Method, device and program for controlling a coverage area of ​​a server satellite of a communication system.

Abstract

The invention relates to a method for controlling a coverage area of ​​a server satellite of a satellite communication system comprising a plurality of satellites, the method comprising steps of determining (300) at least one dimension Rc of a geographical area C to be covered by the server satellite with a particular quality of service, determining (301) an overall interference level in the area C to be covered from the relative positions and transmission powers of the satellites present in an interference area and a characteristic of the ground environment likely to influence said overall interference level, determining (305) a minimum transmission power of the server satellite making it possible to offer a target quality of service in the area C to be covered, taking into account the determined interference level, and configuring (306) the server satellite with the determined transmission power.The invention also relates to a device and a computer program suitable for implementing the method. Figure for the abstract: figure 3.

Description

Title of the invention: Method, device and program for controlling a coverage area of ​​a server satellite of a communication system. Technical field

[0001] The invention relates to the general field of telecommunications. It relates more particularly to the configuration of a satellite communication network and in particular the control of a coverage area.

[0002] The invention finds a preferred but non-limiting application in the context of mobile services based on a satellite communication network. Prior art

[0003] In a manner known per se, a satellite communication network relies on a plurality of satellites placed in orbit and deployed to cover a given geographical area of ​​the Earth's surface. To transmit data to user equipment of the satellite network, a satellite, called a "server satellite", transmits a radio signal to the user equipment with a certain power called a transmission power. It is noted that the server satellite is the one which covers the geographical area in which the user equipment is located and to which the user equipment is connected or associated.

[0004] A satellite comprises one or more transmission spots each covering a geographical area, called the coverage area, at the center of which the power of the signal emitted by the spot is maximum when the transmitter is pointing at the nadir. The power of the signal, and therefore the available throughput, decreases as it moves away from the center of the coverage area. Indeed, the signal emitted by the server satellite undergoes attenuation which is a function of the direct line distance separating the server satellite from the user equipment. Thus, the transmission power and the radius of the area are defined jointly to guarantee a minimum quality of service at any point in the coverage area.

[0005] However, external factors are likely to alter the signal emitted by a satellite and therefore modify the characteristics of the coverage area.

[0006] The received signal may in particular be affected by interference generated by the other satellites of the satellite network which transmit simultaneously using the same resources as the server satellite (typically the same frequency), and by the characteristics of the receiver's environment.

[0007] Each satellite in the satellite network other than the server satellite is in fact likely to generate a signal interfering with the useful signal emitted by the server satellite: the interference thus generated depends on the altitude of the satellite in question, its transmission power and its relative position with respect to the area covered by the server satellite. The resulting impact on the performance of the server satellite is not negligible because all the satellites in the satellite network transmit simultaneously to a large number of user equipment in the same frequency band.

[0008] The signal strength received by user equipment is also affected by the environment of the equipment. For example, whether the receiver is in an urban or rural environment, or whether the equipment is located inside or outside a building affects the useful power received.

[0009] This interference has an impact on the signal power and therefore on the characteristics of the area actually covered by a satellite, in particular on the radius of the area covered.

[0010] The state of the art does not allow one to know a priori whether the characteristics of a spot and / or a satellite, in particular its transmission power, make it possible to cover a given area with a requested quality of service, nor whether it is possible to achieve such an objective by adjusting certain transmission parameters, for example the transmission power. The operator cannot therefore, a priori, guarantee a particular quality of service and coverage to the recipient.

[0011] There is therefore a need for a method for determining and controlling the extent of an area covered by a satellite in which a particular quality of service is required. Summary of the invention

[0012] To this end, a method is proposed for controlling a coverage area of ​​a server satellite of a satellite communication system comprising a plurality of satellites, the method comprising the following steps: - Determination of at least one dimension Rc of a geographical area C to be covered by the server satellite with a particular target quality of service, - Determination of an overall interference level in zone C to be covered based on the positions and relative transmission powers of the satellites present in an interference zone and a characteristic of the ground environment likely to influence said overall interference level, - Determination of a minimum transmission power of the server satellite allowing coverage of zone C with the target quality of service, taking into account the determined level of interference, and - Configuration of the server satellite with the determined transmission power.

[0013] It is thus proposed to adjust the transmission power of a satellite so that the coverage area reaches a particular size, taking into account interference likely to affect the size of this coverage area.

[0014] In this way, the method makes it possible to maintain a coverage area of ​​constant size regardless of the level of interference affecting the signal. For example, by regularly implementing the method, a coverage area of ​​fixed size can be maintained during the movement of the satellite. The method can thus be implemented iteratively, at a frequency that can be determined according to the speed of movement of the satellite and the radius of the current coverage area so as to provide a coverage area of ​​stable dimensions, thus facilitating the configuration of the satellite constellation.

[0015] The method further makes it possible to determine a priori whether or not a user at a given location can be covered by a given satellite with a particular target quality of service, i.e. whether the user is in the effective coverage area taking into account the interfering satellites and the environment of the receiver.

[0016] The target quality of service is a minimum quality of service that a receiver must be able to benefit from at any point in the coverage area.

[0017] A communications satellite may comprise one or more transmission spots, each of which makes it possible to cover a particular geographical area. In this disclosure, the terms "spot" or "satellite" will be used interchangeably to designate a transmission spot from a satellite, so that the formulations "area covered by a satellite" and "area covered by a spot from a satellite" are equivalent here.

[0018] In a particular embodiment, the method is such that at least one dimension Rc of a geographical area C to be covered by the server satellite with a particular target quality of service is determined, at least from the positions of a particular terrestrial receiver and of the server satellite.

[0019] Such an arrangement allows for adjustment of the power at which the satellite will have to transmit a signal so that a receiver at a particular location can be covered with a particular quality of service. For example, when a user is located at the edge of the coverage area and the quality of service he benefits from falls below a threshold value, the method makes it possible to determine the transmission power required to increase the radius of the coverage area in order to include the user. In the event that the maximum transmission power is reached, the receiver can be assigned to another satellite.

[0020] According to a particular embodiment, the step of determining a minimum transmission power of the satellite comprises the following sub-steps: - Determination of a radius Rc' of a zone C' covered by a satellite transmitter from a current transmission power of the satellite and the overall level of interference determined, and - Determination that a particular location is included in the coverage area C' from the determined radius Rc' and the position of the satellite issuer, - When the location is not included in the coverage area C\ determination of the target radius Rc of a coverage area C allowing the location to be included, and - Determination of a minimum transmission power of the server satellite allowing to offer a target quality of service in a coverage area C of radius Rc, taking into account the determined level of interference.

[0021] In this way, the method makes it possible to determine a priori whether a particular location is included in the coverage area of ​​the satellite, that is to say whether the location makes it possible to offer a particular quality of service taking into account the overall level of interference, and to determine if this is not the case a transmission power making it possible to extend the coverage to the location so that it benefits from the expected quality of service.

[0022] According to a particular embodiment, the overall interference level is determined by taking into account the overall relative impact of the other satellites taking into account the local environment of the receiver by a relationship equivalent to the relationship:

[0023] [Math.l] / £ \ V2 /

[0024] in which J denotes the standard deviation of the influence of the local environment of the receiver, rJ denotes the distance separating the receiver from satellite j, with a —11110 / 10.

[0025] Such a relationship makes it possible to model the overall impact of the system topology on the receiver of the useful signal, taking into account both the topology of the satellite network and the topology of the local environment at the receiver.

[0026] The term E^rf characterizes the relative impact of the relative positions of the sources O interference (other satellites, other spots from the same satellite) compared to those of the receiver.

[0027] The transmission power required to cover a particular area in which a receiver is located is thus determined by taking into account the characteristics of the other spots and / or other satellites (in particular their distance from the receiver in question and their transmission power) and the characteristics of the receiver's environment.

[0028] According to a particular embodiment, the method is such that the communication system further comprises at least one reconfigurable intelligent surface RIS adapted to control the way in which the signal is reflected on this surface, the method further comprising the following steps:

[0029] - Selection of a subset of RIS of the communication system taking into account takes into account at least the distance separating a RIS from the terrestrial receiver, and

[0030] - Configuration of the phase of at least one RIS selected from the positions respective of the server satellite, the RIS and the terrestrial receiver, so as to phase the signal received in direct line by the terrestrial receiver with the phase of the signal reflected by the selected RIS and increase the useful power received by the receiver.

[0031] Reconfigurable Intelligent Surfaces (RIS) are a recent technological innovation in the telecommunications sector. A RIS comprises a two-dimensional matrix of elementary cells that can be configured to allow dynamic modification of the characteristics (particularly in terms of direction) of a reflected electromagnetic wave, in response to an incident wave.

[0032] Taking into account RIS near the terminal, and in particular the application of a configuration adapted to one or more RIS makes it possible to improve the quality of the signal to the receiver.

[0033] It is thus proposed to apply a particular configuration to one or more RISs near the terminal which modifies the phase of the reflected signal so as to make it correspond to the phase of the signal received in direct line by the terrestrial receiver. In other words, a part of the signal which would not have reached the receiver is reflected towards it after a phase alignment to increase the power of the received signal.

[0034] The method thus makes it possible to take advantage of the presence of RIS near the terrestrial receiver to apply a particular configuration to the communication system and precisely determine the transmission power necessary to cover a geographical area in which a particular receiver is located.

[0035] The phase of the signal being equal to the distance separating the transmitter and the receiver multiplied by the wave number (i.e. 2 / r / λ, with 2 the wavelength), the phase difference between the direct line signal and the reflected signal can be determined from the difference between the distance separating the satellite and the RIS and the distance separating the satellite and the receiver. This phase difference makes it possible to configure the RIS.

[0036] In a particular embodiment, the step of selecting at least one RIS comprises calculating a product of the distance between the receiver and the RIS by the distance between the RIS and the satellite, a RIS being selected when it minimizes said product.

[0037] Such an arrangement allows the selection of at least one particular RIS from among the RIS which are in proximity to the terrestrial receiver which maximizes the useful power to the receiver.

[0038] When the satellite transmits a power P, the power P received by the receiver is given by the following relation:

[0039] [Math.2] p^K^^l + ta)2

[0040] With:

[0041] [Math.3] WK (r.*r^

[0042] With:

[0043] ' the distance between the server satellite and the receiver,

[0044] ri the distance between the satellite and the RIS i,

[0045] F- the distance between the RIS i and the receiver,

[0046] K, K, the propagation factors of the direct signal and the signals reflected by the RIS i. These factors take into account the gains of the transmitter of the receiver and of the RIS.

[0047] depends on the ratio between the distance separating the transmitter and receiver and the product (f;*f^). Thus, when this product is minimum, the factor w is maximum.

[0048] The effect of a RIS for the receiver, after phase control, results in an increased received power by a factor of Q + ^2.

[0049] Thus, by proposing to select a RIS which minimizes the value of the product The process maximizes the power available to the receiver. It is thus possible to reduce the transmitter power to cover a given area.

[0050] According to another aspect, the invention relates to a device for controlling a coverage area of ​​a server satellite of a satellite communication system comprising a plurality of satellites, the device comprising a processor coupled to a memory in which program instructions configured to implement the following steps are recorded: - Determination of at least one dimension Rc of a geographical area C to be covered by the server satellite with a particular target quality of service, - Determination of an overall interference level in zone C to be covered based on the positions and relative transmission powers of the satellites present in an interference zone and a characteristic of the ground environment likely to influence said overall interference level, - Determination of a minimum transmission power of the server satellite allowing to offer a target quality of service in zone C to be covered, taking into account the determined level of interference, and - Configuration of the server satellite with the determined transmission power.

[0051] In a particular embodiment, the device is configured to determine the transmission power so as to cover an area with a determined target radius Rc at least from the location of a particular terrestrial receiver.

[0052] The invention also relates to a control unit comprising a control device as described above.

[0053] The invention also relates to a communication system comprising such a control unit, a plurality of satellites, and at least one terrestrial receiver.

[0054] In a particular embodiment, the steps of the control method are determined by computer program instructions.

[0055] Consequently, the invention also relates to a computer program comprising instructions adapted to the implementation of the steps of a control method as described above, when the program is executed by a processor.

[0056] This program may use any programming language, and be in the form of source code, object code, or code intermediate between source code and object code, such as in a partially compiled form, or in any other desirable form.

[0057] The invention also relates to a computer-readable information medium on which is recorded a computer program comprising instructions for executing the steps of a control method as described above.

[0058] The information medium may be any entity or device capable of storing the program. For example, the medium may comprise a storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, a flash memory, or a magnetic recording means, such as a hard disk.

[0059] On the other hand, the information medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means. The program according to the invention may be downloaded from an Internet-type network.

[0060] Alternatively, the information carrier may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the method in question.

[0061] The various embodiments or features mentioned above can be added independently or in combination with each other, to the steps of the control method.

[0062] The devices, controllers, systems, programs and information media have advantages similar to those conferred by the control method. Brief description of the figures

[0063] Other characteristics and advantages will appear on reading a preferred embodiment described with reference to the appended drawings among which: - [Fig.l] represents an environment suitable for implementing the control method according to a particular embodiment, - [Fig.2] represents a satellite whose coverage area is affected by interference, - [Fig.3] is a flowchart representing the main stages of a control process according to a particular implementation, - [Fig.4] is a diagram representing the architecture of a device suitable for implementing the control method in a particular embodiment. Detailed description

[0064] In the following description, embodiments are described on the basis of non-limiting examples making it possible to explain the concepts on which the invention is based. In particular, although the examples and the terminology used may refer to certain well-known technologies or standards, these references are not limiting and other technologies may be adapted to implement the concepts of the invention.

[0065] [Fig.l] represents an environment suitable for implementing the control method according to a particular embodiment.

[0066] The environment comprises a communication system 110 comprising a plurality of satellites 100 to 102 of a constellation of LEO (Low Earth Orbit) satellites. The constellation notably comprises a satellite 100 called a “server”, which is adapted to transmit a signal to a terrestrial receiver 103 of the system 110 present in its coverage area. Each satellite may comprise one or more spots configured to emit a signal with a particular configuration.

[0067] The local environment of the receiver 103 includes buildings 104 likely to alter the transmitted signal by generating multi-path type interference for example.

[0068] Optionally, the communication system 110 may comprise reconfigurable reflective surfaces, for example RIS surfaces 105 and 106 adapted to dynamically modify, by configuration, characteristics of a reflected electromagnetic wave, in response to an incident wave. The RIS surfaces 105 and 106 are in particular configured to modify the phase of the reflected signal in response to a particular configuration command.

[0069] The system 110 finally comprises a control unit 107, adapted to communicate with the RIS surfaces 105 and 106, the satellites 100 to 102 and the terminal 103. No limitation is attached to the nature of the controller. For example, it may be a server in a communications network core, or even a piece of equipment particular of a base station of a cellular network. The control unit can communicate with the entities via a wired network, a cellular network, a satellite connection or by any suitable means. Thus, the control unit can receive data from the receiver 103, the RIS surfaces and the satellites, but also transmit data to these devices and in particular transmit a configuration to a particular satellite or RIS surface in order to modify its settings.

[0070] The satellites 100-102, the control unit 107, the receiver 103 and the RIS surfaces 104-105 form a communication system 110. Of course, such a system may include other well-known entities necessary for its operation but which have not been shown for the sake of clarity.

[0071] In such a communication system, a set of satellites is deployed at a certain altitude. When a satellite transmits data to a user on the ground, it emits a radio signal to this user at a certain power. The radio signal covers a particular geographical area, the extent of which depends not only on the characteristics of the satellite, in particular its transmission power and its orbit, but also on the level of interference to which the signal is subject. Of course, the power of the useful signal likely to be received in the covered area varies according to the location and orbital parameters of the satellites: when the satellite is pointing at the nadir, it is maximum at the center of the covered area and decreases as it moves away from the center until it reaches a minimum value below which it is no longer possible to offer a determined quality of service.The coverage area of ​​a satellite is thus defined by the geographical area within which the power of the useful signal is greater than a threshold allowing a target quality of service to be offered. It is thus understood that the dimensions of a satellite coverage area are affected by possible interference.

[0072] Thus, with reference to FIG. 2, a nominal coverage area C of radius Rc of a satellite 200 can be reduced to an area C' of radius Rc due to interference. In other words, in the presence of interference, only the area C' makes it possible to offer a quality of service 5 which would otherwise be available throughout the area C in the absence of interference.

[0073] Under these conditions, the control method makes it possible to determine the transmission power P necessary, taking into account the interference, to cover a particular area, for example the nominal coverage area C.

[0074] A particular embodiment of the control method will now be described in relation to [Fig. 3]. The method is for example implemented by the control unit 107 of the communication system 110 of [Fig. 1].

[0075] During a first step 300, the control unit 107 determines the characteristics of a geographical area to be covered by a satellite or a spot of a particular satellite. When the transmitter is pointing at the nadir, the projection of the signal on the ground is generally circular, the extent of a coverage area can therefore be defined by its radius. Thus, the control unit can determine the radius Rc of an area to be covered C. The radius Rc can correspond to the radius of a nominal coverage area determined by the configuration of the communication system. As we have seen, the geographical area actually covered by a satellite with a particular quality of service may be different from the nominal coverage area, in particular because of interference likely to affect the signal strength in the area.

[0076] The radius Rc can also be determined from the respective positions of a particular terrestrial receiver and the server satellite so that the radius Rc can be determined so as to include the location of a particular receiver in the coverage area. In other words, the radius Rc is at least equal to the distance separating the terrestrial receiver from the center of the coverage area. The center of the area is determined from the orbital parameters of the satellite. For example, the positions of the receiver and the server satellite are respectively obtained by interrogating the receiver 103 when it is equipped with a GNSS (Global Navigation Satellite System) receiver, and from orbital parameters of the satellite in question.

[0077] In step 301, the control unit 107 determines a global interference level determined from the relative positions and transmission powers of the satellites present in an interference zone with respect to those of the receiver, and from a particular topology of the local environment at the receiver likely to influence said global interference level.

[0078] For this, the control unit determines an average value of the SINR (for Signal to Interference plus Noise Ratio in English) of the signal perceived by the receiver 103, which takes into account interference and thermal noise, when considering the impact of the environment and all interfering satellites and spots.

[0079] The inventors first modeled by terms y(r) and T(j) the relative impact of the relative positions and powers of the interference sources (other satellites, other spots of the same satellite) compared to those of the receiver. These are factors which characterize the topology of the system in which the spot is located (other spots belonging to the same satellite, constellation of satellites) compared to the receiver. We can also speak of a sort of "form factor" of the system. In other words y(r) and T(j) characterize the overall impact of the topology of the system on the receiver of the useful signal. These factors are defined by relationships equivalent to:

[0080]

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[0092] [Math.4] [Math.5] in which rj denotes the distance separating an interfering satellite j from the receiver and r the distance between the server satellite and the receiver. The inventors then used the formula [Math 4] to characterize the overall impact of shadowing I(j), that is to say the influence on the signal of the obstacles present in the environment, taking into account the topology of the satellite system, by the relation: [Math.6] = (^2-1) + iy1 / 2 With : " InlO The factors y(r ) and Z( j ) thus make it possible to calculate an average of the interference to useful signal ratio at a particular location, taking into account the impact of shadowing: [Math.7] From the factor (y ), which allows shadowing to be taken into account, the inventors propose to calculate the standard deviation of the useful signal to interference ratio Sf received at the receiver. St then models the impact of interference (without taking into account thermal noise) on the SIR (Signal to Interference Ratio) of the perceived signal, when considering the impact of the receiver's environment and all interfering satellites and spots. [Math. 8] The average my of the interference to useful signal ratio and the square of the standard deviation allow us to calculate a term cf characterizing the average value of the SIR of the perceived signal, which takes into account interference but not thermal noise, when we consider the impact of the environment and all interfering satellites and spots: [Math.9] dzS] Cf — 6»^+^ The influence of thermal noise on the signal is characterized by a dN value such that

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[0108] that : [Math. 10] dN = Or: [Math. 11] m N - in-^p- With Nth the thermal noise, P the emission power and K the propagation constant. It is then possible to define a value mt characterizing the average value of the SINR of the perceived signal, taking into account interference and thermal noise, when considering the impact of the environment and all interfering satellites and spots. [Math. 12] m t - -In[cy+ <Z A ] The term characterizes the impact, in terms of the square of the standard deviation, of interference and thermal noise on the SINR of the perceived signal, when considering the impact of the environment and all interfering satellites and spots. It is given by the formula: [Math. 13] {Cf+d^ J In which: [Math. 14] a f- e2my+a2^ ( - 1 ) And [Math. 15] bN = The control unit can thus determine the average value mt of the SINR of the perceived signal, taking into account interference and thermal noise, and considering the impact of the environment and all interfering satellites and spots. In step 304, the control unit 107 determines the minimum power at which the server satellite must transmit a signal to cover the zone C with a particular quality of service. This minimum power is determined from the following relation: [Math. 16] xf [ lOIoç 1 , P, R. =JJ„e—^dxdS

[0109] Where: - Rc is the radius of the coverage area, - P the satellite's transmission power, - <5 the target quality of service, - the standard deviation of shadowing, - On the surface of the coverage area, either - G is the probability of non-coverage.

[0110] For example, if G = 5%, then for a coverage radius Rc and a power P, then we obtain a quality of service <5 with a probability of 95%. In other words, we have a 5% chance of having a qos lower than 5 in a coverage area of ​​radius Rc with a power P.

[0111] Such a relationship thus makes it possible to determine a power P for a coverage radius Rc and a quality of service 5.

[0112] In the expression [Math 16], Q is a complementary error function such that:

[0113] [Math. 17] erfc (x)-^- fv el~dt - 1 - erf (x)

[0114] During a step 305, the control unit updates the configuration of the satellite from the minimum power determined in step 304. To do this, the control unit transmits a message to the satellite whose transmission power must be updated, the message comprising an identifier of the spot and a command to update a transmission parameter, such as the transmission power.

[0115] The server satellite can thus adapt its transmission power to cover a particular area with a guaranteed minimum quality of service, taking into account the ground environment and the interference likely to be generated by other satellites in the constellation. The satellite is configured with a minimum transmission power to cover the area, which has the effect of limiting energy expenditure and reducing the risk that the transmitted signal interferes with the signals of other satellites using the same resources.

[0116] According to a particular embodiment, the method takes into account reconfigurable reflective surfaces 105 and 106 (or RIS, for Reconfigurable Intelligent Surfaces in English) present in the environment of the receiver 103 to determine the characteristics of the coverage area.

[0117] For this, the method comprises a step 302 during which one or more RIS located near the receiver 103 or a particular location are selected. For example, during this first selection, the control unit 107 selects the RIS which are located at a distance less than a particular threshold from the receiver or the location in question.

[0118] According to a particular embodiment, the control unit 107 determines, among the selected RISs, the RISs which are most likely to positively influence the signal strength at the location.

[0119] For this, the control unit 107 determines, for each selected RIS, a product of the distance} i between the server satellite of the RIS i, with the distance r ■ between the RIS; and the receiver.

[0120] For example, with reference to FIG. 1, the control unit 107 first selects the RISs 105 and 106 because the distance separating them from the terminal 103 is less than a particular threshold. The control unit 107 then determines which of these RISs is most suitable for improving the signal to the receiver. For this, the control unit 107 calculates the product (rf*r;) and the product ( rj*r'j} and selects the RIS which is associated with the product of the lowest value. As seen previously, a RIS which minimizes such a product makes it possible to maximize the power of the signal reflected towards the receiver.

[0121] In step 303, the control unit determines the value of a phase shift of the signal received in direct line at the location of the receiver 103 with the signal reflected by the selected RIS. The control unit can calculate the phase shift by multiplying the difference between the distance traveled by the direct line signal and the distance traveled by the reflected signal by the wave number:

[0122] [Math. 18] (p^k^n + r-) -r)

[0123] With: - r the distance separating the server satellite from the receiver in direct line, - ? i the distance separating the server satellite from the selected RIS, - r'. the distance separating the selected RIS from the receiver, - k = 24- the wave number. Z

[0124] From the calculated phase shift value, the control unit configures the RIS to modify the phase of the reflected signal, so as to align the phase of the reflected signal with the phase of the signal received in direct line by the receiver.

[0125] In this way, the direct line signal and the reflected signal are received in phase by the receiver, thus increasing the power of the resulting signal. More precisely, the effect of an RIS for the receiver, after phase control, results in an increased received power by a factor of (1 + w)2, (V being defined by the relation [Math 3].

[0126] Increasing the power of the useful signal received by configuring one or more RISs nearby allows a reduction in the satellite's transmission power to guarantee quality of service in the area in question. The control unit can then determine a new minimum transmission power so that the satellite server can guarantee a particular quality of service in the zone C of radius Rc considered.

[0127] [Fig. 4] represents the architecture of a device 400 adapted to implement the control method according to a particular embodiment. The device 400 is for example integrated into the control unit 107 represented in [Fig. 1].

[0128] The device 400 comprises a data processing module comprising a storage space 401, for example a memory (MEM), a processing unit 402, equipped for example with a microprocessor (PROC), and controlled by a computer program (PGR) 403 whose instructions are configured to implement the control method as described previously in relation to [Fig.3].

[0129] At initialization, the code instructions of the computer program 403 are for example loaded into the memory 401 before being executed by the processor of the processing unit 402. The microprocessor of the processing unit 402 implements, according to the instructions of the computer program 403, the steps of the control method described above with reference to [Fig.3].

[0130] For this, in addition to the memory 401 and the processor 402, the device comprises communication means 404, allowing it to exchange messages with other devices. These communication means are for example an Ethernet, WiFi, 3G, 4G, 5G, etc. network interface. The communication means 404 in particular allow the device 400 to exchange data with a terrestrial receiver and with a particular satellite, either directly or via one or more communication networks, and / or with RIS reflective panels.

[0131] The device 400 comprises a module 405 for determining at least one dimension of a geographic area to be covered. The module 405 may be implemented by program instructions configured to determine the radius of an area to be covered from the respective positions of a server satellite and a geographic location. In some embodiments, the module 405 determines the radius of an area to be covered such that the area includes a particular terrestrial receiver.

[0132] The device 400 comprises a module 406 for determining an overall interference level in the area to be covered determined by the module 405. The module 406 can be implemented by program instructions configured to determine an overall interference level determined from the relative positions and transmission powers of the satellites present in an interference area with respect to those of the receiver, and from a particular topology of the local environment at the receiver likely to influence said overall interference level. For this, the program instructions of the module 406 are configured to determine an overall interference level taking into account the impact of the satellites present in an interference area by taking into account the local environment and the thermal noise from from the formulas [Math 4] to [Math 15] described above.

[0133] The device 400 comprises a module 407 for determining a minimum transmission power allowing coverage of the area determined by the module 405. The module is implemented by program instructions configured to calculate the expression [Math 16] for a particular coverage radius and a target quality of service.

[0134] The device 400 also comprises a configuration module 408 adapted to apply a particular configuration to the satellite communication system. The configuration module is for example implemented by computer program instructions configured to transmit to a server satellite an update of the transmission power from the power determined by the module 407.

[0135] In a particular embodiment, the device 400 comprises a module 409 for configuring at least one RIS. The configuration module 409 is for example implemented by program instructions which are configured to select one or more RIS according to the distance which separates it from a terrestrial receiver and / or according to the value of a product of the distance between the satellite and the RIS and the distance between the RIS and the receiver. The instructions are further configured to determine, for each selected RIS, a phase shift between the signal received by the receiver in direct line and the phase of the signal reflected by the RIS in question, and to configure the RIS from the calculated phase shift, so as to align the phases of the reflected signal with the phase of the signal received in direct line by the receiver and thus increase the power of the useful signal received.

[0136] In a particular embodiment, the module 407 for determining a minimum transmission power takes into account the effect of the RIS on the useful signal received by the receiver to determine the minimum transmission power required to cover the area defined by the radius determined by the module 405.

[0137] In certain embodiments, the device 400 is integrated into a server of a communication network, for example in a control unit, in a server satellite, in a terrestrial receiver such as a smartphone, a computer, a connected vehicle, a base station, etc.

Claims

Claims

1.

2.

3. Method for controlling a coverage area of ​​a server satellite of a satellite communication system comprising a plurality of satellites, the method comprising the following steps: Determination (300) of at least one dimension Rc of a geographical area C to be covered by the server satellite with a particular target quality of service, Determination (301) of an overall interference level in the area C to be covered from the positions and relative transmission powers of the satellites present in an interference area and a characteristic of the ground environment likely to influence said overall interference level, Determination (305) of a minimum transmission power of the server satellite making it possible to cover the area C with the target quality of service, taking into account the determined interference level, and Configuration (306) of the server satellite with the determined transmission power. The method of claim 1 wherein the at least one dimension Rc of a geographical area C to be covered by the server satellite with a particular target quality of service is determined at least from the positions of a particular terrestrial receiver and the server satellite. A method according to any preceding claim in which the step of determining a minimum transmission power of the satellite comprises the following sub-steps: Determination of a radius Rc' of an area C' covered by a satellite transmitter from a current transmission power of the satellite and the determined overall interference level, and Determination that a particular location is included in the coverage area C' from the determined radius Rc' and the position of the transmitting satellite, When the location is not included in the coverage area C', determination of the target radius Rc of a coverage area C to include the location, and Determination of a minimum transmission power of the server satellite enabling the provision of a target quality of service in a coverage area C of radius Rc, taking into account the determined level of interference.

4. Method according to any one of the preceding claims in which the overall interference level is determined by taking into account the overall relative impact of the other satellites taking into account the local environment of the receiver by a relationship equivalent to the relationship: / „ ' 4in which denotes \ (£4 / / ) / the standard deviation of the influence of the local environment of the receiver, rj denotes the distance separating the receiver from satellite j, with a = 11110 / 10.

5. Method according to any one of the preceding claims wherein the communication system further comprises at least one reconfigurable intelligent surface RIS adapted to control the way in which the signal is reflected on this surface, and wherein the transmission power of the server satellite is determined by taking into account the influence on the signal power at a particular location, of at least one particular RIS configured according to the following steps: - Selecting a subset of RIS of the communication system by taking into account at least the distance separating a RIS from the terrestrial receiver, and - Configuring the phase of at least one RIS selected from the respective positions of the server satellite, the RIS and the terrestrial receiver,so as to phase the signal received in direct line by the terrestrial receiver with the phase of the signal reflected by the selected RIS and increase the useful power received by the receiver.,

6. The method of claim 5 wherein the step of selecting at least one RIS comprises calculating a product of the distance between the receiver and the RIS times the distance between the RIS and the satellite, a RIS being selected when it minimizes said product.

7. Device for controlling a coverage area of ​​a server satellite of a satellite communication system comprising a plurality of satellites, the device comprising a processor (402) coupled to a memory (401) in which are recorded program instructions (403) configured to implement the following steps - Determination of at least one dimension Rc of a geographical area C to be covered by the server satellite with a particular target quality of service, - Determination of an overall interference level on the area C to be covered from the relative positions and transmission powers of the satellites present in an interference area and a characteristic of the ground environment likely to influence said overall interference level, - Determination of a minimum transmission power of the server satellite making it possible to cover the area C with the target quality of service, taking into account the determined interference level,and - Configuration of the server satellite with the determined transmission power.,

8. Device according to claim 7 in which the transmission power is determined so as to cover an area with a target radius Rc determined at least from the location of a particular terrestrial receiver.

9. Control unit comprising a device according to claims 7 or Q

10. O. Computer program comprising instructions adapted to implement the steps of a control method according to any one of claims 1 to 6, when the program is executed by a processor.

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