Methods and apparatus for integrated communication and position, navigation, and timing services

Abstract

This application relates to a method of signal transmission, comprising transmitting communication signals in a plurality of first beams, and transmitting a Positioning, Navigation, and Timing, PNT, signal in a second beam, wherein a beamwidth of the second beam is larger than the beamwidth of each of the first beams, and wherein the second beam overlaps the plurality of first beams. The application further relates to a corresponding method of signal reception, as well as to corresponding apparatus and computer program products.

Description

[0001] METHODS AND APPARATUS FOR INTEGRATED COMMUNICATION AND POSITION, NAVIGATION, AND TIMING SERVICES

[0002] Technical Field

[0003] 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 involve a PNT overlay signal that is overlaid on a plurality of communication signals.

[0004] Background

[0005] The current 3GPP 5G standard (cf. [3GPP 5G NR Rel.18]) embeds a signal component that is referred to as Positioning Reference Signal (PRS). PRS is designed to improve the accuracy of positioning information. It is used by devices to measure the Time of Arrival (ToA) and Angle of Arrival (AoA), which are crucial for determining the device’s location.

[0006] However, the 5G PNT service requires the user to be connected to the network and it is an on- demand service. This contrasts with GNSS positioning, which is a broadcasting service not requiring any network connection. Also, the fact that the PRS resources shall be allocated upon request is creating potential scalability issues in a large coverage area typical of Non-Terrestrial Networks (NTN).

[0007] The Narrowband PRS (NPRS) scaled down signal component is also available in the 3GPP Narrowband Internet of Things (NB-loT) 5G standard (cf. [Kanj 2020]). The loT positioning also represents an important market as the adoption of Global Navigation Satellite Systems (GNSS) in low-cost very low-power loT devices is not considered a viable solution (cf. [Lin 2017]).

[0008] PRS for Terrestrial Networks (TN) shows limitations that seem to limit its applicability to 6G where accurate positioning is among the key design drivers (cf. [6G summit 2019]). The positioning accuracy of PRS is only tens of meters, as the discontinuous signal is hardly tracked, which leads to low range measurement accuracy (cf. [McDermott 2015]). Moreover, there are severe near-far effects between the positioning signals from different BSs which makes the signals from far BSs more difficult to be received (cf. [Sackenreuter 2016]). Consequently, poor geometric distribution of BSs is achieved which further worsens the positioning accuracy. For loT, the current 5G NPRS positioning capabilities also show limitations (cf. [Lin 2017]). A good summary of open challenges for NTN is presented in [Dureppagari 2023], which however focuses on a two-way round trip delay approach for user location verification.

[0009] In addition, using (N)PRS 5G signal components in telecom satellite constellations will suffer from the following issues:

[0010] • By system design, the telecom satellites’ beams will avoid overlapping on the same region to not cause self-interference or to avoid artificially increasing the number of beams required to serve a region when adopting frequency division multiplexing across beams to avoid crosstalk1. In fact, except for the link satellite or beam hand-off phase, the telecom networks will generate a single active beam for each user location.

[0011] • This approach diverges from the need of PNT to have multiple satellites in view (hence beams) for localization purposes. This fundamental system design aspect puts in question the possible exploitation of 3GPP PRS signal component for positioning in a telecom satellite constellation.

[0012] • 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 ineffective2.

[0013] • The satellite system should ensure that the PRS symbols originating from different LEO satellites in view do not overlap in time and frequency. This means that for NB-loT data transmission the LEO constellation spectrum will require PRS segmentation in orthogonal sub-carriers or time slots to avoid co-channel interference from other satellites in view.

[0014] • Furthermore, the Orthogonal Frequency Division Multiplexing (OFDM) cycle prefix shall be able to accommodate the maximum time difference of the PNT PRS slots. This will further

[0015] 1The complexity of the payload front-end is approximately related to the product number of beams times the beam bandwidth. The segmentation in FDM of the coverage region does not have a dramatic impact on the front-end complexity but it makes the overall resource management more complex.

[0016] 2The number of beams a satellite can generate with a digital processor is approximately upper bounded by the product Max_processed_bandwidth= No_beams*Beam_bandwidth. Clearly, spatially overlaying beams as during the hand-over phase reduces the payload capability to serve other traffic areas. reduce the COM system spectral efficiency, in particular when adopting LEO satellites.

[0017] Other solutions, like reduced PRS power transmission, may be envisaged if compatible with the PNT service performance requirements.

[0018] • Other potential issues affecting the exploitation of a satcom constellation for PNT relate to the fact 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. This will further curtail the chances to use the current 5G PRS for positioning.

[0019] • Challenging calibration for steerable beams payload group delay / phase for the PNT derivation also considering center of beam delay / Doppler pre-compensation and beam steering to have a fix center of beam on ground combined with iso-flux gain compensation.

[0020] Thus, there is a need for improved techniques for enabling PNT services for terrestrial terminals that do not require by default the (N)TN connectivity as current PRS, and that can operate with current and future satellites or base stations having direction beams for achieving high spectral efficiency. There is particular need for such techniques that are compatible with the 3GPP 5G standards and beyond 5G standards.

[0021] Summary

[0022] In view of some or all of these needs, the present disclosure proposes methods, apparatus, and computer program products having the features of the respective independent claims.

[0023] An aspect of the disclosure relates to a method of signal transmission. The method may include transmitting communication signals in a plurality of first beams. The plurality of first beams may be (narrow) spot beams. Transmitting the communication signals in the plurality of first beams may relate to providing a communication service in the plurality of first beams. The communication service may relate to two-way or one-way communication with respective terminals (e.g., terrestrial terminals) in the plurality of first beams. Further, transmission of the communication signals in the plurality of first beams may be unicast transmission. The method may further include transmitting a PNT signal (e.g., navigation signal) in a second beam. Transmission of the PNT signal in the second beam may be broadcast or multicast transmission. Therein, a beamwidth of the second beam may be larger than the beamwidth of each of the first beams. For example, the second beam may be a wide-area beam and / or the second beam may have a larger beamwidth (or area of coverage) than a combined beamwidth (or combined area of coverage) of the plurality of first beams. Further, the second beam may overlap the plurality of first beams. Accordingly, the PNT signal may be said to overlay the communication signals in the plurality of first beams.

[0024] Using this method, a navigation service can be provided on top of existing communication services, reusing the communication service infrastructure. Providing a wide-area second beam ensures visibility (e.g., direct line of sight visibility) of a sufficient number of transmitters, thereby enabling reliable PNT estimation at the terminals. Still, the communication service is completely unaffected by the provision of the navigation service.

[0025] In some embodiments, the second beam may overlap and extends beyond an envelope beam of the plurality of first beams. This may further relax visibility constraints on the PNT estimation at the terminals.

[0026] In some embodiments, the PNT signal may be a signal suitable for deriving ranging and timing information at a receiver.

[0027] In some embodiments, the PNT signal may be a direct-sequence spread spectrum (DS-SS) signal. The spreading sequence may be unique to the transmitter to minimize cross-correlation among the transmitted sequences. The DS-SS signal may allow for local correlation at a receiver (i.e., e.g., at the respective terminal), using for example a local replica of the PNT signal or of a signal component of the PNT signal.

[0028] This also allows for sufficient tracking at the receiver-side, despite the PNT signal overlaying the communication signals.

[0029] In some embodiments, the DS-SS signal may be a band-limited DS-SS signal. Further, in some embodiments, the band-limited DS-SS signal may include a plurality of square root raised-cosine (SRRC) pulses. Therein, a pulse-shaping roll-off factor for the pulses may be in the range from 0.1 to 0.25.

[0030] By using a (strictly) band limited DS-SS signal, such as for example square root raised-cosine (SRRC) pulses, the ranging signal chip rate in the communication signal bandwidth can be improved (e.g., maximized), together with its accuracy and multipath and / or interference resistance. Furthermore, the band-limited DS-SS demodulator and chip tracking loop will optimally operate with a sampling rate equal to the chip rate but offset half chip between them. This may allow to achieve a substantial performance improvement and demodulator complexity reduction compared to conventional rectangular chip pulses as adopted by conventional GNSS systems. Further, a pulse-shaping roll-off factor in the range from 0.1 to 0.25, such as 0.2, for example, allows to achieve a good trade-off between ranging performance and chip shaping filter complexity.

[0031] In some embodiments, the PNT signal may include a pilot signal component and may optionally include a data component. The data component may be a low-rate navigation data component, for example. The navigation data may be encoded and time-interleaved to improve the frame error rate in mobile channels.

[0032] In some embodiments, the PNT signal may include first and second signal components in quadrature. The first signal component may be an in-phase component including an l-channel spreading sequence and optionally a low-rate data stream on top of the l-channel spreading sequence. The second signal component may be a quadrature component including an unmodulated Q-channel spreading sequence. The Q-channel spreading sequence may relate to a pilot, for example.

[0033] In some embodiments, the method may further include applying at least one of frequency division multiplexing, time division multiplexing, and code division multiplexing across the plurality of first beams. In particular, the method may include applying orthogonal frequency division multiplexing and / or time division multiplexing and / or code division multiplexing across the plurality of first beams.

[0034] In the proposed methods, multiplexing applied to the plurality of first beams will not affect usability of the PNT overlay signal.

[0035] In some embodiments, the method may further include using the same telecom payload for transmitting the communication signals in the plurality of first beams and for transmitting the PNT signal in the second beam. The telecom payload may include some, any, or all of a beam forming network (BFN) (e.g., a digital BFN), a radio frequency, RF, chain, and an antenna (e.g., array antenna). For terrestrial applications, the telecom payload may relate to transmission equipment, for example.

[0036] Thus, the same telecom payload may be used for providing the communication service and providing a PNT service (e.g., navigation service). Using the digital BFN may enable flexible BFN coefficient settings and hence creation of different beam patterns for different beams (e.g., a wide-beam pattern for the second beam and a spot beam pattern for the plurality of first beams). In some embodiments, the telecom payload may include a plurality of ports (e.g., input ports), each associated with a respective beam. Therein, one of the plurality of ports may be associated with the second beam. Further, each of the remaining ones of the plurality of ports may be associated with a respective one among the plurality of first beams. The ports of the telecom payload may be ports (e.g., input ports)of a BFN, for example. BFN coefficients for the one of the plurality of ports may be chosen to provide a wide coverage area beam as the second beam.

[0037] In some embodiments, the method may further include using the same frequency band for transmitting the communication signals in the plurality of first beams and for transmitting the PNT signal in the second beam. The frequency band may be a 5G-compliant frequency band, for example, or a communication frequency band in general.

[0038] Thus, the same frequency band may be used for providing the communication service and providing the PNT service (e.g., navigation service).

[0039] In some embodiments, a transmission power level of the second beam may be set lower than the transmission power level of each of the plurality of first beams. For example, the transmission power level of the second beam may be set at - 16 dB or below compared to the transmission power level of each of the plurality of first beams. Therein, the transmitted signal components power difference may differ in the received power levels at the user equipment. The relative power setting at the transmitter may be system dependent and may be a trade-off between the admissible telecom signal performance degradation due to the DS-SS PNT signal overlay and the required ranging accuracy in any given estimation time interval.

[0040] The reduced transmission power level of the second beam may help to avoid interference on the communication signals. Moreover, the reduced transmission power level of the second beam may allow for applying beamforming to the second beam, for example by appropriate choice of BFN coefficients, without interfering with the communication signals in the plurality of first beams. Setting a lower transmission power level may specifically allow aiming for an iso-flux antenna pattern / beam pattern for the second beam to counteract the difference in path loss within the wide beam coverage area, for example, without impacting the communication service.

[0041] Thus, in some embodiments, the method may further include applying beamforming to the second beam to reduce a trail-off of power flux towards an edge of the second beam. Applying beamforming to the second beam may include adjusting BFN coefficients to achieve an iso-flux antenna pattern (e.g., substantially constant power flux density across a cross-section of the second beam, for example to counteract the difference in path loss within the wide beam coverage area) or to improve the antenna pattern towards an iso-flux antenna pattern. This may be particularly relevant to satellite applications.

[0042] In some embodiments, the method may further include synchronizing the PNT signal to a reference clock. The reference clock may be a high-accuracy reference clock, for example generated on-board or derived from a GNSS receiver that provides a high-quality frequency and timing reference derived from a plurality (e.g., all) GNSS satellites in view.

[0043] In some embodiments, the method may further include transmitting navigation data in one or more of the plurality of first beams.

[0044] This may be used to provide ancillary navigation data in the narrow beams, for example via 5G / 6G signals. Transmitting the navigation data in the plurality of first beams may allow to achieve a higher probability of data reception or higher data rate compared to the navigation data component transmitted for example in the l-component of the DS-SS signal. This data can also be more efficiently transmitted in broadcast and / or multicast mode, possibly exploiting dedicated telecom frame fields such as the 5G evolved Multimedia Broadcast Multicast Services (eMBMS), for example.

[0045] In some embodiments, the method may further include applying beam hopping to one or more of the plurality of first beams.

[0046] Beam hopping telecom signal (communication signal) bursty transmission may be compatible with a fixed (i.e., non-beam hopping) wide beam required for the PNT signal reception. Thereby, efficiency of providing the communication service is not affected by the PNT overlay signal.

[0047] In some embodiments, the method may be performed at one of a satellite and a base station of a terrestrial communication network. The satellite may be a satellite in LEO, GEO, MEO, or HEO, for example.

[0048] Another aspect of the disclosure relates to a method of signal reception. The method may include receiving a communication signal in one of a plurality of first beams and demodulating the communication signal. The method may further include receiving a PNT signal in a second beam and demodulating the PNT signal. Therein, a beamwidth of the second beam may be larger than the beamwidth of each of the first beams. Further, the second beam may overlap the plurality of first beams. It is understood that the aforementioned method may be complementary to the method of the first-mentioned aspect of the disclosure and that analogous details may apply.

[0049] In some embodiments, the PNT signal may be a DS-SS signal.

[0050] In some embodiments, the DS-SS signal may be a band-limited DS-SS signal. Further, in some embodiments, the band-limited DS-SS signal may include a plurality of SRRC pulses. Therein, a pulse-shaping roll-off factor for the pulses may be in the range from 0.1 to 0.25.

[0051] In some embodiments, the PNT signal may include first and second signal components in quadrature. The first signal component may be an in-phase component including an l-channel spreading sequence and optionally a low-rate data stream on top of the l-channel spreading sequence. The second signal component may be a quadrature component including an unmodulated Q-channel spreading sequence.

[0052] In some embodiments, the method may further include receiving the communication signal in the one of the plurality of first beams and receiving the PNT signal in the second beam in the same frequency band.

[0053] In some embodiments, the method may further include demodulating the communication signal to obtain navigation data. Then, the method may yet further include determining a PNT estimate based at least in part on the obtained navigation data.

[0054] In some embodiments, the method may further include reducing radio interference of the communication signal on the PNT signal using the demodulated communication signal. For example, the demodulated communication signal may be appropriately subtracted to reduce radio interference on the PNT signal.

[0055] Another aspect of the disclosure relates to an apparatus suitable for transmitting radio frequency (RF) signals. The apparatus may include a telecom payload (or equivalently, transmission equipment) and a controller. The controller may be configured to, using the telecom payload, transmit communication signals in a plurality of first beams. The controller may be further configured to, using the telecom payload, transmit a PNT signal in a second beam. Therein, a beamwidth of the second beam may be larger than the beamwidth of each of the first beams. Further, the second beam may overlap the plurality of first beams.

[0056] In some embodiments, the apparatus may further include a reference clock. Then, the controller may be configured to synchronize the PNT signal to the reference clock. Another aspect of the disclosure relates to an apparatus suitable for receiving RF signals. The apparatus may include a receiver and a controller. The receiver may be an integrated COM-PNT receiver, for example. The controller may be configured to, using the receiver, receive a communication signal in one of a plurality of first beams and demodulate the communication signal. The controller may be further configured to, using the receiver, receive a PNT signal in a second beam and demodulate the PNT signal. Therein, a beamwidth of the second beam may be larger than the beamwidth of each of the first beams. Further, the second beam may overlap the plurality of first beams.

[0057] In some embodiments, the PNT signal may be a DS-SS signal.

[0058] In some embodiments, the DS-SS signal may be a band-limited DS-SS signal. Further, in some embodiments, the band-limited DS-SS signal may include a plurality of SRRC pulses. Therein, a pulse-shaping roll-off factor for the pulses may be in the range from 0.1 to 0.25.

[0059] In some embodiments, the PNT signal may include first and second signal components in quadrature. The first signal component may be an in-phase component including an l-channel spreading sequence and optionally a low-rate data stream on top of the l-channel spreading sequence. The second signal component may be a quadrature component including an unmodulated Q-channel spreading sequence.

[0060] In some embodiments, the controller may be further configured to, using the receiver, receive the communication signal in the one of the plurality of first beams and receive the PNT signal in the second beam in the same frequency band.

[0061] In some embodiments, the controller may be further configured to demodulate, using the receiver, the communication signal to obtain navigation data that has been transmitted in the one of the plurality of first beams. The controller may be yet further configured to determine a PNT estimate based at least in part on the obtained navigation data. To this end, the controller may implement a PNT processor (e.g., navigation processor), for example. The controller / receiver may provide the navigation data (e.g., ancillary navigation data) to the PNT processor, to thereby improve accuracy and / or resilience of the PNT estimate, for example.

[0062] In some embodiments, the controller may be further configured to reduce radio interference of the communication signal on the PNT signal using the demodulated communication signal.

[0063] Further aspects of the disclosure relate to corresponding computer programs and computer- readable storage media. The computer programs may include instructions for causing one or more processors, when suitably connected to RF transmission and / or RF reception equipment and when executing the instructions, to perform any of the methods described throughout the disclosure.

[0064] 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.

[0065] Brief Description of the Figures

[0066] Example embodiments of the disclosure are explained below with reference to the accompanying drawings, wherein

[0067] Fig. 1 is a flowchart illustrating an example of a transmission-side method according to embodiments of the disclosure;

[0068] Fig. 2A and Fig. 2B schematically illustrate examples of coverage scenarios according to embodiments of the disclosure;

[0069] Fig. 3 is a functional block diagram of an example of a telecom payload according to embodiments of the disclosure;

[0070] Fig. 4 is a graph showing an example of a Power Spectral Density (PSD) of a PNT DS-SS signal according to embodiments of the disclosure;

[0071] Fig. 5 is a functional block diagram of an example of a PNT DS-SS modulator according to embodiments of the disclosure;

[0072] Fig. 6 is a graph showing an example of PSDs of a communication signal and the PNT DS-SS signal according to embodiments of the disclosure;

[0073] Fig. 7 is a flowchart illustrating an example of a reception-side method according to embodiments of the disclosure;

[0074] Fig. 8 is a functional block diagram of an example of a demodulator according to embodiments of the disclosure; Fig. 9 is a functional block diagram of an example of an l-COMPNT simulator at physical layer level for techniques according to embodiments of the disclosure;

[0075] Fig. 10 is a functional block diagram of an example of a block in Fig. 9; and

[0076] Fig. 11, Fig. 12, and Fig. 13 include diagrams showing performance simulation results of techniques according to embodiments of the disclosure.

[0077] Detailed Description

[0078] Overview

[0079] The present disclosure sets out a concept for integrating communication (COM) and PNT services in a (beyond) 5G satellite Non-Terrestrial Network (NTN), maximizing performance and minimizing the extra PNT service cost. Without intended limitation, the NTN may for example comprise a constellation of Low Earth Orbiting (LEO) satellites, but the disclosure may likewise be applicable to constellation orbits such as Medium Earth Orbit (MEO), Geosynchronous Equatorial Orbit (GEO), or Highly Elliptical Orbit (HEO).

[0080] Moreover, although the present disclosure may focus on satellite NTN components, the proposed techniques are likewise applicable to TNs, such as (Beyond) 5G / 6G TNs, when adopting active antennas for the base stations. In this case, the term payload or telecom payload may represent the base station modulator and radio-frequency front-end including the active antenna (phased- array) typically used for Massive Multiple Input Multiple Output (M-MIMO) 5G terrestrial technologies.

[0081] The development of large communication satellite constellations (e.g., in LEO) provides a unique opportunity to provide complementary PNT services exploiting the same telecom infrastructure and frequency bands. This approach is different from the LEO PNT systems currently considered in Europe and in other parts of the world, as there is no requirement for having a dedicated frequency allocation and satellites (or piggy-back payloads) for the PNT service provision (cf. [Ries 2023]).

[0082] While both concepts may exploit the MEO GNSS layer signals-in-space (SIS) to generate accurate timing and frequency reference on-board the LEO satellites, the integrated COM / PNT (l-COMPNT) concept according to the present disclosure transmits a PNT signal as an overlay signal on top of communication signals. For example, the proposed techniques may transmit a low-power satellite unique DS-SS Code Division Multiple Access (CDMA) overlay signal on top of a 5G / 6G Orthogonal Frequency Division Multiplexing (OFDM) communication signal. This may be done, for example, reusing the same telecom payload and active antenna, but generating a wide beam antenna patten instead of a narrow beam (e.g., spot beam) to maximize the satellite coverage area for the PNT signal. This is in contrast to the telecom payload’s typical requirement to generate multiple narrow beams over the coverage region for unicast service provision.

[0083] Notably, the PNT signal is not necessarily a signal defined in the 5G standard. Indeed, preferred embodiments of the disclosure foresee that the PNT signal is not a 5G signal.

[0084] In addition to basic navigation data included on top of the navigation signal overlay, the system can benefit from the higher rate and more reliable eMBMS capabilities for broadcasting ancillary data services (cf. [He 2020]). The eMBMS 3GPP standard provides high flexibility in terms of resource allocation for this service (e.g., time) which allows to reduce the PNT signaling overhead on the telecom unicast services. The use of the telecom carrier has the advantage of enjoying the (steerable) satellite beam antenna gain. This approach may be of interest also for terrestrial positioning for providing ancillary network-aided data.

[0085] Fig. 1 is a flowchart illustrating an example of a transmitter-side method 100 according to embodiments of the disclosure that is based on the aforementioned idea to overlay a PNT signal (e.g., DS-SS navigation signal) on top of the communication signal(s) (e.g., (3GPP) telecom signals) using different beam forming. Method 100 may be a method of signal transmission, or transmitter-side method in general, and comprises steps S110 and S120. Steps S110 and S120 may be performed in sequence in any order, or in parallel. Likewise, steps S110 and S120 may be repeatedly performed, for example for continuous transmission, again in sequence in any order, or in parallel. Moreover, the steps of method 100 may be performed at a satellite (e.g., satellite in LEO, GEO, MEO, or HEO) or at a base station of a TN, as described in more detail below. Also, the steps of method 100 may be performed (e.g., simultaneously) at each of a constellation of satellites or at each of a plurality of base stations of a TN.

[0086] At step S110. communication signals are transmitted in a plurality of first beams. Transmitting the communication signals in the plurality of first beams may relate to providing a communication service in (each of) the plurality of first beams. The communication services may relate to two-way or one-way communication with respective terminals (e.g., terrestrial terminals) in the plurality of first beams. Accordingly, transmission of the communication signals in the plurality of first beams may be unicast transmission.

[0087] By construction of the overlay of the PNT signal on the communication signals as described throughout the disclosure, any of (orthogonal) frequency division multiplexing, time division multiplexing, and code division multiplexing may be applied across the plurality of first beams without affecting provision of the PNT service. Accordingly, step S110 may comprise applying (orthogonal) frequency division multiplexing and / or time division multiplexing and / or code division multiplexing across the plurality of first beams. Thereby, optimal frequency reuse across the plurality of first beams for the communication service(s) can be maintained, independently of the navigation service provided on top.

[0088] At step S120. a PNT signal is transmitted in a second beam. Transmission of the PNT signal in the second beam may be broadcast or multicast transmission.

[0089] Moreover, transmitting the PNT signal at step S120 may relate to providing a PNT service (e.g., navigation service). To this end, the PNT signal may be a signal suitable for deriving ranging and / or timing information at a receiver (e.g., terminal). Non-limiting examples of suitable signals will be described in more detail in the remainder of the disclosure.

[0090] Importantly, in preferred embodiments, transmitting the communication signals and transmitting the PNT signal may use the same frequency band. That is, the same frequency band may be used for providing the communication service and for providing the PNT service (e.g., navigation service). The frequency band may be a 5G-compliant frequency band, for example, or any other suitable communication frequency band.

[0091] Likewise, same telecom payload may be used for transmission at steps S110 and S120. Details of an example of a suitable telecom payload will be described below with reference to the functional block diagram of Fig. 3. It should also be noted in this regard that while the present disclosure may frequently refer to telecom payloads and common use of telecom payloads, it is understood that this choice of terminology shall not exclude any kind of equivalent transmission equipment used by terrestrial base stations, and that any statements made with respect to telecom payloads shall likewise apply to transmission equipment of terrestrial base stations.

[0092] Fig. 2A and Fig. 2B illustrate examples of coverage scenarios by the afore-mentioned first and second beams, with the former figure relating to a satellite-based implementation of embodiments of the disclosure and the latter relating to a TN-based implementation. In Fig. 2A, each satellite (e.g., LEO satellite) 10, in addition to generating several narrow first beams 25 for the communication services (e.g., two-way communication services), will also transmit (e.g., broadcast) the overlay PNT signal with a wider coverage area 35 in a second beam 30. This may be done using the same telecom payload and / or the same frequency band, as noted above.

[0093] Returning to method 100, the plurality of first beams at step S110 may be (narrow) spot beams, for example. By contrast, the second beam at step S120 may be a wide-area beam. In any case, a beamwidth of the second beam is larger than the beamwidth of each of the first beams. Further, the second beam overlaps the plurality of first beams. With this configuration of beams, the PNT signal (e.g., navigation signal) may be said to overlay the communication signals in the plurality of first beams, as mentioned at the outset. To increase chances that PNT signals from multiple satellites can be received at a given user terminal, it may be preferred that the second beam has a larger beamwidth (or larger area of coverage) than a combined beamwidth (or combined area of coverage) of the plurality of first beams. Specifically, for a given satellite 10, the second beam 30 may overlap and extend beyond an envelope beam 20 of the plurality of first beams 25.

[0094] At the receiver-side, after correlation with a local DS-SS navigation signal local replica, the large integration time possible for the navigation signal allows to minimize the impact of the telecom signals. Simulation results, as presented in more detail below, have shown that indeed a value around -16 dB will be required for NTN. It is also to be noted that the transmitted signal components power difference 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 DS-SS navigation signal overlay and the required ranging accuracy in a given estimation time interval.

[0095] The extension of the satellite-based implementation to a terrestrial network as shown in Fig. 2B is straightforward. Basically, the terrestrial cells 10’ will use the narrow beams 25’ to provide COM unicast services to the mobile users 40, while broadcasting the PNT overlay signal over a wide area 35’ allowing its simultaneous reception from multiple cells 10’. This makes it possible to derive accurate users’ position, which will not be the case when exploiting the single COM signal.

[0096] Payload Description

[0097] As noted above in connection with Fig. 1, preferably, the same telecom payload (or transmission equipment) is used for transmitting the communication signals in the plurality of first beams and for transmitting the PNT signal in the second beam. In other words, the same telecom payload (or transmission equipment) may be used for providing the communication service and for providing the PNT service (e.g., navigation service). While details will be provided below, the telecom payload (or transmission equipment) may in general include some, any, or all of BFN (e.g., a digital BFN), a radio frequency, RF, chain, and an antenna (e.g., multi beam array antenna). Therein, using the digital BFN may enable flexible BFN coefficient settings and hence creation of different beam patterns for different beams (e.g., a wide-beam pattern for the second beam and a spot beam pattern for the plurality of first beams or even implementing Massive Multiple Input Multiple Output pre-coding techniques to maximize COM system throughput). In particular, BFN coefficients for the one of the plurality of ports may be chosen ad hoc to provide a wide coverage area beam as the second beam.

[0098] Also, in general, the telecom payload may comprise a plurality of ports (e.g., (input) ports of a BFN), each associated with a respective beam. One of the plurality of (input) ports is associated with the second beam. Each of the remaining ports is associated with a respective first beam among the plurality of first beams.

[0099] A functional block diagram of an example telecom payload (e.g., integrated COM and PNT (I- COMPNT) payload) 300 is shown in Fig. 3.

[0100] The telecom payload 300 comprises a high accuracy time / frequency reference (e.g., high accuracy reference clock) 310 that is coupled to a communication signals processor 320 and a PNT signal processor (e.g., navigation signals processor) 330. The communication signals processor 320 generates the aforementioned communication signals (e.g., COM narrow beam signals) 325 for transmission in the (narrow) first beams. The PNT signal processor 330 generates the aforementioned PNT signal (e.g., navigation signal, NAV wide beam signal) 332 for transmission in the second beam, as well as (optional) ancillary navigation data (e.g., ancillary NAV data for eMBMS data) 334 for transmission in the first beams, alongside or on top of the communication signals 325.

[0101] Accordingly, method 100 of Fig. 1 may further comprise, in the context of step S110 or as a separate step, transmitting navigation data in one or more of the plurality of first beams. This may be used to provide the afore-mentioned ancillary navigation data in the narrow beams, for example via 5G / 6G signals. Transmitting the navigation data in the plurality of first beams may allow to achieve a higher probability of data reception or higher data rate compared to the navigation data component transmitted for example in the l-component of the DS-SS signal. This data can also be more efficiently transmitted in broadcast and / or multicast mode, possibly exploiting dedicated telecom frame fields such as the 5G evolved Multimedia Broadcast Multicast Services (eMBMS), for example.

[0102] Returning to Fig. 3, the telecom payload 300 further comprises a digital beam forming network and DAC (or BFN in general) 340 with a plurality of input ports and a plurality of output ports. The plurality of input ports respectively correspond to the different signals to be transmitted, or equivalently, to the different beams to be generated (e.g., the plurality of first beams and the second beam). The plurality of output ports respectively correspond to antenna elements 370 of an multi-beam array antenna. Before transmission by respective antenna elements 370, outputs 345 of the BFN 340 are subjected to up-conversion by up-conversion chains 350.

[0103] Outputs 355 of the up-conversion chains 350 are amplified by amplifiers 360, which in turn are coupled to respective antenna elements 370.

[0104] As can be seen from the functional block diagram of Fig. 3, one beam port of the payload will be used for transmitting the navigation signal 332, and ad-hoc BFN coefficients will be selected for providing the required wide coverage area.

[0105] Notably, in preferred embodiments, the satellite antenna elements 370 and RF chains 350 of the telecom payload 350 will be completely in common between the PNT service and the communication service, as the transmission frequency (or transmission frequency band) is the same and the communication payload architecture is fully compatible, despite the vastly different choice of beam shapes for the first and second beams. This concept of reusing the telecom payload also for transmitting a (same-frequency) PNT signal with a completely different and independent antenna beam pattern allows reuse of the NTN space infrastructure with marginal impact in terms of complexity and operational cost.

[0106] It is important to note that the proposed solution will also be compatible with a beam-hopped telecom satellite, as the PNT signal (e.g., navigation signal) will be constantly transmitted to ground by exploiting a separate BFN input port. In this way, the navigation signal will avoid the discontinuous beam hopped transmission as well as any calibration aspects affecting a multibeam communication payload with beam spatial steering and pre-compensation of Doppler / delay.

[0107] Accordingly, method 100 of Fig. 1 may further comprise, in the context of step S110 or as a separate step, applying beam hopping to one or more of the plurality of first beams. As explained above, beam hopping telecom signal (communication signal) bursty transmission is compatible with a fixed (i.e., non-beam hopping) wide beam required for PNT signal reception.

[0108] While the same telecom payload may be reused for providing the communication service via the first beams and the navigation service via the second beam, it is preferred that a transmission power level of the second beam is set lower than the transmission power level of each of the plurality of first beams. For example, the transmission power level of the second beam may be set at - 16 dB or below compared to the transmission power level of each of the plurality of first beams. Notably, the transmitted signal components power difference may differ in the received power levels at the user equipment. The relative power setting at the transmitter may be system dependent and may be a trade-off between the admissible telecom signal performance degradation due to the DS-SS PNT signal overlay and the required ranging accuracy in any given estimation time interval.

[0109] Moreover, when the allocated PNT payload power is (much) lower than the telecom payload power, the PNT BFN coefficients can also be adjusted in amplitude on top of phase, for applying beamforming to the second beam, without interfering with the communication signals in the plurality of first beams. This may be used to achieve an iso-flux antenna pattern (beam pattern) for the second beam with negligible payload power efficiency conversion impact. This in turn will allow to counteract the difference in path loss within the wide beam coverage area and to achieve a constant power flux density (PFD) on ground for the PNT SIS over the wide coverage area. This PNT iso-flux amplitude / phase BFN will be compatible with the telecom BFN phase-only for active antenna required for maximizing the active antenna efficiency reasons, as the PNT SIS power is much lower than the telecom power, as noted above.

[0110] Accordingly, method 100 of Fig. 1 may further comprise, in the context of step S120 or as a separate step, applying beamforming to the second beam to reduce a trail-off of power flux towards an edge of the second beam. As noted above, this may include adjusting BFN coefficients to achieve an iso-flux antenna pattern (e.g., substantially constant power flux density across a cross-section of the second beam, for example to counteract the difference in path loss within the wide beam coverage area) or to improve the antenna pattern towards an iso-flux antenna pattern. This may be particularly relevant to satellite applications.

[0111] Returning to the functional block diagram of Fig. 3, The PNT signal processor 330 will require a very accurate and stable clock for the payload. An elegant and mass / power efficient solution for the high accuracy time / frequency reference 310, which is also considered for LEO PNT (cf. [Kunzi 2024]), is to exploit current GNSS MEO constellations to derive a highly stable time and frequency reference embarking a GNSS multi-constellation receiver. The PNT DS-SS shall be synchronized to this high accuracy on-board reference. The satellite unique DS-SS shall also be typically aligned with the OFDM symbols to ease demodulator operations.

[0112] Accordingly, method 100 of Fig. 1 may further comprise, in the context of step S120 or as a separate step, synchronizing the PNT signal to a reference clock. As noted, the reference clock may be a high-accuracy reference clock, for example generated on-board or derived from a GNSS receiver that provides a high-quality frequency and timing reference derived from all GNSS satellites in view.

[0113] It is noted that the functional block diagram of a satellite telecom payload 300 may likewise apply to a terrestrial base station equipped with a phased array antenna.

[0114] Overlay PNT Signal

[0115] Next, example implementation details of the PNT signal (PNT overlay signal, e.g., navigation signal) for example transmitted in the second beam at step S120 of method 100 will be described.

[0116] To allow for sufficient tracking at the receiver / demodulator, it is foreseen that the PNT overlay signal is a direct-sequence spread spectrum, DS-SS, signal (e.g., overlaid to the 5G OFDM signal using a different payload BFN port). The spreading sequence may be unique to the transmitter (e.g., satellite or TN base station) to minimize cross-correlation among the transmitted sequences. Gold codes are a possible solution adopted in many GNSS constellations which are easy to implement with good auto and cross-correlation properties. Other spreading sequences may also be adopted in the present context. With this choice, the DS-SS signal may allow for local correlation at a receiver / demodulator, using for example a local replica of the PNT overlay signal or of a signal component of the PNT overlay signal.

[0117] Content-wise, it may be assumed that the PNT overlay signal includes a pilot and, optionally, a data component (e.g., low-rate data component, or low-rate navigation data component), as in current GNSS systems. The navigation data of the data component may be encoded and time interleaved to improve the frame error rate in mobile channels. Overall, the PNT low-rate data component has the advantage of providing minimum signaling information for users that are not connected to the (N)TN network. It can be clearly removed if not deemed necessary. For example, the PNT signal may include two components (e.g., first and second signal components) in quadrature. The first signal component may be an in-phase (I) component including an l-channel spreading sequence and optionally a low-rate (low speed) data stream on top of the l-channel spreading sequence. The second signal component may be a quadrature (Q) component including an unmodulated Q-channel spreading sequence. The unmodulated Q- channel spreading sequence may be or may be called a pilot, for example. The pilot signal component has the advantage of not having limits in the coherent integration time at the demodulator side, hence providing more robust acquisition ranging performance compared to the data channel.

[0118] The l-Q PNT components’ power ratio can be modified to optimize the power dedicated to the PNT message. At the limit, the PNT low-rate message component can be eliminated if not required. For ranging estimation, both l-Q components can be exploited to maximize received power utilization.

[0119] Generally, the PNT symbols are first encoded by a Forward Error Correction (FEC) block code such as Turbo or Low-Density Parity Check (LDPC) codes followed by a block interleaver to increase the PNT data reception performance over fading channels.

[0120] The chip pulses are preferably shaped according to a Square Root Raised-Cosine (SRRC) response typically adopted in telecommunication systems and also proposed for Galileo (cf.

[0121] [Schweickert 1999], [Navipedia]). This chip pulse shaping allows to limit the DS-SS bandwidth to BPNT= Rcl + a) where a is the SRRC filter roll-off factor and Rcis the chip rate. Other chip shaping pulses particularly optimized for timing estimation can also be adopted (cf. e.g., [Nossek 2007]).

[0122] Fig. 4 shows an example of a power spectral density as a function of normalized frequency of the DS-SS PNT overlay signal. Graph 410 shows a conventional rectangular (REC) chip pulse and graph 420 shows an SRRC chip pulse for a = 0.2. As can be seen, using a = 0.2 allows to achieve a chip rate improvement of at least 67% compared to a conventional rectangular pulse used in GNSS systems bandlimited to the main signal lobe. When, as is normally the case, the first two sidelobes are transmitted, the chip rate improvement using SRRC rises to 333%. This translates to a corresponding improvement on the ranging accuracy and interference and multipath resilience achievable for the same bandwidth occupancy.

[0123] Thus in general, the DS-SS signal may be a band-limited (e.g., band-limited at base band) DS-SS signal. By using a (strictly) band limited DS-SS signal, such as for example SRRC pulses, the ranging signal chip rate in the communication signal bandwidth can be improved (e.g., maximized), together with its accuracy. Furthermore, the band-limited DS-SS demodulator and chip tracking loop will optimally operate with a sampling rate equal to the chip rate but offset by half a chip between them. This may allow to achieve a substantial performance improvement and demodulator complexity reduction compared to conventional rectangular chip pulses as adopted by GNSS systems.

[0124] The Modified timing Cramer-Rao Bound (MCRB) for the proposed SRRC DS-SS signal normalized to the chip duration Tccan be derived by exploiting the MCRB generic formulation and integrating the product raised cosine power spectral density 5(f) definition (cf. [Navipedia]) times f2. This will yield, for example, where (— ) is the received DS-SS ranging signal power over noise power spectral density, Tobsis the timing estimation observation time and a is the aforementioned SRRC pulse roll-off factor. Observing Eq. (1), it is easy to see that the normalized MCRB can be minimized adopting a = TC2 / 16 « 0.617. However, the minimization of the normalized MCRB does not minimize the effective ranging error as the chip duration Tccan be minimized by fully occupying the COM bandwidth BC0Mas BC0M= (1 + a) / Tc. Taking this into account, the optimum roll-off factor value minimizing the MCRB can be found to be a = 0.13. In practice, a may be chosen based on a trade-off between the ranging performance (or minimized MRCB) and the complexity of the chip shaping filter. For example, a = 0.2 may represent a good trade-off in this regard.

[0125] In general, with the above trade-off in mind, the roll-off factor a may be chosen in the range from 0.1 to 0.25, i.e., 0.1 < a < 0.25. For example, a may be chosen as a = 0.2, as noted above.

[0126] It is noted that the DS-SS MCRB may basically be the same as of an OFDM signal with large number of sub-carriers and the same signaling baud rate for a = 0. For a > 0 there may be a slight advantage compared to OFDM.

[0127] Analytically, the fc-th satellite (or TN base station) DS-SS overlay PNT baseband complex signal can be expressed as, for example, where PPNTis the PNT signal power, 0 < p < 1 is the PNT signal power fraction dedicated to the data channel, cP j- and M isrepresent the j-th chip of the I and Q spreading sequences of length L belonging to satellite k, dP trepresents the Z-th (coded and time interleaved) symbol of the PNT message and gTt) represents the chip transmit pulse (SRRC or others) aiming to bandlimit the PNT signal.

[0128] The band limiting may be performed at signal generation instead of generating a non-band limited signal using a rectangular chip pulse and then sub-optimally band limiting, as is done in conventional GNSS systems.

[0129] A functional block diagram of the PNT DS-SS modulator 500 is shown in Fig. 5.

[0130] The PNT DS-SS modulator 500 comprises a PNT Binary Phase-Shift Keying (BPSK) modulator block 530 feeding a BPSK-modulated PNT signal into an up-sampling block 540. A PNT l-Q spreading sequence generated by PNT l-Q spreading sequence generator block 560 is used for spreading, at spreading block 545, the up-sampled and modulated PNT signal as well as spreading, at spreading block 555, pilot up-sampled symbols 550. Outputs of spreading blocks 545, 555 are subjected to PNT data power level control at respective PNT data power level control blocks 570, 575. After power level control, respective signals are added at adding block 580 and fed to chip pulse shaping filter block 590, yielding a chip pulse filtered signal 595 for output to the telecom payload. The PNT DS-SS modulator 500 further comprises a forward error correcting block 510 for applying forward error correction to formatted NAV data (navigation data, e.g., ancillary navigation data) 505. After forward error correction, the navigation data is time-interleaved in time interleaver block 520, as explained above, for output to the telecom payload.

[0131] Fig. 6 is a graph showing an example of power spectral densities of a communication signal (here COM OFDM signal) 610 and the PNT overlay DS-SS signal 620 when the PNT DS-SS signal power is, without intended limitation, 20 dB lower than the COM OFDM signal power. As can be seen from the figure, there is apparent full overlap in frequency between the two signals. User Demodulator

[0132] Fig. 7 is a flowchart illustrating an example of a receiver-side method 700 according to embodiments of the disclosure that is based on the aforementioned idea to overlay the PNT signal (e.g., DS-SS navigation signal) on top of the communication signal(s) (e.g., (3GPP) telecom signals) using different beam forming. Method 700 may be a method of signal reception and / or demodulation and comprises steps S710 and S720. Steps S710 and S720 may be performed in sequence in any order, or in parallel. Likewise, steps S710 and S720 may be repeatedly performed, again in sequence in any order, or in parallel, for example for continuous reception.

[0133] At step S710. a communication signal is received in one of a plurality of first beams, and the received communication signal is demodulated.

[0134] At step S720. a PNT signal is received in a second beam, and the received PNT signal is demodulated.

[0135] Step S720 may be performed for each of a plurality of satellites (or base stations) that are in view of a receiver-side terminal that performs the method. For example, for TV satellites in view, the communication signal may be received from one of the TV satellites, whereas TV PNT signals will be received in total. These TV PNT signals may then be appropriately used for purposes of PNT estimation, including ranging and position estimation, as the skilled person will appreciate.

[0136] Method 700 may be complementary to method 100 of Fig. 1, for example in that the communication signal received at step S710 may be one of the communication signals transmitted at step S110, and that the PNT signal received at step S720 may be the second signal transmitted at step S120. Accordingly, any statements made above in relation to the signals or beams may likewise to method 700. In particular, a beamwidth of the second beam may be larger than the beamwidth of each of the first beams, and the second beam may overlap the plurality of first beams, as described above.

[0137] Moreover, signal processing at the receiver / demodulator may be the reverse of signal processing at the transmitter / modulator, as explained for example with reference to Fig. 5.

[0138] That said, it is understood that receiving the communication signal in the one of the plurality of first beams and receiving the PNT signal in the second beam may be performed in the same frequency band. Moreover, the same telecom payload (including, for example, a demodulator) may be used for performing steps S710 and S720. Fig. 8 is a functional block diagram of an example of a suitable demodulator (e.g., I-COMPNT demodulator) 800 for implementing receiver-side processing according to techniques proposed by the present disclosure.

[0139] The demodulator 800 comprises an antenna 810 that feeds into an RF front-end 820, which in turn is coupled to an Analog-to-Digital Converter (ADC) 830.

[0140] In addition to a (possibly conventional) NTN COM demodulator 840, the proposed demodulator 800 comprises a NAV demodulator capable of receiving several PNT signals coming from the satellites (or base stations) in view. Compared to conventional GNSS-based solutions, the antenna RF front-end 820 and ADC 830 will be common to the COM demodulator, since the PNT overlay signal uses the same COM frequency band as the communication service. Thereby, complexity, footprint, and power consumption of the receiver-side terminal can be reduced.

[0141] After down-conversion and analog-to-digital conversion, the signal enters, in parallel, the NTN COM demodulator and a bank of PNT signal demodulators 850 of the NAV demodulator, each dedicated to a distinct PNT signal coming from one of the current PNT satellites wide beams in view.

[0142] Thus, the aforementioned NAV demodulator comprises, for each of a plurality of TV satellites (or base stations) in view, a PNT signal demodulator 850-1 850-N. The PNT signal demodulators 850 each are coupled to an output of the ADC 830. They may be similar to conventional GNSS demodulators, with the important exception that they use a strictly bandlimited DS-SS signal and reuse the COM frequency band.

[0143] Each PNT signal demodulator 850 may be virtually implemented and comprises a frequency correction block 851, a chip matched filter and sampling block 852, a PNT l-Q spreading sequence generator block 854, a PNT l-channel down-sample and integrate block 853, a PNT Q-channel down-sample and integrate block 855, a PNT BPSK demodulator and decoder block 856, and a chip timing and frequency error estimation block 857.

[0144] After frequency correction at the frequency correction block 851, the signal is routed through the chip matched filter of the chip matched filter and sampling block 852 and is, for example down- sampled to 2 samples / chip (cf., e.g., [BLQS-CDMA 1992], [DDLL 1993]). This signal downsampling after the chip matched filter allows to reduce the demodulator sampling rate, and hence to reduce the processing complexity compared to conventional GNSS demodulators that use rectangular (non-strictly bandlimited) chip pulses, whereby the sampling rate is related to the RF front-end bandwidth and can be a large multiple of the chip rate. The I and Q digital samples are then correlated with the PNT satellite l-Q spreading sequences generated by the PNT l-Q spreading sequence generator block 854 and integrated over the symbol duration for the I data channel and the pilot integration time for the Q-channel at the PNT l-channel down-sample and integrate block 853 and PNT Q-channel down-sample and integrate block 855, respectively. The on-time digital samples may be used for carrier frequency and phase recovery prior to data demodulation and deinterleaving / decoding which takes place in the PNT BPSK demodulator and decoder block 856. The typically half-chip time offset samples may instead be used in Digital Delay Locked Loop (DDLL) (detailed e.g. in [DDLL 1993], which also provides the equations required to compute the tracking error standard deviation for the SRRC DS-SS signal).

[0145] As noted, processing by each PNT signal demodulator 850 may correspond to a reverse of the processing described above with reference to Fig. 5.

[0146] Optionally, one can consider the possibility to cancel out the COM interference on the PNT signals by subtracting the COM signal once demodulated. By doing so, the PNT signal transmitted power can be further reduced.

[0147] Accordingly, method 700 described above may further comprise, for example in the context of step S720 or as a separate step, reducing radio interference by the communication signal on the PNT signal using the demodulated communication signal (e.g., by appropriately subtracting the demodulated communication signal to reduce radio interference on the PNT signal). This step may be performed for each satellite (or base station) in view.

[0148] A PNT processing unit 860 receives all the ranging measurements and PNT data streams from the TV PNT signal demodulators 850 for solving, for example, the position of the receiver, or in general, determining a PNT estimate based on the ranging measurements.

[0149] In addition, the NTN COM demodulator 840 may provide ancillary navigation data that may be broadcasted by means of the PNT COM eMBMS data component, as described above.

[0150] Thus, method 700 may further include demodulating the communication signal to obtain navigation data. The demodulated navigation data may be used for determining a PNT estimate based at least in part on the navigation data.

[0151] Example Apparatus

[0152] 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). Any statements made above with regard to respective methods are understood to analogously apply to corresponding apparatus (and vice versa).

[0153] An example of such a transmitter-side apparatus includes a telecom payload (or transmission equipment) and a controller coupled to the telecom payload. The controller is configured to, using the telecom payload, transmit communication signals in a plurality of first beams (e.g., as described above in relation to step S11O of method 100). The controller is further configured to, using the telecom payload, transmit a PNT signal in a second beam (e.g., as described above in relation to step S120 of method 100). Again, a beamwidth of the second beam is larger than the beamwidth of each of the first beams, and the second beam overlaps the plurality of first beams.

[0154] An example of a receiver-side apparatus includes a receiver (or demodulator) and a controller coupled to the receiver. The controller is configured to, using the receiver, receive a communication signal in one of a plurality of first beams and demodulate the communication signal (e.g., as described above in relation to step S710 of method 700). The controller is further configured to, using the receiver, receive a PNT signal in a second beam and demodulate the PNT signal (e.g., as described above in relation to step S720 of method 700). In analogy to the above, a beamwidth of the second beam is larger than the beamwidth of each of the first beams, and the second beam overlaps the plurality of first beams.

[0155] 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, cause the one or more processors to perform any of the transmitter-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 receiver-side methods described throughout the disclosure.

[0156] The present disclosure further relates to computer-readable storage media storing such computer programs.

[0157] An analysis of feasibility of techniques according to embodiments of the disclosure as well as technical results will be presented in the following sections. System Level Assumptions

[0158] To assess feasibility of the proposed l-COMPNT concept, preliminary system dimensioning, and link budget estimations have been performed reusing recent 3GPP NTN New Radio system parameters assumptions contained in 3GPP documents Rl-2401988, Rl-2402003, Rl- 2402078, Rl-2402622, Rl-2402902. The proposed system solution can also be easily scaled down to the NB-loT or enhanced Machine Type Communications (eMTC) cases, to which the proposed approach is fully applicable as well.

[0159] The link assumptions correspond to a hand-held type of very low gain linearly polarized antenna with 3 dB polarization losses of a UE with moderate mobile channel impairments on top of non- negligible scintillation losses.

[0160] In summary, 3GPP assumes a LEO satellite system whose characteristics are summarized in Table 1 below, where black font indicates information from 3GPP and grey font in italics indicates non-3GPP information. For consistency, the present analysis assumes 2 GHz as the carrier frequency, although the correct NTN downlink central frequency allocation is 2.2. GHz.

[0161]

[0162] Table 1: Satellite communication system parameters

[0163] The overlay PNT signal assumptions are largely common to the telecom payload except for what is listed in Table 2 below. The COM system analysis assumes that in the worst case the user will see ^sat = 6 PNT satellites simultaneously in view. This is because, as discussed above, the PNT wide beam pattern will increase the number of satellites in view to allow achieving good positioning performance. In practice, the effective number of satellites in view will depend on the constellation design and the user location. To be noted in the example provided is the very limited power dedicated to the PNT payload compared to the COM power, i.e. 2.45 %, despite the very different antenna gain for the two services. This is because the PNT uses a very low data rate for the PNT message broadcasting and due to the long integration time for ranging estimation (e.g., 0.1 seconds or more) compared to the COM signal data rate. Clearly the relative power setting between the COM and PNT services is a matter of system design optimization and also depends on system specifics. The proposed values are merely examples relevant to the current 3GPP 5G NTN reference scenario.

[0164] The current example assumes that the PNT SIS occupies one third of the overall bandwidth available, i.e., 5 MHz. One option will be to extend its occupancy to the full COM service available bandwidth (i.e., 15 MHz), to increase the ranging accuracy at the cost of a wider user equipment (UE) bandwidth and processing requirements.

[0165]

[0166] Table 2: PNT system parameters

[0167] System Analysis

[0168] The COM link budgets have been successfully compared to the 3GPP results before adding the additional parameters marked by grey font in Table 1. The COM link budget results are summarized in Table 3 with the previously mentioned worst-case assumption that there will be 7Vsat= 6 equi-powered satellites broadcasting the PNT signal in the COM band. Parameters in boldface relate to key system assumptions, and parameters in italics relate to link budget results. It is noted that there is a positive margin, slightly inferior (about 1 dB) to the 3GPP link budget provided in 3GPP references mentioned above, because of the extra degradations considered (grey text) in Table 1.

[0169] Referring to the detailed link budgets contained in the Appendix, it is noted that the fact that the PNT overlay SIS contribution to the COM service C / (N + 1) amounts to only 0.06 dB at the -2 dB COM demodulator nominal operating point.

[0170] It is also noted that the present analysis has been done for the S-band (2 GHz) in line with current 3GPP NTN FR1 assumptions. However, the proposed solution is also applicable to different frequency bands such as (but not limited to) the L / C-band or even FR2 (Ku / Ka-bands), if the user terminal is able to simultaneously receive the PNT signals coming from different satellites.

[0171] Table 3: COM link budget results

[0172] The PNT service performance is summarized in Table 4. Parameters in boldface relate to key system assumptions, and parameters in italics relate to link budget results. It is apparent that despite the very low gain of the hand-held type UE antenna, there is a good margin for PNT data reception. For purposes of the present analysis, the ranging standard deviation has been derived adapting the classical Delay Lock Loop (DLL) literature equation (cf. [Holmes 2007]) as where d is the DLL early-late spacing assumed to be equal to 0.5, [C / NRis the ranging C / N over the integration bandwidth, and NpNrepresents the number of PN sequence periods over which the ranging estimation is performed (e.g., 10). However, Eq. (3) is not exact to the DDLL proposed for the SRRC chip pulses. For this case, the correct and overly complex equation is the given in [DDLL 1993], but it has been found that Eq. (3) is sufficiently accurate for the present purpose. Specifically, it has been verified that the difference resulting from use of Eq. (3) compared to [DDLL 1993] amounts to about 8% and is hence considered negligible. The ranging standard deviation lower bound is represented by the MCRB and can be computed for example as where S^f) is the signal power spectral density and Tobsrepresents the integration time. Numerical evaluation of the MCRB showed that it is about 10% smaller than the value adopted for the present analysis.

[0173] For the ranging, assuming a coherent integration time corresponding to the symbol duration (which is presumably a conservative assumption), one finds a 4.5 m standard deviation error under fairly severe channel conditions. This standard deviation can be further reduced by increasing the integration time currently assumed.

[0174]

[0175] Table 4: Summary of PNT link budget results Physical Laver Simulation Architecture

[0176] To verify the correctness of the previous findings based on system level link budgets, a detailed I- COMPNT simulator 900 at physical layer level has been developed. As shown in Fig. 9, the simulator 900 encompasses as an example a COM OFDM modulation as implemented by a COM SIS random data block 910, a COM QAM modulator block 912, an S / P block 914, an l-FFT block 916, and a CP addition block 918. The simulator 900 further comprises an associated user demodulation chain as implemented by a COM Bit Error Rate (BER) counter block 930, a COM QAM demodulator block 932, a P / S block 934, an FFT block 936, and a CP removal block 938. The simulator further comprises reference PNT DS-SS chains implemented by a PNT BPSK modulator block 920, a PNT SIS random data block 921, an up-sampling block 922, a pilot up- sampled symbols block 923, a PNT l-Q spreading sequence generator block 924, a PNT data power level control block 925, a PNT pilot power level control block 926, and a PNT / COM power ratio control block 927 at the transmitter side, and by a PNT BER counter block 940, a PNT BPSK demodulator block 942, a PNT l-channel integrate and dump block 944, a PNT Q-channel integrate and dump block 946, and a PNT l-Q spreading sequence generator block 948 at the user-side. The simulator 900 further comprises an other-PNT-satellites interference generator block 950 (as detailed in Fig. 10) that generates the PNT signals coming from other satellites in view.

[0177] The COM, reference, and interfering PNT signals are added up together with Additive White Gaussian Noise (AWGN) generated by an AWGN generator block 960, before entering the respective demodulation chains. In this way it is possible to simulate the mutual co-channel interference effects with a realistic physical layer model. For simplicity, for the time being no FEC has been included and the COM OFDM bandwidth has been assumed to be equal to the PNT overlay DS-SS bandwidth. The whole simulator 900 has been implemented resorting to the usual signal complex notation with one sample per OFDM channel signal baud rate. This means that the PNT DS-SS signal is oversampled since the chip duration is much shorter than the OFDM symbol.

[0178] The aforementioned COM chain OFDM modulator is flexible and able to generate QPSK or higher order QAM formats, selectable size number of sub-carriers, and includes a programmable size Cycle Prefix (CP).

[0179] For purposes of the present simulation, QPSK modulation has been adopted in line with the 3GPP NTN FR1 current system reference baseline. The demodulator performs the reverse OFDM signal processing, thus generating the l-Q serial symbols samples entering the QAM demodulator. An error counter compares the COM chain demodulated bit streams with the transmitted stream to derive the COM BER statistics. The BER Monte Carlo simulation results are compared to the AWGN COM chain ideal performance and the more realistic performance where the PNT power spectral density is also considered in addition to the AWGN in line with the interference approximation used in the link budgets.

[0180] The reference and interfering PNT chain DS-SS modulator generates a complex baseband signal. The I signal component is generated using the PNT low data rate message BPSK-modulated. Each PNT modulated symbol is then up-sampled to the chip rate and spread by the E5A in-phase Gold code spreading sequence. The Q signal component instead carries the pilot symbols assumed all ones spread by the E5A quadrature Gold code spreading sequence. The relative l-Q arms power can be adjusted to optimize the pilot-to-data component power ratio. The reference DS-SS PNT complex signal is then synchronously added to the COM OFDM signal with a programmable power ratio and then added to the asynchronously interfering Nsat- 1 NTN signals and AWGN.

[0181] The reference PNT DS-SS demodulator correlates the received NsatPNT signals plus COM plus AWGN with the l-Q spreading sequence used in the modulator and samples are accumulated over the number of spreading sequence periods composing a symbol and then dumped (decimated) before entering the BPSK demodulator. The pilot follows a similar processing path. The pilot l-Q correlation dumps can be used to estimate the channel phase before entering the PNT data demodulator. In the present case, as there are no phase uncertainties added in the channel, this step is not required. Finally, the PNT message bits are compared to the transmitted bits to derive the PNT (uncoded) BER.

[0182] Fig. 10 shows a possible implementation 1000 of the other-PNT-satellites interference generator block 950 of Fig. 9. This block includes Nsat- 1 PNT signal generators 1010-1 1010-(Nsat-l), each adopting different Gold spreading sequences and affected by a random propagation delay and carrier frequency offset representative of their different link geometry. To this end, each PNT signal generator 1010 includes a PNT SIS random data block 1011, a PNT BPSK modulator block 1012, an up-sampling block 103, a pilot up-sampled symbols block 1014, a PNT l-Q spreading sequence generator block 1015, a PNT data power level control block 1016, a PNT pilot power level control block 1017, a delay block 1018, and a carrier frequency offset block 1019. Physical Laver Simulation Results

[0183] To validate the correctness of the above link budget analysis, Monte Carlo simulations have been performed with parameters close to the system level assumptions. The physical layer simulator parameters are summarized in Table 5.

[0184] Table 5: COM+PNT system parameters adopted for physical layer simulations All simulations have been performed with a number 7Vsatof co-channel PNT satellites interfering with the COM signal ranging from 4 to 6. It has first been assumed that the satellite payload is linear, i.e., no distortions are present and hence the satellite payload Noise Power Ratio (NPR) is equal to 100 dB. For this case the simulated COM OFDM performance with the PNT DS-SS signal overlay in terms of the bit error rate as a function of Eb / N0for NPR&COI = 100 dB is shown in the diagram of Fig. 11. Here, the top panel including graphs 1110, 1120, and 1130 that respectively indicate the simulated COM BER with AWGN+NPR+COI+PNT overlay, the COM BER with AWGN+NPR+COI no PNT overlay, and the theoretical COM BER with AWGN+NPR+COI+PNT overlay, corresponds to the case of Nsat= 4, and the lower panel including graphs 1150, 1160, and 1170 that respectively indicate the COM BER with AWGN+NPR+COI+PNT overlay, the COM BER with AWGN+NPR+COI no PNT overlay, and the theoretical COM BER with AWGN+NPR+COI+PNT overlay, corresponds to the case of 7sat= 6. It is apparent that the DS-SS PNT signal impact is negligible, considering that with the nominal FEC the OFDM demodulator will operate at Eb / / o=-1.8 dB, i.e., at the leftmost side of the plots where the BER impact is invisible (zoomed area in Fig. 11).

[0185] A more realistic case is when the payload nonlinearity generating intermodulation noise is considered as well, i.e., NPR=15 dB as for the link budget. The corresponding simulation results are shown in Fig. 12. Again, the top panel including graphs 1210, 1220, and 1230 that respectively indicate the COM BER with AWGN+NPR+COI+PNT overlay, the COM BER with AWGN+NPR+COI no PNT overlay, and the theoretical COM BER with AWGN+NPR+COI+PNT overlay, corresponds to the case of Nsat= 4, and the lower panel including graphs 1250, 1260, and 1270 that respectively indicate the simulated COM BER with AWGN+NPR+COI+PNT overlay, the COM BER with AWGN+NPR+COI no PNT overlay, and the theoretical COM BER with AWGN+NPR+COI+PNT overlay, corresponds to the case of Nsat= 6. It is apparent that the NPR intermodulation noise floor reduces the theoretical BER slope and further reduces the PNT DS-SS signal impact at high Eb / No values.

[0186] Finally, the case for which it is assumed that there is other beam co-channel interference corresponding to C / l=12 dB on top of the NPR=15 dB resulting in 10.23 B of global co-channel interference is shown in Fig. 13. Also here, the top panel including graphs 1310, 1320, and 1330 that respectively indicate the COM BER with AWGN+NPR+COI+PNT overlay, the COM BER with AWGN+NPR+COI no PNT overlay, and the theoretical COM BER with AWGN+NPR+COI+PNT overlay, corresponds to the case of Nsat= 4, and the lower panel including graphs 1350, 1360, and 1370 that respectively indicate the COM BER with AWGN+NPR+COI+PNT overlay, the COM BER with AWGN+NPR+COI no PNT overlay, and the theoretical COM BER with AWGN+NPR+COI+PNT overlay, corresponds to the case of 7sat= 6. The BER curve flattening is evident as well as the further reduction of the PNT signal impact.

[0187] If required, the PNT signal component transmitted power level may be further reduced keeping the same ranging estimation error standard deviation by increasing the PNT estimation time (i.e. , DLL correlator coherent or non-coherent integration time).

[0188] In all cases, it has been verified that the PNT uncoded data is received without error for a COM energy per bit over noise power spectral density down to Et / / 0=-9 dB from the link. This in line with the link budgets reported above, showing a PNT data link 6.6 dB margin.

[0189] Conclusion and Further Concept Applications

[0190] This disclosure provides a description of a very efficient approach to combine COM and PNT services on, for example, the same LEO COM constellation space segment and frequency allocation with minimum use of the telecom payload power and complexity increase. The proposed approach overcomes the current limitations for using the 5G PRS signal component and is not requiring users’ connection to the network for getting the positioning for providing accurate PNT services in an NTN LEO system and fully decouples the COM mission coverage from the PNT mission coverage. This will allow independent space segment coverage optimization without mutual design constraints. The NTN signal is bandlimited at baseband level through pulse shaping to maximize the chip rate and hence can achieve a much higher ranging accuracy and interference / multipath resilience compared to current GNSS signals for the same bandwidth occupation. Furthermore, the proposed l-COMPNT solution can leverage the 5G eMBMS signal component to provide reliable ancillary navigation data to the users.

[0191] The proposed solution further allows reducing user terminal complexity, as it does not require a dedicated antenna and RF front-end, and analog to digital converters as for current GNSS receiver embedded in COM terminals.

[0192] Preliminary system analysis and detailed physical layer Monte Carlo simulations based on 3GPP NTN current assumptions for LEO in FR1 S-band confirm the concept feasibility with very minimum impact on the COM performance, thus making the proposed concept an appealing solution for B5G / 6G NTN. The concept can also be applied to different frequency bands. The proposed concept, which has been illustrated numerically for the New Radio case, can also be adopted for eMTC and NB-loT applications may also find applications in B5G / 6G Terrestrial Networks where use of Massive / Mega Multiple Input Multiple Output (M-MIMO) requires the adoption of large active arrays at the base station to maximize frequency reuse and antenna directivity. At the same time, the base station shall have a wider beam to provide signaling information to the non-active users and allowing capacity requests from them. This makes the base station front-end like the one of the satellite NTN, hence capable to support the DS-SS PNT signal broadcasting on top of signaling information to maximize base station spatial coverage reusing the same communication service bandwidth. This solution is considered more appealing than the current 5G PRS for the same very reason that the narrow base station beams will not allow multiple base stations to be viewed by the users.

[0193] Finally, the proposed technique may also be applied to COM signals different from (B)5G or 6G intended to provide similar services.

[0194] Interpretation

[0195] 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.

[0196] 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 embodiment outlined in the present document are principally intended expressly to be only for explanatory 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.

[0197] References

[0198] [3GPP 5G NR Rel.18] ETSI TS 138 300 V18.1.0 (2024-05) 5G; NR; NR and NG-RAN Overall description; Stage-2 (3GPP TS 38.300 version 18.1.0 Release 18) https: / / www.etsi.org / deliver / etsi_ts / 138300_138399 / 138300 / 18.01.00_60 / ts_138300vl801

[0199] OOp.pdf [Kanj 2020] [M. Kanj, V. Savaux and M. Le Guen, "A Tutorial on NB-loT Physical Layer Design," in IEEE Communications Surveys & Tutorials, vol. 22, no. 4, pp. 2408-2446, Fourth quarter 2020, doi: 10.1109 / C0MST.2020.3022751.

[0200] [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:

[0201] 10.1109 / MC0M.2017.1700269.

[0202] [McDermott 2015] K. McDermott, R. M. Vaghefi and R. M. Buehrer, "Cooperative UTDOA Positioning in LTE Cellular Systems," 2015 IEEE Globecom Workshops (GC Wkshps), San Diego, CA, USA, 2015, pp. 1-6, doi: 10.1109 / GL0C0MW.2015.7414171.

[0203] [Sackenreuter 2016] B. Sackenreuter, N. Hadaschik, M. FaBbinder and C. Mutschler, "Low- complexity PDoA-based localization," 2016 International Conference on Indoor Positioning and Indoor Navigation (IPIN), Alcala de Henares, Spain, 2016, pp. 1-6, doi:

[0204] 10.1109 / IPIN.2016.7743692.

[0205] [Dureppagari 2023] H. K. Dureppagari, C. Saha, H. S. Dhillon and R. M. Buehrer, "NTN-Based 6G Localization: Vision, Role of LEOs, and Open Problems," in IEEE Wireless Communications, vol. 30, no. 6, pp. 44-51, December 2023.

[0206] [6G summit 2019] White paper “Key Drivers and Research Challenges for 6G Ubiquitous Wireless Intelligence”, 6G Wireless Summit in Finnish Lapland, 2019 https: / / www.6gflagship.com / key- drivers-and-research-challenges-for-6g-ubiquitous-wireless-intelligence / .

[0207] [He 2020] D. He et al., "Overview of Physical Layer Enhancement for 5G Broadcast in Release 16," in IEEE Transactions on Broadcasting, vol. 66, no. 2, pp. 471-480, June 2020, doi:

[0208] 10.1109 / TBC.2020.2981775.

[0209] [Ries 2023] L. Ries et al., "LEO-PNT for Augmenting Europe's Space-based PNT Capabilities," 2023 I EEE / ION Position, Location and Navigation Symposium (PLANS), Monterey, CA, USA, 2023, pp.

[0210] 329-337, doi: 10.1109 / PLANS53410.2023.10139999.

[0211] [Kunzi 2024] F. Kunzi, B. Braun, M. Markgraf, 0. Montebruck, “First Steps Toward a Fully Operational LEO PNT Payload”, Inside GNSS, February 2024.

[0212] [Schweickert 1999] R. Schweikert, Robert, T. Woerz, R. De Gaudenzi, "On New Signal Structures for GNSS-2," Proceedings of the 1999 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 1999, pp. 109-118. [Navipedia] Navipedia, Square-Root Raised Cosine Signals (SRRC), https: / / gssc.esa.int / navipedia / index.php / Square-Root_.Raised_.Cosine_.SignalsJSRRC)

[0213] [Nossek 2007] J. A. Nossek, F. Antreich, “On chip pulse shape design for precise synchronization of DS-CDMA systems”, Wiley Int. J. Circ. Theor. AppL Volume35, Issue 5-6, September-December 2007, pp. 565-574.

[0214] [BLQS-CDMA 1992] R. De Gaudenzi, C. Elia and R. Viola, "Bandlimited quasi-synchronous CDMA: a novel satellite access technique for mobile and personal communication systems," in IEEE Journal on Selected Areas in Communications, vol. 10, no. 2, pp. 328-343, Feb. 1992, doi: 10.1109 / 49.126984. [DDLL 1993] R. De Gaudenzi, M. Luise and R. Viola, "A digital chip timing recovery loop for bandlimited direct-sequence spread-spectrum signals," in IEEE Transactions on Communications, vol. 41, no. 11, pp. 1760-1769, Nov. 1993, doi: 10.1109 / 26.241756.

[0215] [Holmes 2007] Jack K. Holmes. 2007. Spread Spectrum Systems for GNSS and Wireless Communications (1st. ed.). Artech House, Inc., USA.

[0216] Appendix

[0217] Detailed Link Budgets

[0218] The following tables provide the detailed link budgets for the COM and PNT services under the system level assumptions detailed above. Parameters in grey font and boldface relate to key system assumptions, and parameters in grey font and italics relate to link budget results. .

[0219] July 3, 2024

[0220] European Space Agency 220305PC

[0221] July 3, 2024

[0222] European Space Agency 220305PC

[0223] July 3, 2024

[0224] European Space Agency 220305PC

Claims

Ciaims1. A method of signal transmission, comprising: transmitting communication signals in a plurality of first beams; and transmitting a Positioning, Navigation, and Timing, PNT, signal in a second beam, wherein a beamwidth of the second beam is larger than the beamwidth of each of the first beams; and wherein the second beam overlaps the plurality of first beams.

2. The method according to any one of the preceding claims, wherein the second beam overlaps and extends beyond an envelope beam of the plurality of first beams.

3. The method according to any one of the preceding claims, wherein the PNT signal is a signal suitable for deriving ranging and timing information at a receiver.

4. The method according to any one of the preceding claims, wherein the PNT signal is a direct-sequence spread spectrum, DS-SS, signal.

5. The method according to claim 4, wherein the DS-SS signal is a band-limited DS-SS signal.

6. The method according to claim 5, wherein the band-limited DS-SS signal comprises a plurality of square root raised-cosine, SRRC, pulses, and wherein a pulse-shaping roll-off factor for the pulses is in the range from 0.1 to 0.25.

7. The method according to any one of the preceding claims, wherein the PNT signal comprises a pilot signal component and optionally comprises a data component.

8. The method according to any one of the preceding claims, wherein the PNT signal comprises first and second signal components in quadrature, with the first signal component being an in-phase component including an l-channel spreading sequence and optionally a low-ratedata stream on top of the l-channel spreading sequence, and the second signal component being a quadrature component including an unmodulated Q-channel spreading sequence.

9. The method according to any one of the preceding claims, further comprising applying at least one of frequency division multiplexing, time division multiplexing, and code division multiplexing across the plurality of first beams.

10. The method according to any one of the preceding claims, further comprising: using the same satellite telecom payload or terrestrial transmission equipment for transmitting the communication signals in the plurality of first beams and for transmitting the PNT signal in the second beam.

11. The method according to claim 10, wherein the telecom payload or transmission equipment comprises a plurality of ports, each associated with a respective beam; wherein one of the plurality of ports is associated with the second beam; and wherein each of the remaining ones of the plurality of ports is associated with a respective one among the plurality of first beams.

12. The method according to any one of the preceding claims, further comprising: using the same frequency band for transmitting the communication signals in the plurality of first beams and for transmitting the PNT signal in the second beam.

13. The method according to any one of the preceding claims, wherein a transmission power level of the second beam is set lower than the transmission power level of each of the plurality of first beams.

14. The method according to any one of the preceding claims, further comprising: applying beamforming to the second beam to reduce a trail-off of power flux towards an edge of the second beam.

15. The method according to any one of the preceding claims, further comprising synchronizing the PNT signal to a reference clock.

16. The method according to any one of the preceding claims, further comprising: transmitting navigation data in one or more of the plurality of first beams.

17. The method according to any one of the preceding claims, further comprising: applying beam hopping to one or more of the plurality of first beams.

18. The method according to any one of the preceding claims, wherein the method is performed at one of a satellite and a base station of a terrestrial communication network.

19. A method of signal reception, comprising: receiving a communication signal in one of a plurality of first beams and demodulating the communication signal; and receiving a Positioning, Navigation, and Timing, PNT, signal in a second beam and demodulating the PNT signal, wherein a beamwidth of the second beam is larger than the beamwidth of each of the first beams; and wherein the second beam overlaps the plurality of first beams.

20. The method according to claim 19, wherein the PNT signal is a direct-sequence spread spectrum, DS-SS, signal.

21. The method according to claim 20, wherein the DS-SS signal is a band-limited DS-SS signal.

22. The method according to claim 21, wherein the band-limited DS-SS signal comprises a plurality of square root raised-cosine, SRRC, pulses, and wherein a pulse-shaping roll-off factor for the pulses is in the range from 0.1 to 0.25.

23. The method according to any one of claims 19 to 22, wherein the PNT signal comprises first and second signal components in quadrature, with the first signal component being an in-phase component including an l-channel spreading sequence and optionally a low-ratedata stream on top of the l-channel spreading sequence, and the second signal component being a quadrature component including an unmodulated Q-channel spreading sequence.

24. The method according to any one of claims 19 to 23, further comprising: receiving the communication signal in the one of the plurality of first beams and the PNT signal in the second beam in the same frequency band.

25. The method according to any one of claims 19 to 24, further comprising: demodulating the communication signal to obtain navigation data; and determining a PNT estimate based at least in part on the navigation data.

26. The method according to any one of claims 19 to 25, further comprising: reducing radio interference of the communication signal on the PNT signal using the demodulated communication signal.

27. An apparatus comprising: a telecom payload; and a controller, wherein the controller is configured to, using the telecom payload: transmit communication signals in a plurality of first beams; and transmit a Position, Navigation, and Timing, PNT, signal in a second beam; wherein a beamwidth of the second beam is larger than the beamwidth of each of the first beams; and wherein the second beam overlaps the plurality of first beams.

28. The apparatus according to claim 27, further comprising a reference clock, wherein the controller is configured to synchronize the PNT signal to the reference clock.

29. An apparatus comprising: a receiver; and a controller, wherein the controller is configured to, using the receiver:receive a communication signal in one of a plurality of first beams and demodulate the communication signal; and receive a Positioning, Navigation, and Timing, PNT, signal in a second beam and demodulate the PNT signal, wherein a beamwidth of the second beam is larger than the beamwidth of each of the first beams; and wherein the second beam overlaps the plurality of first beams.

30. The apparatus according to claim 29, wherein the PNT signal is a direct-sequence spread spectrum, DS-SS, signal.

31. The apparatus according to claim 30, wherein the DS-SS signal is a band-limited DS-SS signal.

32. The apparatus according to claim 31, wherein the band-limited DS-SS signal comprises a plurality of square root raised-cosine, SRRC, pulses, and wherein a pulse-shaping roll-off factor for the pulses is in the range from 0.1 to 0.25.

33. The apparatus according to any one of claims 29 to 32, wherein the PNT signal comprises first and second signal components in quadrature, with the first signal component being an in-phase component including an l-channel spreading sequence and optionally a low-rate data stream on top of the l-channel spreading sequence, and the second signal component being a quadrature component including an unmodulated Q-channel spreading sequence.

34. The apparatus according to any one of claims 29 to 33, wherein the controller is further configured to, using the receiver, receive the communication signal in the one of the plurality of first beams and the PNT signal in the second beam in the same frequency band.

35. The apparatus according to any one of claims 29 to 34, wherein the controller is further configured to: demodulate, using the receiver, the communication signal to obtain navigation data that has been transmitted in the one of the plurality of first beams; anddetermine a PNT estimate based at least in part on the navigation data.

36. The apparatus according to any one of claims 29 to 35, wherein the controller is further configured to reduce radio interference of the communication signal on the PNT signal using the demodulated communication signal.

37. A computer program comprising instructions that when executed by one or more processors acting as a controller coupled to a telecom payload, cause the one or more processors to perform the method according to any one of claims 1 to 18.

38. 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 the method according to any one of claims 19 to 26.

39. A computer-readable storage medium storing the computer program according to claim37 or 38.

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