Bluetooth transmission from satellite to ground telecommunications terminal

Abstract

A device (10) mountable on a satellite (1), the device comprising telecommunication means (13) for broadcasting information directly to at least one telecommunication terminal (2) on the ground. The information is broadcasted according to the Bluetooth Low Energy protocol and in AD mode. The device is particularly useful for Earth observation satellites.

Description

Technical Field

[0001] This invention relates to satellites, and more particularly to direct information transmission from a satellite to one or more telecommunications terminals.

[0002] Specifically, this invention applies to satellites equipped with onboard information processing equipment, enabling the direct transmission of information from such processing to one or more telecommunications terminals. Specifically, this invention applies to mobile terminals or smartphones with Bluetooth functionality. Background Technology

[0003] In emergencies such as natural disasters, it is crucial to provide information directly to people living in the affected areas as quickly as possible.

[0004] However, telecommunications infrastructure coverage remains relatively low in some parts of the world, making the transmission of warning messages impossible in many areas or quickly saturating existing infrastructure. This saturation not only hinders all relevant individuals from receiving information early, but also adversely affects communications required for emergency services.

[0005] Furthermore, in the event of natural disasters (floods, earthquakes, fires, etc.), telecommunications infrastructure can be affected and cease to function, thus preventing the transmission of essential information.

[0006] Furthermore, an ever-increasing number of satellites are acquiring an enormous amount of information. More and more satellites are observing our planet, thus providing increasingly precise coverage of the Earth's surface.

[0007] Currently, this information is transmitted from observation satellites to ground stations, where it can be analyzed. The results of these analyses can then be delivered to end users (or "consumers").

[0008] The amount of information to be processed has now reached unusable levels, leading to congestion at ground stations. The delay between capturing information and transmitting it to the user can be detrimental, or even cause the information to be outdated when it is received.

[0009] Research shows that only a small fraction of the captured information is actually developed and used, resulting in useful information being overwhelmed by a large amount of useless information.

[0010] Advances in spaceborne systems mean that satellites (especially observation satellites) are increasingly capable of processing data in terms of onboard memory and digital processing resources (CPU, GPU, dedicated circuits, etc.).

[0011] However, today, these processing capabilities do not allow us to improve the information transmission chain, reach end users quickly, or make effective use of the large amount of available information.

[0012] Therefore, even if observation satellites are able to detect critical situations or their imminence, current mechanisms are not fast enough and direct enough to alert relevant populations, especially in the absence of terrestrial telecommunications infrastructure.

[0013] This inadequacy of existing technology means that it is impossible to minimize the impact of a crisis, for example, by organizing the evacuation of people, or at least by preventing people from unintentionally moving into risk areas, by issuing warnings to avoid panic, by providing instructions on how to act, etc.

[0014] Therefore, there is a need to facilitate the transmission of relevant information to people in places at risk of or impending emergencies, especially where there is no terrestrial communication infrastructure.

[0015] Documents US2022 / 216896A1 and US2018 / 254825A1 relate to satellites with cellular telecommunications devices for broadcasting information to at least one telecommunications terminal on the ground based on terrestrial cellular network infrastructure. Summary of the Invention

[0016] The purpose of this invention is to provide a mechanism for broadcasting information directly from a satellite to a telecommunications terminal. The term "directly" here means that the information transmitted by the satellite is received by the terminal. In other words, terrestrial telecommunications infrastructure (base stations, cellular networks, etc.) is unaffected by this broadcast.

[0017] Therefore, according to a first aspect, the present invention can be implemented by a device suitable for placement on a satellite, the device comprising a telecommunications device for broadcasting information directly to at least one telecommunications terminal on the ground; the telecommunications device being adapted to broadcast the information via Bluetooth Low Energy (BLE) communication protocol according to an "announcement" mode, according to which incoming connections are not accepted, the at least one telecommunications terminal being compatible with the communication protocol and configured to receive the information without sending any connection requests to the satellite communication device, the telecommunications device comprising:

[0018] - A directional antenna adapted to transmit a signal carrying the information in a broadcast cone at a bit rate of at least 125 kbits / s in a frequency band between 2.4 GHz and 2.8 GHz with a transmit power of greater than or equal to several watts.

[0019] The transmit power is determined such that the power of the signal received by at least one of the terminals located in the broadcast cone is higher than the given receive sensitivity of the terminal for the “announcement” mode, as a function of the satellite’s altitude relative to the ground, antenna directivity, satellite pointing parameters, and standard transmission loss related to the atmosphere.

[0020] The satellite can be a communication satellite, an Earth observation satellite (especially a remote sensing satellite), or any other type of satellite.

[0021] This embodiment of the invention also enables the utilization of the ever-growing capabilities of observation satellites and avoids the processing (and non-processing) delays of conventional processing chains.

[0022] To achieve this, the device also includes:

[0023] - At least one sensor for acquiring key information

[0024] - A processing device for analyzing the primary information to detect situations corresponding to a standard within the primary information and to determine secondary information related to the situation; and

[0025] The telecommunications device is provided to transmit the secondary information within the information.

[0026] This secondary information corresponds to information (or a portion of that information) broadcast by a previously defined device. In one implementation, the two terms are equivalent when only secondary information is broadcast.

[0027] According to embodiments, the present invention includes one or more of the following features, which may be used alone, in partial or complete combination with each other:

[0028] The main information is an image.

[0029] Telecommunication devices are adapted to broadcast the information via Bluetooth protocols (e.g., in BLE 125k S=8 mode).

[0030] The processing apparatus is adapted to pre-compensate for frequency shifts related to the Doppler effect, which are functions of the satellite's position, the position of the at least one telecommunications terminal, and the satellite's velocity relative to the ground.

[0031] The secondary information indicates a warning.

[0032] According to the second aspect, the invention can also be implemented by a satellite comprising devices as previously defined, optionally having one or more of the optional features described.

[0033] According to another aspect, the invention can also be implemented by a system comprising at least one such satellite and the at least one telecommunications terminal.

[0034] According to another aspect, the present invention also relates to a method for broadcasting information directly from a satellite to at least one telecommunications terminal on the ground. The method implements the Bluetooth Low Energy protocol (BLE) in an "announcement" mode, according to which the satellite's telecommunications device is adapted to broadcast the information without accepting any incoming connections, and the at least one telecommunications terminal (2) is compatible with the protocol and configured to receive the information without sending any connection requests to the satellite's telecommunications device. The method includes:

[0035] - A signal carrying the information is transmitted in a broadcast cone at a data rate of at least 125 kbits / s in a frequency band between 2.4 GHz and 2.8 GHz using a matched directional antenna and at a transmit power generated by a power amplifier that meets the requirements of the onboard system. The transmit power is greater than or equal to a few watts. The transmit power is determined such that the power of the signal received by at least one of the terminals located in the broadcast cone is higher than the receiving sensitivity of the terminal corresponding to the “announcement” mode, which is a function of the satellite’s altitude relative to the ground, antenna directivity, satellite pointing parameters, and standard transmission loss related to the atmosphere.

[0036] According to the implementation scheme, the method is adapted to implement one or more of the features previously described, with necessary modifications, which can be used individually or in partial or complete combination with each other.

[0037] According to another aspect, the present invention can be implemented by a computer program including instructions that, when executed by a computer, cause the computer to perform the above-described contents.

[0038] Further features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, which are given by way of example and with reference to the accompanying drawings. Attached Figure Description

[0039] The accompanying drawings illustrate the present invention:

[0040] Figure 1 An example of a functional architecture according to one embodiment of the present invention is shown schematically.

[0041] Figure 2 An example of the detailed functional architecture of a processing apparatus according to one embodiment of the present invention is schematically depicted.

[0042] Figure 3 A simulation of the evolution of the received power of a satellite relative to its transmitted power according to one embodiment of the present invention is shown.

[0043] Figure 4A simulation of the evolution of the received power of a satellite relative to its transmitted power according to another embodiment of the invention is shown. Detailed Implementation

[0044] This invention relates to all types of satellites, specifically communication satellites and observation satellites.

[0045] According to the implementation plan, the present invention specifically relates to Earth observation satellites, and in particular, remote sensing satellites.

[0046] The present invention may also relate to constellation-type low Earth orbit communication satellites for relaying information from other satellites (specifically Earth observation satellites) back to Earth.

[0047] The present invention also relates to transmitting information from a ground station via a communication satellite.

[0048] Earth observation satellites are artificial satellites used to conduct geophysical and geographical observations of the Earth from Earth orbit. These satellites are used for purposes such as meteorology, natural resource surveys, geodesy, climate research and modeling, natural disaster prevention and monitoring, and military reconnaissance.

[0049] Most Earth observation satellites fall under the category of remote sensing satellites. Their instruments analyze electromagnetic waves (visible light, as well as ultraviolet, infrared, X-rays, etc.) emitted by the observed object or by wave trains emitted by the satellite. Typically, the instruments used include cameras, spectrometers, radar, and radiometers. For example, the Pleiades, Sentinel, and METEOSAT satellites belong to this type of remote sensing satellite.

[0050] Category II Earth observation satellites perform only in-situ measurements, such as GOCE, which measures the Earth's gravitational field, or SWARM, which measures the Earth's magnetic field, and they are not remote sensing satellites. They use instruments such as magnetometers, passive receivers similar to laser reflectors, GPS, accelerometers, or ion or neutral atom detectors.

[0051] Generally speaking, observation satellites include onboard resources (power, positioning, etc.) for managing the satellite itself and equipment for representing its payload—that is, onboard functions that are useful to third parties but not to its own operation. Therefore, this type of observation satellite equipment includes devices for performing its observation functions (i.e., essentially observation devices) and telecommunications devices for transmitting the observed information to the ground.

[0052] This invention primarily relates to such devices for use in satellite 1, in Figure 1 The middle mark is 10.

[0053] exist Figure 1 In the middle, satellite 1 is located in orbit 30 around Earth at a depth of 40.

[0054] In one embodiment of the invention, the satellite is located in low Earth orbit (LEO), but in other embodiments, it may be located in other orbits (such as GEO (geostationary Earth orbit, etc.)).

[0055] Device 10 is suitable for installation in satellite 1, and Figure 1 It is shown as actually installed in the satellite.

[0056] According to the present invention, the device 10 includes a telecommunications device 13 for broadcasting information directly to at least one telecommunications terminal 2 on the ground 40.

[0057] The signal emitted by the telecommunications device 13 forms a cone 50, the aperture (or solid angle) of which depends on the directivity of these devices (antennas). A mobile terminal located at the center of this broadcast cone 50 receives the signal under optimal conditions.

[0058] If the satellite is an observation satellite, the device 10 may also include:

[0059] - One or more sensors 11, which are used to acquire key information; and

[0060] - Processing device 12, which analyzes the main information to detect a situation corresponding to a predetermined standard within the main information and to determine secondary information related to the situation.

[0061] The telecommunications device 13 is then designed to transmit this secondary information (in other words, it represents the information indicated in the preceding paragraph).

[0062] In the case of communication satellites, information broadcasts can be obtained through other means, such as being received by the satellite from a ground station or another satellite. For example, an observation satellite can transmit secondary information to a transmission satellite, which then broadcasts the secondary information to a ground terminal. This implementation can disable this function of the observation satellites and / or enable them to reach other coverage areas, since each satellite can only broadcast to a defined geographical area (which, in the case of mobile satellites, may change over time).

[0063] The main information acquired or “captured” by sensor 11 corresponds to the various types of information observed by the observation satellite. As previously seen, there are many types of observation satellites, and therefore a wide range of observation spectra: optical, radar, infrared, ultraviolet, listening to radio or electromagnetic signals, ionizing radiation, and so on.

[0064] Examples of electromagnetic signals include AIS (Automatic Identification System) ship beacon signals, which are electronic messages transmitted between ships via VHF radio waves, enabling ship and land-based traffic monitoring systems to understand the identity, status, characteristics, position, heading, and speed of ships in a navigation area. Mechanisms for detecting these signals via satellite have been proposed. Another example is ADS-B (Automatic Dependent Surveillance-Broadcast), a cooperative surveillance system for air traffic control and related applications. ADS-B-equipped aircraft determine their position via a satellite positioning system (“Geographic and Navigation Satellite System” GNSS) and periodically transmit that position and other information to ground stations and other ADS-B-equipped aircraft operating in the area.

[0065] The main information can be extremely rich and diverse.

[0066] In one implementation, the primary information is images. These images can be a two-dimensional representation of the observed portion of the Earth. Typically, observation satellites acquire an image stream, with each image associated with the satellite's position relative to the Earth.

[0067] The image content (i.e., the information associated with each point on the observed Earth's surface) depends on the type of sensor 11: optical (or "photography"), radar, infrared, etc.

[0068] The main information is analyzed by the processing unit 12 of the equipment 10 on satellite 1.

[0069] These processing devices can be adapted to perform the analysis at a structure-specific granularity based on the key information. For example, the analysis can be performed frame by frame.

[0070] This analytical step is performed by Figure 2 The figure in the figure is indicated by reference numeral 121.

[0071] The results of this analysis can be processed in a conventional manner, 122, corresponding to the normal operation of satellite 1. For example, the results can be stored in onboard memory, sent to a ground station for further processing, etc. This step is optional and outside the scope of this invention.

[0072] Test steps 123 are provided to detect the correspondence with the standards within the main information.

[0073] The criteria discussed may vary. Generally, the aim is to distinguish between normal and critical situations within key information. This is a routine problem used for classifying and processing digital data. Various solutions are available to those skilled in the art and do not need to be developed here.

[0074] However, this criterion can be fixed or adaptive. It can be single or multiple. For example, when the analysis is implemented using a multi-layer neural network, it can be formalized as a loss function.

[0075] Existing technologies include ground-based image analysis systems for measuring precipitation, river levels, lava or debris flows, fire detection, storm warnings, and more.

[0076] References include: Jean- Lenat's book "Aléas et surveillance de l'activité volcanique 2: sismologie, déformation et télédétection", ISTEéditions, 2022, ISBN 9781789480450; or the article "Amélioration de la précision d'un" by Bonakdari, H., Zaji, AH, Soltani, K. and Gharabaghi, B. Système d’alerte de crue par télédétection à l’aide d’une méthode de prrétraitement multi-objectifs pour la détection et l’élimination des défauts de signal”, published in Comptes Rendus Géosciences, 352, 73-86 (2020); or Catry, T., Révillion, C., Mouquet, P. and Pennober, G. capteur", published in EchoGéo, (51), 2020.

[0077] As long as no case corresponding to the standard is detected, the mechanism can loop back to step 121 to analyze new parts of the main information (e.g., new images).

[0078] When a situation corresponding to the standard is detected, step 124 is triggered to determine secondary information related to the situation.

[0079] This secondary information may include the results of the analysis performed in step 121.

[0080] Secondary information can be enriched with other data, such as satellite identifiers, timestamps, and satellite locations.

[0081] Generally speaking, due to the processing applied, secondary information corresponds to a higher semantic level than primary information. It is also smaller in size.

[0082] A portion of the secondary information directly provided by analysis 121 may contain data of the same nature as the primary information.

[0083] For example, they may contain images representing geographic regions but also representing semantic data derived from the processing: for example, segments may distinguish image points corresponding to detected critical situations, or different color levels may correspond to different levels of severity of the situation or to the type of situation (flood, fire, destruction, etc.), and labels may be associated with image points or with regions derived from the segments, and may indicate terrain type or cloud cover, etc.

[0084] In addition, other types of data can be derived from analysis 121, but do not have the same properties as the main information: for example, the type of crisis, the estimated severity level, the size of the area involved, the geographical location of the area involved, etc.

[0085] In one implementation, the secondary information represents a warning. The ground terminal may have means for effectively alerting the user based on this secondary information.

[0086] As is well known, there are various possible ways to determine secondary information, which can be appropriately utilized by terrestrial telecommunications terminals equipped with suitable software applications.

[0087] The secondary information is then formatted, step 125, for broadcast by the satellite's onboard telecommunications device 13.

[0088] The purpose of formatting is to convert digital data into analog data according to the specifications of the telecommunications protocol used by the telecommunications device 13 to broadcast information to the ground terminal, usually by modulating the carrier signal.

[0089] Figure 2 Reference numerals 121-125 in the accompanying drawings can be viewed as steps in the process of implementing one embodiment of the invention, but can also be viewed as modules in the functional architecture. The processing device 12 can be implemented by components of electronic circuitry and / or by software modules running on an information processing infrastructure.

[0090] According to one embodiment of the present invention, the protocol used is the Bluetooth protocol.

[0091] According to Wikipedia, "Bluetooth is a telecommunications standard for bidirectional data exchange over short distances using UHF radio waves in the 2.4 GHz band. Its purpose is to simplify connections between nearby electronic devices by eliminating wired links. For example, it can replace cables between computers, tablets, speakers, and cellular phones, or printers, scanners, keyboards, mice, joysticks, cellular phones, PDAs, hands-free systems for microphones or headphones, car radios, digital cameras, barcode scanners, and interactive kiosks." (https: / / fr.wikipedia.org / wiki / Bluetooth)

[0092] One of the advantages of the Bluetooth protocol is that it is implemented in the vast majority of telecommunications terminals on the market.

[0093] Therefore, the proposed mechanism can operate on existing terminals without requiring hardware modifications. Specifically, this mechanism contrasts with the use of specific terminals for satellite communications, such as those suitable for the Iridium network, which are less widespread and more expensive.

[0094] Furthermore, the terrestrial terminal's reception of information is independent of any type of service subscription. This allows all mobile phone users to be addressed even without a carrier subscription and even in areas not covered by terrestrial networks.

[0095] Using this telecommunications protocol to broadcast secondary information via satellite means that the secondary information can be received by most terminals in the world, and thus reach a large number of people, such as alerting to emergencies or detecting risks.

[0096] When the telecommunications terminal is a mobile terminal, especially a "smartphone" type mobile terminal, the user can be notified in a timely manner even when the user is on the move. Regardless of the network coverage, as long as the satellite detects a critical situation or the risk of an impending critical situation, the user can be alerted very quickly.

[0097] In addition, there is the Bluetooth protocol used to broadcast information to a range of terminals. In telecommunications, broadcasting is a technology used to transmit signals one-way (or unidirectionally) to a large number of customers. This is the opposite of multicast and unicast, which represent a direct, personalized, or "connected" link between the sender and receiver.

[0098] Therefore, according to the present invention, the telecommunications device 13 of satellite 1 does not need to know the ground terminal separately, but only needs to transmit. When the ground terminal receives the information, the ground terminal can identify it as a broadcast signal and thus regard itself as a receiver (without indicating its own address in the signal, for example, in unicast or multicast mode).

[0099] Clearly, the Bluetooth protocol is designed for communication between devices in close proximity. Therefore, using it to broadcast information between satellites and ground terminals would be completely destructive.

[0100] The inventors have conducted simulations to demonstrate that, within the context of this invention, the Bluetooth protocol can be used over long distances under certain conditions defined by the inventors.

[0101] Another constraint on the normal operation of the Bluetooth protocol is the initial pairing phase between the two devices before exchanging information. In the context of this invention, it is not possible to establish such a pairing between a satellite and a ground terminal, partly because it would require the transmit power of a ground terminal that is incompatible with the ground terminal's specifications, and also because it would involve a significant amount of weight and payload on the satellite, which would potentially have to pair with thousands of ground terminals, and if the satellite is in motion, the operation would have to be repeated periodically.

[0102] The inventors have identified a specific operating mode of the Bluetooth protocol, called "announcement," which satisfies two constraints: avoiding pairing and allowing broadcasting, and is therefore useful for implementing this invention.

[0103] These aspects of the Bluetooth protocol are described and specified in the "Core Specification" normative document available on the official website http: / / www.bluetoothe.com. This document is currently available in version 5.3, dated July 13, 2021.

[0104] The “announcement” mode allows for several types of connections via the Generic Access Profile (GAP) mechanism described in Section 6.2. Specifically, there is a “broadcaster” mode, in which the sender sends information without allowing (and therefore not waiting for) a return. This mode is commonly used to implement the present invention.

[0105] In one implementation, this operating mode corresponds to the BLE protocol. In one implementation, the BLE protocol is used.

[0106] Bluetooth Low Energy (BLE or BTLE) is a wireless transmission technology created by Nokia in 2006. As an open standard based on Bluetooth, it complements rather than replaces Bluetooth. Since version v4.0 released by the Bluetooth SIG in June 2010, it has been integrated into the Bluetooth standard.

[0107] According to Wikipedia, "BLE offers the same order of magnitude (1 Mbit / s) data rate as Bluetooth, while consuming 10 times less power. This allows the technology to be integrated into new devices such as watches, medical monitoring devices, or motion sensors. The technology enables devices to connect within a radius of approximately 10 meters."

[0108] One of the advantages of the BLE protocol is its low energy consumption, which is an important consideration for equipment installed on satellites.

[0109] Bluetooth devices send packets to broadcast data in Advertisement mode. These are 31-byte blocks that can contain transmitter-specific information. They are also used to enable other devices to connect to them (pairing). There are several types of Advertisement packets, each performing a different function (for direct or indirect advertising, with or without the possibility of connection).

[0110] Bluetooth enables two-way or one-way data exchange using UHF radio waves and operates in the 2.4 GHz band. Forty physical channels are allocated for time and frequency multiplexing, each spaced 2 MHz apart (i.e., from 2.4 GHz to 2.8 GHz). Some channels are used for announcements, while others are used for unicast or multicast transmissions.

[0111] According to the BLE standard, an object can have up to four functionalities. Specifically:

[0112] A broadcaster can act as a server. Therefore, its purpose is to periodically send data to devices, but it does not accept any incoming connections.

[0113] Observer: An object can only listen to and interpret data sent by a broadcaster. In this case, the object cannot send connections to the server.

[0114] In this implementation scheme, the satellite can implement the "broadcaster" part of the BLE protocol operation mode, while the ground telecommunications terminal implements the "observer" part.

[0115] As mentioned earlier, secondary information (due to its high-level semantic content) can be low-volume. Therefore, the use of the BLE protocol is reasonable.

[0116] According to the standard, the BLE protocol can operate at different data rates.

[0117] In one embodiment of the invention, a data rate of 125 kbits / s is used. Alternatively, an S=8 mode can be used. This mode indicates that 8 symbols are used for transmission during modulation for each data item, which reduces the usable data rate but provides greater robustness and therefore greater sensitivity. This BLE protocol mode corresponds to a sensitivity of -103 dBm.

[0118] The BLE protocol is described and specified in the aforementioned normative document. Specifically, on page 218, there is a table summarizing the various possible BLE modes.

[0119] The signal strength received by a terrestrial telephone must be higher than the sensitivity of the receiver.

[0120] According to simulations performed by the inventors, this operating mode of the BLE protocol (125k S=8) enables the use of low-Earth orbit satellites to shut down the link budget using satellite directional antennas, wherein the transmit power is in phase with the transmit power that commercial power amplifiers can generate from low-Earth orbit satellites.

[0121] Antenna directivity can be a trade-off between satellite stability and maximum power consumption. In fact, the stronger the antenna's directivity, the more stable the satellite needs to be in pointing towards Earth, and the lower the required transmission power.

[0122] Figure 3 A simulation illustrating the evolution of the satellite's received power PR (via a terrestrial telecommunications terminal) relative to its transmitted power PT is shown. This simulation was obtained by considering a transmitting antenna with directivity defined by a 20° aperture angle of -3dB and a gain of 18dBi, and a receiver located at the lowest point of the satellite (i.e., a point on the ground vertically positioned between the satellite and the Earth's center).

[0123] This curve shows that for a low transmit power PT, the receive power increases very rapidly. Therefore, the required receiver sensitivity (i.e., -103 dB) was achieved from only a few watts of power transmitted by the satellite. Figure 3 In the exemplary curve, this sensitivity is achieved at a transmit power of approximately 1.5W. Satellite altitude, cloud cover, and satellite pointing parameters all affect this figure.

[0124] Figure 4 Another simulation shows the evolution of the satellite's received power PR (via a terrestrial telecommunications terminal) compared to its transmitted power PT, based on different assumptions, specifically lower antenna gain, and taking into account that the receiver may be located elsewhere except at the lowest point, and specifically at the edge of the coverage area.

[0125] The following is an example of link budget calculation, based on Figure 4 The simulation makes assumptions and applies actual error tolerances to the link budget.

[0126] The following parameters were considered:

[0127] -BLE mode 125k S=8,

[0128] -The satellite's altitude H is 550km.

[0129] -BLE receiver sensitivity: S = -103dBm

[0130] -Link budget margin: Margin = 4dB

[0131] Atmospheric loss at -2.4GHz: L atm =0.5dB,

[0132] -Polarization loss: L pol =3dB,

[0133] - Insertion loss: L i =2dB,

[0134] - The antenna directivity is defined by the aperture angle at -3dB of 20°, which corresponds to the maximum communication range of H = 550km (at the edge of the coverage area): D max =560km,

[0135] - Maximum path loss: PL = 155dB (e.g., as in...) https: / / en.wikipedia.org / wiki / Path_ loss (As indicated on the webpage)

[0136] - Transmit antenna gain: G tx =15dBi, and

[0137] -Average receiver antenna gain: G rx =0.5dBi.

[0138] The minimum point loss of a satellite is defined as follows:

[0139] PL+L atm +L pol +L I =160.5dB, and

[0140] The loss at -3dB is as follows:

[0141] Loss at 3dB = PL + L atm +L pol +L I =163.5dB

[0142] In order for telecommunications terminals to demodulate signals broadcast by satellite in BLE 125k S=8 mode, the minimum receive power required is Min(Prx):

[0143] Min(P rx )=S+Margin=-103+4=-99dBm

[0144] Using this telecommunications equation, the transmit power Ptx can be written as:

[0145] Ptx = Min(Prx) + Loss at 3dB - (G tx +G rx ).

[0146] Substituting the above values ​​yields:

[0147] Ptx = -99 + 163.5 - 15.5 = 49 dBm, which corresponds to approximately 79.5 W.

[0148] Therefore, the satellite's EIRP is: Ptx + Gtx = 64 dBm.

[0149] As can be seen, using the practical assumptions of the calculations described in detail above, the required sensitivity S is achieved at a power of tens of watts, which corresponds to a fairly conventional transmit power value for communication device 13.

[0150] Of course, depending on the telecommunications protocols used for broadcasting information, other curves and therefore other minimum transmit powers are also possible. Specifically, the “BLE 125kbps = 0” protocol (an example of which is described here) may undergo standardization changes in the future, which could affect this performance curve. Furthermore, other modes of the BLE protocol associated with higher data rates (e.g., 250kbits / s, 500kbits / s; 1M or even 2M) may also be used.

[0151] In any case, it is clear that using this Bluetooth standard operating mode enables the broadcasting of information from a satellite to a terrestrial terminal 2, which has the capacity commonly used for telecommunications device 13 and meets the requirements of a spaceborne system.

[0152] Of course, other implementation models are also possible, especially depending on the future evolution of various telecommunications standards or the emergence of new standards.

[0153] In the case of a moving satellite (located in low Earth orbit or other orbits), the movement of the satellite relative to the ground terminal distorts the transmitted signal through the Doppler effect (frequency shift).

[0154] Because the Bluetooth protocol is designed for communication between nearby objects at zero speed or low relative speed, it does not provide devices for naturally recovering these signal distortions.

[0155] Simulations conducted by the inventors have demonstrated a sensitivity loss of approximately 4 dB and a packet loss rate of approximately 10⁻².

[0156] According to one embodiment of the invention, the processing device 12 is adapted to pre-compensate for the frequency shift associated with the Doppler effect, which is a function of the satellite position, the telecommunications terminal position, and the satellite's velocity relative to the ground. This pre-compensation is designed to eliminate or at least significantly reduce sensitivity loss and the increase in packet loss rate.

[0157] This pre-compensation is actually possible as long as the telecommunications device 13 knows the location of the mobile terminal 2 that broadcasts the information to it, since these devices are directional (i.e., within the coverage area of ​​the broadcast cone 50).

[0158] If the solid angle of the scattering cone is small enough, the difference between different locations in the coverage area due to the Doppler effect can be considered negligible.

[0159] The pre-compensation can be performed by device 10 by preprocessing the complex envelope of the signal before broadcasting.

[0160] If the signal to be broadcast is represented as x(n) (therefore, if the Doppler effect is not considered, this signal will actually be broadcast), then according to one implementation, a pre-compensated signal y(n) is formed by the following formula:

[0161] [Mathematical Expression 1]

[0162]

[0163] In this expression, The estimated instantaneous phase represents the Doppler change to be compensated on surface S, which represents the coverage area of ​​diffusion cone 50.

[0164] Therefore, the Doppler effect θ D，S (n) The naturally perturbed received signal will be written as:

[0165] [Mathematical Expression 2]

[0166]

[0167] The quantity w(n) represents the thermal noise of the receiver.

[0168] Using the expression for the pre-compensated signal y(n), this expression can be written as:

[0169] [Mathematical Expression 3]

[0170]

[0171] or:

[0172]

[0173] ε D，S(n) represents the estimation error of the Doppler effect, expressed as:

[0174] [Mathematical Expression 4]

[0175]

[0176] The instantaneous phase caused by the Doppler effect can be qualitatively estimated by knowing the following. Changes:

[0177] Satellite location;

[0178] The location of the area on the ground to which the information will be broadcast (corresponding to the ground coverage area of ​​broadcast cone 50);

[0179] Carrier frequency;

[0180] The relative velocity of the satellite with respect to the ground (or a telecommunications terminal, if it is in motion; remember, given the velocity of the satellite relative to the terminal, the latter can be ignored).

[0181] The estimation aims to minimize the estimation error ε. D,S (n) Minimization.

[0182] The instantaneous phase can be estimated using the physical equations used to calculate the Doppler effect. Various methods for implementing these computational aspects are well described in the technical literature. One example is the article "Doppler Characterization for LEO Satellites" by Irfan Ali, Naofal Al-Dhahir, and John E. Hershey, published in IEEE Transactions on Communications, Vol. 46, No. 3, March 1998.

[0183] Therefore, the telecommunications terminal 2 in the receiving area (the coverage area of ​​the broadcast cone) is able to receive the information broadcast by the satellite with sufficient power so that it can be processed correctly (demodulated with a sufficiently low error rate so that the secondary information determined by the processing device 12 can be reconstructed).

[0184] As already seen, the terminal can be a terminal based on existing technology. Specifically, conventional telecommunications equipment is sufficient to enable them to receive secondary information broadcast by satellite. Therefore, the need for special antennas, demodulation circuits, etc., is eliminated.

[0185] As already seen, one embodiment of the present invention uses the Bluetooth protocol, specifically the BLE125k s=8 operating mode. Most telecommunications terminals are inherently adapted to receive information broadcast using this protocol.

[0186] Telecommunication terminals can be of different types. These can be fixed terminals (computers, televisions, etc.) or mobile terminals (laptops, tablets, cellular phones, etc.).

[0187] The telecommunications terminal includes software applications 20 suitable for continuously receiving data streams in a predetermined channel.

[0188] As explained above, this channel may correspond to the Bluetooth telecommunications protocol, and more specifically to the broadcast mode of this protocol, such as "BLE 125k S=8".

[0189] The software application is also adapted to analyze the contents of the data stream in order to detect the secondary information and, if necessary, determine within the secondary information data that can trigger an action on the human-machine interface of the telecommunications terminal.

[0190] This data may include geographic location and / or situation type.

[0191] The software application can be adapted to compare the geographic location with the terminal's geographic location and trigger an action only if the two geographic locations are sufficiently close. This concept of proximity can be fixed, configurable, or adaptable, for example, depending on the type or severity of the situation.

[0192] The software application can also be adapted to compare this type of situation with parameters set by the user of the telecommunications terminal, which indicate the type of service the user wishes to subscribe to.

[0193] These parameters can be set by the application itself, allowing for the existence of several versions of the application, each corresponding to different types of users (general public, security professionals, etc.) or different application domains.

[0194] An example of this application could be informing affected populations of emergencies (fires, floods, earthquakes, major floods, etc.). Emergencies can be detected by observation satellites using the key information acquired and analyzed as described above. This can also be accomplished through other mechanisms and broadcast via communication satellites.

[0195] When terminal 2 is within the satellite's broadcast area (the coverage area of ​​broadcast cone 50), the terminal receives a Bluetooth broadcast stream. If application 20 is properly configured, it can analyze the incoming stream and determine whether an alarm should be triggered via the human-machine interface (displaying a signal or message on the screen, an audible alarm, vibration, etc.).

[0196] Other applications are also possible, where users may wish to receive alerts for specific situations determined by satellites or other systems.

[0197] For example, this determination could include checking whether the terminal is actually located in an area affected by the emergency (in a more precise way than satellite broadcasting mechanisms can do), or whether the user has actually subscribed to the alert service.

[0198] Therefore, according to the present invention, information is broadcast directly from the satellite to the telecommunications terminal. It is not transmitted through other devices. Thus, in emergency situations such as natural disasters, the mechanism of the present invention makes it unaffected by damage or even destruction of terrestrial telecommunications infrastructure;

[0199] The presence of a terrestrial network in the area involved;

[0200] Subscription to a carrier;

[0201] Congestion of the same infrastructure is caused by the large volume of communications initiated by the crowd during this type of event, as well as the possible partial damage to telecommunications infrastructure equipment.

[0202] Therefore, the present invention enables the flexible maintenance of communication channels with those who may have been affected.

[0203] Furthermore, telecommunications infrastructure (wired, cellular, WiFi, etc.) coverage is very low in some areas, especially in remote rural areas. In such cases, this invention enables the sending of alerts or, more generally, minor information to mobile terminals in the absence of telecommunications infrastructure.

[0204] Furthermore, according to some embodiments of the present invention, by transmitting the analysis results directly to the mobile telecommunications terminal of the end user, it is possible to take advantage of the ever-growing capabilities of observation satellites.

[0205] This allows them to obtain these results as quickly as possible without requiring ground stations to process or even retransmit the information. These processes no longer create bottlenecks, thus lengthening the information transmission chain and slowing down user reception of relevant information.

[0206] This ability to transmit directly from satellite to users paves the way for new applications and services, especially in developing countries or in areas with insufficient terrestrial telecommunications coverage (forest areas, deserts, etc.).

[0207] Of course, the present invention is not limited to the examples and embodiments described and shown, but is defined by the claims. In particular, the present invention is susceptible to various modifications available to those skilled in the art.

Claims

1. A device (10) suitable for installation on a satellite (1), said device comprising a telecommunications device (13) for broadcasting information directly to at least one telecommunications terminal (2) on the ground, characterized in that, The telecommunications device is adapted to broadcast the information via Bluetooth Low Energy (BLE) in an "announcement" mode, wherein incoming connections are not accepted in the "announcement" mode, and the at least one telecommunications terminal (2) is compatible with the communication protocol and configured to receive the information without sending any connection requests to the satellite's communication device. The telecommunications device includes: - A directional antenna adapted to transmit a signal carrying the information in a broadcast cone at a data rate of at least 125 kbits / s in a frequency band between 2.4 GHz and 2.8 GHz with a transmit power greater than or equal to 1.5 watts, the transmit power being determined such that the power of the signal received by at least one of the terminals located in the broadcast cone is higher than a given receive sensitivity of the terminal for the "announcement" mode, the power of the received signal varying as a function of the satellite's altitude relative to the ground, cloud cover, and satellite pointing parameters.

2. The device according to claim 1, further comprising: - At least one sensor (11), said at least one sensor being used to acquire key information, said key information including raw data captured by said at least one sensor, - Processing device (12), the processing device being configured to analyze the primary information to detect a situation corresponding to a standard within the primary information, and to determine secondary information related to the situation, the secondary information including data generated from the analysis of the primary information; and - The telecommunications device (13) is provided to transmit the secondary information within the information.

3. The device according to claim 2, wherein the primary information is an image.

4. The device according to any one of the preceding claims, wherein the telecommunications device is adapted to broadcast the information via Bluetooth Low Energy (BLE) at 125 kbits / s at a rate of 8 symbols per bit, and the sensitivity of the telecommunications terminal is approximately -103 dBm.

5. The apparatus of claim 2, wherein the processing means is adapted to pre-compensate for frequency shifts related to the Doppler effect as a function of the position of the satellite, the position of the at least one telecommunications terminal, and the velocity of the satellite relative to the ground.

6. The device according to claim 2, wherein the secondary information represents a warning.

7. A satellite configured to be in orbit around the Earth, the satellite comprising an onboard satellite management device and a device (10) according to any one of the preceding claims, the onboard satellite management device comprising a power supply device and a positioning device.

8. A system comprising at least one satellite (1) according to the preceding claim and at least one telecommunications terminal (2).

9. A method for broadcasting information directly from a satellite (1) to at least one telecommunications terminal (2) on the ground, characterized in that, The method implements the Bluetooth Low Energy (BLE) protocol in an "announcement" mode, according to which the satellite's telecommunications device is adapted to broadcast the information without accepting any incoming connections, and the at least one telecommunications terminal (2) is compatible with the protocol and configured to receive the information without sending any connection requests to the satellite's communication device. The method includes: - A signal carrying the information is transmitted in a broadcast cone at a data rate of at least 125 kbits / s in a frequency band between 2.4 GHz and 2.8 GHz with a transmit power greater than or equal to 1.5 watts, using a matched directional antenna. The transmit power is determined such that the power of the signal received by at least one of the terminals located in the broadcast cone is higher than the receiving sensitivity of the terminal corresponding to the "announcement" mode. The power of the received signal varies as a function of the satellite's altitude relative to the ground, cloud cover, and satellite pointing parameters.

10. A computer program product comprising instructions which, when executed by a computer, cause the computer to perform the method according to the preceding claim.

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