WO2022200682A1

WO2022200682A1 - Signal compensation

Info

Publication number: WO2022200682A1
Application number: PCT/FI2022/050180
Authority: WO
Inventors: Mads LAURIDSEN; Jeroen Wigard; Frank Frederiksen
Original assignee: Nokia Technologies Oy
Priority date: 2021-03-22
Filing date: 2022-03-21
Publication date: 2022-09-29
Also published as: EP4289085A1

Abstract

According to an example aspect of the present invention, there is provided an apparatus (110) configured to receive, from a network, a non-terrestrial network gateway (130) location, determine, from the non-terrestrial network gateway location, from ephemeris information of a satellite (120) and from a location of the apparatus, a service link (112) delay between the apparatus and the satellite and a feeder link (123) delay between the satellite and the non-terrestrial network gateway, for communication with a cell provided by the non-terrestrial network gateway via the satellite, and employ the determined service link delay and the feeder link delay in communicating, via the satellite, with the cell provided by the non-terrestrial network gateway, wherein the apparatus is a user equipment or configured to be installed in a user equipment.

Description

SIGNAL COMPENSATION

FIELD

[0001] The present disclosure relates to the field of wireless communication, in particular as it relates to satellite-enhanced or satellite-based cellular systems.

BACKGROUND

[0002] Wireless communication may comprise, in general, cellular and non-cellular wireless communication. Cellular systems include terrestrial cellular systems, where a radio-access network is arranged to provide service to a coverage area of the terrestrial cellular system. The radio-access network of the terrestrial cellular system is built on land and comprises, in general, plural base station nodes. Such base station nodes may be referred to using different terms depending on the radio-access technology in use.

[0003] Non-terrestrial cellular systems a networks where space-home, that is, satellite, or airborne vehicles act either as a relay node or as a base station. In the relay case the architecture is named transparent and in the case of base stations, the architecture is referred to as a regenerative architecture.

SUMMARY [0004] According to some aspects, there is provided the subject-matter of the independent claims. Some embodiments are defined in the dependent claims. The scope of protection sought for various embodiments of the invention is set out by the independent claims. The embodiments, examples and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the invention.

[0005] According to a first aspect of the present disclosure, there is provided an apparatus comprising at least one processing core, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processing core, cause the apparatus at least to receive, from a network, a non-terrestrial network gateway location, determine, from the non-terrestrial network gateway location, from ephemeris information of a satellite and from a location of the apparatus, a service link delay between the apparatus and the satellite and a feeder link delay between the satellite and the non-terrestrial network gateway, for communication with a cell provided by the non-terrestrial network gateway via the satellite, and employ the determined service link delay and the feeder link delay in communicating, via the satellite, with the cell provided by the non-terrestrial network gateway, wherein the apparatus is a user equipment or configured to be installed in a user equipment.

[0006] According to a second aspect of the present disclosure, there is provided an apparatus comprising at least one processing core, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processing core, cause the apparatus at least to receive, from a cell, at least one non-terrestrial network gateway location, the apparatus comprising a satellite or an apparatus adapted to be installed in a satellite, transmit at least one of the at least one non-terrestrial network gateway location and ephemeris information of the satellite toward the surface of the Earth, and relay information between user equipments on the surface of the Earth and a specific one from among the at least one non-terrestrial network gateway.

[0007] According to a third aspect of the present disclosure, there is provided a method comprising receiving, in an apparatus, from a network, a non-terrestrial network gateway location, determining, by the apparatus, from the non-terrestrial network gateway location, from ephemeris information of a satellite and from a location of the apparatus, a service link delay between the apparatus and the satellite and a feeder link delay between the satellite and the non-terrestrial network gateway, for communication with a cell provided by the non-terrestrial network gateway via the satellite, and employing the determined service link delay and the feeder link delay in communicating, via the satellite, with the cell provided by the non-terrestrial network gateway, wherein the apparatus is a user equipment or configured to be installed in a user equipment.

[0008] According to a fourth aspect of the present disclosure, there is provided receiving, from a cell, at least one non-terrestrial network gateway location, the apparatus comprising a satellite or an apparatus adapted to be installed in a satellite, transmitting at least one of the at least one non-terrestrial network gateway location and ephemeris information of the satellite toward the surface of the Earth, and relaying information between user equipments on the surface of the Earth and a specific one from among the at least one non-terrestrial network gateway.

[0009] According to a fifth aspect of the present disclosure, there is provided an apparatus comprising means for receiving, from a network, a non-terrestrial network gateway location, means for determining, from the non-terrestrial network gateway location, from ephemeris information of a satellite and from a location of the apparatus, a service link delay between the apparatus and the satellite and a feeder link delay between the satellite and the non-terrestrial network gateway, for communication with a cell provided by the non-terrestrial network gateway via the satellite, and means for employing the determined service link delay and the feeder link delay in communicating, via the satellite, with the cell provided by the non-terrestrial network gateway, wherein the apparatus is a user equipment or configured to be installed in a user equipment.

[0010] According to a sixth aspect of the present disclosure, there is provided an apparatus comprising means for receiving, from a cell, at least one non-terrestrial network gateway location, the apparatus comprising a satellite or an apparatus adapted to be installed in a satellite, means for transmitting at least one of the at least one non-terrestrial network gateway location and ephemeris information of the satellite toward the surface of the Earth, and means for relaying information between user equipments on the surface of the Earth and a specific one from among the at least one non-terrestrial network gateway.

[0011] According to a seventh aspect of the present disclosure, there is provided a non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least receive, from a network, a non-terrestrial network gateway location, determine, from the non-terrestrial network gateway location, from ephemeris information of a satellite and from a location of the apparatus, a service link delay between the apparatus and the satellite and a feeder link delay between the satellite and the non-terrestrial network gateway, for communication with a cell provided by the non-terrestrial network gateway via the satellite, and employ the determined service link delay and the feeder link delay in communicating, via the satellite, with the cell provided by the non-terrestrial network gateway, wherein the apparatus is a user equipment or configured to be installed in a user equipment. [0012] According to an eighth aspect of the present disclosure, there is provided a non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least receiving, from a cell, at least one non-terrestrial network gateway location, the apparatus comprising a satellite or an apparatus adapted to be installed in a satellite, transmitting at least one of the at least one non-terrestrial network gateway location and ephemeris information of the satellite toward the surface of the Earth, and relaying information between user equipments on the surface of the Earth and a specific one from among the at least one non-terrestrial network gateway. [0013] According to a ninth aspect of the present disclosure, there is provided a computer program configured to cause at least the following to be performed, when performed by an apparatus: receiving, from a network, a non-terrestrial network gateway location, determining, from the non-terrestrial network gateway location, from ephemeris information of a satellite and from a location of the apparatus, a service link delay between the apparatus and the satellite and a feeder link delay between the satellite and the non terrestrial network gateway, for communication with a cell provided by the non-terrestrial network gateway via the satellite, and employing the determined service link delay and the feeder link delay in communicating, via the satellite, with the cell provided by the non terrestrial network gateway , wherein the apparatus is a user equipment or configured to be installed in a user equipment.

[0014] According to a tenth aspect of the present disclosure, there is provided a computer program configured to cause at least the following to be performed, when performed by an apparatus: receiving, from a cell, at least one non-terrestrial network gateway location, the apparatus comprising a satellite or an apparatus adapted to be installed in a satellite, transmitting at least one of the at least one non-terrestrial network gateway location and ephemeris information of the satellite toward the surface of the Earth, and relaying information between user equipments on the surface of the Earth and a specific one from among the at least one non-terrestrial network gateway.

BRIEF DESCRIPTION OF THE DRAWINGS [0015] FIGURE 1 illustrates an example system in accordance with at least some embodiments of the present invention;

[0016] FIGURE 2 illustrates a scenario using an inter-satellite link in accordance with at least some embodiments of the present invention; [0017] FIGURE 3 illustrates an example apparatus capable of supporting at least some embodiments of the present invention;

[0018] FIGURE 4 illustrates signalling in accordance with at least some embodiments of the present invention;

[0019] FIGURE 5 illustrates signalling in accordance with at least some embodiments of the present invention;

[0020] FIGURE 6 is a flow graph of a method in accordance with at least some embodiments of the present invention, and

[0021] FIGURE 7 is a flow graph of a method in accordance with at least some embodiments of the present invention.

EMBODIMENTS

[0022] In a non-terrestrial cellular system, NTN, the user equipment, UE, may be provisioned with information which enables the UE to determine a feeder link delay, for example. Further, inter-satellite link delays may be accounted for by the UE when communicating with an NTN gateway, NTN-GW via a satellite. Accounting for these delays enables, for example, the UE to estimate a time, such as a timing advance value required for uplink transmission time alignment. Further, a Doppler correction factor may be determined by the UE, providing the advantage that the network needs to provide relatively less information to the UE, which conserves energy and transmission resources, such as frequency and interference, in the overall system. Further, accurate estimates of service link delay, feeder link delay and the Doppler correction factor facilitates controlling uplink interference. [0023] FIGURE 1 illustrates an example system in accordance with at least some embodiments of the present invention. Illustrated is UE 110, which may comprise, for example, a machine-type communication device, such as a utility meter, connected car or connected aircraft communication module or an industrial control device. Further, UE 110 may comprise a user device such as a smartphone, feature phone, tablet computer, laptop or desktop computer or a smartwatch, for example. UE 110 may be a NTN UE or a dual capability UE which is also capable of communicating via terrestrial wireless systems, such as terrestrial cellular and/or non-cellular systems. Examples of terrestrial cellular systems include long term evolution, LTE, and fifth generation, 5G, also known as new radio, NR. Examples of terrestrial non-cellular systems include wireless local area network, WLAN, and worldwide interoperability for microwave access, WiMAX. Examples of NTN cellular systems include 3^rd generation partnership project, 3GPP, 5G or LTE NTN and satellite Internet of Things.

[0024] UE 110 may be furnished with a satellite navigation capability, for example in the form if a satellite navigation receiver installed in UE 110 and configured to receive signals from a navigation satellite constellation, such as global positioning system, GPS, and/or the Galileo constellation. A satellite navigation capability may be used to determine the location and/or current time at UE 110. The satellite navigation satellite constellation may be distinct from a NTN satellite constellation the UE is configured to use for communication.

[0025] A service link 112 connects UE 110 with satellite 120. Satellite 120 is in orbit about the Earth, for example in low-Earth orbit, LEO, or medium-Earth orbit, MEO. A LEO orbit is usually defined as an orbit of less than 2000 kilometres altitude and an orbital eccentricity of less than 0,25. A MEO orbit, on the other hand, is usually defined as an orbit of higher than 2000 kilometres in altitude and less than the geosynchronous orbit, 35786 kilometres, in altitude. Satellite 120 may be a transparent relay, meaning that satellite 120 acts as an amp lify-and- forward type of relay between UE 110 and an NTN- GW 130 on the Earth’s surface. Satellite 120 may be solar-powered or powered by heat from radioactive decay, for example. The satellite’s orbit 101 is, in part, schematically denoted in FIGURE 1, as is its momentary orbital velocity vector 120v. Service link 112 may convey information in the downlink, from satellite 120 to UE 110, and in the uplink from UE 110 to satellite 120. [0026] Satellite 120 may be configured to provide its ephemeris information to receivers, such as UEs, on the surface. The ephemeris information may comprise information on the satellite’s position and movement, at least for a certain time period. For example, the ephemeris information may comprise at least part of the satellite’s orbital parameters, such as altitude and the direction and amplitude of velocity vector 120v. Each satellite may serve one or more than one cell. Likewise, each NTN-GW 130 may serve one or more than one cell and/or satellite. One base station 134 may control one or more cells. The ephemeris information of satellite 120 may comprise information on at least one inter satellite connection along a signal path from satellite 120 to the non-terrestrial network gateway. In detail, the ephemeris information may comprise the ephemeris information of the satellites along the data path from satellite 120 to the non-terrestrial network gateway. Further, the ephemeris information may be condensed to a smaller size when two or more of the satellites along the signal path from the satellite to the non-terrestrial network gateway have the same orbit. In that case, the orbital parameters need not be included more than once in the ephemeris information.

[0027] Satellite 120 has feeder link 123 with NTN-GW 130. As is the case with service link 112, feeder link 123 can convey information in both directions, uplink and downlink. Service link 112 and feeder link 123 are both wireless links, but they need not comply with the same wireless technology although in some implementations, service link 112 and feeder link 123 are based on the same wireless technology. NTN-GW may comprise a base station node 134, or it may be arranged in connection with a base station node 134, wherefore UE 110 may access a NTN cellular system via satellite 120 such that satellite 120 acts as the bidirectional relay between UE 110 and NTN-GW 130. In at least some embodiments, it is the base station node 134 which has an interface with gateway or core network 140. NTN-GW 130 maybe connected with further nodes via a gateway or core network 140, for example. In particular, satellite 120 may act as a transparent relay which means the satellite acts as an amplify-and- forward type of relay between UE 110 and an NTN-GW 130 on Earth, wherein the satellite does not modify the information content modulated in the signals it relays.

[0028] While satellite 120 and UE 110 are mobile, the satellite moreover moving very fast, NTN-GW 130 is a stationary node and its location is constant. When a constellation of satellites 120 is employed, UE 110 may in principle be almost anywhere, or indeed anywhere, on the Earth’s surface. Compared to terrestrial cellular systems, NTN cellular systems may need enhanced time synchronization and frequency corrections. Such enhancements are more central in NTN systems due to the long propagation distance between UE 110 and satellite 120 over service link 112, but also due to the fast movement of satellites which causes Doppler shifts. The latter applies in particular to LEO satellites, which move about 7.5 km/s relative to the Earth’s surface at an altitude of 600-1200 km, for example, above the surface. Furthermore, in transparent satellites, there is an additional time delay and frequency shift due to feeder link 123 between NTN-GW 130 and satellite 120.

[0029] To be able to estimate an overall delay value, that is, the time a signal takes to propagate from UE 110 to NTN-GW 130 via satellite 120, the UE 110 should know the delay associated with service link 112 and the delay associated with feeder link 123. While the service-link delay may be estimated from the location of UE 110, obtained, for example, from satellite navigation, and the ephemeris information of satellite 120, the feeder- link delay can be estimated if the UE 110 knows the satellite ephemeris and the location of NTN-GW 130. The feeder-link delay will, further, change as a function of time as satellite 120 moves along its orbit. When the location of NTN-GW 130 is known, the feeder-link delay as a function of time is predictable based on the satellite orbit. In general, the NTN-GW location may be expressed in geo-coordinates or as a name of a city where the NTN-GW is located, for example. Further, to apply a correct Doppler correction factor, the movement state of the satellite may be determined, from the satellite ephemeris information. A Doppler correction factor applied at the UE 110 may also correct for Doppler shift between satellite 120 and NTN-GW 130. The overall delay value may also account for possible delay incurred in satellite 120.

[0030] The overall delay value may be used to select a correct timing advance value, such that transmissions from UE 110 will arrive at NTN-GW 130 correctly within the cellular frame structure of the system.

[0031] To enable UE 110 to estimate the overall delay value, UE 110 may be provided the NTN-GW 130 location. This may also enable UE 110 to estimate the overall delay value as a function of time, at least for a limited period of time.

[0032] As a first option, each cell of the NTN cellular system may broadcast, or otherwise transmit, the location of the NTN-GW which the cell is connected through. For example, the NTN-GW location may be broadcast such that the UE need not request it. A system information block may be used for such broadcasting, for example. In some embodiments, the NTN-GW location may be included in the satellite ephemeris information provided from the satellite. In some of these embodiments, the NTN-GW location is not included in each and every satellite ephemeris information transmission. For example, in such embodiments the NTN-GW location may be included in every fifth or every tenth such transmission, for example.

[0033] As a second option, the NTN cellular system may provide locations of plural non-terrestrial network gateways and their associated identities. Each cell may then provide an identity of its NTN-GW, to enable UE 110 to select the correct NTN-GW 130 location based on the identity and the associated location. In some embodiments, the NTN- GW identity may be included in the satellite ephemeris information provided from the satellite. The NTN-GW locations and the mapping to NTN-GW identities may be provided infrequently via broadcast or dedicated radio resource control, RRC, signalling because the information is static. In some variants of the second option, the locations of the plural non terrestrial network gateways and their associated identities are pre-provisioned in the UE, for example at manufacture or at insertion of a subscriber module, such as SIM card, into the UE. The UE could then retrieve the plural locations during use, from a memory internal to the UE.

[0034] As a third option, the system may transmit a mapping of plural non-terrestrial network gateway locations to their associated non-terrestrial network gateway identities and to their associated satellite identifiers. Each satellite may then provide an identifier of the satellite, allowing the UE to determine the associated NTN-GW identity and the location of the associated NTN-GW, based on the mapping.

[0035] FIGURE 2 illustrates a scenario using an inter-satellite link. Some satellite constellations may be configured to support relaying between satellites of the constellation via inter-satellite links 122. In FIGURE 2, two satellites 120, 220 are illustrated with an inter-satellite link 122 arranged between them. Thus service link 112 is from satellite 120 to UE 110. An overall feeder link is from satellite 120 to satellite 220 via inter-satellite link 122, and to NTN GW 130 via link 123. The overall data path from UE 110 to NTN- GW 130 thus traverses both satellite 120 and satellite 220, in both directions.

[0036] In case one or more inter-satellite links are comprised in a data path from UE 110 to NTN-GW 130, the delay(s) of such inter-satellite links may be informed to the UE in the satellite ephemeris information, for example. Further, ephemeris information of each satellite participating in the overall data path may be informed to UE 110. Using inter satellite links the number of NTN-GWs needed may be reduced, as the UE data may be conveyed to a NTN-GW from farther away. The longer is the chain of inter-satellite links, the longer is the possible range to an NTN-GW and consequently the lower is the number of needed NTN-GWs.

[0037] In general, the determined overall delay value and Doppler correction factor may be used by UE 110 when invoking a random access process with NTN-GW 130 to access the NTN cellular system, for example. Inter-satellite links may be radio links, directional microwave links, optical links or laser links, for example.

[0038] The connection between the satellite and the NTN-GW may persist for quite some time, because this feeder link may be facilitated using high-gain directional antennas and relatively high transmit power. This allows to operate the link over longer distances and lower elevation angles, when compared to the service link. Due to longevity of the feeder link, the UE only needs to obtain the NTN-GW location information once per cell, that is, only upon handovers.

[0039] In the second and third options, it may be feasible for the network to broadcast the list of NTN-GW locations infrequently and instead only provide the NTN- GW ID (satellite ID in case of the third option) more frequently. Whenever the UE experiences a handover to another cell of the same satellite it can reuse the previously obtained NTN-GW location and/or identity. If a UE arrives from a cell on another satellite, the UE will already have the NTN-GW locations, and after receiving the broadcasted NTN-GW ID of the new cell the UE can initiate an access attempt.

[0040] In practical implementations, the required number of NTN-GWs is estimated to be around 30-50. Therefore, a mapping with 64 possible NTN-GW identities could suffice. Depending on UE mobility, the number of possible identifiers may be reduced further to 32, for example, and then be reused in various parts of the world such that e.g. NTN GW 1 corresponds to location A in North America and location B when in Asia.

[0041] In some cases, there may be a further delay in routing between NTN-GW and an actual base station, or other network node, of the non-terrestrial cellular system. Such further delays may be handled locally, or signalled toward the UE to thereby cause the UE to add the delay to the overall delay value before initiating connectivity toward the NTN- GW.

[0042] FIGURE 3 illustrates an example apparatus capable of supporting at least some embodiments of the present invention. Illustrated is device 300, which may comprise, for example, a device such as UE 110 or, in applicable parts, satellite 120 of FIGURE 1 or FIGURE 2. Comprised in device 300 is processor 310, which may comprise, for example, a single- or multi-core processor wherein a single-core processor comprises one processing core and a multi-core processor comprises more than one processing core. Processor 310 may comprise, in general, a control device. Processor 310 may comprise more than one processor. Processor 310 may be a control device. A processing core may comprise, for example, a Cortex-A8 processing core manufactured by ARM Holdings or a Zen processing core designed by Advanced Micro Devices Corporation. Processor 310 may comprise at least one Qualcomm Snapdragon and/or Intel Xeon processor. Processor 310 may comprise at least one application-specific integrated circuit, ASIC. Processor 310 may comprise at least one field-programmable gate array, FPGA. Processor 310 may be means for performing method steps in device 300, such as receiving, determining, employing, storing, transmitting and/or relaying, for example. Processor 310 may be configured, at least in part by computer instructions, to perform actions.

[0043] A processor may comprise circuitry, or be constituted as circuitry or circuitries, the circuitry or circuitries being configured to perform phases of methods in accordance with embodiments described herein. As used in this application, the term “circuitry” may refer to one or more or all of the following: (a) hardware -only circuit implementations, such as implementations in only analog and/or digital circuitry, and (b) combinations of hardware circuits and software, such as, as applicable: (i) a combination of analog and/or digital hardware circuit(s) with software/firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation. [0044] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0045] Device 300 may comprise memory 320. Memory 320 may comprise random- access memory and/or permanent memory. Memory 320 may comprise at least one RAM chip. Memory 320 may comprise solid-state, magnetic, optical and/or holographic memory, for example. Memory 320 may be at least in part accessible to processor 310. Memory 320 may be at least in part comprised in processor 310. Memory 320 may be means for storing information. Memory 320 may comprise computer instructions that processor 310 is configured to execute. When computer instructions configured to cause processor 310 to perform certain actions are stored in memory 320, and device 300 overall is configured to run under the direction of processor 310 using computer instructions from memory 320, processor 310 and/or its at least one processing core may be considered to be configured to perform said certain actions. Memory 320 may be at least in part comprised in processor 310. Memory 320 may be at least in part external to device 300 but accessible to device 300.

[0046] Device 300 may comprise a transmitter 330. Device 300 may comprise a receiver 340. Transmitter 330 and receiver 340 may be configured to transmit and receive, respectively, information in accordance with at least one cellular or non-cellular standard. Transmitter 330 may comprise more than one transmitter. Receiver 340 may comprise more than one receiver.

[0047] Device 300 may comprise user interface, UI, 360. UI 360 may comprise at least one of a display, a keyboard, a touchscreen, a vibrator arranged to signal to a user by causing device 300 to vibrate, a speaker and a microphone. A user may be able to operate device 300 via UI 360, for example to accept incoming telephone calls, to originate telephone calls or video calls, to browse the Internet, to manage digital files stored in memory 320 or on a cloud accessible via transmitter 330 and receiver 340 and/or to play games.

[0048] Device 300 may comprise or be arranged to accept a user identity module 370. User identity module 370 may comprise, for example, a subscriber identity module, SIM, card installable in device 300. A user identity module 370 may comprise information identifying a subscription of a user of device 300. A user identity module 370 may comprise cryptographic information usable to verify the identity of a user of device 300 and/or to facilitate encryption of communicated information and billing of the user of device 300 for communication effected via device 300.

[0049] Processor 310 may be furnished with a transmitter arranged to output information from processor 310, via electrical leads internal to device 300, to other devices comprised in device 300. Such a transmitter may comprise a serial bus transmitter arranged to, for example, output information via at least one electrical lead to memory 320 for storage therein. Alternatively to a serial bus, the transmitter may comprise a parallel bus transmitter. Likewise processor 310 may comprise a receiver arranged to receive information in processor 310, via electrical leads internal to device 300, from other devices comprised in device 300. Such a receiver may comprise a serial bus receiver arranged to, for example, receive information via at least one electrical lead from receiver 340 for processing in processor 310. Alternatively to a serial bus, the receiver may comprise a parallel bus receiver.

[0050] Device 300 may comprise further devices not illustrated in FIGURE 3. For example, where device 300 comprises a smartphone, it may comprise at least one digital camera. Some devices 300 may comprise a back- facing camera and a front-facing camera, wherein the back-facing camera may be intended for digital photography and the front- facing camera for video telephony. Device 300 may comprise a fingerprint sensor arranged to authenticate, at least in part, a user of device 300. In some embodiments, device 300 lacks at least one device described above. For example, some devices 300 may lack user identity module 370.

[0051] Processor 310, memory 320, transmitter 330, receiver 340, UI 360 and/or user identity module 370 may be interconnected by electrical leads internal to device 300 in a multitude of different ways. For example, each of the aforementioned devices may be separately connected to a master bus internal to device 300, to allow for the devices to exchange information. However, as the skilled person will appreciate, this is only one example and depending on the embodiment various ways of interconnecting at least two of the aforementioned devices may be selected without departing from the scope of the present invention.

[0052] FIGURE 4 illustrates signalling in accordance with at least some embodiments of the present invention. On the vertical axes are disposed, on the left, UE 110, in the middle, cells 120/1 and 120/2 of satellite 120 and on the right, NTN-GW 130. Time advances from the top toward the bottom.

[0053] Phase 410 represents the feeder link, which is active throughout the process of FIGURE 4, although for the sake of clarity of the illustration it is drawn at the top of the diagram.

[0054] In phase 420, satellite 120 transmits its ephemeris information from cell 120/1. This information is received in UE 110. This ephemeris information includes, in the example of FIGURE 4, also the location of NTN-GW 130, expressed for example in geo coordinates. In phase 430, UE 110 uses the information it received in phase 420 to determine the signal propagation delays of the serving and feeder links, as well as, optionally, a Doppler correction factor between UE 110 and satellite 120.

[0055] In phase 440, data transmission takes place between UE 110 and NTN-GW 130 via satellite 120 and its cell 120/1. In this communication, and/or its initiation, UE 110 employs the signal propagation delays of the serving and feeder links, and the optional Doppler correction factor determined in phase 430. Satellite 120 acts as a transparent relay in phase 440.

[0056] In phase 450, UE 110 determines a need to hand over to cell 120/2. This determination may be based on measurements indicating that cell 120/1 is fading and cell 120/2 gaining in signal strength, for example, the cells may correspond to directional beams from satellite 120, for example.

[0057] In phase 460, satellite 120 transmits its ephemeris information from cell 120/2. This information is received in UE 110. This ephemeris information includes also the location of NTN-GW 130, expressed for example in geo-coordinates. In phase 470, UE 110 uses the information it received in phase 460 to determine the signal propagation delays of the serving and feeder links, as well as a Doppler correction factor between UE 110 and satellite 120.

[0058] In phase 480, data transmission takes place between UE 110 and NTN-GW

130 via satellite 120 and its cell 120/2. In this communication, and/or its initiation, UE 110 employs the signal propagation delays of the serving and feeder links, and the Doppler correction factor determined in phase 470. Satellite 120 acts as a transparent relay in phase 480.

[0059] After the illustrated process, a further handover to a cell of another satellite could be contemplated, for example once more as a response to measured fading of signal strength. Since satellites move all the time, their cells do not remain stationary and UEs are expected to handover to different cells and satellites even if the UEs themselves do not move. The other satellite may transmit its ephemeris information, which may include the location of the NTN-GW it uses, or, in case the UE is provided with the mapping of NTN- GW locations to NTN-GW identities, the ephemeris information of the other satellite need only comprise the NTN-GW identity, enabling the UE to determine the corresponding location using the association it has been previously provided.

[0060] FIGURE 5 illustrates signalling in accordance with at least some embodiments of the present invention. On the vertical axes are disposed, on the left, UE 110, in the middle, cells 120/1 and 120/2 of satellite 120 and on the right, NTN-GW 130. The axis corresponding to cell 120/2 is present only at the bottom part of the figure to enhance clarity of the illustration. Time advances from the top toward the bottom. Cells 120/1 and 120/2 are provided by satellite 120, as in the process of FIGURE 4.

[0061] Feeder link 510 connects satellite 220 and NTN-GW 130, in a continuous manner, as feeder link 410 did in FIGURE 4 for satellite 120. Inter-satellite link 520 connects satellites 120 and 220 in a continuous or semi-continuous manner, despite being illustrated in the top part of the diagram for the sake of clarity. The satellites may have orbits which keep them at a fairly similar distance from each other for at least a limited time, for example.

[0062] In phase 530, satellite 220 provides its ephemeris information to satellite 120. In phase 540, satellite 120 provides, via cell 120/1, to UE 110 the ephemeris information of satellites 120 and 220, the NTN-GW location and information on the signal propagation delay of inter-satellite link 520 between satellites 120 and 220.

[0063] In phase 550, UE 110 uses the information received in phase 540 to determine the overall delay value, including the serving, inter-satellite and feeder link delays, and optionally Doppler correction value. In phase 560, the UE 110 communicates with the NTN cellular system via satellites 120, 220 and NTN-GW 130.

[0064] In phase 570, UE 110 determines a need to hand over to cell 120/2. This determination may be based on measurements indicating that cell 120/1 is fading and cell 120/2 gaining in signal strength, for example. In phase 580, the UE receives ephemeris information of satellites 120 and 220 via cell 120/2, enabling the determination of the overall delay value and Doppler correction for satellite 120 and 220 use, in phase 590. These are employed in phase 5100 to access the NTN cellular system via cell 120/2, inter satellite link 520, feeder link 510 and NTN-GW 130. In detail, here the UE may know how the feeder link delay changes as a function of time.

[0065] Advantages of providing the NTN-GW 130 location to the UE include that provisioning the UE with NTN-GW location(s) requires limited signaling since the NTN- GW locations are static. Compared to signaling functions/tables describing the time varying delay, the signaling savings are significant. Further, Pushing the calculation of feeder link delay variation to the UE reduces network complexity and facilitates an up-to- date and accurate estimate per UE. Knowing UE location, satellite position and base station location makes it possible to perform calculations on all the time-varying components of the system, both service link and feeder link, thereby reducing the need for providing further assistance information, which would need a time -varying component. Since the satellite ephemeris is the only node that is having significant time varying signature and this information is already available at the UE, this would simplify the needed support signalling for providing remaining information to the UE. Having accurate estimate of the overall delay value for timing advance, Doppler shift, and propagation delay for both service and feeder links in the UE reduces the potential uplink interference.

[0066] FIGURE 6 is a flow graph of a method in accordance with at least some embodiments of the present invention. The phases of the illustrated method may be performed in UE 110, or in a control device configured to control the functioning thereof, when installed therein. [0067] Phase 610 receiving, in an apparatus, from a network, a non-terrestrial network gateway location. Phase 620 comprises determining, by the apparatus, from the non-terrestrial network gateway location, from ephemeris information of a satellite and from a location of the apparatus, a service link delay between the apparatus and the satellite and a feeder link delay between the satellite and the non-terrestrial network gateway, for communication with a cell provided by the non-terrestrial network gateway via the satellite. Phase 630 comprises employing the determined service link delay and the feeder link delay in communicating, via the satellite, with the cell provided by the non terrestrial network gateway, wherein the apparatus is a user equipment or configured to be installed in a user equipment. The receiving from the network may comprise receiving from the NTN cellular system, or from a land-based cellular or non-cellular system.

[0068] FIGURE 7 is a flow graph of a method in accordance with at least some embodiments of the present invention. The phases of the illustrated method may be performed in satellite 120, or in a control device configured to control the functioning thereof, when installed therein.

[0069] Phase 710 comprises receiving, from a cell, at least one non-terrestrial network gateway location, the apparatus comprising a satellite or an apparatus adapted to be installed in a satellite. Phase 720 comprises transmitting at least one of the at least one non-terrestrial network gateway location and ephemeris information of the satellite toward the surface of the Earth. Finally, phase 730 comprises relaying information between user equipments on the surface of the Earth and a specific one from among the at least one non terrestrial network gateway.

[0070] It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

[0071] Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Where reference is made to a numerical value using a term such as, for example, about or substantially, the exact numerical value is also disclosed.

[0072] As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[0073] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the preceding description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[0074] While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

[0075] The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", that is, a singular form, throughout this document does not exclude a plurality. INDUSTRIAL APPLICABILITY

[0076] At least some embodiments of the present invention find industrial application in facilitating NTN communication.

ACRONYMS LIST NTN-GW non-terrestrial network gateway UE user equipment

REFERENCE SIGNS LIST

Claims

CLAIMS:

1. An apparatus comprising at least one processing core, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processing core, cause the apparatus at least to:

- receive, from a network, a non-terrestrial network gateway location;

- determine, from the non-terrestrial network gateway location, from ephemeris information of a satellite and from a location of the apparatus, a service link delay between the apparatus and the satellite and a feeder link delay between the satellite and the non-terrestrial network gateway, for communication with a cell provided by the non-terrestrial network gateway via the satellite, and

- employ the determined service link delay and the feeder link delay in communicating, via the satellite, with the cell provided by the non-terrestrial network gateway, wherein the apparatus is a user equipment or configured to be installed in a user equipment.

2. The apparatus according to claim 1, wherein the apparatus is configured to receive the non-terrestrial network gateway location from the cell via the satellite.

3. The apparatus according to claim 1, wherein the apparatus is configured to receive locations of at least one non-terrestrial network gateway, including the non-terrestrial network gateway location, from another cell, and wherein the apparatus is configured to receive an identifier of the non-terrestrial network gateway from the cell via the satellite and to determine the non-terrestrial network gateway location based on the identifier.

4. The apparatus according to claim 1, wherein the apparatus is configured to receive a mapping of plural non-terrestrial network gateway locations to their associated non terrestrial network gateway identities and to their associated satellite identifiers, and wherein the apparatus is configured to receive an identifier of the satellite from the cell via the satellite and to determine the non-terrestrial network gateway location based on the identifier of the satellite.

5. The apparatus according to any of claims 1 - 4, wherein the ephemeris information of the satellite comprises information on at least one inter-satellite connection along a signal path from the satellite to the non-terrestrial network gateway.

6. The apparatus according to any of claims 1 - 5, wherein the apparatus is configured to receive a delay value incurred in routing between the non-terrestrial network gateway and the network node, and to employ the delay value in the communicating with the non terrestrial network gateway.

7. The apparatus according to any of claims 1 - 6, wherein the communicating with the cell provided by the non-terrestrial network gateway location via the satellite comprises initiating a random access process with the cell provided by the non-terrestrial network gateway location via the satellite.

8. The apparatus according to claim 7, wherein the apparatus is configured to employ the service link delay and the feeder link delay in selecting a time when to initiate the random access process.

9. The apparatus according to any of claims 1 - 6, wherein the apparatus is configured to determine a need to hand over to an adjacent satellite, and to receive from the adjacent satellite ephemeris information of the adjacent satellite.

10. The apparatus according to any of claims 1 - 9, wherein the apparatus is further configured to determine, from the non-terrestrial network gateway location, from ephemeris information of a satellite and from a location of the apparatus, a Doppler correction factor, and to employ the Doppler correction factor in the communicating with the non-terrestrial network gateway location via the satellite.

11. An apparatus comprising at least one processing core, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processing core, cause the apparatus at least to:

- receive, from a cell, at least one non-terrestrial network gateway location, the apparatus comprising a satellite or an apparatus adapted to be installed in a satellite; - transmit at least one of the at least one non-terrestrial network gateway location and ephemeris information of the satellite toward the surface of the Earth, and

- relay information between user equipments on the surface of the Earth and a specific one from among the at least one non-terrestrial network gateway.

12. The apparatus according to claim 11, wherein the apparatus is configured to transmit only the location of the specific one from among the at least one non-terrestrial network gateway location.

13. The apparatus according to claim 11, wherein the apparatus is configured to transmit plural non-terrestrial network gateway locations, including the location of the specific non terrestrial network gateway location, and an identifier of the non-terrestrial network gateway.

14. The apparatus according to claim 11, wherein the apparatus is configured to transmit a mapping of plural non-terrestrial network gateway locations to their associated non terrestrial network gateway identities and to their associated satellite identifiers, and an identifier of the satellite.

15. A method comprising:

- receiving, in an apparatus, from a network, a non-terrestrial network gateway location;

- determining, by the apparatus, from the non-terrestrial network gateway location, from ephemeris information of a satellite and from a location of the apparatus, a service link delay between the apparatus and the satellite and a feeder link delay between the satellite and the non-terrestrial network gateway, for communication with a cell provided by the non-terrestrial network gateway via the satellite, and

- employing the determined service link delay and the feeder link delay in communicating, via the satellite, with the cell provided by the non-terrestrial network gateway, wherein the apparatus is a user equipment or configured to be installed in a user equipment.

16. A method comprising:

- receiving, from a cell, at least one non-terrestrial network gateway location, the apparatus comprising a satellite or an apparatus adapted to be installed in a satellite;

- transmitting at least one of the at least one non-terrestrial network gateway location and ephemeris information of the satellite toward the surface of the Earth, and

- relaying information between user equipments on the surface of the Earth and a specific one from among the at least one non-terrestrial network gateway.