Method, device and program for configuring a transmission between a satellite of a satellite communication network and a receiver

Abstract

The invention relates to a method for configuring a satellite communication system comprising a plurality of satellites among which one satellite, referred to as the server, is capable of transmitting a radiofrequency signal to at least one terrestrial receiver, the method comprising steps of estimating (201) at least one characteristic of the signal received by the terrestrial receiver on the basis of an overall level of interference (200) determined on the basis of the relative transmission positions and powers of the satellites present in a region of interference relative to those of the receiver, and of a particular topology of the environment local to the receiver that is liable to affect the overall level of interference, of determining (202), on the basis of the estimated characteristic of the signal, a minimum transmission power that allows the server satellite to deliver a target quality of service to the terrestrial receiver, and of configuring (204) the transmitting satellite with the determined transmission power.

Description

[0001]DESCRIPTION TITLE: Method, device and program for configuring a transmission between a satellite of a satellite communication network and a receiver. Technical field The invention relates to the general field of telecommunications. It relates more particularly to a satellite communication network. The invention finds a preferred but non-limiting application in the context of mobile services based on a satellite communication network. Prior art 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 transmission.Note that the server satellite is the one that covers the geographical area in which the user equipment is located and to which the user equipment is connected or associated. The power of the signal received by the user equipment depends on the transmission power applied by the satellite and on characteristics specific to the satellite such as its orbit (which determines in particular its altitude). The signal transmitted by the server satellite undergoes attenuation which is a function of the direct line distance separating the server satellite from the user equipment. The received signal is also affected by interference generated by other satellites in the satellite network which transmit simultaneously using the same resources as the server satellite (typically the same frequency).Each satellite in the satellite network other than the server satellite is indeed 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. The paper by N. Gupta and S. Bitragunta, entitled "Green Satellite Communication Link Design, Optimization and Performance Analysis", IEEE 7th Uttar Pradesh Section International Conference on Electrical, Electronics and Computer Engineering (UPCON), 2020, pages 1-5, focuses on the performance of a satellite communication network in terms of energy efficiency ^^. ^^, this being defined as the ratio of spectral efficiency and the total power consumed end-to-end by the satellite network, and outage probability, this being derived from energy efficiency. More specifically, Gupta et al. defines energy efficiency ^^ ^^ in the following way [Math1] where ^^^^^^ ^^^^^^ denotes the ratio of useful power and thermal noise power taken at a terrestrial radio station, and ^^ ^^^^^^ the total end-to-end power consumption of the satellite network. The impact of different transmission parameters (antenna gain, channel power gain, etc.) on energy efficiency and outage probability is analyzed by Gupta et al. The possibility of taking interference into account in the calculation of energy efficiency ^^ ^^in the case of frequency spectrum sharing is also briefly mentioned in Gupta et al. However, no indication is given on the nature of the interference in question or on how to do it. Furthermore, this document does not address the impact of the user equipment's environment on the received signal strength. However, the signal strength received by user equipment is also affected by the equipment's environment, such as the urban or rural environment or whether the equipment is located inside or outside a building. Since the quality of service that user equipment can benefit from, and in particular the transmission rate, is very largely linked to the power of the useful signal actually received by the equipment, the approach proposed by N. Gupta and S. Bitragunta does not allow a satellite network operator to guarantee the performance of its network,and in particular to ensure that it provides a given quality of service to user equipment. There is therefore a need for a method for ensuring that the quality of service enjoyed by user equipment under the coverage of a server satellite corresponds to a target quality of service, and for determining a configuration of the communication system for achieving this target quality of service where appropriate. Summary of the invention To this end, a method is proposed for configuring a satellite communication system comprising a plurality of satellites among which a so-called server satellite is adapted to transmit a radiofrequency signal to at least one terrestrial receiver,the method comprising the following steps: - Estimation of at least one characteristic of the signal received by the terrestrial receiver from an overall interference level determined from the positions and relative transmission powers of the satellites present in an interference zone compared to those of the receiver, and from a particular topology of the local environment at the receiver likely to influence said overall interference level, - Determination, from the estimated signal characteristic, of a minimum transmission power allowing the server satellite to provide a target quality of service to the terrestrial receiver, and - Configuration of the transmitting satellite with the determined transmission power. The proposed method thus makes it possible to determine and control the configuration of a communications system consisting of a set of satellites by taking into account the impact of the receiver's environment (urban,rural area inside or outside a building for example) on interference likely to be generated by satellites located in an interference zone. Spots or satellites are present in an interference zone when they cover a geographical area intersecting in whole or in part the geographical coverage area of ​​the server satellite (in which the user equipment is located) and are therefore likely to generate overall interference at the user equipment level which depends on the number of satellites or spots using the same resources as the server satellite in this area, as well as the distance separating each satellite from the receiver. Taking into account the relative positions and transmission powers of the satellites present in an interference zone makes it possible to characterize the impact on the communication in question of the other satellites in the satellite network,and in particular the interference generated by the latter on communication. Advantageously,it is proposed to take into account the way in which the receiver environment affects the interference generated by satellites using the same resources as the server satellite in the interference zone to determine an overall interference level likely to affect the signal at the receiver location. The method thus provides an improved estimate of the characteristics of a signal likely to be received by a terminal at a particular location. Such an estimate makes it possible to determine a priori a parameter setting to be applied to the server satellite to achieve a target quality of service at a particular location. It is thus possible to predict and quantify the performance of the communications system and in particular to know a priori whether it will make it possible to offer a particular quality of service for a receiver depending on its location and its environment. The characteristic of the signal may correspond here to a useful power of the received signal,a flow rate or even a SINR (for Signal-to-Interference plus Noise Ratio in English). The invention applies in a preferred manner to communication in the downlink direction, that is to say from the server satellite to the user equipment. No limitation is attached to the nature of the terrestrial receiver. It can be any receiving device, for example a fixed or mobile client terminal of the satellite network (e.g. a smartphone, a computer, etc.), or a terrestrial radio transmitting / receiving station. A communication satellite can comprise one or more transmission spots, each of which allows a particular geographical area to be covered. For the sake of clarity, the terms "spot" and "satellite" will be used interchangeably in this description to designate a satellite transmission spot,so that the formulations “area covered by a satellite” and “area covered by a spot of a satellite” are equivalent here. According to a particular embodiment, the estimated signal characteristic comprises at least the power of the useful signal received by the receiver, the communication rate, and / or the bandwidth allocated to the communication. According to a particular embodiment, the overall interference level ^^ is determined by a relationship equivalent to the relationship:, in which ^^ denotes the standard deviation of the influence of the receiver's local environment, ^^ ^^ denotes the distance separating the receiver from the satellite ^^, with ^^ = ln 10⁄ 10. 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. ∑ ^ −4 ^^≠0 ^ The term ^^(∑ ^^≠0 ^^−2 ^ ^)2characterizes the relative impact of the relative positions of the interference sources (other satellites, other spots of the same satellite) with respect to those of the receiver. 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: - 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.Reconfigurable Intelligent Surfaces (RIS) are a recent technological innovation in the telecommunications sector. A RIS comprises a two-dimensional matrix of elementary cells that are configured to allow dynamic modification of the characteristics (particularly in terms of direction) of a reflected electromagnetic wave, in response to an incident wave. Taking into account RIS near the terminal, and in particular the application of a suitable configuration to one or more RIS, makes it possible to improve the quality of the signal at the receiver. It is thus proposed to apply a particular configuration to one or more RIS 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 portion of the signal that would not have reached the receiver is reflected back to it after phase alignment to increase the power of the received signal. 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 improve the quality of the signal to the receiver. Since the phase of the signal is equal to the distance separating the transmitter and the receiver multiplied by 2^^ ^^ where ^^ is 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.In a particular embodiment, the step of selecting at least one RIS comprises at least the calculation of 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. Such an arrangement allows the selection of at least one particular RIS from among the RIS which are in the vicinity of the terrestrial receiver. When the satellite transmits a power P, the power p received by the receiver is given by the following relationship:. With : With: ^^ the distance separating the server satellite from the receiver in direct line, ^^ ^^ the distance between the satellite and the RIS ^^, ^^ ′ ^ ^the distance between the RIS ^^ and the receiver,^^, ^^^^ the propagation factors of the direct signal and the signals reflected by the RIS ^^. These factors take into account the gains of the transmitter from the receiver and the RIS. Thus, ^^ depends on the ratio between the distance separating the transmitter and receiver and the product (^^^^ ∗ ^^ ′ ^ ^ ). Thus, when this product is minimum, the factor ^^ is maximum. The effect of a RIS for the receiver, after phase control, results in an increased received power by a factor (^^ + ^^)^^. Thus, by proposing to select a RIS which minimizes the value of the product (^^^^ ∗ ^^ ′ ^ ^), the method maximizes the useful power to the receiver. According to another aspect, there is provided a device for configuring a satellite communication system comprising a plurality of satellites among which a so-called server satellite is adapted to transmit a radiofrequency signal to at least one terrestrial receiver, the device comprising a processor coupled to a memory in which are recorded program instructions adapted to implement the following steps: - Estimation of at least one characteristic of the signal received by the terrestrial receiver from an overall interference level determined from the positions and relative transmission powers of the satellites present in an interference zone with respect to those of the receiver, and of a particular topology of the local environment at the receiver likely to influence said overall interference level, - Determination,from the estimated signal characteristic, a minimum transmission power allowing the server satellite to provide a target quality of service to the terrestrial receiver, and - Configuration of the transmitting satellite with the determined transmission power. In a particular embodiment, the instructions stored in the memory of the device are further configured to implement the following steps, when the communication system comprises at least one reconfigurable intelligent surface RIS adapted to control the way in which the signal is reflected on this surface: - Selection of a subset of RIS of the communication system taking into account at least the distance separating a RIS from the terrestrial receiver, and - Configuration of 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 reflected by the RIS with the signal received in direct line. The invention also relates to a control unit comprising a configuration device as described above. The invention also relates to a communication system comprising such a control unit, a plurality of satellites, and at least one terrestrial receiver. In a particular embodiment, the steps of the configuration method are determined by computer program instructions. Consequently, the invention also relates to a computer program comprising instructions adapted to the implementation of the steps of a configuration method as described above, when the program is executed by a processor. This program can use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code, such as in a partially compiled form,or in any other desirable form. The invention also relates to a computer-readable information medium on which is recorded a computer program comprising instructions for carrying out the steps of a configuration method as described above. 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. Furthermore, 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 a network such as the Internet. 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. The various embodiments or characteristics mentioned above may be added independently or in combination with each other, to the steps of the configuration method. The devices, controllers, systems, programs and information carriers have advantages similar to those conferred by the configuration method. Brief description of the figures Other characteristics and advantages will appear on reading a preferred embodiment described with reference to the appended drawings among which: - Figure 1 represents an environment adapted to implement the configuration method according to a particular embodiment, - Figure 2 is a flowchart representing the main steps of a configuration method according to a particular embodiment,- Figure 3 is a diagram representing the architecture of a device suitable for implementing the configuration method in a particular embodiment. Detailed description 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. Figure 1 represents an environment suitable for implementing the configuration method according to a particular embodiment. The environment comprises 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 present in its coverage area. Each satellite may comprise a plurality of “spots” configured to emit a signal with a particular configuration. The local environment of the receiver 103 comprises buildings 104 likely to alter the transmitted signal by generating multi-path type interference for example. The environment also comprises 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. The environment 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 a particular piece of equipment in a base station of a cellular network. The control unit may communicate with the entities via a wired network, a cellular network, a satellite connection or by any suitable means. Thus, the control unit may receive data from the receiver 103, the RIS surfaces and the satellites, but also transmit data to these pieces of equipment and particularly transmit a configuration to a particular satellite or RIS surface in order to modify its settings. The satellites 100-102, the control unit 107, the receiver 103 and the RIS surfaces 105-106 form a communication system. 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. 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 signal received by the user has a power which depends on the characteristics of the satellite, in particular its transmission power and its orbit. Thus, the receiver 103 receives a useful power coming from the spot of the satellite 100 to which it is connected, and a non-useful power due to all the other spots of this satellite,and other satellites 101 and 102 transmitting simultaneously on the same frequency in an interference zone. A particular embodiment of the configuration method will now be described with reference to FIG. 2. FIG. 2 is a flowchart representing the main steps of a configuration method according to a particular embodiment. During a first step 200, the control unit 107 determines an overall 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 overall interference level. For this, the control unit determines an average value of the SINR 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 the interfering satellites and spots. The inventors first modeled by terms ^^, ( ^^ ) and ^^ ( ^^ ) the relative impact of the relative positions and powers of the interference sources (other satellites, other spots from the same satellite) compared to those of the receiver. These are factors that 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 ^^ ( ^^ ) and ^^ ( ^^ ) characterize the overall impact of the system topology on the receiver of the useful signal. These factors are defined by relationships equivalent to: [Math 1] [Math 2] In which ^^ ^^denotes the distance separating an interfering satellite ^^ from the receiver and ^^ the distance between the server satellite and the receiver. The inventors then used the formula [Math 1] to characterize the overall impact of shadowing ^^(^^) i.e. the influence on the signal of obstacles in the receiver's environment, taking into account the topology of the satellite system, with: [Math 3] With ^ ^^^ ^^^^ ^^ = ^^^^ The factors ^^(^^) and ^^(^^) allow you to calculate an average ^^ ^^ of the interference to useful signal ratio, received at the receiver, taking into account the impact of shadowing: [Math 4] From the factor ^^(^^) allowing shadowing to be taken into account, the inventors propose to calculate the standard deviation of the useful signal to interference ratio ^^ ^^ , received at the receiver. ^^ ^^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 5] The average ^^ ^^ of the interference to useful signal ratio and the square of the standard deviation ^^ ^^ allow you to calculate a term ^^ ^^ characterizing the average value of the SIR of the perceived signal, which takes into account interference but not thermal noise, when considering the impact of the environment and all interfering satellites and spots: [Math 6] The influence of thermal noise on the signal is characterized by a value ^^ ^^ such as: [Math 7] ^^ ^^ ^^ ^^ ^ ^ = ^ ^^ ^^ + ^ ^ ^ ^^ Where: [Math 8] With ^^ ^^^^thermal noise, ^^ the transmission power and ^^ the propagation constant. It is then possible to define a value ^^ ^^ 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 9] 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 10] In which: [Math 11] And: [Math 12] The control unit can thus determine the average value ^^ ^^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 a step 203, the control unit determines the useful power received by the receiver from the estimation of the interference carried out in step 200. For this, the controller uses a relationship equivalent to the following relationship: [Math 13] 2^^ / ^^ − 1 = 10−(^^^^^^−1(^^)+^^^^) / 10In which D is a flow rate and α the probability of not reaching the flow rate D, W the allocated bandwidth, ^^ ^^ the standard deviation of shadowing and ^^ is a complementary error function such as: [Math 14] e rf(^^) The expression [Math 13] makes it possible to determine the throughput achieved or likely to be achieved by a particular receiver. It depends on the transmission power of the spot, since the requirement of a given minimum throughput requires the transmission of data at a particular power. In step 204, the control unit 107 determines a minimum transmission power that must be observed by the server satellite 100 (or the spot on which the receiver depends) in order to guarantee the achievement of a target throughput (or power) at the receiver. For this, the control unit calculates the terms of the relation [Math 13] for different transmission power values ​​P. For example, the control unit calculates the terms of the relation [Math 13] by increasing the transmission power value P with a step of 0.1 dBm, so that when equality is reached, the corresponding power P is that with which the signal must be transmitted.In a particular embodiment, the control unit introduces a tolerance in the determination of the transmission power P making it possible to achieve a target rate D. For example, the control unit can determine a transmission power with a lower margin of 5%, which induces a higher error rate for the same rate. In this case, the control unit sends a signal for activating the FEC (forwarding error correction) to the satellite. During a step 205, the control unit updates the configuration of the satellite from the minimum power determined in step 204. For this, the control unit transmits a message to the satellite whose transmission power must be updated, the message comprising a spot identifier and a command for updating a transmission parameter, such as the transmission power.The server satellite can thus adapt its transmission power in order to guarantee a target quality of service for a receiver, which takes into account the environment of the receiver and the interference likely to be generated by other satellites in the constellation. The satellite is configured with a minimum transmission power, which has the effect of limiting the energy expenditure and reducing the risk that the transmitted signal interferes with the signals of other satellites using the same resources. According to a particular embodiment, the method takes advantage of reconfigurable reflective surfaces 105 and 106 (or RIS, for Reconfigurable Intelligent Surfaces in English) present in the environment of the receiver 103. For this, the method comprises a step 201 during which one or more RIS located near the receiver are selected.For example, during this first selection, the control unit 107 selects the RISs which are located at a distance less than a particular threshold from the receiver. According to a particular embodiment, the control unit determines, among the selected RISs, the RISs which are most likely to positively influence the signal strength at the receiver. For this, the control unit 107 determines, for each selected RIS, a product of the distance ^^. ^^ between the RIS server satellite ^^, with the distance ^^ ^^ ′between the RIS ^^ and the receiver. For example, with reference to Figure 1, the control unit 107 first selects the RIS 105 and 106 because the distance between them and the terminal 103 is less than a particular threshold. The control unit 107 then determines which of these RIS is most suitable for improving the signal to the receiver. For this, the control unit 107 calculates the product (^^^^ ∗ ^^ ′^^ ) and the product (^^^^ ∗ and selects the RIS that is associated with the lowest value product. As seen previously, a RIS that minimizes such a product makes it possible to maximize the power of the signal reflected to the receiver. In step 202, the control unit determines the value of a phase shift of the signal received in direct line by 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 signal in direct line and the distance traveled by the reflected signal by 2^^ / ^^ where ^^ is the wavelength: [Math 14] With: - ^^ the distance separating the server satellite from the receiver in direct line, - ^^ ^^ the distance between the server satellite and the selected RIS, - ^^ ^^ ′the distance separating the selected RIS from the receiver, - ^^ the wavelength. 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. In this way, the direct line signal and the reflected signal are received in phase by the receiver, the power of the resulting signal thus corresponding to the sum of the powers of the received signals. The increase in the power of the useful signal received thanks to the configuration of one or more RIS in proximity allows a reduction in the transmission power of the satellite. The control unit can then determine a new minimum transmission power for the server satellite which makes it possible to guarantee a quality of service to the receiver. According to a particular embodiment, the method is implemented by the server satellite 100.To do this, the ground receiver can transmit to its server satellite, the distance, position, and power data of the interfering satellites, through signaling. This information makes it possible to determine the terms expressions [Math 1] and [Math 3]. It also makes it possible to have precise knowledge of the receiver's position. Such a method of configuring a satellite communication system makes it possible to improve the SINR. This allows the use of less robust coding, which makes it possible, for example, to transmit data with a higher MCS (for Modulation Coding Scheme). For example, it thus becomes possible to go from 32 to 64 QAM (for Quadrature Amplitude Modulation in English). Compared to an algorithmic method, the method allows a simpler analytical approach through the expression [Math 13], which is faster and more efficient.Figure 3 represents the architecture of a device 300 adapted to implement the configuration method in a communication system, according to a particular embodiment. The device 300 is for example integrated the control unit 107 shown in Figure 1. The device 300 comprises a data processing module comprising a storage space 301, for example a memory (MEM), a processing unit 302, equipped for example with a microprocessor (PROC), and controlled by a computer program (PGR) 303 whose instructions are configured to implement the configuration method as described previously in relation to Figure 2. At initialization, the code instructions of the computer program 303 are for example loaded into the memory 301 before being executed by the processor of the processing unit 302.The microprocessor of the processing unit 302 implements, according to the instructions of the computer program 303, the steps of the configuration method described above with reference to FIG. 2. For this, in addition to the memory 301 and the processor 302, the device comprises communication means 304, 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 304 in particular allow the device 300 to exchange data with a terrestrial receiver and with a particular satellite, either directly or via one or more communication networks. The device 300 comprises a module 305 for estimating a characteristic of a signal transmitted by a server satellite to a terrestrial receiver located in its coverage area.The module 305 is for example implemented by computer program instructions configured to estimate at least one characteristic of the signal received by the terrestrial receiver from an overall 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 overall interference level. For this, the program instructions of the module 305 are configured to determine an overall interference level taking into account the impact of the satellites present in an interference zone, the local environment and the thermal noise from the formulas [Math 1] to [Math 12] described above.The device 300 also comprises a module 306 adapted to determine a minimum transmission power by a server satellite which allows a particular receiver under coverage of the satellite to benefit from a particular quality of service. The module 306 is for example implemented by computer program instructions which are configured to evaluate the expression [Math 13] with different transmission power values, for example increasing values ​​in steps of 0.1 dBm, until the target rate is reached. The device 300 also comprises a configuration module 307 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 306.In a particular embodiment, the device 300 comprises a module 308 for configuring at least one RIS. The configuration module 308 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.In a particular embodiment, the module 306 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 of the satellite. In certain embodiments, the device 300 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. Method for configuring a satellite communication system comprising a plurality of satellites among which a so-called server satellite is adapted to transmit a radiofrequency signal to at least one terrestrial receiver, the method comprising the following steps: - Estimation of an overall interference level (200) from a ratio between a distance separating the receiver from the server satellite and at least one distance separating the receiver from a satellite present in an interference zone, and a particular topology of the local environment at the receiver likely to influence said overall interference level, - Determination (202) of a minimum transmission power allowing the server satellite to provide a target quality of service to the terrestrial receiver, comprising a calculation, for different transmission power P values,terms of a relationship between the throughput likely to be achieved by a particular receiver and the transmission power, said relationship taking into account the estimated overall interference level, - Configuration (204) of the transmitting satellite with the minimum transmission power P for which equality of the relationship is achieved.

2. Method according to claim 1 wherein the estimated signal characteristic comprises the power of the useful signal received by the receiver, the throughput of the communication, and / or the bandwidth allocated to the communication.

3. Method according to any one of the preceding claims wherein the influence of a particular topology of the environment on the overall interference level is determined by a relationship equivalent to the relationship:, in which ^^ denotes the standard deviation of the influence of the local environment of the receiver, ^^^^ denotes the distance separating the receiver from the satellite ^^, with ^^ = ln 10⁄ 10.

4. Method according to claim 1 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, the method further comprising the following steps: - Selecting a subset of RIS of the communication system taking into account at least the distance separating a RIS from the terrestrial receiver, - 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.

5. Method according to claim 4 wherein the step of selecting a subset of RIS comprises at least the calculation of a product of the distance between the receiver and a RIS by the distance between the RIS and the satellite, a RIS being selected when it minimizes said product.

6. Device for configuring a satellite communication system comprising a plurality of satellites among which a so-called server satellite is adapted to transmit a radiofrequency signal to at least one terrestrial receiver,the device comprising a processor (302) coupled to a memory (301) in which are recorded program instructions (303) adapted to implement the following steps: - Estimation of an overall interference level from a ratio between the distance separating the receiver from the server satellite and at least one distance separating the receiver from a satellite present in an interference zone compared to those of the receiver, and a particular topology of the local environment at the receiver likely to influence said overall interference level, - Determination of a minimum transmission power allowing the server satellite to provide a target quality of service to the terrestrial receiver, comprising a calculation, for different values ​​of transmit power P, terms of a relationship between the throughput likely to be achieved by a particular receiver and the transmit power, said relationship taking into account the estimated overall interference level, and - Configuration of the transmitting satellite with the minimum transmit power P for which equality of the relationship is achieved. 7.Device according to claim 6 wherein the instructions (303) stored in the memory (301) are further configured to implement the following steps, when the communication system comprises at least one reconfigurable intelligent surface RIS adapted to control the way in which the signal is reflected on this surface: - Selection of a subset of RIS of the communication system taking into account at least the distance separating a RIS from the terrestrial receiver, and - Configuration of 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 reflected by the RIS with the signal received in direct line.

8. Control unit comprising a device according to any one of claims 6 and 7. 9.Communication system comprising a control unit according to claim 8, a plurality of satellites, at least one terrestrial receiver and at least one RIS.

10. Computer program comprising instructions adapted to the implementation of the steps of a configuration method according to any one of claims 1 to 5, when the program is executed by a processor.

11. Information medium readable by a computer on which is recorded a computer program comprising instructions for the execution of the steps of a configuration method according to any one of claims 1 to 5.

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