Methods and apparatus for non-terrestrial network user equipment based positioning

Abstract

This application relates to a method of operating user equipment (UE) capable of wireless communication with a non-terrestrial network. The method comprises receiving, at the UE, a ranging signal component from each of a plurality of satellites, the plurality of satellites belonging to the non-terrestrial network, recording, at the UE, times of reception of the ranging signal components, periodically receiving, at the UE, one or more System Information Blocks, SIBs, from at least one of the plurality of satellites, and determining, at the UE, a position of the UE based on the recorded times of reception of the ranging signal components and positioning assistance information extracted from the received SIBs. The application further relates to a corresponding method of satellite-based signal transmission, as well as to corresponding apparatus and computer program products.

Description

[0001] European Space Agency December 20, 2024

[0002] 220993PC

[0003] METHODS AND APPARATUS FOR NON-TERRESTRIAL NETWORK USER EQUIPMENT BASED POSITIONING

[0004] Technical Field

[0005] This application relates to the field of Position, Navigation, and Timing (PNT) determination. The application particularly relates to techniques for signal transmission and reception that allow for User Equipment (UE)-based positioning, in particular in Non-Terrestrial Networks (NTNs), in a GNSS- independent manner.

[0006] Background

[0007] The history of positioning in cellular networks dates to the mid-nineties and 3GPP Release 9 when enhanced Cell ID (E-CID), Observed Time Difference of Arrival (OTDOA), and network assisted Global Navigation Satellite Systems (GNSS) were originally introduced to the 3GPP Long Term Evolution (LTE) technology as an answer to U.S. Federal Communication Commission’s (FCC) 911 requirement to make cell phone location data available to emergency call dispatchers. Since Release 9, 3GPP positioning developments through Release 13 have primarily focused on enhancing OTDOA, assisted GNSS, and the LTE Positioning Protocol (LPP) with new features to expand applicability. In Release 14 significant advancements were made in positioning of Internet of Things (loT) devices with the introduction of E-CID and OTDOA positioning capabilities for Narrowband-Internet of Things (NB-loT) and LTE-Machine Type Communication (LTE-M) also known as enhanced Machine Type Communication (eMTC). With the introduction of New Radio (NR) technology and a shift towards commercial applications, 3GPP began preparing for the high-accuracy positioning demands of 5G. Key developments included the extension of LPP to support 5G NR, advanced A-GNSS, introduction of two-way positioning (RTT) and angle-based positioning, and support for positioning in FR2 bands.

[0008] NTN represents an extension of traditional cellular networks conceived to offer connectivity services via airborne platforms (e.g., High Altitude Platforms (HAPs)) and spaceborne platforms (e.g., satellites) in different constellations. These platforms carry a transmission equipment relay node European Space Agency December 20, 2024

[0009] 220993PC

[0010] (transparent payload) that simply forwards signals or carry a full base station (e.g., regenerative payload) capable of processing signals onboard.

[0011] A satellite radio access network may include as a minimum the following elements:

[0012] • A constellation of satellites in given Earth orbit. Each satellite carries either a relay node or full base station.

[0013] • An earth-based gateway that connects the satellites to a base station or a core network, depending on the choice of architecture between transparent payload (i.e., only radiofrequency filtering, frequency conversion, and amplification are performed on the signals that pass through the satellite, so that the waveform signal repeated by the payload is unchanged, for example for an onboard relay node) and regenerative payload (i.e., radiofrequency filtering, frequency conversion, amplification, as well as demodulation / decoding, switch and / or routing, coding / modulation are performed onboard the satellite, for example for an onboard full base station).

[0014] • A feeder link that connects a gateway and a satellite.

[0015] • Service link that connects a satellite and a UE.

[0016] Depending on the orbital altitude, a satellite constellation may be categorized as low earth orbit (LEO), medium earth orbit (MEO), or geostationary earth orbit (GEO). LEO constellations, with typical altitudes ranging from 300 - 2000km above the earth's surface and orbital periods ranging from 90 to 120 minutes may represent the main focus of the present disclosure, even though the proposed concepts and techniques are understood to be applicable to other types of orbits.

[0017] An NTN may embark RF or optical inter-satellite links (ISL). This will typically require a regenerative payload architecture. Furthermore, an NTN needs to embark GNSS receivers for precise orbit determination and precise time synchronization, allowing the NTN satellites to align their onboard clock to a reference time, e.g., UTC. It can make use of high accuracy GNSS solutions such as Precise Point Positioning (PPP) for better accuracy.

[0018] 3GPP Release 15 laid the foundation for NTN in 5G by defining a propagation channel model and identifying NTN-specific characteristics compared to terrestrial networks [3GPP TR 38.811]. Building on this, Release 16 addressed NTN-specific challenges— such as long propagation delays, significant Doppler shifts, and moving cells— as detailed in 3GPP TR 38.821. 3GPP SA working European Space Agency December 20, 2024

[0019] 220993PC groups also contributed: SA WG1 defined satellite service requirements (cf. [3GPP TS 22.261]) and examined 5G satellite access use cases (cf. [3GPP TR 22.822]); SA WG2 focused on architectural considerations [3GPP TR 23.737]; and SA WG5 addressed management and orchestration of integrated satellite components in 5G [3GPP TR 28.808]. Release 17 introduced New Radio-based satellite access in FR1 bands, supporting smartphones, and added NB-loT and eMTC via satellite for massive loT applications (cf. [3GPP TR 36.763]). Additionally, solutions for 5G NR / NG-RAN were specified to address NTN-specific needs using transparent payload architecture, FDD mode, and GNSS-enabled UEs. SA WG2 further specified 5G architectural support for satellite access and satellite backhaul with fixed bandwidth and latency. Release 18 built upon these advancements with studies on network-verified UE location for NTN in NR (cf. [3GPP TR 38.882]) and solutions for enhanced coverage, particularly in FR1 and above 10 GHz, along with mobility and service optimizations for NB-loT / eMTC. SA WG1 provided guidelines for extra-territorial 5G systems, including satellite (cf. [3GPP TR 22.926]), while SA WG2 defined solutions for discontinuous coverage. Release 19 continues to enhance the support of loT in NTN with specific improvements in power efficiency, device mobility, and increased capacity.

[0020] Basic loT connectivity was first introduced by 3GPP in Release 13 in the shape of NB-loT as a new narrowband radio technology to support low-power, wide-area (LPWA) connectivity specifically for loT devices. Low data rates, deep indoor coverage, long battery life (e.g., up to 10 years), lightweight protocol stack, and support for a massive number of devices are the main features introduced in Release 13. NB-loT can operate in the following deployments modes: standalone, guard-band, and in-band— allowing it to use LTE spectrum flexibly.

[0021] Release 14 brought the first round of enhancements to NB-loT such as improved data rates, mobility, and positioning, noting that Release 13 NB-loT devices did not support any positioning feature aside from simple Cell Identity (CID). LTE Positioning Protocol (LPP) is used as the positioning protocol for NB-loT devices. E-CID and OTDOA are the two positioning methods added to LPP to support location-based services for loT devices. For E-CID, the positioning is based on received signal power and quality measurements by the UE and Rx-Tx time difference measurements by the evolved NodeB (eNB) along with the cell identity (CID). For OTDOA, the UE measures the time difference of arrival of signals from three or more synchronized eNBs. Specifically, the UE measures the TOA of PRS received from multiple cells and subtracts the TOA of a reference cell from the measured TOAs to form the RSTD measurements, which are the TDOA. To perform these RSTD European Space Agency December 20, 2024

[0022] 220993PC measurements, a narrowband signal equivalent to LTE’s Positioning Reference Signal (NPRS) was introduced for NB-loT. The NPRS occupies one Physical Resource Block (PRB) and is configured to occur periodically in the time domain. The UE reports the measurements to a positioning server which uses this information to estimate the location of the UE.

[0023] There have been limited deployments of these features to date, hence they do not currently form part of the minimum feature baseline. None of the subsequent releases enhanced loT positioning with new capabilities.

[0024] Currently, in LTE Location Service (LCS) procedures, there are two main steps when positioning the UE:

[0025] • Signal measurement, performed by the UE or the serving eNB. This involves measuring signal characteristics necessary for positioning (e.g., TOA, RSTD, received signal power, etc.)

[0026] • Position estimate computation based on the measurement results. In the case of NB-loT and eMTC all RAT-dependent positioning methods operate in network-based mode.

[0027] Positioning in LTE is supported by the architecture presented below and described with greater details in 3GPP TS 36.305. Key components include:

[0028] • Gateway Mobile Location Center (GMLC): The GMLC contains functionality required to support location-based service (LBS). The GMLC is the first node that an external LBS client accesses in a GSM, UMTS, or LTE network.

[0029] • Evolved Serving Mobile Location Centre (E-SMLC): Acts as the core LTE entity responsible for coordinating and managing positioning data from both device-reported and network- calculated sources. Its NR counterpart is called Location Management Function (LMF).

[0030] • eNodeB: This term refers to the base station equipment that handles the radio interface with the mobile devices. This is commonly referred to as base station or cell tower.

[0031] UE: user equipment may be any device used directly by an end-user to communicate. It can be a hand-held telephone, a laptop computer equipped with a mobile broadband adapter, or any other communication device. European Space Agency December 20, 2024

[0032] 220993PC

[0033] Mobility Management Entity (MME): The MME’s primary role is handling control plane signaling between the user equipment and the core network. Essentially, the MME acts as the “brain” of the network, managing and controlling user mobility.

[0034] Fig. 1 schematically illustrates an example of an LTE Positioning Architecture and Protocols with building blocks split between the Evolved Packet Core (EPC) and the Evolved UMTS Terrestrial Radio Access Network (E-UTRAN). The EPC relates to the framework that provides the connection to the rest of the internet in cellular networks and is composed of several functional entities. The E-UTRAN relates to the wireless communication technology used in cellular networks.

[0035] The LPP positioning procedure workflow by which the UE can establish a connection with the network and transition to RRC_CONNECTED mode before commencing an LPP session may be as follows.

[0036] First, the MME initiates a location service or receives a location service request from the UE or GMLC, which is the interface to an external Location Based Services (LBS) client. Second, the MME sends a positioning request to the location server, E-SMLC. The E-SMLC processes the request, determines the UE’s position and sends the result back to the MME. The MME may further forward the results to the UE or GMLC as appropriate. The signaling between the E-SMLC and UE is carried out via the LPP. Through a ProvideAssistanceData message, the E-SMLC can inform the UE about the specific PRS configuration of the suggested reference and neighbor cell list. With the assistance data, the UE knows when the PRS signals are transmitted and can measure TOA based on the PRS signals accordingly. The signaling between the E-SMLC and eNB is carried out via the LPP A (LPPa) protocol.

[0037] Key positioning protocols may include the following:

[0038] • LTE Positioning Protocol (LPP) allows data exchange between UE and LMF through dedicated signaling.

[0039] • Radio Resource Control (RRC) protocol is used for communication between the UE and the eNB. The UE can be in one of two RRC modes: RRC Connected and RRC Idle mode. In the RCC Connected mode, the UE’s radio actively sends and receives messages, making this mode a power demanding mode, as the UE must maintain its synchronization with the European Space Agency December 20, 2024

[0040] 220993PC network. In RCC Idle mode, the UE’s radio performs keep-alive activities such as periodically listening to paging messages.

[0041] • LPPa: LPPa is a communication protocol between an eNodeB and an LCS server for controlplane positioning.

[0042] • Location Services - Application Protocol (LCS-AP): LCS-AP is a logical interface between the MME and the E-SMLC supporting the location services in E-UTRAN. The LTE Positioning Protocols (LPP and LPPa) can be carried in LCS-AP messages which are transparent to the MME.

[0043] In LTE, positioning assistance data can be included in positioning System Information Blocks (posSIBs) as described in TS 36.331 and TS 36.355. The posSIBs and the normal SIBs are carried in RRC System Information (SI) messages. An example of an LTE broadcast procedure may be as follows:

[0044] • E-SMLC instructs the eNB to start broadcasting positioning assistance information. It sends System Information groups that includes one or more posSIBs. If the posSIBs are encrypted, the E-SMLC sends the ciphering keys to the MME which then distributes the keys to authorized UEs.

[0045] • eNB broadcasts the received System Information in its broadcast messages. It may optionally provide feedback to the E-SMLC about the broadcast process.

[0046] • UEs receive the assistance data through standard system information acquisition procedures and perform position estimation.

[0047] If the assistance data changes, the E-SMLC sends updated information to the eNB and the process repeats.

[0048] Fig. 2 schematically illustrates an example of the LTE Broadcast Procedure involving a UE, eNB, MME, and E-SMLC.

[0049] The 3GPP specifications provide for network-verified locations in NR-NTN. Positioning efforts in NTN has been primarily driven by GNSS to support user access to the network, where user terminals are expected to mitigate downlink and uplink Doppler shifts and differential delays by estimating their position and velocity using GNSS, per Release 17 standards. European Space Agency December 20, 2024

[0050] 220993PC

[0051] However, positioning solutions beyond GNSS may be desirable, especially when considering that GNSS information reported by UEs could be spoofed or unreliable. By eliminating the GNSS requirement, the UE power consumption and cost will be mitigated, which is particularly important for loT devices. As a result, Release 18 introduces network verified location to enhance the network’s ability to verify the UE’s reported location independently, focusing on regulatory applications like lawful intercept, emergency calls, billing, etc. In NR-NTN, network verified location involves network-based cross-checking of device-reported locations using Radio Access Technology (RAT)-dependent methods like multi-epoch single satellite Round-Trip Time (RTT). While RTT measurements with a single satellite may provide a typical coarse 10 km positioning accuracy, they prioritize regulatory compliance over high positioning precision, helping the network to roughly verify a UE’s location. This method is not supported in loT-NTN systems.

[0052] With the proliferation of messaging services directly to smartphones via satellite, more and more flagship mobile devices (e.g., Google Pixel™ 9) are now equipped with loT-NTN technology. In addition to loT use cases, such as asset tracking, this development opens a variety of use cases including location-based services (e.g., emergency services, navigation and mapping, target alerts such as emergency warnings, etc.). As these applications require positioning information, designing RAT-dependent positioning methods within loT-NTN becomes appealing as it can unlock new applications and NTN system operation independently of support for GNSS capability at the UE.

[0053] Thus, there is a need for improved techniques for enabling positioning for terrestrial terminals (e.g., UEs) using NTNs that are GNSS independent, that enable positioning even when the terminal is not connected to the network, and / or that that are UE-based stand-alone methods. There is particular need for such techniques that are compatible with the 3GPP 4G standards, 5G standards, and beyond 5G standards.

[0054] Summary

[0055] In view of some or all these needs, the present disclosure proposes methods, apparatus, and computer program products having the features of the respective independent claims.

[0056] The first aspect of the disclosure relates to a method of operating a UE capable of wireless communication with a non-terrestrial network. The UE may have receiving and sending capabilities, in particular radio receiving and sending capabilities, for example receiving and sending capabilities European Space Agency December 20, 2024

[0057] 220993PC conforming to the 3GPP loT-NTN standard (NB-loT, LTE-eMTC) or the 3GPP NR-NTN standard. The method may be a method of positioning the UE and / or in general, a method of signal processing at the UE. The method may include receiving, at the UE, a ranging signal component from each of a plurality of satellites. The plurality of satellites may belong to the non-terrestrial network. The satellites may be satellites in view of the UE, either simultaneously or sequentially. In some implementations, the ranging signal components may include an indication of respective times of transmission, e.g., the ranging signal components may be time-stamped. The method may further include recording, at the UE, times of reception of the ranging signal components. Recording the times of reception of the ranging signal components may relate to or comprise processing the ranging signal components. The method may further include periodically receiving, at the UE, positioning assistance information from at least one of the plurality of satellites. For example, this may correspond to periodically receiving, at the UE, one or more System Information Blocks, SIBs, from the at least one of the plurality of satellites. The SIBs may include the positioning assistance information, Further, the SIBs may correspond to Narrowband loT (NB-loT), Long Term Evolution (LTE), or other cellular communication technologies supported in non-terrestrial networks, for example. Further, the one or more SIBS may be one or more of SIB31 (SIB31-NB in NB-loT) and SIB33 (SIB33-NB in NB-loT), for example as defined in T3GPP S 36.331 (loT-NTN), or one or more new SIBs to broadcast for example ionospheric corrections or ranging signal scheduling. Alternatively, the one or more SIBs may be one or more of SIB19 as defined in 3GPP TS 38.331, or one or more positioning system information blocks (posSIBs) posSlBType 6-1 NR DL-PRS-Assistance Data as defined in 3GPP TS 38.331. The method may yet further include determining, at the UE, a position of the UE based on the recorded times of reception of the ranging signal components and the positioning assistance information. For example, the positioning assistance information may be extracted from the received SIBs.

[0058] Configured as described above, the proposed method allows for UE-based positioning in a GNSS- independent manner. Any signals from the NTN that are required for this purpose will be transmitted in broadcast mode, so that the UE does not have to be connected to the NTN. This allows, in particular, determining an initial estimate of the UE position necessary for actually accessing the NTN. Importantly, the proposed method does not require modifications of legacy UEs, and only requires minimal modifications of the space segment. European Space Agency December 20, 2024

[0059] 220993PC

[0060] In some embodiments, the ranging signal components may relate to Narrowband Positioning Reference Signals ( NPRS), to Long Term Evolution (LTE) Positioning Reference Signals (PRS), or to New Radio Positioning Reference Signals (NR PRS), broadcast by the plurality of satellites. Here, narrowband may mean 180 kHz bandwidth for the case of NB-loT over NTN or 1.04 MHz bandwidth for the case of LTE-eMTC over NTN. In some implementations, the method may utilize NPRS and LTE-M PRS as per 3GPP TS 36.211, or a dense PRS grid, such as the C0MB2 grid defined in 3GPP TS 38.211, or a full PRS grid, to reduce the time required for TOA measurements. The NRPRS may be according to 3GPP TS 38.211.

[0061] In some embodiments, the ranging signal components may relate to primary and secondary synchronization signals. For loT-NTN, the primary and secondary synchronization signals may be Narrowband Primary Synchronization Signals (NPSS) and Narrowband Secondary Synchronization Signals (NSSS) as defined in TS 36.211. For NR-NTN, the primary and secondary synchronization signals may be Primary Synchronization Signals (PSS) and Secondary Synchronization Signals (SSS) as defined in TS 38.211.

[0062] (N)PRS have the advantage that they are capable of extending the pseudorandom sequence length and provide a larger pool of sequences compared to (N)PSS and (N)SSS. Since (N)PSS is an optional feature that is not always implemented, an approach relying on (N)PSS and (N)SSS could be foreseen even if performance may be lower. When (N)PRS is deployed, combining with (N)PSS and (N)SSS may be beneficial.

[0063] In some embodiments, the method may further include determining, at the UE, a respective time of transmission of each ranging signal component, by demodulating the respective ranging signal component. Then, determining, at the UE, the position of the UE may be further based on the determined times of transmission.

[0064] In some embodiments, determining, at the UE, the position of the UE may involve applying an algorithm based on times of arrival, TOA, of the ranging signal components received from the plurality of satellites.

[0065] In some embodiments, the ranging signal components may relate to time-stamped pilot signals. For example, each satellite may timestamp its ranging signal components using an onboard GNSS receiver. European Space Agency December 20, 2024

[0066] 220993PC

[0067] In some embodiments, the method may further include determining, at the UE, time difference of arrival, TDOA, measurements between ranging signal components received from different satellites. Then, determining, at the UE, the position of the UE may be based on the determined TDOA measurements. A reference satellite for TDOA may be the satellite acquired in SIB31 (SIB31-NB in the case of NB-loT, or in general, acquired from the positioning assistance information) or may be selected based on a signal strength or Signal-to-Noise Ratio, SNR, for example.

[0068] In some embodiments, determining, at the UE, the position of the UE may involve applying an algorithm based on observed time differences of arrival (OTDOA) between the ranging signal components received from the plurality of satellites.

[0069] In some embodiments, the positioning assistance information (e.g., the one or more SIBs) may include ephemeris information on the satellites’ ephemeris. The position of the UE may be determined using the satellites’ ephemeris, for example for computing the satellite’s positions and for using the determined satellites’ positions together with the TOAs or TDOAs in determining the position of the UE. Each satellite may periodically transmit positioning assistance information (e.g., SIBs) indicative of its own ephemeris. In some implementations, positioning assistance information (e.g., SIBs) transmitted by the satellites may also include ephemeris information for one or more neighboring satellites.

[0070] In some embodiments, the ephemeris information may include information beyond the six Keplerian elements. That is, the ephemeris information may include the six basic Keplerian elements (i.e. , the semi-major axis, eccentricity, mean anomaly, argument of perigee, inclination, and longitude of the ascending node), accompanied by additional information specifying the satellites’ orbits, for example three additional rate parameters (e.g., mean motion, right ascension rate of change, inclination angle rate of change) and / or six 2ndorder harmonic correction parameters (e.g., amplitude of the cosine and sine harmonic correction term to the argument of latitude, amplitude of the cosine and sine harmonic correction term to the orbit radius, amplitude of the cosine and sine harmonic correction term to the angle of inclination) and polynomial correction coefficients along-, across-, radial track. In addition, the ephemeris information may include an epoch time of the aforementioned satellite ephemeris data.

[0071] In some embodiments, the positioning assistance information (e.g., the one or more SIBs) may include clock correction information on the satellites’ internal clocks. The clock correction European Space Agency December 20, 2024

[0072] 220993PC information on the satellites’ clocks may be used by the UE for correcting the time of transmission of the ranging signal for satellite clock errors. For example, the TOAs or TDOAs may be corrected based on the clock correction information. Each satellite may periodically transmit SIBs indicative of its own clock corrections. This may allow for higher UE positioning accuracy.

[0073] In some embodiments, the positioning assistance information (e.g., the one or more SIBs) may include ionospheric information indicative of a state of the ionosphere. The ionospheric information indicative of a state of the ionosphere may be used by the UE for correcting for an impact of the ionosphere on signal propagation. For example, the TOAs or TDOAs may be corrected based on the ionospheric information. The ionospheric information may be transmitted via dedicated SIBs. These SIBs may be universal among the plurality of satellites. Periodicity of these SIBs may be lower than periodicity of SIBs including ephemeris information and / or clock correction information.

[0074] In some embodiments, the positioning assistance information (e.g., the one or more SIBs) may include configuration information including one or more of periodicity, duration, mapping to frequency-time grid pattern, and frequency band of the ranging signal components from the plurality of satellites.

[0075] In some embodiments, for each of the plurality of satellites, the ranging signal components may be periodically received at the UE, with a common period among the plurality of satellites. The ranging signal components may be transmitted by the satellites in broadcast mode. As noted above, the ranging signal components may relate to narrow-band positioning reference signals (NPRS) or narrow-band primary and secondary synchronization signals (NPSS and NSSS) in case of NB-loT or positioning reference signals (PRS) in case of 4G, or New Radio PRS (NR PRS) or primary and secondary synchronization signals inside the Synchronization Signal Block (SSB) in case of 5G.

[0076] In some embodiments, the ranging signal components may be received from at least three satellites. Alternatively, the ranging signal components may be received from four or more satellites. In the former case, positioning may require additional input from for example a height measurement. In some implementations, the UE may perform batching of several measurements at timings separate from each other and perform processing thereof at a later time, assuming limited UE dynamics. If more than four satellites are in view and there is spectrum available, other satellites NTN signals including (N)PRS may be frequency multiplexed to achieve enhanced throughput and ranging accuracy. European Space Agency December 20, 2024

[0077] 220993PC

[0078] In some embodiments, each ranging signal component may be received in a respective wide beam generated at the respective satellite. Here, a wide beam may be a beam with a half power beam width (HPBW) of at least 104.7 deg as defined in TR 36.763 for Set 4 parameters.

[0079] In some embodiments, the ranging signal components may be received in distinct, non-overlapping frequency bands to avoid mutual crosstalk, taking into account differential satellite Doppler effects. In some implementations, there may be guard bands between respective frequency bands to cope with Doppler uncertainties. Each of the plurality of satellites may provide communication service (e.g., may transmit communication signal components (payload data)) in the specific frequency band in which it (periodically) transmits its ranging signal components.

[0080] In some embodiments, the ranging signal components may be received in a single frequency band, with partial overlap in frequency between the ranging signal components. The single frequency band may be a dedicated frequency band shared by the plurality of satellites for transmitting their ranging signal components. Alternatively, the single frequency band may be a frequency band in which one of the plurality of satellites provides communication service (e.g., transmits communication signal components (payload data). In the latter case, a lower power for the ranging signal components compared to the communication signal components may be required to limit the interference to the communication data components.

[0081] In some embodiments, the UE may be in an unconnected or RCCJDLE state in relation to the nonterrestrial network comprising the plurality of satellites.

[0082] In some embodiments, the method may further include performing, at the UE, compensation of at least one of Doppler shift, time offset, and frequency offset in relation to one of the plurality of satellites based on the determined position of the UE and information indicative of an ephemeris of the one of the plurality of satellites, for deriving a time reference and / or frequency reference locked to a respective reference of the satellite, thereby enabling access to the non-terrestrial network. Broadly speaking, the UE may be capable of operating in a communication mode where it accesses the non-terrestrial network, and a positioning mode, for which the UE does not need to be connected to the non-terrestrial network and only demodulates the ranging signal components and positioning assistance information. These two modes may share a common frequency band and signal structure to optimize resource usage. European Space Agency December 20, 2024

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[0084] In some embodiments, performing, at the UE, compensation of at least one of Doppler shift, time offset, and frequency offset may include receiving a signal from the one of the plurality of satellites. Said performing, at the UE, may further include amplifying the received signal and converting the amplified signal to baseband or close to baseband, using a local oscillator. The local oscillator may be controlled so that a frequency of the local oscillator tracks a frequency of the received signal. Said performing, at the UE, may further include estimating a Doppler frequency shift of the received signal based on the determined position of the UE and the information indicative of the ephemeris of the one of the plurality of satellites. Said performing, at the UE, may further include estimating a satellite carrier frequency of the one of the plurality of satellites based on the frequency of the local oscillator and the estimated Doppler frequency shift. Said performing, at the UE, may yet further include determining at least one of the frequency reference and the timing reference based on the estimated satellite carrier frequency.

[0085] In some embodiments, the method may further include synchronizing uplink transmission in time and frequency based on the performed compensation.

[0086] In some embodiments, communication signals from the one of the plurality of satellites may be received in a narrow beam. Here, a narrow beam may be a beam with for example a HPBW of 4.4 degrees according to Set 1 or a HPBW of 8.8 degrees according to Set 2 from 3GPP TR 36.763, or a HPBW between 4.4 and 8.8 degrees.

[0087] In some embodiments, the method may further include using the determined terminal position for seamless handover between satellites that provide communication service.

[0088] In some embodiments, determining the position of the UE may be GNSS-independent.

[0089] In some embodiments, the UE may relate to a category Ml, NB1, or NB2 device as defined in 3GPP TS 36.102 or a device as defined in 3GPP TS 38.101-5.

[0090] In some embodiments, the satellites may be satellites in Low Earth orbit, LEO, or Medium Earth Orbit, MEO. Further, the method may include integrating positioning signals (e.g., ranging signal components) from satellites in multiple orbital layers, such as LEO and MEO, for improving coverage and accuracy. Further, the method may include integrating positioning signals from High Altitude Platforms (HAPs). European Space Agency December 20, 2024

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[0092] A second aspect of the disclosure relates to a method of satellite-based signal transmission. The method may include transmitting, at a satellite in a non-terrestrial network, a ranging signal component towards Earth. The method may further include transmitting, at the satellite, positioning assistance information towards Earth periodically in broadcast mode. Therein, transmission of the ranging signal component may be performed periodically in broadcast mode. The positioning assistance information may be included in one or more SIBs or positioning System Information Blocks (posSIBs).

[0093] In some embodiments, the ranging signal components may relate to a NPRS, PRS, or NR PRS. Alternatively, the ranging signal components may relate to a longer pseudo random sequence to achieve a dense PRS grid or a full PRS grid as there is no possibility to share the OFDM (N)PRS grid with other satellites. Further alternatively, the ranging signal components may relate to primary and secondary synchronization signals. In some implementations, the method may utilize NPRS and LTE- M PRS as per 3GPP TS 36.211, or a dense PRS grid, such as the COMB2 grid defined in 3GPP TS 38.211, or a full PRS grid, to reduce the time required for TOA measurements. The NR PRS may be configured according to 3GPP TS 38.211.

[0094] In some embodiments, transmission of the ranging signal component may be performed in a wide beam directed towards Earth.

[0095] In some embodiments, the method may further include receiving, at the satellite, positioning assistance information concerning one or more of satellite ephemeris, clock corrections, ionospheric corrections, and a ranging signal component signal configuration from a ground station.

[0096] In some embodiments, the method may further include providing a communication service to a UE.

[0097] In some embodiments, a transmission timing of the ranging signal component at the satellite may be aligned with a transmission timing of a communication signal component of the satellite, such that transmission of the ranging signal component and the communication signal component do not overlap in time.

[0098] In some embodiments, the ranging signal component and a communication signal component of the satellite may be transmitted in the same frequency band.

[0099] In some embodiments, the method may further include dynamically adjusting a beam pattern to provide a first beam for transmitting the ranging signal component and a second beam for providing European Space Agency December 20, 2024

[0100] 220993PC the communication service to a given UE, with a beam width of the second beam being smaller than a beam width of the first beam. Thereby, the satellite may reuse the same satellite payload for transmitting the NPRS or PRS, and for providing the communication service.

[0101] In some embodiments, the method may further include using an active or semi-active antenna to provide a first beam for transmitting the ranging signal component and a number of second beams for providing the communication service to a given UE, with a beam width of the second beams being smaller than a beam width of the first beam.

[0102] In some embodiments, the method may further include generating a plurality of narrow beams for providing communication services to a plurality of UEs. The method may yet further include broadcasting a satellite-specific overlay signal with a wider coverage area for transmitting the ranging signal component. Therein, the plurality of narrow beams and broadcasting the satellitespecific overlay signal may use the same telecom payload and frequency band.

[0103] In some embodiments, the method may further include synchronizing, at the satellite, an internal clock of the satellite with internal clocks of one or more other satellites in the non-terrestrial network based on GNSS signals received at the satellite. Additionally or alternatively, the method may further include synchronizing signal transmission, at the satellite, with signal transmission of one or more other satellites in the non-terrestrial network based on GNSS signals received at the satellite.

[0104] A third aspect of the disclosure relates to a UE. The UE may include a processor and a memory coupled with the processor. The processor may be further coupled with radio communication equipment and may be configured, using the radio communication equipment, to perform the method according to the first aspect and any of its embodiments.

[0105] A fourth aspect of the disclosure relates to a satellite. The satellite may include a processor and a memory coupled to the processor. The processor may be further coupled with radio communication equipment and may be configured, using the radio communication equipment, to perform the method according to the second aspect and any of its embodiments.

[0106] A fifth aspect of the disclosure relates to a system comprising the UE according to the third aspect and any of its embodiments and a plurality of satellites according to the fourth aspect and any of its embodiments as part of a non-terrestrial network.

[0107] Further aspects of the disclosure relate to corresponding computer programs and computer- European Space Agency December 20, 2024

[0108] 220993PC readable storage media. The computer programs may include instructions for causing one or more processors, when suitably connected to radio communication equipment (e.g., RF transmission and / or RF reception equipment) and when executing the instructions, to perform any of the methods described throughout the disclosure.

[0109] It will be appreciated that apparatus features and method steps may be interchanged in many ways. In particular, the details of the disclosed apparatus or system can be realized by the corresponding method of operating the apparatus / system or parts thereof, and vice versa, as the skilled person will appreciate. Moreover, any of the above statements made with respect to the apparatus / system are understood to likewise apply to the corresponding methods, and vice versa. Any reception- related features on the UE side may have corresponding transmission-related features on the satellite side, and any description of details of reception-related features may correspondingly apply to respective reception-related features, and vice versa.

[0110] Brief Description of the Figures

[0111] Example embodiments of the disclosure are explained below with reference to the accompanying drawings, wherein

[0112] Fig. 1 schematically illustrates an example of an LTE positioning architecture;

[0113] Fig. 2 schematically illustrates an example of an LTE Broadcast Procedure involving a UE, eNB, MME, and E-SMLC.

[0114] Fig. 3 is a flowchart illustrating an example of a UE side method according to embodiments of the disclosure;

[0115] Fig. 4 schematically illustrates an example of OTDOA (or OTDOA-based positioning) that may be applied to loT-NTN systems according to embodiments of the disclosure;

[0116] Fig. 5A and Fig. 5B are diagrams illustrating examples of orbit fitting;

[0117] Fig. 6 schematically illustrates an example of TOA (or TOA-based positioning) that may be applied to loT-NTN systems according to embodiments of the disclosure;

[0118] Fig. 7 shows an example of a time-frequency-grid for ranging signal components;

[0119] Fig. 8 shows an example of LEO constellation effects on the time-frequency grid of Fig. 7; European Space Agency December 20, 2024

[0120] 220993PC

[0121] Fig. 9 illustrates an example of an NTN PNT-COM combined system according to embodiments of the disclosure;

[0122] Fig. 10 is a functional block diagram schematically illustrating an example of an NTN PNT-COM combined payload according to embodiments of the disclosure;

[0123] Fig. 11 illustrates another example of a PNT-COM combined system according to embodiments of the disclosure;

[0124] Fig. 12 illustrates yet another example of a PNT-COM combined system according to embodiments of the disclosure;

[0125] Fig. 13 illustrates an example of a frequency plan for data component transmission according to embodiments of the disclosure;

[0126] Figs. 14A, 14B, and 14C schematically illustrate examples of time / frequency plans for ranging signal component and data component transmission according to embodiments of the disclosure;

[0127] Fig. 15A, 15B, 15C, and 15D are diagrams illustrating examples of time-frequency grids for ranging signal components according to embodiments of the disclosure;

[0128] Fig. 16 is a functional block diagram of a possible approach for the time and frequency reference extraction according to embodiments of the disclosure;

[0129] Fig. 17 is a flowchart illustrating an example of a satellite side method according to embodiments of the disclosure;

[0130] Fig. 18 is a block diagram illustrating an example of an apparatus according to embodiments of the disclosure;

[0131] Fig. 19 is a diagram illustrating a PRS symbols pattern from 3GPP TS 36.211;

[0132] Fig. 20 schematically illustrates an example of an overhead satellite pass orbit geometry;

[0133] Fig. 21 schematically illustrates and example of an NB-loT frame structure for NB-loT for DL and UL;

[0134] Fig. 22 is a diagram illustrating an example of LEO SC2 Doppler evolution versus satellite elevation angle; European Space Agency December 20, 2024

[0135] 220993PC

[0136] Fig. 23 is a diagram illustrating an example of LEO SC2 Doppler rate evolution at different altitudes versus the satellite elevation angle;

[0137] Fig. 24 is a diagram illustrating an example of the satellite distance and delay versus the satellite elevation angle for a LEO orbit at 700 km;

[0138] Fig. 25 is a diagram illustrating an example of the satellite distance and delay versus the satellite elevation angle for a LEO orbit at 1200 km;

[0139] Fig. 26 is a diagram illustrating an example of an Anywaves compact S-band TT&C antenna radiation pattern;

[0140] Fig. 27 is a diagram illustrating an example of Anywaves S-band quadrifilar helix antenna pattern;

[0141] Fig. 28 is a diagram illustrating examples of packet loss ratio as a function of average MAC channel load for Slotted ALOHA (SA) and Diversity Slotted ALOHA (DSA);

[0142] Fig. 29 and Fig. 30 are diagrams showing PRACH acquisition probability versus SNR for different repetition number and PRACH periodicity; and

[0143] Fig. 31A and Fig. 31B is a diagram illustrating the maximum number of simultaneous messages and the throughput variation during a simulated emergency event.

[0144] Detailed Description

[0145] Problem Description

[0146] When positioning in wireless systems is seen from the loT point of view, several limitations become evident.

[0147] (Quasi-)Simultaneous loT UE reception from multiple satellites for positioning

[0148] The current NTN loT standard considers that each UE is connected to the satellite in view and that a new session shall be initiated when the satellite is out of coverage due to the displacement of the satellite itself or of the UE. Since positioning is assumed to be GNSS-based, there is no consideration in the standard on the way the UE may be able to quasi-simultaneously receive multiple satellites in view for allowing UE-based positioning. The present disclosure proposes solutions at system level to resolve this issue without impact on the 3GPP NTN loT standard. European Space Agency December 20, 2024

[0149] 220993PC

[0150] Existing positioning mechanisms in TN cannot be directly applied to NTN in a one-to-one manner

[0151] This limitation is a key driver behind the techniques proposed by the present disclosure as they address system challenges for positioning frameworks in wireless systems introduced by the paradigm shift from TN to NTN. Key differences include fast moving satellite transmitting location (e.g., ~7-8 km / s for LEO), long distances from the UE (e.g., 500 - 1200 or more km in LEO), and large cell sizes (e.g., as a minimum 40-50 km but up to 1000 km for loT small satellites). The problems created by these major conceptual differences between TN and NTN are explained in detail below.

[0152] Dependency on external systems for key functions

[0153] To access an NTN system, a UE needs to overcome a significant challenge: achieving uplink time and frequency synchronization, particularly when in the presence of high Doppler frequency offset caused by the relative satell ite-U E velocity that is typical of non-geostationary orbits.

[0154] Currently, UEs rely on GNSS UE localization capabilities and NTN satellite broadcast ephemeris to compute and compensate for these offsets. The UE clock and positioning typical 3GPP accuracy requirements of 0.1 ppm (equivalent to 0.1 microseconds) and several kilometers, respectively, are the target for uplink time and frequency synchronization. Developing independent NTN positioning capabilities as an alternative to GNSS could provide a self-standing access management system, transforming NTN into an integrated self-standing positioning and communication system.

[0155] Battery drain and cost constraints imposed by GNSS in loT devices

[0156] While GNSS based-solutions may be feasible for NR devices, they are not always viable for loT devices, for example due to battery consumption and cost constraints. Even more, it seems that simultaneous GNSS and NTN NB-loT / eMTC operation is typically not assumed. This is problematic because GNSS fixes involve complex procedures such as returning to RRCJDLE mode and reaccessing the network which further contributes to the depletion of the battery and to network signaling overhead generation.

[0157] By leveraging UE-based loT-NTN positioning, devices can maintain synchronization without the need for regular GNSS fix updates, thereby reducing power consumption and latency. This will also potentially avoid the need for a dedicated GNSS antenna and front-end and thus may be an advantageous solution for low-cost devices. Moreover, loT UEs only have a single receive RF chain. European Space Agency December 20, 2024

[0158] 220993PC

[0159] No RAT-dependent positioning methods for 3GPP loT-NTN

[0160] As noted above, the current NB-loT LCS framework based on the LTE positioning architecture, protocols, and methods cannot work for loT-NTN systems unless significant changes are introduced. First of all, the enhanced Cell ID method is not suitable as the cells are very large. This is the case for NTN, with cells size spanning from several tens of kilometers to more than 1000 kilometers.

[0161] Furthermore, OTDOA is applicable to TN only, works in network-based mode, and it requires an active LPP session to retrieve the assistance data needed to perform measurements on NPRS signals. Even more problematic than this lengthy unicast session may be the fact that an LPP session cannot take place while the UE is in RRCJDLE mode. To conduct an LPP session, the UE must establish an RRC connection with the network and transition to RRC_CONNECTED mode. To successfully carry out this process, the UE needs to access the NTN system and thus it needs to perform uplink frequency and time pre-compensation. Nevertheless, this step requires the UE to know its location and the satellite location before it starts the aforementioned procedures. Although the satellites’ location can be retrieved from system information blocks, the UE location currently can be only obtained by GNSS-based means, with limitations described above.

[0162] Current loT-NTN and NR-NTN systems cannot work without GNSS UE capabilities.

[0163] As noted above, some loT devices do not have GNSS capabilities or would prefer to avoid using GNSS capabilities due to the negative impact on battery consumption, or in general, reliance on external systems which may have their own vulnerabilities. Without prior knowledge of its own location, the UE would face significant challenges in establishing an RRC connection in NTN systems.

[0164] This means that while positioning methods that can work in RRCJDLE state and UE-based mode are very appealing for loT-NTN systems, today there is no such RAT-dependent positioning method supported in loT-NTN systems. This is also the case for the single satellite RTT method available in NR-NTN systems to verify the UE location.

[0165] The present disclosure proposes solutions for providing this capability as well as enhancements to OTDOA to make this method an alternative to GNSS in loT devices. An important improvement lies in the use of new System Information Block (SIB) messages to provide the assistance information needed, as these can be retrieved while in RRCJDLE mode. In fact, receiving SIBs during RRCJDLE is essential for the UE to obtain necessary system information required for cell selection, network European Space Agency December 20, 2024

[0166] 220993PC access, and other critical operations. In addition, leveraging the GNSS receivers onboard the NTN satellites and additional assistance information, the Downlink Time of Arrival (DL-TOA) method can be used in loT-NTN systems.

[0167] Handover support in NB-loT

[0168] Seamless handover support relates to the ability to maintain a connection when the serving satellite or the satellite beam is changing due to the UE’s or the satellite’s movements. In case of satellite handover, it requires the transfer from one eNB to another, without service discontinuity.

[0169] Unlike standard LTE devices, in current NB-loT there is no seamless support for handovers in RRC_CONNECTED mode. When the UE loses connection with the serving eNB, it will have to detach and reattach to the new eNB, leading to connection drops and to power and time consumption.

[0170] The UE’s location information, when paired with for example SIB32-NB, can potentially assist in improving mobility management procedures in NB-loT networks by enabling predictive connectivity planning and understanding its position relative to satellite coverage areas. By knowing its own location and the satellites coverage information from for example SIB32-NB, the UE can anticipate when it will approach the edge of a satellite’s coverage area. This foresight can enable the UE to optimize its operational behavior, such as data transmission before losing connectivity or entering low-power mode during anticipated coverage gaps, thereby reducing power consumption typically associated with re-establishing connectivity after a drop.

[0171] The adoption of DL RAT-dependent positioning methods, as proposed below, may be appealing especially due to the ability to perform satellite handover exploiting the EDM downlink structure introduced to orthogonalize the satellite OFDM carriers. This will allow the UE to explore candidate satellites for handover. Another advantage of the proposed solution is that the UE location may be estimated with less energy consumption compared to GNSS.

[0172] Overview

[0173] The present disclosure presents innovative techniques for integrating communication and positioning services for loT wireless devices (e.g., NB-loT / eMTC) in Non-Terrestrial Networks. Specifically, the present disclosure provides practical solutions to allow a single loT device view quasi simultaneous reception from multiple satellite in view without requiring modifications to mass market terminals and with only minor adaptations to the space segment design. European Space Agency December 20, 2024

[0174] 220993PC

[0175] The present disclosure proposes a new positioning method (e.g., for 3GPP specifications) called Downlink Time of Arrival (DL-TOA) and proposes adaptations to the Observed Time Difference of Arrival (OTDOA) method to function effectively in loT-NTN systems. These methods, together with proposed assistance data enhancements, enable RAT-dependent stand-alone UE-based positioning without reliance on GNSS.

[0176] Fig. 3 is a flowchart illustrating an example of a method 300 of operating a UE capable of wireless communication with an NTN according to embodiments of the disclosure. Method 300 may be a method of positioning a UE (or mobile terminal) and / or in general, a method of signal processing at the UE (or mobile terminal). Method 300 comprises steps S310 through S340, each performed at the UE (or mobile terminal). The UE may have receiving and sending capabilities conforming to the 3GPP loT-NTN standard (NB-loT, LTE-eMTC) or the 3GPP NR-NTN standard. Specifically, the UE may relate to a category Ml, NB1, or NB2 device as defined in 3GPP TS 36.102 or to a device as defined in 3GPP TS 38.101-5.

[0177] Atstep S310, a ranging signal component is received, at the UE, from each of a plurality of satellites. The plurality of satellites belongs to the non-terrestrial network. It is understood that the satellites are satellites in view of the UE, either simultaneously or sequentially.

[0178] Further, the satellites may be satellites in LEO or MEO, for example. Also, the proposed technique may involve integrating positioning signals (e.g., ranging signal components) from satellites in multiple orbital layers, such as LEO and MEO, for improving coverage and accuracy. Further, the proposed technique may involve integrating positioning signals from High Altitude Platforms (HAPs) as well.

[0179] In some implementations, the ranging signal components may each include an indication of a respective time of transmission at the respective satellite, or in other words, the ranging signal components may be time-stamped. This may be used, for example, for purposes of TOA-based position determination as described in more detail below.

[0180] At step S320. times of reception of the ranging signal components are recorded at the UE. This recording of the times of reception of the ranging signal components may relate to or comprise processing the ranging signal components.

[0181] At step S330. one or more System Information Blocks (SIBs) are periodically received, at the UE, from at least one of the plurality of satellites. European Space Agency December 20, 2024

[0182] 220993PC

[0183] Atstep S340. a position of the UE is determined, at the UE, based on the recorded times of reception of the ranging signal components and positioning assistance information extracted from the received SIBs. For example, this may be achieved via TDOA or TOA-based techniques, as described in more detail below. Importantly, determining the position of the UE at this step is GNSS- independent.

[0184] In some embodiments, the method may instead of step S330 comprise a step of periodically receiving, at the UE, the positioning assistance information from at least one of the plurality of satellites. In this case, step S340 may omit extracting the positioning assistance information from the received SIBs.

[0185] The ranging signal components received at step S310 may relate to Narrowband Positioning Reference Signals (NPRS), to LTE Positioning Reference Signals (PRS), or to New Radio Positioning Reference Signals (NR PRS) that are respectively broadcast by the plurality of satellites. In the present context, narrowband may mean, for example, 180 kHz bandwidth for the case of NB-loT over NTN or 1.04 MHz bandwidth for the case of LTE-eMTC over NTN.

[0186] In some implementations, the method may utilize NPRS and LTE-M PRS as per 3GPP TS 36.211, or a dense PRS grid, such as the C0MB2 grid defined in 3GPP TS 38.211, or a full PRS grid, to reduce the time required for TOA measurements. The NRPRS may be according to 3GPP TS 38.211.

[0187] Alternatively, the ranging signal components received at step S310 may relate to primary and secondary synchronization signals. For loT-NTN, the primary and secondary synchronization signals may be Narrowband Primary Synchronization Signals (NPSS) and Narrowband Secondary Synchronization Signals (NSSS) as defined in TS 36.211. For NR-NTN, the primary and secondary synchronization signals may be Primary Synchronization Signals (PSS) and Secondary Synchronization Signals (SSS) as defined in TS 38.211.

[0188] The SIBs received at step S330 may correspond to Narrowband loT (NB-loT), Long Term Evolution (LTE), or other cellular communication technologies supported in non-terrestrial networks, for example. Further, the one or more SIBS may be one or more of SIB31 (SIB31-NB in NB-loT) and SIB33 (SIB33-NB in NB-loT), for example as defined in TS 36.331 (loT-NTN), or one or more new SIBs to broadcast for example ionospheric corrections or ranging signal scheduling. Alternatively, the one or more SIBs may be one or more of SIB19 as defined in 3GPP TS 38.331 (NR-NTN), or one European Space Agency December 20, 2024

[0189] 220993PC or more positioning system information blocks (posSIBs), including posSlBType 6-1 NR DL-PRS- Assistance Data as defined in 3GPP TS 38.331.

[0190] System Aspects of Proposed Solutions

[0191] Of the two satellite technologies introduced by 3GPP in 2022, loT-NTN (wide area, low data-rate) and New Radio (NR)-NTN (broadband), the remainder of the present disclosure will focus, without intended limitation, on loT-NTN due to its flexibility in enabling PNT services. Nonetheless, the techniques described throughout the present disclosure can be readily adapted to the NR-NTN case, as the skilled person will appreciate. loT-NTN enables loT devices and smartphones equipped with an NB-loT modem (or UEs, mobile terminals in general) to connect directly to satellites for SMS, voice, and data services without the need for specialized hardware. This development may be seen as somewhat paradoxical because loT modems are typically inexpensive and designed for simple, low-power devices— not traditionally part of high-end smartphones. Satellite spectrum in low frequency range named FR1, such as S- band MSS, allocated for use in 5G is ideal for handheld devices like smartphones and loT sensors with small, integrated antennas, thanks to its wider coverage and low atmospheric attenuation.

[0192] Without intended limitation, the present disclosure will focus on two main system scenarios SCI and SC2 that exploit NB-loT in the FR1 band, allowing direct to smartphone and loT modules service provision by satellites complementing terrestrial networks (TNs):

[0193] • SCI: loT-NTN constellation with LEO satellites featuring multi-beam antennas

[0194] • SC2: loT-NTN constellation with small LEO satellites featuring a single wide area beam antenna

[0195] As described above, the provision of the PNT service will require having multiple (e.g., 4 or more) satellites in view (either simultaneously or sequentially) for the UEs located in the service area. This may be an extra requirement compared to a pure COM system, but requirements can be relaxed if additional information, for example on an altitude of the UE, is available.

[0196] Positioning Methods

[0197] In either of the two scenarios SCI and SC2, two different UE-based positioning methods can be used in the context of the present disclosure, viz., observed time differences of arrival (OTDOA) and TOA. These UE-based positioning methods will be described in the following. European Space Agency December 20, 2024

[0198] 220993PC

[0199] Fig. 4 schematically illustrates an example of OTDOA (or OTDOA-based positioning) that may be applied, for example to loT-NTN systems, for implementing step S340 of method 300.

[0200] In OTDOA-based positioning, a UE 10 (or terminal, mobile terminal in general) receives ranging signal components 20 from each of a plurality of satellites 30 in view of the UE 10. Positioning requires a time of arrival (TOA) of a reference serving satellite (or cell) and the TOAs of several other satellites (or cells) measured at the UE 10. The difference between the TOA of each neighbor satellite (i.e., satellite other than the reference serving satellite) and the TOA of the reference satellite defines a hyperbola 410, 420, 430 within which the UE 10 may be located. If at least 2 neighbor satellites are used, plus a reference satellite, the point at which the hyperboles intersect determines the UE location in the 2D domain. The measurements for OTDOA in connected UEs may be based on Reference Signal Time Difference (RSTD) intra-frequency or inter-frequency measurements using Positioning Reference Signals (PRS).

[0201] A TDOA-based technique as described above may be implemented in the context of aforementioned method 300. Then, the method may further comprise a step of determining, at the UE, time difference of arrival, TDOA, measurements between ranging signal components received from different satellites. A reference satellite for TDOA may be the satellite acquired in SIB31 (SIB31-NB in the case of NB-loT) or may be selected based on a signal strength or Signal-to-Noise Ratio, SNR, for example.

[0202] Further, determining, at the UE, the position of the UE at step S340 may be based on the determined TDOA measurements. Specifically, determining, at the UE, the position of the UE may involve applying an algorithm based on OTDOA between the ranging signal components received from the plurality of satellites.

[0203] NB-loT terrestrial systems support this positioning method since Release 14 as explained above. However, this method works in UE-assisted mode and is enabled by a unicast exchange of information via the LPP protocol and does not apply to loT-NTN systems. Furthermore, OTDOA is not suitable for scenarios where a single satellite is in coverage of a UE, as could be expected in GEO but also for LEO and MEO constellations with discontinuous coverage or with large cell diameters (e.g., several hundreds of km).

[0204] By contrast, the techniques according to the present disclosure seek to provide for UE positioning that is available to UEs that are in an unconnected or RCCJDLE state in relation to the non-terrestrial European Space Agency December 20, 2024

[0205] 220993PC network comprising the plurality of satellites. Moreover, the techniques according to the present disclosure seek to provide for UE positioning that is GNSS independent.

[0206] Specifically, to avoid the use of GNSS as part of the initial access procedure or for applications, the present disclosure proposes the following adaptations for OTDOA to work in RRCJDLE state and UE- based mode in loT-NTN systems.

[0207] The NTN satellites composing the constellation of satellites are equipped with GNSS receivers to perform orbit determination and time synchronization for the satellite payload based on the GNSS signals. ODTS may use an on-board filter, e.g., Kalman filter, a PPP algorithm, and / or ISL ranging measurements.

[0208] Information about the NTN system can be transmitted in what is called a system information message (Sl-message). Each SI message can hold one or several system information blocks in turn. In loT-NTN, the serving satellite and neighboring satellites ephemeris parameters are broadcasted by the NTN system in SIB31-NB, SIB33-NB (see Annex 3). In case of discontinuous coverage, SIB32- NB can be used as well. The existing orbit model used in SIB31-NB and SIB33-NB is very simplistic and consists in the six basic Keplerian parameters (i.e., the semi-major axis, eccentricity, mean anomaly, argument of perigee, inclination, and longitude of the ascending node) or the satellite position vector expressed as XYZ and associated velocity components occupying 300 bits (168 bits + 132 bits). Notably, for an actual positioning system, providing a better ephemeris model may be desired. However, due to the maximum message size limit of 680 bits, careful consideration may be required when accommodating the necessary information. The following additional parameters could be added for a more accurate orbit modelling (e.g., <lm in a 10-minutes fitting interval): three additional rate parameters (e.g., mean motion, right ascension rate, inclination rate) and / or six 2ndorder harmonic correction parameters (e.g., amplitude of the cosine and sine harmonic correction term to the argument of latitude, amplitude of the cosine and sine harmonic correction term to the orbit radius, amplitude of the cosine and sine harmonic correction term to the angle of inclination), and possibly polynomial correction coefficients along-, across-, radial track. In addition, the ephemeris information may include an epoch time of the aforementioned satellite ephemeris data.. These would add up to only an additional 332 bits to the SIB31-NB, which is still below the 680 bits limit. For fitting periods of 5 minutes or of a maximum of 10 minutes, further bit reduction may be European Space Agency December 20, 2024

[0209] 220993PC achieved by removing some of the harmonics and inclination rate without major impact on the orbit accuracy.

[0210] Fig. 5A and Fig. 5B are diagrams illustrating examples of orbit fitting for 550 km altitude (darker curve) and 1200 km altitude (lighter curve) for 10 minutes and 20 minutes , respectively, using the enhanced SIB31-NB model with initial six Keplerian basic parameters, complemented by three rate parameters, and six second-order harmonic corrections.

[0211] In line with the above, in general, the one or more SIBs received at step S330 (or likewise, the positioning assistance information) may include ephemeris information on the satellites’ ephemeris. Then, the position of the UE may be determined at step S340 using the satellites’ ephemeris, for example for computing the satellite’s positions and for using the determined satellites’ positions together with the TDOAs in determining the position of the UE.

[0212] As noted above, each satellite may periodically transmit SIBs indicative of its own ephemeris. In some implementations, SIBs transmitted by the satellites may also include ephemeris information for one or more neighboring satellites.

[0213] Also, the ephemeris information may include information beyond the six Keplerian elements as described above.

[0214] Furthermore, either SIB31-NB / SIB33-NB or a new SIB-NB could be used to disseminate a satellite clock model consisting for example of three parameters (e.g., as in GNSS systems) to allow the UE to adjust the received signal’s timestamp for precise time measurement (e.g., TOA):

[0215] • Clock Bias (a0): The difference between the satellite's clock time and true GNSS time at a reference epoch.

[0216] • Clock Drift (ai): The rate at which the clock bias is changing (first derivative).

[0217] • Clock Drift Rate (a2): The rate at which the clock drift is changing (second derivative).

[0218] In a given reference epoch (to), the satellite clock offset may then be calculated from these coefficients of a polynomial broadcasted in SIB31-NB and SIB33-NB:

[0219] 6tsat= a0+ a (t — t0) + a2(t — t0)2

[0220] (1) European Space Agency December 20, 2024

[0221] 220993PC

[0222] Notably, there are two approaches for dealing with errors of the satellite onboard time (with respect to a common system time):

[0223] • Compensate the errors at generation level through clock steering by means of an onboard GNSS receiver with no need to broadcast corrections.

[0224] • Leave the errors and send the corrections to the users so they can take care of the compensation as proposed above.

[0225] In line with the above, in general, the one or more SIBs received at step S330 (or likewise, the positioning assistance information) may include clock correction information on the satellites’ internal clocks. The clock correction information on the satellites’ clocks may be used by the UE for correcting the time of transmission of the ranging signal for satellite clock errors. For example, the TOAs may be corrected based on the clock correction information. As noted above, each satellite may periodically transmit SIBs indicative of its own clock corrections.

[0226] The present disclosure further proposes an extension to SIB31-NB / SIB33-NB or a new system information block message to broadcast ionospheric corrections periodically. The reason is that NTN systems are expected to operate in a single frequency band (e.g., n256), and ionosphere-free combination that would usually be performed in GNSS systems by leveraging signals on two different frequency bands is not possible for single-frequency NTN systems. For example, a reduction of ionospheric delay error of about 80% can be achieved through broadcasting a NeQuickG model which requires 41 bits. Assuming compensation of satellite clock error at generation level through clock steering (i.e., no need to broadcast corrections) and addition of only mean anomaly, right ascension rate, amplitude of 2ndcosine harmonic coefficient of radius, and amplitude of 2ndsine harmonic coefficient of radius, the ionospheric model proposed above would comfortably fit within the 680 bits size.

[0227] In line with the above, in general, the one or more SIBs received at step S330 (or likewise, the positioning assistance information) may include ionospheric information indicative of a state of the ionosphere. The ionospheric information indicative of a state of the ionosphere may be used by the UE for correcting for an impact of the ionosphere on signal propagation. For example, the TDOAs may be corrected based on ionospheric information. The ionospheric information may be transmitted via dedicated SIBs, as described above. These SIBs may be universal among the European Space Agency December 20, 2024

[0228] 220993PC plurality of satellites. Periodicity of these SIBs may be lower than periodicity of SIBs including ephemeris information and / or clock correction information.

[0229] The present disclosure further proposes that the satellites (e.g., all satellites) broadcast ranging signal components (e.g., (N)PRS signals) with one of the allowed configurations and periodicity.

[0230] Accordingly, at step S310, for each of the plurality of satellites, the ranging signal components may be periodically received at the UE, with a common period among the plurality of satellites.

[0231] The (N)PRS ID needed to generate a satellite specific (N)PRS sequence may be represented by the satellite ID of the serving and neighbor satellites present in, for example, SIB31-NB, SIB33-NB. The configuration of the NPRS signal may be broadcast periodically in a new SIB message.

[0232] Further, the UE in an loT-NTN network may decode SIB1-NB to obtain the scheduling information necessary to receive SIB31-NB, SIB32-NB, SIB33-NB, and the new system information blocks for PRS configuration and ionospheric corrections.

[0233] Accordingly, the one or more SIBs received at step S330 (or likewise, the positioning assistance information) may include configuration information including one or more of periodicity, duration, mapping to frequency-time grid pattern, and frequency band of the ranging signal components from the plurality of satellites.

[0234] The present disclosure further proposes that the loT UE measures, for example in the context of step S340, the Reference Signal Time Difference (RSTD), which is the difference in TOA measurements between the ranging signal components (e.g., (N)PRS signals) broadcast from neighboring satellites and the serving satellite. This measurement helps remove the UE clock bias, since the NTN satellites’ tight synchronization is met by the GNSS onboard (i.e., NTN satellites synchronization is assumed to be ~0). Furthermore, another advantage of OTDOA lies in the fact that there is no need for the satellites to continuously broadcast their exact time of signal transmission which is required in TOA based methods.

[0235] The present disclosure further proposes in the context of TDOA-based positioning, that the loT UE may estimate its location based on OTDOA by solving a least squares problem. If necessary, the height component can be determined by means of a sensor (e.g. barometric pressure sensor) to avoid wasting a TDOA measurement for a coordinate usually not needed. European Space Agency December 20, 2024

[0236] 220993PC

[0237] Fig. 6 schematically illustrates an example of Downlink (DL)-TOA (or DL-TOA-based positioning) that may be applied, for example to loT-NTN systems, for implementing step S340 of method 300.

[0238] In TOA-based positioning, the UE 10 (or terminal, mobile terminal in general) receives ranging signal components 20 from each of a plurality of satellites 30 in view of the UE 10. Positioning requires a ToA of several satellites (or cells) measured at the UE 10. The ToA of each satellite, provided that the time of transmission at the satellite is known, defines a sphere 610, 620, 630 on which the UE 10 may be located. If at least 3 satellites are used, the spheres’ intersection determines the UE location in the 2D domain.

[0239] A TOA-based technique as described above may be implemented in the context of aforementioned method 300. Then, the method may further comprise a step of determining, at the UE, a respective time of transmission of each ranging signal component, by demodulating the respective ranging signal component. For allowing this determination, the ranging signal components may relate to time-stamped pilot signals, for example. Each satellite may timestamp its ranging signal components using an onboard GNSS receiver.

[0240] Further, determining, at the UE, the position of the UE at step S340 may be based on the determined times of transmission. Specifically, determining, at the UE, the position of the UE may involve applying an algorithm based on times of arrival of the ranging signal components received from the plurality of satellites.

[0241] Otherwise, the principles of the TOA-based positioning method may be similar to OTDOA, and the same positioning assistance information (or SIBs) as described above for TDOA may be used. But rather than forming TDOA measurements, this method employs TOA measurements. This assumes that the satellites broadcast respective signal transmission times. Very accurate signal transmission times can be determined onboard based on GNSS steering as explained above. Since the structure of the ranging signal components (e.g., (N)PRS resources) is known to UE, the TOA estimates may be obtained by correlating the received signal against the known pilot resources. The TOA ambiguity resolution may be solved based on observing the (N)PSS and (N)SSS signals which are used to achieve slot synchronization in downlink direction and (N)PRS metadata (e.g., subframe configuration period, starting subframe offset, number of consecutive downlink subframes) as described in TS 36.211 for (N)PRS or TS 38.211 for NR PRS. European Space Agency December 20, 2024

[0242] 220993PC

[0243] The NTN satellites according to the proposed techniques may have an accurate and stable miniature atomic clock synchronized to a global time reference such as Galileo time or UTC through the onboard GNSS receiver. This ensures that each satellite’s clock has minimal drift and provides a common time reference for both the satellite and the UE. The satellites may embed time stamps in the transmitted signals indicating the exact time of transmission, as indicated above, and therefore meet conditions required in TOA concepts.

[0244] Furthermore, as proposed above, through the extension of the positioning assistance information, for example SIB31-NB and SIB33-NB, it is possible for the NTN system to broadcast clock correction parameters that allow the UE to correct for the NTN satellite clock errors.

[0245] In addition to TDOA-based and TOA-based positioning, the present disclosure further proposes a hybrid positioning technique based on OTDOA and Frequency Difference of Arrival (FDOA). By measuring how much the frequency of a signal has shifted between reception and transmission, it is possible to calculate how fast the distance between the transmitter and receiver changes. This information can then be used to estimate the UE’s position. Assuming the satellite positions and velocities are well known from the positioning assistance information or SIBs (e.g., from SIB31-NB and SIB33-NB), the UE can pick up the signals (e.g., ranging signal components) from the satellites to perform the necessary computations. For example, TDOA and FDOA may be measured on synchronization signals (Narrowband Primary Synchronization Signal and Narrowband Secondary Synchronization Signal) to estimate UE position and velocity. This information can then be used to compute and compensate for the residual time and frequency offsets with respect to the reference point of a cell, usually its center point. In cases where Doppler pre-compensation is performed by the base station (BS) on the downlink, the common Doppler shift of the cell must be added back for accurate FOA estimates. These corrections can be derived from satellite ephemeris and the coordinates of the reference point broadcast by each satellite (in the case of Earth Fixed beams) or the beam-specific common Doppler shift value broadcasted on an NTN SIB (for moving beams).

[0246] The proposed loT-NTN positioning concept could be further improved by combining TDOA and FDOA measurements of the ranging signal component (e.g., (N)PRS signal) to improve the estimation of the UE-specific frequency offset (in addition to the use of NPSS / NSSS). Since TOA and FOA measurements suffer from UE clock time and frequency offsets, combining TDOA and FDOA measurements can improve accuracy. The UE may compute the differences between TOA and FOA European Space Agency December 20, 2024

[0247] 220993PC measurements to obtain TDOA and FDOA measurements and then may estimate its position by processing both jointly.

[0248] Once the positioning methods described above are adapted to work in UE-based mode also in RRCJDLE state, as proposed by the present disclosure, those UEs with GNSS capabilities could explore UE-based hybrid positioning using GNSS pseudo-ranges and TOA and / or TDOA measurements to NTN satellites on the NPRS signal.

[0249] Importantly, using the proposed techniques loT-NTN network-based positioning is also supported by making use of LPP protocol and operating in RRC_CONNECTED state. This means that loT devices can perform positioning with assistance data transferred by the network in unicast mode through an LPP session. Nevertheless, for the reasons explained in the above problem description, it will be found that downlink positioning at the user side (UE-based), utilizing broadcast assistance data via SIBs, offers a more appealing and advantageous approach in loT-NTN networks.

[0250] For any of the above positioning methods, the present disclosure proposes that the loT UE may use the location estimated on DL signals and / or the DL signal carrier frequency estimation for various operations, including achieving a GNSS-independent uplink time and frequency pre-compensation, for applications such as an asset tracking, or to report it to the network in case of an emergency situation.

[0251] For instance, method 300 may further comprise performing, at the UE, compensation of at least one of Doppler shift, time offset, and frequency offset in relation to one of the plurality of satellites based on the determined position of the UE and information indicative of an ephemeris of the one of the plurality of satellites, and / or the DL signal carrier frequency estimation for deriving a time reference and / or frequency reference locked to a respective reference of the satellite, thereby enabling access to the non-terrestrial network.

[0252] That is, broadly speaking, the UE may be capable of operating in a communication mode where it accesses the non-terrestrial network, and a positioning mode (e.g., in RCCJDLE state), for which the UE does not need to be connected to the non-terrestrial network and only demodulates the ranging signal components and positioning assistance information. These two modes may share a common frequency band and signal structure to optimize resource usage.

[0253] Method 300 may further comprise, when accessing the NTN, synchronizing uplink transmission in time and frequency based on the performed compensation. European Space Agency December 20, 2024

[0254] 220993PC

[0255] When accessing the NTN and communicating with one of the plurality of satellites (e.g., a serving satellite), communication signals from the satellite may be received in a narrow beam, contrary to the ranging signal components, which may be received in a wide beam. Here, a narrow beam may be understood to be a beam with for example a HPBW of 4.4 degrees according to Set 1 or a HPBW of 8.8 degrees according to Set 2 from 3GPP TR 36.763, or a HPBW between 4.4 and 8.8 degrees.

[0256] As another example of an operation using the determined UE position, method 300 may comprise using the determined terminal position for seamless handover between satellites that provide communication service.

[0257] The position techniques described allow may conventionally be assumed to require at least three (possibly more) satellites in simultaneous view of the UE. Still, the present disclosure is understood to also relate to cases where fewer than 3 satellites are in simultaneous view of the UE.

[0258] For instance, there may be satellite constellations not able to provide a sufficient number of satellites in simultaneous view to allow UE localization. The conventional bare minimum may be to have three satellites in view, assuming that the UE height can be estimated using additional onboard sensors, such as a barometer. If this condition is not satisfied, the UE positioning can still be achieved assuming that the UE is quasi-stationary during the time required to receive signals from 3 or 4 satellites in succession. In this case, the UE will may collect ranging signal component (e.g., (N)PRS) measurements on the current available satellites and then gather the missing measurements as soon as the new satellites will become available (i.e., come into view of the UE).

[0259] In other words, the UE may perform batching of several measurements at timings separate from each other and perform processing thereof at a later time, assuming limited UE dynamics.

[0260] The location estimation accuracy in the above situation may be degraded by the UE clock drift occurring during the successive ranging signal component (e.g., (N)PRS) measurements. However, considering that the NTN has an extended CP capable of absorbing UE position uncertainty up to 30 km, it is considered that there should be no issue to achieve an accuracy of few kilometers for most practical cases. This approach has the advantage of being compatible with less dense constellations, as is often the case for loT applications, and is applicable to the above-mentioned OTDOA and DL-TOA techniques. The assumption of a (quasi)-stationary user is quite realistic for many applications such as for fixed loT devices and hand-held mobile terminals for which during European Space Agency December 20, 2024

[0261] 220993PC network acquisition some cooperation of the user (e.g. being in an open area and not moving) is typically required.

[0262] On the other hand, if more than four satellites are in simultaneous view and there is spectrum available, other satellites NTN signals including (N)PRS may be frequency-multiplexed to achieve enhanced throughput and ranging accuracy.

[0263] NTN (N)PRS exploitation in a LEO constellation

[0264] The ranging signal component (e.g., (N)PRS) symbols may be generated by Gold codes which are gNodeB unique. Collecting enough ranging signal components (e.g., (n)PRS ranging symbols) will allow obtaining the satellites’ (differential) timing information at the UE with one of the techniques described above.

[0265] Fig. 7 shows an example of a time-frequency-grid for ranging signal components (e.g., (N)PRS symbols). Differently shaded diagonals are associated with different transmitters (e.g., satellites, gNodeB).

[0266] For instance, the current (N)PRS grid approach as shown in Fig. 7 is designed for TN to interleave different gNodeB (different color shades) in time and frequency, all synchronized among each other. This approach will allow avoiding mutual interference when limited to a PRS time slot separate from the communication payload symbols.

[0267] For NTN, the (N)PRS orthogonality is heavily affected by the satellites’ (e.g., LEO satellites’) constellation geometry, which can generate differential carrier frequency Doppler and time offset among the satellites’ signals received by the UE. An example of a visual representation of LEO system impact on the PRS symbols grid is shown in Fig. 8. It is apparent that the desired PRS symbols’ orthogonality among the different gNodeB (e.g., satellites) cannot be maintained.

[0268] Other reference signals, such as the (N)PSS and (N)SSS, could also be used for positioning services. The advantages of the synchronization signals is that they are always present, transmitted periodically in subframe 5 of every frame and subframe 9 of every other frame, respectively. These signals are designed for time and frequency synchronization during the initial acquisition and detecting the cell identity number and have a fixed configuration. On the other hand, NPRS and LTE PRS are specific pilot signals dedicated to positioning, they have good auto- and cross-correlation European Space Agency December 20, 2024

[0269] 220993PC properties, due to the use of Gold sequences. Furthermore, they are highly configurable (e.g., in length).

[0270] Following description of possible positioning techniques applicable, inter alia, to the SCI and SC2 system scenarios, an analysis of potential system level issues affecting a combined COM-PNT system exploiting the NTN NB-loT standard will be analyzed and possible solutions will be described. Emphasis will be placed on how to provide communication and positioning services using the same NTN infrastructure independently from GNSS for reducing UE complexity (e.g., enabling use of a single antenna and RF front-end, not requiring a GNSS demodulator), power consumption, cost, and providing additional system resilience.

[0271] It is to be understood however that the solutions presented below for scenarios SCI and SC2 are not limited to these scenarios and may be applied in a more general context, such as for method 300 of Fig. 3 and / or method 1700 of Fig. 17.

[0272] Scenario SCI: loT-NTN constellation with LEO satellites equipped with multi-beam antennas

[0273] SCI is one of the 3GPP NTN reference scenarios dubbed Set 1-FR1. In this case the satellites will likely be able to also support NB-loT on top of 4G legacy and 5G NR standards. The multi-beam satellite allows to increase the system throughput due to the higher satellite antenna gain and spatial discrimination and frequency reuse among the beams. While the multi-beam satellite antenna design provides major advantages for the telecommunication (COM) mission in terms of unicast services, this architecture has significant drawbacks for the PNT service provision as discussed in the following.

[0274] The following system issues may apply to SCI. In practice, when multiple satellites in view are present, the UE may face a differential satellite Doppler / Doppler rate and delay range will be dependent on the system specific design.

[0275] The presence of multiple (narrow) beams per satellite will allow implementing countermeasures for reducing the effects of NTN LEO orbital induced aspects, namely:

[0276] • Center of beam Doppler / Doppler rate and timing pre-compensation to reduce the UE link “stress” caused by the LEO orbit.

[0277] Fixed on ground beam center location to reduce the beam hand-off rate. European Space Agency December 20, 2024

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[0279] Beam shape distortion compensation due to the Earth spherical shape to make the ground cells shape more regular and to “equalize” the link losses affecting UEs with lower satellite elevation angles.

[0280] The impact of the above and possible other countermeasures is system-dependent and can make the satellite network compatible with current 4G / 5G TN UEs as seems to be the case for the Starlink Direct-to-Cell and AST SpaceMobile LEO systems.

[0281] The situation is more involved for NTN SCI positioning service provision. In fact, exploiting the (N)PRS 5G signal components in telecom multi-beam satellite constellations may be difficult for the following reasons:

[0282] • By system design, the telecom satellites’ beams will avoid overlapping on the same region to not cause self-interference or to not artificially increase the number of beams required to serve a region when adopting frequency division multiplexing across beams to avoid crosstalk. This holds for systems operating in FR1 with UE omnidirectional antenna not providing any satellite in view spatial discrimination. The complexity of the payload front-end is approximately related to the product number of beams times the beam bandwidth. The segmentation in EDM of the coverage region does not have a dramatic impact on the frontend complexity but makes the overall resource management more complex. Thus, except for the satellite or beam link hand-off phase, the telecom networks will generate a single active beam for each user location.

[0283] • The telecom approach diverges from the PNT need to have multiple satellites in view (and hence, beams) for classical multi-satellite view-based localization purposes. This will require a wide coverage area for broadcasting the PNT signal, which is contrary to the need to have small beam areas for providing an efficient COM unicast service. This fundamental system design aspect puts the potential exploitation of 3GPP (N)PRS signal components for positioning in a telecom satellite constellation in question, where beam overlap typically is limited to the handover phase to avoid waste of resources.

[0284] • Transmitting only PRS from the other satellites in view to allow PNT ranging measurements appears not attractive in terms of telecom resources exploitation / payload complexity because of the increase in the number of beams to be formed just for PNT which is ineffective. The number of beams that a satellite can generate with a digital processor has European Space Agency December 20, 2024

[0285] 220993PC an approximate upper bound given by the product Max_processed_bandwidth= No_beams*Beam_bandwidth. Clearly, spatially overlaying beams as during the hand-over phase reduces the payload’s capability to serve other traffic areas.

[0286] • If the current NTN signal is adopted for providing COM and PNT services through a satellite wide area beam, this may be at the expense of a major COM service performance degradation in terms of bit rate per user and overall throughput. This degradation may be caused by the drop of the satellite antenna gain moving from a narrow to a wideband beam (e.g., about 30 dB in the 3GPP reference case discussed in the following) and the lack of frequency reuse which is only possible with a multibeam satellite antenna.

[0287] • The satellite system should ensure that the OFDM symbols coming from different LEO satellites in view do not overlap in time and frequency to avoid destructive interference effects. In addition, adequate guard bands (e.g., two times the maximum single satellite Doppler offset) shall be implemented in the system frequency plan. The wider the satellite beam coverage area, the wider guard bands will be required.

[0288] • The situation for (N)PRS may be more subtle. In principle, (N)PRS symbols derived from a known satellite specific Gold code can overlap in time with other (N)PRS symbols from other satellites. One may consider having (N)PRS symbols from different satellites time multiplexed as for TN, accepting the satellite crosstalk. (N)PRS slot overlapping with the data slots will reduce the COM system’s spectral efficiency, so that in particular when adopting LEO satellites, a cycling prefix will not be sufficient to accommodate the maximum differential satellite delay. Other solutions still compatible with the current 3GPP standard, like reduced (N)PRS power transmission, or dedicated band for (N)PRS only transmission by all satellites in view may be envisaged if compatible with the PNT service performance requirements.

[0289] • Another potential issue affecting the exploitation of satcom constellation signals is that they may use a time variant beam hopping pattern or an irregular and time variant (i.e., dynamic) frequency reuse to match the uneven traffic request (cf. [Angeletti 2021]). This may further curtail the chances of using the current 5G PRS for positioning.

[0290] • Yet further potential issues may lie in challenging calibration requirements and associated implementation challenges for steerable beam payload group delay / phase calibration for the PNT derivation, also considering center of beam delay / Doppler pre-compensation and European Space Agency December 20, 2024

[0291] 220993PC beam steering to have a fixed center of beam on ground combined with iso-flux gain compensation.

[0292] A possible first option for exploiting a ranging signal component based (e.g., (N)PRS-based) solution for UE-based NTN positioning will be described next. As described above, for reasons of system economy it may not be under all circumstances envisaged to direct four or more beams carrying ranging signal components (e.g., (N)PRS signals) to each system coverage location to provide PNT services. A possible alternative will be to modify (when possible) the satellite payload beam forming network (BFN) coefficients on the fly when transmitting ranging signal component (e.g., (N)PRS) slots to generate a wide area beam instead of a spot beam. In this way, the number of satellites in simultaneous view to the UEs can be maximized for supporting PNT services.

[0293] The corresponding system concept is illustrated in Fig. 9, which illustrates an example of an NTN PNT-COM combined system for scenario SCI. The system comprises a plurality of satellites 30 that direct beams towards Earth. As can be seen, the system utilizes wide area single beams 910 with wide coverage areas 915 for PRS and narrow-beams 920 for COM services.

[0294] In line with the above, the present disclosure generally proposes that a satellite of a NTN for providing a communication service to a UE and for enabling UE-based, GNSS-independent, and DL- signal-based positioning, for example in the context of method 1700 described below, dynamically adjusts a beam pattern to provide a first beam for transmitting the ranging signal component (e.g., (N)PRS) and a second beam (or plural second beams) for providing the communication service to a given UE, with a beam width of the second beam being smaller than a beam width of the first beam. Doing so, the satellite may reuse the same satellite payload for transmitting the (N)PRS, and for providing the communication service.

[0295] Specifically, the satellite may use an active or semi-active antenna to provide the first beam for transmitting the ranging signal component and a number of second beams for providing the communication service to the UE, with a beam width of the second beams being smaller than a beam width of the first beam.

[0296] Thus, transmission of the ranging signal component by the satellite may be performed in a wide beam directed towards Earth. On the other hand, the communication service may be provided via one or more narrow beams directed towards Earth. European Space Agency December 20, 2024

[0297] 220993PC

[0298] Correspondingly, at the UE side, for example in step S310 of method 300, each ranging signal component (e.g., (N)PRS) may be received in a respective wide beam generated at a respective satellite. Here and elsewhere in the present disclosure, a wide beam may be a beam with a half power beam width (HPBW) of at least 104.7 deg as defined in TR 36.763 for Set 4 parameters.

[0299] The approach according to the presently described first option may be seen as an adaptation to the payload concept described in [De Gaudenzi 2024] for adding a wide area coverage signal to the 3GPP NR signal. In this case the 3GPP applicable standard will be NB-loT or e-MTC and the global coverage broadcast signal will only be represented by the (N)PRS components required for the PNT service instead of a DS-SS signal.

[0300] Fig. 10 is a functional block diagram schematically illustrating an example of an NTN PNT-COM combined satellite payload for generating a wide area single beam for the (N)PRS signal component and one or more narrow-beams (NTN communication beams) for COM services for scenario SCI.

[0301] Frequency and time planning aspects for this first option may be identical to those described below for scenario SC2.

[0302] Some or all of the following more specific features may apply to the presently described first option:

[0303] • The signals generated by the satellite (e.g., its gNodeB) may be time-synchronized. Hence the same time slots can be reserved for transmission of a satellite unique set of (N)PRS symbols (as an example of a unique ranging signal component) using a set of BFN coefficients for generating a wide area beam at a specified center frequency. This center frequency may be satellite-specific to reduce the intersatellite interference. However, in alternative implementations there may be a dedicated center frequency for ranging signal components from different satellites. Details will be described below.

[0304] • Some guard time for payload reconfiguration may be included in the framing (e.g., subframe slot before and after the (N)PRS transmission).

[0305] • This approach will allow overcoming the issue of narrow beams area coverage achieving multiple satellite in view without impacting the telecom payload operation, except for lost resources during the time dedicated to ranging signal component (e.g., (N)PRS) transmission.

[0306] • As discussed in more detail below for scenario SC2, the time variant satellite geometry may cause loss of (N)PRS signal OFDM orthogonality in time and frequency among the different European Space Agency December 20, 2024

[0307] 220993PC satellites. This may cause self-interference and interference from and to the communication signals. The same solutions envisaged in scenarios SC2 Bl and B2 to mitigate cross-satellite interference effects can be applied to SCI.

[0308] • A fraction of the multi-beam payload power may be dedicated to ranging signal component (e.g., (N)PRS) transmission. The ranging signal components (e.g., (N)PRS symbols) can be accumulated at the UE over several consecutive time slots to mitigate the COM co-channel interference. The power to be allocated to the wide beam ranging signal component (e.g., (N)PRS) transmission may be the result of a trade-off between different factors such as the (N)PRS signaling overhead caused by the need to compensate for the reduced gain of the satellite wide beam antenna gain and the possible interference caused to the communication signals in case the ranging signal component will overlap in time. The optimum power dedicated to the ranging signal component may be based on a detailed analysis for the specific system.

[0309] • Overall, the fact that ranging signal component (e.g., (N)PRS) burst reception will be asynchronous among the satellites for obvious geometrical reasons will lead to (N)PRS bursty interference.

[0310] A possible solution for providing communication and PNT services in scenario SCI is extensively discussed in [De Gaudenzi 2024] and includes a non-PRS-based evolution of positioning frameworks in NTN standards. A PRS-based scenario is also possible. The idea is to overlay the (N)PRS signal as a DS-SS navigation signal on top of the (3GPP) telecom signal using a different set of beam forming coefficients. This is schematically illustrated in Fig. 11, where each LEO satellite, in addition to generating several narrow beams for the two-way communication services, will also broadcast a satellite unique overlay (N)PRS signal with a wider coverage area using the same telecom payload and frequency band. After correlation with local (N)PRS signal local replica, the large integration time possible for the navigation signal allows to minimize the impact of the telecom signal. It is to be noted that the transmitted signal components’ power may differ in the received power levels at the user equipment. The relative transmitted components’ power setting at the transmitter may be system-dependent and shall be a trade-off between the telecom signal performance degradation due to the (N)PRS ranging signal overlay and the required ranging accuracy in each estimation time interval. The preference will be to transmit an as dense as possible European Space Agency December 20, 2024

[0311] 220993PC

[0312] (N)PRS grid (e.g., existing C0MB2 or proposed COMBO grids) to reduce the required ranging estimation time. This approach initially proposed for FR1 can be also extended to FR2 provided that the UE is equipped with a quasi-hemispherical antenna and the ranging accuracy achieved is compatible with the system requirements. The main difference is that in FR1 in addition to 3GPP NR also NB-loT or e-MTC can be used.

[0313] The corresponding system concept is illustrated in Fig. 11, which illustrates another example of a PNT-COM combined system for scenario SCI. The system comprises a plurality of satellites 30 that direct beams towards Earth. As can be seen, the system utilizes wide area single beams 1110 with wide coverage areas 1115 for PNT and narrow-beams 1120 for COM services.

[0314] A possible second option for exploiting a ranging signal component based (e.g., PRS-based) solution for UE-based NTN positioning, as an alternative solution to providing multiple satellites in view to the UE in a multi-beam scenario, may be to dedicate one of the beam-forming payload ports of each satellite to generate a narrow-beam which time-hops over the satellite multi-beam coverage region and possibly over adjacent satellites’ areas not covered by the COM beams. This is because for providing the PNT service, typically the hopping shall cover regions outside the current COM beams’ service area as shown in Fig. 11 above. Typically, there should preferably be four beams periodically directed to any service coverage location. Considering that typically center of beam Doppler compensation will be adopted for such system, FOA support to the PVT solution may be less attractive, although possible.

[0315] In this case there should be a complex multi-satellite (N)PRS scheduling put in place to ensure that the (N)PRS slots generated by the different beam hopped satellites arrive within the nominal NTN (N)PRS time slot in a carousel fashion with a repetition period compatible with the user dynamics.

[0316] In addition, the approach according to the second option may require a complex and dynamic calibration on the satellite payload to ensure that the hopped beam phase center is kept within acceptable accuracy and that the beam shape Earth projection distortion, particularly for low satellite elevation, will not cause harmful interference to COM beams.

[0317] Scenario SC2: loT-NTN constellation with small LEO satellites featuring a single wide area beam antenna

[0318] Scenario SC2 corresponds to the 3GPP NTN reference scenario Set-4, but with customized system parameters for an integrated communication and positioning system, for purposes of providing an European Space Agency December 20, 2024

[0319] 220993PC example of performance assessment. In this case the focus is to provide loT-type services and positioning simultaneously, exploiting “small” satellites generating a single beam and relying on the NB-loT standard. While reference is made to the loT-NTN in this regard, the proposed scenario and techniques are not limited thereto and may be more generally applied, for example to NR-NTN including more complex satellites, as the skilled person will appreciate.

[0320] Fig. 12 illustrates an example of an NTN PNT-COM combined system for scenario SC2. The system comprises a plurality of satellites 30 that direct beams towards Earth. As can be seen, the system utilizes wide area single beams 1210 with wide coverage areas 1215 for COM services and PRS.

[0321] Next, communication service aspects in the context of scenario SC2 will be described.

[0322] • If the LEO constellation is made up of satellites with a large number of beams, the range of Doppler and differential delay among the users in the same beam can be mitigated by resorting to Doppler and delay pre-compensation. The narrower the beam size, the better the achievable mitigation effect. However, this approach will not be applicable to the PNT signals, since in this case narrow beams optimized for communication services will not allow to achieve multiple satellites in view required for positioning.

[0323] • In case of wide area single beam satellites (as may be the case for loT services), lack of possible pre-compensation of Doppler and delay may make the range to be dealt with by the system quite large, depending on the LEO orbit height and single beam size.

[0324] • To avoid crosstalk, the satellites overlapping in coverage may need to use different subbands (e.g., may use Frequency Division Multiplexing) with a frequency color-based beams frequency reuse pattern among the beams.

[0325] Fig. 13 illustrates an example of a frequency plan (e.g., for LEO) with and without Doppler effect. The top row 1310 shows the nominal frequency plan without Doppler effect, while the bottom row 1320 shows the dynamic frequency plan with Doppler effect.

[0326] The large differential Doppler (e.g., up to 100 kHz for a 600 km LEO orbit used in the LEO reference system scenario of Annex 1) may require guard bands BGof at least 100 kHz thus with a size comparable to the NB-loT signal bandwidth BNB-IOT=180 kHz, hence potentially causing inefficiencies in the spectrum utilization. European Space Agency December 20, 2024

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[0328] It is also to be noted that no polarization coloring schemes can be adopted in case of FR1 systems for which the UE typically has a linearly polarized antenna whereas the satellite has a circularly polarized antenna.

[0329] • The number of sub-bands required to provide seamless coverage may depend on the constellation geometry and satellite antenna coverage area. Typically, a 4-colored DM choice will be adopted, but other coloring schemes may be possible, although polarization reuse is not considered feasible in FR1 due to the UE simple type of antenna. When more than four satellites overlap over the same geographical region, some satel I ite(s) may have to avoid transmission to avoid harmful interference to the other satellites in view. This is possibly different from TN where iso-frequency cell handover is possible.

[0330] • The NTN frequency plan for different LEO satellites may deal with the guard-band Bguardrequired to ensure the respective OFDM signals’ orthogonality. The guard-band size Bguardmay be dependent on system design. In other words, the center frequency of each OFDM block and the Bguardsize may be selected in a way to ensure satellite signal orthogonality for the specific NTN system parameters.

[0331] • In general, unicast communication may be handled by a single satellite selected based on quality of signal or other KPIs handled by the radio resource management. Multiple satellite reception (typically not at the same time but with the UE able to successfully tune to different sub-bands) may be required during the satellite handover phase when the user communication resources must be passed from one satellite to another.

[0332] Next, navigation service aspects in the context of scenario SC2 will be described.

[0333] As discussed above, for navigation services exploiting the (N)PRS signal component (as a nonlimiting example of a ranging signal component), there is the need to receive at least 4 satellites simultaneously to achieve a satisfactory PNT quasi-real time service. Differently from the communication services that require strict orthogonality between satellite OFDM signals, in this case the issue of co-channel interference between satellites in simultaneous view can be handled in two different ways proposed by the present disclosure: a) SC2_PNT-A: Exploiting satellites’ FDMs among different OFDM blocks to ensure orthogonality for both the (N)PRS and the data frames. European Space Agency December 20, 2024

[0334] 220993PC b) SC2_PNT-B: Exploiting satellites’ TDM among the same OFDM block sub-carriers (SCs) only for the (N)PRS frames, avoiding transmission of data frames on the same frequency for the other satellites in view required for positioning service.

[0335] For both proposed solutions, it will be assumed that no center of beam frequency / time precompensation is possible, due to the need to use a wide area beam to maximize the number of multiple satellites in view.

[0336] The SC2_PNT-A scenario will be described first. Here, in general, the ranging signal components that are received at the UE, for example at step S310 of method 300, may be received in distinct (different), non-overlapping frequency bands (e.g., with sufficiently different center frequencies) to avoid mutual crosstalk. Frequency band selection may take into account differential satellite Doppler effects. For example, there may be guard bands of suitable size between respective frequency bands to cope with Doppler uncertainties. Also, each of the plurality of satellites (e.g., satellites in view) may provide communication service (e.g., may transmit communication signal components (payload data)) in the specific frequency band in which it (periodically) transmits its ranging signal component.

[0337] For communication, scenario SC2_PNT-A may resemble scenario SCI described above. The only difference is that for positioning at least four satellites shall be simultaneously managed by the UE. This will also require a wider system spectrum allocation Btot, where

[0338] Btot= NSP^TBNB-IOT + BG),

[0339] (2) denoting the number of satellites in view that are used for positioning. The PRS extra bandwidth can be used for providing communication services as explained above, thus increasing the single satellite throughput by approximately a factor N^.

[0340] An example of the corresponding time / frequency plan for this scenario is schematically shown in Fig. 14A. The white arrows at the left-hand side indicate the nominal sub-band central frequencies and the dashed light rectangles Bl, B2, B3, B4 indicate the nominal sub-band occupancy in the absence of Doppler shift. For each sub-band 1430, 1440, 1450, 1460, rectangles 1410 indicate data components that are interleaved with periodic ranging signal components, as indicated by squares 1420. European Space Agency December 20, 2024

[0341] 220993PC

[0342] The center carrier frequency of the signals received by the UE will be offset compared to their nominal value because of the constellation geometry. It is apparent that the DM approach with guard bands, for appropriately chosen center frequencies and guard bands, can preserve OFDM satellite signal orthogonality despite the differential frequency and time offset that affects the received satellite signals.

[0343] Using the complete frame of the NTN signal allows exploiting the presence of the OFDM pilot symbols (e.g., Narrowband Reference Signal (NRS) in NB-loT or of the Demodulation Reference Signal (DMRS) in NR) to perform real-time channel estimation, thus allowing coherent combination of the successive (N)PRS blocks considered for the ranging measurement.

[0344] To process (N)PRS symbols (as an example of ranging signal components) belonging to the different satellites, the UE shall be able to correlate the different (N)PRS components from the N™ts satellites in view, each transmitting in its satellite specific sub-band within Btot. This multi sub-band (N)PRS approach may appear to be demanding in terms of UE processing power and energy consumption.

[0345] To avoid this potential issue and to reduce UE complexity, the present disclosure optionally proposes to detect the (N)PRS symbols one satellite at a time, so as to use successive (N)PRS frames for processing the (N)PRS symbols belonging to the following satellites during the positioning phase. This will require a conventional single UE NB-loT demodulator with a fast frequency tuning capability which is typically available for satellite acquisition and handover purposes. Furthermore, except for the very first cold start, the UE will have knowledge of the satellite ephemeris and its previous position, hence the (N)PRS correlation frequency and time uncertainty can be significantly reduced. As the number of (N)PRS symbols to be correlated is similar as in conventional TN (N)PRS multi base-station based positioning, assuming the knowledge of the satellite ephemeris, this will not have a negative impact on power consumption.

[0346] A possible minor drawback of the proposed approach may be that the time required for positioning may be slightly longer, since (N)PRS transmission from different satellites will be asynchronous in time (i.e., no orthogonal time interleaving as in TN will be possible) and some cross-satellite interference may be present although limited due to the good (N)PRS cross-correlation properties especially when longer sequences and denser occupancy of the frequency-time grid is configured European Space Agency December 20, 2024

[0347] 220993PC

[0348] In case more than four satellites are in simultaneous view of the UE and there is enough bandwidth to keep all of them active, the number of sub-bands may be extended to accommodate the additional satellites active for communication and ranging purposes. Otherwise, the number of active satellites over the coverage region shall be kept limited to four.

[0349] The SC2_PNT-B scenario will be described next. This scenario may have two sub-scenarios, SC2_PNT-B1 and SC2_PNT-B2. Both sub-scenarios are based on the idea that all satellites transmit the ranging signal components (e.g., (N)PRS symbols) at the same frequency using a common subband. This is to avoid UE re-tuning during the ranging measurement. The two sub-scenarios differ in the choice of frequency sub-band for providing communication service. The SC2_PNT-B1 subscenario foresees that the common sub-band used for transmission of ranging signal components is also shared with one of the satellites for transmitting communication symbols. By contrast, in the SC2_PNT-B2 sub-scenario, common sub-band used for transmission of ranging signal components is reserved for ranging signal components only.

[0350] In line with the above, in general, the ranging signal components may be received, for example at step S310 of method 300, in a single, shared frequency band (or frequency sub-band), with at least partial overlap in frequency between the ranging signal components. The single frequency band may be a dedicated frequency band shared by the plurality of satellites for transmitting their ranging signal components (e.g., in sub-scenario SC2_PNT-B1). Alternatively, the single frequency band may be a frequency band in which one of the plurality of satellites provides communication service (e.g., transmits communication signal components (payload data)) (e.g., in sub-scenario SC2_PNT-B2). In the latter case, a lower power for the ranging signal components compared to the communication signal components may be chosen to limit the interference to the communication data components.

[0351] Potential advantages of sub-scenarios SC2_PNT-B1 and B2 resulting from avoidance of UE re-tuning may be offset by drawbacks that are specific to the sub-scenarios, as will be discussed in the following. For both sub-scenarios, successive (N)PRS block correlation results cannot be easily combined in a coherent manner because of the lack of NRS pilot symbols allowing proper OFDM channel estimation. This means that a ranging performance loss due to non-coherent combination of PRS block measurement may have to be expected.

[0352] The SC2_PNT-B1 sub-scenario may resemble the TN PRS scenario where the PRS symbols from different base stations may be interleaved in time within the same OFDM block, also using the European Space Agency December 20, 2024

[0353] 220993PC blanking slot capability. However, as described above, the satellites’ geometry for the LEO NTN satellite constellation breaks OFDM orthogonality when PRS are transmitted from different satellites in the same sub-band due to the relative Doppler and time offset specific to each satellite.

[0354] Instead of transmitting in the shared sub-band, the network signaling and communication service data symbols are transmitted in the nominal satellite sub-band to avoid co-channel interference destructive effects, similarly to scenario SC2_PNT_A.

[0355] This is shown in Fig. 14B, which illustrates an example of the corresponding time / frequency plan for this sub-scenario. The white arrows at the left-hand side again indicate the nominal sub-band central frequencies and the dashed light rectangles Bl, B2, B3, B4 indicate the nominal sub-band occupancy in the absence of Doppler shift. For sub-band 1430, which is the shared sub-band for PRS transmission (as an example for ranging signal components) periodic ranging signal components from the plurality of satellites, indicated by squares 1420, are interleaved with data components 1410 of one of the satellites that transmits in sub-band 1430. The other satellites transmit their data components 1410 in different sub-bands 1440, 1450, 1460, where no PRS transmission occurs.

[0356] Using such time / frequency plan avoids the need for re-tuning the UE to collect the PRS symbols from different satellites. However, the PRS overlap may increase the on-ground Power Flux Density, when (N)PRS symbols from different satellites overlap in time, which may affect compliance with regulatory requirements.

[0357] The following demodulation aspects may be considered for scenario SC2_PNT-B1:

[0358] • PRS symbols loss of orthogonality impact on the PRS and data payload symbols.

[0359] • Channel estimation for OFDM coming from different satellites.

[0360] Further, in the NTN SC2_PNT-B1 scenario where simultaneous reception from distinct and spaced apart satellites is expected to adopt TDM within the same OFDM block, the following effects may occur:

[0361] • The signal differential delay will be much larger than for the TN or NTN SC2_PNT-A scenarios because center of beam (COB) time pre-compensation cannot be implemented due to the wide area beam. As shown in Fig. 14B, the differential delay will largely exceed the Cyclic Prefix (CP) equalization capabilities, thus causing crosstalk between (N)PRS from other European Space Agency December 20, 2024

[0362] 220993PC satellites operating in sub-bands B2, B3, B4 and the reference satellite operating in subband Bl.

[0363] • Similarly, the satellites’ differential Doppler among the sub-carriers (SCs) which cannot be pre-compensated in NTN SC2_PNT-B scenario, will generate crosstalk among the SCs.

[0364] The (N)PRS symbol crosstalk may occur among the different satellites but may also impact the payload data OFDM frames. The effect can be quite serious due to the impact of (N)PRS symbols (partially) overlapping in time / frequency with the data symbols present in the frame. This may be mitigated by reducing the (N)PRS symbols transmitted power level, but this will require a longer integration time to achieve similar positioning accuracy.

[0365] The situation for (N)PRS-to-(N)PRS interference is potentially less critical as the other satellites crosstalk mitigation will be provided by the different Gold sequences used by the satellites for (N)PRS which provide a certain level of cross-correlation isolation, which can be enhanced extending the correlation time. Furthermore, (N)PRS acquisition performance statistics will also be impacted as shown in [Gonzalez-Garrido 2024],

[0366] Finally, the COM payload to (N)PRS interference is likely to be more impactful than the (N)PRS-to- (N)PRS interference as the COM to (N)PRS cross-correlation will be less controlled.

[0367] In view of the above, the FDM approach proposed above with reference to (but not limited to) the SC_PNT-A scenario appears preferable, depending on circumstances.

[0368] A possible solution to the (N)PRS interference on the communication data symbols affecting subscenario SC1_PNT-B1 is given by sub-scenario SC2_PNT-B2, which fully dedicates a sub-band to the (N)PRS transmission (as an example of ranging signal component transmission) for all satellites. In this way it may be avoided that PRS symbols interfere with the data carrying time slots of the OFDM frame due to satellite asynchronous reception at the UE.

[0369] The corresponding time / frequency plan is shown in Fig. 14C. The white arrows at the left-hand side again indicate the nominal sub-band central frequencies and the dashed light rectangles Bl, B2, B3, B4 indicate the nominal sub-band occupancy in the absence of Doppler shift. Periodic ranging signal components from the plurality of satellites, indicated by squares 1420, are transmitted in subband 1430, which is the dedicated shared sub-band for PRS transmission (as an example for European Space Agency December 20, 2024

[0370] 220993PC ranging signal components). Data components 1410 of the satellites are transmitted in different sub-bands 1440, 1450, 1460, where no PRS transmission occurs.

[0371] As can be seen from Fig. 14C, the sub-band 1430 (Bl) is nowfully dedicated to (N)PRS transmission from all satellites while the data symbols 1420 are transmitted in orthogonal sub-bands 1440, 1450, 1460 (B2, B3, B4), thus avoiding any crosstalk among them. The partial (N)PRS time overlap from different satellites can be tolerated by proper extension of the correlation time, which is due to the above-mentioned good cross-correlation properties of the distinct Gold sequences assigned to the different satellites.

[0372] The main disadvantages of this configuration may lie in the reduction of system throughput (e.g., by one quarter in the example of Fig. 14C), the extra power spectral flux density on ground when (N)PRS symbols overlap in time and the need to re-tune the UE for ranging measurements.

[0373] (N)PRS Aspects

[0374] The fact that for positioning only the PRS symbols (as an example of ranging signal components in the context of the present disclosure) from other satellites need to be processed largely simplifies demodulator operation, as it normally can exploit the knowledge of the satellite ephemeris and the terminal past location measurement performed to steer the PRS correlation without resorting to a GNSS receiver, as is currently baselined in NTN NB-loT. In this way the time and frequency uncertainty to be dealt with by the correlator is largely reduced, hence complexity and power consumption can be kept similar to TN operation.

[0375] One exception may be for the very first cold start when the user location is unknown although downlink acquisition will provide satellite ephemeris. Here some user-aided approximate position introduction may mitigate the issue.

[0376] As described above, the original (N)PRS symbol grid schemes developed for 3GPP (N)TN may lose losing appeal in LEO PNT context due to the loss of orthogonality among the satellites. For this kind of application when the loT-NTN satellites transmit on different sub-bands, it may make sense to “densify” the NPRS and LTE PRS grid adopted by each single satellite to reduce the time required to perform ranging. The 3GPP NR physical layer specifications (see 3GPP TS 38.211) allow for a much more compact PRS patten, namely C0MB-2, compared to the sparser NPRS and LTE-PRS patterns in the LTE physical layer. This is schematically illustrated in Fig. 15A and Fig. 15B, with the former showing the sparser NPRS and LTE-PRS diagonal patterns used in LTE and NB-loT TN European Space Agency December 20, 2024

[0377] 220993PC positioning and the latter showing a potential evolution to COMB-2 NPRS grids. A COMB-2 grid, as schematically illustrated in Fig. 15C, and even non-standard compliant full grid COMB-O, as schematically illustrated in Fig. 15D, could be envisioned for loT-NTN positioning using NB-loT or eMTC radio. COMB-2 occupies 84 PRS resource elements in 1 ms versus 28 of the current pattern, and hence is three times denser and faster in ranging measurement. As possible standard evolution may consider reusing all 168 resource elements available in the resource grid for NPRS and LTE PRS to reduce the time for obtaining the ranging measurement by 50% compared to COMB-2.

[0378] The present disclosure proposes supporting the NTN loT UE localization in support of uplink synchronization by replacing the use of a GNSS receiver with the NTN downlink ranging signal processing techniques, as described above.

[0379] Examples of NTN uplink time synchronization procedures are described in [Liu 2022] and are fully applicable to the present disclosure. The common UE Time Advance (TA) may be computed by the gNodeB and broadcast to the UEs belonging to the beam. The UE specific TA may be computed by estimating the UE location using the downlink NTN (N)PRS ranging signal components (as examples of the ranging signal components) broadcast by the satellites in view, combined with the use of the constellation’s satellite ephemeris part of the NTN broadcast messages. The target timing accuracy required is less than 0.1 ppm.

[0380] As noted above, one main difference of techniques according to the present disclosure compared to conventional techniques lies in the elimination of the GNSS receiver hosted by the UE and of any need for a two-way connection with the NTN. The UE position accuracy provided by the (N)PRS ranging may be inferior to the GNSS position accuracy depending on the signal bandwidth but is expected to still be sufficient for NB-loT applications.

[0381] Concerning the uplink carrier frequency UE pre-correction based on UE location and satellite ephemeris knowledge, a UE localization error of less than few km may be desirable. A good UE local frequency reference may be derived from the downlink carrier frequency after removing the Doppler offset.

[0382] Fig. 16 is a functional block diagram of a possible approach for the time and frequency reference extraction at the UE receiver. It will be assumed that the UE sequentially tunes to the satellites in view and focus will be put on single satellite signal detection. The signals received from the satellite may be amplified by a Low Noise Amplifier (LNA) and converted to close to baseband by a mixer that European Space Agency December 20, 2024

[0383] 220993PC is driven by a local oscillator (LO), which in turn is controlled in frequency / phase by an error signal derived from a frequency / phase error discriminator. In this way, the locally generated LO frequency fo + fo tracks the input satellite signal at frequency f0+ fD. The UE demodulator may measure the (N)PRS symbols sequence timing and extract the navigation information including the satellite ephemerides. This information may then be passed to a UE position estimator which allows also to derive the expected carrier Doppler fDby satellite orbital geometry modelling relative to the estimated UE position. By removing fDfrom / o+ fDit is possible to estimate the satellite carrier frequency f0from which an accurate frequency and timing reference may be derived, for use by the UE transmitter.

[0384] Satellite Transmission Method

[0385] While the above description is focused on features implemented at the UE side of a NTN, it is understood that the present disclosure likewise relates to corresponding satellite-side techniques, and that features described in relation to the UE side may have corresponding satellite-side features, detailed description of which may however have been omitted for reasons of conciseness.

[0386] Fig. 17 is a flowchart illustrating an example of a transmission method 1700 at a satellite that may be seen as a counterpart method to method 300 of Fig. 3. Method 1700 comprises steps S1710 and S1720.

[0387] At step S1710. a ranging signal component is transmitted, at a satellite, towards Earth. This transmission of the ranging signal component may be performed periodically in broadcast mode.

[0388] The ranging signal components at step S1710 may relate to an NPRS, PRS (LTE-M PRS), or NR PRS. The NPRS and LTE-M PRS may be configured according to 3GPP TS 36.211. The NR PRS may be configured according to 3GPP TS 38.211. Alternatively, the ranging signal components may relate to a dense PRS grid (e.g., a COMB-2 grid defined in 3GPP TS 38.211) or a full PRS grid. This may reduce the time required for TOA measurements at the UE. Further alternatively, the ranging signal components may relate to primary and secondary synchronization signals.

[0389] At step S172O.positionin assistance information included in one or more System Information Blocks, SIBs, or positioning System Information Blocks, posSIBs, is transmitted, at the satellite, towards Earth periodically in broadcast mode. European Space Agency December 20, 2024

[0390] 220993PC

[0391] Although not shown in Fig. 17, the method may further comprise providing a communication service to a UE.

[0392] In this case, a transmission timing of the ranging signal component at the satellite may be aligned with a transmission timing of a communication signal component of the satellite, such that transmission of the ranging signal component and the communication signal component do not overlap in time. In other words ranging signal components and communication signal components (data components) may be interleaved in time.

[0393] Further, in some cases the ranging signal component and the communication signal component of the satellite may be transmitted in the same frequency band, for example in scenario SC2_PNT-A and, at least for one satellite, in scenario SC2_PNT-B1 described above.

[0394] The method may further comprise, optionally, receiving, at the satellite, positioning assistance information concerning one or more of satellite ephemeris, clock corrections, ionospheric corrections, and a ranging signal component signal configuration from a ground station.

[0395] The method may yet further comprise, optionally, synchronizing, at the satellite, an internal clock of the satellite with internal clocks of one or more other satellites in the non-terrestrial network based on GNSS signals received at the satellite, and / or synchronizing signal transmission, at the satellite, with signal transmission of one or more other satellites in the non-terrestrial network based on GNSS signals received at the satellite.

[0396] Further details of steps S1710 and S1720 and further steps of method 1700 may be inferred from corresponding features of the UE-side method described above.

[0397] While methods of signal transmission and reception have been described above, it is understood that the present disclosure likewise relates to corresponding transmitter-side and receiver-side apparatus (e.g., transmitters and receivers in general, or satellites / HAPs and UEs in particular). Any statements made above with regard to respective methods are understood to analogously apply to corresponding apparatus (and vice versa).

[0398] Fig. 18 is a schematic block diagram of an apparatus 1800 for implementing methods according to embodiments of the disclosure. Apparatus 1800 comprises a processor 1810 and a memory 1820 coupled to the processor. The processor 1810 is further coupled with radio communication European Space Agency December 20, 2024

[0399] 220993PC equipment 1830 (e.g., RF transmission equipment and / or RF reception equipment) and configured, using the radio communication equipment 1830, to perform any of the methods described throughout the disclosure, in particular method 300 and / or method 1700. For this, the apparatus 1800 may receive one or more inputs 1840 (e.g., ranging signal components, (pos)SIBs, positioning assistance information, etc. as the case may be) and output one or more outputs 1850 (e.g., the determined UE position, ranging signal components, (pos)SIBs, positioning assistance information, etc. as the case may be).

[0400] For example, apparatus 1800 may relate to a UE (or part thereof), for example for performing method 300, or to a satellite (or part thereof), for example for performing method 1700.

[0401] The present disclosure further relates to a system comprising a UE and a plurality of satellites as part of a non-terrestrial network.

[0402] It is further understood that the present disclosure likewise relates to corresponding computer programs, such as a computer program comprising instructions that when executed by one or more processors acting as a controller coupled to a telecom payload or communication equipment, cause the one or more processors to perform any of the UE-side methods or satellite-side methods described throughout the disclosure, or a computer program comprising instructions that when executed by one or more processors acting as a controller coupled to a receiver, cause the one or more processors to perform any of the UE-side methods or satellite-side methods described throughout the disclosure.

[0403] The present disclosure further relates to computer-readable storage media storing such computer programs.

[0404] System Performance Evaluation Examole

[0405] An analysis of system performance according to embodiments of the disclosure will be presented next.

[0406] A detailed evaluation of system performance for the example LEO PNT NTN NB-loT scenario presented in Annex 1 is given in Annex 2. Here, the main findings are summarized to show an example of the potential proposed system performance in terms of PNT and COM capabilities. European Space Agency December 20, 2024

[0407] 220993PC

[0408] Downlink COM and PNT

[0409] Table 1 provides a summary of the reference LEO PNT system performance following the assumptions contained in Annex 1 and detailed analysis as reported in Annex 2.

[0410] It is apparent that for 15 degrees satellite elevation the poor link budget requires several packet repetitions to achieve the required BLER (32 and 8 for single patch and isoflux satellite antenna respectively). The single satellite downlink throughput amounts to about 500 and 2000 bps for the two satellite antenna cases. Assuming that a typical four colors frequency reuse scheme is in place and four satellites are in simultaneous view, the total system throughput will be four times the single satellite throughput.

[0411] European Space Agency December 20, 2024

[0412] 220993PC

[0413] Table 1: Reference system downlink COM and PNT performance summary

[0414] This throughput obtained for a mass-market mobile phone is compatible with typical public services scenarios envisaged for this system.

[0415] Under the assumption of adopting the COMBO preferred (N)PRS grid configuration described in relation to Fig. 15B, for PNT we have an estimated ranging standard deviation of 88 and 54 meters leading to a DOP of 177 and 208 m for the two satellite antenna cases. This may be considered sufficient for loT applications. Better performance could be achieved using a longer integration time European Space Agency December 20, 2024

[0416] 220993PC compared to the current 80 ms. Clearly, when adopting the C0MB12 (N)PRS symbols configuration currently allowed for NB-loT, the same performance will require extension of the observation time by six times. For C0MB2 supported by the NR 3GPP standard, the observation time will have to be doubled.

[0417] Concerning the UE NTN NB-loT time synchronization requirement of some microseconds (or less), a one sigma timing accuracy of about 0.3 and 0.2 microseconds for the patch and iso-flux antenna cases, respectively, will be obtained from the above ranging accuracy for 80 ms integration time, which is fully in line with requirements. Similar considerations apply to the carrier frequency error, for which a UE localization error of less than 1 km is required, and which is within requirements with large margin.

[0418] Uplink COM

[0419] The uplink COM system performances are summarized in Table 2. Also in this case there is a need for packet repetitions to cope with the low link SNR. The single UE bit rate at 15 degrees satellite elevation ranges from 76 to 208 bps depending on the satellite antenna assumptions (single patch or isoflux). The single satellite throughput ranges from 3.6 kbps to 9 kpbs, which should be multiplied by four when four satellites, each using a different sub-band, are in view.

[0420] Although modest, this throughput is compatible with typical public services scenarios envisaged for this system utilizing a hand-held mobile phone.

[0421] Table 2: Reference system uplink COM performance summary European Space Agency December 20, 2024

[0422] 220993PC

[0423] The present disclosure proposes techniques relating to possible adaptations of the 3GPP NTN NB- loT standard to efficiently support combined COM and PNT services for loT devices over NTN non- geostationary constellations.

[0424] More specifically, the present disclosure proposes:

[0425] • An integrated two-way messaging and positioning solution for personal emergency exploiting loT-NTN and smartphones with loT modems.

[0426] • A way to allow (quasi-)simultaneous loT UE reception from multiple satellites for positioning without necessary modifications to mass market NB-loT devices.

[0427] • A way to remove GNSS dependency for uplink time and frequency synchronization during the initial access to loT-NTN systems.

[0428] • A new DL-TOA positioning mode for NTN systems.

[0429] • An adaptation of TN OTDOA to NTN systems.

[0430] • An adaptation to LTE hybrid positioning frameworks based on GNSS and RAT-dependent positioning.

[0431] • A way to exploit (N)PRS in satellite NTN constellations utilizing single or multi-beam satellites.

[0432] • A way to support handover based on early identification of candidate satellites and predictive planning.

[0433] • A way to correct the satellite clock errors.

[0434] • A way to correct for ionospheric effects on signals broadcast by satellites.

[0435] It is understood that any modules, units, or blocks described above may be implemented by a computer processor or respective computer processors, or the like. Modules, units or blocks described above may further be implemented in a cloud-based manner.

[0436] It should further be noted that the description and drawings merely illustrate the principles of the proposed method and system. Those skilled in the art will be able to implement various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples and embodiments outlined in the present document are principally intended expressly to be only for explanatory European Space Agency December 20, 2024

[0437] 220993PC purposes to help the reader in understanding the principles of the proposed method and system. Furthermore, all statements herein providing principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass equivalents thereof.

[0438] References

[0439] [3GPP TR 38.811] 3GPP TR 38.811, “Study on New Radio (NR) to support non-terrestrial networks (NTN),” V15.2.0, June 2020.

[0440] [3GPP TR 38.821] 3GPP TR 38.821, “Solutions for NR to support non-terrestrial networks (NTN),” V16.1.0, December 2020.

[0441] [3GPP TS 22.261] 3GPP TS 22.261, “Service requirements for the 5G system; Stage 1,” V17.4.0, December 2020.

[0442] [3GPP TS 22.822] 3GPP TS 22.822, “Study on using Satellite Access in 5G; Stage 1,” V16.0.0, December 2018.

[0443] [3GPP TR 23.737] 3GPP TR 23.737, “Study on architecture aspects for using satellite access in 5G,” V16.1.0, March 2020.

[0444] [3GPP TR 28.808] 3GPP TR 28.808, “Study on management and orchestration aspects of integrated satellite components in a 5G network,” V16.1.0, December 2019.

[0445] [3GPP TR 36.763] 3GPP TR 36.763, “Study on Narrowband Internet of Things (NB-loT) support and evolution for LTE,” V15.0.0, March 2018.

[0446] [3GPP TR 38.882] 3GPP TR 38.882, “Study on requirements and use cases for network-verified UE location for non-terrestrial networks (NTN) in NR,” V18.0.0, December 2021.

[0447] [3GPP TR 22.926] 3GPP TR 22.926, “Guidelines for extra-territorial 5G systems such as satellite,” V18.0.0, December 2021.

[0448] [3GPP TS 36.305] 3GPP TS 36.305, “Evolved Universal Terrestrial Radio Access (E-UTRA); User Equipment (UE) positioning in E-UTRA; Stage 2,” V16.0.0, December 2019

[0449] [3GPP TS 37.355] 3GPP TS 37.355, “LTE Positioning Protocol (LPP),” V18.0.0, December 2021. European Space Agency December 20, 2024

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[0451] [Lin 2017] X. Lin et aL, “Positioning for the Internet of Things: A 3GPP Perspective,” in IEEE Communications Magazine, vol. 55, no. 12, pp. 179-185, Dec. 2017, doi: 10.1109 / MC0M.2017.1700269.

[0452] [De Gaudenzi 2024] R. De Gaudenzi, “A proposal for an Integrated LEO Communication and PNT System for Beyond 5G,” ESA TEC-E technical report, vl.O, June 30, 2024.

[0453] [Angeletti 2021] P. Angeletti and R. De Gaudenzi, “Heuristic Radio Resource Management for Massive MIM0 in Satellite Broadband Communication Networks,” in IEEE Access, vol. 9, pp. 147164-147190, 2021, doi: 10.1109 / ACCESS.2021.3123581.

[0454] [Guidotti 2017] A. Guidotti et. al, “Satellite-enabled LTE systems in LEO Constellations,” 2017 IEEE International Conference on Communications (ICC), Paris, May 2017, pp. 876-881, doi: 10.1109 / ICCW.2017.7962769

[0455] [loT book 2022] R. De Gaudenzi, N. Alagha, S. Cioni, “Internet of Things over non-geostationary orbit system and random access aspects,, book chapter from Non-Geostationary Satellite Communications Systems, December 2022, doi 10.1049 / PBTE105E

[0456] [Gonzalez-Garrido 2024] A. Gonzalez-Garrido, J. Querol, H. Wymeersch, S. Chatzinotas, “Interference analysis of Positioning Reference Signals in 5G NTN,” January 2024, arXiv:2401.09157.

[0457] [Zanier 2008] F. Zanier and M. Luise, “Fundamental issues in time-delay estimation of multicarrier signals with applications to next-generation GNSS,” 2008 10th International Workshop on Signal Processing for Space Communications, Rhodes, Greece, 2008, pp. 1-8, doi: 10.1109 / SPSC.2008.4686720.

[0458] [Staudinger 2013] E. Staudinger and A. Dammann, “Sparse subcarrier allocation for timing-based ranging with OFDM modulated signals in outdoor environments,” 2013 10th Workshop on Positioning, Navigation and Communication (WPNC), Dresden, Germany, 2013, pp. 1-6, doi: 10.1109 / WPNC.2013.6533287.

[0459] [Lin 2016] X. Lin, A. Adhikary and Y.-P. Eric Wang, “Random Access Preamble Design and Detection for 3GPP Narrowband loT Systems,” in IEEE Wireless Communications Letters, vol. 5, no. 6, pp. 640- 643, Dec. 2016, doi: 10.1109 / LWC.2016.2609914.

[0460] h httttppss:: / / / / wwwwww..eparirctsicsloen.i.oe / olmoT / -egnu / idbelos-ga / n2dO-1re7s / o3u / rlcoeTs- / DloosTi-tpiornotinogc-oinls--ltaen-sdt-astnadnadradrizdast / ion

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[0463] [Jiang 2018] N. Jiang, Y. Deng, M. Condoluci, W. Guo, A. Nallanathan and M. Dohler, “RACH Preamble Repetition in NB-loT Network,” in IEEE Communications Letters, vol. 22, no. 6, pp. 1244- 1247, June 2018, doi: 10.1109 / LC0MM.2018.2793274.

[0464] [Martiradonna 2019] Martiradonna S, Piro G, Boggia G., “On the Evaluation of the NB-loT Random Access Procedure in Monitoring Infrastructures,” Sensors (Basel), 2019 Jul 23;19(14):3237. doi: 10.3390 / S19143237.

[0465] [Chougrani 2021] H. Chougrani, S. Kisseleff and S. Chatzinotas, "Efficient Preamble Detection and Time-of-Arrival Estimation for Single-Tone Frequency Hopping Random Access in NB-loT,” in IEEE Internet of Things Journal, vol. 8, no. 9, pp. 7437-7449, 1 Mayl, 2021, doi:

[0466] 10.1109 / JI0T.2020.3039004.

[0467] [Matlab PRACH] NB-loT PRACH Detection and False Alarm Conformance Test https: / / it.mathworks.com / help / lte / ug / nb-loT-prach-detection-and-false-alarm-conformance- test.html

[0468] [De Gaudenzi 2018] R. De Gaudenzi, 0. Del Rio Herrero, G. Gallinaro, S. Cioni, P.-D. Arapoglou, “Random access schemes for satellite networks, from VSAT to M2M: a survey,” Wiley Internation Journal of Satellite Communications and Networking, Vol. 36, Issuel, January / February 2018, pp. 66-107.

[0469] [ESA RAN2 2024] 3GPP TSG-RAN WG2 Meeting #127 Contribution R2-2407502, Discussion on DSA and CRDSA Performance, August 2024. httDs: / / academy.nordicsemi.com / courses / cellular-loT-fundamentals / lessons / lesson-l-cellular- fundamentals / topic / lesson-l-power-saving-techniques / https: / / www.ericsson.com / en / reports-and-papers / ericsson-technology-review / articles / 3gpp- satellite-communication

[0470] [Liu 2022] W. Liu, X. Hou, J. Wang, L. Chen and S. Yoshioka, “Uplink Time Synchronization Method and Procedure in Release-17 NR NTN,” 2022 IEEE 95th Vehicular Technology Conference: (VTC2022-Spring), Helsinki, Finland, 2022, pp. 1-5, doi: 10.1109 / VTC2022- Spring54318.2022.9860357. European Space Agency December 20, 2024

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[0472] Annex 1

[0473] Reference System

[0474] Reference system parameters

[0475] To provide numerical examples for a NB-NTN study, the Non-Terrestrial Network (NTN) deployment scenarios contained in Table 3 have been selected. They are summarized below.

[0476] Table 3: Reference Non-Terrestrial Network deployment scenarios European Space Agency December 20, 2024

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[0478] The system application scenarios are detailed in Annex 4.

[0479] As carrier frequency between air / space-borne platform and UE, the S-band, DL: 2170-2200 MHz, UL: 1980-2010 MHz will be considered.

[0480] “Beam pattern” in the present context is understood to stand for “beam coverage pattern”. The footprint of the beams typically is of circular shape. The beam footprint may move over the Earth along with the satellite’s motion on its orbit. Alternatively, the beam footprint may be Earth-fixed, in which case appropriate beam pointing mechanisms (e.g., mechanical or electronic steering features) will compensate for the satellite or the aerial vehicle motion.

[0481] For the scenarios under consideration, FDD (Frequency Division Duplexing) is selected as access scheme. FDD means that the transmitter and the receiver operate at different carrier frequencies. Uplink and downlink sub-bands are separated by the named frequency offset.

[0482] The scenario attribute “Channel Bandwidth (DL + UL) and NPRS configuration” stands for the available bandwidth for channels, for DL and for UL. It depends on the carrier frequencies used.

[0483] NPRS is essentially a 1-PRB LTE-PRS, configured per NB-loT carrier. There are 2 PRS patterns: Part- A and Part-B.

[0484] Part-A is the same pattern as the LTE PRS but extended to have a (N)PRS symbol also at the control / CRS region, i.e., essentially a full diagonal pattern as depicted in Fig. 19.

[0485] Part-A can only be used for stand-alone / guard-band case. This is of interest to the case at hand, since stand-alone deployment is desired. In the present analysis a full grid, COMBO, has been assumed. This frequency-time grid is not supported yet in TS 36.211.

[0486] The subframe configuration is indicated by a 10 / 40-bit bitmap in LPP protocol, indicating one NPRS occasion. 0 / 1 indicates a subframe without / with NPRS.

[0487] Detailed description of the NPRS sequence generation and its specifics is given in 3GPP TS 36.211, clause 7.2. 3GPP TS 36.331 provides information on higher-layer configurations affecting NPRS.

[0488] As NTN architecture option, A2: Access network serving UEs with gNB on board satellite / aerial will be considered.

[0489] In relation to NTN terminal type, the following is noted. European Space Agency December 20, 2024

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[0491] Until Rel-18, the 3GPP specifications limit maximum NTN UE transmission (Tx) power to the level of 23 dBm (0.20 W) for Power Class (PC) 3, with an omnidirectional antenna with 0 dBi gain.

[0492] RP-240857 introduces a new UE class: High Power UE (HPUE) for NR-NTN and loT-NTN (NB-loT and eMTC) in FR1 bands: Power Class 2 (PC2, 26 dBm).

[0493] In a first approach and for evaluation purposes, the PC 3 UE will have a Transmit Power set to 23 dBm (0.20 W). Based on the developments in Rell9 Wl (RP-240857), additional test cases are to be considered.

[0494] Doppler shift analysis in NGSO

[0495] An estimate the Doppler shift of satellites at different altitudes can be computed by the classical equation f fd(t) = vSATcos[a(t)].

[0496] (3)

[0497] The satellite linear speed, vSAT, is constant over time, and it is solely a function of the orbital height.

[0498] It can be expressed as a function of the satellite angular speed, coSAT, as where:

[0499] • G is the gravitational constant

[0500] • M is the mass of the Earth

[0501] • Reis the distance from the center of the Earth to the satellite, which is the sum of the Earth's radius (-6371 km) and the satellite’s altitude above Earth.

[0502] From the system geometry and the sine / cosine theorems, the following equations may be derived (cf. [loT book 2022]): cos aft) European Space Agency December 20, 2024

[0503] 220993PC where with reference to Fig. 20:

[0504] • a is the relative motion angle measured between the mobile satellite direction and the tangential satellite direction

[0505] • fd is the Doppler shift

[0506] • fo is the nominal carrier frequency

[0507] • c is the speed of light (approximately 299,792,458 m / s)

[0508] The Doppler rate can be obtained by taking a time derivative of the Doppler equation. Details can be found for example in [Guidotti 2017], [loT_book_2O22],

[0509] The LEO distance can be computed as

[0510] Fig. 21 schematically illustrates the NB-loT frame structure for NB-loT for DL and UL with 15 kHz subcarrier spacing. The numerical results for Doppler and Doppler rate for h=600 km are summarized in the diagrams of Fig. 22 and Fig. 23, respectively. Key numerical results regarding delay and satellite distance are summarized in Table 4. More complete data is shown in the diagrams of Fig. 24 and Fig. 25, which show the satellite distance and delay versus the satellite elevation angle for a LEO orbit at 700 km and 1200km, respectively. It is apparent that the differential Doppler and delay are well beyond the TN operating conditions and largely exceed the NB-loT 0.5 ms OFDM slot duration and the Radio Frame 10 ms duration (see Fig. 21).

[0511] Clearly the differential Doppler related to distinct satellites will depend on the relative geometry and in the worst-worst-case when two satellites appear in (almost) opposite directions to the user location can be as large as twice the value shown in the aforementioned single satellite diagrams. The differential Doppler and delay statistics shall be performed based on the system constellation parameters. European Space Agency December 20, 2024

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[0513] Table 4: Satellite distance and delay for h=700, 900 and 1200 km and two elevation angles.

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[0516] Annex 2

[0517] Reference System Analysis

[0518] Downlink

[0519] A downlink performance analysis has been performed for the lowest satellite elevation angle (15 degrees) using typical 3GPP NTN Set 4 link assumptions while the satellite payload is in line with current LEO PNT assumptions. The total throughput reported below is related to a single satellite (180 kHz sub-band). In case of four satellites (sub-bands) active on the same region, the total throughput shall be multiplied by 4.

[0520] The ranging coherent integration time of 80 ms is based on the assumption that the UE has knowledge of satellites ephemerides and its approximate location from previous PNT measurement, which allows to pre-correct for carrier Doppler frequency shift.

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[0523] NB-loT (180 kHz) ESA LEO PNTcase European Space Agency December 20, 2024

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[0525] The modified Cramer-Rao (MCRB) bound (of. [Zanier 2008]) has been utilized in the link budget to estimate the NB-loT PRS timing error from which the position accuracy is derived using the DOP assumption. The OFDM MCRB can be obtained following the approach outlined in [Zanier 2008] or more easily following [Staudinger 2013]. In particular, European Space Agency December 20, 2024

[0526] 220993PC where cr2is the noise variance over the ranging integration time Tobs, fscis the OFDM sub-carrier frequency, Nscrepresents the number of (N)PRS

[0527] OFDM sub-carriers and C is the OFDM signal power.

[0528] Denoting the AWGN noise power spectral density by No, one may derive

[0529] Noa 2

[0530] T0bs

[0531] (9)

[0532] In practice, Tobscorresponds to the OFDM subcarrier symbol duration Tscmultiplier by the number of PRS symbols which are effectively used for the ranging measurement, i.e.

[0533] T1obs —1NNsPyRmST1sc-

[0534] (10)

[0535] Expanding the sum

[0536] (ID and substituting Eq. (9) and Eq. (10) into Eq. (8) yields

[0537] In applying this equation, one should take into account how many sub-carriers are active during one (N)PRS OFDM symbol duration. For the current 3GPP NB-loT allowing only the C0MB12 grid configuration this corresponds to Nsc= 2, while for C0MB12 to Nsc= 6 and for COMBO to Nsc= 12. Clearly, the higher the Nscvalue, the lower the MCRB result. European Space Agency December 20, 2024

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[0539] The following tables summarize the 3GPP NB-loT physical layer assumptions considered for assessing the downlink system level performance. It is noted that due to the low SNR without repetition resultingfrom the above link budget analysis, a well-protected low code rate physical layer configuration (MCS) can be selected. The number of repetitions possible are quantized according to the table below. Hence the value used corresponds to the next highest value to the minimum value required from link analysis.

[0540] In NTN NB-loT, the exact number of allowed repetitions for different channels follows similar principles as in terrestrial NB-loT. However, NTN environments (such as satellite-based NB-loT) involve longertransmission distances and higher path losses, leading to a greater need for coverage enhancement. As a result, repetitions are more critical, and specific parameters may differ slightly to accommodate the unique characteristics of NTN.

[0541] The number of downlink repetitions for NTN NB-loT is specified in the same documents as for terrestrial NB-loT, primarily 3GPP TS 36.213, but with additional considerations for the satellite or high-altitude platform system link.

[0542] • Channels involved: NPDCCH (Narrowband Physical Downlink Control Channel), NPDSCH (Narrowband Physical Downlink Shared Channel), and others. European Space Agency December 20, 2024

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[0544] The exact values for allowed repetitions in the downlink are as follows:

[0545] 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048

[0546] For the satellite antenna two possible options have been considered, the first one is a simple patch antenna with peak gain at nadir and lowering gain at the edge of coverage. A more suitable antenna to cover low UE satellite elevation angles is the one following an iso-flux antenna pattern realized by means of a deployable helix. The antenna performances are summarized in Fig. 26 and Fig. 27, which show the Anywaves compact S-band TT&C antenna radiation pattern and Anywaves S-band quadrifilar helix antenna pattern, respectively.

[0547] Uplink The uplink performance analysis has been performed for the lowest satellite elevation angle (15 degrees), using typical 3GPP NTN Set 4 link assumptions while the satellite payload is in line with current LEO PNT assumptions.

[0548] In the return link case, the UE is required to apply Doppler and timing pre-compensation, hence no specific extra guard bands will be required. The reported total throughput is related to a single satellite (180 kHz sub-band). In case of four satellites (sub-bands) active on the same region, the total throughput shall be multiplied by 4 while the UE bit rate remains unchanged.

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[0551] The following tables summarize the 3GPP NB-loT physical layer assumptions considered for the uplink system level performance assessment. It is noted that considering the resulting low SNR link European Space Agency December 20, 2024

[0552] 220993PC budget without repetition reported above, a well-protected low code rate physical layer configuration (MCS) can be selected.

[0553] Allowed uplink repetitions may be as follows: • Channels involved: NPUSCH (Narrowband Physical Uplink Shared Channel) for data transmission and NPRACH (Narrowband Physical Random Access Channel) for random access.

[0554] • The exact values for allowed repetitions in the uplink are:

[0555] O NPUSCH (Data Transmission - Format 1): 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024 o NPUSCH (Control - Format 2): 1, 2, 4, 8, 16, 32

[0556] O NPRACH: 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024

[0557] The 4-step RA mentioned above in the PRACH discussion may also have an impact on the NB-loT uplink throughput. The first step corresponds to a Slotted Aloha (SA) RA whose performance is shown in the diagram of Fig. 28. As recently discussed in 3GPP RAN2 [ESA RAN2_2024], it can be concluded that despite the Msg3 transmission occurring with dedicated (orthogonal) resource assignment, the first RA step throughput limits shall be considered when assessing the system European Space Agency December 20, 2024

[0558] 220993PC throughput. As is evident from Fig. 28, the SA throughput depends on the packet loss ratio (PLR) accepted during the contention phase. The corresponding RA throughput T is simply given by

[0559] T(G) = 1 - PLR(CT),

[0560] (13) with G denoting the Multi Access Communication (MAC) load.

[0561] While for TN a PLR of IO2or slightly above is typically considered acceptable due to the very low retransmission latency, in satellite systems a lower PLR (typically less than IO2) should be targeted. Referring to Fig. 28, at this target PLR the SA throughput is less than IO2bits / symbol which represents a rather poor performance.

[0562] Looking at the LEO-PNT throughput results reported herein, it is noted that the uplink throughput is clearly dependent on the user elevation. The link budget for simplicity assumes that all users are at the same elevation (typically worst-case 15 degrees) which clearly represents an unrealistic assumption for system throughput derivation. Although for a realistic system throughput assessment the effective user distribution on ground should be considered and the multidimensional link budget should be computed considering the constellation geometry evolution over time, the following analysis follows a simplified approach whereby all users are assumed to be at different elevations.

[0563] The corresponding uplink throughput results for various satellite elevations are summarized in Table 5. It is apparent that the patch antenna shape favors higher elevations, while the isoflux antenna has a more homogenous performance with respect to the elevation angle, as expected. A reasonable average throughput may be the throughput corresponding to 35 degrees elevation.

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[0566] Table 5: LEO-PNT simulated uplink throughput as a function of the satellite elevation angle.

[0567] The throughput results indicate that a RA PLR target of 1 • 10-2will limit the uplink throughput. Hence, it is suggested to adopt a PRACH PLR target around 4 • 10-2to avoid this bottleneck. This means that 4% of the requests will have to be repeated because of collisions, which in turn implies a higher maximum transmission latency.

[0568] For the NB-loT uplink, in addition to the payload data link budget, it is also important to size the preamble for the 4-step random access (RA) protocol (PRACH protocol). A detailed description of the PRACH can be found in [Lin 2016] and [Chougrani 2021], while the 4-step RA is described in [Martiradonna 2019]. Noting that a PRACH symbol group (SG) is composed of 1 cyclic prefix and 5 symbols and that the single preamble is composed of 4 SGs, the preamble parameters of Table 6 will be assumed.

[0569] Table 6: PRACH SG and preamble parameters

[0570] Other important PRACH parameters are summarized in Table 7. PRACH detection is possible in the absence of colliding requests and represents the first step required to obtain resource allocation for the Msg3 data transmission. European Space Agency December 20, 2024

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[0572] Clearly, in low SNIR operating conditions (as is the case for the LEO-PNT), preamble repetitions are required to achieve the target PRACH acquisition probability of 99% specified by the standard. This means that the overall preamble duration becomes NRep times the single PRACH preamble duration and the number of repetitions can be NRep =2Kwith k=0,l, 2 7. Extending the total preamble duration will require a corresponding extension of the PRACH periodicity, which according to Table 7 can range from 40 to 5120 ms.

[0573] There is limited literature covering the PRACH acquisition performance, in particular when considering the practical implementation complexity. In addition, the results available are limited to the TN case. Reviewing the existing literature (e.g., [Lin 2016], [Jiang 2018], and [Martiradonna 2019]) it was found that [Chougrani 2021] provides the most practical PRACH detection scheme which avoids the bidimensional (frequency / time) acquisition process by using differential detection of the 4 SGs block composing a preamble followed by a Rife&Boorstyn (R&B) frequency estimator. The MATLAB library includes a program for TN reusing such an algorithm for its acquisition performance assessment [Matlab PRACH], This program has been modified to adopt a more representative AWGN channel instead of a terrestrial multipath fading channel. A more accurate channel will require the inclusion of a land mobile satellite fading and shadowing impairments that goes beyond the scope of the present analysis.

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[0576] Table 7: PRACH SG and preamble parameters European Space Agency December 20, 2024

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[0578] The simulated PRACH acquisition performance for the LEO-PNT cases is reported herein for the 700 km LEO orbit. The corresponding PRACH SNIR calculation is reported in Table 8.

[0579] Table 8: PRACH SNIR calculation for the LEO-PNT case with 700 Km LEO orbit. Fig. 29 illustrates the PRACH acquisition probability versus SNR with NRep=128 and PRACH periodicity 1280 ms, and Fig. 30 illustrates PRACH acquisition probability versus SNR with NRep=64 and PRACH periodicity 640 ms. The simulation results shown in Fig. 29 demonstrate the fact that even adopting the largest NRep value supported by the standard, it is not possible for the satellite patch antenna to achieve the required detection probability performance, i.e. 92.7 % instead of 99%. On the other hand, as shown in Fig. 30, in case of a satellite iso-flux antenna the PRACH detection probability is very close to the target with NRep=64.

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[0582] Annex 3

[0583] SIB31-NB Satellite Ephemeris for NTN

[0584] Selection between the six basic Keplerian parameters and Position State Vector:

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[0587] Annex 4

[0588] Reference Application Scenarios

[0589] The integration of PNT services with two-way messaging capabilities in NTN systems, and in particular loT-NTN systems, is crucial for enhancing modern emergency responses, especially in remote areas and during natural disasters where traditional terrestrial communication infrastructures are compromised.

[0590] Emergency Situation la: SOS Emergency in Remote Areas

[0591] Accurate caller location is vital for Public Safety Answering Points (PSAP) and first responders. In remote areas with poor terrestrial network coverage and degraded GNSS signals— such as forests, deserts, and valleys— the ability to automatically detect and transmit a caller's location can save lives. European directives have mandated the inclusion of caller location capabilities in emergency services, emphasizing technologies like Galileo, EGNOS, and Wi-Fi. LEO-PNT satellites can act as a backup for positioning and messaging, offering reduced performance (e.g., 100 m accuracy) but crucial connectivity when primary systems fail.

[0592] Emergency Situation lb: SOS Emergency After Natural Disasters

[0593] Natural disasters often render communication infrastructures inoperative, hindering individuals from seeking assistance. Accurate location data and communication are essential for efficient rescue operations during events like earthquakes. For instance, the 1989 Loma Prieta earthquake overwhelmed emergency response systems with over 1,000 calls in the first seven hours. LEO-PNT satellites equipped with Non-Terrestrial Network (NTN) payloads can provide backup positioning and messaging services, ensuring that individuals can transmit their location and distress signals even when terrestrial networks are down.

[0594] Emergency Situation 2a: eCall for Vehicles

[0595] The European eCall system automatically initiates emergency calls in case of severe road accidents, transmitting essential data such as vehicle location, time of incident, and identification number to emergency services. While the system relies on GNSS and communication networks, there are scenarios where these networks are unavailable. In such cases, an NTN-equipped satellite terminal can serve as a critical backup communication link, ensuring timely assistance. European Space Agency December 20, 2024

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[0597] Emergency Situation 2b: Special eCall for Cyclists and Motorcyclists

[0598] With a significant number of accidents involving cyclists and motorcyclists— over 94,000 bike accidents in Germany alone in 2023— there is a growing need for "special eCall" systems for these users. Currently, such systems are not mandated, but integrating PNT services and communication modules into bicycles and motorcycles could enhance safety by providing automatic emergency calls and accurate location information, independent of terrestrial network availability.

[0599] Emergency Situation 3: Distress Position Sharing

[0600] In areas without communication networks or during infrastructure failures, individuals in distress may be unable to seek help. Distress position sharing via satellite allows users to broadcast their location and emergency information to nearby equipped users or rescue teams. This capability extends the functionality of personal SOS systems, enabling efficient and timely rescue operations through satellite-based messaging.

[0601] Emergency Situation 4: Position Tracking of First Responders

[0602] Real-time coordination and location tracking of first responders are critical during emergency responses, particularly in remote or disaster-stricken areas where terrestrial infrastructure is compromised. Independent satellite links can convey the precise locations of emergency personnel and equipment, enhancing operational efficiency and safety. Accurate positioning beyond standard regulatory requirements is essential for mission-critical operations, allowing for the rapid location of injured responders and effective coordination among teams.

[0603] Parameters and Setup

[0604] The simulation initializes several key parameters:

[0605] • User Support Interval during an Emergency Event: Set to 30 minutes arbitrarily.

[0606] • Number of Active users during the support interval: Set to a number determined from incidents statistics for each of the scenarios analyzed (Remote SOS situation, Earthquake SOS situation, eCall, special eCall, distress position sharing, and tracking of first responders during an intervention).

[0607] • Number of Messages per Call: Typically set to 6 messages, but can be adjusted (e.g., 1 for eCall according to the principle of operations of the system). European Space Agency December 20, 2024

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[0609] • Message Transmission Duty Cycle: Set to 0.4, indicating the proportion of time the transmitter is active during each message exchange.

[0610] • Message Size: 140 bytes for personal SOS based on the size of an SMS message and 140 bytes for eCall based on ETSI TN 15722:2022.

[0611] • Message Bit Rate: Calculated as the message size in bits divided by 30 seconds, assuming it takes 30 seconds to send a message.

[0612] Simulation Procedure

[0613] Time Resolution and Call Duration:

[0614] • The time resolution is set to 1 second.

[0615] • The duration of an emergency session is calculated based on the number of messages (either 6 messages or 1 as per scenarios addressed in Section 5.3.2), message size, bit rate, and duty cycle.

[0616] Random Start Times:

[0617] • Start times for the emergency messaging sessions are randomly generated within the event duration, ensuring that the call fits within the 30-minute user support interval.

[0618] Activity Matrix Setup:

[0619] • A 2D matrix is initialized to store the activity (on / off) of each call over time.

[0620] • The complete activity pattern for each call is constructed, considering the on / off times based on the duty cycle.

[0621] • For each call, the activity matrix is filled according to its start time and the predefined message activity pattern.

[0622] Calculating Active Messages and Bit Rate:

[0623] • The number of active messages at any given time is computed by summing the activity matrix columns. This shows how the number of active messages varies throughout the user support interval, highlighting the peak load.

[0624] The required bit rate over time is calculated by multiplying the number of active messages European Space Agency December 20, 2024

[0625] 220993PC by the bit rate of each message. This shows the fluctuation in the required bit rate, indicating the maximum throughput needed at any point during the user support interval.

[0626] Example scenario for a natural disaster:

[0627] Data rate: The example scenario assumes a concentration of 1,500 persons in distress during any 30 minutes (the User Support Interval). All other assumptions from previous Emergency Situation

[0628] (ESla) remain the same and are summarized in the tables below.

[0629] Fig. 31A illustrates the maximum number of simultaneous messages during the event. Fig. 31B illustrates the throughput variation during the event.

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Claims

European Space Agency December 20, 2024220993PCClaims1. A method of operating user equipment, UE, capable of wireless communication with a non-terrestrial network, the method comprising: receiving, at the UE, a ranging signal component from each of a plurality of satellites, the plurality of satellites belonging to the non-terrestrial network; recording, at the UE, times of reception of the ranging signal components; periodically receiving, at the UE, positioning assistance information from at least one of the plurality of satellites; and determining, at the UE, a position of the UE based on the recorded times of reception of the ranging signal components and the positioning assistance information.

2. The method according to claim 1, wherein the ranging signal components relate to Narrowband Positioning Reference Signals, NPRS, to Long Term Evolution, LTE, Positioning Reference Signals, PRS, or to New Radio Positioning Reference Signals, NR PRS, broadcast by the plurality of satellites.

3. The method according to claim 1, wherein the ranging signal components relate to primary and secondary synchronization signals.

4. The method according to any one of claims 1 to 3, further comprising: determining, at the UE, a respective time of transmission of each ranging signal component, by demodulating the respective ranging signal component, wherein determining, at the UE, the position of the UE is further based on the determined times of transmission.

5. The method according to claim 4, wherein determining, at the UE, the position of the UE involves applying an algorithm based on times of arrival, TOA, of the ranging signal components received from the plurality of satellites.European Space Agency December 20, 2024220993PC6. The method according to any one of claims 1 to 5, wherein the ranging signal components relate to time-stamped pilot signals.

7. The method according to any one of claims 1 to 3, further comprising: determining, at the UE, time difference of arrival, TDOA, measurements between ranging signal components received from different satellites, wherein determining, at the UE, the position of the UE is based on the determined TDOA measurements.

8. The method according to claim 7, wherein determining, at the UE, the position of the UE involves applying an algorithm based on observed time differences of arrival, OTDOA, between the ranging signal components received from the plurality of satellites.

9. The method according to any one of the preceding claims, wherein periodically receiving, at the UE, the positioning assistance information from the at least one of the plurality of satellites comprises periodically receiving, at the UE, one or more System Information Blocks, SIBs from the at least one of the satellites; and wherein the positioning assistance information is extracted from the one or more SIBs.

10. The method according to claim 9, wherein the one or more SIBs include ephemeris information on the satellites’ ephemeris.

11. The method according to claim 10, wherein the ephemeris information includes information beyond the six Keplerian elements.

12. The method according to any one of claims 9 to 11, wherein the one or more SIBs include clock correction information on the satellites’ internal clocks.

13. The method according to any one of claims 9 to 12, wherein the one or more SIBs include ionospheric information indicative of a state of the ionosphere.European Space Agency December 20, 2024220993PC14. The method according to any one of claims 9 to 13, wherein the one or more SIBs include configuration information including one or more of periodicity, starting subframe, duration, mapping to frequency-time grid pattern, and frequency band of the ranging signal components from the plurality of satellites.

15. The method according to any one of the preceding claims, wherein for each of the plurality of satellites, the ranging signal components are periodically received at the UE, with a common period among the plurality of satellites.

16. The method according to any one of the preceding claims, wherein the ranging signal components are received from at least three satellites; or wherein the ranging signal components are received from four or more satellites.

17. The method according to any one of the preceding claims, wherein each ranging signal component is received in a respective wide beam generated at the respective satellite.

18. The method according to any one of the preceding claims, wherein the ranging signal components are received in distinct, non-overlapping frequency bands to avoid mutual crosstalk, taking into account differential satellite Doppler effects.

19. The method according to any one of claims 1 to 17, wherein the ranging signal components are received in a single frequency band, with partial overlap in frequency between the ranging signal components.

20. The method according to any one of the preceding claims, wherein the UE is in an unconnected or RCCJDLE state in relation to the non-terrestrial network comprising the plurality of satellites.

21. The method according to any one of the preceding claims, further comprising: performing, at the UE, compensation of at least one of Doppler shift, time offset, and frequency offset in relation to one of the plurality of satellites based on the determined position ofEuropean Space Agency December 20, 2024220993PC the UE and information indicative of an ephemeris of the one of the plurality of satellites, for deriving a time reference and / or frequency reference locked to a respective reference of the satellite, thereby enabling access to the non-terrestrial network.

22. The method according to claim 21, wherein performing, at the UE, compensation of at least one of Doppler shift, time offset, and frequency offset comprises: receiving a signal from the one of the plurality of satellites; amplifying the received signal and converting the amplified signal to baseband or close to baseband, using a local oscillator, wherein the local oscillator is controlled so that a frequency of the local oscillator tracks a frequency of the received signal; estimating a Doppler frequency shift of the received signal based on the determined position of the UE and the information indicative of the ephemeris of the one of the plurality of satellites; estimating a satellite carrier frequency of the one of the plurality of satellites based on the frequency of the local oscillator and the estimated Doppler frequency shift; and determining at least one of the frequency reference and the timing reference based on the estimated satellite carrier frequency.

23. The method according to claim 21 or 22, further comprising synchronizing uplink transmission in time and frequency based on the performed compensation.

24. The method according to any one of claims 21 to 23, wherein communication signals from the one of the plurality of satellites are received in a narrow beam.

25. The method according to any one of the preceding claims, further comprising: using the determined terminal position for seamless handover between satellites that provide communication service.

26. The method according to any one of the preceding claims, wherein determining the position of the UE is GNSS-independent.European Space Agency December 20, 2024220993PC27. The method according to any one of the preceding claims, wherein the UE relates to a category Ml, NB1, or NB2 device as defined in 3GPP TS 36.102 or a device as defined in 3GPP TS 38.101-5.

28. The method according to any one of the preceding claims, wherein the satellites are satellites in Low Earth orbit, LEO, or Medium Earth Orbit, MEO.

29. A method of satellite-based signal transmission, comprising: transmitting, at a satellite in a non-terrestrial network, a ranging signal component towards Earth; and transmitting, at the satellite, positioning assistance information towards Earth periodically in broadcast mode, wherein transmission of the ranging signal component is performed periodically in broadcast mode.

30. The method according to claim 29, wherein the ranging signal components relate to a NPRS, PRS, or NR PRS; or wherein the ranging signal components relate to a dense PRS grid or a full PRS grid; or wherein the ranging signal components relate to primary and secondary synchronization signals.

31. The method according to claim 29 or 30, wherein transmission of the ranging signal component is performed in a wide beam directed towards Earth.

32. The method according to any one of claims 29 to 31, wherein the positioning assistance information is included in one or more System Information Blocks, SIBs, or positioning System Information Blocks, posSIBs.

33. The method according to any one of claims 29 to 32, further comprising:European Space Agency December 20, 2024220993PC receiving, at the satellite, positioning assistance information concerning one or more of satellite ephemeris, clock corrections, ionospheric corrections, and a ranging signal component signal configuration from a ground station.

34. The method according to any one of claims 29 to 33, further comprising: providing a communication service to a user equipment, UE.

35. The method according to claim 34, wherein a transmission timing of the ranging signal component at the satellite is aligned with a transmission timing of a communication signal component of the satellite, such that transmission of the ranging signal component and the communication signal component do not overlap in time.

36. The method according to claim 34 or 35, wherein the ranging signal component and a communication signal component of the satellite are transmitted in the same frequency band.

37. The method according to any one of claims 34 to 36, further comprising: dynamically adjusting a beam pattern to provide a first beam for transmitting the ranging signal component and a second beam for providing the communication service to a given UE, with a beam width of the second beam being smaller than a beam width of the first beam.

38. The method according to any one of claims 34 to 37, further comprising: using an active or semi-active antenna to provide a first beam for transmitting the ranging signal component and a number of second beams for providing the communication service to a given UE, with a beam width of the second beams being smaller than a beam width of the first beam.

39. The method according to any one of claims 34 to 38, further comprising: generating a plurality of narrow beams for providing communication services to a plurality of UEs; and broadcasting a satellite-specific overlay (N)PRS signal with a wider coverage area for transmitting the ranging signal component,European Space Agency December 20, 2024220993PC wherein the plurality of narrow beams and broadcasting the satellite-specific overlay signal use the same telecom payload and frequency band.

40. The method according to any one of claims 29 to 39, further comprising: synchronizing, at the satellite, an internal clock of the satellite with internal clocks of one or more other satellites in the non-terrestrial network based on GNSS signals received at the satellite; and / or synchronizing signal transmission, at the satellite, with signal transmission of one or more other satellites in the non-terrestrial network based on GNSS signals received at the satellite.

41. User equipment, UE, comprising a processor and a memory coupled to the processor, wherein the processor is coupled to radio communication equipment and configured, using the radio communication equipment, to perform the method according to any one of claims 1 to 28.

42. A satellite comprising a processor and a memory coupled to the processor, wherein the processor is coupled to radio communication equipment and configured, using the radio communication equipment, to perform the method according to any one of claims 29 to 40.

43. A system comprising the UE according to claim 41 and a plurality of satellites according to claim 42 as part of a non-terrestrial network.

44. A computer program comprising instructions that, when executed by a processor coupled with radio communication equipment, cause the processor, using the radio communication equipment, to perform the method according to any one of claims 1 to 40.

45. A computer-readable storage medium storing the computer program according to claim 44.

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