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 a so-called server satellite is adapted to transmit a radiofrequency signal to at least one receiver, the method comprising steps of estimating an overall interference level from the relative positions and transmission powers of the satellites present in an interference zone with respect to the location of the receiver, and a particular topology of the ground environment at said location, determining, from the estimated overall interference level, a minimum number of transmission channels allowing the server satellite to transmit data to the receiver with a target throughput and quality of service, and configuring the transmitting satellite to allocate the determined number of channels to a transmission from the server satellite to the receiver. Abstract figure: figure 2

Description

Title of the invention: Method, device and program for configuring a transmission between a satellite of a satellite communication network and a receiver. Technical field

[0001] The invention relates to the general field of telecommunications. It relates more particularly to a satellite communication network.

[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] 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 the other satellites in the satellite network which transmit simultaneously using the same resources as the server satellite (typically the same frequency).

[0005] Each satellite in the satellite network other than the server satellite is in fact likely to generate a signal interfering with the useful signal transmitted 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 devices in the same frequency band.

[0006] More precisely, a satellite (or a satellite's transmission spot) has a finite set of transmission channels for a frequency band. The satellite determines the number of channels to allocate to a terminal to satisfy its demand throughput and / or quality of service. Thus, the different transmission channels available to the satellite are distributed among different users on the ground, according to the throughput and / or quality of service they require. Since these radio resources are limited, it is important to allocate only the strict minimum of channels allowing the target throughput to be achieved with the desired quality of service.

[0007] When several satellites share the same set of resources in the same interference zone, for example when they share the same frequency band, the use of a particular channel of this frequency band by a first satellite can interfere with a communication of a second satellite which uses the same channel. Conversely, these satellites can share the same frequency band without producing interference if they do not simultaneously allocate the same channels for their communications.

[0008] 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 from end to end by the satellite network, and outage probability, this being derived from energy efficiency.

[0009] More specifically, Gupta et al. defines energy efficiency £î> as follows log2(i+CA'Æf / / ) where CNReff denotes the ratio of the useful power and the Sn — p ' r M thermal noise power taken at a terrestrial radio station, and Ptot the total end-to-end power consumption of the satellite network.

[0010] The impact of different transmission parameters (antenna gain, channel power gain, etc.) on energy efficiency and on the 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 take this interference into account.

[0011] Furthermore, this document does not address the impact of the environment of the user equipment on the power of the received signal. However, the power of the signal received by a user equipment is also affected by the environment of the equipment, such as the urban or rural environment or whether the equipment is located inside or outside a building.

[0012] Since the quality of service that a 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, and therefore to the level of interference at the equipment level, 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 a user equipment. In particular, it does not allow an operator to determine precisely the number of channels to be allocated to a communication between a satellite and a receiver to achieve a target rate and quality of service. By allocating too few channels, the communication will not be able to achieve the target rate or quality of service. By allocating too many channels, resources are unnecessarily reserved and the efficiency of the communication system is not optimal.Additionally, over-allocated channels are likely to cause interference with other users and reduce the overall efficiency of the system.

[0013] There is thus a need for a technique making it possible to anticipate, control and allocate a necessary and sufficient number of channels to a communication with a user on the ground to enable the communication to achieve a target throughput and quality of service in the area covered by a spot or a satellite, taking into account a level of interference at the location of the receiver. Summary of the invention

[0014] 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 receiver located at a particular location, the method comprising the following steps: - Estimation of an overall interference level from the positions and relative transmission powers of the satellites present in an interference zone in relation to the location of the receiver, and a particular topology of the ground environment at said location, - Determination, from the estimated overall interference level, of a minimum number of transmission channels allowing the server satellite to transmit data to the receiver with a target rate and quality of service, - Configuring the transmitting satellite to allocate the determined number of channels to a transmission from the server satellite to the receiver.

[0015] The proposed system thus makes it possible to determine and control the configuration of a communications system consisting of a set of satellites, taking into account the impact of the receiver's environment (urban, rural, inside or outside a building for example) on the interference likely to be generated by satellites located in an interference zone.

[0016] 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 level of the user equipment which depends on the number of satellites or spots using the same resources as the server satellite in this zone, in particular the number of channels of the same frequency band simultaneously allocated by different satellites in the interference zone, as well as the distance separating each satellite from the receiver.

[0017] 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 considered of the other satellites of the satellite network, and in particular of the interference generated by the latter on the communication.

[0018] Advantageously, it is proposed to take into account how the receiver environment affects 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.

[0019] The method thus provides an improved estimation of the characteristics of a signal likely to be received by a receiver at a particular location. Such an estimation 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 and the number of allocated channels. 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).

[0020] Thus, it is possible to dynamically adapt the number of channels that it is necessary and sufficient to allocate to a terminal so that it benefits from a target flow rate with a particular quality of service. The requirement to achieve a target flow rate in fact requires the allocation of a certain number of channels which depends in particular on the level of interference.

[0021] The method thus allows for optimal channel allocation, which strictly meets the needs of each receiver, taking into account its specific reception conditions. The allocation takes into account in particular the influence interference induced by other satellites using the same resources and the influence of the environment on this interference.

[0022] No limitation is attached to the nature of the 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 transmitting / receiving radio station. The receiver can also be on board an aerial platform or an aircraft.

[0023] A communications satellite may comprise one or more transmission spots, each of which makes it possible to cover a particular geographical area. For the sake of clarity, the terms “spot” and “satellite” will be used interchangeably in this description 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.

[0024] According to a particular embodiment, the overall interference level I is determined by a relationship equivalent to the relationship:

[0025] / y . yV2 Z(j)=e^-^(£^ Worm? /

[0026] in which 17 denotes the standard deviation of the masking effect (or "shadowing" in English) characterizing the influence of the local environment of the receiver, ri denotes the distance separating the receiver from satellite j, with a = ln 10 / 10.

[0027] 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.

[0028] The term E characterizes the relative impact of the relative positions of the sources 77 interference (other satellites, other spots from the same satellite) compared to those of the receiver.

[0029] In this way, the method makes it possible to determine the number of allocated channels from a modeling of the influence of the interference produced globally by other satellites according to their respective positions relative to the receiver, and the impact of the receiver's environment (indoor, outdoor, urban or rural environment for example) on this interference.

[0030] 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:

[0031] - Selection of a subset of RIS of the communication system taking into account at least takes into account the distance separating a RIS from the receiver, and

[0032] - Configuration of the phase of at least one RIS selected from the positions respective of the server satellite, the RIS and the receiver, so as to phase the signal received in direct line by the receiver and the signal received by the receiver after reflection by the selected RIS and increase the useful power received by the receiver.

[0033] Reconfigurable Intelligent Surfaces (RIS) are a recent technological innovation in the telecommunications sector. A RIS comprises a two-dimensional matrix of elementary cells configured to allow dynamic modification of the characteristics (particularly in terms of direction) of a reflected electromagnetic wave, in response to an incident wave.

[0034] Taking into account RIS in the vicinity of 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. Consequently, the use of RIS makes it possible to reduce the number of channels that need to be allocated to a communication to achieve a target throughput and / or quality of service. Unused channels can be allocated to other communications or remain unallocated to limit the risk of interference when this channel is used by another satellite in the interference zone. In this way, the resources of the communication system are used more efficiently.

[0035] It is thus proposed to apply a particular configuration to one or more RISs near the terminal so as to modify the phase of the reflected signal so that it corresponds to the phase of the signal received in direct line by the receiver. In other words, a signal part which would not have reached the receiver is reflected towards it after aligning the phase of the direct signal with the phase reflected by the RIS to increase the power of the received signal and make it possible to limit the number of channels required.

[0036] The method thus makes it possible to determine the minimum number of channels that it is necessary to allocate to a communication to achieve a target flow rate and quality of service when RIS can be used.

[0037] Since the phase of the signal is equal to the distance between the transmitter and the receiver multiplied by 2s. (where 2 is the wavelength), the phase difference between the direct line signal and the reflected signal can be determined from the difference between the distance between the satellite and the RIS and the distance between the satellite and the receiver. This phase difference allows the RIS to be configured.

[0038] 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.

[0039] Such an arrangement allows the selection of at least one particular RIS from among the RIS which are in proximity to the receiver.

[0040] When the satellite transmits a power P, the additional power p received by the receiver is given by the following relation:

[0041] [Math.0] + w)2

[0042] With:

[0043] vr?

[0044] With:

[0045] r the distance separating the server satellite from the receiver in direct line,

[0046] ri the distance between the satellite and the RIS',

[0047] fj the distance between the RIS * and the receiver,

[0048] K, Ki the propagation factors of the direct signal and the signals reflected by the RIS 6 These factors take into account the gains of the transmitter of the receiver and of the RIS.

[0049] Thus, it depends on the ratio between the distance separating the transmitter and receiver and the product so that when this product is minimum, the factor is maximum.

[0050] The effect of a RIS for the receiver, after phase control, results in a received power increased by a factor of ^2.

[0051] Thus, by proposing to select a RIS which minimizes the value of the product, the method maximizes the power useful to the receiver, thus making it possible to achieve a target rate using a minimal number of transmission channels.

[0052] According to another aspect, there is proposed 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 receiver, the device comprising a processor coupled to a memory in which program instructions are recorded adapted to implement the following steps: - Estimation of an overall interference level from the positions and relative transmission powers of the satellites present in an interference zone in relation to the location of the receiver, and a particular topology of the ground environment at said location, - Determination, from the estimated overall interference level, of a minimum number of transmission channels allowing the server satellite to transmit data to the receiver with a target rate and quality of service, - Configuring the transmitting satellite to allocate the determined number of channels to a transmission from the server satellite to the receiver.

[0053] In a particular embodiment, the instructions recorded 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:

[0054] - Selection of a subset of RIS of the communication system taking into account at least takes into account the distance separating a RIS from the receiver, and

[0055] - Configuration of the phase of at least one RIS selected from the positions respective signals of the server satellite, the RIS and the receiver, so as to phase the signal reflected by the RIS with the signal received in direct line.

[0056] The invention also relates to a control unit comprising a configuration device as described above.

[0057] The invention also relates to a communication system comprising such a control unit, a plurality of satellites, and at least one receiver. In a particular embodiment, the system further comprises at least one RIS adapted to reflect a signal transmitted by a satellite towards a receiver of the system.

[0058] In a particular embodiment, the steps of the configuration method are determined by computer program instructions.

[0059] 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.

[0060] This program may 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.

[0061] 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 configuration method as described above.

[0062] The information carrier may be any entity or device capable of storing the program. For example, the carrier may comprise a storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, flash memory, or a magnetic recording medium, such as a hard drive.

[0063] 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.

[0064] 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.

[0065] The various embodiments or features mentioned above may be added independently or in combination with each other, to the steps of the configuration method.

[0066] The devices, controllers, systems, programs and information media have advantages similar to those conferred by the configuration method. Brief description of the figures

[0067] Other characteristics and advantages will appear on reading a preferred embodiment described with reference to the appended drawings among which: - [Fig. 1] represents an environment suitable for implementing the configuration method according to a particular embodiment, - [Fig.2] is a flowchart representing the main steps of a configuration process according to a particular embodiment, - [Fig.3] is a diagram representing the architecture of a device suitable for implementing the configuration method in a particular embodiment. Detailed description

[0068] 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.

[0069] [Fig. 1] represents an environment suitable for implementing the configuration method according to a particular embodiment.

[0070] 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. No limitation is attached to the nature of the receiver 103. It may be a communication terminal, a connected vehicle or for example a base station. The receiver may be on the ground or on board an aircraft, such as a balloon, an airplane or even a drone.

[0071] The local environment of the receiver 103 includes buildings 104 likely to alter the transmitted signal by generating multi-path type interference for example.

[0072] The environment also includes 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.

[0073] 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 receiver 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 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.

[0074] 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.

[0075] 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.

[0076] Thus, the receiver 103 receives useful power from the spot of the satellite 100 to which it is connected, and non-useful power due to all the other spots of this satellite, and from the other satellites 101 and 102 transmitting simultaneously on the same frequency in an interference zone.

[0077] The satellites 100 to 102 use the same resources, for example the same frequency band, to transmit to the ground terminals. They thus share the same set of transmission channels which they can allocate in greater or lesser numbers to communications with receivers depending on the throughput and / or the quality of service required.

[0078] A particular embodiment of the configuration method will now be described with reference to [Fig.2].

[0079] [Fig.2] is a flowchart representing the main steps of a configuration method according to a particular embodiment.

[0080] During a first step 200, 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.

[0081] 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 interfering satellites and spots.

[0082] 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 or to another satellite) compared to the receiver. We can also speak of a sort of "form factor" of the system. In other words j(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:

[0083] [Math.l] \ l (W

[0084] [Math.2] y(r) =

[0085] In these expressions denotes the distance separating an interfering satellite j from the receiver, andr denotes the distance between the server satellite and the receiver.

[0086] The inventors then used the formula [Math 1] to characterize the overall impact of shadowing l(j), i.e. the influence on the signal of obstacles in the receiver's environment, taking into account the topology of the satellite system, with :

[0087] [Math.3] i( J) («^-D + if 2

[0088] With - InlQ

[0089] The factors y ( r ) and I{ j ) make it possible to calculate an average my of the interference ratio on useful signal, received at the receiver, taking into account the impact of shadowing:

[0090] [Math.4]

[0091] From the factor I(j) allowing shadowing to be taken into account, the inventors propose calculating the standard deviation of the useful signal to interference ratio Sj, received at the receiver. Sj then models the impact of interference (without taking into account thermal noise) on the SIR (for Signal-to-Interference Ratio) of the perceived signal, when considering the impact of the receiver's environment and all interfering satellites and spots.

[0092] [Math.5]

[0093] The average my of the interference to useful signal ratio and the square of the standard deviation make it possible to calculate a term ct 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:

[0094] [Math.6] Ct = emy+~T

[0095] The influence of thermal noise on the signal is characterized by a value dN such that:

[0096] [Math.7] aN = emi^ 2

[0097] Where:

[0098] [Math. 8]

[0099] With Nfh the thermal noise affecting an SC channel, Pgç the transmission power on the SC channel, and K the propagation constant.

[0100] It is then possible to define a value mt characterizing the average value of the SINR of the signal of a particular sub-channel, taking into account interference and noise.

[0101]

[0102]

[0103]

[0104]

[0105]

[0106]

[0107]

[0108]

[0109]

[0110] [YES]

[0112]

[0113]

[0114] thermal affecting each channel, when considering the impact of the environment and all interfering satellites and spots. [Math.9] mt = -ln[c,+ dN] + 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 In which: [Math. 11] And : [Math. 12] 1) The control unit can thus determine for a particular channel of a frequency band, 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. During a step 203, the control unit determines the number of channels Nsc to be allocated to a communication with the receiver from a target rate D and an estimation of the interferences carried out in step 200. For this, the controller uses a relation equivalent to the following relation: [Math. 13] N ---LL $-----1----- 1 ' sc — W In which D is a flow rate and £ the probability of not reaching the flow rate D, Wsc the bandwidth allocated to a sub-channel SC, is defined by a relation equivalent to [Math 10] and Q is a complementary error function such as: [Math. 14] erfc^x) =-^]xe~t2dt= l-erf(x) The expression [Math 13] makes it possible to determine a number of channels Nsc necessary and sufficient to achieve a flow rate D in the particular reception conditions of a receiver (i.e. local environment, global interference).

[0115] Thus, for a required quality of service value £, and for a particular location of the receiver, the control unit determines the parameters of the expression [Math 13]. When the target flow rate value D is reached, for a required quality of service (characterized by £), the number of corresponding Nsc channels is that which the spot must allocate.

[0116] For example, if the required value for £ is 1%, this means that the probability of not reaching the flow rate D is 1%. The parameters of the expression [Math 13] determine the number of channels Nsc to meet these requirements. Moreover, if the user's requirement is such that the number of channels should reach a value greater than the maximum number of channels that the spot can allocate, the expression [Math 13] makes it possible to determine that it is not possible to meet the user's requirement. It is then possible to quantify the maximum flow rate value that can be offered to the user, and the quality of service that can be offered to him.

[0117] During a step 204, the control unit updates the configuration of the satellite from the number of channels determined in step 203. To do this, the control unit transmits a message to the satellite whose transmission configuration must be updated, the message comprising an identifier of the spot and a command to update a transmission parameter, such as the number of channels to be allocated to a particular receiver.

[0118] The server satellite can thus determine precisely the number of channels that it is necessary and sufficient to allocate to a terminal to achieve a target throughput and quality of service. The resources are thus allocated optimally, taking into account the environment of the receiver and the interference likely to be generated by other satellites in the constellation. The method thus makes it possible to limit energy expenditure and reduce the risk that the transmitted signal interferes with the signals of other satellites using the same resources.

[0119] According to a particular embodiment, the method determines the number of channels necessary and sufficient by taking into account the presence of reconfigurable reflective surfaces 105 and 106 (or RIS, for Reconfigurable Intelligent Surfaces in English) present in the environment of the receiver 103.

[0120] 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 RIS which are located at a distance less than a particular threshold from the receiver. The control unit uses for this the location of the RIS as well as that of the receiver, obtained for example by interrogating the receiver by an appropriate request, or from location data known from the cellular network.

[0121] According to a particular embodiment, the control unit determines, among the selected RISs, the RISs which are most likely to positively influence the power of the signal to the receiver.

[0122] For this, the control unit 107 determines, for each selected RIS, a product of the distance ri between the server satellite of the RIS \ with the distance r- between the RIS * and the receiver.

[0123] For example, with reference to Figure 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 and the product (F / *rÿ) and selects the RIS which is associated with the lowest value product. As seen previously, an RIS that minimizes such a product maximizes the power of the signal reflected back to the receiver.

[0124] 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 direct line signal and the distance traveled by the reflected signal by 2n7À (where 2 is the wavelength):

[0125] [Math. 15] = + ~r)

[0126] With: - r the distance separating the server satellite from the receiver in direct line, - rî the distance separating the server satellite from the selected RIS, - r\ the distance separating the selected RIS from the receiver, - 2 the wavelength.

[0127] 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.

[0128] In this way, the direct line signal and the reflected signal are received in phase by the receiver, the signal power thus resulting from the sum of the powers of the received signals.

[0129] Increasing the power of the useful signal received by configuring one or more RISs in the vicinity allows a reduction in the transmission power of the satellite and / or a reduction in the number of channels required to provide a target throughput. The control unit can then determine a number of channels that is necessary and sufficient for the server satellite to guarantee quality of service to the receiver.

[0130] The additional power that a receiver can benefit from thanks to the presence of correctly configured RIS can be taken into account in the expression [Math 8] for the estimation of the number of channels necessary to achieve the target rate. In such a situation, the transmission power Psc of the expression [Math 8] for a particular sub-channel SC includes the power defined by the expression [Math 0]. In other words, the power received by the receiver is determined from the power received in direct line and the power received via correctly configured RIS and the number of channels to be used is determined from the transmission power corresponding to this received power.

[0131] Thus, the use of RIS makes it possible to improve the term mN of the expression [Math 8], so that in the expression [Math 13], the terms and mt are such that the number of sub-channels Nsc decreases.

[0132] According to a particular embodiment, the method is implemented by the server satellite 100. For this, the ground receiver can transmit to its server satellite, the distance, position, power data of the interfering satellites, by means of signaling.

[0133] 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 position of the receiver.

[0134] 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 move from 32 to 64 QAM (for Quadrature Amplitude Modulation).

[0135] Compared to an algorithmic method, the process allows a simpler analytical approach through the expression [Math 13], faster and more efficient.

[0136] [Fig. 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 into the control unit 107 shown in [Fig. 1].

[0137] 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 [Fig.2].

[0138] 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 puts into implements, according to the instructions of the computer program 303, the steps of the configuration method described above with reference to [Fig.2].

[0139] 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 allow in particular the device 300 to exchange data with a receiver and / or with a particular satellite, either directly or via one or more communication networks.

[0140] The device 300 comprises a module 305 for estimating an overall interference level at a particular location in the coverage area of ​​the satellite. The module 305 is for example implemented by computer program instructions configured to estimate at least one overall interference level 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 305 are configured to determine an overall interference level taking into account the impact of the satellites present in an interference area, the local environment and the thermal noise from expressions equivalent to the expressions [Math 1] to [Math 15] described above.

[0141] The device 300 also comprises a module 306 adapted to determine the minimum number of channels allowing a target rate to be achieved for a target quality of service. The module 306 is for example implemented by computer program instructions which are configured to evaluate the expression [Math 13] using the interference level determined by the module 305, a target rate and a quality of service corresponding to a probability of not achieving the target rate.

[0142] 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 indication relating to the number of channels that it is necessary to allocate to a particular receiver to achieve a target rate with a particular quality of service.

[0143] 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 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 order to limit the number of channels necessary to achieve the target rate. For this, the instructions are configured to determine a total power of the signal received by the receiver, from a power of the signal received in direct line by the receiver and a power received via properly configured RIS, and to determine the number of channels necessary and sufficient to ensure the target rate and quality of service taking into account this total power received.

[0144] 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 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 receiver located at a particular location, the method comprising the following steps: - Estimation (200) of an overall interference level from the relative positions and transmission powers of the satellites present in an interference zone with respect to the location of the receiver, and of a particular topology of the ground environment at said location, - Determination (203), from the estimated overall interference level, of a minimum number of transmission channels allowing the server satellite to transmit data to the receiver with a target rate and quality of service,- Configuring (204) the transmitting satellite to allocate the determined number of channels to a transmission from the server satellite to the receiver.,

2. Method according to claim 1 in which the influence 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 mask effect characterizing the influence of the local environment of the receiver, ri denotes the distance separating the receiver from satellite j, with a = lnl0 / 10.

3. Method according to any one of the preceding claims in which 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 receiver, - Configuring the phase of at least one RIS selected from the positions of the server satellite, the RIS and the receiver, so as to phase the signal received in direct line by the receiver and the signal received by the receiver after reflection by the selected RIS and increase the useful power received by the receiver.

4. The method of claim 3 wherein the step of selecting at least one RIS comprises at least 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.

5. 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 receiver located at a particular location, 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 the positions and relative transmission powers of the satellites present in an interference zone with respect to the location of the receiver, and of a particular topology of the environment on the ground at said location, - Determination, from the estimated overall interference level,a minimum number of transmission channels allowing the server satellite to transmit data to the receiver with a target throughput and quality of service, - Configuration of the transmitting satellite to allocate the determined number of channels to a transmission from the server satellite to the receiver.,

6. Device according to claim 5 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 smart surface

7.

8.

9.

10. reconfigurable RIS adapted to control how the signal reflects off this surface: - Selection of a subset of RIS of the communication system taking into account at least the distance separating a RIS from the receiver, and - Configuration of the phase of at least one RIS selected from the respective positions of the server satellite, the RIS and the receiver, so as to phase the signal reflected by the RIS with the signal received in direct line. Control unit comprising a device according to any one of claims 5 and 6. Communication system comprising a control unit according to claim 7, a plurality of satellites, at least one receiver and at least one RIS. Computer program comprising instructions adapted to the implementation of the steps of a configuration method according to any one of claims 1 to 4, when the program is executed by a processor. Computer-readable information medium on which is recorded a computer program comprising instructions for executing the steps of a configuration method according to any one of claims 1 to 4.

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