE 810. Monitoring 947 can begin immediately after receiving paging message 946B, or after a predetermined amount of time, allowing the user time to move UE 820 to an area with improved NTN coverage, or once UE 820 has good coverage with NTN 810 (e.g., the received strength of one or more reference signals 942 is above a predetermined threshold), the UE can initiate a paging response message via NTN IE 810. Once UE 820 moves to an area with improved NTN 801 coverage, UE 820 can receive NTN 801 reference signals 942 with signal strength exceeding a predetermined threshold, and can therefore select an NTN 801 cell for connection (i.e., UE 820 reconnects to NTN IE 810). UE 820 can then begin monitoring for paging messages 948B from NTN IE 810 by activating one or more receivers. UE 820 can do this automatically upon reconnecting to NTN IE 810, or it can be explicitly instructed to do so by NTN IE 810. NTN IE 810 can repeatedly send paging messages 948B to UE 820 a predetermined number of times (after sending paging indication 946A to TN 802) to provide sufficient time for UE 820 to relocate to a better NTN 801 coverage location. Therefore, UE 820 can receive paging message 948B from TN base station 830, which causes UE 820 to generate an alarm to prompt the user to move UE 820 to a better NTN 801 coverage location. UE 820 can then begin monitoring paging message 947 from NTN IE 810 at the appropriate time when paging message 948B is sent. NTN IE 810 can send a single paging message 948B, or it can send multiple paging messages 948B within a specific time period, such as periodically.

[0083] In response to detecting (i.e., decoding) a paging message 948B for UE 820 from NTN IE 810, UE 820 may send an indication (not shown) to NTN IE 810 whether it has received the paging message 948B (e.g., a paging response message as part of a NAS procedure). UE 820 may also send an indication (not shown) to TN base station 830 whether it has received the paging message 948B, each indication notifying core network 825. For example, if UE 820 receives the paging message, NTN IE 810 may indicate to core network 825 that UE 820 has reconnected to NTN 801. Conversely, if UE 820 does not receive the paging message 948B, TN base station 830 or NTN IE 810 may notify core network 925 after being informed by UE 820 that UE 820 has not received the paging message 948B. NTN IE 810 can then perform any number of operations, such as retransmitting paging message 948A, or the core network 825 can send another instruction 946A to TN base station 830 that TN base station 830 should page UE 820, to again prompt the user of UE 820 to move UE 820 to a location with improved NTN 801 coverage. Based on NTN IE 810's knowledge that UE 820 has received paging message 948B, NTN IE 810 can stop sending further paging messages 948B. Alternatively, the UE may decide to respond to the paging message via the TN by initiating an RRC connection request.

[0084] Based on the detection (i.e., decoding) of paging message 948B for UE 820 from NTN IE 810, UE 820 can begin monitoring specific downlink resources to receive downlink transmissions (not shown) from NTN IE 810, and can receive downlink transmissions on the monitored resources. Downlink resources may be indicated to UE 820 in some cases via paging messages from NTN IE 810, paging messages from TN base station 830, or independent transmissions from NTN IE 810, or may be pre-configured or predetermined so that UE 820 does not need to be informed of the resources to be monitored.

[0085] Therefore, by utilizing a terrestrial network that shares a core network with a non-terrestrial network, it is possible to page UEs that are registered to a non-terrestrial network but have lost non-terrestrial network coverage and instruct them to move to an area with improved non-terrestrial network coverage so that they can receive paging and downlink transmissions from the non-terrestrial network.

[0086] While Figure 9A illustrates a first example of NTN 801 and TN 802 sharing the same core network, it should be understood that in some cases, NTN 801 may have its own core network 815 separate from the core network 835 of TN 802. However, the steps discussed in conjunction with Figure 9A can be applied similarly. Figure 9B illustrates a second example of such a process, demonstrating communication between NTN core 815, TN core 835, TN base station 830, NT IE 810, and UE 820.

[0087] In step 950 of Figure 9B, UE 820 (via NTN IE 810) registers with NTN core network 815. This can happen at any time, such as immediately before or significantly before subsequent steps in Figure 9B (e.g., when UE 820 is powered on). In step 951, UE 820 (via TN base station 830) registers with TN core network 835. This can happen at any time, such as immediately before or significantly before subsequent steps in Figure 9B (e.g., when UE 820 is powered on), or in response to step 954 discussed below. NTN core network 815 and TN core network 835 can notify each other 952 that UE 820 has registered with the respective network. For example, when registering with TN core network 835, UE 820 can notify TN core network 835 (via TN base station 830) that UE 820 has also registered with NTN 801. Similarly, when registering with NTN core network 815, UE 820 can notify NTN core network 815 (via NTN IE 810) that UE 820 is also registering with TN 802.

[0088] NTN IE 810 transmits (e.g., broadcasts) one or more reference signals 953 for UE 820 to receive (e.g., periodically) in the same manner as discussed above in conjunction with reference signal 942 in Figure 9B. UE 820 measures the received strength of reference signal 953 954 in the same manner as measurement 943 in Figure 9A and determines whether it has lost connection with NTN IE 810 (i.e., NTN 801). Based on the determination that UE 820 has lost connection with NTN IE 810, UE 820 sends an indication 955A indicating that the NTN connection has been lost to TN base station 830 of TN 802 (as shown in Figure 9A). TN base station 830 can configure paging resources for UE 820 in the same manner as described in the relevant description of Figure 9A.

[0089] Based on the received indication 955A that UE 830 has lost its NTN connection, the TN base station can notify the TN core network 835 955B that UE 830 has lost its NTN connection, whereby the TN core network 835 can subsequently notify the NTN core network 815 955C that UE 830 has lost its NTN connection. Alternatively, the TN base station 830 can communicate directly with the NTN IE 810 via the radio access interface (i.e., via the Xn interface) to notify the NTN IE 810 that UE 830 has lost its NTN connection, whereby the NTN IE 810 can subsequently notify the NTN core network 815 that UE 830 has lost its NTN connection. Therefore, the NTN core network 815 can be aware that UE 820 has lost its NTN connection.

[0090] The NTN core network 815 can identify at a specific time 956 that it has data to send to UE 820 (in a manner similar to Figure 9A). Therefore, since the NTN core network 815 learns that UE 820 has lost connection with NTN IE 810, the NTN core network 815 sends an indication 957A to the TN core network 835 to page UE 820, and subsequently, the TN core network 835 sends an indication 957B to the TN base station 830 to page UE 820. Indication 957B can be sent to multiple TN base stations 830 (such as TN base stations 830 providing a specific notification area (e.g., tracking area (TA)) or cell group within the TN 802 where UE 820 is located), or indication 957B can be sent to only a single TN base station 830. Indication 957B can indicate the identifier of UE 820 or the TA identifier. Furthermore, in some examples, TN 802 may have already notified NTN core network 815 of UE 820's TN 820 notification area information (e.g., via TN core network 835 or NTN 810). Therefore, the instruction 957A sent to TN core network 835 can indicate the notification area of ​​TN 802 to be paged.

[0091] Based on the received instruction 957B that UE 820 will be paged, TN base station 830 sends a paging message 957C (or other notification message) to UE 820 in a manner similar to that discussed in conjunction with Figure 9A. That is, UE 820 and TN base station 830 can operate in the same manner as discussed in conjunction with Figure 9A. For example, in response to receiving (and successfully decoding) the paging message 957C, UE 820 can send an acknowledgment (not shown) to TN base station 830. UE 820 can generate an alarm for its user. The alarm can request or instruct the user to move UE 820 to an area covered by the improved NTN 801 (such as outdoors or away from obstacles). NTN core network 815 can also instruct NTN IE 810 959A that UE 820 should be paged (i.e., instruct the NTN IE providing the cell in the tracking area where UE 820 is located). This may occur based on receiving an indication that the UE has been successfully paged by TN 802, or automatically after a predetermined amount of time has elapsed after instructing TN core network 835 957A that UE 820 should be paged.

[0092] After receiving paging message 957C from TN base station 830, UE 820 begins monitoring paging message 959B from NTN IE 810 in a manner similar to that described in conjunction with FIG. 9A, or initiates a paging response message to NTN IE 810 or NTN core network 815 as described above. UE 820 and NTN IE 810 can operate in the same manner as discussed in conjunction with FIG. 9A. For example, in response to detecting (i.e. decoding) paging message 959B for UE 820 from NTN IE 810, UE 820 can send an indication to NTN IE 810 whether paging message 948B has been received, which can notify NTN core network 815. UE 820 can also send an indication (not shown) to TN base station 830 whether paging message 959B has been received, which can notify TN core network 835, which in turn can notify NTN core network 815.

[0093] Similar to the discussion in conjunction with Figure 9A, based on the detection (i.e., decoding) of the paging message 959B for UE 820 from NTN IE 810, UE 820 can begin monitoring specific downlink resources to receive downlink transmissions from NTN IE 810 (not shown), and can receive downlink transmissions on the monitored resources. Therefore, by utilizing a terrestrial network that does not share a core network with the non-terrestrial network, UEs registered to the non-terrestrial network but having lost non-terrestrial network coverage can be paginged and instructed to move to an area with improved non-terrestrial network coverage to receive paging and downlink transmissions from the non-terrestrial network.

[0094] While the examples in Figures 9A and 9B involve UE 820 indicating 944A and 955A to TN base station 830 when it loses connection with NTN IE 810, these steps may not be necessary in some examples. Figure 9C illustrates such an example where NTN 801 and TN share the same core network 825, as shown in Figure 9A. UE 820 registers with core network 825 in a manner similar to that discussed in conjunction with Figure 9A 961. UE 820 sends a notification area (e.g., tracking area) update 962 to core network 825 via NTN IE 810, indicating that UE 820 has entered or left a specific notification area of ​​the NTN cell. Similarly, UE 820 sends a notification area update 963 to core network 825 via TN base station 830, indicating when UE 820 entered or left a specific notification area of ​​the TN cell. Thus, core network 825 can know the last NTN and TN notification areas where UE 820 was located. It should be noted that notification area updates 962 and 963 can also be performed in the examples of Figures 9A and 9B, although not shown.

[0095] The core network 825 can identify at a specific time point 964 that it has data to send to UE 820 (in a manner similar to Figure 9A). Therefore, the core network 825 identifies 965 specific notification areas within the NTN notification area and TN notification area for paging UE 820. For example, the core network 825 can identify the notification area based on the perceived probability of successfully paging UE 820, based on the geographical size of the notification area, and / or based on the estimated number of UEs within the notification area. The core network 825 then issues a paging instruction 966A to the corresponding infrastructure equipment / base station of NTN 801 / TN 802. For example, the core network 825 can identify the NTN notification area in which UE 820 is to be paged, and therefore can send a paging instruction for UE 820 to the NTN IE 810 of that NTN notification area, whereby the NTN IE 810 can then send a paging message 966B to UE 820. Alternatively, the core network 825 can, for example, identify the TN notification area in which UE 820 is to be paged, and thus can send a pager instruction for UE 820 to the TN base station 830 in that TN notification area, wherein the TN base station 830 can then send a paging message to UE 820. More alternatively, the core network 825 can, for example, identify the TN notification area and the NTN notification area for pager UE 820, and thus can send a pager instruction for UE 820 to the TN base station 830 in the TN notification area and the NTN IE 810 in the NTN notification area, wherein the TN base station 830 and the NTN IE 810 can then send a paging message to UE 820.

[0096] If UE 820 successfully receives and / or decodes paging message 966B, UE 820 can send an acknowledgment of the paging message (not shown) to NTN IE 810 or TN base station 830, from which UE 820 receives paging message 966B. NTN IE 810 or TN base station 830 can then notify core network 825 of successful paging of UE 820. However, in some cases, the initial paging may fail, resulting in UE 820 not receiving paging message 966B or failing to successfully decode paging message 966B (e.g., due to poor coverage), or the acknowledgment not being successfully received or decoded at TN base station 830 or NTN IE 810. Therefore, core network 825 determines that paging of UE 820 was unsuccessful. Therefore, the core network 825 can identify one or more other notification areas to page UE 820 and send instruction 969A to the TN base station and / or NTN IE 810 in the other notification areas to page UE 820 969B. For example, if the core network 825 initially instructs paging in the NTN notification area, it can instruct paging in the TN notification area after determining that paging is unsuccessful. Similarly, if the core network 825 initially instructs paging in the TN notification area, it can instruct paging in the NTN notification area after determining that paging is unsuccessful. The core network 825 can also make additional or alternative changes to paging. For example, the core network 825 can determine that different notification areas within the same access network (i.e., NTN 810 or TN 802) should be paged in different paging attempts.

[0097] Therefore, by utilizing a terrestrial network that shares the core network with a non-terrestrial network, UEs can be flexibly paged in any notification area of ​​either the non-terrestrial or terrestrial network, ensuring that UEs can always be paged as long as they have a connection to the NTN or TN.

[0098] Figure 9D illustrates another example arrangement where UE 820 does not need to notify TN base station 830 that UE 820 has lost connection to NTN 801. However, NTN 801 and TN 802 do not share a core network; instead, NTN 801 has its own NTN core network 815 and TN 802 has its own TN core network 835. UE 820 registers with NTN core network 825 981 and TN core network 835 982 in a manner similar to that discussed in conjunction with Figure 9B. NTN core network 815 and TN core network 835 can notify each other 983 that UE 820 has registered to the corresponding network, as discussed in conjunction with Figure 9B. UE 820 can send a notification area (e.g., tracking area) update (not shown) to NTN core network 815 via NTN IE 810, indicating UE 820's entry into or departure from a specific notification area of ​​the NTN cell in a manner similar to the notification area update 962 in Figure 9C. Similarly, UE 820 can send a notification area update (not shown) to TN core network 835 via TN base station 830, indicating UE 820's entry into or departure from a specific notification area of ​​the TN cell in a manner similar to notification area update 963 in Figure 9C. In some cases, TN core network 835 can notify NTN core network 815 of the TN notification area in which UE 820 is believed to be located (e.g., in response to a notification area update from TN base station 830). Therefore, in some cases, NTN core network 815 can know the TN notification area in which UE 820 is believed to be located.

[0099] NTN core network 815 can identify at a specific time 984 that it has data to send to UE 820 (in a manner similar to Figure 9B). NTN core network 815 can therefore instruct 985A that NTN IE 810 of the NTN page UE 820. NTN IE 810 can then send one or more paging messages to UE 820. NTN core network 815 can determine that paging is unsuccessful in a manner similar to that described in conjunction with Figure 9C. Therefore, NTN core network 815 can send a request 987 to TN core network 835, wherein request 987 requests that UE 820 be paged by TN 802. Request 987 may include the identifier of UE 820 (TN core network 835 may cross-reference this identifier with a list of TN notification areas maintained by TN core network 835). Alternatively or additionally, request 987 may include an indication of the TN notification area where UE 820 is believed to be located (if NTN core network 815 has provided such information). The TN core network 835 then sends instruction 988A to one or more TN base stations 830 to page UE 820, wherein the TN base station 830 then sends one or more paging messages to UE 820.

[0100] Based on the received indication 988A that UE 820 will be paged, TN base station 830 sends a paging message 988B (or other notification message) to UE 820 in a manner similar to that discussed in conjunction with Figures 9A and 9B. That is, UE 820 and TN base station 830 can operate in the same manner as discussed in conjunction with Figures 9A and 9B. For example, in response to receiving (and successfully decoding) the paging message 988B, UE 820 can send an acknowledgment (not shown) to TN base station 830. UE 820 can generate an alarm for its user. The alarm can request or instruct the user to move UE 820 to an area covered by the improved NTN 801 (such as outdoors or away from obstacles). NTN core network 815 can also instruct NTN IE 810 990A that UE 820 should be paged (i.e., instruct the NTN IE providing the cell in the tracking area where UE 820 is located). This may occur based on receiving an indication that the UE has been successfully paged by TN 802, or automatically after a predetermined amount of time has elapsed after instructing TN core network 835 987 that UE 820 should be paged.

[0101] After receiving paging message 988B from TN base station 830, UE 820 begins monitoring paging message 990B from NTN IE 810 in a manner similar to that described in conjunction with Figures 9A and 9B. UE 820 and NTN IE 810 can operate in the same manner as discussed in conjunction with Figures 9A and 9B. For example, in response to detecting (i.e., decoding) paging message 990B for UE 820 from NTN IE 810, UE 820 can send an indication to NTN IE 810 whether paging message 990B has been received, which can notify NTN core network 815. UE 820 can also send an indication (not shown) to TN base station 830 whether paging message 990B has been received, which can notify TN core network 835, which in turn can notify NTN core network 815.

[0102] Similar to the discussion in conjunction with Figures 9A and 9B, based on the detection (i.e., decoding) of the paging message 990B for UE 820 from NTN IE 810, UE 820 can begin monitoring specific downlink resources to receive downlink transmissions from NTN IE 810 (not shown), and can receive downlink transmissions on the monitored resources. Therefore, by utilizing a terrestrial network that does not share a core network with the non-terrestrial network, UEs registered to the non-terrestrial network but having lost non-terrestrial network coverage can be paged and instructed to move to an area with improved non-terrestrial network coverage to receive paging and downlink transmissions from the non-terrestrial network without notifying the terrestrial network that the UE has lost NTN connectivity.

[0103] Furthermore, it should be understood that, although not discussed in conjunction with Figures 9C and 9D, in these examples, the NTN IE 810 can transmit a reference signal for reception by the UE 820 as described in conjunction with Figures 9A and 9B. Additionally, the UE 820 can measure the strength of the reference signal in the examples of Figures 9C and 9D in a manner similar to that described in conjunction with Figures 9A and 9B. Therefore, it should be understood that the steps of Figures 9A and 9C can be combined with each other in virtually any way, and the steps of Figures 9B and 9D can be combined with each other in virtually any way.

[0104] Figure 10A illustrates a flowchart of an example method for a communication device (such as UE820 discussed above in conjunction with Figures 8 and 9A-9D and 9B). In step 1001, the communication device measures the strength of one or more reference signals from one or more non-terrestrial infrastructure devices. Step 1002 includes: the communication device sending an indication to the terrestrial infrastructure devices of the terrestrial network that the communication device has moved out of the coverage area of ​​the NTN based on the measured strength of the one or more reference signals dropping below a predetermined threshold. Step 1003 includes: the communication device receiving a paging message from the terrestrial infrastructure devices.

[0105] Figure 10B illustrates a flowchart of an example method for a communication device (such as the UE 820 discussed above in conjunction with Figures 8 and 9A through 9D). In step 1011, the communication device receives a paging message from ground infrastructure equipment of the terrestrial network. In step 1012, based on the paging message received from the ground infrastructure equipment, the communication device generates an alarm for its user, wherein the alarm instructs the user to relocate the communication device to an area with improved NTN coverage. In step 1013, the communication device monitors for one or more paging messages from non-terrestrial infrastructure equipment of the NTN.

[0106] Figure 11 illustrates a flowchart of an example method for a terrestrial infrastructure device (such as infrastructure device 830 discussed above in conjunction with Figures 8 and 9A to 9D). In step 1101, the TN infrastructure device receives an indication from a communication device that the communication device has moved out of the NTN's coverage area. This communication device is configured to send uplink signals to one or more non-terrestrial infrastructure devices forming part of the NTN and / or receive downlink signals from one or more non-terrestrial infrastructure devices. In step 1102, the TN infrastructure device sends the indication that the communication device has moved out of the NTN's coverage area to the network portion of the NTN. In step 1103, the TN infrastructure device receives an indication that the communication device will be paged. In step 1104, the TN infrastructure device sends a paging message to the communication device.

[0107] Figure 12A shows a flowchart of an example method for a core network unit of an NTN (such as core network unit 815 or core network unit 825 discussed above in conjunction with Figures 8 and 9A to 9D). In step 1201, the core network unit receives an indication from the terrestrial network (TN) portion that a communication device has moved out of NTN coverage, the communication device being configured to send uplink signals to one or more non-terrestrial infrastructure devices forming part of the NTN and / or receive downlink signals from one or more non-terrestrial infrastructure devices. In step 1202, the core network unit sends an indication to the TN portion that the communication device should be paged by the TN. In step 1203, the core network unit sends a paging instruction to the non-terrestrial infrastructure devices of the NTN.

[0108] Figure 12B shows a flowchart of an example method for a core network unit (such as core network unit 825 discussed above in conjunction with Figures 8, 9A, and 9C) for NTN and TN. In step 1211, the core network unit receives an indication that a communication device of the NTN has lost NTN coverage. In step 1212, the core network unit sends an indication to the infrastructure equipment of the terrestrial network that the communication device should be paged by the terrestrial network.

[0109] Figure 12C shows a flowchart of an example method for an NTN core network unit (such as core network unit 815 discussed above in conjunction with Figures 8, 9B, and 9D). In step 1221, the core network unit receives an indication that the NTN communication device has lost NTN coverage. In step 1222, the core network unit sends an indication to the core network unit of the terrestrial network to which the communication device is registered that the communication device should be paged by the terrestrial network.

[0110] Figure 12D shows a flowchart of an example method for a core network unit of a TN (such as core network unit 835 discussed above in conjunction with Figures 8, 9B, and 9D). In step 1231, the core network unit receives an instruction from the core network unit of a non-terrestrial network (NTN) that the communication device should be paged by the terrestrial network. In step 1232, the core network unit sends a paging instruction to the infrastructure equipment of the terrestrial network.

[0111] Figure 12E shows a flowchart of an example method for a core network unit (such as core network unit 825 discussed above in conjunction with Figures 8, 9A, and 9C) for NTN and TN. In step 1241, the core network unit identifies one or more tracking areas among the first and second tracking areas based on multiple first tracking areas of the NTN and multiple second tracking areas of the terrestrial network, and in these one or more tracking areas, pagees a communication device registered with the core network unit. In step 1242, the core network unit sends instructions to one or more infrastructure devices associated with the identified one or more tracking areas to send a paging message for the communication device to receive.

[0112] Figure 12F shows a flowchart of an example method for an NTN core network unit (such as core network unit 815 discussed above in conjunction with Figures 8, 9B, and 9D). In step 1251, the core network unit sends a paging instruction to the NTN's non-terrestrial infrastructure equipment. In step 1252, based on the determination that paging is unsuccessful, the core network unit sends an instruction to the core network unit of the terrestrial network to which the communication device is registered, indicating that the communication device should be paging by the terrestrial network.

[0113] Figure 12G illustrates a flowchart of an example method for a core network unit (such as core network unit 835 discussed above in conjunction with Figures 8, 9B, and 9D) for a TN. In step 1261, the core network receives from the core network unit for non-terrestrial networks (NTNs) an instruction that a communication device registered with the core network unit of the terrestrial network should be paged by the terrestrial network. In step 1262, the core network unit sends instructions to one or more infrastructure devices of the terrestrial network to send a paging message for the communication device to receive.

[0114] While Figures 8 through 12G involve using a terrestrial network to page an NTN UE outside of coverage, in some cases, the UE may not be able to connect to any terrestrial network. For example, the UE may not be able to detect any terrestrial network with sufficient signal strength, or the UE may not be able to detect any terrestrial network with sufficient signal strength and connection permission. Therefore, the method described in conjunction with Figures 8 through 12 may not always be applicable.

[0115] Figure 13 illustrates an example procedure where the non-terrestrial infrastructure device (NTN IE) 1310 of NTN IE 1310 pages a UE 1320 outside its coverage area without using a terrestrial network. When the UE 1320 is within the coverage area of ​​a cell provided by the NTN (e.g., non-terrestrial infrastructure device 1310, such as non-terrestrial infrastructure device 710 or 810), the NTN IE 1310 and the UE 1320 exchange reference signals 1331 and 1333 with each other. Specifically, the NTN IE 1310 broadcasts / transmits the downlink reference signal 1331 for the UE 1320 to receive. The downlink reference signal 1331 can be any periodic reference signal whose strength the UE 1320 can measure. For example, the downlink reference signal 1331 can be an SSB, CSI-RS, or DM-RS, PRS, or any other reference signal. The UE 1320 periodically measures the received strength of the reference signal 1331. That is, UE 1320 can measure the strength of each reference signal 1331, or only the strength of a subset of all reference signals 1331 transmitted by NTN IE 1310. When measuring the strength of the reference signals 1331, UE 1320 can measure one or more different signal strength metrics. For example, UE 1320 can measure RSRP, RSSI, RSNR, or any other metric of signal strength or quality. UE 1320 can measure the strength of the reference signals 1331 in low-power modes (e.g., RRC idle or RRC inactive modes) or high-power modes (e.g., RRC connected modes).

[0116] UE 1320 compares the measured signal strength of reference signal 1331 with a predetermined threshold to determine whether UE 1320 has sufficient link budget. In an arrangement such as that shown in Figure 7A, UE 1320 has a clear LOS with the non-terrestrial network portion, and the measured signal strength of reference signal 1331 is higher than the predetermined threshold, causing UE 1320 to determine that it has sufficient link budget to reliably receive downlink transmissions from NTN IE 1310. Conversely, in an arrangement such as that shown in Figure 7B, UE 1320 does not have a clear LOS with the non-terrestrial network portion, and the measured signal strength of reference signal 1331 is lower than the predetermined threshold, causing UE 1320 to determine that it does not have sufficient link budget to reliably receive downlink transmissions from NTN IE 1310.

[0117] Before, during, and / or after NTN IE 1310 transmits downlink reference signal 1331 and UE 1320 measures downlink reference signal 1331, UE 1320 broadcasts / transmits uplink reference signal 1333 for NTN IE 1310 to receive, which measures uplink reference signal 1334. Uplink reference signal 1333 can be any periodic reference signal whose strength can be measured by NTN IE 1310 (i.e., non-terrestrial infrastructure equipment 1310). For example, uplink reference signal 1333 can be a sounding reference signal (SRS) or any other reference signal. NTN IE 1310 periodically measures the received strength of reference signal 1334. That is, NTN IE 1310 can measure the strength of each reference signal 1333, or only the strength of a subset of all reference signals 1333 transmitted by UE 1320. When measuring the strength of the reference signal 1333, the NTN IE 1310 can measure one or more different signal strength metrics. For example, the NTN IE 1310 can measure RSRP, RSSI, RSNR, or any other metric of signal strength or quality.

[0118] The NTN IE 1310 compares the measured signal strength of reference signal 1333 with a predetermined threshold to determine whether the NTN IE 1310 has sufficient link budget. The predetermined threshold for uplink reference signal 1333 can be the same as the predetermined threshold for downlink reference signal 1331. Alternatively, the predetermined threshold for uplink reference signal 1333 can be different from the predetermined threshold for downlink reference signal 1331. For example, the predetermined threshold for uplink reference signal 1333 can be lower than the predetermined threshold for downlink reference signal 1331, allowing the UE 1320 to transmit uplink reference signal 1333 at lower power. However, in some cases, the predetermined threshold for uplink reference signal 1333 can be greater than the predetermined threshold for downlink reference signal 1331. In an arrangement such as that shown in Figure 7A, NTN IE 1310 and UE 1320 have a clear LOS, and the measured signal strength of reference signal 1333 is above a predetermined threshold, causing NTN IE 1310 to determine that it has sufficient link budget to reliably transmit downlink data to UE 1320. Conversely, in an arrangement such as that shown in Figure 7B, NTN IE 1310 and UE 1320 do not have a clear LOS, and the measured signal strength of reference signal 1333 is below a predetermined threshold, causing NTN IE 1310 to determine that it does not have sufficient link budget to reliably transmit downlink data to UE 1320. Although UE 1320 is shown only in the context of FIG. 13 to transmit uplink reference signal 1333 and NTN IE 1310 is shown only in the context of FIG. 13 to measure the strength of uplink reference signal 1333, it should be understood that UE 1320 and NTN IE 1310 may perform the above-described steps related to uplink reference signal 1333 in all embodiments described herein, such as in those embodiments including those related to FIG. 8 through FIG. 12.

[0119] In the example of Figure 13, when measuring reference signal 1331 from NTN IE 1310 (1332), UE 1320 determines that the received strength of reference signal 1331 is below a predetermined threshold, causing UE 1320 to lack sufficient link budget to reliably receive downlink transmissions from NTN IE 1310. Similarly, in the example of Figure 13, when measuring reference signal 1333 from UE 1320 (1334), NTN IE 1310 determines that the received strength of reference signal 1333 is below a predetermined threshold, causing NTN IE 1310 to lack sufficient link budget to reliably transmit downlink transmissions to UE 1320. When UE 1320 determines that it lacks sufficient link budget, UE 1320 can determine that it has lost connection with NTN IE 1310. Furthermore, UE 1320 can determine that it has lost connection with NTN IE 1310 based on the received strength of reference signal 1331 falling below a predetermined threshold within a set number of paging opportunities, paging, or reference signal measurement cycles. For example, UE 1320 can determine that it has lost connection with NTN IE 1310 based on the received strength of reference signal 1331 falling below a predetermined threshold within a set number of consecutive measurement / paging opportunities / cycles, or based on the received strength of reference signal 1331 falling below a predetermined threshold within a specific threshold percentage of measurement / paging opportunities / cycles. Similarly, NTN IE 1310 can determine that it has lost connection with UE 1320 when NTN 801 determines that there is insufficient link budget. Additionally, NTN IE 1310 can determine that it has lost connection with UE 1320 based on the received strength of reference signal 1333 falling below a predetermined threshold within a set number of measurement opportunities or cycles. For example, NTN IE 1310 may determine that it has lost connection with UE 1320 based on the fact that the received strength of reference signal 1333 is below a predetermined threshold for a set number of consecutive measurement opportunities / periods, or based on the fact that the received strength of reference signal 1333 is below a predetermined threshold for a specific percentage of measurement opportunities / periods. UE 1320 and NTN IE 1310 may determine that they have lost connection with each other simultaneously or in any order. For example, UE 1320 may determine that it has lost connection with NTN IE 1310 before NTN IE 1310, or UE 1320 may determine that it has lost connection with NTN IE 1310 after NTN IE 1310.

[0120] Based on UE 1320 determining that it has lost connection with NTN IE 1310, UE 1320 starts a first timer 1336. Similarly, based on NTN IE 1310 determining that it has lost connection with UE 1320, NTN IE 1310 starts a second timer 1335. The first timer 1336 and the second timer 1335 each have a corresponding predetermined length. The predetermined lengths of the corresponding timers 1335 and 1336 can be the same or can be different from each other. For example, the second timer 1335 can be longer than the first timer 1336 to allow UE 1320 to move to an area with improved NTN coverage before the second timer 1335 at NTN IE 1310 expires at 1337.

[0121] When the first timer 1336 at UE 1320 expires (i.e. reaches zero / completes) 1338, UE 1320 generates an alarm 1339 for the user of UE 1320. UE 1320 may also reset and stop the first timer 1336 (i.e., the first timer is reset to its original value and stops running). Alarm 1339 prompts the user of UE 1320 to move UE 1320 to an area with improved NTN coverage. Alarm 1339 can take almost any form. For example, alarm 1339 may include visual alarms, audio alarms, and / or any other form of sensory alarm. Alarm 1339 may also include sending an alarm to one or more other electronic devices connected / communicating with UE 1320 via almost any means, such as wired connection, Wi-Fi, Bluetooth, or any other means. After generating alarm 1339, UE 1320 begins monitoring 1340 for one or more paging messages from NTN IE 1310 during a specific time window. The time window can begin when or immediately after the first timer 1338 expires, or after alarm 1339 is generated. Alternatively, the time window can begin after a predetermined time period has elapsed since the first timer 1338 expires, or after a predetermined time period has elapsed since alarm 1339 is generated. In other words, UE 1320 can begin monitoring paging messages only after a non-zero predetermined time period has elapsed since alarm 1339 is generated, in order to provide the user with time to move UE 1320 to an area with improved NTN coverage.

[0122] While the first timer 1336 is running, the UE 1320 can continue to monitor the downlink reference signal 1331 from the NTN IE 1310 and compare its received strength with a predetermined threshold. If, while the first timer 1336 is running, the UE 1320 detects a reference signal 1331 with a strength higher than the threshold (or a specific number of reference signals 1331), the UE 1320 can reset and stop the first timer 1336 (i.e., the first timer is reset to its original value and stops running). In this example, the UE 1310 can also send an indication to the NTN IE 1310 that the reference signal 1331 has been received, which may cause the NTN IE 1310 to reset and stop the second timer 1335 at the NTN IE 1310. Furthermore, while the first timer 1336 is running, the UE 1320 can continue to send the uplink reference signal 1333 to the NTN IE 1310, allowing the NTN IE 1310 to continue monitoring the uplink reference signal 1333. Alternatively, when the first timer 1336 starts, UE 1320 can stop sending uplink reference signal 1333 to NTN IE 1310, so that NTN IE 1310 knows that UE 1320 has lost the coverage of NTN IE 1310.

[0123] While the second timer 1335 is running, the NTN IE 1310 can continue to monitor the uplink reference signal 1333 from the UE 1320 and compare its received strength with a predetermined threshold. If, while the second timer 1335 is running, the NTN IE 1310 detects a reference signal 1333 with a strength higher than the threshold (or a specific number of reference signals 1333), the NTN IE 1310 can reset and stop the second timer 1335 (i.e., the second timer is reset to its original value and stops running). Furthermore, while the second timer 1335 is running, the NTN IE 1310 can continue to transmit the downlink reference signal 1331 to itself, allowing the UE 1320 to continue monitoring the downlink reference signal 1331.

[0124] After the second timer 1335 at NTN IE 1310 expires (i.e. reaches zero / completes) 1337, NTN IE 1310 begins sending one or more paging messages 1342 to UE 1320. NTN IE 1310 can also reset and stop the second timer 1335 (i.e., the second timer is reset to its original value and stops running). NTN IE 1310 can begin sending paging messages 1341 when or immediately after the second timer 1337 expires. Alternatively, NTN IE 1310 can begin sending paging messages 1341 for a predetermined period after the second timer 1335 expires 1337, to provide the user with time to move UE 1320 to an area of ​​improved NTN coverage before NTN IE 1310 begins sending paging messages 1341. NTN IE 1310 can send paging messages periodically within a specific time window (with a predetermined length).

[0125] If UE 1320 receives one or more paging messages from NTN IE 1310, UE 1320 may send an acknowledgment of paging message 1341 to NTN IE 1310. Alternatively, UE 1320 may not send an acknowledgment to NTN IE 1310. UE 1320 may re-establish a connection with NTN IE 1310 after receiving one or more paging messages 1341. For example, UE 1320 may enter an RRC connection state with NTN IE 1310. UE 1320 may then monitor one or more downlink messages from NTN IE 1310. These procedures are defined at least in [3] and [4]. Therefore, UE 1320, which has lost coverage of NTN IE 1310, can receive paging messages without using any external terrestrial network.

[0126] If UE 1320 does not receive a paging message 1341 from NTN IE 1310 during the time window, the UE may restart the first timer (which may have the original length or a different length, such as a shorter or longer length). Alternatively, the UE may restart the timer based on determining that it is still outside coverage (by measuring a reference signal from the NTN, as discussed above) or subsequently moving out of coverage again. Therefore, the process at UE 1320 can be repeated such that UE 1320 generates another alarm after the first timer expires again. Alternatively, if UE 1320 does not receive one or more paging messages 1341 from NTN IE 1310 during the time window, UE 1320 may generate an additional alarm to prompt the user to move UE 1320 to a location with improved NTN coverage. If NTN IE1310 does not receive acknowledgment of paging message 1341 or UE 1320 does not reconnect to NTN IE 1310 within the time period, NTN IE 1310 may restart the second timer 1337 (this timer may have the original length or a different length, such as a shorter or longer length). Alternatively, NTN IE 1310 may restart the second timer 1337 based on NTN's further determination that NTN does not have a connection with UE 1320 (i.e., NTN determines that it does not have sufficient link budget, as described above). This further determination may determine that NTN IE 1310 still does not have a connection with UE 1320, or that NTN IE 1310 has lost its connection with UE 1320 again.

[0127] Figure 14 illustrates a flowchart of an example method for a communication device (such as UE 1320 discussed above in conjunction with Figure 13). In step 1410, the communication device measures the strength of one or more reference signals from one or more non-terrestrial infrastructure devices. In step 1420, the communication device starts a timer based on the measured strength of one or more reference signals dropping below a predetermined threshold. In step 1430, the communication device generates an alarm for the user of the communication device based on the timer expiring.

[0128] Figure 15 illustrates a flowchart of an example method for a non-terrestrial infrastructure device (such as a non-terrestrial infrastructure device forming part of the NTN IE1310 discussed above in conjunction with Figure 13). In step 1510, the non-terrestrial infrastructure device measures the strength of one or more reference signals from a communication device configured to transmit uplink signals to the infrastructure device and / or receive downlink signals from the infrastructure device. In step 1520, the non-terrestrial infrastructure device starts a timer based on the measured strength of the one or more reference signals dropping below a predetermined threshold. In step 1530, after the timer expires, the non-terrestrial infrastructure device sends a paging message to the communication device.

[0129] The methods discussed above in conjunction with Figures 8 to 12 and Figures 13 to 15 can be combined with each other in any suitable manner. For example, after the UE determines that it has lost connection with the NTN, the UE can first determine whether it can connect to any terrestrial network (as discussed above in conjunction with Figures 8 and 9) before starting the first timer 1336. Similarly, the UE can first start the first timer 1336, and then (while the first timer 1336 is running) determine whether the UE can connect to any terrestrial network. If an available terrestrial network is detected, the UE can operate according to the method discussed in conjunction with Figures 8 and / or 9A / 9B (and if the first timer 1336 is already running, reset and stop the first timer). However, if no terrestrial network is detected, the UE can operate according to the method discussed in conjunction with Figures 13 and 14. In a similar manner, after the NTN determines that it has lost connection with a particular UE (as discussed above in conjunction with Figures 13 and 15), the NTN can determine during the operation of its second timer 1335 whether it has received an indication from the terrestrial network that the UE has connected to the terrestrial network. If the NTN receives such an instruction, the NTN can reset and stop the second timer. Therefore, it should be understood that all the features and examples described above can be combined with each other in any way.

[0130] Therefore, from one perspective, a method, communication device, network infrastructure equipment, core network unit, and circuit system for paging communication devices that may be located outside the coverage area of ​​a non-terrestrial network are described. The communication device registered with the non-terrestrial network is also registered with the terrestrial network and paging from the non-terrestrial network via the terrestrial network.

[0131] Other examples of the combination of features taught in this disclosure are illustrated in the following numbered items: 1. A method of operating a communication device configured to transmit uplink signals to one or more non-terrestrial infrastructure devices forming part of a non-terrestrial network (NTN) and / or receive downlink signals from one or more non-terrestrial infrastructure devices, the method comprising: measuring the strength of one or more reference signals from one or more non-terrestrial infrastructure devices; transmitting an indication to a terrestrial infrastructure device of the terrestrial network that the communication device has moved out of the coverage area of ​​the NTN based on the measured strength of the one or more reference signals decreasing to below a predetermined threshold; and receiving a paging message from the terrestrial infrastructure device.

[0132] 2. The method according to item 1 further includes: entering a low-power mode for ground infrastructure equipment; and waking up from the low-power mode at a predetermined paging time to check the paging message.

[0133] 3. The method according to item 2 further includes: receiving a command from ground infrastructure equipment to enter a low-power mode.

[0134] 4. The method according to item 2 or item 3 further includes: measuring the strength of one or more reference signals from one or more non-ground infrastructure devices while in a low-power mode.

[0135] 5. The method according to any of the preceding items further includes: registering with the terrestrial network before sending an indication that the communication device has moved out of the coverage area of ​​the NTN.

[0136] 6. According to the method of item 5, wherein the communication device registers with the ground network before measuring the strength of one or more reference signals.

[0137] 7. The method according to any of the preceding items further includes: assigning a higher measurement priority to one or more frequencies associated with the NTN than to one or more other frequencies associated with the TN.

[0138] 8. The method according to any of the preceding claims further includes: determining that the intensity of one or more reference signals measured has decreased to below a predetermined threshold during at least a predetermined number of consecutive paging events or measurement instances.

[0139] 9. The method according to any of the preceding claims further includes: establishing a connection with ground infrastructure equipment based on the intensity of one or more measured reference signals decreasing to below a predetermined threshold.

[0140] 10. The method according to item 9, wherein establishing a connection with the ground infrastructure equipment includes: sending an indication that the communication device has been moved out of the coverage area of ​​the NTN.

[0141] 11. According to the method of item 9, wherein the transmission of the instruction that the communication device has moved out of the coverage area of ​​the NTN is separated from the establishment of a connection with the ground infrastructure equipment.

[0142] 12. The method according to any one of items 9 to 11, wherein establishing a connection with the ground infrastructure equipment includes: acquiring the cell provided by the ground infrastructure equipment.

[0143] 13. The method according to any of the preceding claims further includes: re-establishing a connection with one or more non-terrestrial infrastructure devices based on the strength of one or more measured reference signals rising above a predetermined threshold; and receiving downlink transmissions from one or more non-terrestrial infrastructure devices.

[0144] 14. The method according to any of the preceding claims further includes: generating an alarm for a user of the communication device based on receiving a paging message from ground infrastructure equipment, wherein the alarm instructs the user to relocate the communication device to an area with improved NTN coverage.

[0145] 15. The method according to any of the preceding items, wherein one or more reference signals include one or more synchronization signal blocks (SSBs).

[0146] 16. The method according to any of the preceding items further includes: receiving paging configuration information from ground infrastructure equipment.

[0147] 17. The method according to item 16, wherein receiving paging configuration information includes: receiving paging configuration channel (PCCH) configuration.

[0148] 18. The method of item 17, wherein receiving the PCCH includes: identifying the PCCH configuration in a system information block broadcast by ground infrastructure equipment.

[0149] 19. The method according to item 17 further includes: sending a request for PCCH configuration to the ground infrastructure equipment.

[0150] 20. The method according to item 19 further includes: identifying, based on a system information block, whether the terrestrial network has configured PCCH configuration for the communication device; and sending a request for PCCH configuration based on determining that the terrestrial network has configured PCCH configuration for the communication device.

[0151] 21. A communication apparatus comprising: a transceiver configured to transmit uplink signals to one or more non-terrestrial infrastructure devices forming part of a non-terrestrial network (NTN) and / or receive downlink signals from one or more non-terrestrial infrastructure devices; and a controller, wherein the controller, together with the transceiver, is configured to: measure the strength of one or more reference signals from the one or more non-terrestrial infrastructure devices; based on the measured strength of the one or more reference signals decreasing to below a predetermined threshold, transmit an indication to the terrestrial infrastructure devices of the terrestrial network that the communication apparatus has moved out of the coverage area of ​​the NTN; and receive a paging message from the terrestrial infrastructure devices.

[0152] 22. A circuit system for a communication device, the circuit system comprising: transceiver circuitry configured to transmit uplink signals to one or more non-terrestrial infrastructure devices forming part of a non-terrestrial network (NTN) and / or receive downlink signals from one or more non-terrestrial infrastructure devices; and controller circuitry, wherein the controller circuitry, together with the transceiver circuitry, is configured to: measure the strength of one or more reference signals from one or more non-terrestrial infrastructure devices; based on the measured strength of the one or more reference signals decreasing to below a predetermined threshold, transmit an indication to the terrestrial infrastructure devices of the terrestrial network that the communication device has moved out of the coverage area of ​​the NTN; and receive a paging message from the terrestrial infrastructure devices.

[0153] 23. A method of operating a communication device configured to send uplink signals to one or more non-terrestrial infrastructure devices forming part of a non-terrestrial network (NTN) and / or receive downlink signals from one or more NTN devices, the method comprising: receiving a paging message from a terrestrial infrastructure device of the terrestrial network; generating an alarm for a user of the communication device based on the paging message received from the terrestrial infrastructure device, wherein the alarm instructs the user to relocate the communication device to an area of ​​improved NTN coverage; and monitoring one or more paging messages from the NTN's non-terrestrial infrastructure devices.

[0154] 24. A communication apparatus comprising: a transceiver configured to transmit uplink signals to one or more non-terrestrial infrastructure devices forming part of a non-terrestrial network (NTN) and / or receive downlink signals from one or more non-terrestrial infrastructure devices; and a controller, wherein the controller, together with the transceiver, is configured to: receive paging messages from the terrestrial infrastructure devices of the terrestrial network; generate an alarm for a user of the communication apparatus based on the paging messages received from the terrestrial infrastructure devices, wherein the alarm instructs the user to relocate the communication apparatus to an area with improved NTN coverage; and monitor one or more paging messages from the non-terrestrial infrastructure devices of the NTN.

[0155] 25. A circuit system for a communication device, the circuit system comprising: transceiver circuitry configured to transmit uplink signals to one or more non-terrestrial infrastructure devices forming part of a non-terrestrial network (NTN) and / or receive downlink signals from one or more non-terrestrial infrastructure devices; and controller circuitry, wherein the controller circuitry, together with the transceiver circuitry, is configured to: receive paging messages from the terrestrial infrastructure devices of the terrestrial network; generate an alarm for a user of the communication device based on the paging messages received from the terrestrial infrastructure devices, wherein the alarm instructs the user to relocate the communication device to an area with improved NTN coverage; and monitor one or more paging messages from the non-terrestrial infrastructure devices of the NTN.

[0156] 26. A method of operating ground infrastructure equipment forming part of a terrestrial network (TN), the method comprising: receiving from a communication device an indication that the communication device has moved out of the coverage area of ​​the NTN, the communication device being configured to send an uplink signal to one or more non-terrestrial infrastructure devices forming part of the non-terrestrial network (NTN) and / or receive a downlink signal from one or more non-terrestrial infrastructure devices; sending the indication that the communication device has moved out of the coverage area of ​​the NTN to a network portion of the NTN; receiving an indication that the communication device will be paged; and sending a paging message to the communication device.

[0157] 27. The method according to item 26 further includes: sending an instruction to the communication device to cause the communication device to enter a low-power mode.

[0158] 28. The method according to item 26 or 27 further includes: configuring paging resources for sending paging messages to the communication device.

[0159] 29. The method of item 28, wherein the paging resources for sending paging messages to the communication device are shared with one or more other communication devices of the terrestrial network.

[0160] 30. The method of item 28, wherein the paging resources for sending paging messages to the communication device are dedicated to the communication device of the non-terrestrial network.

[0161] 31. The method according to any of the preceding items further includes: registering the terrestrial network communication device before receiving an indication that the communication device has moved out of the coverage area of ​​the NTN.

[0162] 32. The method according to any of the preceding items further includes: establishing a connection with ground infrastructure equipment.

[0163] 33. The method according to item 32, wherein establishing a connection with the communication device includes: receiving an indication that the communication device has moved out of the coverage area of ​​the NTN.

[0164] 34. The method according to item 32, wherein the reception of an indication that the communication device has moved out of the coverage area of ​​the NTN is separated from the establishment of a connection with the ground infrastructure equipment.

[0165] 35. The method according to any one of items 26 to 34, further comprising: sending an indication to the network portion of the NTN of a first tracking area registered by the communication device; wherein receiving the indication that the communication device will be paged includes: receiving an indication that the page should be sent in the first tracking area.

[0166] 36. The method according to any one of items 26 to 35 further includes: receiving an indication that the communication device has restored coverage with the NTN.

[0167] 37. The method according to item 36 further includes: removing the registration of the communication device from a specific cell or tracking area of ​​the terrestrial network based on receiving an indication that the communication device has restored coverage with the NTN.

[0168] 38. The method according to any one of items 26 to 37 further includes: sending paging configuration information to the communication device.

[0169] 39. According to the method of item 38, wherein sending paging configuration information includes: sending paging configuration channel (PCCH) configuration.

[0170] 40. According to the method of item 39, wherein sending the PCCH configuration includes: sending a system information block including the PCCH configuration.

[0171] 41. The method according to item 40 further includes: receiving a request for PCCH configuration from the communication device; and in response to the request for PCCH configuration, sending a system information block containing PCCH configuration to the communication device.

[0172] 42. The method according to item 39 further includes: transmitting a system information block, the system information block including an indication of whether the terrestrial network has configured PCCH configuration for the communication device.

[0173] 43. The method according to any one of items 26 to 42, wherein the network portion of the NTN is a non-terrestrial infrastructure device of the NTN.

[0174] 44. According to any one of items 26 to 43, wherein the network portion of the NTN is the core network portion of the NTN.

[0175] 45. According to the method in item 44, the core network unit of the NTN is also the core network unit of the terrestrial network.

[0176] 46. ​​A ground infrastructure device for a terrestrial network, the ground infrastructure device comprising: a transceiver configured to transmit downlink signals to one or more communication devices and / or receive uplink signals from one or more communication devices; and a controller configured together with the transceiver to: receive from the communication device an indication that the communication device has moved out of the coverage area of ​​an NTN, the communication device being configured to transmit uplink signals to one or more non-terrestrial infrastructure devices forming part of a non-terrestrial network (NTN) and / or receive downlink signals from one or more non-terrestrial infrastructure devices; transmit an indication that the communication device has moved out of the coverage area of ​​the NTN to a network portion of the NTN; receive an indication that the communication device will be paged; and transmit a paging message to the communication device.

[0177] 47. A circuit system for a terrestrial infrastructure device for a terrestrial network, the circuit system comprising: transceiver circuitry configured to transmit downlink signals to one or more communication devices and / or receive uplink signals from one or more communication devices; and controller circuitry configured together with the transceiver circuitry to: receive from the communication devices an indication that the communication devices have moved out of the coverage area of ​​an NTN, the communication devices being configured to transmit uplink signals to one or more non-terrestrial infrastructure devices forming part of a non-terrestrial network (NTN) and / or receive downlink signals from one or more non-terrestrial infrastructure devices; transmit an indication to a network portion of the NTN that the communication devices have moved out of the NTN's coverage area; receive an indication that the communication devices will be paged; and transmit a paging message to the communication devices.

[0178] 48. A method of operating a core network section of a non-terrestrial network (NTN), the method comprising: receiving from a terrestrial network (TN) section an indication that a communication device has moved out of NTN coverage, the communication device being configured to send uplink signals to one or more non-terrestrial infrastructure devices forming part of the NTN and / or receive downlink signals from one or more non-terrestrial infrastructure devices; sending to the TN section an indication that the communication device should be paged by the TN; and sending to the non-terrestrial infrastructure devices of the NTN an instruction to page the communication device.

[0179] 49. The method according to item 48 further includes: receiving from the TN section an indication of a first tracking area where the TN's communication device is located; and wherein sending the indication that the communication device should be paged includes: sending an indication that the page should be sent in the first tracking area.

[0180] 50. The method according to item 48 or 49 further includes: receiving an indication that the communication device has received one or more reference signals transmitted by non-terrestrial infrastructure equipment of the NTN; and, based on the received indication, instructing the TN portion that the communication device has re-established its connection with the NTN.

[0181] 51. The method of item 50, wherein the received indication of one or more reference signals received by the communication device is an uplink reference signal received from the communication device.

[0182] 52. The method according to any one of items 48 to 51 further includes: receiving an indication that the communication device has received a paging message; and, based on the received indication, instructing the TN portion that the communication device has re-established its connection with the NTN.

[0183] 53. According to any one of items 48 to 52, wherein the TN part is the core network part of the TN.

[0184] 54. According to any one of items 48 to 52, wherein the core network part of the NTN is also the core network part of the TN, and wherein the TN part is the infrastructure equipment of the TN.

[0185] 55. A core network unit for a non-terrestrial network, the core network unit comprising: a network interface configured to send and / or receive communications from infrastructure equipment of the non-terrestrial network; and a controller configured together with the network interface to: receive from a terrestrial network (TN) portion an indication that a communication device has moved out of NTN coverage, the communication device being configured to send uplink signals to one or more non-terrestrial infrastructure equipment forming part of the NTN and / or receive downlink signals from one or more non-terrestrial infrastructure equipment; send to the TN portion an indication that the communication device should be paged by the TN; and send instructions to the non-terrestrial infrastructure equipment of the NTN to page the communication device.

[0186] 56. A circuit system for a core network section of a non-terrestrial network, the circuit system comprising: a network interface circuit configured to send and / or receive communications from infrastructure equipment of the non-terrestrial network; and a controller circuit configured together with the network interface circuit to: receive from a terrestrial network (TN) section an indication that a communication device has moved out of NTN coverage, the communication device being configured to send uplink signals to one or more non-terrestrial infrastructure equipment forming part of the NTN and / or receive downlink signals from one or more non-terrestrial infrastructure equipment; send to the TN section an indication that the communication device should be paged by the TN; and send instructions to the non-terrestrial infrastructure equipment of the NTN to page the communication device.

[0187] 57. A method for operating a core network unit for a non-terrestrial network (NTN) and a terrestrial network, the method comprising: receiving an indication that a communication device of the NTN has lost NTN coverage; and sending an indication to the infrastructure equipment of the terrestrial network that the communication device should be paged by the terrestrial network.

[0188] 58. A core network unit for a non-terrestrial network and a terrestrial network, the core network unit comprising: a network interface configured to send and / or receive communications from infrastructure equipment of the non-terrestrial network and infrastructure equipment of the terrestrial network; and a controller configured together with the network interface to: receive an indication that a communication device of the NTN has lost NTN coverage; and send an indication to the infrastructure equipment of the terrestrial network that the communication device should be paged by the terrestrial network.

[0189] 59. A circuit system for a core network section of a non-terrestrial network and a terrestrial network, the circuit system comprising: a network interface circuit configured to send and / or receive communications from infrastructure equipment of the non-terrestrial network and infrastructure equipment of the terrestrial network; and a controller circuit configured together with the network interface circuit to: receive an indication that a communication device of the NTN has lost NTN coverage; and send an indication to the infrastructure equipment of the terrestrial network that the communication device should be paged by the terrestrial network.

[0190] 60. A method for operating the core network unit of a non-terrestrial network (NTN), the method comprising: receiving an indication that a communication device of the NTN has lost NTN coverage; and sending an indication to the core network unit of the terrestrial network to which the communication device is registered that the communication device should be paged by the terrestrial network.

[0191] 61. A core network unit for a non-terrestrial network, the core network unit comprising: a network interface configured to send and / or receive communications from infrastructure equipment of the non-terrestrial network; and a controller configured together with the network interface to: receive an indication that a communication device of an NTN has lost NTN coverage; and send an indication to the core network unit of the terrestrial network to which the communication device is registered that the communication device should be paged by the terrestrial network.

[0192] 62. A circuit system for a core network section of a non-terrestrial network, the circuit system comprising: a network interface circuit configured to send and / or receive communications from infrastructure equipment of the non-terrestrial network; and a controller circuit configured together with the network interface circuit to: receive an indication that a communication device of an NTN has lost NTN coverage; and send an indication to the core network section of the terrestrial network to which the communication device is registered that the communication device should be paged by the terrestrial network.

[0193] 63. A method of operating a core network unit for a terrestrial network, the method comprising: receiving an indication from a core network unit of a non-terrestrial network (NTN) that a communication device should be paged by the terrestrial network; and sending an instruction to the infrastructure equipment of the terrestrial network to page the communication device.

[0194] 64. A core network unit for a terrestrial network, the core network unit comprising: a network interface configured to send and / or receive communications from infrastructure equipment of the terrestrial network; and a controller configured together with the network interface to: receive an indication from a core network unit of a non-terrestrial network (NTN) that a communication device should be paged by the terrestrial network; and to send instructions to the infrastructure equipment of the terrestrial network to page the communication device.

[0195] 65. A circuit system for a core network section of a terrestrial network, the circuit system comprising: a network interface circuit configured to send and / or receive communications from infrastructure equipment of the terrestrial network; and a controller circuit configured together with the network interface circuit to: receive an indication from a core network section of a non-terrestrial network (NTN) that a communication device should be paged by the terrestrial network; and to send instructions to the infrastructure equipment of the terrestrial network to page the communication device.

[0196] 66. A method for operating a core network unit for a non-terrestrial network (NTN) and a terrestrial network, the method comprising: identifying one or more tracking areas among the NTN and the terrestrial network, identifying one or more tracking areas among the first and second tracking areas, paging a communication device registered in the core network unit in the one or more tracking areas; and sending an instruction to one or more infrastructure devices associated with the identified one or more tracking areas for sending a paging message for the communication device to receive.

[0197] 67. A core network unit for a non-terrestrial network and a terrestrial network, the core network unit comprising: a network interface configured to send and / or receive communications from infrastructure equipment of the non-terrestrial network and infrastructure equipment of the terrestrial network; and a controller configured together with the network interface to: identify one or more tracking areas among a plurality of first tracking areas based on an NTN and a plurality of second tracking areas of the terrestrial network, page a communication device registered in the core network unit in the one or more tracking areas; and send instructions to one or more infrastructure equipment associated with the identified one or more tracking areas to send a paging message for the communication device to receive.

[0198] 68. A circuit system for a non-terrestrial network and a core network section of a terrestrial network, the circuit system comprising: a network interface circuit configured to send and / or receive communications from infrastructure equipment of the non-terrestrial network and infrastructure equipment of the terrestrial network; and a controller circuit configured together with the network interface circuit to: identify one or more tracking areas among a plurality of first tracking areas based on an NTN and a plurality of second tracking areas of the terrestrial network, and in the one or more tracking areas, page a communication device registered in the core network section; and send instructions to one or more infrastructure devices associated with the identified one or more tracking areas to send a paging message for the communication device to receive.

[0199] 69. A method for operating a core network unit for a non-terrestrial network (NTN), the method comprising: sending an instruction to a non-terrestrial infrastructure device of the NTN to page a communication device of the NTN; and, based on determining that paging is unsuccessful, sending an indication to the core network unit of the terrestrial network to which the communication device is registered that the communication device should be paged by the terrestrial network.

[0200] 70. A core network unit for a non-terrestrial network, the core network unit comprising: a network interface configured to send and / or receive communications from infrastructure equipment of the non-terrestrial network; and a controller configured together with the network interface to: send an instruction to the non-terrestrial infrastructure equipment of the NTN to page a communication device of the NTN; and, based on determining that paging is unsuccessful, send an indication to the core network unit of the terrestrial network to which the communication device is registered that the communication device should be paged by the terrestrial network.

[0201] 71. A circuit system for a core network section of a non-terrestrial network, the circuit system comprising: a network interface circuit configured to send and / or receive communications from infrastructure equipment of the non-terrestrial network; and a controller circuit configured together with the network interface circuit to: send an instruction to the non-terrestrial infrastructure equipment of the NTN to page a communication device of the NTN; and, based on determining that paging is unsuccessful, send an indication to the core network section of the terrestrial network to which the communication device is registered that the communication device should be paged by the terrestrial network.

[0202] 72. A method of operating a core network unit for a terrestrial network, the method comprising: receiving from a core network unit for a non-terrestrial network (NTN) an indication that a communication device registered in the core network unit of the terrestrial network should be paged by the terrestrial network; and sending an instruction to one or more infrastructure devices of the terrestrial network for sending a paging message for the communication device to receive.

[0203] 73. A core network unit for a terrestrial network, the core network unit comprising: a network interface configured to send and / or receive communications from infrastructure equipment of the terrestrial network; and a controller configured together with the network interface to: receive from a core network unit for non-terrestrial networks (NTNs) an indication that a communication device registered with the core network unit of the terrestrial network should be paged by the terrestrial network; and to send instructions to one or more infrastructure equipment of the terrestrial network to send a paging message for the communication device to receive.

[0204] 74. A circuit system for a core network section of a terrestrial network, the circuit system comprising: a network interface circuit configured to send and / or receive communications from infrastructure equipment of the terrestrial network; and a controller circuit configured together with the network interface circuit to: receive from a core network section for a non-terrestrial network (NTN) an indication that a communication device registered with the core network section of the terrestrial network should be paged by the terrestrial network; and to send instructions to one or more infrastructure equipment of the terrestrial network to send a paging message for the communication device to receive.

[0205] 75. A method of operating a communication device configured to transmit uplink signals to one or more non-terrestrial infrastructure devices forming part of a non-terrestrial network (NTN) and / or receive downlink signals from one or more non-terrestrial infrastructure devices, the method comprising: measuring the strength of one or more reference signals from the one or more non-terrestrial infrastructure devices; starting a timer based on the measured strength of the one or more reference signals decreasing to below a predetermined threshold; and generating an alarm for a user of the communication device based on the timer expiring.

[0206] 76. According to the method of item 43, wherein the alarm instructs the user to relocate to an area with improved NTN coverage.

[0207] 77. The method according to item 75 or 76 further includes: sending a periodic uplink reference signal to one or more non-terrestrial infrastructure devices; and suspending the transmission of the periodic uplink reference signal based on the measured strength of one or more downlink reference signals decreasing to below a predetermined threshold.

[0208] 78. According to the method of item 77, wherein the periodic uplink reference signal includes a sounding reference signal (SRS).

[0209] 79. The method according to any one of items 75 to 78 further includes: sending an indication to one or more non-terrestrial infrastructure devices that the communication device has received one or more reference signals based on the strength of the measured one or more reference signals rising above a predetermined threshold; and stopping the timer based on the strength of the measured one or more reference signals rising above the predetermined threshold.

[0210] 80. The method according to any one of items 75 to 79, wherein one or more reference signals include one or more synchronization signal blocks (SSBs).

[0211] 81. A communication apparatus comprising: a transceiver configured to transmit uplink signals to one or more non-terrestrial infrastructure devices forming part of a non-terrestrial network (NTN) and / or receive downlink signals from one or more non-terrestrial infrastructure devices; and a controller, wherein the controller, together with the transceiver, is configured to: measure the strength of one or more reference signals from the one or more non-terrestrial infrastructure devices; initiate a timer based on the measured strength of the one or more reference signals decreasing below a predetermined threshold; and generate an alarm for a user of the communication apparatus based on the timer expiring.

[0212] 82. A circuit system for a communication device, the circuit system comprising: transceiver circuitry configured to transmit uplink signals to one or more non-terrestrial infrastructure devices forming part of a non-terrestrial network (NTN) and / or receive downlink signals from one or more non-terrestrial infrastructure devices; and controller circuitry, wherein the controller circuitry, together with the transceiver circuitry, is configured to: measure the strength of one or more reference signals from one or more non-terrestrial infrastructure devices; initiate a timer based on the measured strength of the one or more reference signals decreasing below a predetermined threshold; and generate an alarm for a user of the communication device based on the timer expiring.

[0213] 83. A method of operating a non-terrestrial infrastructure device forming part of a non-terrestrial network (NTN), the method comprising: measuring the strength of one or more reference signals from a communication device configured to transmit uplink signals to the infrastructure device and / or receive downlink signals from the infrastructure device; starting a timer based on the measured strength of the one or more reference signals dropping below a predetermined threshold; and sending a paging message to the communication device after the timer expires.

[0214] 84. The method according to item 83 further includes: broadcasting a downlink reference signal for reception by the communication device.

[0215] 85. According to the method of item 84, wherein the periodic downlink reference signal includes one or more synchronization signal blocks (SSBs).

[0216] 86. The method according to any one of items 83 to 85 further includes: receiving from the communication device an indication that the communication device has received one or more reference signals; and stopping the timer based on the measured strength of one or more reference signals rising above a predetermined threshold.

[0217] 87. The method according to item 86, wherein the received indication of one or more reference signals is an uplink reference signal received from the communication device.

[0218] 88. The method according to any one of items 83 to 87, wherein the non-ground infrastructure equipment sends a paging message to the communication device for a predetermined non-zero length of time after the timer expires.

[0219] 89. The method according to any one of items 83 to 88, wherein one or more uplink reference signals include a sounding reference signal (SRS).

[0220] 90. A non-terrestrial infrastructure device for a non-terrestrial network, the non-terrestrial infrastructure device comprising: a transceiver configured to transmit downlink signals to one or more communication devices and / or receive uplink signals from one or more communication devices; and a controller configured together with the transceiver to: measure the strength of one or more reference signals from the communication devices configured to transmit uplink signals to the infrastructure device and / or receive downlink signals from the infrastructure device; initiate a timer based on the measured strength of the one or more reference signals decreasing below a predetermined threshold; and send a paging message to the communication devices after the timer expires.

[0221] 91. A circuit system for a non-terrestrial infrastructure device in a non-terrestrial network, the circuit system comprising: a transceiver circuit configured to transmit downlink signals to one or more communication devices and / or receive uplink signals from one or more communication devices; and a controller circuit configured together with the transceiver to: measure the strength of one or more reference signals from the communication devices configured to transmit uplink signals to the infrastructure device and / or receive downlink signals from the infrastructure device; start a timer based on the measured strength of the one or more reference signals dropping below a predetermined threshold; and send a paging message to the communication devices after the timer expires.

[0222] References

[0223] [1] TR 38.811, “Study on New Radio (NR) to support non terrestrialnetworks (Release 15)”, 3rd Generation Partnership Project, December 2017.

[0224] [2] Holma H. and Toskala A, “LTE for UMTS OFDMA and SC-FDMA basedradio access”, John Wiley and Sons, 2009.

[0225] [3] TS #38.304, v17.6.0, 3GPP

[0226] [4] TS #38.331, v17.6.0, 3GPP

Claims

1. A method of operating a communication device configured to transmit uplink signals to one or more non-terrestrial infrastructure devices forming part of a non-terrestrial network (NTN) and / or receive downlink signals from the one or more non-terrestrial infrastructure devices, the method comprising: Measure the strength of one or more reference signals from the one or more non-ground infrastructure devices; Based on the measured strength of one or more reference signals dropping below a predetermined threshold, an indication is sent to the ground infrastructure equipment of the terrestrial network that the communication device has moved out of the coverage area of ​​the NTN; and a paging message is received from the ground infrastructure equipment.

2. The method according to claim 1, further comprising: Entering a low-power mode for the ground infrastructure equipment; and waking up from the low-power mode at a predetermined paging time to check the paging message.

3. The method according to claim 2, further comprising: Receives a command to enter the low-power mode from the ground infrastructure equipment.

4. The method according to claim 2, further comprising: While in the low-power mode, the intensity of the one or more reference signals from the one or more non-ground infrastructure devices is measured.

5. The method according to claim 1, further comprising: Register with the terrestrial network before sending the indication that the communication device has moved out of the coverage area of ​​the NTN.

6. The method according to claim 5, wherein, The communication device registers with the terrestrial network before measuring the strength of the one or more reference signals.

7. The method according to claim 1, further comprising: One or more frequencies associated with the NTN will be assigned a higher measurement priority than one or more other frequencies associated with the TN.

8. The method according to claim 1, further comprising: It is determined that the intensity of the one or more reference signals measured has decreased to below a predetermined threshold during at least a predetermined number of consecutive paging events or measurement instances.

9. The method according to claim 1, further comprising: A connection is established with the ground infrastructure equipment based on the measured intensity of one or more reference signals dropping below a predetermined threshold.

10. The method according to claim 9, wherein, Establishing the connection with the ground infrastructure equipment includes sending an indication that the communication device has moved out of the coverage area of ​​the NTN.

11. The method according to claim 9, wherein, The transmission of the instruction that the communication device has moved out of the coverage area of ​​the NTN is separated from the establishment of the connection with the ground infrastructure equipment.

12. The method according to claim 9, wherein, Establishing the connection with the ground infrastructure equipment includes: acquiring the cell provided by the ground infrastructure equipment.

13. The method according to claim 1, further comprising: Based on the rise in intensity of the measured one or more reference signals above the predetermined threshold, the connection with the one or more non-ground infrastructure devices is re-established; And receiving downlink transmissions from the one or more non-terrestrial infrastructure devices.

14. The method according to claim 1, further comprising: Based on the paging message received from the ground infrastructure equipment, an alarm is generated for the user of the communication device, wherein the alarm instructs the user to relocate the communication device to an area with improved NTN coverage.

15. The method according to claim 1, wherein, The one or more reference signals include one or more synchronization signal blocks (SSBs).

16. The method according to claim 1, further comprising: Receive paging configuration information from the ground infrastructure equipment.

17. The method according to claim 16, wherein, Receiving the paging configuration information includes receiving the paging configuration channel (PCCH) configuration.

18. The method according to claim 17, wherein, Receiving the PCCH includes: identifying the PCCH configuration in the system information block broadcast by the ground infrastructure equipment.

19. The method of claim 17, further comprising: Send a request for PCCH configuration to the ground infrastructure equipment.

20. The method of claim 19, further comprising: Based on the system information block, it is identified whether the ground network has configured the PCCH configuration for the communication device; And based on determining that the terrestrial network has configured the PCCH configuration for the communication device, the request for the PCCH configuration is sent.

21. A communication device, comprising: The transceiver is configured to transmit uplink signals to one or more non-terrestrial infrastructure devices that form part of a non-terrestrial network (NTN) and / or receive downlink signals from the one or more non-terrestrial infrastructure devices. The transceiver is configured to: measure the strength of one or more reference signals from the one or more non-terrestrial infrastructure devices; based on the measured strength of the one or more reference signals dropping below a predetermined threshold, send an indication to the terrestrial infrastructure devices of the terrestrial network that the communication device has moved out of the coverage area of ​​the NTN; and receive paging messages from the terrestrial infrastructure devices.

22. A circuit system for a communication device, the circuit system comprising: The transceiver circuit is configured to transmit uplink signals to one or more non-terrestrial infrastructure devices that form part of a non-terrestrial network (NTN) and / or receive downlink signals from the one or more non-terrestrial infrastructure devices. The controller circuit, together with the transceiver circuit, is configured to: measure the strength of one or more reference signals from the one or more non-terrestrial infrastructure devices; based on the measured strength of the one or more reference signals dropping below a predetermined threshold, send an indication to the terrestrial infrastructure devices of the terrestrial network that the communication device has moved out of the coverage area of ​​the NTN; and receive paging messages from the terrestrial infrastructure devices.

23. A method of operating a communication device configured to transmit uplink signals to one or more non-terrestrial infrastructure devices forming part of a non-terrestrial network (NTN) and / or receive downlink signals from the one or more non-terrestrial infrastructure devices, the method comprising: Receive paging messages from ground infrastructure equipment of the terrestrial network; Based on receiving the paging message from the ground infrastructure equipment, an alarm is generated for the user of the communication device, wherein the alarm instructs the user to relocate the communication device to an area with improved NTN coverage; And monitor one or more paging messages from the NTN’s non-terrestrial infrastructure equipment.

24. A communication device, comprising: A transceiver configured to transmit uplink signals to one or more non-terrestrial infrastructure devices forming part of a non-terrestrial network (NTN) and / or receive downlink signals from the one or more non-terrestrial infrastructure devices; and a controller configured together with the transceiver to: receive paging messages from terrestrial infrastructure devices of the terrestrial network; generate an alarm for a user of the communication device based on the paging messages received from the terrestrial infrastructure devices, wherein the alarm instructs the user to relocate the communication device to an area with improved NTN coverage; and monitor one or more paging messages from the non-terrestrial infrastructure devices of the NTN.

25. A circuit system for a communication device, the circuit system comprising: The transceiver circuit is configured to transmit uplink signals to one or more non-terrestrial infrastructure devices that form part of a non-terrestrial network (NTN) and / or receive downlink signals from the one or more non-terrestrial infrastructure devices. The controller circuit, together with the transceiver circuit, is configured to: receive paging messages from ground infrastructure equipment of the terrestrial network; generate an alarm for a user of the communication device based on the paging messages received from the ground infrastructure equipment, wherein the alarm instructs the user to relocate the communication device to an area with improved NTN coverage; and monitor one or more paging messages from non-terrestrial infrastructure equipment of the NTN.

26. A method of operating ground infrastructure equipment forming part of a terrestrial network (TN), the method comprising: The communication device receives an indication that it has moved out of the coverage area of ​​the non-terrestrial network (NTN), and the communication device is configured to send uplink signals to one or more non-terrestrial infrastructure devices that form part of the NTN and / or receive downlink signals from the one or more non-terrestrial infrastructure devices. Send an indication to the network portion of the NTN that the communication device has moved out of the NTN's coverage area; receive an indication that the communication device will be paged; and send a paging message to the communication device.

27. A ground infrastructure device for a terrestrial network, the ground infrastructure device comprising: A transceiver is configured to transmit downlink signals to one or more communication devices and / or receive uplink signals from said one or more communication devices; And a controller, which together with the transceiver is configured to: receive from the communication device an indication that the communication device has moved out of the coverage area of ​​the non-terrestrial network (NTN), the communication device being configured to send uplink signals to one or more non-terrestrial infrastructure devices forming part of the NTN and / or receive downlink signals from the one or more non-terrestrial infrastructure devices; Send an indication to the network portion of the NTN that the communication device has moved out of the NTN's coverage area; receive an indication that the communication device will be paged; and send a paging message to the communication device.

28. A circuit system for ground infrastructure equipment for a terrestrial network, the circuit system comprising: A transceiver circuit is configured to transmit downlink signals to one or more communication devices and / or receive uplink signals from the one or more communication devices. And a controller circuit, which together with the transceiver circuit is configured to: receive from the communication device an indication that the communication device has moved out of the coverage area of ​​the non-terrestrial network (NTN), the communication device being configured to send uplink signals to one or more non-terrestrial infrastructure devices forming part of the NTN and / or receive downlink signals from the one or more non-terrestrial infrastructure devices; Send an indication to the network portion of the NTN that the communication device has moved out of the NTN's coverage area; receive an indication that the communication device will be paged; and send a paging message to the communication device.

29. A method for operating the core network unit of a non-terrestrial network (NTN), the method comprising: The communication device receives an indication from the terrestrial network (TN) portion that the communication device has moved out of NTN coverage, the communication device being configured to send uplink signals to one or more non-terrestrial infrastructure devices forming part of the NTN and / or receive downlink signals from the one or more non-terrestrial infrastructure devices; send an indication to the TN portion that the communication device should be paged by the TN; and send an instruction to the non-terrestrial infrastructure devices of the NTN to page the communication device.

30. A core network unit for a non-terrestrial network, the core network unit comprising: The network interface is configured to send and / or receive communications from the infrastructure equipment of the non-terrestrial network; And a controller, together with the network interface, is configured to: receive from the terrestrial network (TN) portion an indication that a communication device has moved out of NTN coverage, the communication device being configured to send uplink signals to one or more non-terrestrial infrastructure devices forming part of the NTN and / or receive downlink signals from the one or more non-terrestrial infrastructure devices; send to the TN portion an indication that the communication device should be paged by the TN; and send to the non-terrestrial infrastructure devices of the NTN instructions to page the communication device.

31. A circuit system for a core network section of a non-terrestrial network, the circuit system comprising: A network interface circuit is configured to send and / or receive communications from the infrastructure equipment of the non-terrestrial network; And a controller circuit, together with the network interface circuit, is configured to: receive from the terrestrial network (TN) portion an indication that a communication device has moved out of NTN coverage, the communication device being configured to send uplink signals to one or more non-terrestrial infrastructure devices forming part of the NTN and / or receive downlink signals from the one or more non-terrestrial infrastructure devices; send to the TN portion an indication that the communication device should be paged by the TN; and send to the non-terrestrial infrastructure devices of the NTN an instruction to page the communication device.

32. A method for operating a core network unit for non-terrestrial networks (NTN) and terrestrial networks, the method comprising: The communication device receiving the NTN has lost the indication that the NTN is under its coverage; And to send an instruction to the infrastructure equipment of the terrestrial network that the communication device should be paged by the terrestrial network.

33. A core network unit for non-terrestrial networks and terrestrial networks, the core network unit comprising: The network interface is configured to send and / or receive communications from the infrastructure equipment of the non-terrestrial network and the infrastructure equipment of the terrestrial network; The controller, together with the network interface, is configured to: receive an indication that a communication device of the NTN has lost coverage of the NTN; and send an indication to the infrastructure equipment of the terrestrial network that the communication device should be paged by the terrestrial network.

34. A circuit system for a core network section of a non-terrestrial network and a terrestrial network, the circuit system comprising: The network interface circuit is configured to send and / or receive communications from the infrastructure equipment of the non-terrestrial network and the infrastructure equipment of the terrestrial network; The controller circuit, together with the network interface circuit, is configured to: receive an indication that a communication device of the NTN has lost coverage of the NTN; and send an indication to the infrastructure equipment of the terrestrial network that the communication device should be paged by the terrestrial network.

35. A method for operating the core network unit of a non-terrestrial network (NTN), the method comprising: An indication that the communication device receiving the NTN has lost the coverage of the NTN; Send an instruction to the core network of the terrestrial network to which the communication device is registered, indicating that the communication device should be paged by the terrestrial network.

36. A core network unit for a non-terrestrial network, the core network unit comprising: The network interface is configured to send and / or receive communications from the infrastructure equipment of the non-terrestrial network; The controller, together with the network interface, is configured to: receive an indication that a communication device of the NTN has lost coverage of the NTN; and send an indication to the core network unit of the terrestrial network to which the communication device is registered that the communication device should be paged by the terrestrial network.

37. A circuit system for a core network section of a non-terrestrial network, the circuit system comprising: A network interface circuit is configured to send and / or receive communications from the infrastructure equipment of the non-terrestrial network; The controller circuit, together with the network interface circuit, is configured to: receive an indication that a communication device of the NTN has lost coverage of the NTN; and send an indication to the core network unit of the terrestrial network to which the communication device is registered that the communication device should be paged by the terrestrial network.

38. A method for operating a core network unit for a terrestrial network, the method comprising: The communication device should receive an instruction from the core network unit of the non-terrestrial network (NTN) that it has been paged by the terrestrial network; And to send instructions to the infrastructure equipment of the terrestrial network to page the communication device.

39. A core network unit for a terrestrial network, the core network unit comprising: The network interface is configured to send and / or receive communications from the infrastructure equipment of the terrestrial network; The controller, together with the network interface, is configured to: receive an indication from the core network unit of the non-terrestrial network (NTN) that the communication device should be paged by the terrestrial network; and send instructions to the infrastructure equipment of the terrestrial network to page the communication device.

40. A circuit system for a core network section of a terrestrial network, the circuit system comprising: A network interface circuit is configured to send and / or receive communications from the infrastructure equipment of the terrestrial network; The controller circuit, together with the network interface circuit, is configured to: receive an indication from the core network unit of the non-terrestrial network (NTN) that the communication device should be paged by the terrestrial network; and send a pager instruction to the infrastructure equipment of the terrestrial network.

41. A method for operating a core network unit for non-terrestrial networks (NTN) and terrestrial networks, the method comprising: Based on multiple first tracking areas of NTN and multiple second tracking areas of the terrestrial network, identify one or more tracking areas among the first tracking areas and the second tracking areas, and page communication devices registered in the core network unit in the one or more tracking areas. And to send instructions to one or more infrastructure devices associated with the identified one or more tracking areas to send paging messages for the communication device to receive.

42. A core network unit for non-terrestrial networks and terrestrial networks, the core network unit comprising: The network interface is configured to send and / or receive communications from the infrastructure equipment of the non-terrestrial network and the infrastructure equipment of the terrestrial network; And a controller, which together with the network interface is configured to: identify one or more tracking areas among the first tracking areas and the second tracking areas of the NTN and to page communication devices registered in the core network unit in the one or more tracking areas. And to send instructions to one or more infrastructure devices associated with the identified one or more tracking areas to send paging messages for the communication device to receive.

43. A circuit system for a core network section of a non-terrestrial network and a terrestrial network, the circuit system comprising: The network interface circuit is configured to send and / or receive communications from the infrastructure equipment of the non-terrestrial network and the infrastructure equipment of the terrestrial network; And a controller circuit, which together with the network interface circuit is configured to: identify one or more tracking areas among the first tracking areas and the second tracking areas based on the NTN and the terrestrial network, and page communication devices registered in the core network unit in the one or more tracking areas. And to send instructions to one or more infrastructure devices associated with the identified one or more tracking areas to send paging messages for the communication device to receive.

44. A method for operating a core network unit for a non-terrestrial network (NTN), the method comprising: Send a command to the non-terrestrial infrastructure equipment of the NTN to page the communication device of the NTN; Based on the determination that the paging is unsuccessful, an instruction is sent to the core network unit of the terrestrial network to which the communication device is registered, indicating that the communication device should be paged by the terrestrial network.

45. A core network unit for a non-terrestrial network, the core network unit comprising: The network interface is configured to send and / or receive communications from the infrastructure equipment of the non-terrestrial network; The controller, together with the network interface, is configured to: send instructions to non-terrestrial infrastructure equipment of the NTN to page the NTN's communication devices; and, based on determining that the paging is unsuccessful, send an indication to the core network of the terrestrial network to which the communication device is registered that the communication device should be paged by the terrestrial network.

46. ​​A circuit system for a core network section of a non-terrestrial network, the circuit system comprising: A network interface circuit is configured to send and / or receive communications from the infrastructure equipment of the non-terrestrial network; The controller circuit, together with the network interface circuit, is configured to: send a paging instruction to the non-terrestrial infrastructure equipment of the NTN; and, based on determining that the paging is unsuccessful, send an indication to the core network unit of the terrestrial network to which the communication device is registered that the communication device should be paged by the terrestrial network.

47. A method for operating a core network unit for a terrestrial network, the method comprising: The system receives an instruction from the core network unit for non-terrestrial networks (NTNs) that a communication device registered with the core network unit of the terrestrial network should be paged by the terrestrial network; and sends instructions to one or more infrastructure devices of the terrestrial network to send a paging message for the communication device to receive.

48. A core network unit for a terrestrial network, the core network unit comprising: The network interface is configured to send and / or receive communications from the infrastructure equipment of the terrestrial network; The controller, together with the network interface, is configured to: receive from the core network unit for non-terrestrial networks (NTNs) an indication that a communication device registered with the core network unit of the terrestrial network should be paged by the terrestrial network; and send instructions to one or more infrastructure devices of the terrestrial network to send a paging message for the communication device to receive.

49. A circuit system for a core network section of a terrestrial network, the circuit system comprising: A network interface circuit is configured to send and / or receive communications from the infrastructure equipment of the terrestrial network; The controller circuit, together with the network interface circuit, is configured to: receive from the core network unit for non-terrestrial networks (NTNs) an indication that a communication device registered with the core network unit of the terrestrial network should be paged by the terrestrial network; and send instructions to one or more infrastructure devices of the terrestrial network to send a paging message for the communication device to receive.

50. A method of operating a communication device configured to transmit uplink signals to one or more non-terrestrial infrastructure devices forming part of a non-terrestrial network (NTN) and / or receive downlink signals from the one or more non-terrestrial infrastructure devices, the method comprising: Measure the strength of one or more reference signals from the one or more non-ground infrastructure devices; A timer is started when the strength of one or more of the measured reference signals drops below a predetermined threshold; and an alarm is generated for the user of the communication device when the timer expires.

51. A communication device, comprising: The transceiver is configured to transmit uplink signals to one or more non-terrestrial infrastructure devices that form part of a non-terrestrial network (NTN) and / or receive downlink signals from the one or more non-terrestrial infrastructure devices. The transceiver is configured to: measure the strength of one or more reference signals from the one or more non-ground infrastructure devices; start a timer based on the measured strength of the one or more reference signals dropping below a predetermined threshold; and generate an alarm for the user of the communication device based on the timer expiring.

52. A circuit system for a communication device, the circuit system comprising: The transceiver circuit is configured to transmit uplink signals to one or more non-terrestrial infrastructure devices that form part of a non-terrestrial network (NTN) and / or receive downlink signals from the one or more non-terrestrial infrastructure devices. The controller circuit, together with the transceiver circuit, is configured to: measure the strength of one or more reference signals from the one or more non-ground infrastructure devices; start a timer based on the measured strength of the one or more reference signals dropping below a predetermined threshold; and generate an alarm for the user of the communication device based on the timer expiring.

53. A method of operating non-terrestrial infrastructure equipment forming part of a non-terrestrial network (NTN), the method comprising: The strength of one or more reference signals from a communication device configured to send uplink signals to and / or receive downlink signals from an infrastructure device is measured; a timer is started based on the measured strength of the one or more reference signals dropping below a predetermined threshold; and a paging message is sent to the communication device after the timer expires.

54. A non-terrestrial infrastructure device for a non-terrestrial network, the non-terrestrial infrastructure device comprising: A transceiver is configured to transmit downlink signals to one or more communication devices and / or receive uplink signals from said one or more communication devices; The transceiver is configured to: measure the strength of one or more reference signals from a communication device configured to send uplink signals to the infrastructure equipment and / or receive downlink signals from the infrastructure equipment; start a timer based on the measured strength of the one or more reference signals dropping below a predetermined threshold; and send a paging message to the communication device after the timer expires.

55. A circuit system for non-terrestrial infrastructure equipment in a non-terrestrial network, the circuit system comprising: A transceiver circuit is configured to transmit downlink signals to one or more communication devices and / or receive uplink signals from the one or more communication devices. The transceiver also includes a controller circuit configured to: measure the strength of one or more reference signals from a communication device configured to transmit uplink signals to the infrastructure device and / or receive downlink signals from the infrastructure device; start a timer based on the measured strength of one or more reference signals dropping below a predetermined threshold; and send a paging message to the communication device after the timer expires.

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