WO2023020673A1

WO2023020673A1 - Improvement of non-terrestrial networks

Info

Publication number: WO2023020673A1
Application number: PCT/DK2022/050168
Authority: WO
Inventors: Henrik Krogh MØLLER; René Brandborg SØRENSEN; Bertel Kærgård BRANDER
Original assignee: Gatehouse Satcom A/S
Priority date: 2021-08-17
Filing date: 2022-08-17
Publication date: 2023-02-23

Abstract

The invention relates to an improvement of non-terrestrial networks wherein the ephemeris of a non-terrestrial communication device (NTCD, sNB), such as satellite or HAP is delivered to terrestrial UEs to allow for prediction of the future placement of the satellite or high-altitude platform (HAP). The invention further encompasses the transmission of beam information, which allows UEs project the beam from the satellite or HAP position to the plane of the UE. Such beam information can be in the format of radio beam parameters, in geometric terms or simply in the form of geo-fence(s). The UE then uses this information to plan wake-up times for initiating transmission itself or monitoring paging and broadcasts from the satellite or HAP. The UE saves power on searching for cells in a 'blind' or 'quasi-blind' manner based on no information or ephemeris information only. Furthermore, the UE may use the beam information - provided that the format allows for the more detailed projection of the beam and prediction of link budget or optimal areas within the beam – to predict the optimal cell and time for synchronization, communication and/or observation. This allows communication to take place in less time taking up less total spectral resources, which saves energy at the UE and spectral resources at a system level increasing the spectral efficiency and increasing the communication system capacity. Additionally, the UE may use the beam and ephemeris information of multiple cells in assisting the assessment of which cell to connect to as the better communication windows can be forecasted and compared in leu of measuring and comparing the instantaneous signal strength. Beam information may also include information on, or be used for, access restriction for UEs within certain areas of the beam.

Description

IMPROVEMENT OF NON-TERRESTRIAL NETWORKS

FIELD OF THE INVENTION

The present invention relates to a device and system configured to communicate with a non-terrestrial network, such as satellites and a method of communication between a device or system and said non-terrestrial network.

BACKGROUND OF THE INVENTION

A non-terrestrial communication device (NTCD), such as a satellite base-station (sNB) in non-terrestrial networks (NTN) move towards and away from user equipment (UE), located on or at earth level, as the sNBs orbit around the earth in contrast to stationary terrestrial base-stations. Thus, cells that are projected by the sNB may move with the sNB unless beam steering is applied. A cell is a logical entity in a radio network spanning a geographic area projected by a beam, i.e. the cell is the area in the plane of the UE where the signal strength projected and received by the sNB is sufficient for the exchange of information.

To use the uplink in an NTN communication system without causing interference UEs must compensate for Doppler and propagation delay. The UE is assumed to have knowledge of its own position and the satellite position. This is a prerequisite for synchronizing and transmitting in the uplink of NTN. The position can either be provisioned to the UE (for stationary UEs) or obtained by e.g. using a GNSS module. In 3GPP cellular 5G NTN an ephemeris or similar information will be broadcast by the sNB regularly, which enables UEs to compute and compensate for Doppler offset or propagation delay.

UEs cannot determine when they will be in coverage based on ephemeris information for sNBs alone, since the sNB's cell coverage is dependent on antenna beam size and direction.

When a UE in poor link conditions transmit a message to an sNB, it will use coding and/or repetitions to make up for the lower carrier-to-noise ratio (CNR). As an example, in NB-IoT the number of repetitions can be up to 128 for sufficiently low CNR meaning a reduction in the potential system capacity of 128, and a reduction in the UE battery lifetime due to a 128-fold increased transmission time. One application of UEs is for location of containers on ships, i.e. a UE is positioned within or on a container and a user may request current position information regarding said container. Current technology requires either large batteries or a continuous supply of power, which is not necessarily possible with containers stacked on a ship.

Hence, an improved device or system to reduce battery life of UEs in intermittent communication with a non-terrestrial network would be advantageous.

OBJECT OF THE INVENTION

Information regarding the ephemeris of the sNB alone is not enough to inform about coverage due to the following:

UEs are not able to predict when there will be coverage because the sNB position and beam are not the same albeit correlated.

UEs are not able to predict when the coverage is optimal because the beamform is unknown.

UEs are not able to select intelligently among multiple cells because the UE only knows the positions of the sNBs and instantaneous measurements such as signal power (reference signal received power (RSRP)/CNR).

Thus, the present invention proposes a technical solution to:

Enable UEs to schedule wake-up timers to sNB beam downlink (DL) coverage.

Enable UEs to schedule transmission initiation for optimal conditions.

Enable UEs to select amongst multiple cells for the cell, which provides optimal coverage window for the UE. In particular, it may be seen as an object of the present invention to provide a beamform-aware cellular satellite system that solves the above-mentioned problems of the prior art, not limited to, but including battery life of UEs.

SUMMARY OF THE INVENTION

Thus, the above-described object and several other objects are intended to be obtained in a first aspect of the invention by providing a communication system comprising

• a base station

• a non-terrestrial communication device (NTCD) moving along a path at an altitude elevated from earth and a UE located a position closer to the earth than the NTCD, such as located at or on the earth; wherein

• the NTCD is in communication, i.e. exchanging information, with a base station wherein the base station is either o comprised in the NTCD with the base station and the NTCD configured to operate in a regenerative mode, or o is located at a position away from the NTCD with the base station and the NTCD is configured to operate in a transparent mode;

• the NTCD is configured for communication within a radio signal beam extending from the NTCD towards the earth, which radio signal beam increases in cross section with the distance from the NTCD and defines a cell as a volume inside the space enclosed by the radio signal beam delimited downwardly by the beam's projection on the earth;

• the UE is configured for communication with the NTCD when the UE is situated with said cell, the UE is further configured to operate in an active mode where communication is enabled and in a hibernation mode where communication is disabled;

• the UE is further configured to o determining the position of the UE o determining the actual position of said cell o forecast when, if occurring, the said position of the UE is with said cell o wake-up to enable communication with the NTCD. As presented herein, the NTCD communication within the radio signal beam and the UE communication with the NTCD is typically radio wave based communication.

A cell as used herein preferably in a manner being ordinary to a skilled person and may in some embodiments be considered as the space enclosed by the radio signal beam delimited by where the radio signal is intelligible to a UE.

In the context of the present invention, a UE is to be understood as a user equipment apparatus or user equipment device, such as a relatively small, i.e. handheld, positioning device, configured to relay a position of the UE to an associated device. However, the invention is not limited to that an UE being configured to relay its position. The UE may further be configured as a data measuring device, configured to measure e.g. temperature or other relevant data and send/receive said data. Furthermore, the UE is configured to receive instructions. A UE may comprise one or more of, at least a first sensor, wireless transmission means, such as antenna and RF transceiver; mixer, modulator/demodulator, filter, baseband processing, -memory means such as non-volatile- or volatile memory, and processing means, such as signal- and/or data-processing circuitry such as a CPU, DSP, FPGA, GPU and/or possibly an ASIC, to process data measured from said at least first sensor and transmit said data to an associated device, such as a satellite. The processing means may further be configured to process instructions received from an associated device, such as instructions relating to a position of the UE and/or instructions for operating the at least first sensor. The processing means may further be configured to update data, such as ephemeris data, stored on the memory means. In some embodiments, the UE may further comprise a user interface, such as a screen, and wherein the UE is configured to receive instructions from a user interacting with said user interface.

In preferred embodiments, the UE may be configured to determining the position of the UE by use of Global Navigation Satellite System (GNSS). Such a GNSS may form part of UE or be a separate GNSS configured to provide the UE with its position.

In the context of the present invention, wake-up is to be understood as a feature wherein the UE enters an operation mode, ready to send/receive communication, as opposed to a hibernation mode, wherein the UE is in a power saving mode with restricted communication availability. In an embodiment of the invention, the UE wake up prior to entering or after having entered a cell or an optimal area within a cell.

In the context of the present invention, ephemeris is to be understood as information regarding position and trajectory of a non-terrestrial communication device (NTCD), such as the position and trajectory of a satellite or high-altitude platform.

In a preferred embodiment of the invention, the UE further comprises battery means configured to power the UE, wherein the battery capacity of the UE may be less than 30.000 mWh, such as less than 15000 mWh, less than 7.500 mh or less than 3.000 mWh or preferably less than 1500 mWh.

In another preferred embodiment of the invention, the operational life-time of the UE is more than a year, preferably several years and even more preferably between five to fifteen years and most preferably between eight to twentyfive years.

The invention is particularly, but not exclusively, advantageous for obtaining a terrestrial to non-terrestrial communication device and system wherein the terrestrial devices, i.e. the UE, has a low power use, thus, enabling for communication devices which can provide positional or other relevant data over prolonged periods of time, such as months or years, without being connected to an external power source, but instead can rely on battery means. The present invention is advantageous for extending the uptime of said batteries and thus the UE significantly relative to existing UEs. As an example, the present invention may provide the UE with a power usage below 1 watt, preferably below 500 milliwatts and most preferably below 200 milliwatts during operation. Furthermore, the invention may allow the UE to spend more time in hibernation, sleep or stand-by states where an advantageous embodiment of the UE might have a power usage of less than 100 milliwatts, preferably less than 50 milliwatts and most preferably less than 10 milliwatts. The invention is further advantageous for limiting the need of battery capacity to the UE, thus reducing the need to consume material for batteries when manufacturing said UEs. It is further to be understood, that during hibernation, an advantageous embodiment of the UE may have a power usage close to 0 milliwatts, such as below 5 milliwatts, 1 milliwatt or even more advantageously below 1 milliwatt.

In some embodiments, the NTCDs are in communication with a ground station, located at a terrestrial level, which may be different from the base station. In other embodiments of the invention, the base station is located at a terrestrial level, configured to relay communication between auxiliary communication equipment and the NTCDs. In yet other embodiments, the UE is configured to relay communication between the NTCDs and auxiliary communication equipment located at terrestrial level.

In the context of the present invention, a non-terrestrial communication device (NTCD) is to be understood as a satellite or satellite base-station. In some embodiments, the NTCD may be a high-altitude platform (HAP) or other device configured to travel at a path above earth level, further configured to communicate or relay communication between a first device, such as a UE, and a second device, such as a base-station located at earth level.

The invention is furthermore advantageous for providing a system wherein data transfer between terrestrial and non-terrestrial devices are only performed when a carrier signal is strong enough to ensure completion of said data transfer, i.e. the UE wakes up when positioned ideally within the cell of a NTCD, so as to ensure strongest possible signal. In another advantageous example, the UE may use the beam information to choose between two cells or more cells covering the UE to initiate a connection for communication. In another advantageous example, the UE wakes up to receive instructions from a first NTCD regarding a request for data transfer, after which the UE returns to a hibernation mode and subsequently returns to active mode when reaching the cell of a second NTCD to complete the data transfer request.

In the context of the present invention, data is to be understood as, but not limited to, spatial data such as position data, temporal data, temperature data, audio or noise data, vibration data or acceleration data, light or LUX data, ambient air composition data, pressure data or radiation data. It is to be understood, that the UE may be configured with any sensor relevant to measure any of the above- mentioned types of data and may further be configured to correlate any relevant sets of data.

In the context of the present invention, a cell is to be understood as a physical volume within a beam projected by the NTCD and/or base station where the radio signal strength is sufficient for communication between a UE and the NTCD and/or base-station. It is noted that a cell may not contain a clear boundary as a radio transmission by an antenna, although being directional, contains a boundary region where the strength of the transmission decreases towards an un-detectable strength.

While a cell may be defined by a covered volume as above, in some embodiments of the invention the cell may be defined by virtually limited within the covered volume or a virtual delimitation around the covered volume. Such a virtual delimitation may be imposed by one or more geofences arranged within the covered volume. Virtually limiting the cell boundary to be within the covered volume has the advantage that communication between a base station/and or a NTCD and a UE is only initiated or in general carried out when the UE is positioned within the geofence, whereby communication is avoided in case of blockage and/or low signal.

In short, a cell is to be understood as a logical entity in a radio network spanning a geographic area within a beam, i.e. the cell is the area, in the plane of the UE, covered by the beam, projected by the NTCD.

In an advantageous embodiment of the invention, the UE is a relatively small device, i.e. the device is smaller than 20x20x20 cm, such as smaller than 10x10x10 cm or such as smaller than 5x5x5 cm. Preferably, the UE has a volume of no more than 8000 cm³, more preferably a volume of no more than 1000 cm³, even more preferably a volume of no more than 125 cm³ and most preferably a volume of no more than 10 cm³.

In a preferred embodiment of the invention, the wake-up to enable data communication with the NTCD comprises the UE waking up to monitor data communication from the NTCD relevant to the UE. This embodiment of the invention is particularly advantageous for ensuring that the UE is configured according to newest available information relevant to the UE, for the UE to continuously function at a lowest possible energy consumption level. As an example, the UE may wake-up and receive information relating to a newly launched NTCD with cell information, relevant to said UE. As another example, a user may have requested data from the UE, and wherein the UE wakes up to receive said data request, after which the UE sends requested data to the user.

In another preferred embodiment of the invention, the wake-up to enable data communication with the NTCD comprises the UE waking up to transmit data from the UE to the NTCD. This embodiment of the invention is particularly advantageous for enabling the transfer of UE-originating information and wherein the UE wakes up while being within a cell of a NTCD, to ensure sufficient data transmission conditions.

In an embodiment of the invention, said data communication is uni-directional either from the NTCD and to the UE or from the UE to the NTCD and/or basestation. This embodiment of the invention may provide a simple system, wherein the UE has a low power consumption due to reduced functionality of said UE.

In an advantageous embodiment of the invention, the data communication is bidirectional between the UE and the NTCD and/or base-station. This embodiment of the invention is particularly advantageous for providing a system which sends/receives relevant data between the UE and NTCD, such as updated information regarding cells to the UE and any relevant data from the UE to the NTCD. In another advantageous embodiment of the invention, the cell is defined by a geofence arranged inside or outside the space, i.e. volume of coverage, of a UE and NTCD and/or base-station pair. This embodiment of the invention is particularly advantageous for triggering an action from the UE. As an example, the UE enters a specific area, such as a harbour, and is then prompted to send data to a NTCD, whenever the cell of a NTCD reaches the UE.

In the context of the present invention, geofence is to be understood as a virtual geographic boundary or volume, defined by e.g. GPS or RFID technology, which enables software to trigger a response when a mobile device enters or leaves a particular area. A geofence may be understood in geometric terms either as shapes and distances on the ground-plane or in terms of angles in the groundplane projection, i.e. elevation angle.

In an advantageous embodiment of the invention, the base station is configured to broadcast information to UEs. This embodiment is particularly advantageous for relaying information or communicating relevant data to UEs, when said UEs are within the cell of a NTCD and/or base-station.

In another advantageous embodiment of the invention, the base station is configured to page a specific UE or a group of specific UEs, said paging includes an instruction to the UE to initiate bidirectional communication with the base station. This embodiment of the invention is particularly advantageous for providing a communication system, which enables communication between NTCDs, UEs and base stations, whether the base station is integrated within a NTCD or located at a terrestrial location.

In yet another advantageous embodiment of the invention, the UE is configured to initiate bidirectional communication with the NTCD when the position of said UE is within said cell. This embodiment of the invention is particularly advantageous for providing a communication system, wherein the UE is enabled for two-way communication with a NTCD, when conditions for data communication is optimal, thus saving energy within the UE. In a preferred embodiment of the invention, the wake-up and/or the bidirectional communication of the UE, is/are initiated when said position of the UE is in an optimal position within the cell for data communication, wherein the optimal position is determined on the basis of a carrier-to-noise ratio (CNR). This embodiment of the invention is particularly advantageous for providing a communication system, wherein the UE is enabled for communication with a NTCD, when conditions for data communication, such as bi-directional data communication, is optimal, enabling for faster data transfer, thus saving energy within the UE.

In an advantageous embodiment of the invention, the base station is configured to broadcast a metric comprising shape and size of said form of beam defined relatively to the NTCD or an antenna on the NTCD and the ephemeris information of the NTCD. This embodiment of the invention is particularly advantageous for providing a communication system, wherein the UE, based on a metric broadcasted from a base station, has an effective way of calculating when to wake-up and how to determine optimal conditions for data communication with a NTCD.

In the context of the present invention, metric is to be understood as any information relevant to calculate a geometrical coverage of a beam, when said beam is projected from a NTCD towards one or more planes on a terrestrial level, such as the circumference or area covered by a cell, at a terrestrial level.

In other embodiments, the metric may comprise metrics comprising information as to zones within the cell, wherein a carrier-to-noise ratio (CNR) is different within each of the zones. As an example, the metrics may comprise information regarding cells of a plurality of NTCDs and wherein metrics regarding a specific cell of a specific NTCD comprises zones for sending/receiving data of non-equal importance to the functioning of the UE. Thus, the UE may be configured to, based on said metrics, postpone communication when in a non-optimal zone of a cell, i.e. a zone of the cell with a low CNR until entering a more optimal zone in a cell, with a high CNR, so as to save energy for the UE and spectral resources in the system and optionally, omit less important data transmissions until optimal conditions for said data transmission is achieved. In another advantageous embodiment of the invention, the determination of the border and position of the cell is determined on the basis of the metrics and said ephemeris information of the NTCD. This embodiment of the invention is particularly advantageous for providing a communication system, wherein optimal positions of the UE or a cell of a NTCD is applied to increase basis for calculation of possible optimal conditions for sending/receiving data between UE and a NTCD.

In a preferred embodiment of the invention, the UE is configured to be in hibernation mode when said position of the UE is not within said cell. This embodiment is particularly advantageous for saving energy within the UE device.

In a second aspect, the invention relates to a method of providing radio communication in a communication system according to the first aspect of the invention, between a NTCD moving along a path at an altitude elevated from earth and a UE located at a position closer to the earth than the NTCD, such as located at or on the earth.

In the context of the present invention, radio communication is to be understood as the provision of a signal which enables the transferring of data between a first and second device, in a wireless manner.

In an advantageous embodiment of the invention, the method further comprises providing radio communication between at least a first NTCD and a second NTCD, wherein a path of the first NTCD is different from a path of the second NTCD. This embodiment of the invention is particularly advantageous for providing a broad communications network at a non-terrestrial level, wherein data relevant to a terrestrial device may be transferred between a first and second NTCD within communication range, and wherein one of the first and second NTCD is on a path towards the terrestrial device and the other NTCD is on a different path.

In a third aspect, the invention relates to a UE, said device (UE) comprising -metrics regarding a cell of at least a first NTCD, -ephemeris information regarding said at least first NTCD, -data communication means, -a hibernation mode, said hibernation mode being a mode in which the UE reduces energy expenditure, -a wake-up mode, wherein the UE is configured to wake-up or hibernate depending on said metrics and ephemeris information to save energy when not within range of communication with the at least first NTCD.

In a preferred embodiment of the invention, the UE wakes up when reaching optimal data transmission conditions within a cell of a NTCD, such as when a carrier-to-noise ratio is low.

The first, second and third aspect of the present invention may each be combined with any of the other aspects. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE FIGURES

The communication system, method of communication system and UE device according to the invention will now be described in more detail with regard to the accompanying figures. The figures show one way of implementing the present invention and is not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

FIG. 1A is an illustration of a satellite base-station centred over a cell to be covered by a beam projected from the satellite base-station.

FIG. IB is an illustration of a satellite base-station non-centred over a cell to be covered by a beam projected from the satellite base-station.

FIG. 2 is an illustration of a satellite base-station travelling along a non-terrestrial path, covering a cell at a terrestrial level.

FIG. 3 is an illustration of a satellite base-station travelling along a non-terrestrial path, covering a cell and an optimal cell, at a terrestrial level. FIG. 4 is an illustration of two satellite base-stations traveling along two respective paths at a non-terrestrial level, each satellite base-station covering a cell at a terrestrial level.

FIG. 5 is a flow-chart of a method according to the invention.

DETAILED DESCRIPTION OF AN EMBODIMENT

FIG. 1A is an illustration of a satellite base-station sNB centred over a cell A to be covered by a beam BM projected from the satellite base-station sNB. The satellite base-station sNB, which is travelling at a path at a non-terrestrial level around the earth, projects a beam BM in the direction of nadir N, projecting a cell A directly underneath the satellite, the cell A being at a terrestrial level. The beam BM is projected transverse from a plane P_sNB from the satellite base-station sNB, at the non-terrestrial level, towards a plane P_A at terrestrial level identical to a plane of the terrestrial cell A, wherein the two planes P_sNB, P_A are parallel.

It is to be understood, that the satellite-base station sNB, may be a nonterrestrial communication device NTCD, such as a satellite or a high altitude platform.

FIG. IB is an illustration of a satellite base-station sNB projecting a beam BM outwards from nadir N. The satellite base-station sNB, which is travelling at a path at a non-terrestrial level around the earth, projects a beam BM, which forms a cell A that is non-centred in nadir N of the satellite, the cell A being at a terrestrial level. The beam BM is projected transverse from a plane P_sNB from the satellite base-station sNB, at the non-terrestrial level, towards a plane P_A at terrestrial level non-identical to a plane of the terrestrial cell A, wherein the two planes P_sNB, P_A are parallel.

Metrics such as the beams effective isotropic radiated power (EIRP), antenna gain (G) and noise temperature (T) and/or the antenna gain over the antenna temperature (G/T) can also be broadcast to allow UEs to calculate the link-budget both in the DL (downlink) and the uplink (UL).

The beamform can either be broadcast, for example along with the ephemeris information, or unicast to selected or 'new' devices attaching to the network. Another option is that UEs are provisioned with this information at least for a set of known satellites at the time of manufacture.

FIG. 2 is an illustration of a satellite base-station sNB travelling along a nonterrestrial path, indicated with arrow, covering a cell A at a terrestrial level. The large circle indicates a cell A, in which a beam transmitted from the sNB covers a cell A, at a terrestrial level. Outside the cell A, a small circle indicates a UE. As the satellite base-station travels along the path, indicated by the arrow, the cell A travels towards the UE. When the UE enters the cell A, as the cell A moves along a terrestrial level, the UE is in range of communication with the satellite basestation sNB.

Based on previously received beamform and ephemeris information the UE can determine the cell A in which the received CNR will be sufficient for detection of the cell and paging observation. The UE can then wake-up, prior to entering this cell A, to observe paging for a satellite or satellite base-station sNB.

This embodiment is particularly advantageous for enabling the UE to wake-up at the right time, e.g. seconds or minutes before entering the cell A, for e.g. paging opportunities. This saves energy at the UE.

FIG. 3 is an illustration of a satellite base-station sNB travelling along a nonterrestrial path, indicated with arrow, covering a cell A and an area within the cell indicated by B, at a terrestrial level. The large circle indicates a cell A, in which a beam transmitted from the sNB covers a cell A, at a terrestrial level. Within cell A, a circle indicates an optimal area B, wherein carrier-to-noise ratio is lower than between cell A and optimal area B. Between the cell A and area B, a small circle indicates a UE. As the satellite base-station travels along the path, indicated by the arrow, the optimal area B travels towards the UE. When the UE enters the optimal area B, as the optimal area B moves along a terrestrial level, the UE is in optimal conditions for communication with the satellite base-station sNB.

A UE that has received the beamform and ephemeris information regarding a satellite network, can calculate the optimal time, when entering cell B, to initiate a transmission exchange based on the link-budget. The UE can do this for both mobile originating (MO)-traffic and mobile terminated (MT)-traffic, i.e. to delay random access after paging has been received.

The UE determines the transmission window by calculating the expected linkbudget over time. Using the expected received carrier-to-noise ratio, the UE can access, such as a in a table, or calculate the transmission time for any given exchange of data as a function of the initiation time by considering the appropriate modulation and coding (AMC) schemes and accounting for propagation delays, synchronization time and any other delays including offsets.

In some embodiments, cell A can be used as a paging area and optimal cell B can be used for initiating data exchange. Thus, the UE will initiate transmission sequences during optimal condition, which means the UE must be awake, receive and transmit for shorter durations and in turn, the system capacity is better utilized. This enables up to a 128x improvement of UL and 2048x improvement for DL in NTN NB-IoT in terms of repetitions; further, a reduction in coding rate can be performed.

In other embodiment, the UE can be configured to exchange certain information while located within cell A and to exchange other information while located within the optimal area B. This embodiment is particularly advantageous for saving energy, as CNR ratio is lower within the optimal area B, than within the rest of cell A.

FIG. 4 is an illustration of two satellite base-stations sNBA, sNBB traveling along two respective paths, indicated with arrows, at a non-terrestrial level, each satellite base-station sNBA, sNBB covering a cell A_A, B_A, at a terrestrial level. The first satellite base-station sNBA covers a cell A_A wherein the optimal area A_B is located within the cell A_A. A UE is located within the optimal area A_B of the first satellite base-station sNBA. The path of the first satellite base-station sNBA, indicated by the arrow, illustrates that optimal area A_B are moving away from the UE. The path of the second satellite base-station sNBB, indicated by the arrow, illustrates that the UE is currently within the first cell B_A and the optimal area B_B are moving towards the UE.

This embodiment of the invention is particularly advantageous for providing cellselection optimisation to the UE. The UE that are close to multiple cells A_A and B_A, with which the UE can choose to communicate, may decide with which cell A_A or B_A to communicate, by measuring the RSRP or a similar quantity and pick the cell A_A or B_A with the strongest signal. However, in the non-terrestrial scenario, the beam of the first satellite base-station sNBA, i.e. cell A_A and the optimal area A_B may quickly move out of range.

Therefore, it is an advantage for UEs to ascertain and compare the transmission windows of multiple cells and sub-cell areas A_A, A_B, B_A, B_B to make an informed decision as to which cell and sub-cell areas A_A, A_B, B_A, B_B to select for data transmission.

In FIG. 4 the beam of the first satellite base-station sNBA has the strongest RSRP in the moment of measurement, due to the location of the UE within the optimal area A_B but the beam of sNBB will provide a longer transmission window and a higher maximal received carrier-to-noise ratio during its pass, due the position and path of the sNBB and thus cell B_A and optimal area B_B, relative to the UE. Thus, this embodiment of the invention provided optimization of the link-budget and avoidance of the "instantaneous RSRP"-trap, i.e. selecting a cell only based on a current RSRP measurement in the moving cell scenario, as shown in FIG. 4.

FIG. 5 shows a flowchart of a method of providing radio communication in a communication system, according to the invention, showing the following steps:

51-providing at least a first satellite or satellite base-station sNB according to the first aspect of the invention,

52-providing UE according to the first aspect of the invention,

53-providing the UE with at least metric and ephemeris information regarding the at least one satellite or satellite base station sNB, and one or more of the following, steps:

54-enabling the UE to schedule wake-up timers to satellite and/or satellite base-station sNB beam coverage, 55-enabling the UE to schedule transmission initiation for optimal conditions,

56-enabling the UE to select amongst multiple cells for the cell, which provides optimal coverage window for the UE.

The mechanism of the communication system is to

(a) determine and define the beam of a cell projected by a non-terrestrial communication device (NTCD), be it a satellite, a satellite base-station (sNB) in LEO (Low Earth Orbit), MEO (Medium Earth Orbit) or GEO (Geostationary Earth Orbit), a quadcopter, an airplane, a balloon, or another high-altitude platform (HAP).

(b) On the NTCD: Broadcasting the beamform as a set of metrics that defines and limits the beam BM in time and space as exemplified in Table 1.

(c) On the UE: Use the received beamform information (including NTCD ephemeris information) to determine and forecast the coverage area of cells to perform operations such as (1), (2) and (3)

Procedure:

1. The beamform parameters are determined based on the cell's beam projected by the NTCD.

2. The beamform parameters are broadcast along with satellite ephemeris information. a. The beam is defined in relation to the NTCD position. b. In LTE-derivatives; such as LTE-A, eMTC and/or NB-IoT, and NR: The beamform parameters can be broadcast in system information blocks.

3. UEs use the beamform parameters in addition to ephemeris information to predict coverage opportunities.

4. UEs act based on coverage predictions and potential restrictions by for example initiating or delaying transmission sequences, performing cell selection and reselection, or scheduling wake-up times.

The beamform parameters can be antenna parameters such as directional angles, half-power bandwidth (HPBW) and gain, potentially in combination with other linkbudget parameters, which enable UEs to calculate the link-budget throughout the beam. See Table 1 below for examples of parameters that may be used to define the beam.

Table 1: Example of parameters that may be used to define the beam.

The cost of this is the transmission of the beamform. Beamform parameters could be on the order of 37 bits for the example ranges of Table 1 for integer accuracy as indicated by Table 2.

Table 2: The size in bits of the beam-parameter examples of Table 1 for various resolutions.

In short, the invention relates to an improvement of non-terrestrial networks wherein the ephemeris, or other information regarding trajectory and position, of a non-terrestrial communication device, such as satellite or HAP, is delivered to terrestrial UEs to allow for prediction of the future placement of the satellite or high altitude platform (HAP). The invention further encompasses the transmission of beam information, which allows UEs project the beam from the satellite or HAP position to the plane of the UE. Such beam information can be in the format of radio beam parameters, in geometric terms or simply in the form of geo-fence(s). The UE then uses this information to plan wake-up times for initiating transmission itself or monitoring paging and broadcasts from the satellite or HAP. The UE saves power on searching for cells in a 'blind' or 'quasi-blind' manner based on no information or ephemeris information only. Furthermore, the UE may use the beam information - provided that the format allows for the more detailed projection of the beam and prediction of link budget or optimal areas within the beam - to predict the optimal cell and time for synchronization, communication and/or observation. This allows communication to take place in less time taking up less total spectral resources, which saves energy at the UE and spectral resources at a system level increasing the spectral efficiency and increasing the communication system capacity. Additionally, the UE may use the beam and ephemeris information of multiple cells in assisting the assessment of which cell to connect to as the better communication windows can be forecasted and compared in leu of measuring and comparing the instantaneous signal strength. Beam information may also include information on, or be used for, access restriction for UEs within certain areas of the beam.

Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

Claims

1. A communication system comprising

• a base station

• an non-terrestrial communication device (NTCD), such as a satellite, moving along a path at an altitude elevated from earth and a UE (UE) located a position closer to the earth than the NTCD, such as located at or on the earth; wherein

• the NTCD is in data communication with a base station wherein the base station is either o comprised in the NTCD with the base station and the NTCD configured to operate in a regenerative mode, or o is located at a position away from the NTCD with the base station and the NTCD is configured to operate in a transparent mode;

• the NTCD is configured for data communication within a radio signal beam (BM) extending from the NTCD towards the earth, which radio signal beam increases in cross section with the distance from the NTCD and defines a cell (A) as at least a volume inside the space enclosed by the radio signal beam delimited downwardly by the beam's projection on the earth;

• the UE is configured for data communication with the NTCD when the UE is situated with said cell, the UE is further configured to operate in an active mode where data communication is enabled and in a hibernation mode where data communication is disabled;

• the UE is further configured to o determining the position of the UE o determining the position of said cell o forecast when, if occurring, the said position of the UE is within said cell o wake-up to enable data communication with the NTCD prior to entering or after having entered said cell.

2. The communication system according to claim 1, wherein the wake-up to enable communication with the NTCD comprises wake-up to monitor data communication from the NTCD relevant to the UE (UE).

3. The communication system according to any one of the preceding claims, wherein the wake-up to enable communication with the NTCD comprises wake-up to transmit data from the UE (UE) to the NTCD.

4. The communication system according to any one of the preceding claims, wherein said communication is uni-directional either from the NTCD and to the UE (UE) or from the UE and to the NTCD.

5. The communication system according to any one of the claims 1 to 3, wherein said communication is bidirectional between the UE and the NTCD.

6. The communication system according to any one of the preceding claims, wherein the cell is defined by a geofence arranged inside the space enclosed by the radio signal.

7. The communication system according to any one of the preceding claims, wherein the base station is configured to broadcast information to UEs.

8. The communication system according to any one of the preceding claims, wherein the base station is configured to page a specific UE, said paging includes an instruction to the UE to initiate bidirectional communication with the base station.

9. The communication system according to any one of the preceding claims, wherein the UE is configured to initiate a bidirectional communication with the NTCD when said position of the UE is within said cell.

10. The communication system according to any one of the preceding claims, wherein said wake-up and/or said bidirectional communication, when dependant on claim 8 is/are initiated when said position of the UE is in an optimal position within the cell for data communication, wherein the optimal position is determined on the basis of a carrier-to-noise ratio.

11. The communication system according to any one of the preceding claims, wherein the base station is configured to broadcast a metric comprising shape and size of said form of beam defined relatively to the NTCD or an antenna on the NTCD and the ephemeris information of the NTCD.

12. The communication system according to any one of the preceding claims, wherein the determination of the actual position of the cell is determined on the basis of said metric and said ephemeris information of the NTCD.

13. The communication system according to any one of the preceding claims, wherein the UE is configured to be in hibernation mode when said position of the UE is not within said cell.

14. A method of providing radio communication in a communication system according to any of claims 1 to 13, between a non-terrestrial communication device (NTCD), such as a satellite, moving along a path at an altitude elevated from earth and a UE located at a position closer to the earth than the NTCD, such as located at or on the earth.

15. The method according to claim 14, the method further providing radio communication between at least a first NTCD and a second NTCD, wherein a path of the first NTCD is different from a path of the second NTCD.

16. A UE configured to communicate with a non-terrestrial communication system, said device (UE) comprising

-metrics regarding beam information regarding a cell of at least a first nonterrestrial communication device (NTCD), such as a satellite, travelling along a path,

-ephemeris information regarding said at least first NTCD,

-data communication means,

-a hibernation mode, said hibernation mode being a mode in which the UE reduces energy expenditure, -a wake-up mode, wherein the UE is configured to wake-up or hibernate depending on said metrics and ephemeris information to save energy when not within range of communication with the at least first NTCD.